[Dynamic function studies with positron computed tomography: measurements of regional myocardial blood flow in...

A major attribute of positron computed tomography (PCT) is its ability to dynamically measure physiologic processes of the heart. However, quantitative data acquisition and analysis are limited by three major problems: bidirectional activity-cross contamination between the myocardium and the blood, the partial volume effect, and the lower temporal resolution of PCT devices. In the present study, we performed serial six-second PCT scans (fast dynamic study) using 13N-ammonia, and evaluated measurements of regional myocardial blood flow. Six patients with hypertrophic cardiomyopathy (HCM) and five normal subjects were observed. 13N ammonia (4.2-13.0 mCi) was intravenously injected as a bolus, and serial six-second PCT scans were initiated at the times of the tracer injections. The results were as follows: 1. Initial passage of the tracer through the right and left sides of the heart were observed with serial six-second images. 2. In patients with HCM, Myocardial 13N activity was determined by assigning a region of interest (ROI) over the myocardium of greater than 25 mm wall thickness as measured by contrast enhanced CT. In these ROIs, corrections for the partial volume effect and spillover of radioactivity from the blood were not necessary. Arterial 13N activity was determined noninvasively by assigning a ROI over the left atrium. 3. The temporal relationships between the arterial input function and myocardial tracer concentrations were demonstrated. Arterial 13N activity was greatest in the second or third frame, and it rapidly declined thereafter. Myocardial 13N activity increased rapidly, reaching a plateau from the sixth to the ninth frame.(ABSTRACT TRUNCATED AT 250 WORDS)