Multigated cardiac blood-pool study using converging collimator in infants

In infants and younger children, the cardiac blood-pool images acquired by using parallel hole collimators are often too small to determine region of interest (ROI) accurately. In order to make them magnified enough, we attempted to perform multigated equilibrium studies with converging (CONV) collimator. Twelve infants (ages; 3 months-4 years, mean 1.8 years old) with various heart diseases were studied with administration of 3-7 mCi of Tc-99m-human serum albumin. CONV studies provided proper magnification and resolution of cardiac images in all cases. Especially, in four small infants, CONV images showed adequate separation between right and left ventricles (LV) which could not be shown by the studies using general purpose collimator. We were able to determine ROI over LV accurately on the CONV images and, thus, LV ejection fractions calculated from CONV study correlated well with those obtained from biplane cineangiograms (r = 0.884, p < 0.01). In addition, phase and amplitude images of CONV studies clearly showed intraventricular circumscribed hemodynamic abnormalities. This method is clinically valuable because it provides the non-invasive and reliable assessment of cardiac function in infants. (author)