The feasibility of breath-hold high-resolution 3D-MRCP obtained with 32 channel torso cardiac coil and T2-prepBTFE

Transcription

1 The feasibility of breath-hold high-resolution 3D-MRCP obtained with 32 channel torso cardiac coil and T2-prepBTFE Poster No.: C-0022 Congress: ECR 2010 Type: Scientific Exhibit Topic: Abdominal Viscera (Solid Organs) - Biliary Tract Authors: K. Nasu, M. Minami; Tsukuba/JP Keywords: MRCP, 32-channel torso cardiac coil, T2-prep-balanced turbo field echo Keywords: Abdomen, Biliary Tract / Gallbladder DOI: /ecr2010/C-0022 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 40

2 Purpose Backgrounds MR cholangiopancreatography (MRCP) is a key imaging method for evaluating the anatomy and lesions of the pancreato-biliary systems. Thick-slice 2D-MRCP, the most commonly used method, can be obtained with a short acquisition time, and is incontrovertibly useful; however, it is difficult to identify the details of the anatomy around the porta hepatis and the confluence of the common hepatic duct and cystic duct using this method alone. 3D-MRCP obtained with T2-TSE simultaneous use of respiratory triggering is usually adopted to evaluate anatomic details; however, this method has several shortcomings, including long acquisition time, relatively lower success rate in patients with irregular respiration cycles, and poor information except for pancreato-biliary systems. 32-channel torso cardiac coil One of the most recent MRI technological developments is a 32-channel torso cardiac coil (32-ch coil)(fig. 1). This item has a far superior signalto-noise ratio to the 16-channel coil, which has up to now been the best available for body imaging. The high image quality obtained with a 32-ch coil amazes all radiologists (Fig. 2). Page 2 of 40

3 Fig.: Fig. 1: 32-channel torso cardiac coil consists of two components (ventral side and dorsal side). Each component has 16 small eleements. References: Radiology, Tsukuba university - Tsukuba/JP Page 3 of 40

4 Fig.: Fig. 2: Comparison of the image quality of 16-ch coil and 32-ch coil is shown. Please pay notice that the noisy area which is observed in the center of the 16-ch-coil image disappears in the 32-ch-coil image. References: Radiology, Tsukuba university - Tsukuba/JP Which sequence is suitable for breath-hold MRCP, TSE or BTFE? Can we develop a breath-hold 3D-MRCP acquisition technique using this high potential of 32-ch coil? Conventional 3D-MRCP has to be obtained under respiratory triggering since it is a T2WI-based sequence and needs long shot-intervals for T1-recovery (Fig. 3). This rules out continuous evoking during breath-hold scanning with conventional 3D-MRCP. However, this does not apply if we employ balanced a turbo field echo (BTFE) sequence instead of T2WI, which can be obtained under continuous evoking and provides similar contrast to T2WI (Fig. 4). The aim of this study is to reveal the technical aspect and feasibility of BTFE-based breath-hold 3DMRCP. Page 4 of 40

5 Fig.: Fig. 3: The scheme of T2-TSE is shown. In T2-TSE, a long shot interval for T1-recovery is necessary. This is because that the respiration trigger is simultaneously used for data acquisition of 3D-MRCP employing T2-TSE. References: Radiology, Tsukuba university - Tsukuba/JP Fig.: Fig. 4: The scheme of BTFE is shown. At BTFE, continuous evaking can be performed. Therefore, BTFE is a more suitable sequence for the breath-hold image acquisition than T2-TSE. References: Radiology, Tsukuba university - Tsukuba/JP Page 5 of 40

6 Images for this section: Fig. 0: Fig. 1: 32-channel torso cardiac coil consists of two components (ventral side and dorsal side). Each component has 16 small eleements. Radiology, Tsukuba university - Tsukuba/JP Page 6 of 40

7 Fig. 0: Fig. 2: Comparison of the image quality of 16-ch coil and 32-ch coil is shown. Please pay notice that the noisy area which is observed in the center of the 16-ch-coil image disappears in the 32-ch-coil image. Radiology, Tsukuba university - Tsukuba/JP Fig. 0: Fig. 3: The scheme of T2-TSE is shown. In T2-TSE, a long shot interval for T1recovery is necessary. This is because that the respiration trigger is simultaneously used for data acquisition of 3D-MRCP employing T2-TSE. Radiology, Tsukuba university - Tsukuba/JP Page 7 of 40

