| 摘要 |
The most common method of determining whether a breast contains cancerous tissue utlizes ionizing radiation, i.e. x-rays, which possibly have tissue damaging properties. Ultrasound and transillumination using visible and non-visible light have been proposed as safe alternatives to x-radiation. It has been found that lasers can be used as a light source in a breast tissue transillumination process. However, due to the high scattering coefficient (or diffusing properties) of breast tissue, it is not possible to obtain images having good resolution using classical transillumination techniques, even when a laser is used as a light source. When passing through a diffusing medium, a laser pulse decomposes into three classes of photons, namely ballistic, snake-like and diffuse photons. In most practical situations, the ballistic photon portion of a laser pulse (1), which travels in a straight line, does not pass through the tissue, i.e. only snake-like (2) and diffuse photons (3) pass through the tissue. It has been suggested to use the natural temporal separation of light passing through highly dispersing medium to separate the snake from the diffuse photons using time-gating techniques. The diffuse photons are then disregarded. Rather than discarding the diffuse photons, it is proposed by this invention to use both the snake-like and diffuse photons in a method involving time gating and multiple field of view techniques to obtain a more precise evaluation of the scattering coefficients, i.e. a map of the interior of a region of a sample, whereby the presence (or absence) of tumors is determined. The use of multiple field of view and time gating techniques will yield a relatively clear picture of the structure of the tissue.
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