WAVE-FRONT AMPLITUDE DISTRIBUTION IN THE FEMALE BREAST

Ultrasound measurements of a large population of wavefronts transmitte d through female breasts at 3 and 4 MHz show that the wavefront amplit ude distribution is close to Rayleigh. This finding is consistent with a fully developed scatter field, implying that the scatter energy rem oved from the coherent incident beam dominates the wavefront. The wave front received from an inhomogeneous medium is the superposition of an incident wave plus a scattered wave. If the scattered field is weak, the received field is dominated by the incident field and the wavefron t amplitude distribution is Rician. If the scattered field is strong, the received field is primarily the scattered field and the wavefront amplitude distribution is Rayleigh. If, in addition to scattering, ref raction between bodies of different refractive indexes occurs, the tot al net effect on the wavefront amplitude distribution is the same as f or strong scattering. This is what we have observed in the highly refr active female breast. This result has implications for the design of h igh lateral-resolution echo scanners that will incorporate adaptive ph ase deaberration algorithms. The published algorithms were developed f or weak scattering and therefore may not be powerful enough. Alternati ves have to be found to deaberrate the severe wavefront distortion in the breast.