Contrast agents for MR imaging of the liver

Genotoxic effects of gadobutrol and gadoversetamide active substances used in magnetic resonance imaging in human peripheral lymphocytes in vitro

Gadobutrol and gadoversetamide are gadolinium-based contrast agents (GBCAs) widely used during magnetic resonance imaging examination. In this study, the genotoxicity of two GBCAs, gadobutrol and gadoversetamide, was investigated by using different endpoints: chromosome aberration (CAs), sister chromatid exchange (SCEs), and micronucleus (MNi). Human peripheral lymphocytes (PBLs) were treated with five concentrations (7 000, 14 000, 28 000, 56 000, and 112 000 μg/mL) of both agents. While a few concentrations of gadobutrol significantly increased abnormal cell frequency and CA/Cell, nearly all the concentrations of gadoversetamide significantly elevated the same aberrations. Similarly, the effect of gadoversetamide on the formation of SCEs was higher than those of gadobutrol. Only one concentration of gadoversetamide significantly increased MN% but no gadobutrol. The comet assay was applied for the only gadobutrol which induced a significant increase in tail intensity at the highest concentration only. On the other hand, significantly decreased mitotic index (MI) was observed following both substances, again gadoversetamide was slightly higher than those of the gadobutrol. The results revealed that both the contrast agents are likely to induce genotoxic risk in PBLs. However, different concentrations and treatment periods should be examined in vitro and specifically in vivo with different test systems for the safer usage of these contrast agents.

Total Bilirubin Level as a Predictor of Suboptimal Image Quality of the Hepatobiliary Phase of Gadoxetic Acid-Enhanced MRI in Patients with Extrahepatic Bile Duct Cancer

Objective

This study aimed to determine a factor for predicting suboptimal image quality of the hepatobiliary phase (HBP) of gadoxetic acid-enhanced MRI in patients with extrahepatic bile duct (EHD) cancer before MRI examination.

Materials and Methods

We retrospectively evaluated 259 patients (mean age ± standard deviation: 68.0 ± 8.3 years; 162 male and 97 female) with EHD cancer who underwent gadoxetic acid-enhanced MRI between 2011 and 2017. Patients were divided into a primary analysis set (n = 184) and a validation set (n = 75) based on the diagnosis date of January 2014. Two reviewers assigned the functional liver imaging score (FLIS) to reflect the HBP image quality. The FLIS consists of the sum of three HBP features, each scored on a 0–2 scale: liver parenchymal enhancement, biliary excretion, and signal intensity of the portal vein. Patients were classified into low-FLIS (0–3) or high-FLIS (4–6) groups. Multivariable analysis was performed to determine a predictor of low FLIS using serum biochemical and imaging parameters of cholestasis severity. The optimal cutoff value for predicting low FLIS was obtained using receiver operating characteristic analysis, and validation was performed.

Results

Of the 259 patients, 140 (54.0%) and 119 (46.0%) were classified into the low-FLIS and high-FLIS groups, respectively. In the primary analysis set, total bilirubin was an independent factor associated with low FLIS (adjusted odds ratio per 1-mg/dL increase, 1.62; 95% confidence interval [CI], 1.32–1.98). The optimal cutoff value of total bilirubin for predicting low FLIS was 2.1 mg/dL with a sensitivity of 95.1% (95% CI: 88.9–98.4) and a specificity of 89.0% (95% CI: 80.2–94.9). In the validation set, the total bilirubin cutoff showed a sensitivity of 92.1% (95% CI: 78.6–98.3) and a specificity of 83.8% (95% CI: 68.0–93.8).

Conclusion

Serum total bilirubin before acquisition of gadoxetic acid-enhanced MRI may help predict suboptimal HBP image quality in patients with EHD cancer.

Influence of injection rate in determining the development of artifacts during the acquisition of dynamic arterial phase in Gd-EOB-DTPA MRI studies

OBJECTIVE

To assess whether different Gd-EOB-DTPA injection rates could influence the development of artifacts during the arterial phase of liver MRI studies.

MATERIALS AND METHODS

All Gd-EOB-DTPA liver MRI studies performed for different clinical indications at a single tertiary referral center were retrospectively evaluated. Each examination was acquired on a 1.5 T scanner with T1 In- and Out-of-Phase, T2 with and without fat-saturation, DWI, and 3D-T1 fat-sat dynamic sequences. Patients were divided into two groups according to the injection rate (1 ml/s and 1.5 ml/s). A single radiologist recorded the presence or absence of artifacts during different acquisition phases, respectively: (1) all examination; (2) only during the arterial phase; (3) only during the portal-venous phase; (4) both in arterial and portal-venous phases. From a total of 748 MRI studies performed, 229 were excluded due to the presence of artifacts during the entire examination. The remaining 519 MRI studies were divided into two groups according to the injection rate.

RESULTS

The first group (flow rate = 1 ml/s) was composed by 312 (60.1%) patients and the second group (flow rate = 1.5 ml/s) by 207 (39.9%) patients. In the first group, 2 (0.6%) patients showed artifacts in all dynamic sequences; 13 (4%) only in the arterial phase, 16 (5%) only in the portal-venous phase, and 38 (12%) both in arterial and portal-venous phases; a total of 243 (78%) showed no artifacts. In the second group, 3 (1.5%) patients had artifacts in all dynamic sequences, 82 (40%) only in the arterial phase, 20 (10%) only in the portal-venous phase, and 53 (25%) both in arterial and portal-venous phases; a total of 49 (23.5%) showed no artifacts. A significant difference between the two groups regarding the absence of artifacts in all examination and the presence of artifacts only during the arterial phase was found (p < 0.001).

CONCLUSION

The development of artifacts during the arterial phase of Gd-EOB-DTPA liver MRI studies could be related to the injection rate and its reduction may help to decrease the incidence of artifacts.

Advances in functional and molecular MRI technologies in chronic liver diseases

MRI has emerged as the most comprehensive non-invasive diagnostic tool for liver diseases. In recent years, the value of MRI in hepatology has been significantly enhanced by a wide range of contrast agents, both clinically available and under development, that add functional information to anatomically detailed morphological images, or increase the distinction between normal and pathological tissues by targeting molecular and cellular events. Several classes of contrast agents are available for contrast-enhanced hepatic MRI, including i) conventional non-specific extracellular fluid contrast agents for assessing tissue perfusion; ii) hepatobiliary-specific contrast agents that are taken up by functioning hepatocytes and excreted through the biliary system for evaluating hepatobiliary function; iii) superparamagnetic iron oxide particles that accumulate in Kupffer cells; and iv) novel molecular contrast agents that are biochemically targeted to specific molecular/cellular processes for staging liver diseases or detecting treatment responses. The use of different functional and molecular MRI methods enables the non-invasive assessment of disease burden, progression, and treatment response in a variety of liver diseases. A high diagnostic performance can be achieved with MRI by combining imaging biomarkers.

Manganese Oxide Nanoparticles As MRI Contrast Agents In Tumor Multimodal Imaging And Therapy

Contrast agents (CAs) play a crucial role in high-quality magnetic resonance imaging (MRI) applications. At present, as a result of the Gd-based CAs which are associated with renal fibrosis as well as the inherent dark imaging characteristics of superparamagnetic iron oxide nanoparticles, Mn-based CAs which have a good biocompatibility and bright images are considered ideal for MRI. In addition, manganese oxide nanoparticles (MONs, such as MnO, MnO2, Mn3O4, and MnOx) have attracted attention as T1-weighted magnetic resonance CAs due to the short circulation time of Mn(II) ion chelate and the size-controlled circulation time of colloidal nanoparticles. In this review, recent advances in the use of MONs as MRI contrast agents for tumor detection and diagnosis are reported, as are the advances in in vivo toxicity, distribution and tumor microenvironment-responsive enhanced tumor chemotherapy and radiotherapy as well as photothermal and photodynamic therapies.

