Application of a Flexible PET Scanner Combined with 3 T MRI Using Non-local Means Reconstruction: Qualitative and Quantitative Comparison with Whole-Body PET/CT

Abstract

Purpose: Flexible positron emission tomography (fxPET) employing a non-local means reconstruction algorithm, was designed to fit existing magnetic resonance imaging (MRI) systems. We aimed to compare the qualitative and quantitative performance of fxPET among fxPET with MR-based attenuation correction (MRAC), fxPET with CT-based attenuation correction (CTAC) using CT as a part of WB PET/CT, and whole-body (WB) PET/CT. Procedures: Sixteen patients with suspected head and neck cancer underwent 2-deoxy-2-[ 18 F]fluoro-D-glucose WB PET/CT scans, followed by fxPET and 3T MRI scans. Phantom data were compared among the three datasets. For registration accuracy, we measured the distance between the center of the tumor determined by fxPET and that in MRI. We compared image quality, detection rates and quantitative values including maximal standardized uptake value (SUVmax), metabolic tumor volume (MTV), total lesion glycolysis (TLG) and tumor-to-muscle ratio (TMR) among the three datasets. A Self-archived copy in Kyoto University Research Information Repository https://repository.kulib.kyoto-u.ac.jp Results:The phantom data in fxPET, except the percent contrast recoveries of 17-mm and 22-mm hot spheres, were inferior to those in WB PET/CT. The mean registration accuracy was 4.4 mm between fxPET using MRAC and MRI. The image quality was comparable between two fxPET datasets, but significantly inferior to WB PET/CT (p < 0.0001). In contrast, detection rates were comparable among the three datasets.SUVmax was significantly higher, and MTV and TLG were significantly lower in the two fxPET datasets compared with the WB PET/CT dataset (p < 0.005). There were no significant differences in SUVmax, MTV and TLG between the two fxPET datasets, or in TMR among the three datasets. All quantitative values had significantly positive correlations.Conclusions: Compared with WB PET/CT, the phantom data and image quality were inferior in fxPET. However, the results of the detection rates and quantitative values suggested the clinical feasibility of fxPET.

Recent Advances in Positron Emission Tomography/Magnetic Resonance Imaging Technology

“…The ring diameter and axial extent of this scanner are 77 and 15 cm, respectively, which enables whole-body sequential PET/MR imaging. 32 In the context of simultaneous data acquisition, the approach adopted by the TRIMAGE consortium should be considered, where simultaneous electroencephalography (EEG)/PET/ MR scans are performed for a comprehensive study of basic mechanisms in the brain. 33 The PET component has an inner diameter and axial FOV of 26 and 16 cm, respectively, inserted into a 1.5 T MR scanner.…”