Potential of gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) for differential diagnosis of nonalcoholic steatohepatitis and fatty liver in rats using magnetic resonance imaging

Liver Biliary Function Evaluation on a 1.5T Magnetic Resonance Imaging Scan by T1 Reduction Rate Assessment Using Variable-Flip-Angle Sequences

OBJECTIVE

Magnetic resonance (MR) relaxometry is an absolute and reproducible quantitative method, compared with signal intensity for the evaluation of liver biliary function. This is obtainable by the T1 reduction rate (T1RR), as it carries a smaller systematic error than the pre/post contrast agent T1 measurement. We aimed to develop and test an MR T1 relaxometry tool tailored for the evaluation of liver T1RR after gadolinium ethoxybenzyl-diethylenetriaminepentaacetic acid administration on 1.5T MR.

METHODS

In vitro/vivo (liver) T1RR values with two 3D FLASH variable-flip-angle sequences were calculated by a MATLAB algorithm. In vitro measurements were done by 2 physicists, in consensus. The prospective in vivo study was approved by the local ethical committee and performed on 13 normal/26 cirrhotic livers. A supplemental test in 5 normal/5 cirrhotic livers, out of the studied series, was done to compare the results of our method (without B1 inhomogeneity correction) and those of a standardized commercial tool (with B1 inhomogeneity correction). All in vivo evaluations were performed by 2 radiologists with 7 years of experience in abdominal imaging. Open-source Java-based software ImageJ was used to draw the free-hand regions of interest on liver section and for the measurement of hepatic T1RR values. The T1RR values of each group of patients were compared to assess statistically significant differences. All statistical analyses were performed with IBM-SPSS Statistics. In vivo evaluations, the intrareader and interreader reliability was assessed by intraclass correlation coefficient.

RESULTS

Our method showed good accuracy in evaluating in vitro T1RR with a maximum percentage error of 9% (constant at various time points) with T1 values in the 200- to 1400-millisecond range. In vivo, a high concordance between the T1RR evaluated with the proposed method and that calculated from the standardized commercial software was verified ( P < 0.05). The median T1RRs were 74.8, 67.9, and 52.1 for the normal liver, Child-Pugh A, and Child-Pugh B cirrhotic groups, respectively. A very good agreement was found, both within intrareader and interreader reliability, with intraclass correlation coefficient values ranging from 0.88 to 0.95 and from 0.85 to 0.90, respectively.

CONCLUSIONS

The proposed method allowed accurate reliable in vitro/vivo T1RR assessment evaluation of the liver biliary function after gadolinium ethoxybenzyl-diethylenetriaminepentaacetic acid administration.

Non-contrast T1ρ dispersion versus Gd-EOB-DTPA-enhanced T1mapping for the risk stratification of non-alcoholic fatty liver disease in rabbit models

PURPOSE

To investigate the diagnostic efficacy of T1ρ dispersion and Gd-EOB-DTPAenhanced T1mapping in the identification of early liver fibrosis (LF) and non-alcoholic steatohepatitis (NASH) in a non-alcoholic fatty liver disease (NAFLD) rabbit model induced by a high-fat diet using histopathological findings as the standard reference.

METHODS

A total of sixty rabbits were randomly allocated into the standard control group (n = 12) and the NAFLD model groups (8 rabbits per group) corresponding to different high-fat high cholesterol diet feeding weeks. All rabbits underwent noncontrast transverse T1ρ mapping with varying spin-locking frequencies (FSL = 0 Hz and 500 Hz), native T1 mapping, and Gd-EOB-DTPA-enhanced T1 mapping during the hepatobiliary phase. The histopathological findings were assessed based on the NASH CRN Scoring System. Statistical analyses were conducted using the intraclass correlation coefficient, analysis of variance, multiple linear regression, and receiver operating characteristics.

RESULTS

Except for native T1, T1ρ, T1ρ dispersion, HBP T1, and △T1 values significantly differed among different liver fibrosis groups (F = 14.414, 18.736, 10.15, and 9.799, respectively; all P < 0.05). T1ρ, T1ρ dispersion, HBP T1, and △T1 values also exhibited significant differences among different NASH groups (F = 4.138, 4.594, 21.868, and 22.678, respectively; all P < 0.05). In the multiple regression analysis, liver fibrosis was the only factor that independently influenced T1ρ dispersion (R2 = 0.746, P = 0.000). Among all metrics, T1ρ dispersion demonstrated the best area under curve (AUC) for identifying early LF (≥ F1 stage) and significant LF (≥ F2 stage) (AUC, 0.849 and 0.916, respectively). The performance of △T1 and HBP T1 (AUC, 0.948 and 0.936, respectively) were better than that of T1ρ and T1ρ dispersion (AUC, 0.762 and 0.769, respectively) for diagnosing NASH.

CONCLUSION

T1⍴ dispersion may be suitable for detecting liver fibrosis in the complex background of NAFLD, while Gd-EOB-DTPA enhanced T1 mapping is superior to nonenhanced T1⍴ mapping (T1⍴ and T1⍴ dispersion) for identifying NASH.

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.

Correlation of histologic, imaging, and artificial intelligence features in NAFLD patients, derived from Gd-EOB-DTPA-enhanced MRI: a proof-of-concept study

OBJECTIVE

To compare unsupervised deep clustering (UDC) to fat fraction (FF) and relative liver enhancement (RLE) on Gd-EOB-DTPA-enhanced MRI to distinguish simple steatosis from non-alcoholic steatohepatitis (NASH), using histology as the gold standard.

MATERIALS AND METHODS

A derivation group of 46 non-alcoholic fatty liver disease (NAFLD) patients underwent 3-T MRI. Histology assessed steatosis, inflammation, ballooning, and fibrosis. UDC was trained to group different texture patterns from MR data into 10 distinct clusters per sequence on unenhanced T1- and Gd-EOB-DTPA-enhanced T1-weighted hepatobiliary phase (T1-Gd-EOB-DTPA-HBP), then on T1 in- and opposed-phase images. RLE and FF were quantified on identical sequences. Differences of these parameters between NASH and simple steatosis were evaluated with χ2- and t-tests, respectively. Linear regression and Random Forest classifier were performed to identify associations between histological NAFLD features, RLE, FF, and UDC patterns, and then determine predictors able to distinguish simple steatosis from NASH. ROC curves assessed diagnostic performance of UDC, RLE, and FF. Finally, we tested these parameters on 30 validation cohorts.

