Figure 6c. Usefulness of image subtraction. (a) Axial precontrast fat-suppressed T1-weighted MR image obtained in a 65-year-old man with RCC shows a high-signal-intensity ablation zone (arrow). (b) Axial gadolinium-enhanced fat-suppressed T1-weighted MR image shows persistent high signal intensity that may be difficult to distinguish from subtle enhancement within the ablation zone (arrow). (c) Subtraction image created by subtracting the precontrast data set from the postcontrast data set shows no enhancement in the region of the ablation zone (arrow).