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3D-MRCP for evaluation of intra- and extrahepatic bile ducts: comparison of different acquisition and reconstruction planes

3D-MRCP for evaluation of intra- and extrahepatic bile ducts: comparison of different acquisition... Background: Magnetic resonance cholangiopancreatography (MRCP) is an established technique for the evaluation of intra- and extrahepatic bile ducts in patients with known or suspected hepatobiliary disease. However, the ideal acquisition and reconstruction plane for optimal bile duct evaluation with 3D technique has not been evaluated. The purpose of our study was to compare different acquisition and reconstruction planes of 3D-MRCP for bile duct assessment. Methods: 34 patients (17f/17 m, mean age 41y) referred for MRCP were included in this prospective IRB-approved study. Respiratory-triggered 3D-T2w-MRCP sequences were acquired in coronal and axial plane. Coronal and axial MIP were reconstructed based on each dataset (resulting in two coronal and two axial MIP, respectively). Three readers in two sessions independently assessed the MIP, regarding visualization of bile ducts and image quality. Results were compared (Wilcoxon test). Intra- and interobserver variability were calculated (kappa-statistic). Results: In case of coronal data acquisition, visualization of bile duct segments was significantly better on coronal reconstructed MIP images as compared to axial reconstructed MIP (p < 0.05). Regarding visualization, coronal MIP of the coronal acquisition were equal to coronal MIP of the axial acquisition (p > 0.05). Image quality of coronal and axial datasets did not differ significantly. Intra- and interobserver agreement regarding bile duct visualization were moderate to excellent (κ-range 0.55-1.00 and 0.42-0.85, respectively). Conclusions: The results of our study suggest that for visualization and evaluation of intra- and extrahepatic bile duct segments reconstructed images in coronal orientation are preferable. The orientation of the primary dataset (coronal or axial) is negligible. Keywords: MRCP, MRC, Magnetic resonance cholangiopancreatography, Bile ducts, Common hepatic duct Background yield a luminal image of the bile ducts that is based on Magnetic resonance cholangiopancreatography (MRCP) is the inherent signal of slow-flowing or stationary bile. an established technique for the evaluation of intra- and Both, single shot projections and multislice techniques extrahepatic bile ducts in patients with known or suspected are available [5], with the latter being distinguished into hepatobiliary disease [1]. It is considered a reliable 2D [6] and 3D techniques [7]. Single shot projections non-invasive alternative to diagnostic endoscopic retrograde are preferred in individuals who are unable to hold their cholangiopancreatography (ERCP) [2,3]. Since the first breath, such as severely sick patients or small children description by Wallner and colleagues in 1991 [4], different [7]. 3D imaging techniques provide better image quality acquisition techniques have evolved. compared to 2D sequences [1,8,9], even though the Most current MRCP techniques are based on heavily combination of different MRCP sequences has proven to T2-weighted fast spin echo (FSE) pulse sequences, which be valuable in the assessment of bile duct anatomy and pathology [10]. 3D FSE sequences are usually acquired with the slab * Correspondence: ringe.kristina@mh-hannover.de in coronal orientation. Maximum intensity projections Department of Diagnostic and Interventional Radiology, Hannover Medical School, Carl-Neuberg Str. 1, Hannover 30625, Germany © 2014 Ringe et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Ringe et al. BMC Medical Imaging 2014, 14:16 Page 2 of 6 http://www.biomedcentral.com/1471-2342/14/16 Table 1 Imaging parameters of the respiratory-triggered (MIP) can then be obtained in any plane [7]. Previous fat-saturated 3D T2-weighted MR cholangiographic studies have addressed the matter of optimal slice thickness sequence for data acquisition [11] and different techniques regarding Parameter 1.5 T Magnetom Avanto respiratory triggering [12]. However, to the best of our knowledge, the ideal acquisition and reconstruction plane, Plane Coronal, Axial in practical terms meaning best suitable for optimal Respiratory triggering Navigator based bile duct visualization with 3D techniques, has not been Repetition time Breathing cycle evaluated. The purpose of this study was to compare Echo time (msec) 700-800 different acquisition and reconstruction planes of Refocusing pulse 140° T2-weighted 3D-MRCP acquisitions for assessment In-plane spatial resolution (mm) 1 × 1 of the intra- and extrahepatic bile ducts. Slab thickness (mm) 60-80 Methods Partitions per slab 60-80 Patients Type of k-space filling Sequential This HIPAA-compliant study was approved by the Partial Fourier factor Allowed institutional review board of Hannover Medical School. Estimated total acquisition time (min) Approximately 5 Written informed consent from each patient was obtained. 