Controlled ultrasound tissue erosion

The ability of ultrasound to produce highly controlled tissue erosion through cavitation was investigated. This study is motivated by the need to develop a noninvasive procedure to perforate the neonatal atrial septum in treatment of hypoplastic left heart syndrome. A total of 232 holes were generated in 40 pieces of porcine atrial wall by a 788 kHz single element transducer. The effect of various parameters (i.e. pulse repetition frequency (PRF), pulse duration (PD) and gas content of liquid) on the erosion rate and energy efficiency was explored. PDs of 3, 6 , 12 and 24 cycles, PRFs between 1.34 kHz and 66.7 kHz, gas saturation of 40-55% and 79-85%, and Ispaa´s between 3000 W/cm², were applied. Results show that very short pulses delivered at an optimum PRF could be the most effective for controlled ultrasound tissue erosion. Results also show that the acoustic backscatter from the bubble cloud in the erosion zone is highly correlated with the erosion process.