The Value On Classification Of Gliomas By Multi-b Value Of DWI

Objective:To identify high-grade and low-grade gliomas using multiple-b values（b=1000s/mm²,4000s/mm²,6000s/mm²,8000s/mm²）diffusion-weightedimaging（DWI）and explore the optimal b value for differentiation.Materials and methods:This study collected 32 cases of gliomas confirmed by pathology after neurosurgery at General Hospital of Tianjin Medical University from May 2016 to December 2017.All lesions were single and supratentorial examined by MRI.There were 21 cases of high grade gliomas（WHOⅢ、Ⅵ）and 11 cases of low grade gliomas（WHOⅠ、Ⅱ）.All patients underwent multiple b-value DWI（b=1000s/mm²,4000s/mm²,6000 s/mm² and 8000s/mm²）examination,the apparent diffusion coefficient（ADC）maps with different b-values were calculated.The mean signal intensity（SI）and mean ADC value of solid portion were measured at b=1000s/mm²,b=4000s/mm²,b=6000s/mm² and b=8000s/mm².The SI and ADC value of the contralateral normal subcortical white matter were also measured.The mean SI and mean ADC values of tumor were corrected by contralateral normal white matter,respectively,and SI ratio（rSI）and the ADC ratio（rADC）were obtained.Images of high and low grade gliomas were analyzed.The rSI,mean ADC,and rADC values were compared between high and low grade gliomas at different b value DWI.The mean ADC values,rADC values and rSI values of high and low grade gliomas and the mean ADC value of normal white matter were compared among the four b values DWI.The relationship between grade of gliomas and mean ADC values was analyzed by Spearman rank correlation,and the ROC curve of the mean ADC value at the different b value was plotted to get optimal b value for differentiate the high and low grade gliomas.Results:At low b value DWI（b=1000s/mm²）,most high-grade gliomas showed high signal,while low-grade gliomas showed equal or slightly higher signal.when b value increased（b=4000s/mm²,6000s/mm²,8000s/mm²）,most high-grade gliomas showed high or equal signals,while low-grade gliomas showed low signal.The difference of signal composition of high-grade gliomas among the 4 b-values was significant（P<0.05）.The rSI of high-grade gliomas was higher than that of low-grade gliomas,and the mean ADC values and rADC values were lower than those of low-grade gliomas,and there were significant differences between the two indicators（P<0.001）.As the b value increased,the mean ADC value were decreased significantly among b values（b=1000s/mm²,4000s/mm²,6000s/mm²,8000s/mm²）regardless of HGG,LGG or normal white matter（P<0.001）.There was a significant negative correlation between the grade of glioma and the mean ADC value（r=-0.759、r=-0.823、r=-0.816、r=-0.802）,and the absolute value of r at low b value was lower than it at high b value,and the absolute value of r is the maximum at b=4000s/mm²（r=-0.823）.TheareaundertheROCcurveat b=1000s/mm²,b=4000s/mm²,b=6000s/mm²,and 8000s/mm² were 0.94,1.00,0.98,0.97,respectively.Whenthemean ADCvaluewas0.77×10^-3mm²/sat b=4000s/mm²,both of the sensitivity and specificity of the differentiation for high-grade and low-grade gliomas were 100%.Conclusions:As the tumor grade increases,its DWI signal intensity tends to increase,and ADC value tends to decrease.As the b-value increases,the difference of signal intensity between high-grade and low-grade gliomas increases,suggesting that high b-values are more sensitive to differentiation of glioma grades.The mean ADC value will decrease as the b-value increases regardless of high-grade or low-grade gliomas.The mean ADC value of high-b-value DWI is more valuable for the differentiation of gliomas grading,and the best results are obtained when b=4000s/mm².