Chapter 12 – Brain Tumors

Cerebral glioma is the most common type of primary brain tumor and remains incurable in the majority of cases despite intensive therapeutic efforts. Structural imaging using contrast-enhanced MRI is the investigation of choice for diagnosing brain tumors, but its capacity to differentiate tumor tissue from nonspecific tissue changes is limited, especially in cerebral glioma. Molecular imaging using PET may provide relevant additional information that allows more accurate brain tumor diagnostics in unclear situations. The most widely used PET tracer, 2-18F-fluorodeoxyglucose, has only limited use in brain tumors because of the high tracer uptake in normal brain tissue. Radiolabeled amino acids exhibit lower uptake in the normal brain and can depict brain tumors with a higher contrast. A key feature of amino acid tracers is the property to pass the intact blood-brain barrier, which allows depiction of the tumor mass beyond contrast enhancement in MRI and differentiation of tumor progression from nonspecific treatment-related changes. Radiolabeled amino acids have become the preferred PET tracers in neurooncology, and the RANO (Response Assessment in Neuro-Oncology) group recommends the use of amino acid PET at all stages of patient management. Amino acid PET may be helpful at primary diagnosis when MRI shows equivocal lesions; for planning biopsy, surgery, and radiation therapy owing to a better delineation of cerebral gliomas; after treatment to differentiate between tumor progression and treatment-related changes; and for monitoring of response to therapy.