New proposal for the staging of nonalcoholic steatohepatitis: evaluation of liver fibrosis on Gd-EOB-DTPA-enhanced MRI

This Is What Metabolic Dysfunction-Associated Steatotic Liver Disease Looks Like: Potential of a Multiparametric MRI Protocol

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a prevalent condition with a broad spectrum defined by liver biopsy. This gold standard method evaluates three features: steatosis, activity (ballooning and lobular inflammation), and fibrosis, attributing them to certain grades or stages using a semiquantitative scoring system. However, liver biopsy is subject to numerous restrictions, creating an unmet need for a reliable and reproducible method for MASLD assessment, grading, and staging. Noninvasive imaging modalities, such as magnetic resonance imaging (MRI), offer the potential to assess quantitative liver parameters. This review aims to provide an overview of the available MRI techniques for the three criteria evaluated individually by liver histology. Here, we discuss the possibility of combining multiple MRI parameters to replace liver biopsy with a holistic, multiparametric MRI protocol. In conclusion, the development and implementation of such an approach could significantly improve the diagnosis and management of MASLD, reducing the need for invasive procedures and paving the way for more personalized treatment strategies.

Assessment of liver function by gadoxetic acid avidity in MRI in a model of rapid liver regeneration in rats

BACKGROUND

This animal study investigates the hypothesis of an immature liver growth following ALPPS (associating liver partition and portal vein ligation for staged hepatectomy) by measuring liver volume and function using gadoxetic acid avidity in magnetic resonance imaging (MRI) in models of ALPPS, major liver resection (LR) and portal vein ligation (PVL).

METHODS

Wistar rats were randomly allocated to ALPPS, LR or PVL. In contrast-enhanced MRI scans with gadoxetic acid (Primovist®), liver volume and function of the right median lobe (=future liver remnant, FLR) and the deportalized lobes (DPL) were assessed until post-operative day (POD) 5. Liver functionFLR/DPL was defined as the inverse value of time from injection of gadoxetic acid to the blood pool-corrected maximum signal intensityFLR/DPL multiplied by the volumeFLR/DPL.

RESULTS

In ALPPS (n = 6), LR (n = 6) and PVL (n = 6), volumeFLR and functionFLR increased proportionally, except on POD 1. Thereafter, functionFLR exceeded volumeFLR increase in LR and ALPPS, but not in PVL. Total liver function was significantly reduced after LR until POD 3, but never undercuts 60% of its pre-operative value following ALPPS and PVL.

DISCUSSION

This study shows for the first time that functional increase is proportional to volume increase in ALPPS using gadoxetic acid avidity in MRI.

Diagnosis of Hepatocellular Carcinoma Using Gd-EOB-DTPA MR Imaging

Gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA; Gadoxetic acid; Gadoxetate disodium) is a hepatocyte-specific MR contrast agent. It acts as an extracellular contrast agent in the early phase after intravenous injection, and then is taken up by hepatocytes later. Using this contrast agent, we can evaluate the hemodynamics of the liver and liver tumors, and can therefore improve the detection and characterization of hepatocellular carcinoma (HCC). Gd-EOB-DTPA helps in the more accurate detection of hypervascular HCC than by other agents. In addition, Gd-EOB-DTPA can detect hypovascular HCC, which is an early stage of the multi-stage carcinogenesis, with a low signal in the hepatobiliary phase. In addition to tumor detection and characterization, Gd-EOB-DTPA contrast-enhanced MR imaging can be applied for liver function evaluation and prognoses evaluation. Thus, Gd-EOB-DTPA plays an important role in the diagnosis of HCC. However, we have to employ optimal imaging techniques to improve the diagnostic ability. In this review, we aimed to discuss the characteristics of the contrast media, optimal imaging techniques, diagnosis, and applications.

Quantification of liver function using gadoxetic acid-enhanced MRI

The introduction of hepatobiliary contrast agents, most notably gadoxetic acid (GA), has expanded the role of MRI, allowing not only a morphologic but also a functional evaluation of the hepatobiliary system. The mechanism of uptake and excretion of gadoxetic acid via transporters, such as organic anion transporting polypeptides (OATP1,3), multidrug resistance-associated protein 2 (MRP2) and MRP3, has been elucidated in the literature. Furthermore, GA uptake can be estimated on either static images or on dynamic imaging, for example, the hepatic extraction fraction (HEF) and liver perfusion. GA-enhanced MRI has achieved an important role in evaluating morphology and function in chronic liver diseases (CLD), allowing to distinguish between the two subgroups of nonalcoholic fatty liver diseases (NAFLD), simple steatosis and nonalcoholic steatohepatitis (NASH), and help to stage fibrosis and cirrhosis, predict liver transplant graft survival, and preoperatively evaluate the risk of liver failure if major resection is planned. Finally, because of its noninvasive nature, GA-enhanced MRI can be used for long-term follow-up and post-treatment monitoring. This review article aims to describe the current role of GA-enhanced MRI in quantifying liver function in a variety of hepatobiliary disorders.

Hyperintensity at fat spared area in steatotic liver on the hepatobiliary phase MRI

PURPOSE

We aimed to investigate the reasons for hyperintensity at fat spared area in steatotic liver at hepatobiliary phase (HBP) on gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) enhanced liver magnetic resonance imaging.

METHODS

Twenty-two patients with focal fat spared area demonstrating hyperintensity on HBP images were included. A region of interest was placed on in- and opposed-phase images at fat spared area and liver to measure the fat. The measurement was also performed on precontrast T1-weighted and HBP images. The signal intensities of spleen, kidney, muscle, intervertebral disc, and spinal cord were also recorded.

RESULTS

The mean fat fraction of liver and fat spared area was 24.86% (8%-46%) and 8.41% (1%-34%), respectively (P < 0.001). There was a significant positive correlation between liver parenchyma fat fraction and delta fat fraction (r=0.74, P < 0.001). The mean signal intensity values of fat spared areas were higher compared with liver on precontrast T1-weighted and HBP images (P < 0.001). The mean relative enhancement ratio of liver and fat spared areas were 0.98 (0.05-1.90) and 1.15 (0.22-2.03), respectively (P < 0.001). However, in 6 patients, the relative enhancement ratio of liver and fat spared areas were almost equal. The uptake of Gd-EOB at fat spared area was not correlated with the degree of steatosis (r = -0.01, P = 0.95).

CONCLUSION

Fat spared area in steatotic liver appears hyperintense on HBP images due to increased relative enhancement ratio and/or baseline hyperintensity on precontrast images.

Qualitative assessment of EOB-GD-DTPA and Gd-BT-DO3A MR contrast studies in HCC patients and colorectal liver metastases

Aim

To compare liver-specific EOB-GD-DTPA and liver-non-specific Gd-BT-DO3A MR, in hepatocellular carcinoma (HCC) and liver colorectal metastases.

Material and methods

Seventy HCC patients with 158 nodules and 90 colorectal liver metastases (mCRC) with 370 lesions were included in the retrospective analysis. HCC patients underwent MR at 0 time (MR0), after 3 (MR3) and 6 months (MR6) using two different CM; 69 mCRC patients underwent MR with Gd-EOB-BTPA and 21 mCRC patients with Gd-BT-DO3A. We evaluated arterial phase hyperenhancement, lesion-to-liver contrast during portal phase, hepatobiliary phase parenchymal hyperenhancement.

