Visualization of multistep hepatocarcinogenesis using various imaging biomarkers

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1 Visualization of multistep hepatocarcinogenesis using various imaging biomarkers Award: Certificate of Merit Poster No.: C-0120 Congress: ECR 2014 Type: Educational Exhibit Authors: S. Kobayashi, T. Gabata, O. Matsui, W. Koda, T. Minami, K. Kozaka, A. Kitao, N. Yoneda, K. Yoshida; Kanazawa/JP Keywords: Abdomen, Liver, CT, MR, Contrast agent-intravenous, Hemodynamics / Flow dynamics, Cancer, Cirrhosis DOI: /ecr2014/C-0120 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 44

2 Learning objectives To describe the detail of various imaging biomarkers of multistep hepatocarcinogenesis. To review the molecular mechanism of Gd-EOB-DTPA as surrogate marker of multistep hepatocarcinogenesis. To provide the overview of detecterbility of multistep hepatocarcinogenesis on various imaging biomarkers Images for this section: Fig. 22: Schematic diagram of transporter expression and mechanism of EOB dynamics in HCC. Page 2 of 44

3 Fig. 23: OATP1B3 expression, EOB uptake and multistep hepatocarcinogenesis (1) Page 3 of 44

4 Fig. 24: OATP1B3 expression, EOB uptake and multistep hepatocarcinogenesis (2) Page 4 of 44

5 Background Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver and the third leading cause of cancer death worldwide. It is well known that HCC develops stepwise manner from low-grade dysplastic nodule to overt HCC, and this process is called multistep hepatocarcinogenesis. Current imaging modalities enable us to visualize the multistep-hepatocarcinogenesis process from various aspects, such as hemodynamic, Kupffer cellular functional and membranous transporter functional aspect. In this exhibit, we are going to review the state-of-art imaging diagnosis methods of multistep hepatocarcinogenesis from various biological aspects, especially focused on Gd-EOB-DTPA, which is newest molecular imaging biomarker of multistephepatocarcinogenesis reflects the cellular membranous transporter function. Images for this section: Page 5 of 44

6 Fig. 1: Schematic diagram of multistep hepatocarcinogenesis. Two types of human hepatocarcinogenesis are currently considered, one is de novo hepatocarcinogenesis and the other is the stepwise development from dysplastic nodule to HCC. Page 6 of 44

7 Fig. 6: Multi-step hepatocarcinogenesis and changes of intranodular blood supply. Page 7 of 44

8 Fig. 20: SPIO enhanced hepatocarcinogenesis. T2-WI signal intensity change during Multistep Page 8 of 44

9 Findings and procedure details (1) Basic knowledge of multistep hepatocarcinogenesis Current concept of human hepatocarcinogenesis are consisted of two types, one is de novo hepatocarcinogenesis and the other is multistep hepatocarcinogenesis (1,2). Fig. 1: Schematic diagram of multistep hepatocarcinogenesis. Two types of human hepatocarcinogenesis are currently considered, one is de novo hepatocarcinogenesis and the other is the stepwise development from dysplastic nodule to HCC. References: Sakamoto M. Hum Pathol (1991) 22: In multistep hepatocarcinogensis process, the nodule shows stepwise development from high-grade DN, high-grade DN with well-differentiated HCC foci, early HCC (highly well- Page 9 of 44

10 differentiated HCC) to moderately or poorly differentiated HCC. The histological features of these hepatocellular nodules are sequential. The International Consensus Group for Hepatocellular Neoplasia organized by the world's leading liver pathologists published consensus report of the definition of these nodules on 2009 (3). Fig. 2: Clinical and pathological correlations of Small nodular lesions in cirrhotic liver. References: Hepatology (2009) 49; L-DNs are vaguely or distinct nodule with mild increase in cell density and no cytological atypia. H-DNs are more likely to show a vaguely nodular pattern with architectural and/or cytological atypia, but the atypia is insufficient for a diagnosis of HCC. Unpaired arteries are found in most lesions, but usually not in great numbers. Page 10 of 44

