Combined DWI,ASL And IVIM Study For Differentiation IDH1/2 Mutational Status In WHO Grade Ⅱ-Ⅲ Astrocytoma

Objective:To explore the diagnostic value of combined application of DWI,IVIM and ASL in the WHOⅡ-Ⅲgrade astrocytoma IDH1/2 mutation status,in order to improve the diagnostic accuracy,guide clinical treatment and determine the prognosis.Materials and methods:39 patients with World Health Organization grade II and III astrocytomas who underwent conventional MR imaging,DWI,IVIM and ASL were reviewed.Minimum ADC,relative minimum ADC,relative D,relative D*,relative f and relative CBF,were compared between IDH1/2-mutant and wild-type tumors using the Mann-Whitney U test.Spearman correlation test was used to assess the correlation between rD*and rCBF,as well as between rD and rADC.Diagnostic performance was calculated using receiver operating characteristic curve（ROC）analysis and logistic regression.For ROC analysis,optimal thresholds of the imaging parameters were determined by maximizing the Youden index（sum of the sensitivity and 1-specificity values）.Results:（1）Minimum ADC,relative minimum ADC and relative D were significantly higher in IDH1/2-mutated grade II and III astrocytomas than in IDH1/2 wild-type tumors（P<0.05）,while relative D*and relative CBF were lower than that of IDH1/2 wild type（P<0.05）.Compared with IDH1/2 wild-type astrocytoma,IDH1/2-mutated astrocytoma was more likely to occur in the frontal lobe（P<0.05）.（2）Area under curve（AUC）of ADC_min was 0.70.ADC_min with the cut-off value of≥1.21×10^-3 mm²/s could differentiate the mutational status with sensitivity,specificity of58.33%,86.67%.The AUC of rADC_min was 0.72,rADC_min with the cut-off value of 1.80could differentiate the mutational status with sensitivity,specificity of 58.33%,93.33%.The AUC of rD was 0.79,the threshold value<1.61 for rD in prediction of IDH1/2mutation provided sensitivity,specificity of 83.33%,73.33%.The AUC of rD*was 0.71,and the optimal threshold of rD*was 0.87.The sensitivity and specificity of identifying the IDH1/2 mutation status of WHOⅡ-Ⅲastrocytoma were 70.83%and 66.67%,respectively.The AUC of rCBF is 0.84,and the optimal threshold of rCBF is 1.16.The sensitivity and specificity of identifying the IDH1/2 mutation status of WHOⅡ-Ⅲastrocytoma were 95.83%and 73.33%,respectively.（3）The sensitivity and specificity of identifying the IDH1/2 mutation status of WHOⅡ-Ⅲastrocytoma by combing use of IVIM and DWI were 83.33%and 66.67%,respectively.The sensitivity and specificity of identifying the IDH1/2 mutation status of WHOⅡ-Ⅲastrocytoma by combing use of IVIM and ASL were 95.83%and 93.33%,respectively,as well as combing use of ASL and DWI.The sensitivity and specificity of identifying the IDH1/2 mutation status of WHOⅡ-Ⅲastrocytoma by combing use of IVIM,ASL and DWI were 95.83%and 93.33%,respectively.（4）The rD*was significantly associated with rADC_min（r=0.72,P<0.001）,whereas rCBF values showed no correlation with rD*（r=0.14,P=0.390）.Conclusion:（1）Conventional MR has limited diagnostic value in differentiation the status of IDH1/2 mutation in WHOII-III astrocytoma,while DWI,ASL and IVIM can be used for differential diagnosis of them.（2）In diagnosis of the WHOⅡ-Ⅲgrade astrocytoma IDH1/2 mutation status,rADC_min value and rCBF value have higher diagnostic efficiency.（3）ASL can be used as the basic sequence for the differential diagnosis of WHOⅡ-Ⅲgrade astrocytoma IDH1/2 mutation status,the combination of DWI or IVIM are helpful for the differential diagnosis of them.（4）The rD value of IVIM is similar to the rADC_minvalue,which can well reflect the degree of water molecule diffusion in tumor tissues.