Patent Publication Number: US-11647984-B2

Title: Gel application system

Description:
RELATED APPLICATIONS 
     The application is a continuation of U.S. application Ser. No. 16/198,678, filed Nov. 21, 2018, which claims priority to U.S. Provisional Patent Application No. 62/589,982, filed on Nov. 22, 2017, the entire contents of each of which are fully incorporated herein by reference. 
    
    
     BACKGROUND 
     Maintaining hygiene and cleanliness is a high priority for health care providers and procedures. One scenario in which hygiene may be compromised is when materials and instruments (e.g., gel or liquid containers and applicators) are reused on different patients. In addition, reusable medical instruments and materials may require intensive cleaning between uses and can be cumbersome for use by a health care provider. 
     SUMMARY 
     According to various embodiments, a gel application system is configured to be disposable such that it is not or need not be reused between more than one subject. In addition, according to various embodiments, the gel application system is configured for ease of use. As such, hygiene and cleanliness can be increased, while allowing health care providers to more efficiently and easily use the system. 
     According to various embodiments, a gel application system includes a container having an enclosed interior volume for containing a gel. An applicator is coupled to the container, for applying gel to a surface. A seal is provided between the container and the applicator. The seal has a first state in which it is configured to block the gel from exiting the gel application system. The seal has a second state in which it is configured to allow at least a portion of the gel to flow from the enclosed interior volume of the container to the applicator or to an environment exterior to the gel application system. 
     In various embodiments, the seal, when in the first state, provides a physical barrier for preventing the gel from flowing beyond the seal, and when in the second state, provides an opening to allow gel to pass the seal. 
     In various embodiments, the seal is made of a rigid material including one or more of a plastic, aluminum, steel, titanium, magnesium, metal alloy or other metal, composite material, carbon fiber, fiber glass, expanded foam, compression molded foam, stereolithography (SLA) or Fused Deposition Modeling (FDM)-made materials, Reaction Injection Molding (RIM) molding material, acrylonitrile butadiene styrene (ABS), thermoplastic olefin (TPO), nylon, polyvinyl chloride (PVC), or fiber reinforced resin. 
     In various embodiments, the seal is configured to be broken to open a pathway to allow the gel to exit the gel application system, wherein the seal is configured to withstand the flow of the gel when unbroken, yet brittle enough to enable a user to break the seal by applying predefined force to the seal. 
     In various embodiments, the seal may be broken or opened upon or in response to a gel pressure within the interior volume of the container reaching or exceeding a magnitude sufficient to cause the seal to break or open. 
     In various embodiments, the seal is configured to be break or open in response to a user squeezing and compressing the container by an amount that increases the gel pressure within the interior volume of the container sufficient to reach or exceed a threshold magnitude. 
     In various embodiments, the seal is configured to be break or open in response to a user puncturing the seal with an implement. 
     In various embodiments, the container is made from a single or uniform material and has no seams such that the container is airtight. 
     In various embodiments, the container is made from one or more of a polymer, a plastic, or a rubber material. 
     In various embodiments, the container is made of one or more materials connected and sealed at one or more seams to form the enclosed interior volume. 
     In various embodiments, the container is made of a material that is sufficiently flexible to allow a user to squeeze the container with manual force by hand, to compress the enclosed interior volume and apply or increase the pressure of the gel in the interior volume. 
     In various embodiments, the container is made of a material that is sufficiently resilient to allow the container to resume its shape before it is squeezed, once the manual force is withdrawn from the container. 
     In various embodiments, the gel includes ultrasound gel for use with ultrasound emitting devices, including Transcranial Doppler (TCD) devices. 
     In various embodiments, the container includes a section having a channel, the channel having a first end in gel flow communication with the interior volume of the container, the channel having a second end that is open or in gel flow communication with an outlet port through which gel may flow from the channel to the applicator or to discharge at least some of the gel from the gel application system. 
     In various embodiments, the seal is located within the channel. 
     In various embodiments, the applicator includes a hole through the applicator. 
     In various embodiments, the hole in the applicator is aligned with the channel such that at least a portion of the gel can flow from the interior volume of the container, through the channel, and through the applicator, to a free end of the applicator. 
     In various embodiments, the applicator includes a soft, flexible, or resilient material, including at least one of a closed cell foam, open cell foam, self-skinning open or closed cell foam material, or a cast, aerated, or extruded silicone or urethane, or polyurethane material. 
     In various embodiments, the applicator includes a hole through the applicator through which at least a portion of the gel can flow from the interior volume of the container, to a free end of the applicator. 
     In various embodiments, the applicator includes a plurality of bristles in a circular arrangement around the hole through the applicator. 
     In various embodiments, the applicator includes a plurality of bristles. 
     In various embodiments, the plurality of bristles are located in a circular arrangement around the hole defined by the applicator. 
     In various embodiments, the bristles include flexible, hair-like bristles having a diameter in the range of about 0.04 mm. to 3.0 mm. 
     In various embodiments, the system further includes an applicator stick attached to the container. 
     In various embodiments, the applicator stick has a generally elongated, rectangular shape corresponding to an elongated plate or flat stick shape, and has an outward-facing surface defining a platform for receiving at least some of the gel from the container. 
     In various embodiments, the applicator stick is made of a rigid wood, plastic, metal, ceramic, composite material, cardboard, or cardstock material. 
     In various embodiments, the applicator stick is formed as part of the container by molding the applicator stick onto a side of the container. 
     In various embodiments, the applicator stick includes an end portion that extends from the container. 
     Further embodiments relate to a method of making a gel application system including providing a container having an enclosed interior volume for containing a gel. The method further includes coupling an applicator coupled to the container, were the applicator is configured for applying gel to a surface. The method further includes providing a seal between the container and the applicator, were the seal has a first state in which it is configured to block the gel from exiting the gel application system, and where the seal has a second state in which it is configured to allow at least a portion of the gel to flow from the enclosed interior volume of the container to the applicator or to an environment exterior to the gel application system. 
     In various embodiments of the method, the seal, when in the first state, provides a physical barrier for preventing the gel from flowing beyond the seal, and when in the second state, provides an opening to allow gel to pass the seal. 
     In various embodiments of the method, the seal is made of a rigid material including one or more of a plastic, aluminum, steel, titanium, magnesium, metal alloy or other metal, composite material, carbon fiber, fiber glass, expanded foam, compression molded foam, stereolithography (SLA) or Fused Deposition Modeling (FDM)-made materials, Reaction Injection Molding (RIM) molding material, acrylonitrile butadiene styrene (ABS), thermoplastic olefin (TPO), nylon, polyvinyl chloride (PVC), or fiber reinforced resin. 
     In various embodiments of the method, the seal is configured to be broken to open a pathway to allow the gel to exit the gel application system, wherein the seal is configured to withstand the flow of the gel when unbroken, yet brittle enough to enable a user to break the seal by applying predefined force to the seal. 
     In various embodiments of the method, the seal may be broken or opened upon or in response to a gel pressure within the interior volume of the container reaching or exceeding a magnitude sufficient to cause the seal to break or open. 
     In various embodiments of the method, the seal is configured to be break or open in response to a user squeezing and compressing the container by an amount that increases the gel pressure within the interior volume of the container sufficient to reach or exceed a threshold magnitude. 
     In various embodiments of the method, the seal is configured to be break or open in response to a user puncturing the seal with an implement. 
     In various embodiments of the method, the container is made from a single or uniform material and has no seams such that the container is airtight. 
     In various embodiments of the method, the container is made from one or more of a polymer, a plastic, or a rubber material. 
     In various embodiments of the method, providing the container includes connecting and sealing one or more materials at one or more seams to form the enclosed interior volume. 
     In various embodiments of the method, the container is made of a material that is sufficiently flexible to allow a user to squeeze the container with manual force by hand, to compress the enclosed interior volume and apply or increase the pressure of the gel in the interior volume. 
     In various embodiments of the method, the container is made of a material that is sufficiently resilient to allow the container to resume its shape before it is squeezed, once the manual force is withdrawn from the container. 
     In various embodiments of the method, the gel includes ultrasound gel for use with ultrasound emitting devices, including Transcranial Doppler (TCD) devices. 
     In various embodiments of the method, providing the container includes providing a container section having a channel, the channel having a first end in gel flow communication with the interior volume of the container, the channel having a second end that is open or in gel flow communication with an outlet port through which gel may flow from the channel to the applicator or to discharge at least some of the gel from the gel application system. 
     In various embodiments of the method, providing the seal includes locating the seal within the channel. 
     In various embodiments of the method, the applicator includes a hole through the applicator. 
     In various embodiments of the method, the hole in the applicator is aligned with the channel such that at least a portion of the gel can flow from the interior volume of the container, through the channel, and through the applicator, to a free end of the applicator. 
     In various embodiments of the method, the applicator includes a soft, flexible, or resilient material, including at least one of a closed cell foam, open cell foam, self-skinning open or closed cell foam material, or a cast, aerated, or extruded silicone or urethane, or polyurethane material. 
     In various embodiments of the method, the applicator includes a hole through the applicator through which at least a portion of the gel can flow from the interior volume of the container, to a free end of the applicator. 
     In various embodiments of the method, the applicator includes a plurality of bristles in a circular arrangement around the hole through the applicator. 
     In various embodiments of the method, the applicator includes a plurality of bristles. 
     In various embodiments of the method, the plurality of bristles is located in a circular arrangement around the hole defined by the applicator. 
     In various embodiments of the method, the bristles include flexible, hair-like bristles having a diameter in the range of about 0.04 mm. to 3.0 mm. 
     In various embodiments, the method further includes attaching an applicator stick to the container. 
     In various embodiments of the method, the applicator stick has a generally elongated, rectangular shape corresponding to an elongated plate or flat stick shape, and has an outward-facing surface defining a platform for receiving at least some of the gel from the container. 
     In various embodiments of the method, the applicator stick is made of a rigid wood, plastic, metal, ceramic, composite material, cardboard, or cardstock material. 
     In various embodiments of the method, the applicator stick is formed as part of the container by molding the applicator stick onto a side of the container. 
     In various embodiments of the method, the applicator stick includes an end portion that extends from the container. 
     According to various further embodiments, a gel application system includes an applicator body having a first surface, a second surface and at least one opening extending through the applicator body from the first surface to the second surface. At least one gel packet is attached to the first surface of the applicator and defining an interior volume containing gel, the interior volume of the gel packet being in fluid flow communication with the at least one opening. The at least one gel packet is made of a material that has sufficient flexibility to allow a user to squeeze and compress the interior volume and expel gel through the at least one opening, by applying a compression force on the gel packet. 
     In various embodiments, the applicator body includes a generally rigid or partially rigid body having an elongated shape that defines a lengthwise dimension with a first end and a second end, and wherein the at least one opening is located closer to the first end than to the second end. 
     In various embodiments, the at least one opening includes a slot-shaped opening having an elongated shape with a lengthwise dimension extending along the lengthwise dimension of the applicator body. 
     In various embodiments, the gel packet includes a large volume end and a small volume end located opposite to the large volume end, wherein the large volume end of the gel packet is configured to retain a larger volume of gel relative to the small volume end of the gel packet. 
     In various embodiments, the large volume end of the gel packet is located adjacent to the second end of the applicator body, and the small volume end of the gel packet is located adjacent to the first end of the applicator body. 
     In various embodiments, the first surface of the applicator body includes a passage or groove extending along at least a portion of the length dimension of the applicator body, forming a channel for enhancing a flow of the gel from the large volume end of the gel packet to the at least one opening in the applicator body. 
     In various embodiments, the gel packet includes at least one sheet of flexible material sealed around a peripheral edge to the applicator body to form a flexible wall around one or more internal volumes that contain the gel between the sheet of flexible material and the applicator body. 
     In various embodiments, the at least one sheet of flexible material of the gel packet includes plastic, rubber or metal foil. 
     In various embodiments, the one or more internal volumes the gel packet are bordered by the flexible wall of the gel packet and the first surface of the applicator body. 
     In various embodiments, the one or more internal volumes the gel packet include one or more envelopes or enclosed pouches of flexible material adhered to the applicator. 
     In various embodiments, the at least one opening includes a plurality of slot-shaped openings, each having an elongated shape. 
     In various embodiments, the applicator body includes a generally rigid or partially rigid body having an elongated shape that defines a lengthwise dimension with a first end and a second end, and wherein the at least one opening includes a plurality of openings located closer to the first end than to the second end. 
     In various embodiments, a peel-off cover is attached to the applicator body to cover and seal the at least one opening to inhibit expulsion of gel from the at least one opening. 
     In various embodiments, the cover includes an adhesive that is sufficiently strong to hold the cover on the applicator body until a user manually removes the cover, by peeling the cover off of the applicator body to allow gel to be expelled from the at least one opening. 
     In various embodiments, the cover includes a sheet of material that covers at least a portion of the second surface of the applicator body and has a surface facing outward from the applicator body on which printed information is provided. 
     In various embodiments, the applicator body is transparent or partially transparent such that gel may be viewable along at least a portion of the applicator body. 
     In various embodiments, the applicator body has an elongated shape that defines a first end and a second end, wherein one or both of the first end and the second end are rounded or have rounded corners or edges. 
     In various embodiments, the gel application system further including at least one of a gel spreading mechanism on the applicator body for adjusting a placement and thickness of expelled gel, or a gel scraper on the applicator body for scraping expelled gel. 
     In various embodiments, the gel spreading mechanism is located along an outer edge of the applicator body. 
     In various embodiments, the applicator body has an elongated shape that defines a lengthwise dimension with a first end and a second end, wherein the at least one opening is located closer to the first end than to the second end, and wherein the gel spreading mechanism extends along an entire edge curvature of the first end of the applicator body. 
     In various embodiments, the gel spreading mechanism: (a) is affixed to or formed on the first surface of the applicator body, or (b) protrudes outward relative to the first surface of the applicator body. 
     In various embodiments, the gel spreading mechanism: (a) is affixed to or formed on the second surface of the applicator body, or (b) protrudes outward relative to the second surface of the applicator body. 
     In various embodiments, the gel spreading mechanism includes a soft material including at least one of rubber, closed cell foam, open cell foam, self-skinning open or closed cell foams, cast, aerated, or extruded silicone or urethane, or polyurethane. 
     In various embodiments, the gel spreading mechanism or the scraper includes a rigid material including at least one of plastic, rubber, silicon, metal, ceramic, composite material, wood, cardboard, or cardstock. 
     In various embodiments, the scraper protrudes outward relative to the first surface of the applicator body. 
     In various embodiments, the gel spreading mechanism protrudes outward relative to the second surface of the applicator body, and the scraper protrudes outward relative to the first surface of the applicator body. 
     In various embodiments, the gel spreading mechanism includes a soft material including at least one of rubber, closed cell foam, open cell foam, self-skinning open or closed cell foams, cast, aerated, or extruded silicone or urethane, or polyurethane; and the scraper includes a rigid material including at least one of plastic, rubber, silicon, metal, ceramic, composite material, wood, cardboard, or cardstock. 
     Further embodiments relate to a method of making a gel application system including providing an applicator body having a first surface, a second surface and at least one opening extending through the applicator body from the first surface to the second surface. The method further includes attaching at least one gel packet to the first surface of the applicator and defining an interior volume containing gel, the interior volume of the gel packet being in fluid flow communication with the at least one opening, wherein the at least one gel packet is made of a material that has sufficient flexibility to allow a user to squeeze and compress the interior volume and expel gel through the at least one opening, by applying a compression force on the gel packet. 
     In various embodiments of the method, the applicator body includes a generally rigid or partially rigid body having an elongated shape that defines a lengthwise dimension with a first end and a second end, and wherein the at least one opening is located closer to the first end than to the second end. 
     In various embodiments of the method, the gel packet includes a large volume end and a small volume end located opposite to the large volume end, wherein the large volume end of the gel packet is configured to retain a larger volume of gel relative to the small volume end of the gel packet. 
     In various embodiments of the method, the large volume end of the gel packet is located adjacent to the second end of the applicator body, and the small volume end of the gel packet is located adjacent to the first end of the applicator body. 
     Various embodiments of the method further includes providing a passage or groove in the first surface of the applicator body, the passage or groove extending along at least a portion of the length dimension of the applicator body to form a channel for enhancing a flow of the gel from the large volume end of the gel packet to the at least one opening in the applicator body. 
     In various embodiments of the method, the attaching at least one gel packet includes sealing at least one sheet of flexible material to the applicator body to form a flexible wall around one or more internal volumes that contain the gel between the sheet of flexible material and the applicator body. 
     In various embodiments of the method, the one or more internal volumes the gel packet are bordered by the flexible wall of the gel packet and the first surface of the applicator body. 
     In various embodiments of the method, the one or more internal volumes the gel packet include one or more envelopes or enclosed pouches of flexible material adhered to the applicator. 
     Various embodiments of the method further include attaching a peel-off cover to the applicator body to cover and seal the at least one opening to inhibit expulsion of gel from the at least one opening. 
     In various embodiments of the method, the peel-off cover includes a sheet of material that covers substantially the entire second surface of the applicator body. 
     In various embodiments of the method, the peel-off cover includes a sheet of material that covers at least a portion of the second surface of the applicator body and has a surface facing outward from the applicator body on which printed information is provided. 
     In various embodiments of the method, providing an applicator body includes providing an applicator body that is transparent or partially transparent such that the gel may be viewable along at least a portion of the applicator body. 
     Various embodiments of the method further include providing at least one of a gel spreading mechanism on the applicator body for adjusting a placement and thickness of expelled gel, or a gel scraper on the applicator body for scraping expelled gel. 
     In various embodiments of the method, the gel spreading mechanism is located along an outer edge of the applicator body. 
     In various embodiments of the method, the applicator body has an elongated shape that defines a lengthwise dimension with a first end and a second end, wherein the at least one opening is located closer to the first end than to the second end, and wherein the gel spreading mechanism extends along an entire edge curvature of the first end of the applicator body. 
     In various embodiments of the method, the gel spreading mechanism: (a) is affixed to or formed on the first surface of the applicator body, or (b) protrudes outward relative to the first surface of the applicator body. 
     In various embodiments of the method, the gel spreading mechanism: (a) is affixed to or formed on the second surface of the applicator body, or (b) protrudes outward relative to the second surface of the applicator body. 
     In various embodiments of the method, the gel spreading mechanism includes a soft material including at least one of rubber, closed cell foam, open cell foam, self-skinning open or closed cell foams, cast, aerated, or extruded silicone or urethane, or polyurethane. 
     In various embodiments of the method, the gel spreading mechanism or the scraper includes a rigid material including at least one of plastic, rubber, silicon, metal, ceramic, composite material, wood, cardboard, or cardstock. 
     In various embodiments of the method, the scraper protrudes outward relative to the first surface of the applicator body. 
     In various embodiments of the method, the gel spreading mechanism protrudes outward relative to the second surface of the applicator body, and the scraper protrudes outward relative to the first surface of the applicator body. 
     According to various further embodiments, a gel application system includes a barrier including a body having a first side and a second side. The gel applicator system further includes a first cover releasably affixed to the first side of the barrier, and a second cover releasably affixed to the second side of the barrier. The first and second covers are sealed with the barrier and form an interior volume containing a gel. 
     In various embodiments, an adhesive material is provided between each of the first and second covers and the body of the barrier, for releasably adhering the first and second covers to the body of the barrier. 
     In various embodiments, the adhesive material is configured such that at least some adhesive material remains on the first side of the body of the barrier after removal of the first cover, and the first side of the barrier is configured to be adhered to a surface by employing the at least some adhesive material that remains on the first side of the body of the barrier. 
     In various embodiments, at least one of the first and second covers includes a tab for allowing a user to grip the at least one cover, for peeling the at least one cover off of the body of the barrier to expose the gel contained by the barrier. 
     In various embodiments, each of the first and second covers includes a tab for allowing a user to grip the cover, for peeling the cover off of the body of the barrier to expose the gel contained by the barrier. 
     In various embodiments, each of the body of the barrier is made of at least one of a plastic, a rubber, a metal, a ceramic, a wood, a paper, a cardboard, a cardstock, or a composite material. 
     In various embodiments, each of the first and second covers is made of at least one of a plastic, a metal sheet or foil, a paper, or a composite material. 
     In various embodiments, the gel includes ultrasound gel for use with ultrasound emitting devices, including Transcranial Doppler (TCD) devices. 
     Further embodiments relate to a method of making a gel application system including providing a barrier including a body having a first side and a second side. The method further includes releasably affixing a first cover to the first side of the barrier, and releasably affixing a second cover to the second side of the barrier. The first and second covers are sealed with the barrier and form an interior volume containing a gel. 
     Various embodiments of the method further include providing an adhesive material between each of the first and second covers and the body of the barrier, for releasably adhering the first and second covers to the body of the barrier. 
     In various embodiments of the method, the adhesive material is configured such that at least some adhesive material remains on the first side of the body of the barrier after removal of the first cover, and the first side of the barrier is configured to be adhered to a surface by employing the at least some adhesive material that remains on the first side of the body of the barrier. 
     Various embodiments of the method further include providing a tab on at least one of the first and second covers for allowing a user to grip the at least one cover, for peeling the at least one cover off of the body of the barrier to expose the gel contained by the barrier. 
     Various embodiments of the method further comprise providing a tab on each of the first and second covers for allowing a user to grip the cover, for peeling the cover off of the body of the barrier to expose the gel contained by the barrier. 
     In various embodiments of the method, each of the body of the barrier is made of at least one of a plastic, a rubber, a metal, a ceramic, a wood, a paper, a cardboard, a cardstock, or a composite material. 
     In various embodiments of the method, each of the first and second covers is made of at least one of a plastic, a metal sheet or foil, a paper, or a composite material. 
     In various embodiments of the method, the gel comprises ultrasound gel for use with ultrasound emitting devices, including Transcranial Doppler (TCD) devices. 
     According to various further embodiments, a gel application system includes a container having an interior volume for containing gel. The container has a first end provided with a first opening and a second end provided with a second opening. A plunger extends through the first opening of the container. The plunger has a first end located within the interior volume of the container and a second end located outside of the container. The plunger is moveable in a first direction within the container to expel gel from the second opening in the second end of the container. The applicator is affixed to the second end of the container for receiving at least a portion of the gel expelled from the container. 
     In various embodiments, the first direction is a direction toward the second end of the container. 
     In various embodiments, the interior volume of the container is pre-filled with a pre-defined quantity of gel. 
     In various embodiments, the container comprises a generally cylindrical shaped barrel having an opening on a first end through which the plunger extends, and an opening on a second end through which gel from the interior volume of the container may be dispensed. 
     In various embodiments, the container is made of a transparent or partially transparent material that allows a user to view contents within the interior volume of the container, to view the amount of gel contained within the interior volume of the container. 
     In various embodiments, the container includes one or more markings along a length dimension, to define one or more volume levels (or amounts) of gel or other material contained in the interior volume of the container. 
     In various embodiments, the container includes a flange on or adjacent the first end of the container, the flange having a surface against which a user&#39;s fingers my press to provide leverage, while pushing the plunger. 
     In various embodiments, the applicator is made of at least one of a flexible or resilient closed cell foam, open cell foam, self-skinning open or closed cell foams, cast, aerated, or extruded silicone or urethane, or polyurethane material. 
     In various embodiments, the applicator has a wedge shape. 