11 A nodule with largely H-DN features containing a subnodule of well-differentiated HCC can be seen. Early HCCs show vaguely nodular pattern and are characterized by various combinations of the following major histologic features; Increased cell density more than two times that of the surrounding tissue, with an increased nuclear/cytoplasm ratio and irregular thin-trabecular pattern Varying numbers of portal tracts within the nodule (intratumoral portal tracts) Pseudo glandular pattern diffuse fatty change Varying numbers of unpaired arteries Any of the features listed above may be diffused throughout the lesion or may be restricted to an expansile subnodule (nodule-in-nodule). Because all of these features may also be found in H-DNs, it is important to note that stromal invasion remains most helpful in differentiating early HCC from H-DNs. Progressed HCC has a distinctly nodular pattern and is mostly moderately differentiated, often with evidence of microvascular invasion. However, the application of these criteria is challenging because most histologic criteria are arrayed on a gradual spectrum and cannot be easily summarized as present or absent. Because of these reasons, we should note that there must be various degree of overlaps among imaging features of these nodules and they may show gradual changes during multi-step hepatocarcinogenesis. (2) Imaging approach of multistep hepatocarcinogenesis from haemodynamic aspect. (I) Sequential changes of feeding vessels and intranodular blood supply during multistep hepatocarcinogenesis Histologically, there were three types of the feeding vessels in hepatocellular nodules during multistep hepatocarcinogenesis, namely, normal portal vein and hepatic artery Page 11 of 44

12 included in the portal tracts and unpaired artery (abnormal artery) not accompanied by bile duct (4, 5). Fig. 3: Histological features of three types of feeding vessels in hepatocellular nodules during multistep hepatocarcinogenesis. References: Radiology - Kanazawa/JP Portal tracts including portal vein and hepatic artery were decreased in accordance with increasing grade of nodular malignancy and virtually absent in HCC. In contrast, abnormal arteries due to tumor angiogenesis developed in atypical AH (high-grade DN) during the course of hepatocarcinogenesis, and were markedly increased in number in moderately differentiated HCC. Computed tomography during intra-arterial injection of contrast medium (angiography assisted CT) includes CT during arterial portography (CTAP) and CT during hepatic arteriography (CTHA) are precise method to evaluate intranodular blood supply in the Page 12 of 44

13 liver, and in spite of its invasiveness, these examinations are widely performed for mainly pre-operative evaluation of hepatic tumors in Japan (6). Fig. 4: CT during arterial portography (CTAP) References: Radiology - Kanazawa/JP Page 13 of 44

14 Fig. 5: CT during hepatic arteriography (CTHA) References: Radiology - Kanazawa/JP The intranodular blood supply evaluated by CTAP and CTHA changes in accordance with the progression of human hepatocarcinogenesis, from DN to overt HCC (7,8). Page 14 of 44

15 Fig. 6: Multi-step hepatocarcinogenesis and changes of intranodular blood supply. References: Matsui O, et al. Abdom Imaging (2011) 36: In accordance with the grade of malignancy of the nodules, intranodular portal blood supply gradually decreased, and almost completely disappeared in the moderately or poorly differentiated HCC. On the other hand, intranodular arterial supply first decreased in DN and borderline lesions, and then acutely increased in accordance with the elevation of the grade of malignancy, and finally markedly increased in moderately differentiated HCC. Page 15 of 44

16 Fig. 7: Intranodular blood supply in hepatocellular nodules associated with cirrhosis in accordance with increasing grades of malignancy. References: Radiology - Kanazawa/JP (II) The relationship between the intranodular blood supply and the prognosis of hepatocellular nodules There is a close correlation between the prognosis of the nodules and the intranodular blood supply. (9) Page 16 of 44

17 Fig. 8: Progress rate from borderline lesion to hypervascular HCC. References: Radiology - Kanazawa/JP In nodules with almost the same intranodular portal and arterial supply relative to the surrounding liver, no transformation to entirely hypervascular HCC (defined as malignant transformation) was seen within approximately 900 days. On the other hand, almost all nodules with partially absent intranodular portal supply or partially increased intranodular arterial supply, and approximately 20-30% of those with decreased but not absent intranodular portal supply or decreased arterial supply, showed malignant transformation within the same periods. Before hypovascular borderline nodules transformed to entirely hypervascular HCC, a small spot with increased arterial supply on CTHA appeared within the hypovascular nodule. So, the detection of a hypervascular spot in a hypovascular nodule is essential both to predict the prognosis of the nodule and to start treatment in early stage of hypervascular HCC. Page 17 of 44

