Method of ultrasound imaging in which vibration-induced localised (LOVIT) displacements code the ultrasound signal at the place of origin, enabling clutter cancellation. The require displacements can be induced by an acoustic radiation force (ARF) generated by an ultrasonic focused beam. One possibility for ARF-LOVIT is to acquire one photoacoustic (PA) image prior to the ARF push, and a second image immediately after the push when the non-zero displacement transient at the focus region is present. A difference image then highlights the signal from optically absorbing structures located inside the displacement region. Direct clutter, in contrast, originates from outside the imaged region where no displacement occurs, and is thus estimated. Echo clutter from acoustic scattering at echogenic structures inside the displacement region also shows up on the difference image, but at a different depth from where it was generated owing to the additional acoustic round-trip time as compared to PA signals.
