Experimental evaluation of accuracy of radiofrequency ablation using conventional ultrasound or a third-dimension navigation tool

Background: Successful radiofrequency-induced ablation is dependent on correct placement of the device. The ultraguide system is a three-dimensional positioning system creating an overlay of the real-time ultrasound image and a virtual image of the device. Methods: Tumor mimics were produced by injecting an agarose/ cellulose/glycerol gel into pig livers on table. The precision of device placement was evaluated either using a freehand ultrasound procedure or using the aid of the ultraguide system either by an experienced or inexperienced surgeon. Tumor mimics were ablated by a protocol yielding an ablation only discretely larger than the mimics to enhance the importance of precise positioning. Results: The sizes of the 40 tumor mimics were: largest diameter 14.1 +/- 2.2 mm, volume 0.89 +/- 0.40 cm(3). The largest diameter of ablation was 25.6 +/- 3.7 mm, the smallest diameter 21.9 +/- 2.9 mm, and the volume 7.20 +/- 2.38 cm(3). The experienced surgeon was successful in 7 of 10 cases with and without the ultraguide, the inexperienced surgeon in 4 of 10 without and 7 of 10 with the ultraguide. Conclusions: The ultraguide system may facilitate precise device placement for the less experienced surgeon. It seems worthwhile to evaluate a possible benefit of the system during placement of devices under operating room conditions.