Bernard E Van Beers

French Institute of Health and Medical Research, Lutetia Parisorum, Île-de-France, France

Are you Bernard E Van Beers?

Claim your profile

Publications (292)733.66 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Magnetic Resonance Elastography (MRE) uses macroscopic shear wave propagation to quantify mechanical properties of soft tissues. Micro-obstacles are capable of affecting the macroscopic dispersion properties of shear waves. Since disease or therapy can change the mechanical integrity and organization of vascular structures, MRE should be able to sense these changes if blood vessels represent a source for wave scattering. To verify this, MRE was performed to quantify alteration of the shear wave speed cs due to the presence of vascular outgrowths using an aortic ring model. Eighteen fragments of rat aorta included in a Matrigel matrix (n=6 without outgrowths, n=6 with a radial outgrowth extent of ~600µm and n=6 with ~850µm) were imaged using a 7 Tesla MR scanner (Bruker, PharmaScan). High resolution anatomical images were acquired in addition to multi-frequency MRE (ν = 100, 115, 125, 135 and 150 Hz). Average cs was measured within a ring of ~900µm thickness encompassing the aorta and were normalized to cs0 of the corresponding Matrigel. The frequency dependence was fit to the power law model cs ~νy. After scanning, optical microscopy was performed to visualize outgrowths. Results demonstrated that in presence of vascular outgrowths (1) normalized cs significantly increased for the three highest frequencies (Kruskal-Wallis test, P = 0.0002 at 125 Hz and P = 0.002 at 135 Hz and P = 0.003 at 150 Hz) but not for the two lowest (Kruskal-Wallis test, P = 0.63 at 100 Hz and P = 0.87 at 115 Hz), and (2) normalized cs followed a power law behavior not seen in absence of vascular outgrowths (ANOVA test, P < 0.0001). These results showed that vascular outgrowths acted as micro-obstacles altering the dispersion relationships of propagating shear waves and that MRE could provide valuable information about microvascular changes.
    No preview · Article · Nov 2015 · NMR in Biomedicine
  • [Show abstract] [Hide abstract]
    ABSTRACT: Purpose: To develop an MRI method for quantifying hepatic fat content and visceral adipose tissue fatty acid composition in mice on a 7.0T preclinical system. Methods: MR acquisitions were performed with a multiple echo spoiled gradient echo with bipolar readout gradients. After phase correction, the number of double bounds (ndb) and the number of methylene interrupted double bounds (nmidb) were quantified with a model including eight fat components, and parametric maps of saturated, monounsaturated, and polyunsaturated fatty acids were derived. The model included a complex error map to correct for the phase errors and the amplitude modulation caused by the bipolar acquisition. Validations were performed in fat-water emulsions and vegetable oils. In vivo, the feasibility was evaluated in mice receiving a high-fat diet containing primarily saturated fatty acids and a low-fat diet containing primarily unsaturated fatty acids. Results: Linear regressions showed strong agreements between ndb and nmidb quantified with MRI and the theoretical values calculated using oil compositions, as well as between the proton density and the fat fractions in the emulsions. At MRI, the mouse liver fat fraction was smaller in mice fed the low-fat diet compared with mice fed the high-fat diet. In visceral adipose tissue, saturated fatty acids were significantly higher, whereas monounsaturated and polyunsaturated fatty acids were significantly lower in mice fed the low-fat diet compared with mice fed the high-fat diet. Conclusion: It is feasible to simultaneously quantify hepatic fat content and visceral adipose tissue fatty acid composition with 7.0T MRI in mice.
    No preview · Article · Nov 2015 · Magnetic Resonance in Medicine
  • Source
    Valérie Vilgrain · Bernard E. Van Beers · Catherine M. Pastor
    [Show abstract] [Hide abstract]