RESULTS

For the derivation group, UDC-derived features from unenhanced and T1-Gd-EOB-DTPA-HBP, plus from T1 in- and opposed-phase, distinguished NASH from simple steatosis (p ≤ 0.001 and p = 0.02, respectively) with 85% and 80% accuracy, respectively, while RLE and FF distinguished NASH from simple steatosis (p ≤ 0.001 and p = 0.004, respectively), with 83% and 78% accuracy, respectively. On multivariate regression analysis, RLE and FF correlated only with fibrosis (p = 0.040) and steatosis (p ≤ 0.001), respectively. Conversely, UDC features, using Random Forest classifier predictors, correlated with all histologic NAFLD components. The validation group confirmed these results for both approaches.

CONCLUSION

UDC, RLE, and FF could independently separate NASH from simple steatosis. UDC may predict all histologic NAFLD components.

CLINICAL RELEVANCE STATEMENT

Using gadoxetic acid-enhanced MR, fat fraction (FF > 5%) can diagnose NAFLD, and relative liver enhancement can distinguish NASH from simple steatosis. Adding AI may let us non-invasively estimate the histologic components, i.e., fat, ballooning, inflammation, and fibrosis, the latter the main prognosticator.

KEY POINTS

• Unsupervised deep clustering (UDC) and MR-based parameters (FF and RLE) could independently distinguish simple steatosis from NASH in the derivation group. • On multivariate analysis, RLE could predict only fibrosis, and FF could predict only steatosis; however, UDC could predict all histologic NAFLD components in the derivation group. • The validation cohort confirmed the findings for the derivation group.

Predictive value of Gd-EOB-DTPA -enhanced magnetic resonance imaging for post-hepatectomy liver failure: a systematic review and meta-analysis

Background

Accurate preoperative diagnosis of post-hepatectomy liver failure (PHLF) is particularly important to improve the prognosis of patients.

Purpose

To evaluate the predictive value of Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI) for post-hepatectomy liver failure.

Material and Methods

A systematic search was performed in the PubMed, Embase, the Cochrane Library, and Web of Science databases to find relevant original articles published up to December 2021. The included studies were assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. The bivariate random-effects model was used to assess the diagnostic authenticity. Meta-regression analyses were performed to analyze the potential heterogeneity.

Results

In total, 13 articles were included. The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and the area under the summary receiver operating characteristic curves were 88% (95% confidence interval [CI] = 0.80–0.94), 80% (95% CI = 0.73–0.86), 4.4 (95% CI = 3.3–5.9), 0.14 (95% CI = 0.08–0.25), 31 (95% CI = 17–57), and 0.91 (95% CI = 0.89–0.94), respectively. There was no publication bias and threshold effect in our study.

Conclusion

Gd-EOB-DTPA-enhanced MRI is a potentially useful for the prediction of PHLF after major hepatectomy.

Gd-EOB-DTPA-enhanced MRI-a noninvasive and short-term assessment method for liver necroinflammation after direct-acting antiviral (DAA) therapy in patients with chronic hepatitis C

PURPOSE

To assess liver necroinflammation in HCV patients undergone antiviral therapy by Gd-EOB-DTPA-enhanced MRI with histopathologic analyses as reference.

METHODS

HCV patients were enrolled in this prospective study before antiviral treatment between 09-2016 and 07-2017. Unenhanced MR, Gd-EOB-DTPA-enhanced MR, and liver biopsy were performed before and 24 weeks after treatment of daclatasvir with asunaprevir (DAA). DWI was obtained using a breath-hold single-shot echo planar spin-echo sequence. Twenty minutes after administration of Gd-EOB-DTPA, the relative enhancement (RE) and the contrast enhancement index (CEI) were recorded. Liver necroinflammatory activity grades (G0-18) were categorized on the Ishak Scoring systems. CEI, RE, and DWI of baseline and 24 weeks after treatment were compared by paired t test. Relationship between MR parameters and histologic scores was evaluated by Pearson's correlation. Receiver operating characteristic analysis evaluated the measurements' diagnostic performance. MRI variability between two readers was assessed using the intraclass correlation coefficient.Results RESULTS: A decrease of liver necroinflammatory activity grade (p < 0.0001) was detected in final cohort (n = 21; mean age 44 years; 23 to 67 years; 11 F, 10 M). Statistical results of 42 person-times in 21 patients at baseline and follow-up showed CEI and ADC were significantly different (p = 0.006 and 0.036) across histologic grades of liver necroinflammation. Significant increase of CEI, RE, and ADC (p = 0.0004, 0.0032, 0.0110) 24 weeks after DAA treatment was seen. Additionally, CEI was correlated to necroinflammatory grade (r =  - 0.596, p = 0.006). AUROC for CEI, ADC, and CEI combined with ADC to differentiate patients with none and mild (G0-6) from patients with moderate and severe necroinflammation (G7-18) was 0.834 (95% CI 0.712-0.956, 0.724(95% CI 0.565-0.884) and 0.837(95% CI 0.717-0.956).

CONCLUSION

Gd-EOB-DTPA-enhanced MRI by CEI could be used as a noninvasive imaging biomarker to distinguish grades of necroinflammatory activity in patients with HCV after DAAs therapy at early stage and CEI combined with ADC could get a better diagnostic accuracy.

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.

Can gadoxetic acid–enhanced magnetic resonance imaging be used to avoid liver biopsy in patients with nonalcoholic fatty liver disease?

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a major cause of liver disease worldwide. The diagnosis of nonalcoholic steatohepatitis (NASH), the most severe form of NAFLD, is crucial and has prognostic and therapeutic implications. However, currently this diagnosis is based on liver biopsy and has several limitations.

AIM

To evaluate the performance of gadoxetic acid–enhanced magnetic resonance imaging (GA-MRI) in differentiating isolated steatosis from NASH in patients with NAFLD.

