Abstract:
Apparatus for positioning at least one sensor in a body lumen, the apparatus including a fixation element, a sensor, and a connecting element that connects the sensor to the fixation element, the connecting element extending at least partially into the lumen so that the sensor is located radially inward from a wall of the lumen.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. §119 to U.S. Provisional Patent Application Ser. No. 60/536,580, entitled “Device for Fixing a Sensor in a Lumen,” filed Jan. 13, 2004, the complete contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     The present invention relates to field of medical devices and more specifically to a device for positioning a sensor in a lumen. 
     BACKGROUND 
     The use of sensors in body lumens is well known. For example, U.S. Pat. No. 4,485,813 describes a sensor that can be permanently implanted in a specific location within the human body in an implantable medical device such as a pacemaker. In other applications sensors are implanted alone in a body lumen. U.S. Pat. No. 6,645,143, 6,053,873, 6,442,413 and U.S. application 2002/0188207 describe medical monitoring sensors designed to be implanted in the vascular system and is capable of sensing and transmitting via a telemetry link to an external monitor. 
     The implanted sensors are utilized for monitoring physical, chemical or physiological parameters in the body. The aim of such sensors is to accurately monitor the desired parameter. 
     The position of the sensor within the lumen can influence the accuracy of the measurement. Positioning of a sensor facing a lumen wall can alter the sensing ability. Furthermore, positioning of a sensor pressing against the lumen wall in blood vessels may encourage responses, such as neo-intimal growth, which can influence and/or impact the long and short terms accuracy of measurements. 
     U.S. patent application publication No. 2002/0188207 discloses a device and method for anchoring a sensor at the center of the lumen. This concept addresses the issue of tissue growth. However, it is problematic to axially align multiple sensors in the same vicinity of a lumen, since a first sensor would block the further sensor(s) from blood flow through the lumen. Thus, it is desirable, and often functionally necessary, to radially and/or circumferentially off-set the sensors of a multiple sensor arrangement, so that they are not coaxially aligned. On the other hand, it is desirable, and often functionally necessary, to operably connect the individual sensors of a multiple sensor arrangement. 
     There are several medical procedures that require insertion of catheters or other devices through a body lumen and especially through the vascular system, for example, Swan-Ganz catheter to the pulmonary artery for monitoring hemodynamic parameters. Thus, a sensor implantation device should not prevent accessibility to a desired location within the vascular system. 
     SUMMARY 
     One embodiment of the invention is an apparatus for positioning at least one sensor in a body lumen, the body lumen having a wall, the apparatus including a fixation element, a sensor, and a connecting element that connects the sensor to the fixation element. The connecting element extends at least partially into the lumen so that the sensor is located radially inward from the lumen wall. Other and further embodiments and aspects of the invention are disclosed and described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be more fully understood and appreciated from the following detailed description taken in conjunction with the figures, in which: 
         FIGS. 1A-1D  are schematic illustrations of a device having a stent-like configured fixation element according to one an embodiment of the invention. 
         FIGS. 2A-2B  are schematic illustrations of a device having a coiled configured fixation element according to another embodiment of the invention. 
         FIGS. 3A-3D  are schematic illustrations of a device having a wing configured fixation element according to yet another embodiment of the invention. 
         FIGS. 4A-4C  are schematic illustrations of a device having a hook configured fixation element according to still another embodiment of the invention 
         FIG. 5  are schematic illustrations of a device having two implants according to a still further embodiment of the invention 
     
    
    
     DETAILED DESCRIPTION 
     The devices disclosed in the following detailed description enable positioning of an implant such as a sensor, a drug reservoir, or other known and/or convenient device within a lumen at a location which is between the inner lumen wall and the lumen center. 
     In one embodiment, the device includes a fixation part and an implant that is positioned between the lumen wall and the center of the lumen. The implant can be directly connected to the fixation part. The device can further include a connecting element for connecting between the fixation part and the implant and/or for positioning the implant at the desired location. The implant can be a sensor such as, for example, a pressure sensor that is implanted in blood vessel for monitoring blood pressure or any other known and/or convenient device. However, any known and/or convenient sensor can be used, including, but not limited to, a flow sensor, a radiation sensor, a temperature sensor, an electrical impedance sensor, other physical measurement sensor, an optical sensor for monitoring Hemoglobin concentrations and/or glucose concentrations or any other measurement, or any type of sensor for monitoring chemical species and/or composition, and/or an electrochemical sensor for monitoring various compounds within the bloods, for example, calcium, potassium, sodium and/or any other measurable compound, molecule, atom, and/or ion. 
