Photoacoustic microscopy

TLDR

Photoacoustic microscopy (PAM) is a hybrid in vivo imaging modality that uses the photoacoustic effect to provide absorption contrast, surpassing the optical diffusion limit (~1 mm) and enabling high‑resolution, multi‑contrast imaging of anatomical, functional, molecular, flow, and metabolic signals up to several millimeters deep. This review examines state‑of‑the‑art developments in PAM, outlining its key features and biomedical applications. It discusses the technical implementations of PAM, including its hybrid optical–acoustic detection and scalable imaging depth, that support its diverse biomedical uses.

Abstract

Abstract Photoacoustic microscopy (PAM) is a hybrid in vivo imaging technique that acoustically detects optical contrast via the photoacoustic effect. Unlike pure optical microscopic techniques, PAM takes advantage of the weak acoustic scattering in tissue and thus breaks through the optical diffusion limit (∼1 mm in soft tissue). With its excellent scalability, PAM can provide high‐resolution images at desired maximum imaging depths up to a few millimeters. Compared with backscattering‐based confocal microscopy and optical coherence tomography, PAM provides absorption contrast instead of scattering contrast. Furthermore, PAM can image more molecules, endogenous or exogenous, at their absorbing wavelengths than fluorescence‐based methods, such as wide‐field, confocal, and multi‐photon microscopy. Most importantly, PAM can simultaneously image anatomical, functional, molecular, flow dynamic and metabolic contrasts in vivo . Focusing on state‐of‐the‐art developments in PAM, this Review discusses the key features of PAM implementations and their applications in biomedical studies.