All-optical in vivo photoacoustic tomography by adaptive multilayer temporal backpropagation

Abstract: Photoacoustic tomography (PAT) offers high optical contrast with acoustic imaging depth, making it essential for biomedical applications. While many all-optical systems have been developed to address limitations of ultrasound transducers, such as limited spatial sampling and optical path obstructions, measuring surface displacements on rough and dynamic tissues remains challenging. Existing methods often lack sensitivity for in vivo imaging or are complex and time-consuming. Here, we present an all-optical PAT system that enables fast, high-resolution volumetric imaging in live tissues. Using full-field holographic microscopy combined with a soft cover layer and coherent averaging, the system maps surface displacements over a 10 mm*10 mm area with 0.5 nm sensitivity in 1 second. A temporal backpropagation algorithm reconstructs 3D images from a single pressure map, allowing rapid, depth-selective imaging. With adaptive multilayer backpropagation, the system achieves imaging depths of up to 5 mm, with lateral and axial resolutions of 158 micrometer and 92 micrometer as demonstrated through in vivo imaging of mouse vasculature.