High-resolution anatomic, diffusion tensor, and magnetization transfer magnetic resonance imaging of the optic chiasm at 3T

Purpose: To evaluate techniques for anatomical and physiological imaging of the intracranial optic nerve (ON), optic chiasm (OC), and optic tract (OT) at 3T with the aim of visualizing axonal damage in multiple sclerosis (MS). Materials and Methods: Imaging was performed on a 3T scanner employing a custom-designed head coil that consisted of a coil array with four coils (30 × 30 cm²). Oblique fast spin echo (FSE) images, magnetization transfer (MT)-enhanced 3D gradient-echo (GRE) time-of-flight (TOF) images, and line scan diffusion images (LSDI) were obtained. Full diffusion tensor (DT) analysis was performed, and apparent diffusion coefficient (ADC), fractional anisotropy (FA), and fiber direction maps were obtained. Results: FSE anatomic images were obtained with an inplane resolution of 0.39 × 0.52 mm ². The in-plane resolution of the MT and LSDI images was 0.78 × 0.78 mm². The OC, intracranial ON, and OT can be seen on these images. The dominant fiber orientations in the OC, ON, and OT, as derived from the DT images, are displayed. Conclusion: This study shows that by using 3T and a custom-designed, four-channel head coil, it is possible to acquire high-resolution anatomical and physiological images of the OC, ON, and OT. The pilot results presented here pave the way for imaging the anterior visual pathway in patients with MS.