FIG 4. These MR imaging scans show regions of interest manually traced on digitized scans to obtain volume measurements. Enhancing tumor is outlined in yellow; resection cavity, central necrosis, and cystic fluid are outlined together in green; and T2 signal abnormalities are outlined in pink. A, Contrast-enhanced T1-weighted sequence shows a rounded, enhancing, tumor volume with central necrosis in the right insular region. B, T2-weighted sequence shows a large hyperintensity representing total tumor, resection cavity, and edema volume. Note the very irregular shape that is neither spherical nor ellipsoid. The computerized volume-rendering program better approximates volume than the commonly used cross-product method, which assumes the shape of the volume is spherical or ellipsoid