Respiratory motion in children and young adults undergoing liver magnetic resonance imaging with intravenous gadoxetate disodium contrast material

BACKGROUND

Gadoxetate disodium, utilized in hepatobiliary magnetic resonance (MR) imaging, has been associated with transient respiratory motion during the arterial phase in adults.

OBJECTIVE

The purpose of this study was to determine the presence and severity of this phenomenon in children imaged awake versus under general anesthesia.

MATERIALS AND METHODS

This retrospective cohort study was approved by the institutional review board; informed consent was waived. One hundred thirty exams of children ≤18 years old who underwent dynamic liver MR imaging with gadoxetate disodium between October 2010 and January 2018 were reviewed. Three pediatric radiologists scored respiratory motion artifacts on all imaging phases using a 5-point Likert scale. Differences in mean motion scores were assessed with analysis of variance and Tukey's multiple comparisons test, and multivariable regression was used to identify predictors of arterial phase motion in awake patients.

RESULTS

One hundred thirty patients (50% [n=65] female; mean age: 9.8±3.7 years, 48.5% [n=63] awake) were included. There were significant differences in mean motion scores between phases in the awake cohort (P<0.0001) but not in the general anesthesia cohort (P=0.051). In the awake cohort, arterial phase motion score (mean: 3.52±0.83) was significantly higher than mean motion score in all other phases (P≤0.0003). There were no significant patient-specific predictors of arterial phase motion score in the awake cohort.

CONCLUSION

Significantly increased arterial phase respiratory motion artifact in awake children undergoing dynamic liver MR imaging with gadoxetate disodium suggests that transient respiratory motion occurs in children. General anesthesia may suppress this phenomenon.

Spatial-temporal perfusion patterns of the human liver assessed by pseudo-continuous arterial spin labeling MRI

PURPOSE

To investigate the capabilities of a modern pseudo-continuous arterial spin labeling (PCASL) technique for non-invasive assessment of the temporal and spatial distribution of the liver perfusion in healthy volunteers on a clinical MR system at 3T.

MATERIALS AND METHODS

A 2D-PCASL multi-slice echo planar imaging sequence was adapted to the specific conditions in liver: a) labeling by PCASL was optimized to the flow characteristics in the portal vein, b) background suppression was applied for reduction of motion related artifacts, c) post labeling delays (PLDs) were varied over a large range (0.7-3.5s) in order to get better insight in the temporal and spatial distribution of tagged blood in the liver, and d) a special timed-breathing protocol was used allowing for recording of 16 to 18 label-control image pairs and a reference M0 image for each of 4 to 6 slices within approx. 5min for one PLD.

RESULTS

Measurements with multiple PLDs showed dominating perfusion signal in macroscopic blood vessels for PLDs up to 1.5 s, whereas pure liver parenchyma revealed maximum perfusion signal for a PLD of approx. 2 s, and detectable signal up to PLDs of 3.5 s. Data fitting to a perfusion model for liver provided a mean global perfusion of 153±15ml/100g/min and a mean transit time of 1938±332ms in liver parenchyma. Measurements with a single PLD of 2 s demonstrated that portal-venous and arterial perfusion components can be measured separately by two measurements with two different positions of the labeling plane (one for labeling of the global hepatopetal blood flow and one for selective labeling of the portal blood flow only). Relative contribution of blood from the hepatic artery to the global liver perfusion, the hepatic perfusion index (HPI), amounted to approx. 23%.

CONCLUSION

Modern and adapted protocols for assessment of liver perfusion by PCASL have the potential to provide perfusion and blood transit time maps in reasonable acquisition time.

Recent advances in non-invasive magnetic resonance imaging assessment of hepatocellular carcinoma

Magnetic resonance (MR) imaging of the liver is an important tool for the detection and characterization of focal liver lesions and for assessment of diffuse liver disease, having several intrinsic characteristics, represented by high soft tissue contrast, avoidance of ionizing radiation or iodinated contrast media, and more recently, by application of several functional imaging techniques (i.e., diffusion-weighted sequences, hepatobiliary contrast agents, perfusion imaging, magnetic resonance (MR)-elastography, and radiomics analysis). MR functional imaging techniques are extensively used both in routine practice and in the field of clinical and pre-clinical research because, through a qualitative rather than quantitative approach, they can offer valuable information about tumor tissue and tissue architecture, cellular biomarkers related to the hepatocellular functions, or tissue vascularization profiles related to tumor and tissue biology. This kind of approach offers in vivo physiological parameters, capable of evaluating physiological and pathological modifications of tissues, by the analysis of quantitative data that could be used in tumor detection, characterization, treatment selection, and follow-up, in addition to those obtained from standard morphological imaging. In this review we provide an overview of recent advanced techniques in MR for the diagnosis and staging of hepatocellular carcinoma, and their role in the assessment of response treatment evaluation.

Diagnostic value of Gd-EOB-DTPA-enhanced MR cholangiography in non-invasive detection of postoperative bile leakage

OBJECTIVE

To assess the diagnostic value of dynamic T₁ weighted (T1w) gadolinium ethoxybenzyl diethylenetriamine penta-acetic acid (Gd-EOB-DTPA)-enhanced MR cholangiography (MRC) for the detection of active bile leaks.

METHODS

A total of 28 patients with suspected biliary leakage who underwent routine T₂ weighted (T2w) MRC and T1w GD-EOB-DTPA-enhanced MRC at our institution from February 2013 to June 2016 were included in this study. The image sets were retrospectively analyzed in consensus by three radiologists. T1w Gd-EOB-DTPA-enhanced MRC findings were correlated with clinical data, follow-up examinations and findings of invasive/surgical procedures. Patients with positive bile leak findings in Gd-EOB-DTPA-enhanced MRC were divided into hepatobiliary phase (HBP) (20-30 min) and delayed phase (DP) (60-390 min) group according to elapsed time between Gd-EOB-DTPA injection and initial bile leak findings in MRC images. These groups were compared in terms of laboratory test results (total bilirubin, liver enzymes) and the presence of bile duct dilatation in T2w MRC images.

RESULTS

In each patient, visualization of bile ducts was sufficient in the HBP. The accuracy, sensitivity and specificity of dynamic Gd-EOB-DTPA-enhanced T1w MRC in the detection of biliary leaks were 92.9%, 90.5% and 100%, respectively (p < 0.001). 19 of 28 patients had bile leak findings in T1w Gd-EOB-DTPA-enhanced MRC [HBP group: N = 7 (36.8%), DP group: N = 12 (63.2%)]. There was no statistically significant difference in terms of laboratory test results and the presence of bile duct dilatation between HBP and DP group (p > 0.05). Three patients, each of them in DP group, showed normal laboratory test results and bile duct diameters.

CONCLUSION

Dynamic T1w Gd-EOB-DTPA-enhanced MRC is a useful non-invasive diagnostic tool to detect bile leak. Advances in knowledge: Prolonged DP imaging may be required for bile leak detection even if visualization of biliary tree is sufficient in HBP and liver function tests, total bilirubin levels and bile duct diameters are normal.

