FREQUENCY-DOMAIN IMAGING OF ABSORBERS OBSCURED BY SCATTERING

Multiple pixel, frequency domain measurements of phase shift, theta, and modulation, m, in a phantom containing an absorber obscured by a relatively non-absorbing scattering solution are presented in combination with a theory of photon migration imaging. Results employing a single point source show that two dimensional theta measurements made in the presence (theta(presence)) and in the absence (theta(absence)) of an absorber can be used to create DELTAtheta images. DELTAtheta (theta(absence) - theta(presence)) images can be used to detect as well as locate the three dimensional position of the absorber. Images of m(presence) measured in the presence of the absorber normalized by m(absence) also provided detection and two dimensional location of its position. Images of % m(presence)/m(absence) at higher modulation frequencies provided greater resolution as predicted by photon migration theory. Neither theta nor m images alone could be used to detect or locate the presence of the absorber.