Spatial Resolution of a Focused Array Transducer for Laser Optoacoustic Tomography

Theoretical and experimental investigations of the point spread function of a focused array transducer of 32 elements for laser optoacoustic (OA) tomography have been carried out. The elements were imposed in the radial plane of a cylindrical surface. Specially developed software was used for numerical modeling of the problem of OA tomography. A diode-pumped, Q-switched Nd:YAG laser was employed for ther-mooptical excitation of probe acoustic transients. Maps of the spatial sensitivity for transducers with aperture angles of 30° and 60° were determined experimentally and theoretically. The possibility of localization of the array sensitivity area at the beam waist in the plane perpendicular to the imaging plane has been shown. The back projection algorithm was employed for image reconstruction based on experimentally obtained OA transients from point sources located at different distances from the array. The transverse and longitudinal resolutions in the imaging plane for the array were determined.