Gd-EOB-DTPA-Enhanced Magnetic Resonance Imaging T1 Mapping For Assessment Of Liver Function

Part 1 Animal research Section 1 Gd-EOB-DTPA-enhanced MRI T1 mapping for assessment of liver function in rabbit fibrosis modelObjective:To investigate the ability of T1 mapping of liver on gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid(Gd-EOB-DTPA)-enhanced magnetic resonance imaging for the estimation of liver function.Materials and Methods: This prospective study was performed after obtaining approval from the institutional animal review board.All experimental animals were purchased from the animal experimentation center of Guangxi Medical University(Nanning,China).Thirty-four healthy New Zealand rabbits(Weighing 2.5-3kg)were randomly enrolled into 2 groups: five in the control group,which was fed a standard diet of rabbit food and water;and 29 in the experimental group,which fed a standard diet and a 5% alcohol solution instead of water.Liver cirrhosis was induced using carbon tetrachloride(CCl4)(Sinopharm Chemical Reagent CO.,LTD,Shanghai,China)as described in previous studies.CCl4 was diluted daily at a concentration of 40% withcommercial olive oil.The treatment started at 0.5ml once a week for the initial 4weeks and 1ml once every 3 days till the 14 th week.ICG clearance rate tests were performed on all animals as described in the previous studies.Pulse-dye densitometry(DDG-330 K,Nihon Kohden,Tokyo,Japan)was used to measure the blood ICG concentration.A dose of 50 mg ICG dissolved in 10 ml distilled water(5mg/ml)was injected via an ear vein based on the body weight of the animal(0.5mg/kg).The blood ICG concentration was monitored at every pulse interval via an optical probe and the ICG retention rate at 15 min(ICG R15)was calculated automatically from the blood ICG concentration time course.All animal were fixed on a board with limbs tied down.Unenhanced and enhanced MRI scans(10m L Gd-EOB-DTPA at 0.25 mmol/m L,Germany Bayer Healthcare Co.)using a Siemens Verio 3.0 T MRI scanner with a 32-channel head phased-array coil.Images were obtained with HASTE,TSE T2 WI axial free breathing with fat suppression,EPI DWI axial with fat suppression,T1 WI VIBE axial fat suppression plain and enhanced scanning.Administration of Gd-EOB-DTPA was done as a bolus with a total 0.025mmol/kg and injection within 3s through the ear vein,followed by 2 ml saline chaser at the same rate.For all animals,T1 WI volumetric interpolated breath-hold examination(VIBE)with Syngo Map It was performed for T1 mapping on pre-enhanced,10 min HBP and 20 min HBP after Gd-EOB-DTPA injection.The parameters were as follows:repetition time(TR)4.8 ms,echo time(TE)1.4 ms,flip angle 5° and 15°,field of view(FOV)101 X 140 mm,Matrix 59X128 mm,2 mm section thickness,and parallel imaging technique(P=2)with generalized auto-calibrating partially parallel acquisition(GAPPA).All of the MRI data were transferred to a Siemens Syngo workstation tomeasure T1 relaxation times using operator-defined regions of interest(ROIs).The ROI with a 0.50 cm2(40-50 pixels)area was drawn manually on the liver superimposing T1 mapping images.Three ROIs were identified from the segment at the edge of the left liver without portal or hepatic veins,or imaging artifacts.In addition,the rr T1 rt between pre-enhanced and post-enhanced phase at each time point was calculated using the following equation: rr T1 rt ={(T1pre-T1 post)/T1pre} X 100,where T1 pre and T1 post were the T1 rt of the liver before and after Gd-EOB-DTPA administration.After MRI examination,all animals were sacrificed.The livers were removed quickly and fixed into phosphate-buffered 10% formalin.Haematoxylin-eosin(HE)staining was performed to observe the hepatic pathologic structure,and Masson staining was performed to evaluate liver fibrosis.Liver fibrosis was staged according to the Xi’an Meeting Scoring System.The classification of the degree of fibrosis was as follows: no fibrosis(F0);F1-portal fibrosis without septa;F2-portal fibrosis and few septa;F3-numerous septa without cirrhosis;F4-cirrhosis.The statistical analysis was performed using the SPSS 20.0 software package.Descriptive statistics(mean ± standard deviation)were provided when appropriate.The One-Way Anova least significant difference(LSD)analysis of variance was used to compare the differences in T1 rt and rr T1 rt.A linear regression analysis was used to analyze the correlation of ICG R15 with T1 rt and rr T1 rt.Any difference with a p value less than 0.05 were considered statistically significant.Results:A total of 34 animals were enrolled in this study.All of the rats in the control group(n = 5)and the experimental group(n =29),the experimental group was divided into three groups according to the degree of liver fibrosis,7for S1 group,7 for S2 group,8 for S3 group,and 7 for S4 