Patent Description:
A number of procedures exist for treating superficial lesions on human and animal skin, some examples of which are as warts, achrocordon, sun spots, and age spots,. Clinicians can remove such lesions through the localized freezing of the skin lesion tissue by using a cooling fluid, such as a liquid refrigerant. Direct spray methods for such localized freezing are governed by the "Joules Thomson" effect due to expansion of the cooling liquid. Physicians have used liquid nitrogen applications, for example, to freeze and remove lesions from a patient's skin. Conventional methods of treatment, however, often have the disadvantages of requiring specialized equipment to dispense the liquid nitrogen, the need for specialized storage devices, and the inherent hazards of handling and dispensing materials having very low boiling points, for example, as low as approximately -<NUM> in the case of liquid nitrogen.

More recently, researchers have developed various methods to treat skin lesions cryosurgically by employing a cooling fluid (e.g., a cryogenic fluid) contained in a handheld pressurized container, for example. Such cryosurgical devices generally rely upon a liquefied (compressed) gas, such as butane, propane, or dimethyl ether (DME), and others to rapidly cool an applicator tip or "bud" based on the principles of "heat of vaporization. " As the compressed gas flows to and contacts a surface of an applicator, such as a porous applicator bud, rapid evaporation of the gas causes the applicator surface to cool to temperatures that are lower than the boiling point of the liquefied gas alone. In several such methods, an effective amount of the cryogenic fluid from the pressurized container can be dispensed into a hollow supply tube having a cotton, fiber, and/or plastic foam bud located at the distal end of the supply tube. The cryogenic fluid accumulates in the applicator and upon evaporation, cools the applicator to temperatures well below freezing. The applicator then contacts the skin surface of the lesion for a period of time sufficient to reduce the temperature of the skin lesion tissue to temperatures that freeze the skin, such that permanent, irreversible rupture of the cellular membranes of the tissue occurs.

Cryosurgical devices currently utilizing the "heat of vaporization" principal in combination with compressed gases, such as dimethyl ether (DME) for example, may incur various types of complications. For example, the effectiveness of the devices can depend significantly upon the particular gas used, and rates of evaporation from the applicator may be relatively long (e.g., on the order of <NUM>-<NUM> seconds). Due to limited reservoirs for the applicator, the effective temperature of the applicator (i.e., the temperature of the applicator that is sufficient to cause freezing of the skin lesion) may be reached for only a short period of time, particularly once the applicator is placed in contact with the warmer surface of the skin lesion, thereby limiting effective freezing of the target tissue.

Various other cryosurgical devices utilize liquid nitrogen, or other liquefied gases such as, for example, chlorofluorocarbons or nitrous oxide, which have significantly lower boiling points and thus can be dispensed at colder temperatures than higher boiling point cryogens such as dimethyl ether (DME). Such cryosurgical devices, however, are generally still relatively complex in their structure, in that they use complicated valving mechanisms and dispensers to deliver the liquefied gas. Accordingly, problems can arise with such devices due to the high pressures exhibited by the gases, the complicated manner in which the cryogenic fluid is moved from the container to the dispensing tip of an applicator, the ease of use, and/or the cost associated with manufacture and/or assembly of the devices, resulting in high per-use costs.

Prior to the development of the present invention, there had yet to be developed cryosurgical devices that are both simple in structure and use, and that are capable of delivering a variety of cryogenic fluids, including more aggressive cooling agents, such as nitrous oxide, carbon dioxide, or other high pressure, low boiling point cryogens in an amount sufficient to achieve effective cryosurgical treatment.

Another complication of currently available cryosurgical devices is that the number of uses for each cryogenic device is often limited, resulting in high per-use costs for existing systems, as well as the miscalculation by system operators of treatment times. Additionally, some cryosurgical systems fail to indicate the number of treatments remaining for a given container of cryogenic liquid, with the potential result that the gas can run out mid-procedure. Additionally, with many portable cryosurgical treatment devices, the liquid gas flow is limited by gravity and therefore the device must be pointed downward to dispense cryogen properly. This often requires the patient/client to be positioned in awkward poses, with the result that the device valve is often difficult to actuate. <CIT> discloses an electrosurgical system that is capable of performing an electrosurgical procedure while cooling the surgical site before, during or after the surgical procedure. <CIT> discloses a device that performs ablation of tissue. <CIT> discloses a method and apparatus for cryogenic spray ablation of gastrointestinal mucosa. <CIT> describes a cryogenic device having a filter device fluidly connected between a valve and a cooling fluid cartridge. "<NUM>/<NUM>-way Diaphragm Valve with plastic body, pneumatically operated, <NUM>/<NUM>"-<NUM>"" (Bürkert Fluid Control Systems) discloses a pilot controlled diaphragm valve enabling high flow rates.

