Utilization of FDG PET in evaluation of brain lesions: A pictorial essay

Learning Objectives 1. To emphasize the role of FDG PET in clinical neurology. 2. To demonstrate common indications of FDG PET in evaluating brain lesions.

Summary: FDG PET yields high-resolution images of brain activity with accurate quantification of a fundamental property of central nervous system function, cerebral glucose metabolism. The most common applications of brain FDG PET are in epilepsy, Alzheimer’s disease (AD), differentiation between post therapy fibrosis/scarring from residual/recurrent brain tumor, cerebral infection especially in HIV positive patients, evaluating metastatic brain lesions and characterization of primary brain tumor. In epilepsy, FDG PET has proven useful as a complementary method in preoperative localization of the epileptogenic region. In AD, FDG PET has been used for early diagnosis, even before onset of symptoms, to differentiate AD from other forms of dementia. In addition, it is a very useful prognostic tool in patients with AD. In contrast to MRI, FDG PET can differentiate between viable brain tumor tissue versus post therapy fibrosis/scarring. In metastatic brain lesions, FDG PET, in conjunction with other imaging modalities, plays an important role in lesion characterization. Occasionally, in evaluating primary brain tumors, it can be used to differentiate between low versus high grade malignancies. Furthermore, FDG PET can differentiate cerebral toxoplasmosis from cerebral lymphoma in HIV patients. Illustrations displayed include examples of some of the common indications of FDG PET brain scan.