LAUSR

Myocardial perfusion imaging (MPI) with singlephoton emission computer tomography (SPECT) is still the most performed and, probably, the most trusted noninvasive imaging modality for the evaluation of patients with suspected or known ischemic heart disease (IHD). Despite the great advancement of all the other imaging modalities that has taken place in the last two decades, the ability of SPECT MPI in terms of in-depth characterization and risk stratification of patients with IHD remains unbeaten, with solid evidence proving its additive value in a wide range of patients subsets (i.e., symptomatic vs asymptomatic subjects; normal weight vs obese; sinus vs paced rhythm) and clinical scenarios (i.e., chronic IHD vs acute coronary syndromes). In particular, among the major advantages of this technology, the intrinsic versatility of SPECT MPI is probably the most relevant. In fact, it can be easily coupled with any of the currently available stress tests (i.e., exercise, vasodilators, dobutamine), allowing obtaining reproducible measures of myocardial ischemic susceptibility in practically every category of patients. Moreover, SPECT MPI study can provide information on LV structure and function that may both contribute to the diagnostic process, and provide independent measures of adverse patients prognosis. Nevertheless, even with the evident advantages of nuclear cardiac imaging, SPECT MPI is also characterized by some relevant drawbacks that should be always taken into account, particularly if traditional Anger cameras are employed. Above all, the relatively high radiation burden of a stress/rest imaging protocol performed with a classical SPECT camera equipped with Na/I scintillating crystals—especially if Tl was used as radiotracer instead of the more favorable Tcbased compounds—has always represented a theoretical limitation of this imaging modality, making the clinician often favor other non-ionizing non-invasive myocardial imaging techniques. Secondly, the relatively lengthy acquisition protocol of traditional myocardial SPECT imaging, still not too infrequently performed on a two-day basis, has made the other non-invasive imaging techniques look more appealing. In the last decade, both those limitations have been practically solved by several improvements consistently both the architecture and software settings of traditional Anger cameras. Regarding innovation in technology, a substantial increase of photon sensitivity and spatial resolution can be also obtained by the implementation of confocal collimators mounted on conventional dual-headed gamma cameras (i.e., IQ SPECT). These collimators are characterized by an intrinsically more convergent field of view at the center, while the convergence is reduced approaching the edges of the field of view. The increased sensitivity of those devices allows reducing the acquisition times to about 4 minutes per scan, with a similar quality of traditional systems. Finally, the introduction of dedicated cardiac cameras built around solid-state Cadmium-Zinc-Telluride (CZT) detectors has represented a real revolution in the field of nuclear cardiac imaging, allowing reducing consistently both the radiation burden and acquisition time of MPI, while maintaining if not improving the overall diagnostic capability. Because of the absence of the photomultipliers tubes, CZT cameras are consistently less bulky than traditional SPECT devices, increasing patients comfort Reprint requests: Alessia Gimelli, MD, Fondazione Toscana/CNR G. Monasterio, Pisa, Italy; [email protected] J Nucl Cardiol 2019;26:786–9. 1071-3581/$34.00 Copyright 2017 American Society of Nuclear Cardiology.