Early Peribiliary Hyperenhancement on MRI in Patients with Primary Sclerosing Cholangitis: Significance and Association with the Mayo Risk Score

The aims of this study are to assess any relationship between peribiliary hyperenhancement on MRI in patients with primary sclerosing cholangitis (PSC) and their Mayo risk score and to assess which timing of peribiliary hyperenhancement correlates best with the Mayo risk score. In this HIPAA-compliant, IRB-approved retrospective study, 101 patients who underwent MRI for known or suspected PSC were identified. Of those, 62 patients (mean age 48 years; 40 males) were diagnosed with PSC by a hepatologist based on findings on MRI, ERCP, and/or liver biopsy, and comprise the final cohort. Data were recorded on whether peribiliary hyperenhancement was present, the post-contrast phase and the extent of involvement. The components to calculate the Mayo risk score were recorded. Statistical analysis was performed using the student T test, Fisher's exact test, and the Kaplan-Meier estimate. Of 62 patients, 41 (66.1%) patients had a low-Mayo risk score (<0), 14 (22.6%) had an intermediate-risk score (≤2 and >0), and 7 (11.3%) had a high-risk score (>2). On MRI, 29 (46.8%) patients demonstrated arterial peribiliary hyperenhancement. Both the presence and extent of peribiliary hyperenhancement showed significant associations with Mayo risk score (p < 0.01). Using the combined end point of liver transplantation or death, there was a statistically significant difference in survival times between those with and those without arterial peribiliary hyperenhancement (p < 0.05). The presence of arterial peribiliary hyperenhancement in patients with PSC on MRI is associated with higher Mayo risk scores and may suggest a poorer prognosis.

MRI contrast agents: Classification and application (Review)

Magnetic resonance imaging (MRI) contrast agents are categorised according to the following specific features: chemical composition including the presence or absence of metal atoms, route of administration, magnetic properties, effect on the magnetic resonance image, biodistribution and imaging applications. The majority of these agents are either paramagnetic ion complexes or superparamagnetic magnetite particles and contain lanthanide elements such as gadolinium (Gd3+) or transition metal manganese (Mn2+). These elements shorten the T1 or T2 relaxation time, thereby causing increased signal intensity on T1-weighted images or reduced signal intensity on T2-weighted images. Most paramagnetic contrast agents are positive agents. These agents shorten the T1, so the enhanced parts appear bright on T1-weighted images. Dysprosium, superparamagnetic agents and ferromagnetic agents are negative contrast agents. The enhanced parts appear darker on T2-weighted images. MRI contrast agents incorporating chelating agents reduces storage in the human body, enhances excretion and reduces toxicity. MRI contrast agents may be administered orally or intravenously. According to biodistribution and applications, MRI contrast agents may be categorised into three types: extracellular fluid, blood pool and target/organ-specific agents. A number of contrast agents have been developed to selectively distinguish liver pathologies. Some agents are also capable of targeting other organs, inflammation as well as specific tumors.

Surrogate arterial phase imaging using a long duration (≈1.5 min) radial acquisition T1-weighted sequence: an alternative in patients unable to breath-hold

BACKGROUND

Pediatric and adult patients unable to suspend respiration generally undergo magnetic resonance (MR) examinations that lack arterial phase imaging, which is a phase that provides substantial information on disease processes. An MR strategy that provides this type of information may be of considerable value.

PURPOSE

To describe and assess the feasibility and enhancement quality of early-phase imaging utilizing long-duration radial 3D-GRE imaging by initiating the sequence prior to starting contrast injection.

MATERIAL AND METHODS

Thirty-three consecutive patients (10 men, 23 women; 50.7 ± 25.5 years) underwent free-breathing gadolinium-enhanced radial 3D-GRE, with sequence initiation 30 s prior to contrast injection. Late hepatic arterial (LHA) phase was chosen for comparison. Images were evaluated for enhancement and overall image quality. Organ enhancement was calculated. Sub-group analysis was performed.

RESULTS

Twenty-two examinations of radial 3D-GRE sequences were acquired during the LHA phase. Organ enhancement scores were of satisfactory to good quality (range, 3.32-3.82). There was a significant trend of superior overall enhancement quality scores in pediatrics and examinations performed at 3 T (P = 0.0225 and 0.0001, respectively).

CONCLUSION

Arterial phase abdominal MR imaging is feasible using conventional radial 3D-GRE by adopting this simplistic proposed approach, which may allow arterial-phase imaging in patients unable to breath-hold.

Super-Paramagnetic Nanoparticles with Spinel Structure: A Review of Synthesis and Biomedical Applications

The study of ceramic materials has attracted the attention of many researchers due to the possibility of their use in nanotechnology. The spinel ferrites form a large group of materials with a broad range of applications. Some examples include electronic devices such as high-frequency transformer cores, antenna rods, induction-tuners, among many others. However, when the ferritic materials display superparamagnetic behavior, their potential for biological applications like drug delivery, hyperthermia, resonance magnetic imaging and magnetic separation, become amazingly high. Therefore, the superparamagnetism is a characteristic strongly desired for spinel ferrites. Since this phenomenon is size-dependent, the methodologies to synthesize these materials has emerged as a crucial step in order to obtain the desired properties. In this regarding, several synthetic processes have been developed. For example, co-precipitation is a fast and cheap method to synthesize superparamagnetic spinel ferrites. However, methodologies involving microwave, ultrasound or polymers frequently result in these kind of materials. Therefore, this review brings a brief historic introduction about spinel ferrites as well as essential concepts to understand their structure and magnetic properties. In addition to this, recent advances in synthesis and applications of the superparamagnetic spinel ferrites are mentioned. Contents of Paper

ESGAR consensus statement on liver MR imaging and clinical use of liver-specific contrast agents

Objectives

To develop a consensus and provide updated recommendations on liver MR imaging and the clinical use of liver-specific contrast agents.

Methods

The European Society of Gastrointestinal and Abdominal Radiology (ESGAR) formed a multinational European panel of experts, selected on the basis of a literature review and their leadership in the field of liver MR imaging. A modified Delphi process was adopted to draft a list of statements. Descriptive and Cronbach’s statistics were used to rate levels of agreement and internal reliability of the consensus.

Results

Three Delphi rounds were conducted and 76 statements composed on MR technique (n = 17), clinical application of liver-specific contrast agents in benign, focal liver lesions (n = 7), malignant liver lesions in non-cirrhotic (n = 9) and in cirrhotic patients (n = 18), diffuse and vascular liver diseases (n = 12), and bile ducts (n = 13). The overall mean score of agreement was 4.84 (SD ±0.17). Full consensus was reached in 22 % of all statements in all working groups, with no full consensus reached on diffuse and vascular diseases.

Conclusions

The consensus provided updated recommendations on the methodology, and clinical indications, of MRI with liver specific contrast agents in the study of liver diseases.

Key points

• Liver-specific contrast agents are recommended in MRI of the liver.

• The hepatobiliary phase improves the detection and characterization of hepatocellular lesions.

• Liver-specific contrast agents can improve the detection of HCC.

Comparison of gadoxetic acid and gadopentetate dimeglumine-enhanced MRI for HCC detection: prospective crossover study at 3 T

Background

Gadoxetic acid and gadopentetate dimeglumine are gadolinium-based contrast agents (GBCAs) with an established role in HCC detection and characterization.

