A SPECKLE TARGET ADAPTIVE IMAGING TECHNIQUE IN THE PRESENCE OF DISTRIBUTED ABERRATIONS

Acoustic velocity inhomogeneities in tissue result in aberration of ul trasound images. These aberrations can be modeled as a near field thin phase screen or as a distributed aberrator. The effect of a near fiel d thin phase screen is to time shift the received echo at each element , while distributed aberrators result in both pulse distortions and ti me shifts from element to element. Most current techniques for the cor rection of distributed aberrators are limited to application on point targets. A new technique is proposed which uses multiple transmits fro m spatially shifted transmit apertures (the translating transmit apert ure algorithm), in conjunction with phase conjugate filters, to correc t for distributed aberrations in the presence of speckle targets. The performance of the translating transmit aperture algorithm in improvin g the correlation between signals received by elements of different sp atial separations is measured, and factors affecting the performance o f this technique are investigated in simulation and experiment.