     In various embodiments, the applicator has a first end and a second end, the second end of the applicator being affixed to the second end of the container, the second end of the applicator is thicker than the first end. 
     In various embodiments, the first end of the applicator defines a free or distal end. 
     In various embodiments, the plunger includes a handle for receiving a pushing force for moving the plunger towards the first end of the container. 
     In various embodiments, the applicator has a hole that is in gel flow communication with the opening in the second end of the container, through which the gel expelled container may flow. 
     In various embodiments, the applicator has a slot-shaped, elongated opening that is in gel flow communication with the opening in the second end of the container, through which the gel expelled container may flow. 
     Further embodiments relate to a method of making a gel application system comprising providing a container having an interior volume for containing gel. The container has a first end provided with a first opening and a second end provided with a second opening. The method includes extending a plunger extending through the first opening of the container. The plunger has a first end located within the interior volume of the container and a second end located outside of the container. The plunger is moveable in a first direction within the container to expel gel from the second opening in the second end of the container. The method further includes affixing an applicator to the second end of the container for receiving at least a portion of the gel expelled from the container. 
     In various embodiments of the method, the first direction is a direction toward the second end of the container. 
     In various embodiments of the method, the interior volume of the container is filled with a pre-defined quantity of gel. 
     In various embodiments of the method, the container comprises a generally cylindrical shaped barrel having an opening on a first end through which the plunger extends, and an opening on a second end through which gel from the interior volume of the container may be dispensed. 
     In various embodiments of the method, the container is made of a transparent or partially transparent material that allows a user to view contents within the interior volume of the container, to view the amount of gel contained within the interior volume of the container. 
     In various embodiments of the method, the container includes one or more markings along a length dimension, to define one or more volume levels (or amounts) of gel or other material contained in the interior volume of the container. 
     In various embodiments of the method, the container includes a flange on or adjacent the first end of the container, the flange having a surface against which a user&#39;s fingers my press to provide leverage, while pushing the plunger. 
     In various embodiments of the method, the applicator is made of at least one of a flexible or resilient closed cell foam, open cell foam, self-skinning open or closed cell foams, cast, aerated, or extruded silicone or urethane, or polyurethane material. 
     In various embodiments of the method, the applicator has a wedge shape. 
     In various embodiments of the method, the applicator has a first end and a second end, the second end of the applicator being affixed to the second end of the container, the second end of the applicator is thicker than the first end. 
     In various embodiments of the method, the first end of the applicator defines a free or distal end. 
     In various embodiments of the method, the plunger includes a handle for receiving a pushing force for moving the plunger towards the first end of the container. 
     In various embodiments of the method, the applicator has a hole that is in gel flow communication with the opening in the second end of the container, through which the gel expelled container may flow. 
     In various embodiments of the method, the applicator has a slot-shaped, elongated opening that is in gel flow communication with the opening in the second end of the container, through which the gel expelled container may flow. 
     According to further embodiments, a gel application system includes a container having an interior volume for containing gel. The container has a first end provided with a first opening and a second end provided with a second opening. A plunger extends through the first opening of the container. The plunger has a first end located within the interior volume of the container and a second end located outside of the container. The plunger is moveable in a first direction within the container to expel gel from the second opening in the second end of the container. An applicator including a generally flat or plate-like body of rigid or partially rigid material has a first end connected to the second end of the container. The applicator has a second end opposite the first end, the second end of the applicator defining a spreading edge or surface. 
     In various embodiments, the first end of the applicator includes a first state for dispensing gel and a second state for stamping or flattening dispensed gel. 
     In various embodiments, the applicator has a valve that has an open state and a closed state wherein, when the valve is in the open state, the valve allows a portion of the volume of the gel within the container to be expelled, and when the valve is in a closed state, the valve provides a pressing surface for manually pressing against a volume portion of gel that has been expelled. 
     In various embodiments, the pressing surface is configured sufficiently flat to provide a gel flattening or spreading operation to flatten or spread the volume portion of gel, when the surface is pressed against the volume portion of gel. 
     In various embodiments, the valve includes an outlet having one or more openings arranged over a defined area, through which a volume portion of the gel may be expelled when the valve is in the open state. 
     In various embodiments, each opening has a shape of one or more of a slot, a logo, a letter, a number or a word. 
     In various embodiments, the one or more openings are arranged or shaped to provide a pattern of openings over a defined area, to expel the volume portion of the gel from the outlet over an area of a surface corresponding to the defined area. 
     In various embodiments, when the valve is in the closed state, the one or more openings of the outlet are covered or closed, to inhibit the passage of gel through the one or more openings. 
     In various embodiments, the valve is operated to transition from the open state to the closed state by rotating a portion of the valve. 
     In various embodiments, the valve includes an outlet plate having one or more openings through the plate, the one or more openings being arranged over a surface area of the outlet plate, through which a volume portion of the gel may be expelled when the valve is in the open state. 
     In various embodiments, when the valve is in the closed state, the one or more openings of the outlet plate are covered or closed, to inhibit the passage of gel through the one or more openings. 
     In various embodiments, the valve includes a second plate arranged against and parallel to the outlet plate, where one or both of the second plate and the outlet plate are rotatable relative to each other between at least a first relative rotary position and a second relative rotary position. 
     In various embodiments, the second plate has an arrangement of openings or other pattern of one or more openings that correspond to or otherwise align with the one or more openings in the outlet plate to allow the passage of gel through the second plate and the outlet plate when the second plate and the outlet plate are in the first rotational position relative to each other, but that are offset from the one or more openings in the outlet plate and inhibit the passage of gel through the second plate and the outlet plate when the second plate and the outlet plate are in the second rotary position relative to each other. 
     In various embodiments, the outlet plate and the second plate may be held within an annular body that is affixed to the second end of the container and that supports one or both of the plates for rotational motion relative to each other. 
     In various embodiments, the interior volume of the container is filled with a pre-defined quantity of gel. 
     In various embodiments, the gel comprises ultrasound gel for use with ultrasound emitting devices, including Transcranial Doppler (TCD) devices. 
     In various embodiments, the container is made of a transparent or partially transparent material that allows a user to view contents within the interior volume of the container, to view the amount of gel contained within the interior volume of the container. 
     In various embodiments, the container includes one or more markings along a length dimension, to define one or more volume levels (or amounts) of gel or other material contained in the interior volume of the container. 
     Various further embodiments relate to a method of making a gel application system, where the method includes providing a container having an interior volume for containing gel, where the container has a first end provided with a first opening and a second end provided with a second opening. The method further includes extending a plunger through the first opening of the container, such that the plunger has a first end located within the interior volume of the container and a second end located outside of the container, where the plunger is moveable in a first direction within the container to expel gel from the second opening in the second end of the container. The method further includes connecting a first end of an applicator to the second end of the container, where the applicator includes a generally flat or plate-like body of rigid or partially rigid material. The method further includes providing a spreading edge or surface on a second end of the applicator, the second end of the applicator being opposite the first end, of the applicator. 
     In various embodiments of the method, the first end of the applicator includes a first state for dispensing gel and a second state for stamping or flattening dispensed gel. 
     In various embodiments of the method, the applicator has a valve that has an open state and a closed state wherein, when the valve is in the open state, the valve allows a portion of the volume of the gel within the container to be expelled, and when the valve is in a closed state, the valve provides a pressing surface for manually pressing against a volume portion of gel that has been expelled. 
     In various embodiments of the method, the pressing surface is configured sufficiently flat to provide a gel flattening or spreading operation to flatten or spread the volume portion of gel, when the surface is pressed against the volume portion of gel. 
     In various embodiments of the method, the valve includes an outlet having one or more openings arranged over a defined area, through which a volume portion of the gel may be expelled when the valve is in the open state. 
     In various embodiments of the method, each opening has a shape of one or more of a slot, a logo, a letter, a number or a word. 
     In various embodiments of the method, the one or more openings are arranged or shaped to provide a pattern of openings over a defined area, to expel the volume portion of the gel from the outlet over an area of a surface corresponding to the defined area. 
     In various embodiments of the method, when the valve is in the closed state, the one or more openings of the outlet are covered or closed, to inhibit the passage of gel through the one or more openings. 
     In various embodiments of the method, the valve is operated to transition from the open state to the closed state by rotating a portion of the valve. 
     In various embodiments of the method, the valve includes an outlet plate having one or more openings through the plate, the one or more openings being arranged over a surface area of the outlet plate, through which a volume portion of the gel may be expelled when the valve is in the open state. 
     In various embodiments of the method, when the valve is in the closed state, the one or more openings of the outlet plate are covered or closed, to inhibit the passage of gel through the one or more openings. 
     In various embodiments of the method, the valve includes a second plate arranged against and parallel to the outlet plate, where one or both of the second plate and the outlet plate are rotatable relative to each other between at least a first relative rotary position and a second relative rotary position. 
     In various embodiments of the method, the second plate has an arrangement of openings or other pattern of one or more openings that correspond to or otherwise align with the one or more openings in the outlet plate to allow the passage of gel through the second plate and the outlet plate when the second plate and the outlet plate are in the first rotational position relative to each other, but that are offset from the one or more openings in the outlet plate and inhibit the passage of gel through the second plate and the outlet plate when the second plate and the outlet plate are in the second rotary position relative to each other. 
     In various embodiments of the method, the outlet plate and the second plate may be held within an annular body that is affixed to the second end of the container and that supports one or both of the plates for rotational motion relative to each other. 
     Various embodiments of the method further comprise filling the interior volume of the container with a pre-defined quantity of gel. 
     In various embodiments of the method, the gel comprises ultrasound gel for use with ultrasound emitting devices, including Transcranial Doppler (TCD) devices. 
     According to further embodiments, a gel application system includes a container having an interior volume for containing gel. The container having a first end provided with a first opening and a second end provided with a second opening. A plunger extends through the first opening of the container. The plunger has a first end located within the interior volume of the container and a second end located outside of the container. The plunger is moveable in a first direction within the container to expel gel from the second opening in the second end of the container. An applicator includes a generally flat or plate-like body of rigid or partially rigid material that has a first end connected to the second end of the container. The applicator has a second end opposite the first end, the second end of the applicator defining a spreading edge or surface. 
     In various embodiments, the first end of the applicator is thinner in a width dimension than the second end of the applicator. 
     In various embodiments, the applicator body has a tapered shape that tapers from the thinner first end, toward the second end. 
     In various embodiments, the second end of the applicator has an edge feature on the spreading edge or surface, the edge feature configured to enhance the ability to spread gel. 
     In various embodiments, the edge feature is formed on and is unitary with the applicator, at the second end of the applicator. 
     In various embodiments, the edge feature is a separate element that is attached to the second end of the applicator by at least one of an adhesive, welding, thermal bonding, snap fitting, or friction or press fitting. 
     In various embodiments, the edge feature is a separate element that is molded or co-molded onto the body of the applicator. 
     In various embodiments, the edge feature includes one or more of an angled or a beveled edge, a stepped or a reduced width edge, or a blade or an edging strip made of silicon, plastic, rubber, metal, or ceramic. 
     In various embodiments, the edge feature includes a blade or an edging strip that is made of a material that is more flexible than the material of the rest of the applicator. 
     In various embodiments, the applicator has one or more interior channels having a first end in gel flow communication with the opening in the second end of the container, the one or more interior channels of the applicator extend along at least a portion of a length dimension of the applicator, from the first end of the applicator, to one or more outlet openings in the applicator. 
     In various embodiments, the one or more outlet openings are located on a first surface of the generally flat or plate-like body of the applicator. 
     In various embodiments, the applicator has a second surface facing opposite to the first surface, the second surface of the applicator being generally flat and devoid of outlet openings, for contacting and spreading gel. 
     In various embodiments, the one or more outlet openings includes a plurality of outlet openings of different sizes or shapes. 
     In various embodiments, the one or more outlet openings includes one or more slot shaped openings. 
     In various embodiments, the one or more outlet openings include a combination of one or more slot-shaped openings and one or more round openings. 
     In various embodiments, the one or more outlet openings includes a plurality of outlet openings arranged along a width dimension of the body of the applicator, so as to dispense gel over a band or area having a width dimension. 
     In various embodiments, the one or more outlet openings are arranged adjacent to and along the second end of the body of the applicator. 
     In various embodiments, the container includes a flange on or adjacent the first end of the container, the flange having a surface against which a user&#39;s fingers my press to provide leverage, while pushing the plunger. 
     In various embodiments, the container includes a second flange at or near the second end of the container, the second flange having a surface against which a user may engage one or more fingers of one hand, while engaging the plunger, to move the second end of the container toward the plunger. 
     In various embodiments, the interior volume of the container is pre-filled with a pre-defined quantity of gel. 
     In various embodiments, the gel comprises ultrasound gel for use with ultrasound emitting devices, including Transcranial Doppler (TCD) devices. 
     In various embodiments, the container is made of a transparent or partially transparent material that allows a user to view contents within the interior volume of the container, to view the amount of gel contained within the interior volume of the container. 
     In various embodiments, the container includes one or more markings along a length dimension, to define one or more volume levels (or amounts) of gel or other material contained in the interior volume of the container. 
     Various further embodiments relate to a method of making a gel application system, where the method includes providing a container having an interior volume for containing gel, the container having a first end provided with a first opening and a second end provided with a second opening; extending a plunger through the first opening of the container, such that the plunger has a first end located within the interior volume of the container and a second end located outside of the container, where the plunger is moveable in a first direction within the container to expel gel from the second opening in the second end of the container; connecting a first end of an applicator to the second end of the container, the applicator including a generally flat or plate-like body of rigid or partially rigid material; and providing a spreading edge or surface on a second end of the applicator, the second end of the applicator being opposite the first end of the applicator. 
     In various embodiments of the method, the first end of the applicator is thinner in a width dimension than the second end of the applicator. 
     In various embodiments of the method, the applicator body has a tapered shape that tapers from the thinner first end, toward the second end. 
     In various embodiments of the method, providing a spreading edge or surface comprises providing the second end of the applicator with an edge feature configured to enhance the ability to spread gel. 
     In various embodiments of the method, providing the second end of the applicator with an edge feature comprises forming the edge feature on and unitary with the applicator, at the second end of the applicator. 
     In various embodiments of the method, providing the second end of the applicator with an edge feature comprises providing the edge feature as a separate element and attaching the edge feature to the second end of the applicator by at least one of an adhesive, welding, thermal bonding, snap fitting, or friction or press fitting. 
     In various embodiments of the method, providing the second end of the applicator with an edge feature comprises providing the edge feature as a separate element and molding or co-molding the edge feature onto the body of the applicator. 
     In various embodiments of the method, the edge feature includes one or more of an angled or a beveled edge, a stepped or a reduced width edge, or a blade or an edging strip made of silicon, plastic, rubber, metal, or ceramic. 
     In various embodiments of the method, the edge feature includes a blade or an edging strip that is made of a material that is more flexible than the material of the rest of the applicator. 
     Various embodiments of the method further comprise providing the applicator with one or more interior channels having a first end in gel flow communication with the opening in the second end of the container, the one or more interior channels of the applicator extend along at least a portion of a length dimension of the applicator, from the first end of the applicator, to one or more outlet openings in the applicator. 
     In various embodiments of the method, the one or more outlet openings are located on a first surface of the generally flat or plate-like body of the applicator. 
     In various embodiments of the method, the applicator having a second surface facing opposite to the first surface, the second surface of the applicator being generally flat and devoid of outlet openings, for contacting and spreading gel. 
     In various embodiments of the method, the one or more outlet openings includes a plurality of outlet openings of different sizes or shapes. 
     In various embodiments of the method, the one or more outlet openings includes one or more slot shaped openings. 
     In various embodiments of the method, the one or more outlet openings include a combination of one or more slot-shaped openings and one or more round openings. 
     In various embodiments of the method, the one or more outlet openings includes a plurality of outlet openings arranged along a width dimension of the body of the applicator, so as to dispense gel over a band or area having a width dimension. 
     In various embodiments of the method, the one or more outlet openings are arranged adjacent to and along the second end of the body of the applicator. 
     Various embodiments of the method further comprise providing the container with a flange on or adjacent the first end of the container, the flange having a surface against which a user&#39;s fingers my press to provide leverage, while pushing the plunger. 
     Various embodiments of the method further comprise providing the container with a second flange at or near the second end of the container, the second flange having a surface against which a user may engage one or more fingers of one hand, while engaging the plunger, to move the second end of the container toward the plunger. 
     Various embodiments of the method further comprising filling the interior volume of the container with a pre-defined quantity of gel. 
     In various embodiments of the method, the gel comprises ultrasound gel for use with ultrasound emitting devices, including Transcranial Doppler (TCD) devices. 
     According to various further embodiments, a gel application system includes a bag made of flexible material. The bag has an enclosed interior volume containing a gel, and is flexible and configured to receive a squeezing force to compress the interior volume. The system further includes a spreader or scraper, wherein the spreader or scraper is attached to the bag, or wherein the gel application system further includes a head portion to which an end of the bag is adhered and to which the spreader or scraper is secured, the head portion having a gel slot in gel flow communication with the interior volume of the bag. 
     In various embodiments, the spreader or scraper is secured to an end of the head portion opposite to an end of the head portion that is adhered to the end of the bag. 
     In various embodiments, the head portion is made of at least one of a plastic, a rubber, a metal, a ceramic, or a composite material. 
     In various embodiments, the bag is made of at least one of a pliable plastic, a rubber, or a metal foil material. 
     In various embodiments, the spreader or scraper is made of at least one of a rubber, closed cell foam, open cell foam, self-skinning open or closed cell foams, cast, aerated, or extruded silicone or urethane, or polyurethane material. 
     In various embodiments, the spreader or scraper is made of at least one of a rigid plastic, silicon, rubber, metal, ceramic, composite material, wood, cardboard, or cardstock material. 
     In various embodiments, the gel in the bag comprises ultrasound gel for use with ultrasound emitting devices, including Transcranial Doppler (TCD) devices. 
     Further embodiments relate to a method of making a gel application system comprising providing a bag made of flexible material, where the bag has an enclosed interior volume containing a gel, and where the bag is flexible and configured to receive a squeezing force to compress the interior volume. The method further comprises attaching a spreader or scraper to the bag, or attaching the spreader or scraper to a head portion and attaching the head portion to the bag, the head portion or the bag having a gel slot in gel flow communication with the interior volume of the bag. 
     In various embodiments of the method, the spreader or scraper is secured to an end of the head portion opposite to an end of the head portion that is adhered to the end of the bag. 
     In various embodiments of the method, the head portion is made of at least one of a plastic, a rubber, a metal, a ceramic, or a composite material. 
     In various embodiments of the method, the bag is made of at least one of a pliable plastic, a rubber, or a metal foil material. 
     In various embodiments of the method, the spreader or scraper is made of at least one of a rubber, closed cell foam, open cell foam, self-skinning open or closed cell foams, cast, aerated, or extruded silicone or urethane, or polyurethane material. 
     In various embodiments of the method, the spreader or scraper is made of at least one of a rigid plastic, silicon, rubber, metal, ceramic, composite material, wood, cardboard, or cardstock material. 
     In various embodiments of the method, the gel in the bag comprises ultrasound gel for use with ultrasound emitting devices, including Transcranial Doppler (TCD) devices. 
     According to various embodiments, a further gel application system comprises a base providing a support structure having a first surface. The base has a central portion separating two side portions and is configured to fold across the central portion. One or more containers is supported by the first surface of the base, on one or both of the side portions of the base. Each container encloses a volume of gel. An applicator is supported at the central portion of the base. 
     In various embodiments, the base comprises a generally flat, plate-like or sheet-like structure. 
     In various embodiments, the one or more containers defines at least one first packet on one of the two side portions of the base, and at least one second packet on the other of the two side portions of the base. 
     In various embodiments, the applicator is located between the at least one first packet and the at least one second packet. 
     In various embodiments, the one or more containers comprises one or more sheets of flexible material that is sealed to the base to form a flexible wall around one or more internal volumes for containing gel between the sheet of flexible material and the base. 
     In various embodiments, the one or more sheets of flexible material comprises plastic, rubber or metal foil. 
     In various embodiments, the base is more rigid than the one or more sheets of flexible material. 
     In various embodiments, the one or more containers comprises one or more envelopes or enclosed pouches made of flexible material adhered to the base. 
     In various embodiments, each of the one or more containers is affixed to the base by adhesives, welding, bonding, one or more hooks and latches, or press fittings. 
     In various embodiments, the one or more containers is molded or co-molded with or on the base. 
     In various embodiments, the applicator is secured to the first surface of the base and is covered by at least one wall of the one or more containers when the gel application system is in an inactivated state, and the at least one wall of the one or more containers is configured to open and expose the applicator upon the base being folded across the central portion to place the gel application system in an activated state. 
     In various embodiments, the at least one wall of the one or more containers is configured to rupture or tear automatically upon the base being folded across the central portion to place the gel application system in the activated state. 
     In various embodiments, the applicator is secured to the second surface of the base and the base includes one or more openings or passages that allow gel to flow through the base to the applicator. 
     In various embodiments, the base has a second surface facing opposite the first surface, and is configured to fold across the central portion to a pivoted state in which the second surface of the two side portions of the base are pivoted toward each other, such that the one or more containers on the first surface of the base are pivoted to face outward from two sides of the folded base. 
     In various embodiments, in the pivoted state of the base, a user may apply a force to the one or more containers by squeezing the one or more containers to expel at least some of the gel onto the applicator. 
     In various embodiments, the base is formed as a single, continuous, uniform sheet or plate of material that is foldable at the center portion. 
     In various embodiments, the single sheet or plate of material includes a fold line across the center portion, the fold line including one or more of a marking, groove, indentation, or series of perforations, to identify a folding orientation or to increase the flexibility of the center portion. 
     In various embodiments, the base side portions are separate members that are connected together at the center portion by a hinge, seam or other connection structure that allows the base side portions to be pivoted relative to each other. 
     In various embodiments, each of the base side portions is wider than the central portion. 
     In various embodiments, the applicator includes a triangular or wedge-shaped body of foam material. 
     Further embodiments relate to a method of making a gel application system comprising providing a base as a support structure having a first surface. The base has a central portion separating two side portions. The base configured to fold across the central portion. The method further comprises supporting one or more containers by the first surface of the base, on one or both of the side portions of the base. The method further comprises enclosing a volume of gel in each container, and supporting an applicator at the central portion of the base. 
     In various embodiments of the method, the base comprises a generally flat, plate-like or sheet-like structure. 
     In various embodiments of the method, supporting the one or more containers comprises supporting at least one first packet on one of the two side portions of the base, and at least one second packet on the other of the two side portions of the base. 
     In various embodiments of the method, supporting the applicator comprises locating the applicator between the at least one first packet and the at least one second packet. 
     In various embodiments of the method, supporting the one or more containers comprises sealing one or more sheets of flexible material to the base to form a flexible wall around one or more internal volumes for containing gel between the sheet of flexible material and the base. 
     In various embodiments of the method, the one or more sheets of flexible material comprises plastic, rubber or metal foil. 
     In various embodiments of the method, the base is more rigid than the one or more sheets of flexible material. 
     In various embodiments of the method, supporting the one or more containers comprises adhering one or more envelopes or enclosed pouches made of flexible material to the base. 
     In various embodiments of the method, supporting the one or more containers comprises affixing each of the one or more containers to the base by adhesives, welding, bonding, one or more hooks and latches, or press fittings. 
