Radioablation settings affecting the size of lesions created ex vivo in porcine livers with monopolar perfusion electrodes.

RATIONALE AND OBJECTIVES

To explore the morphological characteristics of ablated lesions and find which combination of duration, temperature, and power was preferable to create largest lesion size with monopolar perfusion electrodes.

MATERIALS AND METHODS

Using monopolar perfusion electrodes to create 72 lesions in 30 excised porcine livers with radiofrequency radiation at different durations (5, 10, 15, and 20 minutes), temperatures (83 degrees C, 93 degrees C, 103 degrees C, and 113 degrees C), and powers (20, 30, and 40 W). Lesion volumes were calculated from longitudinal diameters and transverse diameters. Morphological characteristics were assessed microscopically from slides stained with hematoxylin and eosin.

RESULTS

Positive correlations were found between duration and longitudinal diameter (r = 0.66; P < .001), transverse diameter (r = 0.66; P < .001), distance of ablation beyond the electrode tip (r = 0.56; P < .001), and volume of lesions (r = 0.66; P < .001). Temperature was also positively correlated with longitudinal diameter (r = 0.70; P < .001), transverse diameter (r = 0.72; P < .001), distance of ablation beyond the electrode tip (r = 0.61; P < .001), and lesion volume (r = 0.711; P < .001). Lesion size did not increase when duration was longer than 15 minutes and temperature was higher than 103 degrees C. Power was not correlated with lesion size. Lesion size did not increase with increasing power. Macroscopically, all lesions were elliptical in cross section and appeared three zones: a central zone (I), a coagulated necrotic zone (II), and a hemorrhagic and edematous zone (III) from inside to outside. Microscopically, cells morphology and the nucleus were irregular or even disappeared in zone I. In zone II and III, cells did not appear deformation.

CONCLUSION

Duration and temperature, not power, affected lesion size. The largest lesion size was about 3.5 cm x 2.5 cm x 2.5 cm as temperature and duration was 15 minutes/103 degrees C.