34 patients (17 female, 17 male, mean age 41.5 years, range 18-79 years) who were referred for liver MRI and dedicated at least eight years of experience in abdominal MR MRCP were included in this prospective study. Inclusion imaging. Readers were blinded to each patient’shistory criteria were as follows: completion of the entire MR examination; patient age equal or greater than 18 years. and other imaging findings. A single coronal and axial maximum intensity projection Indications for performing MRI were as follows: primary (MIP) covering the central, left, right and peripheral bile sclerosing cholangitis (n = 16), status post liver trans- plantation (n = 7), tumor (n = 6), suspicion of Caroli’s ducts was generated from each acquired MRCP dataset, resulting in two coronal and two axial MIP datasets, disease (n = 2), stone disease (n = 2) and recurrent respectively. Care was taken to exclude the renal pelvis, pancreatitis (n = 1). ureter of both kidneys and spinal canal to allow for blinded reading. Each reader performed two reading sessions MR imaging technique separated by an interval of two weeks, evaluating the MR examinations were performed on a 1.5 T system (Magnetom Avanto, Siemens, Erlangen, Germany) using reconstructed MIP in the following way: 1, Coronal reconstructed MIP of the coronal acquisition vs. cor- dedicated multichannel surface coils covering the onal reconstructed MIP of the axial acquisition; 2, abdomen. Prior to image acquisition, patients received 200 mL of anegativeoralcontrastagent (Lumirem®; Axial reconstructed MIP of the coronal acquisition vs. axial reconstructed MIP of the axial acquisition. After Guerbet, Sulzbach, Germany) for suppression of gastro- each reading session the readers were asked to choose enteric fluid signal, as well as 20 mg butylscopolamine (Buscopan®; Boehringer Ingelheim, Ingelheim, Germany; the preferred image dataset of any given comparison. The readers had no knowledge of initial MRCP dataset administered as a bolus over approximately 20 s) i.v. for orientation. spasmolysis. All patients underwent a clinical routine im- aging protocol of the liver, including a respiratory-triggered Depiction of bile duct segments was assessed by using the following four-point scale proposed by Papanikolaou 3D MR cholangiography in the coronal (dataset A) as well and colleagues [13]: 1, segment not seen; 2, segment as in the axial (dataset B) plane. MRCP-sequences were acquired prior to intravenous contrast injection. The faintly seen; 3, segment well seen but portion of the duct or the confluence not seen; and 4, excellent depiction specific MRCP sequences had sequential k-space fill- including the proximal and distal portions. This scale ing with partial Fourier filling allowed, resulting in acquisition of central k-space lines approximately was applied to the following sections (segments) of the biliary tract: the common bile duct (CBD), the right 3 minutes after the start of the sequence. MRCP se- anterior bile duct, the right posterior bile duct, the left quence parameters are provided in detail in Table 1. hepatic duct, and third-order biliary branches. Overall technical image quality was assessed using a four-point Image evaluation scale proposed by Lim and colleagues [14]: 1, poor quality Three readers (D.H., C.F., H.J.R.) independently performed image evaluation in terms of visibility of different bile duct with severe artifacts; 2, satisfactory quality with few rd artifacts; 3, good quality with minimal artifacts; and 4, segments up to the 3 order and assessment of technical excellent quality without artifacts. quality. All readers were board certified radiologists with Ringe et al. BMC Medical Imaging 2014, 14:16 Page 3 of 6 http://www.biomedcentral.com/1471-2342/14/16 Figure 1 Comparison of coronal MIP reconstructions of coronal and axial acquired datasets. 35-year old male patient with diagnosis of primary rd sclerosing cholangitis (PSC). Coronal MIP of a coronal (A) and axial (B) acquired MRCP dataset. Bile duct visualization up to the 3 order is equal on both datasets (see also Table 2), even though the image impression is more blurred on the MIP derived from the axial acquired dataset (B). In addition, a total score was defined as the sum of the MIP of the axial acquisition (dataset B) (p > 0.05) visibility and quality scores for each dataset to determine (Figure1;Table 2).Axial MIPofthe axialacquisition which of the two acquired MRCP datasets (coronal or (dataset B) were significantly better than axial MIP of axial) yielded the most diagnostic information. the coronal acquisition (dataset A) for visualization of third order biliary branches whereas lower order branches Statistical analysis did not show a difference (Figures 2 and 3). Statistical analysis was performed using GraphPad Prism Intraobserver agreement regarding bile duct visualization software (version 6; GraphPad Software, Inc., La Jolla, CA). was good to excellent (weighted Κ-range 0.63-1.0). Interob- Results regarding bile duct visualization and overall server agreement was moderate to good, regarding bile technical image quality were compared with a two-sided duct visualization in both datasets (coronary acquisition: Wilcoxon signed-rank test (with a p-value <0.05 deemed weighted Κ range 0.51-0.75; axial acquisition: weighted Κ significant) in the following way: 1, Coronal reconstructed range 0.42-0.67). MIP of the coronal acquisition vs. coronal reconstructed MIP of the axial acquisition; 2, Axial reconstructed MIP Technical image quality of the coronal acquisition vs. axial reconstructed MIP of Regarding overall technical image quality (including axial the axial acquisition; 3, Coronal vs. axial reconstructed and coronal reconstructed MIP of a given dataset), there MIP of the coronal acquired dataset; 4. Coronal vs. axial was no significant difference between the coronal and axial reconstructed MIP of the axial acquired dataset. acquired dataset (p > 0.05). At detailed dataset analysis