METHODS

In this prospective study, 56 patients with NAFLD (18 with isolated steatosis and 38 with NASH) underwent GA-MRI. The contrast enhancement index (CEI) was calculated as the rate of increase of the liver-to-muscle signal intensity ratio from before and 20 min after intravenous GA administration. Between-group differences in mean CEI were examined using Student's t test. The area under the receiver operator characteristic curve and the diagnostic performance of gadoxetic acid–enhanced magnetic resonance imaging were evaluated.

RESULTS

The mean CEI for all subjects was 1.82 ± 0.19. The mean CEI was significantly lower in patients with NASH than in those with isolated steatosis (P = 0.008). Two CEI cut-off points were used: < 1.66 (94% specificity) to characterize NASH and > 2.00 (89% sensitivity) to characterize isolated steatosis. CEI values between 1.66 and 2.00 indicated liver biopsy, and the procedure could be avoided in 40% of patients with NAFLD.

CONCLUSION

GA-MRI is an effective noninvasive method that may be useful for the differentiation of NASH from isolated steatosis, and could help to avoid liver biopsy in patients with NAFLD.

Hepatic steatosis in patients undergoing resection of colorectal liver metastases: A target for prehabilitation? A narrative review

The prevalence of elevated intra-hepatic fat (IHF) is increasing in the Western world, either alone as hepatic steatosis (HS) or in conjunction with inflammation (steatohepatitis). These changes to the hepatic parenchyma are an independent risk factor for post-operative morbidity following liver resection for colorectal liver metastases (CRLM). As elevated IHF and colorectal malignancy share similar risk factors for development it is unsurprisingly frequent in this cohort. In patients undergoing resection IHF may be elevated due to excess adiposity or its elevation may be induced by neoadjuvant chemotherapy, termed chemotherapy associated steatosis (CAS). Additionally, chemotherapy is implicated in the development of inflammation termed chemotherapy associated steatohepatitis (CASH). Following cessation of chemotherapy, patients awaiting resection have a 4-6 week washout period prior to resection that is a window for prehabilitation prior to surgery. In patients with NAFLD dietary and pharmacological interventions can reduce IHF within this timeframe but this approach to modifying IHF is untested in this population. In this review, the aetiology of CAS and CASH is reviewed with recommendations to identify those at risk. We also focus on the post-chemotherapy washout period, reviewing dietary interventions applied to the metabolic population and suggest this window may be used as an opportunity to optimise IHF with such a regime as part of a pre-operative prehabilitation programme to produce improved patient outcomes.

Influence of hepatic fibrosis and inflammation: Correlation between histopathological changes and Gd-EOB-DTPA-enhanced MR imaging

Objective

To evaluate the influence of an active inflammatory process in the liver on Gd-EOB-DTPA-enhanced MR imaging in patients with different degrees of fibrosis/cirrhosis.

Material and methods

Overall, a number of 91 patients (61 men and 30 women; mean age 58 years) were included in this retrospective study. The inclusion criteria for this study were Gd-EOB-DTPA-enhanced MRI of the liver and histopathological evaluation of fibrotic and inflammatory changes. T1-weighted VIBE sequences of the liver with fat suppression were evaluated to determine the relative signal change (RE) between native and hepatobiliary phase (20min). In simple and multiple linear regression analyses, the influence of liver fibrosis/cirrhosis (Ishak score) and the histopathological degree of hepatitis (Modified Hepatic Activity Index, mHAI) on RE were evaluated.

Results

RE decreased significantly with increasing liver fibrosis/cirrhosis (p < 0.001) and inflammation (mHAI, p = 0.004). In particular, a correlation between RE and periportal or periseptal boundary zone hepatitis (moth feeding necrosis, mHAI A, p = 0.001) and portal inflammation (mHAI D, p < 0.001) was observed. In multiple linear regression analysis, both the degree of inflammation and the degree of fibrosis were significant predictors for RE (p < 0.01).

Conclusion

The results of this study suggest that the MR-based hepatic enhancement index RE is not only influenced by the degree of fibrosis, but also by the degree of inflammation.

Noninvasive Assessment of Liver Fibrosis in Patients with Chronic Hepatitis B or C by Contrast-Enhanced Magnetic Resonance Imaging

Background and Aim. To develop a noninvasive magnetic resonance imaging (MRI) method for evaluation of liver fibrosis. We evaluate the utility of hepatocyte-phase Gadoxetate disodium-enhanced magnetic resonance (MR) imaging in staging hepatic fibrosis and compare it with histological analysis as the reference standard (liver biopsy). Methods. Prospective cohort of 78 patients, who received Gadoxetate disodium dynamic contrast-enhanced MRI (DCE-MRI), were divided into three groups. The first group (n=19) was a control group of healthy individuals without liver injury and remaining 59 subjects were chronic hepatitis B and C patients who underwent liver biopsy. These patients were divided into the mild fibrosis F1-F2 (n=32) and advanced fibrosis F3-F4 (n=27) groups. Patients were examined by generated DCE-MRI in 20th minute. Variables such as liver surface changes, homogeneities, and quantitative contrast liver/spleen ratio-Q-LSCR were evaluated and these results were consequently compared between the three groups. Results. Gd-EOB-DTPA contrast-enhanced dynamic liver MRI examination (DCE-MRI) can in the 20th minute differentiate mild stage of liver fibrosis (F1-F2) from severe stage of liver fibrosis (F3-F4) on the basis of liver surface changes, homogeneities, and quantitative contrast liver/spleen ratio-Q-LSCR. Diagnostic MRI criteria were created and named MRI Triple test. This test correctly identified 96% of patients with F3-F4 fibrosis and 91% of patients with the F1-F2 fibrosis in the liver biopsy. This test correctly identified 42,1% of patients in the control group (presumed F0 fibrosis without liver disease). Spearman's rank correlation coefficient (r = 0,86, P < .001) confirmed high agreement of biopsy and MR Triple test. MR Triple test's sensitivity was 96.30% (95%CI 81.03% to 99.91%), specificity 90.62% (95%CI 74.98% to 98.02%), positive predictive value 89.66% (95%CI 74.64% to 96.23%), and negative predictive value 96.67% (95%CI 80.86% to 99.50%) for discrimination between F3-4 and F1-2 fibrosis on liver biopsy. Conclusions. Gd-EOB-DTPA contrast-enhanced MRI liver examination in 20th minute is able to reliably differentiate mild stage of liver fibrosis (F1-F2) from severe stage fibrosis (F3-F4) on the basis of Triple test (liver surface changes, homogeneities, and quantitative contrast liver/spleen ratio-Q-LSCR).

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.

Does gadoxetate disodium affect MRE measurements in the delayed hepatobiliary phase?

OBJECTIVES

To assess if the administration of gadoxetate disodium (Gd-EOB-DTPA) significantly affects hepatic magnetic resonance elastography (MRE) measurements in the delayed hepatobiliary phase (DHBP).

METHODS

A total of 47 patients (15 females, 32 males; age range 23-78 years, mean 54.28 years) were assigned to standard hepatic magnetic resonance imaging (MRI) with application of Gd-EOB-DTPA and hepatic MRE. MRE was performed before injection of Gd-EOB-DTPA and after 40-50 min in the DHBP. Liver stiffness values were obtained before and after contrast media application and differences between pre- and post-Gd-EOB-DTPA values were evaluated using a Bland-Altman plot and the Mann-Whitney-Wilcoxon test. In addition, the data were compared with regard to the resulting fibrosis classification.

RESULTS

Mean hepatic stiffness for pre-Gd-EOB-DTPA measurements was 4.01 kPa and post-Gd-EOB-DTPA measurements yielded 3.95 kPa. We found a highly significant individual correlation between pre- and post-Gd-EOB-DTPA stiffness values (Pearson correlation coefficient of r = 0.95 (p < 0.001) with no significant difference between the two measurements (p =0.49)). Bland-Altman plot did not show a systematic effect for the difference between pre- and post-stiffness measurements (mean difference: 0.06 kPa, SD 0.81). Regarding the classification of fibrosis stages, the overall agreement was 87.23% and the intraclass correlation coefficient was 96.4%, indicating excellent agreement.

CONCLUSIONS

Administration of Gd-EOB-DTPA does not significantly influence MRE stiffness measurements of the liver in the DHBP. Therefore, MRE can be performed in the DHBP.

KEY POINTS

• MRE of the liver can reliably be performed in the delayed hepatobiliary phase. • Gd-EOB-DTPA does not significantly influence MRE stiffness measurements of the liver. • MRE performed in the delayed hepatobiliary-phase is reasonable in patients with reduced liver function.

Diagnostic performance of Gd-EOB-DTPA-enhanced MRI for evaluation of liver dysfunction: a multivariable analysis of 3T MRI sequences

OBJECTIVE

The aim of this study was to evaluate the diagnostic performance of a multiparametric gadolinium ethoxybenzyl-diethylenetriaminepentaacetic acid (Gd-EOB-DTPA)-enhanced MRI examination for the estimation of liver dysfunction classified by the Model for End-Stage Liver Disease (MELD) score.

RESULTS

Liver dysfunction can be assessed by different methods. In a logistic regression analysis, T1- and T2-weighted images were affected by impaired liver function. In the assessment of liver dysfunction, the reduction rate in T1 mapping sequences showed a significant correlation in simple and multiple logistic regression.

CONCLUSION

Changes in Gd-EOB-DTPA-enhanced MRI between plain images and images obtained during the hepatobiliary phase allowed good prediction of liver dysfunction, especially when using T1 mapping sequences.

MATERIALS AND METHODS

A total of 199 patients underwent contrast-enhanced MRI with a hepatocyte-specific contrast agent at 3T. In the multivariable analysis, the full range of available MRI sequences was used to estimate the liver dysfunction of patients with various MELD scores.

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.

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.

Magnetic Resonance Elastography and Other Magnetic Resonance Imaging Techniques in Chronic Liver Disease: Current Status and Future Directions

Recent advances in the noninvasive imaging of chronic liver disease have led to improvements in diagnosis, particularly with magnetic resonance imaging (MRI). A comprehensive evaluation of the liver may be performed with the quantification of the degree of hepatic steatosis, liver iron concentration, and liver fibrosis. In addition, MRI of the liver may be used to identify complications of cirrhosis, including portal hypertension, ascites, and the development of hepatocellular carcinoma. In this review article, we discuss the state of the art techniques in liver MRI, namely, magnetic resonance elastography, hepatobiliary phase MRI, and liver fat and iron quantification MRI. The use of these advanced techniques in the management of chronic liver diseases, including non-alcoholic fatty liver disease, will be elaborated.

T2* Mapping from Multi-Echo Dixon Sequence on Gadoxetic Acid-Enhanced Magnetic Resonance Imaging for the Hepatic Fat Quantification: Can It Be Used for Hepatic Function Assessment?

Objective

To evaluate the diagnostic value of T2^* mapping using 3D multi-echo Dixon gradient echo acquisition on gadoxetic acid-enhanced liver magnetic resonance imaging (MRI) as a tool to evaluate hepatic function.

Materials and Methods

This retrospective study was approved by the IRB and the requirement of informed consent was waived. 242 patients who underwent liver MRIs, including 3D multi-echo Dixon fast gradient-recalled echo (GRE) sequence at 3T, before and after administration of gadoxetic acid, were included. Based on clinico-laboratory manifestation, the patients were classified as having normal liver function (NLF, n = 50), mild liver damage (MLD, n = 143), or severe liver damage (SLD, n = 30). The 3D multi-echo Dixon GRE sequence was obtained before, and 10 minutes after, gadoxetic acid administration. Pre- and post-contrast T2^* values, as well as T2^* reduction rates, were measured from T2^* maps, and compared among the three groups.

Results

There was a significant difference in T2^* reduction rates between the NLF and SLD groups (−0.2 ± 4.9% vs. 5.0 ± 6.9%, p = 0.002), and between the MLD and SLD groups (3.2 ± 6.0% vs. 5.0 ± 6.9%, p = 0.003). However, there was no significant difference in both the pre- and post-contrast T2^* values among different liver function groups (p = 0.735 and 0.131, respectively). A receiver operating characteristic (ROC) curve analysis showed that the area under the ROC curve for using T2^* reduction rates to differentiate the SLD group from the NLF group was 0.74 (95% confidence interval: 0.63–0.83).

Conclusion

Incorporation of T2^* mapping using 3D multi-echo Dixon GRE sequence in gadoxetic acid-enhanced liver MRI protocol may provide supplemental information for liver function deterioration in patients with SLD.

