Effect of multipeak spectral modeling of fat for liver iron and fat quantification: correlation of biopsy with MR imaging results

Evaluation of MRI proton density fat fraction in hepatic steatosis: a systematic review and meta-analysis

BACKGROUND

Amidst the global rise of metabolic dysfunction-associated steatotic liver disease (MASLD), driven by increasing obesity rates, there is a pressing need for precise, non-invasive diagnostic tools. Our research aims to validate MRI Proton Density Fat Fraction (MRI-PDFF) utility, compared to liver biopsy, in grading hepatic steatosis in MASLD.

METHODS

A systematic search was conducted across Embase, PubMed/Medline, Scopus, and Web of Science until January 13, 2024, selecting studies that compare MRI-PDFF with liver biopsy for hepatic steatosis grading, defined as grades 0 (< 5% steatosis), 1 (5-33% steatosis), 2 (34-66% steatosis), and 3 (> 66% steatosis).

RESULTS

Twenty-two studies with 2844 patients were included. The analysis showed high accuracy of MRI-PDFF with AUCs of 0.97 (95% CI = 0.96-0.98) for grade 0 vs ≥ 1, 0.91 (95% CI = 0.88-0.93) for ≤ 1 vs ≥ 2, and 0.91 (95% CI = 0.88-0.93) for ≤ 2 vs 3, diagnostic odds ratio (DOR) from 98.74 (95% CI = 58.61-166.33) to 23.36 (95% CI = 13.76-39.68), sensitivity and specificity from 0.93 (95% CI = 0.88-0.96) to 0.76 (95% CI = 0.63-0.85) and 0.93 (95% CI = 0.88-0.96) to 0.89 (95% CI = 0.84-0.93), respectively. Likelihood ratio (LR) + ranged from 13.3 (95% CI = 7.4-24.0) to 7.2 (95% CI = 4.9-10.5), and LR - from 0.08 (95% CI = 0.05-0.13) to 0.27 (95% CI = 0.17-0.42). The proposed MRI-PDFF threshold of 5.7% for liver fat content emerges as a potential cut-off for the discrimination between grade 0 vs ≥ 1 (p = 0.075).

CONCLUSION

MRI-PDFF is a precise non-invasive technique for diagnosing and grading hepatic steatosis, warranting further studies to establish its diagnostic thresholds.

CLINICAL RELEVANCE STATEMENT

This study underscores the high diagnostic accuracy of MRI-PDFF for distinguishing between various grades of hepatic steatosis for early detection and management of MASLD, though further research is necessary for broader application.

KEY POINTS

MRI-PDFF offers precision in diagnosing and monitoring hepatic steatosis. The diagnostic accuracy of MRI-PDFF decreases as the grade of hepatic steatosis advances. A 5.7% MRI-PDFF threshold differentiates steatotic from non-steatotic livers.

State-of-the-Art Quantification of Liver Iron With MRI-Vendor Implementation and Available Tools

The role of MRI to estimate liver iron concentration (LIC) for identifying patients with iron overload and guiding the titration of chelation therapy is increasingly established for routine clinical practice. However, the existence of multiple MRI-based LIC quantification techniques limits standardization and widespread clinical adoption. In this article, we review the existing and widely accepted MRI-based LIC estimation methods at 1.5 T and 3 T: signal intensity ratio (SIR) and relaxometry (R2 and R2*) and discuss the basic principles, acquisition and analysis protocols, and MRI-LIC calibrations for each technique. Further, we provide an up-to-date information on MRI vendor implementations and available offline commercial and free software for each MRI-based LIC quantification approach. We also briefly review the emerging and advanced MRI techniques for LIC estimation and their current limitations for clinical use. Lastly, we discuss the implications of MRI-based LIC measurements on clinical use and decision-making in the management of patients with iron overload. Some of the key highlights from this review are as follows: 1) Both R2 and R2* can estimate accurate and reproducible LIC, when validated acquisition parameters and analysis protocols are applied, 2) Although the Ferriscan R2 method has been widely used, recent consensus and guidelines endorse R2*-MRI as the most accurate and reproducible method for LIC estimation, 3) Ongoing efforts aim to establish R2*-MRI as the standard approach for quantifying LIC, and 4) Emerging R2*-MRI techniques employ radial sampling strategies and offer improved motion compensation and broader dynamic range for LIC estimation. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY: Stage 2.

Improved liver fat and R 2 * quantification at 0.55 T using locally low-rank denoising

PURPOSE

To improve liver proton density fat fraction (PDFF) andR 2 * $$ {R}_2^{\ast } $$ quantification at 0.55 T by systematically validating the acquisition parameter choices and investigating the performance of locally low-rank denoising methods.

METHODS

A Monte Carlo simulation was conducted to design a protocol for PDFF andR 2 * $$ {R}_2^{\ast } $$ mapping at 0.55 T. Using this proposed protocol, we investigated the performance of robust locally low-rank (RLLR) and random matrix theory (RMT) denoising. In a reference phantom, we assessed quantification accuracy (concordance correlation coefficient [ρ c $$ {\rho}_c $$ ] vs. reference values) and precision (using SD) across scan repetitions. We performed in vivo liver scans (11 subjects) and used regions of interest to compare means and SDs of PDFF andR 2 * $$ {R}_2^{\ast } $$ measurements. Kruskal-Wallis and Wilcoxon signed-rank tests were performed (p < 0.05 considered significant).

RESULTS

In the phantom, RLLR and RMT denoising improved accuracy in PDFF andR 2 * $$ {R}_2^{\ast } $$ withρ c $$ {\rho}_c $$ >0.992 and improved precision with >67% decrease in SD across 50 scan repetitions versus conventional reconstruction (i.e., no denoising). For in vivo liver scans, the mean PDFF and meanR 2 * $$ {R}_2^{\ast } $$ were not significantly different between the three methods (conventional reconstruction; RLLR and RMT denoising). Without denoising, the SDs of PDFF andR 2 * $$ {R}_2^{\ast } $$ were 8.80% and 14.17 s-1. RLLR denoising significantly reduced the values to 1.79% and 5.31 s-1 (p < 0.001); RMT denoising significantly reduced the values to 2.00% and 4.81 s-1 (p < 0.001).

CONCLUSION

We validated an acquisition protocol for improved PDFF andR 2 * $$ {R}_2^{\ast } $$ quantification at 0.55 T. Both RLLR and RMT denoising improved the accuracy and precision of PDFF andR 2 * $$ {R}_2^{\ast } $$ measurements.

Development and validation of MRI-PDFF cutoffs for living liver donor eligibility assessment

Hepatic steatosis (HS) criteria for living donor liver transplantation (LDLT) donor eligibility should be based on large droplet fat as per Banff consensus recommendations. We aimed to establish magnetic resonance imaging proton density fat fraction cutoffs for HS assessment in potential LDLT donors. This retrospective study included consecutive potential LDLT donors who underwent MRI and liver biopsy between 2013 and 2023 at 2 tertiary institutions, each as development (n = 3062; 2015 men; median [IQR] age of 32 [25-38] y) and external validation (n = 472; 287 men; 35 [26-44] y) data sets. Proton density fat fraction (PDFF) was measured using dedicated MRI sequences. Histologic HS, defined as a large droplet fat fraction, was used as the reference standard. Dual PDFF cutoffs aimed at 95% sensitivity or 95% specificity, for diagnosing histologic HS of ≥10%, ≥20%, ≥30%, and ≥40%, were determined in the development data set using 10-fold cross-validation. The cutoffs were then validated in the external validation data set. The equation for estimating histologic HS from PDFF was also derived using linear regression. The PDFF cutoffs for histologic HS of ≥10%, ≥20%, ≥30%, and ≥40%, targeting 95% sensitivity, were 3.7%, 5.5%, 8.0%, and 10.0%, respectively. External validation demonstrated high sensitivities ≥97.9% with specificities ranging from 60.9% to 95.1%. The PDFF cutoffs targeting 95% specificity were 6.3%, 8.0%, 9.1%, and 10.1%, respectively. External validation rendered high specificities ranging from 88.5% to 95.3%, with sensitivities ranging from 76.6% to 100%. For diagnosing histologic HS ≥30%, which is the most prevalently used threshold for LDLT donor eligibility assessment, the PDFF cutoffs achieved sensitivities and specificities of over 90%. The equation of (Histologic HS = -2.95 + 1.93 × PDFF) was derived.

Optimization of regions of interest sampling strategies for proton density fat-fraction MRI of hepatic steatosis before liver transplantation in ex vivo livers

Objectives

The quantity of regions of interest (ROIs) constitutes the primary determinant of the time investment in image analysis. In the context of proton density fat-fraction (PDFF) magnetic resonance imaging (MRI) conducted on liver grafts in ex vivo conditions, this research systematically examines various ROI sampling strategies. The findings of this study furnish essential insights, offering a foundation for optimizing time efficiency while ensuring precise assessment of hepatic steatosis before the crucial process of liver transplantation.

Methods

This was a retrospective analysis of a prospective study and included 35 liver grafts with histopathological steatosis that underwent 3T PDFF MRI in ex vivo. One ROI of 1 cm2 was selected for each hepatic segment, and any combination of ROIs in 1-8 liver segments was used, resulting in 511 combinations. Using intraclass correlation coefficients (ICCs) and Bland-Altman analyses, the PDFFs of all these combinations were compared with the 9-ROI average PDFF. There was a moderate correlation between the average PDFF and the histological findings (R = 0.47, P＜0.01).

Results

The average 9-ROI PDFF of all liver grafts was 4.07 ± 4.35 % (0.870-20.904). All strategies with ≥5 ROIs had intraclass correlation coefficient (ICC) ≥ 0.995 and absolute limits of agreement (|LOA|)≤ 1.5 %. Overall, 54 of 84 (67.5 %) 3-ROI sampling strategy had ICC ≥0.995, and 70 of 84 (70 %) had |LOA|≤ 1.5 %. A total of 111 of 126 (88.1 %) 4-ROI sampling strategy had ICC ≥0.995, and 125 of 126 (99.2 %) had |LOA| ≤ 1.5 %.

Conclusions

The employment of the 5-ROI sampling strategy proves instrumental in both time conservation and precise assessment of hepatic steatosis within liver grafts during the ex vivo phase preceding liver transplantation.

Practical approach to quantitative liver and pancreas MRI in children

Quantitative abdominal magnetic resonance imaging (MRI) offers non-invasive, objective assessment of diseases in the liver, pancreas, and other organs and is increasingly being used in the pediatric population. Certain quantitative MRI techniques, such as liver proton density fat fraction (PDFF), R2* mapping, and MR elastography, are already in wide clinical use. Other techniques, such as liver T1 mapping and pancreas quantitative imaging methods, are emerging and show promise for enhancing diagnostic sensitivity and treatment monitoring. Quantitative imaging techniques have historically required a breath-hold, making them more difficult to implement in the pediatric population. However, technological advances, including free-breathing techniques and compressed sensing imaging, are making these techniques easier to implement. The purpose of this article is to review current liver and pancreas quantitative techniques and to provide a practical guide for implementing these techniques in pediatric practice. Future directions of liver and pancreas quantitative imaging will be briefly discussed.

Computed Tomography and Magnetic Resonance Imaging in Liver Iron Overload: From Precise Quantification to Prognosis Assessment

Liver iron overload is associated with conditions such as hereditary hemochromatosis, thalassemia major, and chronic liver diseases. The liver-related outcomes, patient outcomes, and treatment recommendations of these patients differ depending on the cause and extent of iron overload. Accurate quantification of the liver iron concentration (LIC) is critical for effective patient management. This review focuses on the application of computed tomography (CT) and magnetic resonance imaging (MRI) for the precise quantification and prognostic assessment of liver iron overload. In recent years, the use of dual-energy CT and the emergence of MRI-based sequences (such as UTE, QSM, Dixon, and CSE technologies) have significantly increased the potential for noninvasive liver iron quantification. However, the establishment of internationally standardized imaging parameters, postprocessing procedures, and reporting protocols is urgently needed for better management of patients with liver iron overload.

Prediction of MRI R 2 * $$ {\mathrm{R}}_2^{\ast } $$ relaxometry in the presence of hepatic steatosis by Monte Carlo simulations

To develop Monte Carlo simulations to predict the relationship ofR 2 * $$ {\mathrm{R}}_2^{\ast } $$ with liver fat content at 1.5 T and 3.0 T. For various fat fractions (FFs) from 1% to 25%, four types of virtual liver models were developed by incorporating the size and spatial distribution of fat droplets. Magnetic fields were then generated under different fat susceptibilities at 1.5 T and 3.0 T, and proton movement was simulated for phase accrual and MRI signal synthesis. The synthesized signal was fit to single-peak and multi-peak fat signal models forR 2 * $$ {\mathrm{R}}_2^{\ast } $$ and proton density fat fraction (PDFF) predictions. In addition, the relationships betweenR 2 * $$ {\mathrm{R}}_2^{\ast } $$ and PDFF predictions were compared with in vivo calibrations and Bland-Altman analysis was performed to quantitatively evaluate the effects of these components (type of virtual liver model, fat susceptibility, and fat signal model) onR 2 * $$ {\mathrm{R}}_2^{\ast } $$ predictions. A virtual liver model with realistic morphology of fat droplets was demonstrated, andR 2 * $$ {\mathrm{R}}_2^{\ast } $$ and PDFF values were predicted by Monte Carlo simulations at 1.5 T and 3.0 T.R 2 * $$ {\mathrm{R}}_2^{\ast } $$ predictions were linearly correlated with PDFF, while the slope was unaffected by the type of virtual liver model and increased as fat susceptibility increased. Compared with in vivo calibrations, the multi-peak fat signal model showed superior performance to the single-peak fat signal model, which yielded an underestimation of liver fat. TheR 2 * $$ {\mathrm{R}}_2^{\ast } $$ -PDFF relationships by simulations with fat susceptibility of 0.6 ppm and the multi-peak fat signal model wereR 2 * = 0.490 × PDFF + 28.0 $$ {\mathrm{R}}_2^{\ast }=0.490\times \mathrm{PDFF}+28.0 $$ (R 2 = 0.967 $$ {R}^2=0.967 $$ ,p < 0.01 $$ p<0.01 $$ ) at 1.5 T andR 2 * = 0.928 × PDFF + 39.4 $$ {\mathrm{R}}_2^{\ast }=0.928\times \mathrm{PDFF}+39.4 $$ (R 2 = 0.972 $$ {R}^2=0.972 $$ ,p < 0.01 $$ p<0.01 $$ ) at 3.0 T. Monte Carlo simulations provide a new means forR 2 * $$ {\mathrm{R}}_2^{\ast } $$ -PDFF prediction, which is primarily determined by fat susceptibility, fat signal model, and magnetic field strength. AccurateR 2 * $$ {\mathrm{R}}_2^{\ast } $$ -PDFF calibration has the potential to correct the effect of fat onR 2 * $$ {\mathrm{R}}_2^{\ast } $$ quantification, and may be helpful for accurateR 2 * $$ {\mathrm{R}}_2^{\ast } $$ measurements in liver iron overload. In this study, a Monte Carlo simulation of hepatic steatosis was developed to predict the relationship betweenR 2 * $$ {\mathrm{R}}_2^{\ast } $$ and PDFF. Furthermore, the effects of fat droplet morphology, fat susceptibility, fat signal model, and magnetic field strength were evaluated for theR 2 * $$ {\mathrm{R}}_2^{\ast } $$ -PDFF calibration. Our results suggest that Monte Carlo simulations provide a new means forR 2 * $$ {\mathrm{R}}_2^{\ast } $$ -PDFF prediction and this means can be easily generated for various regimes, such as simulations with higher fields and different echo times, as well as correction of magnetic susceptibility measurements for liver iron quantification.

Advanced MRI techniques in abdominal imaging

Magnetic resonance imaging (MRI) is a crucial modality for abdominal imaging evaluation of focal lesions and tissue properties. However, several obstacles, such as prolonged scan times, limitations in patients' breath-hold capacity, and contrast agent-associated artifacts, remain in abdominal MR images. Recent techniques, including parallel imaging, three-dimensional acquisition, compressed sensing, and deep learning, have been developed to reduce the scan time while ensuring acceptable image quality or to achieve higher resolution without extending the scan duration. Quantitative measurements using MRI techniques enable the noninvasive evaluation of specific materials. A comprehensive understanding of these advanced techniques is essential for accurate interpretation of MRI sequences. Herein, we therefore review advanced abdominal MRI techniques.

Childhood maltreatment and risk of metabolic dysfunction-associated steatotic liver disease - Evidence of sex-specific associations in the general population

BACKGROUND AND AIMS

Childhood maltreatment (CM) is linked to self-reported liver disease in adulthood. However, specific diagnostic entities, e.g., metabolic dysfunction-associated steatotic liver disease (MASLD) as the most frequent chronic liver disease, and sex-differences have previously not been considered.

METHODS

Cross-sectional analyses were conducted in 4188 adults from a population-based cohort in Northeastern Germany after excluding individuals with excessive alcohol consumption, cirrhosis, or chronic viral hepatitis. CM-exposure was assessed using the Childhood Trauma Questionnaire (CTQ). Liver-related outcomes included serologic liver enzymes, fibrosis-4 score (FIB-4) and, in 1863 subjects who underwent magnetic resonance imaging examination, liver fat content. Sex-stratified linear regression and logistic regression models predicting liver-related outcomes and risk for MASLD, respectively, from overall CTQ scores were adjusted for age, school education, alcohol consumption, and waist circumference. Exploratory analyses investigated effects of CTQ-subscales on liver-related outcomes and risk for MASLD.

RESULTS

In both sexes, overall CM-exposure was associated with higher levels of serum aspartate aminotransferase and FIB-4 score. In men, effects were mainly driven by physical abuse, and in women by emotional neglect. Only in men, overall CM-exposure (β = 0.70, 95%-CI 0.26-1.13, p = 0.002) and four CTQ-subscales were associated with greater liver fat content, and physical abuse (aOR = 1.22, 95%-CI 1.02-1.46, p = 0.034) and physical neglect (aOR = 1.25, 95%-CI 1.04-1.49, p = 0.015) were associated with higher risk for MASLD.

CONCLUSIONS

These results suggest sex differences in the association between CM and objective serum and imaging markers of MASLD in adulthood. For men especially, a history of CM-exposure may increase risk of developing MASLD in adulthood.

Exploring factors associated with non-alcoholic fatty liver disease using longitudinal MRI

BACKGROUND

To identify factors associated with non-alcoholic fatty liver disease over a 5-year period.

METHODS

Three hundred seven participants, including 165 women, with a mean age of 55.6 ± 12.0 years underwent continuous quantitative MRI of the liver using the proton-density fat fraction (PDFF). The liver's fat fractions were determined at baseline and 5 years later, and the frequency of participants who developed fatty liver disease and potential influencing factors were explored. Based on significant factors, a model was generated to predict the development of fatty liver disease.

RESULTS

After excluding participants with pre-existing fatty liver, the baseline PDFF of 3.1 ± 0.9% (n = 190) significantly increased to 7.67 ± 3.39% within 5 years (p < 0.001). At baseline, age (OR = 1.04, p = 0.006, CI = 1.01-1.07), BMI (OR = 1.11, p = 0.041, CI = 1.01-1.23), and waist circumference (OR = 1.05, p = 0.020, CI = 1.01-1.09) were identified as risk factors. Physical activity was negatively associated (OR = 0.43, p = 0.049, CI = 0.18-0.99). In the prediction model, age, physical activity, diabetes mellitus, diastolic blood pressure, and HDL-cholesterol remained as independent variables. Combining these risk factors to predict the development of fatty liver disease revealed an AUC of 0.7434.

CONCLUSIONS

Within a five-year follow-up, one-quarter of participants developed fatty liver disease influenced by the triggering factors of age, diabetes mellitus, low HDL-cholesterol, and diastolic blood pressure. Increased physical activity has a protective effect on the development of fatty liver.

Associations of Intrapancreatic Fat Deposition With Incident Diseases of the Exocrine and Endocrine Pancreas: A UK Biobank Prospective Cohort Study

INTRODUCTION

To investigate whether increased intrapancreatic fat deposition (IPFD) heightens the risk of diseases of the exocrine and endocrine pancreas.

METHODS

A prospective cohort study was conducted using data from the UK Biobank. IPFD was quantified using MRI and a deep learning-based framework called nnUNet. The prevalence of fatty change of the pancreas (FP) was determined using sex- and age-specific thresholds. Associations between IPFD and pancreatic diseases were assessed with multivariate Cox-proportional hazard model adjusted for age, sex, ethnicity, body mass index, smoking and drinking status, central obesity, hypertension, dyslipidemia, liver fat content, and spleen fat content.

RESULTS

Of the 42,599 participants included in the analysis, the prevalence of FP was 17.86%. Elevated IPFD levels were associated with an increased risk of acute pancreatitis (hazard ratio [HR] per 1 quintile change 1.513, 95% confidence interval [CI] 1.179-1.941), pancreatic cancer (HR per 1 quintile change 1.365, 95% CI 1.058-1.762) and diabetes mellitus (HR per 1 quintile change 1.221, 95% CI 1.132-1.318). FP was also associated with a higher risk of acute pancreatitis (HR 3.982, 95% CI 2.192-7.234), pancreatic cancer (HR 1.976, 95% CI 1.054-3.704), and diabetes mellitus (HR 1.337, 95% CI 1.122-1.593, P = 0.001).

DISCUSSION

FP is a common pancreatic disorder. Fat in the pancreas is an independent risk factor for diseases of both the exocrine pancreas and endocrine pancreas.

An Empirical Approach to Derive Water T1 from Multiparametric MR Images Using an Automated Pipeline and Comparison With Liver Stiffness

BACKGROUND

Water T1 of the liver has been shown to be promising in discriminating the progressive forms of fatty liver diseases, inflammation, and fibrosis, yet proper correction for iron and lipid is required.

PURPOSE

To examine the feasibility of an empirical approach for iron and lipid correction when measuring imaging-based T1 and to validate this approach by spectroscopy on in vivo data.

STUDY TYPE

Retrospective.

POPULATION

Next to mixed lipid-iron phantoms, individuals with different hepatic lipid content were investigated, including people with type 1 diabetes (N = 15, %female = 15.6, age = 43.5 ± 14.0), or type 2 diabetes mellitus (N = 21, %female = 28.9, age = 59.8 ± 9.7) and healthy volunteers (N = 9, %female = 11.1, age = 58.0 ± 8.1).

FIELD STRENGTH/SEQUENCES

3 T, balanced steady-state free precession MOdified Look-Locker Inversion recovery (MOLLI), multi- and dual-echo gradient echo Dixon, gradient echo magnetic resonance elastography (MRE).

ASSESSMENT

T1 values were measured in phantoms to determine the respective correction factors. The correction was tested in vivo and validated by proton magnetic resonance spectroscopy (1 H-MRS). The quantification of liver T1 based on automatic segmentation was compared to the T1 values based on manual segmentation. The association of T1 with MRE-derived liver stiffness was evaluated.

STATISTICAL TESTS

Bland-Altman plots and intraclass correlation coefficients (ICCs) were used for MOLLI vs. 1 H-MRS agreement and to compare liver T1 values from automatic vs. manual segmentation. Pearson's r correlation coefficients for T1 with hepatic lipids and liver stiffness were determined. A P-value of 0.05 was considered statistically significant.

RESULTS

MOLLI T1 values after correction were found in better agreement with the 1 H-MRS-derived water T1 (ICC = 0.60 [0.37; 0.76]) in comparison with the uncorrected T1 values (ICC = 0.18 [-0.09; 0.44]). Automatic quantification yielded similar liver T1 values (ICC = 0.9995 [0.9991; 0.9997]) as with manual segmentation. A significant correlation of T1 with liver stiffness (r = 0.43 [0.11; 0.67]) was found. A marked and significant reduction in the correlation strength of T1 with liver stiffness (r = 0.05 [-0.28; 0.38], P = 0.77) was found after correction for hepatic lipid content.

DATA CONCLUSION

Imaging-based correction factors enable accurate estimation of water T1 in vivo.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 1.

Non-invasive hepatic fat quantification: Can multi-echo Dixon help?

Objective

To evaluate the diagnostic accuracy of multi-echo Dixon magnetic resonance imaging (MRI) in hepatic fat quantification, in comparison with that of magnetic resonance spectroscopy (MRS), on 3.0-T MRI.

Materials and Methods

Fifty-five adults with no known liver disease underwent MRI in a 3.0-T scanner for determination of the hepatic fat fraction, with two techniques: multi-echo Dixon, in a manually drawn region of interest (ROI) and in the entire liver parenchyma (automated segmentation); and MRS. The diagnostic accuracy and cutoff value for multi-echo Dixon were determined, with MRS being used as the reference standard.

Results

The mean fat fraction obtained by multi-echo Dixon in the manually drawn ROI and in the entire liver was 5.2 ± 5.8% and 6.6 ± 5.2%, respectively, whereas the mean hepatic fat fraction obtained by MRS was 5.7 ± 6.4%. A very strong positive correlation and good agreement were observed between MRS and multi-echo Dixon, for the ROI (r = 0.988, r2 = 0.978, p < 0.001) and for the entire liver parenchyma (r = 0.960, r2 = 0.922, p < 0.001). A moderate positive correlation was observed between the hepatic fat fraction and body mass index of the participants, regardless of the fat estimation technique employed.

Conclusion

For hepatic fat quantification, multi-echo Dixon MRI demonstrated a very strong positive correlation and good agreement with MRS (often considered the gold-standard noninvasive technique). Because multi-echo Dixon MRI is more readily available than is MRS, it can be used as a rapid tool for hepatic fat quantification, especially when the hepatic fat distribution is not homogeneous.

SPARCQ: A new approach for fat fraction mapping using asymmetries in the phase-cycled balanced SSFP signal profile

PURPOSE

To develop SPARCQ (Signal Profile Asymmetries for Rapid Compartment Quantification), a novel approach to quantify fat fraction (FF) using asymmetries in the phase-cycled balanced SSFP (bSSFP) profile.

METHODS

SPARCQ uses phase-cycling to obtain bSSFP frequency profiles, which display asymmetries in the presence of fat and water at certain TRs. For each voxel, the measured signal profile is decomposed into a weighted sum of simulated profiles via multi-compartment dictionary matching. Each dictionary entry represents a single-compartment bSSFP profile with a specific off-resonance frequency and relaxation time ratio. Using the results of dictionary matching, the fractions of the different off-resonance components are extracted for each voxel, generating quantitative maps of water and FF and banding-artifact-free images for the entire image volume. SPARCQ was validated using simulations, experiments in a water-fat phantom and in knees of healthy volunteers. Experimental results were compared with reference proton density FFs obtained with 1 H-MRS (phantoms) and with multiecho gradient-echo MRI (phantoms and volunteers). SPARCQ repeatability was evaluated in six scan-rescan experiments.

RESULTS

Simulations showed that FF quantification is accurate and robust for SNRs greater than 20. Phantom experiments demonstrated good agreement between SPARCQ and gold standard FFs. In volunteers, banding-artifact-free quantitative maps and water-fat-separated images obtained with SPARCQ and ME-GRE demonstrated the expected contrast between fatty and non-fatty tissues. The coefficient of repeatability of SPARCQ FF was 0.0512.

CONCLUSION

SPARCQ demonstrates potential for fat quantification using asymmetries in bSSFP profiles and may be a promising alternative to conventional FF quantification techniques.

ACR Appropriateness Criteria® Abnormal Liver Function Tests

Liver function tests are commonly obtained in symptomatic and asymptomatic patients. Various overlapping lab patterns can be seen due to derangement of hepatocytes and bile ducts function. Imaging tests are pursued to identify underlying etiology and guide management based on the lab results. Liver function tests may reveal mild, moderate, or severe hepatocellular predominance and can be seen in alcoholic and nonalcoholic liver disease, acute hepatitis, and acute liver injury due to other causes. Cholestatic pattern with elevated alkaline phosphatase with or without elevated γ-glutamyl transpeptidase can be seen with various causes of obstructive biliopathy. Acute or subacute cholestasis with conjugated or unconjugated hyperbilirubinemia can be seen due to prehepatic, intrahepatic, or posthepatic causes. We discuss the initial and complementary imaging modalities to be used in clinical scenarios presenting with abnormal liver function tests. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

1.5-T MR relaxometry in quantifying splenic and pancreatic iron: retrospective comparison of a commercial 3D-Dixon sequence and an established 2D multi-gradient echo sequence

OBJECTIVES

To compare the quantitative measurement of splenic and pancreatic iron content using a commercial 3D-Dixon sequence (qDixon) versus an established fat-saturated R2* relaxometry method (ME-GRE).

METHODS

We analyzed splenic and pancreatic iron levels in 143 MR examinations (1.5 T) using the qDixon and a ME-GRE sequence (108 patients: 65 males, 43 females, mean age 61.31 years). Splenic and pancreatic R2* values were compared between both methods using Bland-Altman plots, concordance correlation coefficients (CCC), and linear regression analyses. Iron overload (R2* > 50 1/s) was defined for both organs and compared using contingency tables, overall agreement, and Gwet's AC1 coefficient.

RESULTS

Of all analyzable examinations, the median splenic R2* using the qDixon sequence was 25.75 1/s (range: 5.6-433) and for the ME-GRE sequence 35.35 1/s (range: 10.9-400.8) respectively. Concerning the pancreas, a median R2* of 29.93 1/s (range: 14-111.45) for the qDixon and 31.25 1/s (range: 14-97) for the ME-GRE sequence was found. Bland-Altman analysis showed a mean R2* difference of 2.12 1/s with a CCC of 0.934 for the spleen and of 0.29 1/s with a CCC of 0.714 for the pancreas. Linear regression for the spleen/pancreas resulted in a correlation coefficient of 0.94 (p < 0.001)/0.725 (p < 0.001). Concerning iron overload, the proportion of overall agreement between the two methods was 91.43% for the spleen and 93.18% for the pancreas.

CONCLUSIONS

Our data show good concordance between R2* values obtained with a commercial qDixon sequence and a validated ME-GRE relaxometry method. The 3D-qDixon sequence, originally intended for liver assessment, seems to be a reliable tool for non-invasive evaluation of iron content also in the spleen and the pancreas.

KEY POINTS

• A 3D chemical shift imaging sequence and 2D multi-gradient echo sequence show good conformity quantifying splenic and pancreatic R2* values. • The 3D chemical shift imaging sequence allows a reliable analysis also of splenic and pancreatic iron status. • In addition to the liver, the analysis of the spleen and pancreas is often helpful for further differential diagnostic clarification and patient guidance regarding the iron status.

Changes in pancreatic exocrine function, fat and fibrosis in diabetes mellitus: analysis using MR imaging

OBJECTIVE

To evaluate the relationships between hemoglobin A1c (HbA1c) levels with exocrine pancreatic function using cine-dynamic magnetic resonance cholangiopancreatography (MRCP) and the pancreatic parenchyma using fat-suppressed T1 mapping and the proton density fat fraction (PDFF).

METHODS

Patients who underwent 3T-MRI and HbA1c measurement were retrospectively recruited. MRI included cine-dynamic MRCP with a spatially selective inversion-recovery (SS-IR) pulse, fat-suppressed Look-Locker T1 mapping and multiecho 3D Dixon-based PDFF mapping. The pancreatic exocrine secretion grade on cine-dynamic MRCP, T1 values, and PDFF were analyzed in non-diabetic (n = 32), pre-diabetic (n = 44) and diabetic (n = 23) groups defined using HbA1c.

RESULTS

PDFF was weakly correlation with HbA1c (ρ = 0.30, p = 0.002). No correlations were detected between HbA1c and secretion grade (ρ = - 0.16, p = 0.118) or pancreatic parenchymal T1 (ρ = 0.13, p = 0.19). The secretion grade was comparable between the three groups. The T1 value was higher in diabetic (T1 = 1006.2+/- 224.8 ms) than in non-diabetic (T1 = 896.2+/- 86.3 ms, p = 0.010) and pre-diabetic (T1 = 870.1+/- 91.7 ms, p < 0.010) patients. The PDFF was higher in diabetic (FF = 11.8+/- 8.7 %) than in non-diabetic (FF = 6.8+/- 4.2 %, p = 0.014) patients.

CONCLUSION

Pancreatic exocrine function, T1, and FF showed no correlation with HbA1c. Pancreatic T1 and fat fraction is increased in patients with Type 2 diabetes mellitus.

ADVANCES IN KNOWLEDGE

This study demonstrates unaffected exocrine function in pre-diabetes and diabetes and confirms that pancreatic parenchymal T1 and FF are increased in patients with diabetes.

Quantification of Liver Iron Overload with MRI: Review and Guidelines from the ESGAR and SAR

Accumulation of excess iron in the body, or systemic iron overload, results from a variety of causes. The concentration of iron in the liver is linearly related to the total body iron stores and, for this reason, quantification of liver iron concentration (LIC) is widely regarded as the best surrogate to assess total body iron. Historically assessed using biopsy, there is a clear need for noninvasive quantitative imaging biomarkers of LIC. MRI is highly sensitive to the presence of tissue iron and has been increasingly adopted as a noninvasive alternative to biopsy for detection, severity grading, and treatment monitoring in patients with known or suspected iron overload. Multiple MRI strategies have been developed in the past 2 decades, based on both gradient-echo and spin-echo imaging, including signal intensity ratio and relaxometry strategies. However, there is a general lack of consensus regarding the appropriate use of these methods. The overall goal of this article is to summarize the current state of the art in the clinical use of MRI to quantify liver iron content and to assess the overall level of evidence of these various methods. Based on this summary, expert consensus panel recommendations on best practices for MRI-based quantification of liver iron are provided.

The relationship between homoarginine and liver biomarkers: a combination of epidemiological and clinical studies

Homoarginine (hArg) is a non-essential cationic amino acid which inhibits hepatic alkaline phosphatases to exert inhibitory effects on bile secretion by targeting intrahepatic biliary epithelium. We analyzed (1) the relationship between hArg and liver biomarkers in two large population-based studies and (2) the impact of hArg supplementation on liver biomarkers. We assessed the relationship between alanine transaminase (ALT), aspartate aminotransferase (AST), γ-glutamyltransferase (GGT), alkaline phosphatases (AP), albumin, total bilirubin, cholinesterase, Quick's value, liver fat, and Model for End-stage Liver Disease (MELD) and hArg in appropriately adjusted linear regression models. We analyzed the effect of L-hArg supplemention (125 mg L-hArg daily for 4 weeks) on these liver biomarkers. We included 7638 individuals (men: 3705; premenopausal women: 1866, postmenopausal women: 2067). We found positive associations for hArg and ALT (β 0.38 µkatal/L 95% confidence interval (CI): 0.29; 0.48), AST (β 0.29 µkatal/L 95% CI 0.17; 0.41), GGT (β 0.033 µkatal/L 95% CI 0.014; 0.053), Fib-4 score (β 0.08 95% CI 0.03; 0.13), liver fat content (β 0.016% 95% CI 0.006; 0.026), albumin (β 0.030 g/L 95% CI 0.019; 0.040), and cholinesterase (β 0.003 µkatal/L 95% CI 0.002; 0.004) in males. In premenopausal women hArg was positively related with liver fat content (β 0.047% 95%CI 0.013; 0.080) and inversely with albumin (β - 0.057 g/L 95% CI - 0.073; - 0.041). In postmenopausal women hARG was positively associated with AST (β 0.26 µkatal/L 95% CI 0.11; 0.42). hArg supplementation did not affect liver biomarkers. We summarize that hArg may be a marker of liver dysfunction and should be explored further.

Perirenal fat thickness and liver fat fraction are independent predictors of MetS in adults with overweight and obesity suspected with NAFLD: a retrospective study

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) has a multidirectional relationship with metabolic syndrome (MetS) and used to be considered a hepatic manifestation of MetS. Perirenal fat, as a part of visceral adipose tissue (VAT), was reported to be correlated with MetS components, but data for intraorgan fat are lacking. This study was undertaken to assess the value of peripheral and intraorgan fat to predict MetS in adults with overweight and obesity with suspected NAFLD.

METHODS

We studied 134 sequential adults (mean age, 31.5 years; 47% female) with overweight and obesity with suspected NAFLD. All participants underwent abdominal magnetic resonance imaging (MRI) examination. Anthropometric and metabolic parameters and perirenal fat thickness (PRFT), subcutaneous adipose tissue thickness (SATT), liver fat fraction (LFF), pancreas fat fraction (PFF), and lumbar spine fat fraction (LSFF) were collected. MetS was defined according to the International Diabetes Federation (IDF) criteria. Statistical analyses included basic statistics, linear correlation and logistic regression analysis.

RESULTS

A total of 63 adults with MetS and 71 adults with advanced liver steatosis (grades 2 and 3) were included in our study. Patients with MetS had greater PRFT (p = 0.026) and LFF (p < 0.001), as well as greater homeostasis model assessment of insulin resistance (HOMA-IR), alanine transaminase (ALT), aspartate transaminase (AST), and decreased SATT. MetS patients had a higher proportion of advanced steatosis than those without MetS (P < 0.001). The MetS score was associated with PRFT and LFF. Logistic regression analysis showed that the PRFT and LFF were independent predictors of MetS after adjusting for age and sex. A cutoff of 9.15 mm for PRFT and 14.68% for LFF could be predictive of MetS.

CONCLUSIONS

This study shows that the absolute cutoff level of 9.15 mm for PRFT and 14.68% for LFF may be clinically important markers for identifying patients who are at high risk of MetS among adults with overweight and obesity with suspected NAFLD, irrespective of sex and age. Moreover, ectopic fat levels in pancreas and lumbar spine are positively associated with PRFT.

TRIAL REGISTRATION

Not applicable.

Relation of Liver Siderosis to Liver Fibrosis in Hemodialysis Patients With Severe Hyperferritinemia Secondary to High Doses of Intravenous Iron Supplementation

OBJECTIVE

Aggressive iron substitution in hemodialysis (HD) patients leads to iron overload. The association between liver siderosis and fibrosis is still debatable. We studied the association of liver siderosis with liver fibrosis in HD patients. Furthermore, we studied the performance of liver stiffness measurements (LSMs) in identifying advanced liver fibrosis. We investigated the performance of biochemical indicators of iron status in identifying advanced liver fibrosis.

METHODS

Fifty-five HD patients (average HD duration 6 ± 2 years) with hyperferritinemia secondary to intravenous iron supplementation (weakly iron dose 252.7 ± 63 mg; median blood transfusions 3 [2-5]) were recruited. The liver fibrosis grade was determined with Fibroscan, aminotransferase-to-platelet ratio index (APRI), and Fib-4 index. Liver iron concentration (LIC) was estimated with magnetic resonance imaging (MRI). Iron parameters and liver function biochemical indicators were also assessed.

RESULTS

The median serum ferritin and transferrin saturation (TSAT) were 3531 μg/L and 77%, respectively. 34.5%, 20%, and 45.5% of the patients showed mild, moderate, or severe liver siderosis, respectively. All patients with severe liver siderosis showed advanced liver fibrosis. Patients with severe liver siderosis and advanced liver stiffness showed higher serum iron, TSAT, aspartate aminotransferase (AST), alanine aminotransferase (ALT), serum bilirubin, APRI, and Fib-4 index scores than those with mild liver siderosis. Serum iron and TSAT showed good utility in identifying advanced liver fibrosis determined with Fibroscan, APRI, and Fib-4 index. Liver stiffness exhibited good utility in identifying advanced liver fibrosis diagnosed with APRI and Fib-4 index.

CONCLUSIONS

High weekly intravenous iron dose associated with severe hyperferritinemia, high serum iron, and TSAT might lead to severe liver siderosis and concomitant liver fibrosis in HD patients. Serum iron, TSAT, Fibroscan, Fib-4, and APRI scores might offer noninvasive tools for identifying advanced liver fibrosis in those patients.

Multicenter Reproducibility of Liver Iron Quantification with 1.5-T and 3.0-T MRI

Background MRI is a standard of care tool to measure liver iron concentration (LIC). Compared with regulatory-approved R2 MRI, R2* MRI has superior speed and is available in most MRI scanners; however, the cross-vendor reproducibility of R2*-based LIC estimation remains unknown. Purpose To evaluate the reproducibility of LIC via single-breath-hold R2* MRI at both 1.5 T and 3.0 T with use of a multicenter, multivendor study. Materials and Methods Four academic medical centers using MRI scanners from three different vendors (three 1.5-T scanners, one 2.89-T scanner, and two 3.0-T scanners) participated in this prospective cross-sectional study. Participants with known or suspected liver iron overload were recruited to undergo multiecho gradient-echo MRI for R2* mapping at 1.5 T and 3.0 T (2.89 T or 3.0 T) on the same day. R2* maps were reconstructed from the multiecho images and analyzed at a single center. Reference LIC measurements were obtained with a commercial R2 MRI method performed using standardized 1.5-T spin-echo imaging. R2*-versus-LIC calibrations were generated across centers and field strengths using linear regression and compared using F tests. Receiver operating characteristic (ROC) curve analysis was used to determine the diagnostic performance of R2* MRI in the detection of clinically relevant LIC thresholds. Results A total of 207 participants (mean age, 38 years ± 20 [SD]; 117 male participants) were evaluated between March 2015 and September 2019. A linear relationship was confirmed between R2* and LIC. All calibrations within the same field strength were highly reproducible, showing no evidence of statistically significant center-specific differences (P > .43 across all comparisons). Calibrations for 1.5 T and 3.0 T were generated, as follows: for 1.5 T, LIC (in milligrams per gram [dry weight]) = -0.16 + 2.603 × 10-2 R2* (in seconds-1); for 2.89 T, LIC (in milligrams per gram) = -0.03 + 1.400 × 10-2 R2* (in seconds-1); for 3.0 T, LIC (in milligrams per gram) = -0.03 + 1.349 × 10-2 R2* (in seconds-1). Liver R2* had high diagnostic performance in the detection of clinically relevant LIC thresholds (area under the ROC curve, >0.98). Conclusion R2* MRI enabled accurate and reproducible quantification of liver iron overload over clinically relevant ranges of liver iron concentration (LIC). The data generated in this study provide the necessary calibrations for broad clinical dissemination of R2*-based LIC quantification. ClinicalTrials.gov registration no.: NCT02025543 © RSNA, 2022 Online supplemental material is available for this article.

