Liver and Soft Tissue Ablation

 

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General Procedural Information

Radiofrequency Ablation (RFA) is a less invasive procedure used to destroy lesions in which the deposition of radiofrequency energy produces thermal injury to the target tissue. RFA can be performed using an open, percutaneous, or laparoscopic technique.

RFA is used to treat liver lesions either in conjunction with surgery or when surgical resection is not a treatment option. In fact, only 15 - 30% of patients with hepatic lesions are actual candidates for surgical resection. This is due to various factors, including the total number, size and location of lesions within the liver. For example, a patient with bilobular disease may not be a candidate for surgical resection because too much of the liver would have to be removed, making surgery incompatible with recovery.

A patient is also not a surgical candidate if a hepatic lesion abuts a major blood vessel, since the lesion cannot be safely resected. Additionally, the presence of co-morbidities may render a patient ineligible for a surgical approach.   

During radiofrequency ablation of soft tissue lesions, high frequency alternating current – radiofrequency energy – is delivered to the targeted tissue. Ions within the tissue attempt to follow the directional changes of current, producing ionic agitation. Ionic agitation results in frictional heating.

Heating of soft tissue above 50°C causes numerous changes at the cellular level including denaturation of protein and loss of intracellular fluids – a process called desiccation.

The thermal effects that produce tissue ablation cause a decrease in the ability of soft tissue cells to conduct electrical current. This causes a rise in the level of resistance to current flow, also referred to as tissue impedance. This rising level of impedance eventually decreases current flow. Importantly, impedance can be used to measure the progress of tissue ablation during application of RF energy.

During RF ablation procedures, the radiofrequency current travels through an intact pathway called the circuit. The RF circuit is a monopolar system similar to an electrosurgical circuit. It consists of the generator, an active electrode, the patient, and the dispersive (or passive) electrode. The dispersive electrode is sometimes referred to as a return electrode or grounding pad. The radiofrequency circuit is created when the current from the generator is delivered to the patient via the active electrode, and then returns to the generator via the dispersive electrodes.

DINPER4546 - PSST6570