Liashko D.O. The use of focused ultrasound for differential diagnosis of human hearing. - Qualification scientific work on the right of manuscript.
Thesis for the degree of Philosophy Doctor, in specialty 171 “Electronics”. - National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute", Kyiv, 2021.
The dissertation shows the following first scientific results:
1. A review of modern scientific research of focused ultrasound in audiology and methods of differential diagnosis of human hearing was conducted.
2. A passive ultrasound system using an acoustic focusing lens was developed for the first time to detect human inner ear inflammation.
3. An experimental study of a focused ultrasound system for differential diagnosis of human hearing was conducted.
4. The electrical parameters of a complex electroacoustic piezoelectric transducer have been calculated by the four-pole method.
5. For the first time the analytical calculations of the acoustic field of the flat phased multielement lattice of piezoelements in the pulse mode of operation for dynamic focusing on the helix of the human inner ear have been carried out.
6. An improved method for objective differential assessment of the human auditory system by means of electroencephalography, when the system is exposed to a complex audio signal in the entire audible frequency range.
The content of the dissertation research is set out in five chapters, which present the results of the study and the justification of the main results of the work.
The introduction substantiates the relevance of the dissertation work, formulates the purpose and lists the objectives of the study, describes the research methods used, lists the tasks set for the study. In addition, information on the relevance, scientific novelty and practical significance of the results obtained was given.
The first chapter presents an analytical review of the literature, which shows the current state of the problem areas - the study of the state of hearing by using focused ultrasound, types of emitter designs for focusing ultrasound (US), analysis of the optimal parameters of ultrasound exposure, analysis of studies on the perception of music as a stimulating material and new methods of diagnosing human hearing.
The second chapter shows the possibility of using passive acoustothermometry to determine the inflammation of the human inner ear. In the dissertation, a single-channel acoustothermometer using the focusing of acoustic radiation by means of an elliptical (aberration-free) lens is calculated, which allows to obtain the required accuracy of temperature measurement in real time not worse than 0.2 oC. The third chapter presents the calculations of a cylindrical continuous wavefront and the use of a multielement array in an electroacoustic transducer. The calculations of the acoustic field distribution along the depth with the change of the angle of deviation from the axis and the pulse duration were carried out. This type of piezoelectric transducer will allow changing the angle of ultrasonic wave radiation to affect all parts of the human curl and choose a certain duration for safe exposure. A mathematical description of the piezoelectric elements is carried out to find the relationship between the input electrical and output acoustic quantities in the radiation mode and vice versa - in the receiving mode. Each element of the array is represented as a four-pole.
The fourth chapter shows the results of calculations and the designs of measuring instruments: a high-frequency wattmeter without active elements for measuring the electrical power consumed by the piezoelectric transducer, a radiometer for measuring the acoustic power of focused ultrasonic beams. It is shown that the calculated intensity is sufficient for both diagnostic and therapeutic use of the developed acoustic system.
The fifth chapter shows the results of studies of the spectral characteristics of the bioelectrical activity of the brain of students when listening to complex audio signals, namely, musical compositions of different component-structural composition, differing in the presence of melodic components and playback speed. An experimental methodology is proposed to test the effect of a number of musical compositions on the rhythms of the brain, in particular alpha, beta, delta and theta rhythms. According to the processing of EEG data, it was possible to estimate statistically significant changes in the brain EEG associated not only with the influence of individual characteristics of the listened compositions, but also to identify their mutual influence on the emotional state of a person.
The practical significance of the results obtained in the dissertation is that the results of the research can be used for experimental study of the effect on the cochlea of the human inner ear and its further implementation in medical institutions.
