Emerging clinical applications of photoacoustic imaging

Photoacoustic (PA) or optoacoustic imaging is a relatively new imaging modality based on the detection of light-excited ultrasound waves, has emerged as one of the most exciting research areas in biomedical imaging over the past decade [1-4]. In PA imaging, nanosecond pulsed (or modulated) electromagnetic radiation is delivered into tissues to excite ultrasound waves via photon absorption and thermos-elastic expansion. Subsequently ultrasound detection and image reconstruction are performed to generate an image of tissue optical absorption. This hybrid imaging technique thus combines advantages from both optical and ultrasound imaging, by encoding discriminative optical absorption contrast into ultrasound waves. Furthermore, PA imaging is capable of scaling its spatial resolution and imaging depth, enabling imaging of subjects ranging from organelles, cells, tissues, to organs, and with spatial resolution ranging from submicrometres to sub-millimetres. As such, PA imaging holds tremendous potential for a wide range of clinical applications.