Differentiating Nonenhancing Grade II Gliomas from Grade III Gliomas Using Diffusion Tensor Imaging and Dynamic Susceptibility Contrast MRI.

BACKGROUND: Contrast enhancement in a brain tumor on magnetic resonance imaging is typically indicative of a high-grade glioma. However, a significant proportion of nonenhancing gliomas can be either grade II or III. While gross total resection remains the primary goal, imaging biomarkers may guide management when surgery is not possible, especially for nonenhancing gliomas. The utility of diffusion tensor imaging and dynamic susceptibility contrast magnetic resonance imaging was evaluated in differentiating nonenhancing gliomas. METHODS: Retrospective analysis was performed on imaging data from 72 nonenhancing gliomas, including grade II (n = 49) and III (n = 23) gliomas. Diffusion tensor imaging and dynamic susceptibility contrast data were used to generate fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity as well as cerebral blood volume, cerebral blood flow, and mean transit time maps. Univariate and multivariate logistic regression and area under the curve analyses were used to measure sensitivity and specificity of imaging parameters. A subanalysis was performed to evaluate the utility of imaging parameters in differentiating between different histologic groups. RESULTS: Logistic regression analysis indicated that tumor volume and relative mean transit time could differentiate between grade II and III nonenhancing gliomas. At a cutoff value of 0.33, this combination provided an area under the curve of 0.71, 70.6% sensitivity, and 64.3% specificity. Logistic regression analyses demonstrated much higher sensitivity and specificity in the differentiation of astrocytomas from oligodendrogliomas or identification of grades within these histologic subtypes. CONCLUSIONS: Diffusion tensor imaging and dynamic susceptibility contrast imaging can aid in differentiation of nonenhancing grade II and III gliomas and between histologic subtypes.

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.