A new study shows that imaging with PET/MR provides better diagnostic information than with PET/CT, reports EurekAlert!, the science news service run by the American Association for the Advancement of Science (AAAS). Published in the March issue of the Journal of Nuclear Medicine from the Society of Nuclear Medicine and Molecular Imaging (SNMMI), the study compared the image quality and diagnostic performance between the two methods when used to obtain more information about undiagnosed foot pain from twenty-two patients. In their evaluation, PET/MR was found to have significantly higher image quality while providing more diagnostic relevant findings.
With very promising results, PET/MR may be favored over PET/CT in the future. An added benefit to PET/MR is that because there is no radiation with MR, patients will receive less exposure.
X-Z LAB’s Basic Detector Module (BDM) | PET Detector Module is digital and modular, allowing for easier construction or upgrades of a digital PET system, including PET/MR and PET/CT. Armed with LYSO+SiPM detector blocks, it is the first All Digital PET detector that is compatible with the magnetic field.
Abstract
Our objective was to compare the quality and diagnostic performance of 18F-fluoride PET/MR imaging with that of 18F-fluoride PET/CT imaging in patients with foot pain of unclear cause.
Methods: Twenty-two patients (9 men, 13 women; mean age, 48 ± 18 y; range, 20–78 y) were prospectively included in this study and underwent a single-injection dual-imaging protocol with 18F-fluoride PET/CT and PET/MR. At a minimum, the PET/MR protocol included T1-weighted spin echo and proton-density fat-saturated sequences in 2 planes each with simultaneous acquisition of PET over 20 min. PET/CT included a native isotropic (0.6 mm) diagnostic CT scan (80 kV, 165 mAs) and a subsequent PET scan (2 min per bed position). By consensus, 2 masked interpreters randomly assessed both PET datasets for image quality (3-point scale) and for the presence of focal lesions with increased 18F-fluoride uptake (maximum of 4 lesions). For each dataset (PET/CT vs. PET/MR), the diagnoses were defined using both PET and a morphologic dataset. Standardized uptake values (SUVs) from the 2 devices were compared using linear correlation and Bland–Altman plots. Moreover, we estimated the potential for dose reduction for PET/MR compared with PET/CT considering the longer acquisition time of PET/MR analyzing count rate statistics.
Results: Image quality was rated diagnostic for both PET datasets. However, with a mean rating of 3.0/3 for PET/MR and 2.3/3 for PET/CT, image quality was significantly superior for PET/MR (P < 0.0001). The sensitivity of the PET datasets in PET/MR and PET/CT was equivalent, with the same 42 lesions showing focal 18F-fluoride uptake. In PET/MR, the mean SUVmean was 10.4 (range, 2.0–67.7) and the mean SUVmax was 15.6 (range, 2.9–94.1). In PET/CT, the corresponding mean SUVmean of PET/CT was 10.2 (range, 1.8–55.6) and the mean SUVmax was 16.3 (range, 2.5–117.5), resulting in a high linear correlation coefficient (r = 0.96, P < 0.0001, for SUVmean and for SUVmax). A final consensus interpretation revealed the most frequent main diagnoses to be osteoarthritis, stress fracture, and bone marrow edema. PET/CT was more precise in visualizing osteoarthritis, whereas PET/MR was more specific in nondegenerative pathologies because of the higher soft-tissue and bone marrow contrast. The longer acquisition time of MR compared with CT would potentially allow 18F-fluoride dose reduction using hybrid 18F-fluoride PET/MR imaging of at least 50% according to the counting rate analysis.
Conclusion: In patients with foot pain of unclear cause, 18F-fluoride PET/MR is technically feasible and is more robust in terms of image quality and SUV quantification than 18F-fluoride PET/CT. In most patients, 18F-fluoride PET/MR provided more diagnostic information at a higher diagnostic certainty than did PET/CT. Thus, PET/MR combines the high sensitivity of 18F-fluoride PET to pinpoint areas with the dominant disease activity and the specificity of MR imaging for the final diagnosis with the potential for a substantial dose reduction compared with PET/CT.
Document Credits
Isabel Rauscher*,1, Ambros J. Beer*,1,2, Christoph Schaeffeler3,4, Michael Souvatzoglou1, Moritz Crönlein5, Chlodwig Kirchhoff5, Gunther Sandmann5, Sebastian Fürst1, Robert Kilger6, Michael Herz1, Sybille Ziegler1, Markus Schwaiger1 and Matthias Eiber1
1Department of Nuclear Medicine, Klinikum rechts der Isar, Technische Universität München, Munich, Germany
2Department of Nuclear Medicine, University Hospital Ulm, Ulm, Germany
3Musculoskeletal Imaging, Department of Radiology, Kantonsspital Graubünden, Chur, Switzerland
4Department of Radiology, Klinikum rechts der Isar, Technische Universität München, Munich, Germany
5Department of Trauma Surgery, Klinikum rechts der Isar, Technische Universität München, Munich, Germany
6University of Applied Sciences Fresenius, Munich, Germany