Adaptive correction of the effects of propagation through inhomogeneous tissue is critical to the improvement of current ultrasonic imaging systems. Currently, estimation and correction of time-delay errors is more feasible than other more sophisticated approaches. Data acquisition, time-delay estimation and compensation have been implemented on the SONOLINE Elegra system using the system CPU, the Crescendo image processor, and the existing front-end electronics. Experimental results with this implementation will be reported. The effects of compensating the transmit beam is studied using the waveform similarity factor and single transmit imaging. On an RMI404 phantom plus a 1-D aberration layer with a rms time fluctuation of 40 ns and correlation length of 5 mm, the waveform similarity factor of randomly scattered waveforms improved from 0.362 to 0.477 by iteration. Correspondingly, the −20 dB lateral resolution improved from 1.62 to 0.77 mm, and the image contrast improved by 8.5 dB (speckle region is 6 dB brighter while echo-free region is 2.5 dB darker). Experiments with a 2-D aberration layer and with a special phase aberration phantom showed less image improvements. Preliminary body scans with adaptive imaging showed improved image contrast and details in some cases but the results are mixed and influenced by such factors as isoplanatic patch size and complex scattering structures. [Study partially supported by NIH R29 CA81688.]

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