Patent Description:
Cryosurgical probes are instruments use in medical procedures. One such procedure is cryoablation. During cryoablation, an extremely cold fluid (liquid, gas, mixed, or other phase) may be passed through a probe in thermal contact with a target tissue. Heat from the tissue passes from the tissue, through the probe, and into the fluid that removes heat from the targeted tissue. This removal of heat causes tissue to freeze, resulting in the destruction of the targeted tissue. The thermal performance of the probe depends on the rate at which it can remove heat from the tissue.

<CIT> discloses a cryosurgical instrument that includes: an external shaft with a cryotip; a heat exchanger that cools a portion of the external shaft and the tip when cryogen is received thereby; and a flow diverter that receives a flow of cryogen, that splits the received flow of cryogen into two or more split cryogen flows, and that delivers the split cryogen flows to the heat exchanger, the flow diverter including a first passage with one or more inlet ports at an upstream side of the diverter that receive the flow of cryogen and two or more outlet ports at a downstream side of the diverter and in fluid communication with the heat exchanger.

<CIT> discloses a cryosurgical device including: a tubular housing; a cryogen supply passage; a heat exchange enhancing member in the housing, disposed along a longitudinal axis of the housing; an annular cooling passage between the heat exchange enhancing member and the tubular housing; a tip cooling and cryogen flow directing section that transmits a temperature of a cryogen flow to the tip, and an insulation element in the tubular housing.

<CIT> discloses a cryocatheter for treatment of tissue includes a coolant line communicating with a cryochamber having a coolant receiving interior and a thermally conductive wall for contacting and conductively treating tissue. A return line returns spent coolant, and an insert or partition in the cryochamber conditions flow or channels fluid from the coolant line to the return line to enhance the rate or uniformity of cooling. The partition may extend axially to define an elongated sub-chamber which is preferentially cooled, or it may isolate one side to define an uncooled side of the cryochamber. The partition may extend axially to define a sub-chamber extending along a segmented length around a partial circumference of the catheter tip, or may channel the coolant from a central region outwardly against the peripheral wall of the cryochamber. The return line may be a vacuum return line.

According to a first aspect of the present invention, there is provided a probe as defined in claim <NUM>. According to a second aspect of the present invention, there is provided a system as defined in claim <NUM>.

In some embodiments the second and third members comprise different materials.

Some embodiments include an insulating member configured to surround the second member.

The embodiments described herein are directed to cryosurgical probes that have improved thermal performance over existing designs. The improved performance of the embodiments described herein can result in shorter times to cool and freeze tissues, freeze larger volumes of tissues, or both. Increased thermal performance also results in using less fluid for a given procedure, resulting in both cost savings and lowering the outlet mass flowrate of the fluid.

The probe may be coupled to a fluid supply and return, and fluid may flow within the probe, including within the passage defined between the first and third members.

The features and advantages of the present disclosures will be more fully disclosed in, or rendered apparent by the following detailed descriptions of example embodiments. The detailed descriptions of the example embodiments are to be considered together with the accompanying drawings wherein like numbers refer to like parts and further wherein:.

The description of the preferred embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of these disclosures. While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments are shown by way of example in the drawings and will be described in detail herein. The objectives and advantages of the claimed subject matter will become more apparent from the following detailed description of these exemplary embodiments in connection with the accompanying drawings.

It should be understood, however, that the present disclosure is not intended to be limited to the particular forms disclosed. The terms "couple," "coupled," "operatively coupled," "operatively connected," and the like should be broadly understood to refer to connecting devices or components together either mechanically, electrically, wired, wirelessly, or otherwise, such that the connection allows the pertinent devices or components to operate (e.g., communicate) with each other as intended by virtue of that relationship.

