Quantitative Assessment Of Hepatic Function With Hepatocyte Fraction Based On Gd-EOB-DTPA-enhanced MRI

Objective:The purpose of this study is to assess quantification of the hepatocyte fraction(HeF)based on simple pharmacokinetics using Gd-EOB-DTPA evaluate liver function.This study evaluated the liver function of the subject in the Child-Pugh classification method which is still the most commonly applied method for evaluating liver function in clinical.Material&Methods A total of 129 patients(male 95 cases,female 34 cases,years of age 23-72 years,average age 50.26±10.61 years)with clinically-suspected cirrhosis underwent Gd-EOB-DTPA-enhanced MRI and T1-mapping MRI.The severity of liver cirrhosis was classified according to the Child Pugh Score and thus,38 patients with normal liver function regard as control group(38 cases,male 25 cases,female 13 cases,years of age 19-56 years,average age 47.66±10.30 years),liver cirrhosis group(91 cases,male 78 cases,female 17 cases,years of age 22-82 years,average age 51.32±6.87 years),91 patients were subdivided into Child-Pugh class A(n = 49 cases),B(n = 30 cases)and C(n = 12 cases),respectively.The patients were enrolled in our study according to the diagnosis of cirrhosis with chronic hepatitis was based on laboratory investigations,physical findings,laboratory investigations,imaging findings and histopathological findings.The patients with numerous focal liver lesions(FLLs)which may hinder liver parenchymal evaluation were excluded.All the patients were scanned with a 3T clinical scanner(Ahiveva TX,Philips,the Netherlands).Look-Locker sequence was performed pre and 15-20 minutes post-contrast administration with following imaging parameters:19 inversion delay time points from 78ms to 2200ms,TE/TR=2/7ms,FOV = 350x250mm,acquired matrix = 100x110,FA=7,single-slice,SENSE factor-2 and scan duration =20 sec with breath holding.T1 maps and subsequent hepatocyte fraction map were calculated.The Gd-EOB-DTPA Pharmacokinetics model from Look-Locker sequence was expressed by equation Hepatocyte Fraction=△R1Hepatobiliary/△R1Hepatobiliary+△RiBloodEES.Two radiologists who were blind to the Child-Pugh(CP)scores and endoscopy findings measured the data of patients,HeF value and T1 related relaxation time parameters were measured with a quantitative analysis software Hepatocyte Fraction(Philips,the Netherlands).The methods as follows:Firstly,outlining the spleen area according to the spleen contour;ROIs were placed on one region of the left lobe and three different regions of the right lobe of the liver parenchyma,respectively.FLLs and major branches of the hepatic vessels were carefully avoided.The mean values of the left lobe and the right lobe were calculated as the measurements of the liver.Thus,HeF value,T1 relaxation times of 20 minutes post-contrast administration(Tlpost value),as well as reduction rate of T1 relaxation time(rrTl value)were obtained.All statistical analysis were conducted by SPSS for Windows version 13.0 and Medcalc for Windows version 15.8.The interclass correction coefficient(ICCs)was calculated to derive the data variability for two different radiologists,a reproducibility was demonstrated when ICC>0.75.HeF,T1post and rrT1 values were represented by mean±standard deviation.The hepatocyte fraction values of Child-Pugh class A,B and C patients were compared statistically using the one-way ANOVA and Post Hot Comparisons(Duncan’s new multiple range test,Dunnett’s-test).Spearman test was used for the correlation between parameters and Child-Pugh liver function classification.Receiver operating characteristic(ROC)curve was used to evaluate the prediction ability of HeF,T1post and rrT1 values for liver function classification,and estimate the area under the ROC curve(AUC)and the optimal cut-off according to the Youden Index(sensitivity + specificity-1).The confidence interval of average values was set to 95%,p-value<0.05 was considered to indicate a significant difference in all statistical tests.Results A total of 91 cases of liver cirrhosis and 38 cases of normal liver function were evaluated by two different radiologists respectively.ICC between two radiologists of the HeF value was 0.998;ICC between two radiologists of the T1post value was 0.996;ICC between two radiologists of the rrT1 value was 0.994.The repeatability of HeF,T1post and rrT1 between two radiologists was good,the best is HeF.The average whole liver HeF,Tlpost and rrT1 value of normal liver group was(83.15±2.52)%,(243.95±29.26)ms and(71.32±3.53)%,respectively.The average whole liver HeF,T1post and rrT1 value of liver cirrhosis group was(67.07±17.89)%,(334.35±129.57)ms and(61.76±12.17)%,respectively.The mean values of HeF of Child-Pugh class A,B and C were(77.39±4.27)%,(65.73±9.44)%,(28.29±13.61)%,respectively;The mean values of Tlpost of Child-Pugh class A,B and C were(257.23±36.01)ms,(358.29±86.37)ms,(589,34±114.26)ms,respectively;The mean values of rrTl of Child-Pugh class A,B and C were(69.33±4.07)%,(58.86±8.73)%,(38.16±7.22)%,respectively.The Tlpost and rrT1 value were no significantly different between normal liver function group and cirrhosis group(P=0.331,P=0.096,respectively).The HeF,Tlpost and rrT1 were significantly different among groups classified according to Child-Pugh scores among A,B and C(One-way ANOVA,p value<0.0001),The HeF and rrT1 were decreased with deteriorated liver function,the Tlpost was increased with deteriorated liver function.Spearman correlation analysis results of HeF,Tlpost and rrT1 were positively correlated with Child-Pugh liver function classification,and the correlation coefficients were(r=-0.844;0.821 and-0.835 respectively,p value<0.0001).ROC curve analysis obtained the cut-off values of HeF,T1post and rrT1 between Child-Pugh different classifications of liver function,as well as the area under the ROC curve(AUC).The cut-off value of HeF between Child-Pugh class A and class B,class A and class C,class B and class C were 73.69%,58.94%and 40.88%,respectively;The cut-off value of T1post between Child-Pugh class A and class B,class A and class C,class B and class C were 289.48ms,375.18ms and 406.76ms,respectively;The cut-off value of HeF between Child-Pugh class A and class B,class A and class C,class B and class C were 65.13%,52.00%and 48.23%,respectively.The AUC of HeF between Child-Pugh class A and class B,class A and class C,class B and class C were 0.914,1.000 and 0.981,respectively.Conclusion The hepatocyte fraction could be considered as a promising method for the quantitative assessment of liver function.