Non-uniqueness in fluorescence-enhanced continuous wave diffuse optical tomography

Fluorescence imaging is an attractive imaging modality for understanding biological mechanisms. Among such techniques, continuous wave fluorescence-enhanced diffuse optical tomography (CW-fDOT) is interesting since it is adapted to CCD cameras which allow non-contact measurements on a large number of detection elements for low cost. Here, by extending the derivations previously applied to continuous wave diffuse optical tomography (CW-DOT), we demonstrate that multiple optical configurations may lead to the same sets of optical measurements. We first explain in a ideal case and then in a 'real-world' example when such situations happen. Therefore, one cannot absolutely quantify the fluorescence amount from CW-fDOT measurements without adding priors.