Diffusion Weighted MR in Imaging Pancreatico-biliary & Gall Bladder Pathologies: friend or foe?

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1 Diffusion Weighted MR in Imaging Pancreatico-biliary & Gall Bladder Pathologies: friend or foe? Poster No.: C-0595 Congress: ECR 2014 Type: Educational Exhibit Authors: K. LIM; SINGAPORE/SG Keywords: Pancreas, Liver, Biliary Tract / Gallbladder, MR-Diffusion/ Perfusion, MR-Functional imaging, Imaging sequences, Cholangiography, Cancer, Infection, Inflammation DOI: /ecr2014/C-0595 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 18

2 Learning objectives 1) To understand the difficulties in radiological diagnosis of various pathologies affecting the biliary, including the gall bladder, and pancreatic ductal system. 2) To understand the principles and techniques of abdominal diffusion weighted imaging (DWI). 3) To gain awareness of the added values of DWI in detection and diagnosis of various malignancies and inflammatory conditions affecting the pancreatico-biliary ductal system. 4) To have a briefing of the literature on DWI in imaging these pathologies. 5) To gain awareness of the potential weaknesses and pitfalls of using DWI in imaging these pathologies. Background Introduction A myriad of disease processes commonly affect the ductal system of the biliary tree, including the gall bladder, and the pancreas. They broadly fall into two main pathogeneses: cancer and inflammation. While they infer drastically different prognosis and necessitate different treatment approach, their clinical and radiological manifestations are remarkably similar. Morphological imaging using MRI has now superseded CT in this area thanks to superior contrast resolution. However, diagnostic efficacy deserves improvement. DWI has been widely studied and now used to aid radiological diagnosis of a host of abdominal malignancies, including those affecting pancreatico-biliary system. DWI DWI measures movement of water molecules in biological tissue. It does so by applying a pair of equal and symmetrical motion-proding gradients on either side of the 180 degree refocusing pulse in a T2 echoplanar spin echo gradient. Mobile water molecules are dephased by the first gradient but not rephrased by the second and thus lose their T2 Page 2 of 18

3 signal rapidly ie free diffusion. In contrast, immobile water molecules are rephased and retain their signals as the diffusion-weighting (b value) of the DWI increases ie restricted diffusion. The rate of signal decay may be mathematically expressed as an apparent diffusion co-efficient (ADC);the more restricted the diffusion, the lower the ADC value. Biological tissues with restricted diffusion e,g. cancer tissue with its hypercellularity and complex cellular environment, and pus with its viscous and hypercellular nature, naturally remain hyperintense on high b-value DWI and have low ADC values. Findings and procedure details Gall bladder Gall bladder cancer (GBCA) is the commonest biliary malignancy. Its clinical presentation is insidious and indistinguishable form benign GB diseases such as calculous disease. Radiologically it may manifest as diffuse wall thickening, polypoid or infiltrative mass. DWI has been shown to improve diagnostic differentiation of GBCA from 1,2,3,4 inflammatory diseases. GBCA typically appear DW hyperintense with low ADC, compared to inflammatory GB conditions (Figures 1,2,3). As GBCA and cholecystitis may co-exist in the same GB, as they share common aetiology (ie calculus), DWI may aid detecting malignant focus in the midst of inflammatory changes (Figure 4). DWI may also help in diagnosis of cholecystitis complicated by abscess formation, as abscess is typically DW hyperintense in its content (Figure 5). Biliary tree The ductal wall of biliary tree is fertile ground for malignant and inflammatory processes, both presenting with diffuse or focal wall thickening, morphologically indistinguishable on imaging. DWI has been reported to improve detection of cholangiocarcinoma (CC) 5, 6 over other morphological techniques such as MRCP. CC is typically DW hyperintense with lower ADC compared with inflamamtory wall thickening (Figures 6, 7). This is potentially useful in the detection of CC on the background of chronic stricturing cholangitis (Figure 8). Page 3 of 18

