Hepatic radiofrequency ablation--an overview from an engineering perspective.

Radiofrequency (RF) ablation is receiving increasing attention as treatment for primary and metastatic liver cancer. RF ablation can be performed during open surgery, or minimally invasive through a small incision. An electrode is introduced into the liver tumor, and RF energy is applied. Tissue surrounding the electrode heats up, and is killed above approximately 50 degrees C, where tissue coagulation occurs. Ultrasound imaging is typically used to place the electrode, and monitor the ablation procedure; the exact dimension of the coagulation zone is not visible under ultrasound. Current devices can create coagulation zones between 4 and 7 cm diameter. For large tumors often multiple sequential applications are required, since current devices can only use a single electrode at a time. Current limitations include inadequate imaging modalities, uncontrolled shapes and size of coagulation zones, and inability to reach adequate temperatures close to large vessels. When future devices are available that improve upon these shortcomings, RF ablation may replace classical surgery as the standard treatment for liver cancer.