A novel Fourier transform based reconstruction algorithm for solving the inverse problem in optoacoustic imaging is presented, which improves reconstruction efficiency and image quality. Fourier algorithms make use of an interpolation law when signal Fourier components are mapped to source Fourier components. To overcome inadequacies affiliated with interpolation methods such as nearest neighbour, linear, cubic or spline interpolation, together with signal data zero padding, we present a regularized interpolation method based on a forward model explicitly formulated for the compactly supported signal data. Simulations performed on a digital tissue phantom reveal the potential of this novel reconstruction method, which results in images of enhanced quality but without the need of using time-consuming zero-padding.

Photoacoustic imaging, based on ultrasound detected after laser irradiation, is an extension to diagnostic ultrasound for imaging the vasculature, blood oxygenation and the uptake of optical contrast media with promise for cancer diagnosis. For versatile scanning, the irradiation optics is preferably combined with the acoustic probe in an epi-style arrangement avoiding acoustically dense tissue in the acoustic propagation path from tissue irradiation to acoustic detection. Unfortunately epiphotoacoustic imaging suffers from strong clutter, arising from optical absorption in tissue outside the image plane, and from acoustic backscattering. This limits the imaging depth for useful photoacoustic image contrast to typically less than one centimeter. Deformation-compensated averaging (DCA), which takes advantage of clutter decorrelation induced by palpating the tissue with the imaging probe, has previously been proposed for clutter reduction. We demonstrate for the first time that DCA results in reduced clutter in real-time freehand clinical epiphotoacoustic imaging. For this purpose, combined photoacoustic and pulse-echo imaging at 10-Hz frame rate was implemented on a commercial scanner, allowing for ultrasound-based motion tracking inherently coregistered with photoacoustic frames. Results from the forearm and the neck confirm that contrast is improved and imaging depth increased by DCA.

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