Accuracy of the measurements of left ventricular volume and ejection fraction determined by multigated blood pool tomography

: Accuracy of the measurements of LV volumes and ejection fraction determined from multigated blood pool tomography (MGBPT) was tested in 23 patients with various heart diseases who underwent cineventriculography (CV). Preliminary phantom studies showed that a 42% threshold value was found to provide the best relationship between measured and actual volumes (r = 0.99, standard error of the estimate (SEE) = 4.7 ml). The patients studies were performed at 16 frames/cardiac cycle at 18 angles over a 180 degrees rotation for one minute per angle. Long-axis horizontal views were reconstructed. The numbers of LV voxel with counts above the threshold value were summed and multiplied by the known volume of a voxel. Measurements of LV volume (r = 0.82, SEE = 29 ml), end-systolic LV volume (r = 0.83, SEE = 25 ml), end-diastolic LV volume (r = 0.68, SEE = 33 ml), and ejection fraction (r = 0.73, SEE = 10%) determined from MGBPT correlated well with those determined by CV. However, the ratios (Y) of the difference of the MGBPT-volume from the CV-volume to the CV-volume were decreased progressively and negatively as the CV-volumes (X) were smaller (Y = 38-3,996/X). Thus, we conclude that the determinations of volume by MGBPT would lead to more errors with the smaller volumes.