Mathias Fink

French National Centre for Scientific Research, Lutetia Parisorum, Île-de-France, France

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Publications (640)1304.56 Total impact

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    ABSTRACT: Arterial stiffness is related to age and collagen properties of the arterial wall and can be indirectly evaluated by the pulse wave velocity (PWV). Ultrafast ultrasound imaging, a unique ultrahigh frame rate technique (>10 000 images/s), recently emerged enabling direct measurement of carotid PWV and its variation over the cardiac cycle. Our goal was to characterize the carotid diastolic-systolic arterial stiffening using ultrafast ultrasound imaging in healthy individuals and in vascular Ehlers-Danlos syndrome (vEDS), in which collagen type III is defectuous. Ultrafast ultrasound imaging was performed on common carotids of 102 healthy individuals and 37 consecutive patients with vEDS. Results are mean ± standard deviation. Carotid ultrafast ultrasound imaging PWV in healthy individuals was 5.6 ± 1.2 in early systole and 7.3 ± 2.0 m/s in end systole, and correlated with age (r = 0.48; P < 0.0001 and r = 0.68; P < 0.0001, respectively). Difference between early and end-systole PWV increased with age independently of blood pressure (r = 0.54; P < 0.0001). In patients with vEDS, ultrafast ultrasound imaging PWV was 6.0 ± 1.5 in early systole and 6.7 ± 1.5 m/s in end systole. Carotid stiffness change over the cardiac cycle was lower than in healthy people (0.021 vs. 0.057 m/s per mmHg; P = 0.0035). Ultrafast ultrasound imaging can evaluate carotid PWV and its variation over the cardiac cycle. This allowed to demonstrate the age-induced increase of the arterial diastolic-systolic stiffening in healthy people and a lower stiffening in vEDS, both characterized by arterial complications. We believe that this easy-to-use technique could offer the opportunity to go beyond the diastolic PWV to better characterize arterial stiffness change with age or other collagen alterations.
    Journal of Hypertension 09/2015; 33(9):1890-6. DOI:10.1097/HJH.0000000000000617 · 4.22 Impact Factor
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    Journal of ultrasound in medicine: official journal of the American Institute of Ultrasound in Medicine 08/2015; 34(8):1-12. DOI:10.7863/ultra. · 1.53 Impact Factor
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    ABSTRACT: Electromagnetic cavities are used in numerous domains of applied and fundamental physics, from microwave ovens and electromagnetic compatibility to masers, quantum electrodynamics (QED), and quantum chaos. The wave fields established in cavities are statically fixed by their geometry, which are usually modified by using mechanical parts like mode stirrers in reverberation chambers or screws in masers and QED. Nevertheless, thanks to integral theorems, tailoring the cavity boundaries theoretically permits us to design at will the wave fields they support. Here, we show in the microwave domain that it is achievable dynamically simply by using electronically tunable metasurfaces that locally modify the boundaries, switching them in real time from Dirichlet to Neumann conditions. We prove that at a high modal density, counterintuitively, it permits us to create wave patterns presenting hot spots of intense energy. We explain and model the physical mechanism underlying the concept, which allows us to find a criterion ensuring that modifying parts of a cavity’s boundaries turn it into a completely different one. We finally prove that this approach even permits us, in the limiting case where the cavity supports only well-separated resonances, to choose the frequencies at which the latter occur.
