Abstract:
A cryogenic probe design is provided containing, for example, an inner coil injection tube with a continuous flow of circulating liquid and an outer jacket enclosing the inner coil injection tube. A transducer may monitor parameters in the region between the inner coil injection tube and the outer jacket. An outer jacket serves to prevent gas leakage. One or more embodiments of a probe design provide continuous flow for example via a continuous and controlled path from inlet to outlet and an expanded thermally transmissive region. Expanding a thermally transmissive region of the cooling zone may be provided, for example, in one or more embodiments of injection tube designs.

Description:
RELATED APPLICATIONS 
     This application is related to and claims the benefit under 35 U.S.C. §119 of U.S. provisional patent application Ser. No. 61/078,216, entitled “Tip Design for Cryogenic Probe with Inner Coil Injection Tube,” filed on Jul. 3, 2008, which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The field of this invention relates, for example, to a design for a cryogenic probe, and more specifically to various embodiments of cryogenic probes with, for example, one or more inner coil injection tubes and an outer jacket. 
     BACKGROUND 
     The use of cryogenic probes in surgical or percutaneous transcatheter applications has been in existence for quite some time. There are several designs of cryorefrigerant systems for medical applications: Joule Thomson (with or without phase change) (“JT”) and circulating liquid (“CL”) where cooling occurs through direct heat transfer without a Joule Thomson effect. For cardiovascular applications, designers may be concerned with maximizing cooling performance while at the same time detecting and/or preventing fluid egress from the probe since this may result in catastrophic gas emboli in the bloodstream. 
     In a JT system, the fluid (gas or liquid) flows though an injection line to the cooling tip and undergoes a rapid pressure drop, and potentially a phase change, expansion at the nozzle tip of the injection line. It is this expansion, called Joule Thomson effect, with or without phase change that is endothermic and creates cold in the surrounding region. A number of systems have been designed to detect and prevent gas egress in such cases: double balloons, tip pressure containment and tip pressure detection. 
     In a CL system, a refrigerant (usually liquid) flows though the injection line and returns through a return line. The tip is cooled through a direct heat exchange between the injection line and the inner surface of the tip. Unlike the JT system, the refrigerant does not undergo a Joule Thomson expansion inside the tip and cooling occurs through direct heat transfer. Early CL systems used saline or other materials that are liquid at atmospheric room temperature. New CL systems now under development, as in U.S. Pat. No. 7,083,612 to Littrup, are using high pressure fluids such as Nitrogen (so called Critical Nitrogen) or other compressed liquid gasses in the injection line. These new systems have the potential to be much more powerful but also carry the added risk for cardiovascular applications due to high pressures and associated leaks leading to gas emboli entering into the bloodstream. 
     Accordingly, a need exists for an improved system design for example, to an efficient heat transfer at the tip and to both monitor and contain a leak in the system. 
     SUMMARY OF THE INVENTION 
     One embodiment of the invention is provided, by example, with a cryogenic probe containing an inner coil injection tube with a continuous flow of circulating liquid and an outer jacket enclosing the inner coil injection tube. Also located within the outer jacket enclosure may be a temperature and/or a pressure transducer. 
     In another embodiment of the present invention, the cryogenic probe may contain an insulator or chamber that is enclosed by an outer jacket containing an inner coil injection tube. In this embodiment, the outer jacket may be designed or made of material, for example, that maintains relatively isotropic thermal and barometric conditions within the jacket and a temperature and/or pressure transducer may be located within the jacket. The outer jacket material may be polymeric, metallic or some combination thereof. The outside surface may be smooth or not depending on the mechanical characteristics desired for that particular application. 
     In another embodiment of the present invention, the cryogenic probe contains an insulator or chamber that is enclosed by an inner jacket with an inner coil injection tube partially embedded therein and an outer jacket enclosing the inner coil injection tube. In this embodiment a temperature and/or pressure transducer may be located within the jacket. 
     Certain alternative embodiments of the present invention include various alternative designs for end loops in various locations, densities, and amounts, in, for example, an inner coil element to improve upon flow and temperature transfer efficiencies, particularly for example near the tip of embodiments of the probe. Further alternative aspects may include discontinuities in the tubes to allow coolant to reach the interior surface of the probe more directly but, in certain examples, vary the degree and amount of flow by various holes, discontinuities, sizes of tubes, diameters, and amount of return tubes. Alternative embodiments of certain elements may include solid interior probes or probes with interiors filled with conductive or nonconductive materials and, in some embodiments, discontinuous coils allowing direct contact by the coolant with the inner surface of the probe between the filler material and covering surface material, varying the hollow configurations of the probe that are filled with coolant. Additional variations for certain elements may include inner barriers to form controlled containers for coolant filled by tubes that take up some portion of the interior of the probe closest to the outside surface. 