Purpose

To compare gadopentetate dimeglumine and gadoxetic acid-enhanced magnetic resonance imaging (MRI) for image quality and hepatocellular carcinoma (HCC) detection/conspicuity.

Material and Methods

In this IRB approved cross-over pilot prospective study, 12 patients (all men; mean age, 56 years) with chronic liver disease at risk of HCC underwent two repeat MRI examinations using gadopentetate dimeglumine and gadoxetic acid (mean interval between studies, 5 days). Two independent observers analyzed images for image quality and HCC detection/conspicuity. Per-lesion sensitivity, positive predictive value, quantitative enhancement, and lesion-to-liver contrast ratio were calculated for both contrast agents.

Results

There was no significant difference in image quality scores between both GBCAs (P = 0.3). A total of 20 HCCs were identified with reference standard in 12 patients (mean size 2.6 cm, range, 1.0–5.0 cm). Higher sensitivity was seen for observer 1 for gadoxetic acid-set in comparison with gadopentetate dimeglumine-set (sensitivity increased from 85.7% to 92.8%), while no difference was noted for observer 2 (sensitivity of 78.5%). Lesion conspicuity was significantly higher on hepatobiliary phase (HBP) images compared to arterial phase images with both GBCAs for both observers (P < 0.05). Lesion-to-liver contrast ratios were significantly higher for HBP compared to all dynamic phases for both agents (P < 0.05).

Conclusion

Our initial experience suggests that gadoxetic acid-set was superior to gadopentetate dimeglumine-set in terms of HCC detection for one observer, with improved lesion conspicuity and liver-to-lesion contrast on HBP images.

The efficiency of Gd-EOB-DTPA-enhanced magnetic resonance cholangiography in living donor liver transplantation: a preliminary study

The aim of this study was to evaluate utility of gadoxetic acid disodium (Gd-EOB-DTPA)-enhanced magnetic resonance cholangiography (MRC) for the detection of biliary complications after living donor liver transplantation (LDLT). A total of 18 patients with suspected biliary complications underwent MRC. T2-weighted MRC and contrast-enhanced MRC (CE-MRC) were used to identify the biliary complications. MRC included routine breath-hold T2-weighted MRC using half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences and Gd-EOB-DTPA-enhanced MRC T1-weighted volumetric interpolated breath-hold examination (VIBE) sequences. Before confirming the biliary complications, one observer reviewed the MRC images and the CE-MRC images separately. The verification procedures and MRC findings were compared, and the sensitivity, specificity, and accuracy of both techniques were calculated for the identification of biliary complications. The observer found six of seven biliary complications using CE-MRC. The sensitivity was 85.7% and the accuracy was 94.4%. Using MRC alone, sensitivity was 57.1% and accuracy was 55.5%. The accuracy of Gd-EOB-DTPA-enhanced MRC was superior to MRC in locating biliary leaks (p < 0.05). The usage of Gd-EOB-DTPA-enhanced MRC yields information that complements the MRC findings that improve the identification of biliary complications. We recommend the use of MRC in addition to Gd-EOB-DTPA-enhanced MRC to increase the preoperative accuracy when assessing the biliary complications after LDLT.

Diagnosis of biliary stone disease: T1-weighted magnetic resonance cholangiography with Gd-EOB-DTPA versus T2-weighted magnetic resonance cholangiography

OBJECTIVE

We aimed to compare diagnostic performance of gadoxetic-acid-enhanced-T1-weighted-MR cholangiography (MRC) with that of conventional T2-weighted-MRC in diagnosing biliary stone disease.

MATERIALS AND METHODS

Ninety patients who underwent MRC for evaluation of biliary disease were included. Presence of stones in extrahepatic duct, gallbladder and intrahepatic duct, and presence of acute cholecystitis were evaluated. Sensitivity, specificity, and accuracy of biliary stone disease diagnosis in each biliary duct location according to each image sets were measured.

RESULTS

There was no significant difference in diagnostic performance between two sets of MRC in diagnosing biliary stone disease.

CONCLUSIONS

Diagnostic performance of T1-MRC with gadoxetic-acid in diagnosing biliary stone disease is comparable to that of T2-MRC.

Hepatocellular carcinoma 20 mm or smaller in cirrhosis patients: early magnetic resonance enhancement by gadoxetic acid compared with gadopentetate dimeglumine

PURPOSE

To evaluate the differences in enhancement pattern of hepatocellular carcinoma (HCC) 20 mm or smaller and enhancement effects of hepatic vessels on early dynamic contrast-enhanced magnetic resonance imaging (MRI) obtained with gadoxetic acid and gadopentetate dimeglumine in the same patients with cirrhosis.

METHODS

We reviewed MR images using gadoxetic acid and gadopentetate dimeglumine in the same 34 patients with 42 histologically confirmed HCCs (median diameter, 14.5 mm). The percentage enhancements (PEs) of HCC, the hepatic artery and portal vein and relative contrasts (RCs) between HCC and the liver were calculated and analyzed statistically.

RESULTS

The PEs of HCC, the hepatic artery and portal vein were significantly lower for gadoxetic acid in comparison with gadopentetate dimeglumine in the arterial phase (p = 0.0256 for HCC, p < 0.0001 for hepatic artery) and portal phase (p < 0.0001 for HCC, portal vein). The RC between HCC and the liver was significantly lower for gadoxetic acid in comparison with gadopentetate dimeglumine in the arterial phase (p = 0.0422), but was not significantly different in the portal phase (p = 0.1133). Forty-one of the 42 (97.62 %) nodules showed arterial hypervascularization. Of these, 31 (75.61 %) nodules were hypointense in the portal phase for gadoxetic acid, and 22 (53.66 %) were hypointense for gadopentetate dimeglumine (p = 0.038).

CONCLUSIONS

Compared with gadopentetate dimeglumine, gadoxetic acid-enhanced MRI demonstrated a different enhancement pattern of inferior arterial enhancement and was more rapidly hypointense in the portal phase for HCC. It showed markedly lower enhancement for hepatic artery and portal vein in the patients with cirrhosis.

Non-invasive detection of biliary leaks using Gd-EOB-DTPA-enhanced MR cholangiography: comparison with T2-weighted MR cholangiography

Objective

To evaluate the added role of T1-weighted (T1w) gadolinium ethoxybenzyl diethylenetriamine penta-acetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance cholangiography (MRC) compared with T2-weighted MRC (T2w-MRC) in the detection of biliary leaks.

Methods

Ninety-nine patients with suspected biliary complications underwent routine T2w-MRC and T1w contrast-enhanced (CE) MRC using Gd-EOB-DTPA to identify biliary leaks. Two observers reviewed the image sets separately and together. MRC findings were compared with those of surgery and percutaneous transhepatic cholangiopancreatography. The sensitivity, specificity and accuracy of the techniques in identifying biliary leaks were calculated.

Results

Accuracy of locating biliary leaks was superior with the combination of Gd-EOB-DTPA-enhanced MRC and T2w-MRC (P < 0.05).The mean sensitivities were 79 % vs 59 %, and the mean accuracy rates were 84 % vs 58 % for combined CE-MRC and T2w-MRC vs sole T2w-MRC. Nineteen out of 21 patients with biliary-cyst communication, 90.4 %, and 12/15 patients with post-traumatic biliary extravasations, 80 %, were detected by the combination of Gd-EOB-DTPA-enhanced MRC and T2w-MRC images, P < 0.05.

