Radiofrequency Ablation of Hepatic Lesions: A Review

Venkataramu N. Krishnamurthy, MD; V. Javier Casillas, MD; Lina Latorre, MD

Disclosures

Appl Radiol. 2003;32(10) 

In This Article

Mechanism of RF Ablation

An RF ablation system consists of a very high frequency (200 to 1200 KHz) alternating current generator, RF needle (monopolar electrode), grounding pad (which serves as a large dispersive electrode) and the patient must all be connected in series. In this circuit, electric current enters through both the electrodes with the patient as resistor. As the electric current alternates in directions at high frequency, tissue ions that are attempting to follow the direction of the current get agitated. Due to natural high resistivity in the living tissue, ionic agitation produces frictional heat at the immediate vicinity of electrodes. Because the grounding pad has a very large surface area, the electrical resistance is low; hence, the production of frictional heat is concentrated at the needle electrode. Thus, deposition of electromagnetic energy from electric current produces thermal injury. The extent and nature of this injury are dependent on two important factors: temperature and RF application duration.[21,22] To produce irreversible cell damage, it takes several hours at 45°C, but it takes only 4 to 5 minutes at 50°C to 55°C. At temperatures between 60°C and 100°C, there is immediate tissue coagulation (due to irreversible damage to mitochondrial and cytosolic enzymes by heat-induced denaturation of proteins). Above 100°C, tissue simply vaporizes. Therefore, temperatures between 50°C and 100°C are ideal for RF ablation.

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