Magnetic resonance imaging of the orbit: Basic principles and anatomy

This review article gives a basic introduction to the technical principles of magnetic resonance imaging for ophthalmologists and orbital surgeons and describes the anatomical structures that can be identified on high-resolution magnetic resonance images of the orbit. The meaning of general imaging parameters, specific weighting of the images, and the use of contrast agents, fat suppression techniques and surface coils is explained. Possible artifacts are also described. The advantages and disadvantages of MRI in comparison with computed tomography (CT) are discussed in order to give recommendations for the use of the appropriate imaging modality in patients with orbital disorders. Apart from delineating the course of the extraocular muscles, high-resolution MRI is able to depict not only all important blood vessels and cranial nerves of the orbit but also major septa of the orbital connective tissue system. Clinical applications are also mentioned to show that high-resolution MRI may contribute to a specific diagnosis in orbital disease.