Performance Characteristics of the Whole-Body Discovery IQ PET/CT System

Abstract

The aim of this study was to assess the physical performance of a new PET/CT system, the Discovery IQ with 5-ring detector blocks. Methods: Performance was measured using the National Electrical Manufacturers Association NU2-2012 methodology. Image quality was extended by accounting for different acquisition parameters (lesion-to-background ratios [8:1, 4:1, and 2:1] and acquisition times) and reconstruction algorithms (VUE-point HD [VPHD], VPHD with point-spread-function modeling [VPHD-S], and Q.Clear). Tomographic reconstruction was also assessed using a Jaszczak phantom. Additionally, 30 patient lesions were analyzed to account for differences in lesion volume and SUV quantification between reconstruction algorithms. Results: Spatial resolution ranged from 4.2 mm at 1 cm to 8.5 mm at 20 cm. Sensitivity measured at the center and at 10 cm was 22.8 and 20.4 kps/kBq, respectively. The noise-equivalent counting rate peak was 124 kcps at 9.1 kBq/cm 3 . The scatter fraction was 36.2%. The accuracy of correction for count losses and randoms was 3.9%. In the image quality test, contrast recovery for VPHD, VPHD-S, and Q.Clear ranged from 18%, 18%, and 13%, respectively (hot contrast; 10-mm sphere diameter; ratio, 2:1), to 68%, 67%, and 81%, respectively (cold contrast; 37-mm sphere diameter; ratio, 8:1). Background variability ranged from 3.4%, 3.0%, and 2.1%, respectively (ratio, 2:1), to 5.5%, 4.8%, and 3.7%, respectively (ratio, 8:1). On Q.Clear reconstruction, the decrease in the penalty term (b) increased the contrast recovery coefficients and background variability. With the Jaszczak phantom, image quality increased overall when a reconstruction algorithm modeling the point-spread function was used, and use of Q.Clear increased the signal-to-noise ratio. Lesions analyzed using VPHD-S and Q.Clear had an SUV mean of 6.5 6 3 and 7 6 3, respectively (P , 0.01), and an SUV max of 11 6 4.8 and 12 6 4, respectively (P , 0.01). No significant difference in mean lesion volume was found between algorithms. Conclusion: Among the various Discovery bismuth germanium oxide-based PET/CT scanners, the IQ with 5-ring detector blocks has the highest overall performance, with improved sensitivity and counting rate performance. Q.Clear reconstruction improves the PET image quality, with higher recovery coefficients and lower background variability. PETi maging has the ability to offer valuable functional information, playing a key role in the diagnosis, staging, and evaluation of cancer; the planning of radiotherapy; and the diagnosis of some types of dementia (1). Improvements in hardware and reconstruction methods have improved the performance of PET scanners (2). Since the introduction of hybrid PET/CT scanners, and especially with the latest-generation tomographs, most commercial manufacturers have opted to include high-time-resolution detectors, based on lutetium oxyorthosilicate (3,4) and lutetium-yttrium oxyorthosilicate (5-8) crystals, to improve time-of-flight localization. However, GE Healthcare maintains a line of PET/CT...

Phantom, clinical, and texture indices evaluation and optimization of a penalized‐likelihood image reconstruction method (Q.Clear) on a BGO PET/CT scanner

“…The improvement depends on the studied conditions and the penalization factor. A β value of 350 and 200 appears to be the optimal value for F‐FDG oncology and brain PET/CT using the Q.Clear reconstruction algorithm in a BGO scanner. For torso scans, this value assures a compromise in image quality and quantitation accuracy.…”

“…The Discovery IQ with 5 rings (D‐IQ‐5) system (General Electric Healthcare (GEH), Milwaukee, WI, USA) combines a BGO‐based PET tomograph with a 16‐slice CT scanner. Scanner performance has been previously described . In short, the D‐IQ‐5 PET enables an axial and transaxial physical field of view (FOV) of 26 and 70 cm respectively, with 79 image planes and 3.27 mm plane spacing.…”

“…Due to the vast number of TI, we focused in a subset of indices described in previous publications . From the co‐occurrence matrix, the second order parameters of Homogeneity, Entropy, and Correlation were calculated.…”

“…Scanner performance has been previously described. 18 In short, the D-IQ-5 PET enables an axial and transaxial physical field of view (FOV) of 26 and 70 cm respectively, with 79 image planes and 3.27 mm plane spacing. The system includes the Q.Clear reconstruction, and two OSEM iterative reconstruction algorithms, marketed as VUE Point HD (VPHD), and the VPHD with PSF correction (VPHD-S).…”

“…On clinical practice, different PET applications have different count statistics. The Q.Clear algorithm has a dependence on the region activity, allowing a window to optimize it depending on each application, as could be torso 18 F-FDG protocols for oncological scans, brain studies or other specific imaging goals.…”