Hepatobiliary MRI: current concepts and controversies

Intrahepatic bile duct variation: MR cholangiography and implication in hepatobiliary surgery

Background

The aim of this study was to assess the prevalence of biliary anatomical variants using 3-T MR cholangiography (MRC) with its impact in reduction of the complication of hepatobiliary surgical techniques.

Results

MRC was applied to 120 subjects (24 potential liver donors and 96 volunteers) and the right posterior hepatic duct insertion was documented, and accordingly, the biliary variants were classified based on Huang classification (Huang et al, Transplant Proc 28: 1669–1670, 1996).

Biliary anatomic variants were divided based on Huang classification: Huang A1, 65.83% (n = 79); Huang A2, 11.67% (n = 14); Huang A3, 13.3% (n = 16); Huang A4, 7.5% (n = 9); and Huang A5, 1.67% (n = 2). The total frequency for A2, A3, A4, and A5 was 34.17% (n = 41). The distance between RPHD insertion and the junction of right and left hepatic ducts (L) was measured, and Huang A1 cases were then subtyped into S1 subtype (L > 1 cm) and S2 subtype (L ≤ 1 cm). We had 52 subjects with subtype S1 (43.33%) and 27 subjects with subtype S2 (22.5%).

Twenty-three subjects had bile duct exploration or intraoperative cholangiograms and showed Huang type A1 in 14 (60.87%), type A2 in 3 (13.05%), and type A3 in 6 (26.08%). Twenty-two (95.65%) had the same classification in MRC and intraoperative while only one case (4.35%) was considered as A2 at MRC but the intraoperative classification was Huang A3, which was attributed to the insertion of the RPHD insertion at the distal end of the left hepatic duct.

Conclusion

MRC is an accurate tool for biliary tract mapping before hepatobiliary surgery to provide excellent identification of biliary variants which can reduce the incidence of biliary complications.

Nephrogenic systemic fibrosis risk after liver magnetic resonance imaging with gadoxetate disodium in patients with moderate to severe renal impairment: results of a prospective, open-label, multicenter study

Objective

The objective of this study was to assess the risk of gadoxetate disodium in liver imaging for the development of nephrogenic systemic fibrosis (NSF) in patients with moderate to severe renal impairment.

Materials and Methods

We performed a prospective, multicenter, nonrandomized, open-label phase 4 study in 35 centers from May 2009 to July 2013. The study population consisted of patients with moderate to severe renal impairment scheduled for liver imaging with gadoxetate disodium. All patients received a single intravenous bolus injection of 0.025-mmol/kg body weight of liver-specific gadoxetate disodium. The primary target variable was the number of patients who develop NSF within a 2-year follow-up period.

Results

A total of 357 patients were included, with 85 patients with severe and 193 patients with moderate renal impairment, which were the clinically most relevant groups. The mean time period from diagnosis of renal disease to liver magnetic resonance imaging (MRI) was 1.53 and 5.46 years in the moderate and severe renal impairment cohort, respectively. Overall, 101 patients (28%) underwent additional contrast-enhanced MRI with other gadolinium-based MRI contrast agents within 12 months before the start of the study or in the follow-up. No patient developed symptoms conclusive of NSF within the 2-year follow-up.

Conclusions

Gadoxetate disodium in patients with moderate to severe renal impairment did not raise any clinically significant safety concern. No NSF cases were observed.

Diagnosis and cure experience of hepatolithiasis-associated intrahepatic cholangiocarcinoma in 66 patients

BACKGROUND

The management of hepatolithiasis combined with intrahepatic cholangicarcinoma (IHHCC) remains a challenge due to poor prognosis. The aim of this study was to summarize our diagnosis and cure experience of IHHCC over the recent 10 years.

METHODS

From January 1996 to January 2006, 66 patients with IHHCC were reviewed retrospectively.