18 Fig. 9: Example of hypervascular spot in a hypovascular nodule on angiography assisted CT. References: Radiology - Kanazawa/JP Usually, on the arterial dominant phase of dynamic CT or MRI, DN shows no definite stain. However, when a small focus of enhancement is demonstrated in a hypovascular nodule, it should be treated as overtly malignant, because this finding correspond to small hypervascular spot within hypovascular borderline lesion on CTHA. Dynamic CT using multidetector CT and/or multislice dynamic MRI is useful to find out hypervascular spot within hypovascular nodule, and a focus more than 5 mm in diameter can be seen (10). Page 18 of 44

19 Fig. 10: Detectability of definite increased arterial flow spot (hypervascular foci) within decreased arterial flow nodule with various imaging modalities. References: Radiology - Kanazawa/JP Page 19 of 44

20 Fig. 11: Multistep hepatocarcinogenesis on angiography assisted CT and multiphasic contrast enhanced CT. References: Radiology - Kanazawa/JP (III) Multi-step changes of drainage flow during hepatocarcinogenesis To evaluate in vivo hemodynamics of hypervascular classical HCC we use single level dynamic CTHA. With this method, we can visualize the arterial blood flow into the tumor drains into surrounding hepatic sinusoids (corona enhancement) (11-13). Corona enhancement, which reflects the drainage area of HCC, was well visualized in the late phase of CTHA which was taken after the stoppage of the infusion of the contrast medium into the hepatic artery. Page 20 of 44

21 Histological examination revealed continuity between a tumor sinusoid and a portal venule in the pseudo capsule (encapsulated HCC) or surrounding hepatic sinusoids (HCC without pseudo capsule) [5, 12]. Fig. 12: Schematic diagram of blood supply, drainage flow and corona enhancement of hyparvascular HCC. References: Radiology - Kanazawa/JP Page 21 of 44

22 Fig. 13: Drainage pathway of moderately differentiated HCC observed on histopathological specimen. References: Radiology - Kanazawa/JP According to the histological study correlated with CTAP and CTHA, the main drainage vessels of hepatocellular nodules change from hepatic veins to hepatic sinusoids and then to portal veins during multi-step hepatocarcinogenesis, mainly due to disappearance of the hepatic veins from the nodules [5]. Page 22 of 44

23 Fig. 14: Multi-step changes of drainage vessels and peritumoral enhancement during hepatocarcinogenesis. References: Radiology - Kanazawa/JP Therefore, in early HCC, no perinodular corona enhancement is seen on portal to equilibrium phase CT, but it is definite in hypervascular classical HCC. Corona enhancement is thicker in encapsulated HCC and thin in HCC without pseudo capsule. The drainage flow from hypervascular HCC variously modified the imaging findings, a feature useful for differential diagnosis. Drainage flow from the tumor makes the tumor appear larger than it really is on various kinds of blood flow imaging findings. Page 23 of 44

24 Drainage area might be the first site of the intrahepatic metastasis of HCC, and daughter nodules are commonly seen in this area. Iodized oil flowed into the surrounding liver through this drainage route and enhanced the effect of transcatheter arterial chemoembolization [14]. Fig. 15: Hemodynamics of hyparvascular HCC and mechanism of intrahepatic metastasis. References: Radiology - Kanazawa/JP The drainage area should be included in RFA area to prevent local recurrence. Page 24 of 44

25 Fig. 16: Intrahepatic metastasis observed in the drainage area of hypervascular HCC. References: Radiology - Kanazawa/JP (3) Imaging approach of multistep hepatocarcinogenesis from the aspect of nodular signal intensities of T1 and T2-weighted MRI. Borderline lesions, such as DN, usually showed hypointensity relative to the surrounding cirrhotic liver on T2-weighted images (15). On the other hand, almost all moderately differentiated HCC demonstrated hyperintensity (16). Well-differentiated HCC demonstrated a strong tendency to show isointensity. Page 25 of 44

26 Fig. 17: MR signal intensity change during Multistep hepatocarcinogenesis. References: Radiology - Kanazawa/JP The reason why borderline lesions or early HCC show hypointensity on T2-weighted images is unknown. It may be probably due to decreased intranodular sinusoids induced by hyperplastic changes of hepatocytes (16). Malignant foci in borderline lesions can be seen as more hyperintense spots. This finding is clinically important as a sign of definite malignant transformation of the nodule. On T1-weighted images, almost all borderline lesions and the majority of welldifferentiated HCC show hyperintensity. The hyperintensity on T1-weighted images was due to fat deposition in one-third of cases; however, in the remaining two-thirds, the reason was unknown. Page 26 of 44

