LAUSR

The success of nuclear cardiology relies on the use of a combination of highly specific signals provided by radiotracers, as well as the use of improved electronic nuclear instrumentation to specifically trace in-vivo the metabolic reaction of interest. Since the development of the first clinical positron imaging device by Brownell and Aronow in 1953, incredible progresses have been made. Some of these progresses involved the fusion of PET and CT in an hybrid device, the development of full-ring PET as well as the discovery of fast ceriumdoped lutetium oxyorthosilicate (LSO) with interesting physical properties allowing the clinical implementation of time-of-flight (TOF) technology. This constant query for modern devices with sophisticated reconstruction algorithms has clinical and therapeutic implications, since PET/CT provides semi-quantitative, as well as quantitative parameters of the myocardial blood flow (MBF). These parameters are used as ‘‘gatekeeper’’ for coronary angiography in patients with known or suspected coronary artery disease or for the follow-up of coronary allograft vasculopathy. Recent technological progresses have led to the introduction of the silicon photomultiplier (SiPM)-based TOF technology. Briefly, it consists of multiple columns of single-photon avalanche photodiodes, which are operated in Geiger mode. The resulting photon from the annihilation produces a charge avalanche after hitting on the cell, leading to the formation of a discrete electrical impulse. In the socalled digital SiPM, the signal of each individual cell is first digitalized, and the timing and energy information is obtained after summation of the corresponding cells that produces a single count. Other aspects of the detector accounts for its performance, such as the length of the scintillator crystal, the coupling time between the scintillator and the photodetector as well as the novelty in the signal processing. Phillips was the first constructor to introduce SiPM technology 2014, followed by General Electric and more recently by Siemens and others. This technology led to improvement of the timing resolution, with TOF performance actually down to 214 picoseconds, as well as to significant improvement of the spatial resolution. This improvement led to better image quality, increased sensitivity for the detection of small lesions with consequently upstaging of the disease in oncologic PET. Whether this improvement has a significant impact on the accuracy of the evaluation of myocardial perfusion imaging (MPI) is unknown. This hypothesis has been questioned in the present study by Koenders et al. The authors investigated the accuracy of digital SiPM (dSiPM) PET/CT as compared to the high-resolution photomultiplier tube (hrPMT) PET/CT in the evaluation of semi-quantitative as well as quantitative MPI. For this purpose, 30 patients underwent 2 sets of rest and regadenoson-induced stress Rubidium (Rb)-82 MPI, beginning with the hrPMT PET/CT followed by the dSiPM PET/CT within 3 weeks. The images were analyzed by two independent nuclear medicine experts for their quality and the presence of possible defects in the semi-quantitative as well as in the quantitative MBF parameters. The authors described an improvement in the image quality using dSiPM PET/CT as compared to hrPMT PET/CT with Reprint requests: John Prior, PhD, MD, Department of Nuclear Medicine and Molecular Imaging, CHUV, Rue du Bugnon 46, 1011 Lausanne, Switzerland; [email protected] J Nucl Cardiol 2022;29:213–5. 1071-3581/$34.00 Copyright 2020 American Society of Nuclear Cardiology.