Method and apparatus for adjustable frequency scanning in ultrasound

Abstract

Method for scanning a field of view using a scan format, wherein the carrier frequency of the imaging pulse is higher in the center of the field of view than at the edges. The frequency variation can be accomplished on transmit by modulating appropriately delayed programmable initial waveform information samples with a programmable carrier frequency. This results in a pulse transmitted into the body whose frequency is highest in the center portion of the scan, and is reduced in a controlled fashion as the steering angle is increased in order to mitigate grating lobe artifacts. The technique preserves signal energy because modulation merely translates the signal in frequency substantially without modification of the pulse shape itself. The technique is also useful on receive, wherein demodulation to or near baseband followed by post-beamformation pre-detection remodulation can correct for systematic scan-line-to-scan-line phase variations to ensure scan-line-to-scan-line phase coherency for subsequent coherent processing across scan lines or for coherent image formation using the phase and amplitude information from multiple beams.