Association Between Magnetic Resonance Imaging-Proton Density Fat Fraction and Liver Histology Features in Patients With Nonalcoholic Fatty Liver Disease or Nonalcoholic Steatohepatitis

Severe hepatic steatosis promotes increased liver stiffness in the early stages of metabolic dysfunction-associated steatotic liver disease

BACKGROUND & AIMS

The predictors of progression from steatosis to more advanced stages of metabolic dysfunction-associated steatotic liver disease (MASLD) remain unclear. We evaluated the association between the quantity of hepatic steatosis and longitudinal changes in liver stiffness measurements (LSMs) using magnetic resonance elastography (MRE) in patients with MASLD.

METHODS

We retrospectively analysed patients with MASLD who underwent at least two serial MRE and magnetic resonance imaging-based proton density fat fraction (MRI-PDFF) examinations at least 1 year apart. Fine-Gray competitive proportional hazard regression was used to identify LSM progression and regression factors.

RESULTS

A total of 471 patients were enrolled. Factors linked to LSM progression were steatosis grade 3 (MRI-PDFF ≥17.1%, adjusted hazard ratio [aHR] 2.597; 95% confidence interval [CI] 1.483-4.547) and albumin-bilirubin grade 2 or 3 (aHR 2.790; 95% CI 1.284-6.091), while the only factor linked to LSM regression was % decrease rate of MRI-PDFF ≥5% (aHR 2.781; 95% CI 1.584-4.883). Steatosis grade 3 correlated with a higher incidence rate of LSM progression than steatosis grade 1 (MRI-PDFF <11.3%) in patients with LSM stage 0 (<2.5 kilopascal [kPa]), and a % annual decrease rate of MRI-PDFF ≥5% correlated with a higher incidence rate of LSM regression than that of MRI-PDFF >-5% and <5% in patients with LSM stage 1 or 2-4 (≥2.5 kPa).

CONCLUSIONS

Severe hepatic steatosis was linked to significant LSM progression in patients with MASLD and low LSM (<2.5 kPa).

Multiparametric ultrasound imaging for early-stage steatosis: Comparison with magnetic resonance imaging-based proton density fat fraction

BACKGROUND

The prevalence of liver diseases, especially steatosis, requires a more convenient and noninvasive tool for liver diagnosis, which can be a surrogate for the gold standard biopsy. Magnetic resonance (MR) measurement offers potential, however ultrasound (US) has better accessibility than MR.

PURPOSE

This study aims to suggest a multiparametric US approach which demonstrates better quantification and imaging performance than MR imaging-based proton density fat fraction (MRI-PDFF) for hepatic steatosis assessment.

METHODS

We investigated early-stage steatosis to evaluate our approach. An in vivo (within the living) animal study was performed. Fat inclusions were accumulated in the animal livers by feeding a methionine and choline deficient (MCD) diet for 2 weeks. The animals (n = 19) underwent US and MR imaging, and then their livers were excised for histological staining. From the US, MR, and histology images, fat accumulation levels were measured and compared: multiple US parameters; MRI-PDFF; histology fat percentages. Seven individual US parameters were extracted using B-mode measurement, Burr distribution estimation, attenuation estimation, H-scan analysis, and shear wave elastography. Feature selection was performed, and the selected US features were combined, providing quantification of fat accumulation. The combined parameter was used for visualizing the localized probability of fat accumulation level in the liver; This procedure is known as disease-specific imaging (DSI).

RESULTS

The combined US parameter can sensitively assess fat accumulation levels, which is highly correlated with histology fat percentage (R = 0.93, p-value < 0.05) and outperforms the correlation between MRI-PDFF and histology (R = 0.89, p-value < 0.05). Although the seven individual US parameters showed lower correlation with histology compared to MRI-PDFF, the multiparametric analysis enabled US to outperform MR. Furthermore, this approach allowed DSI to detect and display gradual increases in fat accumulation. From the imaging output, we measured the color-highlighted area representing fatty tissues, and the fat fraction obtained from DSI and histology showed strong agreement (R = 0.93, p-value < 0.05).

CONCLUSIONS

We demonstrated that fat quantification utilizing a combination of multiple US parameters achieved higher performance than MRI-PDFF; therefore, our multiparametric analysis successfully combined selected features for hepatic steatosis characterization. We anticipate clinical use of our proposed multiparametric US analysis, which could be beneficial in assessing steatosis in humans.

Can liquid biopsies for MASH help increase the penetration of metabolic surgery? A narrative review

This narrative review highlights current evidence on non-invasive tests to predict the presence or absence as well as the severity of metabolic dysfunction-associated steatohepatitis (MASH) and liver fibrosis. Metabolic dysfunction-associated steatotic liver disease (MASLD) is a common condition characterized by fat accumulation in the liver that affects 32 % of the world population. The most severe form of MASLD is MASH in which hepatocyte ballooning and inflammation are present together with steatosis; MASH is often associated with liver fibrosis. MASH diagnosis is determined by invasive liver biopsy. Hence, there is a critical need for non-invasive MASH tests. Plasma biomarkers for MASH diagnosis generally have low sensitivity (62-66 %), and specificity (78-82 %). Monocyte levels of Perilipin2 (PLIN2) predict MASH with an accuracy of 92-93 %, and sensitivity and specificity of 90-95 % and 88-100 %, respectively. This liquid biopsy test can facilitate the study of MASH prevalence in general populations and also monitor the effects of lifestyle, surgical, and pharmacological interventions. Without any FDA-approved MASH therapeutic, and with metabolic surgery markedly surpassing the efficacy of lifestyle modification, an accurate and reliable liquid biopsy could help more people choose surgery as a treatment for MASH.

Quantification of Hepatic Steatosis on Dual-Energy CT in Comparison With MRI mDIXON-Quant Sequence in Breast Cancer

OBJECTIVE

The study aimed to evaluate the correlation and diagnostic value of liver fat quantification in unenhanced dual-energy CT (DECT) using quantitative magnetic resonance imaging (MRI) mDIXON-Quant sequence as reference standard in patients with breast cancer.

METHODS

Patients with breast cancer were prospectively recruited between June 2018 and April 2020. Each patient underwent liver DECT and MRI mDIXON-Quant examination. The DECT-fat volume fraction (FVF) and liver-spleen attenuation differences were compared with the MRI-proton density fat fraction using scatterplots, Bland-Altman plots, and concordance correlation coefficient. Receiver operating characteristic curves were established to determine the diagnostic accuracy of hepatic steatosis by DECT.

RESULTS

A total of 216 patients with breast cancer (mean age, 50.08 ± 9.33 years) were evaluated. The DECT-FVF correlated well with MRI-proton density fat fraction ( r2 = 0.902; P < 0.001), which was higher than the difference in liver-spleen attenuation ( r2 = 0.728; P < 0.001). Bland-Altman analysis revealed slight positive bias; the mean difference was 3.986. The DECT-FVF yielded an average concordance correlation coefficient of 0.677, which was higher than the difference of liver-spleen attenuation (-0.544). The DECT-FVF and the difference in liver-spleen attenuation both lead to mild overestimation of hepatic steatosis. The areas under the curve of DECT-FVF (0.956) were higher than the difference in liver-spleen attenuation (0.807) in identifying hepatic steatosis ( P < 0.001).

CONCLUSIONS

Dual-energy CT-FVF may serve as a reliable screening and quantitative tool for hepatic steatosis in patients with breast cancer.

Diagnosis and Monitoring of Nonalcoholic Steatohepatitis: Current State and Future Directions

Nonalcoholic fatty liver disease (NAFLD) is a common liver disease, with a worldwide prevalence of 25%. NAFLD is a spectrum that includes nonalcoholic fatty liver defined histologically by isolated hepatocytes steatosis without inflammation and nonalcoholic steatohepatitis (NASH) is the inflammatory subtype of NAFLD and is associated with disease progression, development of cirrhosis, and increased rates of liver-specific and overall mortality. The differentiation between NAFLD and NASH as well as staging NASH are important yet challenging clinical problems. Liver biopsy is currently the standard for disease diagnosis and fibrosis staging. However, this procedure is invasive, costly, and cannot be used for longitudinal monitoring. Therefore, several noninvasive quantitative imaging biomarkers have been proposed that can estimate the severity of hepatic steatosis and fibrosis. Despite this, noninvasive diagnosis of NASH and accurate risk stratification remain unmet needs. In this work, the most relevant available imaging biomarkers are reviewed and their application in patients with NAFLD are discussed.

Potential applications of PET/MRI in non-oncologic conditions within the abdomen and pelvis

PET/MRI is a relatively new imaging modality with several advantages over PET/CT that promise to improve imaging of the abdomen and pelvis for specific diagnostic tasks by combining the superior soft tissue characterization of MRI with the functional information acquired from PET. PET/MRI has an established role in staging and response assessment of multiple abdominopelvic malignancies, but the modality is not yet established for non-oncologic conditions of the abdomen and pelvis. In this review, potential applications of PET/MRI for non-oncologic conditions of abdomen and pelvis are outlined, and the available literature is reviewed to highlight promising areas for further research and translation into clinical practice.

Accuracy of attenuation coefficient measurement (ACM) for real-time ultrasound hepatic steatometry: Comparison of simulator/phantom data with magnetic resonance imaging proton density fat fraction (MRI-PDFF)

Objectives

To evaluate the accuracy and reproducibility of real time ultrasound (US) steatometry with the Attenuation Coefficient (AC) measurement in comparison with magnetic resonance imaging with proton density software module (MRI-PDFF).

Methods

This study was conducted between January 2021 and October 2021. The comparison of instrumental methods for assessing and grading hepatic steatosis using a multimodal phantom simulator of different fat and water ratios was performed. The study involved 3 radiological centers. The steatophantom was simultaneously investigated using three methods: magnetic resonance imaging with proton density software module (MRI-PDFF) and 128-slice multidetector computed tomography, and then by 2 different US scanner for steatosis assessment via Measurement Attenuation Imaging (ATI) ant Attenuation Coefficient Measurement (ACM).