Intra- and interobserver agreement was assessed by means however, in case of coronal data acquisition (dataset A) of a kappa-statistic and classified as follows: a Κ value of technical image quality of the coronal MIP was significantly less than 0.20 indicated poor agreement; Κ values of better as compared to the axial reconstructed MIP 0.21-0.40, fair agreement; Κ values of 0.41-0.60, moderate (p < 0.05). In case of axial data acquisition (dataset B), agreement; Κ values of 0.61-0.80, good agreement; and Κ there was no significant difference regarding technical values of 0.80-1.00, excellent agreement [14]. image quality of the reconstructed MIP (p > 0.05). Table 2 P-values for each reader and biliary segment: Results comparison of coronal reconstructed MIP of coronal and Bile duct visualization axial acquired datasets regarding bile duct visualization In case of coronal data acquisition (dataset A), visualization nd Reader No. CBD Right Right Left hepatic 2 and of bile duct segments was significantly better on coronal rd (Session No.) posterior anterior duct 3 order reconstructed MIP as compared to axial reconstructed bile duct bile duct branches MIP (p < 0.05). This was true for visualization of the CBD, 1 (1) 0.424 0.923 0.499 0.685 0.305 right anterior hepatic duct, left hepatic duct and third 1 (2) 0.766 0.309 0.236 0.783 0.790 order biliary branches. In case of axial data acquisition 2 (1) 1.000 1.000 0.536 0.358 0.145 (dataset B), a significant better visualization of the CBD 2 (2) 1.000 0.609 0.400 0.891 0.393 and left hepatic duct on coronal reconstructed MIP as compared to axial reconstructed MIP was observed only 3 (1) 0.174 0.943 0.305 0.266 0.627 by one reader. 3 (2) 0.345 0.898 0.143 0.627 0.608 Regarding bile duct visualization, coronal MIP of the P values were calculated with the two-sided Wilcoxon Test to compare coronal acquisition (dataset A) were equal to coronal depiction scores of coronal axial acquired datasets. Ringe et al. BMC Medical Imaging 2014, 14:16 Page 4 of 6 http://www.biomedcentral.com/1471-2342/14/16 Figure 2 Comparison of axial MIP reconstructions of coronal and axial acquired datasets. 79-year old male patient status post radiofrequency st nd ablation of a colorectal liver metastasis. Axial MIP of a coronal (A) and axial (B) acquired MRCP dataset. Bile duct visualization of 1 and 2 order branches rd is equal on both datasets, whereas 3 order branches are depicted significantly better on the axial dataset. Intraobserver agreement regarding technical image are seen better on a left posterior images obtained at a quality was moderate to excellent (weighted Κ range steeper angle [15]. Especially in children with segmental 0.55-0.96); interobserver agreement was moderate (weighted liver transplants sagittal oblique planes are preferred due Κ range 0.42-0.59). to the more anteroposterior orientation of the neo-porta hepatis [16]. In a first approach towards projection Choice of preferred image dataset cholangiography by means of MRI in 1991, Wallner and When reading coronal reconstructed MIP, the readers colleagues used a heavily T2-weighted gradient echo preferred coronal acquisitions over axial acquisitions in sequence for assessment of bile duct dilatation [4]. They 66% of the readings. Regarding axial MIP reconstruction, concluded that imaging in the coronal plane provided a axial acquisitions were preferred over coronal acquisitions good view of the biliary system, whereas no additional in 80% of the readings. information was found by imaging in the sagittal plane. Intraobserver agreement regarding choice of the In this study we compared different acquisition and re- preferred image dataset was excellent (weighted Κ construction planes of T2-weighted 3D-MRCP acquisitions range 0.94-1.00); interobserver agreement was moderate for assessment of the intra- and extrahepatic bile ducts. In to excellent (weighted Κ range 0.57-0.85). contrast to single shot techniques, 3D MRCP has the advantage to facilitate secondary reconstructions. Coronal reconstructions were preferred, regardless of the initial Discussion acquisition plane. These findings were supported by good To the best of our knowledge the ideal acquisition and intra- and interobserver agreement. One of the reasons reconstruction plane for optimal bile duct evaluation for coronal image preference might be the fact that these with 3D techniques has not yet been evaluated. For images are similar to image impressions of ERCP and single shot FSE techniques it has been suggested that conventional cholangiograms. straight coronal and initial left posterior oblique images There are other studies that evaluated secondary clearly depict the common hepatic duct and the left reconstruction techniques for MRCP. Schaible and hepatic duct, whereas the CBD and right hepatic ducts Figure 3 Comparison of axial MIP reconstructions of coronal and axial acquired datasets. 