Cryosurgical equipment: a critical review.

BACKGROUND

Cryosurgery is frequently used by family physicians to treat benign and premalignant epithelial disease. A professional medical team consisting of a practicing cryotherapist and a mechanical engineer independently critically evaluated the design, function, and performance of selected cryosurgical equipment.

METHODS

Qualitative observations and quantitative measurements were performed on seven nitrous oxide cryosurgical units and one liquid nitrogen unit, representing seven manufacturers and distributors. Specific isotherm generation distributions, lateral spread of freeze and refreeze measurements, defrost intervals, recovery zone sizes, relative ease of use, and component characteristics were comparatively assessed.

RESULTS

The in vitro mean lateral spread of freeze distance at 180 seconds varied between 5.8 mm for the Frigitronics CryoPlus and 4.6 mm for the Leisegang LM-900. The mean -20 degrees C isotherm generation time, measured by a thermocouple 3 mm lateral to the cryoprobe tip margin, ranged from 229 seconds for the Wallach WA-1000B to 361 seconds for the Spembly PCG 9R. Defrost times varied between 2 seconds for the Wallach WA-1000B and 320 seconds for the Brymill Mini-Cryogun. Refreeze time was quickest (36 seconds) using the GyneTech GT-1S. The mean in vitro recovery zones varied between 1.6 mm and 2.1 mm.

CONCLUSIONS

This evaluation documented both differences and similarities among various cryosurgical units in terms of design, function, and performance. The Wallach, Frigitronics, and GyneTech nitrous oxide cryosurgical units demonstrated the best overall performance.