Acoustic Nonlinear Behaviour of Microbubble Contrast Agent

We have investigated the nonlinear characteristics of a microbubble contrast agent Sonazoid (Nycomed,Norway),including the second,thire,1/2-order,3/2-order and 5/2-order harmonics,We have measured the 1/2-order subharmonic response to different transmission sound pressures.We have found that subharmonic signals connot be generated until the acoustic pressure reaches a certain value,which is the most different subharmonic from high harmonics,This results is favourable for the further study of the subharmonic in the bubble liquid.The 3/2-order ultraharmonic response to acoustic pressure was also measured.