Value Of High-resolution Enhanced MR Imaging For Diagnosis Of Benign And Malignant Bile Duct Disorders And For Preoperative Evaluation Of Hilar Cholangiocarcinoma

Part One Value of High-resolution Enhanced MR Imaging for Diagnosis of benign and Malignant Bile Duct DisordersObjectives:To recommend the optimal slice thickness of high-resolution MR imaging by comparing images of different slice thickness.The value of high-resolution MR imaging in the diagnosis of benign and malignant biliary disorders is discussed.Methods:Seventy-six patients with biliary disorders during October 2015 to August 2016 are included in this prospective study.All patients underwent high-resolution enhanced MR imaging on Philips 3.0 T MR scanner(Ingenia).In addition to the conventional scanning sequences,high-resolution MR images with three different slice thickness(1.0 mm 1.2 mm and 1.5 mm)were acquired during delay and hepatobiliary specific phases.Both the axial images and oblique coronal images were acquired.Oblique coronal images were obtained along the hepatic duct and left and right hepatic duct bifurcation.The display of bile ducts on the high-resolution images were analyzed.Two observers scored the high-resolution images with three different slice thickness(from 1 to 5 points,the higher score represents the better display of the bile ducts).The scores were statistically analyzed to get the optimal slice thickness.The images were divided into two sets:(a)the conventional image set;(b)the combined set with conventional image and high-resolution images(high-resolution images with the optimal slice thickness).Two observers independently analyzed two sets of images to give the judge of benign or malignant disease,respectively,and recorded the confidence value(from 1 to 5 points,the higher score represents the more confident).The diagnosis were confirmed by surgery or biopsy pathology,or confirmed by follow-up after effective clinical diagnosis and treatment.The accuracy of diagnosis by two observers was compared respectively.For the cases that were correctly diagnosed by both observers,the diagnostic confidence of the two observers was compared.The consistency test of diagnostic confidence value of two observers was carried out for the two sets of images.Results:There are significant differences among the scores of images with three different slice thickness(P<0.05).The scores of images with slice thickness of 1.2mm(4.12±0.80)and 1.5mm(4.05±0.82)are higher than that of 1.0mm(2.93±0.91),and the differences are statistically significant(P<0.0167).There is no significant difference between the scores of images with slice thickness of 1.2mm and 1.5mm(P=0.297),but the score of images with slice thickness of 1.2mm(4.12±0.80)is higher than that of 1.5mm(4.05±0.82).There is no statistical difference among the scores of common bile duct and common hepatic duct,cystic duct,left and right hepatic duct and their confluence(P>0.05).There are statistical differences in the scores of the left and right secondary bifurcation and the distal bile duct(P<0.05).The score of the left secondary bifurcation and the distal bile duct on the images with slice thickness of 1.2mm(3.32±0.57)is higher than that of 1.0mm(3.01 10.76)andl.5mm(3.04±0.77),and the difference is statistically significant(P<0.0167).The score of left secondary bifurcation and distal bile duct on the images with slice thickness of 1.5mm(3.04±0.77)is higher than that of 1.0mm(3.01 ±0.76),but the difference is not statistically significant(P=0.695).The score of the right secondary bifurcation and distal bile duct on the images with slice thickness of 1.2mm(3.24±0.73)is higher than that of 1.0mm(3.00±0.73)and 1.5mm(2.89±0.78),and the difference is statistically significant(P<0.0167).The score of the right secondary bifurcation and distal bile duct on the images with slice thickness of 1.0mm(3.00±0.73)is higher than that of 1.5mm(2.89±0.78),but the difference is not statistically significant(P=0.021).Thirty-seven benign diseases and 39 malignant diseases were included in the study.The diagnostic accuracy of the two observers through the combined image set[97.4%(Observer 1)and 96.1%(Observer 2)]is both higher than that of the conventional image set[96.1%(Observer 