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Positron emission tomography imaging of brain tumors

2002; Elsevier BV; Volume: 12; Issue: 4 Linguagem: Inglês

10.1016/s1052-5149(02)00033-3

1557-9867

Terence Z. Wong, Gert J. Van Der Westhuizen, R. Edward Coleman,

Advanced MRI Techniques and Applications

Tumours of the central nervous system are a heterogeneous group with an annual incidence rate of 23.41 per 100,000 people in the United States, the most common being meningiomas (38.5%) and gliomas (25.5%).1,2 Whilst 98% of meningiomas are benign, 54% of gliomas are highly malignant glioblastomas. Neuroimaging allows the non-invasive evaluation of glioma and is one of the key factors for guiding individualised therapy and patient management, since accurate diagnosis and demarcation of viable tumour tissue are required for treatment planning, as well as assessment of any treatment response. Conventional imaging modalities like MRI and CT reveal morphological information but are of comparatively limited value for the assessment of specific and reproducible information about the biology and metabolic activity of a tumour. Molecular imaging with PET is increasingly implemented in neuro-oncology, as it provides additional metabolic information about the tumour, both for patient management and for evaluation of newly developed therapeutics. Some studies have demonstrated the diagnostic limitations of [18F]FDG PET in the evaluation of brain tumours.22,23 Glucose is the primary substrate of energy supply to the brain, providing approximately 95% of the required ATP, and is also tightly connected to neuronal activity. High physiologic brain glucose metabolism will then correlate with high uptake of [18F]FDG in the brain. The diagnostic accuracy of [18F]FDG is hampered by the high normal physiologic glucose metabolism in different brain areas, such as the cerebral cortex, the basal ganglia and the thalamus, significantly limiting the sensitivity for detection, as well as the specificity for delineation of glioma-involved tissue from adjacent normal brain. Amino acid and analogue amino acid PET tracers constitute an additional class of tumour-imaging agents.28,29 They are particularly useful for imaging brain tumours because of the high uptake in tumour tissue and low uptake in normal brain tissue and, thus, higher tumour-to-normal contrast ratio than [18F]FDG. Amino acids are transported into the cell via several carrier-mediated processes.29 Amino acid imaging is based on the observation that amino acid transport is generally increased in malignant transformation.30,31 In summary, an accurate, more comprehensive assessment of brain tumour extent and biology is frequently more feasible with metabolic [11C]methionine amino acid PET imaging compared to morphologic contrast-enhanced, high-resolution MRI or CT scans.