     In various embodiments of the method, the supporting the one or more containers comprises molding or co-molding the one or more containers with or on the base. 
     In various embodiments of the method, the supporting the applicator comprises securing the applicator to the first surface of the base. In such embodiments, the method further comprises covering the applicator by at least one wall of the one or more containers when the gel application system is in an inactivated state, and configuring the at least one wall of the one or more containers to open and expose the applicator upon the base being folded across the central portion to place the gel application system in an activated state. 
     In various embodiments of the method, configuring the at least one wall of the one or more containers to open comprises configuring the at least one wall to rupture or tear automatically upon the base being folded across the central portion to place the gel application system in the activated state. 
     In various embodiments of the method, supporting the applicator comprises securing the applicator to the second surface of the base and the base includes one or more openings or passages that allow gel to flow through the base to the applicator. 
     In various embodiments of the method, the base has a second surface facing opposite the first surface, and is configured to fold across the central portion to a pivoted state in which the second surface of the two side portions of the base are pivoted toward each other, such that the one or more containers on the first surface of the base are pivoted to face outward from two sides of the folded base. 
     In various embodiments of the method, in the pivoted state of the base, a user may apply a force to the one or more containers by squeezing the one or more containers to expel at least some of the gel onto the applicator. 
     In various embodiments of the method, supporting the applicator comprises securing the applicator to the first surface of the base, and wherein the method further comprises covering the applicator by at least one wall of the one or more containers when the gel application system is in an inactivated state, and configuring the at least one wall of the one or more containers to open and expose the applicator upon the base being folded across the central portion to place the gel application system in an activated state. 
     In various embodiments of the method, configuring the at least one wall of the one or more containers to open comprises configuring the at least one wall to rupture or tear automatically upon the base being folded across the central portion to place the gel application system in the activated state. 
     In various embodiments of the method, providing the base comprises forming the base as a single, continuous, uniform sheet or plate of material that is foldable at the center portion. 
     In various embodiments of the method, providing the base further comprises providing the single sheet or plate of material with a fold line across the center portion, the fold line including one or more of a marking, groove, indentation, or series of perforations, to identify a folding orientation or to increase the flexibility of the center portion. 
     In various embodiments of the method, the base side portions are separate members that are connected together at the center portion by a hinge, seam or other connection structure that allows the base side portions to be pivoted relative to each other. 
     In various embodiments of the method, each of the base side portions is wider than the central portion. 
     In various embodiments of the method, the applicator includes a triangular or wedge-shaped body of foam material. 
     According to various further embodiments, a gel application system includes a gel packet made of a flexible material that forms an enclosed interior volume containing a gel. The gel packet has one or more tear sections, each tear section being configured to be at least partially torn away from the rest of the gel packet to form an opening into the interior volume of the gel packet through which gel may be expelled from the gel packet. In addition, either (a) the one or more tear sections includes a first tear section along an entire width dimension of the gel packet, and a second tear section across a corner of the gel packet, or (b) the gel packet can have a handle shape, or a shape that has a wider end portion for gripping and squeezing in a user&#39;s hand and a narrower end portion for extending out from the user&#39;s hand in a controllable direction, and wherein the one or more tear sections includes a tear section across the narrower end of the gel packet. 
     In various embodiments, the one or more tear sections includes the first tear section along the entire width dimension of the gel packet, and the second tear section across the corner of the gel packet, the gel packet has a generally rectangular shape, and the first tear section extends from one lengthwise edge to an opposite lengthwise edge of the generally rectangular shape, adjacent and along a widthwise edge of the generally rectangular shape. 
     In various embodiments, upon tearing away the first tear section, the interior volume of the gel packet is opened along the entire width dimension of the gel packet to allow a relatively high rate of gel flow from the gel packet. 
     In various embodiments, upon tearing away the second tear section, the interior volume of the gel packet is opened along the corner of the gel packet to allow a relatively low rate of gel flow from the gel packet. 
     In various embodiments, each of the first tear section and the second tear section includes one or more lines of perforations, indentations, thin regions or weaker regions on or in the flexible material of the gel packet, to enhance the ability of the gel packet to tear along the tear section. 
     In various embodiments, upon tearing away the second tear section, the interior volume of the gel packet is opened along the corner of the gel packet to allow a relatively low rate of gel flow from the gel packet. 
     In various embodiments, the gel packet has the handle shape, or the shape that has the wider end portion for gripping and squeezing in the user&#39;s hand and the narrower end portion for extending out from the user&#39;s hand in a controllable direction, wherein the one or more tear sections includes the tear section across the narrower end of the gel packet; and wherein the tear section across the narrower end of the gel packet includes one or more lines of perforations, indentations, thin regions or weaker regions on or in the flexible material of the gel packet, to enhance the ability of the gel packet to tear along the tear section. 
     In various embodiments, each tear section includes one or more lines of perforations, indentations, thin regions or weaker regions on or in the flexible material of the gel packet, to enhance the ability of the gel packet to tear along the tear section. 
     In various embodiments, the gel packet is made of one or more sheets of flexible material that is folded or sealed at peripheral edges to form the enclosed interior volume. 
     In various embodiments, the gel packet is made of one or more of a flexible plastic, rubber, or metal foil material. 
     In various embodiments, the gel packet is transparent or partially transparent to allow a user to view the gel inside of the gel packet from outside of the gel packet. 
     In various embodiments, the gel in the gel packet comprises ultrasound gel for use with ultrasound emitting devices, including Transcranial Doppler (TCD) devices. 
     Further embodiments relate to a method of making a gel application system comprising providing a gel packet made of a flexible material that forms an enclosed interior volume containing a gel. The method further comprises providing the gel packet with one or more tear sections, each tear section being configured to be at least partially torn away from the rest of the gel packet to form an opening into the interior volume of the gel packet through which gel may be expelled from the gel packet. In addition, either (a) the one or more tear sections includes a first tear section along an entire width dimension of the gel packet, and a second tear section across a corner of the gel packet, or (b) the gel packet can have a handle shape, or a shape that has a wider end portion for gripping and squeezing in a user&#39;s hand and a narrower end portion for extending out from the user&#39;s hand in a controllable direction, and wherein the one or more tear sections includes a tear section across the narrower end of the gel packet. 
     In various embodiments of the method, the one or more tear sections includes the first tear section along the entire width dimension of the gel packet, and the second tear section across the corner of the gel packet, the gel packet has a generally rectangular shape, and the first tear section extends from one lengthwise edge to an opposite lengthwise edge of the generally rectangular shape, adjacent and along a widthwise edge of the generally rectangular shape. 
     In various embodiments of the method, upon tearing away the first tear section, the interior volume of the gel packet is opened along the entire width dimension of the gel packet to allow a relatively high rate of gel flow from the gel packet. 
     In various embodiments of the method, upon tearing away the second tear section, the interior volume of the gel packet is opened along the corner of the gel packet to allow a relatively low rate of gel flow from the gel packet. 
     In various embodiments of the method, each of the first tear section and the second tear section includes one or more lines of perforations, indentations, thin regions or weaker regions on or in the flexible material of the gel packet, to enhance the ability of the gel packet to tear along the tear section. 
     In various embodiments of the method, upon tearing away the second tear section, the interior volume of the gel packet is opened along the corner of the gel packet to allow a relatively low rate of gel flow from the gel packet. 
     In various embodiments of the method, the gel packet has the handle shape, or the shape that has the wider end portion for gripping and squeezing in the user&#39;s hand and the narrower end portion for extending out from the user&#39;s hand in a controllable direction, and wherein the one or more tear sections includes the tear section across the narrower end of the gel packet; and wherein the tear section across the narrower end of the gel packet includes one or more lines of perforations, indentations, thin regions or weaker regions on or in the flexible material of the gel packet, to enhance the ability of the gel packet to tear along the tear section. 
     In various embodiments of the method, each tear section includes one or more lines of perforations, indentations, thin regions or weaker regions on or in the flexible material of the gel packet, to enhance the ability of the gel packet to tear along the tear section. 
     In various embodiments of the method, the gel packet is made of one or more sheets of flexible material that is folded or sealed at peripheral edges to form the enclosed interior volume. 
     In various embodiments of the method, the gel packet is made of one or more of a flexible plastic, rubber, or metal foil material. 
     In various embodiments of the method, the gel packet is transparent or partially transparent to allow a user to view the gel inside of the gel packet from outside of the gel packet. 
     In various embodiments of the method, the gel in the gel packet comprises ultrasound gel for use with ultrasound emitting devices, including Transcranial Doppler (TCD) devices. 
     According to further embodiments, a gel application system includes one or more gel packets, where each gel packet has an interior volume containing a gel. The gel application system further includes a gel packet container for receiving one of the one or more gel packets. The gel packet container has a force applicator to apply a compression force on the gel packet, when the gel packet is received by the gel packet container. 
     In various embodiments, the gel packet container has a base portion and a lid portion, the base portion having a receptacle for receiving the gel packet, the lid portion being configured to close over the base portion when the gel packet is received in the receptacle of the base portion. 
     In various embodiments, the force applicator is supported on the lid portion and is arranged to apply the compression force on the gel packet, when the gel packet is located within the gel packet container and the lid portion is closed over the base portion. 
     In various embodiments, the force applicator includes a squeezing member located on the interior-facing side of the lid portion, a trigger or handle located on the exterior-facing side of the lid portion, and a central section connecting the squeezing member and the trigger or handle together, wherein the central section of the force applicator extends through a slot-shaped opening in the lid portion and allows the force applicator to move along the length of the slot-shaped opening relative to the lid portion. 
     In various embodiments, the squeezing member is arranged to impart a compression force onto the gel packet, as the force applicator is moved along a direction of the slot-shaped opening in the lid portion, to cause at least some of the gel to be expelled through an outlet portion of the gel packet, when the outlet portion is open. 
     In various embodiments, the base portion and the lid portion are each made from one or more generally rigid plastic, metal, wood, cardboard, ceramic, or composite material. 
     In various embodiments, the lid portion is coupled to the base portion through a hinge portion. 
     In various embodiments, the hinge portion is a living hinge that is unitary with the base portion and the lid portion. 
     In various embodiments, the hinge portion includes a hinge structure that connects the lid portion with the base portion and allows the lid portion to pivot between an open and a closed position relative to the base portion. 
     In various embodiments, the base portion includes one or more registration features for alignment of the gel packet within the receptacle region. 
     In various embodiments, each gel packet includes one or more registration features for alignment of the gel packet within the receptacle region of the base portion. 
     In various embodiments, the base portion includes one or more first registration features, and each gel packet includes one or more second registration features for alignment of the gel packet within the receptacle region of the base portion. 
     In various embodiments, the one or more first registration features are configured to engage the one or more second registration features when the gel packet with the first registration features is properly aligned within a receptacle region of the base portion. 
     In various embodiments, the lid portion of the container is configured to be closed shut over the base portion to at least partially enclose the gel packet within the gel packet container, once the gel packet is properly aligned within the gel packet container. 
     In various embodiments, the second registration features include a pair of slot-shaped openings, and the first registration features include a pair of elongated protrusions configured to fit within the slot-shaped openings. 
     In various embodiments, the first and second registration features include one or more holes, openings, indentations or other mating shapes. 
     In various embodiments, the gel packet includes an outlet portion and a tear section that seals the outlet portion and inhibits gel from flowing from the interior volume of the gel packet, but that is removable by tearing to open the outlet portion and allow gel to be expelled from the interior volume of the gel packet. 
     In various embodiments, the gel packet includes a narrowed neck portion coupling the interior volume with the outlet portion, wherein the tear section is located across the neck portion. 
     In various embodiments, the one or more second registration features comprise at least one registration feature arranged adjacent each respective side of the narrowed or neck portion of the gel packet. 
     In various embodiments, the tear section includes one or more lines of perforations, indentations, thin regions or weaker regions on or in the gel packet, to enhance the user&#39;s ability to tear the tear section. 
     In various embodiments, the gel packet container includes an outlet opening through which gel expelled from the gel packet is expelled from the gel packet container, wherein the outlet opening of the gel packet container is formed as a gap or open space between the base portion and the lid portion, when the lid portion is closed over the base portion. 
     In various embodiments, the outlet opening of the container receives a portion of an outlet opening end of the gel packet, when the gel packet is properly received and registered within the container. 
     Various further embodiments relate to a method of making a gel application system, where the method comprises providing one or more gel packets, each gel packet having an interior volume containing a gel, providing a gel packet container for receiving one of the one or more gel packets, and coupling a force applicator to the gel packet container, to apply a compression force on the gel packet, when the gel packet is received by the gel packet container. 
     In various embodiments of the method, the gel packet container has a base portion and a lid portion, the base portion having a receptacle for receiving the gel packet, the lid portion being configured to close over the base portion when the gel packet is received in the receptacle of the base portion. 
     In various embodiments of the method, coupling the force applicator comprises supporting the force applicator on the lid portion and arranging the force applicator to apply the compression force on the gel packet, when the gel packet is located within the gel packet container and the lid portion is closed over the base portion. 
     In various embodiments of the method, the force applicator includes a squeezing member located on the interior-facing side of the lid portion, a trigger or handle located on the exterior-facing side of the lid portion, and a central section connecting the squeezing member and the trigger or handle together, wherein the central section of the force applicator extends through a slot-shaped opening in the lid portion and allows the force applicator to move along the length of the slot-shaped opening relative to the lid portion. 
     In various embodiments of the method, the squeezing member is arranged to impart a compression force onto the gel packet, as the force applicator is moved along a direction of the slot-shaped opening in the lid portion, to cause at least some of the gel to be expelled through an outlet portion of the gel packet, when the outlet portion is open. 
     A gel application system according to various further embodiments includes a flexible tip member having a first end, a second end and a gel flow channel connecting the first end and the second end, the second end of the flexible tip member having a self-closing outlet tip. The gel application system also includes a container defining an interior volume containing gel and having one end coupled in gel flow communication with the gel flow channel of the flexible tip member. The self-closing outlet tip is configured to remain in a closed (or sealed) state with sufficient force that gel is not able to pass through the outlet tip, unless an external force above a threshold is applied to the gel in the gel container. 
     In various embodiments, the container is made of a material that has sufficient flexibility to allow a user to squeeze and compress the interior volume and expel gel through the one end, into the gel flow channel of the flexible tip member, by applying a compression force on the container. 
     In various embodiments, the outlet tip is configured to open from its closed state to open to expel at least some of the gel upon the application of an external force above a threshold to the gel in the gel container. 
     In various embodiments, the outlet tip of the flexible tip member is made of a flexible silicone material. 
     In various embodiments, the outlet tip of the flexible tip member has a slot-shaped opening through which gel may be expelled. 
     In various embodiments, the flexible tip member is attached to the container by at least one of an adhesive, welding, thermal bonding, a threaded connector, a snap connector, or a friction or press fit connection. 
     In various embodiments, the container is made of one or more materials connected and sealed at one or more seams by one or more of vacuum sealing, heat sealing, or adhesive, to form an enclosed, hollow interior volume. 
     In various embodiments, the container is made of a single sheet of flexible material that is folded and sealed at its peripheral edge to form an enclosed interior volume for containing the gel. 
     In various embodiments, the container is made of two sheets of flexible material that are sealed together at their peripheral edges to form an enclosed interior volume for containing the gel. 
     In various embodiments, the gel comprises an ultrasound gel for use in connection with an ultrasound emitting device. 
     Various further embodiments relate to a method of making a gel application system, where the method comprises providing a flexible tip member having a first end, a second end and a gel flow channel connecting the first end and the second end, the second end of the flexible tip member having a self-closing outlet tip. The method further includes coupling one end of a container in gel flow communication with the gel flow channel of the flexible tip member, the container defining an interior volume containing gel, where the self-closing outlet tip is configured to remain in a closed (or sealed) state with sufficient force that gel is not able to pass through the outlet tip, unless an external force above a threshold is applied to the gel in the gel container. 
     In various embodiments of the method, the container is made of a material that has sufficient flexibility to allow a user to squeeze and compress the interior volume and expel gel through the one end, into the gel flow channel of the flexible tip member, by applying a compression force on the container. 
     In various embodiments of the method, the outlet tip is configured to open from its closed state to open to expel at least some of the gel upon the application of an external force above a threshold to the gel in the gel container. 
     In various embodiments of the method, the outlet tip of the flexible tip member is made of a flexible silicone material. 
     In various embodiments of the method, the outlet tip of the flexible tip member has a slot-shaped opening through which gel may be expelled. 
     In various embodiments of the method, coupling one end of the container with the flexible tip member comprises attaching the flexible tip member to the container by at least one of an adhesive, welding, thermal bonding, a threaded connector, a snap connector, or a friction or press fit connection. 
     In various embodiments of the method, the container is made of one or more materials connected and sealed at one or more seams by one or more of vacuum sealing, heat sealing, or adhesive, to form an enclosed, hollow interior volume. 
     In various embodiments of the method, the container is made of a single sheet of flexible material that is folded and sealed at its peripheral edge to form an enclosed interior volume for containing the gel. 
     In various embodiments of the method, the container is made of two sheets of flexible material that are sealed together at their peripheral edges to form an enclosed interior volume for containing the gel. 
     In various embodiments of the method, the gel comprises an ultrasound gel for use in connection with an ultrasound emitting device. 
     According to various further embodiments, a gel applicator comprises an applicator body including a generally rigid or partially rigid body having an elongated shape that defines a length dimension with a first end and a second end, a first surface and a second surface facing opposite the first surface. A gel controlling mechanism is secured or formed on or near the first end of the length dimension of the applicator body. The applicator body includes a handle at or near a second end of its length dimension. The handle is configured for a user to grip and hold the applicator body. The gel controlling mechanism includes one or more of: (a) a raised lip extending along an edge of the first end of the applicator body and along a portion of at least one side edge of the applicator body; (b) a side edge and an end edge that are extend along the first surface of the applicator body and form a generally flat, spatula-shaped end portion; or (c) a set of bristles. 
     In various embodiments, the first end of the applicator body is rounded such that the raised lip shape is rounded around the edge of the first end of the applicator body. 
     In various embodiments, the raised lip of the gel controlling mechanism includes a first length portion that extends along a first length of one side edge of the applicator body and a second length portion that extends along a second length of a second side edge of the applicator body. The second side edge of the applicator body is opposite to the first side of the applicator body. 
     In various embodiments, the second length is shorter than the first length. 
     In various embodiments, the second length equal to the first length. 
     In various embodiments, the first end and the second end of the applicator body have a rounded corner or edge. 
     In various embodiments, the applicator body has a recessed or indented surface having a shape for receiving a user&#39;s thumb at or near the second end of the applicator body. 
     In various embodiments, the applicator body includes one or more textured features within the recessed or indented surface for enhancing the user&#39;s grip. 
     In various embodiments, the applicator body includes a raised peripheral lip round its outer edge, or one or more protrusions or raised elements forming a textured surface adjacent the second end of the applicator body. 
     In various embodiments, the gel controlling mechanism: (a) is affixed to or formed on the first surface of the applicator body, or (b) protrudes outward relative to the first surface of the applicator body. 
     In various embodiments, the gel controlling mechanism comprises a soft material including at least one of rubber, closed cell foam, open cell foam, silicone, urethane, or polyurethane. 
     In various embodiments, the applicator body comprises a rigid material including at least one of plastic, rubber, silicon, metal, ceramic, composite material, wood, cardboard, or cardstock. 
     In various embodiments, the gel controlling mechanism is made of a silicone material. 
     Further embodiments relate to a method of making a gel applicator, where the method comprises providing an applicator body including a generally rigid or partially rigid body having an elongated shape that defines a length dimension with a first end and a second end, a first surface and a second surface facing opposite the first surface. The method further comprises securing a gel controlling mechanism on or near the first end of the length dimension of the applicator body. The applicator body includes a handle at or near a second end of its length dimension. The handle is configured for a user to grip and hold the applicator body. The gel controlling mechanism includes one or more of: (a) a raised lip extending along an edge of the first end of the applicator body and along a portion of at least one side edge of the applicator body; (b) a side edge and an end edge that are extend along the first surface of the applicator body and form a generally flat, spatula-shaped end portion; or (c) a set of bristles. 
     In various embodiments of the method, the first end of the applicator body is rounded such that the raised lip shape is rounded around the edge of the first end of the applicator body. 
     In various embodiments of the method, the raised lip of the gel controlling mechanism includes a first length portion that extends along a first length of one side edge of the applicator body and a second length portion that extends along a second length of a second side edge of the applicator body, the second side edge of the applicator body being opposite to the first side of the applicator body. 
     In various embodiments of the method, the second length is shorter than the first length. 
     In various embodiments of the method, the second length equal to the first length. 
     In various embodiments of the method, the first end and the second end of the applicator body have a rounded corner or edge. 
     In various embodiments of the method, the applicator body has a recessed or indented surface having a shape for receiving a user&#39;s thumb at or near the second end of the applicator body. 
     In various embodiments of the method, the applicator body includes one or more textured features within the recessed or indented surface for enhancing the user&#39;s grip. 
     In various embodiments of the method, the applicator body includes a raised peripheral lip round its outer edge, or one or more protrusions or raised elements forming a textured surface adjacent the second end of the applicator body. 
     In various embodiments of the method, securing the gel controlling mechanism comprises affixing the gel controlling mechanism to or forming the gel controlling mechanism on the first surface of the applicator body. 
     In various embodiments of the method, the gel controlling mechanism comprises a soft material including at least one of rubber, closed cell foam, open cell foam, self-skinning open or closed cell foams, cast, aerated, or extruded silicone or urethane, or polyurethane. 
     In various embodiments of the method, the applicator body comprises a rigid material including at least one of plastic, rubber, silicon, metal, ceramic, composite material, wood, cardboard, or cardstock. 
     In various embodiments of the method, the gel controlling mechanism is made of a silicone material. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Features and aspects will become apparent from the following description and the accompanying example embodiments shown in the drawings, which are briefly described below. 
         FIG.  1 A  illustrates a top view of a gel application system according to various embodiments. 
         FIG.  1 B  illustrates a front view of the gel application system shown in  FIG.  1 A  according to various embodiments. 
         FIG.  2 A  illustrates a top view of a gel application system according to various embodiments. 
         FIG.  2 B  illustrates a front view of the gel application system shown in  FIG.  2 A  according to various embodiments. 
         FIG.  3 A  illustrates a plurality of components of a gel application system according to various embodiments. 
         FIG.  3 B  illustrates a top view of the components of the gel application system shown in  FIG.  3 A  after manufacturing according to various embodiments. 
         FIG.  3 C  illustrates a front view of the gel application system shown in  FIG.  3 B  according to various embodiments. 
         FIG.  4    illustrates a top view of a gel application system according to various embodiments. 
         FIG.  5 A  illustrates a perspective view of a gel application system according to various embodiments. 
         FIG.  5 B  illustrates an exploded view of a gel application system according to various embodiments. 
         FIG.  6 A  illustrates a perspective view of a gel application system according to various embodiments. 
         FIG.  6 B  illustrates a perspective view of a gel application system according to various embodiments. 
         FIGS.  6 C- 6 I  illustrate perspective views of gel application systems according to various embodiments. 
         FIG.  7 A  illustrates a perspective view of a gel application system according to various embodiments. 
         FIG.  7 B  illustrates a side view of a head of a subject and the gel application system shown in  FIG.  7 A  attached thereto according to various embodiments. 
