Imaging scattering media from a distance: Theory and applications of noncontact optical tomography

Optical tomography of turbid media, has been largely limited to systems that require fixed geometries or measurements employing fibers. Noncontact optical measurements from diffuse media, could facilitate the use of large detector arrays at multiple angles that are well-suited for tomography applications. Such imaging strategies eliminate the need for individual fibers in contact with the highly scattering volume, the use of restricted geometries and the need for matching fluids. Here we review the different approaches and systems developed for noncontact optical measurements and concurrent registration of the three-dimensional surface information of the diffuse medium. We present the basic theoretical formulation and its experimental validation, finally applying it to the specific case of fluorescence tomography of small animals. We discuss how these new technologies can considerably simplify experimental procedures and improve our ability to visualize functional and molecular processes in vivo. Future perspectives and work are also outlined.