group.A total of 80 experimental animals,the death rate of the animal as: 4/80 died before model establishment(mortality 5%),29/76 died during the model establishment(mortality 38.2%),8 died for pre-experiment consumed,5/39 died during the experiments(mortality 12.8%).T1rt showed a significant decrease after Gd-EOB-DTPA enhancement in all groups.At 10 min delay imaging,our data did not show a significant difference in T1 rt between F1 and F2(p>0.05),and did not show a significant difference in T1 rt between F3 and F4(p>0.05),T1 rt showed a significant difference among others groups(p<0.05).At 20 min delay imaging,our data did not show a significant difference in T1 rt between F1 and F2 either(p>0.05),T1 rt showed a significant difference among others groups(p<0.05)The T1 rt on 20 min HBP showed significant correlation with ICG R15(p<0.05).Pearson correlation coefficient= 0.607(p=0.001,t=-3.309).The distribution of residual columnar distribution is basically consistent with the normal distribution.The rr T1 rt on 20 min HBP showed significant inverse correlation with ICG R15(p<0.05).Pearson correlation coefficient= 0.739(p=0.000,t=-5.592).The distribution of residual columnar distribution is basically consistent with the normal distribution.Conclusion: 1.The Gd-EOB-DTPA enhancement curve of liver was different in different degree of liver fibrosis in rabbits.2.The T1 rt and rr T1 rt on20 min HBP showed significant correlation with ICG R15.3.a delay phase of 20 minutes T1 mapping after Gd-EOB-DTPA enhanced MRI can evaluated liver function effectively in rabbit hepatic fibrosis models.Section 2: Gd-EOB-DTPA-enhanced MRI T1 mapping for assessment of liver function in rabbit fibrosis model: comparison of hepatobiliary phase images obtained 10 min and 20 minObjective:To compare hepatobiliary phase(HBP)images obtained 10 minutes and 20 minutes after Gd-EOB-DTPA-enhanced MRI for assessment of liver function in rabbit fibrosis model on 3.0 T MR imaging.Materials and Methods:the same as Section 1The statistical analysis was performed using the SPSS 20.0 software package.Descriptive statistics(mean ± standard deviation)were provided when appropriate.The One-Way Anova least significant difference(LSD)analysis of variance was used to compare the differences in T1 rt and rr T1 rt.A linear regression analysis was used to analyze the correlation of ICG R15 with T1 rt and rr T1 rt.Any difference with a p value less than 0.05 were considered statistically significant.Results:Liver cirrhosis was induced by CCl4 and treatment of the experimental group was continued for 14 weeks.The initial experimental design was to divide all animals into 5 groups,F0-F4 fibrosis stages,and 5-7 animals for each group.Although the fibrosis stages of animals were related to time,but not strictly.The final animal quantity of liver fibrosis stage at different time intervals was presented in Table 1.All animal’s fibrosis stages were diagnosed based on pathological proofs(Fig1).We had expected that T1 rt and/or rr T1 rt would show differences in all fibrosis stages.However,our data did not show a significant difference in T1 rt between F1 and F2,and did not show a significant difference in T1 rt between F3 and F4(data not shown).Thus,we combined the stage of F1 and F2 into mild fibrosis group,and the stage of F3 and F4 into severe fibrosis group according to the difference in the fibrosis degree.Finally,all animals were separated into three groups: 5 in a control group;14 in a mild fibrosis group and 15 in a severe fibrosis group.T1rt showed a decrease in both 10 min HBP and 20 min HBP T1 mapping.The control group and the mild fibrosis group showed significant decreases and the severe fibrosis group showed a mild decrease.T1 rt on pre-enhancement imaging showed no significant difference(p>0.05)among all groups.T1 rt and rr T1 rt on both 10 min HBP and 20 min HBP showed significant difference(p<0.05)among all groups.The T1 rt between 10 min HBP and 20 min HBP showed no-significant difference(p>0.05)in three groups,the rr T1 rt between 10 min HBP and 20 min HBP showed no-significant difference(p>0.05)in three groups.T1rt on both of 10 min and 20 min HBP showed significant correlation with ICG R15(p<0.05);rr T1 rt on both 10 min HBP and 20 min HBP showed significant inverse correlation with ICG R15(p<0.05).Conclusions: Comparing 10 min HBP and 20 min HBP T1 mapping after Gd-EOB-DTPA enhancement,our results suggest that 10 min HBP T1 mapping is feasible for quantitatively assessing liver function.Part 2 Clinical research Section 1 Evaluating segmental liver function using T1 mapping on Gd-EOB-DTPA-enhanced MRI with a 3.0 TeslaObjective:To investigate the value of Gd-EOB-DTPA-enhanced MRI for evaluating liver function of each segment by using T1 mapping at 3 Tesla MRI.Materials and Methods:This study was designed as a prospective study that included 103 consecutively enrolled patients who underwentGd-EOB-DTPA-enhanced MRI examination,at The First Affiliated Hospital of Guangxi Medical University and Affiliated Hospital of Guilin Medical University,from October 2014 to December 2015.This study was approved by the ethics committees of the First Affiliated Hospital of Guangxi Medical University and the Affiliated Hospital of Guilin Medical University.All patients signed informed consents before the contrast agent was injected.The inclusion criteria consisted of the following:(1)patients with available clinical examination and biochemical tests that can be classified as a Child-Pugh score.