A Research On Tumor Pathological Grading And Angiogenesis Of Astrocytic Tumor Evaluated By Susceptibility Weighted Imaging And Dynamic Contrast Enhanced Perfusion Imaging

Part I:Correlation between semi-quantitative evaluations of susceptibility-weighted imaging and pathological grading in patients with astocytic tumorObjective:To assess the clinical value of susceptibility-weighted imaging (SWI) for astrocytic tumor of histological grade and to find a simply and efficient semiquantitative indexes of SWI which can accurately reflect pathologic grade.Materials and Methods:98patients with astrocytic tumors confirmed by surgery and pathology were analyzed. Male,56and female42, The age range was8-79. According to the World Health Organization (WHO) classification of central nervous system tumors and grading criteria:8cases of pilocytic astrocytoma (grade Ⅰ),1case of Pleomorphic Xanthoastrocytoma (grade Ⅱ),23cases of astrocytoma (grade Ⅱ),22cases of anaplastic astrocytoma (grade Ⅲ) and44cases of glioblastoma (grade IV) were included. All cases underwent conventional, contrast MRI scan and SWI examination by using Siemens3.0T magnetic resonance imaging system before the operation. Magnitude image, phase image, susceptibility image and minimums intensity projection image were obtained by SWI on the post-processing workstation. Intratumor susceptibility hypo intensity area(ITSHIA) was observed and semiquantitative data were acquired in accordance with the different grading indexes as follows:ITSHIA biggest diameter (cm), ITSH1A frequency, ITSHIA biggest diameter score, ITSHIA frequency score, ITSHIA area ratio score, ITSHIA comprehensive score (The product of the frequency score and area ratio score), focal distribution punctiform ITSHIA around the tumor necrosis, beaded/line ITSHIA on the tumor edge or necrosis edge, ITSHIA morphology description. Semiquantitative ITSHIA data of astrocytic tumors with various grades were compared and their relationships with pathologic grade were analyzed. Area under the curve (AUC) was used to compare the effectiveness of different methods in distinguish the high grade tumors from the lows with recommended threshold and the corresponding sensitivity and specificity and to select the best index reflecting grading.Results:There exists an obvious difference in the semiquantitative data of ITSHIA among different levels of astrocytic tumor. The values of ITSHIA for malignant astrocytic tumors (Ⅲ,Ⅳ) were higher than that in low level, whereas values of ITSHIA exist a general overlapping between the pilocytic astrocytma and the high level astrocytic tumor."Focal distribution punctiform ITSHIA around the tumor necrosis"(rs=0.691) and "beaded/line ITSHIA on the tumor edge or necrosis edge"(rs=0.627) showed highest relevance with pathological grading among all the indexes of ITSHIA. The relevance between comprehensive score, obtained from the SWI with no contrast, and pathological grading was highest of all the other indexes obtained by SWI with no contrast, whereas was slightly lower than that of enhanced SWI indexes. According to the performance of various semiquantitative indexes which can be used to distinguish high level astrocytic tumor by ROC, comprehensive score(area under curve, AUC=0.926) was the highest, the cutoff point was3,the rate for sensitivity was80.3%,for specificity87.5%; the " beaded/line ITSHIA on the tumor edge or necrosis edge "(0.924) was the second, the cutoff point is l,the rate for sensitivity was84.8%,for specificity100%; and the "focal distribution point like ITSHIA around the tumor necrosis "(0.911) was also useful, the cutoff point was1, the rate for sensitivity was86.4%, for specificity95.8%.Conclusion:The semiquantitative indexes of SWI could reflect angiogenesis in astrocytic tumors, and the semiquantitative data was linear related with the histological grade markedly after excluding the cases of pilocytic astrocytoma. The indexes such as "comprehensive score", the " beaded/line ITSHIA on the tumor edge or necrosis edge", the "focal distribution punctiform ITSHIA around the tumor necrosis" of astrocytic tumors had a higher value for pathologic grading. Part II:Correlation between the semiquantitative evaluations of susceptibility-weighted imaging and perfusion imaging in patients with astrocytic tumorObjective:To evaluate the correlations between the indexes of SWI and those of PI in astrocytic tumors