Diffusion- and Perfusion-Weighted Magnetic Resonance Imaging Methods in Nonenhancing Gliomas.

Routine diagnostic magnetic resonance imaging (MRI) uses enhancement of the tumor tissue as a marker of malignancy in intracranial gliomas. However, several high-grade tumors do not exhibit enhancement, and, conversely, some low-grade gliomas do demonstrate enhancement. Hence conventional MRI has a limited role in accurate grading of gliomas. Advanced MRI methods that evaluate the tissue microstructure and tumor hemodynamics provide a better understanding of tumor biology and promise to provide more accurate grading. These advanced MRI methods include diffusion-weighted imaging, diffusion tensor imaging, diffusion kurtosis imaging, arterial spin labeling imaging, dynamic susceptibility contrast imaging, and dynamic contrast-enhanced imaging. This review focuses on the utility of these methods for better characterization and grading of nonenhancing gliomas, as it is more difficult to accurately devise an optimal treatment strategy for these tumors compared with enhancing gliomas.