Application Of Dynamic Susceptibility Contrast-enhanced MR Imaging And ASL Technique In The Pre-operation Evaluation Of Brain Tumors

【Objective】1,To evaluate the value of DSC in the pre-operation of brain tumors by studying the characteristics of dynamic susceptibility contrast-enhanced(DSC) MR imaging of different brain tumors with high-magnetic field(3.0 T) MR System.2,To explore the potential clinical application of ASL technique in the pre-operation of brain tumors by comparing an arterial spin labeling(ASL) technique with DSC MR imaging.【Materials and Methods】1,Clinical data41 cases of brain tumors were performed with MR perfusion weighted imaging (MR-PWI),including dynamic susceptibility contrast-enhanced(DSC) and flow-sensitive alternating inversion recovery(FAIR) MR imaging.All the cases were verified histologically,including 8 patients of high-grade gliomas,16 patients low-grade gliomas,7 patients metastases,and 10 patients of meningiomas.All 41 cases of patients underwent the MR examinations with one 3.0T superconducting magnetic resonance imaging device(Signa EXCITE HD GE,USA) for the following sequences:axial spin-echo T1-weighted,fast spin-echo T2-weighted, axial fluid-attenuated inversion recovery(FLAIR),flow-sensitive alternating inversion recovery(FAIR),dynamic susceptibility contrast-enhanced MR imaging and contrast-enhanced axial,sagittal,coronal spin-echo T1-weighted.2,Instruments and scanning sequences(1) 3.0T GE Signa Excite HD Superconducting MR scanner with 8-channel phased array head coil;(2) GE ADW4.3 workstation and GE Functool software for data analysis.All the patients underwent conventional axial MR spin-echo T1-weighted imaging(T1WI),fast spin-echo T2-weighted imaging(T2WI),fluid-attenuated inversion recovery(FLAIR),and contrast-enhanced axial,sagittal and coronal spin-echo T1WI.MR perfusion weighted imaging(PWI) including dynamic susceptibility contrast-enhanced MR imaging(DSC) and flow-sensitive alternating inversion recovery(FAIR).(3) DSC sequences:imaging sequence,GRE-EPI,TR/TE1500/minimum, matrix128×128,flip angle90°,FOV240×240,5mm thickness with 1.5mm gap,50 times with totally scan time 1min20sec.(4)FAIR sequences:imaging sequence,GRE-EPI,TR/TE/TI800/minimum/ 1400ms,matrix128×128,FOV240×240,5mm thickness with 1.5mm gap,32 phases with totally scan time 2min24sec.3,Data processing and analysis(1) Data processing:All the primitive data were sent to ADW4.3 workstation for post-processing.Relative cerebral blood volume(rCBV) map and relative cerebral blood flow(rCBF) map were automatically generated by using GE Functool software brain perfusion software for DSC;Only relative cerebral blood flow(rCBF) map was automaticalIy generated by using GE Functool software fair perfusion software for FAIR.(2) Slection of ROIs:Referring to conventional MR imaging,maximal rCBV and rCBF were obtained by identifying regions of maximal perfusion from color maps.Three different circular regions of interest were placed on the highest color levels of the solid region of tumoral lesion,one centimeter region and two centimeters region of peri-tumor respectively.The size of each region of interest was between 50-60mm~2.The rCBV and rCBF values were then normalized by dividing lesional rCBV and rCBF values to the values from the contralateral healthy white matter.And thus the maximal rCBV and rCBF ratios of the lesions were obtained for DSC.For FAIR,only the maximal rCBF ratios of ROIs were obtained.Signal intensity-time curves were automatically generated when ROIs were selected for DSC.4,Statistics analysisSPSS 13.0 software package was applied to statistical analysis in both parts of this study.All data were recorded as(mean±standard deviation).The statistically significant difference was set at P＜0.05.MR perfusion parameters obtained by DSC and ASL(the maximal rCBV and rCBF ratios) were compared with general linear model repeated measures.If P＜0.05, the best classification threshold was found by analyzing ROC curve,and then calculating its sensitivity,specificity and accuracy.Pearson correlation analysis was used between the maximal rCBV and rCBF ratios of the same tumor at the same region.Linear Regression analysis was performed to detect the correlation between the two maximal rCBF ratios obtained by DSC and ASL.【Results】1,DSC(1)Comparison of the solid region of brain tumors:Statistically significant differences(P＜0.05) existed in the mean maximal rCBV and rCBF ratios between low-grade gliomas and the other three groups of tumors,with higher perfusion parameters at the the other three groups.The mean maximal rCBV and rCBF ratios in the solid regions of high-grade gliomas,low-grade gliomas,metastases and meningiomas were 7.997±3.648,3.148±1.701,8.505±2.652,8.570±4.699 and 7.817±3.330,2.924±1.201,8.873±2.832,8.572±4.617 respectively.(2) Comparison of the one or two centimeters region of peri-tumor:Statistically significant differences(P＜0.05) existed in the mean maximal rCBV and rCBF ratios between high-grade gliomas and the other three groups of tumors in the one centimeter region of peri-tumor,with higher perfusion parameters at the high-grade gliomas;the difference was statistically significant(P＜0.05) between low-grade gliomas and metastases at the same region,with higher perfusion parameters at the low-grade gliomas.The mean maximal rCBV and rCBF ratios in the one centimeter region of peri-tumor of high-grade gliomas,low-grade gliomas,metastases and meningiomas were 2.662±1.340,0.992±0.292,0.586±0.123,0.920±0.516 and 2.754±1.272,0.961±0.330,0.602±0.143,0.762±0.298 respectively.The difference was not statistically significant(P＞0.05) among different tumors at the two centimeters region of peri-tumor.