Quantification of ablation size in ex vivo bovine liver using cool-tip™ radiofrequency ablation system

Abstract

Radiofrequency ablation (RFA) is a minimally invasive technique that is useful in treating soft tissue tumour. Although RFA has been widely used in treating patients, more studies on its biophysical principles are needed to improve the RFA techniques. The purpose of this study was to characterize the ablation size in the bovine liver in terms of the RFA duration, the temperature of the cooling system to the RFA electrode and the RF generator's ablation mode. RFA were performed on ex vivo bovine livers using Cooltip ™ single electrode kits and Cool-tip™ RF Ablation System. A 12-channel thermometer was used to record the temperature distribution in the ablation volume. The thermometer probes were placed at 10, 20 and 30 mm radially away from the RFA electrode. A Perspex jig with custom drilled holes was used for placing the RFA electrode and temperature probes at the precise location. Fifty monopolar RFAs were performed in 16 different modes of parameters. The duration of RFA was set at 5, 7, 10 and 12 minutes. Distilled water was used as the cooling system to the RFA electrode at 5°±1°C and 25°±1°C. The Cool-tip™ RF Ablation System has two modes of ablation, which are the impedance control and manual control, where the power output was always set at maximum during the ablation. The ablation size increased as the duration of RFA increased. Larger ablation size was created when the Cool-tip™ RF Ablation System was switched to impedance control, as compared to the manual control. Smaller ablation size and charring was observed in manual-controlled RFAs. © 2008 Springer-Verlag.