8 Fig. 0: Fig. 4: The scheme of BTFE is shown. At BTFE, continuous evaking can be performed. Therefore, BTFE is a more suitable sequence for the breath-hold image acquisition than T2-TSE. Radiology, Tsukuba university - Tsukuba/JP Page 8 of 40

9 Methods and Materials BTFE + 32-ch coil + high SENSE factor BTFE has been used to image pancreato-biliary systems in the past. However, the simultaneous use of a 32-ch coil and a higher SENSE factor allows acquisition of thinner and more numerous slices, and thus more detailed anatomical information about the pancreato-biliary system. Movie 1 shows BTFE images of multiple gallbladder polyps with spatial resolution of 1.2 x 1.2 x 1.2 mm. These 60 axial slices were acquired under 24-secondsingle-breath-holding. Fig.: Movie 1: thin slice BTFE images of multiple gallbladder polyps. These images are obtained under single breath-hold. References: Radiology, Tsukuba university - Tsukuba/JP BTFE-based 3D-MRCP The chief shortcoming of BTFE when applied to pancreato-biliary imaging is that both pancreato-biliary systems and vessels are depicted hyperintensely, thus impeding intuitive comprehension of the biliary-tree anatomy. The fine Page 9 of 40

10 3D-MRCP shown as Movie 2 is made from the BTFE images in the previous slide; however, it needs painstaking post-processing maneuvers, which are not suitable procedures in the clinical scenario, to delete the portal vein. Fig.: Movie 2: The 3D-MRCP made from the source images shown as movie 1. However, the author spent about an hour to delete the signals of the portal vein. References: Radiology, Tsukuba university - Tsukuba/JP T2-prep; A novel preparation pulse In the MR system (Achieva 1.5T dual gradient Rel. 2.6) we currently use, a new preparation pulse for BTFE named "T2-prep" is available. In short, this Page 10 of 40

11 preparation pulse is a T2-TSE with a short echo train length that makes the contrast of BTFE images more T2-enhaced and suppresses blood vessel signals (Fig. 5). Fig.: Fig. 5: A scheme of T2-prep. This preparation pulse is a T2-TSE sequence having short echo trains and makes the contrast of BTFE more T2WI like. References: Radiology, Tsukuba university - Tsukuba/JP T2-prep-BTFE The images shown below are a conventional BTFE image and a BTFE images with simultaneous use of T2-prep (T2-prep-BTFE). On the T2-prepBTFE image, we can more intuitively recognize the common bile duct than in a conventional BTFE image (Fig. 6). Page 11 of 40

12 Fig.: Fig. 6: Comparison between the BTFE images with and without T2prep. On the T2-prep BTFE image, the signal of vessels including the portal vein is suppressed as comparison with the conventional BTFE images. The signals of the liver and pancreas are also lower in T2-prep-BTFE than in conventional BTFE. References: Radiology, Tsukuba university - Tsukuba/JP Divided acquisition technique Divided acquisition of T2-prep-BTFE into two or three enables coverage from the intrahepatic bile ducts to the duodenal papilla. This method takes less than 2 minutes, including breathing time, making it a far more timeefficient imaging technique than conventional 3D-MRCP using T2-TSE and respiratory triggering, which needs at least 5 minutes (Fig. 7). Fig.: Fig.7 : The scheme of divided image acquisition technique. The indipendently obtained BTFE image sets can be gathered and integrated as a single 3D-MRCP by postprocessing procedures. References: Radiology, Tsukuba university - Tsukuba/JP Case presentation; Hepatic hilar carcinoma The movies shown below (Movie 3a-c) are made from T2-prep-BTFE images of a case of hepatic hilar carcinoma obtained (63-year-old female) using the divided acquisition technique. We can easily see that the tumor discretely obstructs and dilates the intrahepatic bile ducts. T2-prep BTFE images provide more information on the structures around the bile ducts than the source images from conventional 3D-MRCP. Page 12 of 40

13 Fig.: Movie 3a: The upper third of the BTFE images of a case of hepatic hilar carcinoma. References: Radiology, Tsukuba university - Tsukuba/JP Page 13 of 40

14 Fig.: Movie 3b: The middle third of the BTFE images of a case of hepatic hilar carcinoma. References: Radiology, Tsukuba university - Tsukuba/JP Page 14 of 40

15 Fig.: Movie 3c: The lower third of the BTFE images of a case of hepatic hilar carcinoma. References: Radiology, Tsukuba university - Tsukuba/JP When the 3D-MRCP reconstructed from T2-prep-BTFE (Movie 4a) is compared with the conventional 3D-MRCP (Movie 4b), we can obtain the same information about the biliary tree from both MRCPs; however, the quality of T2-prep-BTFE-MRCP is, frankly speaking, inferior to conventional 3D-MRCP since the strong background signal, which is one of the advantages of T2-prep BTFE, impairs the clarity of the 3D images. Page 15 of 40

