Photoacoustic Tomography System

Abstract

Based on the pulsed photoacoustic effect, we set up an experimental system to obtain bi-dimensional images ofoptically-opaque samples embedded within the bulk of turbid medium. The turbid medium was made of agar gelmixed with single-sized nanoparticles; with these materials we induce an optical absorption and an optical scatteringlike that appearing in human tissues. The PA signals are generated from the absorption processes in the buriedtarget, and then traveling through the bulk of scatter medium. The optical absorption properties and the shape oftarget, defines the amplitude and shape of the PA signals. This time the laser pulses are set from a pulsed Nd: YAGlaser, with pulse width of 10 ns, at rate repetition of 10 Hz and wavelength set at 1064 nm. The signals generated inthis way are registered by means of an ultrasonic transducer with resonance cut at 10 MHz. The sample was rotatedto obtain as many as 36 projections which are used to feed an image reconstruction forward-projection algorithmbased on the Radon Transform. As result we obtain 2D tomographic slices of three different samples.