Numerical and experimental investigation of the influence of tumor size on laser-induced ultrasonics in soft tissue

The generation and propagation of laser-induced ultrasonic waves in soft tissue systems are investigated using the finite element method. Taking into account the effects of thermal diffusion, optical penetration, tumor elastic modulus and finite laser pulse duration, the transient temperature distribution is obtained. Using this temperature field as thermal loading in structural analysis, the thermoelastic stress field and laser-induced ultrasound waves in soft tissues are obtained. The results show that the intensity of the positive peak in the ultrasound wave increases and the arrival of the longitudinal wave takes place sooner as the tumor size becomes larger. It is also found that the duration of the laser ultrasound signal becomes shorter as the size of the tumor decreases. Meanwhile, the percentage of the received ultrasonic signal in the high-frequency region increases as the size of the tumor decreases, as has been proved by the experimental results. (paper)