Results

Modeling of hepatic steatosis using a series of phantom simulators allows evidence-based medicine to determine the diagnostic accuracy of the latest US techniques for steatosis. The ACM and ATI of both US systems on phantoms correlated well with each other and with MRI-PDFF and, thus, can provide good diagnostic value in the assessment of hepatic steatosis. MDCT was less sensitive to mild steatosis than AC and MRI-PDFF.

Conclusion

Measurement of ACs in US studies by devices from different vendors compared to other modalities of radiological imaging (MDCT and MRI-PDFF) by special phantoms is an accurate and promising method for noninvasive quantification of hepatic steatosis.

Head-to-head comparison of magnetic resonance elastography-based liver stiffness, fat fraction, and T1 relaxation time in identifying at-risk NASH

BACKGROUND AND AIMS

The presence of at-risk NASH is associated with an increased risk of cirrhosis and complications. Therefore, noninvasive identification of at-risk NASH with an accurate biomarker is a critical need for pharmacologic therapy. We aim to explore the performance of several magnetic resonance (MR)-based imaging parameters in diagnosing at-risk NASH.

APPROACH AND RESULTS

This prospective clinical trial (NCT02565446) includes 104 paired MR examinations and liver biopsies performed in patients with suspected or diagnosed NAFLD. Magnetic resonance elastography-assessed liver stiffness (LS), 6-point Dixon-derived proton density fat fraction (PDFF), and single-point saturation-recovery acquisition-calculated T1 relaxation time were explored. Among all predictors, LS showed the significantly highest accuracy in diagnosing at-risk NASH [AUC LS : 0.89 (0.82, 0.95), AUC PDFF : 0.70 (0.58, 0.81), AUC T1 : 0.72 (0.61, 0.82), z -score test z >1.96 for LS vs any of others]. The optimal cutoff value of LS to identify at-risk NASH patients was 3.3 kPa (sensitivity: 79%, specificity: 82%, negative predictive value: 91%), whereas the optimal cutoff value of T1 was 850 ms (sensitivity: 75%, specificity: 63%, and negative predictive value: 87%). PDFF had the highest performance in diagnosing NASH with any fibrosis stage [AUC PDFF : 0.82 (0.72, 0.91), AUC LS : 0.73 (0.63, 0.84), AUC T1 : 0.72 (0.61, 0.83), |z| <1.96 for all].

CONCLUSION

Magnetic resonance elastography-assessed LS alone outperformed PDFF, and T1 in identifying patients with at-risk NASH for therapeutic trials.

Non-invasive evaluation of liver steatosis with imaging modalities: New techniques and applications

In the world, nonalcoholic fatty liver disease (NAFLD) accounts for majority of diffuse hepatic diseases. Notably, substantial liver fat accumulation can trigger and accelerate hepatic fibrosis, thus contributing to disease progression. Moreover, the presence of NAFLD not only puts adverse influences for liver but is also associated with an increased risk of type 2 diabetes and cardiovascular diseases. Therefore, early detection and quantified measurement of hepatic fat content are of great importance. Liver biopsy is currently the most accurate method for the evaluation of hepatic steatosis. However, liver biopsy has several limitations, namely, its invasiveness, sampling error, high cost and moderate intraobserver and interobserver reproducibility. Recently, various quantitative imaging techniques have been developed for the diagnosis and quantified measurement of hepatic fat content, including ultrasound- or magnetic resonance-based methods. These quantitative imaging techniques can provide objective continuous metrics associated with liver fat content and be recorded for comparison when patients receive check-ups to evaluate changes in liver fat content, which is useful for longitudinal follow-up. In this review, we introduce several imaging techniques and describe their diagnostic performance for the diagnosis and quantified measurement of hepatic fat content.

Leucine aminopeptidase 3:a promising serum biomarker candidate for nonalcoholic steatohepatitis diagnosis

BACKGROUND & AIMS

Nonalcoholic steatohepatitis (NASH) is a highly prevalent liver disease that lacks targeted therapeutic drugs and non-invasive diagnostic methods. Increasing evidence demonstrated that aberrant expression of leucine aminopeptidase 3 (LAP3) is involved in NASH. Herein, we aimed to investigate whether LAP3 can be a promising serum biomarker for NASH diagnosis.

METHODS

Liver tissues and serum from NASH rats, serum from NASH patients, and liver biopsies from chronic hepatitis B (CHB) patients combined with NASH (CHB+NASH) were obtained to evaluate the LAP3 level. Correlation analysis was conducted to evaluate the association between LAP3 expression and clinical indexes in CHB patients and CHB+NASH patients. ROC curve analysis of LAP3 in the serum and liver was applied to assess whether LAP3 can be a promising biomarker for NASH diagnosis.

RESULTS

LAP3 was significantly upregulated in serum and hepatocytes of NASH rats and patients with NASH. Correlation analysis revealed that LAP3 in the liver of CHB patients and CHB+NASH patients showed a strong positive correlation with lipidome indicators total cholesterol (TC) and triglyceride (TG), and liver fibrosis indicator hyaluronic acid (HA), which showed a negative correlation with the international normalized ratio of prothrombin coagulation (INR) and liver injury indicator aspartate aminotransferase (AST). For NASH, the diagnostic accuracy of ALT > LAP3 > AST, the sensitivity LAP3 (0.87) > ALT (0.5957) > AST (0.2941), the specificity AST (0.975) > ALT (0.9) > LAP3 (0.5).

CONCLUSION

Our data urge that LAP3 can serve as a promising serum biomarker candidate for NASH diagnosis.

The diagnostic value of novel ultrasound attenuation analysis in detecting liver steatosis identified by the controlled attenuation parameter: a diagnostic accuracy study

Background

Ultrasound attenuation analysis (USAT) is a type of novel ultrasound attenuation imaging that can be used to detect hepatic steatosis based on the attenuation coefficient. We sought to evaluate the diagnostic accuracy for assessing the severity of liver steatosis by USAT using the controlled attenuation parameter (CAP) as a reference in patients with non-alcoholic fatty liver diseases (NAFLD) and chronic hepatitis B (CHB) infections.

Methods

In total, 326 consecutive subjects with or without chronic liver diseases were enrolled in this study who underwent CAP examination and USAT to evaluate hepatic steatosis from October 2022 to November 2022 at The Fourth Affiliated Hospital of Zhejiang University School of Medicine. Hepatic steatosis stage (S) was determined by CAP according to the following cut-off values recommended by the manufacturer: S ≥ S1 (≥11%, mild): 238 dB/m; S ≥ S2 (≥34%, moderate): 259 dB/m; and S ≥ S3 (≥67%, severe): 292 dB/m, and thus the optimal cut-off values for the USAT were acquired. The area under the receiver operating characteristic curves (AUROCs) for the categories of steatosis were used to measure the diagnostic accuracy of USAT.

Results

A total of 296 patients were recruited, including 101 (34.1%) patients with NAFLD, 172 (58.1%) with CHB and the remainder were healthy control subjects (7.8%). We used the CAP as the reference standard and found that the USAT increased gradually as the stage of steatosis increased (P<0.001). A strong positive correlation was found between USAT and CAP (r=0.787, P<0.001). In the whole population, the AUROCs of the USAT for S ≥ S1, S ≥ S2 and S ≥ 3 were 0.89, 0.90, and 0.90, respectively, and the cut-off values according to the Youden index for S ≥ S1, S ≥ S2, and S ≥ 3 were 0.62, 0.66, and 0.72 dB/cm/MHz, respectively. Our study showed that the USAT had a good ability to detect hepatic steatosis in NAFLD and CHB patients.

Conclusions

USAT had a strong association with CAP and a good diagnostic capability in the detection of hepatic steatosis, which appears to be a promising tool for the non-invasive detection and quantification of hepatic steatosis.

Assessment of hepatic fat content and prediction of myocardial fibrosis in athletes by using proton density fat fraction sequence

PURPOSE

To explore the characteristics of the hepatic fat content in athletes, and predict late gadolinium enhancement (LGE) based on magnetic resonance imaging-proton density fat fraction (MRI-PDFF).

MATERIAL AND METHODS

From March 2020 to March 2021, 233 amateur athletes and 42 healthy sedentary controls were prospectively recruited. The liver fat content of four regions of interest (ROIs 1-4), the mean liver fat fraction (FF), cardiac function, and myocardium LGE were recorded, respectively. The values of ROIs 1-4 and FF were compared between athletes and controls. According to the liver fat content threshold for distinguishing athletes and controls, the cutoff total exercise time that induced a change in liver fat was obtained. The correlations among the liver fat content, cardiac function, and other parameters were analyzed. Moreover, the liver fat content was used to predict myocardium LGE by logistic regression.

RESULTS

There were significant differences for the values of ROI 1, ROI 3, ROI 4, and FF between athletes and controls (allp< 0.05). The cutoff total exercise time for inducing a change in the liver fat content was 1680 h (area under the curve [AUC] = 0.593, specificity = 83.3,p< 0.05). Blood indexes, cardiac function, and basic clinical parameters were related to liver fat content (allp< 0.05). The prediction model for LGE had an AUC value of 0.829 for the receiver operator characteristic curve.

CONCLUSION

MRI-PDFF could assess liver fat content and predict cardiac fibrosis in athletes for risk stratification and follow-up.