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.

Age dependence of spleen- and muscle-corrected hepatic signal enhancement on hepatobiliary phase gadoxetate MRI

OBJECTIVES

To identify correlations of signal enhancements (SE) and SE normalized to reference tissues of the spleen, kidney, liver, musculus erector spinae (MES) and ductus hepatocholedochus (DHC) on hepatobiliary phase gadoxetate-enhanced MRI with patient age in non-cirrhotic patients.

METHODS

A heterogeneous cohort of 131 patients with different clinical backgrounds underwent a standardized 3.0-T gadoxetate-enhanced liver MRI between November 2008 and June 2013. After exclusion of cirrhotic patients, a cohort of 75 patients with no diagnosed diffuse liver disease was selected. The ratio of signal intensity 20 min post- to pre-contrast administration (SE) in the spleen, kidney, liver, MES and DHC, and the SE of the kidney, liver and DHC normalized to the reference tissues spleen or MES were compared to patient age.

RESULTS

Patient age was inversely correlated with the liver SE normalized to the spleen and MES SE (both p < 0.001) and proportionally with the SE of the spleen (p = 0.043), the MES (p = 0.030) and the kidney (p = 0.022). No significant correlations were observed for the DHC (p = 0.347) and liver SE (p = 0.606).

CONCLUSION

The age dependence of hepatic SE normalized to the enhancement in the spleen and MES calls for a cautious interpretation of these quantification methods.

KEY POINTS

• Patient age was inversely correlated with spleen- and MES-corrected liver rSE (p < 0.001). • Patient age was correlated with spleen (p = 0.043) and MES SE (p = 0.030). • Patient age may confound quantitative liver function assessment using gadoxetate-enhanced liver MRI.

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.

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.

Volume change and liver parenchymal signal intensity in Gd-EOB-DTPA-enhanced magnetic resonance imaging after portal vein embolization prior to hepatectomy

Purpose. To investigate the liver volume change and the potential of early evaluation by contrast-enhanced magnetic resonance imaging (MRI) using gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) after portal vein embolization (PVE). Materials and Methods. Retrospective evaluations of computed tomography (CT) volumetry of total liver and nonembolized areas were performed before and 3 weeks after PVE in 37 cases. The percentage of future liver remnant (%FLR) and the change ratio of %FLR (%FLR ratio) were calculated. Prospective evaluation of signal intensities (SIs) was performed to estimate the role of Gd-EOB-DTPA-enhanced MRI as a predictor of hypertrophy in 16 cases. The SI contrast between embolized and nonembolized areas was calculated 1 week after PVE. The change in SI contrast before and after PVE (SI ratio) was also calculated in 11 cases. Results. %FLR ratio significantly increased, and SI ratio significantly decreased (both P < 0.01). There were significant negative correlations between %FLR and SI contrast and between %FLR and SI ratio (both P < 0.01). Conclusion. Hypertrophy in the nonembolized area after PVE was indicated by CT volumetry, and measurement of SI contrast and SI ratio in Gd-EOB-DTPA-enhanced MRI early after PVE may be useful to predict the potential for hepatic hypertrophy.

Hepatobiliary magnetic resonance imaging in patients with liver disease: correlation of liver enhancement with biochemical liver function tests

OBJECTIVES

To evaluate hepatobiliary magnetic resonance imaging (MRI) using Gd-EOB-DTPA in relation to various liver function tests in patients with liver disorders.

METHODS

Fifty-one patients with liver disease underwent Gd-EOB-DTPA-enhanced liver MRI. Based on region-of-interest (ROI) analysis, liver signal intensity was calculated using the spleen as reference tissue. Liver-spleen contrast ratio (LSCR) and relative liver enhancement (RLE) were calculated. Serum levels of total bilirubin, gamma glutamyl transpeptidase (GGT), aspartate aminotransferase (AST), alanine aminotransferase (ALT), glutamate dehydrogenase (GLDH), lactate dehydrogenase (LDH), serum albumin level (AL), prothrombin time (PT), creatinine (CR) as well as international normalised ratio (INR) and model for end-stage liver disease (MELD) score were tested for correlation with LSCR and RLE.

RESULTS

Pre-contrast LSCR values correlated with total bilirubin (r = -0.39; p = 0.005), GGT (r = -0.37; p = 0.009), AST (r = -0.38; p = 0.013), ALT (r = -0.29; p = 0.046), PT (r = 0.52; p < 0.001), GLDH (r = -0.55; p = 0.044), INR (r = -0.42; p = 0.003), and MELD Score (r = -0.53; p < 0.001). After administration of Gd-EOB-DTPA bilirubin (r = -0.45; p = 0.001), GGT (r = -0.40; p = 0.004), PT (r = 0.54; p < 0.001), AST (r = -0.46; p = 0.002), ALT (r = -0.31; p = 0.030), INR (r = -0.45; p = 0.001) and MELD Score (r = -0.56; p < 0.001) significantly correlated with LSCR. RLE correlated with bilirubin (r = -0.40; p = 0.004), AST (r = -0.38; p = 0.013), PT (r = 0.42; p = 0.003), GGT (r = -0.33; p = 0.020), INR (r = -0.36; p = 0.011) and MELD Score (r = -0.43; p = 0.003).

CONCLUSIONS

Liver-spleen contrast ratio and relative liver enhancement using Gd-EOB-DTPA correlate with a number of routinely used biochemical liver function tests, suggesting that hepatobiliary MRI may serve as a valuable biomarker for liver function. The strongest correlation with liver enhancement was found for the MELD Score.

KEY POINTS

• Relative enhancement (RLE) of Gd-EOB-DTPA is related to biochemical liver function tests. • Correlation of RLE with bilirubin, ALT, AST, GGT, INR and MELD Score is reverse. • The correlation of relative liver enhancement with prothrombin time is positive. • AST, ALT, GLDH, prothrombin time, INR and MELD Score correlate with pre-contrast liver-spleen contrast ratio. • Such biomarkers may help to evaluate liver function.

