title: Impact of MR-Based Attenuation Correction on Neurologic PET Studies.
abstract: Hybrid PET and MR scanners have become a reality in recent years, with the benefits of reduced radiation exposure, reduction of imaging time, and potential advantages in quantification. Appropriate attenuation correction remains a challenge. Biases in PET activity measurements were demonstrated using the current MR-based attenuation-correction technique. We aimed to investigate the impact of using a standard MR-based attenuation correction technique on the clinical and research utility of a PET/MR hybrid scanner for amyloid imaging.
  
  
  
  Florbetapir scans were obtained for 40 participants on a hybrid scanner with simultaneous MR acquisition. PET images were reconstructed using both MR- and CT-derived attenuation maps. Quantitative analysis was performed for both datasets to assess the impact of MR-based attenuation correction to absolute PET activity measurements as well as target-to-reference ratio (SUVR). Clinical assessment was also performed by a nuclear medicine physician to determine amyloid status based on the criteria in the Food and Drug Administration prescribing information for florbetapir.
  
  
  
  MR-based attenuation correction led to underestimation of PET activity for most parts of the brain, with a small overestimation for deep brain regions. There was also an overestimation of SUVRs with cerebellar reference. SUVR measurements obtained from the 2 attenuation-correction methods were strongly correlated. Clinical assessment of amyloid status resulted in identical classification as positive or negative regardless of the attenuation-correction methods.
  
  
  
  MR-based attenuation correction causes biases in quantitative measurements. The biases may be accounted for by a linear model, although the spatial variation cannot be easily modeled. The quantitative differences, however, did not affect clinical assessment as positive or negative.
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri suy@mir.wustl.edu.
authors.forename: Yi
authors.initials: Y
authors.lastname: Su
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri.
authors.forename: Brian B
authors.initials: BB
authors.lastname: Rubin
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri.
authors.forename: Jonathan
authors.initials: J
authors.lastname: McConathy
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri.
authors.forename: Richard
authors.initials: R
authors.lastname: Laforest
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri.
authors.forename: Jing
authors.initials: J
authors.lastname: Qi
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri.
authors.forename: Akash
authors.initials: A
authors.lastname: Sharma
authors.affiliation: Siemens Medical Solutions, St. Louis, Missouri; and.
authors.forename: Agus
authors.initials: A
authors.lastname: Priatna
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri Department of Neurological Surgery, Washington University School of Medicine, St. Louis, Missouri.
authors.forename: Tammie L S
authors.initials: TL
authors.lastname: Benzinger
mesh_terms: D000682:Amyloid / Q000378:metabolism; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography
chemical_list: D000682:Amyloid
keywords: PET/MR; amyloid imaging; attenuation correction
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