The preliminary study of the blood perfusion and ammonia metabolism of pituitary using dynamic ~(13)N-NH_3 PET imaging

Objective To preliminarily study the blood perfusion and ammonia metabolism of pituitary using dynamic 13 N-NH_3 PET imaging. Methods 13 N-NH_3 PET imaging was performed on 21 subjects without pituitary diseases, 6 of them underwent dynamic PET imaging, and 8 of them underwent brain MRI in addition to PET. PET images were registered with MRI. Results The pituitary could be clearly seen in 13 N-NH_3 PET images, and being confirmed by PET/MRI image fusion. The size of pituitary was (1.07±0.17) cm×(1.09±0.15) cm×(1.14±0.17) cm, the standard uptake value (SUV) was 3.84±1.75, and the radioactivity ratio of pituitary to thalamus was 1.35±0.63. Pituitary image was seen at 10 s after the internal carotid was seen in dynamic 13 N-NH_3 PET imaging. 13 N-NH_3 was retained in pituitary, and was hardly cleaned out within 20 min. The radioactivity ratio of pituitary to internal carotid was 0.75±0.13 when the radioactivity of internal carotid was at its highest level. Conclusions The blood flow and ammonia metabolism of pituitary can be observed with dynamic 13 N-NH_3 PET imaging. Ammonia is highly extracted by pituitary, and metabolized in pituitary cells.