Residual renal cancer cell (RCC) in right kidney, six months after cryoablation. Pre-treatment contrast-enhanced cortico-medullary phase CT scan (a) shows exophytic solid tumor with heterogeneous contrast-enhancement. Post-treatment perfusional CT (b) shows a nodular enhancing component (ROI 3) in the medial portion of the ablation zone with peripheral linear enhancement in the peri-renal fat, suggestive for residual tumour. Regions of interest were placed in abdominal aorta (ROI 1), normal renal cortex (ROI 2) and nodular solid enhancement area (ROI 3) to measure perfusional parameters. Time/Density curve (c) shows a typical contrast enhancement pattern in residual tumour area with fast and early wash-in, a plateau trend and a slow, progressive and uniform wash-out (curve 3). Color maps superimposed on gray-scale images (d, Blood Volume, BV; e, Blood Flow, BF) of right kidney show high colour encoding in corresponding residual tumour area: (d) BV (mean, 140,68 ± 24,48 mL/100 g wet tissue/min), (e) BF (mean, 562,72 ± 97,96 mL/100 g wet tissue).