and to compare the clinic value in pathological grading before the operation.Materials and Methods:The study objects and image processing methods were similar to those in the first part. All patients were underwent conventional, contrast MR scan, SWI and PI scan by Siemens3.0T magnetic resonance imaging system. Pseudo color pictures of CBV were obtained by PI on the post-processing workstation. ROI placement was placed through application of hot spots analysis. Maximum relative rCBV values of solid part within the tumor (rrCBVintra max), surrounding area of tumor (rrCBVperi max) were calculated. Comparison of the rrCBVintra max and rrCBVperi max in astrocytic tumor of different grade were performed. The corresponding situation between hot spot of PI and ITSHIA were evaluated and correlation between SWI and PI were compared. To analyze SWI and PI in the diagnostic value of high level of astrocytic tumor with ROC curves analysis.Results:rrCBVmtramax (rs=0.662, P=0.000) of astrocytic tumors was related positively linearly with pathological grade. rrCBVperi max (rs=0.794, P=0.000) was also markedly related. The rrCBVintra max of pilocytic astrocytoma was higher than that of astrocytoma(Ⅱ), which was similar to that of grade Ⅲ, whereas rrCB Vperi max showed no differences compared with astrocytoma(Ⅱ) and markedly lower than the tumor of high grade. The semiquantitative data of ITSHIA had a typical positive correlation with rrCBVintra max and rrCBVperimsx respectively. The area including hot spot in PI was not to be able completely correspondent with ITSHIA. According to the performance of various PI indexes which could be used to distinguish high level astrocytic tumor by ROC, rrCBVintra max (area under curve, AUC=0.951) was the highest, the cutoff point is3.300, the rate for sensitivity was90.3%, for specificity91.7%; the rrCBVperi max was the second, the cutoff point was1.000, the rate for sensitivity was97.3%,for specificity83.3%. The rrCBVintra max showed some advantages over semiquantitative indexes of SWI in evaluating the pathological grade of astrocytic tumor.Conclusion:semiquantitative indexes of SWI were closely related to that of PI. Both PI and SWI may be used as sensitive indexes of evaluating pathological grade of astrocytic tumor. PI was correlated with grading closely than SWI. The incompletely correspondent between hot spot and ITSHIA may be due to an association with different machismos of PI and SWI.Part Ⅲ:Correlation between indexes of SWI、PI and MVD、 VEGF expression in astrocytic tumorObjective:To detect the expression of MVD and VEGF in astrocytic tumor and their correlation with the semiquantivative indictors of SWI and rrCBVintra max, rrCBVperi max of PI for further clarifying the mechanism and clinical application.Materials and Methods:The study objects and image processing methods were similar to those in the first and second part. Pathological sections were obtained after operation. Immunohistochemical assay was employed to detect the expression of VEGF and to make a MVD count. According to the degrees of VEGF expression, patients in our study were divided into two groups:VEGF expression degree including high expression and low expression. Correlation between MVD、VEGF and indexes of PI and SWI were analyzed.Results:The MVD count (rs=0.550, P=0.000) and VEGF expression (rs=0.456P=0.000) were positive correlated with pathologic grading of astrocytic tumor. rrCBVintra max and rrCBVperi max of PI、most semiquantitative indexes of SWI showed markedly correlation with MVD and VEGF, respectively. Correlation analysis suggested a close relationship among the expression of VEGF and "beaded/line ITSHIA on the tumor edge or necrosis edge", the "focal distribution punctiform ITSHIA around the tumor necrosis" of astrocytic tumors shown on SWI with contrast. The above indexes were found significantly different between the2groups of VEGF expression degree with high expression and low expression (P<0.01) except for other semiquantitative indexes of SWI (P>0.05).Conclusion:Both PI and SWI showed obviously correlation with angiogenesis and both are effective marker in evaluation angiogenesis preoperatively. High expression of VEGF was not only relevant to high perfusion area within or around the tumor, but also related to " beaded/line ITSHIA on the tumor edge or necrosis edge", the "focal distribution punctiform ITSHIA around the tumor necrosis".