Optoacoustic (OA) imaging will experience broadest clinical application if implemented in epi-style with the irradiation optics and the acoustic probe integrated in a single probe. This will allow most flexible imaging of the human body in a combined system together with echo ultrasound (US). In such a multimodal combination, the OA signal could provide functional information within the anatomical context shown in the US image, similar to what is already done with colour flow imaging. Up to date, successful deep epi-OA imaging was difficult to achieve, owing to clutter and acoustic aberrations. Clutter signals arise from strong optical absorption in the region of tissue irradiation and strongly reduce contrast and imaging depth. Acoustic aberrations are caused by the inhomogeneous speed of sound and degrade the spatial resolution of deep tissue structures, further reducing contrast and thus imaging depth. In past years we have developed displacement-compensated averaging (DCA) for clutter reduction based on the clutter decorrelation that occurs when palpating the tissue using the ultrasound probe. We have now implemented real-time DCA on a research ultrasound system to evaluate its clutter reduction performance in freehand scanning of human volunteers. Our results confirm that DCA significantly improves image contrast and imaging depth, making clutter reduction a basic requirement for a clinically successful combination of epi-OA and US imaging. In addition we propose a novel technique which allows automatic full aberration correction of OA images, based on measuring the effect of aberration spatially resolved using echo US. Phantom results demonstrate that this technique allows spatially invariant diffraction-limited resolution in presence of a strong aberrator.

Date Published: 3 March 2014
PDF: 10 pages
Proc. SPIE 8943, Photons Plus Ultrasound: Imaging and Sensing 2014, 89430Q (3 March 2014); doi: 10.1117/12.2058125

Published in SPIE Proceedings Vol. 8943:
Photons Plus Ultrasound: Imaging and Sensing 2014
Alexander A. Oraevsky; Lihong V. Wang, Editor(s)