How is percutaneous radiofrequency ablation (RFA) of liver tumors performed?

Updated: Nov 25, 2019
  • Author: Badar Bin Bilal Shafi, MBBS, MRCP, FRCR, CCT, EBIR; Chief Editor: Kurt E Roberts, MD  more...
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Answer

In radiofrequency (RF) ablation (RFA), the heat is created from electrical energy. The heat is generated at a specific target from the frictional heat created by rapidly vibrating adjacent cells. The end point that defines adequate necrosis can be based on either temperature or impedance, depending on the needle manufacturer.

During an RFA procedure, an ablation needle is placed directly into the target tissue. One or more electrodes are deployed from the end of the needle into the tissue. The generator is turned on, and a target temperature is set. The RF energy flows through the electrodes and causes ionic agitation. This agitation and friction of ions creates heat, and once sufficient temperatures have been reached, the heat kills the target tissue.

Tiny thermometers (thermocouples) incorporated into the tips of the electrodes allow continuous monitoring of tissue temperatures. Power is automatically adjusted so that the target temperatures remain constant. As tissue temperature increases above 50ºC, cell protein is permanently damaged and coagulation necrosis starts. Above 60ºC, cell death occurs almost instantly. Performing a 3- to 5-cm ablation takes approximately 15-30 minutes.

Ultrasonography (US) is typically used to monitor the treatment process for increased echogenicity. This increase in echogenicity corresponds to the formation of tissue and water vapor bubbles from the treated tissue and is used as a rough estimate of the size of the ablation site. Multiple ablations can be overlapped to decrease the chance of local tumor recurrence.

The size of the ablated area is determined largely by the size of the electrode needle, the temperature of the tissue, and the duration of time the energy is applied. A sharp boundary separates dead tissue and unaffected surrounding tissue.

The above principles of RFA are common to most needle systems. Different types of needles and techniques necessitate some differences of approach.


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