Fractional Anisotropy Using Diffusion Tensor MRI In Patients With Astrocytoma

Objective: To quantify the characteristic of cerebral astrocytoma by using conventional MRI and Fractional anisotropy (FA) map. FA values were calculated in solid tumor region, tumor cystic region, peritumoral edema region and contralateral normal white matter in FA map. Comparison was made by analysis of the statistical difference of FA value among with these regions of astrocytoma, and between low-grade astrocytoma and high-grade astrocytoma. To evaluation the clinical value of Fractional anisotropy using diffusion tensor MRI in patients with astrocytoma.Methods and materials: Thirty-four patients with astrocytoma diagnosed (Twenty-six patients with low-grade astrocytoma and eight patients with high-grade astrocytoma) underwent conventional MRI and diffusion tensor MR imaging before therapy. Examinations were performed on a 3T clinical scanner (Signa 3T MR, GE) and a quadrature head coil. T1 weighted sequence, T2 weighted sequence and FLAIR sequence were first performed in every case, and then diffusion tensor imaging. To get post-contrast T1 weighted sequences after injecting contrast material. All data was transmited to the post-deal workstation. FA maps were generated by using functool software exploited by company GE. FA value was measured on the center slice image of the largest focus. Tumor, cystic, edema and normal white matter regions of brain were determined on T1 weighted image, T2 weighted image and contrast-enhanced T1 weighted image. Three regions of interest (ROI) were placed on each area of tumor, cystic, edema, and normal white matter. FA value was measured in each region of interest (ROI). And then statistical analysis was maked.Results:1.On FA map, tumor appeared isointense or hypointense, cystic and the edema appeared hypointense, normal white matter was shown as hyperintensity signal on FA map, but not clearly seen on conventional MR images. As for low-grade astrocytoma, tumor mostly displayed as hypointensity signal with clear margin on FA map. White matter surrounded tumor showed as hyperintensity signal. As for high-grade astrocytoma, tumor mostly demonstrated as hypointensity signal with unclear margin on FA map. There were no significantly difference of FA value between tumor and edema on FA map. FA was significantly different in tumor and edema from normal white matter in all cases. It means that FA map can distinguish tumor and edema from normal white matter, but cannot distinguish tumor from edema. Comparison was made between FA map and T2 weighted imaging. The range of astrocytoma on FA map was as equal as that on T2 weighted image in low-grade astrocytoma, was beyond that on T2 weighted image in high-grade astrocytoma.2. In low-grade astrocytoma, FA value was the highest in normal white matter (0.387±0.139), the lowest in tumor cystic (0.096±0.021) and the middle in solid tumor (0.137±0.055) and peritumoral edema (0.179±0.056).In high-grade astrocytoma, FA value in normal white matter is 0.379±0.063,that in tumor cystic, solid tumor and peritumoral edema are 0.151±0.040,0.075±0.028 and 0.168±0.073.3. Comparison was made among regions in low-grade astrocytoma. There have significant statistical difference compared with each other in solid tumor region, tumor cystic region, peritumoral edema region and normal white matter region. And the FA value of the three before region are all descended. In high-grade astrocytoma, there all have significant statistical difference of the FA value compared with each other, except for between solid tumor region and peritumoral edema region.4. No statistical difference of the FA value in solid tumor region, tumor cystic region and peritumoral edema region between high-grade astrocytoma and low-grade astrocytoma.Conclusion:1. As for low-grade astrocytoma, tumor mostly displayed as hypointensity signal with clear margin on FA map. White matter surrounded the tumor showed as hyperintensity signal. As for high-grade astrocytoma, tumor mostly demonstrated as hypointensity signal with unclear margin on FA map. It means that FA map can distinguish tumor and edema from normal white matter, but cannot distinguish tumor from edema. Comparison was made between FA map and T2 weighted image. The range of astrocytoma on FA map was as equal as that on T2 weighted image in low-grade astrocytoma, was beyond that on T2 weighted image in high-grade astrocytoma. FA map was helpful in definiting of the range of astrocytoma and differentiating between low-grade astrocytoma and high-grade astrocytoma.2. The FA value of solid tumor region, tumor cystic region and peritumoral edema region all descended in low-grade astrocytoma and high-grade astrocytoma. The different regions in low-grade astrocytoma can be differentiated through FA value, so FA value is help for definiting the range of low-grade astrocytoma. FA value can not differentiate solid tumor and peritumoral edema in high-grade astrocytoma, so FA value have no significance in definiting the range of high-grade astrocytoma.3. The FA value of solid tumor , tumor cystic and the peritumoral edema all can not be used to distinguish high-grade astrocytoma from low-grade astrocytoma. So FA value may not predict the degree of malignancy of astrocytoma.4.Randomized block design was first used in the study evaluating the clinical value of Fractional anisotropy using diffusion tensor MRI in patients with astrocytoma. This is a breakthrough in similarity domestic study.