    ABSTRACT: The incidence of hepatocellular carcinomas (HCCs) has increased worldwide in line with an improved screening by high-resolution imaging of cirrhotic livers. Besides abdominal ultrasonography and computerised tomography, magnetic resonance imaging (MRI) is an important tool to detect HCCs. With commercialisation of MR hepatobiliary contrast agents that cross membrane transporters in hepatocytes or tumour cells, MRI adds new information to detect and characterise HCCs. When tumour cells lose Organic Anion Transporting Polypeptides (OATP1B1/B3) in cell membranes facing sinusoidal blood, tumour appears hypointense (decreased contrast agent concentrations) in comparison to surrounding normal or cirrhotic liver that retains OATP1B1/B3 expression. However, expression, regulation, and prognostic significance of transporter evolution along carcinogenesis are incompletely known. Moreover, understanding signal intensities in focal lesions also relies on transport functions of cellular efflux transporters. This manuscript reviews all the publications that associate liver imaging with hepatobiliary contrast agents and expression of transporters. The regulation of transporters along carcinogenesis to anticipate the prognosis of focal lesions is also included.
    Preview · Article · Nov 2015 · Journal of Hepatology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Background: Steatosis assessed by histology is commonly considered to be a significant risk factor for liver surgery. MRI is considered as the new gold standard for noninvasive liver fat quantification. The purpose was to assess whether liver steatosis determined by preoperative MRI is an independent risk factor of complications after major liver resection. Methods: All patients who underwent liver MRI before major liver resection in our institution between January 2001 and December 2011 were included in this retrospective study. The liver fat fraction (LFF) was assessed on in- and opposed-phase T1-weighted dual echo gradient echo MRI and steatosis was defined as a MRI LFF of ≥5%. The association between steatosis and postoperative complications (Clavien-Dindo classification, ascites >500 mL at day 5, 50-50 criteria, fistula/collection, blood liver test alterations, pulmonary complications, nonpulmonary complications, >1 complication, duration of stay in the intensive care unit, duration of hospital stay, and death) was assessed by multivariate analysis using the appropriate model. Results: A MRI LFF of ≥5% was associated with severe postoperative complications (Clavien-Dindo score ≥ IIIa; P = .04), more pulmonary complications (P = .02), and longer duration of hospital stay (P = .02) on the multivariate model adjusted for confounding factors. The postoperative aminotransferase levels were higher in patients with a MRI LFF of ≥5%, than in other patients (P = .0008). Conclusion: Liver steatosis assessed by routine preoperative MRI is shown to be an independent risk factor of severe postoperative complications after major liver resection.
    No preview · Article · Nov 2015 · Surgery
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We have recently reported cannabinoid-induced rapid changes in the structure of individual neurons. In order to investigate the presence of similar effects at the regional level, measures of brain tissue biomechanics are required. However, cannabinoids are known to alter cerebral blood flow (CBF), putatively resulting in presently unexplored changes in cerebral tissue biomechanics. Here we used magnetic resonance elastography (MRE) and flow-sensitive alternating inversion recovery (FAIR) imaging to measure in vivo alterations of mechanical properties and CBF, respectively, in the rat hippocampus, a brain region with a high density of type-1 cannabinoid receptors (CB1R). Systemic injection of the cannabinoid agonist CP55,940 (0.7 mg/kg) induced a significant stiffness decrease of 10.5�1.2% at 15 minutes. FAIR imaging indicated a comparable decrease (11.3�1.9%) in CBF. Both effects were specific to CB1R activation, as shown by pretreatment with the CB1R-specific antagonist AM251. Strikingly, similar rapid parallel changes of brain elasticity and CBF were also observed after systemic treatment with the hypotensive drug nicardipine. Our results reveal important drug-induced parallel changes in CBF and brain mechanical characteristics, and show that blood flowdependent tissue softening has to be considered as an important putative confounding factor when cerebral viscoelastic changes are investigated. http://jcb.sagepub.com/content/early/2015/09/23/0271678X15606923.abstract
    Full-text · Article · Oct 2015 · Journal of Cerebral Blood Flow & Metabolism
  • Maxime Ronot · Bernard E Van Beers · Valérie Vilgrain

