Viscoelasticity imaging of biological tissues with phase-resolved photoacoustic measurement

A method for noninvasive viscoelasticity imaging of biological tissues using phase-resolved photoacoustic measurement is presented. We deduced the process of photoacoustic effect on the basis of thermal viscoelasticity theory, and established the relationship between the photoacoustic phase delay and the viscosity-elasticity ratio for soft solids. Agar phantoms with different densities and different absorption coefficients were used to verify the dependence of photoacoustic phase-resolved viscoelasticity measurements. Moreover, viscoelasticity imaging of tissues was obtained with a photoacoustic point scanning system. The photoacoustic phase-resolved method provides a basis for viscoelasticity imaging, which can potentially be used for detection of viscoelastic properties and lesions of biological tissues.