Clinical Utility of Magnetic Resonance Imaging Biomarkers for Identifying Nonalcoholic Steatohepatitis Patients at High Risk of Progression: A Multicenter Pooled Data and Meta-Analysis

BACKGROUND & AIMS

Nonalcoholic fatty liver disease (NAFLD) is increasing in prevalence worldwide. NAFLD is associated with excess risk of all-cause mortality, and its progression to nonalcoholic steatohepatitis (NASH) and fibrosis accounts for a growing proportion of cirrhosis and hepatocellular cancer and thus is a leading cause of liver transplant worldwide. Noninvasive precise methods to identify patients with NASH and NASH with significant disease activity and fibrosis are crucial when the disease is still modifiable. The aim of this study was to examine the clinical utility of corrected T1 (cT1) vs magnetic resonance imaging (MRI) liver fat for identification of NASH participants with nonalcoholic fatty liver disease activity score ≥4 and fibrosis stage (F) ≥2 (high-risk NASH).

METHODS

Data from five clinical studies (n = 543) with participants suspected of NAFLD were pooled or used for individual participant data meta-analysis. The diagnostic accuracy of the MRI biomarkers to stratify NASH patients was determined using the area under the receiver operating characteristic curve (AUROC).

RESULTS

A stepwise increase in cT1 and MRI liver fat with increased NAFLD severity was shown, and cT1 was significantly higher in participants with high-risk NASH. The diagnostic accuracy (AUROC) of cT1 to identify patients with NASH was 0.78 (95% CI, 0.74-0.82), for liver fat was 0.78 (95% CI, 0.73-0.82), and when combined with MRI liver fat was 0.82 (95% CI, 0.78-0.85). The diagnostic accuracy of cT1 to identify patients with high-risk NASH was good (AUROC = 0.78; 95% CI, 0.74-0.82), was superior to MRI liver fat (AUROC = 0.69; 95% CI, 0.64-0.74), and was not substantially improved by combining it with MRI liver fat (AUROC = 0.79; 95% CI, 0.75-0.83). The meta-analysis showed similar performance to the pooled analysis for these biomarkers.

CONCLUSIONS

This study shows that quantitative MRI-derived biomarkers cT1 and liver fat are suitable for identifying patients with NASH, and cT1 is a better noninvasive technology than liver fat to identify NASH patients at greatest risk of disease progression. Therefore, MRI cT1 and liver fat have important clinical utility to help guide the appropriate use of interventions in NAFLD and NASH clinical care pathways.

A reappraisal of the diagnostic performance of B-mode ultrasonography for mild liver steatosis

OBJECTIVES

Previous studies have shown that ultrasonography has high specificity (80-100%) but low sensitivity (50-70%) in diagnosing fatty liver, sensitivity is especially low for mild steatosis. In this study, we aimed to reappraise the diagnostic performance of B-mode ultrasonography for fatty liver disease.

METHODS

We performed a retrospective, multinational, multi-center, cross-sectional, observational study (six referral centers from three nations). We included 5056 participants who underwent both B-mode ultrasonography and magnetic resonance proton density fat fraction (MRI-PDFF) within a 6-month period. The diagnostic performance of B-mode ultrasonography was compared to MRI-PDFF as a reference standard for fatty liver diagnosis, using sensitivity, specificity, positive and negative predictive values, diagnostic accuracy, and area under the receiver operating characteristic curve (AUC).

RESULTS

B-mode ultrasonography showed a sensitivity of 83.4%, specificity of 81.0%, and AUC of 0.822 in diagnosing mild liver steatosis (6.5% ≤ MRI-PDFF ≤ 14%). The sensitivity, specificity, and AUC in diagnosing the presence of fatty liver disease (MRI-PDFF ≥ 6.5%) were 83.4%, 81.0%, and 0.822, respectively. Mean PDFF of B-mode ultrasonography-diagnosed non-fatty liver differed significantly from that of diagnosed mild liver steatosis (3.5 ± 2.8% vs. 8.5 ± 5.0%, p < 0.001). The inter-institutional variability of B-mode ultrasonography in diagnosing fatty liver was similar in diagnostic accuracy among the six centers (range, 82.8-88.6%, p = 0.416).

CONCLUSIONS

B-mode ultrasonography was an effective, objective method to detect mild liver steatosis using MRI-PDFF as comparison, regardless of the etiologies and comorbidities.

Non-invasive diagnosis and staging of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is considered to be the hepatic manifestation of the metabolic syndrome and is characterized by ectopic accumulation of triglycerides in the cytoplasm of hepatocytes, i.e., steatosis. NAFLD has become the most common chronic liver disease, with an estimated global prevalence of 25%. Although the majority of NAFLD patients will never experience liver-related complications, the progressive potential of NAFLD is indisputable, with 5-10% of subjects progressing to cirrhosis, end-stage liver disease, or hepatocellular carcinoma. NAFLD patients with advanced fibrosis are at the highest risk of developing cardiovascular and cirrhosis-related complications. Liver biopsy has hitherto been considered the reference method for evaluation of hepatic steatosis and fibrosis stage. Given the limitations of biopsy for widescale screening, non-invasive tests (NITs) for assessment of steatosis and fibrosis stage, including serum-based algorithms and ultrasound- and magnetic resonance-based methods, will play an increasing role in the management of NAFLD patients. This comprehensive review presents the advantages and limitations of NITs for identification of steatosis and advanced fibrosis in NAFLD. The clinical implications of using NITs to identify and manage NAFLD patients are also discussed.

Liver Stiffness Measurements by 2D Shear-Wave Elastography: Effect of Steatosis on Fibrosis Evaluation

Background: Hepatic steatosis has been shown to not effect liver stiffness measurements (LSM) by MR elastography (MRE). However, the effect of steatosis on LSM by 2D shear-wave elastography (SWE) remains controversial. Objective: To evaluate the effect of hepatic steatosis on the diagnostic performance of LSM from 2D SWE (hereafter, LSM2D-SWE) for evaluation of liver fibrosis, using LSM from MRE (hereafter, LSMMRE) as the reference standard. Methods: This retrospective study included 888 patients (442 women, 446 men; median age, 67 years) with chronic liver disease who underwent LSM by both 2D SWE and MRE within a 3-month window. Steatosis was also assessed on the ultrasound examinations by ultrasound-guided attenuation parameter (UGAP) and on the MRI examinations by MRI-based proton-density fat fraction (MRI-PDFF). Fibrosis stages and steatosis grades were classified using previously established thresholds. The effect of steatosis on LSM2D-SWE was evaluated using Kruskal-Wallis tests with post hoc tests and ROC analysis. Results: LSM2D-SWE was significantly higher in patients with severe steatosis than no steatosis by MRI-PDFF among patients with F0 fibrosis [5.5 (interquartile range [IQR], 4.7-6.0) vs 4.7 (IQR, 4.2-5.5), p=.009)] and F1 fibrosis [6.3 (IQR, 6.0-7.2) vs 5.9 (IQR, 5.0-6.6), p=.009]. LSM2D-SWE was significantly higher in patients with severe steatosis than no steatosis by UGAP among patients with F1 fibrosis [6.6 (IQR, 5.9-7.3) vs 5.9 (IQR, 5.1-6.5), p=.008)]. Otherwise, LSM2D-SWE did not vary significantly across steatosis grades at a given fibrosis stage (all p>.05). Sensitivity and specificity for ≥F1 fibrosis were 63.8% and 91.5% in patients without, versus 60.4% and 80.9% in patients with, severe steatosis by MRI-PDFF, and were 62.4% and 91.5% in patients without, versus 72.1% and 78.3% in patients with, severe steatosis by UGAP. Conclusion: Severe hepatic steatosis may result in overestimation of LSM2D-SWE in patients with no or mild steatosis, thus reducing specificity for liver fibrosis detection. Clinical impact: UGAP performed at the time of 2D SWE may help identify patients in whom LSM2D-SWE should be assessed with caution. In patients with no or mild steatosis by 2D SWE and severe steatosis by UGAP, MRE may help provide a more reliable measure of liver fibrosis.

Prevalence and predictors of non-alcoholic steatohepatitis in patients with morbid obesity

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is highly prevalent in morbid obesity (MO). A considerable proportion of patients with MO have non-alcoholic steatohepatitis (NASH). Liver biopsy (LB) is the only procedure that reliably differentiates NASH from other stages of NAFLD, but its invasive nature prevents it from being generalisable. Hence, non-invasive assessment is critical in this group of patients.

OBJECTIVES

To report NAFLD/NASH prevalence in a cohort of patients with MO and to identify predictors of NASH.

METHODS

Fifty-two consecutive patients subjected to bariatric surgery in a University hospital in Spain underwent LB. Anthropometric, clinical and biochemical variables were registered. According of the results of the LB, individuals were classified by whether they had NASH or not. Multiple logistic regression analysis was performed to identify independent factors associated with NASH.

RESULTS

NAFLD was reported in 94.2% of the patients, simple steatosis was present in 51.92% and NASH in 42.31%. Meanwhile, 17.3% of patients exhibited significant fibrosis (≥F2). HIGHT score for NASH risk was established using five independent predictors: systemic Hypertension, Insulin resistance, Gamma-glutamyl transferase, High density lipoprotein cholesterol and alanine Transaminase. This score ranges from 0 to 7 and was used to predict NASH in our cohort (area under the receiver operator characteristic curve 0.846). A score of 4 or greater implied high risk (sensitivity 77.3%, specificity 73.3%, positive predictive value 68%, negative predictive value 81.5%, accuracy 75%).

CONCLUSIONS

NAFLD is practically a constant in MO with a considerable proportion of patients presenting NASH. The combination of five independent predictors in a scoring system may help the clinician optimise the selection of patients with MO for LB.

