Amino Acid Tracer PET MRI in Glioma Management: What a Neuroradiologist Needs to Know

Abstract

PET with amino acid tracers provides additional insight beyond MR imaging into the biology of gliomas that can be used for initial diagnosis, delineation of tumor margins, planning of surgical and radiation therapy, assessment of residual tumor, and evaluation of posttreatment response. Hybrid PET MR imaging allows the simultaneous acquisition of various PET and MR imaging parameters in a single investigation with reduced scanning time and improved anatomic localization. This review aimed to provide neuroradiologists with a concise overview of the various amino acid tracers and a practical understanding of the clinical applications of amino acid PET MR imaging in glioma management. Future perspectives in newer advances, novel radiotracers, radiomics, and cost-effectiveness are also outlined.ABBREVIATIONS: AAT ¼ amino acid tracer; AA ¼ amino acid; ASCT ¼ alanine-serine-cysteine transporter; BTV ¼ biologic tumor volume; GBM ¼ glioblas-G liomas represent approximately 80% of malignant brain tumors, with an annual incidence rate of 5.6 cases per 100,000 individuals worldwide. Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor, representing approximately 50% of all gliomas and 16% of all brain tumors. 1 Depending on the size and extent of these tumors, the standard of care for newly diagnosed GBMs usually includes maximal surgical resection followed by radiation and chemotherapy. Despite substantial development in managing high-grade gliomas (HGGs), the median survival is ,15 months, with 1-and 5-year survival rates of 40% and 5.5%, respectively. 2 Imaging is crucial for diagnosing, guiding biopsy, surgical planning, and distinguishing treatment-related changes (TRC) from recurrence in glioma management. MR imaging is the primary imaging technique; however, it lacks specificity to distinguish between viable neoplastic tissue and tumor-free areas.Advanced MR imaging techniques such as PWI, DWI, DTI, MRS, and molecular imaging (PET) facilitate visualization and quantification of different metabolic processes and improve overall diagnostic performance in brain tumors. Hybrid PET MR imaging with novel radiotracers provides a noninvasive, simultaneous assessment of brain tumor morphologic, functional, metabolic, and molecular parameters. 3,4 This review aimed to provide neuroradiologists with a concise overview of the various amino acid tracers (AATs) and a practical understanding of the clinical applications of amino acid (AA) PET MR imaging in glioma management. We will review the current literature regarding AA-PET MR imaging in glioma treatment and discuss its role in the initial diagnosis, delineation of tumor margin, planning of radiation therapy, assessment of residual tumor, and evaluation of treatment response. We will sum up with future perspectives on newer advances, novel radiotracers, radiomics, and cost-effectiveness. RadiopharmaceuticalsThe Joint European Association of Nuclear Medicine (EANM)/ European Association of Neuro-Oncology (EANO)/Response Assessment in Neuro-Oncology (RA...

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