Glioma is one of the most frequently observed and aggressive brain tumors.
Glioma forms 50-60% of brain tumors including astrocytoma, oligodendroglioma, and
glioblastoma. Although the integrity of the blood-brain barrier (BBB) is destroyed
somehow in glioblastoma (high-grade glioma) patients, similar to many central nervous
system diseases, the main anatomical obstacle remains BBB in effective diagnosis,
imaging, and therapy.
The survival rate of glioblastoma patients is very low. Early and accurate diagnosis of
glioma is essential for therapy chance. When compared with other techniques, noninvasive
medical imaging methods provide high specificity and sensitivity. Although
MRI is one of the most commonly used modalities in glioma diagnosis and imaging, it
possesses limited differentiation in tumor recurrence and pseudoprogression after
radiotherapy and combined chemotherapy. Improved MRI techniques can exhibit
higher potential in evaluating the pathological features and grading of gliomas before
treatment. As a novel method, molecular imaging techniques such as PET/CT can
detect genetic mechanisms and related molecular and metabolic differentiation for
accurate diagnosis of diseases.
18F-FDG, one of the most commonly used PET radiopharmaceuticals, is highly
accumulated in the cerebral cortex. Therefore, 18F-FDG is a non-specific agent in
glioma diagnosis and imaging. Non-specific radiopharmaceuticals are not sufficient
depending on low sensitivity and specificity in early diagnosis and imaging of
proliferation index of tumor cells, the place of hypoxic focuses, tumor load,
differentiation of tumor/necrosis, and tumor/inflammation and therapy monitoring of
glioma. Therefore, target-specific radiocontrast/contrast agents have been searched for
accurate diagnosis, imaging, and therapy monitoring of glioma. Specific PET agents
provide differentiation of tumor, necrosis, or inflammation. More specific glioma
imaging agents including novel specific Gd or SPIO comprising MRI contrast agents,
amino acid tracers like 18F-FET, and peptide tracers like αvβ3 integrin specific 68Ga-
RGD and radiolabeled, targeted drug delivery systems have been searched for accurate
and early diagnosis of all stages of glioma.
Keywords: Blood-brain barrier, Diagnosis, Enhanced-permeability and retention effect,
Glioma, Glioma targeting, Imaging, Multifunctional drug delivery systems, Nanocarriers,
Radiopharmaceuticals, Specific probes, Theranostics for glioma.