27 (4) Imaging approach of multistep hepatocarcinogenesis from Kupffer cell functional aspect. Fig. 18: Schematic diagram of the liver structure. References: Radiology - Kanazawa/JP Page 27 of 44

28 Fig. 19: Behavior of the SPIO in the liver. References: Radiology - Kanazawa/JP Imai et al. reported that the ratio of the intensity of tumorous lesion to that of nontumorous area on SPIO-enhanced MR images (SPIO intensity ratio) correlated inversely with Kupffer-cell-count ratio in HCCs and dysplastic nodules, and increased as the degree of differentiation of HCCs decreased, indicating that the uptake of SPIO in HCCs decreased as the degree of differentiation of HCCs declined (17). Page 28 of 44

29 Fig. 20: SPIO enhanced T2-WI signal intensity change during Multistep hepatocarcinogenesis. References: Radiology - Kanazawa/JP And they concluded that SPIO-enhanced MR imaging reflects Kupffer-cell numbers in HCCs and dysplastic nodules, and is useful for estimation of histological grading in HCCs, although uncertainties persist in differentiating dysplastic nodules from well-differentiated HCCs. (5) Imaging approach of multistep hepatocarcinogenesis membranous transporter functional aspect. from cellular (I) Significance of Gd-EOB-DTPA Gd-EOB-DTPA (EOB) is a recently developed hepatobiliary-specific contrast material for magnetic resonance (MR) imaging that has high sensitivity in the detection of malignant liver tumors (18-25). Page 29 of 44

30 Because EOB is taken up by hepatocytes and then excreted into the bile ducts (26), hepatic focal lesions without normal hepatobiliary function can be definitively depicted as hypointense areas compared with the well-enhanced hyperintense background liver in the hepatobiliary phase of EOB-enhanced MR imaging (18,27). Fig. 21: Behavior of the EOB in the liver. References: Radiology - Kanazawa/JP In addition, EOB can be used in the same way as gadopentetate dimeglumine to evaluate the hemodynamics of hepatic lesions in the dynamic phase after an intravenous bolus injection (18, 19, 21-23). (II) Mechanism of hepatocellular uptake of EOB Page 30 of 44

31 Kitao et al. (28) performed an imaging-molecular-pathologic correlation study to compare HCCs that were hypointense to surrounding liver with those that were iso- or hyperintense on hepatobiliary phase of EOB enhanced MRI. And they revealed that the expression of the uptake transporter organic anion transporting polypeptide (OATP)1B3 (synonym of OATP8) and the export transporter MRP3 in HCC cells significantly correlated with the Signal intensity of HCCs in the hepatobiliary phase of EOB enhanced MRI. In human HCC cells, OATP1B3 and MRP3 are probably the uptake transporter and export transporter of EOB, respectively. Fig. 22: Schematic diagram of transporter expression and mechanism of EOB dynamics in HCC. References: Kitao A, et al. Radiology (2010) 256: (III) EOB uptake during hepatocarcinogenesis Page 31 of 44

32 Kitao et al. (29) clarified that the OATP1B3 expression significantly decreased during multistep hepatocarcinogenesis and correlated with the continuous decrease in the enhancement ratio. Fig. 23: OATP1B3 expression, EOB uptake and multistep hepatocarcinogenesis (1) References: Radiology - Kanazawa/JP The expression of uptake transporter OATP1B3 significantly decreases during multistep hepatocarcinogenesis, which might explain the decrease in the enhancement ratio of hepatocellular nodules in the hepatobiliary phase of EOB-enhanced MR imaging. Page 32 of 44

33 Fig. 24: OATP1B3 expression, EOB uptake and multistep hepatocarcinogenesis (2) References: Radiology - Kanazawa/JP Calculating the enhancement ratio in the hepatobiliary phase using the static T1 values may be useful for estimating the grade of malignancy of hepatocellular nodules. (IV) Biologic Features of HCC and Signal Intensity on EOB-enhanced MRI Kitao et al. (30) revealed that hyperintense HCCs on hepatobiliary phase of EOBenhanced MRI showed significantly higher differentiation grades, less frequent portal vein invasion, and lower recurrence rates than did hypointense HCCs. Moreover, hyperintense HCCs showed significantly lower expression of AFP and PIVKAII than did hypointense HCCs. Page 33 of 44