    No preview · Article · Sep 2015 · Diagnostic and interventional imaging
  • Bernard E. Van Beers · Jean-Luc Daire · Philippe Garteiser

    No preview · Article · Sep 2015 · Journal of Hepatology
  • Source
    Bernard E. Van Beers · Jean-Luc Daire · Philippe Garteiser

    Preview · Article · Jun 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To determine the pathogenesis of liver nodules, and lesions similar to obliterative portal venopathy, observed after portosystemic shunts or portal vein thrombosis in humans. We conducted an experimental study comparing portacaval shunt (PCS), total portal vein ligation (PVL), and sham (S) operated rats. Each group were either sacrificed at 6 weeks (early) or 6 months (late). Arterial liver perfusion was studied in vivo using CT, and histopathological changes were noted. Liver mRNA levels were quantified by RT-QPCR for markers of inflammation (Il10, Tnfa), proliferation (Il6st, Mki67, Hgf, Hnf4a), angiogenesis: (Vegfa, Vegfr 1, 2 and 3; Pgf), oxidative stress (Nos2, and 3, Hif1a), and fibrosis (Tgfb). PCS and PVL were compared to the S group. Periportal fibrosis and arterial proliferation was observed in late PCS and PVL groups. CT imaging demonstrated increased arterial liver perfusion in the PCS group. RT-QPCR showed increased inflammatory markers in PCS and PVL early groups. Tnfa and Il10 were increased in PCS and PVL late groups respectively. All proliferative markers increased in the PCS, and Hnf4a in the PVL early groups. Mki67 and Hnf4a were increased in the PCS late group. Nos3 was increased in the early and late PCS groups, and Hif1a was decreased in the PVL groups. Markers of angiogenesis were all increased in the early PCS group, and Vegfr3 and Pgf in the late PCS group. Only Vegfr3 was increased in the PVL groups. Tgf was increased in the PCS groups. Portal deprivation in rats induces a sustained increase in intrahepatic markers of inflammation, angiogenesis, proliferation, and fibrosis.
    Full-text · Article · May 2015 · PLoS ONE
  • Source
    Bernard E Van Beers