Quantitative study of 3T MRI qDixon-WIP applied in pancreatic fat infiltration in patients with type 2 diabetes mellitus

OBJECTIVE

To investigate the application value of 3T MRI qDixon-WIP technique in the quantitative measurement of pancreatic fat content in patients with type 2 diabetes mellitus (T2DM).

METHODS

The 3T MRI qDixon-WIP sequence was used to scan the livers and the pancreas of 47 T2DM patients (experimental group) and 48 healthy volunteers (control group). Pancreatic fat fraction (PFF), hepatic fat fraction (HFF), Body mass index (BMI) ratio of pancreatic volume to body surface area (PVI) were measured. Total cholesterol (TC), subcutaneous fat area (SA), triglyceride (TG), abdominal visceral fat area (VA), high density lipoprotein (HDL-c), fasting blood glucose (FPC) and low-density lipoprotein (LDL-c) were collected. The relationship between the experimental group and the control group and between PFF and other indicators was compared. The differences of PFF between the control group and different disease course subgroups were also explored.

RESULTS

There was no significant difference in BMI between the experimental group and the control group (P=0.231). PVI, SA, VA, PFF and HFF had statistical differences (P<0.05). In the experimental group, PFF was highly positively correlated with HFF (r=0.964, P<0.001), it was moderately positively correlated with TG and abdominal fat area (r=0.676, 0.591, P<0.001), and it was weakly positively correlated with subcutaneous fat area (r=0.321, P=0.033). And it had no correlation with FPC, PVI, HDL-c, TC and LDL-c (P>0.05). There were statistical differences in PFF between the control group and the patients with different course of T2DM (P<0.05). There was no significant difference in PFF between T2DM patients with a disease course ≤1 year and those with a disease course <5 years (P>0.05). There were significant differences in PFF between the groups with a disease course of 1-5 years and those with a disease course of more than 5 years (P<0.001).

CONCLUSION

PVI of T2DM patients is lower than normal, but SA, VA, PFF, HFF are higher than normal. The degree of pancreatic fat accumulation in T2DM patients with long disease course was higher than that in patients with short disease course. The qDixon-WIP sequence can provide an important reference for clinical quantitative evaluation of fat content in T2DM patients.

Cutoff Values for Diagnosing Hepatic Steatosis Using Contemporary MRI-Proton Density Fat Fraction Measuring Methods

OBJECTIVE

To propose standardized MRI-proton density fat fraction (PDFF) cutoff values for diagnosing hepatic steatosis, evaluated using contemporary PDFF measuring methods in a large population of healthy adults, using histologic fat fraction (HFF) as the reference standard.

MATERIALS AND METHODS

A retrospective search of electronic medical records between 2015 and 2018 identified 1063 adult donor candidates for liver transplantation who had undergone liver MRI and liver biopsy within a 7-day interval. Patients with a history of liver disease or significant alcohol consumption were excluded. Chemical shift imaging-based MRI (CS-MRI) PDFF and high-speed T2-corrected multi-echo MR spectroscopy (HISTO-MRS) PDFF data were obtained. By temporal splitting, the total population was divided into development and validation sets. Receiver operating characteristic (ROC) analysis was performed to evaluate the diagnostic performance of the MRI-PDFF method. Two cutoff values with sensitivity > 90% and specificity > 90% were selected to rule-out and rule-in, respectively, hepatic steatosis with reference to HFF ≥ 5% in the development set. The diagnostic performance was assessed using the validation set.

RESULTS

Of 921 final participants (624 male; mean age ± standard deviation, 31.5 ± 9.0 years), the development and validation sets comprised 497 and 424 patients, respectively. In the development set, the areas under the ROC curve for diagnosing hepatic steatosis were 0.920 for CS-MRI-PDFF and 0.915 for HISTO-MRS-PDFF. For ruling-out hepatic steatosis, the CS-MRI-PDFF cutoff was 2.3% (sensitivity, 92.4%; specificity, 63.0%) and the HISTO-MRI-PDFF cutoff was 2.6% (sensitivity, 88.8%; specificity, 70.1%). For ruling-in hepatic steatosis, the CS-MRI-PDFF cutoff was 3.5% (sensitivity, 73.5%; specificity, 88.6%) and the HISTO-MRI-PDFF cutoff was 4.0% (sensitivity, 74.7%; specificity, 90.6%).

CONCLUSION

In a large population of healthy adults, our study suggests diagnostic thresholds for ruling-out and ruling-in hepatic steatosis defined as HFF ≥ 5% by contemporary PDFF measurement methods.

US Backscatter for Liver Fat Quantification: An AIUM-RSNA QIBA Pulse-Echo Quantitative Ultrasound Initiative

Nonalcoholic fatty liver disease (NAFLD) is believed to affect one-third of American adults. Noninvasive methods that enable detection and monitoring of NAFLD have the potential for great public health benefits. Because of its low cost, portability, and noninvasiveness, US is an attractive alternative to both biopsy and MRI in the assessment of liver steatosis. NAFLD is qualitatively associated with enhanced B-mode US echogenicity, but visual measures of B-mode echogenicity are negatively affected by interobserver variability. Alternatively, quantitative backscatter parameters, including the hepatorenal index and backscatter coefficient, are being investigated with the goal of improving US-based characterization of NAFLD. The American Institute of Ultrasound in Medicine and Radiological Society of North America Quantitative Imaging Biomarkers Alliance are working to standardize US acquisition protocols and data analysis methods to improve the diagnostic performance of the backscatter coefficient in liver fat assessment. This review article explains the science and clinical evidence underlying backscatter for liver fat assessment. Recommendations for data collection are discussed, with the aim of minimizing potential confounding effects associated with technical and biologic variables.

European guideline on obesity care in patients with gastrointestinal and liver diseases - Joint ESPEN/UEG guideline

BACKGROUND

Patients with chronic gastrointestinal (GI) disease such as inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), celiac disease, gastroesophageal reflux disease (GERD), pancreatitis, and chronic liver disease (CLD) often suffer from obesity because of coincidence (IBD, IBS, celiac disease) or related pathophysiology (GERD, pancreatitis and CLD). It is unclear if such patients need a particular diagnostic and treatment that differs from the needs of lean GI patients. The present guideline addresses this question according to current knowledge and evidence.

OBJECTIVE

The objective of the guideline is to give advice to all professionals working in the field of gastroenterology care including physicians, surgeons, dietitians and others how to handle patients with GI disease and obesity.

METHODS

The present guideline was developed according to the standard operating procedure for ESPEN guidelines, following the Scottish Intercollegiate Guidelines Network (SIGN) grading system (A, B, 0, and good practice point (GPP)). The procedure included an online voting (Delphi) and a final consensus conference.

RESULTS

In 100 recommendations (3x A, 33x B, 24x 0, 40x GPP, all with a consensus grade of 90% or more) care of GI patients with obesity - including sarcopenic obesity - is addressed in a multidisciplinary way. A particular emphasis is on CLD, especially fatty liver disease, since such diseases are closely related to obesity, whereas liver cirrhosis is rather associated with sarcopenic obesity. A special chapter is dedicated to obesity care in patients undergoing bariatric surgery. The guideline focuses on adults, not on children, for whom data are scarce. Whether some of the recommendations apply to children must be left to the judgment of the experienced pediatrician.

CONCLUSION

The present guideline offers for the first time evidence-based advice how to care for patients with chronic GI diseases and concomitant obesity, an increasingly frequent constellation in clinical practice.

Measurement and Modeling of the Optical Properties of Adipose Tissue in the Terahertz Range: Aspects of Disease Diagnosis

In this paper, the measurement and modeling of optical properties in the terahertz (THz) range of adipose tissue and its components with temperature changes were performed. Spectral measurements were made in the frequency range 0.25-1 THz. The structural models of main triglycerides of fatty acids are constructed using the B3LYP/6-31G(d) method and the Gaussian03, Revision B.03 program. The optical density (OD) of adipose tissue samples decreases as temperature increases, which can be associated mostly with the dehydration of the sample. Some inclusion of THz wave scattering suppression into the OD decrease can also be expected due to refractive index matching provided by free fatty acids released from adipocytes at thermally induced cell lipolysis. It was shown that the difference between the THz absorption spectra of water and fat makes it possible to estimate the water content in adipose tissue. The proposed model was verified on the basis of molecular modeling and a comparison with experimental data for terahertz spectra of adipose tissue during its heating. Knowing the exact percentage of free and bound water in adipose tissue can help diagnose and monitor diseases, such as diabetes, obesity, and cancer.

European guideline on obesity care in patients with gastrointestinal and liver diseases - Joint European Society for Clinical Nutrition and Metabolism / United European Gastroenterology guideline

BACKGROUND

Patients with chronic gastrointestinal (GI) disease such as inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), celiac disease, gastroesophageal reflux disease (GERD), pancreatitis, and chronic liver disease (CLD) often suffer from obesity because of coincidence (IBD, IBS, celiac disease) or related pathophysiology (GERD, pancreatitis and CLD). It is unclear if such patients need a particular diagnostic and treatment that differs from the needs of lean GI patients. The present guideline addresses this question according to current knowledge and evidence.

OBJECTIVE

The objective of the guideline is to give advice to all professionals working in the field of gastroenterology care including physicians, surgeons, dietitians and others how to handle patients with GI disease and obesity.

METHODS

The present guideline was developed according to the standard operating procedure for European Society for Clinical Nutrition and Metabolism guidelines, following the Scottish Intercollegiate Guidelines Network grading system (A, B, 0, and good practice point [GPP]). The procedure included an online voting (Delphi) and a final consensus conference.

