***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVE : Magnetic resonance cholangiopancreatography ( MRCP ) is an accurate diagnostic test for detecting abnormalities of the pancreaticobiliary system . Because it is noninvasive , MRCP appears to be more tolerable than ERCP , although this has not been studied . The purpose of this study is to compare patient satisfaction after MRCP and ERCP performed sequentially . METHODS : We prospect ively recruited 34 patients undergoing ERCP , for whom an MRCP was able to be performed before ERCP .  Patient satisfaction was assessed by vali date d question naires using seven-point Likhert scales ( individual ratings and direct comparisons ) . The following dimensions were explored : anxiety , pain , discomfort , tolerability ( relative to expectations ) , willingness to repeat the procedure , and overall preference . χ2 and Student 's t tests ( paired and unpaired ) were performed , and 95 % CIs were provided . RESULTS : Two patients ( 5.9 % ) were unable to undergo MRCP because of claustrophobia . The remaining 32 completed both tests ( 94 % same day ) and all question naires . Average age was 56 ± 18 yr , and 66 % were women . In 23 patients , some degree of biliary obstruction was suspected ; nine patients had pancreatitis . Patients reported a lower degree of pain ( p < 0.001 ) and discomfort ( p = 0.047 ) with MRCP , but MRCP was more difficult than they expected ( p = 0.012 ) . Patients were marginally more willing to repeat MRCP ( ns , p = 0.09 ) . On direct comparisons , patients were more satisfied with MRCP  regarding anxiety ( p = 0.04 ) and pain ( p = 0.001 ) . Patients displayed a higher overall preference  for MRCP compared with ERCP ( p = 0.01 ) ; however , only 59 % clearly preferred MRCP over ERCP . The most common problem with MRCP  was claustrophobia or noise ( n = 15 ) , and the differences were more striking in the subgroup without this problem . The subgroup undergoing purely diagnostic ERCPs showed clear preferences for MRCP . CONCLUSIONS : In many respects , MRCP is well tolerated , and certain subgroups , especially those undergoing diagnostic ERCPs , prefer MRCP over ERCP . As an endoscopist , one needs to be aware of the limitations of MRCP and relay these to the patient , as it seems that patients find MRCP more difficult than anticipated , and a significant number still prefer ERCP over MRCP  . Patient satisfaction may be further improved by reducing noise and claustrophobia with selective premedication , earplugs , and the use of the new quieter fenestrated magnetic resonance imaging scanners OBJECTIVE In this investigation we compared the diagnostic performance of unenhanced helical CT , oral contrast-enhanced CT cholangiography , and MR cholangiography for the diagnosis of choledocholithiasis . SUBJECTS AND METHODS Fifty-one patients referred for endoscopic retro grade cholangiography of suspected biliary stones were studied with unenhanced helical CT , MR cholangiography , and helical CT performed after oral administration of a cholangiographic contrast agent ( iopodic acid ) . The studies were r and omized for interpretation . Two radiologists evaluated the images by consensus and determined the presence and location of stones . We used retro grade cholangiography findings as the st and ard of reference . Sensitivity and specificity ( with 95 % confidence intervals [ CIs ] ) of the three examinations were calculated and compared using the exact form of the McNemar test . RESULTS Bile duct stones were revealed with retro grade cholangiography in 26 patients ( 51 % ) . Sensitivity was 65 % ( 95 % CI , 44.4 - 82 % ) for unenhanced helical CT , 92 % ( 95 % CI , 73 - 99 % ) for CT cholangiography , and 96 % ( 95 % CI , 78 - 99 % ) for MR cholangiography . Specificity was 84 % ( 95 % CI , 63 - 95 % ) for unenhanced helical CT , 92 % ( 95 % CI , 73 - 99 % ) for CT cholangiography , and 100 % ( 95 % CI , 83 - 100 % ) for MR cholangiography . The sensitivity of CT cholangiography and MR cholangiography was significantly higher than that of unenhanced helical CT ( p<0.01 ) . Differences in specificity were not significant . CONCLUSION Our results indicate that oral contrast-enhanced CT cholangiography and MR cholangiography are significantly more sensitive than unenhanced helical CT for the detection of bile duct calculi