FIGURE 1. Process of defining semiautomated ROIs in patient with CL of 231.5 mL/min/1.73 m2. (A) Preliminary ROIs for kidneys, liver, and background area between kidneys. (B) Intermediary binary image generated with image subtraction. (C) Final binary image. Intersections of diagonals of preliminary kidney ROIs are superimposed. (D) Renal and subrenal background ROIs as final products.