Operator dependent variability in quantitative analysis of myocardial perfusion images.

The purpose of this study was to evaluate variability in the quantification of myocardial perfusion images obtained by a group of experienced operators using two widely used programs. The Cedars Emory quantitative analysis program (CEqual) was used to quantify the size of perfusion defects and the Cedars-Sinai quantitative gated single-photon emission tomography program was used to quantify left ventricular function. Five patients with reversible apical defects, five with fixed apical defects and three patients with normal perfusion were selected. Eight experienced medical laboratory technologists processed the studies from raw projection data. The manual steps consisted of defining two alignment axes parallel to the long axis of the left ventricle, and for the CEqual program selecting apex and base in the short axis slices in the rest and stress studies. Wide variability between the operators in the quantification of reversibility could be seen in all three vascular territories. A range >10% was found in at least one vascular territory for nine of the 13 patients. The differences in left ventricular ejection fraction (LVEF) between operators were <5% for all 13 patients. The large variability in the quantification of reversible apical perfusion defects may influence the clinical interpretation and cause false conclusions. In contrast, inter-operator variability for the quantification of the LVEF was low.