Performance characterisation of a new clinical spectroscopic epiphotoacoustic scanner

A clinical spectroscopic eiphotoacoustic scanner is presented, evaluated and optimised. The scanner combines a clinical ultrasound scanner with commercially available lasers to generate photocoustic images that are inherently coregistered with the ultrasound images and can be acquired by freehand scanning. Arrays of graphite rods are used to determine the point spread function (PSF), signal-to-noise (SNR) and signal-to-clutter ratios (SCR) of the system and optimise the image quality by varying the illumination geometry. At a distance of 26 mm, mall spatial PSF extents are found (lateral 399 ± 80 μm, axial 340 ± 20 μm, elevational 1.43 ± 0.26 mm) and hence a high solution is obtained. Due to the strong optical scattering in biological tissue, the illumination geometry has virtually no effect on the image intensity, SNR and SCR, and hence practicality is the main concern when designing the clinical scan-head geometry.