Localization of temporal epilepsy foci by subtraction ictal perfusion single photon emission computed tomography is enhanced when using 3D-OSEM iterative reconstruction.
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.
Ben Mahmoud
Sinan
S
Department of Nuclear Medicine, CHU-Nancy, Nancy, France. sbenmahmoud@gmail.com
Maillard
Louis
L
Poussier
Sylvain
S
Koessler
Laurent
L
El Khawaja
Mohamed Safa
MS
Laurens
Marie H
MH
Vespignani
Hervé
H
Karcher
Gilles
G
Marie
Pierre Y
PY
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