         FIG.  8    illustrates a perspective view of a gel application system according to various embodiments. 
         FIG.  9 A  illustrates a perspective view of a gel application system according to various embodiments. 
         FIG.  9 B  illustrates a side view of a gel application system according to various embodiments. 
         FIG.  9 C  illustrates an applicator of a gel application system shown in  FIG.  9 B  in an open state for a gel application system according to various embodiments. 
         FIG.  9 D  illustrates an applicator in a closed state for a gel application system according to various embodiments. 
         FIG.  9 E  illustrates a side view of a gel application system according to various embodiments. 
         FIG.  9 F  illustrates a side view of a portion of an applicator of the gel application system shown in  FIG.  9 E . 
         FIG.  10    illustrates a perspective view of a gel application system according to various embodiments. 
         FIG.  11 A  illustrates a side view of a gel application system that is inactive according to various embodiments. 
         FIG.  11 B  and  FIG.  11 C  illustrate perspective views of the gel application system shown in  FIG.  11 A  that is activated according to various embodiments. 
         FIG.  12 A ,  FIG.  12 B , and  FIG.  12 C  illustrate various views of the gel application system shown in  FIGS.  11 A- 11 C  according to various embodiments. 
         FIG.  13 A  and  FIG.  13 B  illustrate views of a gel application system according to various embodiments. 
         FIG.  14 A  illustrates a side view of a gel application system according to various embodiments. 
         FIG.  14 B  illustrates a side view of a user utilizing the gel application system shown in  FIG.  14 A  according to various embodiments. 
         FIG.  15 A ,  FIG.  15 B ,  FIG.  15 C ,  FIG.  15 D ,  FIG.  15 E  and  FIG.  15 F  illustrate perspective views of various gel application systems according to various embodiments. 
         FIG.  16 A  illustrates a perspective view of a gel packet of a gel application system according to various embodiments. 
         FIG.  16 B  illustrates a perspective view of a gel packet container of the gel application system according to various embodiments. 
         FIG.  16 C  illustrates a side view of the gel application system including the gel packet container and the gel packet therein according to various embodiments. 
         FIG.  17 A  illustrates a side view of a gel application system according to various embodiments. 
         FIG.  17 B  illustrates a side view of a user utilizing the gel application system shown in  FIG.  17 A  according to various embodiments. 
         FIG.  18 A  and  FIG.  18 B  illustrate various views of a gel application system according to various embodiments. 
         FIG.  19    illustrates a perspective view of a gel applicator according to various embodiments. 
         FIG.  20 A ,  FIG.  20 B , and  FIG.  20 C  illustrate various views of a gel application system according to various embodiments. 
         FIG.  21 A ,  FIG.  21 B ,  FIG.  21 C , and  FIG.  21 D  illustrate various gel applicators according to various embodiments. 
         FIG.  22 A ,  FIG.  22 B ,  FIG.  22 C , and  FIG.  22 D  illustrate various views of a gel applicator according to various embodiments. 
         FIG.  23 A ,  FIG.  23 B , and  FIG.  23 C  illustrate various perspective views of gel applicators according to various embodiments and  FIG.  23 D  illustrates a cross-section view of a portion of the gel applicator of  FIG.  21 A . 
         FIG.  24 A  and  FIG.  24 B  illustrate various views of a gel application system according to various embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts. 
     In the following description of various embodiments, reference is made to the accompanying drawings which form a part hereof and in which are shown, by way of illustration, specific embodiments that may be practiced. It is to be understood that other embodiments may be utilized, and structural changes may be made without departing from the scope of the various embodiments disclosed in the present disclosure. 
     In some embodiments, gel application systems are disposable and provide increased ease of use. Accordingly, in some embodiments, health care providers dispose of (or otherwise do not reuse) gel containers after a single use on a single patient or subject, thereby decreasing risk of the spread of bacteria. Furthermore, certain embodiments are configured to provide a user-friendly packaging that includes different components for administering gel onto a subject (e.g., the gel itself, an applicator, and the like), healthcare providers can more quickly and easily administer health care to patients. In addition, by providing a pre-determined amount of gel within each disposable gel application system appropriate for conducting a healthcare procedure, a healthcare provider does not have to determine or measure an amount of gel to apply to a subject, and can therefore focus on other more significant aspects of the healthcare procedure. 
       FIG.  1 A  illustrates a top view of a gel application system  100  according to various embodiments.  FIG.  1 B  illustrates a front view of the gel application system  100  shown in  FIG.  1 A  according to various embodiments. 
     In some embodiments, the gel application system  100  includes a container  102 , a pre-measured amount of gel  104 , a seal  106 , an applicator  108 , and a channel  110 , in a single tool or device, for ease of use. The container  102  defines an enclosed, pocket-like, hollow interior volume for containing the gel  104  therein. In some embodiments, the container  102  is made from a single or uniform material and has no seams such that the container  102  is airtight. In some embodiments, the container  102  is made from any suitable material for retaining the gel  104 , such as, but not limited to, polymer, plastic, rubber, and the like. In other embodiments, the container  102  is made of one or more materials connected and sealed at one or more seams to form an enclosed, hollow interior volume. For example, the container  102  may be sealed along the edges thereof by any suitable mechanism including, but not limited to vacuum sealing, heat sealing, and the like. In some embodiments, the container  102  is made of a material that is sufficiently flexible to allow a user to squeeze the container  102  with manual force (such as by hand), to compress the pocket-like hollow interior and apply or increase the pressure of the fluid (or gel) in the pocket-like hollow interior. In some embodiments, the container  102  is made of a material that is also sufficiently resilient to allow the container  102  to resume its shape (the shape before it is squeezed), once squeezing pressure is withdrawn from the container. 
     In some embodiments, the gel  104  includes a suitable gel used in conjunction with healthcare, including, but not limited to, ultrasound gel used in connection with ultrasound emitting devices (e.g., Transcranial Doppler (TCD) devices). In other embodiments, the gel  104  may be other suitable gel, liquid, powder, composite material, or the like, for other types of procedures. 
     In some embodiments, the container  102  further includes a section having a channel  110 . The channel  110  has a first end in gel or fluid flow communication with the interior volume of the pocket of the container  102 . The channel  110  has a second end that is open to (or in gel or fluid flow communication with) an outlet port through which gel may flow from the channel to the applicator  108  or to the environment external to the container  102 , to discharge the gel  104  from the gel application system  100 . The seal  106  is located within the channel  110 . In other examples, the seal  106  may be located on or adjacent one of the first or second ends of the channel  110 . The seal  106  has a first state, in which it is configured to block the gel  104  from exiting the gel application system  100  through the channel  110 . For example, the seal  106 , when in the first state, can provide a physical barrier for preventing the gel  104  from flowing beyond the seal  106 . The seal  106  has a second state, in which it is configured to allow gel  104  to pass through the channel  110 , from the interior volume (or pocket), to and out of the outlet port. In some embodiments, the seal  106  is configured to be broken to open the pathway of the channel  110  to allow the gel  104  to exit the gel application system  100 . In some embodiments, the seal  106  is strong enough to withstand the flow of the gel  104  when unbroken, yet brittle enough to enable a user to break the seal  106  by applying force thereto. 
     In some embodiments, the seal  106  is made from any suitable rigid material, such as, but not limited to, hard plastic, metals, aluminum, steel, titanium, magnesium, various alloys, rigid plastics, composites, carbon fiber, fiber glass, expanded foam, compression molded foam, stereolithography (SLA) or Fused Deposition Modeling (FDM)-made materials, Reaction Injection Molding (RIM) molding, acrylonitrile butadiene styrene (ABS), thermoplastic olefin (TPO), nylon, polyvinyl chloride (PVC), fiber reinforced resins, or the like. In other embodiments, the seal  106  may be made of a material having some flexibility, but being sufficiently rigid to open, break or rupture upon receiving a sufficient force as described herein. In some embodiments, a user breaks the seal  106  by snapping the seal  106  into two or more pieces, by puncturing the seal  106  with a tool or finger that applies a force on the seal  106 , or by any other suitable implementation for allowing flow of the gel  104  through the channel  110 . In some embodiments, the seal  106  may be broken (or otherwise opened) upon and in response to a user inserting a tool (such as, but not limited to a needle or other puncturing tool) into the channel  110  a sufficient distance to contact and puncture (or otherwise open) the seal  106 . In some embodiments, the seal  106  may be broken (or otherwise opened) upon or in response to a fluid (or gel) pressure within the interior volume of the container  102  reaching or exceeding a sufficient threshold magnitude to cause the seal  106  to break (or otherwise open). In particular embodiments, the seal  106  may be broken (or otherwise opened) upon or in response to a user squeezing and compressing the container  102  by an amount that increases the fluid (or gel) pressure within the interior volume of the container  102  sufficient to reach or exceed the threshold magnitude. 
     In some embodiments, the seal  106  may include a valve or other suitable structure that is selectively opened (or opened and closed), in response to fluid (or gel) pressure within interior volume (pocket) of the container being greater than a defined threshold magnitude. In such embodiments, the valve may be a manually operated valve that includes a manual operator located on the container  102  or the applicator  104  that allows a user to selectively and manually open the valve. In yet other embodiments, the valve may include an electronic, magnetic, or electromagnetic valve that is operated by an electronic, magnetic or electromagnetic controller, to selectively open. 
     In some embodiments, the applicator  108  is attached to the container  102 . In some embodiments, the applicator  108  is permanently attached to the container  102 , for example, by welding, adhesive, one or more hooks and latches, press fittings, or the like. In other embodiments, the applicator  108  is releasably attached to the container  102 , for example, by snap fittings, screw fittings, and the like. In some embodiments, the applicator  108  includes a soft, flexible, or resilient material, such as, but not limited to, closed cell foam, open cell foam, self-skinning open or closed cell foams, cast, aerated, or extruded silicone or urethane, polyurethane, or the like. In some embodiments, the applicator  108  includes a hole through the applicator material. The hole is aligned with the channel  110  such that the gel  104  can travel from within the container  102 , through the channel  110 , and through the applicator  108 , to the free end of the applicator  108 . Accordingly, the gel  104  can be excreted onto the applicator  108  so that a user can apply the gel  104  onto a subject using the applicator  108 . In other embodiments, the gel  104  is discharged directly onto a subject. 
     In some embodiments, the hole through the applicator  108  is of a suitable size for allowing the gel  104  to pass through the applicator  108 . The hole can be relatively large (e.g., to allow a relatively high gel flow rate through the applicator) or relatively small (e.g., to allow a relatively low gel flow rate through the applicator), depending on the application of use of the gel application system  100 . In some embodiments, the hole is located in the center of the applicator  108 . In other embodiments, the hole is located at other suitable positions with respect to the applicator  108 , such as, but not limited to, along an edge thereof. In other embodiments, the hole is located in the container  102  (at the second end of the channel  110 ), separate from and above or below the applicator  108 . 
     Accordingly, in some embodiments, a user of the gel application system  100  breaks (or otherwise opens) the seal  106  to allow flow of the gel  104  from within the container  102  through the channel  110 . Then, the user is able to squeeze the gel  104  out through the channel  110  onto a subject or onto the applicator  108 . The user then uses the applicator  108  to spread or otherwise apply the gel  104  onto a subject (e.g., onto a side of the subject&#39;s head). 
       FIG.  2 A  illustrates a top view of a gel application system  200  according to various embodiments.  FIG.  2 B  illustrates a front view of the gel application system  200  shown in  FIG.  2 A  according to various embodiments. 
     In some embodiments, the gel application system  200  includes a container  102 , gel  104  and a seal  106 , which may be the same or similar to those components of the gel application system  100 . However, the gel application system  200  includes an applicator  202  that is different from the applicator  108  of the system  100 . In particular, the gel application system  200  includes a brush-like applicator  202  that includes a plurality of bristles  204 . In some embodiments, the applicator  202  has a hole in fluid (or gel) flow communication with the channel  110  such that the gel  104  may be discharged from the container  102 , onto a patient or subject or onto the bristles  204  for application on the patient or subject. In some embodiments, the bristles  204  are configured to move the hair of a subject so as to clear the area of the subject that is to receive the gel  104  (e.g., to clear a temporal window of the subject). 
     In some embodiments, the bristles  204  are located in a circular arrangement around the hole defined by the applicator  202 . In other embodiments, the bristles  204  are arranged in any other suitable shaped arrangements, such as, but not limited to, a triangle, a square, an ellipse, and the like. The bristles  204  may be connected to the applicator  202  by any mechanism, including but not limited to adhering or embedding one end of each of the bristles  204  to the applicator  202 . A second (or distal) end of each of the bristles faces outward and is free to contact the skin or surface of a patient or subject. 
     In some embodiments, the size of the bristles  204  range from relatively thick comb-like bristles to relatively fine hair-like bristles, depending on the desired application. As non-limiting examples, bristles  204  can have a diameter in the range of about 0.04 mm. to about 3.0 mm. In other examples, the bristles  204  can be thinner than about 0.04 mm. or thicker than about 3.0 mm. The bristles  204  may be relatively flexible, so as to bend, when pressed against a patient or subject. In some embodiments, the bristles  204  are made from any suitable material for adjusting a subject&#39;s hair and/or for applying the gel  104  to the subject, such as, but not limited to, plastic, metal, nylon, animal hair, carbon fiber, and the like. 
       FIG.  3 A  illustrates a plurality of components  300   a ,  300   b  of a gel application system  300  according to various embodiments.  FIG.  3 B  illustrates a top view of the components of the gel application system  300  shown in  FIG.  3 A  after manufacturing and assembly according to various embodiments.  FIG.  3 C  illustrates a front view of the gel application system  300  shown in  FIG.  3 B  according to various embodiments. In some embodiments, the gel application system  300  includes a container  102 , gel  104  and a seal  106 , which may be similar to those components of the gel application system  100 . However, the gel application system  300  also includes a further applicator, in the form of an applicator stick  302 . 
     In some embodiments, the gel application system  300  is made from the plurality of components including a first side component  300   a , a second side component  300   b , and the applicator stick  302 . In such embodiments, the first side component  300   a , the second side component  300   b , and the applicator stick  302  are connected together and form the gel application system  300 . In some embodiments, the first side component  300   a  and the second side component  300   b  are identical components, with each of the first side component  300   a  and the second side component  300   b  including about half of a container (e.g., the container  102 ). The first side component  300   a  and the second side component  300   b  connect together at peripheral edges to form the hollow volume (or pocket) between the side components  300   a  and  300   b , for receiving gel  104 . In certain examples, each of the first side component  300   a  and the second side component  300   b  include half of an applicator including a row (or a plurality of rows) of bristles  304 . In some embodiments, the first side component  300   a  and the second side component  300   b  are affixed together by any suitable method, including, but not limited to, adhesive bonding, vacuum sealing, thermos sealing, and the like. 
     In some embodiments, the applicator stick  302  has a generally elongated, rectangular shape (corresponding to an elongated plate or flat stick shape), and has an outward-facing surface that can define a platform for receiving at least some of the gel  104  discharged from the container  102 . Once some or all of the gel  104  is discharged from the container  102  onto the applicator stick  302  or directly onto the patient or subject (or on both the applicator stick  302  and the patient or subject), a user can apply and spread the gel  104  onto a patient or subject via the applicator stick  302 . In some embodiments, the applicator stick  302  is made from any suitable rigid material for applying the gel  104  to a subject, such as, but not limited to, wood, plastic, metal, ceramic, composite material, cardboard, cardstock, and the like. In some embodiments, the applicator stick  302  is securely affixed to the container  102  by any suitable means, such as, but not limited to, welding, adhesive, one or more hooks and latches, press fittings, or the like. In other embodiments, the applicator stick  302  may be formed as part of the container  102  (or as part of the second side component  300   b ), for example, by molding the applicator stick onto the side (or side component) of the container  102 . In some embodiments, a first end portion of the applicator stick  302  is affixed to the second side component  300   b  of the container  102 , while a second end portion of the applicator stick  302  extends from (and is not further affixed) to the container  102  (e.g., such that the second portion of the applicator stick  302  is sufficiently free from the container  102  to allow gel  104  to be easily dispersed onto the applicator stick  302  and applied to a subject). In some embodiments, the second end of the applicator stick  302  has rounded corners or rounded edges (or both), to minimize sharp corners or edges. 
     In some embodiments, the gel application system  300  includes a plurality of bristles  304  (e.g., similar to bristles  204 , as described above) configured to contact and adjust hair of a patient or subject, to clear an area for applying the gel  104 . In the example of  FIG.  3 C , the bristles  304  are arranged in two, generally parallel rows, with one row arranged on one side of the channel  110  and the other row arranged on the opposite side of the channel  110 . Thus, the first side component  300   a  includes a first row of bristles  304 , and the second side component  300   b  includes a second row of bristles  304 . In other embodiments, more than one row of bristles  304  may be provided on each side component  300   a  and  300   b . In yet other embodiments, other arrangements of bristles may be provided at one or both side components  300   a  and  300   b . In some embodiments, the gel application system  300  defines a seam or connection line  306 , where the first side component  300   a  and the second side component  300   b  connect to each other. The seam or connection line  306  extends along the length dimension of the gel application system  300 . 
       FIG.  4    illustrates a top view of a gel application system  400  according to various embodiments. In some embodiments, the gel application system  400  includes a container  102  and gel  104  which may be similar to those components of the gel application system  100 . In some embodiments the gel application system  400  may include a seal (not shown in  FIG.  4   ), similar to the seal  106  in the gel application system  100 . 
     In some embodiments, the gel application system  400  includes the applicator stick  302 , which may be similar to the applicator stick  302  of the gel application system  300 . In some embodiments, the gel application system  400  does not include the plurality of bristles  304  discussed above with respect to the gel application system  300 . 
     In some embodiments, the container  102  (and the gel  104  therein) is sealed on one end by a tear section  102   a  of material that is connected to, but separated from the rest of the container  102 , through a perforated portion (such as a line  402  of perforations in the material of the container  102 ). In some embodiments, the tear section  102   a  forms an end barrier that blocks the gel  104  from flowing out of the container  102  through the channel  110 . However, to enable the flow of the gel  104  out of the container  102  through the channel  110 , a user may rip the tear section  102   a  from the container  102  at the perforated line  402 , to open the second end of the channel  110  such that the gel  104  can be dispersed from the container, onto a patient or subject, or onto the applicator stick  302  (or both). 
       FIG.  5 A  illustrates a perspective view of a gel application system  500  according to various embodiments.  FIG.  5 B  illustrates an exploded view the gel application system  500  shown in  FIG.  5 A . 
     In some embodiments, the gel application system  500  includes a gel packet  502  and an applicator  504 . The gel packet  502  is configured to define an enclosed, interior volume (within the gel packet  502 , or between the gel packet  502  and the applicator  504 ) that is configured to retain gel (e.g., ultrasound gel, as described herein with respect to gel  104 ). In some embodiments, the gel packet  502  includes a container made from any suitable material for retaining the gel, such as, but not limited to, the material of the container  102 , as described herein. In some embodiments, the gel packet  502  may be composed of one sheet (or a plurality of sheets) of flexible material, such as, but not limited to plastic, rubber, metal foil, or the like, that is (are) sealed around a peripheral edge to the applicator  504  to form a flexible wall around one or more internal volumes for containing gel between the sheet of flexible material and the applicator  504 . In such embodiments, the one or more internal volumes the gel packet  502  may be bordered by the flexible wall of the gel packet  502  and a first surface of the applicator  504 . In other embodiments, the gel packet  502  may have other suitable forms including, but not limited to one or more envelopes or enclosed pouches of flexible material adhered to the applicator  504 . 
     In some embodiments, the gel packet  502  is made of a material that has sufficient flexibility to allow a user to squeeze and compress the interior volume, for example, by applying a force on the gel packet  502  with the user&#39;s hand, thumb or finger, while gripping and holding the gel application system  500  with the same hand. In some embodiments, the gel packet  502  is affixed (such as, permanently affixed) to the first surface of the applicator  504 , for example, but not limited to, by welding, adhesive, one or more hooks and latches, press fittings, or the like. In some embodiments, the gel packet  502  may be molded onto the applicator  504 . For example, the gel packet  502  may be molded with the applicator  504 , and of the same material as the applicator. Alternatively, the gel packet  502  may be a separate material that is co-molded with, or over-molded onto the applicator  504 . In some embodiments, the gel packet  502  includes a large volume end  502   a  (the end on the right side of  FIGS.  5 A and  5 B ) that is configured to retain a larger volume of gel  510 , relative to the opposite, smaller volume end  502   b  (the end on the left side of  FIGS.  5 A and  5 B ) of the gel packet  52 . Accordingly, the gel located at the large volume end  502   a  (e.g., in a default or resting state) can be guided with precision, including the flow rate of the gel, towards the end of the gel packet  502  via the small volume end  502   b  due to the transition from the large volume end  502   a  to the smaller volume end  502   b  of the gel packet  502 . In some embodiments, more than one (a plurality of) gel packets  502  are affixed to the first surface of the applicator  504 . 
     In some embodiments, the applicator  504  of the gel application system  500  comprises a generally rigid or partially rigid body such as, but not limited to an applicator stick that may be made of a similar material as the applicator stick  302 , described above. In some embodiments, the applicator  504  defines a slot  506  (or a plurality of slots) extending through the applicator  504 , and open on a second surface of the applicator  504  that faces opposite to the first surface on which the gel packet  502  is affixed. The slot  506  is located adjacent or below the smaller volume end portion of the gel packet  52  (the left end in  FIGS.  5 A and  5 B ). In some embodiments, the applicator  504  includes one or more gel slots  506 , where a user is able to select and open one or more of the gel slots as desired, or partially open one or more of the gel slots. 
     In some embodiments, the body of the applicator  504  has an elongated shape that defines a first end and a second end. One or both of the first end and the second end may be rounded or have rounded corners or edges (or both), to avoid sharp corners or edges. In some embodiments, the slot  506  is located on an end portion adjacent the first end (for example, a top end) of the elongated shape of the applicator  504 . In some embodiments, the large volume end  502   a  of the gel packet  502  is located on an end portion adjacent the second end (for example, a bottom end) of the elongated shape of the applicator  504 . However, in other embodiments, the location of the slot  506  and the large volume end  502   a  of the gel packet  502  may be reversed relative to the above-described locations. 
     In some embodiments, gel  510  that is stored or retained within the gel packet  502  is configured to be discharged from the gel packet  502 , through the gel slot  506  (e.g., onto a patient or subject), when the gel slot  506  is opened. Accordingly, in some embodiments, the interior volume of the gel packet  502  is in fluid (or gel) flow communication with the gel slot  506 , to enable flow of the gel  510  from the gel packet  502  through the gel slot  506 . Accordingly, once the gel slot  506  is opened, a user may regulate the dispensing rate of gel through the slot  506  by applying pressure to (for example, by squeezing and compressing the large volume end  502   a  of the gel packet  502 ), to force a desired volume of gel from the larger volume portion of the gel packet  502  to the smaller volume portion of the gel packet  502  and, then, out through the slot  506  in the applicator  504 . The location of the slot  506  under the smaller volume portion  502   b  of the gel packet  502  can provide the user with a greater amount of control over the dispensing rate, by limiting the dispensing rate, as compared to an embodiment in which the slot  506  is located under the larger volume portion  502   a  of the gel packet  502 . However, in other embodiments, one or more slots  506  may be located in the applicator  504 , under the larger volume portion of the gel packet  502 . 
