Qualitative comparison of 3-T and 1.5-T MRI in the evaluation of epilepsy.
OBJECTIVE
MRI at 3 T, which has a higher signal-to-noise ratio than 1.5-T MRI, is potentially more sensitive and specific at delineating epileptogenic lesions and may influence management of refractory epilepsy. The purposes of the current study were to compare image quality of 3-T MRI with that of 1.5-T MRI in the evaluation of epilepsy and, in cases of focal epilepsy, to compare the two field strengths in terms of lesion detection and characterization.


METHODS
Retrospective review was performed on 50 sets of MR images of 25 patients who underwent both 3-T and 1.5-T brain imaging with a dedicated epilepsy protocol, including fast spin-echo T2-weighted, coronal FLAIR, coronal fast multiplanar inversion recovery, and 3D spoiled gradient-recalled echo pulse sequences. Parameters assessed were distortion and artifact, lesion conspicuity, gray-white matter differentiation, and motion. Each pulse sequence was graded on a 4-point scale. Reviewers performed qualitative assessments of the site of abnormality and the most likely diagnosis.


RESULTS
MRI at 3 T outperformed MRI at 1.5 T in all four parameters and was statistically superior (p < 0.05) to 1.5-T MRI in all categories except motion. On 3-T MRI, lesions were detected in 65 of 74 cases compared with 55 of 74 cases at 1.5 T (p = 0.0364), and lesions were accurately characterized in 63 of 74 cases compared with 51 of 74 cases at 1.5 T (p = 0.0194). The odds ratios showed identification of a focal epileptogenic lesion with 3-T MRI 2.57 times as likely as identification with 1.5-T MRI and accurate characterization of lesions 2.66 times as likely as characterization with 1.5-T MRI.


CONCLUSIONS
In evaluation of epilepsy, MRI at 3 T performed better than 1.5-T MRI in image quality, detection of structural lesions, and characterization of lesions. High-field-strength imaging should be considered for patients with intractable epilepsy and normal or equivocal findings on 1.5-T MRI.
Phal
Pramit M
PM
Division of Neuroradiology, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd,, Mail Code CR 135, Portland, OR 97239, USA.
Usmanov
Alexander
A
Nesbit
Gary M
GM
Anderson
James C
JC
Spencer
David
D
Wang
Paul
P
Helwig
Jonathan A
JA
Roberts
Colin
C
Hamilton
Bronwyn E
BE
D000293:Adolescent; D000328:Adult; D000368:Aged; D001921:Brain / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D004827:Epilepsy / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007223:Infant; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity