Experimental validation of photoacoustic k-Space propagation models

Propagation models to predict the temporal output of a sensor in response to an arbitrary photoacoustically generated initial pressure distribution have been developed. k-space (frequency-wavenumber) implementations have been studied with the aim of producing fast and accurate predictions. The k-space models have several advantages. They may be implemented using the Fast Fourier transform, which makes them efficient, and the impulse response of the sensor may be straightforwardly included, which makes them more accurate. Also, there is a closely related inverse scheme - a 3D photoacoustic imaging algorithm. Studying the forward problem provides insight into the inverse problem and may indicate ways in which the imaging can be improved. For instance, a validated model of the detector response may be used to improve the spatial resolution of an image reconstructed from measurements via deconvolution. The propagation models were experimentally validated. Broadband (30 MHz) ultrasonic pulses were generated in water by illuminating thin polymer sheets and other optically-absorbent targets with a Q switched Nd:YAG laser (1064 nm, 6 ns pulse duration). The output of the Fabry Perot polymer film sensor was compared to the models' predictions.