Results

In HCC patients arterial phase hyperenhancement degree was statistically higher (p = 0.03) with Gd-BT-DO3A (mean 4) than GD-EOB-DTPA (mean 2.6), while we found no significant statistical differences among mean (2.6) values at MR0 and MR6 using GD-EOB-DTPA. For all 209 patients underwent Gd-EOB-DTPA, we found that lesion-to-liver contrast during portal phase mean value was 4 while for patients underwent MR with Gd-BT-DO3A was 3 (p = 0.04). For HCC hepatobiliary phase parenchymal hyperenhancement mean value was 2.4. For mCRC patients: among 63 patients underwent previous chemotherapy hepatobiliary phase parenchymal hyperenhancement mean value was 3.1 while for 6 patients no underwent previous chemotherapy was 4 (p = 0.05).

Conclusions

Gd-EOB-DTPA should be chosen in pre surgical setting in patients with colorectal liver metastases.

Assessment of liver fibrosis with gadoxetic acid-enhanced MRI: comparisons with transient elastography, ElastPQ, and serologic fibrosis markers

OBJECTIVES

To compare the diagnostic performance of gadoxetic acid-enhanced magnetic resonance imaging (MRI), ultrasonography (US)-based elastography, and serologic fibrosis markers in assessing the stage of liver fibrosis.

MATERIALS AND METHODS

This retrospective study included 67 patients (55 male and 12 female; mean age 62.5 years) who underwent gadoxetic acid-enhanced MRI and liver stiffness measurements before liver biopsy or surgery between January 2014 and January 2018. Measurements were performed using transient elastography (TE), ultrasound shear wave elastography point quantification (ElastPQ), and blood tests. The following MRI-based fibrosis markers were assessed: contrast enhancement index (CEI), liver-spleen contrast ratio (LSC), liver-portal vein contrast ratio (LPC), and signal intensity ratio (SIR). The diagnostic performances of fibrosis markers were compared using the area under the receiver operating characteristic curve (AUC), with histopathologic fibrosis stage as the reference standard.

RESULTS

The fibrosis stages were F0-F1 (n = 17), F2 (n = 7), F3 (n = 20), and F4 (n = 23). MRI-based fibrosis markers negatively correlated with histologic stage: CEI (r = -0.786); LSC (r = - 0.718); LPC (r = - 0.448); and SIR (r = - 0.617; all P < 0.001). For diagnosis of either significant liver fibrosis (≥ F2) or cirrhosis (F4), the CEI provided better diagnostic accuracy (AUC = 0.898 and 0.881) than the aspartate aminotransferase-to-platelet ratio index (APRI) (AUC = 0.699 and 0.715; all P < 0.05). The CEI displayed similar diagnostic accuracy for ≥ F2 or F4 when using TE (AUC = 0.866 and 0.884, both P > 0.05) or ElastPQ [AUC = 0.751 (P = 0.021) and AUC = 0.786 (P = 0.234)].

CONCLUSIONS

The CEI measured by gadoxetic acid-enhanced MRI allows the staging of liver fibrosis, with a diagnostic accuracy comparable to that of TE and superior to that of ElastPQ or APRI.

Comparison between dynamic gadoxetate-enhanced MRI and 99mTc-mebrofenin hepatobiliary scintigraphy with SPECT for quantitative assessment of liver function

Objectives

To compare Gd-EOB-DTPA dynamic hepatocyte-specific contrast-enhanced MRI (DHCE-MRI) with ^99mTc-mebrofenin hepatobiliary scintigraphy (HBS) as quantitative liver function tests for the preoperative assessment of patients undergoing liver resection.

Methods

Patients undergoing liver surgery and preoperative assessment of future remnant liver (FRL) function using ^99mTc-mebrofenin HBS were included. Patients underwent DHCE-MRI. Total liver uptake function was calculated for both modalities: mebrofenin uptake rate (MUR) and Ki respectively. The FRL was delineated with both SPECT-CT and MRI to calculate the functional share. Blood samples were taken to assess biochemical liver parameters.

Results

A total of 20 patients were included. The HBS-derived MUR and the DHCE-MRI-derived mean Ki correlated strongly for both total and FRL function (Pearson r = 0.70, p = 0.001 and r = 0.89, p < 0.001 respectively). There was a strong agreement between the functional share determined with both modalities (ICC = 0.944, 95% CI 0.863–0.978, n = 20). There was a significant negative correlation between liver aminotransferases and bilirubin for both MUR and Ki.

Conclusions

Assessment of liver function with DHCE-MRI is comparable with that of ^99mTc-mebrofenin HBS and has the potential to be combined with diagnostic MRI imaging. This can therefore provide a one-stop-shop modality for the preoperative assessment of patients undergoing liver surgery.

Key Points

• Quantitative assessment of liver function using hepatobiliary scintigraphy is performed in the preoperative assessment of patients undergoing liver surgery in order to prevent posthepatectomy liver failure.

• Gd-EOB-DTPA dynamic hepatocyte-specific contrast-enhanced MRI (DHCE-MRI) is an emerging method to quantify liver function and can serve as a potential alternative to hepatobiliary scintigraphy.

• Assessment of liver function with dynamic gadoxetate-enhanced MRI is comparable with that of hepatobiliary scintigraphy and has the potential to be combined with diagnostic MRI imaging.

Electronic supplementary material

The online version of this article (10.1007/s00330-019-06029-7) contains supplementary material, which is available to authorized users.

Staging of liver fibrosis using Gd-EOB-DTPA and Gd-BOPTA enhanced magnetic resonance imaging

The severity of cirrhosis is closely related to its clinical treatment. Therefore, it is important to stage liver fibrosis accurately. Although liver biopsy can accurately stage the degree of cirrhosis, it has certain limitations in clinical application because of its invasive nature. Magnetic resonance imaging (MRI) has been used in the diagnosis of liver diseases. In recent years, two new contrast agents, gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) and gadobenate dimeglumine (Gd-BOPTA), have been successfully used for noninvasive liver imaging. They can be used for liver fibrosis staging and assessment of liver function. Cirrhotic patients with different liver function levels have a statistical difference in the liver parenchyma enhancement after giving contrast agents. This article briefly summarizes the progress of Gd-EOB-DTPA and Gd-BOPTA enhanced MRI in staging liver fibrosis stage.

Evaluation of hepatic function using dynamic contrast-enhanced magnetic resonance imaging in melanocortin 4 receptor-deficient mice as a model of nonalcoholic steatohepatitis

INTRODUCTION

Melanocortin 4 receptor-deficient (MC4R-KO) mice fed a high-fat diet (HFD) develop liver pathology similar to human nonalcoholic steatohepatitis (NASH). However, although liver histology and blood biochemistry have been reported, hepatic function has not been evaluated. In the present study, we evaluated hepatic function in MC4R-KO mice fed an HFD using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with gadolinium‑ethoxybenzyl‑diethylenetriamine pentaacetic acid (Gd-EOB-DTPA).

MATERIALS AND METHODS

Wild type (WT) mice and MC4R-KO mice were fed a standard diet (SD) or an HFD for 20 weeks. The hepatic signal intensity was obtained from DCE-MRI images, and relative enhancement (RE), the time to maximum RE (T_max), and the half-life of RE elimination (T_1/2) were calculated. Histopathological analysis was then performed.