The portable cryosurgical device of the invention can be used in methods for the application of cryogenic liquids, including carbon dioxide and nitrous oxide or similar high pressure, low boiling point gases. The device can be used for cryosurgical destruction of unwanted skin lesions and for dispensing cryo-gases for other purposes, such as aesthetics.

The device provides a new platform that is economical, easy to use and operate, and delivers cryogenic material in any direction or orientation. The device delivers many cryogenic materials to the patients' skin, including nitrous oxide and carbon dioxide gas. The delivered materials destroy target tissue using extremely cold temperatures and the abrasives formed when the cryogenic material becomes a solid.

The device provides many additional benefits not previously realized by existing systems. The invention provides economical per-use costs over existing devices. The device provides measured and metered treatment times while providing an indication of the cryogen levels available for use. The system provides repeated uses and does not require disposable components. The system components of the device are designed and manufactured to enable multi-direction application of the cryogens to affected areas and eliminates patient and clinician contortions. With the device, clinicians can provide a focused application of cryogenic material to patients' affected areas. The small diameter application translates to a focused treatment spot and less damage to adjacent healthy tissue. Further, the device includes ergonomically-designed and manufactured actuation systems, including electro-mechanical valves and applicators.

The device provides a measured delivery of cryogenic material to an affected area. For example, the system can be configured for <NUM>- or <NUM>-second treatment durations of a cryogen, including carbon dioxide or nitrous oxide, and other low boiling point pressurized gas intended to destroy unwanted skin lesions. Time settings as low as <NUM> second to a high setting of a continuous spray may be used. The application of the cryogenic materials to the patients' affected areas using varying times allows clinicians to customize freeze-and-thaw cycle times to optimize treatment of the affected areas. Clinicians can also use an illumination source on the tip of the wand to illuminate the treatment area for accurate delivery of the cryogenic material.

The invention includes a portable cryosurgical device including a portable countertop enclosure housing a cryogen source, a cryogen flow tube connected in fluid communication with the cryogen source, and a flow path assembly. The flow path assembly includes a solenoid valve positioned between the cryogen source and the cryogen flow tube and in fluid communication with the cryogen source and the cryogen flow tube. The solenoid valve includes a valve body with a valve seat, an inlet port on an inlet side of the valve seat that introduces the cryogen from the cryogen source into the valve body, an outlet port on an outlet side of the valve seat that receives the cryogen from the valve body, and a piston movable to cause the valve seat to move from a closed position preventing passage of the cryogen from the inlet side of the valve seat to the outlet side of the valve seat to an open position permitting the passage of the cryogen from the inlet side of the valve seat to the outlet side of the valve seat. In the device of the invention, the valve body from the inlet port to the outlet port includes a dead volume of less than <NUM>µL. In some example embodiments of the invention, the valve body from the inlet port to the outlet port includes a dead volume of less than <NUM>µL, and in other example embodiments of the invention, the valve body from the inlet port to the outlet port includes a dead volume of less than <NUM>µL.

In some embodiments of the invention, the flow path assembly can include a quick connect cryogen tank adapter that includes a pin valve receiver portion, a post, and a lever, and the pin valve receiver portion receives a pin valve of a cryogen tank and actuating the lever moves the post to press on a pin in a pin valve of the cryogen tank to open the pin valve to allow the cryogen to flow into the flow path assembly. Additionally, the adapter can include a vent that allows the cryogen in the flow path between the adapter and the solenoid valve to vent.

In some embodiments of the invention, the flow path assembly further includes an in-line cryogen filter that blocks foreign material from entering the solenoid valve while allowing the cryogen to flow freely. The flow path assembly can further deliver a liquefied compressed gas from the cryogen source to a terminal end of the cryogen flow tube without a phase change occurring in the flow path.

The portable cryosurgical device of the invention delivers a metered volume of cryogen based on a predetermined dispense time. Also, the volume of cryogen delivered can be further metered based on a flow rate through the cryogen flow tube. The flow rate through the cryogen flow tube can be based on length of the cryogen flow tube and/or inside diameter of the cryogen flow tube.

The portable countertop enclosure of the device can include a treatment time selector, and the predetermined dispense time can be from one second to a continuous dispense.

