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Lethal tissue temperature during cervical cryotherapy with a small flat cryoprobe
1Department of Family Medicine, Medical College of Georgia, Augusta 30912-3500.
Background:
Some female patients, especially those with cervical intraepithelial neoplasia III (CIN III), are not successfully cured following cervical cryotherapy, for which a small flat cryoprobe tip is commonly used. The thermodynamic effect produced in the cervical tissue by this device has not been previously described. This study examined the capability of a small flat cryoprobe tip to generate a lethal temperature during thermocouple-monitored cryosurgery of the cervix.
Methods:
A thermocouple was placed in the cervix 5 mm from the cryoprobe margin, and a pyrometer indicated temperatures generated by nitrous oxide cryosurgery. Iceball lateral spread of freeze was measured with a cryosurgical iceball gauge.
Results:
A minimum temperature of -2C degrees was generated at the termination of freeze (6 1/2 minutes). The maximum lateral spread of freeze at termination was 6.2 mm. A lethal zone of 4.2 mm was estimated based on a 2-mm recovery zone.
Conclusions:
When compared with morphometric studies of cervical dysplasia depth of involvement, an estimated 12.5% of CIN III would be inadequately treated based on our in vivo data. A small flat cryoprobe is incapable of eradicating all severe premalignant cervical disease deep within the glandular clefts. An alternative treatment method, such as electrosurgical loop excision of the cervical transformation zone (ELECTZ), therefore, may be the preferred treatment modality for CIN III: