Research Papers: Imaging

Multispectral reflectance imaging of brain activation in rodents: methodological study of the differential path length estimations and first in vivo recordings in the rat olfactory bulb

[+] Author Affiliations
Rémi Renaud, Claire Martin, Hirac Gurden, Frédéric Pain

Université Paris-Sud, CNRS UMR8165, Orsay F-91405, France

J. Biomed. Opt. 17(1), 016012 (Feb 08, 2012). doi:10.1117/1.JBO.17.1.016012
History: Received September 9, 2011; Revised November 18, 2011; Accepted November 18, 2011
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Abstract.  Dynamic maps of relative changes in blood volume and oxygenation following brain activation are obtained using multispectral reflectance imaging. The technique relies on optical absorption modifications linked to hemodynamic changes. The relative variation of hemodynamic parameters can be quantified using the modified Beer-Lambert Law if changes in reflected light intensities are recorded at two wavelengths or more and the differential path length (DP) is known. The DP is the mean path length in tissues of backscattered photons and varies with wavelength. It is usually estimated using Monte Carlo simulations in simplified semi-infinite homogeneous geometries. Here we consider the use of multilayered models of the somatosensory cortex (SsC) and olfactory bulb (OB), which are common physiological models of brain activation. Simulations demonstrate that specific DP estimation is required for SsC and OB, specifically for wavelengths above 600  nm. They validate the hypothesis of a constant path length during activation and show the need for specific DP if imaging is performed in a thinned-skull preparation. The first multispectral reflectance imaging data recorded in vivo during OB activation are presented, and the influence of DP on the hemodynamic parameters and the pattern of oxymetric changes in the activated OB are discussed.

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© 2012 Society of Photo-Optical Instrumentation Engineers

Citation

Rémi Renaud ; Claire Martin ; Hirac Gurden and Frédéric Pain
"Multispectral reflectance imaging of brain activation in rodents: methodological study of the differential path length estimations and first in vivo recordings in the rat olfactory bulb", J. Biomed. Opt. 17(1), 016012 (Feb 08, 2012). ; http://dx.doi.org/10.1117/1.JBO.17.1.016012


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