Are ejection fractions from gated SPECT perfusion studies clinically useful? A comparison with radionuclide ventriculography

Gated SPECT (GSPECT) was evaluated fur the measurement of left ventricular ejection fraction (LVEF) by comparing with equilibrium Sated radionuclide v entriculography (RNVG). A total of 99 subjects: underwent GSPECT and RNVG i maging. All studies were acquired in list mode with GSPECT studies processe d to give 16- and 8-frames per R-R interval, and RNVG studies 24 Frames per R-R interval. The Cedars-Sinai QGS software was used to calculate ejection fraction fi om GSPECT studies. RNVG studies were processed using a manuall y drawn single legion of interest technique. Comparison of LVEF from GSPECT with RNVG yielded correlation coefficients of 0.82 and 0.81 for 16- and 8- frame GSPECT studies respectively. The mean 95% prediction interval was 33 +/- 11 percentage points for both 16- and 8-frame studies, indicating a gre at disparity between predicted ejection fraction values from GSPECT and act ual RNVG values. Subgroup analysis of 29 patients with pathological Q-wave evidence of myocardial infarction demonstrated a poorer correlation coeffic ient of r = 0.69. Subgroup analysis of 32 patients with end-diastolic volum es < 100 mi demonstrated a poorer correlation coefficient of r = 0.32. Ejec tion fl actions calculated from 16- and 8-frame studies showed a correlatio n of 0.99 with a mean 95% prediction interval of 8.7 +/-0.04 percentage poi nts. The 8-frame studies underestimated LVEF by 3.6 +/- 2.3% compared to th e 16-frame studies. In conclusion, left ventricular ejection fractions calc ulated using the QGS algorithm from GSPECT studies are inadequate for use i n clinical practice.