Non-invasive methods for imaging hepatic steatosis and their clinical importance in NAFLD

Hepatic steatosis is a key histological feature of nonalcoholic fatty liver disease (NAFLD). The non-invasive quantification of liver fat is now possible due to advances in imaging modalities. Emerging data suggest that high levels of liver fat and its temporal change, as measured by quantitative non-invasive methods, might be associated with NAFLD progression. Ultrasound-based modalities have moderate diagnostic accuracy for liver fat content and are suitable for screening. However, of the non-invasive imaging modalities, MRI-derived proton density fat fraction (MRI-PDFF) has the highest diagnostic accuracy and is used for trial enrolment and to evaluate therapeutic effects in early-phase clinical trials in nonalcoholic steatohepatitis (NASH). In patients with NAFLD without advanced fibrosis, high levels of liver fat are associated with rapid disease progression. Furthermore, changes on MRI-PDFF (≥30% decline relative to baseline) are associated with NAFLD activity score improvement and fibrosis regression. However, an inverse association exists between liver fat and complications of cirrhosis. Liver fat decreases as liver fibrosis progresses towards cirrhosis, and the clinical importance of quantitative measurements of liver fat differs by NAFLD status. As such, patients with NAFLD should be stratified by fibrosis severity to investigate the utility of quantitative measurements of liver fat for assessing NAFLD progression and prognosis.

Application of machine learning with multiparametric dual-energy computed tomography of the breast to differentiate between benign and malignant lesions

BACKGROUND

Multiparametric dual-energy computed tomography (mpDECT) is widely used to differentiate various kinds of tumors; however, the data regarding its diagnostic performance with machine learning to diagnose breast tumors is limited. We evaluated univariate analysis and machine learning performance with mpDECT to distinguish between benign and malignant breast lesions.

METHODS

In total, 172 patients with 214 breast lesions (55 benign and 159 malignant) who underwent preoperative dual-phase contrast-enhanced DECT were included in this retrospective study. Twelve quantitative features were extracted for each lesion, including CT attenuation (precontrast, arterial, and venous phases), the arterial-venous phase difference in normalized effective atomic number (nZ_eff), normalized iodine concentration (NIC), and slope of the spectral Hounsfield unit (HU) curve (λ_Hu). Predictive models were developed using univariate analysis and eight machine learning methods [logistic regression, extreme gradient boosting (XGBoost), stochastic gradient descent (SGD), linear discriminant analysis (LDA), adaptive boosting (AdaBoost), random forest (RF), decision tree, and linear support vector machine (SVM)]. Classification performances were assessed based on the area under the receiver operating characteristic curve (AUROC). The best performances of the conventional univariate analysis and machine learning methods were compared using the Delong test.

RESULTS

The univariate analysis showed that the venous phase λ_Hu had the highest AUROC (0.88). Machine learning with mpDECT achieved an excellent and stable diagnostic performance, as shown by the mean classification performances in the training dataset (AUROC, 0.88-0.99) and testing (AUROC, 0.83-0.96) datasets. The performance of the AdaBoost model based on mpDECT was more stable than the other machine learning models and superior to the univariate analysis (AUROC, 0.96 vs. 0.88; P<0.001).

CONCLUSIONS

The performance of the AdaBoost classifier based on mpDECT data achieved the highest mean accuracy compared to the other machine learning models and univariate analysis in differentiating between benign and malignant breast lesions.

Development of the Eurotransplant Discard Risk Index to Predict Acceptance of Livers for Transplantation: A Retrospective Database Analysis

OBJECTIVES

The utilization of liver allografts could be optimized if nonacceptance is predicted. This study aimed to evaluate the prognostic ability of an updated Discard Risk Index in Eurotransplant.

MATERIALS AND METHODS

Potential deceased donors from January 2010 to December 2015 who had been reported to Eurotransplant were included in our analyses. Liver utilization was defined by transplant status as the primary outcome to evaluate the performance of the Eurotransplant-developed Discard Risk Index.

RESULTS

Of 11670 potential livers, 9565 (81%) were actually transplanted. Donor sex, age, history of diabetes, drug abuse, use of vasopressors, body mass index category, serum sodium, cause of death, donor type, and levels of C-reactive protein, bilirubin, aspartate and alanine aminotransferases, international normalized ratio, and gamma-glutamyltranspeptidase were associated with discard and combined in the Eurotransplant-developed Discard Risk Index. Correlation between the two Discard Risk Indexes was high (r = 0.86), and both achieved high C statistics of 0.72 and 0.75 (P < .001), respectively. Despite strong calibration, discard rates of 0.8% for overall donors and 6% of donors after circulatory death could be predicted with 80% accuracy.

CONCLUSIONS

The Eurotransplant-developed Discard Risk Index showed a high prognostic ability to predict liver utilization in a European setting. The model could therefore be valuable for identifying livers at high risk of not being transplanted in an early stage. These organs might profit the most from modified allocation strategies or advanced preservation techniques.

Non-Alcoholic Fatty Liver Disease and Its Association With Diabetes Mellitus

There is a bidirectional relationship between non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (T2DM). The liver has a vital role in the pathophysiology of both diseases as it leads to the development of insulin resistance (IR), which in turn results in NAFLD and T2DM. It has been shown that T2DM increases the risk of NAFLD progression. Furthermore, the presence of NAFLD raises the probability of T2DM complications, which explains the increased rates of NAFLD screening in patients with T2DM. In addition, there are common management options for the two diseases. Lifestyle changes can play a role in the initial management of both diseases. Medications that are used to treat T2DM are also used in the management of NAFLD, such as metformin, thiazolidinediones (TZD), glucagon-like peptide-1 (GLP-1) analogues, and dipeptidyl peptidase-4 (DPP4) inhibitors. Bariatric surgery is often used as a last resort and has shown promising results. Lifestyle interventions with diet and exercise are important postoperatively to maintain the weight loss. There are many novel treatments that are being investigated for the treatment of NAFLD, targeting multiple pathophysiologic pathways. This review aims to shed some light on the intricate relationship between NAFLD and T2DM and how IR links both diseases. We also try to raise awareness among clinicians about this relationship and how the presence of one disease should raise a high index of suspicion for the existence of the other.

Magnetic Resonance-Based Assessments Better Capture Pathophysiologic Profiles and Progression in Nonalcoholic Fatty Liver Disease

BACKGROUND

Several noninvasive tools are available for the assessment of nonalcoholic fatty liver disease (NAFLD) including clinical and blood biomarkers, transient elastography (TE), and magnetic resonance imaging (MRI) techniques, such as proton density fat fraction (MRI-PDFF) and magnetic resonance elastography (MRE). In the present study, we aimed to evaluate whether magnetic resonance (MR)-based examinations better discriminate the pathophysiologic features and fibrosis progression in NAFLD than other noninvasive methods.

METHODS

A total of 133 subjects (31 healthy volunteers and 102 patients with NAFLD) were subjected to clinical and noninvasive NAFLD evaluation, with additional liver biopsy in some patients (n=54).

RESULTS

MRI-PDFF correlated far better with hepatic fat measured by MR spectroscopy (r=0.978, P<0.001) than with the TE controlled attenuation parameter (CAP) (r=0.727, P<0.001). In addition, MRI-PDFF showed stronger correlations with various pathophysiologic parameters for cellular injury, glucose and lipid metabolism, and inflammation, than the TE-CAP. The MRI-PDFF and TE-CAP cutoff levels associated with abnormal elevation of serum alanine aminotransferase were 9.9% and 270 dB/m, respectively. The MRE liver stiffness measurement (LSM) showed stronger correlations with liver enzymes, platelets, complement component 3, several clinical fibrosis scores, and the enhanced liver fibrosis (ELF) score than the TE-LSM. In an analysis of only biopsied patients, MRE performed better in discriminating advanced fibrosis with a cutoff value of 3.9 kPa than the TE (cutoff 8.1 kPa) and ELF test (cutoff 9.2 kPa).

CONCLUSION

Our results suggest that MRI-based assessment of NAFLD is the best non-invasive tool that captures the histologic, pathophysiologic and metabolic features of the disease.

Prevalence and predictors of non-alcoholic steatohepatitis in patients with morbid obesity

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is highly prevalent in morbid obesity (MO). A considerable proportion of patients with MO have non-alcoholic steatohepatitis (NASH). Liver biopsy (LB) is the only procedure that reliably differentiates NASH from other stages of NAFLD, but its invasive nature prevents it from being generalisable. Hence, non-invasive assessment is critical in this group of patients.

OBJECTIVES

To report NAFLD/NASH prevalence in a cohort of patients with MO and to identify predictors of NASH.

METHODS

Fifty-two consecutive patients subjected to bariatric surgery in a University hospital in Spain underwent LB. Anthropometric, clinical and biochemical variables were registered. According of the results of the LB, individuals were classified by whether they had NASH or not. Multiple logistic regression analysis was performed to identify independent factors associated with NASH.

RESULTS

NAFLD was reported in 94.2% of the patients, simple steatosis was present in 51.92% and NASH in 42.31%. Meanwhile, 17.3% of patients exhibited significant fibrosis (≥F2). HIGHT score for NASH risk was established using five independent predictors: systemic Hypertension, Insulin resistance, Gamma-glutamyl transferase, High density lipoprotein cholesterol and alanine Transaminase. This score ranges from 0 to 7 and was used to predict NASH in our cohort (area under the receiver operator characteristic curve 0.846). A score of 4 or greater implied high risk (sensitivity 77.3%, specificity 73.3%, positive predictive value 68%, negative predictive value 81.5%, accuracy 75%).

CONCLUSIONS

NAFLD is practically a constant in MO with a considerable proportion of patients presenting NASH. The combination of five independent predictors in a scoring system may help the clinician optimise the selection of patients with MO for LB.

