title: Quality control for quantitative multicenter whole-body PET/MR studies: A NEMA image quality phantom study with three current PET/MR systems.
abstract: OBJECTIVE
  Integrated positron emission tomography/magnetic resonance (PET/MR) systems derive the PET attenuation correction (AC) from dedicated MR sequences. While MR-AC performs reasonably well in clinical patient imaging, it may fail for phantom-based quality control (QC). The authors assess the applicability of different protocols for PET QC in multicenter PET/MR imaging.
  
  
  METHODS
  The National Electrical Manufacturers Association NU 2 2007 image quality phantom was imaged on three combined PET/MR systems: a Philips Ingenuity TF PET/MR, a Siemens Biograph mMR, and a GE SIGNA PET/MR (prototype) system. The phantom was filled according to the EANM FDG-PET/CT guideline 1.0 and scanned for 5 min over 1 bed. Two MR-AC imaging protocols were tested: standard clinical procedures and a dedicated protocol for phantom tests. Depending on the system, the dedicated phantom protocol employs a two-class (water and air) segmentation of the MR data or a CT-based template. Differences in attenuation- and SUV recovery coefficients (RC) are reported. PET/CT-based simulations were performed to simulate the various artifacts seen in the AC maps (μ-map) and their impact on the accuracy of phantom-based QC.
  
  
  RESULTS
  Clinical MR-AC protocols caused substantial errors and artifacts in the AC maps, resulting in underestimations of the reconstructed PET activity of up to 27%, depending on the PET/MR system. Using dedicated phantom MR-AC protocols, PET bias was reduced to -8%. Mean and max SUV RC met EARL multicenter PET performance specifications for most contrast objects, but only when using the dedicated phantom protocol. Simulations confirmed the bias in experimental data to be caused by incorrect AC maps resulting from the use of clinical MR-AC protocols.
  
  
  CONCLUSIONS
  Phantom-based quality control of PET/MR systems in a multicenter, multivendor setting may be performed with sufficient accuracy, but only when dedicated phantom acquisition and processing protocols are used for attenuation correction.
authors.affiliation: Department of Radiology and Nuclear Medicine, VU Medical Center, Amsterdam 1081 HV, The Netherlands; European Association of Nuclear Medicine Research Ltd., Vienna 1060, Austria; and European Association of Nuclear Medicine Physics Committee, Vienna 1060, Austria.
authors.forename: Ronald
authors.initials: R
authors.lastname: Boellaard
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna 1090, Austria.
authors.forename: Ivo
authors.initials: I
authors.lastname: Rausch
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna 1090, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Beyer
authors.affiliation: GE Healthcare and University Hospital of Zurich, Zurich 8091, Switzerland.
authors.forename: Gaspar
authors.initials: G
authors.lastname: Delso
authors.affiliation: Department of Radiology and Nuclear Medicine, VU Medical Center, Amsterdam 1081 HV, The Netherlands.
authors.forename: Maqsood
authors.initials: M
authors.lastname: Yaqub
authors.affiliation: Institute of Medical Physics, University of Erlangen-Nuremberg, Erlangen 91052, Germany; Erwin L. Hahn Institute for MRI, University of Duisburg-Essen, Essen 45141, Germany; and High Field and Hybrid MR-Imaging, University Hospital Essen, Essen 45147, Germany.
authors.forename: Harald H
authors.initials: HH
authors.lastname: Quick
authors.affiliation: Department of Nuclear Medicine, University Hospital of Leipzig, Leipzig 04103, Germany and European Association of Nuclear Medicine Physics Committee, Vienna 1060, Austria.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Sattler
mesh_terms: D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D064847:Multimodal Imaging / Q000295:instrumentation*; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000295:instrumentation*; D011786:Quality Control; D051598:Whole Body Imaging / Q000295:instrumentation*