Systematic Comparison of the Performance of Integrated Whole-Body PET/MR Imaging to Conventional PET/CT for ¹⁸F-FDG Brain Imaging in Patients Examined for Suspected Dementia.
Technologic specifications of recently introduced integrated PET/MR instrumentation, such as MR-based attenuation correction, may particularly affect brain imaging procedures. To evaluate the qualitative performance of PET/MR in clinical neuroimaging, we systematically compared results obtained with integrated PET/MR with conventional PET/CT in the same patients examined for assessment of cognitive impairment.


METHODS
Thirty patients underwent a single-injection ((18)F-FDG), dual-imaging protocol including PET/CT and integrated PET/MR imaging in randomized order. Attenuation and scatter correction were performed using low-dose CT for the PET/CT and segmented Dixon MR imaging data for the PET/MR. Differences between PET/MR and PET/CT were assessed via region-of-interest (ROI)-based and voxel-based statistical group comparison. Analyses involved attenuation-corrected (AC) and non-attenuation-corrected (NAC) data. Individual PET/MR and PET/CT datasets were compared versus a predefined independent control population, using 3-dimensional stereotactic surface projections.


RESULTS
Generally, lower measured PET signal values were obtained throughout the brain in ROI-based quantification of the PET signal for PET/MR as compared with PET/CT in AC and NAC data, independently of the scan order. After elimination of global effects, voxel-based and ROI-based group comparison still revealed significantly lower relative tracer signal in PET/MR images in frontoparietal portions of the neocortex but significantly higher relative signal in subcortical and basal regions of the brain than the corresponding PET/CT images of the AC data. In the corresponding NAC images, the discrepancies in frontoparietal portions of the neocortex were diminished, but the subcortical overestimation of tracer intensity by PET/MR persisted.


CONCLUSIONS
Considerable region-dependent differences were observed between brain imaging data acquired on the PET/MR, compared with corresponding PET/CT images, in patients evaluated for neurodegenerative disorders. These findings may only in part be explained by inconsistencies in the attenuation-correction procedures. The observed differences may interfere with semiquantitative evaluation and with individual qualitative clinical assessment and they need to be considered, for example, for clinical trials. Improved attenuation-correction algorithms and a PET/MR-specific healthy control database are recommended for reliable and consistent application of PET/MR for clinical neuroimaging.
Department of Nuclear Medicine, Technische Universität München, Munich, Germany Stefan.c.hitz@gmail.com cornelia.habekost@gmail.com.
Stefan
S
Hitz
Department of Nuclear Medicine, Technische Universität München, Munich, Germany Stefan.c.hitz@gmail.com cornelia.habekost@gmail.com.
Cornelia
C
Habekost
Department of Nuclear Medicine, Technische Universität München, Munich, Germany.
Sebastian
S
Fürst
Department of Nuclear Medicine, Technische Universität München, Munich, Germany.
Gaspar
G
Delso
Department of Nuclear Medicine, Technische Universität München, Munich, Germany TUM Neuroimaging Center (TUM-NIC), Technische Universität München, Munich, Germany.
Stefan
S
Förster
Department of Nuclear Medicine, Technische Universität München, Munich, Germany.
Sibylle
S
Ziegler
Department of Nuclear Medicine, Technische Universität München, Munich, Germany.
Stephan G
SG
Nekolla
Department of Nuclear Medicine, Technische Universität München, Munich, Germany.
Michael
M
Souvatzoglou
Department of Nuclear Medicine, Technische Universität München, Munich, Germany.
Ambros J
AJ
Beer
Department of Psychiatry and Psychotherapy, Technische Universität München, Munich, Germany.
Timo
T
Grimmer
Department of Radiology, Technische Universität München, Munich, Germany; and.
Matthias
M
Eiber
Department of Nuclear Medicine, Technische Universität München, Munich, Germany.
Markus
M
Schwaiger
Department of Nuclear Medicine, Technische Universität München, Munich, Germany Department of Nuclear Medicine, University Hospital of Cologne, Cologne, Germany.
Alexander
A
Drzezga
D000328:Adult; D000368:Aged; D001921:Brain / Q000000981:diagnostic imaging*; D003704:Dementia / Q000175:diagnosis* / Q000000981:diagnostic imaging; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography; D014057:Tomography, X-Ray Computed; D051598:Whole Body Imaging
D019788:Fluorodeoxyglucose F18
Dixon MRI sequence; PET/CT; PET/MR; brain imaging; neurodegeneration