Improved ultrasound contrast detection combining harmonic power Doppler with a release-burst

Harmonic power Doppler (HPD) is sensitive for detecting ultrasound contrast agents. In HPD, multiple pulses are transmitted along each beam in the image, and changes from pulse to pulse are detected. The sensitivity of HPD relies on efficient destruction of the contrast agent. Destruction increases with amplitude and pulse length, but amplitude is bounded by safety limitations while long pulses degrade spatial image resolution. To circumvent the implicit trade-off between detection sensitivity and imaging resolution in HPD, the authors propose to combine HPD with a single high energy ultrasound pulse (the release-burst, RE). A few detection pulses are transmitted first, followed by the RE and a second series of detection pulses. The authors propose to combine the pulse sequence with a special polynomial prediction filter to remove clutter. The method has been tested in vitro in a capillary phantom using three different contrast agents, and compared to HPD. The results indicate that the RE can improve the sensitivity of HPD for all agents, also in presence of moving tissue.