Development and validation of a short-lag spatial coherence theory for photoacoustic imaging

We previously derived a theoretical expression for spatial coherence in photoacoustic data and utilized it to study properties of the short-lag spatial coherence (SLSC) beamformer applied to photoacoustic imaging. In this paper, an updated version of our theoretical equation is evaluated to generate SLSC images of a point target, a 1.2 mm diameter target, and corresponding lateral profiles through the target centers. We compared SLSC images simulated solely based on our theory to SLSC images created after beamforming acoustic channel data from k-Wave simulations of a 1.2 mm-diameter disc target. This process was repeated for a point target and the full width at half of the maximum signal amplitude in each point target image was measured to estimate the resolution of each simulated imaging system. Resolution was measured as a function of lag (i.e., transducer element spacing), and excellent agreement was obtained in the short-lag region corresponding to 3-11% of the receive aperture. Beyond this region, resolution measurements diverged by a maximum of 1 mm between the two types of simulated images. These results indicate the potential for both simulation methods to be utilized as independent resources to study coherence-based photoacoustic beamformers.