     Various aspects and embodiments of the present invention, as described in more detail and by example below, address some of the shortfalls of the background technology and emerging needs in the relevant industries. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention that together with the description serve to explain the principles of the invention. In the drawings: 
         FIG. 1  is a cut-away view of an embodiment of a cryogenic injection probe; 
         FIG. 2  is a cut-away view of an alternate embodiment of a cryogenic injection probe; 
         FIG. 3  is a cut-away view of an alternate embodiment of a cryogenic injection probe; 
         FIG. 4  is a cut-away view of an alternate embodiment of a cryogenic injection probe; 
         FIGS. 5   a - 5   c  are a side, perspective and cut-away view of an alternate embodiment of a cryogenic injection probe; 
         FIGS. 6   a - 6   b  are a perspective and close up view of an alternate embodiment of the injection tube of the present invention; 
         FIG. 7  is a perspective view of an alternate embodiment of a cryogenic injection probe; 
         FIGS. 8   a - 8   c  are perspective and cut-away views of an alternate embodiment of a cryogenic injection probe; 
         FIGS. 9   a - 9   c  are perspective and cut-away views of an alternate embodiment of a cryogenic injection probe; 
         FIGS. 10   a - 10   c  are perspective and cut-away views of an alternate embodiment of a cryogenic injection probe; 
         FIGS. 11   a - 11   b  are perspective and cut-away views of an alternate embodiment of a cryogenic injection probe; 
         FIGS. 12   a - 12   b  are perspective and cut-away views of an alternate embodiment of a cryogenic injection probe; 
         FIGS. 13   a - 13   d  are perspective and cut-away views of an alternate embodiment of a cryogenic injection probe; 
         FIGS. 14   a - 14   b  are perspective views of an alternate embodiment of a cryogenic injection probe; 
         FIGS. 15   a - 15   c  are perspective views of alternate embodiments of a cryogenic injection probe; 
         FIGS. 16   a - 16   c  are a side, perspective and cut-away views of an alternate embodiment of a cryogenic injection probe. 
         FIGS. 17   a - 17   g  are perspective and cut-away views of an alternate embodiment of a cryogenic injection probe. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention will now be described more fully with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, the embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. 
     It is to be understood that the present invention is not limited to the particular methodology, compounds, materials, manufacturing techniques, uses, and applications described herein, as these may vary. It is also to be understood that the terminology used herein is used for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention. It must be noted that as used herein and in the appended claims, the singular forms “a,” “an,” and “the” include the plural reference unless the context clearly dictates otherwise. Thus, for example, a reference to “an element” is a reference to one or more elements and includes equivalents thereof known to those skilled in the art. Similarly, for another example, a reference to “a step” or “a means” is a reference to one or more steps or means and may include sub-steps and subservient means. All conjunctions used are to be understood in the most inclusive sense possible. Thus, the word “or” should be understood as having the definition of a logical “or” rather than that of a logical “exclusive or” unless the context clearly necessitates otherwise. Structures described herein are to be understood also to refer to functional equivalents of such structures. Language that may be construed to express approximation should be so understood unless the context clearly dictates otherwise. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this invention belongs. Preferred methods, techniques, devices, and materials are described, although any methods, techniques, devices, or materials similar or equivalent to those described herein may be used in the practice or testing of the present invention. Structures described herein are to be understood also to refer to functional equivalents of such structures. 
     All patents and other publications identified are incorporated herein by reference for the purpose of describing and disclosing, for example, the methodologies described in such publications that might be used in connection with the present invention. These publications are provided solely for their disclosure prior to the filing date of the present application. Nothing in this regard should be construed as an admission that the inventors are not entitled to antedate such disclosure by virtue of prior invention or for any other reason. 
     Broadly described, the present invention improves the safety of the use of a cryogenic probe through the use, for example, of double-wall containment of liquid gas refrigerant while maximizing thermal conductivity with, for example, insulating cores and increased contact surfaces. Particular aspects of the present invention may also improve the monitoring of a refrigerant leak within the probe by placing, for example, a transducer in the region between the injection coil and outer jacket. The present invention may also enlarge or increase the thermally transmittive area at the distal end of the catheter or probe (the tip region). The liquid gas refrigerant or cryogen may stay in liquid form from entry into the tip region until exit from the tip area while the flow is continuous and controlled, in a predictable (designed) path in the cooling zone of the catheter or probe. Multiple design features illustrated can be combined. Certain examples of the contemplated improvements are described in more detail below. 
