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Proceedings Paper

Optimization of wavelengths sets for multispectral reflectance imaging of rat olfactory bulb activation in vivo
Author(s): Rémi Renaud; Mounir Bendahmane; Romain Chery; Claire Martin; Hirac Gurden; Frederic Pain
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Paper Abstract

Wide field multispectral imaging of light backscattered by brain tissues provides maps of hemodynamics changes (total blood volume and oxygenation) following activation. This technique relies on the fit of the reflectance images obtain at two or more wavelengths using a modified Beer-Lambert law1,2. It has been successfully applied to study the activation of several sensory cortices in the anesthetized rodent using visible light1-5. We have carried out recently the first multispectral imaging in the olfactory bulb6 (OB) of anesthetized rats. However, the optimization of wavelengths choice has not been discussed in terms of cross talk and uniqueness of the estimated parameters (blood volume and saturation maps) although this point was shown to be crucial for similar studies in Diffuse Optical Imaging in humans7-10. We have studied theoretically and experimentally the optimal sets of wavelength for multispectral imaging of rodent brain activation in the visible. Sets of optimal wavelengths have been identified and validated in vivo for multispectral imaging of the OB of rats following odor stimulus. We studied the influence of the wavelengths sets on the magnitude and time courses of the oxy- and deoxyhemoglobin concentration variations as well as on the spatial extent of activated brain areas following stimulation. Beyond the estimation of hemodynamic parameters from multispectral reflectance data, we observed repeatedly and for all wavelengths a decrease of light reflectance. For wavelengths longer than 590 nm, these observations differ from those observed in the somatosensory and barrel cortex and question the basis of the reflectance changes during activation in the OB. To solve this issue, Monte Carlo simulations (MCS) have been carried out to assess the relative contribution of absorption, scattering and anisotropy changes to the intrinsic optical imaging signals in somatosensory cortex (SsC) and OB model.

Paper Details

Date Published: 8 May 2012
PDF: 12 pages
Proc. SPIE 8427, Biophotonics: Photonic Solutions for Better Health Care III, 84271O (8 May 2012); doi: 10.1117/12.922566
Show Author Affiliations
Rémi Renaud, IMNC-UMR 8165, CNRS, Univ. Paris-Sud 11 (France)
Mounir Bendahmane, IMNC-UMR 8165, CNRS, Univ. Paris-Sud 11 (France)
Romain Chery, IMNC-UMR 8165, CNRS, Univ. Paris-Sud 11 (France)
Claire Martin, IMNC-UMR 8165, CNRS, Univ. Paris-Sud 11 (France)
Hirac Gurden, IMNC-UMR 8165, CNRS, Univ. Paris-Sud 11 (France)
Frederic Pain, IMNC-UMR 8165, CNRS, Univ. Paris-Sud 11 (France)

Published in SPIE Proceedings Vol. 8427:
Biophotonics: Photonic Solutions for Better Health Care III
Jürgen Popp; Wolfgang Drexler; Valery V. Tuchin; Dennis L. Matthews, Editor(s)

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