     In some embodiments, the surface of the applicator  504  adjacent the gel packet  502  forms a passage or groove  512  along the length dimension of the applicator  504 , that serves as a channel for enhancing control of fluid (or gel) flow from the large volume end  502   a  of the gel packet  502  to the slot  506  in the applicator  504 . In some embodiments, the passage or groove has one end that is open to the slot  506 . 
     In some embodiments, the gel application system  500  includes a closing mechanism, such as, but not limited to a peel-off cover  508  configured to attach to the applicator  504  (on a surface facing opposite the surface on which the gel packet  502  is located), to cover and seal the gel slot  506  such that the gel  510  cannot be discharged therefrom. The cover  508  may be made of any suitable material such as, but not limited to a plastic, metal sheet or foil, paper, composite material, or the like. The cover  508  (or the applicator  504 , or both) may include an adhesive that is sufficiently strong to hold the cover  508  in place until a user manually removes the cover  508 , by peeling the cover  508  off of the applicator  504 . As such, in some embodiments, once a user removes (e.g., peels off) the cover  508 , flow of the gel  510  out of the gel application system  500  is enabled. In some embodiments, a surface of the cover  508  facing the applicator  504  includes an adhesive layer such that the cover  508  is affixed to the applicator  504  and covers the gel slot  506 . In other embodiments, other slot closing mechanisms may be used to allow a user to selectively open the slot  506  from a closed state. For example, in some embodiments, a slot closing mechanism may include one or more of a pivotal, rotatable, or sliding panel or door, that pivots, rotates or slides between a first position in which it blocks the slot and inhibits gel from being expelled through the slot, and a second position in which it opens the slot and allows gel to be expelled through the slot. In such embodiments, the panel or door may include or be coupled to a tab or trigger that can be engaged by a user to move the panel or door between the first and second positions. In yet other embodiments, a slot closing mechanism may include a cork or stopper that selectively fits at least partially in or over the slot, to selectively close the slot and inhibit the passage of gel through the slot, and that can be removed from the slot to selectively open the slot and allow the passage of gel through the slot. 
     In some embodiments, a user may use the gel application system  500  by peeling off the cover  508  to open the gel slot  506 . Then, the user squeezes the large volume portion of the gel packet  502  to selectively discharge the gel  510  from the gel slot  506  onto a patient or subject (e.g., onto a head of the subject for use with a TCD device) or on the applicator  504  itself (e.g., by turning the gel application system  500  upside down to allow the discharged gel to seep onto the surface of the applicator  504  for application of the gel onto a desired surface. In some embodiments, once some or all of the gel  510  is discharged onto the patient or subject, the applicator  504  is utilized to move the gel  510  into desired locations or to spread the gel  510  evenly or as desired on the subject. 
     In  FIGS.  5 A and  5 B , the gel slot  506  is located adjacent, but spaced from a distal end edge of the applicator  504  and is oriented such that the length dimension of the slot  506  extends along (or parallel to) the length dimension of the body of the applicator  504 . In other embodiments, the gel slot  506  is positioned at other locations or orientations on the applicator  504 , such as, but not limited to, at or long a distal end edge of the applicator  504 . In some embodiments, the gel slot  506  is positioned in different orientations, such as, but not limited to, lengthwise along the applicator  504 , widthwise (e.g., perpendicular to lengthwise) across the applicator  504 , diagonally, or other suitable location or arrangement. In some embodiments, the applicator  504  defines a plurality of gel slots  506 . In certain embodiments, a plurality of gel slot  506  having a corresponding plurality of different shapes is provided, such as, but not limited to, a circle, a star, a cross, and the like. In certain embodiments, a plurality of gel slot  506  having a corresponding plurality of different opening sizes (for providing a plurality of different dispensing rates at a given fluid pressure) is provided. In embodiments in which multiple slots are provided, each slot may include a separate cover  508  (or other closing mechanism) to allow the user to selectively open (or leave closed) one or more of the plurality of slots or portions thereof. 
     In some embodiments, the body of the applicator  504  is transparent or partially transparent, such that a user can view the amount of remaining gel or the flow of gel  510  along at least a portion of the applicator  504 . 
       FIGS.  6 A- 6 I  illustrate perspective views of gel application systems that may be similar to the gel application system  500 , but include further features or differences described herein and shown in the drawings. 
     For example,  FIG.  6 A  illustrates a perspective view of a gel application system  600  according to various embodiments. 
     In some embodiments as shown in  FIG.  6 A , the gel application system  600  includes the gel packet  502 , the applicator  504 , the gel slot  506 , and the gel  510 , which may be the same or similar to those components described above in the gel application system  500 . In some embodiments, the gel application system  600  further includes a gel spreading mechanism  602  configured to contact gel  510  that is applied onto a patient or subject, and adjust placement and thickness of the gel  510  (e.g., along a temporal window or other defined area of the patient or subject). In some embodiments, the gel spreading mechanism  602  is located along an outer edge of a surface (the bottom surface) of the applicator  504 . In some embodiments, the gel spreading mechanism  602  extends along the entire edge curvature of one end of the applicator  504  (for example, the end of the applicator  504  adjacent or closest to the gel slot  506 ), but does not extend along the rest of the edge of the applicator  504 . In other embodiments, the gel spreading mechanism  602  extends along and around the entire edge of the applicator  504 , or along one or more selected portions of the edge of the applicator. 
     In some embodiments, the gel spreading mechanism  602  is affixed to or formed on one surface of the applicator  504 , such as the surface facing opposite to the surface on which the gel packet  502  is located. In other embodiments, the gel spreading mechanism  602  is affixed to or formed on the same side of the applicator  504  on which the gel packet  502  is located. In some embodiments, a gel spreading mechanism  602  is affixed to each or both surfaces of the applicator  504 . In some embodiments, the gel spreading mechanism  602  is located at the edge of the end portion of the applicator  504  that is proximate the gel slot  506 , as discussed above and shown in the drawings. In other embodiments, the gel spreading mechanism  602  is located at the edge of end portion of the applicator  504  that is opposite the end portion that is proximate the gel slot  506 . 
     In some embodiments, the gel spreading mechanism  602  is made from any suitable soft material, such as, but not limited to, rubber, closed cell foam, open cell foam, self-skinning open or closed cell foams, cast, aerated, or extruded silicone or urethane, polyurethane, or the like. In other embodiments, the gel spreading mechanism  602  is made from any suitable rigid material, such as, but not limited to, plastic, rubber, silicon, metal, ceramic, composite material, wood, cardboard, cardstock and the like. In some embodiments, the gel spreading mechanism  602  is made of a combination of such soft and rigid materials. In some embodiments, the gel spreading mechanism  602  is affixed (e.g., permanently affixed) to the applicator  504  by, for example, but not limited to, welding, adhesive, one or more hooks and latches, friction or press fittings, or the like. In some embodiments, the gel spreading mechanism  602  may be formed directly on the applicator  504  by any suitable manufacturing techniques, including, but not limited to molding, machining, or the like. In some embodiments, after discharging the gel  510  onto a subject, a user may employ the gel spreading mechanism  602  to adjust the thickness and position of the gel  510  on the patient or subject as desired. The gel spreading mechanism  602  can provide the user with a relatively fine control of the thickness and placement of the gel  510 . In some embodiments, the gel spreading mechanism  602  can have any suitable shape or configuration for spreading or controlling gel. For example, the gel spreading mechanism may have one or more generally flat, tapered or curved surfaces that extend outward from a surface of the applicator  504  (extend outward from the surface facing opposite to the surface on which the gel packet  502  is located) and form one or more tapered or pointed distal edges). In some examples, the generally flat, tapered or curved surfaces of the gel spreading mechanism has a curvature that curves around (or partially around) the first end of the applicator  504 . 
       FIG.  6 B  illustrates a perspective view of a gel application system  650  according to various embodiments. 
     In some embodiments, the gel application system  650  is similar to the gel application system  600  described above, and includes the gel packet  502 , the applicator  504  and the slot  506 , which may be the same or similar to those components described above for the gel applicator system  602 . In some embodiments, the gel application system  650  includes a gel spreading mechanism  652 , which may be similar to the gel spreading mechanism  602  discussed above, or may have a different configuration such as described below and shown in  FIG.  6 B . In some embodiments, the gel application system  650  also includes a scraper  654 , and a string or lanyard  656 . 
     In some embodiments, the gel spreading mechanism  652  protrudes outward relative to the surface of the applicator  504  opposite to the surface on which the gel packet  502  is located, and extends along one side edge and a portion of the first end (top end) edge of that surface of the applicator  504 . In some embodiments, the scraper  654  is located adjacent the gel spreading mechanism  652  and protrudes outward relative to the surface of the applicator on which the gel packet  502  is located, and extends along one side edge and a portion of the first end (top end) edge of that surface of the applicator  504 . In other embodiments, the gel spreading mechanism  652  and the scraper  654  are located at opposite ends of the applicator  504 . In some embodiments, the scraper  654  is configured to move and lift gel  510  from a patient or subject (e.g., for cleaning the patient or subject). In some embodiments, the scraper  654  is made from any suitable rigid material, including, but not limited to, plastic, silicon, rubber, metal, ceramic, composite material, wood, cardboard, cardstock and the like. In some embodiments, the scraper  654  includes a raised lip along its outer edge configured such that the scraper  654  can lift gel  510  off of a subject. 
     In some embodiments, the string or lanyard  656  is formed in a loop shape to allow a user to easily grip the gel application system  650 . In other embodiments, the string or lanyard  656  includes a strip or piece of material that a user can grip while utilizing the gel application system  650 , or for grabbing in the event the gel application system  650  is dropped (e.g., within a TCD system) such that the user can easily retrieve the gel application system  650 . In some embodiments, the string or lanyard  656  is attached (e.g., permanently attached) to the applicator  504  by, for example, but not limited to, welding, adhesive, one or more hooks and latches, press fittings, or the like. In other embodiments, the string or lanyard  656  is attached to the applicator  504  in a releasable manner, to allow the string or lanyard  656  to be removed from the applicator  504 , if desired. The string or lanyard  656  is made from any suitable material, such as, but not limited to, nylon, plastic, fabric, cotton, metal, or the like. 
     For example,  FIG.  6 C- 6 I  illustrate various gel application systems  660 ,  665 ,  670 ,  675 ,  680 ,  685  and  690  having various different slot or opening configurations or gel packet configurations, according to various embodiments. In some embodiments, the gel application systems  660 ,  665 ,  670 ,  675 ,  680 ,  685  and  690  are the same or similar to the gel application systems  500 ,  600 , and  650 , as described above, but with the differences described and shown herein. 
     For example, the gel application system  660  in  FIG.  6 C  includes a gel packet  662  that has a narrow or neck section  662   a  and a wider reservoir section  662   b . The narrow or neck section  662   a  is narrower in width than the wider reservoir section  662   b , and extends over a slot-shaped opening on an applicator  664  (such as the slot-shaped opening  506  described above). In other embodiments, the neck section  662   a  extends over one or more openings having other shapes or arrangements that fit under the neck section  662   a . The narrower neck section  662   a  can provide a limited flow rate and, thus, can provide the user with a greater level of control over the rate of flow of gel to (and through) the slot-shaped opening, from the wider reservoir section  662   b  of the gel packet  662  (as compared to a gel packet configuration of the gel application system  665  and  670  as shown in  FIGS.  6 D and  6 E ). In other embodiments such as shown in  FIGS.  6 D and  6 E , the gel packet  662  may have other shapes or configurations, for example, that cover all (or substantially all) of the first surface of the applicator  664 . 
     In various embodiments described herein, the gel application system includes one or more gel slots or other shaped openings in the applicator. Examples of some, but not all, slot or opening configurations are shown in  FIGS.  6 F- 6 I , including a configuration having a single slot (such as the gel application system  675  in  FIG.  6 F ), a configuration having a plurality of slots arranged generally parallel to each other (such as the gel application system  680  in  FIG.  6 G ) and a configuration having an arrangement of a plurality of round openings (such as the gel application system  685  in  FIG.  6 H  or the gel application system  690  in in  FIG.  6 I ). In other embodiments, other suitable opening configurations or arrangements may be employed, to provide a desired pattern or rate of flow of gel from the gel application system. 
     In further examples of any of the embodiments of  FIGS.  5 A- 6 I , the gel application system includes a peel away seal (such as described above with regard to seal  508 ) that is removably adhered to the second surface of the applicator and covers the one or more openings in the applicator, to inhibit the flow of gel from the gel application system until or unless the seal is peeled away. In other embodiments, the gel application system includes a pivotal, rotatable or sliding panel or door, cork or stopper for selectively closing and opening the gel slot (such as described above). In some embodiments, a peel away seal may cover the one or more openings and a limited area of the applicator around the one or more openings (but not cover the entire second surface of the applicator). In other embodiments, the peel away seal may cover substantially the entire second surface of the applicator, as shown in  FIG.  6 I . The peel away seal may include a surface (facing outward) that provides an area for printed information including, but not limited to, directions for use, product or manufacturer name or information, date of manufacture or of expiration, other date information, or the like. 
     In further examples of any of the embodiments of  FIGS.  5 A- 6 I , the applicator is transparent such that a user can view gel in the gel packet or view can the flow of gel along the applicator. Alternatively or in addition, any of the embodiments of  FIGS.  5 A- 6 I  may include a gel spreading mechanism  602 , a scraper  652 , a string or lanyard  656 , or any combination thereof. 
       FIG.  7 A  illustrates a perspective view of a gel application system  700  according to various embodiments.  FIG.  7 B  illustrates a side view of a head of a subject  750  and the gel application system  700  shown in  FIG.  7 A  attached thereto according to various embodiments. 
     In some embodiments, the gel application system  700  includes a barrier  706  and a cover  702   a  or  702   b  at each side of the barrier  706 . In some embodiments, the covers  702   a  and  702   b  are configured to seal with the barrier and form an interior volume for containing a gel  708  within the barrier  706  and between the two covers  702   a  and  702   b . In some embodiments, each of the top surface and the bottom surface of the edges of the barrier  706  includes an adhesive layer  710  thereon such that the two respective covers  702   a  and  702   b  are releasably affixed to the two respective sides of the barrier  706 . More specifically, the cover  702   a  is releasably affixed to a first side of the barrier  706 , while the cover  702   b  is releasably affixed to a second side of the barrier  706  (opposite to the first side). In other embodiments, each of the covers  702   a  and  702   b  includes the adhesive layer  710 , or both the barrier  706  and each of the covers  702   a  and  702   b  include adhesive layers  710 . In some embodiments, each of the covers  702   a  and  702   b  includes a tab  704  for allowing a user to easily grip the cover  702   a  or  702   b , for peeling back one or both covers  702   a  and  702   b  and exposing the gel  708  enclosed by the barrier  706 . 
     In some embodiments, a user peels a first cover  702   a  from the first side of the barrier  706  using the tab  704 , to expose one side of the volume of gel  708  that is contained by the barrier  706  and the second cover  702   b . In some embodiments, at least some adhesive material remains on the first side of the body of the barrier  706 , after removal of the first cover. Then, the side of the barrier  706  from which the first cover  702   a  was removed is affixed to the patient or subject (for example, to a defined location on the patient&#39;s or subject&#39;s head  750 ), for example, by employing the adhesive material that remains on the first side of the body of the barrier  706 . Then, the second cover  702   b  is removed from the second side of the barrier  706  such that a second side of the volume of gel  708  contained by the barrier  706  is exposed, while the barrier (and a volume of gel contained within the barrier) is held on the patient or subject (for example, on the head  750  of the patient or subject). The barrier  706 , thus, forms a reservoir of gel  708  that defines an area that a medical device (such as, but not limited to, a TCD device) can scan. In some examples, a film or sheet of plastic or other suitable material may be provided across one side of the barrier  706  (i.e., the side facing outward from the subject or patient&#39;s head, when the barrier  706  is secured to the patient or subject), to help retain gel within the barrier  706 . Alternatively or in addition, the gel can be held within an envelope or membrane secured to the barrier  706 , to help retain gel within the barrier  706 . In such embodiments, the film, sheet, envelope or membrane may be configured of material that is sufficiently flexible or pliable to allow the gel to be depressed within the barrier  706 , when the film, sheet, envelope or membrane are contacted or pressed by an image device probe. 
     In some embodiments, the barrier  706  is an annular body made from a rigid or partially flexible (non-rigid) material suitable for containing a volume of gel  708  and holding the volume of gel on the patient or subject (such as, but not limited to on a patient&#39;s or subject&#39;s head  750 ), such as, but not limited to, plastic, rubber, metal, ceramic, wood, paper, cardboard, cardstock, composite material and the like. In some embodiments, the barrier  706  has a generally rectangular, annular shape. In other embodiments, the barrier  706  may have a round or rounded annular shape, a square annular shape or other suitable annular shapes. Each cover  702   a  and  702   b  may be made of any suitable material such as, but not limited to plastic, metal sheet or foil, paper, composite material, or the like. 
       FIG.  8    illustrates a perspective view of a gel application system  800  according to various embodiments. In some embodiments, the gel application system  800  includes a syringe-type system. 
     The gel application system  800  includes a plunger  802 , a container or barrel  806 , and an applicator  808 . In some embodiments, the barrel  806  is pre-filled with gel, or with a pre-defined quantity of gel. The barrel  806  in  FIG.  8    comprises a generally cylindrical shaped container having an enclosed interior volume for containing gel, an opening on a first end  806   a  for receiving the plunger  802 , and an opening on a second end  806   b  through which gel from the interior volume of the container may be dispensed. In other embodiments, the barrel  806  has other suitable shapes for containing and retaining a quantity of gel. The barrel  806  may be made of any suitable material having sufficient rigidity to operate as described herein, including, but not limited to plastic, metal, ceramic, composite material or the like. In some embodiments, the barrel  806  is made of a transparent or partially transparent material that allows a user to view contents within the interior volume of the barrel  806 , for example, to view the amount of gel contained within the barrel  806 . In some embodiments, the barrel  806  includes one or more markings along a length dimension, to define one or more volume levels (or amounts) of gel or other material contained in the interior volume of the barrel  806 . In some embodiments, a flange  804  is provided on or adjacent the first end  806   a  of the barrel  806 . The flange  804  can provide a surface against which a user&#39;s fingers my press to provide leverage, while pushing the plunger  802  with a thumb. 
     In some embodiments, the applicator  808  is the same or similar to any of the applicators described herein, including, but not limited to a soft, flexible, or resilient material, such as, but not limited to, closed cell foam, open cell foam, self-skinning open or closed cell foams, cast, aerated, or extruded silicone or urethane, polyurethane, or the like. For example, in some embodiments, the applicator  808  is made of the same or similar material as described herein with regard to the applicator  108 , such as, but not limited to a foam material. The applicator  808  is affixed to the second end  806   b  of the barrel  806  by any suitable attachment mechanism including, but not limited to those described herein for attaching the applicator  108  to the container  102 . The applicator  808  may have any suitable shape or configuration, including, but not limited to those described herein with regard to the applicators  108  and  202 . However, in some embodiments, the applicator  808  has a wedge shape to enable effective adjustment of gel on a subject. The applicator  808  has a first end and a second end of different widths. In some embodiments, the second end of the applicator  808  is thicker than the first end of the applicator  808 , and is affixed to the second end  806   b  of the barrel  806  as described above. The first end of the applicator  808  (e.g., a thinner end of the wedge-shaped applicator  808  in  FIG.  8   ) defines a free or distal end for contacting gel on a patient or subject during use. In other embodiments, the applicator  808  has any other suitable shape, such as, but not limited to, a triangle, a curve, a rectangle, or the like. 
     The plunger  802  is moveably received within the barrel  806  and extends partially out from the first end  806   a  of the barrel  806 . In some embodiments, the plunger  802  includes a head portion (not in view) located within the interior volume of the barrel  806 , a handle portion  802   a  located outside of the barrel  806 , and a length portion  806   b  extending from the handle portion  802   a  to the head portion. In some embodiments, the plunger  802  is formed as a single, unitary structure of a single, uniform material. In other embodiments, the plunger  802  is made of multiple materials and/or components formed or coupled together. The plunger  802  may be made of any suitable material having sufficient rigidity to operate as described herein, including, but not limited to a plastic, metal, ceramic, composite material or the like. 
     A user imparts a pushing force on the handle portion  802   a  of the plunger  802 , towards the first end  806   a  of the barrel  806 . The pushing force on the plunger  802  causes the plunger  802  to move within the barrel  806 , toward the second end  806   b  of the barrel  806 , and imparts a force and increases pressure on the gel contained within the barrel  806 . Once sufficient force or pressure is imparted on the gel, some or all of the gel is pushed through the opening in the first end  806   a  of the barrel  806 , to the applicator  808  or to the environment outside of the gel application system  800 . In some embodiments, the applicator  808  defines a hole  810  that is in fluid (or gel) flow communication with opening in the second end  806   b  of the barrel  806 , such that gel is expelled onto the applicator  808  or through the applicator  808  and onto a subject via the hole  810 , in response to the pushing force of the plunger  802 . In some embodiments, the flange  804  may provide the user with additional support and leverage for application of the pushing force on the plunger  802 , as described herein. 
       FIG.  9 A  illustrates a perspective view of a gel application system  900  according to various embodiments. 
     In some embodiments, the gel application system  900  includes a plunger  902 , a flange  904 , a barrel  906 , and an applicator  908 , which may be similar to the plunger  802 , the flange  804 , the barrel  806  and the applicator  808  of the gel application system  800  described herein. However, the gel application system  900  a wider body and opening (or outlet port) for wider application of gel, as compared to the gel application system  800 . 
     For example, in the embodiment of  FIG.  9 A , the barrel  906  has a wider and flatter configuration, with a generally rectangular cylinder shape (cylindrical shape with a generally rectangular cross-section), as compared to the rounded cylinder shape (cylinder shape with a generally round cross-section) of  FIG.  8   . The wider configuration can accommodate a wider, more elongated outlet opening or slot in the second end of the barrel  906 , for a wider distribution of gel from the gel application system  900 , as compared to gel application systems having a smaller outlet opening. 
     In some embodiments, the applicator  908  defines a gel opening or slot  910  that has a generally wide, flat configuration (having a greater width than height), that aligns with the opening in the second end of the barrel  906 . A user may cause gel  912  to expel from barrel  906 , through the slot  910  in the applicator  908 , to the environment external to the gel application system  900  (for example, onto the patient or subject), in response to the plunger  902  imparting a force on the gel within the barrel  906  in a manner similar to the operation of the gel application system  800  described herein. However, because the gel application system  900  has a relatively wide structure, the gel  912  can be applied in layers relatively evenly, and can be easily and quickly applied over a relatively wide area of a patient or subject. 
     In some embodiments, a gel application system having a barrel and plunger (or syringe-type) configuration, such as but not limited to the configurations of  FIGS.  8  and  9 A , may include other types of applicators. For example,  FIGS.  9 B- 9 D  show a further embodiment of a gel application system  920  that include a plunger  922  moveable within a container or barrel  926 , and to which an applicator  928  is affixed. For example,  FIGS.  9 E- 9 F  show yet a further embodiment of a gel application system  940  that include a plunger  942  moveable within a container or barrel  946 , and to which an applicator  948  is affixed. The applicator  928  or  948  may be affixed to a second end of the barrel  926  or  946  by any suitable attachment mechanism including, but not limited to those described herein for attaching the applicator  108  to the container  102 . In some embodiments, the plunger and container or barrel of the gel application systems  920  and  940  may be configured and operated similar to the plunger  802  or  902  and the barrel  806  or  906  described with regard to the gel application system  800  or  900 . In some embodiments, the barrel  926  or  946  is pre-filled with gel, or with a pre-defined quantity of gel. 
