Application Study Of Combined DWI,3D-ASL And MRS In Children With Brain Tumors

Objective:To explore the value of magnetic resonance weighted imaging（DWI）,arterial spin labeling（ASL）and magnetic resonance spectroscopy（MRS）in the classification and Grading of brain tumors in children before surgery.Methods:A retrospective analysis was performed on 77 children with brain tumors confirmed by surgical pathology in Wuhan Children’s Hospital from November 2018 to December 2019.They were divided into low-grade tumor groups（17 cases of WHO levelⅠ,10 cases of grade II）)and high-grade tumor group（11 cases of WHO III,39 cases of grade IV）based on postoperative pathological results.According to the location of the tumor,it was divided into the posterior cranial fossa group（53 cases）,the cerebral hemisphere group（16 cases）,and the thalamus group（8 cases）.All the research subjects used 3.0T MRI scanner for conventional plain scan,DWI,ASL,MRS and enhanced scan before operation.All image data were transmitted to the GE AW4.6 workstation for post-processing analysis,and the apparent diffusion coefficient of the solid part of the tumor（ADC）value,cerebral blood flow（CBF）value,Cho/NAA,Cho/Cr,NAA/Cr value,and ADC value and CBF value of the contralateral normal brain parenchyma area,and then divide to get rADC value and rCBF value.The above parameters were compared with the pathological results of brain tumors,and SPSS23.0 and Medcacl19.0 were used for statistical analysis,and the differences were considered statistically significant at P<0.05.Results:1.The ADC value and rADC value of the low-grade tumor group were significantly higher than those of the high-grade tumor group（P<0.05）,and the pathological grade of brain tumor was significantly negatively correlated with the ADC value and rADC value.The highest（r=0.884,P<0.05）;2.The CBF value and rCBF value of the low-grade tumor group were significantly lower than those of the high-grade tumor group（P<0.05）,and the pathological grade of brain tumor was positively correlated with the CBF value and rCBF value.The highest correlation was with rCBF（r=0.621,P<0.05）;3.Cho/NAA and Cho/Cr in the low-grade tumor group were significantly lower than those in the high-grade tumor group（P<0.05）,while the low-grade tumor group.The NAA/Cr value was significantly higher than that in the high-grade tumor group（P<0.05）.The pathological grade of brain tumors was positively correlated with Cho/NAA and Cho/Cr,and negatively correlated with NAA/Cr values.The correlation is highest（r=0.719,P<0.05）;4.After ROC curve analysis,the area under the curve（AUC=0.974）of the ADC obtained by DWI is larger than rADC（AUC=0.947）（P<0.05）.When the ADC threshold value is 0.965×10^-9mm²/s,the sensitivity to distinguish low-grade and high-grade tumors is 92.6%,and the specificity is 92.0%;the area under the curve of rCBF obtained by 3D-ASL（AUC=0.946）is larger than CBF（AUC=0.883）（P<0.05）.When the threshold of rCBF is 0.99,the sensitivity of distinguishing low-level and high-level tumors is 98.0%,and the specificity is 85.2%;Obtained by MRS,the area under the Cho/NAA curve（AUC=0.884）is larger than Cho/Cr（AUC=0.721）and NAA/Cr（AUC=0.816）（P<0.05）.When the threshold of Cho/NAA is 2.70,it distinguishes between low-level and high-grade tumors had a sensitivity of86.0%and a specificity of 77.8%.When the three sequences were used in combination,the area under the ADC+rCBF+Cho/NAA curve was 0.993,and the sensitivity to distinguish high-grade and low-grade tumors was 96.3%,and the specificity was 96.0%.5.In posterior cranial fossa tumors,the ADC value and rADC value can distinguish pilocytic astrocytoma from medulloblastoma or pilocytic astrocytoma from AT/RT（P<0.05）,but cannot completely distinguish ependymoma from pilocytic astrocytoma.Pilocytic astrocytoma（P>0.05）;CBF value and rCBF value can distinguish pilocytic astrocytoma from ependymoma,medulloblastoma and AT/RT（P<0.05）.Conclusion:DWI,ASL,and MRS can better diagnose the preoperative grading of children’s brain tumors;DWI and ASL have certain value in the diagnosis of posterior fossa tumors in children;Combined DWI,ASL and MRS can increase the accuracy of tumors’grading before forebrain children’s surgery,the three techniques can be promoted as routine MRI examination methods for children with brain tumors before surgery.