RESULTS

Histological analysis with nonalcoholic fatty liver disease activity score (NAS) revealed that MC4R-KO mice fed an HFD achieved the NAS of 5. There was moderate fibrosis in MC4R-KO mice fed an HFD. DCE-MRI with Gd-EOB-DTPA showed that T_max and T_1/2 were significantly longer in MC4R-KO mice fed an HFD compared with wild type (WT) mice (T_max, WT, 3.9 ± 0.4 min; MC4R-KO, 7.4 ± 1.5 min; T_1/2, WT, 23.7 ± 1.9 min; MC4R-KO, 62.5 ± 18.5 min). T_max and T_1/2 were significantly correlated with histopathologic score (steatosis vs. Tmax, rho = 0.48, P = 0.04; steatosis vs. T_1/2, rho = 0.50, P = 0.03; inflammation vs. Tmax, rho = 0.55, P = 0.02; inflammation vs. T_1/2, rho = 0.61, P < 0.01; ballooning vs. T_1/2, rho = 0.51, P = 0.03;fibrosis vs T_max, rho = 0.72, P < 0.01; fibrosis vs T_1/2, rho = 0.75, P < 0.01).

CONCLUSIONS

MC4R-KO mice fed an HFD developed obesity and NASH. The liver kinetics of Gd-EOB-DTPA were significantly different in MC4R-KO mice fed an HFD from WT mice, and correlated with the histopathologic score. These results suggest that MC4R-KO mice fed an HFD mimic the hepatic pathology and liver function of human NASH, and therefore might be useful for the study of hepatic dysfunction during the fibrotic stage of NASH.

A radiologist's point of view in the presurgical and intraoperative setting of colorectal liver metastases

Multidisciplinary management of patients with metastatic colorectal cancer requires in each phase an adequate choice of the most appropriate imaging modality. The first challenging step is liver lesions detection and characterization, using several imaging modality ultrasound, computed tomography, magnetic resonance and positron emission tomography. The criteria to establish the metastases resectability have been modified. Not only the lesions number and site but also the functional volume remnant after surgery and the quality of the nontumoral liver must be taken into account. Radiologists should identify the liver functional volume remnant and during liver surgical procedures should collaborate with the surgeon to identify all lesions, including those that disappeared after the therapy, using intraoperative ultrasound with or without contrast medium.

The role of imaging in prediction of post-hepatectomy liver failure

Post-hepatectomy liver failure (PHLF) is not only a leading cause of mortality but also a leading cause of life-threatening complications in patients undergoing liver resection. The ability to accurately detect the emergence of PHLF represents a crucially important step. Currently, PHLF can be predicted by a comprehensive evaluation of biological, clinical, and anatomical parameters. With the development of new technologies, imaging methods including elastography, diffusion-weighted magnetic resonance imaging, and gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid-enhanced MRI play a more significant role in the pre-operative prediction and assessment of PHLF. In this review, we summarize the mainstream studies, with the aim of evaluating the role of imaging and improving the clinical value of existing scoring systems for predicting PHLF.

Thin-slice Free-breathing Pseudo-golden-angle Radial Stack-of-stars with Gating and Tracking T1-weighted Acquisition: An Efficient Gadoxetic Acid-enhanced Hepatobiliary-phase Imaging Alternative for Patients with Unstable Breath Holding

Purpose:

To compare four free-breathing scan techniques for gadoxetic acid-enhanced hepatobiliary phase imaging with conventional breath-hold scans.

Materials and Methods:

Gadoxetic acid-enhanced hepatobiliary phase imaging with six image acquisition sets performed in 50 patients. Image acquisition sets included fat-suppressed 3D T₁-weighted turbo field echo with free-breathing pseudo-golden-angle radial stack-of-stars (FBRS) acquisition, FBRS with track (FBRS_T), FBRS with gate and track (FBRS_G&T), thin-slice FBRS with gate and track (thin-slice FBRS_G&T), free-breathing Cartesian acquisition (Cartesian_FB), and breath-hold Cartesian acquisition (Cartesian_BH). Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and image quality compared to the six-image acquisition sets.

Results:

Signal-to-noise ratio and CNR were significantly higher in FBRS, FBRS_T, FBRS_G&T, and thin-slice FBRS_G&T than in Cartesian_FB and Cartesian_BH (P < 0.001). Based on sharpness, motion artifacts, visibility of intrahepatic vessels, and overall image quality, thin-slice FBRS_G&T had the highest image quality followed by Cartesian_BH and FBRS_G&T (P < 0.001). Severe motion artifacts were observed in 25 patients in Cartesian_FB and three patients in Cartesian_BH, whereas image quality remained above the acceptable range in FBRS_G&T, FBRS_T, FBRS, and thin-slice FBRS_G&T in all cases.

Conclusion:

Thin-slice FBRS_G&T demonstrated excellent image quality compared with conventional Cartesian_BH in gadoxetic acid-enhanced hepatobiliary phase imaging. It can be apply to supplemental sequences of patients with unstable breath holding.

Current Modalities for the Assessment of Future Remnant Liver Function

While imaging studies such as computed tomography or magnetic resonance imaging allow the volumetric assessment of the liver segments, only indirect information is provided concerning the quality of the liver parenchyma and its actual functional capacity. Assessment of liver function is therefore crucial in the preoperative workup of patients who require extensive liver resection and in whom portal vein embolization is considered. This review deals with the modalities currently available for the measurement of liver function. Passive liver function tests include biochemical parameters and clinical grading systems such as the Child-Pugh and MELD scores. Dynamic quantitative tests of liver function can be based on clearance capacity tests such as the indocyanine green (ICG) clearance test. Although widely used, discrepancies have been reported for the ICG clearance test in relation with clinical outcome. Nuclear imaging studies have the advantage of providing simultaneous morphologic (visual) and physiologic (quantitative functional) information about the liver. In addition, regional (segmental) differentiation allows specific functional assessment of the future remnant liver. Technetium-99m (^99mTc)-galactosyl human serum albumin scintigraphy and ^99mTc-mebrofenin hepatobiliary scintigraphy potentially identify patients at risk for post-resectional liver failure who might benefit from liver-augmenting techniques. As there is no one test that can measure all the components of liver function, liver functional reserve is estimated based on a combination of clinical parameters and quantitative liver function tests.

Evaluation of hepatic fibrosis: a review from the society of abdominal radiology disease focus panel

Hepatic fibrosis is potentially reversible; however early diagnosis is necessary for treatment in order to halt progression to cirrhosis and development of complications including portal hypertension and hepatocellular carcinoma. Morphologic signs of cirrhosis on ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) alone are unreliable and are seen with more advanced disease. Newer imaging techniques to diagnose liver fibrosis are reliable and accurate, and include magnetic resonance elastography and US elastography (one-dimensional transient elastography and point shear wave elastography or acoustic radiation force impulse imaging). Research is ongoing with multiple other techniques for the noninvasive diagnosis of hepatic fibrosis, including MRI with diffusion-weighted imaging, hepatobiliary contrast enhancement, and perfusion; CT using perfusion, fractional extracellular space techniques, and dual-energy, contrast-enhanced US, texture analysis in multiple modalities, quantitative mapping, and direct molecular imaging probes. Efforts to advance the noninvasive imaging assessment of hepatic fibrosis will facilitate earlier diagnosis and improve patient monitoring with the goal of preventing the progression to cirrhosis and its complications.

Gadoxetic acid-enhanced high temporal-resolution hepatic arterial-phase imaging with view-sharing technique: Impact on the LI-RADS category

PURPOSE

To evaluate the value of view-sharing multi-hepatic arterial-phase (mHAP) imaging for diagnosis of hypervascular hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Forty-seven consecutive patients with HCC underwent gadoxetic acid-enhanced magnetic resonance (MR) imaging before angiographic and lipiodol CT. Hepatic arterial-phase images were obtained at 5 consecutive phases with shared central k-space of 25%, followed by portal venous, late (2 and 3min), and hepatobiliary phase imaging. One-hundred-eight HCC nodules (size: 5-88mm, mean size: 18.2mm) confirmed on angiographic CT and lipiodol CT were evaluated for LI-RADS category and compared with single arterial-phase and mHAP findings regarding wash out, capsule, corona enhancement, and image quality.