Conclusions

Gd-EOB-DTPA-enhanced MRC yields information that complements T2w-MRC findings and improves the identification and localisation of the bile extravasations (84 % accuracy, 100 % specificity, P < 0.05). We recommend Gd-EOB-DTPA-enhanced MRC in addition to T2w-MRC to increase the preoperative accuracy of identifying and locating extravasations of bile.

Key Points

• Magnetic resonance cholangiography (MRC) does not always detect bile leakage and cysto-biliary communications.

• Gd-EOB-DTPA-enhanced MRC helps by demonstrating extravasation of contrast material into fluid collections.

• Gd-EOB-DTPA-enhanced MRC also demonstrates the leakage site and bile duct injury type.

• Combined Gd-EOB-DTPA-enhanced and T2w-MRC can provide comprehensive information about biliary system.

• Gd-EOB-DTPA-enhanced MRC is non-invasive and does not use ionising radiation.

Optimization of the dynamic, Gd-EOB-DTPA-enhanced MRI of the liver: the effect of the injection rate

BACKGROUND

Tissue-specific gadolinium-based contrast agents such as Gd-BOPTA, Gd-EOB-DTPA are increasingly used for liver imaging. Despite the added value of the hepatobiliary phase a proper arterial phase is still critical, especially in patients with chronic liver diseases. So far, there are limited data in the literature about the effect of the injection speed of Gd-EOB-DTPA in liver and vessel enhancement.

PURPOSE

To evaluate the effect of injection rate on the enhancement of liver parenchyma and vasculature in Gd-EOB-DTPA-enhanced liver MRI.

MATERIAL AND METHODS

Eighty patients who underwent Gd-EOB-DTPA-enhanced liver MRI (1.5T multi-channel MR-system) were retrospectively evaluated. We used a Care Bolus technique with an injection rate of 2 mL/s in group 1 (n = 40) and a Care Bolus technique with an injection rate of 1 mL/s in group 2 (n = 40) to determine the start of the arterial-dominant phase. Signal intensities were measured in vascular structures and liver parenchyma. Signal-to-noise-ratio (SNR), SNR increase (SNRi), and percentage enhancement (PE) were calculated and compared by a students t-test.

RESULTS

The SNR, SNRi, and PE of the aorta in the arterial phase were significantly higher in group 2 in comparison to group 1 (P = 0.007, P = 0.0043, and P < 0.001, respectively). There were no significant differences concerning the SNR, SNRi, or PE of the portal vein and the normal liver parenchyma between both groups at all time points.

CONCLUSION

The study shows that a lower injection rate of 1 mL/s enables a higher enhancement in the aorta in the arterial phase compared with Gd-EOB-DTPA-enhanced MRI with the more commonly used injection rate of 2 mL/s.

Enhancement of the liver and pancreas in the hepatic arterial dominant phase: comparison of hepatocyte-specific MRI contrast agents, gadoxetic acid and gadobenate dimeglumine, on 3 and 1.5 Tesla MRI in the same patient

PURPOSE

To evaluate the relative enhancement of liver, pancreas, focal nodular hyperplasia (FNH), pancreas-to-liver index, and FNH-to-liver index in the hepatic arterial dominant phase (HADP) after injection of hepatocyte-specific MRI contrast agents, gadoxetic acid and gadobenate dimeglumine, on 3 and 1.5 Tesla (T) MRI in the same patient.

MATERIALS AND METHODS

The MRI database was retrospectively searched to identify consecutive patients who underwent abdominal MRI at 3T and 1.5T systems, using both 0.025 mmol/kg gadoxetic acid-enhanced and 0.05 mmol/kg gadobenate dimeglumine-enhanced MRI at the same magnetic strength field system. 22 patients were identified, 10 were scanned at 3T system and 12 at 1.5T system. The enhancement of liver, pancreas, and FNH was evaluated quantitatively on MR images.

RESULTS

The relative enhancement of liver in HADP in the gadobenate dimeglumine-enhanced group in all subjects was significantly higher than that in gadoxetic acid-enhanced group (P = 0.023). The gadobenate dimeglumine-enhanced group in HADP had better relative enhancement of pancreas and FNH, pancreas-to-liver index, and FNH-to-liver index than gadoxetic acid-enhanced group, but the difference was not statistically significant.

CONCLUSION

The 0.05 mmol/kg gadobenate dimeglumine-enhanced abdominal MRI studies at 3T and 1.5T MR systems are superior in relative enhancement of the liver in HADP to 0.025 mmol/kg gadoxetic acid-enhanced MRI. This type of assessment may provide comparative effectiveness data.

Liver specific magnetic resonance imaging contrast medium for evaluation of focal liver lesions - Initial experience at a service hospital

BACKGROUND

Contrast enhanced MRI is today considered the investigation modality of choice in detection and characterization of focal liver lesions. The conventional MRI contrast media like Gadolinium (Gd) chelates undergo elimination through the urinary pathway and are not selectively concentrated or metabolized in the liver. Gadobenate dimeglumine (Chemical name: Gadolinium-BOPTA) is a promising newer liver specific MRI contrast medium having additional properties of selective uptake and biliary excretion by hepatocytes. Our study was designed as a pilot study to evaluate the utility of Gd-BOPTA in detection and characterization of focal liver lesions.

METHODS

Fifty-three consecutive patients with focal liver lesions (excluding only simple hepatic cysts) detected on ultrasonography and CT abdomen, were prospectively subjected to standardized MRI protocol for the liver, using Gd-BOPTA as the intravenous contrast medium. An additional T1W axial scan of the liver was incorporated in the study protocol, at a delay of 2 h post-contrast, in all patients.

RESULTS

In the study population, the combination of USG and contrast enhanced CT abdomen findings were adequate to reach a definitive diagnosis in 70% of the patients. The liver specificity of Gd-BOPTA contributed to improved lesional characterization in 9/50 patients (18%) on the delayed phase images.

CONCLUSION

The study revealed that the liver specific properties of Gd-BOPTA can be used to obtain additional information to improve characterization of focal hepatic lesions, when delayed phase scans are included in the study protocol.

Use of magnetic resonance imaging contrast agents in the liver and biliary tract

This article presents an overview of liver and biliary contrast agents including their mechanisms of action, dosage and elimination, current clinical indications, and potential future uses.

Clinical and diagnostic imaging findings in dogs with zygomatic sialadenitis: 11 cases (1990-2009)

OBJECTIVE

To describe clinical and diagnostic imaging features of zygomatic sialadenitis in dogs.

DESIGN

Retrospective case series.

ANIMALS

11 dogs with zygomatic sialadenitis and 20 control dogs without evidence of retrobulbar disease.

PROCEDURES

Medical records were searched for dogs with zygomatic sialadenitis that underwent some combination of magnetic resonance imaging (MRI), computed tomography (CT), and ultrasonography. Signalment, clinical signs, results of clinicopathologic tests, cytologic and histologic diagnosis, treatment, qualitative disease features, and disease course were recorded. Images obtained via MRI or CT were analyzed for pre- and postcontrast signal intensity or density, respectively; zygomatic salivary gland area was determined. Results were compared with those of control dogs that underwent the same imaging procedures (n = 10/method). Ultrasonographic images of affected dogs were assessed qualitatively.