MRI-based estimation of liver function: Gd-EOB-DTPA-enhanced T1 relaxometry of 3T vs. the MELD score

Gd-EOB-DTPA is a hepatocyte-specific MRI contrast agent. Due to its hepatocyte-specific uptake and paramagnetic properties, functioning areas of the liver exhibit shortening of the T1 relaxation time. We report the potential use of T1 relaxometry of the liver with Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI) for estimating the liver function as expressed by the MELD score. 3 T MRI relaxometry was performed before and 20 min after Gd-EOB-DTPA administration. A strong correlation between changes in the T1 relaxometry and the extent of liver disease, expressed by the MELD score, was documented. Reduced liver function correlates with decreased Gd-EOB-DTPA accumulation in the hepatocytes during the hepatobiliary phase. MRI-based T1 relaxometry with Gd-EOB-DTPA may be a useful method for assessing overall and segmental liver function.

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.

Assessing liver function by liver enhancement during the hepatobiliary phase with Gd-EOB-DTPA-enhanced MRI at 3 Tesla

OBJECTIVES

The purpose of this study was to evaluate the usefulness of Gd-EOB-DTPA-enhanced 3-T MRI to determine the hepatic functional reserve expressed by the model for end-stage liver disease (MELD) score.

METHODS

A total of 121 patients with normal liver function (NLF; MELD score ≤ 10) and 29 patients with impaired liver function (ILF; MELD score > 10) underwent contrast-enhanced MRI with a hepatocyte-specific contrast agent at 3T. T1-weighted volume interpolated breath-hold examination (VIBE) sequences with fat suppression were acquired before and 20 min after contrast injection. Relative enhancement (RE) between plain signal intensity and contrast-enhanced signal intensity was calculated and was used to determine Gd-EOB-DTPA uptake into the liver parenchyma for patients with different MELD scores.

RESULTS

RE differed significantly (p ≤ 0.001) between patients with NLF (87.2 ± 29.5 %) and patients with ILF (45.4 ± 26.5 %). The optimal cut-off value for RE to differentiate NLF from ILF was 47.7 % (AUC 0.87). This cut-off value showed a sensitivity of 82.8 % and a specificity of 92.7 % for the differentiation of the analysed groups.

CONCLUSION

Gd-EOB-DTPA uptake in hepatocytes is strongly affected by liver function. Gd-EOB-DTPA-enhanced MRI and assessment of RE during the hepatobiliary phase (HBP) may serve as a useful image-based test in liver imaging for determining regional and global liver function.

KEY POINTS

Hepatic uptake of Gd-EOB-DTPA is strongly affected by liver function. Relative enhancement during HBP in GD-EOB-DTPA MRI correlates with the MELD score. Assessment of relative enhancement may help improve treatment in routine clinical practice.

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 ∆%.

Clinical utility of imaging for evaluation of hepatocellular carcinoma

The hemodynamics of a hepatocellular nodule is the most important imaging parameter used to characterize various hepatocellular nodules in liver cirrhosis, because sequential changes occur in the feeding vessels and hemodynamic status during hepatocarcinogenesis. Therefore, the imaging criteria for hepatocellular carcinoma (HCC) are also usually based on vascular findings, eg, early arterial uptake followed by washout in the portal venous and equilibrium phases. Contrast-enhanced ultrasonography, dynamic multidetector-row computed tomography (MDCT), and dynamic magnetic resonance (MR) imaging with gadopentetate dimeglumine (Gd-DTPA) are useful for detecting hypervascular HCC on the basis of vascular criteria but are not as useful for hypovascular HCC. Contrast-enhanced MR imaging with gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA), a hepatocyte-specific MR contrast agent, is superior to dynamic MDCT and dynamic MR imaging with Gd-DTPA in detecting both hypervascular and hypovascular HCC. Moreover, Gd-EOB-DTPA-enhanced MR imaging can display each histologically differentiated HCC as hypointense relative to the liver parenchyma. ¹⁸F-fluorodeoxyglucose positron emission tomography imaging might not be suitable for the screening and detection of HCC, given its lower diagnostic performance. However, this technique plays an important role in determining whether HCC has spread beyond the liver.

Assessment of clinical signs of liver cirrhosis using T1 mapping on Gd-EOB-DTPA-enhanced 3T MRI

OBJECTIVES

To assess the differences between normal and cirrhotic livers by means of T1 mapping of liver parenchyma on gadoxetic acid (Gd-EOB-DTPA)-enhanced 3 Tesla (3T) MR imaging (MRI).

METHODS

162 patients with normal (n = 96) and cirrhotic livers (n = 66; Child-Pugh class A, n = 30; B, n = 28; C, n = 8) underwent Gd-EOB-DTPA-enhanced 3T MRI. To obtain T1 maps, two TurboFLASH sequences (TI = 400 ms and 1000 ms) before and 20 min after Gd-EOB-DTPA administration were acquired. T1 relaxation times of the liver and the reduction rate between pre- and post-contrast enhancement images were measured.

RESULTS

The T1 relaxation times for Gd-EOB-DTPA-enhanced MRI showed significant differences between patients with normal liver function and patients with Child-Pugh class A, B, and C (p < 0.001). The T1 relaxation times showed a constant significant increase from Child-Pugh class A up to class C (Child-Pugh class A, 335 ms ± 80 ms; B, 431 ms ± 75 ms; C, 557 ms ± 99 ms; Child-Pugh A to B, p < 0.001; Child-Pugh A to C, p < 0.001; Child-Pugh B to C, p < 0.001) and a constant decrease of the reduction rate of T1 relaxation times (Child-Pugh class A, 57.1% ± 8.8%; B, 44.3% ± 10.2%, C, 29.9% ± 6.9%; Child-Pugh A to B, p < 0.001; Child-Pugh A to C,p < 0.001; Child-Pugh B to C, p < 0.001).

CONCLUSION

Gd-EOB-DTPA-enhanced T1 mapping of the liver parenchyma may present a useful method for determining severity of liver cirrhosis.

Nonalcoholic fatty liver disease: intravoxel incoherent motion diffusion-weighted MR imaging-an experimental study in a rabbit model

PURPOSE

To evaluate the feasibility of using intravoxel incoherent motion (IVIM) diffusion-weighted imaging with multiple b values for the noninvasive diagnosis of nonalcoholic fatty liver disease (NAFLD).

