STUDY ON METHOD FOR MANAGING LOCATION AND PARAMETERS OF FOCAL SPOT FOR NON-INVASIVE SURGERY
E.G. Dombrugova, N.N. Chernov
The paper is dedicated to approbation of method for managing location and parameters of focal spot by changing physical characteristics of matching layer. A method is proposed for determining the speed of sound in matching layer for adjusting focal spot by calculating layer thickness-averaged speed of sound in biological tissues on the path of ultrasonic waves. A description of the experimental setup and research methodology is given. The influence of changes in the physical parameters of the matching layer on the distribution of the pressure amplitude in the frontal section of the acoustic field generated by the ultrasonic emitter when the angle of its inclination to the interface varies is estimated. The experimental data are compared with the results of mathematical modeling performed with the same input parameters. The results of calculations of the acoustic field generated by a focusing antenna array in a layered inhomogeneous medium (simulation layers) are presented and the influence of changes in the physical characteristics of the matching layer on the spatial distribution of the acoustic pressure amplitude in the focal region is estimated. The study results showed the possibility of using a matching layer with calculated parameters to control the location of the focal spot in the direction of ultrasonic waves propagation. The developed method for correcting the location of the focal spot can be used both for antenna arrays and for single emitters having the shape of a spherical segment.
Keywords: layer thickness averaged speed of sound, experimental setup, focused ultrasound, matching layer, refraction of ultrasonic waves.