Optical computed tomography for biomedical objects based on coherent detection imaging method

Abstract

This paper summarizes a series of studies aiming at realization of computed tomography imaging (CT) by laser beam for actual in vitro biological samples, which is the first successful trial achieved in the world. The method is realized first by image reconstruction, which detects and selects only the weak transmitted light component buried in stronger multiple scattered light, using the optical heterodyne detection with a very high directivity and sensitivity. This is called coherent detection imaging (CDI). To realize the optical CT using the laser light based on the projection theorem, the following three conditions should essentially be satisfied: (1) The direct‐transmitted light component in the biological system with multiple scattering should accurately be selected and detected. (2) The Lambert‐Beer law should be applied to the selectively detected direct‐transmitted light component. (3) There must exist a direct‐transmitted light component in the medium with complex distribution of refraction index as well as complex boundaries. The authors examined the medium in which the sample is buried and cannot be observed, not only by the naked eye but also by the traditional direct detection method. It was verified experimentally that the three conditions for the realization of the optical CT are applicable, and it was demonstrated that optical CT imaging is feasible for actual samples using the CDI method.