<FIG> illustrates perspective view of a probe <NUM> in accordance with some embodiments presented herein. Probe <NUM> has a first member <NUM> that has a first end portion <NUM> and a second end portion <NUM>. First member <NUM> may have elongated, hollow structure extending from the first end portion <NUM> to the second end portion <NUM>. This structure may be tubular, having a generally circular inner and outer diameters, and may have a generally constant inner and outer dimensions (e.g., radii) between the first end portion <NUM> and second end portion <NUM>. The first end portion <NUM> is coupled to a handle <NUM>. The first end portion <NUM> may be referred to as the proximal end of the first member <NUM> because of this connection to the handle <NUM>. Likewise, second end portion <NUM> may be referred to the distal end of the first member <NUM> because it is more distant from the handle <NUM> as well as other equipment (e.g., a fluid supply, a fluid return, electrical connections for temperature sensors, etc.).

The first member <NUM> may comprise various materials including stainless steel, Inconel, titanium, or other materials.

Handle <NUM> serves two primary functions. First, the handle <NUM> improves a surgeon's ability to physically manipulate the probe location and orientation. Second, the handle <NUM> may provide physical connections between the inlet and outlet fluid flow paths within the first member <NUM> and a fluid supply and a fluid return, respectively, as well as for any electrical connections between components of the first member <NUM> and support equipment. These connections may be physically grouped together in a bundle <NUM> that may be operably coupled to cryogen source <NUM> (which may include a fluid return, or the return may be separated therefrom), console <NUM> (cryogen source <NUM> may be integrated with console <NUM>).

Fluids utilized by probe <NUM> may include, but are not limited to, argon, gaseous nitrogen, helium, refrigerants, liquid nitrogen, and other fluids.

<FIG> is a perspective, cutaway view of the second end portion <NUM> of a probe <NUM>. The first member <NUM> is coupled to a tip <NUM> at the extreme distal end of probe <NUM>. Tip <NUM> may be rounded, or it may be sharpened to aid movement of the probe through tissue. Tip <NUM> may have a surface <NUM> that engages a surface <NUM> of the first member <NUM>. Once engaged, the tip <NUM> may be secured to the first member <NUM>. As shown In <FIG>, the surface <NUM> of tip <NUM> may be located on a flange that engages an inner surface <NUM> of the first member <NUM>, although other arrangements may be made. The Tip <NUM> may have an inner surface <NUM> that this conical, as shown in <FIG>, flat, rounded, or hollow.

Also shown in <FIG> is the second member <NUM>. Second member <NUM> may provide at least part of the pathway for fluid from the fluid supply to the probe tip <NUM>. The second member <NUM> is positioned within first member <NUM> such that the second member <NUM> extends within the first member <NUM>. This extension may be adjacent to the second end portion <NUM> of probe <NUM>. This extension may be along a longitudinal axis of the first member <NUM>, around which the second member <NUM> may be centered. However, all embodiments are not so limited, and in some embodiments the second member <NUM> may extend generally along the longitudinal axis of the first member <NUM> but be displaced from the longitudinal axis. In some embodiments, the second member <NUM> may extend from the handle <NUM> at the first end portion <NUM> almost to the probe tip <NUM>. The second member <NUM> has an elongated, hollow structure and is tubular. Second member <NUM> may be comprised of various materials including stainless steel, copper, Inconel, titanium, brass ceramic, or other materials.

Like the second member <NUM>, the third member <NUM> may be have a hollow structure that extends along the longitudinal axis of first member <NUM>, and it may be generally tubular. The third member <NUM> is disposed outward, and may radially circumscribe the second member <NUM>, along at least a portion of the extension of the second member <NUM>. In some embodiments, the third member <NUM> may be in contact with and secured to the second member <NUM>, for example, by brazing. A distal end <NUM> of the third member <NUM> substantially encloses a portion of the second member <NUM>, for example, by radially circumscribing the second member <NUM>. Both the second member <NUM> and the third member <NUM> have a distal end <NUM> and <NUM>, respectively, forming a surface that is generally perpendicular to the longitudinal axis of the first member <NUM>. As shown in <FIG>, these distal ends <NUM> and <NUM> of the second member <NUM> and third member <NUM>, respectively, may be coplanar with one another, although such an arrangement of the distal ends <NUM> and <NUM> of the second member <NUM> and third member <NUM> is not in accordance with the claimed invention.

The third member <NUM> may comprise stainless steel, copper, ceramic, Inconel, titanium, brass, plastic or other materials.