     In alternate embodiments, the device can further include a second implant located either in contact with the wall or at the vicinity of the wall or in any other convenient location within a lumen. The second implant can be a second sensor such as, for example, a flow sensor for monitoring flow in the cardiovascular system or an energy source such as a battery or any other known and/or convenient device. The second implant can be connected to the first implant. For example, a first implant which is a sensor can be electrically connected, using an isolated electric wire, to a second implant which is an energy source such as battery for enabling energy transfer from the energy source to the sensor. 
     In one embodiment, a first implant, which can be a sensor, can be located between the lumen wall and the center of the lumen and a second implant, which can be an energy source, can be located in contact with the lumen wall and electrically connected to the sensor. This configuration enables miniaturizing of the first implant since the energy source is not a part of the sensor. 
     The insertion of the device into a body lumen can be performed via a catheterization procedure. The device can be mounted on a delivery system, in a compressed configuration so as to enable navigation through the lumen, and delivered through the lumen to the desired deployment site. At the desired deployment site the expandable technique and/or any other known and/or convenient method and/or mechanism. 
     Other techniques for inserting a device into a lumen, such as making an incision in the lumen and suturing the device at the desired location can be applied. Additionally, the device can be connected to other implants. 
     Reference is now made to  FIGS. 1A-1D  illustrating a device that includes a fixation element having a stent-like configuration according to an embodiment of the invention. The devices shown in the embodiments include a fixation element  100 , a connecting element  12  and a sensor  20 . For convenience and clarity, the lumen  30  is shown in cross-section. 
     In the embodiment shown in  FIG. 1A , fixation element  100  can be manufactured from a wire, a laser cut tube or a chemical etched tube or sheet made of metal, for example Nickel-Titanium alloy, stainless steel titanium, cobalt-based alloy, or a polymer including a shape memory polymer with or without the addition of radio-opaque material e.g. barium sulfate or can be manufactured from any known and/or convenient material using any known and/or convenient method and having any convenient shape. In the embodiment shown in  FIG. 1A , the struts  10  cross section can be round, oval, rectangular or any convenient shape. In the embodiment shown in  FIG. 1A , the struts are arranged in a zigzag configuration. However in alternate embodiments, the struts can have any convenient configuration. The thickness of struts  10  is in the range of 0.05-0.5 mm. However in alternate embodiments, various other thicknesses can be used. The struts can further includes ridges or hooks for preventing migration within the lumen. 
       FIG. 1A  shows fixation element  100  having a radial zigzag configuration that is in contact with the inner side of the lumen wall. The sensor  20  can be connected to a connecting element  12  for connecting sensor  20  to fixation element  100  and for positioning sensor  20  at a desired location distanced from the lumen wall. The sensor  20  can be located between the lumen wall and the center of the lumen. In some embodiments, the sensor can be distanced from the lumen wall between 0.05 mm and 0.8 r wherein r is the lumen radius. For example, for blood vessel having radius of r=10 mm the sensor can be positioned at a distance of 0.05 to 8 mm from the vessel wall. 
     In some embodiments, connecting element  12  can be made of metal such as Nickel-Titanium alloy, stainless steel, titanium, cobalt-based alloy, or using tantalum, Gold, Platinum or Platinum-Iridium for enhance radio-opacity, or a polymer including a shape memory polymer with or without the addition of radio-opaque material e.g. barium sulfate, and/or composed of any known and/or convenient material and or made in any know and/or convenient shape using any known and/or convenient method. 
     In some embodiments, connecting element  12  can be rigid so as to maintain sensor  20  at constant position or can be flexible as illustrated in  FIG. 1D , so as to enable movement of the sensor within the lumen. In alternate embodiments, sensor  20  can be connected directly to strut  10  of fixation element  100 . In selected embodiments, the sensor  20 , can be located in a position proximal to the fixation element  100  to reduce neo intima and cell proliferation. 
     In alternate embodiments, sensor  20  can be oriented parallel, perpendicular or at any other angle to the lumen wall. In still further alternate embodiments, the active face of the sensor  20  can be oriented towards the lumen center, the lumen wall or tangential and/or in any other convenient location. 
