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Hybrid optoacoustic and ultrasound imaging in three dimensions and real time by optical excitation of a passive element

Pulse-echo ultrasound and optoacoustic imaging possess very different, yet highly complementary, advantages of mechanical and optical contrast in living tissues. Integration of pulse-echo ultrasound with optoacoustic imaging may therefore significantly enhance the potential range of clinical applications. Nonetheless, efficient integration of these modalities remains challenging owing to the fundamental differences in the underlying physical contrast, optimal signal acquisition and image reconstruction approaches. We report on a new method for hybrid three-dimensional optoacoustic and pulse-echo ultrasound imaging based on passive generation of ultrasound with a spherical optical absorber, thus avoiding the hardware complexity of active ultrasound generation. The proposed approach allows for acquisition of complete hybrid datasets with a single laser interrogation pulse, resulting in simultaneous rendering of ultrasound and optoacoustic images at a rate of 10 volumetric frames per second. Real time image rendering for both modalities is enabled by using parallel GPU-based implementation of the reconstruction algorithms. Performance is first characterized in tubing phantoms followed by in vivo measurements in healthy human volunteers, confirming general clinical applicability of the method.