Time Reversal Acoustic focusing using layered membranes structure

In recent years numerous Time Reversal Acoustic Focusing Systems (TRA FS) employing various reverberation chambers ("acoustic cavities") accumulating acoustic energy in time were described in the literature. We investigated new kind of TRA FS that uses single transmitter and water filled reverberators that were built for Atrial Fibrillation treatment and can be placed into human heart. The improvement of the TRA FS includes incorporation of additional source of reverberation as series of spatially distributed arbitrary shaped membranes with varying thickness in the range from one quarter to half wavelength of ultrasound. Random spatial variation of ultrasound reflection from such membranes leads to randomization of the acoustic field that highly improves TRA focusing of the system. The dependence of the focal structure and focused waveform was investigated for the thermoformed balloon intravascular ultrasound ablation catheter for Atrial Fibrillation and exemplary various material planar membrane structures. Ultrasonic signals were radiated by cylindrical and piston transducers with frequency of 9 MHz and 3.3 MHz respectively. Experiments demonstrated effective TRA focusing by membrane arrangement that can be used for ultrasound focusing and steering in various minimally-invasive biomedical applications.