Association between Visceral Adipose Tissue and Non-Alcoholic Steatohepatitis Histology in Patients with Known or Suspected Non-Alcoholic Fatty Liver Disease

(1) Purpose: To determine the association between visceral adipose tissue (VAT) and proton density fat fraction (PDFF) with magnetic resonance imaging (MRI), and hepatic steatosis (HS), non-alcoholic steatohepatitis (NASH) and hepatic fibrosis (HF) in patients with known or suspected non-alcoholic fatty liver disease (NAFLD). (2) Methods: 135 subjects that had a liver biopsy performed within 3 months (bariatric cohort) or 1 month (NAFLD cohort) of an MRI exam formed the study group. VAT volume was quantified at L2-L3 level on opposed-phase images with signal intensity-based painting using a semi-quantitative software. Liver PDFF and pancreas PDFF were calculated on fat fraction maps. Liver volume (Lvol) and spleen volume (Svol) were also calculated using a semi-automated 3D volume tool available on PACS. A histological analysis was performed by an expert hepatopathologist blinded to imaging findings. (3) Results: The mean Lvol, Svol, liver PDFF, pancreas PDFF and VAT of the study population were 2492.2 mL, 381.6 mL, 13.2%, 12.7% and 120.6 mL, respectively. VAT showed moderate correlation with liver PDFF (r = 0.41, p < 0.001) and weak correlation with Lvol (r = 0.38, p < 0.001), Svol (r = 0.20, p = 0.025) and pancreas PDFF (r_s = 0.29, p = 0.001). VAT, Lvol and liver PDFF were significantly higher in patients with HS (p < 0.001), NASH (p < 0.05) and HF (p < 0.05). VAT was also significantly higher in the presence of lobular inflammation (p = 0.019) and hepatocyte ballooning (p = 0.001). The cut-off VAT volumes for predicting HS, NASH and HF were 101.8 mL (AUC, 0.7), 111.8 mL (AUC, 0.64) and 111.6 mL (AUC, 0.66), respectively. (4) Conclusion: The MRI determined VAT can be used for predicting the presence of HS, NASH and HF in patients with known or suspected NAFLD.

Week 4 Liver Fat Reduction on MRI as an Early Predictor of Treatment Response in Participants with Nonalcoholic Steatohepatitis

Background Pharmacologic treatment of nonalcoholic steatohepatitis (NASH) is long term in nature; thus, early noninvasive treatment response assessment is important for therapeutic decision making. Purpose To investigate potential early predictors of the 12-week treatment response estimated by using the MRI-based proton-density fat fraction (PDFF). Materials and Methods In this secondary analysis of a prospective phase Ib clinical trial evaluating a candidate treatment (MET409, a farnesoid X receptor agonist) for NASH, participants were analyzed at baseline and at 4 and 12 weeks after either active treatment with MET409 or placebo treatment between June 2019 and January 2020. Correlation and multiple linear regression analyses were used to identify clinical, laboratory, and imaging predictors of the relative PDFF change at week 12 (W12). Multivariate logistic regression analysis was used to develop predictive models for an at least 30% relative PDFF reduction at W12, a well-validated indicator of histologic improvement. Model performance was characterized by using area under the receiver operating characteristic curve (AUC) analysis, sensitivity, and specificity. Results A total of 48 participants were analyzed (median age, 57 years; age range, 40-62 years; 32 women), among whom 30 received MET409 and 18 received a placebo. The week 4 (W4) relative changes in PDFF (regression coefficient = 1.24, P < .001) and the serum alkaline phosphatase (ALP) level (regression coefficient = -0.29, P = .03) were predictors of the W12 relative PDFF change. An at least 19.3% relative PDFF reduction at W4 yielded an AUC of 0.98 (sensitivity, 89%; specificity, 95%) for predicting an at least 30% relative PDFF reduction at W12. The addition of ALP to the predictive model did not improve model performance. Conclusion In participants with nonalcoholic steatohepatitis enrolled in a phase Ib treatment trial, the relative change in the MRI-based proton-density fat fraction (PDFF) at week 4 was highly predictive of the treatment response estimated by using the week 12 MRI-based PDFF. © RSNA, 2021 Online supplemental material is available for this article.

Mapping of fatty acid composition with free-breathing MR spectroscopic imaging and compressed sensing

Nonalcoholic fatty liver disease (NAFLD) is a growing health problem, and a major challenge in NAFLD management is identifying which patients are at risk of progression to more serious disease. Simple measurements of liver fat content are not strong predictors of clinical outcome, but biomarkers related to fatty acid composition (ie, saturated vs. unsaturated fat) may be more effective. MR spectroscopic imaging (MRSI) methods allow spatially resolved, whole-liver measurements of chemical composition but are traditionally limited by slow acquisition times. In this work we present an accelerated MRSI acquisition based on spin echo single point imaging (SE-SPI), which, using appropriate sampling and compressed sensing reconstruction, allows free-breathing acquisition in a mouse model of fatty liver disease. After validating the technique's performance in oil/water phantoms, we imaged mice that had received a normal diet or a methionine and choline deficient (MCD) diet, some of which also received supplemental injections of iron to mimic hepatic iron overload. SE-SPI was more resistant to the line-broadening effects of iron than single-voxel spectroscopy measurements, and was consistently able to measure the amplitudes of low-intensity spectral peaks that are important to characterizing fatty acid composition. In particular, in the mice receiving the MCD diet, SE-SPI showed a significant decrease in a metric associated with unsaturated fat, which is consistent with the literature. This or other related metrics may therefore offer more a specific biomarker of liver health than fat content alone. This preclinical study is an important precursor to clinical testing of the proposed method. MR-based quantification of fatty acid composition may allow for improved characterization of non-alcoholic fatty liver disease. A spectroscopic imaging method with appropriate sampling strategy allows whole-liver mapping of fat composition metrics in a free-breathing mouse model. Changes in metrics like the surrogate unsaturation index (UIs) are visible in mice receiving a diet which induces fat accumulation in the liver, as compared to a normal diet; such metrics may prove useful in future clinical studies of liver disease.

Longitudinal changes on liver proton density fat fraction differ between liver segments

Background

To study the spatial heterogeneity of liver fat fraction changes during a long-term lifestyle intervention study using magnetic resonance imaging (MRI).

Methods

Thirty-two subjects underwent two MRI-scans in a span of one year. A chemical shift encoding-based water-fat separation method was applied to measure liver proton density fat fraction (PDFF) maps. The PDFF changes in the two liver lobes and the Couinaud segments were compared with the mean liver PDFF change.

Results

The slope of the relationship between mean liver PDFF changes and PDFF liver lobe changes was higher in the right compared to the left lobe (slope_{mean PDFF whole liver ~ mean PDFF right lobe} =1.08, slope_{mean PDFF whole liver ~ mean PDFF left lobe} =0.93, P<0.001). The highest slope of agreement between PDFF changes in each specific liver segment and mean liver PDFF changes was observed in segment VII (slope =1.12). The lowest slope of agreement between PDFF changes in each specific liver segment and mean liver PDFF changes was observed in segment I (slope =0.77).

Conclusions

Larger PDFF changes in the right liver lobe were observed compared to PDFF changes in the left liver lobe (LLL) in subjects with both increasing and decreasing mean liver PDFF after one year. The results are in line with the existing literature reporting a heterogeneous spatial distribution of liver fat and highlight the need to spatially resolve liver fat fraction changes in longitudinal studies.

Comparison between magnetic resonance and ultrasound-derived indicators of hepatic steatosis in a pooled NAFLD cohort

BACKGROUND & AIMS

MRI-based proton density fat fraction (PDFF) and the ultrasound-derived controlled attenuation parameter (CAP) are non-invasive techniques for quantifying liver fat, which can be used to assess steatosis in patients with non-alcoholic fatty liver disease (NAFLD). This study compared both of these techniques to histopathological graded steatosis for the assessment of fat levels in a large pooled NAFLD cohort.

METHODS

This retrospective study pooled N = 581 participants from two suspected NAFLD cohorts (mean age (SD) 56 (12.7), 60% females). Steatosis was graded according to NASH-CRN criteria. Liver fat was measured non-invasively using PDFF (with Liver MultiScan's Iterative Decomposition of water and fat with Echo Asymmetry and Least-squares estimation method, LMS-IDEAL, Perspectum, Oxford) and CAP (FibroScan, Echosens, France), and their diagnostic performances were compared.

RESULTS

LMS-IDEAL and CAP detected steatosis grade ≥ 1 with AUROCs of 1.00 (95% CI, 0.99-1.0) and 0.95 (95% CI, 0.91-0.99), respectively. LMS-IDEAL was superior to CAP for detecting steatosis grade ≥ 2 with AUROCs of 0.77 (95% CI, 0.73-0.82] and 0.60 (95% CI, 0.55-0.65), respectively. Similarly, LMS-IDEAL outperformed CAP for detecting steatosis grade ≥ 3 with AUROCs of 0.81 (95% CI, 0.76-0.87) and 0.63 (95% CI, 0.56-0.70), respectively.

CONCLUSION

LMS-IDEAL was able to diagnose individuals accurately across the spectrum of histological steatosis grades. CAP performed well in identifying individuals with lower levels of fat (steatosis grade ≥1); however, its diagnostic performance was inferior to LMS-IDEAL for higher levels of fat (steatosis grades ≥2 and ≥3).

TRIAL REGISTRATION

ClinicalTrials.gov (NCT03551522); https://clinicaltrials.gov/ct2/show/NCT03551522. UMIN Clinical Trials Registry (UMIN000026145); https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000026145.

Clinical Feasibility of Quantitative Ultrasound Imaging for Suspected Hepatic Steatosis: Intra- and Inter-examiner Reliability and Correlation with Controlled Attenuation Parameter

This study was aimed at investigating the clinical feasibility of quantitative ultrasound (QUS) imaging in the evaluation of suspected hepatic steatosis through assessment of the reliability of measurements and its correlation with the controlled attenuation parameter (CAP). This retrospective study included 117 patients who underwent liver B-mode ultrasound (US) with QUS imaging with a clinical US machine (RS85, Samsung Medison, Seoul, Korea) and CAP measurements between December 2019 and March 2020. For QUS examination, tissue attenuation imaging (TAI) and tissue scatter-distribution imaging (TSI) parameters were obtained. Intra- and inter-examiner reliability were assessed using intra-class correlation coefficients (ICCs), and QUS imaging parameters were correlated with CAP measurements using Spearman's correlation analysis. TAI and TSI revealed excellent intra- and inter-examiner reliability with ICCs of 0.994 and 0.975 and 0.991 and 0.947, respectively. Both TAI and TSI were significantly positively correlated with CAP values. QUS imaging provided good intra-and inter-observer reliability and correlated well with CAP in assessing suspected hepatic steatosis.