     Similar to the above-described operation of the gel application system  800  and  900 , a user imparts a pushing force on a handle portion of the plunger  922  or  942 , towards a first end of the barrel  926  or  946 . The pushing force on the plunger  922  or  942  causes the plunger to move within the barrel  926  or  946 , toward the second end of the barrel, and imparts a force and increases pressure on the gel contained within the barrel. Once sufficient force or pressure is imparted on the gel, some or all of the gel is pushed through an open end or opening in the first end of the barrel  926  or  946 , to the applicator  928  or  948 . 
     In some embodiments, the gel application system  920  includes an applicator  928  that is configured to provide a gel stamping or flattening mechanism. In some embodiments, the applicator  928  has a valve that has an open state and a closed state. When in the open state, the valve of the applicator  928  allows a portion of the volume of the gel within the barrel  924  to be expelled, for example, onto a surface of a patient or a subject (such as, but not limited to a surface of a patient&#39;s or subject&#39;s head). When in a closed state, the valve of the applicator  928  provides a surface for manually pressing against a volume portion of gel that has been expelled onto the surface. In some embodiments, the surface is configured sufficiently flat to provide a gel flattening or spreading operation to flatten or spread (or both) the volume portion of gel, when the surface is pressed against the volume portion of gel. 
     In some embodiments, the valve includes an outlet, such as, but not limited to an outlet plate, having a plurality of openings or an arrangement of one or more openings over a defined area (or surface area of the outlet plate). The one or more opening provide fluid (gel) flow outlet openings through which gel may be expelled from the barrel  926 , when the valve of the applicator  928  is in an open state and the plunger  922  is operated (pushed toward the second end of the barrel  926 ). An example of an arrangement of a plurality of openings over an area of an outlet plate of a valve is shown in  FIG.  9 B . Other embodiments include other arrangements and shapes of openings. For example, other embodiments may include one or more slot-shaped openings, one or more openings that have a shape of a logo, a letter, a number or a word. In some embodiments, the arrangement or shape (or both) of openings provides a pattern of openings over a defined area (such as, but not limited to the area of an outlet plate), such that gel may be expelled from the outlet over an area of a surface (such as, a surface of a patient or subject) corresponding to the defined area. In some embodiments, the defined area over which gel may be expelled is configured to be sufficiently large to cover a relatively large surface area on a surface of the patient or subject, quickly and efficiently, but in a controlled manner, by operating the plunger as described herein. 
     In some embodiments, the valve of the applicator  928  includes a closed state in which the one or more openings of the outlet (or outlet plate) are covered or closed, to inhibit the passage of gel through the one or more openings. In some embodiments, the valve of the applicator  928  may be operated to transition from the open state to the closed state by rotating a portion of the valve. For example, in some embodiments, the valve of the applicator includes a second plate arranged against and parallel to the outlet plate, where one or both of the plates are rotatable relative to each other between at least a first relative rotary position and a second relative rotary position of the plates. The second plate has an arrangement of openings or other pattern of one or more openings that correspond to or otherwise align with the one or more openings in the outlet plate to allow the passage of gel through the plates when the second plate and the outlet plate are in the first rotational position relative to each other, but that are offset from the one or more openings in the outlet plate and inhibit the passage of gel through the plates when the second plate and the outlet plate are in the second rotary position relative to each other. In some embodiments, the outlet plate and the second plate may be held within an annular body that is affixed to the second end of the barrel  926 , as described above, and that supports one or both of the plates for rotational motion relative to each other. In some embodiments, one or both of the plates are arranged on respective rotational sections of the annular body, for rotation relative to each other, upon a user gripping and rotating the respective rotational section of the annular body. In other embodiments, one or both of the plates supported for rotational motion include an outward extending tab (not shown) that can be engaged by a user to manually rotate the one plate relative to the other, or both plates relative to each other. 
     In some embodiments, when the outlet plate and the second plate are rotated to a first state (an open state of the valve), the one or more openings in the respective plates are sufficiently aligned to allow gel to be expelled from the barrel  926 , when the plunger  922  is moved toward the second end of the barrel  928 , to dispense a volume of gel over a relatively large area of a surface of a patient or subject. In some embodiments, when in the plates are then rotated to the second rotary position, the outward facing surface of the arrangement of plates is sufficiently flat and defines a relatively wide surface area. In that state the applicator  928  may be used as a gel stamping or flattening tool. In that state, a user may grip the barrel  926  and press the second end of the barrel downward onto the volume of gel that has been dispensed over the surface area of the patient or subject, for example, to spread or flatten the gel over that surface area, or to enlarge the gel covered surface area. 
     In some embodiments, the applicator  928  (including the valve) is removably affixed to the second end of the barrel  926 , and is selectively removable from the barrel  926 . In such embodiments, the applicator  928  (and valve) may be removed and disposed of, after a desired time of use. In other embodiments, the entire gel application system  920  is configured to be disposed of, after a desired time of use. 
     In further embodiments, the applicator  948  of the gel application system  940  (in  FIGS.  9 E and  9 F ), is configured for gel dispensing and gel spreading. In some embodiments, the applicator  948  includes a generally flat or plate-like body of rigid or partially rigid material that has a first end  948   a  connected to the second end of the barrel  946 . The applicator  948  has a second end (a distal end)  948   b  that defines a spreading edge or surface (or both). The first end  948   a  of the applicator  948  is thinner in a width dimension than the second end  948   b  of the applicator  948 . In some embodiments, the applicator body has a tapered shape that tapers from the thinner first end  948   a , toward the wider second end  948   b . In some embodiments, the applicator  948  may have a spatula-like shape or configuration, with a suitable thickness dimension to include one or more interior channels as described below. 
     The applicator  948  may be made of any suitable rigid or partially rigid material such as, but not limited to plastic, rubber, silicon, metal, wood, ceramic, composite material, or the like. In some embodiments, the material of the applicator  948  is sufficiently rigid to hold its shape, but has some flexibility to allow the applicator  948  to bend slightly across its length dimension, when a user grips the barrel  948  and manually presses the second end (distal end)  948   b  against a surface. In other embodiments, the material of the applicator  948  is sufficiently rigid so as to inhibit bending during use. 
     In some embodiments, the wider, second end of the applicator  948  has an edge feature  950  configured to enhance the ability to spread gel. In some embodiments, the edge feature  950  is formed on and is unitary with the body of the applicator (at the second end  948   b  of the applicator  948 ). In other embodiments, the edge feature  950  is a separate element that is attached to the second end of the body of the applicator  948  by any suitable attachment mechanism including, but not limited to an adhesive, welding, thermal bonding, snap fitting, friction or press fitting, or the like. In some embodiments, the edge feature  950  is a separate element that is molded or co-molded onto the body of the applicator  948 . 
     In some embodiments, the edge feature  950  includes one or more of an angled or a beveled edge, a stepped or a reduced width edge, or a blade or an edging strip made of silicon, plastic, rubber, metal, ceramic or the like. In some embodiments, the edge feature  950  includes a blade or an edging strip that is made of a material that is more flexible (and less rigid) than the material of the rest of the applicator  948 . 
     In some embodiments, the applicator  948  has one or more interior channels (or a hollow interior) having a first end in fluid (gel) flow communication with the opening in the second end of the barrel  946 . The one or more interior channels of the applicator  948  extend along at least a portion of the length dimension of the applicator  948 , from the first end of the applicator  948 , to one or more (or a plurality of) outlet openings  952 . In some embodiments, such as shown in  FIG.  9 F , the one or more (or plurality of) outlet openings  952  are located on one side (a first surface) of the generally flat or plate-like body of the applicator  948 . In some embodiments, the opposite side (a second surface facing opposite to the first surface) of the generally flat or plate-like body of the applicator  948  defines a generally flat surface that is devoid of outlet openings, and is suitable for contacting and spreading gel, such as shown in  FIG.  9 E . 
     In some embodiments, the one or more outlet openings  952  includes a plurality of outlet openings of different sizes or shapes (or both). In some embodiments, the one or more outlet openings  952  include one or more (or a plurality of) slot shaped openings. In some embodiments, the one or more outlet openings  952  include one or more (or a plurality of) round openings, or a combination of one or more slot-shaped openings and one or more round openings. In some embodiment, the one or more openings includes a plurality of openings arranged along a width dimension of the body of the applicator  948 , so as to dispense gel over a relatively wide band or area. In some embodiments, the one or more outlet openings  952  are arranged adjacent to and along the wider second end  948   b  of the body of the applicator  948  (closer to the second end  948   b  than to the first end  948   a ). In some embodiments, the one or more outlet openings  952  are arranged adjacent to the second end  948   b , but spaced a short distance (such as, but not limited to 0.1 to 100 mm) from the second end  948   b  of the body of the applicator  948 . 
     In some embodiments, the barrel  946  includes a second flange or lip  954  at or near the second end of the barrel  946 . The second flange or lip  954  provides a surface against which a user may press one or more (or a pair) of fingers of one hand, while pushing the plunger  942  toward the second end of the barrel  946  with a thumb or the palm of the same hand. The second flange or lip  954  can provide leverage to assist the user in pushing the plunger  942  toward the second end of the barrel  946  (or drawing/pulling the second end of the barrel  946  toward the handle end of the plunger). In some embodiments, a second flange or lip (such as the second flange or lip  954 ) may be included in any of the other embodiments employing a plunger and barrel configuration in  FIGS.  8  and  9 A- 9 F . 
     In some embodiments, the gel dispensing system  940  is gripped by a user and the applicator  948  is oriented and directed toward or adjacent a surface of a patient or subject, with the surface or side of the applicator body having the one or more openings  952  facing the surface. In that orientation, the plunger  942  is moved toward the second end of the barrel  948 , to dispense a volume of gel from the one or more outlet openings  952 , over a relatively wide or large area of a surface of a patient or subject. In some embodiments, the gel dispensing system  940  may be rotated so that the second side of the body of the applicator  948  is directed toward and faces the surface of the patient or subject. In that orientation, the flat surface of the body of the applicator  948  or the edge feature of the applicator may be applied to contact the volume of gel that has been dispensed on the surface of the patient or subject, to spread gel or enlarge the surface area covered by the gel. Alternatively or in addition, the gel dispensing system  940  may be held in an orientation in which the side (the first surface) having the one or more openings  952  is oriented upward while the plunger  942  is moved toward the second end of the barrel  948 , such that a desired volume portion of the gel is dispensed from the one or more outlet openings  952  onto that side (first surface) and adjacent the second end  948   b  of the applicator  948 . Then, the user may orient the gel application system  940  such that the side (first surface) of the applicator  948  is directed and moved toward a surface of the patient or subject to apply or spread (or both) the volume portion of gel onto the surface. 
       FIG.  10    illustrates a perspective view of a gel application system  1000  according to various embodiments. 
     In some embodiments, the gel application system  1000  includes a bag  1002 , a gel slot  1004 , and a spreader or scraper  1006 . The bag  1002  has an interior volume configured to contain an amount of gel therein. The bag  1002  is made of a material that is flexible and malleable to allow a user to squeeze and compress the bag  1002  to expel gel through the gel slot  1004 . The bag  1002  is made from any suitable pliable material, such as, but not limited to, plastic, rubber, metal foil, and the like. In some embodiments, the gel in the bag  1002  is discharged from the gel application system  1000  via the gel slot  1004  (e.g., by a user squeezing the bag  1002 ) and directing the gel slot  104  toward a patient or subject. 
     In some embodiments, the spreader or scraper  1006  includes or is made from any suitable soft material, such as, but not limited to, rubber, closed cell foam, open cell foam, self-skinning open or closed cell foams, cast, aerated, or extruded silicone or urethane, polyurethane, or the like. In other embodiments, the spreader or scraper  1006  includes or is made from any suitable rigid material, such as, but not limited to, plastic, silicon, rubber, metal, ceramic, composite material, wood, cardboard, cardstock and the like. In some embodiments, the spreader or scraper  1006  includes a combination of such soft and rigid materials. In some embodiments, the spreader or scraper  1006  is the same or similar to the scraper  654 , as described above. In some embodiments, the spreader or scraper  1006  is used to spread, adjust or remove gel that is discharged from the gel application system  1000  (e.g., on a patient or subject). In some embodiments, the spreader or scraper  1006  is similar to the scraper  654 , as described above. 
     In some embodiments, the gel application system  1000  includes a head portion  1008 , to which an open end of the bag  1002  is adhered, where the head portion  1008  include the gel slot  1004  in fluid (or gel) flow communication with the interior volume of the bag  1002 . In such embodiments, the spreader or scraper  1006  may be secured to an end of the head portion  1008  opposite to the end of the head portion  1008  to which the bag  1002  is adhered. In such embodiments, the head portion  1008  may be made of any suitable material having sufficient rigidity to operate as described herein, including, but not limited to, plastic, rubber, metal, ceramic, composite material, and the like. In other embodiments, the head portion  1008  may be omitted, such that the gel slot  1004  is provided in an end portion of the bag  1002 , and the spreader or scraper  1006  is adhered directly to the bag  1002 . 
       FIG.  11 A  illustrates a side view of a gel application system  1100  before activation (in an inactivated state) according to various embodiments.  FIG.  11 B  and  FIG.  11 C  illustrate perspective views of the gel application system  1100  shown in  FIG.  11 A  that is being activated (in an activated state) according to various embodiments. 
     In some embodiments, the gel application system  1100  includes one or more gel containers  1102  defining one or more (or a plurality of) gel packets or pouches, an applicator  1104 , and a base  1106 . In the embodiment of  FIG.  11 A , the one or more gel packets or pouches includes two gel packets or pouches  1102   a  and  1102   b . In other embodiments, the gel container(s)  1102  may define a single gel packet or pouch (e.g.  1102   a  or  1102   b ), or more than two gel packet or pouches. In some embodiments, the one or more gel containers  1102  may be composed of one sheet (or a plurality of sheets) of flexible material, such as, but not limited to plastic, rubber, metal foil, or the like, that is (are) sealed around a peripheral edge to the base  1106  to form a flexible wall around one or more internal volumes for containing gel between the sheet of flexible material and the base  1106 . In other embodiments, the one or more gel containers  1102  may have other suitable forms including, but not limited to one or more envelopes or enclosed pouches of flexible material adhered to the base  1106 . The flexible material of the one or more gel containers  1102  is more flexible and malleable than the material of the base  1106 . 
     In some embodiments, the base  1106  includes a generally flat, plate-like or sheet-like support structure that has sufficient rigidity to provides a support for the one or more containers  1102  and the applicator  1104 . In some embodiments, each of the one or more gel containers  1102  is disposed on a first surface of the base  1106 . In some embodiments, each of the one or more gel containers  1102  (defining the one or more gel packets or pouches) is permanently affixed to the base  1106  by any suitable connection mechanism including, but not limited to adhesives, welding, bonding, one or more hooks and latches, press fittings, or the like. In some embodiments, the one or more gel containers  1102  are molded or co-molded with or on the base  1106 . 
     In some embodiments, the one or more gel containers  1102  defines at least two gel packets or pouches  1102   a  and  1102   b  that are located at opposite end portions  1106   a  and  1106   b  of the base  1106  (on opposite sides of a center portion  1106   c  of the base), as shown in  FIG.  11 A . In other embodiments, the plurality of gel pouches includes more than two gel pouches  1102   a  or  1102   b  on one side portion  1106   a  or  1106   b  of the base  1106  (on one side of the center portion  1106   c  of the base  1106 ). In other embodiments, the plurality of gel pouches includes more than two gel pouches on each side portion  1106   a  and  1106   b  of the base  1106  (on each side of the center portion  1106   c  of the base  1106 ). 
     The base  1106  is made of any suitable material that provides sufficient rigidity to operate as described herein, including, but not limited to plastic, wood, metal, ceramic, cardboard, cardstock, composite material or the like. The base  1106  provides a surface (the first surface) for supporting the one or more gel pouches  1102   a  and  1102   b  on the side portions  1106   a  and  1106   b , respectively, and is configured to bend or fold at the center portion  1106   c  to pivot the second surface of the base side portions  1106   a  and  1106   b  toward each other, with the gel pouches  1102   a  and  1102   b  located on outward facing surface (the first surface) of each of the base side portions  1106   a  and  1106   b , as shown in  FIGS.  11 B and  11 C . In the pivoted (or activated) state, a user may apply a sufficient amount of force to squeeze the one or more gel pouches  1102   a  and  1102   b  between the user&#39;s thumb and one or more fingers (to apply a compression pressure to the one or more gel pouches  1102   a  and  1102   b ), as shown in  FIGS.  11 B  and  11 C. In other embodiments, the base  1106  is configured to bend or fold at the center portion  1106   c  to move the first surface of each of those base side portions  1106   a  and  1106   b  toward each other a sufficient amount to squeeze the one or more gel pouches  1102   a  and  1102   b  between the two side portions  1106   a  and  1106   b  of the base  1106  (and apply a compression pressure to the one or more gel pouches  1102   a  and  1102   b ), as shown in  FIGS.  11 B and  11 C . In such other embodiments, the applicator  1104  may be secured to the second surface of the base  1106 , and the base  1106  may include one or more openings or passages that allow gel to flow through the base  1106  to the applicator  1104 . 
     In some embodiments, the base  1106  is made of a material or configuration (or both) that allows bending or folding at the center portion  1106   c , while the base side portions  1106   a  and  1106   b  remain relatively rigid. In some embodiments, the base  1106  is formed as a single, continuous, uniform sheet or plate of material that is foldable at the center portion  1106   c . In such embodiments, the single sheet or plate of material may include a fold line across the center portion  1106   c , defined by one or more of a marking, groove, indentation, series of perforations, or the like, to identify a desired folding orientation or to increase the flexibility of the center portion  1106   c  (or both). In other embodiments, the base side portions  1106   a  and  1106   b  are separate members that are connected together at the center portion  1106   c  by a hinge, seam or other connection structure that allows the base side portions  1106   a  and  1106   b  to be folded together, as described herein. 
     The base  1106  may have any suitable shape formed, for example, from a generally flat, plate-like or sheet-like material. In the embodiments of  FIGS.  11 A-C , the base  1106 , before activation (in an inactivated state of  FIG.  11 A ) has an hourglass-like shape or other shape that has two end portions  1106   a  and  1106   b  at opposite ends of its length dimension, where the two end portions  1106   a  and  1106   b  are wider (in a dimension perpendicular to the length dimension) than a narrower center portion  1106   c  located between the two end portions  1106   a  and  1106   b . In some embodiments, the wider end portions of the base  1106  can support a container  1102  of greater volume, while the narrower center portion can enhance the ability of the base  1106  to bend or fold into an activated state. 
     The applicator  1104  is supported in the center portion  1106   c  of the base  1106 . In some embodiments, the applicator  1104  is affixed directly to the first surface of the base  1106 , for example, between the two gel pouches  1102   a  and  1102   b . In other embodiments, the applicator  1104  is affixed to the one or more containers  1102  on the base  1106 . The applicator  1104  may be affixed to the base (or to the container(s)  1102 ) by any suitable affixing mechanism including, but not limited to welding, bonding, adhesive, one or more hooks and latches, press fittings, or the like. In some embodiments, the applicator  1104  may be made of a material and configuration that is similar to any of the applicators described herein (including, but not limited to applicators  108 ,  202 ,  808 , or  908 ). In some embodiments, the applicator  1104  includes a triangular or wedge-shaped body of foam material. In some embodiments, each of the gel pouches  1102   a  and  1102   b  has an opening or an end portion in fluid (gel) flow communication with the applicator  1104 , through which gel may be expelled from each gel pouch into or onto the applicator  1104 , when a sufficient compression pressure is applied to the gel pouches. In some embodiments, the applicator  1104  is sufficiently porous or includes one or more holes or slots through which gel expelled from the gel pouches  1102   a  and  1102   b  may pass to the exterior environment of the gel application system  1100 . 
     In its inactivated state (e.g., as shown in  FIG.  11 A ), the gel application system  1100  is arranged with the base  1106  in an unfolded or elongated and flat orientation. In the inactivated state, the gel pouches  1102   a  and  1102   b  may be in an uncompressed (or a low pressure) state, in which gel is not expelled from the gel pouches. The gel application system  1100  may be packaged, shipped, stored and transported to an environment of use, while in its inactivated state. In some embodiments, the gel application system  1100 , when in the inactivated state, has a relatively flat, elongated configuration suitable for efficient packaging, shipping and storage. 
     To activate the gel application system and cause gel to be expelled from the gel pouches  1102  onto the applicator  1104  (or directly onto a patient or subject), a user folds the gel application system  1100  and imparts a sufficient squeezing force to cause a desired volume of gel to be expelled. In some embodiments, the gel application system  1100  is configured of a size and a shape to be gripped between a thumb and one or more fingers of a user&#39;s hand, and squeezed in the activated state, to expel gel in a one-handed operation. In such embodiments, the user&#39;s thumb and fingers may contact and apply the squeezing force onto the gel pouches  1102   a  and  1102   b , as shown in  FIG.  11 C . In some embodiments, by controlling the squeezing force, the user can easily control the rate of flow of gel from the gel pouches  1102   a  and  1102   b . A typical user may have relatively fine control of the squeezing forces that the user can apply between a thumb and one or more fingers and, thus, can provide a relatively fine control of the gel flow rate. 
     In some embodiments, the one or more containers  1102  includes one or more seals that retain and seal the gel within the one or more gel pouches (e.g., gel pouches  1102   a  and  1102   b ). The one or more seals may include any suitable seal material and configuration including, but not limited to those discussed herein for example, with respect to seal  106 . In some embodiments, the one or more seal is configured to break (or otherwise open), to allow gel to be expelled out of the one or more gel pouches and onto the applicator  1104  (or directly onto the patient or subject) as described herein. In some embodiments, the one or more seals are configured to break (or otherwise open) automatically, upon the base  1106  being folded or bent in the center portion  1106   c  a sufficient amount. In some embodiments, the one or more seals are configured to break (or otherwise open) automatically, upon the user applying a squeezing force that increases the pressure of the gel within the one or more gel pouches  1102   a  and  1102   b  above a predefined amount. For example, the gel pressure may act directly on the one or more seals, to cause the one or more seals to rupture, upon the gel pressure exceeding the predefined amount or threshold. Accordingly, in some embodiments, a user can fold the base  1106  and squeeze the one or more gel pouches  1102   a  and  1102   b  to provide a sufficient force to break (or otherwise open) the seal and continue to squeeze, to expel a desired volume of gel from the one or more pouches  1102   a  and  1102   b  (e.g., onto the applicator  1104  or onto a patient or subject). 
