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Tomographie optique diffuse résolue en temps : Applications fonctionnelles en neurosciences.

Abstract : Diffuse optical tomography is a new modality of functional medical imaging. Its application to the study of brain activity is very promising. In this context, this work deals with understanding light propagation through the head thanks to simulations based on the diffusion equation which is solved by the finite element method on models obtained by the segmentation of MRI. These simulations show the weak penetration of light in the brain because of the particular optical properties of the head which implies a strong influence of superficial layer in the signal detected at the surface. We built a time-resolved photon counting system suited for clinical environment based on picosecond laser diodes at four different wavelengths. Its performances have been optimized considering the clinical environment. We obtained an apparatus with a shot noise limited signal to noise ratio and with and impulse response function around 100-300 ps at half maximum. This system allowed the detection of the variation of cerebral activity. The cerebral origin of the absorption variations detected at the head surface has been proved thanks to the comparison of experiments and simulations of brain activation. Simulations results allowed to propose original methods to spatially localize cerebral activity based on the "microscopic Beer-Lambert law" which is a function of photons time of flight. These methods allow to obtain depth-related information on the variations of oxy- and deoxy-hemoglobin concentration due to the cerebral hemodynamic response thanks to the time-resolved concentration difference maps.
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https://tel.archives-ouvertes.fr/tel-00125499
Contributor : Bruno Montcel <>
Submitted on : Saturday, January 20, 2007 - 12:40:45 AM
Last modification on : Wednesday, November 20, 2019 - 3:10:56 AM
Long-term archiving on: : Tuesday, April 6, 2010 - 8:19:43 PM

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Bruno Montcel. Tomographie optique diffuse résolue en temps : Applications fonctionnelles en neurosciences.. Biophysique [physics.bio-ph]. Université Louis Pasteur - Strasbourg I, 2005. Français. ⟨tel-00125499⟩

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