RESULTS

Of the 66 patients, 52 underwent surgical resection (radical resection in 38 and palliative in 14) and 8 patients abdominal exploration, while the other 6 cases received endoscopic retrograde biliary internal drainage and stent implantation. In this series, correct diagnosis of advanced stage was made during operation in 8 cases (8/60, 13.3%) and all of them (underwent unnecessary abdominal exploration, among them the positive rate of CA19-9 was 100%, and the positive rate of CEA was 87.6% (7/8), incidence rate of ascites was 100% and short-term significant weight loss was 100%, with median overall survival of only 4 months.

CONCLUSION

Radical resection is mandatory for IHHCC patient to achieve long-term survival, the CT and MR imaging features of IHHCC being concentric enhancement. Patients with IHHCC have significant higher CA199 and significant higher CEA and short-term significant weight loss and ascites should be considered with advanced stage of IHHCC and unnecessary non-therapeutic laparotomies should be avoided.

Usefulness of magnetic resonance cholangiopancreatography in pancreatobiliary abnormalities in pediatric patients

BACKGROUND

Magnetic resonance cholangiopancreatography (MRCP) is an innovative and noninvasive technique for evaluating the biliary tree and pancreatic duct in children. The aim of this study was to assess the usefulness of MRCP as a noninvasive method to evaluate the biliary system in children.

METHODS

We retrospectively reviewed the records of patients undergoing MRCP between October 2002 and May 2007 for suspected biliary system abnormalities. MRCP findings were compared with other imaging modalities, operative findings, and clinical endpoints.

RESULTS

Complete data were available for 60 patients (35 girls, 25 boys; mean age 2 years, 33 children less than 1 year old). Ultrasound was performed in all 60 patients. Twenty-two patients had choledochal cyst, and 19 had a thin or invisible gall bladder. Endoscopic retrograde cholangiopancreatography was done in two patients. The sensitivities and specificities of MRCP for diagnosing choledochal cyst and biliary atresia were 100.0% and 100.0% and 86.7% and 100.0%, respectively. Surgery was performed in 37 patients, including 21 with a choledochal cyst, 14 with biliary atresia, and 1 with a pancreatic duct stone.

CONCLUSION

MRCP is useful method for evaluation of the pancreaticobiliary system in pediatric patients. It yields a high degree of accuracy in the diagnosis of biliary atresia and choledochal cyst.

Gadopentetate dimeglumine-enhanced MR cholangiopancreatography in infants with cholestasis

BACKGROUND

Biliary atresia (BA) is a progressive, obliterative cholangiopathy that occurs in neonates with hepatic portoenterostomy the treatment of choice, but early surgery is important for optimum outcomes. MRI, including MR cholangiopancreatography (MRCP) may be a diagnostically useful alternative to US, but the heavily T2-weighted sequences used include not only bile duct signals, but also other heterogeneously high signal intensities from surrounding structures.

OBJECTIVE

To evaluate the effects of gadolinium when used to decrease background signal intensity on T2-weighted MR cholangiopancreatography (MRCP) in infants and to evaluate the qualitative improvement of the depiction of the common bile duct (CBD) for evaluating neonatal cholestasis.

MATERIALS AND METHODS

Our Institutional Review Board approved this prospective study. MRCP was performed with gadopentetate dimeglumine injection using a 1.5-T scanner. Pre- and postcontrast MRCP images were compared. Forty-nine infants (male:female = 21:28; age 0-12 months, mean 2.3) were included. The final diagnoses were biliary atresia (BA) in 28 cases and non-BA in 21. Quantitative analysis was conducted using region-of-interest measurements of mean signal intensities of the liver, pancreatic head and gallbladder (if defined). Qualitative analysis was performed by four radiologists who subjectively scored image confidence in the presence of CBD on a 4-point scale (0 for definitely absent, 1 for probably absent, 2 for probably present, and 3 for definitely present).

RESULTS

The signal-to-noise ratios were significantly decreased in the liver and pancreatic head after contrast medium enhancement (mean 5.7→4.0 in liver and mean 44.9→12.7 in the pancreatic head; P < 0.0001), and this finding was constant in both the BA and the non-BA group. The mean confidence score in the presence of CBD decreased in the BA group (0.9→0.5; P < 0.0001), but did not change significantly in the non-BA group (2.0→2.1; P = 0.459) after contrast medium enhancement. Both intra- and interobserver agreement was higher after contrast medium enhancement (P = 0.046).