16 Fig.: Movie 4a: 3D-MRCP made from T2-prep-BTFE images. As comparison with movie 4b, the 3D-MRCP made from T2-TSE, the clarity of the T2-prep-BTFE-based MRCP is inferior to the T2-TSE-based-MRCP, although both MRCPs provide the same clinical informations. References: Radiology, Tsukuba university - Tsukuba/JP Page 16 of 40

17 Fig.: Movie 4b: 3D-MRCP made from T2-TSE. See the anotation of movie 4a. References: Radiology, Tsukuba university - Tsukuba/JP However, if we limit the T2-prep BTFE images for 3D-recontruction to the area around the tumor, and select volume rendering instead of maximal intensity projection for the reconstruction algorithm, we can obtain a high quality 3D-MRCP that is far better than one would expect knowing that the source images of this MRCP were obtained in only a 24-second single breath-hold (Movie 4c). Page 17 of 40

18 Fig.: Movie 4c: "Targed" 3D-MRCP made from the T2-prep-BTFE images which are obtained with single breath-hold. References: Radiology, Tsukuba university - Tsukuba/JP Case presentation: A rare variation of biliary tract branching, Vol. 1 T2-prep BTFE is especially useful for gaining an understanding of the anatomical variations of the biliary tree. For example, in the case shown below (A 60-year old female), the independently-branched B6 merges with the cystic duct, and the common channel of B6 and the cystic duct joins the common hepatic duct (CHD) (Fig. 8). Page 18 of 40

19 Fig.: Fig. 8: A relatively rare branching variation of the biliary tree. T2-prepBTFE images clearly depict the detaild anatomy of the biliary tree. References: Radiology, Tsukuba university - Tsukuba/JP Case presentation: A rare variation of biliary tract branching, Vol. 2 In the case shown in this paragraph (A 68-year-old male, MIP image), the independently branched B5 merges with the common hepatic duct, and the cystic duct joins the common hepatic duct just below the confluence of B5 and the common bile duct (Fig. 9). These anatomical details are crucial to the success of laparoscopic cholecystectomy. We can readily obtain this degree of anatomical information about the biliary tree from T2-prep BTFE images. Page 19 of 40

20 Fig.: Fig.9: A relatively rare branching variation of the biliary tree is shown. Such anatomical information is important esprcially before the lapaloscopic cholecystectomy. The shown MIP image is made from BTFE images obtained with sigle breath-hold. References: Radiology, Tsukuba university - Tsukuba/JP Page 20 of 40

21 Page 21 of 40

22 Images for this section: Fig. 9: Movie 1: thin slice BTFE images of multiple gallbladder polyps. These images are obtained under single breath-hold. Radiology, Tsukuba university - Tsukuba/JP Page 22 of 40

23 Fig. 8: Movie 2: The 3D-MRCP made from the source images shown as movie 1. However, the author spent about an hour to delete the signals of the portal vein. Radiology, Tsukuba university - Tsukuba/JP Page 23 of 40

24 Fig. 0: Fig. 5: A scheme of T2-prep. This preparation pulse is a T2-TSE sequence having short echo trains and makes the contrast of BTFE more T2WI like. Radiology, Tsukuba university - Tsukuba/JP Fig. 0: Fig. 6: Comparison between the BTFE images with and without T2-prep. On the T2-prep BTFE image, the signal of vessels including the portal vein is suppressed as comparison with the conventional BTFE images. The signals of the liver and pancreas are also lower in T2-prep-BTFE than in conventional BTFE. Radiology, Tsukuba university - Tsukuba/JP Page 24 of 40

25 Fig. 0: Fig.7 : The scheme of divided image acquisition technique. The indipendently obtained BTFE image sets can be gathered and integrated as a single 3D-MRCP by postprocessing procedures. Radiology, Tsukuba university - Tsukuba/JP Page 25 of 40

26 Fig. 5: Movie 3a: The upper third of the BTFE images of a case of hepatic hilar carcinoma. Radiology, Tsukuba university - Tsukuba/JP Page 26 of 40

27 Fig. 6: Movie 3b: The middle third of the BTFE images of a case of hepatic hilar carcinoma. Radiology, Tsukuba university - Tsukuba/JP Page 27 of 40