RESULTS

Twenty-four HCCs (22.2%) (size: 6-19mm, mean size: 12.3mm) were categorized as LR-3 based on the single arterial-phase. Capsule appearance (25.9%) and washout (57.4%) were most frequently observed in late phase (2min). Corona enhancement was observed in 73.1% of all HCCs on mHAP. For the 24 HCCs of LR-3, corona enhancement was observed in 75% on mHAP and contributed to upgrade category. No significant difference was found in the frequency of corona enhancement between mHAP and angiographic CT (P=0.11). Image quality was valued as good or excellent in all cases.

CONCLUSION

View-sharing mHAP was feasible without compromising image quality and contributed to the improvement in diagnostic confidence for hypervascular HCC in gadoxetic acid-enhance MR imaging.

Hepatic gadoxetic acid uptake as a measure of diffuse liver disease: Where are we?

MRI has emerged as the most comprehensive noninvasive diagnostic tool for focal liver lesions and diffuse hepatobiliary disorders. The introduction of hepatobiliary contrast agents, most notably gadoxetic acid (GA), has expanded the role of MRI, particularly in the functional imaging of chronic liver diseases, such as nonalcoholic fatty liver disease (NAFLD). GA-enhanced MRI (GA-MRI) may help to distinguish between the two subgroups of NAFLD, simple steatosis and nonalcoholic steatohepatitis. Furthermore, GA-MRI can be used to stage fibrosis and cirrhosis, predict liver transplant graft survival, and preoperatively estimate the risk of liver failure should major resection be undertaken. The amount of GA uptake can be estimated, using static images, by the relative liver enhancement, hepatic uptake index, and relaxometry of T1-mapping during the hepatobiliary phase. On the contrary, the hepatic extraction fraction and liver perfusion can be measured on dynamic imaging. Importantly, there is currently no clear consensus as to which of these MR-derived parameters is the most suitable for assessing liver dysfunction. This review article aims to describe the current role of GA-enhanced MRI in quantifying liver function, primarily in diffuse hepatobiliary disorders.

LEVEL OF EVIDENCE

3 J. Magn. Reson. Imaging 2017;45:646-659.

Comparison of the effect of region-of-interest methods using gadoxetic acid-enhanced MR imaging with diffusion-weighted imaging on staging hepatic fibrosis

OBJECTIVE

To evaluate the utility of T1 mapping on gadoxetic acid-enhanced MRI and DWI for staging liver fibrosis and assess the influence of ROI positioning on interobserver variability, T1 relaxation time and ADC value.

METHODS

This retrospective study was approved by the institutional review board and included 150 patients (mean age 58 years old; 91 men and 59 women). Liver fibrosis stages (S) were histopathologically determined. T1 relaxation time and ADC value of liver were measured by three distinct ROI protocols (the whole left lobe liver, the whole right lobe liver and the individual ROIs). T1 relaxation time measurements were compared with ADC values according to S scores. Interobserver variability for the T1 relaxation times and ADC values by the three distinct ROI protocols was analyzed by calculating the ICC.

RESULTS

T1 relaxation time measurements by the three distinct ROI protocols on severe fibrosis stage were significantly higher than the relative values on mild fibrosis stage. The mean ADC values on severe fibrosis stage showed no significantly different when measured by means of the whole right lobe liver (p = 0.057) and the individual ROIs (p = 0.10), compared with the relative values on mild fibrosis stage. AUCs of T1 relaxation time and ADC value by the means of the three distinct ROI protocols were 0.614, 0.676, 0.677 and 0.656, 0.585, 0.575 for identification of severe fibrosis stage. The interobserver reproducibility was excellent for measuring the right lobe liver T1 relaxation time and the individual ROIs T1 relaxation time (ICC 0.814, 0.883, respectively).

CONCLUSIONS

T1 relaxation time measurements by means of the three distinct ROI protocols on gadoxetic acid-enhanced MR imaging were a potential biomarker in staging of hepatic fibrosis, which were more accuracy than DWI-ADC measurements. The more reproducible results were obtained when measuring T1 relaxation time of the whole right lobe liver and the individual ROIs.

Gd-EOB-DTPA-enhanced-MR imaging in the inflammation stage of nonalcoholic steatohepatitis (NASH) in mice

OBJECTIVE

The purpose of this study is to investigate the correlation between the liver kinetics of gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) and liver histopathology in a mouse model of NASH by using dynamic contrast-enhanced MRI.

MATERIALS AND METHODS

Twenty male C57/BL6 mice aged 8weeks were fed a methionine-choline-deficient (MCD) diet for 2, 4 and 6weeks (MCD groups: MCD 2w, 4w, or 6w). Gd-EOB-DTPA-enhanced MR imaging of the liver was performed at 2, 4 and 6weeks after the MCD feeding. The signal intensity of the liver was obtained from dynamic MR images and relative enhancement (RE), and the time to maximum RE (Tmax) and half-life of elimination RE (T1/2) were calculated. After MRI scan, histopathological scores of hepatic steatosis and inflammation and blood biochemistry data, such as aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels, were obtained.

RESULTS

Plasma AST and ALT levels were significantly increased in mice fed MCD. Histopathological scores indicated that steatohepatitis progressed with the MCD feeding period from 2 to 6weeks, but significant fibrosis was observed only in mice fed MCD for 6weeks. Gd-EOB-DTPA-enhanced MRI showed that Tmax was significantly prolonged in the livers of the 6-week group compared to the control group (control, 4.0±0.7min; MCD 6w, 12.1±1.6min), although there was no alteration in the 2- and 4-week groups. T1/2 was significantly prolonged in mice fed MCD for 4 and 6weeks compared to the control group (control, 19.9±2.0min; MCD 4w, 46.7±8.7min; MCD 6w, 65.4±8.8min). The parameters of Gd-EOB-DTPA kinetics (Tmax and T1/2) in the liver were positively correlated with the liver histopathological score (steatosis vs Tmax, rho=0.69, P=0.0007; inflammation vs Tmax, rho=0.66, P=0.00155; steatosis vs T1/2, rho=0.77, P<0.0001; inflammation vs T1/2, rho=0.73, P=0.0003).

CONCLUSIONS

The liver kinetics of Gd-EOB-DTPA correlated well with the inflammation score in the mouse model of NASH, suggesting the possibility of detecting the steatohepatitis stage without fibrosis by Gd-EOB-DTPA-enhanced MR imaging.

Gadoxetic acid: pearls and pitfalls

Gadoxetic acid is a hepatocyte-specific magnetic resonance imaging contrast agent with the ability to detect and characterize focal liver lesions and provide structural and functional information about the hepatobiliary system. Knowledge of the pharmacokinetics of gadoxetic acid is paramount to understanding imaging protocol and lesion appearance and facilitates identification and avoidance of undesired effects with use of this intravenous contrast agent. This article reviews the utility of gadoxetic acid in liver and biliary imaging, with emphasis on the hepatobiliary phase.

Liver-specific magnetic resonance contrast medium in the evaluation of chronic liver disease

The hepatobiliary-specific contrast medium (gadoxetic acid - Primovist®) is primarily used to improve detection and characterization of focal hepatic lesions, such as in chronic liver disease patients with suspected hepatocellular carcinoma. Since the contrast medium is selectively taken up by functioning hepatocytes in the late hepatobiliary phase, it helps to detect typical hepatocellular carcinoma, which show low signal intensity on this phase. This imaging feature also assists in differentiating regenerative/dysplastic nodules from early hepatocellular carcinomas (with over 90% accuracy), as well as hypervascular hepatocellular carcinomas from arterial pseudo-enhancement foci. Future perspectives include its use in quantification of hepatic function and fibrosis.