18-year old male patient with jaundice and rd suspicion of cholelithiasis. Axial MIP of a coronal (A) and axial (B) acquired MRCP dataset. Bile duct visualization up to the 3 order is equal on both datasets, even though the image impression is more blurred on the MIP derived from the coronal acquired dataset (A). Ringe et al. BMC Medical Imaging 2014, 14:16 Page 5 of 6 http://www.biomedcentral.com/1471-2342/14/16 colleagues evaluated selective MIP reconstructions of evaluation of the bile ducts coronal reconstructions are respiratory-triggered 3D MRCP versus standard MIP preferred. In this context, the orientation of the primary reconstructions and single-shot MRCP [17]. Single-shot dataset (coronal or axial) is negligible. and standard MIP reconstructions of 3D MRCP were Competing interests comparable in terms of anatomical bile duct visualization, The authors declare that they have no competing interests. whereas selective MIP postprocessing proved useful for Authors’ contributions detection of pathological alterations. In a retrospective KIR and DH conceived and designed the experiments, KIR, DH and CF study, Morita and colleagues compared volume rendering performed the experiments and acquisition of data. KIR, DH, CF, FW and HJR (VR) and MIP of 3D TSE MRCP sequences to define analyzed and interpreted the data. FW and HJR contributed materials and analysis tools. All authors participated in drafting and revising the biliary anatomy mostly in patients without major biliary manuscript. All authors read and approved the final manuscript. tract anomaly [18]. Definition of biliary anatomy was found to be more accurate using VR reformation than Received: 27 January 2014 Accepted: 14 May 2014 Published: 19 May 2014 MIP. However, the assessment of VR images was not thepurpose of thepresent study. Onedisadvantageof References VR reconstructions is that the detection degree of 1. Sodickson A, Mortele KJ, Barish MA, Zou KH, Thibodeau S, Tempany CM: Three-dimensional fast-recovery fast spin-echo MRCP: comparison with each structure depends on the setting of display two-dimensional single-shot fast spin-echo techniques. Radiology 2006, parameters, particularly on the lower threshold of the 238:549–559. opacity curve. Therefore VR images need to be evaluated 2. Holzknecht N, Gauger J, Sackmann M, Thoeni RF, Schurig J, Holl J, Weinzierl M, Helmberger T, Paumgartner G, Reiser M: Breath-hold MR cholangiography interactively [18]. with snapshot techniques: prospective comparison with endoscopic Our study had some limitations. We did not perform retrograde cholangiography. Radiology 1998, 206:657–664. quantitative SNR measurements of the MRCP datasets 3. Hekimoglu K, Ustundag Y, Dusak A, Erdem Z, Karademir B, Aydemir S, Gundogdu S: MRCP vs. ERCP in the evaluation of biliary pathologies: as the focus of our study was to qualitatively evaluate review of current literature. J Dig Dis 2008, 9:162–169. visualization of intra- and extrahepatic bile ducts 4. Wallner BK, Schumacher KA, Weidenmaier W, Friedrich JM: Dilated biliary using multiple readers. This seemed closer to the tract: evaluation with MR cholangiography with a T2-weighted contrast-enhanced fast sequence. Radiology 1991, 181:805–808. clinical reality than SNR values that are difficult to 5. Laubenberger J, Buchert M, Schneider B, Blum U, Hennig J, Langer M: measurefor smallbile ducts.Wedid notevaluatethe Breath-hold projection magnetic resonance-cholangio-pancreaticography added value of acquisition or reconstruction planes. (MRCP): a new method for the examination of the bile and pancreatic ducts. Magn Reson Med 1995, 33:18–23. In 1999, Boraschi and colleagues compared axial and 6. Bilgin M, Shaikh F, Semelka RC, Bilgin SS, Balci NC, Erdogan A: Magnetic coronal 2D FSE sequences with 3D MIP projection resonance imaging of gallbladder and biliary system. Top Magn Reson images in patients with suspected hepatobiliary disease Imaging 2009, 20:31–42. 7. Chavhan GB, Babyn PS, Manson D, Vidarsson L: Pediatric MR [19]. A higher global accuracy for axial and coronal FSE cholangiopancreatography: principles, technique, and clinical T2-weighted sequences was found regarding the diagnosis applications. Radiographics 2008, 28:1951–1962. of the level and probable cause of biliary obstruction in 8. Yoon LS, Catalano OA, Fritz S, Ferrone CR, Hahn PF, Sahani DV: Another dimension in magnetic resonance cholangiopancreatography: comparison depiction of small intraductal pathology such as calculi or of 2- and 3-dimensional magnetic resonance cholangiopancreatography neoplastic lesions. for the evaluation of intraductal papillary mucinous neoplasm of the We have limited our analysis to reconstructed rather pancreas. J Comput Assist Tomogr 2009, 33:363–368. 9. Yun EJ, Choi CS, Yoon DY, Seo YL, Chang SK, Kim JS, Jy W: Combination of thin-slice source images as the purpose of this specific magnetic resonance cholangiopancreatography and computed was to directly compare acquisition and reconstruction tomography for preoperative diagnosis of the Mirizzi syndrome. planes for MIP assessment. A well-known limitation of J Comput Assist Tomogr 2009, 33:636–640. 10. Kinner S, Dechene A, Ladd SC, Zöpf T, de Dechene EM, Gerken G, MIP is that small filling defects may be obscured due to Lauenstein TC: Comparison of different MRCP techniques for the partial volume effects [20]. Further, overestimation of depiction of biliary complications after liver transplantation. Eur Radiol ductal narrowing and pseudostricture may result from 2010, 20:1749–1756. 11. Ikenoue H, Ito S, Yamada M, Takikawa Y, Yamamuro O: Comparison MR the nature of MIP reconstruction [21]. Therefore it is cholangiopancreatography with 3D-fast recovery fast spin echo in important, that MIP reconstructions should not be several different slice thicknesses. Nihon Hoshasen Gijutsu Gakkai Zasshi appraised separately, but always in combination with the 2010, 66:749–757. 12. Matsunaga K, Ogasawara G, Tsukano M, Iwadate Y, Inoue Y: Usefulness of the original acquired dataset and in combination with other navigator-echo triggering technique for free-breathing three-dimensional morphological sequences. magnetic resonance cholangiopancreatography. Magn Reson Imaging 2012, 31:396–400. 