N-13 ammonia myocardial positron computed tomography, (3)

N-13 ammonia myocardial positron computed tomography (PCT) was performed at rest and during exercise in 11 cases including 3 normal subjects. The exercise was done using supine bicycle ergometer with a graded work load and N-13 ammonia was injected 30-60 seconds before the termination of the exercise. In 3 normal cases, tracer distribution was homogeneous in the left ventricular myocardium at rest and during exercise. Of 8 cases with coronary artery disease, decreased tracer uptake in regional myocardium was observed in 6 cases (75%) in resting images and 7 cases (88%) in exercise images. Furthermore, exercise induced ischemia was delineated in 6 of the 7 cases with angina pectoris. For quantitative analysis, mean tracer activity in regional myocardium was assessed as percent dose of ammonia administration per gram tissue by locating 5 regions of interest in the left ventricular myocardium in each section. In normal myocardium, tracer activity was 104+-14x10-4%dose/g at rest and it was slightly increased during exercise (117+-24x10-4%dose/g) (p<0.001). In stenosed myocardium, tracer activity was 98+-27x10-4%dose/g at rest and it was significantly decreased during exercise (75+-25x10-4%dose/g) (p<0.001). We conclude that quantitative and quantitative analysis of myocardial perfusion by N-13 ammonia PCT at rest and during exercise is a valuable technique for evaluation of coronary artery disease. (author)