Average Value Method: A New Approach to Practical Optical Computed Tomography for a Turbid Medium Such as Human Tissue

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Abstract
We propose a new algorithm for optical computed tomography to determine the concentrations of absorber in turbid media such as human tissue. Our method does not require the measurement of a reference phantom, so that it is free from significant errors caused by geometric and structural differences between the target and reference media. We use an imaginary reference medium for which the optical properties are specified by the average or quasi-average values measured for the real target medium. Since we can calculate the weight function and re-emission for such an imaginary medium, tomographic images can be reconstructed based on the difference in values measured for the target medium and determined for the imaginary reference. The validity of our method was confirmed by measuring an 80-mm-diameter cylindrical, tissue-like phantom containing three different absorbers. The image quality such as image distortion and the capability for quantifying the concentrations of absorber are also discussed.