RESULTS

Most (9/11) affected dogs were medium- or large-breed males (mean age, 8 years) with unilateral disease. Affected dogs had clinical signs of retrobulbar disease and cytologic or histologic evidence of zygomatic sialadenitis. Sialoceles were detected in 7 affected glands. Compared with values for control dogs, MRI findings in affected dogs (n = 7) included gland enlargement, T1-weighted hypointensity, T2-weighted hyperintensity, and increased contrast enhancement; CT features in affected dogs (2) included gland enlargement and hypodensity on unenhanced images. Retrobulbar masses were identified via ultrasonography in 9 of 10 orbits examined, and zygomatic salivary gland origin was detected in 4.

CONCLUSIONS AND CLINICAL RELEVANCE

Visualization of anatomic structures for diagnosis of zygomatic sialadenitis and evaluation of adjacent structures was excellent via MRI and CT Ultrasonography was less definitive but useful for sample collection.

Gadoxetate disodium-enhanced hepatobiliary phase MRI of hepatocellular carcinoma: correlation with histological characteristics

OBJECTIVE

The purpose of this study was to assess whether gadoxetate disodium-enhanced hepatobiliary phase MRI could predict the histologic factors of hepatocellular carcinomas (HCCs).

MATERIALS AND METHODS

Fifty-three HCCs histopathologically proved by surgery in 51 patients were evaluated retrospectively. All patients underwent gadoxetate disodium-enhanced MRI before surgical resection. The differences in contrast enhancement ratio of the lesions and differences in contrast-to-noise ratio (CNR) among the histologic grades of HCC were compared by using the Kruskal-Wallis test. The Spearman method was used to determine the correlations among contrast enhancement ratio, CNR, cell density ratio, and positivity for anti-hepatocyte antibody, keratin 7, and keratin 19.

RESULTS

Of 53 HCCs, 50 showed low signal intensity on hepatobiliary phase images, whereas three HCCs were hyperintense on hepatobiliary phase images compared with surrounding hepatic parenchyma. Although well-differentiated HCCs tended to show higher contrast enhancement, there was no statistical significance between contrast enhancement ratio of the tumors and histologic grade (p = 0.414). No significant difference was observed between CNR and histologic grade (p = 0.965). The contrast enhancement ratios of the tumors were significantly lower in the keratin 19-positive group than in the keratin 19-negative group (p = 0.015). There was no significant correlation among contrast enhancement ratio, anti-hepatocyte antibody positivity, cell density ratio, and keratin 7 positivity (p > 0.05).

CONCLUSION

The contrast enhancement ratio and CNR of HCCs were not correlated with histologic grades. The contrast enhancement ratio was significantly lower in keratin 19-positive HCCs.

The role of hepatocyte-specific staining in liver pathology

The advantages of MRI in the investigation of liver disease are well documented. Recent developments, including fast scanning technique and new MRI contrast agents, enable improved detection and characterization of focal liver lesions. Therefore, a definitive diagnosis can be made avoiding invasive procedures, such as liver biopsy. In this article, a special emphasis is placed on the clinical use of combined perfusional and hepatocyte-selective MRI contrast agents, which allow us to obtain morphologic and vascular information, owing to the dynamic study, as well as functional information, owing to the hepatocyte-selective phase of enhancement. Different clinical scenarios are considered in order to highlight the proper use of the hepatocyte phase to noninvasively characterize and detect different focal liver lesions.

Realce por contraste de lesões hepáticas em pacientes com cirrose: estudo cruzado comparativo de dois agentes de contraste para RM realizado em uma única instituição. Resultados preliminares

OBJETIVO: Comparar, prospectivamente, gadopentato de dimeglumina (Gd-DTPA) e gadobenato de dimeglumina (Gd-BOPTA), ambos em dose plena, na detecção de lesões hepáticas focais, por meio de RM em pacientes com doença hepática crônica. MATERIAIS E MÉTODOS: Oito pacientes com cirrose hepática e forte suspeita de um pequeno carcinoma hepatocelular, baseada em RM anterior, foram submetidos a exames de RM contrastada, um com dose plena de Gd-DTPA e outro com dose plena de Gd-BOPTA. Os exames foram realizados com um intervalo de 72 a 108 horas. Dois radiologistas independentes realizaram avaliação às cegas das imagens, considerando número, caracterização e realce das lesões, além de preferências subjetivas. RESULTADOS: Não houve diferença estatisticamente significante entre os dois exames quanto à detecção e caracterização das lesões. Observou-se um incremento de 18% no realce da lesão dominante pelo Gd-BOPTA, em comparação com o Gd-DTPA. Na maioria dos casos, ambos os observadores cegos subjetivamente preferiram as imagens utilizando Gd-BOPTA àquelas com Gd-DTPA, com base no maior realce e melhor definição das margens das lesões. CONCLUSÃO: Em doses plenas equivalentes, Gd-BOPTA e Gd-DTPA são similares na detecção e caracterização de lesões hepáticas focais em pacientes com doença hepática crônica. Entretanto, o Gd-BOPTA foi superior em relação ao realce da lesão, assim como na preferência subjetiva dos observadores.

Quarter-dose (0.025 mmol/kg) gadobenate dimeglumine for abdominal MRI in patients at risk for nephrogenic systemic fibrosis: preliminary observations

OBJECTIVE

The purpose of this study is to evaluate the feasibility of 0.025 mmol/kg gadobenate dimeglumine, which is one quarter of the standard dose, for abdominal 3-T MRI studies in patients considered to be at risk for nephrogenic systemic fibrosis, using qualitative and quantitative measures and comparison with higher doses.

MATERIALS AND METHODS

The MRI database was retrospectively searched to select consecutive patients who underwent quarter-dose gadobenate dimeglumine-enhanced abdominal MRI at 3 T, between January 1, 2009, and January 15, 2010, and who underwent half-dose (0.05 mmol/kg) gadobenate dimeglumine-enhanced abdominal MRI at 3 T during one randomly chosen month. There were 25 patients in the final quarter-dose group (16 men and nine women; mean age, 57 years) and 44 patients in the half-dose group (21 men and 23 women; mean age, 58 years). The enhancement of abdominal organs and aorta was evaluated qualitatively and quantitatively on contrast-enhanced images. The overall quality of abdominal enhancement was also evaluated.

RESULTS

Reviewers rated the diagnostic enhancement of the evaluated organs in all phases of enhancement for both studied doses, but the half dose had significantly higher ratings than did the quarter dose in all comparisons (p, 0.034 to < 0.0001), except in the pancreas in the early hepatic venous phase (p = 0.095 for reviewer 1; p = 0.0611 for reviewer 2). The overall enhancement quality of the quarter dose was rated as good in all phases of enhancement, although it was significantly lower than that for the half dose (p ≤ 0.0001). The liver, pancreas, renal cortex, and aorta had 1.52-1.93-fold, 1.53-1.90-fold, 1.46-1.77-fold, and 1.58-1.84-fold, respectively, higher percentages of enhancement with the half dose than with the quarter dose (p, 0.0049 to < 0.0001).

CONCLUSION

A one-quarter dose of gadobenate dimeglumine at 3 T is a feasible alternative for abdominal MRI in patients at risk for nephrogenic systemic fibrosis. Our results might have important clinical implications, because greater safety may be conferred on patients with poor renal function with this low dose of contrast agent.

Chronic hepatitis and cirrhosis on MR imaging

This article focuses on the current role of magnetic resonance imaging in the detection and characterization of chronic hepatitis and cirrhosis. In particular, the characteristic MR imaging features of morphologic changes and focal manifestations of chronic liver disease are highlighted.

