title: The Effects of Misalignment between PET and CT Scans on Brain PET Study Using CT-based Attenuation Correction: A Phantom Study.
abstract: The aim of this study was to evaluate the effects of inaccurate attenuation correction due to the misalignment between the computed tomography (CT)-based μ-map and the positron emission tomography (PET) data on a brain PET.
  
  
  
  CT and PET scans were performed on a 3-dimension (3D) brain phantom, in which the grey matter region was filled with18F-fluorodeoxyglucose (18F-FDG), and the skull region was filled with/without the bone-equivalent solution. The shifted PET images relative to the CT image were generated by the software-based translation of PET data in the cephalad/caudal and right directions, with a magnitude of the shift up to 30 mm and a step size of 5 mm. The regions of interest (ROIs) were drawn on the areas of the temporal lobes, parietal lobes, thalami, and cerebellums in the no-shifted image (reference). For each ROI, the radioactivity concentrations in the shifted images were compared with those of the reference.
  
  
  
  The errors in the radioactivity concentrations were increased with the increasing magnitude of the shift in all brain regions except for thalamus. For a 5 mm shift in the right direction, ± 10% errors were observed in the left/right temporal lobes. The accuracy of the radioactivity concentration in the temporal lobe was very sensitive to misalignment in the right directions.
  
  
  
  The misalignment between CT-based μ-map and PET data had larger effects on the surface regions of the brain rather than on deep brain structures.
authors.affiliation: Department of Radiology, National Cerebral and Cardiovascular Center.
authors.forename: Akihide
authors.initials: A
authors.lastname: Shimizu
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Terakawa
authors.forename: Naomi
authors.initials: N
authors.lastname: Morita
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Koshino
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Iida
mesh_terms: D001921:Brain / Q000000981:diagnostic imaging*; D006801:Humans; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000379:methods; D012984:Software; D014057:Tomography, X-Ray Computed / Q000379:methods