The portable cryosurgical device of the invention can further include a dispensing wand that receives and houses the cryogen flow tube. The dispensing wand is omni-directional and delivers the cryogen from a wand tip independent of the orientation of the dispensing wand in relation to a target treatment area. In some embodiments of the invention, the dispensing wand delivers a liquid cryogen from the wand tip.

The portable cryosurgical device of the invention can have a cryogen source that is a single refillable cylinder, and the refillable cylinder can include an amount of liquid cryogen from twelve ounces to twenty ounces.

The portable cryosurgical device of the invention can include a cryogen source level indicating that provides an indication of an amount of the cryogen remaining in the cryogen source. The cryogen can be liquefied compressed gases at pressures of up to <NUM> MPa (<NUM> psi). In some implementations of the invention, the cryogen can be liquid carbon dioxide, nitrous oxide, R125, and/or R410A.

In another implementation of the invention, the portable cryosurgical device includes a portable countertop enclosure housing a cryogen source, a cryogen flow tube connected in fluid communication with the cryogen source, a closed cryogen flow path assembly between the cryogen source and the cryogen flow tube and in fluid communication with the cryogen source and the cryogen flow tube that receives a cryogen from the cryogen source and provides the cryogen to the cryogen flow tube, and a dispensing wand that receives and houses the cryogen flow tube, where the dispensing wand is omni-directional and delivers the cryogen from a wand tip independent of the orientation of the dispensing wand in relation to a target treatment area.

The portable electro-mechanical device of the invention provides applications of cryogenic materials to patient anatomical treatment areas for the cryosurgical destruction of unwanted skin lesions.

As shown in <FIG>, the system <NUM> includes a portable countertop enclosure <NUM> and a wand <NUM>. <FIG> shows an internal portion of the portable countertop enclosure <NUM> with the control panel <NUM> removed. Portable countertop enclosure <NUM> houses a cryogen supply (shown in <FIG>, for example), system electronics <NUM>, flow path assembly <NUM> (shown in detail in <FIG>), and wand wiring <NUM>. Cryogen flow tube <NUM> extends from the flow path assembly <NUM> through the wand mount <NUM> and out to the wand <NUM>.

The device includes many features that ensure its ease of use and facilitate human factors. As shown in <FIG>, the control panel <NUM> faces front and is angled up and slightly back for easy user interaction. In this configuration, a clinician can easily see all indicators and controls from standing and sitting positions. Four buttons <NUM>, <NUM>, <NUM>, <NUM> control the system functions. Standby actuator <NUM> activates the system <NUM> and serves as an on/off switch. Treatment time selector <NUM> sets the treatment time interval while the wand light actuator <NUM> turns on an illumination source on the tip of the wand <NUM> to illuminate the treatment area. Reset actuator <NUM> interrupts a treatment and returns the system <NUM> to a standby state. The actuators can be buttons, switches, relays, and other devices for making and breaking a connection in an electrical circuit.

The control panel <NUM> also includes a cryogen source level indicator <NUM> that provides an indication to the user of how much cryogenic material remains in the system. <FIG> shows cryogen source level indicator <NUM> as an LED bar on the control panel <NUM> in an example configuration, but the source level indicator <NUM> can include other types of level gauges indicate to the user the amount of cryogenic material available for use. The level indicator provides an indication of the amount of cryogenic material remaining in the cryogen tank. When a new tank is installed, the cryogen source level indicator <NUM> is reset to "full. " As treatments are performed, the switch PCB (reference numeral <NUM> in <FIG>) tracks the number of treatments and the duration of each treatment. The input PCB <NUM> calculates the amount of cryogenic material used in those treatments based on number and duration and subtracts it from the "full" level. The system <NUM> provides a visual indication of the amount of cryogen remaining in the cryogen tank by illuminating cryogen source level indicator <NUM> on control panel <NUM>.

As shown in <FIG>, the system <NUM> includes a faceplate <NUM>. Clinicians can use the system in a number of different treatment environments, including medical treatments, veterinary treatments, and aesthetic treatments. Aesthetic treatments can include superficially or deeply freezing unwanted topical lesions as well as delivering cold gases to stimulate circulation and increase localized oxygenation. Different system configurations provide different options, depending upon the treatment environment. For example, treatment times in the medical environment differ from treatment times in the aesthetic environment. Veterinary treatments may incorporate different cryogenic materials than aesthetic treatments. The system <NUM> is configured for the desired environment, and the example faceplates shown in <FIG> provide an indication of the system configuration with aesthetic faceplate <NUM>, veterinary faceplate <NUM>, and medical faceplate <NUM>. <FIG> shows an assembled veterinary system <NUM> with control panel <NUM> and veterinary faceplate <NUM>.

