title: Iterative reconstruction or filtered backprojection for semi-quantitative assessment of dopamine D₂ receptor SPECT studies?
abstract: OBJECTIVE
  In routine clinical practice striatal dopamine D(2) receptor binding is generally assessed using data reconstructed by filtered backprojection (FBP). The aim of this study was to investigate the use of an iterative reconstruction algorithm (ordered subset expectation maximization, OSEM) and to assess whether it may provide comparable or even better results than those obtained by standard FBP.
  
  
  METHODS
  In 56 patients with parkinsonian syndromes, single photon emission computed tomography (SPECT) scans were acquired 2 h after i.v. application of 185 MBq [(123)I]iodobenzamide (IBZM) using a triple-head gamma camera (Siemens MS 3). The scans were reconstructed both by FBP and OSEM (3 iterations, 8 subsets) and filtered using a Butterworth filter. After attenuation correction the studies were automatically fitted to a mean template with a corresponding 3-D volume of interest (VOI) map covering striatum (S), caudate (C), putamen (P) and several reference VOIs using BRASS software.
  
  
  RESULTS
  Visual assessment of the fitted studies suggests a better separation between C and P in studies reconstructed by OSEM than FBP. Unspecific background activity appears more homogeneous after iterative reconstruction. The correlation shows a good accordance of dopamine receptor binding using FBP and OSEM (intra-class correlation coefficients S: 0.87; C: 0.88; P: 0.84). Receiver-operating characteristic (ROC) analyses show comparable diagnostic power of OSEM and FBP in the differentiation between idiopathic parkinsonian syndrome (IPS) and non-IPS.
  
  
  CONCLUSIONS
  Iterative reconstruction of IBZM SPECT studies for assessment of the D(2) receptors is feasible in routine clinical practice. Close correlations between FBP and OSEM data suggest that iteratively reconstructed IBZM studies allow reliable quantification of dopamine receptor binding even though a gain in diagnostic power could not be demonstrated.
authors.affiliation: Department of Nuclear Medicine, University of Munich, Marchioninistr. 15, 81377 Munich, Germany. walter.koch@med.uni-muenchen.de
authors.forename: Walter
authors.initials: W
authors.lastname: Koch
authors.forename: Christine
authors.initials: C
authors.lastname: Suessmair
authors.forename: Klaus
authors.initials: K
authors.lastname: Tatsch
authors.forename: Gabriele
authors.initials: G
authors.lastname: Pöpperl
mesh_terms: D000465:Algorithms; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D017448:Receptors, Dopamine D2 / Q000378:metabolism*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013997:Time Factors; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
chemical_list: D017448:Receptors, Dopamine D2