34 Fig. 25: Biologic features and signal intensity on EOB-enhanced MRI of hypervascular HCC. References: Kitao A. Radiology (2012) 265: Hyperintense HCCs on hepatobiliary phase of EOB-enhanced MRI may be a particular form of hypervascular HCC with biologically less aggressive features than those of hypointense HCCs. Images for this section: Page 34 of 44

35 Fig. 6: Multi-step hepatocarcinogenesis and changes of intranodular blood supply. Page 35 of 44

36 Fig. 14: Multi-step changes of drainage vessels and peritumoral enhancement during hepatocarcinogenesis. Page 36 of 44

37 Fig. 17: MR signal intensity change during Multistep hepatocarcinogenesis. Page 37 of 44

38 Fig. 20: SPIO enhanced hepatocarcinogenesis. T2-WI signal intensity change during Multistep Page 38 of 44

39 Fig. 23: OATP1B3 expression, EOB uptake and multistep hepatocarcinogenesis (1) Page 39 of 44

40 Conclusion Knowledge of imaging diagnosis methods about multistep hepatocarcinogenesis from various biological aspects, especially focused on Gd-EOB-DTPA, might be important for distinguish HCC from various kinds of hepatocellular nodules under hepatocarcinogenesis process. Fig. 26: Detectability of multistep hepatocarcinogenesis on various imaging biomarkers. References: Radiology - Kanazawa/JP Personal information Satoshi Kobayashi, MD, PhD Page 40 of 44

41 Dept. of Radiology Graduate School of Medical Science Kanazawa University References 1) Arakawa M, Kage M, Sugihara S et al. Emergence of malignant lesions within an adenomatous hyperplastic nodule in a cirrhotic liver. Observations in five cases. Gastroenterology 1986; 91: ) Sakamoto M, Hirohashi S, Shimosato Y. Early stages of multistep hepatocarcinogenesis: adenomatous hyperplasia and early hepatocellular carcinoma. Hum Pathol 1991; 22: ) International Consensus Group for Hepatocellular Neoplasia. Pathologic diagnosis of early hepatocellular carcinoma: a report of the international consensus group for hepatocellular neoplasia. Hepatology 2009; 49: ) Ueda K, Terada T, Nakanuma Y, Matsui O. Vascular supply in adenomatous hyperplasia of the liver and hepatocellular carcinoma: a morphometric study. Hum Pathol 1992; 23: ) Kitao A, Zen Y, Matsui O, Gabata T, Nakanuma Y. Hepatocarcinogenesis: multistep changes of drainage vessels at CT during arterial portography and hepatic arteriographyradiologic-pathologic correlation. Radiology 2009; 252: ) Matsui O, Gabata T, Kobayashi S, et al. Imaging of multistep human hepatocarcinogenesis. Hepatol Res. 2007; 37 Suppl 2: S ) Hayashi M, Matsui O, Ueda K, et al. Correlation between the blood supply and grade of malignancy of hepatocellular nodules associated with liver cirrhosis: evaluation by CT during intraarterial injection of contrast medium. Am J Roentgenol 1999; 172: ) Matsui O, Kadoya M, Kameyama T, et al. Benign and malignant nodules in cirrhotic livers: distinction based on blood supply. Radiology 1991; 178: Page 41 of 44