1)and 94.7%(Observer 2)],but there is no significant statistical difference(P>0.05).The diagnostic confidence scores of the two observers through the combined image set[4.82 1(observer)and 4.77(2)observer]are higher than that of the conventional image set[3.52 1(observer)and 3.86(2)observer],and there are significant statistical differences(p<0.05).The observers were in moderate agreement regarding the conventional image set,Kappa=0.457(P<0.05).The observers were in good agreement regarding the combined image set,Kappa=0.778(P<0.05).Conclusions:There are significant differences among the scores of images with three different slice thickness.The scores of the images with slice thickness of 1.2mm and 1.5mm are higher than that of 1.0mm.The score of the left and right secondary bifurcation and distal bile duct on the images with slice thickness of 1.2mm is higher than that of 1.5mm and 1.0mm.Therefore,the slice thickness of 1.2mm is the recommended slice thickness for high-resolution MR imaging.The diagnostic confidence of the observers could be improved significantly through high-resolution enhanced MR images.Part Two Hilar Cholangiocarcinoma:Value of High-resolution Enhanced MR Imaging for Preoperative EvaluationObjectives:To assess the accuracy of high-resolution enhanced MRI images in the preoperative evaluation of biliary and vascular invasion in hilar cholangiocarcinomas.Methods:This retrospective study included 36 patients with hilar cholangiocarcinoma who underwent enhanced HR-MRI with an effective section thickness of 1.2 mm at 3.0 T before surgery.Two types of hepatobiliary specific contrast agents were used:Gd-BOPTA or Gd-EOB-DTPA.Contrast enhanced axial high-resolution images with slice thickness of 1.2mm were acquired by using mDixon sequence:arterial phase(15-25s),portal phase(60-70 s),equilibrium phase(2min),delay phase(10 min),and hepatobiliary specific phase(90 min for Gd-BOPTA and 20min for Gd-EOB-DTPA).Oblique coronal high-resolution images with section thickness of 1.2mm were acquired during delay phase(3min)and hepatobiliary specific phase(90 min for Gd-BOPTA and 20min for Gd-EOB-DTPA)after contrast injection.Oblique coronal images were obtained along the hepatic duct and left and right hepatic duct bifurcation.The images were analyzed by two observers.(1)Bile duct system:According to the Bismuth-Corlette classification system of hilar cholangiocarcinoma,combined high-resolution enhanced images and MRCP images were compared with MRCP in evaluating the extent of biliary infiltration.At the same time,the involvement of different parts of the bile duct system was evaluated,and the bile duct system was divided into 6 sections for evaluation.(2)Vascular system:The vascular involvement was evaluated and analyzed according to the International Cholangiocarcinoma Group Staging System.The evaluation of portal vein system and hepatic artery system included 4 segments,and the involvement of vascular system was analyzed by 4-point scale method.To determine the suitable criterion for high-resolution MRI in predicting vessel invasion,Labeling 180 and 90 of circumferential contact of the tumor with the vessel were used to predict the invasion.The correlation between imaging findings and surgical and histopathological records was statistically analyzed.Results:The accuracy in detecting biliary neoplastic invasion was higher for combined high-resolution MRI images(97.2%)than MRCP images(86.1%).High-resolution MRI images increased the accuracy in delineation of the tumor biliary extent(p<0.05).The accuracy of Labeling 90(98.6%in portal venous system and 98.0%in hepatic arterial system)was higher than that of Labeling 180(96.5%in portal venous system and 94.6%in hepatic arterial system).However,there was no significant statistic difference between them(p>0.05).Interobserver agreement was high with respect to biliary tract,portal venous and hepatic arterial system involvement.Conclusions:Enhanced high-resolution MRI images showed excellent capability for assessing tumor extent and vascular invasion in hilar cholangiocarcinomas.More than 90° of circumferential contact of the tumor with the vessel on high-resolution MRI may be an appropriate criterion for predicting invasion.