<FIG> shows a diagram of an example configuration of the system electronics <NUM>. System electronics <NUM> includes an input PCB <NUM> connected to wand PCB <NUM> via wand cable <NUM>. Switch PCB <NUM> provides connections between the input PCB <NUM> and user interface switches (standby actuator <NUM> and reset actuator <NUM> shown in <FIG>). Input PCB <NUM> provides power and logic to energize solenoid coil <NUM> to open and close solenoid valve <NUM>. System electronics <NUM> are powered by power supply <NUM> via power entry connector <NUM>. Power supply <NUM> can be a battery power supply or an AC power supply regulated to provide suitable power to input PCB <NUM> and the other system electronics. A battery <NUM> provides power to the memory circuits when the system electronics is not fully powered.

Clinicians and other users provide cryogenic material to patient treatment areas using wand <NUM> shown in <FIG>, and <FIG>. Also, <FIG> and <FIG> show example wands <NUM>, <NUM>. The wands <NUM>, <NUM> fit ambidextrously and comfortably into a user's hand and, because the device includes a closed gas flow architecture, the wands are omni-directional, allowing clinicians to treat lesions in any direction or orientation. As shown in <FIG>, treatment activation button <NUM> is positioned on the wand <NUM> so it can be activated with a light force from either the user's index finger or thumb. As shown in <FIG>, the wand <NUM> includes an illumination source <NUM>, such as an LED light for example, for extra illumination of the treatment area if the user chooses. To select the wand illumination source <NUM>, the user selects wand light actuator <NUM> on the control panel <NUM> as shown in <FIG>.

As shown in <FIG>, a user can carry the system <NUM> of the invention by one or both of the handles <NUM>, <NUM> located at the top of the portable countertop enclosure <NUM>. The design and manufacture of the system, including the center of mass of the enclosure <NUM>, ensures that the unit swings minimally and hangs as expected under the handles <NUM>, <NUM> when a user lifts the unit. As shown in <FIG>, the enclosure <NUM> includes feet <NUM>, <NUM>, <NUM>, <NUM> positioned under the enclosure to assure stability and prevent sliding when the system is in operation.

An external, low voltage power supply (reference numeral <NUM> shown in <FIG>) provides power to the system <NUM>. As shown in <FIG> and <FIG>, a power jack <NUM> is located on the back of the system (rear of enclosure <NUM>). In one example configuration, the power supplied by the external supply also maintains an internal battery (shown as reference numeral <NUM> in <FIG>) for electronics memory (not shown separately) which keeps track of cryogen usage via cryogen source level indicator <NUM>. In one example configuration, the entire system is powered by an external battery providing additional portability and ease of use.

Internal to the portable countertop enclosure <NUM>, the system <NUM> includes a cryogen source and a specially developed flow control path. <FIG> show flow path assembly <NUM> along with other internal and external system components with the portable countertop enclosure <NUM> removed.

The cryogen tank <NUM> has been developed to be durable, convenient to use, shippable, and provides an interface that is manufactured in high volume and for proven reliability. The cryogen tank <NUM> stores a volume of cryogen (cryogenic material <NUM>, for example) during shipping and storage. The cryogen tank <NUM> is housed inside the rear of the portable countertop enclosure <NUM> and connects to the flow control path (such as flow path assembly <NUM>, for example) through a pin valve (not shown separately), installed in the cryogen tank <NUM>, that seals the cryogen tank <NUM> during shipping and storage. The quick-change high pressure cylinder adapter <NUM> engages and opens the pin valve in the cryogen tank <NUM> when lever <NUM> is actuated. The quick-change high pressure cylinder adapter <NUM> works in tandem with burst disk <NUM> on the pin valve assembly <NUM> of the cryogen tank <NUM> that controls overpressure, providing additional safety measures. Cryogen tank <NUM> interfaces with a main cryogen supply valve via a thread and O-ring combination (not shown separately). When installed in the enclosure <NUM>, the top of the tank <NUM> protrudes only minimally above the handles <NUM>, <NUM> of the system enclosure <NUM> to both mechanically protect the tank <NUM> and to limit the torque a user can apply when threading the tank <NUM> to the main cryogen supply valve. A large lever <NUM> is part of the flow path assembly <NUM> and engages at the neck <NUM> of the tank <NUM> to deliver the cryogen (cryogenic materials <NUM>) to the rest of the flow path assembly <NUM>. When activated, the lever <NUM> opens the pin valve in the cryogen tank <NUM>. A flow block <NUM> supports the components of the flow path (assembly) <NUM> and includes O-ring seals <NUM>, <NUM> for the components.