28 Fig. 7: Movie 3c: The lower third of the BTFE images of a case of hepatic hilar carcinoma. Radiology, Tsukuba university - Tsukuba/JP Page 28 of 40

29 Fig. 3: Movie 4a: 3D-MRCP made from T2-prep-BTFE images. As comparison with movie 4b, the 3D-MRCP made from T2-TSE, the clarity of the T2-prep-BTFE-based MRCP is inferior to the T2-TSE-based-MRCP, although both MRCPs provide the same clinical informations. Radiology, Tsukuba university - Tsukuba/JP Page 29 of 40

30 Fig. 4: Movie 4b: 3D-MRCP made from T2-TSE. See the anotation of movie 4a. Radiology, Tsukuba university - Tsukuba/JP Page 30 of 40

31 Fig. 2: Movie 4c: "Targed" 3D-MRCP made from the T2-prep-BTFE images which are obtained with single breath-hold. Radiology, Tsukuba university - Tsukuba/JP Page 31 of 40

32 Fig. 0: Fig. 8: A relatively rare branching variation of the biliary tree. T2-prep-BTFE images clearly depict the detaild anatomy of the biliary tree. Radiology, Tsukuba university - Tsukuba/JP Page 32 of 40

33 Fig. 0: Fig.9: A relatively rare branching variation of the biliary tree is shown. Such anatomical information is important esprcially before the lapaloscopic cholecystectomy. The shown MIP image is made from BTFE images obtained with sigle breath-hold. Radiology, Tsukuba university - Tsukuba/JP Page 33 of 40

34 Results Result at the current time Table 1 is a provisional result of bile duct imaging using T2-prep BTFE. The images are evaluated to decide whether the confluences of cystic duct, B1r and B1l to the main stream of the biliary trees can be observed or not. In cases with bile duct dilatation, all the confluences of these ducts can be confirmed. On the other hand, in cases without bile duct dilatation, all confluences of cystic ducts can be observed, and the confluences of B1r and B1l can also be confirmed in about one-third of cases. Fig.: Table 1: The current results of T2-prep-BTFE about the visualization of the cystic duct and intrahepatic bile ducts of the caudate lobe. References: Radiology, Tsukuba university - Tsukuba/JP The shortcoming of the divided acquisition technique for T2-prep-BTFE is that the image quality of 3D-MRCP is hopelessly impaired if respiratory mis-registration occurs (Movie 5). Of course, we simultaneously use slice tracking during divided acquisition of T2-prep-BTFE, but the accuracy of the slice level correction is not yet good enough. Page 34 of 40

35 Fig.: Movie 5: The shortcomings of divided acquisition technique is shown. The image quality of T2-prep-BTFE-based MRCP is easily impaired when the resiratory misregistration occurs. References: Radiology, Tsukuba university - Tsukuba/JP Page 35 of 40

36 Images for this section: Fig. 0: Table 1: The current results of T2-prep-BTFE about the visualization of the cystic duct and intrahepatic bile ducts of the caudate lobe. Radiology, Tsukuba university - Tsukuba/JP Page 36 of 40

37 Fig. 1: Movie 5: The shortcomings of divided acquisition technique is shown. The image quality of T2-prep-BTFE-based MRCP is easily impaired when the resiratory misregistration occurs. Radiology, Tsukuba university - Tsukuba/JP Page 37 of 40

38 Conclusion Conclusions In conclusion, we can cope with breath-hold imaging acquisition and detailed imaging of the bile ducts if a 32-ch coil and T2-prep-BTFE are employed. We can obtain numerous thin slices with fine image quality with singlebreath hold using this combination. We can produce T2-prep-BTFE-MRCP covering from the intrahepatic bile ducts to the duodenal papilla by using the divided acquisition technique. Currently, the image quality of T2-prep-BTFE-MRCP is inferior to that of conventional MRCP; however, T2-prep-BTFE can provide a much finerresolution MRCP than with the conventional method if the range of the imaging is limited and if the source images can be obtained in a single breath-hold. Page 38 of 40

39 References References Bilgin M et al. Magnetic resonance imaging of gallbladder and biliary system. Top Magn Reson Imaging ;20: Hoad CL et al. Quantification of T(2) in the abdomen at 3.0 T using a T(2)prepared balanced turbo field echo sequence. Magn Reson Med. 2009;13. Page 39 of 40

40 Personal Information Katsuhiro Nasu, MD Manabu Minami, MD Department of radiology Institute of clinical medicine Tsukuba University Corresponding author: Katsuhiro Nasu Page 40 of 40