13. Papanikolaou N, Karantanas AH, Heracleous E, Costa JC, Gourtsoyiannis N: Conclusions Magnetic resonance cholangiopancreatography: comparison between In conclusion, we compared different acquisition and respiratory-triggered turbo spin echo and breath hold single-shot turbo reconstruction planes of T2-weighted 3D-MRCP acquisi- spin echo sequences. Magn Reson Imaging 1999, 17:1255–1260. 14. Lim JS, Kim MJ, Myoung S, Park MS, Choi JY, Choi JS, Kim SI: MR tions for assessment of the intra- and extrahepatic bile cholangiography for evaluation of hilar branching anatomy in ducts in patients with different hepatobiliary pathologies. transplantation of the right hepatic lobe from a living donor. AJR Am J The results of our study suggest that for visualization and Roentgenol 2008, 191:537–545. Ringe et al. BMC Medical Imaging 2014, 14:16 Page 6 of 6 http://www.biomedcentral.com/1471-2342/14/16 15. Vitellas KM, Keogan MT, Spritzer CE, Nelson RC: MR cholangiopancreatography of bile and pancreatic duct abnormalities with emphasis on the single-shot fast spin-echo technique. Radiographics 2000, 20:939–957. 16. Arcement CM, Meza MP, Arumanla S, Towbin RB: MRCP in the evaluation of pancreaticobiliary disease in children. Pediatr Radiol 2001, 31:92–97. 17. Schaible R, Textor J, Kreft B, Neubrand M, Schild H: Value of selective MIP reconstructions in respiratory triggered 3D TSE MR-cholangiography on a workstation in comparison with MIP standard projections and single-shot MRCP. Röfo 2001, 173:416–423. 18. Morita S, Saito N, Suzuki K, Mitsuhashni N: Biliary anatomy on 3D MRCP: comparison of volume-rendering and maximum-intensity-projection algorithms. J Magn Reson Imaging 2009, 29:601–606. 19. Boraschi P, Braccini G, Gigoni R, Geloni M, Perri G: MR cholangiopancreatography: value of axial and coronal fast Spin-Echo fat-suppressed T2-weighted sequences. Eur J Radiol 1999, 32:171–181. 20. Anderson CMSD, Tsuruda JS, Shapeero LG, Lee RG: Artifacts in maximum-intensity-projection display of MR angiograms. AJR Am J Roentgenol 1990, 153:623–629. 21. David V, Reinhold C, Hochman M, Chuttani R, McKee J, Waxman I, Wang L, Li W, Kaplan R, Edelmann RR: Pitfalls in the interpretation of MR cholangiopancreatography. AJR Am J Roentgenol 1998, 170:1055–1059. doi:10.1186/1471-2342-14-16 Cite this article as: Ringe et al.: 3D-MRCP for evaluation of intra- and extrahepatic bile ducts: comparison of different acquisition and reconstruction planes. BMC Medical Imaging 2014 14:16. Submit your next manuscript to BioMed Central and take full advantage of: • Convenient online submission • Thorough peer review • No space constraints or color figure charges • Immediate publication on acceptance • Inclusion in PubMed, CAS, Scopus and Google Scholar • Research which is freely available for redistribution Submit your manuscript at www.biomedcentral.com/submit http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png BMC Medical Imaging Springer Journals

3D-MRCP for evaluation of intra- and extrahepatic bile ducts: comparison of different acquisition and reconstruction planes

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Copyright © 2014 by Ringe et al.; licensee BioMed Central Ltd.
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Medicine & Public Health; Imaging / Radiology
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Abstract

Background: Magnetic resonance cholangiopancreatography (MRCP) is an established technique for the evaluation of intra- and extrahepatic bile ducts in patients with known or suspected hepatobiliary disease. However, the ideal acquisition and reconstruction plane for optimal bile duct evaluation with 3D technique has not been evaluated. The purpose of our study was to compare different acquisition and reconstruction planes of 3D-MRCP for bile duct assessment. Methods: 34 patients (17f/17 m, mean age 41y) referred for MRCP were included in this prospective IRB-approved study. Respiratory-triggered 3D-T2w-MRCP sequences were acquired in coronal and axial plane. Coronal and axial MIP were reconstructed based on each dataset (resulting in two coronal and two axial MIP, respectively). Three readers in two sessions independently assessed the MIP, regarding visualization of bile ducts and image quality. Results were compared (Wilcoxon test). Intra- and interobserver variability were calculated (kappa-statistic). Results: In case of coronal data acquisition, visualization of bile duct segments was significantly better on coronal reconstructed MIP images as compared to axial reconstructed MIP (p < 0.05). Regarding visualization, coronal MIP of the coronal acquisition were equal to coronal MIP of the axial acquisition (p > 0.05). Image quality of coronal and axial datasets did not differ significantly. Intra- and interobserver agreement regarding bile duct visualization were moderate to excellent (κ-range 0.55-1.00 and 0.42-0.85, respectively). Conclusions: The results of our study suggest that for visualization and evaluation of intra- and extrahepatic bile duct segments reconstructed images in coronal orientation are preferable. The orientation of the primary dataset (coronal or axial) is negligible. Keywords: MRCP, MRC, Magnetic resonance cholangiopancreatography, Bile ducts, Common hepatic duct Background yield a luminal image of the bile ducts that is based on Magnetic resonance cholangiopancreatography (MRCP) is the inherent signal of slow-flowing or stationary bile. an established technique for the evaluation of intra- and Both, single shot projections and multislice techniques extrahepatic bile ducts in patients with known or suspected are available [5], with the latter being distinguished into hepatobiliary disease [1]. It is considered a reliable 2D [6] and 3D techniques [7]. Single shot projections non-invasive alternative to diagnostic endoscopic retrograde are preferred in individuals who are unable to hold their cholangiopancreatography (ERCP) [2,3]. Since the first breath, such as severely sick patients or small children description by Wallner and colleagues in 1991 [4], different [7]. 