Performance Characteristics of the Biograph Vision Quadra PET/CT System with a Long Axial Field of View Using the NEMA NU 2-2018 Standard

Abstract

Purpose: To evaluate the performance of the Biograph Vision Quadra (Siemens Healthineers) PET/CT system. This new system is based on the Siemens Biograph Vision 600, using the same silicon photomultiplier-based detectors with 3.2×3.2×20-mm lutetium-oxoorthosilicate crystals. The Quadra's 32 detector rings provide a fourfold larger axial field of view (AFOV) of 106 cm, enabling imaging of major organs in one bed position.Methods: Physical performance of the scanner was evaluated according to the National Electrical Manufacturers Association NU 2-2018 standard with additional experiments to characterize energy resolution. Image quality was assessed with foreground to background ratios of 4:1 and 8:1. Additionally, a clinical 18 F-FDG-PET study was reconstructed with varying frame durations. In all experiments, data were acquired using the Quadra's maximum ring distance of 322 crystals (MRD 322), while image reconstructions could only be performed with a maximum ring distance of 85 crystals rings (MRD 85). Results:The spatial resolution at full width half maximum in radial, tangential and axial directions were 3.3, 3.4 and 3.8 mm respectively. The sensitivity was 83 cps/kBq for MRD 85 and 176 cps/kBq for MRD 322. The NECRs at peak were 1613 kcps for MRD 85 and 2956 kcps for MRD 322, both at 27.5 kBq/mL. The respective scatter fractions at peak NECR equaled 36 % and 37 %. The TOF resolution at peak NECR was 228 ps for MRD 85 and 230 ps for MRD 322. Image contrast recovery ranged from 69.6% to 86.9 % for 4:1 contrast ratios and from 77.7 % to 92.6 % for 8:1 contrast ratios reconstructed using PSF-TOF with 8 iterations and 5 subsets. Thirty seconds frames provided readable lesion detectability and acceptable noise levels in clinical images. Conclusions:The Biograph Vision Quadra PET/CT has similar spatial and time resolution compared to the Biograph Vision 600 but exhibits improved sensitivity and NECR due to its extended AFOV. The reported spatial resolution, time resolution, and sensitivity makes it a competitive new device in the class of PET-scanners with extended AFOV.

Evaluation of a High-Sensitivity Organ-Targeted PET Camera

“…The Radialis PET Camera exhibits much higher efficiency at peak count rate when compared to current WB systems. The SiPM-based total-body PET technology of uExplorer [50] and Biograph Vision Quadra [51] provides superior sensitivity in comparison to the WB systems, achieved with detectors that can completely cover the axial length of a patient's body. Radialis' SiPM-based organ-targeted technology applies the same approach: The geometric coverage of the Radialis SiPM arrays is larger than the organ being imaged.…”

Influences on PET Quantification and Interpretation

“…To address this problem, the FOV length or–more accurately–the system’s sensitivity in cps/kBq would have to be included in the formula to calculate the required injected activity. This becomes especially evident with recent PET systems with extra-large axial FOV of >25 cm and their potential to substantially reduce required acquisition times [ 47 , 149 , 150 ].…”

Exposure Stability of Quantitative Fluorine-18 Measurements On The Biograph Vision Quadra PET/CT System

“…Two facts limit the informative value of this work: First, at the time of this study the Biograph Vision Quadra was using a maximum ring distance of 85 (MRD 85), thus using maximally one fourth of the crystal rings for image acquisitions. While this gives the Quadra a homogenous sensitivity over the entire AFOV [13], a future update using the full ring distance of (MRD 322) will bring forth an increase in sensitivity. Second, at the time of this study, the Biograph Vision Quadra was not equipped 311 with continuous bed motion, and thus this feature could not be studied here.…”

“…Besides enabling 54 the simultaneous imaging of distant anatomical regions, the long AFOV increases count rate and thus 55 sensitivity. The Quadra's current clinical high sensitivity mode, where not all lines of response are used 56 to form the PET image, increases sensitivity by a factor of five when compared to the preceding 57 Biograph Vision 600 [12,13]. A future upgrade to an ultra-high sensitivity mode, with all lines of response used, will raise sensitivity even further.…”