| 摘要 |
<p>An ultrasonic diagnostic imaging method and apparatus are presented which separates broadband linear and nonlinear echo signal components while simultaneously distinguishing the effects of motion. The inventive method maps ultrasonic echo signals in the r.f. (time) domain to Doppler shift frequencies in the Doppler domain in a way that depends upon the linearity of the echoes. The inventive method does this by analyzing the phase shifts between successive echoes. Apparatus is described in which a Doppler echo ensemble is acquired by a transmit sequence of cyclically phase-varying waveforms. When the echoes of the ensemble are combined during Doppler processing, the resulting Doppler spectrum is divided into separate regions, with odd harmonics (e.g., linear signal components) residing in one region and even harmonics (e.g., second harmonic signal components) residing in another region. In a preferred embodiment a Doppler wall filter is used to delineate a particular type of signal information for processing, such as tissue motion, harmonic contrast agent, or tissue harmonic imaging information. <IMAGE></p> |
