P.175 Direct Visualization of Thalamic Nuclei using 7 Tesla MRI and quantification in patients with temporal lobe epilepsy.

Abstract

Background: Most individual thalamic nuclei cannot be directly visualized on routine clinical MRI. Stereotactic targeting techniques are indirect, relying on histological atlases and electrophysiological recording. We investigate whether high-field MRI can directly visualize the thalamic nuclei in vivo and allow for analysis of disease-related changes. Methods: Thirty-two healthy individuals were imaged with 7T MRI at a resolution of 0.7mm³. To obtain a high-resolution composite image, these were registered across subjects and averaged together. Three thalamic structures closely integrated in seizure propagation, the anterior thalamic nucleus (ATN), mammillothalamic tract (MTT), and centromedian nucleus (CM) were manually segmented in a subset of healthy subjects and patients with temporal lobe epilepsy (TLE). Results: There is sufficient resolution within the thalamus at 7T for visualization of the ATN, CM, and MTT. In the small subset of 5 controls and 5 TLE patients examined, there was no significant difference (p>0.05) in volume or mean T1map for the three thalamic sturctures of interest. Conclusions: MRI at 7T provides a method of direct visualization of thalamic nuclei, uncovering substructures not previously identifiable in vivo. These advances will enable quantitative analysis of disease-related changes to these structures and improved clinical targeting as demonstrated in this initial ‘proof-of-concept’ subset analysis.