     Reference is now made to  FIG. 1B , illustrating one configuration of the device having two fixation elements  100  at both sides, proximal and distal to the sensor  20 . In the embodiment shown in  FIG. 1B , proximal and distal fixation elements  100  can be connected at one or more points and sensor  20  can be connected to fixation element  100  by one connecting element. That is, sensor  20  can be connected to the distal or proximal strut or can be connected to the distal and proximal strut. Sensor  20  can be oriented parallel, perpendicular or at any other angle to the lumen wall. The active face of the sensor  20  can be oriented towards the lumen center, the lumen wall or tangential or in any convenient orientation. In some embodiments, connecting element  12  can be rigid so as to maintain sensor  20  at constant position or can be flexible so as to allow movement of sensor  20 . 
     Reference is now made to  FIG. 1C , illustrating an alternate configuration of fixation element  100  in which the struts are configured in a closed cell zigzag arrangement. However in some embodiments, any known and/or convenient strut configuration can be used. Furthermore, it will be appreciated that other configurations can be used. 
     Reference is now made to  FIGS. 2A-2B  illustrating a device having a coiled fixation element  200  according to an embodiment of the invention. The device can include coiled configured fixation element  200 , connecting element  12  and sensor  20 . For clarity and convenience the lumen  30  is shown in cross-sectional view. 
     The coiled fixation element  200  can be manufactured from a wire, a laser cut tube or a chemical etched tube or sheet made of metal, for example Nickel-Titanium alloy, stainless steel titanium, cobalt-based alloy, or a polymer including a shape memory polymer with or without the addition of radio-opaque material e.g. barium sulfate or composed of any known and/or convenient material, in any convenient shape and/or using any known and/or convenient method. The fixation element cross-section may be round, oval, rectangular etc. The thickness of strut  10  of coiled fixation element  200  is in the range of 0.05-0.5 mm. Additionally in selected embodiments, the strut can further includes ridges or hooks for preventing migration within the lumen. 
     The coiled fixation element  200  configuration can be radial and can be in contact with the lumen wall. The sensor  20  can be connected to a connecting element  12  for connecting sensor  20  to fixation element  200  and/or for positioning sensor  20  at a desired location distanced from the lumen wall. In alternate embodiments, sensor  20  can be connected directly to coil fixation element  200 . In various embodiments, the sensor can be located between the lumen wall and the center of the lumen. In alternate embodiments the sensor can be distanced from the lumen wall between 0.05 mm and 0.8 r wherein r is the lumen radius. However in alternate embodiments, the sensor can be located at any convenient distance from the lumen wall. For example, for blood vessel having radius of r=10 mm the sensor can be positioned at a distance of 0.05 to 8 mm of the vessel wall. In selected embodiments, connecting element  12  can be made of metal such as Nickel-Titanium alloy, stainless steel titanium, cobalt-based alloy, or using tantalum, Gold, Platinum or Platinum-Iridium for enhance radio-opacity, or a polymer including a shape memory polymer with or without the addition of radio-opaque material e.g. barium sulfate, or any known and/or convenient material, in any convenient shape and manufactured in any known and/or convenient manner. In selected embodiments, connecting element  12  can be rigid so as to maintain sensor  20  at constant position or can be flexible so as to allow movement of sensor  20 . 
     The sensor  20  may be oriented parallel, perpendicular or at any other angle to the lumen wall. The active face of the sensor  20  can be oriented towards the lumen center, the lumen wall, tangential to the lumen wall or at any other convenient angle within the lumen. In selected embodiments, sensor  20  can be oriented parallel, perpendicular or at any other angle to the lumen wall. 
     Reference is now made to  FIG. 2B , illustrating a device having coiled fixation element  200  at both sides, of sensor  20 . In the embodiment shown in  FIG. 2B , proximal and distal coiled fixation element  200  can be connected at one or more points. Connecting element  12  can be rigid so as to maintain sensor  20  at constant position or can be flexible so as to allow movement of sensor  20 . Additionally, sensor  20  can be oriented parallel, perpendicular or at any other angle to the lumen wall. The active face of the sensor  20  can be oriented towards the lumen center, the lumen wall or tangential. Furthermore, sensor  20  can be oriented parallel, perpendicular or at any other angle to the lumen wall. As will be apparent to those skilled in the art, other configurations can be used. 
     Reference is now made to  FIGS. 3A-3D , illustrating a device having a wing-configured fixation element. In the embodiments shown in  FIGS. 3A-3D , the device includes wing-configured fixation element  300 , connecting element  12  and a sensor  20 . For convenience and clarity, the lumen  30  is shown in cross-sectional view. 
