Evaluation of the Quantitative Gated SPECT (QGS) software program in the presence of large perfusion defects

Objectives: To evaluate the reproducibility and operator dependence for the quantitative regional left ventricular functional parameters (LVFP) assessed by Cedars-Sinai’s Quantitative automated gated SPECT (QGS) software. Methods: The QGS algorithm was reviewed in detail and potential operator dependencies were defined. Series of prototypes were selected, consisting of (a) normal perfusion, (b) perfusion defects in all perfusion regions, (c) perfusion studies of patients with angiographic confirmed normal coronary arteries, proximal (≥70% stenoses) single and multiple vessel disease, and (d) spurious activity in close proximity. While defining and re-orienting the volume containing the left ventricle, the operator adjusted 8 variables/degrees of freedom (DF). The software was used without further operator interventions. Results were expressed as a coefficient of variation (COV). Separate COV were calculated per distinct DF. A␣segment was considered not robust when the COV did exceed 20% in a single DF, 15% in at least 2 DF, or 10% in at least 3 DF. Results: Regional left ventricular EF and volumes showed excellent reproducibility. Normal perfusion and the vessel disease prototypes showed an excellent COV (for all re-orientation steps [33/prototype]) mostly below 5% for LVFP. However, regional wall motion and thickening became less reliable in the presence of large perfusion defects or artifacts. Conclusions: Quantitative estimates for regional left ventricular functional data show excellent reproducibility using automated gated SPECT. However, there may be substantial operator dependency in the presence of large defects or spurious activity in close proximity.