42 9) Hayashi M, Matsui O, Ueda K, Kawamori Y, Gabata T, Kadoya M. Progression to hypervascular hepatocellular carcinoma: correlation with intranodular blood supply evaluated with CT during intraarterial injection of contrast material. Radiology. 2002; 225: ) Shinmura R, Matsui O, Kobayashi S et al. Cirrhotic nodules: association between MR imaging signal intensity and intranodular blood supply. Radiology 2005; 237: ) Terayama N, Matsui O, Ueda K, et al. Peritumoral rim enhancement of liver metastasis: hemodynamics observed on single-level dynamic CT during hepatic arteriography and histopathologic correlation. J Comput Assist Tomogr 2002; 26: ) Ueda K, Matsui O, Kawamori Y, et al. Hypervascular hepatocellular carcinoma: evaluation of hemodynamics with dynamic CT during hepatic arteriography. Radiology 1998; 206: ) Matsui O, Kobayashi S, Sanada J, et al. Hepatocelluar nodules in liver cirrhosis: hemodynamic evaluation (angiography-assisted CT) with special reference to multi-step hepatocarcinogenesis. Abdom Imaging. 2011; 36: ) Terayama N, Matsui O, Gabata T, et al. Accumulation of iodized oil within the nonneoplastic liver adjacent to hepatocellular carcinoma via the drainage routes of the tumor after transcatheter arterial embolization. Cardiovasc Intervent Radiol 2001; 24: ) Kadoya M, Matsui O, Takashima T, Nonomura A. Hepatocellular carcinoma: correlation of MR imaging and histopathologic findings. Radiology 1992; 183: ) Matsui O, Kadoya M, Kameyama T et al. Adenomatous hyperplastic nodules in the cirrhotic liver: differentiation from hepatocellular carcinoma with MR imaging. Radiology 1989; 173: ) Imai Y, Murakami T, Yoshida S, et al. Superparamagnetic iron oxide-enhanced magnetic resonance images of hepatocellular carcinoma: correlation with histological grading. Hepatology 2000; 32: Page 42 of 44

43 18) Vogl TJ, Kümmel S, Hammerstingl R, et al. Liver tumors: comparison of MR imaging with Gd-EOB-DTPA and Gd-DTPA. Radiology 1996; 200: ) Huppertz A, Balzer T, Blakeborough A, et al. Improved detection of focal liver lesions at MR imaging: multicenter comparison of gadoxetic acid-enhanced MR images with intraoperative findings. Radiology 2004; 230: ) Bluemke DA, Sahani D, Amendola M, et al. Efficacy and safety of MR imaging with liver-specific contrast agent: U.S. multicenter phase III study. Radiology 2005; 237: ) Huppertz A, Haraida S, Kraus A, et al.. Enhancement of focal liver lesions at gadoxetic acid-enhanced MR imaging: correlation with histopathologic findings and spiral CT-initial observations. Radiology 2005; 234: ) Zech CJ, Herrmann KA, Reiser MF, Schoenberg SO. MR imaging in patients with suspected liver metastases: value of liver-specific contrast agent Gd-EOB-DTPA. Magn Reson Med Sci 2007; 6: ) Reimer P, Schneider G, Schima W. Hepatobiliary contrast agents for contrastenhanced MRI of the liver: properties, clinical development and applications. Eur Radiol 2004; 14: ) Saito K, Kotake F, Ito N, et al. Gd-EOB-DTPA enhanced MRI for hepatocellular carcinoma: quantitative evaluation of tumor enhancement in hepatobiliary phase. Magn Reson Med Sci 2005; 4: ) Kogita S, Imai Y, Okada M et al. Gd-EOB-DTPA-enhanced magnetic resonance images of hepatocellular carcinoma: correlation with histological grading and portal blood flow. Eur Radiol 2010; 20: ) Schuhmann-Giampieri G, Schmitt-Willich H, Press WR, Negishi C, Weinmann HJ, Speck U. Preclinical evaluation of Gd-EOB-DTPA as a contrast agent in MR imaging of the hepatobiliary system. Radiology 1992; 183: ) Hamm B, Staks T, Mühler A, et al. Phase I clinical evaluation of Gd-EOB-DTPA as a hepatobiliary MR contrast agent: safety, pharmacokinetics, and MR imaging. Radiology. 1995; 195: Page 43 of 44

44 28) Kitao A, Zen Y, Matsui O, et al. Hepatocellular carcinoma: signal intensity at gadoxetic acid-enhanced MR Imaging--correlation with molecular transporters and histopathologic features. Radiology. 2010; 256: ) Kitao A, Matsui O, Yoneda N, et al. The uptake transporter OATP8 expression decreases during multistep hepatocarcinogenesis: correlation with gadoxetic acid enhanced MR imaging. Eur Radiol. 2011; 21: ) Kitao A, Matsui O, Yoneda N, et al. Hypervascular hepatocellular carcinoma: correlation between biologic features and signal intensity on gadoxetic acid-enhanced MR images. Radiology. 2012; 265: Page 44 of 44