There are three basic types of systems used for RF ablation procedures. The specific RFA system and guidance method are chosen based on location and size of the tumor to be treated, proximity of large vessels, bleeding risk, the pathway that the needle-electrode has to take to enter the tumor, and the importance of minimizing collateral damage.
The systems differ based on the length and configuration of the active tip of the needle-electrode. There are simple straight needles and straight needles that contain multiple curved, retractable electrodes that are kept inside the needle until the tip is positioned within the tumor.
In addition, some systems have cold water flowing through the electrode in order to avoid overcooking (or charring) of the tissue during the ablation procedure. All of the different needle-electrode systems connect to a radiofrequency generator and to grounding pads that are placed on the patient’s back or thighs.
The goal of RFA is to heat the tumor cells to temperatures greater than 60 degrees Celsius. At these temperatures, intracellular proteins and cell membranes are destroyed, killing tumor cells. This creates a region of necrosis surrounding the electrodes.
All of the different systems available are able to heat tissue to temperatures exceeding 100 degrees Celsius. Conductive heat is emitted from the treated tissue, which creates a zone of ablation around the tumor. The size of the ablation zone corresponds to the size of the probe used. Therefore, probes are selected based on the size of the tumor being treated.
New RFA probes are being developed to treat larger hepatic tumors. At this time, the largest zone of ablation we are able to create is 7 cm.