     The wing-configured fixation element  300  may be manufactured from a wire, a laser cut tube or a chemical etched tube or sheet made of metal, for example Nickel-Titanium alloy, stainless steel titanium, cobalt-based alloy, or a polymer including a shape memory polymer with or without the addition of radio-opaque material, e.g. barium sulfate, or can be comprised of any known and/or convenient material, can be manufactured using any known and/or convenient shape and can be made using any known and/or convenient method. 
     The struts  10  of wing configured fixation element  300  may have a round, oval, rectangular etc. cross section. The thickness of struts  10  is in the range of 0.05-0.5 mm. The thickness of the struts may be any convenient thickness. Additionally, the struts can further include ridges or hooks for preventing migration within the lumen. 
       FIG. 3A  is a three dimensional view of the device having wing configured fixation element  300  and  FIGS. 3B and 3C  illustrate longitudinal and lateral cross sections, respectively. 
     The sensor  20  may be connected to a connecting element  12  for connect sensor  20  to fixation element  300  and for position sensor  20  at a desired location distanced from the lumen wall. In other embodiment sensor  20  can be connected directly to fixation element  300 . The sensor can be located between the lumen wall and the center of the lumen. In one embodiment the sensor can be distanced from the lumen wall between 0.05 mm and 0.6 r wherein r is the lumen radius. For example, for blood vessel having radius of r=10 mm the sensor can be positioned at a distance of 0.05 to 8 mm of the vessel wall. However in alternate embodiments, the sensor can be located at any convenient location within the lumen. Additionally, connecting wire  12  can be made of metal such as Nickel-Titanium alloy, stainless steel titanium, cobalt-based alloy, or using tantalum, Gold, Platinum or Platinum-Iridium for enhance radio-opacity, or a polymer including a shape memory polymer with or without the addition of radio-opaque material e.g. barium sulfate, or any known and/or convenient material, made in any convenient shape using any known and/or convenient manufacturing process. 
     In alternate embodiments, connecting element  12  can be made of metal such as Nickel-Titanium alloy, stainless steel titanium, a polymer or any known and/or convenient material. The connecting element  12  can be rigid so as to maintain sensor  20  at constant position or can be flexible so as to enable movement of the sensor within the lumen. In alternate embodiments, sensor  20  can be connected directly to fixation element  300 . 
     In the embodiments shown in  FIGS. 3A-3C , sensor  20  can be oriented parallel, perpendicular or at any other angle to the lumen wall. The active face of the sensor  20  can be oriented towards the lumen center, the lumen wall, tangential to the lumen wall or at any other convenient angle. 
       FIG. 3D  illustrates a lateral cross section of another configuration of the wing fixation element  300 . In the configuration shown in  FIG. 3D , the sensor is at the same level as the strut. In those embodiments in which the struts  10  are made of superelastic Nickel-Titanium alloy, intermediate levels of expansion can be implemented such that the predetermined distances of the sensor from the vessel wall can be achieved. 
     Reference is now made to  FIGS. 4A-4C , illustrating a device having a hook configured fixation element according to an embodiment of the invention. The device includes hook configured fixation element  400 , connecting element  12  and a sensor  20 . Cross section of lumen  30 , for example a blood vessel, is shown. 
     Fixation element  400  can be manufactured from a wire, a laser cut or a chemical etched tube or sheet made of metal, for example Nickel-Titanium alloy, stainless steel titanium, cobalt-based alloy, or a polymer including a shape memory polymer with or without the addition of radio-opaque material e.g. barium sulfate or of any known and/or convenient material, can be manufactured in any convenient shape using any known and/or convenient method of manufacture. The strut of fixation element  400  cross section can be round, oval, rectangular or have any convenient shape The thickness of struts is in the range of 0.05-1 mm. The struts can have any convenient thickness and/or dimensions. Additionally, the struts can further includes ridges or hooks for anchoring fixation element  400  within the lumen and preventing migration within the lumen. 
       FIG. 4A  shows a device having a hook configured fixation element  400  that is hooked into the lumen wall at least at two points. Hooking can be at the longitudinal axis of the lumen as shown in  FIG. 4A  or at the transverse axis (not shown). 
