Optimizing image resolution in three-dimensional photoacoustic tomography with line detectors

摘要

Photoacoustic tomography (PAT) with line detectors is based on line integrals of the acoustic pressure field generated by a photoacoustic source. From these line integrals, which are measured around the source, a two-dimensional (2D) projection image of the initial pressure is reconstructed. From many such projections in different directions finally a three-dimensional (3D) image is obtained by applying the inverse Radon transform. In this study the use of an optical beam as line detector is demonstrated. The beam is part of an optical interferometer. To optimize the image resolution the beam is focused in the vicinity of the object. The influence of finite beam length, finite width and varying width on the measured signal is investigated using simulations and experiments. It is found that although the finite beam diameter limits the temporal resolution, the beam can be treated as almost perfect line detector within the focal range of the optical lens. An image of a phantom reveals an achievable resolution on the order of about 100 μm or less.