CONCLUSION

Gadopentetate dimeglumine-enhanced MRCP increased the diagnostic confidence of absence of the CBD in cholestatic infants with increased intra- and interobserver agreement.

Comparison of three-dimensional negative-contrast CT cholangiopancreatography with three-dimensional MR cholangiopancreatography for the diagnosis of obstructive biliary diseases

PURPOSE

The purpose of our study was to compare three-dimensional (3D) negative-contrast CT cholangiopancreatography (3D-nCTCP) with 3D MR cholangiopancreatography (3D-MRCP) for the diagnosis of obstructive biliary diseases.

MATERIALS AND METHODS

3D-nCTCP and 3D-MRCP were performed on seventy clinically documented obstructive biliary diseases patients. The accuracy of each technique in determining the location and cause of biliary obstruction was evaluated compared with the final clinical diagnoses.

RESULTS

Both methods achieved 100% of accuracy in the diagnosis of the presence and location of biliary obstruction, and had a similar sensitivity, specificity, accuracy in differentiating benign from malignant biliary obstruction or calculous from noncalculous biliary obstruction (p>0.05). At 3D-nCTCP, six patients with stones were misinterpreted as cholangitis (N=2), papillitis (N=3), or bile duct adenocarcinoma (N=1); two metastases were mistaken as acute pancreatitis or pancreatic head carcinomas, and one intrahepatic cholangiocarcinoma was misled as bile duct adenoma. At 3D-MRCP, one small stone, one ampullary adenoma, and one intrahepatic cholangiocarcinoma were mistaken as cholangitis, ampullary stone, and intrahepatic bile duct stone, respectively, and three gallbladder carcinomas and another intrahepatic cholangiocarcinoma were misdiagnosed as hilar cholangiocarcinoma (N=3) or common hepatic duct stone (N=1); four metastases were mistaken as pancreatic head carcinomas (N=3) or distal cholangiocarcinoma (N=1). The overall accuracy in making specific diagnosis of the cause of biliary obstruction was 87.1% for 3D-nCTCP and 84.3% for 3D-MRCP, respectively, (p>0.05).

CONCLUSION

3D-nCTCP has the similar effects as 3D-MRCP for the diagnosis of biliary obstruction and, the location and the cause of biliary obstruction. In view of selected cases contraindications for MRI, 3D-nCTCP is a potential substitute.

Liver MRI Technique: Pulse Sequences and Contrast Agents

Developments in magnetic resonance imaging (MRI) techniques have expanded the role of MRI in evaluating the liver. Although a single optimized protocol for standard hepatic MRI examination has not been established or agreed on, key elements to a successful exam are generally accepted. In determining the "best" protocol, one must first understand the numerous pulse sequences and contrast agents available to the technologist and how each contributes to the final interpretation by the radiologist. This article will attempt to review the most commonly used pulse sequences for imaging the liver, with comment on their uses, advantages, and limitations. The spectrum of contrast agents available for use in liver MRI will also be discussed.

Clinical applications of magnetic resonance imaging in the diagnosis of hepatic diseases: present status

Magnetic resonance imaging (MRI) is one of the most important imaging modalities commonly used for the diagnosis of various human diseases. With the advance in MRI technique, MRI has been widely used to diagnose abdominal diseases, including hepatic diseases. Here, we will review the indications, contraindications and techniques of MRI as well as its diagnostic advantages and disadvantages for hepatic diseases.

Fast spin-echo triple-echo Dixon: initial clinical experience with a novel pulse sequence for fat-suppressed T2-weighted abdominal MR imaging

PURPOSE

To evaluate a prototype fast spin echo (FSE) triple-echo-Dixon (fTED) technique for breath-hold, fat-suppressed, T2-weighted abdominal imaging.

MATERIALS AND METHODS

Forty patients underwent breath-hold T2-weighted abdominal imaging with fTED and conventional fast recovery (FR) FSE with chemical shift-selective saturation (CHESS). FRFSE and fTED images were compared for overall image quality, homogeneity of fat suppression, image sharpness, anatomic detail, and phase artifact. Depiction of disease was recorded separately for FRFSE and fTED images.

