Imaging objects in tissue like media with optical tagging and the diffuse photon differential transmittance

In a proof-of-concept experiment, we optically tagged objects embedded in an inhomogeneous and multiple-scattering medium and measured the difference between the transmitted diffuse photons at two optical wavelengths, one at and the other off a sharp absorption peak of the exogenous contrast agent. We demonstrated that the visibility of tagged objects was significantly enhanced hi comparison with that of untagged objects. From our analysis it seems possible to use dual-wavelength differential transmittance spectrometry together with monoclonal-antibody-delivered optical contrast agents to detect tumors as small as 0.1-0.3 cm in size and embedded as deeply as a few centimeters beneath a tissue sm face. (C) 1997 Optical Society of America.