Quantitative Gated Myocardial SPECT: Effect of Collimation on Left-Ventricular Ejection Fraction

Objective: Left-ventricular ejection fraction (LVEF) can be computed from gated myocardial perfusion SPECT studies using quantitative algorithms. The purpose of this study was to compare the LVEF obtained using the conventional high-resolution parallel-hole collimator (HRC) to the CardiofocalTM collimator (CFC) (Siemens Medical Systems, Hoffman Es-tates, IL) using a quantitative LVEF program. Methods: Thirty-four patients (15 men, 19 women; mean age 5 62 y) had either treadmill or pharmacological stress testing with 25–30 mCi 99mTc sestamibi injected at peak stress. Conventional gated SPECT imaging was performed approximately 30 min poststress, first with the HRC collima-tor, then with the CFC, using the same acquisition parameters on a single-head gamma camera. Traditional (TRAD) determi-nation of LVEF using planar gated blood pool and/or cardiac catherization also was obtained for each patient. Results: The correlation in LVEF between the CFC and HRC acquisitions was excellent, r 5 0.99. The correlation between CFC and TRAD LVEF was good, r 5 0.95, as was the HRC and TRAD correlation, r 5 0.97. The mean LVEF value for HRC was slightly less than TRAD (54 % vs. 55.4%), while the CFC mean LVEF was higher (62 % vs. 55.4%). Although CFC LVEF correlated well with HRC, mean LVEF value using CFC was higher than HRC. Conclusion: The choice of collimator may alter the LVEF obtained from gated SPECT perfusion studies. Key Words: gated myocardial imaging; collimators; gated perfusion SPEC