Figure 1.

Principles of photoacoustic imaging (PAI) presented for a potential clinical application: diagnostic breast imaging by integrated real-time photoacoustic/ultrasound imaging. The laser sends nano-second pulses of near-infrared light through the transducer into the tissue. This light is then absorbed inside the tissue (at different levels for each tissue type/component) causing a localized transient thermoelastic expansion. This expansion leads to the emission of pressure waves (ultrasound), which can be detected by the array in the transducer. Finally, a photoacoustic image is calculated and displayed in real-time. At the same time, the ultrasound system can be used in its b-mode to provide structural information about the tissue, in addition to the functional/molecular information obtained by PAI, and both images can be displayed on the view