3D imaging techniques provide better image quality acquisition techniques have evolved. compared to 2D sequences [1,8,9], even though the Most current MRCP techniques are based on heavily combination of different MRCP sequences has proven to T2-weighted fast spin echo (FSE) pulse sequences, which be valuable in the assessment of bile duct anatomy and pathology [10]. 3D FSE sequences are usually acquired with the slab * Correspondence: ringe.kristina@mh-hannover.de in coronal orientation. Maximum intensity projections Department of Diagnostic and Interventional Radiology, Hannover Medical School, Carl-Neuberg Str. 1, Hannover 30625, Germany © 2014 Ringe et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Ringe et al. BMC Medical Imaging 2014, 14:16 Page 2 of 6 http://www.biomedcentral.com/1471-2342/14/16 Table 1 Imaging parameters of the respiratory-triggered (MIP) can then be obtained in any plane [7]. Previous fat-saturated 3D T2-weighted MR cholangiographic studies have addressed the matter of optimal slice thickness sequence for data acquisition [11] and different techniques regarding Parameter 1.5 T Magnetom Avanto respiratory triggering [12]. However, to the best of our knowledge, the ideal acquisition and reconstruction plane, Plane Coronal, Axial in practical terms meaning best suitable for optimal Respiratory triggering Navigator based bile duct visualization with 3D techniques, has not been Repetition time Breathing cycle evaluated. The purpose of this study was to compare Echo time (msec) 700-800 different acquisition and reconstruction planes of Refocusing pulse 140° T2-weighted 3D-MRCP acquisitions for assessment In-plane spatial resolution (mm) 1 × 1 of the intra- and extrahepatic bile ducts. Slab thickness (mm) 60-80 Methods Partitions per slab 60-80 Patients Type of k-space filling Sequential This HIPAA-compliant study was approved by the Partial Fourier factor Allowed institutional review board of Hannover Medical School. Estimated total acquisition time (min) Approximately 5 Written informed consent from each patient was obtained. 34 patients (17 female, 17 male, mean age 41.5 years, range 18-79 years) who were referred for liver MRI and dedicated at least eight years of experience in abdominal MR MRCP were included in this prospective study. Inclusion imaging. Readers were blinded to each patient’shistory criteria were as follows: completion of the entire MR examination; patient age equal or greater than 18 years. and other imaging findings. A single coronal and axial maximum intensity projection Indications for performing MRI were as follows: primary (MIP) covering the central, left, right and peripheral bile sclerosing cholangitis (n = 16), status post liver trans- plantation (n = 7), tumor (n = 6), suspicion of Caroli’s ducts was generated from each acquired MRCP dataset, resulting in two coronal and two axial MIP datasets, disease (n = 2), stone disease (n = 2) and recurrent respectively. Care was taken to exclude the renal pelvis, pancreatitis (n = 1). ureter of both kidneys and spinal canal to allow for blinded reading. Each reader performed two reading sessions MR imaging technique separated by an interval of two weeks, evaluating the MR examinations were performed on a 1.5 T system (Magnetom Avanto, Siemens, Erlangen, Germany) using reconstructed MIP in the following way: 1, Coronal reconstructed MIP of the coronal acquisition vs. cor- dedicated multichannel surface coils covering the onal reconstructed MIP of the axial acquisition; 2, abdomen. Prior to image acquisition, patients received 200 mL of anegativeoralcontrastagent (Lumirem®; Axial reconstructed MIP of the coronal acquisition vs. axial reconstructed MIP of the axial acquisition. After Guerbet, Sulzbach, Germany) for suppression of gastro- each reading session the readers were asked to choose enteric fluid signal, as well as 20 mg butylscopolamine (Buscopan®; Boehringer Ingelheim, Ingelheim, Germany; the preferred image dataset of any given comparison. The readers had no knowledge of initial MRCP dataset administered as a bolus over approximately 20 s) i.v. for orientation. spasmolysis. All patients underwent a clinical routine im- aging protocol of the liver, including a respiratory-triggered Depiction of bile duct segments was assessed by using the following four-point scale proposed by Papanikolaou 3D MR cholangiography in the coronal (dataset A) as well and colleagues [13]: 1, segment not seen; 2, segment as in the axial (dataset B) plane. MRCP-sequences were acquired prior to intravenous contrast injection. The faintly seen; 3, segment well seen but portion of the duct or the confluence not seen; and 4, excellent depiction specific MRCP sequences had sequential k-space fill- including the proximal and distal portions. This scale ing with partial Fourier filling allowed, resulting in acquisition of central k-space lines approximately was applied