Long-term inter-platform reproducibility, bias, and linearity of commercial PDFF MRI methods for fat quantification: a multi-center, multi-vendor phantom study

Discordance diagnosis between B-mode ultrasonography and MRI proton density fat fraction for fatty liver

We aimed to evaluate the frequency and causes of discordant results in fatty liver (FL) diagnosis between B-mode ultrasonography (B-USG) and magnetic resonance imaging proton density fat fraction (MRI-PDFF). We analyzed patients who underwent both B-USG and MRI-PDFF within a 6-month interval. We made a confusion matrix for FL diagnosis between B-USG and MRI-PDFF and identified four discordant groups as follows: (1) the "UFL-MnFL-wo" group [B-USG FL-MRI-PDFF no FL without chronic liver disease (CLD) or liver cirrhosis (LC)]; (2) the "UFL-MnFL-w" group (B-USG FL-MRI-PDFF no FL with CLD or LC); (3) the "UnFL-MFL-wo" group (B-USG no FL-MRI-PDFF FL without CLD or LC); and (4) the "UnFL-MFL-w" group (B-USG no FL-MRI-PDFF FL with CLD or LC). We compared the "UFL-MnFL-wo" group with the control group in terms of various parameters. We found 201 patients (201/1514, 13.3%) with discordant results for FL diagnosis between B-USG and MRI-PDFF. The "UFL-MnFL-wo" group accounted for the largest portion at 6.8% (103/1514), followed by the "UFL-MnFL-w" group (79/1514, 5.2%) and the "UnFL-MFL-w" group (16/1514, 1.1%). The mean and right PDFF values, body mass index, and abdominal wall thickness were significantly higher in the "UFL-MnFL-wo" group than in the control group (p ≤ 0.001). The frequency of discordant results in the diagnosis of FL between B-USG and MRI-PDFF could be identified. The causes of discordant results were that B-USG was fairly accurate in diagnosing FL disease and that accompanying CLD or LC hindered the evaluation of FL.

Quantitative MRI of diffuse liver diseases: techniques and tissue-mimicking phantoms

Quantitative magnetic resonance imaging (MRI) techniques are emerging as non-invasive alternatives to biopsy for assessment of diffuse liver diseases of iron overload, steatosis and fibrosis. For testing and validating the accuracy of these techniques, phantoms are often used as stand-ins to human tissue to mimic diffuse liver pathologies. However, currently, there is no standardization in the preparation of MRI-based liver phantoms for mimicking iron overload, steatosis, fibrosis or a combination of these pathologies as various sizes and types of materials are used to mimic the same liver disease. Liver phantoms that mimic specific MR features of diffuse liver diseases observed in vivo are important for testing and calibrating new MRI techniques and for evaluating signal models to accurately quantify these features. In this study, we review the liver morphology associated with these diffuse diseases, discuss the quantitative MR techniques for assessing these liver pathologies, and comprehensively examine published liver phantom studies and discuss their benefits and limitations.

Development and accuracy validation of a fat fraction imaging biomarker for sialadenitis in the parotid gland

BACKGROUND

The diagnosis of sialadenitis, the most frequent disease of the salivary glands, is challenging when the symptoms are mild. In such cases, biomarkers can be used as definitive diagnostic indicators. Recently, biomarkers have been developed by extracting and analyzing pathological and morphological features from medical imaging. This study aimed to establish a diagnostic reference for sialadenitis based on the quantitative magnetic resonance imaging (MRI) biomarker IDEAL-IQ and assess its accuracy.

METHODS

Patients with sialadenitis (n = 46) and control subjects (n = 90) that underwent MRI were selected. Considering that the IDEAL-IQ value is a sensitive fat fractional marker to the body mass index (BMI), all subjects were also categorized as under-, normal-, and overweight. The fat fraction of parotid gland in the control and sialadenitis groups were obtained using IDEAL-IQ map. The values from the subjects in the control and sialadenitis groups were compared in each BMI category. For comparison, t-tests and receiver operating characteristic (ROC) curve analyses were performed.

RESULTS

The IDEAL-IQ fat faction of the control and sialadenitis glands were 38.57% and 23.69%, respectively, and the differences were significant. The values were significantly lower in the sialadenitis group (P), regardless of the BMI types. The area under the ROC curve (AUC) was 0.83 (cut-off value: 28.72) in patients with sialadenitis. The AUC for under-, normal-, and overweight individuals were 0.78, 0.81, and 0.92, respectively.

