Fast dynamic study in cardiac positron CT using 13N-ammonia in man.

Fast dynamic studies with positron computed tomography (PCT) of the heart have been relatively few because of the technical limitations of prevalently used PCT devices. In the present study, we used a high-sensitivity, whole-body multislice PCT device (POSITOLOGICA-II) and performed serial 6-s PCT scans after the intravenous bolus injection of 13N-ammonia in 15 cardiac patients and 5 normal subjects. On the first image (0-6 s), 13N activity was primarily in the right atrium and ventricle. On the third image (12-18 s), it was primarily in the left atrium and ventricle. These blood-pool images permit evaluation of size and configuration of ventricles and atria in cardiac patients and normal subjects. Clearance of 13N activity in the blood pools and lungs occurred primarily during the 1st min. Thereafter, the myocardial images were delineated. In patients with heart failure, delayed clearance of the tracer from the blood pools and lungs was observed. The results indicate that initial passage of the tracer through the heart can be observed with the use of fast dynamic PCT.