Radiofrequency tissue ablation: Physical principles and techniques for increasing coagulation necrosis

Radiofrequency tumor ablation has been demonstrated as a reliable method fo r creating thermally-induced coagulation necrosis using either a percutaneo us approach with image-guidance or direct surgical placement of thin electr odes into tissues to be treated. Early clinical trials with this technology have studied the treatment of hepatic, cerebral, and bony malignancies. Th e extent of coagulation necrosis induced with conventional monopolar radiof requency electrodes is dependent on overall energy deposition, the duration of radiofrequency application, and radiofrequency electrode tip length and gauge. This article will discuss these technical considerations with the g oal of defining optimal parameters for radiofrequency ablation. Strategies to further increase induced coagulation necrosis including: multiprobe and bipolar arrays, and internally-cooled radiofrequency electrodes, with or wi thout pulsed-radiofrequency or cluster technique will be presented. The dev elopment and laboratory results for many of these radiofrequency techniques and potential biophysical limitations to radiofrequency induced coagulatio n, such as perfusion mediated tissue cooling (vascular flow) will likewise be discussed.