<FIG> is an end-view cross section of a probe <NUM> in accordance with some embodiments, although this figure omits the second member <NUM>. As illustrated, the third member <NUM> has an outer surface <NUM> that engages the inner surface <NUM> of the first member <NUM> at one or more points <NUM>. The third member <NUM> may be constructed such that it has an outer dimension 'D' that is sufficiently near to an inner dimension of the first member <NUM> such that the third member <NUM> is held in position with the first member <NUM>. The outer surface <NUM> of the third member <NUM> may also have one or more sections <NUM> that have a dimension, measured across the longitudinal axis of the first member <NUM>, that is less than the outer dimension 'D'. This section(s) <NUM>, points of engagement <NUM>, and the inner surface <NUM> of the first member <NUM> together define a passage <NUM> that may extend along a longitudinal length of the third member <NUM>. This passage(s) <NUM> may be an annular passage. Section(s) <NUM> may be formed by machining the outer surface <NUM> of the third member <NUM>.

In operation, a fluid may flow through the passage(s) <NUM> between the third member <NUM> and the first member <NUM> after having first passed through the second member <NUM> and a region near tip <NUM>. This region may provide for the expansion of the fluid. By designing the passage(s) <NUM> with a small cross-sectional area, the bulk of the cooling fluid is closer to the inner surface <NUM> of the first member <NUM> than in designs (such as that referenced below) that use larger passages. Additionally, the velocity of the fluid in these passages is higher than in older designs in which the fluid passages have larger cross-sectional areas, such as that seen in <CIT>, thereby reducing fluid boundary layer thickness and promoting heat transfer between the fluid and the first member <NUM> that is in thermal communication with surrounding tissue. Both of these features contribute to the improved thermal performance of the probes disclosed herein.

In some embodiments, some of the passages <NUM> may provide for an incoming fluid flow path from the proximal to the distal end of probe <NUM>, replacing some or all of the function and use of the second member <NUM> as describe above. In some embodiments, some of the other passages <NUM> may provide for an outgoing fluid flow path from the distal to proximal ends of probe <NUM>. In some embodiments, all of the passages <NUM> may be provide an inlet fluid flow path and second member <NUM> may provide the outlet fluid flow path.

The inventor has found that the location of the cross-sectional area of the passage(s) <NUM>, relative to the inner surface <NUM> of the first member <NUM>, has a significant effect on thermal performance. These cross-sectional area(s) of the passage(s) <NUM> are taken perpendicular to the longitudinal (major) axis of the first member <NUM>. This relative positioning of the cross-sectional area <NUM> of the passage(s) <NUM>, as seen in <FIG>, can be defined by the percentage of the cross-sectional area located between an inner surface <NUM> of the first member <NUM>, and a boundary <NUM> located inwardly from the inner surface <NUM> of the first member <NUM>. This boundary is inwardly offset from the inner surface <NUM> of the first member <NUM> by a distance 'D2' that is <NUM>% of the largest inside cross sectional radius defined by the inner surface <NUM> of the first member <NUM>. For example, in the case of a first member <NUM> having a circular inner cross section, the boundary is a circle that has a diameter that is <NUM>% of the inside diameter of first member <NUM>. Significant improvements in thermal performance have been observed when at least <NUM>% of the total cross-sectional area of the passage(s) <NUM> is located in this region between the inner surface <NUM> of the first member <NUM> and this boundary. In some embodiments, at least <NUM>% of the total cross-sectional area of the passage(s) <NUM> is located in this same region. In some embodiments, at least <NUM>% of the total cross-sectional area of the passage(s) <NUM> is located in this region. In some embodiments, at least <NUM>% of the total cross-sectional area of the passage(s) <NUM> is located in this region.

The inventor has also found that particular ratios of the cross-sectional area of the passage(s) <NUM> to the cross-sectional area of the first member <NUM> exhibit improvements in the thermal performance of probe <NUM>. In these ratios, the inner surface <NUM> of the first member <NUM> defines the cross-sectional area within the first member <NUM>. The total cross sectional flow area of the passage(s) <NUM>, taken perpendicular to the longitudinal (major) axis of the first member <NUM>, is defined by the engagement of the third member <NUM> with the first member <NUM>. Ratios of the total cross-sectional flow area of the passage(s) <NUM> to the cross sectional area circumscribed within first member <NUM> by itself, having improved thermal performance include <NUM>-<NUM>.

