Quantitative Evaluation Of Liver Fat Content In Obese Children By Magnetic Resonance Multi-echo Dixon Technique

Objective:To explore the value of proton density fat fraction（PDFF）,a quantitative parameter of magnetic resonance multiple echo Dixon technique,in the quantitative evaluation of liver fat content in obese children.Materials and Methods:From December 2019 to December 2020,73obese children were recruited in Hunan Children’s Hospital as experimental group,which were divided into obese group A（n=29）,obese group B（n=21）and obese group C（n=23）,and 27 children with normal body mass index were recruited as control group.Multiple-echo Dixon sequence scanning of the liver was performed to obtain the quantitative parameter proton density fat fraction（PDFF）,and abdominal ultrasound,morphological indicators,liver function,kidney function,blood lipid,blood glucose and insulin data of all children under test were collected at the same time.Eighteen patients in the experimental group underwent liver biopsy,which was divided into five grades.The correlation between the steatosis grade and the quantitative parameter PDFF was analyzed by Spearman’s grade.The one-way analysis of variance was used to compare the PDFF and obesity indicators among groups,and the differences between groups were compared.Receiver operating characteristic curve analyzed the PDFF parameters and calculated the best cutoff,sensitivity,specificity,and Area Under Curve（AUC）.Correlation analysis was performed on clinical obesity indicators and PDFF.Multivariate linear regression was used to analyze the independent factors of clinical obesity indicators on PDFF.Results:1.There was no significant difference in age and gender（P>0.05）but significant difference in BMI between the control group and the experimental group（P<0.05）.2.There were 18 cases of liver biopsy in the experimental group,including 1 case in F1 phase.There were 2 cases in F2 stage,9 cases in F3 stage and 6 cases in F4 stage.The steatosis grade has significant correlation with the quantitative parameter PDFF（r=0.816,P<0.05）.3.The mean values of whole,right and left liver PDFF in the control group,obesity group A,obesity group B and obesity group C were gradually increased,and there were statistical differences between the two groups（P<0.05）.4.ROC curve shows that the area under ROC curve（AUC）of whole liver PDFF in the identification control group and obesity group A,obesity group A and obesity group B,obesity group B and obesity group C are 0.710,0.831 and 0.826,respectively.The AUCs of the right liver PDFF for the identification control group and obesity group A,obesity group A and obesity group B,obesity group B,and obesity group C were0.691,0.842,and 0.851,respectively.The AUCs of the PDFF for the left liver in the identification control group and obesity group A,obesity group A and obesity group B,obesity group B,and obesity group C were0.709,0.811,and 0.787,respectively.5.In correlation analysis,PDFF of whole liver,right liver and left liver positively correlated with BMI,WC,ALT,AST,UA,TG,INS and HOMA-IR significantly,and negatively correlated with AST/ALT and HDL significantly,but not significantly correlated with GLU and LDL.6.Multivariate linear analysis showed that the equation composed of WC,ALT and HDL was optimal,wherein the whole liver PDFF formula was Y=15.60+0.92X₁+1.37X₂-40.8X₃,and R²=0.705;The PDFF formula for right liver was Y=10.19+1.22X₁+1.43X₂-48.6X₃,and R²=0.662;The PDFF formula for left liver is Y=27.67+0.63X₁+1.37X₂-37.60X₃,and R²=0.705（PDFF is the dependent variable Y,and WC,ALT and HDL are X₁,X₂and X₃,respectively）.Conclusion:Multi-echo Dixon technique can effectively quantify liver fat content and find abnormal changes in liver fat content in early obese children.Its quantitative parameter PDFF is closely related to the degree of liver steatosis and clinical obesity indicators,and it is a sensitive and reliable imaging index for evaluating liver fat content in obese children.