Focused array transducer for 2D OA tomography

Theoretical and experimental investigations of point spread function of focused 32 elements array transducer 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 the problem of OA tomography. Diode-pumped Q-switched Nd:YAG laser was employed for thermo-optical excitation of probe acoustic transients. The correspondence between numerically calculated and measured temporal profiles of acoustic transients detected by a single transducer over wide area around it focal zone was demonstrated. The maps of spatial sensitivity for transducers with aperture angles 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. 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 size of the images allowed to determine transverse and longitudinal resolutions in the imaging plane.