A Simple And Efficient Acquisition Strategy Of Hepatobiliary Phase In Gd-EOB-DTPA-enhanced MRI

At present,Gadoxetic acid disodium（GD-EOB-DTPA）-enhanced MRI is widely used in clinical application.Hepatobiliary phase（HBP）of Gd-EOB-DTPA-enhanced MRI can improve the detection rate of hepatic focal lesions and be used as an effective means to evaluate liver function,liver fibrosis and predict the progression of liver cirrhosis.Previously,obtaining adequate and appropriate HBP in clinical practice usually required an empirical 20-min delay time after intravenous injection,which resulted in decreased patient comfort and compliance,reduced MRI scanner throughput,and increased the probability of MRI artifacts,thus causing the risk of diagnostic pitfall.Due to the difference in liver function,the uptake and excretion of Gd-EOB-DTPA in different individuals is various greatly.How to determine the appropriate acquisition time of HBP for different individuals and end MRI scan as soon as possible while obtaining sufficient diagnostic information is a concern of radiologists and clinical investigators.Several studies have demonstrated that when detecting liver focal foci in patients with normal liver function,10-min delay time is sufficient and reasonable to obtain HBP,while the reasonable delay time for patients with mild cirrhosis is recommended to be 15 min.However,there are still different views on the reasonable HBP delay time for patients with moderate and severe liver cirrhosis.Most investigators deem that the delay time is longer than the conventional 20 min and extended to 30 min,which can improve liver enhancement so as to increase the comparison between lesions and liver and improve the detection of lesions.However,determining the delay time of HBP based on the degree of liver function impairment requires clear liver function in advance,which is not feasible.（2016）European Society of Gastrointestinal and Abdominal Radiology（ESGAR）consensus statement on liver MRI and clinical use of Gd-EOB-DTPA deems that adequate HBP can be obtained when hepatic bile duct opacification can be detected after injection of Gd-EOB-DTPA and the signal intensity（SI）of intrahepatic vessels is significantly lower than that of liver parenchyma.However,in order to obtain sufficient HBP the radiological technologist in the process of scanning often require continuous tracking and comparing the SI changes of hepatic bile duct,the liver parenchyma,blood vessels and other structures in the liver,which increase the workload of radiological technologists and the probability of misjudgment,meanwhile,judgment process will virtually increase the examination time for patients.Combining previous studies and our clinical experience,we assume that adequate HBP can be collected at a delay time of 5 min after the initial visualization of the common bile duct（CBD）,and verify our hypothesis with adequate HBP recommended by（2016）ESGAR expert consensus statement as a standard of reference,then compare which takes less time.A total of 130 patients with suspected or known liver disease,who were required to perform GD-EOB-DTPA-enhanced MRI,were prospectively enrolled in the Eighth Medical Center of PLA General Hospital,and the patients were divided into non-cirrhosis group（45）,Child-Pugh（C-P）A group（45）and C-P B/C group（40）according to the C-P grading of liver function.We obtained 8 HBP from 5 min to 40 min with an interval of 5 min after administration of injection.We selected5-min delay time after CBD opacification as HBP_proposedfor adequate HBP,and the delay time was Time_proposed.In addition,according to the definition of adequate HBP by expert consensus statement in（2016）ESGAR,we obtained HBP_ESGARand corresponding Time _ESGAR.We evaluated the enhancement characteristics of all liver foci on HBP_proposedand HBP_ESGARusing a 4-point scale,respectively.The differences in relative enhancement ratio（RER）of liver,contrast-to-noise ratio（CNR）and signal-to-noise ratio（SNR）of focal lesions between HB_PESGARand HBP_proposedwere analyzed using Paired t-test in three groups,respectively;the differences between Time_proposedand Time _ESGARwere also compared using Paired t-test in three groups,then,one-way ANOVA and Dunnett’s multiple comparison between groups were utilized to test the statistical significance of the difference;Kappa test was used to evaluate the consistency of enhancement characteristics of liver focal lesions between HBP_ESGARand HBP_proposed,and P<0.05 was considered as significant difference.Statistical results demonstrated that there were no significant differences in RER,CNR and SNR between HBP_ESGARand HBP_proposedin three groups（all P>0.05）,while the paired difference of Time _ESGARand Time_proposedin three groups was 1.33±3.75min,2.33±4.07min,4.88±4.00min,respectively（all P<0.05）,and the paired difference between Time _ESGARand Time_proposedwas significantly greater in patients with severe cirrhosis than that in non-cirrhosis group and C-P A group（P<0.05）.The enhancement characteristics of hepatic focal lesions were significantly consistent between HBP_ESGARand HBP_proposed（κ=0.74）.We verify that sufficient HBP could be obtained after 5min of CBD opacification.This acquisition strategy is simple and feasible,and saves more delay time than（2016）ESGAR recommended by expert consensus statement,especially in patients with moderate and severe cirrhosis.