Medical Imaging with Light

Imaging of scattering media such as tissue using light provides the potential to achieve safe and inexpensive instruments and allows for the use of spectroscopy. I describe some fundamental aspects of optical imaging in scattering media and discuss the information that can be obtained by recording elastically scattered light. I describe two complementary approaches, one based on the coherence properties of light, where speckle occurs, and the other which neglects coherence at optical frequencies and employs diffusion modeling, which forms the basis of optical diffusion tomography. Imaging through many centimeters of tissue is then possible. Optical contrast can be enhanced through fluorescence, and, with targeting, high sensitivity is possible. A clinical instrument would be driven by a disease detection or health monitoring capability not provided by other modalities.