Training for renal ablative technique using an agarose-based renal tumour-mimic model

OBJECTIVE: To assess whether a recently developed porcine tumour-mimic model can serve as a training model for radiofrequency ablation (RFA) of renal masses, as the increased diagnosis of small occult renal masses has led to the development of nephron-sparing treatments, including RFA, and the techniques required for effective tumour ablation can be difficult to master. MATERIALS AND METHODS: Tumour mimics were created by injecting 0.7 mL of an agarose mixture into the parenchyma of a porcine kidney, producing 1-cm spherical lesions which were hyperechoic on ultrasonography (US). The ex vivo experiment included creating 40 tumour mimics followed by RFA using US-guided needle placement. The ablation diameter was set to 15 mm to produce a margin of grossly ablated tissue around the mimic lesions. The in vivo portion involved creating 20 tumour mimics and ablating them under direct laparoscopic vision with US-guided probe placement. In each case, the mimic lesion size by US and gross examination, ablation diameter, and completion (accuracy) of ablations were recorded. RESULTS: Accurate placing of the RFA needle by US guidance was difficult to learn, as all tumour-mimic lesions were either endophytic or completely intraparenchymal. The ex vivo model required ≈ 15 ablations before the needle was placed consistently into the lesions. The in vivo model was equally difficult to learn, with five positive margins by gross examination in the first 10 ablations, while the subsequent 10 had no positive margins. CONCLUSION: The agarose-based tumour mimic is a useful target model for learning and improving US-guided ablative techniques in both the ex vivo and in vivo settings. The tumour-mimic allows the surgeon to assess targeting accuracy in an animal model. Further studies are needed to determine this model's utility as a clinical training aid.