Breaking Limits in Photoacoustic Imaging: Deeper, Faster, and More colorful

By acoustically detecting the optical absorption contrast in biological tissues, photoacoustic imaging (PAI) has proven increasingly powerful for multi-scale anatomical, functional, and molecular imaging. In PAI, a short-pulsed laser beam illuminates the biological tissue to generate a small but rapid temperature rise, which leads to emission of ultrasonic waves due to thermoelastic expansion. The wideband ultrasonic waves are detected to form a high-resolution tomographic image that maps the original optical absorption in the tissue. My talk will focus on several major new fronts of PAI that have collectively enabled fast, deep, and high-sensitivity biomedical applications in functional neuronal imaging, drug testing, early cancer detection, and interventional therapy. First, PAI has broken the penetration limit and achieved super-deep (~10 cm) imaging by using advanced internal light delivery, extending its applications ready into internal organ imaging on large animal models. Second, by innovating novel scanning technologies, PAI has been accelerated by more than 1000 times in imaging speed with a large field of view and high spatial resolution, allowing for the monitoring of highly dynamic biological processes, particularly for brain activities. Third, by adapting novel fabrication technologies in optics and acoustics, miniaturized PAI has achieved handheld, wearable and head-mounted imaging with high spatial–temporal resolutions and high throughput. Lastly, taking advantage of switchable or tunable near-infrared photoacoustic-specific probes, PAI has improved its sensitivity and specificity by more than 1000 times, enabling highly sensitive detection of malignant cancer, tissue hypoxia, and neuronal activities.