The Application Of Mono-exponential Model,bi-exponential Model And Stretched-exponential Model DWI For Preoperative Grading Of Gliomas

Objective:To explore the diagnostic performance of mono-exponential model,bi-exponential model and stretched-exponential model DWI for preoperative grading of gliomas,and evaluate the correlation between perfusion parameters and cerebral blood flow（CBF）.Methods:34 patients with pathological confirmed glioma including 17 low-grade glioma patients and 17 high-grade glioma patients who were treated in our hospital from March 2017to July 2018,including 22 males and 12 females,aged 15 to 69 years.Before operation,the subjects were underwent coventionional MRI,three demensional arterial spin labeling（3DASL）and multi-b value DWI.By using the mono-exponential model of FUNCTION TOOL software the apparent diffusion coefficient（ADC）was calculated;using bi-exponential model the fast ADC（D^*）,fraction of perfusion（f）and slow ADC（D）were calculated,using the stretched-exponential model the distribute diffusion coefficient（DDC）and alpha（α）were calculated,the CBF was obtained by 3DASL software.Combined with T2-weighted imaging and T1-enhanced scanning,the largest level of the solid area of the tumor and the adjacent upper and lower levels were selected,and the average of the three was taken.All statistical analysis was performed by SAS 9.4 statistical software,P<0.05 was considered statistically significant.（1）The ADC,D,D^*,f,DDC andαvalues of the high and low grade glioma groups were analyzed by independent sample t test,P<0.05,the difference was statistically significant;（2）The ROC curves of ADC,D,D^*,f,DDC andαvalues in high and low grade glioma grades were analyzed.The diagnostic performance of each parameter was analyzed and the area under the curve（AUC）was calculated to obtain the diagnostic threshold,sensitivity and specificity.（3）Spearman correlation analysis was used between D^*and CBF values of all investigators.Results:The mean ADC,D,f,DDC,andɑvalues in high-grade glioma were lower than low-grade glioma(LGGS:1.22±0.14×10^-3mm²/s,0.89±0.12×10^-3mm²/s,0.46±0.10%,1.35±0.27×10^-33 mm²/s,0.92±0.04;HGGS:0.82±0.16×10^-3mm²/s,0.55±0.12×10^-3mm²/s,0.31±0.08%,0.84±0.22×10^-3mm²/s,0.80±0.05),and the D^*value was higher in high-grade glioma（LGGS:2.47±0.33×10^-33 mm²/s;HGGS:3.95±2.24×10^-33 mm²/s）,P<0.05;There was positive correlation between D^*and CBF of all the subjects（r=0.51,P<0.05）;The ROC curve analysis showed that when the threshold values ofαwas 0.88×10^-3mm²/s,the sensitivity and specificity were 93%and 94%,respectively.The AUC ofα,D,DDC and ADC values were0.9690,965,0.961,0.957 respectively.When the threshold values of D was 0.86×10^-3mm²/s,the sensitivitiey and specificity were 80%and 100%,respectively.When the threshold values of DDC was 1.10×10^-3mm²/s,the sensitivitiey and specificity were 87%and 94%,respectively.When the threshold values of ADC was 1.11×10^-3mm²/s,the sensitivitiey and specificity were 87%and 94%,respectively.The AUC of D^*and f values were 0.816 and0.878,respectively.When the threshold values of D^*was 2.77×10^-3mm²/s,the sensitivitiey and specificity were 93%and 65%,respectively.When the threshold values of f was 0.39,the sensitivitiey and specificity were 93%and 76%,respectively.Conclusion:Mono-exponential model,bi-exponential model and stretched-exponential model DWI can provide more diagnostic information of glioma before surgery,andɑ,D,DDC,ADC values are of high value in identifying high-and low-grade gliomas.The perfusion parameter D^*was positively correlated with CBF.