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FIGURE 1. 11C-Metomidate (left column) and 18F-FDG (right column) PET images of patients with adrenal incidentalomas: a left-sided hormonally inactive adenoma (patient 11) (A and B), a right-sided cortisol-secreting adenoma (patient 2) (C and D), a right-sided adrenocortical carcinoma (patient 13) (E and F), and a right-sided hepatocellular carcinoma described as "pseudoadrenal mass" (patient 20) (G and H). The images are coronal sections through the midabdomen obtained between 25 and 45 min (11C-metomidate) or 45 and 65 min (18F-FDG) after injection. Tumor is indicated in each case by a white arrow, and normal adrenal, when visible in the same section, by a black arrow. All adrenocortical tumors (first 3 rows) have much higher uptake of 11C-metomidate than of 18F-FDG, whereas the opposite is true for the noncortical neoplasia shown in the lowest row. In this case (G), uptake of 11C-metomidate is not confined to tumor but occurs in a rim of adrenal tissue (black arrow) displaced by the mass. Initially, the high 18F-FDG uptake of the adenoma in 1 d was misjudged as metastasis, with an average SUV of 3.9 (maximum, 6). Liver has invariably high uptake of 11C-metomidate, and tracer excreted in the urinary tract presents the highest radioactivity in 18F-FDG images.