     In one embodiment, as shown in  FIG. 1 , the cryogenic probe  100  has an inner injection coil  110  which may be made of, for example, a formed tube containing a narrow bore  111  for which the refrigerant may pass through. After the refrigerant travels through the inner injection coil  110 , it exits the probe though the return line  120 . The capillary tube is preferably made of the shape memory alloy Nitinol (NiTi) but other materials may be used containing the preferred properties of high thermal conductivity and flexibility. It is, for example in certain embodiments preferred that the capillary tube be continuous to eliminate any connecting points that are generally the most common leak points. 
     Alternative embodiments, however, may more preferably contain discontinuous tubes as, for example, depicted in other embodiments below to increase the transfer of coolant more directly to the probe material closest to the tissue and potentially further enlarge the contact area between the cooling component and the tissue. This discontinuity may, for example, improve heat transfer to the tissue. 
     An outer jacket  140  encloses the coil  110  and forms the probe chamber  130 . The outer jacket is made of a thermally conductive material. In a preferred embodiment, the inner coil  110  is in contact with the outer jacket  140  to maximize the heat transfer capability of the probe. The outer jacket is in certain embodiments preferably polyurethane but can be any product thermally transmissive and also preferably flexible and perhaps multilayered. 
     A transducer  150  may be located within the probe chamber  130  and may monitor pressure or temperature or both for sudden changes in parameters, indicating a leak in the capillary tube. The transducer may be, for example MEMS or fiber optic, but can also be any other suitable pressure or temperature or combined transducer. 
     In another embodiment, as shown in  FIG. 2 , the cryogenic probe  200  has the inner injection coil  210  located within an inner jacket  260  and both are encapsulated by outer jackets  240 . The inner jacket  260  is preferably designed or made of a material to transmit pressure and temperature variations so that the transducer  250  that is also located within the inner jacket  260  may monitor the temperature or pressure or both within the inner jacket. The probe chamber  230  may be filled with an insulating or thermally reflective material to maximize the thermal transmission between the inner injection coil  210  and the outer portion of the outer jacket  240 . 
     In yet another embodiment, as shown in  FIG. 3 , the cryogenic probe  300  has the inner injection coil  310  partially embedded into an inner jacket  360 . The inner jacket  360  forms a probe chamber  330 . An outer jacket  340  encloses the coil  310  and forms a jacket chamber  370 . A transducer  350  is located within the jacket chamber  370  and may monitor pressure or temperature or both for sudden changes in parameters, indicating a leak in the capillary tube. 
     The inner jacket  360  is made of an insulating or a thermally reflective material so that the thermal transmission between the inner injection coil  310  and the outer jacket  340  is maximized. 
     In yet another embodiment, as shown in  FIG. 4 , the probe  400  contains a sensor  470  adjacent to the inner injection coil  410  which may be, for example, one or multiple ECG sensor(s). Probe  400  also includes a probe tip  490 . One or multiple pull wire(s)  481  is connected to probe tip  490  at connection point  480 . The operator of the probe  400  may be able to change the shape of the probe  400  through the pushing and pulling of the pull wire  481 . Both the sensor wire  471  and the pull wire  481  run along with the return line  420  through the middle portion of the probe  400 . An outer jacket  440  encloses the coil  410  and transducer  450  is located within the probe and may monitor pressure or temperature or both. 
       FIGS. 5   a - 5   c  depict a further embodiment wherein a single injection tube  510  may be shaped in a longitudinal manner to increase the mass of the cryogen at the distal section of the probe. The distal section may have a length, for example, between 15 mm and 50 mm and/or may be encapsulated with a metal tip or thin polymeric sleeve  540 . The space between the injection tube  510  and the sleeve  540  may be filled or packed with conductive filler materials, including, for example, conductive foam, conductive gel, steel or copper wool. In an alternate embodiment, not shown, the injection tube may be coated with a conductive material to increase thermal conductivity. 
     In another embodiment, as shown in  FIGS. 6   a - 6   b , a single injection tube  610  may be shaped in a spherical form at the distal end ( 9 F- 15 F). This spherical form may produce an ice ball as the cryogen flows through the single injection tube  610 . The tip of the probe may be encapsulated or, alternatively, the catheter or probe may be designed with the spherical section of the tube protruding from the shaft, thus allowing the injection tube to contact tissue directly. 
