title: Impact of attenuation correction on clinical [(18)F]FDG brain PET in combined PET/MRI.
abstract: BACKGROUND
  In PET/MRI, linear photon attenuation coefficients for attenuation correction (AC) cannot be directly derived, and cortical bone is, so far, usually not considered. This results in an underestimation of the average PET signal in PET/MRI. Recently introduced MR-AC methods predicting bone information from anatomic MRI or proton density-weighted zero-time imaging may solve this problem in the future. However, there is an ongoing debate if the current error is acceptable for clinical use and/or research.
  
  
  METHODS
  We examined this feature for [(18)F] fluorodeoxyglucose (FDG) brain PET in 13 patients with clinical signs of dementia or movement disorders who subsequently underwent PET/CT and PET/MRI on the same day. Multiple MR-AC approaches including a CT-derived AC were applied.
  
  
  RESULTS
  The resulting PET data was compared to the CT-derived standard regarding the quantification error and its clinical impact. On a quantitative level, -11.9 to +2 % deviations from the CT-AC standard were found. These deviations, however, did not translate into a systematic diagnostic error. This, as overall patterns of hypometabolism (which are decisive for clinical diagnostics), remained largely unchanged.
  
  
  CONCLUSIONS
  Despite a quantitative error by the omission of bone in MR-AC, clinical quality of brain [(18)F]FDG is not relevantly affected. Thus, brain [(18)F]FDG PET can already, even now with suboptimal MR-AC, be utilized for clinical routine purposes, even though the MR-AC warrants improvement.
authors.affiliation: Department of Nuclear Medicine, Leipzig University Hospital, Leipzig, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Werner
authors.affiliation: Department of Nuclear Medicine, Leipzig University Hospital, Leipzig, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Rullmann
authors.affiliation: Department of Nuclear Medicine, Leipzig University Hospital, Leipzig, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Bresch
authors.affiliation: Department of Nuclear Medicine, Leipzig University Hospital, Leipzig, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Tiepolt
authors.affiliation: Department of Nuclear Medicine, Leipzig University Hospital, Leipzig, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Jochimsen
authors.affiliation: Department of Neuroradiology, Leipzig University Hospital, Leipzig, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Lobsien
authors.affiliation: Day Clinic for Cognitive Neurology, Leipzig University Hospital and Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
authors.forename: M L
authors.initials: ML
authors.lastname: Schroeter
authors.affiliation: Department of Nuclear Medicine, Leipzig University Hospital, Leipzig, Germany.
authors.forename: O
authors.initials: O
authors.lastname: Sabri
authors.affiliation: Department of Nuclear Medicine, Leipzig University Hospital, Leipzig, Germany. henryk.barthel@medizin.uni-leipzig.de.
authors.forename: H
authors.initials: H
authors.lastname: Barthel
keywords: Attenuation correction; FDG imaging; PET/MR