Precooling system for Joule-Thomson probe

A miniature cryosurgical system, comprising:

• a closed primary loop for circulating a primary refrigerant, with a high pressure primary flow path and a low pressure primary flow path, said primary loop including a primary compressor, and a primary expansion element for expanding said primary refrigerant from a high pressure gaseous state in said high pressure primary flow path to a low pressure gaseous state in said low pressure primary flow path;
• and
• a closed secondary loop for circulating a secondary refrigerant, with a high pressure secondary flow path and a low pressure secondary flow path, said secondary loop including a secondary compressor, a condenser, a primary-to-secondary heat exchanger, and a secondary expansion element within said primary-to-secondary heat exchanger for vaporizing and expanding said secondary refrigerant from a liquid state in said high pressure secondary flow path to a gaseous state in said low pressure secondary flow path;
• wherein said high pressure primary refrigerant and said low pressure secondary refrigerant pass through said primary-to-secondary heat exchanger in a heat exchange relationship;
• and
• wherein said low pressure primary refrigerant bypasses said primary-to-secondary heat exchanger.

A method for performing cryosurgery on selected tissue, comprising:

• providing a closed primary loop, said primary loop including at least one primary-to-primary heat exchanger and a primary expansion element distal of said primary-to-primary heat exchanger;
• providing a closed secondary loop, said secondary loop including a primary-to-secondary heat exchanger and a secondary expansion element within said primary-to-secondary heat exchanger;
• compressing a secondary refrigerant in said secondary loop;
• vaporizing and expanding said secondary refrigerant to a lower temperature within said primary-to-secondary heat exchanger, with said secondary expansion element;
• adding enthalpy to said expanded secondary refrigerant in said primary-to-secondary heat exchanger;
• compressing a primary refrigerant, different from said secondary refrigerant, in said primary loop;
• removing enthalpy from said compressed primary refrigerant in said primary-to-secondary heat exchanger;
• removing enthalpy from said compressed primary refrigerant in said primary-to-primary heat exchanger;
• expanding said primary refrigerant with said primary expansion element to still further remove enthalpy from said primary refrigerant;
• applying said expanded primary refrigerant to a cold tip of a cryosurgical probe, to lower the temperature of said cold tip;
• and
• applying said cold tip to the selected tissue.

A method for cooling a cold tip of a cryosurgical probe, comprising:

• providing a closed primary loop having a compressor, at least one primary-to-primary heat exchanger, and a primary expansion element adjacent to a heat transfer element in said cold tip;
• providing a closed secondary loop having a compressor unit and a primary-to-secondary heat exchanger;
• compressing and condensing a secondary refrigerant in said secondary loop;
• vaporizing and expanding said secondary refrigerant in a low pressure secondary section of said primary-to-secondary heat exchanger;
• compressing a primary refrigerant, different from said secondary refrigerant, to a selected pressure pressure lower than said secondary refrigerant;
• removing enthalpy from said compressed primary refrigerant in said high pressure primary section of said primary-to-secondary heat exchanger;
• expanding said primary refrigerant in said primary expansion element to further cool said primary refrigerant to a selected temperature;
• and
• absorbing heat from said heat transfer element by contact with said expanded primary refrigerant, to cool said heat transfer element to a selected temperature.