title: Evaluation of 2 scatter correction methods using a striatal phantom for quantitative brain SPECT.
abstract: OBJECTIVE
  Scatter correction is an important factor in quantitative SPECT. In this study, we evaluated 2 methods of scatter correction for brain SPECT. The first is based on thresholding the energy spectrum (ES), and the second is based on a modification of the transmission-dependent convolution subtraction (TDCS) method.
  
  
  METHODS
  SPECT imaging of a skull striatal phantom was performed using a triple-head camera with and without scatter correction. The striatal compartments were filled with (123)I, and the brain shell cavity (background) was filled with varying concentrations of (123)I to obtain striatal-to-background ratios of 2, 5, 10, 15, 20, and 25 to 1, respectively, which were considered to be the expected ratios. SPECT-measured ratios of striatal-to-background counts were determined with scatter correction (both ES and TDCS methods) and without scatter correction and were then compared with the expected ratios.
  
  
  RESULTS
  Without scatter correction, measured striatal-to-background ratios were underestimated by an average of 41.7%, compared with the expected ratios. The ES method of scatter correction underestimated the striatal-to-background ratios by an average of 27.4%, a significant improvement (P < 0.04) over those without scatter correction. With the TDCS method of scatter correction, the ratios were underestimated by only 3.3% (P < 0.03). TDCS ratios were significantly (P < 0.04) higher than ES ratios and were nearly identical to the expected ratios.
  
  
  CONCLUSIONS
  These results suggest that scatter correction significantly improves the striatal-to-background ratios. The TDCS method appears to correct scatter more effectively than does the ES method for the striatal phantom, thus providing more accurate quantification.
authors.affiliation: Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-0135, USA. douglas.vines@nih.gov
authors.forename: Douglass C
authors.initials: DC
authors.lastname: Vines
authors.forename: Masanori
authors.initials: M
authors.lastname: Ichise
authors.forename: Jeih-San
authors.initials: JS
authors.lastname: Liow
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Toyama
authors.forename: Robert B
authors.initials: RB
authors.lastname: Innis
mesh_terms: D000465:Algorithms; D003342:Corpus Striatum / Q000000981:diagnostic imaging*; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods*; D019047:Phantoms, Imaging; D012542:Scattering, Radiation; D015899:Tomography, Emission-Computed, Single-Photon / Q000295:instrumentation* / Q000379:methods*