    Physical Review Letters 07/2015; 115(1):017701. DOI:10.1103/PhysRevLett.115.017701 · 7.51 Impact Factor
  • Physical Review B 06/2015; 91(22):224202. DOI:10.1103/PhysRevB.91.224202 · 3.74 Impact Factor
  • IET Microwaves Antennas & Propagation 04/2015; · 0.97 Impact Factor
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    ABSTRACT: In the field of shear wave elastography, a specific technique called Supersonic Shear Imaging (SSI) was developed since almost 15 years. This technique is based on two concepts: By means of the acoustic radiation pressure phenomena shear waves are generated directly within tissues. Then, shear wave propagation is caught in real time by using an ultrafast ultrasound device (up to 20,000 frames/s). As shear wave speed is directly related to stiffness of tissues, such a concept allows to recover elastic maps of organs. Nevertheless, stiffness is not always only sufficient to better understand organs pathologies and behaviors. So, there is a need to add new parameters for a better characterization. In this context, SSI technique can be extended in order to reach new mechanical parameters, which can potentially help physicians. By looking at the shear wave dispersion, viscosity of tissues can be retrieved by using the right rheological model. Elastic anisotropy is recovered by rotating the probe at the surface of the investigated organ. For each position, the shear wave speed is calculated allowing to deduce orientation of fibers. At last, the change in tissue stiffness as a function of the pressure applied over medium, also called acoustoelasticity theory, allows the assessment of the nonlinear elastic properties. The combination of all these new parameters, viscosity, anisotropy, and nonlinearity, with stiffness offer new possibilities of diagnosis for physicians to better understand organs pathologies.
    The Journal of the Acoustical Society of America 04/2015; 137(4):2363-2363. DOI:10.1121/1.4920586 · 1.56 Impact Factor
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    ABSTRACT: We report on the passive measurement of time-dependent Green's functions in the optical frequency domain with low-coherence interferometry. Inspired by previous studies in acoustics and seismology, we show how the correlations of a broadband and incoherent wave-field can directly yield the Green's functions between scatterers of a complex medium. Both the ballistic and multiple scattering components of the Green's function are retrieved. This approach opens important perspectives for optical imaging and characterization in complex scattering media.
    Physical Review Letters 01/2015; 114:023901. DOI:10.1103/PhysRevLett.114.023901 · 7.51 Impact Factor
  • Josselin Garnier · Mathias Fink
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    ABSTRACT: This paper presents a detailed analysis of time-reversal experiments involving a moving point source that emits a pulse. Different configurations are addressed with full-aperture or partial-aperture time-reversal mirrors and with subsonic or supersonic sources. Doppler effects and lack of source-receiver reciprocity significantly affect the time-reversal refocusing when the velocity of the source becomes comparable as or larger than the speed of propagation. The main result is that refocusing can be enhanced when the velocity of the source becomes close to the speed of propagation compared to the classical diffraction-limited refocusing properties when the source does not move, and this super-resolution effect can be quantified by simple and explicit formulas.
    Wave Motion 11/2014; 53. DOI:10.1016/j.wavemoti.2014.11.005 · 1.30 Impact Factor
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    ABSTRACT: Purpose: This work proposes shear wave elastography to quantify the elastic anisotropy of the cornea. Methods: Experiments were conducted on enucleated porcine eyeballs and anesthetized swine. We used the Supersonic Shear wave Imaging (SSI) method implemented on a dedicated 15 MHz rotating linear ultrasound array. This setup allows determining the shear wave speed variations for a set of radial propagation directions. Results: All the results showed a local anisotropy with one main direction of maximal stiffness. The influence of pulsatility was observed in vivo and ECG gating was consequently performed for all anesthetized swine. On ex vivo corneas, we performed N = 27 acquisitions in the limbus region, where the collagen fibrils are reported to run tangentially to the sclera. It was shown a good match between the direction of maximal stiffness and the expected direction of the collagen fibrils. Conclusions: This preliminary study demonstrates the potential of SSI for the assessment of corneal anisotropy in both ex vivo and in vivo conditions.
