The probability that a scattered wave with unit amplitude (in arbitrary units) is measured at the th detector at instant can be expressed as:8Display Formula
(1)where is a constant that depends on the characteristics of the scatterers and is the instant at which a wave generated at (inside ) and scattered at (inside ) arrives at the th detector. The probability that the signal captured at the th detector at instant corresponds to a direct (uninterrupted) propagation is given by 7: Display Formula
(2)where being the probability that the signal captured at the th detector at instant is distorted due to acoustic scattering. As the distortion in the signal is produced when the amplitude of the scattered wave is above the noise level, we consider that is proportional to [Eq. (1)] and can be estimated via:8Display Formula
(3)where is a weighting parameter that depends on the internal object’s features to be determined heuristically. corresponds to the histogram yielded by means of the Monte Carlo method by randomly generating pairs of points in and , respectively.