to the following sections (segments) of the biliary tract: the common bile duct (CBD), the right 3 minutes after the start of the sequence. MRCP se- anterior bile duct, the right posterior bile duct, the left quence parameters are provided in detail in Table 1. hepatic duct, and third-order biliary branches. Overall technical image quality was assessed using a four-point Image evaluation scale proposed by Lim and colleagues [14]: 1, poor quality Three readers (D.H., C.F., H.J.R.) independently performed image evaluation in terms of visibility of different bile duct with severe artifacts; 2, satisfactory quality with few rd artifacts; 3, good quality with minimal artifacts; and 4, segments up to the 3 order and assessment of technical excellent quality without artifacts. quality. All readers were board certified radiologists with Ringe et al. BMC Medical Imaging 2014, 14:16 Page 3 of 6 http://www.biomedcentral.com/1471-2342/14/16 Figure 1 Comparison of coronal MIP reconstructions of coronal and axial acquired datasets. 35-year old male patient with diagnosis of primary rd sclerosing cholangitis (PSC). Coronal MIP of a coronal (A) and axial (B) acquired MRCP dataset. Bile duct visualization up to the 3 order is equal on both datasets (see also Table 2), even though the image impression is more blurred on the MIP derived from the axial acquired dataset (B). In addition, a total score was defined as the sum of the MIP of the axial acquisition (dataset B) (p > 0.05) visibility and quality scores for each dataset to determine (Figure1;Table 2).Axial MIPofthe axialacquisition which of the two acquired MRCP datasets (coronal or (dataset B) were significantly better than axial MIP of axial) yielded the most diagnostic information. the coronal acquisition (dataset A) for visualization of third order biliary branches whereas lower order branches Statistical analysis did not show a difference (Figures 2 and 3). Statistical analysis was performed using GraphPad Prism Intraobserver agreement regarding bile duct visualization software (version 6; GraphPad Software, Inc., La Jolla, CA). was good to excellent (weighted Κ-range 0.63-1.0). Interob- Results regarding bile duct visualization and overall server agreement was moderate to good, regarding bile technical image quality were compared with a two-sided duct visualization in both datasets (coronary acquisition: Wilcoxon signed-rank test (with a p-value <0.05 deemed weighted Κ range 0.51-0.75; axial acquisition: weighted Κ significant) in the following way: 1, Coronal reconstructed range 0.42-0.67). MIP of the coronal acquisition vs. coronal reconstructed MIP of the axial acquisition; 2, Axial reconstructed MIP Technical image quality of the coronal acquisition vs. axial reconstructed MIP of Regarding overall technical image quality (including axial the axial acquisition; 3, Coronal vs. axial reconstructed and coronal reconstructed MIP of a given dataset), there MIP of the coronal acquired dataset; 4. Coronal vs. axial was no significant difference between the coronal and axial reconstructed MIP of the axial acquired dataset. acquired dataset (p > 0.05). At detailed dataset analysis Intra- and interobserver agreement was assessed by means however, in case of coronal data acquisition (dataset A) of a kappa-statistic and classified as follows: a Κ value of technical image quality of the coronal MIP was significantly less than 0.20 indicated poor agreement; Κ values of better as compared to the axial reconstructed MIP 0.21-0.40, fair agreement; Κ values of 0.41-0.60, moderate (p < 0.05). In case of axial data acquisition (dataset B), agreement; Κ values of 0.61-0.80, good agreement; and Κ there was no significant difference regarding technical values of 0.80-1.00, excellent agreement [14]. image quality of the reconstructed MIP (p > 0.05). Table 2 P-values for each reader and biliary segment: Results comparison of coronal reconstructed MIP of coronal and Bile duct visualization axial acquired datasets regarding bile duct visualization In case of coronal data acquisition (dataset A), visualization nd Reader No. CBD Right Right Left hepatic 2 and of bile duct segments was significantly better on coronal rd (Session No.) posterior anterior duct 3 order reconstructed MIP as compared to axial reconstructed bile duct bile duct branches MIP (p < 0.05). This was true for visualization of the CBD, 1 (1) 0.424 0.923 0.499 0.685 0.305 right anterior hepatic duct, left hepatic duct and third 1 (2) 0.766 0.309 0.236 0.783 0.790 order biliary branches. In case of axial data acquisition 2 (1) 1.000 1.000 0.536 0.358 0.145 (dataset B), a significant better visualization of the CBD 2 (2) 1.000 0.609 0.400 0.891 0.393 and left hepatic duct on coronal reconstructed MIP as compared to axial reconstructed MIP was observed only 3 (1) 0.174 0.943 0.305 0.266 0.627 by one reader. 3 (2) 0.345 0.898 0.143 0.627 0.608 Regarding bile duct visualization, coronal MIP of the P values were calculated with the two-sided Wilcoxon Test to compare coronal acquisition (dataset A) were equal to coronal depiction scores of coronal axial acquired datasets. Ringe et al. BMC Medical Imaging 2014, 14:16 Page 4 of 6 http://www.biomedcentral.com/1471-2342/14/16 Figure 2 Comparison of axial MIP reconstructions of coronal and axial acquired datasets. 