Optimising the detection parameters for deep tissue photoacoustic imaging

For deep tissue photoacoustic imaging, piezoelectric ultrasound detectors with large element sizes (>1mm) and relatively low centre frequencies (<5MHz) are generally used, as they can provide the required high sensitivity to achieve imaging depths of several centimetres. However, these detectors are generally not optimised in terms of element size and bandwidth. To identify these parameters in order to improve SNR and spatial resolution, two models were employed. The first was a numerical model and was used to investigate the effect of varying the detector element size on the amplitude and SNR of photoacoustic images. The second model was used to optimise the detector bandwidth. For this, the frequency content of simulated photoacoustic signals were studied for a range of depths and acoustic source sizes. The model was based on an analytical solution to the wave equation for a cylindrical source and incorporated the effects of frequency dependent acoustic attenuation. These models provide a new framework for optimising the design of photoacoustic scanners for breast and other deep tissue imaging applications.