CONCLUSIONS

The fat fraction marker based on the IDEAL-IQ method was useful as an objective indicator for diagnosing sialadenitis. This marker would aid less-experienced clinicians in diagnosing sialadenitis.

Fatty change of the pancreas: the Pandora's box of pancreatology

Prevention of common diseases of the pancreas or interception of their progression is as attractive in theory as it is elusive in practice. The fundamental challenge has been an incomplete understanding of targets coupled with a multitude of intertwined factors that are associated with the development of pancreatic diseases. Evidence over the past decade has shown unique morphological features, distinctive biomarkers, and complex relationships of intrapancreatic fat deposition. Fatty change of the pancreas has also been shown to affect at least 16% of the global population. This knowledge has solidified the pivotal role of fatty change of the pancreas in acute pancreatitis, chronic pancreatitis, pancreatic cancer, and diabetes. The pancreatic diseases originating from intrapancreatic fat (PANDORA) hypothesis advanced in this Personal View cuts across traditional disciplinary boundaries with a view to tackling these diseases. New holistic understanding of pancreatic diseases is well positioned to propel pancreatology through lasting research breakthroughs and clinical advances.

Associations of myosteatosis with disc degeneration: A 3T magnetic resonance imaging study in individuals with impaired glycaemia

BACKGROUND

Intervertebral disc degeneration (IVDD) may be linked to dysregulations of skeletal muscle glucose metabolism and fatty alterations of muscle composition (Myosteatosis). Our aim was to evaluate the different associations of magnetic resonance imaging (MRI)-based paravertebral myosteatosis with lumbar disc degeneration in individuals with impaired glucose metabolism and normoglycaemic controls.

METHODS

In total, 304 individuals (mean age: 56.3 ± 9.1 years, 53.6% male sex, mean body mass index [BMI]: 27.6 ± 4.7 kg/m² ) from a population-based cohort study who underwent 3-Tesla whole-body chemical-shift-encoded (six echo times) and T2-weighted single-shot-fast-spin-echo MRI were included. Lumbar disc degeneration was assessed at motion segments L1 to L5, categorized according to the Pfirrmann score and defined as Pfirrmann grade > 2 and/or disc bulging/herniation on at least one segment. Fat content of the autochthonous back muscles and the quadratus lumborum muscle was quantified as proton density fat fraction (PDFF_muscle ). Logistic regression models adjusted for age, sex, BMI and regular physical activity were calculated to evaluate the association between PDFF_muscle and outcome IVDD.

RESULTS

The overall prevalence of IVDD was 79.6%. There was no significant difference in the prevalence or severity distribution of IVDD between participants with or without impaired glucose metabolism (77.7% vs. 80.7%, P = 0.63 and P = 0.71, respectively). PDFF_muscle was significantly and positively associated with an increased risk for the presence of IVDD in participants with impaired glycaemia when adjusted for age, sex and BMI (PDFF_{autochthonous back muscles} : odds ratio [OR] 2.16, 95% confidence interval [CI] [1.09, 4.3], P = 0.03; PDFF_{quadratus lumborum} : OR 2.01, 95% CI [1.04, 3.85], P = 0.04). After further adjustment for regular physical activity, the results attenuated, albeit approaching statistical significance (PDFF_{autochthonous back muscles} : OR 1.97, 95% CI [0.97, 3.99], P = 0.06; PDFF_{quadratus lumborum} : OR 1.86, 95% CI [0.92, 3.76], P = 0.09). No significant associations were shown in healthy controls (PDFF_{autochthonous back muscles} : OR 0.62, 95% CI [0.34, 1.14], P = 0.13; PDFF_{quadratus lumborum} : OR 1.06, 95% CI [0.6, 1.89], P = 0.83).

CONCLUSIONS

Paravertebral myosteatosis is positively associated with intervertebral disc disease in individuals with impaired glucose metabolism, independent of age, sex and BMI. Regular physical activity may confound these associations. Longitudinal studies will help to better understand the pathophysiological role of skeletal muscle in those with concomitant disturbed glucose haemostasis and intervertebral disc disease, as well as possible underlying causal relationships.

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.