  Ultrasound-modulated optical tomography (UOT) is a technique that images
optical contrast deep inside scattering media. Heterodyne holography is a
promising tool able to detect the UOT tagged photons with high efficiency. In
this work, we describe theoretically the detection of the tagged photon in
heterodyne holography based UOT, show how to filter the untagged photon, and
discuss the effect of shot noise. The discussion considers also speckle
decorrelation. We show that optimal detection sensitivity can be reached, if
the frame exposure time of the camera used to perform the holographic detection
is of the order of the decorrelation time.
