Research projects

Near-infrared laser scanning tomography of biological tissue with CDI system

Various optical techniques that use near-infrared light based on light–tissue interactions such as scattering and absorption have been widely studied for monitoring or visualizing biological tissue noninvasively, including time-resolved measurements, the frequency-domain method,continuous-intensity measurements, and the coherence-gated method. 

  We demonstrate, what is to the best of our knowledge, a novel optical tomographic method for the visualization of the inner structure of scattering media such as biological tissue in the near-infrared region. We constructed a scanning confocal imaging system with a cross-axes arrangement using optical fibers. This system is based on the optical heterodyne technique and enables the detection of very weak

coherence photons that are generated in the spatially restricted confocal region and scattered laterally

(90°) against an incident beam. To evaluate the fundamental imaging capabilities of the system, we assessed measurements from scattering phantoms composed of an Intralipid suspension with varying volume concentrations. The results of this study demonstrate that the right-angled scattered light adheres to the Lambert–Beer law and that the present system can detect light propagating through a distance of ~31l of the mean free path. An inclusion as small as 100 mm can be discriminated in a scattering media with an optical thickness of 4. We investigated the potential of the proposed system for imaging biological tissues in preliminary experiments using samples of chicken breast tissue.


Mailing address:2-24-16, Naka-cho, Koganei, Tokyo 184-8588 JAPAN





and Systems Engineering






Tokyo University

of Agriculture

and Technology

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        Medical Photonics Group

             Biomedical Photonics Laboratory