title: Evaluation of differential magnification during brain SPECT acquisition.
abstract: OBJECTIVE
  We developed a modification of the acquisition zoom technique, referred to as differential magnification (DM), to improve the pixel resolution with fanbeam collimators. This study evaluated the effects of DM on brain SPECT image quality.
  
  
  METHODS
  SPECT imaging was performed using a triple-head camera with and without DM for a line source in air, Jaszczak and Hoffman phantoms, and 15 clinical patients having regional cerebral blood-flow scans with 99mTc ECD. Full width at half maximum (FWHM) and contrast ratios were measured on the line source and Jaszczak phantom data, respectively. Visual image evaluation was performed by 2 independent, blinded observers for the Hoffman brain phantom images and clinical patient studies.
  
  
  RESULTS
  FWHM improved on the fanned axis (transverse plane) by 0.05 mm (P < 0.001), and the unfanned axis (longitudinal plane) by 0.66 mm (P < 10(-6)), when DM was used. The mean improvement of contrast ratios for the spheres on the Jaszczak phantom with DM was 11.4% (P < 0.004). The images with DM were rated superior to those without, for the Hoffman brain phantom and the clinical patients.
  
  
  CONCLUSIONS
  This study has demonstrated that SPECT acquisition with fanbeam collimators and DM significantly improves both FWHM and image contrast, resulting in superior image quality. DM techniques may be useful in improving clinical brain SPECT images.
authors.affiliation: Department of Nuclear Medicine, Mount Sinai Hospital, University of Toronto, Ontario, Canada.
authors.forename: D C
authors.initials: DC
authors.lastname: Vines
authors.forename: M
authors.initials: M
authors.lastname: Ichise
mesh_terms: D000328:Adult; D000368:Aged; D001921:Brain / Q000000981:diagnostic imaging*; D003545:Cysteine / Q000031:analogs & derivatives; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008297:Male; D008875:Middle Aged; D015609:Organotechnetium Compounds; D019047:Phantoms, Imaging; D019275:Radiopharmaceuticals; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods
chemical_list: D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; C059659:technetium Tc 99m bicisate; D003545:Cysteine