    Preview · Article · May 2015 · Journal of Hepatology
  • [Show abstract] [Hide abstract]
    ABSTRACT: To evaluate the value of diffusion-weighted imaging (DWI) in detecting residual tumours (RTs) in colorectal liver metastases (CLMs) following chemotherapy, with a focus on tumour periphery. From January 2009-January 2012, 57 patients who underwent liver resection for CLMs with preoperative MRI (<3 months) including DWI were retrospectively included. CLMs were classified into three response groups on pathology: (1) major histological (MHR, RTs ≤ 10 %), (2) partial histological (PHR, RT = 10-49 %), and (3) no histological (NHR, RT ≥ 50 %). On DWI, regions of interest (ROIs) were drawn around the entire tumour and tumour periphery. Apparent diffusion (ADC) and pure diffusion (D) coefficients were calculated using a monoexponential fit, and compared using Kruskal-Wallis test on a lesion-per-lesion analysis. 111 CLMs were included. Fourteen (12.5 %), 42 (38 %) and 55 (49.5 %) CLMs presented a MHR, PHR and NHR, respectively. ADC and D of the peripheral ROIs were significantly higher in the MHR group (P = 0.013/P = 0.013). ADC and D from the entire tumour were not significantly different among the groups (P = 0.220/P = 0.103). In CLM treated with chemotherapy, ADC and D values from the entire tumour are not related to the degree of RT, while peripheral zone diffusion parameters could help identify metastases with MHR. • Peripheral ADC and D of CLMs were higher with major pathological responses. • Global ADC and D of CLMs were not different according to residual tumour. • Diffusion-weighted images of CLM periphery could be an interesting biomarker of MHR. • Diffusion-weighted images could be used to help tailor treatment.
    No preview · Article · May 2015 · European Radiology
  • [Show abstract] [Hide abstract]
    ABSTRACT: PurposeTo evaluate between-site agreement of apparent diffusion coefficient (ADC) measurements in preclinical magnetic resonance imaging (MRI) systems.Materials and MethodsA miniaturized thermally stable ice-water phantom was devised. ADC (mean and interquartile range) was measured over several days, on 4.7T, 7T, and 9.4T Bruker, Agilent, and Magnex small-animal MRI systems using a common protocol across seven sites. Day-to-day repeatability was expressed as percent variation of mean ADC between acquisitions. Cross-site reproducibility was expressed as 1.96 × standard deviation of percent deviation of ADC values.ResultsADC measurements were equivalent across all seven sites with a cross-site ADC reproducibility of 6.3%. Mean day-to-day repeatability of ADC measurements was 2.3%, and no site was identified as presenting different measurements than others (analysis of variance [ANOVA] P = 0.02, post-hoc test n.s.). Between-slice ADC variability was negligible and similar between sites (P = 0.15). Mean within-region-of-interest ADC variability was 5.5%, with one site presenting a significantly greater variation than the others (P = 0.0013).Conclusion Absolute ADC values in preclinical studies are comparable between sites and equipment, provided standardized protocols are employed. J. Magn. Reson. Imaging 2015.
    No preview · Article · May 2015 · Journal of Magnetic Resonance Imaging
  • [Show abstract] [Hide abstract]
    ABSTRACT: Purpose: To compare qualitative and quantitative magnetic resonance (MR) imaging characteristics of hepatic hemangiomas in patients with normal, fibrotic and cirrhotic livers. Meterials and Methods: Retrospective, institutional review board approved study (waiver of informed consent). Eighty-nine consecutive patients with 231 hepatic hemangiomas who underwent liver MR imaging for lesion characterization were included. Lesions were classified into three groups according to the patients' liver condition: no underlying liver disease (group 1), fibrosis (group 2) and cirrhosis (group 3). Qualitative and quantitative characteristics (number, size, signal intensities on T1-, T2-, and DW MR images, T2 shine-through effect, enhancement patterns (classical, rapidly filling, delayed filling), and ADC values) were compared. Results: There were 160 (69%), 45 (20%), and 26 (11%) hemangiomas in groups 1, 2 and 3, respectively. Lesions were larger in patients with normal liver (group 1 vs. groups 2 and 3; P=.009). No difference was found between the groups on T2-weighted images (fat-suppressed fast spin-echo (P=.82) and single-shot (P=.25)) and in enhancement patterns (P=.56). Mean ADC values of hemangiomas were similar between groups 1, 2 and 3 (2.11±.52×10-3mm2/s, 2.1±.53×10-3mm2/s and 2.14±.44×10-3mm2/s, P=87, respectively). T2 shine-through effect was less frequently observed in cirrhosis (P=.02). Conclusion: MR imaging characteristics of hepatic hemangioma were similar in patients with normal compared to fibrotic and cirrhotic livers. Smaller lesion size was observed with liver disease and less T2 shine-through effect was seen in hemangiomas developed on cirrhosis, the latter being an important finding to highlight in these patients at risk of developing hepatocellular carcinoma.