Quantitative multiparametric magnetic resonance imaging can aid non-alcoholic steatohepatitis diagnosis in a Japanese cohort

BACKGROUND

Non-invasive assessment of non-alcoholic steatohepatitis (NASH) is increasing in desirability due to the invasive nature and costs associated with the current form of assessment; liver biopsy. Quantitative multiparametric magnetic resonance imaging (mpMRI) to measure liver fat (proton density fat fraction) and fibroinflammatory disease [iron-corrected T1 (cT1)], as well as elastography techniques [vibration-controlled transient elastography (VCTE) liver stiffness measure], magnetic resonance elastography (MRE) and 2D Shear-Wave elastography (SWE) to measure stiffness and fat (controlled attenuated parameter, CAP) are emerging alternatives which could be utilised as safe surrogates to liver biopsy.

AIM

To evaluate the agreement of non-invasive imaging modalities with liver biopsy, and their subsequent diagnostic accuracy for identifying NASH patients.

METHODS

From January 2019 to February 2020, Japanese patients suspected of NASH were recruited onto a prospective, observational study and were screened using non-invasive imaging techniques; mpMRI with LiverMultiScan^®, VCTE, MRE and 2D-SWE. Patients were subsequently biopsied, and samples were scored by three independent pathologists. The diagnostic performances of the non-invasive imaging modalities were assessed using area under receiver operating characteristic curve (AUC) with the median of the histology scores as the gold standard diagnoses. Concordance between all three independent pathologists was further explored using Krippendorff’s alpha (a) from weighted kappa statistics.

RESULTS

N = 145 patients with mean age of 60 (SD: 13 years.), 39% females, and 40% with body mass index ≥ 30 kg/m² were included in the analysis. For identifying patients with NASH, MR liver fat and cT1 were the strongest performing individual measures (AUC: 0.80 and 0.75 respectively), and the mpMRI metrics combined (cT1 and MR liver fat) were the overall best non-invasive test (AUC: 0.83). For identifying fibrosis ≥ 1, MRE performed best (AUC: 0.97), compared to VCTE-liver stiffness measure (AUC: 0.94) and 2D-SWE (AUC: 0.94). For assessment of steatosis ≥ 1, MR liver fat was the best performing non-invasive test (AUC: 0.92), compared to controlled attenuated parameter (AUC: 0.75). Assessment of the agreement between pathologists showed that concordance was best for steatosis (a = 0.58), moderate for ballooning (a = 0.40) and fibrosis (a = 0.40), and worst for lobular inflammation (a = 0.11).

CONCLUSION

Quantitative mpMRI is an effective alternative to liver biopsy for diagnosing NASH and non-alcoholic fatty liver, and thus may offer clinical utility in patient management.

Multiparametric ultrasound imaging for the assessment of normal versus steatotic livers

Liver disease is increasing in prevalence across the globe. We present here a multiparametric ultrasound (mpUS) imaging approach for assessing nonalcoholic fatty liver disease (NALFD). This study was performed using rats (N = 21) that were fed either a control or methionine and choline deficient (MCD) diet. A mpUS imaging approach that includes H-scan ultrasound (US), shear wave elastography, and contrast-enhanced US measurements were then performed at 0 (baseline), 2, and 6 weeks. Thereafter, animals were euthanized and livers excised for histological processing. A support vector machine (SVM) was used to find a decision plane that classifies normal and fatty liver conditions. In vivo mpUS results from control and MCD diet fed animals reveal that all mpUS measures were different at week 6 (P < 0.05). Principal component analysis (PCA) showed that the H-scan US data contributed the highest percentage to the classification among the mpUS measurements. The SVM resulted in 100% accuracy for classification of normal and high fat livers and 92% accuracy for classification of normal, low fat, and high fat livers. Histology findings found considerable steatosis in the MCD diet fed animals. This study suggests that mpUS examinations have the potential to provide a comprehensive estimation of the main components of early stage NAFLD.

Relationship Between Histological Features of Non-alcoholic Fatty Liver Disease and Ectopic Fat on Magnetic Resonance Imaging in Children and Adolescents

Objectives: To investigate the association between ectopic fat content in the liver and pancreas, obesity-related metabolic components, and histological findings of non-alcoholic fatty liver disease (NAFLD) in children. Methods: This cross-sectional study investigated 63 children with biopsy-proven NAFLD who underwent magnetic resonance imaging (MRI), anthropometry, laboratory tests, and body composition analysis. Clinical and metabolic parameters, MRI-measured hepatic fat fraction (HFF) and pancreatic fat fraction (PFF), and histological findings were analyzed. Results: In a total of 63 children (48 boys, median age 12.6 years, median body mass index z-score 2.54), HFF was associated with histological steatosis [10.4, 23.7, and 31.1% in each steatosis grade, P < 0.001; Spearman's rho coefficient (rs) = 0.676; P < 0.001] and NAFLD activity score (rs = 0.470, P < 0.001), but not with lobular inflammation, hepatocyte ballooning, and hepatic fibrosis. PFF was not associated with any histological features of the liver. Waist circumference-to-height ratio and body fat percentage were associated with the steatosis grade (P = 0.006 and P = 0.004, respectively). Alanine aminotransferase was not associated with steatosis but was associated with lobular inflammation (P = 0.008). Lobular inflammation was also associated with high total cholesterol and low-density lipoprotein cholesterol and metabolic syndrome (P = 0.015, P = 0.036, and P = 0.038, respectively). Conclusions: Hepatic steatosis on MRI was only associated with the histological steatosis grade, while elevated serum levels of liver enzymes and lipids were related to the severity of lobular inflammation. Therefore, MRI should be interpreted in conjunction with the anthropometric and laboratory findings in pediatric patients.

Evaluation of hepatic steatosis before liver transplantation in ex vivo by volumetric quantitative PDFF-MRI

PURPOSE

Over the last two decades, extended criteria have promoted an increased number of donor livers available for liver transplantation. But posttransplant graft loss is still a major concern. Macrovesicular hepatic steatosis (MHS) is recognized as the most significant prognostic histologic parameter in predicting posttransplant graft loss. We aimed to evaluate the utility of ex vivo volumetric quantitative MRI for quantifying MHS before liver transplantation using proton density fat-fraction (PDFF-MRI) histogram analysis.

METHODS

PDFF-MRI was performed at 3.0T in 40 livers. We obtained histogram parameters of whole-liver volume of interest, including the mean, median, 5th, 10th, 25th, 75th, 90th, and 95th percentile PDFF; skewness; kurtosis; entropy; and volume.

RESULTS

Livers from 40 cadaveric donors were included, and histologic ex vivo fat quantification was available for 33 livers. Ten livers had MHS and 23 had normal fat content. The MHS group had higher mean, median, 5th, 10th, 25th, 75th, 90th, and 95th percentile PDFF, and entropy than the group with normal fat content (P < .05). Median PDFF had greater area under the curve value than other parameters. Mean PDFF showed an excellent correlation with entropy and a moderate correlation with MHS quantification on histology.

CONCLUSIONS

Ex vivo volumetric quantitative PDFF-MRI histogram analysis is a very useful and noninvasive method to detect MHS before liver transplantation. Median PDFF was the best predictor of the presence of MHS. Entropy is a very promising parameter.

Effect of noise and estimator type on bias for analysis of liver proton density fat fraction

PURPOSE

Proton-density fat-fraction (PDFF) is typically measured from PDFF maps by calculating the mean PDFF value within a region of interest (ROI). However, the mean estimator has been shown to result in bias when signal-to-noise ratio (SNR) is low, resulting from a skewed distribution of PDFF noise statistics. Thus, the purpose of this work was to determine the relative performance of three estimation methods (mean, median, maximum likelihood estimators (MLE)) for analysis of liver PDFF maps.

METHODS

Observational study of adult patients (n = 56) undergoing abdominal MRI. Both 2D-sequential CSE-MRI ('low-SNR') and 3D CSE-MRI ('high-SNR') acquisitions were obtained. Single-voxel MRS formed the independent reference measurement of hepatic PDFF. Intra-class correlation was tested on a subset of 'low-SNR' acquisitions. ROIs were semi-automatically co-registered across all acquisitions. Bland-Altman analysis and intra-class correlation coefficients were used for statistical analysis. A p-value of <0.05 was considered significant.

RESULTS

For in vivo low-SNR acquisitions, the mean estimator had a larger error than either the median or MLE values (bias ~ -1% absolute PDFF). The intra-class correlation coefficient was significantly greater for median and maximum likelihood estimators (0.992 and 0.993, respectively) compared to the mean estimator (0.973).

CONCLUSION

Alternative ROI analysis strategies, such as MLE or median estimators, are useful to avoid SNR-related PDFF bias. Median may be the most clinically practical strategy given its ease of calculation.

Screening and follow-up of chronic liver diseases with understanding their etiology in clinics and hospitals

BACKGROUND AND AIM

Considering the increasing prevalence of non-alcoholic fatty liver disease and non-alcoholic steatohepatitis (NASH), the development of an effective screening and follow-up system that enables the recognition of etiological changes by primary physicians in clinics and specialists in hospitals is required.

METHODS

Chronic hepatitis B (HBV) and C (HCV), NASH, and alcoholic steatohepatitis (ASH) patients who were assayed for Mac-2-binding protein glycosylation isomer (M2BPGi) (n = 272) and underwent magnetic resonance elastography (MRE) (n = 119) were enrolled. Patients who underwent MRE were also tested by ultrasound elastography (USE) (n = 80) and for M2BPGi (n = 97), autotaxin (ATX) (n = 62), and platelet count (n = 119), and their fibrosis-4 (FIB-4) index was calculated (n = 119).

