title: CT-Based Attenuation Correction in Brain SPECT/CT Can Improve the Lesion Detectability of Voxel-Based Statistical Analyses.
abstract: BACKGROUND
  Integrated SPECT/CT enables non-uniform attenuation correction (AC) using built-in CT instead of the conventional uniform AC. The effect of CT-based AC on voxel-based statistical analyses of brain SPECT findings has not yet been clarified. Here, we assessed differences in the detectability of regional cerebral blood flow (CBF) reduction using SPECT voxel-based statistical analyses based on the two types of AC methods.
  
  
  METHODS
  N-isopropyl-p-[123I]iodoamphetamine (IMP) CBF SPECT images were acquired for all the subjects and were reconstructed using 3D-OSEM with two different AC methods: Chang's method (Chang's AC) and the CT-based AC method. A normal database was constructed for the analysis using SPECT findings obtained for 25 healthy normal volunteers. Voxel-based Z-statistics were also calculated for SPECT findings obtained for 15 patients with chronic cerebral infarctions and 10 normal subjects. We assumed that an analysis with a higher specificity would likely produce a lower mean absolute Z-score for normal brain tissue, and a more sensitive voxel-based statistical analysis would likely produce a higher absolute Z-score for in old infarct lesions, where the CBF was severely decreased.
  
  
  RESULTS
  The inter-subject variation in the voxel values in the normal database was lower using CT-based AC, compared with Chang's AC, for most of the brain regions. The absolute Z-score indicating a SPECT count reduction in infarct lesions was also significantly higher in the images reconstructed using CT-based AC, compared with Chang's AC (P = 0.003). The mean absolute value of the Z-score in the 10 intact brains was significantly lower in the images reconstructed using CT-based AC than in those reconstructed using Chang's AC (P = 0.005).
  
  
  CONCLUSIONS
  Non-uniform CT-based AC by integrated SPECT/CT significantly improved sensitivity and the specificity of the voxel-based statistical analyses for regional SPECT count reductions, compared with conventional uniform Chang's AC.
authors.affiliation: Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kato
authors.affiliation: Department of Molecular Imaging of Medicine, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Eku
authors.initials: E
authors.lastname: Shimosegawa
authors.affiliation: Department of Radiology, Osaka University Hospital, Suita, Osaka, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Fujino
authors.affiliation: Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Hatazawa
mesh_terms: D000367:Age Factors; D001921:Brain / Q000000981:diagnostic imaging* / Q000473:pathology*; D016022:Case-Control Studies; D002544:Cerebral Infarction / Q000000981:diagnostic imaging*; D019992:Databases as Topic; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D000072098:Single Photon Emission Computed Tomography Computed Tomography; D013223:Statistics as Topic