    No preview · Article · Jan 2015 · European journal of radiology
  • Source
    Bernard E. Van Beers · Jean-Luc Daire · Philippe Garteiser
    [Show abstract] [Hide abstract]
    ABSTRACT: Newly developed or advanced methods at ultrasonography and MR imaging provide combined anatomical and quantitative functional information regarding diffuse and focal liver diseases. Dynamic contrast-enhanced ultrasonography may improve tumor characterization and ultrasound elastography has a central role for staging liver fibrosis and an increasing role in grading portal hypertension. In clinical practice, MR imaging examinations currently include diffusion-weighted and dynamic MR imaging enhanced with extracellular or hepatobiliary contrast agents. Moreover, quantitative parameters obtained at diffusion-weighted MR imaging, dynamic contrast-enhanced MR imaging and MR elastography have the potential to further characterize diffuse and focal liver diseases by adding information about tissue cellularity, perfusion, hepatocyte transport function and visco-elasticity. The multiparametric capability of ultrasonography and more markedly of MR imaging gives the opportunity of high diagnostic performance by combining imaging biomarkers. The image acquisition and post-processing methods should be further standardized and validated in multicenter trials.
    Preview · Article · Oct 2014 · Journal of Hepatology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Purpose: To compare the value of enhancement and pharmacokinetic parameters measured at dynamic gadoxetate-enhanced magnetic resonance (MR) imaging in determining hepatic organic anion transporter expression in control rats and rats with advanced liver fibrosis. Materials and methods: Institutional animal review board approval was received before the study began. Advanced liver fibrosis was created in rats by means of carbon tetrachloride injections over an 8-week period. In 17 rats with liver fibrosis and eight control rats, dynamic gadoxetate-enhanced MR images of the liver were obtained during 1 hour after injection of 0.025 mmol gadoxetate per kilogram of body weight. Enhancement parameters (maximum enhancement [Emax], time to peak [Tmax], and elimination half-life) were measured on enhancement-versus-time curves, and pharmacokinetic parameters (hepatic extraction fraction [HEF] and mean residence time [MRT]) were obtained by means of deconvolution analysis of the concentration-versus-time curves in the liver and the portal vein. The parameters were correlated at simple and multiple regression analysis with the expression of the hepatic anion uptake transporter organic anion-transporting polypeptide 1A1 (Oatp1a1), the hepatobiliary transporter multidrug resistance-associated protein 2 (Mrp2), and the backflux transporter Mrp4, as determined with reverse transcription polymerase chain reaction. Results: In rats with advanced liver fibrosis, the Emax, Tmax, HEF, and MRT decreased significantly relative to those in control rats, whereas the elimination half-life increased significantly. The enhancement and pharmacokinetic parameters correlated significantly with the expression of the transporters at simple regression analysis. At multiple regression analysis, HEF was the only parameter that was significantly associated with the expression of Oatp1a1 and Mrp2 (P < .001, r = 0.74 and P < .001, r = 0.70, respectively). Conclusion: The pharmacokinetic parameter HEF at dynamic gadoxetate-enhanced MR imaging is independently correlated with hepatic organic anion transporter expression.
    No preview · Article · Oct 2014 · Radiology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objectives To prospectively assess the stiffness of incidentally discovered focal liver lesions (FLL) with no history of chronic liver disease or extrahepatic cancer using shearwave elastography (SWE). Methods Between June 2011 and May 2012, all FLL fortuitously discovered on ultrasound examination were prospectively included. For each lesion, stiffness was measured (kPa). Characterization of the lesion relied on magnetic resonance imaging (MRI) and/or contrast-enhanced ultrasound, or biopsy. Tumour stiffness was analysed using ANOVA and non-parametric Mann-Whitney tests. Results 105 lesions were successfully evaluated in 73 patients (61 women, 84 %) with a mean age of 44.8 (range: 20‒75). The mean stiffness was 33.3 ± 12.7 kPa for the 60 focal nodular hyperplasia (FNH), 19.7 ± 9.8 k Pa for the 17 hepatocellular adenomas (HCA), 17.1 ± 7 kPa for the 20 haemangiomas, 11.3 ± 4.3 kPa for the five focal fatty sparing, 34.1 ± 7.3 kPa for the two cholangiocarcinomas, and 19.6 kPa for one hepatocellular carcinoma (p
    No preview · Article · Sep 2014 · European Radiology