The cross-sectional profile of the third member <NUM> illustrated in <FIG> is a roughly hexagonal polygon having six locations of contact <NUM> between the third member <NUM> outer surface <NUM> and the inner surface <NUM> of the first member <NUM>, together defining a total of six passages <NUM> for the flow of the fluid. This profile is but one example. Another example is illustrated in <FIG>, a perspective view of the cross-sectional area for fluid flow within a portion of a probe <NUM> in accordance with some embodiments. This profile is largely similar to that provided in <FIG>, however, the locations <NUM> at the outer surface <NUM> of the third member <NUM> that engage the inner surface <NUM> of the first member <NUM> have a reduced width, measured perpendicular to the longitudinal axis of the first member <NUM> and, roughly, around the circumference of the third member <NUM>, such that the locations <NUM> are more akin to a point (or line when viewed along the length of third member <NUM>) of contact rather than an area, giving third member <NUM> the six sides of a hexagon.

Another exemplary cross-sectional area for fluid flow is illustrated in <FIG>. As shown, the engagement of third member <NUM> with the inner surface <NUM> of the first member <NUM> occurs in four locations <NUM>, defining four passages <NUM>. While this and earlier embodiments illustrate that the third member has a polygonal, or generally polygonal shape (which the expectation of possibly curved portions connecting the flat portions of the outer surface <NUM>), the third member <NUM> is not limited to having a polygonal outer shape.

Likewise, the number of locations <NUM> at which the outer surface <NUM> of the third member <NUM> engages the inner surface <NUM> of the first member <NUM> can vary from as little as one (where that location may extend over an area around the circumference of the third member <NUM>), to two, three, four, five, six, or even more. In turn, the number of locations <NUM> of engagement of the third member <NUM> and the first member <NUM> determines the number of passages between the two members.

A POSA will recognize that other shapes of the third member <NUM> may still result in the thermal improvements enabled by the features discussed herein.

The outer surface <NUM> of the third member <NUM> may have formed therein a plurality of channels <NUM> that direct the flow of fluid within, and sometimes between, the passages <NUM>. These channels <NUM> may have various shapes, as illustrated in <FIG> which are top-down views of the outer surface <NUM> of the third member <NUM> looking along the extension of the third member. As can be seen, these channels <NUM> may have a stepped shape, a series of alternating faces parallel and then perpendicular to the extension of third member <NUM> (<FIG>), a series of zig-zag shapes (<FIG>). In some embodiments, the shape may resemble zig-zag but using a series of continuously curving surfaces (<FIG>). In some embodiments, the channels <NUM> may spiral around the third member <NUM> along its extension (<FIG>). By alternating the direction of the fluid flow, channels <NUM> may cause a reduced boundary layer thickness of the fluid, thereby increasing the heat transfer coefficient. A POSA will recognize that other channel designs/patterns may be used to direct the flow of fluid within the passage(s) <NUM>.

Returning to <FIG>, the third member <NUM> may have a proximal end <NUM> that may be located radially outward of and surround the second member <NUM>, in embodiments in which the second member <NUM> extends through the length of the third member <NUM>. A fourth member <NUM> is located between the handle <NUM> and the proximal end <NUM> of the third member <NUM>. In some embodiments, fourth member <NUM> serves as a return line for the fluid after it has flowed through the passages <NUM>. The fourth members <NUM> may be a double wall construction, with or without a vacuum or insulating material in between, and insulates the proximal end of <NUM> from the cold working fluid, serving as a termination point of the cooling portion of the first member <NUM>. The fourth member <NUM> may be a hollow structure that extends within the first member <NUM>. This structure may be tubular, and may comprise stainless steel, Inconel, titanium, ceramic, or other materials. As shown in <FIG>, the fourth member <NUM> may be coaxial with and radially surround second member <NUM> (or other member that provides at least a portion of the flow path the fluid to the tip <NUM>). In some embodiments, such as that illustrated in <FIG>, a bulk head component <NUM>, may be utilized to seal around and isolate inlet and outlet tubing, that may be of the second member <NUM> and fourth member <NUM>, respectively. The inlet and outlet tubes may optionally be coaxial where they pass through the bulk head component <NUM>. The region proximal to the bulk head component <NUM> may be insulated by physical insulation material, by vacuum, or both.

