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Abstract

Purpose/Introduction: In presurgical evaluation of epilepsy patients, MRI has an important role in defining location and extent of a potentially epileptogenic focus that can be subject to surgical resection. If clinical MR is negative, chances of a post-operative seizure freedom are inferior compared to patients with a visually apparent lesion. But even with optimal methodology, a significant proportion of patients will still have a normal MRI on visual inspection and are difficult or impossible to introduce to a potentially curative surgical therapy. Here, we investigated whether imaging of epilepsy patients in 9.4T provides increased image resolution and contrast compared to standard clinical protocols at 3T MRI in order to improve post processing to detect otherwise invisible epileptogenic lesions. Subjects and Methods: We included 12 patients of the university hospital of Tuebingen having presurgical monitored focal epilepsy (including video-EEG and clinical 3 Tesla MRI) as well as 40 healthy controls (21 at 3T, 19 at 9.4T). The standard clinical procedure showed that 2 patients of those had a visible focal cortical dysplasia as epileptogenic lesion, 10 patients had a normal MRI (=cryptogenic). Examination at 9.4T included whole brain 0.8 mm isotropic MP2RAGE (TE = 2.3 ms, TR = 6 ms, TI1 = 900 ms, TI2 = 3500 ms, FA1 = 4, FA2 = 6) and a T2 * -weighted GRE sequence with 0.4 9 0.4 9 0.8 mm resolution (TE = 6–30 ms in steps of 6 ms, TR = 35 ms, FA = 11) For comparison, 1 mm isotropic MRP2RAGE images (TE = 2.98 ms, TR = 5000 ms, TI1 = 700 ms, TI2 = 2500 ms, FA1 = 4, FA2 = 5) were acquired at 3 T using the standard protocols for clinical diagnosis. In order to compare the image quality at 3T and 9.4T, voxel based morphometry (VBM, SPM12) derived from MP2RAGE images as well as quantitative analysis of the T2 * maps was performed. Results: VBM of the 3T data showed in 4/10 cryptogenic patients a finding concordant to the clinical hypothesis of seizure origin. However, in the 9.4T images, 10/10 cryptogenic patients showed abnormalities in the suspected region, which could be retraced in the high resolution images. The visible focal cortical dysplasia in the 2 other patients were correctly detected by VBM of the 9.4T data, whereas only 1 was recognized in the 3T images. Discussion/Conclusion: The application of 9.4T MRI in epilepsy patients can help to visualize lesions, that were undetectable using standard 3T routines. This may improve presurgical evaluation by facilitating MR negative patients a surgical treatment and by better visualization of the true extent of epileptogenic lesions to reduce risk of incomplete resection.