BACKGROUND Traditionally , ERCP has been the only reliable method for imaging the biliary tree , but it is invasive and carries a risk of complications . Magnetic resonance cholangiopancreatography ( MRCP ) is a noninvasive method for imaging the biliary tree . The aim of this study was to prospect ively assess the accuracy of MRCP in a large number of patients . METHODS Consecutive patients referred to a teaching hospital for ERCP were eligible for study entry . MRCP was performed within 24 hours before ERCP . MRCP findings were compared with ERCP findings or , when the initial ERCP was unsuccessful , with results of repeat ERCP , percutaneous transhepatic cholangiography , or surgery . RESULTS One hundred forty-six patients underwent 149 ERCP/MRCP procedures , of which 129 were evaluable with successful MRCP and ERCP or an ERCP-equivalent study . Diagnoses included choledocholithiasis in 46 and biliary stricture in 12 patients . The sensitivity , specificity , positive , and negative predictive values for MRCP in the diagnosis of choledocholithiasis were 97.9 % , 89.0 % , 83.6 % , and 98.6 % , respectively . All 12 strictures were diagnosed by MRCP ( sensitivity 100 % , specificity 99.1 % ) . CONCLUSIONS MRCP is an accurate , noninvasive alternative to ERCP for imaging the biliary tree . Choledocholithiasis and biliary strictures can be reliably diagnosed or excluded by MRCP . MRCP should be used increasingly in patients with suspected biliary obstruction to select those who require a therapeutic procedure OBJECTIVE The purpose of this study was to correlate a new three-dimensional turbo spin-echo MR cholangiopancreatography technique with endoscopic cholangiopancreatography or percutaneous cholangiography to determine the efficacy of the new technique for visualizing and diagnosing diseases of the pancreatic and biliary ducts . It was hypothesized that the new technique would provide diagnostic images without prolonged breath holding or a surface coil as required by previous MR techniques . SUBJECTS AND METHODS We describe a respiratory-triggered , heavily T2-weighted , three-dimensional , multislab turbo spin-echo sequence for MR cholangiopancreatography .  Thirty patients with suspected biliary or pancreatic disease were r and omly selected from referrals for endoscopic retro grade cholangiopancreatography . All patients were imaged with the optimized MR technique prior to attempted endoscopic or percutaneous cholangiopancreatography . The MR images were evaluated without additional clinical or radiographic information by consensus opinion of two of the authors for visualization and caliber of the ducts . When the ducts were abnormal , the level and probable cause were categorized as follows : normal , periampullary stricture , localized duct stenosis , multifocal strictures , calculous disease , duct anomalies , and cystic disease . The images obtained by conventional percutaneous or endoscopic cholangiopancreatography were evaluated in the same manner with the exception that additional clinical and radiologic information was provided . The diagnostic categories determined by MR and direct cholangiopancreatography were compared . Patients were included in the analysis only if endoscopic or percutaneous opacification of the biliary or pancreatic ducts was successful . RESULTS Diagnostic MR images were obtained in 29 ( 97 % ) of 30 patients .  Endoscopic or percutaneous cholangiopancreatography  was successful in 21 of the 29 patients for the common bile duct and in 17 of the 29 patients for the pancreatic duct . The diagnosis for the common bile duct by the MR technique agreed with the diagnosis by endoscopic or percutaneous cholangiopancreatography  in 19 ( 90 % ) of 21 patients . For diagnosis of diseases of the pancreatic duct , there was agreement in 15 ( 88 % ) of 17 patients . CONCLUSION Respiratory-triggered , multislab , three-dimensional turbo spin-echo MR cholangiopancreatography is a noninvasive technique for visualization of the pancreatic and biliary ductal systems . It is capable of providing diagnostic information equivalent to invasive techniques in a large percentage of patients and should be the technique of choice when invasive techniques are incomplete , unsuccessful , or technically difficult Abstract . The aim of this study was to compare prospect ively a breath-hold projection magnetic resonance cholangiopancreatography ( MRCP ) technique with diagnostic endoscopic retro grade cholangiopancreatography ( ERCP ) .  