The fourth member <NUM> and a member providing at least a portion of the inlet flow path (which may be second member <NUM>) may be surrounded by an insulating structure <NUM> between these members and first member <NUM>. Insulating structure <NUM> serves to reduce the transfer of heat between tissue surrounding the first member <NUM> and fluid, thereby serving as a termination point of the working, cooling portion of the first member <NUM>. Insulating structure <NUM> may comprise materials having low thermal conductivity, such as ceramics, and may utilize vacuum to aid in reducing heat transfer. This vacuum may be permanent, in that a vacuum is drawn in a sealed volume within structure <NUM>, or it may be actively drawn during operating of the probe by a pump.

Turning to <FIG>, illustrated is a probe <NUM> in which the second member <NUM> contains an extension <NUM>, otherwise <FIG> is largely similar to that of <FIG>. Extension <NUM> serves to impinge the fluid upon the inner surface <NUM> of the tip <NUM>. Additionally, extension <NUM> of second member <NUM> serves to reduce the cross-sectional flow areas closer to the tip <NUM>. Both of these features may provide for improved heat transfer rates nearer the tip <NUM>.

In accordance with the present invention and as can be seen in <FIG>, second members <NUM> and third members <NUM> are positioned within a first member <NUM> such that a distance measured between the distal end <NUM> of the extension <NUM> of the second member <NUM> and the tip <NUM> is less than a second distance measured between the distal end <NUM> of third member <NUM> and the tip <NUM>. In some embodiments, the outer dimension 'D' of the third member <NUM> may be larger than an inner dimension between the tip <NUM> where the tip engages the first member <NUM>. This larger dimension prevents the third member <NUM> from extending as far into the tip as the second member <NUM>. Extension <NUM> has a sufficiently smaller outer dimension such that it can extend within the tip <NUM> to a location that is radially surrounded by both surface <NUM> and <NUM> of the tip <NUM> and the first member <NUM>, respectively.

In some embodiments, such as that seen in <FIG>, distancing members <NUM>, or projections, can be added to the distal face of third member <NUM>, to prevent the third member <NUM> and the second member <NUM> from extending too far in the distal direction towards the tip <NUM>. For example, distancing members <NUM> may have a combined width that is greater than the width of the tip <NUM> at its proximal end such that the distancing members <NUM> would engage a proximal surface of tip <NUM>, thereby preventing the third member <NUM> and the second member <NUM> from extending too far in the distal direction towards the tip <NUM>.

An extension <NUM> may also be added to the third member <NUM> such that a portion of the third member <NUM> extends into a region within the tip <NUM> such that the extension <NUM> is radially surrounded by a portion of the tip <NUM>, first member <NUM>, or both. Such an embodiment is shown in the cross-section view of the tip <NUM> of probe <NUM> of <FIG>. The third member <NUM> contains a first portion having an outer dimension 'D' that is larger than an inner dimension of the tip <NUM>, for example, between the surfaces <NUM> that engage first member <NUM>. Third member <NUM> may also contain a second portion, extension <NUM>, having an outer dimension which is less than the inner dimension of tip <NUM> at this same location. Extension <NUM> further reduces the cross-section flow area for the fluid, thereby increasing the heat transfer coefficient of the fluid in the region of the tip in the same manner as described above for the passages <NUM> between the third member <NUM> and the first member <NUM>, and beyond that by merely providing an extended second member <NUM>.

In some embodiments, the third member <NUM> may have a portion <NUM> between the larger first portion and the extended second portion. Portion <NUM> may be smooth. As used herein, 'smooth' describes a surface generally free of discontinuities (or "continuous"). Portion <NUM> may be smooth between its distal and proximal endpoints and be smooth or have a gradual transition between the first and second portions of the third member <NUM>. This smooth transition provided by portion <NUM> reduces resistance to the flow of fluid within probe <NUM>.

