Realtime adaptive imaging

Sound speed variations within the human body degrade contrast and resolution in ultrasound images. Many algorithms have been proposed to compensate for these variations, but few have been tested on human subjects. We describe a programmable, adaptive imager that allows the realtime implementation of a wide class of algorithms, those which modify the imager's beamforming based upon individual transducer signals. A GE LOGIQ 700 imager is connected to a commercial multiprocessor system. The imager's channel data are captured in the multiprocessor system, which calculates arrival time errors for each beamforming channel. These errors are used to correct the imager's beamforming time delays at the acoustic frame rate. We describe an algorithm which iteratively estimates time-delay errors by correlating the signal from each element in a multirow transducer with the beamsum signal. The system successfully corrects for two-dimensional model aberrations during realtime scanning of tissue-mimicking phantoms and human subjects.