Kidney function: glomerular filtration rate measurement with MR renography in patients with cirrhosis

PURPOSE

To assess the accuracy of glomerular filtration rate (GFR) measurements obtained with low-contrast agent dose dynamic contrast material-enhanced magnetic resonance (MR) renography in patients with liver cirrhosis who underwent routine liver MR imaging, with urinary clearance of technetium 99m ((99m)Tc) pentetic acid (DTPA) as the reference standard.

MATERIALS AND METHODS

This HIPAA-compliant study was institutional review board approved. Written informed patient consent was obtained. Twenty patients with cirrhosis (14 men, six women; age range, 41-70 years; mean age, 54.6 years) who were scheduled for routine 1.5-T liver MR examinations to screen for hepatocellular carcinoma during a 6-month period were prospectively included. Five-minute MR renography with a 3-mL dose of gadoteridol was performed instead of a routine test-dose timing examination. The GFR was estimated at MR imaging with use of two kinetic models. In one model, only the signal intensities in the aorta and kidney parenchyma were considered, and in the other, renal cortical and medullary signal intensities were treated separately. The GFR was also calculated by using serum creatinine levels according to the Cockcroft-Gault and modification of diet in renal disease (MDRD) formulas. All patients underwent a (99m)Tc-DTPA urinary clearance examination on the same day to obtain a reference GFR measurement. The accuracies of all MR- and creatinine-based GFR estimations were compared by using Wilcoxon signed rank tests.

RESULTS

The mean reference GFR, based on (99m)Tc-DTPA clearance, was 74.9 mL/min/1.73 m(2) ± 27.7 (standard deviation) (range, 10.3-120.7 mL/min/1.73 m(2)). With both kinetic models, 95% of MR-based GFRs were within 30% of the reference values, whereas only 40% and 60% of Cockcroft-Gault- and MDRD-based GFRs, respectively, were within this range. MR-based GFR estimates were significantly more accurate than creatinine level-based estimates (P < .001).

CONCLUSION

GFR assessment with MR imaging, which outperformed the Cockcroft-Gault and MDRD formulas, adds less than 10 minutes of table time to a clinically indicated liver MR examination without ionizing radiation.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101338/-/DC1.

Manganese-enhanced MRI predicts the histological grade of hepatocellular carcinoma in potential surgical candidates

AIM

To evaluate the role of manganese-enhanced magnetic resonance (Mn-MRI) in predicting tumour differentiation prior to liver transplant or resection for hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

The inclusion criteria were patients with HCC who underwent Mn-MRI prior to transplantation or resection from 2001-2008. T1-weighted MRI images were acquired at 0 and 24h after manganese dipyridoxal diphosphate (MnDPDP) intravenous contrast medium and reviewed prospectively. Manganese retention at 24h was correlated with tumour differentiation and disease-free survival.

RESULTS

Eighty-six patients underwent Mn-MRI (transplantation 60, resection 26); 114/125 lesions (91%) that were arterialised as evidenced at computed tomography (CT) and had manganese uptake on MRI were HCC. There were 11 false positives (9%) that were regenerative nodules. Ten of fourteen non-manganese-retaining HCC (71%) were poorly differentiated, compared with only 13/114 manganese-retaining HCC (11%) (p<0.0001). Sensitivity, specificity, positive and negative predictive values of non-retention of MnDPDP in predicting poorly differentiated tumours were 0.43, 0.96, 0.71 and 0.88. Median disease-free survival of patients with non-manganese-retaining HCC was less than for patients with manganese-retaining HCC (14±5 months versus 39±3 months, log rank p=0.025).

CONCLUSION

Non-manganese-retaining HCCs are likely to be poorly differentiated and have a poor prognosis. Manganese-enhanced MRI appears to have a role in preoperative assessment of HCC and warrants further evaluation.

Enhancement of liver parenchyma after injection of hepatocyte-specific MRI contrast media: a comparison of gadoxetic acid and gadobenate dimeglumine

PURPOSE

To compare enhancement of liver parenchyma in MR imaging after injection of hepatocyte-specific contrast media.

MATERIALS AND METHODS

Patients (n = 295) with known/suspected focal liver lesions randomly received 0.025 mmol gadoxetic acid/kg body weight or 0.05 mmol gadobenate dimeglumine/kg body weight by means of bolus injection. MR imaging was performed before and immediately after injection, and in the delayed phase at approved time points (20 min after injection of gadoxetic acid and 40 min after injection of gadobenate dimeglumine). The relative liver enhancement for the overall population and a cirrhotic subgroup was compared in T1-weighted GRE sequences. An independent radiologist performed signal intensity measurements. Enhancement ratios were compared using confidence intervals (CIs).

RESULTS

The relative liver enhancement in the overall population was superior with gadoxetic acid (57.24%) versus gadobenate dimeglumine (32.77%) in the delayed-imaging phase. The enhancement ratio between the contrast media was statistically significant at 1.75 (95% CI: 1.46-2.13). In the delayed phase, the enhancement of cirrhotic liver with gadoxetic acid (57.00%) was comparable to that in the overall population. Enhancement with gadobenate dimeglumine was inferior in cirrhotic liver parenchyma (26.85%).

CONCLUSION

In the delayed, hepatocyte-specific phase, liver enhancement after injection of gadoxetic acid was superior to that obtained with gadobenate dimeglumine.

MR imaging of liver fibrosis: current state of the art

Chronic liver disease is a major public health problem worldwide. Liver fibrosis, a common feature of almost all causes of chronic liver disease, involves the accumulation of collagen, proteoglycans, and other macromolecules within the extracellular matrix. Fibrosis tends to progress, leading to hepatic dysfunction, portal hypertension, and ultimately cirrhosis. Liver biopsy, the standard of reference for diagnosing liver fibrosis, is invasive, costly, and subject to complications and sampling variability. These limitations make it unsuitable for diagnosis and longitudinal monitoring in the general population. Thus, development of a noninvasive, accurate, and reproducible test for diagnosis and monitoring of liver fibrosis would be of great value. Conventional cross-sectional imaging techniques have limited capability to demonstrate liver fibrosis. In clinical practice, imaging studies are usually reserved for evaluation of the presence of portal hypertension or hepatocellular carcinoma in cases that have progressed to cirrhosis. In response to the rising prevalence of chronic liver diseases in Western nations, a number of imaging-based methods including ultrasonography-based transient elastography, computed tomography-based texture analysis, and diverse magnetic resonance (MR) imaging-based techniques have been proposed for noninvasive diagnosis and grading of hepatic fibrosis across its entire spectrum of severity. State-of-the-art MR imaging-based techniques in current practice and in development for noninvasive assessment of liver fibrosis include conventional contrast material-enhanced MR imaging, double contrast-enhanced MR imaging, MR elastography, diffusion-weighted imaging, and MR perfusion imaging.

