Electrocardiographic gated positron emission tomography with POSITOLOGICA II

Electrocardiographic (ECG) synchronized multiple gated data acquisition was employed with POSITOLOGICA II, a whole body positron emission tomograph to avoid blurring of cardiac image due to heart motion. Coincidence events at two cardiac phases (end-systole and end-diastole for example) are collected during predetermined cardiac cycles and then reconstructed. Delay time from triggering R-pulse can be varied 0 - 999 msec and data sampling time can be varied 10 - 999 msec. Fixed radiation sources were imaged with and without gating, and reconstruction errors of the both images were compared to evaluate the magnitude of errors due to non-uniform sampling caused by the gated data acquisition. The result was that although the reconstruction errors due to non-uniform sampling were dominant at very small numbers of accumulated pulses, they rapidly decreased with the increased number of pulses and became negligible to statistical noises at clinical conditions. Gated cardiac images of a normal case was taken after intravenous injection of N-13 ammonia solution. Left ventricular wall motion and changes of wall thickness were readily apparent in the gated images. (author)