Pictorial essay: Ophthalmologic abnormalities in FDG PET/CT

Learning Objectives 1. Be able to recognize both subtle and apparent abnormalities within the orbit and its contents on both PET and CT. 2. Review both common and uncommon abnormalities seen within the orbit. 3. To recognize the impact of findings on patient management and appropriate follow up.

Positron emission tomography (PET) using fluorine-18-2-deoxy-D-glucose (18F-FDG) diagnoses, stages, and restages many cancers and is often better than anatomical imaging alone. The fusion of functional (PET) and anatomic (CT) imaging continues to evolve and provide valuable clinical information. These findings, however, may be subtle on either modality alone. This is especially apparent when dealing with abnormalities within the orbit since this region is typically at the edge of the field of view for the standard base of skull to upper thigh FDG PET-CT scans. The various types of findings within the orbit will be discussed as well as techniques helpful for interpretation. Some examples of over 20 cases include lymphoma, melanoma, meningioma, squamous cell carcinoma, metastasis, benign calcifications, post-surgical changes, artificial eye, evisceration of the globe and Tolosa-Hunt syndrome. This review of abnormalities will be of value for both residents and attending physicians alike