(2)Absence of a liver resection surgery,radiofrequency ablation,chemotherapy or liver embolization procedure.(3)Absence of biliary obstruction or diffuse liver diseases caused by biliary tract disease.(4)The size of lesions was smaller than the segment which lesion existed.As a result,103 patients(82 men and 21 women,with a mean age of54.2±13.2 years)were included in the study.All patients were classified into one of 4 groups: a normal liver function(NLF)group(n=38),a liver cirrhosis with Child-Pugh A(LCA)group(n=33),a liver cirrhosis with Child-Pugh B(LCB)group(n=21),and a liver cirrhosis with Child-Pugh C(LCC)group(n=11).For the groups comprised of patients with focal liver lesions,the size of the lesions had no effect on the T1 relaxation time measurements.All patients underwent unenhanced and enhanced MRI scans(10 m L Gd-EOB-DTPA at 0.25 mmol/m L,Germany Bayer Healthcare Co.)using a Siemens Verio 3.0 T MRI scanner with a 12-channel body phased-array coil.Images were obtained with HASTE,TSE T2 WI axial free breathing with fat suppression,EPI DWI axial breath hold with fat suppression,T1 WI VIBE axial fat suppression plain and enhanced scanning.The Gd-EOB-DTPA wasadministered as a bolus,which was injected at a rate of 2 m L/s through the cubital vein;this was followed by a 20 m L saline chaser,which was administered at the same rate.For all patients,T1 WI VIBE with Syngo Map It included: repetition time(TR)3.9 ms,echo time(TE)1.4 ms,flip angle 5° and15°,field of view(FOV)273 X 380 mm,Matrix 161X320 mm,3 mm section thickness,and parallel imaging technique(P=2)with generalized auto-calibrating partially parallel acquisition(GAPPA),performed for T1 mapping on pre-enhanced,5,10 and 20 min delay phases after Gd-EOB-DTPA administration.All the obtained data were transferred to a Siemens Syngo workstation to measure T1 relaxation times using operator-defined regions of interest(ROIs).The ROI with a 2.15 cm2(140-180 pixels)area was drawn manually on the liver superimposing T1 mapping images.Three ROIs were identified from the segment at the edge of the liver to the central liver segments S2-S8,one ROI was identified on liver segment S1,without focal lesions,major branches of portal or hepatic veins,or imaging artifacts.In addition,the rate of T1 relaxation time between pre-enhanced and post-enhanced phase at each time point was calculated using the following equation: rr T1 rt = {(T1pre-T1 post)/T1pre} X 100,where T1 pre and T1 post were the T1 rt of the liver before and after Gd-EOB-DTPA administration.The statistical analysis was performed using the SPSS 20.0 software package.Descriptive statistics(mean ± standard deviation)were provided when appropriate.The One-Way Anova least significant difference(LSD)analysis of variance was used to compare the differences in T1 relaxation time of liver segment for each group with the same segment.Receiver operating characteristic(ROC)curves were used to determine the diagnostic performanceof T1 relaxation time and rr T1 of T1 relaxation time for liver function.Corresponding areas under the ROC curve,sensitivities and specificities were calculated with 95% confidence interval(CI),the best cut-off value was predicted by the Maximum Youden-Index: Sensitivity + Specificity-1.Any difference with a p value less than 0.05 was considered statistically significant.Results : The T1 relaxation times for each liver segment decreased gradually in the NLF and LCA groups from 5 min to 20 min after Gd-EOB-DTPA administration.The average T1 relaxation times at 20 min imaging delay ranged from 125.4 to 212.5 ms in the NLF group and from 138.4to 228.2 ms in the LCA group.The T1 relaxation times for each liver segment varied unpredictably in the LCB and LCC groups from one time point to the next(5 to 20 min after the Gd-EOB-DTPA enhancement).The average T1 relaxation times at 20 min imaging delay ranged from 152.3 to 363.1 ms in the LCB group and from 315.6 to 485.4 ms in the LCC group..The T1 relaxation times in different segments of liver were not significantly different between groups before enhancement.After 5 min of Gd-EOB-DTPA enhancement,the