Erosion of tissue-mimicking phantom by acoustic droplet vaporization

Phase-changed droplets can be triggered to vaporize into gaseous bubbles via acoustic droplet vaporization (ADV), and this technique has showed the potential in tumor ablation therapy. This study demonstrated the backward erosion phenomenon caused by ADV within a gel chamber phantom which has the Young´s modulus similar to that in cancer tissue. The erosion experiments were performed in an integrated acoustooptical system. A 2-MHz high-intensity focus ultrasound transducer was used to transmit 3-cycIe pulses to induce the perfluoro pentane droplets vaporization at the peak negative pressure (PNP) of 9 MPa and pulse repetition frequency (PRF) of 18 Hz. The backward erosion by ADV was due to the attenuation effect by gas bubbles, and it was proven by estimating the degree of attenuation with different droplet concentrations in through-transmission attenuation measurements. The erosion rates with different sonication parameters such as PNP (6-10 MPa), PRF (9-72 Hz) and pulse durations (1.5-100 J.ls) in the presence of dilute ration of concentration (1000-50000) were also quantified.