Seventy-six patients with suspected strictures or choledocholithiasis were referred for MRCP and subsequent ERCP examination  , which were performed within 4 h of each other . The MRCP technique was performed using fat-suppressed rapid acquisition with relaxation enhancement ( RARE ) projection images obtained in st and ardised planes with additional targeted projections as required by the supervising radiologist . Two radiologists ( in consensus ) assessed the MRCP results prospect ively and independently for the presence of bile duct calculi , strictures , non-specific biliary dilatation and pancreatic duct dilatation , and recorded a single primary diagnosis . The ERCP was assessed prospect ively and independently by a single endoscopist and used as a gold st and ard for comparison with MRCP . Diagnostic agreement was assessed by the Kappa statistic . The MRCP technique failed in two patients and ERCP in five . In the remaining 69 referrals ERCP demonstrated normal findings in 23 cases , strictures in 19 cases , choledocholithiasis in 9 cases , non-specific biliary dilatation in 14 cases and chronic pancreatitis in 4 cases . The MRCP technique correctly demonstrated 22 of 23 normal cases , 19 strictures with one false positive ( sensitivity 100 % , specificity 98 % ) , all 9 cases of choledocholithiasis with two false positives ( sensitivity 100 % , specificity 97 % ) , 12 of 14 cases of non-specific biliary dilatation and only 1 of 4 cases of chronic pancreatitis . There was overall good agreement for diagnosis based on a kappa value of 0.88 . Breath-hold projection MRCP can provide non-invasively comparable diagnostic information to diagnostic ERCP for suspected choledocholithiasis and biliary strictures and may allow more selective use of therapeutic ERCP Background Magnetic resonance cholangiography ( MRC ) is a new technique for non-invasive imaging of the biliary tract . Aim To assess the results of MRC in patients with suspected bile duct stones as compared with those obtained with reference imaging methods . Patients / Methods 70 patients ( 34 men and 36 women , mean ( SD ) age 71 ( 15.5 ) years ; median 75 ) with suspected bile duct stones were included ( cholangitis , 33 ; pancreatitis , three ; suspected post-cholecystectomy choledocholithiasis , nine ; cholestasis , six ; stones suspected on ultrasound or computed tomography scan , 19 ) . MR cholangiograms with two dimensional turbo spin echo sequences were acquired . Endoscopic retro grade cholangiography with or without sphincterotomy ( n = 63 ) , endosonography ( n = 5 ) , or intraoperative cho- langiography ( n = 2 ) were the reference imaging techniques used for the study and were performed within 12 hours of MRC . Radiologists were blinded to the results of endoscopic retro grade cholangiography and previous investigations . Results 49 patients ( 70 % ) had bile duct stones on reference imaging ( common bile duct , 44 , six of which impacted in the papilla ; intrahepatic , four ; cystic duct stump , one ) . Stone size ranged from 1 to 20 mm ( mean 6.1 , median 5.5 ) . Twenty seven patients ( 55 % ) had bile duct stones smaller than 6 mm . MRC diagnostic accuracy for bile duct lithiasis was : sensitivity , 57.1 % ; specificity , 100 % ; positive predictive value , 100 % ; negative predictive value , 50 % . Conclusions Stones smaller than 6 mm are still often missed by MRC when st and ard equipment is used . The general introduction of new technical improvements is needed before this method can be considered reliable for the diagnosis of bile duct stones PURPOSE To evaluate the test performance of magnetic resonance ( MR ) cholangiography for help in diagnosing choledocholithiasis . MATERIAL S AND METHODS Fast spin-echo MR cholangiography was performed by using a torso multicoil array in 110 patients suspected of having bile duct obstruction . Axial and coronal images were review ed by two observers who were blinded to results of direct cholangiography and final diagnoses . The final diagnosis was established by using direct cholangiographic ( n = 103 ) 
    Output:
    
Conclusion MRCP is a comparable diagnostic investigation in comparison to ERCP for diagnosing biliary obstruction