Use of High-Resolution Microscopy Coil MRI for Depicting Orbital Anatomy

Objective: High-resolution MRI (HR-MRI) is a powerful noninvasive tool that provides images of higher spatial resolution and enables visualization of tissues previously unidentified with conventional techniques. The utilization of HR-MRI in the eye and orbit is essential due to the minute structure with great tissue diversity. The purpose of this study is to investigate the use of a novel surface coil and to explore the potential of this approach to depict normal anatomy. Methods: MR images were acquired using a commonly available 1.5T scanner. Ten normal volunteers were imaged using a surface microscopy coil of 47 mm inner diameter. T1-and T2-weighting and fat suppression techniques were used. HR-MR images were compared with conventional head coil MR images. Results: Overall exquisite anatomic detail of the eye and orbit is revealed. The in-plane resolution was 312 mu m and the displayed pixel dimension 156 mu m. Previously unobserved distinction of the globe layers and muscle groups is possible. To our best knowledge, our group was the first to demonstrate Tenon's capsule and the tarsal plate with MRI. The ciliary body and zonules of the lens are clearly visible. The superior muscle group is illustrated, being apparently divided into its components, namely the superior rectus and the levator palpebrae superioris muscles. Finally, the retrobulbar fat and parts of its connective tissue are depicted. Conclusion: High-resolution microscopy coil MRI improves the image resolution dramatically and enables a detailed tissue depiction of the orbital and globe structures. Therefore, its introduction in routine clinical use can facilitate diagnosis and pre-operative planning in challenging cases.