RESULTS

In 100 recommendations (3x A, 33x B, 24x 0, 40x GPP, all with a consensus grade of 90% or more) care of GI patients with obesity - including sarcopenic obesity - is addressed in a multidisciplinary way. A particular emphasis is on CLD, especially fatty liver disease, since such diseases are closely related to obesity, whereas liver cirrhosis is rather associated with sarcopenic obesity. A special chapter is dedicated to obesity care in patients undergoing bariatric surgery. The guideline focuses on adults, not on children, for whom data are scarce. Whether some of the recommendations apply to children must be left to the judgment of the experienced pediatrician.

CONCLUSION

The present guideline offers for the first time evidence-based advice how to care for patients with chronic GI diseases and concomitant obesity, an increasingly frequent constellation in clinical practice.

Non-invasive methods for iron overload evaluation in dysmetabolic patients

INTRODUCTION

Although hyperferritinemia may reflect the inflammatory status of patients with non-alcoholic fatty liver disease (NAFLD), approximately 33% of hyperferritinemia cases reflect real hepatic iron overload.

AIM

To evaluate a non-invasive method for assessing mild iron overload in patients with NAFLD using 3T magnetic resonance imaging (MRI) relaxometry, serum hepcidin, and the expression of ferritin subunits.

METHODS

This cross-sectional study assessed patients with biopsy-proven NAFLD. MRI relaxometry was performed using a 3T scanner in all patients, and the results were compared with iron content determined by liver biopsy. Ferritin, hepcidin, and ferritin subunits were assessed and classified according to ferritin levels and to siderosis identified by liver biopsy.

RESULTS

A total of 67 patients with NAFLD were included in the study. MRI revealed mild iron overload in all patients (sensitivity, 73.5%; specificity, 70%). For mild (grade 1) siderosis, the transverse relaxation rate (R2*) threshold was 58.9 s-1 and the mean value was 72.5 s-1 (SD, 33.9), while for grades 2/3 it was 88.2 s-1 (SD, 31.9) (p < 0.001). The hepcidin threshold for siderosis was > 30.2 ng/mL (sensitivity, 87%; specificity, 82%). Ferritin H and ferritin L subunits were expressed similarly in patients with NAFLD, regardless of siderosis. There were no significant differences in laboratory test results between the groups, including glucose parameters and liver function tests.

CONCLUSIONS

MRI relaxometry and serum hepcidin accurately assessed mild iron overload in patients with dysmetabolic iron overload syndrome.

Association between hepatic iron overload assessed by magnetic resonance imaging and glucose intolerance states in the general population

BACKGROUND AND AIM

While there is evidence that iron overload disorders are associated with type 2 diabetes, the relationship between hepatic iron overload and prediabetes remains unclear. We aimed to investigate the association between hepatic iron overload, as assessed by magnetic resonance imaging (MRI), and different glucose intolerance states in the population-based Study.

METHODS AND RESULTS

We included data from 1622 individuals with MRI data, who did not have known type 2 diabetes (T2DM). Using an oral glucose tolerance testing, participants were classified as having isolated impaired fasting glucose (i-IFG), isolated impaired glucose tolerance (i-IGT), combined IFG and IGT (IFG + IGT) or previously unknown T2DM. Hepatic iron and fat contents were assessed through quantitative MRI. We undertook linear and multinomial logistic regression models adjusted for potential confounders and MRI-assessed hepatic fat content to examine the association of hepatic iron overload with different glucose intolerance states or continuous markers of glucose metabolism. MRI-assessed hepatic iron overload was positively associated only with both 2-h plasma glucose (β = 0.32; 95%CI 0.04-0.60) and the combined IFG + IGT category (relative risk ratio = 1.87; 95%CI 1.15-3.06). No significant associations were found between hepatic iron overload and other glucose intolerance states or biomarkers of glucose metabolism, independently of potential confounders.

CONCLUSIONS

MRI-assessed hepatic iron overload was associated with higher 2-h glucose concentrations and the combined IFG + IGT category, but not with other glucose intolerance states. Our findings suggest a weak adverse impact of hepatic iron overload on glucose metabolism, but further studies are needed to confirm these findings.

Chemotherapy-associated steatohepatitis was concomitant with epicardial adipose tissue volume increasing in breast cancer patients who received neoadjuvant chemotherapy

OBJECTIVES

To investigate the prevalence of chemotherapy-associated steatohepatitis, quantitate the epicardial adipose tissue (EAT) volume in breast cancer patients, and explore the mediating effect of liver fat content on EAT volume in breast cancer patients who received neoadjuvant chemotherapy (NAC).

METHODS

From October 2018 to April 2020, patients were retrospectively reviewed and divided into breast cancer non-NAC and NAC groups. The prevalence of chemotherapy-associated steatohepatitis was evaluated through quantitative MRI mDIXON-Quant examinations by using defined proton density fat fraction cutoffs of liver fat. The EAT volume was quantified on chest CT by semi-automatic volume analysis software. Bootstrap analysis was used in the breast cancer NAC group to test the significance of the mediating effect of liver fat content on EAT volume.

RESULTS

A total of 662 breast cancer patients (non-NAC group: 445 patients; NAC group: 217 patients) were included. The prevalence of chemotherapy-associated steatohepatitis in the NAC group was significantly higher than the prevalence of hepatic steatosis in the non-NAC group (42.8% vs. 33.3%, p < 0.001). EAT volume was measured in 561 of 662 breast cancer patients, and was significantly higher in the NAC group than in the non-NAC group (137.26 ± 53.48 mL vs. 125.14 ± 58.77 mL, p = 0.020). In the breast cancer NAC group, the indirect effect of liver fat content on EAT volume was 2.545 (p < 0.001), and the contribution rate to the effect was 69.1%.

CONCLUSIONS

EAT volume was significantly higher in the BC-NAC group than in the BC-non-NAC group.

KEY POINTS

• The prevalence of CASH was as high as 42.8% in BC patients. • NAC significantly increased the EAT volume in BC patients. • The liver fat content caused the change of EAT volume through mediating effect.

Low cardiopulmonary fitness is associated with higher liver fat content and higher gamma-glutamyltransferase concentrations in the general population - "The Sedentary's Liver"

BACKGROUND

We investigated the association between low cardiorespiratory fitness and liver fat content (LFC) in the general population.

MATERIALS AND METHODS

We evaluated data from 2151 adults (51.1% women) from two population-based cohorts of the Study of Health in Pomerania (SHIP-2 and SHIP-TREND-0). We analysed the cross-sectional associations of peak oxygen uptake (VO_2peak ) with LFC, assessed by magnetic resonance imaging proton density fat fraction, as well as serum gamma-glutamyltransferase (GGT) and aminotransferase concentrations by multivariable regression models.

RESULTS

We observed significant inverse associations of VO_2peak with LFC and serum GGT, but not with serum aminotransferase levels. Specifically, a 1 L/min lower VO_2peak was associated with a 1.09% (95% confidence interval [CI]: 0.45-1.73; P = .002) higher LFC and a 0.18 μkatal/L (95% CI: 0.09-0.26; P < .001) higher GGT levels. The adjusted odds ratio (OR) for the risk of prevalent hepatic steatosis (HS) by a 1 L/min decrease in VO_2peak was 1.61 (95% CI: 1.22-2.13; P = .001). Compared to subjects with high VO_2peak , obese and overweight individuals with low VO_2peak had 1.78% (95% CI: 0.32-3.25; P = .017) and 0.94% (95% CI: 0.15-1.74; P = .021) higher mean LFC, respectively. Compared to those with high VO_2peak , low VO_2peak was independently associated with a higher risk of prevalent HS in the obese (adjusted-OR 2.29, 95% CI=1.48-3.56; P < .001) and overweight (adjusted OR 1.57, 95% CI=1.16-2.14; P = .04) groups.

CONCLUSIONS

Lower VO_2peak was significantly associated with greater LFC and higher serum GGT levels in a population-based cohort of adult individuals. Our results suggest that low VO_2peak might be a risk factor for HS.

Associations of liver volume and other markers of hepatic steatosis with all-cause mortality in the general population

AIMS

We examined the associations between liver volume and other quantitative and qualitative markers of hepatic steatosis with all-cause mortality in the general population.

METHODS

We included 2769 German middle-aged individuals with a median follow-up of 8.9 years (23,898 person-years). Quantitative markers used were serum liver enzymes and FIB-4 score, while qualitative markers of hepatic steatosis included magnetic resonance imaging (MRI) measurements of liver fat content and total liver volume. Cox proportional hazards models, adjusted for confounding factors, were undertaken to investigate the associations of liver volume and other markers of hepatic steatosis with all-cause mortality.

RESULTS

A larger MRI-assessed liver volume was associated with a nearly three-fold increased risk of all-cause mortality (Hazard Ratio = 3.16; 95% confidence interval 1.88; 5.30), independent of age, sex, body mass index, food frequency score, alcohol consumption and education level. This association was consistent in all subgroups considered (men vs. women; presence or absence of overweight/obesity, metabolic syndrome or diabetes). Higher serum liver enzyme levels and FIB-4 score were also significantly associated with higher all-cause mortality in the total population and in all subgroups. No independent associations were found between other quantitative and qualitative markers of hepatic steatosis and the risk of all-cause mortality.

CONCLUSIONS

We showed for the first time that larger liver volume was associated with a three-fold increase in long-term risk of all-cause mortality. This association remained significant after adjustment for age, sex, alcohol consumption, obesity and other coexisting metabolic disorders.

Association between thyroid function and assessment of hepatic fat and iron contents by magnetic resonance imaging

The associations of thyroid function parameters with non-alcoholic fatty liver disease (NAFLD) and hepatic iron overload are not entirely clear. We have cross-sectionally investigated these associations among 2734 participants of two population-based cross-sectional studies of the Study of Health in Pomerania. Serum levels of thyroid-stimulating hormone (TSH), free tri-iodothyronine (fT3), and free thyroxine (fT4) levels were measured. Liver fat content (by proton-density fat fraction) as well as hepatic iron content (by transverse relaxation rate; R2*) were assessed by quantitative MRI. Thyroid function parameters were associated with hepatic fat and iron contents by median and logistic regression models adjusted for confounding. There were no associations between serum TSH levels and liver fat content, NAFLD, or hepatic iron overload. Serum fT4 levels were inversely associated with liver fat content, NAFLD, hepatic iron contents, and hepatic iron overload. Serum fT3 levels as well as the fT3 to fT4 ratio were positively associated with hepatic fat, NAFLD, hepatic iron contents, but not with hepatic iron overload. Associations between fT3 levels and liver fat content were strongest in obese individuals, in which we also observed an inverse association between TSH levels and NAFLD. These findings might be the result of a higher conversion of fT4 to the biologically active form fT3. Our results suggest that a subclinical hyperthyroid state may be associated with NAFLD, particularly in obese individuals. Furthermore, thyroid hormone levels seem to be more strongly associated with increased liver fat content compared to hepatic iron content.