  • No preview · Conference Paper · Jul 2014

  • No preview · Conference Paper · May 2014
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: PURPOSE: The presence of micro-obstacles can influence the propagation of the shear waves 1 and hence alter the apparent mechanical properties 2 as assessed via Magnetic Resonance Elastography (MRE). Disease or therapies can change the mechanical integrity and organization of vascular structures. If blood vessels represent a source for wave scattering (i.e represent micro-obstacles), MRE should be able to sense these changes. We follow the hypothesis that the presence of an underlying fractal-like stiff structure is capable of generating on the macroscopic scale apparent power law behavior in an otherwise non-dispersive material. To verify this hypothesis, multi-frequency MRE was performed to quantify alteration of the shear wave speed (Cs) due to the presence of vascular outgrowth using a rat aortic ring model. The model is based on the capacity of fragments of aorta to generate vascular outgrowth once cultivated in Matrigel 3 . METHODS: Eighteen fragments of rat aortas were immersed in Matrigel and cultivated. At 1 day (D1, n=6), 5 days (D5, n=6) and 8 days (D8, n=6) after their inclusion, the fragments were imaged at 7T (Bruker, Pharmascan). T2-weighted images (113μm in plane resolution) and 3D steady-state MRE at different 5 frequencies (ω=100, 115, 125, 135 and 150Hz; 300μm in plane resolution) were recorded 4
    Full-text · Conference Paper · May 2014
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To assess in a high-resolution model of thin liver rat slices which viscoelastic parameter at three-dimensional multifrequency MR elastography has the best diagnostic performance for quantifying liver fibrosis. The study was approved by the ethics committee for animal care of our institution. Eight normal rats and 42 rats with carbon tetrachloride induced liver fibrosis were used in the study. The rats were sacrificed, their livers were resected and three-dimensional MR elastography of 5±2 mm liver slices was performed at 7T with mechanical frequencies of 500, 600 and 700 Hz. The complex shear, storage and loss moduli, and the coefficient of the frequency power law were calculated. At histopathology, fibrosis and inflammation were assessed with METAVIR score, fibrosis was further quantified with morphometry. The diagnostic value of the viscoelastic parameters for assessing fibrosis severity was evaluated with simple and multiple linear regressions, receiver operating characteristic analysis and Obuchowski measures. At simple regression, the shear, storage and loss moduli were associated with the severity of fibrosis. At multiple regression, the storage modulus at 600 Hz was the only parameter associated with fibrosis severity (r = 0.86, p<0.0001). This parameter had an Obuchowski measure of 0.89+/-0.03. This measure was significantly larger than that of the loss modulus (0.78+/-0.04, p = 0.028), but not than that of the complex shear modulus (0.88+/-0.03, p = 0.84). Our high resolution, three-dimensional multifrequency MR elastography study of thin liver slices shows that the storage modulus is the viscoelastic parameter that has the best association with the severity of liver fibrosis. However, its diagnostic performance does not differ significantly from that of the complex shear modulus.
    Full-text · Article · Apr 2014 · PLoS ONE

Publication Stats

6k Citations
733.66 Total Impact Points

Institutions

  • 2011-2015
    • French Institute of Health and Medical Research
      • Center of Biomedical Research Bichat-Beaujon
      Lutetia Parisorum, Île-de-France, France
  • 2010-2015
    • Assistance Publique – Hôpitaux de Paris
      • Department of Radiology
      Lutetia Parisorum, Île-de-France, France
  • 2008-2015
    • Paris Diderot University
      • Centre de recherche biomédicale Bichat, Beaujon (CRB3) UMR-S 773
      Lutetia Parisorum, Île-de-France, France
  • 2013
    • Unité Inserm U1077
      Caen, Lower Normandy, France
  • 1988-2011
    • Catholic University of Louvain
      • • Department of Radiology and Medical Imaging - RAIM
      • • Laboratory of Hepatogastroenterology
      Лувен-ла-Нев, Wallonia, Belgium
  • 2008-2010
    • The Catholic University of America
      Washington, Washington, D.C., United States
  • 1992-2007
    • Cliniques Universitaires Saint-Luc
      • • Division of Radiology
      • • Department of Medical Imaging
      Bruxelles, Brussels Capital, Belgium
  • 1990-1997
    • University Hospital Brussels
      • Department of Radiology
      Bruxelles, Brussels Capital Region, Belgium
  • 1988-1993
    • Centre Hospitalier Universitaire Mont-Godinne
      Yvoir, Wallonia, Belgium
  • 1988-1989
    • Université Paris-Sud 11
      Orsay, Île-de-France, France