<FIG> is a perspective view of a third member <NUM> having an extension and a portion <NUM>.

In accordance with some embodiments, a probe <NUM> having a fifth member <NUM> adjacent to the tip <NUM> as illustrated in <FIG>. Since fifth member <NUM> does not extend along the entire length of the third member <NUM>, a section <NUM> of the third member <NUM> provides at least a portion of the incoming fluid flow path upstream of the fifth member <NUM>. Second member <NUM> may extend along the longitudinal axis of the first member <NUM> near the proximal end of third member <NUM>, and may engage third member <NUM> to provide a portion of the inlet fluid flow path.

In some embodiments, the third member <NUM> may comprise the fifth member <NUM> in a unitary component, as illustrated in <FIG>. Third member <NUM> may still engage second member <NUM> at its proximal end. Manufacturing a unitary third member <NUM> / fifth member <NUM> component providing for the function of both the third member <NUM> and the fifth member <NUM> may simplify assembly by reducing the number of components that may need to be connected to one another.

As shown in <FIG>, the second member <NUM> may be surrounded by the third member <NUM> at the proximal end of the third member <NUM>, and the second member <NUM> may provide the fluid flow path into the section <NUM> of the third member <NUM>. This arrangement provides for a greater ability to exchange heat between incoming fluid in section <NUM> and fluid flowing in the passages <NUM> between the third member <NUM> and the first member <NUM>. This internal heat transfer between the fluid allows for more consistent temperatures along the length of the probe <NUM>. As illustrated, member <NUM> may have a first inner dimension at its distal and proximal ends at which it engages fifth member <NUM> and second member <NUM>, respectfully, and a second inner dimension between its distal and proximate ends. This second inner dimension allows the fluid to flow closer to the passages <NUM>, and provides for a reduced radial thickness of the third member <NUM> in the section <NUM> when compared to its distal and proximal ends.

<FIG> is a block diagram of unclaimed method <NUM> of using a probe designed in accordance with some embodiments. The method starts at block <NUM>. At block <NUM>, a probe designed in accordance with one or more of the embodiments provided herein is provided. This probe is then coupled to a fluid supply and a fluid return at block <NUM>. At block <NUM>, the probe is positioned such that it is in contact with a target issue. Fluid is then supplied to the probe at block <NUM>, and then exhausted from the probe to the fluid return at block <NUM>. The method may end at block <NUM>. A POSA will recognize that other, conventional methods and procedures for running fluid to and from a probe may be utilized with probe <NUM> as described in the embodiments herein.

The improvements to the internal design of a cryoprobe which utilizes an internal fluid (liquid, gas, mixed, or other phase) as the cooling medium disclosed herein improves the cooling performance of the probe. These improvements increase the heat transfer rate between the outer surface of the probe and the internal working fluid. This increased heat transfer rate can be used to either cool/freeze tissue more quickly, freeze larger regions of tissue, consume less fluid or energy for the same amount of cooling or freezing performance, provide for a more uniform temperature along the probe, or a combination of any of the aforementioned advantages.

Claim 1:
A cryosurgical probe, comprising:
a first member (<NUM>) having a first end portion (<NUM>) and a second end portion (<NUM>);
a tip (<NUM>) coupled to the first member (<NUM>) at the second end portion (<NUM>);
a second member (<NUM>), having an elongated, hollow structure and being tubular, positioned within the first member (<NUM>) such that the second member (<NUM>) extends within the first member (<NUM>); and
a third member (<NUM>) operably engaging an inner surface of the first member (<NUM>) to define at least one fluid passage (<NUM>) between the third member (<NUM>) and the first member (<NUM>), wherein the third member (<NUM>) is disposed outward from the second member (<NUM>) along at least a portion of the second member (<NUM>), and wherein a portion of the third member (<NUM>) substantially encloses at least a portion of the second member (<NUM>);
wherein the second member (<NUM>) and third member (<NUM>) are positioned within the first member (<NUM>) such that a first distance between a distal end (<NUM>) of the second member (<NUM>) and the tip (<NUM>) is less than a second distance between the distal end (<NUM>) of the third member (<NUM>) and the tip.