Simple diameter measurement as predictor of liver volume and liver parenchymal disease

To investigate the accuracy of liver diameters for estimation of liver size and to evaluate their application as tool for assessment of parenchymal liver disease. In the course of a population-based study, (SHIP) one thousand nine hundred thirty-nine volunteers underwent magnetic resonance imaging (MRI) of the liver including 3D gradient echo MRI sequences. Maximum liver diameters were measured in cranio-caudal (CC), anterior–posterior (AP), medial–lateral (ML) orientation. Diameters were compared with true liver volume assessed by liver segmentation. Additionally, age-dependent reference values for diameters were defined. Finally, accuracy of liver diameters was assessed to discriminate volunteers with healthy livers and participants with parenchymal changes, measured by MRI and laboratory. Reference values of liver diameters within the healthy population (n = 886) were defined as follows (mean ± standard deviation, confidence interval CI in cm): CC 17.2 ± 2, CI 13.6/21.2; AP 15.8 ± 1.9, CI 12.6/19.8; ML 19.7 ± 2.3, CI 15.8/24.6. There was a poor correlation using linear regression between liver diameter and true liver volume; CC 0.393, AP 0.359; ML 0.137. The AP direction shows the best correlation to discriminate between healthy and pathologic liver changes; AUC 0.78; p < 0.001, CC AUC 0.53; p < 0.001 and ML AUC 0.52; p = 0.008. Measurement of liver diameter, especially in the anterior–posterior direction is a simple option to detect chronic liver disease but less suitable for prediction of liver volume.

SHIP-MR and Radiology: 12 Years of Whole-Body Magnetic Resonance Imaging in a Single Center

The Study of Health in Pomerania (SHIP), a population-based study from a rural state in northeastern Germany with a relatively poor life expectancy, supplemented its comprehensive examination program in 2008 with whole-body MR imaging at 1.5 T (SHIP-MR). We reviewed more than 100 publications that used the SHIP-MR data and analyzed which sequences already produced fruitful scientific outputs and which manuscripts have been referenced frequently. Upon reviewing the publications about imaging sequences, those that used T1-weighted structured imaging of the brain and a gradient-echo sequence for R2* mapping obtained the highest scientific output; regarding specific body parts examined, most scientific publications focused on MR sequences involving the brain and the (upper) abdomen. We conclude that population-based MR imaging in cohort studies should define more precise goals when allocating imaging time. In addition, quality control measures might include recording the number and impact of published work, preferably on a bi-annual basis and starting 2 years after initiation of the study. Structured teaching courses may enhance the desired output in areas that appear underrepresented.

Automated Whole-Liver MRI Segmentation to Assess Steatosis and Iron Quantification in Chronic Liver Disease

Background Standardized manual region of interest (ROI) sampling strategies for hepatic MRI steatosis and iron quantification are time consuming, with variable results. Purpose To evaluate the performance of automatic MRI whole-liver segmentation (WLS) for proton density fat fraction (PDFF) and iron estimation (transverse relaxometry [R2*]) versus manual ROI, with liver biopsy as the reference standard. Materials and Methods This prospective, cross-sectional, multicenter study recruited participants with chronic liver disease who underwent liver biopsy and chemical shift-encoded 3.0-T MRI between January 2017 and January 2021. Biopsy evaluation included histologic grading and digital pathology. MRI liver sampling strategies included manual ROI (two observers) and automatic whole-liver (deep learning algorithm) segmentation for PDFF- and R2*-derived measurements. Agreements between segmentation methods were measured using intraclass correlation coefficients (ICCs), and biases were evaluated using Bland-Altman analyses. Linear regression analyses were performed to determine the correlation between measurements and digital pathology. Results A total of 165 participants were included (mean age ± standard deviation, 55 years ± 12; 96 women; 101 of 165 participants [61%] with nonalcoholic fatty liver disease). Agreements between mean measurements were excellent, with ICCs of 0.98 for both PDFF and R2*. The median bias was 0.5% (interquartile range, -0.4% to 1.2%) for PDFF and 2.7 sec^-1 (interquartile range, 0.2-5.3 sec^-1) for R2* (P < .001 for both). Margins of error were lower for WLS than ROI-derived parameters (-0.03% for PDFF and -0.3 sec^-1 for R2*). ROI and WLS showed similar performance for steatosis (ROI AUC, 0.96; WLS AUC, 0.97; P = .53) and iron overload (ROI AUC, 0.85; WLS AUC, 0.83; P = .09). Correlations with digital pathology were high (P < .001) between the fat ratio and PDFF (ROI r = 0.89; WLS r = 0.90) and moderate (P < .001) between the iron ratio and R2* (ROI r = 0.65; WLS r = 0.64). Conclusion Proton density fat fraction and transverse relaxometry measurements derived from MRI automatic whole-liver segmentation (WLS) were accurate for steatosis and iron grading in chronic liver disease and correlated with digital pathology. Automated WLS estimations were higher, with a lower margin of error than manual region of interest estimations. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Moura Cunha and Fowler in this issue.

MRI-derived proton density fat fraction

Reflecting the growing interest in early diagnosis of nonalcoholic fatty liver disease in recent years, the development of noninvasive and reliable fat quantification methods is required. Fat quantification by magnetic resonance imaging (MRI), especially MRI-derived proton density fat fraction (MRI-PDFF) obtained by quantitative chemical shift imaging such as the multi-point Dixon method, is highly correlated with histological evaluation and fat quantification with MR spectroscopy (MRS). In recent years, MRI-PDFF has been increasingly used as a reference standard for image-based fat quantification instead of MRS because it is possible to evaluate the whole liver with a single breath-hold. Furthermore, recent advances in MR imaging have led to the application of multiparametric MRI for the diagnosis of nonalcoholic fatty liver disease with specific liver tissue quantification of fat, iron, and fibrosis. One of the advantages of multiparametric MRI is that whole organ imaging to exclude sampling variability and organ-specific tissue quantification can be done simultaneously. Therefore, multiparametric MRI methods offer an attractive option for noninvasive and comprehensive liver assessment beyond the quantitative assessment of liver steatosis. In this review article, we mainly focus on a technical explanation and clinical interpretation of MRI-PDFF in the quantitative assessment of liver steatosis. Furthermore, we would like to mention future perspectives of MR imaging of the liver in relation to elastography and other specific multiparametric MRI methods such as R2* and T1 mapping.

Free-breathing 3D stack-of-radial MRI quantification of liver fat and R2* in adults with fatty liver disease

PURPOSE

To investigate the agreement, intra-session repeatability, and inter-reader agreement of liver proton-density fat fraction (PDFF) and R₂* quantification using free-breathing 3D stack-of-radial MRI, with and without self-gated motion compensation, compared to reference breath-hold techniques in subjects with fatty liver disease (FLD).

METHODS

In this institutional review board-approved prospective study, thirty-eight adults with FLD and/or iron overload (24 male, 58 ± 12 years) were imaged at 3T using free-breathing stack-of-radial MRI, breath-hold 3D Cartesian MRI, and breath-hold single-voxel MR spectroscopy (SVS). Each sequence was acquired twice in random order. To assess agreement compared to reference breath-hold techniques, the dependency of liver PDFF and/or R₂* quantification on the sequence, radial sampling factor, and radial self-gating temporal resolution was assessed by calculating the Bayesian mean difference (MD_B) of the posteriors. Intra-session repeatability and inter-reader agreement (two independent readers) were assessed by the coefficient of repeatability (CR) and intraclass correlation coefficient (ICC), respectively.

RESULTS

Thirty-five participants (21 male, 57 ± 12 years) were included for analysis. Both free-breathing radial MRI techniques (with and without self-gating) achieved ICC ≥ 0.92 for quantifying PDFF and R₂*, and quantified PDFF with MD_B < 1.2% compared to breath-hold techniques. Free-breathing radial MRI required self-gating to accurately quantify R₂* (MD_B < 10s^-1 with self-gating; MD_B < 50s^-1 without self-gating). The radial sampling factor affected PDFF and R₂* quantification while the radial self-gating temporal resolution only affected R₂* quantification. Repeated self-gated free-breathing radial MRI scans achieved CR < 3% and CR < 27 s^-1 for PDFF and R₂*, respectively.

CONCLUSION

A free-breathing stack-of-radial MRI technique with self-gating demonstrated agreement, repeatability, and inter-reader agreement compared to reference breath-hold techniques for quantification of liver PDFF and R₂* in adults with FLD.

Association between hepatic fat and subclinical vascular disease burden in the general population

OBJECTIVE

It is still controversial if increased hepatic fat independently contributes to cardiovascular risk. We aimed to assess the association between hepatic fat quantified by MRI and various subclinical vascular disease parameters.

DESIGN

We included two cross-sectional investigations embedded in two independent population-based studies (Study of Health in Pomerania (SHIP): n=1341; Cooperative Health Research in the Region of Augsburg (KORA): n=386). The participants underwent a whole-body MRI examination. Hepatic fat content was quantified by proton-density fat fraction (PDFF). Aortic diameters in both studies and carotid plaque-related parameters in KORA were measured with MRI. In SHIP, carotid intima-media thickness (cIMT) and plaque were assessed by ultrasound. We used (ordered) logistic or linear regression to assess associations between hepatic fat and subclinical vascular disease.

RESULTS

The prevalence of fatty liver disease (FLD) (PDFF >5.6%) was 35% in SHIP and 43% in KORA. In SHIP, hepatic fat was positively associated with ascending (β, 95% CI 0.06 (0.04 to 0.08)), descending (0.05 (0.04 to 0.07)) and infrarenal (0.02 (0.01 to 0.03)) aortic diameters, as well as with higher odds of plaque presence (OR, 95% CI 1.22 (1.05 to 1.42)) and greater cIMT (β, 95% CI 0.01 (0.004 to 0.02)) in the age-adjusted and sex-adjusted model. However, further adjustment for additional cardiometabolic risk factors, particularly body mass index, attenuated these associations. In KORA, no significant associations were found.

CONCLUSIONS

The relation between hepatic fat and subclinical vascular disease was not independent of overall adiposity. Given the close relation of FLD with cardiometabolic risk factors, people with FLD should still be prioritised for cardiovascular disease screening.

