Head-to-head comparison of ¹⁸F-sodium fluoride coronary PET imaging between a silicon photomultiplier with digital photon counting and conventional scanners

Background: We compared silicone photomultipliers with digital photon counting (SiPM) and photomultiplier tubes (PMT) positron emission tomography (PET) in imaging coronary plaque activity with ¹⁸F-sodium fluoride (¹⁸F–NaF) and evaluated comprehensively SiPM PET reconstruction settings. Methods: In 25 cardiovascular disease patients (mean age 67 ± 12 years), we conducted ¹⁸F–NaF PET on a SiPM (Biograph Vision) and conventional PET (Discovery 710) on the same day as part of a prospective clinical trial (NCT03689946). Following administration of 250 MBq of ¹⁸F–NaF, patients underwent a contrast-enhanced CT angiography and a 30-min PET acquisition in list-mode on each PET consecutively. Image noise was defined as mean standard deviation of blood pool activity within the left atria. Target-to-background ratio (TBR) and signal-to-noise ratio (SNR) were measured within the whole-vessel tubular three-dimensional volumes of interest on the cardiac motion and attenuation-corrected ¹⁸F–NaF PET images using dedicated software. Results: There were significant differences in image noise and background activity between the two PETs (Image noise (%), PMT: 7.6 ± 3.7 vs SiPM: 4.0 ± 2.3, P < 0.001; background activity, PMT: 1.4 ± 0.4 vs SiPM: 1.0 ± 0.3, P < 0.001). Similarly, the SNR and TBR were significantly higher in vessels scanned with the SiPM PET (SNR, PMT: 16.3 ± 11.5 vs SiPM: 32.7 ± 29.8, P < 0.001; TBR, PMT: 0.8 ± 0.4 vs SiPM: 1.1 ± 0.6, P < 0.001). SiPM PET image reconstruction with a 256 matrix, 1.4 mm pixel, and 2 mm Gaussian filter provided best trade off in terms of maximal SNR, TBR, and clinically practical file size. Conclusions: In ¹⁸F–NaF coronary PET imaging, the SiPM PET showed superior image contrast and less image noise compared with PMT PET.