       FIGS.  12 A- 12 C  illustrate various views of a gel application system  1100  according to further embodiments. In the embodiment of  FIGS.  12 A- 12 C , the material forming the wall of the container  1102  includes a central portion that extends along the applicator  1104  (and extends between the gel pouches  1102   a  and  1102   b ), where the central portion of the wall of the container  1102  is configured to rupture, tear or break (or otherwise open) when the base  1106  is folded toward the activation state by a sufficient amount. In some embodiments, the material of the container  1102  wall may be configured to have a thinner, weaker or breakable portion in the center portion of the container  1102  (adjacent the applicator  1104 ) as compared to other portions of the container  1102  wall. In such embodiments, the action of folding the base  1106  causes the wall of the container  1102  to be pulled or stretched over the applicator  1104  a sufficient amount to rupture, tear or break (or otherwise open) the central region of the wall of the container  1102 , as shown in  FIGS.  12 A and  12 B . In addition, the rupture, tear or break (or opening) of the central region of the wall of the container  1102  exposes at least a portion of the (or the entire) applicator  1104 , as shown in  FIGS.  12 B and  12 C . 
     Accordingly, in some embodiments, the wall of the container  1102  is configured to automatically open and allow the release of gel from one or more gel pouches formed by the container  1102  wall, and to automatically expose the applicator  1104 , when the gel application system is folded or bent from an inactivated state to an activated state. In some embodiments, gel is expelled from the one or more gel pouches, only upon the user applying a squeezing force above a defined threshold needed to sufficiently compress the one or more gel pouches, once the gel application system has been folded into an activated state. 
       FIG.  13 A  and  FIG.  13 B  illustrate views of a gel application system  1300  according to various embodiments. 
     In some embodiments, the gel application system  1300  includes a gel packet  1301  that contains a predetermined amount of gel (e.g., ultrasound gel or other gel as described herein). In some embodiments, the gel packet  1301  is made of one or more sheets of flexible material such as, but not limited to plastic, rubber, metal foil, or the like, that is folded or sealed (or both) at peripheral edges to form a pouch or pocket-like, enclosed interior volume for containing and retaining the gel. In some embodiments, the gel packet  1301  is flexible and malleable to allow a user to squeeze the gel packet  1301  to compress the interior volume of the gel packet and increase the gel pressure within the interior volume. In some embodiments, some or all of the material of the gel packet  1301  is transparent to allow a user to view the gel inside of the gel packet from outside of the gel packet. In some embodiments, the gel application system  1300  has one or more tear sections, each of which is configured to be torn away from the rest of the gel packet  1301 , to form an opening into the interior volume of the gel packet, through which gel may be expelled from the gel packet. Each tear section may include one or more lines of perforations, indentations, thin regions or weaker regions on or in the flexible material forming the gel packet  1301 , to enhance the user&#39;s ability to tear the tear section from the rest of the packet  1301 . In some embodiments, the tear section is configured to be torn off of and fully removed from the rest of the gel packet  1301 . In other embodiments, the tear section is configured to be torn partially off of the rest of the gel packet  1301 , but also remain partially attached to the gel packet  1301 . 
     In some embodiments, the gel application system  1300  has a first tear section  1302  along an entire width dimension of the gel packet  1301 . For example, the gel packet  1301  may have a generally rectangular shape, where the first tear section  1302  extends from one lengthwise edge to an opposite lengthwise edge of the generally rectangular shape, adjacent and along a widthwise edge of the generally rectangular shape. Upon tearing away the first tear section from the rest of the gel packet  1301 , the interior volume of the gel packet  1301  is opened along the entire width dimension of the gel packet  1301 , which allows for a high rate of gel flow from the gel packet  1301 . 
     In some embodiments, the gel application system  1300  has a second tear section  1304  along a corner of the gel packet  1301 , in addition to or as an alternative to the first tear section  1302 . The second tear section  1304  may have any suitable configuration for enhancing the ability of the user to tear the second tear section  1304  from the rest of the gel packet  1301  including, but not limited to, a configuration as described above for the first tear section  1304 . Upon tearing away the second tear section  1304  from the corner of the gel packet  1301 , an opening is formed to the interior of the gel packet  1301  that is smaller than the opening formed by removing the first tear section  1402 . Accordingly, the opening formed by removing the second tear section  1305  allows for a lower rate of gel flow. 
     In some embodiments, the first tear section  1302  enables fast discharge of the gel from within the gel packet  1301 , and the second tear section  1304  enable slower and more controlled discharge of the gel, as desired. In other embodiments, one or more additional or other tear sections are included at the gel packet (such as, but not limited to one or more of: a tear section along a portion or the entire length dimension of the gel packet  1301 , a tear section across one or more other corners, or tear sections across other corners but at mutually different distances from the corners to form different size openings at different corners). 
       FIG.  14 A  illustrates a side view of a gel application system  1400  according to various embodiments.  FIG.  14 B  illustrates a side view of a user utilizing the gel application system  1400  shown in  FIG.  14 A  according to various embodiments. 
     In some embodiments, the gel application system  1400  includes a gel packet  1402  that contains a predetermined amount of gel (e.g., ultrasound gel or other gel as described herein). In some embodiments, the gel packet is made of one or more sheets of flexible material such as, but not limited to plastic, rubber, metal foil, or the like, that is folded or sealed (or both) at peripheral edges to form a pouch or pocket-like, enclosed interior volume for containing and retaining the gel. In some embodiments, some or all of the material of the gel packet is transparent to allow a user to view the gel inside of the gel packet from outside of the gel packet. 
     The gel packet  1402  that has a shape that allows a user to easily grip or grab the gel packet for squeezing the gel therefrom (e.g., as shown in  FIG.  14 B ). For example, the gel packet can have a handle shape, or a shape that has a wider end portion (for easily gripping and squeezing between a user&#39;s thumb and fingers) and a narrower end portion (for extending out from between the user&#39;s thumb and finger in a easily controllable direction). 
     In some embodiments, the gel application system  1400  includes a tear section  1404  at the narrower end of the gel packet. The tear section  1404  may have a configuration similar to the tear sections  1302  and  1304  described herein. After tearing away the tear section  1404 , a user can squeeze gel from the gel application system  1400  by applying a squeezing pressure on the gel packet  1402  to discharge a desired amount of gel from the interior of the gel packet, through an opening formed by the removal of the tear section  1404 . In some embodiments, to expel the gel from the gel packet, the user pinches the wider end of the gel packet  1402 , or bends or folds the packet over. 
     In some embodiments, the gel application system  1400  is made from multiple materials that create an integrated, semi-rigid tip that aids in applying and controlling the application of gel from the gel packet  1402 . For example, the gel application system  1400  can be manufactured using two separate sheets of material that are attached to each other along their edges (e.g., via vacuum sealing, heat sealing, and the like). In some embodiments, a first sheet is made from a flexible, non-rigid material, such as, but not limited to a flexible plastic, rubber, metal foil, or the like, and may be transparent for allowing a user to view the remaining gel in the packet. In some embodiments, the second sheet is made from a more rigid material, such as, but not limited to, cardstock or cardboard, rigid plastic, metal, ceramic, composite material and the like, to provide a user more control when dispensing the gel. 
       FIG.  15 A ,  FIG.  15 B ,  FIG.  15 C ,  FIG.  15 D ,  FIG.  15 E  and  FIG.  15 F  illustrate perspective views of various gel application systems  1500 ,  1502 ,  1504 ,  1506 , and  1508  according to various embodiments. 
     Each of the gel application systems  1500 ,  1502 ,  1504 ,  1506 , and  1508  includes a packet  1510 ,  1512 ,  1514 ,  1516 ,  1518 , respectively, that contains a predetermined amount of gel therein. In some embodiments, the packet  1510 ,  1512 ,  1514 ,  1516  or  1518  may be composed of a material and configuration as described above with regard to the packet  1301  or the packet  1402 . Each of the gel application systems  1500 ,  1502 ,  1504 ,  1506 , and  1508  also includes a straw or tube  1520 ,  1522 ,  1524 ,  1526  and  1528 , respectively, for affixing to a sealed opening of the gel packet for allowing flow of the gel from within the packet, through the tube, and to outside of the gel application system. In some embodiments, affixing of the tube to the packet breaks a seal in the packet to open a pathway for the gel. In some embodiments, the tube is affixed to the packet by a threaded section of the packet on which the tube is screwed on. In other embodiments, the tube is snapped into place within the opening of the packet. In other embodiments, the tube is inserted into the opening of the packet and held in place by friction or press fitting within the opening. In some embodiments, the tube has side flanges or protrusion attached thereon to allow a user to easily grip the tube (such as, but not limited to butterfly wing shaped grips). In some embodiments, the packet is made of a material that is transparent or partially transparent to allow a user to view the contents of the packet. 
     Referring to  FIG.  15 A , the tube  1520  is configured to connect and secure to the packet  1510  by placing an end of the tube  1520  into a tube receptacle of the packet  1510 , and rotating the tube  1520  or packet  1510  relative to each other in a first direction about the longitudinal axis of the tube  1520 , and to disconnect from the packet  1510  by rotating in the opposite direction. In such embodiments, the tube  1520  and the receptacle of the packet  1510  may be configured in any suitable interface for providing connection upon rotation, including but not limited to a screw threading interface, a slot and groove interface, or the like. 
     Referring to  FIG.  15 B , in some embodiments, the gel application system  1502  includes a packet  1520  and a straw  1522  extending from the packet  1520 . In some embodiments, the packet  1520  is shaped like a handle (or shaped as described above with regard to the packet  1402 ), to fit inside a user&#39;s hand such that the user can easily squeeze the packet. In some embodiments, the straw  1522  has a relatively long lengthwise dimension, for allowing a user to reach locations on a patient or a subject that are, otherwise, hard to access (e.g., because a TCD device or other medical device may otherwise obstruct a path to the patient or the subject). In some embodiments, the tip of the straw has a wide and/or flat mouth (distal end) opposite to the end extending into the packet  1520 . 
     Referring to  FIG.  15 C , in some embodiments, the gel application system  1504  is similar to the gel application system  1500 , except that the tube  1524  is configured to puncture the packet  1514  to enable flow therefrom and through the tube. In some embodiments, the tube  1524  has a sharpened end for puncturing the gel packet  1514 . 
     Referring to  FIG.  15 D , in some embodiments, the gel application system  1506  includes a compressible gel container  1516  that has a tube-like structure. The gel container  1516  has a threaded port  1517 . The straw  1526  has a correspondingly threaded end that can be screwed onto the port  1517  of the gel container  1516 . Referring to  FIG.  15 E , in some embodiments, the gel application system  1508  includes a large tube-like gel container  1518  that includes a sealed opening at the end of the container. The sealed opening is configured to be selectively opened, for example, by puncturing or otherwise, to allow the discharge of gel from the container  1518 . The packet  1510 ,  1512 ,  1514 ,  1516 ,  1518  of each of the gel application systems  1500 ,  1502 ,  1504 ,  1506 , and  1508  has a size and is made of a material that is sufficiently flexible to allow the packet to be gripped by a user in one hand, as shown in  FIG.  15 F , and squeezed to compress the interior volume of the packet and cause a volume portion of gel to be expelled through the straw or tube  1520 ,  1522 ,  1524 ,  1526  and  1528 . 
       FIG.  16 A  illustrates a perspective view of a gel packet  1602  of a gel application system  1600  according to various embodiments.  FIG.  16 B  illustrates a perspective view of a gel packet container  1604  of the gel application system  1600  according to various embodiments.  FIG.  16 C  illustrates a side view of the gel application system  1600  including the gel packet container  1604  having the gel packet  1602  therein, according to various embodiments. 
     In some embodiments, the gel packet container  1604  includes a base portion  1604   a  and a lid portion  1604   b . The base portion  1604   a  and the lid portion  1604   b  are each made from a generally rigid material, such as, but not limited to plastic, metal, wood, cardboard, ceramic, composite material or the like. In some embodiments, the gel packet container  1604  is configured to be disposed of after use or after a predefined number of uses. The lid portion  1604   b  is coupled to the base portion  1604   a  through a hinge portion  1604   c . In some embodiments, the hinge portion  1604   c  is a living hinge that is unitary with the base portion  1604   a  and the lid portion  1604   b . In other embodiments, the hinge portion  1604   c  includes any suitable hinge structure that connects the lid portion  1604   b  with the base portion  1604   a  and allows the lid portion  1604   b  to pivot between an open and a closed position relative to the base portion  1604 . 
     The base portion  1604   a  of the gel packet container  1604  includes a receptacle region in which the gel packet  1602  may be received. In some embodiments, the base portion  1604   a  includes one or more (or a plurality) of registration features  1606  for alignment of the gel packet  1602  within the receptacle region. In some embodiments, the gel packet  1602  includes one or more (or a plurality of) registration features  1608  for alignment of the gel packet  1602  within the receptacle region of the base portion  1604   a . In some embodiments, each of the gel packet  1602  and the base portion  1604   a  include one or more (or a plurality of) registration features  1606  and  1608  for alignment of the gel packet  1602 . 
     In the embodiment of  FIGS.  16 A and  16 B , the registration features  1608  on the gel packet  1602  are a pair of slot-shaped holes or slits. In the embodiment of  FIGS.  16 A and  16 B , the registration features  1606  on the base portion  1604   a  are a pair of elongated protrusions configured to fit within the slot-shaped openings. In other embodiments, the registration features  1608  may include holes, openings, indentations or the like, of any suitable shape and arrangement, and the registration features  1606  may include shapes that correspond with or otherwise mate with the shape and arrangement of registration features  1608 . In other embodiments, the registration features  1606  may include one or more slits, holes, openings, indentations or the like, while the registration features  1608  include one or more protrusions configured to engage (or mate with) the registration features  1606 . The registration features are configured or arranged (or both) such that when the gel packet container  1604  is properly received with in the receptacle region of the base portion  1604   a , the registration features  1606  and the registration features  1608  mate. However, if the gel packet container  1604  is not properly aligned within the receptacle region of the base portion  1604   a , then the registration features  1606  and  1608  do not mate. In some embodiments, once the gel packet  1602  is properly placed and aligned within the gel packet container  1604 , the lid portion  1604   b  of the container  1604  can be closed shut over the base portion  1604   a , to enclose (or partially enclose) the gel packet  1602  within the container  1604 . 
     The gel packet  1602  may be composed of a material and configuration as described above with regard to any one or more of the packets  1301 ,  1402 ,  1510 ,  1512 ,  1514 ,  1516  or  1518 . In some embodiments, the gel packet  1602  includes an interior volume  1602   a  for containing gel, where the interior volume includes a narrowed neck portion  1602   b  and an outlet portion  1602   c . In some embodiments, the gel packet  1602  includes a tear section  1602   d  located across the outlet portion  1602   c , to seal the outlet portion (and inhibit gel from flowing from the interior volume of the gel packet  1602 , but that is removable (by tearing) to open the outlet portion  1602   c  and allow gel to be expelled from the gel packet  1602 . In some embodiments, the tear section  1602   d  on the gel packet  1602  is configured the same or similar to other tear sections described herein, such as tear sections  102   a ,  1302 ,  1304  and  1404 . The tear section  1602   d  may include one or more lines of perforations, indentations, thin regions or weaker regions on or in the flexible material forming the gel packet  1602 , to enhance the user&#39;s ability to tear the tear section, as described above. In some embodiments, the registration features  1606  on the gel packet  1602  are arranged adjacent, and on both sides of the narrowed or neck portion  1602   b  of the interior volume of the gel packet  1602 . In that manner, the registration features  1606 , when engaged with the registration features  1608 , ensure proper lateral alignment of the gel packet  1602  within the container  1604 , such that the outlet portion  1602   c  is properly aligned with an outlet opening of the container  1604 . In addition, the registration features  1606  and  1608 , when engaged, help retain the gel packet  1602  within the container  1604  and inhibit movement of the gel packet  1602 , during operation. 
     The lid portion  1604   b  of the container  1604  includes a force applicator (or squeezing) feature  1610 , that allows a user to apply a squeezing (or compression) force on the gel packet  1602  within the container  1604 , in a controlled manner. The force applicator feature  1610  includes a squeezing member  1610   a  located on the interior-facing side of the lid portion  1604   b , a trigger or handle  1610   b  located on the exterior-facing side of the lid portion  1604   b , and a central section  1610   c  connecting the squeezing member and the trigger or handle together. The central section  1610   c  of the force applicator feature  1610  extends through a slot-shaped opening  1612  in the lid portion  1604   b  and allows the force applicator feature  1610  to move (or slide) along the length of the slot-shaped opening  1612 , relative to the lid portion  1604   b . The slot-shaped opening  1612  extends along at least a portion of the length dimension of the lid portion  1604   b  (and of the container  1604 ). In some embodiments, the slot-shaped opening  1612  extends along at least a portion of the length extending from a location adjacent one end of the lid portion  1604   b  to a location adjacent the position of the registration members  1608  in the base portion  1604   a . The squeezing member  1610   a  and the trigger or handle  1610   b  are larger in width than the width of the slot-shaped opening  1612  and, thus, retain the force applicator feature  1610  on the lid portion  1604   b.    
     In some embodiments, the force applicator feature  1610 , including the squeezing member  1610   a , the trigger or handle  1610   b  and the central section  1610   c  are formed in multiple parts that are connected together. In other embodiments, the force applicator feature  1610  may be formed as a single, unitary structure. The force applicator feature  1610  may be made of one or more of any suitable materials having sufficient rigidity to operate in the manner described herein including, but not limited to plastic, rubber, metal, wood, ceramic, composite material or the like. The squeezing member  1610   a  is formed of a body having sufficient size and rigidity to impart a squeezing or compression force on gel packet  1602  located within the container  1604 , to increase the fluid (or gel) pressure in the interior volume of the gel packet  1602  to cause gel to be expelled from the gel packet  1602  when the outlet portion  1602   c  is open. In some embodiments, the squeezing member  1610   a  is moveable relative to the lid portion  1604   b , in the direction of the slot-shaped opening  1612 , between a first position in which the squeezing member  1610   a  is located adjacent one end of the container (and one end of the slot-shaped opening  1612 ) to a second position in which the squeezing member  1610   a  is located adjacent the location of the registration members  1608  (and the second end of the slot-shaped opening  1612 ). 
     In operation, a gel packet  1602  as described herein is opened (outlet portion  1602   c  opened) and placed within the container  1604 . Then the lid portion  1604   b  is closed over the base portion  1604   a  of the container  1604  while the squeezing member  1610   a  is in the first position. In that position, the squeezing member  1610   a  aligns with one end of the gel packet  1602  (the end opposite to end having the outlet portion  1602   c ) and imparts a compression force onto the gel packet  1602 . From that first position, the squeezing member  1610   a  is moveable toward the outlet portion  1602   c  end of the gel packet  1602 , along the direction of the slot-shaped opening  1612  in the lid portion  1604   b . In some embodiments, the squeezing member  1610   a  is moved by a user, upon a user imparting a sufficient force on the trigger or handle  1610   b  to move the trigger or handle  1610   b  in the direction of the outlet portion  1602   c  end of the gel packet  1602 , as shown in  FIG.  16 C . As the trigger or handle  1610   b  (and, thus, the squeezing member  1610   a ) is moved toward the outlet portion  1602   c  end of the gel packet  1602 , the squeezing member  1610   a  imparts a force onto the gel packet  1602  to cause gel to be expelled from the open outlet portion  1602   c  of the gel packet  1602 . The user may control the amount and rate of flow of gel from the gel packet  1602 , by controlling the amount and rate of movement of the trigger or handle  1610   b.    
     In some embodiments, the container  1604  includes an outlet opening through which gel expelled from the gel packet  1602  is expelled from the container  1604 , for example, onto patient or subject, or onto an applicator or the like. In some embodiments, the outlet opening of the container  1604  may be formed as a gap or open space between the base portion  1604   a  and the lid portion  1604   b , when the lid portion  1604   b  is closed over the base portion  1604   a . In other embodiments, the outlet opening of the container  1604  may be provided in the base portion  1604   a  or in the lid portion  1604   b . In some embodiments, the outlet opening of the container  1604  may form a relatively wide slot for dispensing a relatively wide band of gel or dispensing gel at a relatively fast dispensing rate. In other embodiments, the outlet opening of the container  1604  may be formed narrower, to provide a narrower dispensing band or a lower dispensing rate. 
     In some embodiments, the outlet opening of the container  1604  receives a portion of the outlet opening  1602   c  end of the gel packet  1602 , when the gel packet  1602  is properly received and registered within the container  1604 . The engagement of the registration members  1606  and  1608  as described herein can help hold the gel packet  1602  in place, such that the outlet opening  1602   c  of the gel packet  1602  remains properly aligned with the outlet opening of the container  1604 , while the squeezing member  1610   a  moves to impart a compression force on the gel packet  1602 . 
     Accordingly, the container  1604  and one or more gel packets  1602  provide a gel application system that allows a user to control the dispensing of gel from one or more gel packets  1602  in a controlled manner. In some embodiments, the gel packet container  1604  is configured to be reusable with respect to a single patient, and a user can replace gel packets  1602  within the gel packet container  1604  during use. 
       FIG.  17 A  illustrates a side view of a gel application system  1700  according to various embodiments.  FIG.  17 B  illustrates a side view of a user utilizing the gel application system  1700  shown in  FIG.  17 A  according to various embodiments. 
     In some embodiments, the gel application system  1700  includes a syphon device  1702  and a gel container  1704 . In some embodiments, the syphon device includes an elongated tube or straw section  1702   a  and a squeezable (compressible) section  1702   b . The squeezable section  1702   b  has an enclosed, hollow interior volume that is in fluid flow communication one end of the straw section  1702   a . The squeezable section  1702   b  is made of any suitable material that is sufficiently flexible and resilient to operate as described herein, such as, but not limited to rubber, plastic or the like. In some embodiments, the squeezable section  1702   b  is made of a material that is sufficiently flexible and resilient to be squeezed and compressed by the squeezing force of a user&#39;s hand, and to return to its pre-squeezed shape when the squeezing force is removed. In some embodiments, the squeezable section  1702   b  has a partially spherical or ball-shaped portion that easily fits within a user&#39;s hand. 
     The tube or straw section  1702   a  may be made of the same material as the squeezable section  1702   b , or may be made of a different material, such as a more rigid material including, but not limited to plastic, rubber, metal, ceramic, cardstock, composite material, or the like. In some embodiments, the tube or straw section  1702   a  is made of a material that is transparent or partially transparent to allow a user to view a volume of gel within the tube or straw section. In some embodiments, the tube or straw section  1702   a  also includes markings along its length dimension to identify one or more (or a plurality of) levels corresponding to amounts or volume measures of gel within the tube or straw section. The tube or straw section  1702   a  has an open end or tip through which gel contained in the tube or straw section  1702   a  may be dispensed. The open end or tip is opposite to the end connected in fluid flow communication with the interior volume of the squeezable section  1702   b . The open end or tip of the tube or straw section may include an angled or beveled edge. The angled or beveled end can provide an enlarged opening relative to a perpendicular end, for increased flow rate. Alternatively or in addition, the angled or beveled end can allow a user to apply a relatively wide band of gel from the tip of the tube or straw section  1702   a.    
     The squeezable section  1702   b  is configured to be squeezed by a user to force air or fluid from the interior volume of the squeezable section  1702   b  into the tube or straw section  1702   a , to increase the fluid pressure within the tube or straw section. Release of a squeezing force on the squeezable section  1702   b  allows the squeezable section  1702   b  to return to its un-squeezed state (and allows the interior volume of the squeezable section  1702   b  to expand), and apply a suction force on fluid within the tube or straw section. 