Hepatic steatosis and hepatic iron overload modify the association of iron markers with glucose metabolism disorders and metabolic syndrome

BACKGROUND

Iron status has been linked with impaired glucose metabolism (IGM), type 2 diabetes mellitus (T2DM) and the metabolic syndrome (MetS), but the role of hepatic steatosis or iron overload on these associations remains uncertain.

METHODS

We analysed data from 2310 participants without known T2DM of the population-based Study of Health in Pomerania (SHIP-TREND, Germany) through logistic regression models. We tested additive and multiplicative interactions between ferritin and hepatic steatosis or iron overload.

RESULTS

Serum ferritin was positively associated with IGM (OR per 100 µg/L: 1.11 [1.01, 1.23]), T2DM (OR per 100 µg/L: 1.20 [1.06, 1.36]) and MetS (OR per 100 µg/L: 1.11 [1.02, 1.20]) in the total population as well as in participants without hepatic iron overload. However, the synergistic effect of higher ferritin concentrations and hepatic iron overload showed stronger associations with IGM and T2DM. Similarly, while ferritin was positively associated with T2DM and MetS even in the absence of hepatic steatosis, the synergistic effect of higher ferritin concentrations and hepatic steatosis showed stronger associations with IGM, T2DM and MetS. Transferrin was associated with isolated impaired glucose tolerance but not with T2DM and MetS.

CONCLUSIONS

Our study suggests that ferritin may be associated with glucose metabolism disorders and MetS even in people without hepatic steatosis or iron overload. However, in individuals with higher ferritin concentrations, the presence of hepatic steatosis may indicate stronger risk for glucose metabolism disorders and MetS, while the presence of hepatic iron overload may indicate stronger risk only for glucose metabolism disorders.

Assessing the difficulty of annotating medical data in crowdworking with help of experiments

BACKGROUND

As healthcare-related data proliferate, there is need to annotate them expertly for the purposes of personalized medicine. Crowdworking is an alternative to expensive expert labour. Annotation corresponds to diagnosis, so comparing unlabeled records to labeled ones seems more appropriate for crowdworkers without medical expertise. We modeled the comparison of a record to two other records as a triplet annotation task, and we conducted an experiment to investigate to what extend sensor-measured stress, task duration, uncertainty of the annotators and agreement among the annotators could predict annotation correctness.

MATERIALS AND METHODS

We conducted an annotation experiment on health data from a population-based study. The triplet annotation task was to decide whether an individual was more similar to a healthy one or to one with a given disorder. We used hepatic steatosis as example disorder, and described the individuals with 10 pre-selected characteristics related to this disorder. We recorded task duration, electro-dermal activity as stress indicator, and uncertainty as stated by the experiment participants (n = 29 non-experts and three experts) for 30 triplets. We built an Artificial Similarity-Based Annotator (ASBA) and compared its correctness and uncertainty to that of the experiment participants.

RESULTS

We found no correlation between correctness and either of stated uncertainty, stress and task duration. Annotator agreement has not been predictive either. Notably, for some tasks, annotators agreed unanimously on an incorrect annotation. When controlling for Triplet ID, we identified significant correlations, indicating that correctness, stress levels and annotation duration depend on the task itself. Average correctness among the experiment participants was slightly lower than achieved by ASBA. Triplet annotation turned to be similarly difficult for experts as for non-experts.

CONCLUSION

Our lab experiment indicates that the task of triplet annotation must be prepared cautiously if delegated to crowdworkers. Neither certainty nor agreement among annotators should be assumed to imply correct annotation, because annotators may misjudge difficult tasks as easy and agree on incorrect annotations. Further research is needed to improve visualizations for complex tasks, to judiciously decide how much information to provide, Out-of-the-lab experiments in crowdworker setting are needed to identify appropriate designs of a human-annotation task, and to assess under what circumstances non-human annotation should be preferred.

Association of hepatic steatosis derived from ultrasound and quantitative MRI with prediabetes in the general population

The aim of our study was to investigate the association of hepatic steatosis derived from quantitative ultrasound and magnetic resonance imaging (MRI) with prediabetes in a large population-based study conducted in Northeast Germany. Hepatic steatosis was assessed through transabdominal ultrasound and quantitative MRI. For analysis we included 1622 subjects with MRI who participated in an oral glucose tolerance test and reported no known type 2 diabetes mellitus (T2DM). We classified participants as proposed by the American Diabetes Association: isolated impaired fasting glucose (i-IFG), isolated impaired glucose tolerance (i-IGT), combined IFG and IGT (IFG + IGT), and undiagnosed T2DM. Regression models were adjusted for age, sex body mass index and alcohol consumption. We observed positive associations of hepatic steatosis with glycated hemoglobin, fasting glucose and insulin, 2-h glucose and insulin, as well as homeostasis model assessment-insulin resistance index. Similarly, individuals having hepatic steatosis as defined by MRI had a higher relative risk ratio (RR) to be in the prediabetes groups i-IFG (RR = 1.6; 95% confidence interval (CI) 1.2; 2.2), i-IGT (RR = 3.3, 95% CI 2.0; 5.6) and IFG + IGT (RR = 2.5, 95% CI 1.6; 3.9) or to have undiagnosed T2DM (RR = 4.8, 95% CI 2.6; 9.0). All associations were attenuated when defining hepatic steatosis by ultrasound. Hepatic steatosis is associated with prediabetes and undiagnosed T2DM in the general population. Quantitative liver MRI revealed stronger associations with prediabetes and undiagnosed T2DM compared to ultrasound, which indicates the higher sensitivity and specificity of MRI to determine hepatic steatosis.

Whole-body R2∗ mapping to quantify tissue iron in iron storage organs: reference values and a genotype

AIM

To define reference values for the transverse relaxation rate (R2∗) in iron storage organs and to investigate the role of human haemochromatosis protein (HFE) genotype on iron storage.

MATERIALS AND METHODS

Whole-body magnetic resonance imaging (MRI) including a five-echo gradient-echo sequence was performed in 483 volunteers (269 men, mean age 59.3 ± 12.2 years) without clinical evidence of an iron storage disease at 1.5 T. R2∗ values were assessed for liver, spleen, pancreas, heart, bones, and brain parenchyma. The HFE genotype was determined regarding the single nucleotide polymorphisms (SNPs) rs74315324, rs1799945, rs41303501, rs1800562, rs1800730. R2∗ values were compared among participants without and with at least one mutation. R2∗ reference values were defined using volunteers without any mutation.

RESULTS

Three hundred and one participants had no mutations in any HFE SNP, 182 had at least one mutation. HFE gene mutations were distributed as (heterozygous/homozygous) rs1799945:132/9, rs1800562:33/1, and rs1800730:11/0. Mean R2∗ values ± SD (per second) in the group without mutation were: liver: 33.4 ± 12.7, spleen: 24.1 ± 13.8, pancreas: 27.2 ± 6.6, heart: 32.7 ± 11.8, bone: 69.3 ± 21.0, brain parenchyma: 13.9 ± 1.2. No significant difference in R2∗ values were found between participants with and without the HFE gene mutation for any examined iron storage organ (p_liver=0.09, p_spleen=0.36, p_pancreas = 0.08, p_heart = 0.36, p_bone = 0.98, p_brain=0.74).

CONCLUSION

Reference values of R2∗ in iron storage organs are feasible to support the diagnosis of iron storage diseases. Non-specific mutations in HFE SNPs appear not to affect the phenotype of tissue iron accumulation.

Long-term outcome of incidental cystic liver tumors in the general population

Aim of this study was to investigate frequency, incidence and risk factors of liver cysts in the general population in a longitudinal survey. Cyst frequency was investigated in 607 adult volunteers (288 women, 319 men, mean age 55 years) using strong T2-weighted magnetic resonance imaging. Risk factors were investigated for occurrence, frequency and size of cystic lesions at baseline. Incidence and physiological growing of the lesions were observed in a 5-years follow-up. At baseline, 431 volunteers had 1,479 cysts (71.0%). The mean number of cysts per person was 3.4 ± 9.0. The mean size of cysts was 13.1 ± 11.7 mm. Women had a higher number of cysts than men (p = 0.026). Older and male volunteers demonstrated a higher cyst frequency (p = 0.002 and p = 0.025). Per one-year increase in age the chance for a liver cyst increased by 2%. Four-hundred seventeen volunteers had cysts in the follow-up, in 24.6% new lesions had occurred. Lesion size significantly increased in follow-up (p < 0.001). Age and male sex were associated with the occurrence of at least one liver cyst. Women had a higher average number of cysts. Cystic lesion progression is a physiological phenomenon in the long-term follow-up.

Morphological characterization of hepatic steatosis and Monte Carlo modeling of MRI signal for accurate quantification of fat fraction and relaxivity

Chemical-shift-based fat-water MRI signal models with single- or dual-R2 * correction have been proposed for quantification of fat fraction (FF) and assessment of hepatic steatosis. However, there is a void in our understanding of which model truly mimics the underlying biophysical mechanism of steatosis on MRI signal relaxation. The purpose of this study is to morphologically characterize and build realistic steatosis models from histology and synthesize MRI signal using Monte Carlo simulations to investigate the accuracy of single- and dual-R2 * models in quantifying FF and R2 *. Fat morphology was characterized by performing automatic segmentation on 16 mouse liver histology images and extracting the radius, nearest neighbor (NN) distance, and regional anisotropy of fat droplets. A gamma distribution function (GDF) was used to generalize extracted features, and regression analysis was performed to derive relationships between FF and GDF parameters. Virtual steatosis models were created based on derived morphological and statistical descriptors, and the MRI signal was synthesized at 1.5 T and 3 T. R2 * and FF values were calculated using single- and dual-R2 * models and compared with in vivo R2 *-FF calibrations and simulated FFs. The steatosis models generated with regional anisotropy and NN distribution closely mimicked the true in vivo fat morphology. For both R2 * models, predicted R2 * values showed positive correlation with FFs, with slopes similar to those of the in vivo calibrations (P > 0.05), and predicted FFs showed excellent agreement with true FFs (R2  > 0.99), with slopes close to unity. Our study, hence, demonstrates the proof of concept for generating steatosis models from histologic data and synthesizing MRI signal to show the expected signal relaxation under conditions of steatosis. Our results suggest that a single R2 * is sufficient to accurately estimate R2 * and FF values for lower FFs, which agrees with in vivo studies. Future work involves characterizing and building steatosis models at higher FFs and testing single- and dual-R2 * models for accurate assessment of steatosis.