Contrast-enhanced MRI is the most common way for evaluating neuroepithelial tumor grading and monitoring for tumor recurrence,but the ability to predict tumor behavior remains very limited.In this study, the investigators will use multi-b-value diffusion-weighted imaging(DWI),three-dimensional arterial spin labeling(3D-ASL) and dynamic contrast-enhanced MRI imaging(DCE) to evaluate neuroepithelial tumor grading and monitor for tumor recurrence.

Glioma is classified into 4 grades, with worse prognosis for more advanced grades.Previous studies have suggested that different therapeutic strategies should be applied for gliomas at different grades,so glioma grading before the operation is therefore of important clinical significance for guiding the grade-dependent therapeutic strategy.

Combination temozolomide and radiation significantly prolongs survival compared with radiation alone and has become standard treatment for Patients with high-grade glioma. Response assessment in these patients is difficult as a result of the frequent occurrence of early imaging changes indistinguishable from tumor progression, termed pseudoprogression. The majority of patients remain clinically stable. It is often unclear whether current therapy should be maintained or second-line therapy initiated.

The ADC value can potentially reveal the differences in cellularity and nuclear atypia of gliomas1. Theoretically, high cellularity in advanced gliomas may impede free water diffusion and thus lead to a decreased ADC value.In several previous studies,recurrent tumors have shows significantly higher cellularity than those shown by pseudoprogression.Such high cellularity is associated with relative reductions in extracellular space when compared with low cellularity, resulting in decreased diffusivity of water molecules in the former circumstance when compared with the latter. DWI measures the degree of water diffusion within tissue Apparent diffusion coefficient (ADC) values quantify the mobility of water molecules at the cellular level, holding the potential to differentiate between necrosis, edema and recurrent tumor.

A potential mechanism of pseudoprogression is that radiation-induced vascular changes may lead to focal transient increase in gadolinium enhancement.Three-dimensional arterial spin labeling(3D-ASL) and dynamic contrast-enhanced (DCE) MRI imaging provides a noninvasive means for quantifying tumor vascular properties.

Inclusion Criteria:

• Among the patients with high-grade glioma (glioblastoma multiforme or anaplastic astrocytoma), who received concurrent chemoradiation (CCRT) with temozolomide, the patients show the measurable enhancing portion (1 cm in the long diameter according to the RANO criteria) in the immediate f/up MRI after CCRT.

Exclusion Criteria:

• Among the patients with high-grade glioma (glioblastoma multiforme or anaplastic astrocytoma), who received concurrent chemoradiation (CCRT) with temozolomide, the patients do not show the measurable enhancing portion (1 cm in the long diameter according to the RANO criteria) in the immediate f/up MRI after CCRT.

Patients with high-grade glioma (glioblastoma multiforme or anaplastic astrocytoma), who receive concurrent chemoradiation (CCRT) with temozolomide