Performance characteristics of silicon photomultiplier based 15-cm AFOV TOF PET/CT

Abstract

Background This paper describes the National Electrical Manufacturers Association (NEMA) system performance of the Discovery MI 3-ring PET/CT (GE Healthcare) installed in Bruges, Belgium. This time-of-flight (TOF) PET camera is based on silicon photomultipliers instead of photomultiplier tubes. Methods The NEMA NU2-2012 standard was used to evaluate spatial resolution, sensitivity, image quality (IQ) and count rate curves of the system. Timing and energy resolution were determined. Results Full width at half maximum (FWHM) of spatial resolution in radial, tangential and axial direction was 4.69, 4.08 and 4.68 mm at 1 cm; 5.58, 4.64 and 5.83 mm at 10 cm; and 7.53, 5.08 and 5.47 mm at 20 cm from the centre of the field of view (FOV) for the filtered backprojection reconstruction. For non-TOF ordered subset expectation maximization (OSEM) reconstruction without point spread function (PSF) correction, FWHM was 3.87, 3.69 and 4.15 mm at 1 cm; 4.80, 3.81 and 4.87 mm at 10 cm; and 7.38, 4.16 and 3.98 mm at 20 cm. Sensitivity was 7.258 cps/kBq at the centre of the FOV and 7.117 cps/kBq at 10-cm radial offset. Contrast recovery (CR) using the IQ phantom for the TOF OSEM reconstruction without PSF correction was 47.4, 59.3, 67.0 and 77.0% for the 10-, 13-, 17- and 22-mm radioactive spheres and 82.5 and 85.1% for the 28- and 37-mm non-radioactive spheres. Background variability (BV) was 16.4, 12.1, 9.1, 6.6, 5.1 and 3.8% for the 10-, 13-, 17-, 22-, 28- and 37-mm spheres. Lung error was 8.5%. Peak noise equivalent count rate (NECR) was 102.3 kcps at 23.0 kBq/ml with a scatter fraction of 41.2%. Maximum accuracy error was 3.88%. Coincidence timing resolution was 375.6 ps FWHM. Energy resolution was 9.3% FWHM. Q.Clear reconstruction significantly improved CR and reduced BV compared with OSEM. Conclusion System sensitivity and NECR are lower and IQ phantom’s BV is higher compared with larger axial FOV (AFOV) scanners like the 4-ring discovery MI, as expected from the smaller solid angle of the 3-ring system. The other NEMA performance parameters are all comparable with those of the larger AFOV scanners.

Comparison of NEMA characterizations for Discovery MI and Discovery MI-DR TOF PET/CT systems at different sites and with other commercial PET/CT systems

“…It is noteworthy that the results for the two systems are similar with, for instance, a spatial resolution for DMI and DMI-DR of 4.62 vs 4.58 for FBP, 3.85 vs 4.13 for VPHD (3D OSEM) and 2.70 vs 2.84 for VPHD-S (3D OSEM + PSF) at 1-cm radial offset. For the DMI evaluation, the results obtained at our institution are compared with previous results from Stanford and Uppsala Universities [2], Tokyo [3] and Brugge [4] in Fig. 1a-c.…”

“…Figure 2c, d presents the results obtained for the DMI system at Stanford and Uppsala Universities [2], Tokyo [3] and Brugge [4] in comparison with the results obtained at our institution using the VPFX algorithm. It is noteworthy that image quality results are very similar across centers, apart from the BV obtained at Brugge for the [2], Tokyo [3] and Brugge [4] measurements for DMI (c-d) and to Southampton-Poole-Plymouth [5] for DMI-DR (e-f) 3-ring system, with a minimum/maximum relative deviation of 74%/50% from our results is obtained. Figure 2e, f shows similar image quality results obtained at Southampton-Poole-Plymouth [5] and our center for the DMI-DR system.…”

“…The scatter fraction of the two systems was slightly different over the range of activity concentrations, with values of 40.5% vs 36.5% at peak NECR, and 38.7% vs 34.3 % at 5 kBq/mL, for the DMI and DMI-DR systems, respectively. Figure 4c compares the DMI scatter fraction to results from Stanford and Uppsala Universities [2], Tokyo [3] and Brugge [4]. Table 2 summarizes the count rate and scatter fraction results obtained for the two systems at different sites.…”

“…In addition, a comparison of NEMA data at our site with publicly available data for the 4-ring DMI system at Stanford and Uppsala Universities [2] and Tokyo [3] will be provided. A comparison with the 3-ring DMI system installed at Brugge [4] will be also presented. For the DMI-DR system, previous work from Southampton-Poole-Plymouth [5] will be considered for comparison.…”

Evaluation of a Bayesian penalized likelihood reconstruction algorithm for low-count clinical 18F-FDG PET/CT

“…Scans were performed on a TOF 3-ring Discovery 710 PET/CT scanner with lutetium yttrium orthosilicate (LYSO) crystals (GE Healthcare), see [21] for an overview of the performance of the system. Images were reconstructed using 3 different algorithms, each using low dose CT information for attenuation correction and the same normalization correction factors with scatter and randoms corrected.…”