In optoacoustic imaging, short laser pulses irradiate highly scattering human tissue and adiabatically heat embedded absorbing structures, such as blood vessels, to generate ultrasound transients by means of the thermoelastic effect. We present an optoacoustic vascular imaging system that records these transients on the skin surface with an ultrasound transducer array and displays the images online. With a single laser pulse a complete optoacoustic B-mode image can be acquired. The optoacoustic system exploits the high intrinsic optical contrast of blood and provides high-contrast images without the need for contrast agents. The high spatial resolution of the system is determined by the acoustic propagation and is limited to the submillimeter range by our 7.5-MHz linear array transducer. A Q-switched alexandrite laser emitting short near-infrared laser pulses at a wavelength of 760 nm allows an imaging depth of a few centimeters. The system provides real-time images at frame-rates of 7.5 Hz and optionally displays the classically generated ultrasound image alongside the optoacoustic image. The functionality of the system was demonstrated in vivo on human finger, arm and leg. The proposed system combines the merits and most compelling features of optics and ultrasound in a single high-contrast vascular imaging device.

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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.

We investigated vapor bubbles generated upon irradiation of gold nanoparticles with nanosecond laser pulses. Bubble formation was studied both with optical and acoustic means on supported single gold nanoparticles and single nanoparticles in suspension. Formation thresholds determined at different wavelengths indicate a bubble formation efficiency increasing with the irradiation wavelength. Vapor bubble generation in Bac-1 cells containing accumulations of the same particles was also investigated at different wavelengths. Similarly, they showed an increasing cell damage efficiency for longer wavelengths. Vapor bubbles generated by single laser pulses were about half the cell size when inducing acute damage.