Multimodal Optoacoustic Imaging

Optical imaging is one of the oldest and most frequently used imaging techniques. Even though the first optical imaging device, the light microscope, has been invented around 1590, the human eye has served the same purpose for centuries before that. With the advent of new technologies, such as efficient electronics, powerful lasers, sensitive detectors, and high-precision optics, it became possible to improve the quality of the acquired images and to leverage physical phenomena that were previously inaccessible. For example, the introduction of femtosecond lasers enabled the exploitation of nonlinear optical phenomena, including higher harmonic generation or two-photon absorption, for high-resolution imaging. Similarly, with advances in ultrasound detection technology, phenomena such as the optoacoustic (photoacoustic) effect became effectively utilizable, which is the centerpiece of this chapter. With its resurrection in 1981, optoacoustics became a mainstream noninvasive imaging technology. The strength of optoacoustic imaging is that it enables biomedical imaging at multiple scales, from macroscopy all the way down to microscopy. Additionally, it readily allows for the combination with other imaging modalities. Based on the optoacoustic phenomenon, multiple imaging systems were introduced in the last decades, and this technology has been used for a multitude of applications, such as neuroimaging and cancer research.