| Abstract: | A technique for the semiautomatic calculation of left ventricular volumes from multigated blood-pool tomograms (MGBPT) was tested in a series of 12 patients undergoing contrast ventriculography within 48 hr of gated tomography. The parameters necessary for the calculation of volume were developed in a chest phantom study performed with a series of 99mTc-filled balloons representing the right and left ventricles. The images were analyzed for volume using a percentage of peak count-threshold of the left ventricular balloon. This technique resulted in a correlation of r = 0.99 of the calculated to the true phantom volumes (y = 0.87x + 27.4, p less than 0.01, s.e.e. = 7.87 ml). The patient studies were recorded at 16 frames/cardiac cycle at each of 60 angles over a 360 degree rotation. Reconstructed data were presented in an endless loop cine format producing a set of sequential "beating tomographic slices" in the transverse, apical four-chamber, short-axis, and long-axis oblique views. Measurements of end systolic volume (y = 0.79x + 30, r = 0.93, p less than 0.001, s.e.e. = 24 ml), end-diastolic volume (y = 0.63x + 60, r = 0.94, p less than 0.0001, s.e.e. = 20 ml) and ejection fraction (y = 0.88x - 0.02, r = 0.92, p less than 0.001, s.e.e. = 0.08) determined from the semiautomated volume method correlated well with those determined by left ventricular contrast angiography. A qualitative comparison of MGBPT, planar imaging, and left ventricular angiography in 12 patients revealed that the visual assessment of wall motion using the 16-frame tomographic slices had significant advantages over planar and single plane angiographic data in the identification of inferior, basal, and septal wall motion abnormalities as well as the extent of involvement by aneurysm formation. A quantitative comparison of wall motion in the long-axis oblique view of the MGBPT to the RAO 30 degree ventriculogram (y = 0.74x + 8.7, r = 0.82, p less than 0.0001, s.e.e. = 14%) confirmed the qualitative similarity of these two views. We conclude that MGBPT is promising as a method for accurately measuring left ventricular volumes and assessing regional wall motion. |