     The gel container  1704  includes one or more container walls and a base portion that define and surround an interior volume containing gel. The gel contained by the container  1802  may be any suitable gel used in conjunction with healthcare, including, but not limited to, ultrasound gel used in connection with ultrasound emitting devices (e.g., Transcranial Doppler (TCD) devices) and other gel as described herein with regard to gel  104 . The container (including the one or more walls and base portion) may be made as a single, unitary structure or may be made from multiple components connected together, and may be made of any suitable material or materials including, but not limited to plastic, metal, ceramic, composite material, and the like. The container  1704  has an opening at one end (the top end in  FIG.  17 A ), opposite to an end (the bottom end in  FIG.  17 A ) at which the base portion is located. The base portion may have a flat or sufficiently horizontal surface configuration to allow the container to rest on a horizontal surface (such as, but not limited to a table top surface, a tray surface, or the like), with the open end of the container  1704  facing upward. The open end of the container has a size and a shape to receive the tube or straw section  1702   a  of the syphon device  1700 , for example, as shown in  FIG.  17 A . In some embodiments, the container wall defines a container volume have a depth large enough to receive a sufficiently length of the tube or straw section  1702   a  to allow the syphon device  1700  to be supported by the container  1704  in an orientation in which the squeezable section  1702   b  is located outside of the container  1704  and can be easily gripped by a user. 
     In some embodiments, the elongated tube or straw section  1702   a  of the syphon device  1702  is submerged into the gel container such that the gel can flow from the container into the syphon device. A user may create suction to draw gel into the syphon device  1702 , by squeezing and compressing the squeezable section  1702   b  and then releasing the squeezing (compression) force from the squeezable section  1702   b  while the tip end of the tube or straw section  1702   a  is submerged in gel within the container  1704 . In some embodiments, the gel flows into the tube or straw section  1702   a , but not into the squeezable section  1702   b . In other embodiments, the gel flows into the tube or straw section  1702   a  and into the squeezable section  1702   b . Then, the user can squeeze the squeezable section  1702   b  to selectively discharge gel from the syphon device  1702  onto a patient or subject (e.g., as shown in  FIG.  17 B ). 
       FIG.  18 A  and  FIG.  18 B  illustrate various views of a gel application system  1800  according to various embodiments. 
     In some embodiments, the gel application system  1800  includes a roller applicator assembly. For example, the gel application system  1800  includes a container  1802  having an interior volume for containing a gel. The gel contained by the container  1802  may be any suitable gel used in conjunction with healthcare, including, but not limited to, ultrasound gel used in connection with ultrasound emitting devices (e.g., Transcranial Doppler (TCD) devices) and other gel as described herein with regard to gel  104 . The gel application system  1800  also includes a roller applicator  1804 , such as a roller ball attached to an end of the container and in contact with (on an interior facing portion of its surface) gel contained within the container  1802 . The roller ball of the roller applicator  1804  may fit within a socket that allows the roller ball to rotate or roll within the socket. The roller boll and socket of the roller applicator  1804  may be made of any suitable material or materials having sufficient rigidity to operate as described herein, including, but not limited to plastic, rubber, metal, ceramic, composite material, or the like. 
     The container  1802  may be made of any suitable material having sufficient flexibility and rigidity to operate as described herein, including, but not limited to plastic, rubber, metal, ceramic, composite material, or the like. In some embodiments, the container  1802  is made of a material having sufficient flexibility and resilience to be squeezed and compressed by a user&#39;s hand, and then return to its un-squeezed shape upon removal of the squeezing force. In such embodiments, a user may squeeze the container  1802  to compress and increase the fluid (or gel) pressure of the interior volume of the container  1802 , to force gel out of the container  1802  and around the roller applicator  1804 . 
     In some embodiments, the gel application system  1800  is configured such that a user may hold the container  1802  in one hand and press the roller ball of the roller applicator  1804  against a surface (e.g., a side of a patient&#39;s or subject&#39;s head) such that the roller ball becomes recessed within its socket on the container a sufficient amount to form (or enlarge) one or more openings or a circular slit along the outer surface of the roller ball, to allow gel to seep through the openings and onto the roller ball of the roller applicator  1804 . In some embodiments, the user squeezes the container to increase the fluid (or gel) pressure within the container, to push gel onto and around the roller ball of the roller applicator  1804 . As such, the user can control the release of gel onto a patient or subject via the roller applicator  1804 . 
       FIG.  19    illustrates a perspective view of a gel applicator  1900  according to various embodiments. 
     In some embodiments, the gel applicator  1900  is configured to apply gel onto a patient or subject (for example, but not limited to a patient&#39;s or subject&#39;s head) or adjust positioning of gel that is already applied. In some embodiments, the gel applicator  1900  includes a handle  1902 , a lanyard  1904 , a sponge  1906 , and an edge member  1908 . In some embodiments, the handle  1902  has a first end to which the sponge  1906  is attached and a second end (opposite the first end) to which the lanyard  1904  is attached. The edge member  1908  is attached to an edge of the sponge  1906  or is formed on an edge of the sponge  1906 . 
     In some embodiments, the edge member  1908  is made of a silicone material to define a silicone edge or tip for allowing a user to control the spreading or adjustment of gel. In other embodiments, the edge member  1908  may be made of other suitable material including, but not limited to plastic, rubber, metal, ceramic, cardstock, cardboard, composite material or the like. In some embodiments, the edge member  1908  has a generally wedge or beveled shape to form a small width distal edge. 
     The sponge  1906  may be made of any suitable material, for example, a soft, flexible, or resilient material, such as, but not limited to, closed cell foam, open cell foam, self-skinning open or closed cell foams, cast, aerated, or extruded silicone or urethane, polyurethane, or the like. The sponge  1906  may be attached to the handle  1902  in any suitable manner including, but not limited to welding, adhesives, friction or press fittings, or the like. In some embodiments, the sponge  1906  is attached to the handle  1902  by heat sealing or other mechanisms that do not require additional materials, to minimize potential contaminants. 
     The lanyard  1904  may have a string or rope-like configuration and may be made of any suitable material such as, but not limited to, nylon, plastic, fabric, cotton, metal, or the like. The lanyard  1904  may be attached to the handle  1902  in any suitable manner including, but not limited to tying, adhesives, or the like. In some embodiments, the second end of the handle  1902  has an opening through which the lanyard  1904  extends in a loop. 
     The handle  1902  may be made of any suitable material having sufficient rigidity to support the sponge  1906  and operate as described herein, including, but not limited to plastic, rubber, metal, wood, ceramic, composite material, or the like. The handle  1902  may have a length dimension of sufficient length to allow a user to grip the handle  1902  and move the sponge  1906  and the edge member  1908  along a surface of a patient or subject (e.g., along a surface of the patient&#39;s or subject&#39;s head) to apply, spread or scrape gel on the surface of the patient or subject. 
       FIG.  20 A ,  FIG.  20 B , and  FIG.  20 C  illustrate various views of a gel application system  2000  according to various embodiments. 
     In some embodiments, the gel application system  2000  includes a gel container  2002  and a flexible tip member  2004 . The gel container  2002  may be made from any suitable material for retaining gel as described herein such as, but not limited to, polymer, plastic, rubber, and the like. In some embodiments, the gel container  2002  may be made of one or more materials and a configuration that is the same or similar to that of other gel containers described herein, including gel container  102 ,  806 ,  809 ,  1002 ,  1301 ,  1402 ,  1510 ,  1512 ,  1514 ,  1516 ,  1518  or  1602 . The gel container  2002  has an interior volume containing gel. 
     In other embodiments, the container  2002  is made of one or more materials connected and sealed at one or more seams to form an enclosed, hollow interior volume. In some embodiments, the gel container  2002  is made of one sheet of flexible material that is folded and sealed at its peripheral edge to form an enclosed interior volume for containing the gel. In other embodiments, the gel container  2002  is made of two sheets of flexible material that are sealed together at their peripheral edges to form an enclosed interior volume for containing the gel. The container  2002  may be sealed along its edge or edges by any suitable mechanism including, but not limited to vacuum sealing, heat sealing, adhesives and the like. In some embodiments, the container  2002  is made of a material that is sufficiently flexible to allow a user to squeeze the container  2002  with manual force (such as by hand), to compress the pocket-like hollow interior and apply or increase the pressure of the fluid (or gel) in the interior volume of the gel container  2002 . 
     The gel contained by the container  2002  may be any suitable gel used in conjunction with healthcare, including, but not limited to, ultrasound gel used in connection with ultrasound emitting devices (e.g., Transcranial Doppler (TCD) devices) and other gel as described herein with regard to gel  104 . The gel container  2002  has an end through which gel may be expelled from the interior volume, and that is connected to flexible tip member  2004  such that the interior volume of the container  2002  is in fluid (or gel) flow communication with the tip member  2004 . 
     The flexible tip member  2004  has a first end connected to the container  2002 , in flow communication with the interior volume of the container  2002 , a second end that defines an outlet tip, and a central passage through which gel may pass from the first end to the second end and be expelled through the outlet tip. The flexible tip member  2004  may be attached to the gel container  2002  in any suitable manner including, but not limited to adhesive, welding, thermal bonding, threaded connector, snap connector, friction or press fit connection, or the like. The flexible tip member  2004  may be made of any suitable material having sufficient flexibility and resilience to operate as described herein, including, but not limited to silicon, rubber, plastic, or the like. 
     In some embodiments, the outlet tip of the flexible tip member  2004  includes a self-closing flexible tip (such as, but not limited to a flexible silicon tip) that is flexible and is configured to remain in a closed (or sealed) state with sufficient force that gel is not able to pass through the outlet tip unless an external force above a threshold is applied to the gel container  2002 . In such embodiments, the material of the flexible tip member  2004  may have a natural resilience or may be configured to provide or enhance its resilience to be in a closed (or sealed) state, unless the external force above the threshold is applied. In some embodiments, the external force is provided by a user squeezing the gel container  2002  with a sufficient force to increase the fluid (or gel) pressure within the gel container  2002  and the flexible tip member  2004 , which causes the outlet tip of the flexible tip member  2004  to open and allow gel to flow out of the outlet tip, as shown in  FIG.  20 C . However, once the external force is removed, the outlet tip of the flexible tip member  2004  closes under its own resilience as shown in  FIG.  20 A  and  FIG.  20 B . In some embodiments, the outlet tip of the flexible tip member  2004  has a slot-shaped opening that is elongated in one direction (e.g., a width dimension) relative to another direction (e.g., a height dimension). In some embodiments, the elongated shape of the slot-shaped opening and the flexible material of the outlet tip enhances the ability of the outlet tip to automatically close with sufficient force and inhibit flow of gel out of the slot shaped opening, once the external force is removed. 
     In some embodiments, the gel application system  2000  is configured such that a user may hold the container  2002  in one hand and direct the flexible tip member  2004  toward or against a surface (e.g., a side of a patient&#39;s or subject&#39;s head). In some embodiments, the user applies a force (by squeezing) the container  2002  to increase the fluid (or gel) pressure within the container, to push gel out of the container  2002  and through the central channel of the flexible tip member  2004  to, and through the outlet tip of the flexible tip member  2004 . The user may remove the applied force, to cause the outlet tip to close and reseal itself, once a suitable volume of gel has been expelled. Accordingly, the user can control the release of gel onto a patient or subject and easily stop the flow of gel by simply removing or reducing the squeezing force on the container  2002  sufficient to allow the flexible tip member  2004  to close and seal itself. 
       FIG.  21 A ,  FIG.  21 B ,  FIG.  21 C , and  FIG.  21 D  illustrate gel applicators  2100 ,  2102 ,  2104 , and  2106  according to various embodiments. 
     In some embodiments, the gel applicator  2100  includes a scoop, shell or cup-shaped body  2100   a  that is made from any suitable rigid, but partially flexible material, such as, but not limited to, plastic, silicon, rubber, cardstock, cardboard, ceramic, composite material, or the like. In some embodiments, the body  2100   a  of the gel applicator  2100  includes a ridge  2100   b  such that a user can easily grip the gel applicator  2100 . In some embodiments, the ridge  2100   b  is located on one edge and forms a handle that allows a user to grip the gel applicator  2100  and move the shell or cup-shaped body of the gel applicator  2100  as a scoop to scoop up or hold a volume of gel. In some embodiments, the ridge or handle portion  2100   b  of the gel applicator  2100  is formed thicker than other portions of the body forming the scoop, to provide greater stability and control on the handle portion. In some embodiments, the body of the gel applicator includes an edge  2100   c  that is formed relatively thin, compared to other portions of the body, for assisting with guiding, spreading or scraping gel. 
     In some embodiments, as shown in the example of the gel applicator  2102  of  FIG.  21 B , the body  2102   a  of the gel applicator may have a generally symmetrical shape (symmetrical about a center axis  2102   b  of the body). In some embodiments, as shown in the example of  FIG.  21 C , the body  2104   a  of the gel applicator may have a gel controlling mechanism along its edge. For example, the gel applicator  2104  has a thin, silicone edge  2104   b  for aiding in guiding the gel. In other embodiments, the gel controlling mechanism may include other edge configurations or materials or other features attached to the edge to allow the user to spread, layer, scrape or otherwise control the application of gel on a surface of a patient or subject. 
     In any of the embodiments of  FIG.  21 A ,  FIG.  21 B ,  FIG.  21 C , and  FIG.  21 D , gel can be scooped into, poured, or otherwise directly applied onto the shell or cup-shaped body of the gel applicator, for then applying to a patient or subject from the gel applicator. In some embodiments, gel may be applied to the patient or the subject from the gel applicator, by spreading and guiding gel from the gel applicator onto the patient or subject. In any of those or other embodiments, the body of the gel applicator may have one or more grooves or ribs  2106   a  forming a ribbed pattern, as shown in the example of the gel applicator  2106  of  FIG.  22 D . In such embodiments, gel that is applied to the body of the gel applicator is held within the grooves or between ribs and less likely to inadvertently spill from the gel applicator (e.g., when transporting the gel to the subject with the gel applicator). 
       FIG.  22 A ,  FIG.  22 B ,  FIG.  22 C , and  FIG.  22 D  illustrate various views of a gel applicator  2200  according to various embodiments. 
     In some embodiments, the gel applicator  2200  includes a handle  2202  and an application section  2204 . The handle  2202  has a length dimension, and the application section  2204  is provided on or near one end of the length dimension of the handle. The application section  2204  may be secured to the handle  2202  in any suitable manner including, but not limited to adhesive, welding, thermal boding, friction or press fit, or the like. In some embodiments, the application section  2204  is molded onto or co-molded with the handle  2202 . In some embodiments, the application section  2204  is formed integral with the handle  2202 , as a unitary body. 
     The handle  2202  may be made of any suitable material having sufficient rigidity to operate as described herein such as, but not limited to plastic, metal, wood, ceramic, composite material, cardboard, or the like. In some embodiments, the application section  2204  includes a plurality of bristles. In some embodiments, the bristles are made from any suitable material for guiding and spreading gel, such as, but not limited to, silicone, plastic, rubber, or the like. The bristles are configured and arranged to retain a volume of gel. Accordingly, when a volume of gel that is applied to the gel applicator  2200 , the gel is held within the bristles. The handle  2202  and application section  2204  are configured to provide the user with improved guiding capabilities, for controlling and guiding the application of the gel onto a surface of a patient or a subject. 
     In some embodiments, a lanyard  2206  (such as described above with regard to the lanyard  656 ) is attached to the handle  2202 . The lanyard  2206  may be attached to the handle  2202  in any suitable manner including, but not limited to the manners described above for lanyard  656 , as well as by looping the lanyard  2206  through a hole in the handle (such as, but not limited to, a hole near the second end of the handle, opposite to the end to which the application section  2204  is attached, as shown in  FIG.  22 C ). 
     In some embodiments, the handle  2202  is configured to be gripped and held by a hand of a user along its length dimension, with the application section  2204  extending out from the user&#39;s hand, for example, as shown in  FIG.  22 D . The user may apply gel to a surface of a patient or subject by contacting the surface with the application section  2204 , or with gel retained by the application section  2204  and move or swipe the surface to spread the gel along the surface in a controlled manner. 
       FIG.  23 A ,  FIG.  23 B ,  FIG.  23 C  and  FIG.  23 D  illustrate various gel applicators  2300 ,  2310 , and  2320  according to various embodiments. Each of the gel applicators  2300 ,  2310 , and  2320  includes a handle and a gel controlling mechanism on the handle. The handle has a length dimension, and the gel controlling mechanism is provided on or near one end of the length dimension of the handle. The gel controlling mechanism may be secured to the handle in any suitable manner including, but not limited to adhesive, welding, thermal boding, friction or press fit, or the like. In some embodiments, the gel controlling mechanism is molded onto or co-molded with the handle. In some embodiments, the gel controlling mechanism is formed integral with the handle, as a unitary body. 
     The handle may be made of any suitable material having sufficient rigidity to operate as described herein such as, but not limited to plastic, metal, wood, ceramic, composite material, cardboard, or the like. In some embodiments, the gel controlling mechanism is made from silicone (or other suitable material as described with regard to the gel spreading mechanisms  602  and  652  and the scraper  654 ) and is raised and has a scooped edge for guiding gel. In some embodiments, the gel controlling mechanism may have a configuration and operates as described herein with regard to the gel spreading mechanism  602  or  652 , or the scraper  654 . In other embodiments, the gel controlling mechanism may have other suitable configurations for controlling the application of gel. 
     In some embodiments, as shown in  FIG.  23 A , the gel applicator  2300  includes a handle  2302  and a gel controlling mechanism  2304  that extends around one end of the handle  2302  and has a first length portion  2304   a  that extends along a first length of one side edge of the handle  2304  and a second length portion  2304   b  that extends along a second length of a second side (opposite to the first side) of the handle  2302 . The second length is shorter than the first length. Accordingly, the gel applicator  2300  provides the user with a controlling mechanism  2304  having two different side edges, for different levels of control of application or spreading of gel. 
     In some embodiments, as shown in  FIG.  23 B , the gel applicator  2310  has handle  2312  and a gel controlling mechanism  2314  that extends around one end and about equal distances along each of both sides edges of the handle  2312 . In some embodiments, as shown in  FIG.  23 C , the gel applicator  2404  has a gel controlling mechanism that is along one edge of the handle but not along the opposite edge of the handle. 
     In any of the embodiments of  FIG.  23 A ,  FIG.  23 B , and  FIG.  23 C , the second end of the handle (the end opposite the end to which the gel controlling mechanism is attached) may include one or more features for enhancing a user&#39;s grip including, but not limited to a textured surface (having ribs, grooves, protrusions or the like), a shaped surface. For example, as shown in  FIG.  23 A  and  FIG.  23 D , the handle  2302  may include a recessed or indented surface  2302   a  having a shape for receiving a user&#39;s thumb at or near the second end of the handle, for enhancing the ability of a user to grip the handle by pinching the handle between a thumb and one or more fingers of one hand. In some embodiments, the handle may include one or more textured features within the recessed or indented surface for further enhancing the user&#39;s grip. Alternatively or in addition, the handle may include a raised peripheral lip round its outer edge, as shown in  FIG.  23 B . Alternatively or in addition, the handle may include one or more protrusions or raised elements forming a textured surface adjacent the second end of the handle, as shown in  FIG.  23 C . 
     In any of the embodiments of  FIG.  23 A ,  FIG.  23 B , and  FIG.  23 C , a lanyard (such as described above with regard to the lanyard  656  or lanyard  2206 ) may be attached to the handle in any suitable manner including, but not limited to the manners described above for lanyard  656  and lanyard  2206 . For example, the handle in any of the embodiments of  FIG.  23 A ,  FIG.  23 B , and  FIG.  23 C  may include a hole (such as a hole adjacent the second end of the handle as shown in  FIG.  23 C ) through which a lanyard may be looped as described above with regard to the lanyard  2206 . 
       FIG.  24 A  and  FIG.  24 B  illustrate various views of a gel application system  2400  according to various embodiments. 
     In some embodiments, the gel application system  2400  includes a dispenser body  2402 , a tip  2404 , and a gel cartridge  2406 . In some embodiments, the dispenser body  2402  includes a slot for receiving the gel cartridge  2406 . The dispenser body further includes a handle  2402  for allowing a user to grip the gel application system  2400 , a plunger for pushing the gel out of the gel application system  2400 , and a trigger for actuating the plunger and controlling discharge of the gel. The plunger may be spring loaded or biased to provide a pushing force on the gel cartridge  2406 , after the plunger has been pulled back against the spring or bias force and the trigger is actuated. In some embodiments, the tip  2404  is configured to be attached to the dispenser body  2402  (e.g., by screwing or snapping thereto), and the tip  2404  is tapered to focus the gel out of the narrow opening at the end of the tip  2504 . In some embodiments, the tip  2404  and the gel cartridge  2406  are disposable. In some embodiments, the tip  2404  has a configuration and is made of a material the same or similar to the tip  2004  described herein. In some embodiments, a user loads the gel cartridge  2406  into the dispenser body  2402  and pulls back the plunger. The user then pulls the trigger to actuate the plunger and excrete gel from the tip  2404  via the pushing force exerted onto the gel by the plunger. 
     Although the above description refers to gel, any suitable substance for dispensing out of the gel application systems described herein can be used. For example, any type of gel, liquid, paste, and the like can be housed within the gel application systems described herein, such as, but not limited to, medical-related substances (e.g., ultrasound gel, ointment, cream, and the like), non-medical device substances (e.g., cosmetic products, lotions, and the like), culinary products (e.g., condiments, seasoning, sauces, and the like), and so on. In some embodiments, the substance housed in the gel application systems described herein includes gel used in conjunction with ultrasound medical devices, such as, but not limited to, ultrasound scanners, ultrasound imaging, ultrasound sonography, TCD, and the like. 
     In some embodiments, the amount or volume of gel housed in the gel packets, packets, or gel application systems described herein is a predetermined amount, and the amount can vary depending on application of the systems described herein. For example, a first amount of gel can be housed within a system described herein when used for a TCD scan, while a second amount different from the first amount of gel can be housed within a system described herein when used for ultrasound sonography. In some embodiments, the gel housed within the systems described herein is color-coded based on particular purposes. For example, gel used for ultrasound sonography can have a particular color (e.g., red), gel used for TCD scanning can have a different color (e.g., purple), gel that is hypoallergenic can have another color (e.g., green), and so on. 
     The above used terms, including “held fast,” “mount,” “attached,” “coupled,” “affixed,” “connected,” “secured,” and the like are used interchangeably. In addition, while certain embodiments have been described to include a first element as being “coupled” (or “attached,” “connected,” “fastened,” etc.) to a second element, the first element may be directly coupled to the second element or may be indirectly coupled to the second element via a third element. 
     The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Unless specifically stated otherwise, the term “some” refers to one or more. All structural and functional equivalents to the elements of the various aspects described throughout the previous description that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for.” 
     It is understood that the specific order or hierarchy of steps in the processes disclosed is an example of illustrative approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged while remaining within the scope of the previous description. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented. 
     The previous description of the disclosed implementations is provided to enable any person skilled in the art to make or use the disclosed subject matter. Various modifications to these implementations will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of the previous description. In addition, features described and included in any one embodiment may be readily incorporated into any of the other embodiments, including, but not limited to a gel applicator, a gel spreader, a gel scraper, a lanyard, a self-closing nozzle, bristles, tube or straw, tear section or the like. Thus, the previous description is not intended to be limited to the implementations shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.