Quantitative bicomponent imaging with single-wavelength by using a transmission-mode photoacoustic microscope

Abstract

Quantitative images of multiple molecular components in tissues have significance in understanding tissue functions. However, most imaging methods of quantifying a multicomponent mixture often rely on multiple excitations with different wavelengths or intensities. In this study, a transmission-mode photoacoustic microscope is developed to achieve quantitative images of two components in specimen slices. Different from other methods, the proposed method only scans the specimen one time by using a single-wavelength laser. After each laser excitation, the ultrasound transducer detects two signals: One is only related to optical absorption and the other is associated with both absorption and scattering. A linear equation system is proposed to describe the relationship between the signal magnitude and the molecular concentrations of thin-specimen. Solving these equations, we extract quantitative images of components in the thin-specimen from the two signals excited by a single-wavelength laser. Experiments demonstrate that the scheme accurately quantifies the concentrations of various mixtures of sterile sheep blood and milk, moreover, correctly revealing the concentration gradient due to molecular diffusion along the boundary between different components. This method could overcome the limitations induced by multiple excitations, and it will be helpful in developing a quantitative multiple-molecular imaging system.