As shown further in <FIG>, the cryogen tank <NUM> interfaces and seals to an adapter <NUM>. As outlined above, adapter <NUM> is a quick change, high-pressure cylinder interface with a pressure relief port for easy installation when changing the cryogen cylinder (tank <NUM>). A user does not need any special tools to exchange cryogen cylinders. The mating threads of the cryogen tank pin valve thread with the mating threads of the adapter <NUM>, and the combination assembly can be quickly changed out when the cryogen is depleted. The adapter <NUM> includes a post in a base. As a user screws the adapter <NUM> into the cryogen tank <NUM>, the pressure from the cryogen tank pushes the post to a closed (sealed) position in the adapter <NUM> that prevents cryogen gas and/or cryogen liquid from flowing out of the adapter. When the user installs the combination of the cryogen tank <NUM> and adapter <NUM> into the flow path assembly <NUM>, the lever <NUM> receives the adapter <NUM> and pushes on the post, which depresses the pin valve <NUM> in the cryogen tank <NUM> enabling the cryogen <NUM> to flow into the flow path assembly <NUM>. Solenoid valve <NUM> is normally closed, which prevents the cryogen from dispensing until the clinician initiates treatment.

To open the cryogen tank <NUM> to allow the flow of cryogenic material <NUM> through the flow path assembly <NUM>, an operator engages lever <NUM>, which in turn pushes a post in the pin valve assembly that opens the cryogen tank pin valve.

Once a user engages the lever <NUM>, the cryogenic material <NUM> from the cryogen tank <NUM> begins to flow through flow path assembly <NUM>. In-line filter <NUM> blocks any foreign material from entering the remaining flow path while allowing the cryogenic material <NUM> to flow freely.

After the system filters the cryogenic material <NUM> and assures that the pressure of the cryogenic material <NUM> is within acceptable limits, the cryogenic material <NUM> continues through the flow path assembly <NUM> to the solenoid valve <NUM>. The specifically designed high pressure electromechanical solenoid valve <NUM> provides treatment time control. The solenoid valve <NUM> handles (receives) the high-pressure cryogenic materials in the flow path and allows placement of the cryogen flow tube <NUM> very close to the solenoid valve seat <NUM>. This close placement of the cryogen flow tube <NUM> to the valve seat <NUM> provides an improved response time as measured from the time the user activates the treatment activation button <NUM> and the time the system delivers the cryogenic material to the treatment area. Previous systems included solenoid valves that did not provide the operating pressure and flow rate characteristics of the solenoid valves of the invention. The solenoid valves of the invention include improved valve seat and valve base geometries to provide substantially a zero dead volume, leading to improved response times. In some example implementations of the invention, the response time from activation of the treatment button to delivery of the cryogen to the treatment area is less than two (<NUM>) seconds. Previous systems and cryogenic valves had a much slower response times, which resulted in inaccurate patient treatment times.

The system electronics <NUM> housed in the portable countertop enclosure <NUM> triggers the solenoid valve <NUM> to allow cryogenic material <NUM> to flow for a predetermined time. For example, during manufacture, the system electronics <NUM> can be configured to provide and deliver two different treatment times. That is the amount of time that the cryogen will be delivered to the patient treatment area each time the treatment activation button <NUM> on the wand <NUM> is pushed. In one example configuration, the first treatment time is set to a five (<NUM>) second treatment of cryogenic material to the patient treatment area. Similarly, a second treatment time of delivery of cryogenic material to the patient treatment area can be configured, such as ten (<NUM>) seconds. Users can determine and program treatment times based on the clinical environment and patient needs.