(3) Comparison of different regions at the same tumor:Statistically significant differences(P＜0.05) existed in the mean maximal rCBV and rCBF ratios between the solid region and the other two regions at the same tumor,with higher perfusion parameters at the solid region.The difference was statistically significant(P＜0.05) in the mean maximal rCBV and rCBF ratios between the one centimeter and two centimeters region of peri-tumor at high-grade gliomas and metastases.Perfusion parameters in the one centimeter region of peri-tumor were higher than at the two centimeters in high-grade gliomas;however,higher perfusion parameters appeared at the two centimeters region in metastases.(4) Analysis of ROC curve and Pearson correlation:The classification threshold for the values of the mean maximal rCBV and rCBF ratios between high-grade. gliomas and low-grade gliomas in the solid regions were 4.967,5.335 respectively, with the sensitivity,specificity and accuracy of 87.5%,87.5%,87.5%and 87.5%, 100%,95.8%respectively.The classification threshold for the values of the mean maximal rCBV and rCBF ratios between high-grade gliomas and metastases in the one centimeter region of peri-tumor were 1.235,1.176 respectively,with the sensitivity,specificity and accuracy of 87.5%,100%,93.3%.There were significant positive correlations between the maximal rCBV and rCBF ratios of the same tumor at the same region based on Pearson correlation.2,ASL(1) Comparison of the solid portion of brain tumors:Statistically significant differences(P＜0.05) existed in the mean maximal rCBF ratios between low-grade gliomas and the other three groups of tumors,with higher perfusion parameters at the other three groups.The mean maximal rCBF ratios at the solid regions of high-grade gliomas,low-grade gliomas,metastases and meningiomas were 2.268±0.680,1.301±0.249,2.318±0.590,2.272±0.774 respectively.(2) Comparison of the one or two centimeters region of peri-tumor:The difference was not statistically significant(P＞0.05) among different tumors at the one or two centimeters region of peri-tumor.(3) Comparison of different regions at the same tumor:Statistically significant differences(P＜0.05) existed in the mean maximal rCBF ratios between the solid region and the other two regions at the same tumor,with higher perfusion parameters at the solid region.The difference was not statistically significant(P＞0.05) between one centimeter and two centimeters region of peri-tumor.(4) ROC curve analysis:The classification threshold for the values of the mean maximal rCBF ratios between high-grade and low-grade gliomas in the solid region were 1.432,with the sensitivity,specificity and accuracy of 100%,87.5%,91.7% respectively.(5)Linear regression analysis:There were significant correlation between the two mean maximal rCBF ratios in the solid region obtained by DSC and ASL based on linear regression analysis,correlation coefficient R=0.907.【Conclusions】1,DSC can be an useful method to obtain hemodynamic information of brain tumors, which can reflecting tumor angiogenesis.There were significant positive correlations between the maximal rCBV and rCBF ratios of the same tumor at the same region based on Pearson correlation.Both the maximal rCBV and rCBF ratios can reflect tumor angiogenesis,and can be useful in the evaluation of the histopathological grade and the differentiation of brain tumors.2,With DSC,both the maximal rCBV and rCBF ratios can be used to distinguish high-grade gliomas from low-grade gliomas.Statistically significant differences existed in the mean maximal rCBV and rCBF ratios between high-grade and low-grade gliomas,with higher perfusion parameters at high-grade gliomas.The classification threshold for the values of the mean maximal rCBV and rCBF ratios in the solid region were 4.967,5.335 respectively,with the sensitivity,specificity and accuracy of 87.5%,87.5%,87.5%and 87.5%,100%,95.8%respectively.3,With DSC,statistically significant differences existed in the mean maximal rCBV and rCBF ratios between high-grade gliomas and metastases in the one centimeter region of peri-tumor,with higher perfusion parameters at high-grade gliomas.The classification threshold for the values of the mean maximal rCBV and rCBF ratios in the one centimeter region of peri-tumor were 1.235,1.176 respectively,with the sensitivity,specificity and accuracy of 87.5%,100%,93.3%.4,Both DSC and ASL can be used to evaluate tumor angiogenesis and obtained hemodynamic information of tumor and peri-tumor tissues.There were significant correlation between the two mean maximal rCBF ratios obtained by DSC and ASL based on linear regression analysis,with correlation coefficient R=0.907.Both DSC and ASL can be used to evaluate the histopathological grade of brain tumors.5,With ASL,The maximal rCBF ratios obtained by ASL can be used to distinguish high-grade gliomas from low-grade gliomas.Statistically significant differences existed in the mean maximal rCBF ratios between the two groups of tumors,with higher perfusion parameters at high-grade gliomas.The classification threshold for the values of the mean maximal rCBF ratios in the solid region were 1.432,with the sensitivity,specificity and accuracy of 100%,87.5%,91.7%respectively.6,ASL is a kind of MR perfusion imaging method to evaluate the hemodynamic information of brain tumors.It is simple and can be carried out without injection of contrast medium.ASL can be a suitable candidate as a conventional sequence for the pre-operation assessment of brain tumors.