Quantitative Assessment of Composition-Dependent Mechanical Properties of Atherosclerotic Plaques by Photoacoustic Elasticity and Viscosity Imaging.

Evaluating the mechanical properties of atherosclerotic plaques is crucial for precisely identifying rupture-prone lesions, as different plaque constituents dictate local biomechanical instability and directly inform targeted therapeutic intervention. In this study, we further achieved quantitative photoacoustic elasticity imaging (PAEI) and photoacoustic viscosity imaging (PAVI) by analyzing the rise time of the thermoelastic displacement and by measuring the phase delay of the photoacoustic signal relative to the laser pulse, respectively. Experiments on mice aortas have shown that PAVI is more sensitive to the changes in lipid core area during lipid plaque stage, whereas PAEI is more effective at detecting changes in fibrous cap thickness during fibrous plaque stage. Furthermore, PAEI and PAVI can effectively distinguish lipid plaques and fibrous plaques from normal vascular tissue. All results indicate that the PAEI-PAVI imaging system enables label-free, high-resolution visualization of the component-based biomechanical properties of atherosclerotic plaques, facilitating early detection and rupture risk assessment.