Dual-contrast nonlinear photoacoustic sensing based on quasi-CW single-pulsed laser

Abstract

Photoacoustic tomography (PAT) is a non-invasive imaging technique which provided high lateral resolution and axial resolution. Conventional linear photoacoustic (PA) imaging has been widely applied to state-of-art PA system, which excited by short pulse laser. Recently, nonlinear photoacoustic effect has been excavated and utilized, which indicates the different character with linear PA by dual-pulse laser. In this paper, we report a dual-contrast photoacoustic sensing by quasi-CW nonlinear PA effect. Using the high-repetition pulsed laser, and two different contrast imaging were extracted. Unless conventional contrast that using short laser pulse by detected tissue light absorption, we extracted another contrast that indicated the rising of temperature. The quasi-CW nonlinear PA effect could be illustrated by a simple mathematical derivation. The dual-contrast PA imaging have been demonstrated by experiment in vitro and ex vivo imaging. The results indicate different heat absorbency of different materials, which could be utilized to distinguish materials and intensify imaging contrast. Compared with conventional PA imaging, the proposed method has more scope of works and potential applications.