Objective     To assess the utility of diffusion-weighted magnetic resonance imaging (DWI) in monitoring glioma neovascularization using apparent relative diffusion coefficient (rADC) analysis in rat C6 glioma model. Methods          Thirty SD rats were intracranially injected with C6 glioma cells to establish a rat model orthotopic transplantation tumor. Routine T2WI and DWI were performed to longitudinally monitor tumor growth and obtain ADC values at days 4

8

12

16

20 and 24 after tumor cell transplantation. Path

ological and immunohistochemical examinations were used to evaluate microvessel density (MVD) and neovascularization pattern in tumor tissues resected at different time points. The correlation of rADC with MVD and neovascularization was analyzed.  Results      All SD rats successfully developed C6 gliomas. In T2WI

high signal intensity was detected in tumors. In DWI

greater restricted diffusion was found in tumor area compared to contralateral normal brain tissue. ADC values were increased along with tumor progression（F=27.9，P0.05）. Correlation analysis demonstrated a strong positive correlation between rADC and MVD (R

2

=0.515

P0.05）. Histopathological staining showed that C6 glioma neovascularization was mostly formed from sprout angiogenesis and intussusceptive microvascular growth. Moreover

both sprout angiogenesis and intussusceptive microvascular growth were positively correlated to rADC（R

2

=0.586 and 0.537，P0.05）. Conclusion      DWI parameter ADC is positively correlated with MVD

sprout angiogenesis and intussusceptive microvascular growth

indicating that DWI could be served as well-defined imaging-based biomarker for glioma neovascularization.