Broadband model-based inversion enables optoacoustic microscopy beyond the acoustic diffraction limit

TL;DR

This paper introduces a model-based inversion framework for acoustic-resolution optoacoustic microscopy that surpasses the acoustic diffraction limit, enabling super-resolution imaging of opaque tissues in vivo and in vitro.

Contribution

It presents a novel model-based reconstruction method exploiting scanning symmetries and L1 regularization to achieve super-resolution in AR-OAM beyond traditional diffraction limits.

Findings

Outperforms synthetic aperture focusing in contrast and resolution

Resolves structures indistinguishable with previous methods

Validated through simulations, phantom, and in vivo experiments

Abstract

Acoustic-resolution optoacoustic microscopy (AR-OAM) retrieves anatomical and functional contrast from living tissues at depths not reachable with optical microscopy. The imaging performance of AR-OAM has been advanced with image reconstruction algorithms providing high lateral resolution ultimately limited by acoustic diffraction. In this work, we suggest a new model-based framework efficiently exploiting scanning symmetries for high-resolution reconstruction of AR-OAM images. The model accurately accounts for the spatial impulse response and large detection bandwidth of a spherical polyvinylidene difluoride sensor, which facilitates significantly outperforming synthetic aperture focusing technique commonly employed in AR-OAM image reconstruction in terms of image contrast and resolution. Furthermore, reconstructions based on L1-norm regularization enabled resolving structures indistinguishable with other methods, which was confirmed by numerical simulations as well as phantom and in vivo experiments. The achieved performance demonstrates the applicability of AR-OAM as a super-resolution imaging method capable of breaking through the limits imposed by acoustic diffraction, thus opening unprecedented capabilities for the microscopic interrogation of optically opaque tissues in preclinical and clinical studies.