4 In the author's experience, DWI is extremely helpful in detecting small intraductal (papillary) CC, which are often poorly visualized on morphological sequences (figure 9). Peripheral hyperintensity with central hyponintensity on high -value DWI ("target-sign") has been reported to be a useful sign in differentiating 7 peripheral (mass-forming) CC from hepatocellular carcinoma (Figure 10). DWI has also been shown to be highly sensitive in detecting small ampullary 8 cancers which are often not visualised on morphological images (Figure 11). Pancreas As with biliary duct, pancreatic duct frequently produces malignant and inflammatory lesions with similar clinical and radiological features. DWI has been shown to be highly sensitive and equally accurate in 9,10 detecting small ductal cancer as contrast enhanced MDCT (Figure 12). This is particularly relevant in patients with renal impairment where CT and MR contrast agents are contra-indicated. In contrast, mass forming chronic pancreatitis has been reported to be DW isointense with pancreatic parenchyma and of higher ADC (Figure 13). 11 than cancer A significantly lower ADC has also been reported in auto-immune 12 pancreatitis (AIP) compared with carcinoma. AIP however is typically DW hyperintense and reduction in this hyperintensity correlates well with treatment response with steroid 13. In author's experience, DWI is extremely sensitive in demonstrating intraductal malignant lesions which are often poorly seen on other T2weighted sequences (Figure 14). This is particularly important in cases where contrast is contra-indicated. Pitfalls Page 4 of 18

5 Inflammation, particularly in acute setting, may cause significant restricted diffusion and therefore mimic malignancy (Figure 15). It may also obscure co-existing malignant lesion (Figure 16). Conversely, certain malignant lesions may not exhibit restricted diffusion, either due to small size or well-differentiation 14. Similarly, cystic malignancy with minimal solid component or solid malignancy with significant fluid (eg mucin) component may not show significant restricted diffusion (Figure 17). In these cases, correlation with morphological images is vital to reduce misinterpretations. Images for this section: Fig. 1: A). Coronal SSFSE image shows irregular wall thickening of the gall bladder (arrow) which also contains calculi. A faint T2 hyperintense lesion is also seen in the right liver lobe (arrowhead). B) Corresponding contrast-enhanced venous image shows patchy enhancement of the wall thickening (arrow) and rim enhancement of the liver lesion (arrowhead). C) Corresponding DWI (b=1000) image and D) ADC map (at a lower level) show significant restricted diffusion in the thickened wall (arrow) and the liver lesion (arrowhead). Histology confirmed gall bladder carcinoma with liver metastasis. Page 5 of 18

6 Fig. 2: A). Coronal FFFSE image through the gall bladder shows a fundal soft-tissue mass (arrow). B) Axial contrast-enhanced late arterial image shows patchy enhancement of the fundal mass (arrow). C) Corresponding DWI (b=1000) image shows significant restricted diffusion in the fundal mass (arrow). Surgical histology confirmed invasive carcinoma. Page 6 of 18

7 Fig. 3: A) T2 fat-sat axial image through the gall bladder shows diffuse double-layered GB wall thickening with a thin barely visible hypointense inner layer and a intermediate signal outer later. B) Axial contrast-enhanced venous image shows a double-layered GB wall thickening with a smooth, thin and mildly-enhancing inner layer and a non-enhancing outer layer, in keeping with acute inflammation. C) Corresponding DWI (b=1000) image and D) ADC map do not show significant restricted diffusion in the thickened GB wall. Calculi are also noted. Post-surgical histology confirmed acute cholecystitis. Page 7 of 18

8 Fig. 4: A) T2-fat-sat axial image through the gall bladder shows diffuse double-layered GB wall thickening with a distinct thin hypointense inner layer and a broadened hyperintense outer layer. This is in keeping with wall oedema, probably inflammatory. However, there is an indeterminate intramural hypointense focus (arrow). B) Corresponding axial contrastenhanced delayed image shows smooth enhancement of the inner wall layer relative to the outer layer, in keeping with inflammation. There is delayed enhancement of the intramural focus. C) Corresponding DWI (b=1,000) and D) ADC map show no significant hyperintensity in the diffuse wall thickening. The intramural focus (arrow), however, shows restricted diffusion, suspicious for malignancy. Post-surgical histology confirmed cholecystitis and focal carcinoma. Page 8 of 18

9 Fig. 5: A) Axial T2 fat-sat image through the gall bladder shows no-specific intramural cystic foci, either micro-abscesses or dilated sinuses. B) Corresponding DWI (b=1000) and D) ADC map show restricted diffusion within the contents of these cystic foci, suggestive of purulent fluid. Surgical histology confirmed acute cholecystitis with intramural micro-abscesses. Fig. 6: A) Coronal SSFSE image shows diffuse stricturing of the common hepatic and bile duct with wall thickening. B) Corresponding contrast-enhanced delayed image shows mild enhancement of the thickened wall. C) Axial DWI (b=1000) through the pancreatic head region shows hyperintensity in the thickened biliary wall (arrow). Cholangiocarcinoma was confirmed on ERCP and subsequent histology. Page 9 of 18

