Purpose <p>The cadmium–zinc–telluride (CZT) camera has generated renewed interest in single-photon emission computed tomography (SPECT)-myocardial flow reserve (MFR) assessments in patients with coronary artery disease (CAD). However, discussion regarding the relationship between MFR and conventional indices or their role in improving CAD diagnosis is limited. This study evaluated how left ventricular (LV) phase analysis indices—such as bandwidth, phase standard deviation (SD), and entropy—calculated from myocardial perfusion imaging (MPI), contribute to improving CAD diagnosis by comparing them with MFR.</p> Methods <p>We retrospectively analyzed the clinical images of 60 patients (42 men and 18 women; mean age, 66.8 ± 10.0&#xa0;years) who underwent dynamic CZT SPECT for suspected CAD. Receiver operating characteristic (ROC) and multivariate ROC analyses were used to assess the improvement in CAD diagnosis when using MPI (summed stress score [SSS]) alone, MPI combined with MFR, or MPI combined with LV phase analysis indices (stress indices).</p> Results <p>The area under the ROC curve (AUC) for SSS using MPI alone was 0.87, whereas that for SSS combined with MFR was 0.93, confirming a significant improvement in CAD diagnosis (<i>p</i> = 0.04). The AUCs for bandwidth, phase SD, and entropy combined with SSS were 0.93, 0.91, and 0.91, respectively, with no significant differences when compared individually. However, combining all LV phase indices yielded a significant improvement, with an AUC of 0.94 (<i>p</i> = 0.04).</p> Conclusion <p>A similar diagnostic accuracy for CAD was obtained by combining the SSS from MPI with either the MFR or the three phase indices.</p>