ABSTRACT
This chapter discusses the principles and applications of an emerging biomedical imaging technique termed photoacoustic imaging. The basic principle centers on the physics of sequence of events: A pulse laser light energy illuminates on a living tissue results in a temperature change (heat), which leads to a pressure change that subsequently converted to an acoustic wave to be captured by an ultrasound probe. In short, it is a “light in sound out” process. The significant advantage of photoacoustic imaging over other optical imaging rests on the unique characteristics of acoustic wave in minimum light scattering, resulting in higher spatial resolution of image production. In this chapter, the mathematical equations governing the photoacoustic wave formation are delineated and explained. The potential clinical applications in assisting disease diagnosis and treatment are discussed. Although some limitations, such as depth, speed, and quantitation, existed for photoacoustic imaging technique, its ability to provide a mapping for both endogenous substances (hemoglobin, melanin, fat, water) and exogenous agents (dye, fluorescence, nanoparticles) gives it a substantial advantage over other optical imaging techniques as it can provide functional and molecular information. Furthermore, photoacoustic imaging can be combined with other techniques to give even greater power of medical imagery.
