title: Localization of temporal epilepsy foci by subtraction ictal perfusion single photon emission computed tomography is enhanced when using 3D-OSEM iterative reconstruction.
abstract: OBJECTIVE
  Subtraction ictal single photon emission computed tomography (SPECT) images, provided by filtered back-projection (FBP), may exhibit a confusing high level of noise. This study was aimed at assessing an optimized three-dimensional ordered subset expectation maximization (3D-OSEM) iterative reconstruction in this setting.
  
  
  METHODS
  On phantom images, parameters of 3D-OSEM reconstruction were selected as those providing the higher signal/noise ratio but a high enough spatial resolution, equivalent to that of conventional FBP reconstruction (full width at half-maximum = 11 mm). Thereafter, subtraction ictal ethylene cysteine dimer-SPECT coregistered to MRI and reconstructed with either FBP or 3D-OSEM were compared in 21 patients with well-characterized temporal epilepsy foci (subsequent successful surgical treatment).
  
  
  RESULTS
  On subtraction images, the use of the selected 3D-OSEM reconstruction (five iterations, 16 subsets and a 9 mm Gauss filter) instead of FBP was associated with: (i) marked reductions in background activity (0.05 ± 0.09 vs. 0.25 ± 0.18 cps, P < 0.001) and in the size of temporal foci (10 ± 7 vs. 14 ± 11 cm, P = 0.01) and (ii) a trend toward higher accuracy in identifying the involved temporal lobes (86 vs. 76%).
  
  
  CONCLUSIONS
  Localization of temporal epilepsy foci by subtraction ictal SPECT is likely to be enhanced by using 3D-OSEM rather than FBP reconstruction because of marked reductions in background activity and in the size of detected foci.
authors.affiliation: Department of Nuclear Medicine, CHU-Nancy, Nancy, France. sbenmahmoud@gmail.com
authors.forename: Sinan
authors.initials: S
authors.lastname: Ben Mahmoud
authors.forename: Louis
authors.initials: L
authors.lastname: Maillard
authors.forename: Sylvain
authors.initials: S
authors.lastname: Poussier
authors.forename: Laurent
authors.initials: L
authors.lastname: Koessler
authors.forename: Mohamed Safa
authors.initials: MS
authors.lastname: El Khawaja
authors.forename: Marie H
authors.initials: MH
authors.lastname: Laurens
authors.forename: Hervé
authors.initials: H
authors.lastname: Vespignani
authors.forename: Gilles
authors.initials: G
authors.lastname: Karcher
authors.forename: Pierre Y
authors.initials: PY
authors.lastname: Marie
mesh_terms: D000293:Adolescent; D000328:Adult; D004833:Epilepsy, Temporal Lobe / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D013382:Subtraction Technique; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D055815:Young Adult