10 Fig. 7: A). Coronal reconstructed contrast-enhanced CT image shows diffuse irregular wall thickening of the intra- and extra-hepatic biliary duct. B) SSFSE axial image confirms ductal wall thickening (arrow) which appears T2 hyponintense (arrow). C) Corresponding DWI (b=0) and D) DWI (b=1000) shows no significant restricted diffusion in the thickened wall (arrow). Repeated histology shows a mixture of inflammation and fibrosis. The wall thickening appears stable over 18 months. Page 10 of 18

11 Fig. 8: Past history of oriental cholangio-hepatitis treated with left hepatectomy and hepatico-jejunostomy now presenting with obstructive jaundice. A). Coronal MIP T2-fat sat image shows gross right lobar ductal dilatation. B) Axial contrast-enhanced veous image shows suspicion of ill-defined hypovascular hilar mass obstructing the ducts (arrow). C) Corresponding DWI (b=1000) image shows significant restricted diffusion in the mass (arrow). Surgical histology confirmed hilar cholangiocarcinoma. Fig. 9: A). T2 fat-sat FSE axial image through the liver shows left lobar ductal dilatation with ill-defined intraductal filling defect (arrow)in the left hepatic duct. B) Corresponding contrast-enhanced venous image shows subtle enhancement of the intraductal lesion which is otherwise barely visible (arrow). C) Corresponding DWI (b=1,000) image shows the lesion and the overlying ductal wall (arrow) to be hyperintense in keeping with restricted diffusion, suspicious for malignancy. Histology shows intraductal cholangiocarcinoma. Fig. 10: A)Contrast-enhanced axial arterial phased image shows a mass in right liver lobe with peripheral continuous enhancement. B) Corresponding contrast-enhanced delayed image shows central filling of the mass. C) Corresponding DWI (b=1000) image shows peripheral rim of hyperintensity, giving rise to a "target-sign". Histology confirmed cholangiocarcinoma. Page 11 of 18

12 Fig. 11: A) Coronal SSFSE image shows diffuse dilatation of the common bile duct with no obvious culprit seen. B) Corresponding contrast-enhanced delayed image shows no obvious obstructing lesion either. C) Axial DWI (b=1,000) through the ampullary region shows a small focus of restricted diffusion (arrow), suspicious for a small ampullary malignancy. This was confirmed on ERCP and subsequent histology. Fig. 12: A) Coronal MIP T2-fat sat image shows pancreatic ductal dilatation with abrupt cut-off in the neck/head region (arrow). B) Axial unenhanced T1-fat-sat an illdefined hypointense lesion (arrow) just adjacent to the superior mesenteric vein. C) Corresponding DWI (b=1000) image and D) ADC map shows the lesion to be of significant restricted diffusion (arrow). Histology confirmed carcinoma. Page 12 of 18

13 Fig. 13: A) T2 fat-sat axial image through the pancreas shows ductal dilatation in the tail region, due to a T2 hypointense mass (arrow). B) Corresponding contrast-enhanced late arterial image shows the mass to be hypovascular (arrow). C) Corresponding DWI (b=1000) image shows no restricted diffusion in the mass (arrow). Follow-up imaging does not show progression. The mass is presumed to be due to mass-forming chronic pancreatitis. Fig. 14: A) T2 fat-sat axial image through the pancreas shows diffuse ductal dilatation (arrow). No obvious intraductal or extrinsic mass is seen. B) Corresponding contrastenhanced late arterial image shows the presence of intraductal enhancing mass, expanding the duct (arrow). C) Corresponding DWI (b=1000) image and D) ADC Page 13 of 18

14 map shows significant restricted diffusion in the mass (arrow). Histology shows neuroendocrine (carcinoid) tumour. Fig. 15: A) T2 fat-sat axial image through the gall bladder shows diffuse wall thickening with an invasive fundal mass (arrow) containing intramural hyperintense foci. B) Corresponding contrast-enhanced late arterial image shows avid enhancement of the fundal mass (arrow). C) Corresponding DWI (b=1000) image and D) ADC map show significant restricted diffusion in the fundal mass (arrow), suspicious for malignancy. Histology shows xanthogranulomatous cholecystitis. Page 14 of 18

