Purpose: Curative neurosurgical treatment options for patients with focal epilepsies demand accurate anatomical identification of the epileptogenic lesion by MR imaging. The most typical lesion in temporal epilepsies is a hippocampal sclerosis. Therefore, the aim of this study is to implement and test an adopted imaging protocol at 7 Tesla in patients with known hippocampal sclerosis focussed on maximum spatial resolution and scan time.
Material and methods: Seven patients with hippocampal sclerosis were investigated with T1-, T2-, T2*- and FLAIR-weighted sequences at 7 Tesla (Magnetom 7T, Siemens, Erlangen; 8-channel transmit/receive-head coil, Rapid Biomedical, Würzburg). Depiction of the hippocampus and its internal structures (hippocampal sulcus, dentate gyrus, CA1–4) was compared to routine 1.5 Tesla images.
Results: Maximum spatial resolution was 0.2×0.2mm2 in T2*- and 0.5×0.5mm2 in all other sequences. In contrast to 1.5 Tesla, especially the hippocampal sulcus and the dentate gyrus were best visualized in T2*-weighted images. In 5 of 7 patients the intrahippocampal CA1–4-regions and the dentate gyrus could be identified. In 4 of 7 patients individual regional patterns of atrophy are detectable. Nevertheless, strong susceptibility effects also increased artifacts and accordingly in 2 of 7 patients the hippocampus could not be analyzed.
Conclusion: Ultrahigh-resolution imaging at 7 Tesla is promising in epilepsy. „New“ T2*-contrasts together with very high spatial resolution may allow the presurgical differentiation of distinct regional patterns of atrophy. In future, this method may help improving presurgical patient selection and may increase the detection of very small intrahippocampal lesions.