Hepatobiliary contrast agents: differential diagnosis of focal hepatic lesions, pitfalls and other indications

The characterization of focal liver lesions is very important. Magnetic resonance imaging is considered the best imaging method for evaluating such lesions, but does not allow for the diagnosis in all cases. The use of hepatobiliary contrast agents increases the diagnostic accuracy of magnetic resonance imaging and reduces the number of non-specific liver lesions. The main indications for the method include: differentiation between focal nodular hyperplasia and adenoma; characterization of hepatocellular carcinomas in cirrhotic patients; detection of small liver metastases; evaluation of biliary anatomy; and characterization of postoperative biliary fistulas. The use of hepatobiliary contrast agents may reduce the need for invasive diagnostic procedures and further investigations with other imaging methods, besides the need for imaging follow-up.

Visual assessment of biliary excretion of Gd-EOB-DTPA in patients with suspected diffuse liver disease - A biopsy-verified prospective study

OBJECTIVES

To qualitatively evaluate late dynamic contrast phases, 10, 20 and 30 min, after administration of Gd-EOB-DTPA with regard to biliary excretion in patients presenting with elevated liver enzymes without clinical signs of cirrhosis or hepatic decompensation and to compare the visual assessment of contrast agent excretion with histo-pathological fibrosis stage, contrast uptake parameters and blood tests.

METHODS

29 patients were prospectively examined using 1.5 T MRI. The visually assessed presence or absence of contrast agent for each of five anatomical regions in randomly reviewed time-series was summarized on a four grade scale for each patient. The scores, including a total visual score, were related to the histo-pathological findings, the quantitative contrast agent uptake parameters, expressed as K Hep or LSC_N, and blood tests.

RESULTS

No relationship between the fibrosis grade or contrast uptake parameters could be established. A negative correlation between the visual assessment and alkaline phosphatase (ALP) was found. Comparing a sub-group of cholestatic patients with fibrosis score and Gd-EOB-DTPA dynamic parameters did not add any additional significant correlation.

CONCLUSIONS

No correlation between visually assessed biliary excretion of Gd-EOB-DTPA and histo-pathological or contrast uptake parameters was found. A negative correlation between the visual assessment and alkaline phosphatase (ALP) was found.

Histogram analysis of gadoxetic acid-enhanced MRI for quantitative hepatic fibrosis measurement

PURPOSE

The diagnosis and monitoring of liver fibrosis is an important clinical issue; however, this is usually achieved by invasive methods such as biopsy. We aimed to determine whether histogram analysis of hepatobiliary phase images of gadoxetic acid-enhanced magnetic resonance imaging (MRI) can provide non-invasive quantitative measurement of liver fibrosis.

METHODS

This retrospective study was approved by the institutional ethics committee, and a waiver of informed consent was obtained. Hepatobiliary phase images of preoperative gadoxetic acid-enhanced MRI studies of 105 patients (69 males, 36 females; age 56.1±12.2) with pathologically documented liver fibrosis grades were analyzed. Fibrosis staging was F0/F1/F2/F3/F4 (METAVIR system) for 11/20/13/15/46 patients, respectively. Four regions-of-interest (ROI, each about 2 cm2) were placed on predetermined locations of representative images. The measured signal intensity of pixels in each ROI was used to calculate corrected coefficient of variation (cCV), skewness, and kurtosis. An average value of each parameter was calculated for comparison. Statistical analysis was performed by ANOVA, receiver operating characteristic (ROC) curve analysis, and linear regression.

RESULTS

The cCV showed statistically significant differences among pathological fibrosis grades (P<0.001) whereas skewness and kurtosis did not. Univariable linear regression analysis suggested cCV to be a meaningful parameter in predicting the fibrosis grade (P<0.001, β = 0.40 and standard error  = 0.06). For discriminating F0-3 from F4, the area under ROC score was 0.857, standard deviation 0.036, 95% confidence interval 0.785-0.928.

CONCLUSION

Histogram analysis of hepatobiliary phase images of gadoxetic acid-enhanced MRI can provide non-invasive quantitative measurements of hepatic fibrosis.

New perspectives in the assessment of future remnant liver

In order to achieve microscopic radical resection margins and thus better survival, surgical treatment of hepatic tumors has become more aggressive in the last decades, resulting in an increased rate of complex and extended liver resections. Postoperative outcomes mainly depend on the size and quality of the future remnant liver (FRL). Liver resection, when performed in the absence of sufficient FRL, inevitably leads to postresection liver failure. The current gold standard in the preoperative assessment of the FRL is computed tomography volumetry. In addition to the volume of the liver remnant after resection, postoperative function of the liver remnant is directly related to the quality of liver parenchyma. The latter is mainly influenced by underlying diseases such as cirrhosis and steatosis, which are often inaccurately defined until microscopic examination after the resection. Postresection liver failure remains a point of major concern that calls for accurate methods of preoperative FRL assessment. A wide spectrum of tests has become available in the past years, attesting to the fact that the ideal methodology has yet to be defined. The aim of this review is to discuss the current modalities available and new perspectives in the assessment of FRL in patients scheduled for major liver resection.

Potential of (99m)Tc-MIBI SPECT imaging for evaluating non-alcoholic steatohepatitis induced by methionine-choline-deficient diet in mice

Background

Hepatic mitochondrial dysfunction has been implicated in pathological conditions leading to non-alcoholic steatohepatitis (NASH). Technetium-99 m-2-methoxyisobutyl-isonitrile (^99mTc-MIBI), a lipophilic cationic myocardial perfusion agent, is retained in the mitochondria depending on membrane potential. The aim of this study was to investigate the feasibility of ^99mTc-MIBI for evaluating the hepatic mitochondrial dysfunction induced by methionine-choline-deficient (MCD) diet in mice.

Methods

Male C57Black6J/jcl mice were fed a MCD diet for up to 4 weeks. SPECT scan (N =6) with ^99mTc-MIBI was performed at 2 and 4 weeks after MCD diet. Mice were imaged with small-animal SPECT/CT under isoflurane anesthesia. Radioactivity concentrations of the liver were measured, and the time of maximum (T_max) and the elimination half-life (T_1/2) were evaluated. After SPECT scan, liver histopathology was analyzed to evaluate steatosis and inflammation. Non-alcoholic fatty liver disease (NAFLD) activity score was obtained from the histological score of hepatic steatosis and inflammation. Blood biochemistry and hepatic ATP content were also measured (N =5 to 6).

Results

Plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were significantly elevated at 2 and 4 weeks after MCD diet. A decrease in hepatic ATP content was also observed in MCD-fed mice. ^99mTc-MIBI SPECT imaging clearly showed the decrease of hepatic ^99mTc-MIBI retention in MCD-fed mice compared to control mice. T_1/2 after ^99mTc-MIBI injection was significantly decreased in the liver of MCD-fed mice (control, MCD 2 weeks, and MCD 4 weeks, T_1/2 = 57.6, 37.6, and 19.8 min, respectively), although no change in T_max was observed in MCD-fed mice. SPECT data and histological score showed that the negative correlation (r = −0.74, p <0.05) between T_1/2 and NAFLD activity score was significant.

Conclusions

Hepatic ^99mTc-MIBI elimination was increased with increase in NAFLD activity score (NAS) in mice fed MCD diet for 2 and 4 weeks. These results suggest that ^99mTc-MIBI SPECT imaging might be useful for detecting hepatic mitochondrial dysfunction induced by steatosis and inflammation such as NAFLD or NASH.

