Transport in complex media

Transport in complex media

Overview

Our research activity focus on the study of light transport in biological media using mainly modeling and numerical simulation approaches. The applications targeted are the optical diagnosis of cancerous tumors and their treatments by phototherapy. The team is made of two permanent members (1 CNRS researcher and 1 associate professor).

Importance and issues

The non-invasive and early diagnosis of cancerous tumors is a major public health issue. From a radiative standpoint, biological tissues are absorbing, due to the presence of (oxygenated and deoxygenated) hemoglobin, of melanin and of their water content. Moreover, their heterogeneities give them a high scattering character (the cells nucleuses belong to the main light scatters). This diagnosis can be achieved due to the differences between healthy tissue and cancerous tissue. Indeed, a tumor is a highly vascularized biological structure. This extra supply of blood modifies the absorption properties of tumor tissue as compared with healthy tissue. From a morphological standpoint, the main differences between these tissues are the size and shape of cancer cells nucleus (which are larger and more heterogeneous than those of healthy cells). This means that such changes could be used to discriminate between healthy and cancerous tissue. The technique consists in illuminating the tissue with a laser source in the visible or near-infrared spectrum and in exploiting the signals obtained in the medium or backscattered on the medium surface.

Objectives of the planned work

Our first objective is to contribute to the understanding and to the numerical simulation of light transport in biological media. We rigorously model the light transport at the mesoscopic scale using the Radiative Transfer Equation (RTE). We developed an original numerical method based on modified Finite Volumes to solve accurately the RTE in 2D and 3D complex geometries. We have also a null-collision Monte Carlo method for solving the equation.

Our second objective is to develop innovative non-invasive optical imaging techniques for cancerous tumors diagnosis. We can reconstruct efficiently the 2D and 3D optical properties (absorption and scattering coefficients) of biological tissues without and with exogenous markers (fluorescence technique). The sensitivity analysis showed that the scattering anisotropy factor g (of the Henyey-Greenstein phase function) is the most sensitive parameter of the forward model. Thanks to our forward model based on the RTE, we can reconstruct the g factor as a new endogenous optical contrast agent for cancerous tumors diagnosis. Our multifrequency reconstruction algorithm is based on the adjoint method applied to the RTE.

We are currently working on photoacoustic imaging of biological tissues. The interest of this promising imaging technique, which combines laser and ultrasound, is to obtain a better resolution and to image deeper biological tissues.

Finally, our third objective is to contribute to the understanding and to the numerical simulation of heat transfer in biological media for some applications related to the treatment of tumors by phototherapy.

Our computational codes are parallelized and turn on the EXPLOR Mesocenter of University of Lorraine.

International and national collaborations

  • ILM (Institute of Laser Technologies in Medicine and Metrology) from University of Ulm in Germany (Pr A. Kienle)
  • LORIA (Laboratoire Lorrain de Recherche en Informatique et ses Applications – UMR 7503) from University of Lorraine (Pr S. Contassot-Vivier)
  • IECL (Institut Élie Cartan de Lorraine – UMR 7502) from University of Lorraine (Pr J. R. Roche)
  • LAPLACE (Laboratoire plasma et conversion d’énergie – UMR 5213) from University of Toulouse (Pr R. Fournier

Participation to national networks

GDRs Ondes and Tamarys

Contact