Figure 1. Typical placement of regions of interest (ROIs) for the measurement of CT values. ROIs in the right lobe of the liver, spleen, and portal trunk are drawn as large as possible, avoiding large vessels. ROIs in the liver and spleen have margins not less than 5 mm from the organ surfaces; this avoids partial volume effects and artefacts from the ribs. An enhanced area in segment 7 indicates hepatocellular carcinoma (arrow).