ABSTRACT
Background Cancerous transformation entails major biochemical changes including modifications of the energy metabolism of the cell, e.g. utilization of glucose and other substrates, protein synthesis, and expression of receptors and antigens. Tumor growth also leads to heterogeneity in blood flow owing to focal necrosis, angiogenesis, and metabolic demands, as well as disruption of transport mechanisms of substrates across cell membranes and other physiological boundaries such as the blood-brain barrier. These biochemical and histological changes, along with their macroscopic anatomical effects, can be assessed with different non-invasive imaging tools, such as X-ray computed tomography (CT), magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), positron emission tomography (PET), and single photon emission computed tomography (SPECT). Whereas anatomical imaging (i.e. CT and MRI) is aimed at defining the size and exact localization of brain tumors, along with the assessment of invasion of surrounding structures, functional imaging (MRS, PET, SPECT) is better suited for characterization of the biological properties. The identification of a tumoral mass and the assessment of its size and vascularization are best achieved with CT and MRI, while functional imaging can provide additional information that is crucial for tumor classification, differential diagnosis, and follow-up.1
