Stereological analysis of liver biopsy histology sections as a reference standard for validating non-invasive liver fat fraction measurements by MRI

© 2016 St. Pierre et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Background and Aims: Validation of non-invasive methods of liver fat quantification requires a reference standard. However, using standard histopathology assessment of liver biopsies is problematical because of poor repeatability. We aimed to assess a stereological method of measuring volumetric liver fat fraction (VLFF) in liver biopsies and to use the method to validate a magnetic resonance imaging method for measurement of VLFF. Methods: VLFFs were measured in 59 subjects (1) by three independent analysts using a stereological point counting technique combined with the Delesse principle on liver biopsy histological sections and (2) by three independent analysts using the HepaFat-Scan® technique on magnetic resonance images of the liver. Bland Altman statistics and intraclass correlation (IC) were used to assess the repeatability of each method and the bias between the methods of liver fat fraction measurement. Results: Inter-analyst repeatability coefficients for the stereology and HepaFat-Scan® methods were 8.2 (95% CI 7.7-8.8)% and 2.4 (95% CI 2.2-2.5)% VLFF respectively. IC coefficients were 0.86 (95% CI 0.69-0.93) and 0.990 (95% CI 0.985-0.994) respectively. Small biases (=3.4%) were observable between two pairs of analysts using stereology while no significant biases were observable between any of the three pairs of analysts using Hepa-Fat-Scan®. A bias of 1.4±0.5% VLFF was observed between the HepaFat-Scan® method and the stereological method. Conclusions: Repeatability of the stereological method is superior to the previously reported performance of assessment of hepatic steatosis by histopathologists and is a suitable reference standard for validating non-invasive methods of measurement of VLFF

Perfusion MR imaging of the liver with a vascular contrast agent

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Liver fat volume fraction quantification in patients with chronic liver diseases with separated estimation of fat and water relaxation times at 1.5 and 3.0T

International audiencePurpose: To validate a magnitude-based method, transposable on any imaging system and for all current clinical fields (1.5 and 3.0 T) for liver fat volume fraction (FVF) quantification without dominant component ambiguity problems. Methods and Materials: MR imaging was performed at 1.5 and 3.0 T using a multiple-angle multiple-gradient echo acquisition. A quantification algorithm cor- recting for relaxation time effects using a disjointed estimation of T1 and T2* of fat and water and accounting for the NMR spectrum of fat was developed. Validations were performed in a prospective comparative study with histology on 28 patients with chronic liver diseases. Results: MR-estimated FVF and histological results were strongly correlated (ρ=0.96). ROC analysis showed that FVF allowed the diagnosis of a mild (cut-off= 5.5%) and a moderate steatosis (cut-off=15.2%) with a sensitivity/specificity of 100%. Water relaxation times (T1 and T2*) were found significantly reduced in patients with iron deposition (p < 0.01), whereas water T1 was found significantly increased in patients with cirrhosis (p < 0.01). Conclusion: This method that can be performed at 1.5 and 3.0 T on all imaging systems provide an accurate quantification of the FVF in patients with chronic liver disease. FVF could be a relevant biomarker for the clinical follow-up of patients with NAFLD as well as to quantify steatosis in the full spectrum of chronic liver diseases. Interestingly, thanks to the separated estimation of fat and water relaxation times, detection of cofactors such as iron deposition or cirrhosis in patients with NAFLD could be achieve

IRM de perfusion hépatique avec un agent de contraste a rámanence vasculaire

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Perfusion MR imaging of the liver with a vascular contrast agent

International audienc

Comment construire une base de données en microbiologie alimentaire ? Projet national Sym'previus

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MR-liver steatosis assessment using a magnitude-based technique with independent fat and water T2* estimations, T1-related bias correction and accounting for spectral complexity of fa

National audienc

Liver fat volume fraction quantification with fat and water T1 and T2* estimation and accounting for NMR multiple components in patients with chronic liver disease at 1.5 and 3.0 T

International audienceObjective To validate a magnitude-based method for fat volume fraction (FVF) quantification in the liver without any dominant component ambiguity problems and with the aim of transferring this method to any imaging system (clinical fields of 1.5 and 3.0 T). Methods MR imaging was performed at 1.5 and 3.0 T using a multiple-angle multiple-gradient echo sequence. A quantification algorithm correcting for relaxation time effects using a disjointed estimation of T1 and T2* of fat and water and accounting for the NMR spectrum of fat was developed. Validations were performed on fat-water emulsion at 1.5 and 3.0 T and compared with 1H-MRS. This was followed by a prospective in-vivo comparative study on 28 patients with chronic liver disease and included histology. Results Phantom study showed good agreement between MRI and MRS. MR-estimated FVF and histological results correlated strongly and FVF allowed the diagnosis of mild (cutoff = 5.5 %) and moderate steatosis (cutoff = 15.2 %) with a sensitivity/specificity of 100 %. Conclusion FVF calculation worked independently of the field strength. FVF may be a relevant biomarker for the clinical follow-up of patients (1) with or at risk of NAFLD (2) of steatosis in patients with other chronic liver diseases

3D-liver perfusion MRI with the MS-325 blood pool agent: A noninvasive protocol to asses liver fibrosis

International audiencePurpose: To evaluate a 1.5T magnetic resonance imaging (MRI) protocol, including a dedicated acquisition sequence and a postprocessing tool for the quantitative analysis of hepatic tissue perfusion. Estimated perfusion parameters and histological results based on the METAVIR classification were prospectively compared for hepatic fibrosis assessment. Materials and Methods: The study protocol was approved by the experimentation Ethics Committee and informed consent was obtained. Sixteen patients (6 women, 10 men; average age, 52.4 ± 14.8 years) with chronic liver diseases were prospectively enrolled after a liver biopsy. MS-325 (paramagnetic blood pool agent)-enhanced MRI was performed using a free-breath 3D-VIBE T1w sequence. Image volumes were registered by an automatic rigid method. Liver perfusion was modeled by a dual-input-one-compartment model and quantitative perfusion parameters such as arterial, portal, and total perfusion mean transit time (MTT) and hepatic perfusion index (HPI) were obtained using in-house developed software. Results: Arterial perfusion increased with METAVIR stage, whereas portal perfusion decreased leading to an HPI increase with fibrosis stage. MTT increased with F3, F4. A nonparametric Mann-Whitney test demonstrated that HPI and portal perfusion were relevant in discriminating between advanced and nonadvanced fibrosis, between fibrosis and cirrhosis, then between nonfibrosis and fibrosis (P < 0.01). A strong correlation was found between portal perfusion fall-off and HPI increase (r = −0.97; P < 0.001). HPI and portal perfusion were strongly correlated with fibrosis stage (r = 0.83 and −0.88; P < 0.001, respectively). Conclusion: HPI and portal perfusion could be relevant indicators for the clinical follow-up in patients with chronic liver diseases