Combining MRCP With High-resolution Diffusion-weighted Imaging For The Assessment Of The Acalculous Biliary Obstruction: A Preliminary Study

ObjectivesTo investigate the diagnostic value of combining MRCP with High-ResolutionDiffusion-weighted Imaging (HR-DWI) for the disease of acalculous extrahepaticbiliary obstruction.Materials and MethodsThis retrospectively study analyzed43cases with acalculous extrahepatic biliaryobstruction from August2013to February2014on1.5T MR.The MRCP, the routineMRI, STD-DWI (matrix128x128,FOV=44x44cm2,S group) HR-DWI (matrix196x96,FOV=31x15.5cm2, H group) b=600s/mm2were performed by all cases.Benign:Malignant=18:24,M:F=19:24, mean age:61.53±12.54years.The imagesresolution of both DWI sequences were calculated.Two radiologists (R1,R2) blindlyreviewed the image quality and mearsured theADCs of S and H on the biliaryobstructive point of each lesions (a) and the adjacent bile duct near the lesions (b)respectively.Respectively using the Cohens’Kappa test for image quality&ICC test fortheADCs were performed to verify the consistency of the two observers, If theconsistency is good,then,the data sets with lower SD was chosen as the statisticaldata.Using Chi-Square tests were used on the mark between S&H.On theADCs of a, bin S&H were measured by two Wilcoxon rank.Using ROC curve analysis of group H ona, b’sADCs to identify the diagnosis value of maligant biliary obstruction end.The imaging characteristics of MRCP on the end of biliary obstruction, with reference toBaron’s Standard,compute its diagnosis coincidence rate of benign and malignantlesions;Two readers commonly diagnosed43cases through GA: MRCP, GB: MRCP+T2WI, GC:MRCP+STD-DWI, GD:MRCP+HR-DWI. Using Chi-Square Tests on themark between four groups.TheAUCs,Accuracy, Sensitivity, Specificity,PPV and NPVfor the four groups of images in representation of the malignant lesions.ResultsThe S and H’s image resolution were3.4and1.6cm/pixel,respectively.The imagequality of S and H from two readers were (3.20±0.56vs.3.23±0.61),=0.867and(3.81±0.39vs.3.79±0.41),=0.927.The Pearson Chi-Square between S1and H1was15.878, p=0.000.TheADCs and its ICC test of the S,H by the two readers were shownin a format of Sa (R1,R2):Sb (R1,R2) vs. Ha (R1,R2): Hb (R1,R2) as following(1.81±0.51,2.02±0.46):(1.87±0.61,2.04±0.47) vs.(1.78±1.28,1.79±1.15):(1.78±1.33,1.78±1.19)×10-3mm2/s,respecially.The ICC values were0.996、0.998、0.970、0.943,respectively.The positive coincidence rate of benign lesions betweenMRCP and pathology was7/13,53.85%,The positive coincidence rate of maligantlesions between MRCP and pathology was19/30,63.33%.In STD-DWI,There were nosignificant differences on theADCs of a&b between benign and maligant lesions(Z=-1.330,-1.404; P=0.184,0.160). In HR-DWI,There were significant differences ontheADCs of a&b between benign and maligant lesions (Z=-2.327,-2.413; P=0.020,0.016).TheAUCs of the H1a&H1b were0.710&0.718for diagnosising the maligantlesions.The mean of Group A,B,C,D marks were2.49±0.51,2.47±0.67,2.47±0.67,2.42±0.82,respectively.All of p of Pearson Chi-Square were less than0.05between fourgroups’marks. The diagnosticAUCs, accuracy, sensitivity, specificity,PPV and NPV ofthe Group A, B, C, D were shown as following (0.681,0.811,0.854,0.944) vs.(67.44%,79.07%,83.72%,97.62%) vs.(64.00%,80.00%,84.00%,100%)vs.(72%,77.8%,83.3%,88.9%) vs.(76.19%,83.33%,87.50%,92.59%)vs.(59.09%,73.68%,78.95%,100%). ConclusionHR-DWI technique has higher resolution than STD-DWI.Furthermore,HR-DWItechnique has potential for improving the diagnostic efficiency of malignant lesions ofobstruction of bile duct.The ADCs of the HR-DWI will be helpful for diagnosis ofacalculous extrahepatic biliary obstruction.