Patent Application
20060111765
n/a
n/a
The present invention relates to a method and system for thermally affecting tissue.
Researchers and physicians have long recognized the consequences of reduction of body temperature in mammals, including induction of stupor, tissue damage, and death. Application of freezing and near freezing temperatures to selected tissue is commonly employed to preserve tissue and cell (e.g. sperm banks); and application of extreme cold (far below freezing) is effective for tissue ablation. However, localized cooling (not freezing) of tissue has generally been limited to the placement of an “ice-pack” or a “cold compress” on injured or inflamed tissue to reduce swelling and the pain associated therewith. Localized cooling of internal organs, such as the brain, has remained in large part unexplored.
For example, “brain cooling” has been induced by cooling the blood supply to the brain for certain therapies. However, as the effects of the cool blood cannot be easily localized, there is a systemic temperature reduction throughout the body that can lead to cardiac arrhythmia, immune suppression and coagulopathies.
Although attempts have been made to localize cooling of the brain with wholly external devices, such as cooling helmets or neck collars, there are disadvantages associated with external cooling to affect internal tissue. For example, external methods do not provide adequate resolution for selective tissue cooling, and some of the same disadvantages that are associated with systemic cooling can occur when using external cooling devices. Further, internal cooling devices have also been developed, but are often limited in their ability to conform to the shapes of brain tissue targeted for cooling. Exemplary devices include catheters and inflatable balloons through which heated or cooled fluids are circulated. While it is known to use balloons to contact tissue surfaces along the length of a catheter that is inserted into a vessel, a need arises for a device to apply localized thermal energy in alternate treatment scenarios.
Moreover, it is also desirable to avoid creating unnatural openings in a human body. However, when a medical need mandates creating an opening, making as small an opening as possible is advantageous. The need to keep openings to a minimum is particularly applicable when dealing with openings in a human skull, yet a device is needed to apply or remove thermal energy to or from a tissue area with a larger surface area than the opening through which the catheter is inserted.
Further, problems of uniform thermal distribution arise with known thermal transfer devices. When a thermally transmissive fluid is infused into a space, the distribution of thermal energy is governed by the function of thermal convection. As such, in many situations thermal energy is not evenly distributed throughout the space.
In view of the above limitations, it would be desirable to provide a device which evenly distributes or removes thermal energy from tissue and is capable of thermally affecting large tissue areas while remaining implantable through a small opening in a patient.
The present invention advantageously provides a medical device which evenly distributes or removes thermal energy from tissue and is capable of thermally affecting large tissue areas while remaining implantable through a small opening in a patient.
In an exemplary embodiment, the medical device includes a heat exchanger that defines a chamber adapted to receive a first fluid, which can circulate through the heat exchanger. The medical device further includes a deployment member secured to at least a portion of the heat exchanger, with the deployment member capable of receiving a second fluid. Either of the two fluids can be thermally transmissive fluids which are chilled to below body temperature.
The medical device can be constructed from pliant materials, thereby enabling the device to deform when in contact with tissue. Further, the pressure of the second fluid located within the deployment member can be modified for a desired rigidity of the deployment member. Moreover, the deployment member can be constructed from a material whose rigidity can be modified by changes in temperature, and can further be detachable from the heat exchanger.
A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:
Referring to
Particularly, as shown in
The heat exchanger 14 can be constructed from a pliant material, including various plastic or silicone elastomer materials, or any other such material that would allow the heat exchanger 14 to deform when pressure is affixed to it such as by placement in contact with tissue. The deformability of the heat exchanger 14 allows the medical device to conform to an uneven or irregular tissue surface, thereby enhancing the ability of the device to thermally affect the tissue. Additionally, the heat exchanger 14 can be constructed from thermally transmissive materials having properties that influence the thermal conductivity, and thus the resulting effectiveness of the heat exchanger in thermally affecting the tissue. The heat exchanger 14 can have an essentially circular shape, essentially rectangular shape, or can be constructed to mirror the shape of a tissue region that will be thermally affected by the medical device of the present invention.
The deployment member 18 provides an expansive element that ensures that the medical device expands to proper shape after being temporarily deformed to fit through a small surgical opening. The deployment of the medical device ensures that the heat exchanger 14 covers the maximum amount of surface area of the tissue to be thermally affected. Moreover, the deployment member 18 provides structural rigidity for the medical device while maintaining the pliability of the heat exchanger 14, thereby reducing the difficulty in placing the medical device into the desired position in contact with the tissue to be thermally affected. The deployment member 18 can be constructed from a thermally transmissive material, and can further be disposed on an interior or exterior perimeter of the heat exchanger 14 or any portion of a surface thereof. Moreover, the deployment member 18 can also be located within a portion of the chamber of the heat exchanger 14.
The deployment member 18 can have a shape that is substantially similar to the shape of the heat exchanger 14, as shown in
In an exemplary embodiment, the deployment member 18 is a single inflatable element, as shown in
The first fluid that circulates through the heat exchanger 14 can be a thermally transmissive fluid, and can further be chilled to below body temperature in order to enhance the thermal effectiveness of the medical device. In an exemplary application, the first fluid can be cooled to a temperature of 4° C. to 37° C. Furthermore, the first fluid can be pressurized up to 1.0 psig, however, to maximize the pliability of the heat exchanger, the first fluid is preferably kept as low as possible while maintaining flow through the circulation path of the heat exchanger 14, as well as achieving a desired thermal result.
The second fluid that can be located in the deployment member 18 can be a thermally transmissive fluid. The second fluid can be pressurized to a predetermined pressure, wherein the predetermined pressure corresponds to a desired rigidity of the deployment member 18. The rigidity of the deployment member 18 can be modified to attain a desired level of expansion for the heat exchanger 14, as well as achieve differing levels of manipulability in order to ease the placement of the medical device into thermal contact with the tissue.
The circulation path can be configured such that the first fluid flows directly into and out of the chamber of the heat exchanger 14. Additionally, at least a portion of the circulation path can be looped around itself into a coil configuration, as shown in
While an exemplary embodiment of the present invention includes introducing a fluid into the deployment member 18 for varying levels of rigidity, it is also beneficial to employ a deployment member 18 that does not include a fluid nor an inflation lumen for introducing a fluid, as shown by the cross-sectional illustration of
Moreover, the deployment member 18 can be constructed from a shape memory material. Shape memory materials are generally known in the art, and have the ability to undergo structural alterations when exposed to various temperatures. The deployment member may additionally include a spring mechanism that slowly expands the heat exchanger when placed in thermal communication with the tissue.
Turning now to
It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention, which is limited only by the following claims.
