RT Journal Article SR Electronic T1 Dynamic 13N-Ammonia PET: A New Imaging Method to Diagnose Hypopituitarism JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 44 OP 47 VO 46 IS 1 A1 Zhang Xiangsong A1 Yue Dianchao A1 Tang Anwu YR 2005 UL http://jnm.snmjournals.org/content/46/1/44.abstract AB We have developed a new imaging method to evaluate the blood perfusion and ammonia metabolism of the pituitary gland, and we preliminarily assessed its role in the diagnosis of hypopituitarism. Methods: Six female healthy volunteers (age range, 20–46 y) and 6 female patients (age range, 23–42 y) were enrolled in this study. Dynamic 13N-NH3 PET was performed. Time-activity curves for the pituitary gland and internal carotid artery were generated by setting regions of interest on the transverse planes of the pituitary gland. The standardized uptake value of the pituitary gland, the radioactive ratio of pituitary to thalamus (P/T), and the first-pass uptake rate of ammonia in the pituitary gland were calculated. Results: 13N-Ammonia was extracted rapidly by pituitary tissue in the first 120 s after injection and trapped in pituitary tissue in the healthy volunteers. Three to 20 min after injection, the pituitary gland was clearly seen in the healthy volunteers, and the mean (±SD) size of the pituitary gland on 13N-ammonia PET images was (1.09 ± 0.17 cm) × (1.08 ± 0.14 cm) × (1.12 ± 0.09 cm). However, in patients with hypopituitarism, the first-pass uptake rate of ammonia in the pituitary gland was significantly lower than that in healthy volunteers (0.35 ± 0.10 vs. 0.75 ± 0.07). On images of patients, the pituitary gland was absent or could not clearly be found, was small or malformed, and showed significantly lower uptake of 13N-NH3 than in healthy volunteers (standardized uptake value, 1.15 ± 0.34 vs. 3.74 ± 1.44; P/T, 0.65 ± 0.23 vs. 1.24 ± 0.34). Conclusion: Dynamic 13N-ammonia PET can provide information on blood perfusion and metabolism of the pituitary gland and is useful in early monitoring of damage to the pituitary gland and in diagnosing hypopituitarism.