15 Fig. 16: A) Coronal MIP MRCP image shows dilatation of both common bile duct and main pancreatic duct (double-duct sign). B and C) DWI images (b=1000) shows diffuse hyperintensity throughout the whole pancreas and peri-pancreatic region, in keeping with pancreatitis. No obvious obstructing lesion is seen in the head region. This is because both malignancy and inflammation may cause restricted diffusion. The morphological images (not shown) do not show any obstructing lesion either. Surgical histology showed pancreatic head carcinoma with peri-pancreatic extension. Page 15 of 18

16 Fig. 17: A) T2 fat-sat axial image through the pancreas shows diffuse ductal dilatation, cause by a T2-bright mass in the head region (arrow). B) Corresponding contrastenhanced late arterial image shows faint enhancement of the obstructing mass (arrow). C) Corresponding DWI (b=1000) image and D) ADC map show no significant restricted diffusion in the mass (arrow). Histology showed mucinous non-cystic (colloid) carcinoma. Page 16 of 18

17 Conclusion DWI has been shown to be of great value in aiding the detecting of malignancy lesions in pancreatico-biliary system, including the gall bladder, and their differentiation form benign lesions. This is particular important in cases where contrast is contra-indicated. There are however pitfalls which can be reduced by cross-referencing with morphological images. Personal information References 1) Irie H, Kamochi N, Nojiri J, Egashira Y, Sasaguri K, Kudo S. High b-value diffusionweighted MRI in differentiation between benign and malignant polypoid gallbladder lesions. Acta Radiol. 2011;52(3): ) Kim SJ, Lee JM, Kim H, Yoon JH, Han JK, Choi BI. Role of diffusion-weighted magnetic resonance imaging in the diagnosis of gallbladder cancer. J Magn Reson Imaging. 2013;38(1): ) Lee NK, Kim S, Kim TU, Kim DU, Seo HI, Jeon TY. Diffusion-weighted MRI for differentiation of benign from malignant lesions in the gallbladder. Clin Radiol ) Sugita R, Yamazaki T, Furuta A, Itoh K, Fujita N, Takahashi S. High b-value diffusionweighted MRI for detecting gallbladder carcinoma: preliminary study and results. Eur Radiol. 2009;19(7): ) Cui XY, Chen HW. Role of diffusion-weighted magnetic resonance imaging in the diagnosis of extrahepatic cholangiocarcinoma. World J Gastroenterol. 2010;16(25): ) Cui XY, Chen HW, Cai S, et al. Diffusion-weighted MR imaging for detection of extrahepatic cholangiocarcinoma. Eur J Radiol. 2012;81(11): ) Park HJ, Kim YK, Park MJ, Lee WJ. Small intrahepatic mass-forming cholangiocarcinoma: target sign on diffusion-weighted imaging for differentiation from hepatocellular carcinoma. Abdom Imaging. 2013;38(4): Page 17 of 18

18 8) Jang KM, Kim SH, Lee SJ, Park HJ, Choi D, Hwang J. Added value of diffusion-weighted MR imaging in the diagnosis of ampullary carcinoma. Radiology. 2013;266(2): ) Takakura K, Sumiyama K, Munakata K, et al. Clinical usefulness of diffusion-weighted MR imaging for detection of pancreatic cancer: comparison with enhanced multidetectorrow CT. Abdom Imaging. 2011;36(4): ) Shinya S, Sasaki T, Nakagawa Y, Guiquing Z, Yamamoto F, Yamashita Y. Usefulness of diffusion-weighted imaging (DWI) for the detection of pancreatic cancer: 4 case reports. Hepatogastroenterology. 2008;55(81): ) Fattahi R, BalciNC, Perman WH, et al. Pancreatic diffusion-weighted imaging (DWI): comparison between mass-forming focal pancreatitis (FP), pancreatic cancer (PC), and normal pancreas. J Magn Reson Imaging. 2009;29(2): ) Muhi A, Ichikawa T, Motosugi U, et al. Mass-forming autoimmune pancreatitis and pancreatic carcinoma: differential diagnosis on the basis of computed tomography and magnetic resonance cholangiopancreatography, and diffusion-weighted imaging findings. J Magn Reson Imaging. 2012;35(4): ) Taniguchi T, Kobayashi H, Nishikawa K, et al. Diffusion-weighted magnetic resonance imaging in autoimmune pancreatitis. Jpn J Radiol. 2009;27(3): ) Fukukura Y, Takumi K, Kamimura K, et al. Pancreatic Adenocarcinoma: Variability of Diffusion-weighted MR Imaging Findings. Radiology Page 18 of 18