Purpose. Methods and Materials

Transcription

1 MR cholangiopancreatography: Comparison between 3D fast recovery fast spin echo and 2D single shot fast spin echo sequences in the evaluation of choledocholithiasis. Poster No.: C-1193 Congress: ECR 2012 Type: Scientific Exhibit Authors: C. X.-Y. Goh, C. H. Tan; Singapore/SG Keywords: Abdomen, Gastrointestinal tract, Biliary Tract / Gallbladder, MR, Imaging sequences, Statistics, Diagnostic procedure, Calcifications / Calculi DOI: /ecr2012/C-1193 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 17

2 Purpose Magnetic resonance cholangiopancreatography (MRCP) has similar accuracy when compared with diagnostic endoscopic retrograde cholangiopancreatography (ERCP) in the evaluation of biliary pathology (1-4) and in many centers is now the preferred initial mode of investigation. MRCP using 3D fast recovery fast spin echo (3D FRFSE) sequences has been shown to offer improved spatial resolution when compared with conventional 2D single shot fast spin echo (2D SSFSE) sequences (5,6). Additionally, the isotropic volumetric acquisition in 3D sequences allows for high quality multiplanar reconstruction and maximum intensity projections (MIP) (7). However, there are relatively few studies evaluating whether 3D FRFSE MRCP has improved diagnostic accuracy in the evaluation of pancreaticobiliary disease. In 2010, our department MRCP protocol was changed to include coronal respiratory triggered 3D FRFSE sequences instead of coronal 2D SSFSE sequences. In addition, axial 2D SSFSE and axial LAVA sequences were also obtained. The objective of this study was to determine if the improved spatial resolution of the 3D FRFSE sequence translated into improved diagnostic accuracy in the detection of choledocholithiasis. Methods and Materials Patient Population Patients at our institution who underwent MRCP followed by endoscopic retrograde cholangiopancreatography (ERCP) within 4 weeks from 2008 to 2010 were included in our study. Cases were identified by performing a search on our hospital's radiology information system for patients who had underwent MRCP, followed by ERCP. 196 cases were identified, out of which 7 were excluded due to either incomplete MRCP sequences or incomplete ERCP and 1 was excluded due to imaging artifacts on MRCP. In total MRCP studies of 106 consecutive patients (56 male, 50 female; age range, years; median age, 63.5 years) who underwent coronal 2D SSFSE imaging in and 82 consecutive patients (44 male, 38 female; age range, years; Page 2 of 17

3 median age, 68 years) who underwent coronal respiratory triggered 3D FRFSE in 2010 were retrospectively reviewed. The median time between MRCP and ERCP was 3.5 days (range 0-28 days) for the 2D SSFSE studies and 2 days (range 0-27 days) for the 3D FRFSE studies. Imaging Technique Images were acquired on 3 separate MRI machines. Two are GE Signa HDxt 1.5 T scanners while one is a Siemens Magneton Trio 3.0 T scanner. Table 1: Table 1: Summary of MRCP scan parameters References: C. X.-Y. Goh; Department of Diagnostic Radiology, Tan Tock Seng Hospital, Singapore, SINGAPORE A body coil was used for image acquisition. The 2D SSFSE sequences used a multibreath hold technique, while the 3D FRFSE sequences used free breathing with respiratory triggering. Image Evaluation The coronal images were reviewed independently by two radiologists who were blinded to the ERCP results. They determined if a stone was present in the intra-hepatic or common ducts. For cases where there was a discrepancy in findings between the two radiologists, the images were reviewed again and a consensus decision was made. The other sequences obtained in the MRCP studies were not considered for the purposes of this study. Page 3 of 17

4 Data Analysis Sensitivity, specificity, positive predictive value and negative predictive value of the 3D FRFSE and 2D SSFSE coronal sequences were calculated using ERCP findings as the reference standard. Images for this section: Table 1: Table 1: Summary of MRCP scan parameters Page 4 of 17

5 Results Results 53 out of 106 cases (50.0%) with 2D SSFSE MRCP and 58 out of 82 cases (68.9%) with 3D FRFSE MRCP had intra-ductal stones on ERCP. Table 2: Table 2: Results of 2D SSFSE MRCP vs 3D FRFSE MRCP References: C. X.-Y. Goh; Department of Diagnostic Radiology, Tan Tock Seng Hospital, Singapore, SINGAPORE The sensitivity and specificity of the coronal 2D SSFSE sequence in the detection of choledocholithiasis were 100% and 63.6% respectively (area under ROC curve 0.818, 95% CI ), while the sensitivity and specificity of the coronal 3D FRFSE sequence were 94.8% and 66.7% respectively (area under ROC curve 0.807, 95% CI ). There was no statistically significant difference between the two sequences (P = 0.44). Discussion Page 5 of 17

6 The 3D FRFSE sequence produced images with higher spatial resolution, with isotropic voxels allowing for high quality MIP and multiplanar reconstructions. Frontal MIP reconstructions resemble fluoroscopic images obtained during ERCP. Figure 1 illustrates a case of malignant biliary obstruction in one case imaged with 3D FRFSE MRCP. Fig. 1: Figure 1: A malignant common duct stricture (white arrow) as visualised on coronal 3D FRFSE MRCP, MIP reconstruction and ERCP. References: C. X.-Y. Goh; Department of Diagnostic Radiology, Tan Tock Seng Hospital, Singapore, SINGAPORE Figure 2 demonstrates sagittal reconstructions of 3D FRFSE and 2D SSFSE sequences. The 2D SSFSE sequence has lower spatial resolution in the slice selection direction, resulting in artifacts on the reconstruction. Page 6 of 17

