Refrigeration – Using electrical or magnetic effect – Thermoelectric; e.g. – peltier effect
Reexamination Certificate
2002-08-01
2003-10-07
Doerrler, William C. (Department: 3744)
Refrigeration
Using electrical or magnetic effect
Thermoelectric; e.g., peltier effect
C062S293000
Reexamination Certificate
active
06629417
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to cryosurgical probes, and in particular to a cryoprobe system utilizing a passive, insulated, hand-held thermal mass having a low temperature tip for cryosurgical medical applications and the like, as well as a heat extraction base configured to interface with the thermal mass to quickly and efficiently reduce the heat of the thermal mass to cryogenic temperatures.
The heat extraction base of the preferred embodiment of the present invention is configured to interface with the tip of the thermal mass, such that the tip plugs in securely to the base, to permit an efficient thermal transfer of heat from the thermal mass through the base via a heat exchange system communicating with the base which employs a low temperature cryo-refrigeration unit.
The cryo-refrigeration unit may comprise a single low temperature compressor to reduce the temperature of the base to around minus one hundred degrees Centigrade utilizing off-the-shelf cryogenic refrigeration methods, or may utilize a series of more conventional refrigeration units in a primary and secondary heat extraction arrangement, which method may further utilize thermocouple or Peltier effect device assist to further reduce the temperature of the heat extraction base to the required temperature.
The thermal mass is configured to be cooled to an optimal temperature for cryogenic applications, removed from the base, the tip of the otherwise insulated thermal mass then applied to the surface to be treated, typically tissue on a patient, wherein the cooled thermal mass provides a heat sink via the tip to cryogenically cool the treated surface.
The present invention also contemplates utilization of a heat pipe attachment for Endo-Cervical Cryogenic Treatment, which heat pipe has first and second ends, the first end configured to engage the tip of the thermal mass, the second end configured to engage remote tissue of a patient (i.e., the cervix) for cryogenic treatment of same. The length of the heat pipe may be insulated, with the treatment end (the second end) exposed or engaging a specially configured thermal application tip.
BACKGROUND OF THE INVENTION
Cryosurgery, or cryo-ablation, employs the technique of destructively freezing, or ablating, targeted biological tissue to destroy same. A large array of systems for cryosurgery have been developed since its inception utilizing low and high pressure cryogenic liquid refrigerants, closed refrigeration systems, to solid state thermoelectric devices.
By far the most common method of performing cryosurgery involves the utilization of fluids having a low boiling point, either applied directly to the tissue of the patient or utilized to cool a probe or applicator tip. Liquid Nitrogen, Nitrous Oxide, Carbon Dioxide, or aerosol (Histofreezer) comprise the most widely used cryosurgical modalities currently in use of this type.
Liquid nitrogen has been widely utilized for cryosurgery since the 1940's, when it became more readily available. In low pressure applications, typically a Dewar-type storage flask is required to store the liquid, which must be replenished on a regular basis. The physician may spray the liquid on the tissue to be applied, or may dip a cotton swab or the like into the liquid nitrogen to absorb said liquid, thereafter applying the swab to the portion to be treated.
While Liquid Nitrogen has a boiling point of −196 degrees Centigrade, when employed in cryosurgery, erratic temperatures can arise. For example, when dabbed on with a cotton swab, skin surface temperatures can be as high as −0 degrees Centigrade, but can go as low as −100 degrees Centigrade if a continuous flow of LN
2
is applied to the skin rapidly.
Alternatively, a probe having a tip configured to conform to the anatomy to be applied may be chilled to cryogenic temperatures by the liquid, flowing therethrough, and allowing same to boil to adsorb heat, allowing the tip to act as a heat sink. Utilization of such a probe is preferred in gynecologic, oral, rectal, or other invasive applications, where the probe can be formed to conform with the anatomy to which it is applied. As the evaporation of the fluid is the principle behind its cooling properties, an emission of the gas occurs in the area in which it is employed.
Nonetheless, liquid Nitrogen provides the most effective, widely utilized cryogen fluid, having a low boiling point of −196 degrees Centigrade. This low temperature in and of itself provides risks, due to possible over application and associated over freezing, as well as risks of spills, and possible splattering during handling, as even indirect contact to tissue can result in tissue damage. Protective eyewear, clothing, and gloves are therefore required, and the material must be stored and administered under Federal OSHA guidelines.
Nitrous Oxide and Carbon Dioxide are similarly used, but are stored in a pressurized tanks, so they have the benefit of not being depleted during storage. However, studies have shown that Nitrous Oxide can be harmful to a Fetus, and breathing Nitrous Oxide can result in reduced fertility in females. Further, liquid Nitrous Oxide boils at a higher temperature (−89 degrees Centigrade) than Nitrogen, which can result in a less effective treatment. Carbon dioxide when evaporated displaces oxygen in the treatment area, and has even a higher boiler point (−78 degrees Centigrade) than Nitrous Oxide, which makes it far less suitable as a refrigerant. Nitrous oxide can employ a J-T expansion tip to reach tip temperatures down to about −89 degrees centigrade, and is favored as a reliable temperature delivery system, but suffers as its downside the above mentioned health risks.
HISTOFREEZE is a liquid refrigerant formulation comprising an aerosol which may be dispensed to a cotton swab or other application tip via an aerosol can. However, the refrigerant has a much higher boiling point than nitrogen, resulting in less cooling to the tissue (about −2 degrees Centigrade) to be treated, and is thereby far less effective. Like the above refrigerants, the aerosol evaporates into the atmosphere of the treatment area which can be breathed by its occupants, unless it is vented.
The liquid nature of the above refrigerants makes it very difficult to precisely cool the treated area to an exact temperature, resulting in the tissue often being undercooled or overcooled. While the degree of cooling varies with the type of tissue and depth and type of abnormality, the area should generally be exposed to at least −20 degrees Centigrade, and ideally −50 degrees centigrade to effectively treat malignant tissue.
In addition to the above methods, cryosurgical treatment devices utilizing self contained cooling apparatus have also been employed, but these units have often proved expensive, cumbersome and difficult to use, while rarely providing the cooling effectiveness of liquid nitrogen. Accordingly, such devices have not been employed in any significant extent compared with the above systems.
A list of patents which may have some pertinence to the present invention include:
U.S. Pat. No.
Inventor
Date of Issue
5132089
Lightfoot
Jul. 21, 1992
4037631
Schulze et al
Jul. 26, 1977
4519389
Gudkin et al
May 28, 1985
5207674
Hamilton
May 4, 1993
3502080
Hirschhorn
Mar. 24, 1970
3668888
Roslonski
Jun. 13, 1972
3451395
Thyberg
Jun. 24, 1969
5992158
Goddard et al
Nov. 30, 1999
3575176
Crump
Apr. 20, 1971
6096032
Rowland
Aug. 1, 2000
U.S. Pat. No. 5,132,089 to Lightfoot teaches a “Hand-Held Cryofixation Apparatus” wherein “a metal block is precooled by immersion into a cryogen such as liquid nitrogen or helium.”
U.S. Pat. No. 4,037,631 to Schulze et al teaches a “Method of Charging a Cryogenic probe” wherein a probe is inserted in a cryogenic liquid container (FIG.
4
-
7
).
U.S. Pat. No. 3,502,080 and 4,519,389 teach diverse cryogen probes having application tips which are cooled via thermocouple or Peltier effect devices.
U.S. Pat. No. 3,668,888 teaches a “device for frostin
Bailey Richard
Haas Michael
Krentel Jerome F.
Cimex BioTech, L.C.
Doerrler William C.
Regard Ltd Joseph T
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