Radiofrequency Interstitial Tissue Ablation (RITA or RFA) is a minimally invasive procedure in which a thin needle electrode is inserted into an unresectable liver or bone lesion under ultrasound or CT guidance. Electrical energy is delivered through the electrode to the lesion which produces heat within the cells surrounding the electrode. When all cells within the lesion, as well as a margin around it, are heated beyond the lethal threshold (53°C), the procedure is complete (30 minutes for a 7 cm ablation zone).