Super-resolution photoacoustic fluctuation imaging with multiple speckle illumination

In deep tissue photoacoustic imaging, the spatial resolution is inherently limited by acoustic diffraction. Moreover, as the ultrasound attenuation increases with frequency, resolution is often traded off for penetration depth. Here, we report on super-resolution photoacoustic imaging by use of multiple speckle illumination. Specifically, we demonstrate experimentally that the analysis of second-order fluctuations of the photoacoustic images enables the resolution of optically absorbing structures beyond the acoustic diffraction limit, with a resolution enhancement of about 1.4. In addition, deconvolution was implemented to fully exploit the highest spatial frequencies available and resulted in an effective resolution enhancement of at least 1.6 in the lateral direction. Our method introduces a new framework that could potentially lead to deep tissue photoacoustic imaging with subacoustic resolution.