     A further embodiment, shown in  FIG. 7 , may comprise a single injection tube  710  which enters the metal tip  740  and then loops back out of the tip  740  through an exit tube  720 . In one exemplary embodiment it may be contemplated to include from, for example, one to twenty micro holes  715  that may be drilled, via laser or other method known in the art, into the single injection tube  710  to allow some cryogen to strategically flow onto the inner surface of the tip  740 , providing a localized “cooling boost.” A plug  735  may, for example, be provided to seal the proximal end of the probe chamber  730  formed by the metal tip  740 . The amount of cryogen flowing out of the micro holes  715  may, for example, be controlled by adjusting injection pressure and backpressure applied to the small tube  725  that returns leaked cryogen. The cryogen may, in certain embodiments, remain in liquid form. 
     In yet another embodiment, shown in  FIGS. 8   a - 8   c , the liquid cryogen may, for example, flow through the injection tube  810  to the distal end of the tip. The injection tube  810  may, for example, bring to and release cryogen to the proximal portion of the tip by various alternative embodiments. An outer jacket or sleeve  840  encapsulates the injection tube  810 . The cryogen may be released from the injection tube  810  at the distal tip and then spiral back through a grooved fitting  811  to be collected by an exit tube  820 . Cryogen may, for example, spiral on the grooves to the distal end of the tip and then may further spiral back through a different return groove such as the depicted helical groove. The spiral movement keeps a flow of liquid cryogen at the inside surface of the tip at all times. The grooved fitting may, for example, preferably be of highly conductive metal although for certain embodiments an insulating material may be desired. A fitting may, for example consist of two helical grooves concentrically aligned and connected at the distal end. 
     In a further embodiment, shown in  FIGS. 9   a - 9   c , the single injection tube  910  which may, or may not, be discontinuous or perforated, may be encapsulated by a metal cap or polymeric sleeve  940 . The liquid cryogen may flow through the injection tube  910 . An inner cap or sleeve  941  inside the metal cap or polymeric sleeve  940  may, for example, be positioned inside the single injection tube  910 .  FIG. 9   c  shows an embodiment which may improve thermal transmissivity by packing the space between the inner cap  941  and outer cap  940  with conductive filler materials  942 , such as, for example, conductive foam, conductive gel, steel or copper wool.  FIGS. 9   b  and  9   c  depict an embodiment wherein the single injection tube  910  is coated with a conductive coating or sleeve  911 , to increase thermal conductivity. In  FIGS. 10   a - 10   c , the injection tube may, for example, be double wound  1010  between the inner cap  1041  and outer cap  1040 . 
     In yet a further embodiment, shown in  FIGS. 11   a - 11   b , a double wound injection tube  1110  may, for example, be insert molded into a solid metal tip  1140 . This embodiment may maximize thermal conductivity by having fewer or no spaces, and thus less or no convection. The tip molding material may, for example, be a highly conductive metal such as silver, copper or gold. 
     In a further embodiment, shown in  FIGS. 12   a - 12   b , an injection tube  1210  may be configured to enter a closed tip  1240  and disperse, for example, liquid cryogen. Fins  1212  within the tip  1240  may be configured to distribute the cryogen, causing increased heat transfer. The liquid cryogen may exit the tip  1240  through the return line  1220 . 
     In yet a further embodiment, shown in  FIGS. 13   a - 13   d , a single continuous, or alternatively discontinuous or perforated, injection tube  1310  may loop at least once at the distal end of a tip encased in a thin polymer sleeve  1340 . One or more metal support rings  1343  may be provided to create a flexible cylindrical cooling structure. These rings may also serve as conducting fins to increase the heat flow from the surface of the sleeve  1340 . The injection tube  1300  may then flex in one plane, as shown in  FIG. 13   b . The cooling segment may also able to conform to tissue. As shown in  FIGS. 13   c - 13   d , one or more pull wires  1381  may be added to make the cooling segment deflectable. The pull wires  1381  may pass alongside the rings  1343  or through holes in the rings  1343  and be anchored to the most distal ring. 
       FIG. 14   a  depicts an embodiment of the present invention wherein a metal spring  1444  provides a flexible cylindrical cooling structure for a single continuous injection tube  1410  to pass through. Pull wires  1481  may also be incorporated and anchored at the distal end of the tip  1440 . 
