Hepatobiliary MR imaging with gadolinium-based contrast agents

Abstract

The advent of gadolinium-based "hepatobiliary" contrast agents offers new opportunities for diagnostic magnetic resonance imaging (MRI) and has triggered great interest for innovative imaging approaches to the liver and bile ducts. In this review article we discuss the imaging properties of the two gadolinium-based hepatobiliary contrast agents currently available in the U.S., gadobenate dimeglumine and gadoxetic acid, as well as important pharmacokinetic differences that affect their diagnostic performance. We review potential applications, protocol optimization strategies, as well as diagnostic pitfalls. A variety of illustrative case examples will be used to demonstrate the role of these agents in detection and characterization of liver lesions as well as for imaging the biliary system. Changes in MR protocols geared toward optimizing workflow and imaging quality are also discussed. It is our aim that the information provided in this article will facilitate the optimal utilization of these agents and will stimulate the reader's pursuit of new applications for future benefit.

Figure 1

Suggested liver imaging protocol overview for gadoxetic acid (Gd-EOB-DTPA) and gadobenate dimeglumine (Gd-BOPTA). Conventional T2w and DWI imaging can be performed after the administration of gadoxetic acid during the period prior to 20 minute delayed imaging. Note that post-contrast DWI imaging can alter quantitative estimates of the apparent diffusion coefficient (ADC), although has minimal impact on qualitative DWI imaging. Heavily T2w MRCP should always be performed prior to the administration of contrast, particularly gadoxetic acid.

Figure 2

Characteristic enhancement patterns of a FNH using gadoxetic acid (top row) and gadobenate dimeglumine (lower row) in a 37 year-old woman imaged on two different dates. Note the hyperintensity of the scar on T2w images (white open arrows). The intense arterial hyper-enhancement of the FNH is followed by rapid equilibration during the portal venous and early delayed images. Note the hyper-enhancement of the scar on gadobenate dimeglumine 6 minute images (black open arrows) related to the extracellular behavior of gadobenate dimeglumine on this time scale, in comparison the relative hypointensity with gadoxetic acid (*) due to the intense uptake of gadolinium into hepatocytes at this time. The scar finally shows relative hypointensity on delayed images with both agents, while the main lesion is isointense to the adjacent liver parenchyma.

Figure 3

Characterization of a hepatic adenoma using gadoxetic acid (Gd-EOB-DTPA, top row) and gadobenate dimeglumine (Gd-BOPTA, lower row) in a 51 year-old woman presenting for follow-up of liver lesions. Multiple hepatic adenomas were found. Slight hyperintensities in precontrast T2w are non-specific. Arterial and portal venous enhacement, lack of a central scar, and delayed hypointensity help to differentiate the hepatic adenoma from a FNH. Note the marked, relative hypointensity of the adenoma using gadoxetic during the specific hepatobiliary phase as opposed gadobenate dimeglumine mirroring the pharmacocinetics of both agents. At 6 minutes, gadobenate dimeglumine still shows slight hyperintensity, and the delayed phase is iso- to hypointense.

Figure 4

Detection and characterization of HCC using gadoxetic acid. Images from this 68 year-old male with known multifocal HCC include findings after chemotherapy and TACE procedure. Two hypointense lesions are seen on pre-contrast and delayed T1w images (B, E, F): The white open arrow indicates the untreated HCC with characteristic T2w hyperintensity, intense arterial enhancement, and rapid portal venous phase washout. N indicates a necrotic area after radiofrequency ablation (RFA). Note the wedge-shaped perfusion deficit (white arrowheads) associated with a thrombosis of the right portal vein (not shown). Also note the contrast in the biliary tract, on 20 minute post-contrast images (E) using gadoxetic acid as compared to figs. 1 and 3.

Figure 5

Findings in a rare case of fibrolamellar HCC evaluated with gadobenate dimeglumine in a 42 year-old male with elevated liver function tests and jaundice. This enormous liver tumor demonstrated heterogeneous pre-contrast T2w and T1w signal properties. The solid components of the tumor showed a similar rapid arterial contrast enhancement and portal venous wash-out as the HCC lesion in figure 5. The radial septae with progressive delayed enhancement (E, F) mirror the fibrous components of this tumor. Also note the contrast in the dilated biliary duct in the posterior right lobe on the 120 minute image (white arrows).

Figure 6

Gadoxetic acid for the characterization of a cavernous hemangioma. Relative hypointensity on delayed images (C) is caused by the relative hyperenhancement of the liver. Note that the signal intensity of the hemangioma parallels that in the aorta on all T1w contrast enhanced images including the 20 minute delayed image. This finding is contrary to the typical hyperintensity on delayed images using gadobenate dimeglumine (Figure 7), but is easily explained by the known pathophysiology of hemangiomas and the pharmacokinetics of gadoxetic acid. The dynamic phase images (B, arterial phase [dur] only) depict the characteristic contrast enhancement pattern of cavernous hemangiomas with centripetally progressing enhancement.

