Diagnosis Value Of Diffusion Tensor Magnetic Resonance Imaging In The Cerebral Astrocytomas

Purpose To evaluate clinical significance of diffusion tensor imaging (DTI) in astrocytomas and to report characteristic DTI patterns that may be helpful in grading astrocytomas.Materials and Methods 28 patients of astrocytomas with pathologic confirmation underwent routine MRI, enhanced and diffusion tensor imaging examination. They are divided into two groups:12 patients of low-grade astrocytomas(LGA),16 patients of high-grade astrocytomas(HGA), including 7 patients of anaplastic astrocytoma(AA) and 9 patients of glioblastoma multiforme(GBM). The DTI maps were calculated as well as measurements of mean diffusivity (MD) and FA values of the region of interest, including the enhancement,necrosis,edema,outside edema and cerebral parenchyma of the normal side. A corresponding the MD,FA were obtained from both the regions of enhancement, necrosis, edema and corresponding normal brain of each group and that of between two groups. Fiber tractography was reconstructed that diaplay the encountered patterns of tumor-related alteration to cerebral white matter.Results We observed decreased FA value ofastrocytoma which displayed as hypointense signal in FA image, most of the lesions displayed isodensity or hyperintense signal, In the regions of interest, the MD FA values changed significantly by comparing with that of normal control of brain tissue. A significant difference also existed with the MD value in the region of enhancement between the two groups of astrocytoma (1.061±0.182,0.882±0.088×10-3 mm2/s, P<0.05), with which the FA value exested in the region of edema(0.535±0.079,0.418±0.105, P<0.05) and outside edema(0.563±0.027,0.493±0.072,P<0.05).No significant difference exited with MD FA values in the regions of necrosis between the two groups(P>0.05). Furthermore, Fiber tractography and FA map can gave a quick and intuitive overview of the displaced course of white matter tracts in three-dimensional space.Conclusion The values are helpful to diagnosis the grade of astrocytomas, which is the MD value in the region of enhancement, FA value in the regions of edema and outside edema.combined with conventional MRI, DTI may improve diagnostic accuracy of astrocytoma and provides a helpful technique of quantitative analysis for grading on MR images. Fiber tractography can display the detailed relationship between tumors and nearby white matter tract,thus it is useful for plan before surgery.