MR imaging of liver fibrosis: current state of the art

Chronic liver disease is a major public health problem worldwide. Liver fibrosis, a common feature of almost all causes of chronic liver disease, involves the accumulation of collagen, proteoglycans, and other macromolecules within the extracellular matrix. Fibrosis tends to progress, leading to hepatic dysfunction, portal hypertension, and ultimately cirrhosis. Liver biopsy, the standard of reference for diagnosing liver fibrosis, is invasive, costly, and subject to complications and sampling variability. These limitations make it unsuitable for diagnosis and longitudinal monitoring in the general population. Thus, development of a noninvasive, accurate, and reproducible test for diagnosis and monitoring of liver fibrosis would be of great value. Conventional cross-sectional imaging techniques have limited capability to demonstrate liver fibrosis. In clinical practice, imaging studies are usually reserved for evaluation of the presence of portal hypertension or hepatocellular carcinoma in cases that have progressed to cirrhosis. In response to the rising prevalence of chronic liver diseases in Western nations, a number of imaging-based methods including ultrasonography-based transient elastography, computed tomography-based texture analysis, and diverse magnetic resonance (MR) imaging-based techniques have been proposed for noninvasive diagnosis and grading of hepatic fibrosis across its entire spectrum of severity. State-of-the-art MR imaging-based techniques in current practice and in development for noninvasive assessment of liver fibrosis include conventional contrast material-enhanced MR imaging, double contrast-enhanced MR imaging, MR elastography, diffusion-weighted imaging, and MR perfusion imaging.

Biliary MR imaging with Gd-EOB-DTPA and its clinical applications

The hepatocyte-specific contrast agent gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) was developed to improve the detection and characterization of focal liver lesions at magnetic resonance (MR) imaging. Approximately 50% of the injected dose is taken up into the functional hepatocyte and is excreted via the biliary system. Because of this property, Gd-EOB-DTPA has the potential to be a biliary contrast agent. When combined with T2-weighted MR cholangiography, Gd-EOB-DTPA-enhanced MR imaging can allow morphologic and functional assessment of the biliary system. Gd-EOB-DTPA-enhanced MR cholangiography could be effective in evaluation of biliary anatomy, differentiation of biliary from extrabiliary lesions, diagnosis of cholecystitis, assessment of bile duct obstruction, detection of bile duct injury including leakage and stricture, evaluation of biliary-enteric anastomoses, postprocedure evaluation, differentiation of biloma from other pathologic conditions, and evaluation of sphincter of Oddi dysfunction. However, the clinical applications of this imaging technique have not yet been fully explored, and further investigations are needed to determine the utility of Gd-EOB-DTPA-enhanced MR cholangiography in a clinical setting.

Magnetic resonance imaging of gallbladder and biliary system

Gallbladder and biliary system pathologic component is a spectrum of benign and malignant conditions. Standard magnetic resonance imaging techniques when used together with magnetic resonance cholangiopancreatography (MRCP) can evaluate gallbladder and biliary system pathologic conditions. Inflammatory diseases are characterized by thickening and intense mucosal contrast enhancement of the affected bile ducts and or gallbladder wall. Postinflammatory changes can be appreciated on MRCP with short or long segment strictures of the bile ducts. Serial contrast-enhanced images show reactive inflammatory changes in the liver parenchyma. Neoplastic diseases of the gallbladder and the biliary tree are evaluated on T2-weighted fat-suppressed echo train and serial contrast-enhanced images and their obstructive effect can be displayed on MRCP images. In this paper, we will review the spectrum of MRI findings of gallbladder and biliary system pathologic conditions.

Advances in radiological imaging of gastrointestinal tumors

This article summarizes the recent advances in radiological imaging in the hepatogastrointestinal field in terms of detection, characterization and staging of tumors. Introduction of multidetector row computed tomography technology has helped computed tomography to excel in its already established indications, and has expanded its capabilities by adding new clinical applications, such as computed tomography angiography, liver perfusion, computed tomography enterography or enteroclysis, and virtual colonoscopy. Contrast-enhanced ultrasound has dramatically changed the role of ultrasound in liver tumor characterization, detection, and other applications. Combining the advantages of unsurpassed soft tissue contrast and lack of ionizing radiation, magnetic resonance imaging of the gastrointestinal tract has become increasingly used clinically. Moreover, substantial progress in molecular and cellular magnetic resonance imaging has been achieved in the past few years. Particularly, the increasing number of available specific contrast agents dedicated to the evaluation of the liver and lymph nodes shows promises in the area of oncologic abdominal imaging.

Liver MR Imaging: 1.5T versus 3T

This article focuses on technical challenges in transferring 1.5T liver protocols to 3T systems and the overall comparison of MR sequences, highlighting the advantages and disadvantages of imaging at the higher field strength. An important benefit is the capacity of acquiring high-quality, thin-section postgadolinium T1-weighted three-dimensional gradientecho sequences, most clinically relevant for the detection and characterization of small hypervascular malignant diseases. Further research and development is necessary to overcome disadvantages, such as with in- and out-of phase T1-weighted gradient-echo sequences, and to minimize artifacts that appear at 3T.

MR contrast agents for liver imaging: what, when, how

The major classes of contrast agents currently used for magnetic resonance (MR) imaging of the liver include extracellular agents (eg, low-molecular-weight gadolinium chelates), reticuloendothelial agents (eg, ferumoxides), hepatobiliary agents (eg, mangafodipir), blood pool agents, and combined agents. Mechanisms of action, dosage, elimination, toxic effects, indications for use, and MR imaging technical considerations vary according to class. Gadolinium chelates are the most widely used. Ferumoxides are a useful adjunct for detection of hepatocellular carcinoma, particularly when used in combination with gadolinium to achieve improved lesion-to-liver contrast over that achievable with gadolinium alone. Mangafodipir is a prototype hepatobiliary agent that is taken up by lesions with functioning hepatocytes. It may be used for MR cholangiography as well as liver imaging. Although mangafodipir is no longer commercially available in the United States, it is currently marketed and used in Europe. Blood pool agents have not yet been approved for human use in the United States. However, a new combined MR contrast agent, gadobenate dimeglumine, recently was approved, and other agents are in various stages of development.

Laparoscopic liver surgery: Shifting the management of liver tumors

Laparoscopic liver surgery has evolved rapidly over the past 5 years in a select number of centers. The growing experience with these procedures has resulted in a shift in the diagnostic and therapeutic approach to common liver tumors. The fact that resection of benign and malignant hepatic masses can now be accomplished laparoscopically with relatively low morbidity has influenced the decision-making process for physicians involved in the diagnosis and management of these lesions. For example, should a gastroenterologist or hepatologist seeing a 32-year-old woman with an asymptomatic 4 cm hepatic lesion that is radiologically indeterminate for adenoma or focal nodular hyperplasia (FNH): (1) continue to observe with annual computed tomography/magnetic resonance imaging (CT/MRI) scans, (2) subject the patient to a liver biopsy, or (3) refer for laparoscopic resection? For a solitary malignant liver tumor in the left lateral segment, should laparoscopic resection be considered the new standard of care, assuming the surgeon can perform the operation safely? We present current data and representative case studies on the use of laparoscopic liver resection at 2 major medical centers in the United States. We propose that surgical engagement defined by the managing physician's decision to proceed with a surgical intervention is increasingly affected by the availability of, and experience with, laparoscopic liver resection.

MR contrast agents, the old and the new

Magnetic resonance (MR) contrast agents are increasingly being used to help detect and characterize various neoplastic, inflammatory and functional abnormalities. The extracellular, non-specific contrast agents gadolinium chelates are by far the most widely used. Over the past few years a number of MR organ specific contrast agents have been introduced. MRI contrast agents are generally safe and well tolerated. The present review summarizes the properties, main characteristics and imaging applications of commercially available compounds as well as safety of these agents in normal and high-risk patients.