Phase aberration correction using near-field signal redundancy. I.Principles [Ultrasound medical imaging]

摘要

The signal redundancy principle in the near field is analyzednquantitatively. It is found that common midpoint signals are notnidentical (or redundant) for echoes coming from arbitrary targetndistributions in the near field. A dynamic near-field correction isnproposed to reduce the difference between common midpoint signals fornechoes coming from the region of interest. When phase aberrations arenpresent, it is shown that the dynamic correction can generally be donenassuming no phase aberration, and the relative time-shift between commonnmidpoint signals can be used to measure phase-aberration profiles. Anphase-aberration correction algorithm based on that principle isnproposed. In this algorithm, after common midpoint signals are collectednthey are dynamically corrected for near-field effects andncross-correlated with one another. In a related way, the phase errorsnare measured from peak positions of these cross-correlation functions.nThe phase-aberration profile across the array is derived from thesenmeasurements. The relationship between the errors in the derived phasenaberration profile and the errors in the measured relative time-shiftnbetween common midpoint signals is derived. A method for treating thensituation of different transmission and reception phase-aberrationnprofiles is also proposed. This algorithm works for general targetndistributions, iteration is not required, and it can be used in othernnear-field, pulse-echo, imaging systems