title: Evaluation of brain activity in FDG PET studies.
abstract: OBJECTIVE
  A tool (Gemini) was developed for quantifying regions of interest (ROIs) in registered MR and PET data. Its use was validated through phantom and simulated studies.
  
  
  METHODS
  Hot spheres were imaged in a phantom (3:1 and 5:1 target-to-nontarget ratios). The computerized 3D Hoffman brain phantom was used to simulate PET studies. Spherical local activity features of two diameters (4 and 10 mm) and five intensities (5, 15, 25, 50, and 100% increase over gray matter) were added to the data in the thalamus and Brodmann area 37. The data were reprojected into sinograms and blurred with a 7 mm kernel. Poisson noise was added, and the sinograms were then reconstructed and analyzed using both SPM96 and Gemini spherical ROIs.
  
  
  RESULTS
  Based on phantom and simulated data, the 95th percentile of intensity within a Gemini ROI afforded a reasonable joint optimization of variance (reliability) and accuracy (validity). SPM96 and Gemini results were similar for the larger (10 mm) feature, but in this application, Gemini was more sensitive than SPM96 for the small feature (4 mm).
  
  
  CONCLUSIONS
  Gemini, a tool for display and measurement of spherical ROIs in registered PET and MR data, is precise and accurate for testing hypotheses of differences in localized brain activity, comparing favorably with SPM96.
authors.affiliation: PET Center, Division of Radiological Sciences, Wake Forest University School of Medicine, Winston-Salem, NC 27157-1061, USA.
authors.forename: F H
authors.initials: FH
authors.lastname: Fahey
authors.forename: F B
authors.initials: FB
authors.lastname: Wood
authors.forename: D L
authors.initials: DL
authors.lastname: Flowers
authors.forename: C G
authors.initials: CG
authors.lastname: Eades
authors.forename: H D
authors.initials: HD
authors.lastname: Gage
authors.forename: B A
authors.initials: BA
authors.lastname: Harkness
mesh_terms: D001921:Brain / Q000378:metabolism*; D003198:Computer Simulation; D007089:Image Enhancement; D008279:Magnetic Resonance Imaging; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D014055:Tomography, Emission-Computed