Configuring the system electronics (using dip switches, integrated circuits, RC networks, oscillators, and other timing circuitry) for the predetermined times opens the solenoid valve <NUM> for that predetermined time when the clinician activates the treatment activation button <NUM> on the wand <NUM> (shown in <FIG>). The solenoid valve <NUM> operates consistently and effectively at the pressures exerted by the cryogenic material <NUM>. The valve seal (not shown separately) is designed and manufactured to avoid swelling and failure when exposed to the cryogen. That is, the valve seal maintains its original geometry when exposed to compatible cryogens. While components of any valve (body, bonnet, stem, stem seals, ball, seats, etc.) will contract and expand at different rates because of different material composition or the amount of time exposed to the cryogenic material, the solenoid valve <NUM> provides a positive cryogenic seal that inhibits cryogenic material flow when the valve <NUM> is shut. The solenoid valve <NUM> interfaces with the flow block <NUM> via a solenoid valve base <NUM>.

The solenoid valve base <NUM> holds the solenoid valve <NUM> and forms the seat against which the valve <NUM> seals. The valve base <NUM> was designed and manufactured to minimize the seal area to allow high-pressure operation. Also, the "dead volume" (the volume between the flow restrictor (i.e., the point where the flow path assembly <NUM> transitions to the cryogen flow tube <NUM>) and the valve seat <NUM>) of the valve <NUM> was minimized in the device as described above, as the solenoid valve <NUM> and cryogen flow tube <NUM> are in close proximity. The low dead volume of the valve <NUM> translates to a rapid flow response when the user actuates the treatment activation button <NUM> on the wand <NUM> and delivers the cryogenic material <NUM> to the treatment area.

Once the cryogenic material <NUM> flows through the solenoid valve <NUM>, the cryogenic material <NUM> moves through the wand mount <NUM> and leaves the portable countertop enclosure <NUM> of the system <NUM> traveling toward the wand <NUM>. The cryogenic material <NUM> flows through wand cable <NUM> via cryogen flow tube <NUM>.

As shown in <FIG>, wand cable <NUM> includes cryogen flow tube <NUM> that is a conduit for transporting cryogenic material <NUM> from the flow path assembly <NUM> to the wand and as a conduit for electrical wiring <NUM> used in concert with the treatment activation button <NUM> (shown in <FIG>, for example). As shown in <FIG>, in one example implementation of the invention, wand cable <NUM> includes the cryogen flow tube <NUM> at the central axis of the wand cable <NUM>. Arranged about the circumference of the cryogen flow tube <NUM> are wand wiring cables <NUM>(a), <NUM>(b), <NUM>(c), and <NUM>(d), which provide power and logic to the wand <NUM> from the system electronics <NUM> in the internal portion of the portable countertop enclosure <NUM>. Filler material <NUM>, such as fiberglass fillers, for example, can be used to provide additional rigidity and stability to the wand cable <NUM>. A deformable filler with lubricating properties <NUM>(b) can serve as a covering of the outer circumference of the wand wiring <NUM> and fillers <NUM>. For example, PTFE tape can be used as a covering <NUM>(b) of the wand wiring <NUM> and fillers <NUM>. A braided shield <NUM> can protect the wand wiring cables <NUM> and can also provide an electronic ground point for the cables <NUM>. Another layer of deformable filler with lubricating properties <NUM>(a), for example, PTFE tape, can cover the outer circumference of the braided shield <NUM>. A wand cable jacket <NUM> provides protection for the internal components of the wand cable <NUM>.

Cryogen flow tube <NUM> (inside wand cable <NUM>) restricts and controls the flow of the cryogenic material <NUM> so that the system <NUM> delivers the correct cryogenic material dose to the patient treatment area. In contrast to previously-available systems with dispensing devices which are limited by having to point downward in order to assure liquid cryogen flow, the cryogen flow tube <NUM> and wand cable <NUM> allows the omni-directional delivery of the cryogenic material to the treatment area and allows the user to apply cryogenic material in any direction while continually supplying liquid cryogen to the restrictor inlet in the wand mount <NUM> (i.e., the transition point from the flow path assembly to the cryogen flow tube <NUM>).

A critical design feature of cryogen delivery devices is their ability to meter the flow of high-pressure cryogenic gases that are discharged from the unit. Previous devices primarily controlled the flow of the cryogenic gases by employing large metal valves and regulators to control and dispense liquid cryogens through a (typically) small orifice. The device controls the flow of the cryogenic materials using the physical dimensions of the flow restrictor tube (cryogen flow tube <NUM>).

The device incorporates a cryogen flow tube <NUM> designed and manufactured to provide flow rates comparable to existing systems while eliminating cumbersome and problematic valving mechanisms. For example, the invention uses tubing (i.e., cryogen flow tube <NUM>) from the flow block <NUM> to the tip of the wand <NUM> to dispense cryogen. Early in development, it was initially thought that the capillary flow equation shown below would govern the design and dimensions of the tubing. Specifically, <MAT>.

