There are many different methods being developed for generating images through tissue using light as the transmitted beam. The potential advantages are enormous: at low intensities, the procedure is safe requiring no ionizing radiation, and is therefore suitable for continuous monitoring of patients (such as those with head trauma), or for use in screening operations (such as mammography). Furthermore, the apparatus will be inexpensive when compared with MRI, CT, and PET scanners, and will have the capability of providing information about the tissue oxygenation status, rather than merely providing morphological information.
John C. Haselgrove,
"Optical imaging in a highly scattering medium", Proc. SPIE 1894, Clinical Applications of Modern Imaging Technology, (17 September 1993); doi: 10.1117/12.154963; https://doi.org/10.1117/12.154963