Background: Hippocampal sclerosis (HS) is a common cause of drug-resistant focal epilepsy (DRFE) and amenable to neurosurgical treatment. Detection relies on MRI but can be challenging. 7 Tesla (T) ultra-high field MRI and automated MRI post-processing tools have independently been shown to improve radiological diagnosis of HS. However, combining these approaches remains underexplored. This study evaluated whether AID-HS, a tool for HS detection developed using 3T MRI, generalises to 7T MRI data. Methods: We collated a dataset of paired 3T and 7T T1-weighted MRI from four epilepsy centres, including 23 patients with HS, 39 healthy controls, and 23 individuals with focal cortical dysplasia as disease controls. Histopathology served as the gold standard for defining HS where available (n=7), otherwise radiological findings (n=16). AID-HS was applied to images acquired at both field strengths, and sensitivity and specificity for detection and lateralisation of HS were compared. Additionally, agreement of hippocampal features across 3T and 7T was evaluated. Results: We found no evidence of a difference in performance of AID-HS between 3T and 7T. Sensitivity for detection of unilateral HS was 63% (12/19) at 3T and 68% (13/19) at 7T (McNemar's exact test p=1.0). Specificity in controls was 97% (60/62) at 3T and 100% (62/62) at 7T (p=0.5). Bilateral HS was correctly flagged in 3 of 4 cases using feature-based criteria, with high specificity in controls. Quantitative hippocampal features showed moderate to good agreement across field strengths (ICC 0.70 to 0.98), with small differences observed for volume and thickness estimates. Conclusion: AID-HS provides robust detection and lateralisation of HS across multiple 7T MRI centres, highlighting its potential to enhance lesion detection. Future work is needed to investigate whether models trained on 7T data can leverage the improved image quality for further gains in HS detection performance.
C. Kronlage, M. Ripart, R. Piper et al.· medRxiv· 0 citations
OBJECTIVE
The detection of subtle epileptogenic lesions such as focal cortical dysplasias (FCDs) is a clinical challenge in the management of drug-resistant focal epilepsy (DRFE). Ultra-high-field (UHF) magnetic resonance imaging (MRI) offers increased signal-to-noise ratios and spatial resolution compared to 3-T MRI and may improve diagnostic yield.
METHODS
We recruited n = 21 DRFE patients (with 3-T MRI findings: two positive, three equivocal, 16 negative) undergoing presurgical workup and n = 20 healthy controls for 9.4-T MRI (.8 mm isotropic magnetization-prepared 2 rapid acquisition gradient echo [MP2RAGE], slabs of .375 × .375 × .8 mm T2*-weighted gradient echo) and 3-T MRI (magnetization prepared rapid acquisition gradient echo [MPRAGE], magnetization-prepared 2 rapid acquisition gradient echo [MP2RAGE], fluid-attenuated inversion recovery [FLAIR]) acquisitions. Visual review for possible epileptogenic lesions was performed by clinical experts. For histopathologically confirmed FCDs, we extracted surface-based quantitative features (cortical thickness, quantitative T1, FLAIR, T2*, and quantitative susceptibility mapping values) across cortical depths and distances from the lesion center and performed high-resolution cortical profiling of 9.4-T T2* values.
RESULTS
In two patients with histopathologically confirmed FCD IIb, lesions were visible with distinct qualitative and quantitative features at both field strengths. One of these type IIb FCDs showed a focal cortical T2* reduction at 9.4 T that could be quantified via automated cortical profiling, consistent with the previously described "black line sign." No new epileptogenic lesions were identified at 9.4 T in 3-T MRI-negative patients, who also had no histological evidence of such lesions.
SIGNIFICANCE
9.4-Tesla MRI findings in epileptogenic lesions underlying DRFE are consistent with those on 3-T MRI. UHF T2*-weighted sequences may be useful to detect the black line sign and thereby refine surgical or ablation targeting for some FCDs. Assessment of the diagnostic yield of 9.4-T MRI was limited by the lack of 3-T MRI-negative but histopathologically confirmed cases and by the unavailability of parallel transmit and FLAIR at 9.4 T. Further optimization of UHF protocols and analysis methods on larger cohorts may enhance clinically applicable diagnostic benefits.
Cornelius Kronlage, Pascal Martin, Benjamin Bender et al.· Epilepsia· 0 citations
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