RESULTS

FTED successfully reconstructed water-only and fat-only images from source images in all 40 cases. Water and fat separation was perfect in 36 (0.90) patients. Homogeneity of fat suppression was superior on the fTED images in 38 (0.95) of 40 cases. FTED images showed better anatomic detail in 27 (0.68), and less susceptibility artifact in 20 (0.50). FRFSE images showed less vascular pulsation artifact in 30 (0.75) cases, and less phase artifact in 21 (0.53) cases. There was no difference in depiction of disease for FRFSE and fTED images.

CONCLUSION

FTED is a robust sequence providing breath-hold T2-weighted images with superior fat suppression, excellent image quality, and at least equal depiction of disease compared to conventional breath-hold T2-weighted FRFSE imaging.

Imaging of liver cancer

Improvements in imaging technology allow exploitation of the dual blood supply of the liver to aid in the identification and characterisation of both malignant and benign liver lesions. Imaging techniques available include contrast enhanced ultrasound, computed tomography and magnetic resonance imaging. This review discusses the application of several imaging techniques in the diagnosis and staging of both hepatocellular carcinoma and cholangiocarcinoma and outlines certain characteristics of benign liver lesions. The advantages of each imaging technique are highlighted, while underscoring the potential pitfalls and limitations of each imaging modality.

Pediatric MR cholangiopancreatography: principles, technique, and clinical applications

High-quality magnetic resonance (MR) cholangiopancreatographic images are difficult to obtain in children due to the small caliber of the pediatric bile ducts and to motion artifacts. However, there has been ongoing improvement in image quality, thanks to better coil technology, increased speed of acquisition, refinement in respiratory compensation techniques, and newer sequences. Heavily T2-weighted fast spin-echo (FSE) and single-shot FSE MR imaging sequences with long echo times are used to image the biliary and pancreatic ducts. Secretin has been shown to improve the visualization of the pancreatic duct and pancreaticobiliary junction. Factors that affect image quality in pediatric MR cholangiopancreatography include sedation, negative oral contrast material, radiofrequency coil selection, respiratory compensation techniques, echo time, echo train length, section-slab thickness, planes of scanning, field of view, and number of signals acquired. However, giving proper attention to these factors and tailoring the study to the body size of the patient (which varies considerably) can lead to high-quality diagnostic MR cholangiopancreatographic images. Use of MR cholangiopancreatography in children is limited by the need for sedation or anesthesia, high cost, limited availability, and long scanning times. Nonetheless, this modality can be a viable alternative to endoscopic retrograde cholangiopancreatography (ERCP) in the evaluation of various entities such as choledochal cyst, recurrent pancreatitis, primary sclerosing cholangitis, and a transplanted liver, and may obviate ERCP.

The diagnostic MRCP examination: overcoming technical challenges to ensure clinical success

The magnetic resonance cholangiopancreatography (MRCP) examination has all but replaced the diagnostic endoscopic retrograde cholangiopancreatography (ERCP) examination for imaging the biliary tree and pancreatic ducts in many practical aspects of the clinical setting. Despite this increase in popularity, many magnetic resonance imaging (MRI) radiographers still find aspects of the MRCP examination quite challenging. The aim of this tutorial paper is to provide useful technical advice on how to overcome such perceived challenges and thus produce a successful diagnostic MRCP examination. This paper will be of interest to novice MRI radiographers who are at the beginning of their learning curve in MRCP examination. Other MRI radiographers who are interested in practical tips for protocol variations may also find the paper useful.

