title: Fractal analysis of cerebral blood flow distribution in Alzheimer's disease.
abstract: This study describes a method for quantifying cerebral blood flow (CBF) distribution in Alzheimer's disease (AD) from SPECT images obtained with (99m)Tc-hexamethylpropyleneamine oxime (HMPAO) by 3-dimensional fractal analysis (3D-FA).
  
  
  METHODS
  HMPAO SPECT was performed on 68 patients with probable AD and 14 healthy control subjects. We delineated the CBF images using 4 cutoff levels (35%, 40%, 45%, and 50% of the maximal voxel radioactivity) and measured the total number of voxels in the areas surrounded by the contours obtained with each cutoff level. We calculated fractal dimensions from the relationship between the total number of voxels and the cutoff levels transformed into natural logarithms.
  
  
  RESULTS
  The fractal dimensions (mean +/- SD) for patients with probable AD and healthy subjects were 0.74 +/- 0.33 and 0.52 +/- 0.09, respectively. A significant difference in the fractal dimension was found between groups (P = 0.001). Statistically significant correlations were obtained between the fractal dimension and the Mini-Mental State Examination score (r = -0.598; P < 0.0001) and between the fractal dimension and the AD Assessment Scale (r = 0.670; P < 0.0001). The fractal dimensions for subjects with clinical dementia rates (CDRs) of 0, 1, 2, and 3 were 0.52 +/- 0.09, 0.63 +/- 0.21, 0.77 +/- 0.23 (P < 0.05 vs. the group with a CDR of 1), and 1.43 +/- 0.49 (P < 0.0001 vs. the group with a CDR of 2), respectively.
  
  
  CONCLUSIONS
  Quantification of CBF distribution on SPECT images in AD was possible using 3D-FA. The fractal dimension was well correlated with the cognitive impairment, as assessed in neuropsychologic tests. 3D-FA may be a useful method for objectively evaluating the progression of AD.
authors.affiliation: Department of Radiology, Ehime University School of Medicine, Shitsukawa, Shigenobu-cho, Onsen-gun, Ehime 791-0295, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Nagao
authors.forename: K
authors.initials: K
authors.lastname: Murase
authors.forename: T
authors.initials: T
authors.lastname: Kikuchi
authors.forename: M
authors.initials: M
authors.lastname: Ikeda
authors.forename: A
authors.initials: A
authors.lastname: Nebu
authors.forename: R
authors.initials: R
authors.lastname: Fukuhara
authors.forename: Y
authors.initials: Y
authors.lastname: Sugawara
authors.forename: H
authors.initials: H
authors.lastname: Miki
authors.forename: J
authors.initials: J
authors.lastname: Ikezoe
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002560:Cerebrovascular Circulation; D005260:Female; D017709:Fractals; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D019275:Radiopharmaceuticals; D019690:Technetium Tc 99m Exametazime; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D019275:Radiopharmaceuticals; D019690:Technetium Tc 99m Exametazime