Scattering Characteristics of Photon Density Waves from an Object Embedded in a Spherical Two-layer Turbid Medium

Y. Yao et al. (1995)


We present an analytic solution to the amplitude and phase distributions of photon density waves in strongly scattering, spherically symmetric, two-layer media containing a spherical object. The normal mode series method is employed to solve the inhomogeneous Helmholtz equation of the outer layer when the object is present to when it is absent, we evaluate the potential sensitivity of an optical imaging system to inhomogeneities in absorption and scattering. For four types of background media which are different in their absorption and scattering properties, we determine: i) the modulation frequency that achieves an optimal compromise between signal detection reliability and sensitivity to the presence of object; ii) the minimum detectable object radius; iii) the smallest detectable change in its absorption coefficient; and iv) scattering coefficient for a fixed object size. A discussion of the qualitative and quantitative findings is given.