Treatment by thermal ablation – Principles
Thermal ablation (also known as thermo-coagulation) is an ablative technique alternative to cryotherapy to treat CIN lesions. Earlier, the technique was also known as “cold coagulation”, because the temperature used (100 °C) is lower than that used for electrocautery (few hundred degree C). Thermal ablation uses a probe heated to 100 °C that is applied to the transformation zone for 20–30 seconds. The heat causes the intracellular water to boil and vaporize. Thus, the normal and abnormal cells of the transformation zone are destroyed. The destroyed cells are discharged and gradually replaced by healthy epithelium within a few weeks.
The ablative effect of heat damages cervical tissue up to a depth of 7 mm from the surface. As a result, any CIN extending to the crypts (usually the maximum length of a crypt is 5 mm) is adequately treated with thermal ablation. Multiple overlapping applications of the probe are feasible with thermal ablation to completely cover a large transformation zone. Hence, unlike cryotherapy, the technique is not limited by the disparity between the size of the lesion and that of the probe.
The rest of the principles and indications for treatment by thermal ablation are the same as those for cryotherapy. Thermal ablation is as safe and as effective as cryotherapy in treating all grades of CIN lesion.