Diffusion Tensor MR Imaging Of Cerebral Astrocytic Tumors

PURPOSE: To evaluate the usefulness of diffusion tensor imaging (DTI) in the diagnosis of cerebral astrocytic tumors. MATERIALS AND METHODS: 32 patients with pathologically confirmed cerebral astrocytic tumors underwent contrast-enhanced MR imaging and diffusion tensor imaging before surgery,including gradeⅠastrocytomas(n=5), gradeⅡ astrocytomas(n=10), gradeⅢ astrocytomas(n=9) and grade Ⅳ astrocytomas(n=8). In the abnormal group, solid components of tumor , necrotic tumor core, edematous brain and apparently normal white matter regions were determined on DTI compared with T2WI and contrast-enhanced T1WI. Apparent Diffusion Coefficient(ADC)values and Fractional anisotropy (FA) values were measured and compared in each tissue type and differentregions. In the normal group , ADC values and FA values were calculated in different cerebral parenchyma in 20 healthy volunteers. The data described with standard ±deviation. Differences in these values among the tissue types were assessed with one-way ANOVA standard analysis. RESULTS: In normal group, gray matter and white matter were low intensity signal on ADC maps. No significant differences in ADC values were found in the two types. All white matter were hyper intensity signal and all gray matter were low on FA maps. FA values in the two types were significantly different. In abnormal group, solid components of tumor , necrotic tumor core and edematous brain were hyper intensity signal on ADC maps , while low intensity signal on FA maps. ADC was highest in necrotic tumor core (1782.28±598.09)×10-6mm2/s,followed by edematous brain(1677.02±168.35)×10-6mm2/s,solid components of tumor(1198.60±327.02)×10-6mm2/s and normal white matter(733.45±59.21)×10-6mm2/s. FA was highest in the normal white matter(0.54±0.06),followed by solid components of tumor(0.21±0.07),edematous brain(0.14±0.04) and necrotic tumor core(0.13±0.03). ADC values and FA values were significantly different in all couples of four tissues(P<0.05) , except necrotic tumor core with edematous brain(P>0.05). The ADC values of edematous brain and of solid components of tumors in the malignant were different statistically to that in the benign, while FA values only of edematous brain in the malignant were different statistically to that in the benign. CONCLUSION: ADC values and FA values can be used to differentiate normal white matter, edematous brain, solid components of tumor and necrotic tumor core. ADC values and FA values may be predictive of astrocytic tumor classification. The FA maps could directly display the relationship between tumor and nearby white matter tracts. The technique has a prospect of drawing neurosurgical treatment program.