Trial Projection of High Speed Optical Computed-Tomograph using Large Transmitted Light Image

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Optical computed tomography (Optical CT) has been expected to offer specific diagnostics information on the physiological activities and defects. However, the strong diffusion of light in biological tissues hinders the detection of projection data, i. e. the intensity of light is integrated along straight lines, which is necessary for the CT image reconstruction algorithm currently used for x-ray CT.Several methods have been proposed to detect quasi-straightforward-propagating (QSP) photons of the biological tissue. In our previous research, we investigated the method using light polarization to extract light components traveling along a nearly straight line in a diffused medium.A method utilizing light polarization was applied to take the projection data of absorbers in a highly scattering medium. The floor level of the projection data due to diffused light was significantly suppressed by detection of photons which preserved initial polarization. An optical CT image was reconstructed from the projection data taken by this method and exhibited higher special resolution than the image reconstructed from the projection data by conventional method.In summary, it was confirmed that the contrast of projection data for the optical CT was improved by the detection of transmitted light component which preserved the initial polarization as a result of suppression of the diffused light. The optical CT image of two absorbers in the test scattering medium (1.2% aqueous solution of "Intralipid 10%") 75mm thick was reconstructed from the projection data measured by the method using a phase-modulator. The two absorbers were clearly separated in the CT image, but were not separated in that reconstructed from the total transmitted intensity.