79-year old male patient status post radiofrequency st nd ablation of a colorectal liver metastasis. Axial MIP of a coronal (A) and axial (B) acquired MRCP dataset. Bile duct visualization of 1 and 2 order branches rd is equal on both datasets, whereas 3 order branches are depicted significantly better on the axial dataset. Intraobserver agreement regarding technical image are seen better on a left posterior images obtained at a quality was moderate to excellent (weighted Κ range steeper angle [15]. Especially in children with segmental 0.55-0.96); interobserver agreement was moderate (weighted liver transplants sagittal oblique planes are preferred due Κ range 0.42-0.59). to the more anteroposterior orientation of the neo-porta hepatis [16]. In a first approach towards projection Choice of preferred image dataset cholangiography by means of MRI in 1991, Wallner and When reading coronal reconstructed MIP, the readers colleagues used a heavily T2-weighted gradient echo preferred coronal acquisitions over axial acquisitions in sequence for assessment of bile duct dilatation [4]. They 66% of the readings. Regarding axial MIP reconstruction, concluded that imaging in the coronal plane provided a axial acquisitions were preferred over coronal acquisitions good view of the biliary system, whereas no additional in 80% of the readings. information was found by imaging in the sagittal plane. Intraobserver agreement regarding choice of the In this study we compared different acquisition and re- preferred image dataset was excellent (weighted Κ construction planes of T2-weighted 3D-MRCP acquisitions range 0.94-1.00); interobserver agreement was moderate for assessment of the intra- and extrahepatic bile ducts. In to excellent (weighted Κ range 0.57-0.85). contrast to single shot techniques, 3D MRCP has the advantage to facilitate secondary reconstructions. Coronal reconstructions were preferred, regardless of the initial Discussion acquisition plane. These findings were supported by good To the best of our knowledge the ideal acquisition and intra- and interobserver agreement. One of the reasons reconstruction plane for optimal bile duct evaluation for coronal image preference might be the fact that these with 3D techniques has not yet been evaluated. For images are similar to image impressions of ERCP and single shot FSE techniques it has been suggested that conventional cholangiograms. straight coronal and initial left posterior oblique images There are other studies that evaluated secondary clearly depict the common hepatic duct and the left reconstruction techniques for MRCP. Schaible and hepatic duct, whereas the CBD and right hepatic ducts Figure 3 Comparison of axial MIP reconstructions of coronal and axial acquired datasets. 18-year old male patient with jaundice and rd suspicion of cholelithiasis. Axial MIP of a coronal (A) and axial (B) acquired MRCP dataset. Bile duct visualization up to the 3 order is equal on both datasets, even though the image impression is more blurred on the MIP derived from the coronal acquired dataset (A). Ringe et al. BMC Medical Imaging 2014, 14:16 Page 5 of 6 http://www.biomedcentral.com/1471-2342/14/16 colleagues evaluated selective MIP reconstructions of evaluation of the bile ducts coronal reconstructions are respiratory-triggered 3D MRCP versus standard MIP preferred. In this context, the orientation of the primary reconstructions and single-shot MRCP [17]. Single-shot dataset (coronal or axial) is negligible. and standard MIP reconstructions of 3D MRCP were Competing interests comparable in terms of anatomical bile duct visualization, The authors declare that they have no competing interests. whereas selective MIP postprocessing proved useful for Authors’ contributions detection of pathological alterations. In a retrospective KIR and DH conceived and designed the experiments, KIR, DH and CF study, Morita and colleagues compared volume rendering performed the experiments and acquisition of data. KIR, DH, CF, FW and HJR (VR) and MIP of 3D TSE MRCP sequences to define analyzed and interpreted the data. FW and HJR contributed materials and analysis tools. All authors participated in drafting and revising the biliary anatomy mostly in patients without major biliary manuscript. All authors read and approved the final manuscript. tract anomaly [18]. Definition of biliary anatomy was found to be more accurate using VR reformation than Received: 27 January 2014 Accepted: 14 May 2014 Published: 19 May 2014 MIP. However, the assessment of VR images was not thepurpose of thepresent study. Onedisadvantageof References VR reconstructions is that the detection degree of 1. Sodickson A, Mortele KJ, Barish MA, Zou KH, Thibodeau S, Tempany CM: Three-dimensional fast-recovery fast spin-echo MRCP: comparison with each structure depends on the setting of display two-dimensional single-shot fast spin-echo techniques. 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AJR Am J Roentgenol 1998, 170:1055–1059. doi:10.1186/1471-2342-14-16 Cite this article as: Ringe et al.: 3D-MRCP for evaluation of intra- and extrahepatic bile ducts: comparison of different acquisition and reconstruction planes. BMC Medical Imaging 2014 14:16. Submit your next manuscript to BioMed Central and take full advantage of: • Convenient online submission • Thorough peer review • No space constraints or color figure charges • Immediate publication on acceptance • Inclusion in PubMed, CAS, Scopus and Google Scholar • Research which is freely available for redistribution Submit your manuscript at www.biomedcentral.com/submit

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BMC Medical Imaging – Springer Journals

Published: May 19, 2014

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