Diagnostic Value Of Susceptibility-Weighted Imaging In Grading Diffusely Infiltrating Astrocytomas

Purpose To investigate the diagnostic value of susceptibility-weighted imaging in grading diffusely infiltrating astrocytomas.Materials and Methods 43 patients with diffusely infiltrating astrocytomas pathologically proven were enrolled in this study. All the patients were classified into 3 groups including 17 diffuse astrocytomas (WHOⅡ),14 anaplastic astrocytomas (WHOⅢ) and 12 glioblastoma multiforms (WHOⅣ), according to the 2007 WHO classification of tumors of the central nervous system. All the patients underwent MRI conventional sequences, including T1WI,T2WI,FLAIR, and SWI.35 of them received both contrast enhancement T1WI and SWI (CE-T1WI and CE-SWI). The small vessels and cerebral microbleeds of the tumors were counted, and the sectional area of non cerebral microbleeds were measured layer by layer on the images of all sequences. The ability of showing small vessels and blood products were analysed between SWI and conventional imaging techniques; the signal intensity, distribution of venous structures and bleeding incidence of the tumors were observed respectively on SWI; the number of small vessels and cerebral microbleeds, and the sectional area of non cerebral microbleeds were compared within the three group of astrocytomas.Results There were significant differences between SWI (SWI and CE-SWI) and conventional sequences in displaying small vessels and blood products (P<0.01), and no significant differences were found between SWI and CE-SWI (P>0.05). Low grade astrocytomas (WHOⅡ) displayed mainly as hyhersignal intensity, while high grade astrocytomas (WHOⅢ,Ⅳ) showed mainly equisignal or mild low signal intensity on SWI; venous structures inside low grade astrocytomas were sparse, while mainly abundant inside high grade astrocytomas; the incidence of hemorrhage in low grade astrocytomas was higher than which in high grade astrocytomas. The amount of vein in three grades were 3.77±1.11,11.86±1.22 and 20.00±1.32 respectively. The differences among three groups were all significant (P<0.01). The amount of cerebral microbleeds were 0.47±0.39,3.32±0.42 and 4.38±0.46 respectively. There were statistically significant differences between diffuse astrocytomas and anaplastic astrocytomas, diffuse astrocytomas and glioblastoma multiformes for cerebral microbleeds (P<0.01), but no significant differences between anaplastic astrocytomas and glioblastoma multiformes (P>0.05). The sectional area of non cerebral microbleeds were 0.78cm2,3.05cm2 and 4.23cm2 respectively. There were statistically significant differences between diffuse astrocytomas and anaplastic astrocytomas, diffuse astrocytomas and glioblastoma multiformes for non cerebral microbleeds (P<0.01), but no significant differences between anaplastic astrocytomas and glioblastoma multiformes (P>0.05).Conclusion SWI was more sensitive compare to conventional imaging techniques for showing small vessels and blood products in astrocytomas. The signal intensity, distribution of venous structures and bleeding incidence of the tumors were significant different between low grade and high grade astrocytomas. The amount of small vessels and cerebral microbleeds, and the sectional area of non cerebral microbleeds on SWI may help physician to facilitate the tumor grading in clinical practice.