title: Simultaneous PET/MR imaging in a human brain PET/MR system in 50 patients--current state of image quality.
abstract: OBJECTIVE
  The present work illustrates the current state of image quality and diagnostic accuracy in a new hybrid BrainPET/MR.
  
  
  METHODS
  50 patients with intracranial masses, head and upper neck tumors or neurodegenerative diseases were examined with a hybrid BrainPET/MR consisting of a conventional 3T MR system and an MR-compatible PET insert. Directly before PET/MR, all patients underwent a PET/CT examination with either [18F]-FDG, [11C]-methionine or [68Ga]-DOTATOC. In addition to anatomical MR scans, functional sequences were performed including diffusion tensor imaging (DTI), arterial spin labeling (ASL) and proton-spectroscopy. Image quality score of MR imaging was evaluated using a 4-point-scale. PET data quality was assessed by evaluating FDG-uptake and tumor delineation with [11C]-methionine and [68Ga]-DOTATOC. FDG uptake quantification accuracy was evaluated by means of ROI analysis (right and left frontal and temporo-occipital lobes). The asymmetry indices and ratios between frontal and occipital ROIs were compared.
  
  
  RESULTS
  In 45/50 patients, PET/MR examination was successful. Visual analysis revealed a diagnostic image quality of anatomical MR imaging (mean quality score T2 FSE: 1.27±0.54; FLAIR: 1.38±0.61). ASL and proton-spectroscopy was possible in all cases. In DTI, dental artifacts lead to one non-diagnostic dataset (mean quality score DTI: 1.32±0.69; ASL: 1.10±0.31). PET datasets of PET/MR and PET/CT offered comparable tumor delineation with [11C]-methionine; additional lesions were found in 2/8 [(68)Ga]-DOTATOC-PET in the PET/MR. Mean asymmetry index revealed a high accordance between PET/MR and PET/CT (1.5±2.2% vs. 0.9±3.6%; mean ratio (frontal/parieto-occipital) 0.93±0.08 vs. 0.96±0.05), respectively.
  
  
  CONCLUSIONS
  The hybrid BrainPET/MR allows for molecular, anatomical and functional imaging with uncompromised MR image quality and a high accordance of PET results between PET/MR and PET/CT. These results justify the application of this technique in further clinical studies and may contribute to the transfer into whole-body PET/MR systems.
authors.affiliation: Department of Diagnostic and Interventional Radiology, Eberhard-Karls University Tübingen, Tübingen, Germany. nina.schwenzer@med.uni-tuebingen.de
authors.forename: N F
authors.initials: NF
authors.lastname: Schwenzer
authors.forename: L
authors.initials: L
authors.lastname: Stegger
authors.forename: S
authors.initials: S
authors.lastname: Bisdas
authors.forename: C
authors.initials: C
authors.lastname: Schraml
authors.forename: A
authors.initials: A
authors.lastname: Kolb
authors.forename: A
authors.initials: A
authors.lastname: Boss
authors.forename: M
authors.initials: M
authors.lastname: Müller
authors.forename: M
authors.initials: M
authors.lastname: Reimold
authors.forename: U
authors.initials: U
authors.lastname: Ernemann
authors.forename: C D
authors.initials: CD
authors.lastname: Claussen
authors.forename: C
authors.initials: C
authors.lastname: Pfannenberg
authors.forename: H
authors.initials: H
authors.lastname: Schmidt
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000175:diagnosis*; D004867:Equipment Design / Q000639:trends; D019544:Equipment Failure Analysis; D005260:Female; D006258:Head and Neck Neoplasms / Q000175:diagnosis*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000639:trends; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000295:instrumentation* / Q000639:trends; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique / Q000295:instrumentation* / Q000639:trends; D055815:Young Adult