Analysis of 18F-fluorodeoxyglucose positron emission tomography findings in patients with pituitary lesions

BACKGROUND/AIMS Although magnetic resonance imaging (MRI) is a good visual modality for the evaluation of pituitary lesions, it has limited value in the diagnosis of mixed nodules and some cystic lesions. We evaluated the usefulness of (18)F-fluorodeoxyglucose positron emission tomography (FDG PET) for patients with pituitary lesions. METHODS (18)F-FDG PET and MRI were performed simultaneously in 32 consecutive patients with pituitary lesions. The relationships between FDG uptake patterns in PET and MRI findings were analyzed. RESULTS Of 24 patients with piuitary adenomas, 19 (79.2%) showed increased uptake of (18)F-FDG in the pituitary gland on PET scans. All patients with pituitary macroadenomas showed increased (18)F-FDG uptake on PET scans. Meanwhile, only five (50%) of the 10 patients with pituitary microadenomas showed positive PET scans. Interestingly, of two patients with no abnormal MRI findings, one showed increased (18)F-FDG uptake on PET. For positive (18)F-FDG uptake, maximum standardized uptake values (SUV(max)) > 2.4 had 94.7% sensitivity and 100% specificity. In addition, SUV(max) increased in proportion to the size of pituitary adenomas. Most cystic lesions did not show (18)F-FDG uptake on PET scans. CONCLUSIONS About 80% of pituitary adenomas showed positivity on PET scans, and SUV(max) was related to the size of the adenomas. PET may be used as an ancillary tool for detection and differentiation of pituitary lesions.