    Investigative Ophthalmology &amp Visual Science 10/2014; 55(11). DOI:10.1167/iovs.14-15127 · 3.66 Impact Factor
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    ABSTRACT: In this article we propose to use electronically tunable metasurfaces as spatial microwave modulators. We demonstrate that like spatial light modulators, which have been recently proved to be ideal tools for controlling light propagation through multiple scattering media, spatial microwave modulators can efficiently shape in a passive way complex existing microwave fields in reverberating environments with a non-coherent energy feedback. Unlike in free space, we establish that a binary-only phase state tunable metasurface allows a very good control over the waves, owing to the random nature of the electromagnetic fields in these complex media. We prove in an everyday reverberating medium, that is, a typical office room, that a small spatial microwave modulator placed on the walls can passively increase the wireless transmission between two antennas by an order of magnitude, or on the contrary completely cancel it. Interestingly and contrary to free space, we show that this results in an isotropic shaped microwave field around the receiving antenna, which we attribute again to the reverberant nature of the propagation medium. We expect that spatial microwave modulators will be interesting tools for fundamental physics and will have applications in the field of wireless communications.
    Scientific Reports 10/2014; 4:6693. DOI:10.1038/srep06693 · 5.58 Impact Factor
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    ABSTRACT: We present an approach for two-dimensional (2D) imaging through a single single-mode or multimode fiber without the need for scanners. A random scattering medium placed next to the distal end of the fiber is used to encode the collected light from every input spatial position with a different random spectral signature. We demonstrate 2D imaging of objects illuminated by a white-light fiber-coupled LED from a single measured spectrum. The technique is insensitive to fiber bending, an advantage for endoscopic applications.
    Optics Letters 10/2014; 40(4). DOI:10.1364/OL.40.000534 · 3.18 Impact Factor
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    ABSTRACT: Very high frame rate ultrasound imaging has recently allowed for the extension of the applications of echography to new fields of study such as the functional imaging of the brain, cardiac electrophysiology, and the quantitative imaging of the intrinsic mechanical properties of tumors, to name a few, non-invasively and in real time. In this study, we present the first implementation of Ultrafast Ultrasound Imaging in 3D based on the use of either diverging or plane waves emanating from a sparse virtual array located behind the probe. It achieves high contrast and resolution while maintaining imaging rates of thousands of volumes per second. A customized portable ultrasound system was developed to sample 1024 independent channels and to drive a 32??×??32 matrix-array probe. Its ability to track in 3D transient phenomena occurring in the millisecond range within a single ultrafast acquisition was demonstrated for 3D Shear-Wave Imaging, 3D Ultrafast Doppler Imaging, and, finally, 3D Ultrafast combined Tissue and Flow Doppler Imaging. The propagation of shear waves was tracked in a phantom and used to characterize its stiffness. 3D Ultrafast Doppler was used to obtain 3D maps of Pulsed Doppler, Color Doppler, and Power Doppler quantities in a single acquisition and revealed, at thousands of volumes per second, the complex 3D flow patterns occurring in the ventricles of the human heart during an entire cardiac cycle, as well as the 3D in vivo interaction of blood flow and wall motion during the pulse wave in the carotid at the bifurcation. This study demonstrates the potential of 3D Ultrafast Ultrasound Imaging for the 3D mapping of stiffness, tissue motion, and flow in humans in vivo and promises new clinical applications of ultrasound with reduced intra?and inter-observer variability.
    Physics in Medicine and Biology 09/2014; 59(19):L1. DOI:10.1088/0031-9155/59/19/L1 · 2.92 Impact Factor
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    ABSTRACT: In the manufacturing of cheese, the cutting of the curd is an essential step which depends on the firmness of the curds and significantly affects the yield of the cheese and its quality. In this work, we present a technique to measure elastic properties of the curd during coagulation that could be used to quantitatively determine the cutting time. The technique uses ultrasound to generate and measure shear waves. These waves do not propagate in liquids and their velocity of propagation depends on the viscoelastic characteristics of the medium. Hence, they can be used to identify the beginning of coagulation and subsequently to monitor the evolution of the coagulum firmness. Our results showed this technique is sensitive to changes of the medium structure during coagulation. It also proved reproducible and sensitive to different coagulation conditions. Therefore this technique can be used to develop a system suitable for the dairy industry.
