Laser optoacoustic imaging systems for medical tomography and sensing

This self-review of the work performed in our laboratory discusses principles and medical applications of the laser optoacoustic imaging systems (LOIS). The basic ideas of optoacoustic tomography are that (1) laser pulses may be effectively used to produce acoustic sources in tissues with enhanced optical absorption, and (2) ultrasonic waves can propagate in biological tissues with minimal distortion and deliver diagnostic information to the surface of tissue where they may be detected. We present two principal modifications of LOIS and their utilization in characterization of tissue heterogeneous and layered structures. The first is the two-dimensional system for optoacoustic tomography in a forward mode, OAT-F, where ultrasonic signal propagates towards the acoustic transducer along the axis of laser irradiation. The second is the tomography in a backward mode, OAT-B, where ultrasonic signals detected at the site of laser irradiation. OAT-B utilizes confocal optoacoustic schemes for high spatial resolution of images of up to 10-20 μm