Abstract

We report the first known experimental demonstration of computer-assisted laser tomography of actual biological objects that uses coherent detection imaging (CDI) based on the optical heterodyne technique for two-dimensional resolution.¹ In order to use optical absorption tomography for biomedical applications on the basis of the projection-slice theorem, the following three conditions should be satisfied in principle: (1) Detection sensitivity must be excellent to distinguish the directly transmitted beam component from the widely spread, multiple scattering of light, (2) Lambert-Beer's law must be established for the directly transmitted beam, and (3) The directly transmitted component must be detectable, even in the presence of complex distributions and refractive-index boundaries in the media. We have experimentally verified the fulfillment of these basic conditions by means of the optical heterodyne technique and have used the CDI method in highly scattering, absorptive media in which an object is completely hidden from normal visual observation and from the conventional direct-detection technique. The first successful imaging of laser-computed tomography was achieved with actual biological objects in vitro and in vivo by means of our new CDI method. This method will provide valuable spectroscopic images over the significant thickness of biomedical objects and should be able to exploit their biochemical and physiological information by the use of tunable lasers in the near future.

© 1990 Optical Society of America