Analysis of $^{18}F$-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. Consclusions: 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.