The measurement of attenuation in nonlinearly attenuating media by the zero crossing method.

A closed form expression relating the zero crossing density to the material parameters of media with nonlinear frequency dependent attenuation is derived for the case of Gaussian excitation. This expression indicates that for tissues which exhibit a small degree of such nonlinearity, significant errors in the determination of the material parameter result if the nonlinearity is ignored. This result is similar to that shown earlier [Narayana and Ophir (1983) Ultrasound in Med. & Biol. 9, 357-361] for frequency shift techniques.