Utility of 13N-Ammonia PET/CT to Detect Pituitary Tissue in Patients with Pituitary Adenomas.

RATIONALE AND

OBJECTIVES

It is clinically essential, but sometimes challenging, to distinguish pituitary tissue from pituitary adenomas (PAs). It is helpful to avoid damage of pituitary tissue during management. We evaluated the ability of 13N-ammonia positron emission tomography (PET)/computed tomography (CT) to locate and distinguish pituitary tissue from PAs.

MATERIALS AND

METHODS

Forty-eight patients (four with prolactinoma, 10 with Cushing's disease, 12 with acromegaly, and 22 with nonfunctional PAs) prospectively underwent magnetic resonance imaging (MRI), 13N-ammonia PET/CT, 18F-FDG PET/CT, prior to surgery.

RESULTS

Pituitary position could be determined in 31 (64.5%) patients by 13N-ammonia PET/CT, and by MRI in 26 (54.2%) patients. It was detected by 13N-ammonia PET/CT and MRI in eight of eight patients (100%) with pituitary microadenoma, tumor maximum diameter (TMD) <1 cm, and in nine of 10 patients (90%) with PAs with TMD ≥1 cm, but <2 cm. In 16 patients with PAs with TMD ≥2 cm, but <3 cm, pituitary tissue position was detected by 13N-ammonia PET/CT in nine (56%), and by MRI in 8 (50.0%) patients by MRI. In 14 patients with PAs with TMD ≥3 cm, pituitary tissue position was detected by 13N-ammonia PET/CT in five (35.7%) patient, and by MRI in 1 (7.1%). In seven patients, the pituitary tissue could be detected by 13N-ammonia PET, but not by MRI, and in two patients by MRI, but not by 13N-ammonia PET.

CONCLUSION

13N-ammonia PET/CT imaging is a sensitive means for locating and distinguishing pituitary tissue from PAs, particularly those with TMD <2 cm. It is potentially valuable in detection of pituitary tissue in patients with PAs.