Refrigeration – Hand manipulable tool
Reexamination Certificate
1999-06-25
2001-05-29
Doerrler, William (Department: 3744)
Refrigeration
Hand manipulable tool
C062S006000, C062S114000, C062S335000
Reexamination Certificate
active
06237355
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is in the field of cooling biological tissues to very low temperatures, for treatment of medical conditions, as in cryosurgery.
2. Background Information
It is desirable to be able to selectively cool miniature discrete portions of biological tissue to very low temperatures in the performance of cryosurgery, without substantially cooling adjacent tissues of the organ. Cryosurgery has become an important procedure in medical, dental, and veterinary fields. Particular success has been experienced in the specialties of gynecology and dermatology. Other specialties, such as neurosurgery and urology, could also benefit from the implementation of cryosurgical techniques, but this has only occurred in a limited way. Unfortunately, currently known cryosurgical instruments have several limitations which make their use difficult or impossible in some such fields. Specifically, known systems can not achieve the necessary temperature and cooling power to optimally perform cryosurgical ablation, such as in cardiac ablation to correct arrhythmia.
In the performance of cryosurgery, it is typical to use a cryosurgical application system designed to suitably freeze the target tissue, thereby destroying diseased or degenerated cells in the tissue. The abnormal cells to be destroyed are often surrounded by healthy tissue which must be left uninjured. The particular probe, catheter, or other applicator used in a given application is therefore designed with the optimum shape, size, and flexibility or rigidity for the application, to achieve this selective freezing of tissue. Where a probe or catheter is used, the remainder of the refrigeration system must be designed to provide adequate cooling, which involves lowering the operative portion of the probe to a desired temperature, and having sufficient power or capacity to maintain the desired temperature for a given heat load. The entire system must be designed to place the operative portion of the probe or catheter at the location of the tissue to be frozen, without having any undesirable effect on other organs or systems.
It is an object of the present invention to provide a method and apparatus for precooling a primary loop high pressure refrigerant to a point below its critical temperature, to liquefy the primary refrigerant, with a secondary loop refrigeration cycle. This allows the use of a liquid primary refrigerant having a critical temperature below the operating room temperature, in order to achieve the lower temperature possible with such a primary refrigerant.
BRIEF SUMMARY OF THE INVENTION
The present invention comprises a miniature refrigeration system, including a method for operating the system, including precooling of the primary high pressure refrigerant below its critical temperature, to liquefy the primary refrigerant, with a secondary refrigeration cycle using a second refrigerant with a higher critical temperature, to maximize the available cooling power of the primary refrigerant, and to achieve the lowest possible temperature.
The cooling power is an important design parameter of a cryosurgical instrument. With greater cooling power, more rapid temperature decreases occur, and lower temperatures can be maintained at the probe tip during freezing. This ultimately leads to greater tissue destruction. The power of a J-T cryosurgical device is a function of the enthalpy difference of the primary refrigerant and the mass flow rate. Pre-cooling a refrigerant below its critical temperature and liquefying the refrigerant will increase the enthalpy difference available for cooling power.
An example of a suitable primary refrigerant is SUVA-95, a mixture of R-23 and R-116 refrigerants made by DuPont Fluoroproducts, of Wilmington, Del. SUVA-95 has a critical temperature of 287K, with cooling capacity at temperatures as low as 185K at one atmosphere. An example of a suitable secondary refrigerant is AZ-20, an R-410a refrigerant made by Allied Signal of Morristown, N.J. AZ-20 has a critical temperature of 345K, with cooling capacity at temperatures as low as 220K at one atmosphere.
The high pressure primary refrigerant is fed as a gas into a high pressure passageway within a primary-to-secondary heat exchanger. The primary-to-secondary heat exchanger can be a coiled tube heat exchanger or a finned tube heat exchanger. The liquid secondary refrigerant is vaporized and expanded into a low pressure passageway in the primary-to-secondary heat exchanger. Heat exchange between the low pressure secondary refrigerant vapor and the high pressure primary refrigerant cools and liquefies the high pressure refrigerant. The liquid high pressure primary refrigerant is then vaporized and expanded at the cooling tip of a cryosurgical catheter to provide the cooling power necessary for effective ablation of tissue. The method and apparatus of the present invention can be used equally well in a rigid hand held cryoprobe, or in a catheter.
The primary-to-secondary heat exchanger is part of the secondary refrigeration system, which can have a secondary compressor and a secondary expansion element, in addition to the primary-to-secondary heat exchanger. The liquid high pressure secondary refrigerant, having a higher critical temperature than the primary refrigerant, can be at a temperature which is relatively higher than the critical temperature of the primary refrigerant. However, the vaporized and expanded low pressure secondary refrigerant is at a temperature which is low enough to cool the primary refrigerant below its critical temperature. Since the secondary refrigerant has a critical temperature above normal operating room temperature, it can easily be provided in the liquid state in an operating room environment, whereas the primary refrigerant, which has a critical temperature significantly below normal operating room temperature, can not.
The liquid high pressure primary refrigerant is conducted from the heat exchanger to the inlet of a primary Joule-Thomson expansion element located in the cold tip of the probe or catheter, where the primary refrigerant is vaporized and expanded to a lower pressure and a lower temperature.
The primary refrigerant exiting the primary Joule-Thomson expansion element is exposed to the inner surface of a heat transfer element at the cold tip. The vaporized and expanded primary refrigerant cools the heat transfer element to a lower temperature and then returns through the low pressure return passageway of the catheter or probe.
The novel features of this invention, as well as the invention itself, will be best understood from the attached drawings, taken along with the following description, in which similar reference characters refer to similar parts, and in which:
REFERENCES:
patent: 2991633 (1961-07-01), Simon
patent: 3048021 (1962-08-01), Coles et al.
patent: 3401533 (1968-09-01), Maybury
patent: 3415078 (1968-12-01), Liston
patent: 3431750 (1969-03-01), LeFranc
patent: 3696813 (1972-10-01), Wallach
patent: 4829785 (1989-05-01), Hersey
patent: 4840043 (1989-06-01), Sakitani et al.
patent: 4875346 (1989-10-01), Jones et al.
patent: 4951471 (1990-08-01), Sakitani et al.
patent: 4990412 (1991-02-01), Hersey
patent: 5063747 (1991-11-01), Jones et al.
patent: 5157938 (1992-10-01), Bard et al.
patent: 5207674 (1993-05-01), Hamilton
patent: 5275595 (1994-01-01), Dobak, III
patent: 5595065 (1997-01-01), Boiarski et al.
patent: 5617739 (1997-04-01), Little
patent: 5724832 (1998-03-01), Little et al.
patent: 5758505 (1998-06-01), Dobak et al.
patent: 5759182 (1998-06-01), Varney et al.
patent: 5807391 (1998-09-01), Wijkamp
patent: WO95/13025 (1995-05-01), None
patent: WO 99/15093 (1999-04-01), None
Chang, Z.;Development of a High Performance Multiprobe Cryosurgical Device; 09/1994; Biomedical Instrumentation and Technology; pp. 383-390.
Little, W.;Advances in Joule-Thomson Cooling; pp. 1-10; place and date of publication un
CryoGen, Inc.
Doerrler William
Spinks Gerald W.
LandOfFree
Precooled cryogenic ablation system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Precooled cryogenic ablation system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Precooled cryogenic ablation system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2540660