At peak exercise, or 4 min after completion of dipyridamole infusion, a bolus of 155 MBq of 99mTc-sestamibi was intravenously injected [12, 13]. For stress imaging studies, recordings were obtained by cadmium-zinc telluride (CZT)-SPECT (D-SPECT, Spectrum Dynamics, Caesarea, Israel) system using 9 pixilated CZT crystal detector columns mounted vertically spanning a 90° geometry [14]. Each of the columns consists of 1024 (16 × 64) 5-mm thick CZT crystal elements (2.46 × 2.46 mm). Square hole tungsten collimators are fitted to each of the detectors, which are shorter than conventional low-energy, high-resolution collimators, yielding significantly better geometric speed. Data were acquired focusing on the heart by the detectors rotating in synchrony and saved in list mode. Images were obtained with the patient in a semi-recumbent position. A 10-s pre-scan acquisition was performed to identify the location of the heart and to set the angle limits of scanning for each detector (region of interest-centric scanning). Using the myocardial count rate from the pre-scan acquisition, the time per projection was set to target the recording of 1000 myocardial kcounts. For rest-optional images, a second intravenous bolus of 370 MBq of 99mTc-sestamibi was injected followed by rest imaging recording. The duration of the scans was less than 10 min for stress and 4 min for rest. Summed and gated projections were reconstructed with an iterative maximum likelihood expectation maximization algorithm using 7 and 4 iterations, respectively [15].