Artifacts and pitfalls in MR imaging of the orbit: a clinical review

High-resolution magnetic resonance (MR) imaging of the orbit has become widely accepted as a valuable diagnostic technique. However, there are a number of artifacts and pitfalls associated with orbital MR imaging. Chemical shift artifacts may be induced by orbital fat or silicone oil used to treat retinal detachment. Motion artifacts are caused primarily by unavoidable globe motion during imaging. Artifacts due to a nonuniform magnetic field are particularly noticeable at air-tissue interfaces but may also be caused by incomplete fat saturation or highly magnetic materials near the orbit. Protocol errors may cause artifacts such as saturation, phase wraparound, truncation, shading, and partial-volume artifacts. This information can be used to improve orbital image quality and avoid misinterpretation of image artifacts. Use of fat saturation, silicone saturation, and careful patient screening for metal near the eyes and instruction to reduce motion can help reduce the occurrence of artifacts. In addition, optimal imaging technique is essential and should include use of proper surface coils, plane of section, and pulse sequences.