Liver imaging at 3.0 T: diffusion-induced black-blood echo-planar imaging with large anatomic volumetric coverage as an alternative for specific absorption rate-intensive echo-train spin-echo sequences: feasibility study

Institutional Review Board approval and signed informed consent were obtained by all participants for an ongoing sequence optimization project at 3.0 T. The purpose of this study was to evaluate breath-hold diffusion-induced black-blood echo-planar imaging (BBEPI) as a potential alternative for specific absorption rate (SAR)-intensive spin-echo sequences, in particular, the fast spin-echo (FSE) sequences, at 3.0 T. Fourteen healthy volunteers (seven men, seven women; mean age +/- standard deviation, 32.7 years +/- 6.8) were imaged for this purpose. Liver coverage (20 cm, z-axis) was always performed in one 25-second breath hold. Imaging parameters were varied interactively with regard to echo time, diffusion b value, and voxel size. Images were evaluated and compared with fat-suppressed T2-weighted FSE images for image quality, liver delineation, geometric distortions, fat suppression, suppression of the blood signal, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR). An optimized short- (25 msec) and long-echo (80 msec) BBEPI provided full anatomic, single breath-hold liver coverage (100 and 50 sections, respectively), with resulting voxel sizes of 3.3 x 2.7 x 2.0 mm and 3.3 x 2.7 x 4.0 mm, respectively. Repetition time was 6300 msec, matrix size was 160 x 192, and an acceleration factor of 2.00 was used. b Values of more than 20 sec/mm(2) showed better suppression of the blood signal but b values of 10 sec/mm(2) provided improved volume coverage and signal consistency. Compared with fat-suppressed T2-weighted FSE, the optimized BBEPI sequence provided (a) comparable image quality and liver delineation, (b) acceptable geometric distortions, (c) improved suppression of fat and blood signals, and (d) high CNR and SNR. BBEPI is feasible for fast, low-SAR, thin-section morphologic imaging of the entire liver in a single breath hold at 3.0 T.

Extending slice coverage for breathhold fat-suppressed T2-weighted fast spin-echo of the liver at 3.0T: application of variable-rate selective-excitation (VERSE) RF pulses

PURPOSE

To determine the benefits of variable-rate selective-excitation (VERSE) radio frequency (RF) pulses for increased slice coverage in breathhold (BH) fat-suppressed T2-weighted fast spin-echo (FS-T2W-FSE) liver imaging at 3.0T.

MATERIALS AND METHODS

A total of 12 healthy volunteers were imaged on 3.0T, using FS-T2W-FSE. Slice coverage and specific absorption rate (SAR) levels were monitored for VERSE-RF and standard-RF (sRF), respectively. BH time was 25 seconds; slice thickness 3.5 mm. Maximum coverage was recorded for interactive variation of repetition time (TR), bandwidth (BW), and echo-train length (ETL). Image quality was assessed qualitatively and quantitatively.

RESULTS

Total slice coverage was always higher using VERSE-RF, but varied depending on the selected parameters. For BW > or = 62.5 kHz, slice coverage using VERSE increased between 38% (TR = 8200 msec) and 58% (TR = 2500 msec). Maximum coverage was obtained for TR = 5000 msec, ETL = 12, and BW > or = 62.5 kHz; with a mean of 31.8 slices for VERSE-RF and 22.5 slices for sRF, respectively (P < 0.005, 41% increased coverage). SAR was lower for VERSE-RF using BW < 41.67 kHz (P < 0.05), and equal to sRF for higher BW. Image quality was best for TR < or = 5000 msec (P < 0.05). FS was more homogeneous for lower ETL (P < 0.05). Blood suppression was best for TR < or = 5000 msec (P < 0.05).

CONCLUSION

VERSE-RF pulses can be applied for thin-slice BH FS-T2W liver imaging at 3.0T, with significantly improved slice coverage.

Biliary tract neoplasms: diagnosis and staging

Most biliary tract neoplasms are malignant and have been traditionally divided into cancers of the gallbladder, the extrahepatic bile ducts, and ampulla of Vater. Although infrequent, bile duct carcinomas and cancer of the gallbladder are not rare. In the United States, an estimated 6000-7000 new cases of carcinoma of the gallbladder and 3000-4000 new cases of carcinoma of the bile ducts are diagnosed annually. Familiarity with the imaging characteristics of gallbladder and bile duct neoplasms is important to expedite the diagnosis and appropriate treatment of patients who often present with non-specific symptoms of right upper quadrant pain, jaundice, and weight loss.