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Two-dimensional optoacoustic tomography of large-scale phantoms

The aim of present report is to demonstrate some new approaches in OA imaging. An optoacoustic (OA) method for non-invasive diagnostics allows to detect inhomogeneities (defects) differing from surrounding tissues with their optical absorption -- the only way to obtain information about optical properties of deep tissue layers. An experimental setup for 2D OA imaging includes pulsed light source (Nd:YAG laser), a set of acoustical receivers with amplifiers, computer-based system for data acquisition and scanning control and specialized software for image reconstruction. We used quasi-resonant ultrasonic receivers in 2-5 MHz frequency range with various directivities. Various methods of OA scanning: mechanical rotating transmission system, set of fixed low-directive receivers, transducer phased arrays and single-probe mechanical angle scanners -- have been studied and discussed. Artificial phantoms simulating biological tissues were used in the experiments as well as samples of real soft tissues. Experimentally obtained OA tomograms of phantoms containing optical inhomogeneities have acceptable contrast; measured geometrical dimensions correspond to real object parameters. The results of the performed investigation have been showed that angular scanning system is preferable for OA imaging of human organs because it provides one-side access to the body and is based on ultrasonic transducers widely used in ultrasonic imaging. This work was supported by Russian Foundation for Basic Research (Projects # 00-02-16600, 03-02-17042) and 6th competition-expertise of young scientists of Russian Academy of Sciences (Project #399).