Histogram analysis of hepatobiliary phase MR imaging as a quantitative value for liver cirrhosis: preliminary observations

PURPOSE

To investigate whether histogram analysis of the hepatobiliary phase on gadoxetate enhanced-MRI could be used as a quantitative index for determination of liver cirrhosis.

MATERIALS AND METHODS

A total of 63 patients [26 in a normal liver function (NLF) group and 37 in a cirrhotic group] underwent gadoxetate-enhanced MRI, and hepatobiliary phase images were obtained at 20 minutes after contrast injection. The signal intensity of the hepatic parenchyma was measured at four different regions of interest (ROI) of the liver, avoiding vessels and bile ducts. Standard deviation (SD), coefficient of variation (CV), and corrected CV were calculated on the histograms at the ROIs. The distributions of CVs calculated from the ROI histogram were examined and statistical analysis was carried out.

RESULTS

The CV value was 0.041±0.009 (mean CV±SD) in the NLF group, while that of cirrhotic group was 0.071±0.020. There were statistically significant differences in the CVs and corrected CV values between the NLF and cirrhotic groups (p<0.001). The most accurate cut-off value among CVs for distinguishing normal from cirrhotic group was 0.052 (sensitivity 83.8% and specificity 88.5%). There was no statistically significant differences in SD between NLF and cirrhotic groups (p=0.307).

CONCLUSION

The CV of histograms of the hepatobiliary phase on gadoxetate-enhanced MRI may be useful as a quantitative value for determining the presence of liver cirrhosis.

Noninvasive differentiation of simple steatosis and steatohepatitis by using gadoxetic acid-enhanced MR imaging in patients with nonalcoholic fatty liver disease: a proof-of-concept study

PURPOSE

To determine whether gadoxetic acid-enhanced magnetic resonance (MR) imaging can be used to distinguish between simple steatosis and nonalcoholic steatohepatitis (NASH) in patients with nonalcoholic fatty liver disease (NAFLD), defined according to the steatosis activity and fibrosis (SAF) scoring system, which is based on the semiquantitative scoring of steatosis activity and liver fibrosis.

MATERIALS AND METHODS

The local institutional review committee approved this study and waived written informed consent. This was a retrospective study of gadoxetic acid-enhanced 3-T MR imaging performed in 81 patients with NAFLD (45 men [56%]; mean age, 56 years; range, 25-78 years). The MR images were analyzed by using the relative enhancement (the ratio of signal intensities of the liver parenchyma before and 20 minutes after intravenous administration of gadoxetic acid). Univariate and multiple regression analyses were applied to identify variables associated with relative enhancement measurements. The ability of relative enhancement to allow differentiation between simple steatosis and NASH was assessed by using area under the receiver operating characteristic (ROC) curve analysis.

RESULTS

Relative enhancement negatively correlated with the degree of lobular inflammation (r = -0.59, P < .0001), ballooning (r = -0.44, P < .0001), and fibrosis (r = -0.59, P ≤ .0001), but not with steatosis (r = -0.16, P = .15). Patients with NASH had a significantly lower relative liver enhancement (0.82 ± 0.22) than those with simple steatosis (1.39 ± 0.52) (P < .001). Relative enhancement measurements performed well in the differentiation between simple steatosis and NASH, with an area under the ROC curve of 0.85 (95% confidence interval: 0.75, 0.91) (cutoff = 1.24, sensitivity = 97%, specificity = 63%).

CONCLUSION

Gadoxetic acid relative enhancement was significantly lower in patients with NASH than in patients with simple steatosis, but further prospective studies are warranted.

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.

Usefulness of T1 mapping on Gd-EOB-DTPA-enhanced MR imaging in assessment of non-alcoholic fatty liver disease

OBJECTIVES

This study evaluates the value of Gd-EOB-DTPA-enhanced MRI for diagnosis and staging of non-alcoholic fatty liver disease (NAFLD) in an animal model by T1 relaxation time measurement.

METHODS

Thirty-four rabbits were divided into the control group (n = 10) and NAFLD group, which was split into four groups (n = 6) with a high-fat diet for an interval of 3 weeks. A dual flip angle was performed before and at the hepatobiliary phase (HBP). T1 relaxation times of the liver parenchyma and the decrease rate (∆%) were calculated. Histological findings according to semi-quantitative scoring of steatosis, activity and fibrosis were the standard of reference.

RESULTS

HBP and ∆% T1 relaxation time measurement showed significant differences between normal and NAFLD groups, between non-alcoholic steatohepatitis (NASH) and NAFLD without NASH (p = 0.000-0.049), between fibrosis groups (p = 0.000-0.019), but no difference between F1 and F2 (p = 0.834). The areas under the receiver operating characteristic curves (AUCs) of T1 relaxation time for HBP and ∆% were 0.86-0.93 for the selection of NASH and activity score ≥2, and 0.86-0.95 for the selection of F ≥ 1, 2, 3. No significant difference was found for diagnostic performance between HBP and ∆% T1 relaxation time.

CONCLUSIONS

HBP T1 relaxation time measurement of Gd-EOB-DTPA-enhanced MRI was useful to evaluate NAFLD according to the SAF score. HBP T1 relaxation time measurement was as accurate as ∆% T1 relaxation time.

KEY POINTS

• Gd-EOB-DTPA-enhanced MRI could give useful information on NAFLD. •HBP T 1 relaxation time measurement was useful for the evaluation of NAFLD. • HBP T 1 relaxation time measurement was as accurate as ∆%.

Hepatic steatosis: effect on hepatocyte enhancement with gadoxetate disodium-enhanced liver MR imaging

PURPOSE

To investigate the effect of hepatic steatosis on enhancement of liver parenchyma with gadoxetate disodium-enhanced MR imaging.

MATERIALS AND METHODS

Gadoxetate disodium-enhanced MR images of 166 patients were analyzed. Liver-spleen contrast and liver-spleen relative enhancement ratio on three-dimensional gradient echo T1-weighted images with fat suppression 20 minutes after injection of gadoxetate disodium were evaluated in correlation with fat signal fraction using the Pearson correlation coefficient and also compared between patients with normal liver parenchyma (n = 115) and with liver steatosis (n = 51) using the Student t-test.

RESULTS

The liver-spleen contrast at hepatobiliary phase showed inverse correlations with the fat signal fraction (r = -0.36; P < 0.01), while the liver-spleen relative enhancement ratio showed no statistical correlation with the fat signal fraction (P = 0.80). The liver-spleen contrast in the group with steatotic liver was significantly lower than that in the group with normal livers (P < 0.001). There was no significant difference in the relative enhancement ratio between the two groups (P = 0.85).

CONCLUSION

Our results may suggest that hepatic steatosis does not affect the uptake of gadoxetate disodium into hepatocytes and are considered crucial as background knowledge in extending the use of gadoxetate disodium-enhanced MR imaging to quantitate liver function.

The role of hepatocyte-specific contrast agents in hepatobiliary magnetic resonance imaging

Hepatocyte-specific contrast agents have been made available in the last 15 years for magnetic resonance imaging of the liver. These agents are differentially taken up by functioning hepatocytes and excreted in the biliary system. They can help distinguish focal liver lesions of hepatocellular origin from lesions of nonhepatocellular origin, and can also be used in the evaluation of the biliary tree. The purpose of this review is to summarize the different types of hepatocyte-specific contrast agents presently available, their use in the characterization of focal liver lesions, their role in the evaluation of biliary pathology, and their potential future applications.