Delta P is known from the bottle pressure of the cryogen. For CO<NUM> it is <NUM> psi (<NUM> kPA). For N<NUM>O it is <NUM> psi (<NUM> kPa). The pressure drop is to nominally atmosphere (<NUM> pressure) along the length of the cryogen flow tube.

In using this capillary flow equation, the dynamic viscosity of the cryogen is difficult to measure and quantify, so measurements of flow rates through relatively short tubing lengths were used to determine the expected flow rate through longer tubing.

Since µ (dynamic viscosity) is difficult to measure, Ilaboratory comparisons were used to make the cryogen flow tube length determinations. A measured experiment determined that <NUM> of <NUM>" Ø tubing (that is, <NUM> Ø, which is <NUM> radius) provided the desired flow rate of the cryogen. To determine the necessary length, L, of cryogen flow tube for <NUM>" Ø tubing (that is, <NUM> Ø, which is <NUM> radius), the capillary flow equation provided: <MAT>.

To determine the length of the <NUM>" Ø tubing, the capillary flow equation dictated:.

Using measurements of various lengths of tubing, the viscosity, µ, was eliminated as a variable in the capillary flow equation by using the ratio of the known flow for short tubing to a longer length/different diameter tubing. Since ΔP, µ, and Q are all constant for the system, the capillary flow equation relationships reduce to: <MAT>.

Solving for L2, the unknown length of <NUM>" Ø tubing, the capillary flow equation dictated: <MAT>.

Using the actual measurements provided: <MAT> <MAT> <MAT>.

Using the capillary flow equation, unexpectedly, the length of the tube is predicted to be much longer than experiments show is necessary. Specifically, the calculation predicted that a <NUM>" ID tube would need to be <NUM> long to provide the target dispense rate.

However, actual experiments showed that a tubing length of only <NUM> is the correct length to match the target flow rate. Additionally, different tubing materials and outside diameters also impacted the quality of a CO<NUM> "ice" dispersion. The choice of cryogen flow tube materials affected performance of the solenoid seal when switching between different cryogenic materials. For example, polytetrafluoroethylene (PTFE) worked well in delivering cryogenic material, but did not provide an optimal seal.

When the correct tubing material, length, and ID are chosen, the flow rate of CO2 is correct, and CO<NUM> ice is dispensed as expected. Conversely for example, if non-polymeric tubing is used, no ice sprays at all, and only CO<NUM> gas exits the cryogen flow tube. These discoveries lead to a conclusion that a phase transformation of the cryogen is taking place at some distance along the tubing flow path. This phase transformation from the liquid cryogen to a solid, in the case of CO<NUM>, is the reason that the experimental flow rates diverge from the theoretical flow rates. When the length of tubing is too long (such as when using the calculated and/or expected lengths of tubing), no ice sprays at all, and only cryogenic gas exits the cryogen flow tube. The cryogenic materials appear to gain heat as they flow along the greater length of tubing. Additionally, when the length of the cryogen flow tube is too short, the dose of cryogenic material delivered to the patient is too high-the system blasts ice onto the affected area. The ratio of the inner diameter of the cryogen flow tube to the length helps maintain the liquid state of the delivered cryogenic material.

The system of the invention incorporates the unexpected experimental observations to meet the design and performance targets for the system while ensuring ease of operation. The predicted flow path for the tubing would have been much longer and cumbersome for a practitioner to operate.

The device provides improvements in operation over existing cryosurgery systems in both usability of the device and reliability of the system. For example, the portable countertop enclosure <NUM>, wand cable <NUM>, and wand <NUM> ship separated from cryogen tank <NUM>. When setting up and configuring the system <NUM>, the user places the cryogen tank <NUM> in the rear of the portable countertop enclosure <NUM>. The user threads the cryogen tank <NUM> (including pin valve assembly <NUM>) into place until its rotation stops. An external O-ring on the pin valve assembly <NUM> seals the tank <NUM>, so the cryogen tank <NUM> properly seats with only a very light torque. Once the cryogen tank <NUM> is in place, the user lifts up the lever <NUM> to activate the adapter <NUM> to enable the flow of cryogenic material.

