Pharmacological experiment of 13N-ammonia as PET imaging agent

Objective: To study the pharmacological characteristics of 13N-ammonia, the clinical PET imaging methods of 13N-ammonia, and its application in myocardial blood flow perfusion. Methods: The uptakes of 13N-ammonia in the myocardium and other organs in dogs were measured by whole body scanning and chest dynamic PET scanning. The regional myocardial blood flow (rMBF) in healthy volunteers was also measured by the dynamic and static PET imaging following intravenous bolus administration of 13N-ammonia. Results: The heart and lungs were the first-pass organs that was found out by PET imaging with 13N-ammonia in dogs and human volunteers, the highest uptake of 13N-ammonia in the myocardium was also observed. At 30 s after injection the radioactivity in the blood pool of left and right ventricles reached its peak, at 1 min it began to drop, and at 4-20 min after injection the lower radioactivity was kept on. Regional analysis of PET imaging showed that the myocardial uptake of 13N-ammonia began at 10 s after injection, and the uptake in the septum wall was higher than that in the lateral wall; but in the septum wall was slightly higher than in the lateral wall at 2 min after injection. The radioactivity in the liver and lungs reached its peak at 30 s and was sharply declined hereafter. The uptake of 13N-ammonia in the liver and lungs remained at the lower levels and the heart-to-blood, heart-to-liver and heart-to-lung ratios were above 2.0 after 5 min. Whole-body PET scanning for dogs showed that 13N-ammonia was distributed primarily in the organs with rich blood flow and its clearance was observed in the kidney. The images of regional myocardial blood flow (rMBF) acquired from the dynamic or static PET imaging following intravenous bolus administration of 13N-ammonia were of no difference. Conclusions: The analysis of distribution of 13N-ammonia indicates that the heart-to-blood, heart-to-liver and heat-to-lung ratios were high and the PET images were clear. 13N-ammonia is an ideal myocardial blood flow perfusion imaging agent. rMBF can be measured accurately and noninvasively by 13N-ammonia dynamic and static PET imaging