Amide Proton Transfer Imaging In Predicting Glioma Grade And Ki-67 Expression

Background:gliomas are the most common malignant primary central nervous system tumors,which are classified into 4 grades based on histopathological type and biological behavior.The clinical treatment and prognosis of gliomas mainly depend greatly on tumor grade and proliferation.Accurate preoperative evaluation of tumor grade and proliferation has been a hot spot of research.Conventional magnetic resonance imaging(MRI)has significant limitations in grading diagnosis of gliomas and can not provide biological information of tumor.Amide proton transfer-weighted imaging(APT)is a novel molecular MRI imaging technique,based on chemical exchange saturation transfer(CEST)and the signal is mainly derived from mobile endogenous proteins and peptides in the tissue.Since it was first reported,APT imaging has shown great application prospects in the classification diagnosis,therapeutic evaluation and prediction of molecular genetics of gliomas,and has become a research hotspot in the field of imaging.Purpose:to evaluate the value of amide proton transfer imaging in grading diagnosis and prediction of proliferation in gliomas.Materials and methods:this prospective study was approved by the institutional review board of Guangdong General Hospital,Guangdong Academy of Medical Sciences.From June 2016 to April 2018,this study included 38 patients with pathologically confirmed gliomas(females:n=16;male:n=22),including 12 patients with low-grade glioma and 26 patients with high-grade glioma(grade ?:n=11;grade ?:n?15).All patients didn't have any treatment before MRI examination.Conventional MRI and amide proton transfer imaging were performed on the same 3.0T MRI scanner.Two experienced neuroradiologists independently evaluated APT imaging,and placed ROIs in the tumor solid part with the highest APT signal.The signal intensity of APT was defined as asymmetric magnetization transfer ratio(MTRasym)at 3.5ppm.Interobserver agreement of tumor core MTRasym(3.5ppm)value between the two readers was assessed by the interclass correlation coefficient(ICC).Independent sample t test or Chi-Squared Test were used to compare differences in age and gender between high-/low-grade gliomas.Independent sample t test or Mann-Whitney U test were used to compare difference in MTRasym(3.5ppm)value and Ki-67 labeling index between the high-and low-grade gliomas.Receiver operating characteristic curve(ROC)was used to evaluated the accuracy of the MTRasym(3.5ppm)for grading gliomas,and the area under the curve(AUC),specificity,sensitivity and cut-off value was calculated,respectively.The correlation between MTRasym(3.5ppm)value and Ki-67 labeling index was evaluated by Spearman correlation analysis.Results:Interobserver agreement of MTRasym(3.5ppm)value between the two readers was excellent,with an intraclass correlation coefficient of 0.975 and a regression equation of y=1.05x-0.085.There was no statistical significance in the age and gender composition between high-and low-grade gliomas(p=0.341,p=0.330).The MTRasym(3.5ppm)value in high-grade gliomas were significantly higher than that in low-grade gliomas(4.47± 1.29%versus 2.72±1.02%,p<0.001),and the AUC was 0.869,the sensitivity and specificity values were 57.7%and 100%,respectively,at the cut-off value of 4.35%.There were positive correlations between MTRasym(3.5ppm)value and Ki-67 labeling index(r=0.632,p<0.001).Conclusion:APT imaging can evaluate the histopathological grades of gliomas,and the MTRasym(3.5ppm)may serve as a imaging biomarker to evaluate proliferation.