Textbook in PDF format Photoacoustic imaging (also called optoacoustic imaging) is a hybrid modality based on the generation and detection of ultrasound in response to optical absorption of tissue. It combines advantages from both optical and ultrasound imaging, providing functional, molecular and microstructural information of tissue at scalable spatial resolution and depth. This technology has undergone exponential growth over the last two decades, and it is now widely viewed as one of the most exciting biomedical imaging modalities