Abstract: A phased array ultrasonic imaging system performs a scan in which beamforming time delay errors due to nonuniformity in ultrasound speed within the transmission medium are corrected by estimating and correcting phase aberrations in accordance with the maximum likelihood theory. The system employs a multiple-channel transmitter and receiver, and estimates phase values, not phase difference values, thereby eliminating any need to perform an integration to produce the phase aberration profile. The method can be implemented in real-time, allowing correct data to flow out of the circuit which at the same time can be receiving new input data. Delays can be added to allow for phase aberration correction of past measurements. The method allows tracking, to some extent, of variations that may occur in the phase aberrations. Depending on the number of channels that are simultaneously considered, different closed loop circuits can be employed.

Abstract: An ultrasonic imaging system for performing a scan in which beamforming time delay errors due to nonuniformity in ultrasound propagation speed within the transmission medium are corrected. The system employs a multiple-channel transmitter and receiver. The method estimates and corrects phase aberrations in phased array imaging systems, taking into account additional information associated with array elements which are not necessarily adjacent to each other. The method uses Kalman filtering to obtain an estimate of the phase differences associated with complex samples of pairs of adjacent receive channels. The method incorporates a scheme to detect and correct for the 2.pi. phase slips that may occur in the data. Because the method provides information on measurement variances, better estimates are obtained by weighting the measurements according to their variances.