Automatic quantification of left ventricular ejection fraction from gated blood pool SPECT

Background Cardiac gated blood pool single photon emission computed tomogra phy (GBPS) better separates cardiac chambers compared with planar radionucl ide ventriculography (PRNV), We have developed a completely automatic algor ithm to measure quantitatively the left ventricular ejection fraction (LVEF ) from gated technetium 99m-red blood cells (RBC) GBPS short-axis 3-dimensi onal image volumes. Methods and Results. The algorithm determines an ellipsoidal coordinate sys tem for the left ventricle and then computes a static estimate of the endoc ardial surface by use of counts and count gradients. A dynamic surface repr esenting the endocardium is computed for each interval of the cardiac cycle by use of additional information from the temporal Fourier transform of th e image data sets. The algorithm then calculates the left ventricular volum e for each interval and computes LVEF from the end-diastolic and end-systol ic volumes. The algorithm was developed in a pilot group (N = 45) and valid ated in a second group (N = 89) of patients who underwent PRNV and 8-interv al GBPS, Technically inadequate studies (N = 38) were rejected before group ing and processing. Automatic identification and contouring of the left ven tricle was successful in 121/172 patients (70%) globally and in 76/89 patie nts (85%) in the validation group. Correlation between LVEFs measured from GBPS and PRNV was high (y = 2.00 + 1.01x, r = 0.89), with GBPS LVEF signifi cantly higher than PRNV LVEF (average difference = 2.8%, P < .004). Conclusions. Our automatic algorithm agrees with conventional radionuclide measurements of LVEF and provides the basis for 3-dimensional analysis of w all motion.