Stratifying differences on ictal/interictal subtraction SPECT images.
OBJECTIVE
Subtraction of interictal from ictal single-photon emission computed tomography (SPECT) yields numerous foci that encompass a range of pixel values scattered in the brain. This preliminary study evaluated the significance of this range of values.


METHODS
Subtraction images were obtained by registering, normalizing, and subtracting interictal from ictal SPECT for 13 patients. Pixel values of the resulting foci were divided into two groups: group I with 75-100% and group II with 50-75% of the maximal pixel value. Locations of these foci were determined, and concordance with surgical outcomes and scalp and invasive EEG findings was evaluated.


RESULTS
In 10 of 13 cases, group I foci showed good concordance with ictal scalp EEG. In addition, group I foci corresponded well to invasive EEG findings in nine of 10 cases. Group I foci had bilateral distributions in seven of 13 cases. In 10 of 13 cases, group I foci corresponded well to regions of surgical resection. Of these 10 patients, nine showed good concordance with scalp EEG, eight showed good invasive EEG concordance, and eight were seizure free after resection. Conversely, group II foci had good concordance with ictal scalp EEG in only five of 13 cases, and invasive EEG findings, in only five of 10 cases. Group II foci had bilateral distributions in 10 of 13 cases. All 10 cases underwent unilateral surgical resections, and all had good surgical outcomes. In six of 13 cases, group II foci showed concordance with surgical sites. Of these six foci, four had poor concordance with scalp EEG, one had poor concordance with invasive EEG, and five had good surgical outcomes. Sensitivity and specificity for seizure localization of Group I foci were 40% and 88% respectively while sensitivity and specificity of Group II foci were 20% and 79% respectively.


CONCLUSIONS
Our data demonstrate that foci with 75-100% of maximal pixel values show good concordance with seizure foci, whereas foci of 50-75% may not. Therefore stratifying ictal/interictal differences may improve the specificity and localizing value of subtraction SPECT.
Koo
Chi Wan
CW
The Department of Radiology, Division of Nuclear Medicine, New York University School of Medicine, New York, New York 10016, USA.
Devinsky
Orrin
O
Hari
Kim
K
Balasny
Jennifer
J
Noz
Marilyn E
ME
Kramer
Elissa L
EL
D000293:Adolescent; D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging* / Q000601:surgery; D001931:Brain Mapping / Q000379:methods; D002648:Child; D002675:Child, Preschool; D003545:Cysteine / Q000031:analogs & derivatives*; D004569:Electroencephalography / Q000379:methods / Q000706:statistics & numerical data; D004827:Epilepsy / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000601:surgery; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007223:Infant; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D015609:Organotechnetium Compounds; D012189:Retrospective Studies; D013382:Subtraction Technique / Q000706:statistics & numerical data; D015899:Tomography, Emission-Computed, Single-Photon / Q000706:statistics & numerical data; D016896:Treatment Outcome
D015609:Organotechnetium Compounds; C059659:technetium Tc 99m bicisate; D003545:Cysteine