The study included 25 patients (18 females and 7 males). Their ages ranged between 1 and 57 years.
Inclusion criteria
25 consecutive patients with history of primary idiopathic epilepsy and their MRI revealed epileptogenic lesions were prospectively included in the study. All age groups were included.
Exclusion criteria
Patients with space occupying lesions, inflammatory pathology and vascular malformations.
All patients were subjected to
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1.
Thorough history taking.
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2.
Conventional MRI epilepsy protocol, including:
All patients in this study were imaged using 3T magnet MRI machines; GE Discovery closed configuration whole body scanner using a standard head coil.
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A.
Three dimensional (3D) T1 weighted image utilizing a repetition time (TR) of 8 ms, an echo time (TE) of 3 ms, an isometric slice thickness of 1 mm, FOV = 230 × 180 mm.
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B.
Axial and coronal T2 weighted image utilizing a repetition time (TR) of 4000 ms, an echo time (TE) of 100 ms, a slice thickness of 5 mm, FOV = 230 × 180 mm.
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C.
Three dimensional (3D) FLAIR utilizing a repetition time (TR) of 7500 ms, an echo time (TE) of 110 ms, TI of 2000 ms, an isometric slice thickness of 1 mm and FOV = 230 × 180 mm.
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3.
Double inversion recovery (DIR) sequence:
We used a three dimensional double inversion recovery (DIR) sequence utilizing a repetition time (TR) of 7000 ms, an echo time (TE) of 80 ms, inversion times (TI) of 3400/325 ms, a slice thickness of 1×1×2 mm and FOV= 230 × 180 mm.
Image analysis
All images were analyzed by two experienced neuroradiologists. To test the impact of DIR sequence, the two observers assess, for each sequence and lesion, variable semiological aspects assigned as following:
1. Mesial temporal lobe sclerosis:
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A.
Visual evaluation: the examiners evaluate for hippocampal hyperintensity, compared to the contralateral side.
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B.
Quantitative assessment: Measuring signal intensities of both hippocampi on the coronal DIR, FLAIR, and T2 images, round small regions of interest (ROIs) of similar size are manually drown on bilateral hippocampi, and signal intensities are acquired independently at the head, body, and tail levels of the hippocampus. The mean value denotes the signal intensity of the whole hippocampus. The ROIs are placed to include as much of the hippocampal tissues as possible while avoiding the adjacent CSF spaces to diminish the effects of partial volume from the CSF. From the measured signal intensities of bilateral hippocampi on the coronal DIR, FLAIR, and T2 images, the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), contrast ratio (CR), and asymmetry index (AI) are calculated for all patients.
SNR = SI1/SDno
CNR = |SI1 − SI2|/SDno,
CR = |SI1 − SI2|/SI2
AI = 100 (%) × |SI1 − SI2|/ [(SI1 + SI2)/2]
where SI1 is the signal intensity of affected hippocampus,
SI2 is the signal intensity of contralateral hippocampus.
SDno is the SD of the noise,
2. Focal cortical dysplasia:
A. Visual evaluation: the examiners evaluate for each sequence and lesion, variable semiological aspects assigned as following:
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1.
Cortical Thickness (CT): examiners evaluate the lesion for cortical thickness comparing it to the contralateral healthy side and giving a result of no difference or increased cortical thickness (CT).
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2.
Cortical Signal Intensity (CSI): the examiners evaluate a given lesion, compared with contralateral healthy side, giving a result of no difference or CSI change (hypointensity on T1 sequence and hyperintensity on T2, FLAIR and DIR sequences)
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3.
GM/WM junction blurring: the examiners evaluate whether blurring is present, or not.
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Subcortical WM hyperintensity: the examiners evaluate if white matter subcortical hyperintensity is detected, or not.
B. Quantitative assessment: calculating average signal intensities of the lesions manually on the coronal DIR, FLAIR, and T2 images. For sake of comparison, the contralateral side for each lesion is further segmented and average intensity is measured. Then the signal-to-noise ratio (SNR), contrast to- noise ratio (CNR), contrast ratio (CR), and asymmetry index (AI) are calculated.
3. Lesions for visual analysis only:
A. Heterotopia / Polymicrogyria / Schizencephaly: the examiners are asked to evaluate each lesion according to visibility, each lesion is classified as better, similar, or lower visible between DIR versus T1, T2 and FLAIR sequences.
B. Tuberous sclerosis:
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1.
Counting of cortical tubers: the examiners are asked to count all the lesions on T2, FLAIR and DIR, each sequence will be assessed separately from the others, starting by T2 sequence followed by the FLAIR and ending by the DIR.
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2.
Lesion visibility: the examiners are asked to evaluate each lesion according to its visibility, where each lesion is classified as better, similar, or lower visible between DIR versus T2 and FLAIR sequences.
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3.
GM/WM junction blurring: the examiners are asked to evaluate if blurring is present, or not.
C. Other lesions:
The examiners are asked to evaluate each lesion according to its visibility, where each lesion is classified as better, similar, or lower visible between DIR versus T2 and FLAIR sequences.
Statistical analysis
The statistical analysis of lesions on the different pulse sequences will be performed patient and lesion wise. All data will be gathered, statistically analyzed, and tabulated. Qualitative data will be described using number and percent. Quantitative data will be described using mean and standard deviation. Significance of the obtained results will be judged at the 5% level (P value of < 0.05 was considered statistically significant). Significance between periods was done using Post Hoc Test (adjusted Bonferroni) comparing between different periods using F test (ANOVA).