Radiofrequency ablation lesions in a pig liver model

Background Radiofrequency (RF) ablation has been reported as a means of liv er tumor destruction. This study evaluates the use of ultrasound monitoring of radiofrequency lesion creation and describes the morphology, histologic characteristics, and vascular effects of radiofrequency ablations in a pig liver model. Materials and methods, Hemodynamic monitoring was established and laparotom ies were performed in 50-kg pigs. Under ultrasound guidance, radiofrequency needle probes were placed in the liver at predetermined locations. Radiofr equency energy was applied over 15 min to generate lesions 3 cm in diameter . Eighty lesions were generated in 10 animals. At the completion of the exp eriment, the lesions were examined with ultrasound and then excised for CT, gross, and histologic examination. Results. There were no adverse systemic effects. Ultrasound imaging demonst rated the size, shape, and position of the lesions. Gross examination demon strated a core of ablated tissue with a surrounding 1- to 2-mm hemorrhagic perimeter. Lesion volumes averaged 12.8 cc(3) (range 5-34 cc(3)). Final les ion shape and size were frequently altered by the cooling effect of local b lood how. Histologic stains demonstrated microvascular thrombosis and coagu lative necrosis within the lesions. There appeared to be 100% cellular dest ruction within the lesion by cytochemical staining. Conclusions. We demonstrated that RF ablation is capable of killing large v olumes of normal liver tissue; however, local vasculature plays a significa nt a role in defining the ultimate size and shape of the lesion created. Th is may interfere with the utility of radiofrequency ablation as a modality for local tumor control, (C) 1999 Academic Press.