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Journal of Biomedical Optics • Open Access

Time-gated optical system for depth-resolved functional brain imaging

Paper Abstract

We present a time-domain optical system for functional imaging of the adult head. We first describe the instrument, which is based on a Ti:Sapphire pulsed laser (wavelength 750–850 nm) and an intensified CCD camera enabling parallel detection of multiple fibers. We characterize the system in terms of sensitivity and signal-to-noise ratio, instrument response function, cross-talk, stability, and reproducibility. We then describe two applications of the instrument: the characterization of baseline optical properties of homogeneous scattering media, and functional brain imaging. For the second application, we developed a two-part probe consisting in two squares of 4×4 sources and 3×3 detectors. The laser source is time-multiplexed to define 4 states of 8 sources that can be turned on during the same camera frame while minimizing cross-talk. On the detection side, we use for each detector 7 fibers of different lengths creating an optical delay, and enabling simultaneous detection in 7 windows (by steps of 500 ps) for each detector. This multiple window detection allows depth sensitivity. The imaging probe was tested on dynamic phantoms and a preliminary result on an adult performing a motor task shows discrimination between superficial and cortical responses to the stimulus on both hemispheres.

Paper Details

Date Published: 1 July 2006
PDF: 13 pages
J. Biomed. Opt. 11(4) 044008 doi: 10.1117/1.2337320
Published in: Journal of Biomedical Optics Volume 11, Issue 4
Show Author Affiliations
Juliette J. Selb, Massachusetts General Hospital (United States)
Danny Kalathil Joseph, Massachusetts General Hospital (United States)
David A. Boas, Massachusetts General Hospital (United States)

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