Simultaneous Photoacoustic and Laser-Induced Ultrasound Imaging of Animals and Humans via a Semi-Transparent Ultrasound Transducer

Combined photoacoustic (PA) and ultrasound (US) imaging, a promising modality for preclinical and clinical studies, can provide anatomical, physiological, and molecular information about biological tissues. However, common implementations of US imaging require an external pulser to transmit US waves, which makes integrated PA/US imaging systems relatively complicated and suboptimal. Here, without using a US pulser, simultaneous PA and laser-induced US (LUS) imaging is demonstrated through a semi-transparent ultrasound transducer (sTUT). Some portion of excitation laser energy is converted to US waves when the beam passes through the sTUT, transmitting the focused US waves to targets. The other portion of light is directly delivered to the tissues to generate PA signals. This integrated bimodal approach not only eliminates the need for an electrical-pulser but also allows the sTUT to be incorporated with a preamplifier to increase the PA signal-to-noise ratio. Further, the light, compact sTUT is easily integrated as part of a handheld PA/LUS system for in vivo studies of small animals and humans. Here, it photoacoustically and ultrasonically visualize not only different structures and functions of small animals but also human skin structures. The simplified handheld PA/LUS microscopic imaging system has great potential for broadband preclinical and clinical studies.