MRI-based correction for partial-volume effect improves detectability of intractable epileptogenic foci on 123I-iomazenil brain SPECT images.
(123)I-Iomazenil brain SPECT has been used for the detection of epileptogenic foci, especially when surgical intervention is considered. Although epileptogenic foci exhibit a decrease in (123)I-iomazenil accumulation, normal cerebral cortices often exhibit similar findings because of thin cortical ribbons, gray matter atrophy, or pathologic brain structures. In the present study, we created (123)I-iomazenil SPECT images corrected for gray matter volume using MRI and tested whether the detectability of the epileptogenic foci improved.


METHODS
Seven patients (1 male patient and 6 female patients; mean age +/- SD, 34 +/- 17 y) with intractable epilepsy were surgically treated by resecting the cerebral cortex after surface electroencephalography. Histopathologic examination of the resected specimens and a good outcome after surgery indicated that the resected lesions were epileptogenic foci. These patients underwent (123)I-iomazenil SPECT and 3-dimensional T1-weighted MRI examinations before their operations. Each SPECT image was coregistered to the corresponding MR image, and its partial-volume effect (PVE) was corrected on a voxel-by-voxel basis with a smoothed gray matter distribution image. Four nuclear medicine physicians visually evaluated the (123)I-iomazenil SPECT images with and without the PVE correction. The SPECT count ratio of the suspected focus to the contralateral cerebral cortex was evaluated as an asymmetry index (%) based on the volume of interest.


RESULTS
The sensitivity, specificity, and accuracy of focus detection by visual assessment were higher after PVE correction (88%, 99%, and 98%, respectively) than before correction (50%, 92%, and 87%, respectively). The mean asymmetry index for the surgically resected lesions was significantly higher on the PVE-corrected SPECT images (22%) than on the PVE-uncorrected ones (16%) (P = 0.006).


CONCLUSIONS
MRI-based PVE correction for (123)I-iomazenil brain SPECT improves the sensitivity and specificity of the detection of cortical epileptogenic foci in patients with intractable epilepsy.
Kato
Hiroki
H
Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, Suita, Japan.
Shimosegawa
Eku
E
Oku
Naohiko
N
Kitagawa
Kazuo
K
Kishima
Haruhiko
H
Saitoh
Youichi
Y
Kato
Amami
A
Yoshimine
Toshiki
T
Hatazawa
Jun
J
D000328:Adult; D016477:Artifacts; D001921:Brain / Q000000981:diagnostic imaging* / Q000473:pathology; D004827:Epilepsy / Q000175:diagnosis* / Q000473:pathology; D005260:Female; D005442:Flumazenil / Q000031:analogs & derivatives* / Q000032:analysis; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods; D007457:Iodine Radioisotopes / Q000032:analysis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
D007457:Iodine Radioisotopes; D005442:Flumazenil; C063038:iomazenil