Principles and techniques
The treatment of thermoablation with RF exploits the conversion of the energy of an electromagnetic wave into heat. A generator is used that converts normal energy supplied by an electric alternating current of 90 Hz into the RF band of 500 KHz.
The current passes through a needle inserted in tumor and dispersed through the plate.
In this way, a resistive type of heating is produced, particularly around the exposed point of the needle electrode
One potential limitation of conventional monopolar RF techniques is that the diameter of tissue coagulated is limited by heat dispersion to a maximum of approximately 1.6 cm. Increasing tip temperatures to greater than 100°C does not result in greater volumes of coagulation necrosis, because of tissue vaporization and charring. This situation leads to increased local tissue impedance and thereby limits RF deposition, heat diffusion, and coagulation necrosis. To overcome these limitations, several strategies have been proposed. These strategies include the use of bipolar electrodes, multiprobe arrays, saline injection during treatment, and cooled-tip electrodes.
Two prospective trials compared the effectiveness of RFA performed by using different models for the treatment of HCC until 3.0 cm in size
There was no significant difference in local effectiveness, major complications, local tumor progression, and overall survival (OS).
1. Unresectable primary liver tumors
2. Colorectal and neuroendocrine liver metastases
3. Bridge to liver transplant for HCC
4. As substitutes for surgical resection in those who have medical contraindications to surgery
5. RFA is the favored modality for coagulopathic patients because of the intrinsic cautery effect decreasing bleeding complications
Local Recurrence rates are high as compared to Local Resection
Overall survival was highest (58% at 5 years) after liver resection (median follow-up 21 months).