Noninvasive evaluation of hepatic fibrosis in hepatitis C virus-infected patients using ethoxybenzyl-magnetic resonance imaging

BACKGROUND AND AIMS

Liver biopsy is the gold standard test to determine the grade of fibrosis, but there are associated problems. Because gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid is secreted partially in hepatocytes and bile, it is possible that ethoxybenzyl-magnetic resonance imaging (EOB-MRI) correlates with liver function and liver fibrosis. The aim of this study was to compare the fibrosis seen in liver biopsy samples to the signal intensity of the hepatobiliary phase measured on EOB-MRI in hepatitis C virus (HCV)-infected patients.

METHODS

Two hundred twenty-four (estimation 149, validation 75) HCV-infected patients with histologically proven liver tissue who underwent EOB-MRI were studied. Overall, fibrosis staging was 15/24/19/46/45 for F0/F1/F2/F3/F4, respectively. A 1.5-Tesla magnetic resonance system was used, and the regions of interest of the liver were measured. Four methods were used: (i) relative enhancement: (post-enhanced signal intensity [SI] - pre-enhanced intensity)/pre-enhanced intensity; (ii) liver-to-intervertebral disk ratio (LI): post-enhanced (liver SI/interdisc SI)/pre-enhanced (liver SI/inter disc SI); (iii) liver-to-muscle ratio: post-enhanced (liver SI/muscle SI)/pre-enhanced (liver SI/muscle SI); and (iv) liver-to-spleen ratio: post-enhanced (liver SI/spleen SI)/pre-enhanced (liver SI/spleen SI).

RESULTS

To discriminate F0-1 versus F2-4 or F0-2 versus F3-4 or F0-3 versus F4, LI at 25 min (LI25) had the highest area under receiver operating characteristic (0.88, 0.87, and 0.87, respectively) in these four methods and also in the validation set.

CONCLUSION

LI at 25 min seems to be a useful method to determine the staging of fibrosis as a non-invasive method in HCV-infected hepatitis or cirrhosis patients.

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.

Liver analysis using gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging: Correlation with histological grading and quantitative liver evaluation prior to hepatectomy

AIM

  To examine the effectiveness of gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) in the assessment of parenchymal liver fibrosis and quantitative liver function prior to hepatectomy.

METHODS

  Between July 2008 and September 2011, the data of 93 consecutive patients undergoing preoperative Gd-EOB-DTPA-enhanced MRI were analyzed, including serum fibrosis marker levels (hyaluronic acid, type IV collagen), 15-min retention rates of indocyanine green (ICG-R15) in the ICG clearance test, and technetium-99m galactosyl serum albumin scintigraphy results. Liver intensity values were obtained by calculating the differences between the intensity of the liver and that of other organs in the hepatobiliary phase. Degrees of liver fibrosis were quantitatively assessed (F0-4). MRI data were correlated with the prospectively acquired clinical data.

RESULTS

  Varying degrees of liver fibrosis were detected in 31 of the 93 patients. The intensity ratio of the liver to spinal cord on MRI negatively correlated with hepatic fibrosis (R = -0.479, P < 0.001) and ICG-R15 (R = -0.492, P < 0.001). When patients with F0-2 (normal/moderate) and F3-4 (severe) liver fibrosis were compared, the intensity ratio of the enhanced liver to spinal cord (IRLS) on MRI was significantly lower in the F3-4 group than in the F0-2 group. IRLS was correlated with liver fibrosis, and, when an IRLS criterion of less than 1.702 was used, severe liver fibrosis could be predicted with 68.8% sensitivity and 93.5% specificity.

CONCLUSION

  Preoperative Gd-EOB-DTPA-enhanced MRI analysis can detect quantitative indicators of liver fibrosis and function, thus aiding the assessment of hepatic remnants prior to hepatectomy.

Primovist, Eovist: what to expect?

Gadolinium ethoxybenzyl dimeglumine (Gd-EOB-DTPA, Primovist in Europe and Eovist in the USA) is a liver-specific magnetic resonance imaging contrast agent that has up to 50% hepatobiliary excretion in the normal liver. After intravenous injection, Gd-EOB-DTPA distributes into the vascular and extravascular spaces during the arterial, portal venous and late dynamic phases, and progressively into the hepatocytes and bile ducts during the hepatobiliary phase. The hepatocyte uptake of Gd-EOB-DTPA mainly occurs via the organic anion transporter polypeptides OATP1B1 and B3 located at the sinusoidal membrane and biliary excretion via the multidrug resistance-associated proteins MRP2 at the canalicular membrane. Because of these characteristics, Gd-EOB-DTPA behaves similarly to non-specific gadolinium chelates during the dynamic phases, and adds substantial information during the hepatobiliary phase, improving the detection and characterization of focal liver lesions and diffuse liver disease. This information is particularly relevant for the detection of metastases, and for the detection and characterization of nodular lesions in liver cirrhosis, including early hepatocellular carcinomas. Finally, GD-EOB-DTPA-enhanced magnetic resonance imaging may provide quantitative assessment regarding liver perfusion and hepatocyte function in diffuse liver diseases. The full potential of GD-EOB-DTPA-enhanced magnetic resonance imaging has to be established further. It is already clear that GD-EOB-DTPA-enhanced magnetic resonance imaging provides anatomic and functional information in the setting of focal and diffuse liver disease that is unattainable with magnetic resonance imaging enhanced with non-specific contrast agents.

Separation of advanced from mild hepatic fibrosis by quantification of the hepatobiliary uptake of Gd-EOB-DTPA

OBJECTIVES

To apply dynamic contrast-enhanced (DCE) MRI on patients presenting with elevated liver enzymes without clinical signs of hepatic decompensation in order to quantitatively compare the hepatocyte-specific uptake of Gd-EOB-DTPA with histopathological fibrosis stage.

METHODS

A total of 38 patients were prospectively examined using 1.5-T MRI. Data were acquired from regions of interest in the liver and spleen by using time series of single-breath-hold symmetrically sampled two-point Dixon 3D images (non-enhanced, arterial and venous portal phase; 3, 10, 20 and 30 min) following a bolus injection of Gd-EOB-DTPA (0.025 mmol/kg). The signal intensity (SI) values were reconstructed using a phase-sensitive technique and normalised using multiscale adaptive normalising averaging (MANA). Liver-to-spleen contrast ratios (LSC_N) and the contrast uptake rate (K (Hep)) were calculated. Liver biopsy was performed and classified according to the Batts and Ludwig system.

RESULTS

Area under the receiver-operating characteristic curve (AUROC) values of 0.71, 0.80 and 0.78, respectively, were found for K (Hep), LSC_N10 and LSC_N20 with regard to severe versus mild fibrosis. Significant group differences were found for K (Hep) (borderline), LSC_N10 and LSC_N20.

CONCLUSIONS

Liver fibrosis stage strongly influences the hepatocyte-specific uptake of Gd-EOB-DTPA. Potentially the normalisation technique and K (Hep) will reduce patient and system bias, yielding a robust approach to non-invasive liver function determination.

Assessment of liver function in thioacetamide-induced rat acute liver injury using an empirical mathematical model and dynamic contrast-enhanced MRI with Gd-EOB-DTPA

PURPOSE

To evaluate thioacetamide (TAA)-induced acute liver injury in rats using an empirical mathematical model (EMM) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA).

