NEMA NU 4-2008 and in vivo imaging performance of RAYCAN trans-PET/CT X5 small animal imaging system

Abstract

The system resolution defined as full width half maximum (FWHM) was 2.07 mm, 2.11 mm and 1.31 mm for the tangential, radial and axial resolution, respectively, at the center of the field of view. The peak noise equivalent count rate (NECR) values measured were 61 kcps at 0.19 MBq/mL for the rat size phantom and 126 kcps at 1.53 MBq/mL for the mouse size phantom. Scatter fractions were 24% and 14% for the rat and mouse phantom. The measured peak sensitivity of the system was 1.70 %. Image quality in static imaging was deemed sufficient based on the image quality phantom study, with average activity concentration of 155 ± 8.6 kBq/mL and image uniformity of 5.57% when using two-dimensional filtered backprojection algorithm (2D-FBP). Rods in the image quality phantom were visualized easily up to 2 mm in size. In dynamic in-vivo PET imaging, time-activity-curves from several regions were successfully measured, characterizing the radioactivity distribution in myocardial blood pool, liver, left ventricle and the lung.In conclusion, the RAYCAN Trans-PET/CT X5 system can be considered a suitable option for basic imaging needs in preclinical imaging.

NEMA NU‐4 2008 performance evaluation of Xtrim‐PET: A prototype SiPM‐based preclinical scanner

“…Previous studies showed that that the spatial resolution of the majority of PET scanners is slightly larger than crystal dimensions . The radial FWHM of our scanner is 2.01 at 5 mm radial offset obtained from 18 F source, which is close to or better than the corresponding values reported for FLEX Triumph X‐PET (2.0 mm), microPET R4 (2.13 mm), microPET P4 (2.29 mm), Mosaic HP (2.32 mm), ClairvivoPET (2.16 mm), and Trans‐PET/CT X5 (2.11) with approximately similar crystal dimensions. The effective transaxial resolution of our prototype is 2.02 at 5 mm radial distance whereas the ratio of the effective transverse resolution to the crystal size is about 1.02, which is in line with those reported for the microPET P4 (1.02), microPET Focus 120 (1.18), microPET Focus 220 (1.19), Inveon (1.08), Mosaic HP (1.17), Argus (1.14) and VrPET (1.15) .…”

“…The overall energy resolution of the system was about 12.4% with a mean peak to valley ratio of 43.8 at 25°C temperature and 28 V bias voltage, which is better than the Inveon (14.6%), NanoPET(19%), LabPET (25%) and Argus (26%) . Moreover, it is slightly better than recently designed LYSO/SiPM‐based systems, such as MRS‐PET (14.6%), MADPET4 (13.7%), RAYCAN (15%), Hyperion (12.7%) and scanners reported by Lee et al (13.2%), Ko et al (14.2%) and Goertzen et al (12.5%) but lower than the β‐cube PET scanner (12%) …”

“…Expectedly higher scatter fraction was obtained for rat‐like phantom in comparison to mouse‐like phantom which is owing to increasing the numbers of scattered event with object size. Scatter fraction for mouse‐like phantom (12%) compares favorably well with scanners using the same energy window like ClairvivoPET (17.7%), MRS‐PET (21%), NanoPET/CT (15%), NanoScan PET/MRI (17.3%), and RAYCAN(14%) …”

“…The slight non‐uniformity of the spatial resolution across the transaxial FOV, particularly in the axial direction (Figures and ), is severely hampered by SSRB and FBP reconstruction for scanners with polygon or other irregular geometries . This issue is more severe for small‐animal imaging which could be explained by the combined effects of rebinning, lack of scatter and attenuation corrections and multi‐bed reconstruction where the reconstructed images of each bed position are stitched together considering the axial overlap.…”

“…To ensure a fair comparison between different scanners and objectively optimize data acquisition and reconstruction protocols for a variety of applications, the National Electrical Manufacturers Association (NEMA) provided a specific standard (NEMA NU‐4) for the evaluation and performance characterization of preclinical PET scanners in terms of spatial resolution, sensitivity, scatter fraction, count rate characteristics and overall imaging performance . Subsequently, the majority of commercial small‐animal PET scanners and prototype models have been characterized according to the NEMA NU‐4 standards …”