title: Study of myocardial cell inhomogeneity of the human heart: Simulation and validation using polarized light imaging.
abstract: OBJECTIVE
  The arrangement or architecture of myocardial cells plays a fundamental role in the heart's function and its change was shown to be directly linked to heart diseases. Inhomogeneity level is an important index of myocardial cell arrangements in the human heart. The authors propose to investigate the inhomogeneity level of myocardial cells using polarized light imaging simulations and experiments.
  
  
  METHODS
  The idea is based on the fact that the myosin filaments in myocardial cells have the same properties as those of a uniaxial birefringent crystal. The method then consists in modeling the myosin filaments of myocardial cells as uniaxial birefringent crystal, simulating the behavior of the latter by means of the Mueller matrix, and measuring the final intensity of polarized light and consequently the inhomogeneity level of myocardial cells in each voxel through the use of crossed polarizers. The method was evaluated on both simulated and real tissues and under various myocardial cell configurations including parallel cells, crossed cells, and cells with random orientations.
  
  
  RESULTS
  When myocardial cells run perfectly parallel to each other, all the polarized light was blocked by those parallel myocardial cells, and a high homogeneity level was observed. However, if myocardial cells were not parallel to each other, some leakage of the polarized light was observed, thus causing the decrease of the polarized light amplitude and homogeneity level. The greater the crossing angle between myocardial cells, the smaller the amplitude of the polarized light and the greater the inhomogeneity level. For two populations of myocardial cell crossing at an angle, the resulting azimuth angle of the voxel was the bisector of this angle. Moreover, the value of the inhomogeneity level began to decrease from a nonzero value when the voxel was not totally homogeneous, containing for example cell crossing.
  
  
  CONCLUSIONS
  The proposed method enables the physical information of myocardial tissues to be estimated and the inhomogeneity level of a volume or voxel to be quantified, which opens new ways to study the microstructures of the human myocardium and helps understanding how heart diseases modify myocardial cells and change their mechanical properties.
authors.affiliation: CREATIS, CNRS UMR 5220, INSERM U1206, University of Lyon, INSA Lyon, Lyon 69621, France and TIMC-IMAG, CNRS UMR 5525, University of Grenoble Alps, Grenoble 38706, France.
authors.forename: Paul Audain
authors.initials: PA
authors.lastname: Desrosiers
authors.affiliation: TIMC-IMAG, CNRS UMR 5525, University of Grenoble Alps, Grenoble 38043, France and Genetics Department, CHU Grenoble-Alps, CS 10217 Grenoble, Grenoble Cedex 9 38043, France.
authors.forename: Gabrielle
authors.initials: G
authors.lastname: Michalowicz
authors.affiliation: TIMC-IMAG, CNRS UMR 5525, University of Grenoble Alps, Grenoble 38043, France and Genetics Department, CHU Grenoble-Alps, CS 10217 Grenoble, Grenoble Cedex 9 38043, France.
authors.forename: Pierre-Simon
authors.initials: PS
authors.lastname: Jouk
authors.affiliation: TIMC-IMAG, CNRS UMR 5525, University of Grenoble Alps, Grenoble 38706, France.
authors.forename: Yves
authors.initials: Y
authors.lastname: Usson
authors.affiliation: CREATIS, CNRS UMR 5220, INSERM U1206, University of Lyon, INSA Lyon, Lyon 69621, France.
authors.forename: Yuemin
authors.initials: Y
authors.lastname: Zhu
mesh_terms: D000465:Algorithms; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D006321:Heart / Q000528:radiation effects; D006801:Humans; D008859:Microscopy, Polarization / Q000379:methods; D008955:Models, Cardiovascular; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism; D055620:Optical Phenomena