     The sensor  20  can be connected to a connecting wire  12 , which is configured so as to distances the sensor from the lumen wall. The connecting wire  12  is connected to the fixation element  400 . The sensor can be located between the lumen wall and the center of the lumen. In one embodiment the sensor can be distanced from the lumen wall between 0.05 mm and 0.8 r wherein r is the lumen radius. For example, for blood vessel having radius of r=10 mm the sensor can be positioned at a distance of 0.05 to 8 mm of the vessel wall. However in alternate embodiments, the sensor can be located at any convenient location within the lumen. 
     Connecting element  12  can be made of metal such as Nickel-Titanium alloy, stainless steel titanium, cobalt-based alloy, or using tantalum, Gold, Platinum or Platinum-Iridium for enhance radio-opacity, or a polymer including a shape memory polymer with or without the addition of radio-opaque material e.g. barium sulfate or any known and/or convenient material, can have any convenient shape and can be manufactured using any convenient manufacturing process. Connecting element  12  can be rigid so as to maintain sensor  20  at constant position or can be flexible as illustrated in  FIG. 4B , so as to enable movement of the sensor within the lumen. In other embodiment sensor  20  can be connected directly to fixation element  400 . 
     The sensor  20  can be oriented parallel, perpendicular or at any other angle to the lumen wall. The active face of the sensor  20  can be oriented towards the lumen center, the lumen wall, tangential to the lumen wall or at any other convenient angle. 
     Reference is now made to  FIG. 4C , illustrating another configuration of fixation element  400  in which the fixation element  400  is inserted in the lumen similarly to the insertion of a drawing pin. The sensor  20  can be directly connected to fixation element  400  or connected via a connecting wire. 
     The sensor  20  can be oriented parallel, perpendicular or at any other angle to the lumen wall. The active face of the sensor  20  can be oriented towards the lumen center, the lumen wall, tangential to the lumen wall or any other convenient angle. Additionally, it will be appreciated that other configurations can be used. 
     Reference is now made to  FIG. 5  which is a schematic illustration of a device having two implants according to an embodiment of the invention. The device includes a fixation element  100 , a first implant  20 , a second implant  22 , and a connecting element  12 . For convenient and clarity, the lumen, which can be a blood vessel, is shown in cross-section. 
     It will be appreciated that fixation element  100  can have any other configuration such as, for example, coil, wing, hook and/or any other known and or convenient configuration. 
     A first implant  20  may be located between the lumen wall and the center of the lumen. First implant  20  can be distanced from the lumen wall between 0.05 mm and 0.8 r wherein r is the lumen radius. For example, for blood vessel having radius of r=10 mm the first implant can be positioned at a distance of 0.05 to 8 mm of the vessel wall. Second implant  22  can be in contact with the lumen wall or distances from the lumen wall. However in alternate embodiments, the first and second implants can be located at any convenient locations within the lumen and relative to each other. 
     The first implant  20  and second implant  22  may be connected by connecting element  12 . Second implant  22  can be directly connected to fixation element  100  or connected through an additional connecting element. 
     The connecting element  12  may be made of metal such as Nickel-Titanium alloy, stainless steel titanium, cobalt-based alloy, or using tantalum, Gold, Platinum or Platinum-Iridium for enhance radio-opacity, or a polymer including a shape memory polymer with or without the addition of radio-opaque material e.g. barium sulfate, or of any other know and/or convenient material. 
     The connecting element  12  may be rigid so as to maintain first implant  20  at constant position or can be flexible so as to enable movement of first implant  20  within the lumen. Connecting element  12  that connects first implant  20  to second implant  22  can be a metallic or a plastic tube that includes an electric wire for enabling electric communication between first and second implants. The connection between first implant  20  and second implant  22  can be achieved using mechanical means, crimp, adhesives, welding or any other convenient mechanism and/or material. In alternate embodiments, the connection between the first implant  20  and second implant  22  can be wireless, wired or made in any other known and/or convenient manner. Furthermore, in embodiments in which the second implant  22  is physically connected with the first implant and/or the fixation element  100 , the connection element can support both the first implant and the second implant. Alternately, each implant can have an separate connection element  12  to connect the implant with the fixation element. 
     In one embodiment first implant  20  can be a sensor such as pressure sensor and second implant  22  can be an energy source such as a battery. The sensor and the battery can be connected by electric wire for enabling energy transfer from the battery to the sensor. 
     While the invention is susceptible to various modifications, and alternative forms, specific examples thereof have been shown in the drawings and are herein described in detail. It should be understood, however, that the invention is not to be limited to the particular embodiments or methods disclosed, but to the contrary, the invention is to cover all modifications, equivalents and alternatives falling within the scope of the appended claims.