The lever <NUM> action opens the cryogen tank pin valve (not shown separately) and pressurizes the cryogen flow path in the flow path assembly <NUM>. The user then connects the system power supply (not shown separately). Once power is applied to the system, the user resets the cryogen source level indicator <NUM> to full, indicating installation of a new cryogen tank <NUM>. For example, in one example configuration of the invention, the user operates a small magnet, shipped with the cryogen tank <NUM>, to set the cryogen source level indicator <NUM> to "full. " As the system <NUM> is used to perform cryosurgical procedures and to treat affected patient areas, an internal memory tracks the usage of the cryogenic material <NUM> and shows an approximate amount of cryogenic material <NUM> remaining in the cryogen tank <NUM>. Finally, the user follows the treatment instructions (outlined below) to execute a single treatment, such as a ten (<NUM>) second treatment, which primes the components along the cryogen flow path. Once primed, the initial system set up is complete.

When the user is ready to begin a treatment, the user connects the system <NUM> to external power supply (not shown separately). The user presses the standby button (actuator <NUM>) to activate the system <NUM>. The user presses the treatment time button (selector <NUM>) to select the desired treatment time. When the user presses the treatment time selector <NUM>, the treatment time cycles through two pre-determined and pre-configured treatment time options. In one example configuration of the invention, the two treatment times are <NUM> seconds and <NUM> seconds. So when the user presses the treatment time selector <NUM>, the treatment time cycles from <NUM> seconds to <NUM> seconds. When the user presses the treatment time selector <NUM> again, the treatment time cycles from <NUM> to <NUM> seconds. When the treatment time is zero seconds, both treatment time <NUM> indicator <NUM> and treatment time <NUM> indicator <NUM> are off. When the treatment time cycles to <NUM> seconds (i.e., the first pre-determined and pre-configured treatment time), treatment time <NUM> indicator <NUM> illuminates. When the treatment time cycles to <NUM> seconds (i.e., the second pre-determined and pre-configured treatment time), treatment time <NUM> indicator <NUM> illuminates. As indicated above, the treatment times can be configured using the system electronics <NUM> (e.g., timing circuits, DIP switches, RC networks, etc.).

Additionally, the user can choose to illuminate the treatment area at any time by selecting the wand light actuator <NUM>. Once the user selects the desired treatment time and illuminates the treatment area, if desired, the user positions the wand <NUM> for treatment of the affected patient area and presses the treatment activation button <NUM> on the wand <NUM>. This selection initiates the treatment, allowing the cryogenic material to spray. Once the user presses the treatment activation button <NUM> on the wand <NUM>, the system <NUM> will deliver the cryogenic material <NUM> to the treatment area for the full treatment time, whether or not the user holds the treatment activation button <NUM> the entire treatment time. This allows the user to change position of the wand <NUM> as necessary to complete an effective treatment of the patient area.

Once the cryogenic material application completes (i.e., the system has delivered the cryogenic material for the full selected treatment time), the user must re-press the treatment activation button <NUM> on the wand <NUM> to initiate another delivery of the cryogenic material. Each time the user presses the treatment activation button <NUM> to start the cryogenic material delivery, the user will need to re-press the button <NUM> to initiate another spray. If the user wishes to terminate a treatment, the user presses the Reset button (actuator <NUM>). The reset actuator <NUM> places the system <NUM> back into the standby mode, stopping any initiated treatment in the process.

Claim 1:
A portable cryosurgical device comprising:
a portable countertop enclosure (<NUM>) housing a cryogen source;
a cryogen flow tube (<NUM>) connected in fluid communication with the cryogen source;
a flow path assembly (<NUM>), wherein the flow path assembly (<NUM>) includes:
a solenoid valve (<NUM>) positioned between the cryogen source and the cryogen flow tube (<NUM>) and in fluid communication with the cryogen source and the cryogen flow tube (<NUM>), wherein the solenoid valve (<NUM>) includes a valve body with:
a valve seat (<NUM>),
an inlet port on an inlet side of the valve seat (<NUM>) that introduces the cryogen (<NUM>) from the cryogen source into the valve body;
an outlet port on an outlet side of the valve seat (<NUM>) that receives the cryogen (<NUM>) from the valve body;
a piston movable to cause the valve seat (<NUM>) to move from a closed position preventing passage of the cryogen (<NUM>) from the inlet side of the valve seat (<NUM>) to the outlet side of the valve seat (<NUM>) to an open position permitting the passage of the cryogen (<NUM>) from the inlet side of the valve seat (<NUM>) to the outlet side of the valve seat (<NUM>);
characterised in that
the valve body from the inlet port to the outlet port includes a dead volume of less than <NUM>µL.