7 Fig. 2: Figure 2: A - Sagittal reconstruction of 3D FRFSE MRCP showing a stone in a dilated common duct. B - Sagittal reconstruction of 2D SSFSE MRCP depicting the gallbladder. References: C. X.-Y. Goh; Department of Diagnostic Radiology, Tan Tock Seng Hospital, Singapore, SINGAPORE Figure 3 shows an impacted ampullary stone on coronal 2D SSFSE MRCP with frontal MIP reconstruction. MIP reconstructions in the plane of acquisition do not suffer from the same image degradation as reconstructions in other planes. Page 7 of 17

8 Fig. 3: Figure 3: An impacted ampullary stone (white arrow) depicted on coronal 2D SSFSE MRCP and MIP reconstruction. References: C. X.-Y. Goh; Department of Diagnostic Radiology, Tan Tock Seng Hospital, Singapore, SINGAPORE Despite the higher spatial resolution of the 3D FRFSE sequence, there was no improvement in diagnostic accuracy. This suggests that the resolution of the 2D SSFSE sequence is sufficient for diagnosis of choledocholithiasis and that other factors play a more important role in diagnostic inaccuracy. Of the 8 false positive and 3 false negative cases on coronal 3D FRFSE MRCP, 9 (81.8%) were present in the distal common duct (as confirmed on other MRCP sequences or ERCP). 17 out of 20 (85%) of the false positive cases on coronal 2D SSFSE MRCP were in the distal common duct. As described by other investigators, impacted stones in the distal duct can lead to diagnostic difficulty, as the stones are not completely surrounded by hyperintense bile (8). Figure 4 shows a signal void at the ampulla, with dilatation of the common bile duct, which both reviewers called a calculus. This was not seen during ERCP. Page 8 of 17

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10 Fig. 4: Figure 4: Signal void at the distal common duct (white arrow) with proximal biliary dilatation. References: C. X.-Y. Goh; Department of Diagnostic Radiology, Tan Tock Seng Hospital, Singapore, SINGAPORE In 1 false negative case a malignant stricture was identified (Figure 1), and the small stone was also not visible on retrograde cholangiography, but only discovered during dredging of the bile duct. In this case, small size of the stone, together with the concurrent biliary pathology, contributed to diagnostic difficulty. Limitations While ERCP was used as the reference standard in this study, it is an operator dependent procedure and may not reflect the true disease state. Also, in the interval between MRCP and ERCP, passage of stones may erroneously cause a false positive result. As a retrospective study examining MRCP cases that proceeded to ERCP, there is a selection bias towards cases which are clinically symptomatic or where MRCP and clinical findings are discordant. This may falsely lower the observed sensitivity and specificity. The 2D SSFSE and 3D FRFSE sequences were performed in different patient groups with different disease prevalence, which may also lead to bias. As only the coronal sequences were evaluated, this likely reduces diagnostic accuracy. Images for this section: Page 10 of 17

11 Table 2: Table 2: Results of 2D SSFSE MRCP vs 3D FRFSE MRCP Fig. 1: Figure 1: A malignant common duct stricture (white arrow) as visualised on coronal 3D FRFSE MRCP, MIP reconstruction and ERCP. Page 11 of 17

12 Fig. 2: Figure 2: A - Sagittal reconstruction of 3D FRFSE MRCP showing a stone in a dilated common duct. B - Sagittal reconstruction of 2D SSFSE MRCP depicting the gallbladder. Page 12 of 17

13 Fig. 3: Figure 3: An impacted ampullary stone (white arrow) depicted on coronal 2D SSFSE MRCP and MIP reconstruction. Page 13 of 17

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15 Fig. 4: Figure 4: Signal void at the distal common duct (white arrow) with proximal biliary dilatation. Page 15 of 17

16 Conclusion While the 3D FRFSE sequence provided images of higher spatial resolution compared to the 2D SSFSE sequence in MRCP, scan times were longer. Use of the 3D FRFSE sequence did not translate into improved diagnostic accuracy in the detection of choledocholithaisis. References (1) Hintze RE, Adler A, et al. Clinical significance of magnetic resonance cholangiopancreatography (MRCP) compared to endoscopic retrograde cholangiopancreatography (ERCP). Endoscopy 1997;29: (2) Taylor ACF, Little AF, et al. Prospective assessment of magnetic resonance cholangiopancreatography for noninvasive imaging of the biliary tree. Gastrointestinal Endoscopy 2002;55: (3) Varghese JC, Liddel RP, et al. The diagnostic accuracy of magnetic resonance cholangiopancreatography and ultrasound compared with direct cholangiography in the detection of choledocholithiasis. Clinical Radiology 1999;54: (4) Vitellas KM, Keogan MT, et al. MR cholangiopancreatography of bile and pancreatic duct abnormalities with emphasis on the single-shot fast spin-echo technique. RadioGraphics 2000;20, (5) Reinhold C, Bret PM. Current status of MR cholangiopancreatography. AJR 1996;166: (6) Sodickson A, Mortele KJ, et al. Three-dimensional fast-recovery fast spin-echo MRCP: Comparison with two-dimensional single-shot fast spin-echo techniques. Radiology 2006;238: (7) Soto JA, Barish MA, et al. MR cholangiopancreatography: findings on 3D fast spin-echo imaging. AJR 1995;165: (8) Becker CD, Grossholz M, et al. Choledocholithiasis and bile duct stenosis: Diagnostic accuracy of MR cholangiopancreatography. Radiology 1997;205: Personal Information Page 16 of 17

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