MATERIALS AND METHODS

This study was approved by the institutional animal care and use committee. Twenty-seven 8-week-old rabbits were fed a variety of diets (from a standard diet to a high-fat, high-cholesterol diet) before IVIM diffusion-weighted imaging was performed with seven b values by using a 3-T magnetic resonance (MR) imaging unit. At histologic analysis of the animals, livers were categorized by NAFLD severity as normal, NAFLD, borderline nonalcoholic steatohepatitis (NASH), or NASH. The apparent diffusion coefficient and IVIM-derived parameters including true diffusion coefficient, pseudodiffusion coefficient, and perfusion fraction of the liver parenchyma were measured. Each parameter was correlated with NAFLD severity, and optimal cutoff values were determined by means of receiver operating characteristics analysis.

RESULTS

Perfusion fraction was significantly lower in rabbits with NAFLD than in those with a normal liver, and it decreased further as severity of NAFLD increased, with medians of 22.2%, 14.8%, 11.3%, and 9.5% in the rabbits in the normal, NAFLD, borderline, and NASH groups, respectively (ρ = -0.83, P < .001). Apparent diffusion coefficient, true diffusion coefficient, and pseudodiffusion coefficient were not significantly different between the NAFLD severity groups. In terms of the diagnostic performance of perfusion fraction, area under the curve values were 0.984 (normal vs NAFLD or more severe disease), 0.959 (NAFLD or less severe vs borderline or more severe disease), and 0.903 (borderline or less severe vs NASH) with optimal cutoff values of 15.2%, 13.2%, and 11.0%, respectively.

CONCLUSION

Perfusion fractions extracted from IVIM diffusion-weighted imaging may help in the differentiation of early stage NASH from simple steatosis.

Nonalcoholic Fatty Liver Disease: Intravoxel Incoherent Motion Diffusion-weighted MR Imaging-An Experimental Study in a Rabbit Model

Purpose To evaluate the feasibility of using intravoxel incoherent motion (IVIM) diffusion-weighted imaging with multiple b values for the noninvasive diagnosis of nonalcoholic fatty liver disease (NAFLD). Materials and Methods This study was approved by the institutional animal care and use committee. Twenty-seven 8-week-old rabbits were fed a variety of diets (from a standard diet to a high-fat, high-cholesterol diet) before IVIM diffusion-weighted imaging was performed with seven b values by using a 3-T magnetic resonance (MR) imaging unit. At histologic analysis of the animals, livers were categorized by NAFLD severity as normal, NAFLD, borderline nonalcoholic steatohepatitis (NASH), or NASH. The apparent diffusion coefficient and IVIM-derived parameters including true diffusion coefficient, pseudodiffusion coefficient, and perfusion fraction of the liver parenchyma were measured. Each parameter was correlated with NAFLD severity, and optimal cutoff values were determined by means of receiver operating characteristics analysis. Results Perfusion fraction was significantly lower in rabbits with NAFLD than in those with a normal liver, and it decreased further as severity of NAFLD increased, with medians of 22.2%, 14.8%, 11.3%, and 9.5% in the rabbits in the normal, NAFLD, borderline, and NASH groups, respectively (ρ = -0.83, P < .001). Apparent diffusion coefficient, true diffusion coefficient, and pseudodiffusion coefficient were not significantly different between the NAFLD severity groups. In terms of the diagnostic performance of perfusion fraction, area under the curve values were 0.984 (normal vs NAFLD or more severe disease), 0.959 (NAFLD or less severe vs borderline or more severe disease), and 0.903 (borderline or less severe vs NASH) with optimal cutoff values of 15.2%, 13.2%, and 11.0%, respectively. Conclusion Perfusion fractions extracted from IVIM diffusion-weighted imaging may help in the differentiation of early stage NASH from simple steatosis. © RSNA, 2013.

Liver failure after major liver resection: risk assessment by using preoperative Gadoxetic acid-enhanced 3-T MR imaging

PURPOSE

To determine if gadoxetic acid-enhanced magnetic resonance (MR) imaging with measurement of relative liver enhancement (RLE) on hepatobiliary phase images can allow preoperative assessment of the risk of liver failure after major liver resection.

MATERIALS AND METHODS

The local institutional review committee approved this retrospective analysis and waived written informed consent. The study included 73 patients (39 men; median age, 64.4 years) who underwent gadoxetic acid-enhanced 3-T MR imaging before resection of three or more liver segments. RLE was calculated as the ratio of signal intensity measurements of the liver parenchyma before and 20 minutes after intravenous administration of gadoxetic acid. RLE was assessed in each liver segment and the mean value of all segments was used for analysis. Posthepatectomy liver failure was defined according to the "50-50 criteria" (ie, prothrombin time <50% and serum bilirubin >50 µmol/L on postoperative day 5) and the International Study Group of Liver Surgery (ISGLS) classification. The association of RLE and liver failure was tested with univariate and multivariate logistic regression analysis. In addition to RLE, the latter also included demographic, clinical, operative, and histologic variables.

RESULTS

Patients with liver failure according to the 50-50 criteria (n = 3) had significantly lower RLE (54.5%) than those without (125.6%) (P = .009). According to ISGLS criteria, RLE was 112.5% in patients with grade A liver failure (n = 20), 88.4% in patients with grade B (n = 7), 41.7% (n = 2) in patients with grade C, and 136.5% (P < .001) in those without liver failure. In a logistic regression analysis, RLE was inversely related to the probability of liver failure according to the 50-50 (P = .02) and ISGLS (P < .001) criteria. In a multivariate analysis, RLE was independently associated with a higher probability of liver failure according to ISGLS classification (P = .003).

CONCLUSION

Gadoxetic acid-enhanced MR imaging can help with the assessment of the risk for liver failure after major liver resection.

