title: Effect of Attenuation Correction on Regional Quantification Between PET/MR and PET/CT: A Multicenter Study Using a 3-Dimensional Brain Phantom.
abstract: A spatial bias in brain PET/MR exists compared with PET/CT, because of MR-based attenuation correction. We performed an evaluation among 4 institutions, 3 PET/MR systems, and 4 PET/CT systems using an anthropomorphic brain phantom, hypothesizing that the spatial bias would be minimized with CT-based attenuation correction (CTAC).
  
  
  METHODS
  The evaluation protocol was similar to the quantification of changes in neurologic PET studies. Regional analysis was conducted on 8 anatomic volumes of interest (VOIs) in gray matter on count-normalized, resolution-matched, coregistered data. On PET/MR systems, CTAC was applied as the reference method for attenuation correction.
  
  
  RESULTS
  With CTAC, visual and quantitative differences between PET/MR and PET/CT systems were minimized. Intersystem variation between institutions was +3.42% to -3.29% in all VOIs for PET/CT and +2.15% to -4.50% in all VOIs for PET/MR. PET/MR systems differed by +2.34% to -2.21%, +2.04% to -2.08%, and -1.77% to -5.37% when compared with a PET/CT system at each institution, and these differences were not significant (P ≥ 0.05).
  
  
  CONCLUSIONS
  Visual and quantitative differences between PET/MR and PET/CT systems can be minimized by an accurate and standardized method of attenuation correction. If a method similar to CTAC can be implemented for brain PET/MRI, there is no reason why PET/MR should not perform as well as PET/CT.
authors.affiliation: Turku PET Centre, Turku University Hospital and University of Turku, Turku, Finland jarmo.teuho@tyks.fi.
authors.forename: Jarmo
authors.initials: J
authors.lastname: Teuho
authors.affiliation: Turku PET Centre, Turku University Hospital and University of Turku, Turku, Finland.
authors.forename: Jarkko
authors.initials: J
authors.lastname: Johansson
authors.affiliation: Turku PET Centre, Turku University Hospital and University of Turku, Turku, Finland.
authors.forename: Jani
authors.initials: J
authors.lastname: Linden
authors.affiliation: Department of Clinical Physiology, Nuclear Medicine, and PET, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Adam Espe
authors.initials: AE
authors.lastname: Hansen
authors.affiliation: Department of Clinical Physiology, Nuclear Medicine, and PET, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Søren
authors.initials: S
authors.lastname: Holm
authors.affiliation: Department of Clinical Physiology, Nuclear Medicine, and PET, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Sune H
authors.initials: SH
authors.lastname: Keller
authors.affiliation: PET/CT-MR Center, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Gaspar
authors.initials: G
authors.lastname: Delso
authors.affiliation: PET/CT-MR Center, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Veit-Haibach
authors.affiliation: Section of Nuclear Medicine, Department of Radiology, Hokkaido University Hospital, Sapporo, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Magota
authors.affiliation: Turku PET Centre, Turku University Hospital and University of Turku, Turku, Finland.
authors.forename: Virva
authors.initials: V
authors.lastname: Saunavaara
authors.affiliation: Turku PET Centre, Turku University Hospital and University of Turku, Turku, Finland.
authors.forename: Tuula
authors.initials: T
authors.lastname: Tolvanen
authors.affiliation: Turku PET Centre, Turku University Hospital and University of Turku, Turku, Finland Department of Medical Physics, Turku University Hospital, Turku, Finland; and.
authors.forename: Mika
authors.initials: M
authors.lastname: Teräs
authors.affiliation: National Cerebral and Cardiovascular Center, Osaka, Japan.
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Iida
mesh_terms: D001921:Brain / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D064847:Multimodal Imaging / Q000295:instrumentation*; D019047:Phantoms, Imaging; D000072078:Positron Emission Tomography Computed Tomography / Q000295:instrumentation*
keywords: PET/CT; PET/MR; attenuation correction; phantom; quantification