[Experimental radiofrequency ablation in porcine liver ex vivo with "wet" unipolar electrode]

To observe the effects of radiofrequency ablation in porcine liver ex vivo with "wet" RITA UniBlate unipolar electrode, evaluate the morphologic characteristic of the ablated zones and explore the impact upon the ablation lesions of time, temperature and set power of "wet" monopolar electrodes.

The maximal effective ablation electrode length of this "wet" unipolar electrode is 2.5 cm. According to ablation time, temperature and power respectively, the experiment was divided into three major groups of A, B, C (11 sub-groups). The investigators observed the morphological characteristics of ablation lesions, measured the longitudinal and transverse distance of ablation beyond the electrode tip and calculated the volume of ablation lesion. Statistical analysis was performed with one-way ANOVA upon the above-mentioned four parameters. And the pathological examinations were made with HE staining.

(1) All of ablated zones were ellipsoid. The cross-section of ablation lesions appeared to have 3 zones from the inside out: central zone, coagulated zone, hemorrhage and edema zone. (2) When ablating time and temperature increased to 15 min and 103 degrees C respectively, the ablated zones peaked: longitudinal diameter, transverse diameter, ablation distance beyond electrode tip and volume of each ablated zone was (3.49 +/- 0.09) cm, (2.40 +/- 0.13) cm, (0.79 +/- 0.09) cm and (10.6 +/- 1.3) cm(3) respectively. With power as a variable, different sizes between ablated zones showed no statistical significance. (3) The morphology of ablated zones became irregular when the electrodes were located around larger blood vessels.

The ablating time and temperature are the major factors of affecting the size of radiofrequency ablation lesion with RITA "wet" unipolar electrode.