     In yet a further embodiment of the invention, shown in  FIGS. 15   a - 15   c , a solid tip  1540  may be molded over the injection tube  1510 . The tip  1540  may be a highly conductive polymer which exhibits flexible characteristics and may conform to tissue. It may also be able to elastically bend when compressed. Newly engineered polymers are available, such as, for example, CoolPoly® E-series thermal conductive polymer, which has thermal conductivity up to K=100 W/mK. In comparison, stainless steel has K=20 W/mK. The highly thermal conductive polymer can, for example, be combined with other known polymers to formulate the desired flexibility.  FIG. 15   b  depicts a flexible thermal conductive polymer tip  1540  overmolded onto the injection tube  1510  with an inner cavity  1546 . This inner cavity  1546  may provide space for deflecting wires or deflection mechanisms consisting of one or more shims.  FIG. 15   c  shows a flexible thermal conductive polymer tip  1540  overmolded with holes or channels  1583  for the placement of pull wires. The pull wires may be anchored to a metal fitting at the distal end of the tip  1540 . 
     In yet a further embodiment, shown in  FIGS. 16   a - 16   c , the single component, continuous injection tube  1610  may be flared at the inner and outer diameters to create a bulb  1647  at the distal cooling section. This bulb  1647  may increase the volume capacity of liquid Nitrogen and thus increase the cooling capacity at this section of the cryogenic probe. 
     In an embodiment, shown in  FIGS. 17   a - 17   g , the exemplary single component, continuous injection tube  1710  may be surrounded by one or more fittings to, for example, increase the thermal transmissive region. These fittings may be placed with constant or variable spacing to provide desired flexibility and heat transfer capability. The fittings may be made of, for example, metal or thermal conductive polymer. In  FIGS. 17   a - 17   b , the fitting  1713  is, for example, provided as a donut shaped ring surrounding the injection tube  1710 . In a further embodiment,  FIGS. 17   c - 17   d , the thermal conductive fitting may be a curved, triangular shape  1714 , which provides for increased contact area with the outer wall of a sleeve or cap (not shown), thus allowing more heat absorption from or transfer to the tissue.  FIGS. 17   e - 17   f  show another fitting  1715  comprising one or more crescent shapes, providing more surface area contact with the inner wall of a sleeve or cap. This embodiment may also provide a cylindrical structure to the tip area, thereby supporting a flexible sleeve. In a further embodiment, a thermal conductive sleeve  1716 , may replace the interspaced fittings on the injection tube  1710 . The sleeve may be a flexible thermal conductive material and may be provided as a unitary body or in segments. 
     It should be noted that the continuous single loop injection tube as shown, for example, in  FIGS. 13   a - 15   c , may be looped more than once longitudinally. For example,  FIG. 5   a  depicts an injection tube looped five times. Depending on the size of the injection tube and the cooling segment length, the cooling segment may retain some flexibility even with multiple looping. 
     Further, it should be appreciated that the various embodiments of tubes, although depicted as cylindrical, may be provided in any shape capable of providing a passageway, including but not limited to oval, rectangular, expanded in portions, punctured or with windows or apertures. These tubes may also be configured, for example, like a bendable straw with an accordion portion to increase flexibility and heat transfer capability or adjust proximity to an outer sheath or tissue. Any of these tubes may be provided with various configurations of encapsulation or enshrouding to adjust transmissive properties and/or flexibility of the probe assembly. 
     Although the embodiments as in the figures discussed above depict, as examples, that there may be substantial space between each subsequent winding, this depiction is only for the purposes of schematically showing each of the components of the cryogenic probe. It is preferred in certain embodiments, that the windings of the coil be placed as closely as possible so as to maximize thermal conductivity but with some space to allow for probe flexibility. Additionally, the length of the portion of the inner injection coil may, for example, vary depending on the application. 
     In certain of these embodiments, the transducer may, for example, preferably be monitoring the pressure in the region between the injection coil and the outer jacket. Because of the outer jacket, a leak in the injection coil may not result in gas entering into the bloodstream. Additionally, the transducer may, for example, preferably detect the change in pressure or temperature or both of the area, for example, enclosed by the outer jacket. System monitoring equipment may then quickly shut down the system before the internal leak has any chance of spreading. 
     The embodiments described above are exemplary only. One skilled in the art may recognize variations from the embodiments specifically described here, which are intended to be within the scope of this disclosure. As such, the invention is limited only by the following claims. Thus, it is intended that the present invention cover the modifications of this invention provided they come within the scope of the appended claims and their equivalents. Further, specific explanations or theories regarding the formation or performance of electrochemical devices according to the present invention are presented for explanation only and are not to be considered limiting with respect to the scope of the present disclosure or the claims.