For clinical combined optoacoustic (OA) and ultrasound (US) imaging, maximum flexibility is provided when irradiation optics and ultrasound detector are integrated in one handheld probe. The drawback of this epi-illumination geometry is the relatively high laser intensity close to the ultrasound probe. This generates strong background signals that clutter the OA image, thus limiting imaging depth (see Figure, phantom study). We investigate various different techniques for clutter reduction, among them localized vibration tagging (LOVIT): A long pulsed ultrasound beam generates acoustic radiation force (ARF) that induces localized tissue displacement at its focus. Subtraction of OA images acquired before and after the ARF push preserves true OA signal in the displacement focus while eliminating the clutter background (see Figure). We are implementing a clinically realistic setup where the same linear array probe is used both for imaging and ARF generation.
