Dedicated cardiac SPECT scanners have significantly improved in recent years, 1 reducing imaging time and radiation dose. In particular, cardiac scanners have entered clinical practice, 2,3 which use solid-state Cadmium-Zinc-Telluride (CZT) crystal detectors and feature innovative gantry designs, focusing on the heart. These new systems allow improvement in photon sensitivity (5-8 times higher) 4,5 for cardiac imaging, as well as image resolution (up to 2 times higher). 5 While solidstate CZT detectors are more expensive than traditional NaI(Tl) crystal detectors with photomultipliers, they do have important imaging advantages. The CZT detectors have improved energy response, which significantly reduces the scatter component of measured data. They also offer superior intrinsic spatial resolution compared to conventional Anger cameras. The use of less-bulky detectors (no need for photomultipliers) has resulted in more compact scanner size which has facilitated smallfootprint dedicated cardiac camera designs with custom imaging geometries and high-sensitivity collimation. There is a growing evidence, including large multicenter studies, that these solid-state SPECT systems demonstrate excellent diagnostic and prognostic utility in cardiac imaging. [6][7][8] In the last few years, the equipment companies have also introduced general-purpose CZT-based SPECT systems to enable applications other than cardiac imaging. These cameras benefit from improved energy and image resolution due to the CZT detectors and have demonstrated improved image quality in early clinical implementation as compared to general-purpose Angerbased systems. 9,10 GE has introduced general-purpose CZT-based cameras, the Discovery NM/CT 670 and 870, equipped with conventional collimators and CT attenuation correction. These cameras are not only designed for general-purpose imaging but also targeting cardiac imaging applications. The conventional collimator design of these cameras may avoid the difficulties in cardiac imaging, specific to the multipinhole collimation and small field-of-view on the dedicated cardiac cameras. 11 It is important, however, to point out that the general-purpose CZT cameras offer the same photon sensitivity as the conventional Anger systems, because the count sensitivity is related to the collimator and not the crystal. Thus, dedicated CZT cameras with specialized collimators can achieve much higher count sensitivity, consequently allowing faster acquisitions and lower injected doses. In particular, the 19-pinhole collimator, with each pinhole operating at a different focal depth, allows stationary image acquisition. Photons are acquired simultaneously through all the pinholes, allowing improved sensitivity as compared to the conventional camera with parallel collimators and rotating heads. For example, the reported measured system sensitivity of the Discovery NM/CT 670 CZT camera was 78 counts/s/MBq 12 compared to 460 counts/ s/MBq 5 for the dedicated GE 530 CZT design. Thus, in absolute terms, the sensitivity of the gen...