[Positron computed tomography for the assessment of myocardial infarction]

Positron computed tomography (PCT) was performed on 2 normal subjects and 3 patients with myocardial infarction. The PCT device "Positologica-II" developed at the National Institute of Radiological Science Japan was used in this study (Fig. 1). This is a whole body positron CT consisting of 3 detector rings that provide 5 sliced images simultaneously. The radiopharmaceutical 13N-ammonia (13NH3) synthesized by the cyclotron at the institute was used as an indicator of myocardial blood flow. Immediately after the intravenous administration of 13NH3, five serial 1-min PCT scans were performed with 3 additional scans that provided 15 static images spaced 6 mm apart. Cardiac blood pool images were obtained from the first scan. A patient with extensive anterior myocardial infarction revealed an outward bulging of the blood pool compatible with aneurysmal formation (Fig. 2). Three additional late scans provided high quality cross-sectional images of the distribution of 13N in the left ventricular myocardium. Although 13N distribution in myocardium was uniform in normal subjects (Figs. 3 & 4), the patients with myocardial infarction revealed defects in the accumulation of 13N at the sites corresponding to the infarction (Figs. 5, 6, 7 & 8). The conclusions are as follows: (1) serial PCT scans with 13NH3 provide cardiac blood pool images, and (2) myocardial 13N tissue concentration seems to reflect myocardial blood flow.