Apparatus and methods are provided including directing acoustic radiation toward a region of interest within a subject's body. Light is transmitted from a light emitter to a light detector such that a first light portion is transmitted without passing through the subject's tissue, and a second light portion is transmitted via the region of interest. Scattered light of the second light portion contains a tagged component corresponding to photons tagged by the acoustic radiation, and an untagged component corresponding to photons untagged by the acoustic radiation. Light of the first light portion undergoes an interaction with light of the second light portion at the light detector. A property of tissue of the region of interest is determined, by decoupling from each other the tagged and untagged components of the second light portion, based upon the interaction between the light of the first and second light portions.