Figure 7

Cavernous hemangioma and simple cyst depicted using gadobenate dimeglumine. 56 year-old female referred to MR with multiple indeterminate lesions and history of uterine cancer. The cyst is easily characterized by its “light bulb” bright appearance on T2w images and lack of enhancement on post-contrast images. The cavernous hemangioma shows slightly lower T2w hyperintensity, and centripetal contrast enhancement (open black arrows). Note near isointensity of the hemangioma on the 80 minute delayed gadobenate dimeglumine images as opposed to relative hypointensity using gadoxetic acid (Figure 6).

Figure 8

Characterization of a cholangiocarcinoma using gadobenate dimeglumine. In this 80yo female an intrahepatic CC with characteristic pre-contrast imaging findings, rapid T1w contrast enhancement and portal venous washout was depicted. Slight capsular enhancement can be appreciated (D) consistent with either compressed neovasculature or fibrous tissue. Of special note is the isointensity of the CC in the delayed phase (18min, F) compared to the relative hypointensity when imaging with gadoxetic acid (Figure 9).

Figure 9

Large necrotic cholangiocarcinoma depicted using gadoxetic acid. Findings in this 81yo female show the 6-month progression of the disease (same patient as that shown in Figure 8) with marked dilation of left lobar biliary ducts (white arrows, insert in A). The viable portions of the CC (white arrowheads) demonstrate the characteristic enhancement pattern. The central tumor necrosis (N) has progressed (increased T2w signal in A) and there is progressive peripheral enhancement of fibrous components. Importantly, the CC shows relative hypointensity to liver tissue on delayed images (F). Note that there is no excretion in the left biliary ducts at 20min high-resolution images, probably due to biliary obstruction. Please also note the subtle geographical hypointensity in the vicinity of the tumor at 20min, most likely due to segmental portal vein thromboses (not shown).

Figure 10

Metastatic disease imaged with gadoxetic acid in a 73 year old female with known rectal carcinoma. Typical enhancement patterns of a hypo-vascular metastasis can be appreciated: slight hyper-intensity on T2w images, marked hypointensity on T1w pre contrast, peripherally dominant and slow central enhancement leading to the previously described ‘target sign’ with marked hyperintensity on the 120min hepatobiliary phase. A small cyst (*) is also noted, adjacent to the lesion of interest.

Figure 11

Enhancement patterns of breast cancer metastasis using gadobenate dimeglumine in a 43 year-old female. Characteristic hyperintensity on T2w images and hypointensity of metastases is seen on pre-contrast T1w and delayed phase. Owing to hypervascularity, the metastasis follows the enhancement pattern of the blood pool.

Figure 12

Characteristic hypointense appearance of metastases using gadoxetic acid in a 53 year-old male with a metastatic sacral chordoma. Although a rare metastasis to the liver, some metastases, such as the chordoma, maintain the signal properties of the original tumor. In this chordoma metastasis, the lobulated T2w hyperintense appearance and the lack of contrast enhancement is similar to other metastatic lesions to the liver.

Figure 13

T1w MR cholangiography using gadobenate dimeglumine (B) in comparison to T2w MRCP (A). Both techniques demonstrate the right posterior duct branching into the left hepatic biliary duct (white arrow). In this 30yo female with cholecystectomy, T1w MRC proves the patency of the anastomosis by contrast passage to the duodenum. (*) indicates the pancreatic duct which cannot be visualized with hepatobiliary GBCA. Both methods provide anatomical information, while the T1w MRC also provides functional information demonstrating the patency of the sphincter of Oddi.

Figure 14

Gadoxetic acid for T1w MRC in a 35-year-old male with ulcerative colitis. Subtle, alternating strictures and beading are with both T2w MRCP (A) and T1w MRC (B). Note the apparent stenosis in B (open white arrows) that is caused by layering of contrast in the dilated duct (see cross-sectional magnifications in C). Asterisks indicate slightly dilated bile ducts not seen by T2w MRCP due to incomplete coverage by the limited slab thickness of the MRCP.

Figure 15

Beaded appearance of the biliary tract imaged with gadoxetic acid in a 44yo male with known primary sclerosing cholangitis (PSC). Although the high liver signal limits the ability to fully appreciate MIP representations of the bile ducts in the same manner as MRCP, the axial detail allows for identification of biliary duct irregularities PSC with exquisite detail.

Figure 16

Bile leak in a 53 year-old after laparoscopic cholecystectomy using gadoxetic acid. (A) T2w MRCP with the cystic duct remnant (*) and a surgical drainage pigtail catheter (‡) placed in the gallbladder fossa. Axial T2w imaging (B) shows postsurgical fluid collection in the fossa (white arrow). 30min after injection of gadoxetic acid, there is contrast agent accumulation in the fossa (white open arrow, C). (D) shows contrast within the pigtail catheter (‡). The T1w MRC MIP in (E) demonstrated an abrupt termination of the contrast column in the common duct superior to the level at which the contrast leaks entirely into the gall bladder fossa and subsequently into the pigtail drainage catheter. This example demonstrates the advantage of the functional information that can be obtained using hepatobiliary agents. CHD = common hepatic duct; PD = pancreatic duct; RLBD and LLBD = right and left biliary duct, respectively.