    Journal of Food Engineering 09/2014; 136:73–79. DOI:10.1016/j.jfoodeng.2014.03.026 · 2.58 Impact Factor
  • Mathias Fink
    Nature Material 08/2014; 13(9):848-9. DOI:10.1038/nmat4067 · 36.43 Impact Factor
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    ABSTRACT: The recent concept of metasurfaces is a powerful tool to shape waves by governing precisely the phase response of each constituting element through its resonance properties. While most efforts are devoted to realize reconfigurable metasurfaces that allow such complete phase control, for many applications a binary one is sufficient. Here, we propose and demonstrate through experiments and simulations a binary state tunable phase reflector based on the concept of hybridized resonators as unit cell for a possible metasurface. The concept presents the great advantages to be very general, scalable to all frequency domains and above all very robust to fluctuations induced by the tunable mechanism, as we prove it at microwave frequencies using electronically tunable patch reflectors.
    Optics Express 08/2014; 22(16). DOI:10.1364/OE.22.018881 · 3.49 Impact Factor
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    ABSTRACT: Although conventional pulse-wave Doppler has proved to be a valuable diagnostic method for many vascular pathologies, it is hampered by issues related to repeatability as well as problems associated with quantification and system-dependent variability. These limitations are due to intrinsic spectral broadening on the Doppler spectrum, resulting from the directivity pattern of the ultrasound focused beam. Here, we develop a new spatial statistical technique, Doppler frequency spatial analysis (DFSA), which is based on ultrafast plane-wave imaging. Similar to standard pulse-wave Doppler, which is commonly used by sonographers, it yields a two-dimensional output (frequency versus time), while dramatically reducing the presence of intrinsic spectral broadening on the Doppler spectra. Therefore, the technique is much more sensitive to the velocity profile and turbulences than the standard pulse-wave Doppler. The proposed technique could improve diagnosis of vascular diseases, including arterial plaque characterization. Moreover, by summarizing all main information contained in the ultrafast Doppler acquisition, it permits a direct visualization of the data within the velocity profile. Here, we have compared our novel statistical technique to the standard pulse-wave Doppler approach during in vivo imaging of the human carotid artery. Notably, we achieved a greater than 4-fold reduction in intrinsic spectral broadening.
    IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 08/2014; 61(8):1396-1408. DOI:10.1109/TUFFC.2014.3049 · 1.50 Impact Factor

Publication Stats

15k Citations
1,304.56 Total Impact Points


  • 1993–2015
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
  • 2011–2014
    • Institut Laue-Langevin
      Grenoble, Rhône-Alpes, France
  • 1998–2014
    • University of Paris-Est
      La Haye-Descartes, Centre, France
  • 1994–2014
    • École Supérieure de Physique et de Chimie Industrielles
      • Langevin Institute
      Lutetia Parisorum, Île-de-France, France
  • 2009–2013
    • Unité Inserm U1077
      Caen, Lower Normandy, France
  • 1996–2013
    • Paris Diderot University
      • Laboratoire Ondes et Acoustique (LOA) UMR 7587
      Lutetia Parisorum, Île-de-France, France
  • 2009–2012
    • ParisTech
      Lutetia Parisorum, Île-de-France, France
  • 2010
    • Institute Langevin
      Lutetia Parisorum, Île-de-France, France
  • 1991–2009
    • Laboratoire de Mécanique et d’Acoustique
      Marsiglia, Provence-Alpes-Côte d'Azur, France
  • 2008
    • Philips
      Eindhoven, North Brabant, Netherlands
  • 2007
    • The University of Hong Kong
      Hong Kong, Hong Kong
    • Supersonic Imagine
      Aix, Provence-Alpes-Côte d'Azur, France
  • 2003
    • Institut Curie
      Lutetia Parisorum, Île-de-France, France