MATERIALS AND METHODS

Eighteen rats were divided into three groups (normal control [n = 6], TAA [140] [n = 6], and TAA [280] groups [n = 6]). The rats of the TAA (140) and TAA (280) groups were intravenously injected with 140 and 280 mg/kg body weight (BW) of TAA, respectively, while those of the normal control group were intravenously injected with the same volume of saline. DCE-MRI studies were performed using Gd-EOB-DTPA (0.025 mmol Gd/kg; 0.1 mL/kg BW) as the contrast agent 48 hours after TAA or saline injection. After the DCE-MRI study, blood was sampled and serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were measured. We calculated the rate of contrast uptake (α), the rate of contrast washout (β), the elimination half-life of relative enhancement (RE) (T(1/2)), the maximum RE (RE(max)), and the time to (RE(max)) (T(max)) from time-signal intensity curves using EMM.

RESULTS

The RE(max) values in the TAA (140) groups and TAA (280) groups were significantly smaller than that in the normal control group. The T(max) value in the TAA (280) group was significantly greater than that in the normal control group. The β value in the TAA (280) group was significantly smaller than those in the normal control and TAA (140) groups, whereas there were no significant differences in β among groups. The T(1/2) value in the TAA (280) group was significantly greater than those in the normal control and TAA (140) groups. The RE(max), T(max), β, and T(1/2) values significantly correlated with AST and ALT.

CONCLUSION

The EMM is useful for evaluating TAA-induced acute liver injury using DCE-MRI with Gd-EOB-DTPA.

MR prediction of liver fibrosis using a liver-specific contrast agent: Superparamagnetic iron oxide versus Gd-EOB-DTPA

PURPOSE

To examine whether the uptake of a liver-specific contrast agent in the liver parenchyma was correlated with the degree of liver fibrosis.

MATERIALS AND METHODS

This retrospective study included 54 and 63 patients who underwent superparamagnetic iron oxide (SPIO)- and gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced MRI before liver surgery, respectively. For each patient, we calculated ΔR2* and ΔR2, which represent differences in R2* and R2 values of the liver parenchyma before and after administration of SPIO; and the increase rate of liver-to-spleen signal intensity ratio (LSR) on the hepatobiliary phase compared with the precontrast image. The correlation of each MR parameter with the degree of liver fibrosis (F0 to F4) was assessed using Spearman's rank correlation test.

RESULTS

The increase rate of LSR was best correlated with the degree of liver fibrosis and significantly decreased as the liver fibrosis progressed (rho = -0.641; P < 0.0001). It showed sensitivity of 76.9% and specificity of 83.3% in differentiating F3 or greater fibrosis when 1.126 or less was set up as a cut-off value. No significant correlation was obtained between ΔR2* or ΔR2 and the degree of liver fibrosis.

CONCLUSION

The uptake of Gd-EOB-DTPA in the liver parenchyma decreased as the liver fibrosis progressed. J. Magn. Reson. Imaging 2012;36:664-671. © 2012 Wiley Periodicals, Inc.

[New developments in MRI of the liver]

Radiology has gained an exceptional position in medicine because a correct diagnosis is the most crucial issue in determining an accurate and personalized therapeutic strategy. This has a direct influence not only on the individual patient but also on the socio-economic aspects of healthcare services in terms of shortening the time interval to establish a diagnosis and to avoid risk-associated invasive diagnostic methods or long-term, cost-intensive follow-up. Magnetic resonance imaging (MRI) is an excellent example of this which due to continuous technological developments and emerging techniques allows a non-invasive diagnosis of the different hepatic diseases. In this article, we illustrate the direct correlation between the recent technical advances in MRI, such as 3.0 T, diffusion-weighted imaging, perfusion imaging, spectroscopy, texture analysis and MR elastography and obtaining a confident non-invasive diagnosis of focal and diffuse liver diseases.

Magnetic resonance imaging of focal liver lesions: approach to imaging diagnosis

This article is a review of magnetic resonance imaging (MRI) of incidental focal liver lesions. This review provides an overview of liver MRI protocol, diffusion-weighted imaging, and contrast agents. Additionally, the most commonly encountered benign and malignant lesions are discussed with emphasis on imaging appearance and the diagnostic performance of MRI based on a review of the literature.

Quantifying differences in hepatic uptake of the liver specific contrast agents Gd-EOB-DTPA and Gd-BOPTA: a pilot study

OBJECTIVES

To develop and evaluate a procedure for quantifying the hepatocyte-specific uptake of Gd-BOPTA and Gd-EOB-DTPA using dynamic contrast-enhanced (DCE) MRI.

METHODS

Ten healthy volunteers were prospectively recruited and 21 patients with suspected hepatobiliary disease were retrospectively evaluated. All subjects were examined with DCE-MRI using 0.025 mmol/kg of Gd-EOB-DTPA. The healthy volunteers underwent an additional examination using 0.05 mmol/kg of Gd-BOPTA. The signal intensities (SI) of liver and spleen parenchyma were obtained from unenhanced and enhanced acquisitions. Using pharmacokinetic models of the liver and spleen, and an SI rescaling procedure, a hepatic uptake rate, K (Hep), estimate was derived. The K (Hep) values for Gd-EOB-DTPA were then studied in relation to those for Gd-BOPTA and to a clinical classification of the patient's hepatobiliary dysfunction.

RESULTS

K (Hep) estimated using Gd-EOB-DTPA showed a significant Pearson correlation with K (Hep) estimated using Gd-BOPTA (r = 0.64; P < 0.05) in healthy subjects. Patients with impaired hepatobiliary function had significantly lower K (Hep) than patients with normal hepatobiliary function (K (Hep) = 0.09 ± 0.05 min(-1) versus K (Hep) = 0.24 ± 0.10 min(-1); P < 0.01).

CONCLUSIONS

A new procedure for quantifying the hepatocyte-specific uptake of T (1)-enhancing contrast agent was demonstrated and used to show that impaired hepatobiliary function severely influences the hepatic uptake of Gd-EOB-DTPA.

KEY POINTS

• The liver uptake of contrast agents may be measured with standard clinical MRI. • Calculation of liver contrast agent uptake is improved by considering splenic uptake. • Liver function affects the uptake of the liver-specific contrast agent Gd-EOB-DTPA. • Hepatic uptake of two contrast agents (Gd-EOB-DTPA, Gd-BOPTA) is correlated in healthy individuals. • This method can be useful for determining liver function, e.g. before hepatic surgery.

Signal profile on Gd-EOB-DTPA-enhanced MR imaging in non-alcoholic steatohepatitis and liver cirrhosis induced in rats: correlation with transporter expression

OBJECTIVES

To compare the transporter expression and signal profile on Gd-EOB-DTPA-enhanced MRI between non-alcoholic steatohepatitis (NASH) and cirrhotic liver induced in rats, and investigate the correlation of the transporter expression and fibrosis rate in both diseases.

METHODS

Forty-eight rats were divided into four groups of 12: TAA (cirrhosis), NASH 7- and 10-week, and control groups. Each group was divided into two subgroups: Group 1 for MRI and Group 2 for transporter examinations.

RESULTS

The relative enhancement of the TAA group was significantly lower than those of other groups (p < 0.01). The T(max) and T(1/2) of the NASH 10-week group was significantly prolonged in comparison with the TAA group (p < 0.01). There was no significant difference in the oatp1 expression, whereas the mrp2 expression of the TAA group was significantly higher than those of other groups (p < 0.01). There was no significant correlation between the fibrosis rate and oatp1 expression, whereas a paradoxical correlation was found between the fibrosis rate and mrp2 expression (NASH: negative correlation, r = 0.91, p < 0.01; TAA: positive correlation, r = 0.85, p < 0.01).

CONCLUSIONS

Our findings showed that the mrp2 expression in cirrhosis increases in comparison with NASH, and there was a paradoxical correlation between the fibrosis rate and mrp2 expression.