Improved Sensitivity in Large Field of View Multispectral Laser-Scanning Photoacoustic Microscopy for Measuring Oxygen Saturation In Vivo

Abstract

Multispectral photoacoustic microscopy (PAM) using stimulated Raman scattering (SRS) has been employed to measure oxygen saturation (sO₂) in biological tissue. However, laser-scanning photoacoustic microscopy (LS-PAM) inherently suffers from low detection sensitivity due to the use of a flat transducer and non-coaxial alignment of the transducer with the optical scan. Although wide-field-of-view LS-PAM has been implemented, it typically results in coarser lateral resolution and hence lower sensitivity than existing LS-PAM systems. Here, we present a wide-field multispectral LS-PAM system for measuring sO₂ in biological tissue. Instead of relying on two discrete wavelengths, our method employs two wavelength groups—a isosbestic group (532 nm and 545 nm) and a deoxyhemoglobin-dominant group (545 nm and 558 nm). We demonstrate that using these groups improves the signal-to-noise ratio (SNR) of the detected signals, leading to more accurate sO₂ measurements. The performance of this system is validated through both phantom and in vivo studies.