RESULTS

FIB-4 index >2, excluding HBV-infected patients, M2BPGi >0.5, ATX >0.5, and platelet count <20 × 104/μL were the benchmark indices, and we took into consideration other risk factors, such as diabetes mellitus and age, to recommend further examinations, such as USE, based on the local situation to avoid overlooking hepatocellular carcinoma (HCC) in the clinic. During specialty care in the hospital, MRE exhibited high diagnostic ability for fibrosis stages >F3 or F4; it could efficiently predict collateral circulation with high sensitivity, which can replace USE. We also identified etiological features and found that collateral circulation in NASH/ASH patients tended to exceed high-risk levels; moreover, these patients exhibited more variation in HCC-associated liver stiffness than the HBV and HCV patients.

CONCLUSIONS

Using appropriate markers and tools, we can establish a stepwise, practical, noninvasive, and etiology-based screening and follow-up system in primary and specialty care.

Acetyl-CoA carboxylase inhibition disrupts metabolic reprogramming during hepatic stellate cell activation

BACKGROUND & AIMS

Non-alcoholic steatohepatitis (NASH) is a chronic liver disease characterized by hepatic lipid accumulation, inflammation, and progressive fibrosis. Acetyl-CoA carboxylase (ACC) catalyzes the rate-limiting step of de novo lipogenesis and regulates fatty acid β-oxidation in hepatocytes. ACC inhibition reduces hepatic fat content and markers of liver injury in patients with NASH; however, the effect of ACC inhibition on liver fibrosis has not been reported.

METHODS

A direct role for ACC in fibrosis was evaluated by measuring de novo lipogenesis, procollagen production, gene expression, glycolysis, and mitochondrial respiration in hepatic stellate cells (HSCs) in the absence or presence of small molecule inhibitors of ACC. ACC inhibitors were evaluated in rodent models of liver fibrosis induced by diet or the hepatotoxin, diethylnitrosamine. Fibrosis and hepatic steatosis were evaluated by histological and biochemical assessments.

RESULTS

Inhibition of ACC reduced the activation of TGF-β-stimulated HSCs, as measured by both α-SMA expression and collagen production. ACC inhibition prevented a metabolic switch necessary for induction of glycolysis and oxidative phosphorylation during HSC activation. While the molecular mechanism by which inhibition of de novo lipogenesis blocks glycolysis and oxidative phosphorylation is unknown, we definitively show that HSCs require de novo lipogenesis for activation. Consistent with this direct antifibrotic mechanism in HSCs, ACC inhibition reduced liver fibrosis in a rat choline-deficient, high-fat diet model and in response to chronic diethylnitrosamine-induced liver injury (in the absence of hepatic lipid accumulation).

CONCLUSIONS

In addition to reducing lipid accumulation in hepatocytes, ACC inhibition also directly impairs the profibrogenic activity of HSCs. Thus, small molecule inhibitors of ACC may lessen fibrosis by reducing lipotoxicity in hepatocytes and by preventing HSC activation, providing a mechanistic rationale for the treatment of patients with advanced liver fibrosis due to NASH.

LAY SUMMARY

Hepatic fibrosis is the most important predictor of liver-related outcomes in patients with non-alcoholic steatohepatitis (NASH). Small molecule inhibitors of acetyl-CoA carboxylase (ACC) reduce hepatic fat content and markers of liver injury in patients with NASH. Herein, we report that inhibition of ACC and de novo lipogenesis also directly suppress the activation of hepatic stellate cells - the primary cell responsible for generating fibrotic scar in the liver - and thus fibrosis. These data provide further evidence for the use of ACC inhibitors to treat patients with NASH and advanced fibrosis.

A composite biomarker using multiparametric magnetic resonance imaging and blood analytes accurately identifies patients with non-alcoholic steatohepatitis and significant fibrosis

Non-alcoholic steatohepatitis (NASH) is major health burden lacking effective pharmacological therapies. Clinical trials enrol patients with histologically-defined NAFLD (non-alcoholic fatty liver disease) activity score (NAS) ≥ 4 and Kleiner-Brunt fibrosis stage (F) ≥ 2; however, screen failure rates are often high following biopsy. This study evaluated a non-invasive MRI biomarker, iron-corrected T1 mapping (cT1), as a diagnostic pre-screening biomarker for NASH. In a retrospective analysis of 86 biopsy confirmed NAFLD patients we explored the potential of blood and imaging biomarkers, both in isolation and in combination, to discriminate those who have NAS ≥ 4 and F ≥ 2 from those without. Stepwise logistic regression was performed to select the optimal combination of biomarkers, diagnostic accuracy was determined using area under the receiver operator curve and model validated confirmed with and fivefold cross-validation. Results showed that levels of cT1, AST, GGT and fasting glucose were all good predictors of NAS ≥ 4 and F ≥ 2, and the model identified the combination of cT1-AST-fasting glucose (cTAG) as far superior to any individual biomarker (AUC 0.90 [0.84–0.97]). This highlights the potential utility of the composite cTAG score for screening patients prior to biopsy to identify those suitable for NASH clinical trial enrolment.

Usefulness of Different Imaging Modalities in Evaluation of Patients with Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are becoming some of the major health problems in well-developed countries, together with the increasing prevalence of obesity, metabolic syndrome, and all of their systemic complications. As the future prognoses are even more disturbing and point toward further increase in population affected with NAFLD/NASH, there is an urgent need for widely available and reliable diagnostic methods. Consensus on a non-invasive, accurate diagnostic modality for the use in ongoing clinical trials is also required, particularly considering a current lack of any registered drug for the treatment of NAFLD/NASH. The aim of this narrative review was to present current information on methods used to assess liver steatosis and fibrosis. There are several imaging modalities for the assessment of hepatic steatosis ranging from simple density analysis by computed tomography or conventional B-mode ultrasound to magnetic resonance spectroscopy (MRS), magnetic resonance imaging proton density fat fraction (MRI-PDFF) or controlled attenuation parameter (CAP). Fibrosis stage can be assessed by magnetic resonance elastography (MRE) or different ultrasound-based techniques: transient elastography (TE), shear-wave elastography (SWE) and acoustic radiation force impulse (ARFI). Although all of these methods have been validated against liver biopsy as the reference standard and provided good accuracy, the MRS and MRI-PDFF currently outperform other methods in terms of diagnosis of steatosis, and MRE in terms of evaluation of fibrosis.

High rates of ineligibility for participation in trials of new therapies in non-alcoholic steatohepatitis: a systematic review

BACKGROUND AND AIMS

Non-alcoholic fatty liver disease is common and there are a number of treatments in development. Patients with non-alcoholic steatohepatitis (NASH) and significant fibrosis are thought to be the population most in need of treatment. Identification of this group requires liver biopsy. The aim of this study was to identify the proportion of patients screened for phase 2 randomised controlled trials who subsequently entered these studies.

METHODS

Large, multicentre, phase 2 randomised controlled trials of pharmacological therapies for NASH were identified by systematic review. The pooled proportion of potential participants who entered the trials was estimated by meta-analysis. The reasons for trial ineligibility were separately extracted and analysed.

RESULTS

Thirteen reports of 14 trials were included. Overall, there were 4014 screened individuals included in the quantitative analyses and 53% were subsequently enrolled in a trial. Considering trials in which the entry criteria matched the current paradigm for treatment, that is, the presence of NASH and significant fibrosis, only 35% of screened individuals were eligible for trial entry. More than half of ineligible individuals were excluded on the basis of liver histology most often due to insufficient disease activity with or without insufficient fibrosis.

CONCLUSION

The majority of patients considered at risk of NASH and fibrosis sufficient for treatment in randomised controlled trials are ineligible for trial entry. Most often, this is due to ineligible liver histology. These findings have implications for the design of future trials in NASH and for the applicability of treatments after licensing.

Noninvasive Evaluation of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent liver diseases and can progress to advanced fibrosis and end-stage liver disease. Thus, intensive research has been performed to develop noninvasive methods for the diagnosis of nonalcoholic steatohepatitis (NASH) and fibrosis. Currently, no single noninvasive tool covers all of the stages of pathologies and conditions of NAFLD, and the cost and feasibility of known techniques are also important issues. Blood biomarkers for NAFLD may be useful to select subjects who need ultrasonography (US) screening for NAFLD, and noninvasive tools for assessing fibrosis may be helpful to exclude the probability of significant fibrosis and to predict advanced fibrosis, thus guiding the decision of whether to perform liver biopsy in patients with NAFLD. Among various methods, magnetic resonance-based methods have been shown to perform better than other methods in assessing steatosis as well as in detecting hepatic fibrosis. Many genetic markers are associated with the development and progression of NAFLD. Further well-designed studies are needed to determine which biomarker panels, imaging studies, genetic marker panels, or combinations thereof perform well for diagnosing NAFLD, differentiating NASH and fibrosis, and following-up NAFLD, respectively.

Tissue fat quantification by magnetic resonance imaging: proton density fat fraction in polycystic ovary syndrome

RESEARCH QUESTION

What are the potential differences between lean women with and without polycystic ovary syndrome (PCOS) in fat content in liver, vertebrae, paraspinal muscles, pancreas, subcutaneous (SCAT) and visceral adipose tissue (VAT)? Magnetic resonance imaging proton density fat fraction (PDFF) was used to establish these differences. This is a novel, non-invasive, operator-independent method with comparable diagnostic sensitivity and specificity to histologic examination for fatty liver disease, and strong correlation with muscle strength in neuromuscular studies.

