Large aperture phase error measurement and effects

Clinical measurements and computer simulations were conducted to determine the effects of phase errors on image quality in large aperture systems. Using a 3.5-MHz 24.5-mm receive aperture, phase errors were measured across the left breasts of female volunteers at the Duke University Medical Center. These results were compared to results from the authors´ previous studies with small aperture systems. Using a beamforming computer program, point spread functions (PSFs) were generated in the presence of the measured phase error profiles. Data from sections of the aperture were used to demonstrate that phase aberration causes more severe degradation as aperture length increases. Highly similar phase error profiles (correlation coefficient=0.98) were found to produce quite different PSFs (correlation coefficient=0.66) for large aperture systems