T1 relaxation times in some segments started to differ,particularly most segments in the LCC group started to show markedly different T1 relaxation times than the liver segments of the other groups(p<0.05).After 10 min of Gd-EOB-DTPA enhancement,more T1 relaxation times of liver segment became different among groups,some segments in the LCB group and all in the LCC group were significantly different from those in the NLF and LCA groups(p<0.05).Finally,after 20 min of Gd-EOB-DTPA enhancement,the T1 relaxation time of all liver segments in the LCC group were different from those in all the other groups,and more liver segments fromthe LCB and LCA groups different from the NLF group(p<0.05).The ROC curves of LCB and LCC groups were used to compare the diagnostic performance of T1 relaxation time and rr T1 of T1 relaxation time for assessment of liver segment function.The corresponding sensitivity,specificity and best cut-off value were calculated.For the LCB group,different liver segments showed different diagnostic performances.However,all liver segments consistently showed good diagnostic performance in the LCC group.Conclusions: 1.The T1 relaxation times for each liver segment decreased gradually in the NLF and LCA groups from 5 min to 20 min after Gd-EOB-DTPA administration.2.LCB patients,the two best segments for determining the diagnosis were S6 and S7.3.For LCB patients,segmental liver function evaluation is possible using Gd-EOB-DTPA-enhanced MRI T1 mapping,and calculation of the rr T1 of T1 relaxation time may be more efficient for evaluation of segmental liver function.4.For LCC patients,all liver segments can be used to evaluate liver function and both T1 relaxation time and the rr T1 of T1 relaxation time have good diagnostic performance.Section 2 Gd-EOB-DTPA-enhanced MRI T1 mapping for assessment of liver function in rabbit fibrosis model: comparison of hepatobiliary phase images obtained 10 min and 20 minObjective:To compare hepatobiliary phase(HBP)images obtained 10 minutes and 20 minutes after Gd-EOB-DTPA-enhanced MRI for assessment of liver function in rabbit fibrosis model on 3.0 T MR imaging.Materials and Methods:the same as Section 1The statistical analysis was performed using the SPSS 20.0 software package.Descriptive statistics(mean ± standard deviation)were provided whenappropriate.The One-Way Anova least significant difference(LSD)analysis of variance was used to compare the differences in T1 rt and rr T1 rt.A linear regression analysis was used to analyze the correlation of ICG R15 with T1 rt and rr T1 rt.Any difference with a p value less than 0.05 were considered statistically significant.Results:Liver cirrhosis was induced by CCl4 and treatment of the experimental group was continued for 14 weeks.The initial experimental design was to divide all animals into 5 groups,F0-F4 fibrosis stages,and 5-7 animals for each group.Although the fibrosis stages of animals were related to time,but not strictly.The final animal quantity of liver fibrosis stage at different time intervals was presented in Table 1.All animal’s fibrosis stages were diagnosed based on pathological proofs(Fig1).We had expected that T1 rt and/or rr T1 rt would show differences in all fibrosis stages.However,our data did not show a significant difference in T1 rt between F1 and F2,and did not show a significant difference in T1 rt between F3 and F4(data not shown).Thus,we combined the stage of F1 and F2 into mild fibrosis group,and the stage of F3 and F4 into severe fibrosis group according to the difference in the fibrosis degree.Finally,all animals were separated into three groups: 5 in a control group;14 in a mild fibrosis group and 15 in a severe fibrosis group.T1rt showed a decrease in both 10 min HBP and 20 min HBP T1 mapping.The control group and the mild fibrosis group showed significant decreases and the severe fibrosis group showed a mild decrease.T1 rt on pre-enhancement imaging showed no significant difference(p>0.05)among all groups.T1 rt and rr T1 rt on both 10 min HBP and 20 min HBP showed significant difference(p<0.05)among all groups.The T1 rt between 10 min HBP and 20 min HBP showed no-significant difference(p>0.05)in three groups,the rr T1 rt between 10 min HBP and 20 min HBP showed no-significant difference(p>0.05)in three groups.T1rt on both of 10 min and 20 min HBP showed significant correlation with ICG R15(p<0.05)(Table 5,Fig 3);rr T1 rt on both 10 min HBP and 20 min HBP showed significant inverse correlation with ICG R15(p<0.05).Conclusions: 1.Both T1 rt and rr T1 rt on pre-enhanced MRI are not available for assessing liver function in clinic.2.Comparing 10 min HBP and 20 min HBP T1 mapping after Gd-EOB-DTPA enhancement,our results suggest that 10 min HBP T1 mapping is feasible for quantitatively assessing liver function in clinic.