Automation of gated tomographic left ventricular ejection fraction.

BACKGROUND: The feasibility of determining left ventricular (LV) ejection fraction (EF) from 99mTc-labeled sestamibi gated tomography (GSPECT) is well established. To improve precision of measurement, rules used by observers in processing tomograms were encoded for automation. METHODS AND
RESULTS: LV centers were estimated from activity centroids of time-difference images exceeding 50% of maximum counts. End diastole and end systole were defined by time-varying maximum count extremes. Endocardial borders were generated by fitting maximum locations with fifth-order two-dimensional harmonics, searching inward to predetermined thresholds, and reconciling endocardial with valve plane points. Regression analysis of GSPECT EF yielded r = 0.87 versus equilibrium gated blood pool in 75 patients and r = 0.87 versus gated first pass in 65 patients. GSPECT EF interobserver variability was r = 0.92 and intraobserver automatic versus manual linear correlation was r = 0.94. A subgroup of 25 studies was analyzed by six independent observers, for whom EF agreement with the core laboratory ranged from r = 0.93 to r = 0.96. Experienced observers judged it necessary to alter end-diastolic or end-systolic frames in 7% of patients, endocardial borders in 14%, and LV centers in 28%.
CONCLUSION: Results of automated GSPECT LV EF correlated well with those of manual GSPECT and gated first-pass and equilibrium blood pool values and were highly reproducible.