A simple and inexpensive system for controlling body temperature in small animal experiments using MRI and the effect of body temperature on the hepatic kinetics of Gd-EOB-DTPA

The purpose of this study was to develop a simple and inexpensive system for controlling body temperature in small animal experiments using magnetic resonance imaging (MRI) and to investigate the effect of body temperature on the kinetic behavior of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) in the liver. In our temperature-control system, body temperature was controlled using a feedback-regulated heated or cooled air flow generated by two Futon dryers. The switches of the two Futon dryers were controlled using a digital temperature controller, in which the rectal temperature of a mouse measured by an optical fiber thermometer was used as the input. In experimental studies, male ICR mice aged 8weeks old were used and allocated into 5 groups (39-, 36-, 33-, 30-, and 27-degree groups, n=10), in which the body temperature was maintained at 39 °C, 36 °C, 33 °C, 30 °C, and 27 °C, respectively, using our system. The dynamic contrast-enhanced MRI (DCE-MRI) data were acquired with an MRI system for animal experiments equipped with a 1.5-Tesla permanent magnet, for approximately 43min, after the injection of Gd-EOB-DTPA into the tail vein. After correction of the image shift due to the temperature-dependent drift of the Larmor frequency using the gradient-based image registration method with robust estimation of displacement parameters, the kinetic behavior of Gd-EOB-DTPA was analyzed using an empirical mathematical model. With the use of this approach, the upper limit of the relative enhancement (A), the rates of contrast uptake (α) and washout (β), the parameter related to the slope of early uptake (q), the area under the curve (AUC), the maximum relative enhancement (REmax), the time to REmax (Tmax), and the elimination half-life of the contrast agent (T1/2) were calculated. The body temperature of mice could be controlled well by use of our system. Although there were no significant differences in α, AUC, and q among groups, there were significant differences in A, REmax, β, Tmax, and T1/2, indicating that body temperature significantly affects the kinetic behavior of Gd-EOB-DTPA in the liver. In conclusion, our system will be useful for controlling body temperature in small animal experiments using MRI. Because body temperature significantly affects the kinetic behavior of Gd-EOB-DTPA in the liver, the control of body temperature is essential and should be carefully considered when performing DCE-MRI studies in small animal experiments.

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.

Impact of liver cirrhosis on liver enhancement at Gd-EOB-DTPA enhanced MRI at 3 Tesla

PURPOSE

The purpose of this study was to assess differences in enhancement effects of liver parenchyma between normal and cirrhotic livers on dynamic, Gd-EOB-DTPA enhanced MRI at 3T.

MATERIALS AND METHODS

93 patients with normal (n=54) and cirrhotic liver (n=39; Child-Pugh class A, n=18; B, n=16; C, n=5) underwent contrast-enhanced MRI with liver specific contrast media at 3T. T1-weighted volume interpolated breath hold examination (VIBE) sequences with fat suppression were acquired before contrast injection, in the arterial phase (AP), in the late arterial phase (LAP), in the portal venous phase (PVP), and in the hepatobiliary phase (HBP) after 20 min. The relative enhancement (RE) of the signal intensity of the liver parenchyma was calculated for all phases.

RESULTS

Mean RE was significantly different among all evaluated groups in the hepatobiliary phase and with increasing severity of liver cirrhosis, a decreasing, but still significant reduction of RE could be shown. Phase depending changes of RE for each group were observed. In case of non-cirrhotic liver or Child-Pugh Score A cirrhosis mean RE showed a significant increase between AP, LAP, PVP and HBP. For Child-Pugh B+C cirrhosis RE increased until PVP, however, there was no change in case of B cirrhosis (p=0.501) and significantly reduced in case of C cirrhosis (p=0.043) during HBP.

CONCLUSION

RE of liver parenchyma is negatively affected by increased severity of liver cirrhosis, therefore diagnostic value of HBP could be limited in case of Child Pugh B+C cirrhosis.

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.

Prediction of Advanced Fibrosis in Nonalcoholic Fatty Liver Disease: An Enhanced Model of BARD Score

Background/Aims

The BARD score is a model to detect advanced liver fibrosis in nonalcoholic fatty liver disease (NAFLD) patients. The aims of this study were to identify additional factors and then to build an enhanced version of the BARD score.

Methods

One hundred seven patients with biopsy-proven NAFLD were enrolled retrospectively. Logistic regressions were performed to identify independent risk factors for advanced liver fibrosis (stage 3 or 4). An enhanced model of the BARD score (BARDI score) was built and evaluated with a receiver operating characteristic (ROC) curve.

Results

In multivariate analysis, age (odds ratio [OR], 0.89; p=0.04), aspartate aminotransferase/alanine aminotransferase ratio (OR, 1.73; p<0.01), and international normalized ratio (INR) (OR, 8.85; p<0.01) were independently significant factors. The BARDI score was created by adding the INR to the BARD. The area under the ROC curve of the BARDI score was significantly larger than that of the BARD score (0.881 vs 0.808, p<0.01). A BARDI score of 3 or more showed a positive predictive value (PPV) of 51.0% and a negative predictive value (NPV) of 96.0%.

Conclusions

The BARDI score had an improved PPV over the BARD score and maintained an excellent NPV. Further study is warranted for its external validation and comparison with other models.

Usefulness of Gd-EOB-DTPA-enhanced MR imaging in the evaluation of simple steatosis and nonalcoholic steatohepatitis

PURPOSE

To evaluate the usefulness of gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA)-enhanced MR imaging (EOB-MRI) in differentiating between simple steatosis and nonalcoholic steatohepatitis (NASH), as compared with MR in-phase/out-of-phase imaging. The correlations between the MR features and histological characteristics were preliminarily investigated.

MATERIALS AND METHODS

From April 2008 to October 2011, 25 patients (13 simple steatosis and 12 NASH) who underwent both EOB-MRI and in-phase/out-of-phase imaging were analyzed. The hepatobiliary-phase enhancement ratio and signal intensity loss on opposed-phase T1-weighted images (fat fraction) were compared between the simple steatosis and NASH groups. In the simple steatosis and NASH groups, the correlations between enhancement ratio and histological grade/stage were explored. In the NASH group, fat fraction was correlated with the steatosis score.

RESULTS

The enhancement ratio in NASH was significantly lower than that in simple steatosis (P = 0.03). In the simple steatosis and NASH groups, the enhancement ratio was significantly correlated with the fibrosis stage (r = -0.469, P = 0.018). Fat fraction in NASH was strongly correlated with the steatosis score (r = 0.728, P = 0.007).

CONCLUSION

In simple steatosis and NASH, the hepatobiliary-phase enhancement ratio of EOB-MRI showed significant association with fibrosis stage, and may be a useful discriminating parameter compared with the fat fraction measured by in-phase/out-of-phase imaging.

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.