Research Papers: General

Extraction of optical properties and prediction of light distribution in rat brain tissue

[+] Author Affiliations
Mehdi Azimipour

University of Wisconsin-Milwaukee, Electrical and Computer Engineering Department, Milwaukee, Wisconsin 53211

Ryan Baumgartner

University of Wisconsin-Milwaukee, Electrical and Computer Engineering Department, Milwaukee, Wisconsin 53211

Yuming Liu

University of Wisconsin at Madison, Laboratory for Optical and Computational Instrumentation, 1675 Observatory Drive, Madison, Wisconsin 53706

Steven L. Jacques

Oregon Health Science University, Department of Biomedical Engineering, 3303 SW Bond Avenue, Portland, Oregon 97239

Oregon Health Science University, Department of Dermatology, 3303 SW Bond Avenue, Portland, Oregon 97239

Kevin Eliceiri

University of Wisconsin at Madison, Laboratory for Optical and Computational Instrumentation, 1675 Observatory Drive, Madison, Wisconsin 53706

Ramin Pashaie

University of Wisconsin-Milwaukee, Electrical and Computer Engineering Department, Milwaukee, Wisconsin 53211

J. Biomed. Opt. 19(7), 075001 (Jul 04, 2014). doi:10.1117/1.JBO.19.7.075001
History: Received April 14, 2014; Revised June 4, 2014; Accepted June 5, 2014
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Abstract.  Predicting the distribution of light inside any turbid media, such as biological tissue, requires detailed information about the optical properties of the medium, including the absorption and scattering coefficients and the anisotropy factor. Particularly, in biophotonic applications where photons directly interact with the tissue, this information translates to system design optimization, precision in light delivery, and minimization of unintended consequences, such as phototoxicity or photobleaching. In recent years, optogenetics has opened up a new area in deep brain stimulation with light and the method is widely adapted by researchers for the study of the brain circuitries and the dynamics of neurological disorders. A key factor for a successful optogenetic stimulation is delivering an adequate amount of light to the targeted brain objects. The adequate amount of light needed to stimulate each brain object is identified by the tissue optical properties as well as the type of opsin expressed in the tissue, wavelength of the light, and the physical dimensions of the targeted area. Therefore, to implement a precise light delivery system for optogenetics, detailed information about the optical properties of the brain tissue and a mathematical model that incorporates all determining factors is needed to find a good estimation of light distribution in the brain. In general, three measurements are required to obtain the optical properties of any tissue, namely diffuse transmitted light, diffuse reflected light, and transmitted ballistic beam. In this report, these parameters were measured in vitro using intact rat brain slices of 500 μm thickness via a two-integrating spheres optical setup. Then, an inverse adding doubling method was used to extract the optical properties of the tissue from the collected data. These experiments were repeated to cover the whole brain tissue with high spatial resolution for the three different cuts (transverse, sagittal, and coronal) and three different wavelengths (405, 532, and 635 nm) in the visible range of the spectrum. A three-dimensional atlas of the rat brain optical properties was constructed based on the experimental measurements. This database was linked to a Monte Carlo toolbox to simulate light distribution in the tissue for different light source configurations.

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© 2014 Society of Photo-Optical Instrumentation Engineers

Citation

Mehdi Azimipour ; Ryan Baumgartner ; Yuming Liu ; Steven L. Jacques ; Kevin Eliceiri, et al.
"Extraction of optical properties and prediction of light distribution in rat brain tissue", J. Biomed. Opt. 19(7), 075001 (Jul 04, 2014). ; http://dx.doi.org/10.1117/1.JBO.19.7.075001


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