Abstract
Localized cooling produced at the tip of a cryogenic probe which is insulated by a vacuum jacket up to about 1 mm from its extremity, is controlled by a closed circuit apparatus. A multi-valve distributor controls the circulation of fluid through several parts of the apparatus. Another multi-valve distributor controls the communication of the apparatus with the probe itself. This apparatus regulates the fluid expansion and thus, consequently, gives the desired temperatures of cooling with a precision of 1°C. At the tip of the probe, inserted in the brain, the range of cooling obtained is from −20° to +20°C. A particular level of cooling is reached within 5 sec and the return of 37°C is within 10 sec. For cooling applied to the brain of an anaesthetized cat (37°C) for one minute at +5°C, there are isotherms of +20°C and +37°C which encircle the tip of the probe just above the tip at about 2 mm and 3 mm respectively. The +20°C isotherm includes a sphere which has a diameter of about 2.6 mm. Areas of the cerebral cortex can also be cooled by special thermodes in anaesthetized or in freely moving animals.
Published Version
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