DESIGN

Twenty lean women with PCOS (mean age 23.9 ± 2.3; body mass index [BMI] 22.4 ± 2.0) and 20 age- and BMI-matched healthy women (mean age 24.9 ± 1.5; BMI 21.5 ± 1.9) were enrolled in this cross-sectional study. Anthropometric, biochemical and hormonal evaluations along with magnetic resonance imaging proton density fat fraction were carried out.

RESULTS

PDFF% measurements of liver, SCAT and VAT were higher in the PCOS group, indicating increased fat content in these areas in lean women with PCOS compared with controls (P = 0.045, 0.030 and 0.037, respectively). In contrast, PDFF% values of vertebrae and paraspinal muscles in the PCOS group were lower than controls (P = 0.038 and 0.05, respectively). Pancreatic PDFF% measurements were similar between the groups. In the PCOS group, PDFF% of VAT was positively correlated with free androgen index (r = 0.69, P = 0.002).

CONCLUSIONS

PDFF% measurement, an MRI-based novel biomarker, reveals increased fat in liver, SCAT and VAT, and decreased fat in vertebral bones and paraspinal muscles of lean women with PCOS.

Gut microbiota and human NAFLD: disentangling microbial signatures from metabolic disorders

Gut microbiota dysbiosis has been repeatedly observed in obesity and type 2 diabetes mellitus, two metabolic diseases strongly intertwined with non-alcoholic fatty liver disease (NAFLD). Animal studies have demonstrated a potential causal role of gut microbiota in NAFLD. Human studies have started to describe microbiota alterations in NAFLD and have found a few consistent microbiome signatures discriminating healthy individuals from those with NAFLD, non-alcoholic steatohepatitis or cirrhosis. However, patients with NAFLD often present with obesity and/or insulin resistance and type 2 diabetes mellitus, and these metabolic confounding factors for dysbiosis have not always been considered. Patients with different NAFLD severity stages often present with heterogeneous lesions and variable demographic characteristics (including age, sex and ethnicity), which are known to affect the gut microbiome and have been overlooked in most studies. Finally, multiple gut microbiome sequencing tools and NAFLD diagnostic methods have been used across studies that could account for discrepant microbiome signatures. This Review provides a broad insight into microbiome signatures for human NAFLD and explores issues with disentangling these signatures from underlying metabolic disorders. More advanced metagenomics and multi-omics studies using system biology approaches are needed to improve microbiome biomarkers.

Analysis of muscle, hip, and subcutaneous fat in osteoporosis patients with varying degrees of fracture risk using 3T Chemical Shift Encoded MRI

Osteoporosis (OP) is a major disease that affects 200 million people worldwide. Fatty acid metabolism plays an important role in bone health and plays an important role in bone quality and remodeling. Increased bone marrow fat quantity has been shown to be associated with a decrease in bone mineral density (BMD), which is used to predict fracture risk. Chemical-Shift Encoded magnetic resonance imaging (CSE-MRI) allows noninvasive and quantitative assessment of adipose tissues (AT). The aim of our study was to assess hip or proximal femoral bone marrow adipose tissue (BMAT), thigh muscle (MUS), and subcutaneous adipose tissue (SAT) in 128 OP subjects matched for age, BMD, weight and height with different degrees of fracture risk assessed through the FRAX score (low, moderate and high). Our results showed an increase in BMAT and in MUS in high compared to low fracture risk patients. We also assessed the relationship between fracture risk as assessed by FRAX and AT quantities. Overall, the results of this study suggest that assessment of adipose tissue via 3T CSE-MRI provides insight into the pathophysiology fracture risk by showing differences in the bone marrow and muscle fat content in subjects with similarly osteoporotic BMD as assessed by DXA, but with varying degrees of fracture risk as assessed by FRAX.

Whole hepatic lipid volume quantification and color mapping by multi-slice and multi-point magnetic resonance imaging

AIM

Current approaches for hepatic steatosis assess only a small point within the liver and might cause inaccuracy for longitudinal observation. We aimed to establish a reliable non-invasive method for whole hepatic lipid content evaluation.

METHODS

A total of 52 patients with hepatic steatosis underwent liver biopsy. Hepatic lipid content was assessed by Dixon in-phase/out-of-phase magnetic resonance imaging and proton magnetic resonance spectroscopy. Using multi-slice and multi-point magnetic resonance imaging, we calculated the lipid intensity of every voxel throughout the liver and showed the color-mapped lipid distributions. This new analysis could also quantify the whole hepatic lipid and whole liver volumes absolutely. The diagnostic performance of hepatic lipid content between the new analysis and proton magnetic resonance spectroscopy methods was compared by receiver operating characteristic curve analysis referring to the steatosis scores of the liver biopsy.

RESULTS

Areas under the receiver operating characteristic for the diagnosis of steatosis scores ≥1, ≥2, and ≥3 using magnetic resonance imaging and proton magnetic resonance spectroscopy were 0.86 (95% confidence interval [CI] 0.70-1.00) and 0.98 (95% CI 0.93-1.00), 0.94 (95% CI 0.87-1.00) and 0.93 (95% CI 0.86-1.00), and 0.95 (95% CI 0.89-1.00) and 0.97 (95% CI 0.93-1.00), respectively, showing comparable diagnostic accuracies. However, color mapping showed some inconsistencies between the methods.

CONCLUSIONS

We described a non-invasive and repeatable evaluation method of whole hepatic lipid accumulation with absolute quantification and color mapping. Hepatic steatosis was accurately evaluated regardless of heterogeneous lipid accumulation. The whole hepatic lean volume, reflecting the hepatic parenchymal condition, can also be determined by this method.

Changes in Pancreatic Fat Content Following Diet-Induced Weight Loss

Background: Obesity can lead to ectopic pancreatic fat accumulation and increase the risk for type 2 diabetes. Smaller intervention trials have shown a decrease in pancreatic fat content (PFC) with weight loss, and we intended to investigate the effects of weight loss on PFC in a larger trial. Methods: Data from the HELENA-Trial, a randomized controlled trial (RCT) among 137 non-diabetic obese adults were used. The study cohort was classified into 4 quartiles based on weight change between baseline and 12 weeks post-intervention. Changes in PFC (baseline, 12 weeks and 50 weeks post-intervention) upon weight loss were analyzed by linear mixed models. Spearman’s coefficients were used to obtain correlations between anthropometric parameters, blood biochemical markers, and PFC. Results: At baseline, PFC only showed a significant correlation with visceral adipose tissue (VAT) (r = 0.41). Relative changes in PFC were significantly (p = 0.01) greater in Q4 (−30.8 ± 5.7%) than in Q1 (1.3 ± 6.7%). These differences remained similar after one year. However, when adjusting the statistical analyses for changes in VAT, the differences in PFC between Q1 and Q4 were no longer statistically significant. Conclusion: Weight loss is associated with a decrease in PFC. However, the reduction of PFC is not independent from reductions in VAT. Unlike VAT, PFC was not associated with metabolic biomarkers.

Diagnostic and Treatment Implications of Nonalcoholic Fatty Liver Disease and Nonalcoholic Steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) affects 75 to 100 million adults in the United States and is the leading cause of chronic liver disease worldwide, fueled by the rising epidemic of obesity and metabolic syndrome. NAFLD is the hepatic manifestation of metabolic syndrome; thus, accurately assessing and managing comorbid metabolic syndrome components is paramount. Nonalcoholic steatohepatitis (NASH) is a subset of NAFLD that includes a more progressive and advanced form of the disease, with a greater risk of fibrosis progression. Correctly diagnosing and staging NAFLD and distinguishing the subset of NASH patients is not only critical for disease monitoring and prognostication, but also holds potential implications for therapies. Although the current therapeutic landscape for NAFLD does not offer many options, future therapies are on the horizon. Properly staging the severity of disease and fibrosis is especially important when considering the eligibility and cost-effectiveness of these therapies.

Accuracy and precision of proton density fat fraction measurement across field strengths and scan intervals: A phantom and human study

BACKGROUND

Complex-based chemical shift imaging-based magnetic resonance imaging (CSE-MRI) is emerging as a preferred method for noninvasively quantifying proton density fat fraction (PDFF), a promising quantitative imaging biomarker (QIB) for longitudinal hepatic steatosis measurement.

PURPOSE

To determine linearity, bias, repeatability, and reproducibility of the PDFF measurement using CSE-MRI (CSE-PDFF) across scan intervals, MR field strengths, and readers in phantom and nonalcoholic fatty liver disease (NAFLD) patients.

STUDY TYPE

Institutional Review Board (IRB)-approved prospective.

SUBJECTS

Fat-water phantom and 20 adult patients.

FIELD STRENGTH/SEQUENCE

1.5 T and 3.0 T MR systems and a commercially available CSE-MRI sequence (IDEAL-IQ).

ASSESSMENT

Two independent readers measured CSE-PDFF of fat-water phantom and NAFLD patients across two field strengths and scan intervals (same-day and 2-week) each and in a combination of both. MR spectroscopy-based PDFF (MRS-PDFF) was used as the reference standard for phantom PDFF.

STATISTICAL TESTS

Linearity and bias of measurement were evaluated by linear regression analysis and Bland-Altman plots, respectively. Repeatability and reproducibility were assessed by coefficient of variance and repeatability / reproducibility coefficients (RC). The intraclass correlation coefficient was used to validate intra- and interobserver agreements.

RESULTS

CSE-PDFF showed high linearity and small bias (-0.6-0.4 PDFF%) with 95% limits of agreement within ±2.9 PDFF% across field strengths, 2-week interscan period, and readers in the clinical scans. CSE-PDFF was highly repeatable and reproducible both in phantom and clinical scans, with the largest observed RC across field strengths and 2-week interscan period being 3 PDFF%.

DATA CONCLUSION

CSE-PDFF is a robust QIB with high linearity, small bias, and excellent repeatability/reproducibility. A change of more than 3 PDFF% across field strengths within 2 weeks of scan interval likely reflects a true change, which is well within the clinically acceptable range.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:305-314.