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Information × Registration Number 0209U006037, 0106U003125 , R & D reports Title The application of time-reversal acoustics method for research of biological tissues mechanical properties popup.stage_title Head Tovstjak Volodimir Vasilevich; Barannik Evgen Olexandrovich, Registration Date 19-01-2009 Organization Kharkov national university named after V.N. Karazin popup.description2 In accordance with the technical project the purpose of the study was theoretical and an experimental research of opportunities of enhancement of parameters of acoustic systems of a focalizing, including systems on principles of time reverse acoustics which are capable to create in heterogeneous biological mediums local shear strains and waves with the help of force of acoustic radiation pressure. A research object is muscles tissues. Also the complex of theoretical and experimental operations concerning the off-the-shelf methods of ultrasonic visualization of viscoelastic properties of tissues on principles vibroelastography and a remote ultrasonic palpation is scheduled. On the basis of the carried out researching and with the help of the comparative analysis of the received results physical and mathematical models of explored processes are developed, deductions concerning optimization of algorithms of machining of the Doppler signals are made and advantages and disadvantages of the pointed methods of diagnostic of the viscoelastic properties of the soft tissues are discovered. In particularly theoretical investigation of bases ultrasonic vibroelastography as method of visualization of viscoelastic properties of the soft tissues is carried out. Optimum parameters of this method which stream from realistic model of elastic deformations which are induced in tissues by an ambient pressure or a motion of the ultrasonic probing transducer are discovered. Heterogeneous phantoms of the soft tissues, phantoms with biological tissues in vitro, ultrasonic transducers and hydrophones for calibrations of acoustic fields are manufactured. The complex of experimental researches of the viscoelastic properties of phantoms of the soft biological tissues is carried out and methods of mapping of their mechanical properties are fulfilled. As a result of the experimental and theoretical examinations the adequate physical and mathematical model of mechanical response of biological tissues on local shear excitation and biunique conformity between the measured parameters and the viscoelastic properties of medium are made. Deductions concerning necessary power of ultrasonic waves for focalizing systems on principles of time reverse acoustics are made and properties Doppler ultrasonic signals caused by local perturbation of shear strains and waves under effect of pressure of focalized ultrasonic radiation are explored. Physical-mathematical model of the response of biological tissues has defined more exactly that allowed to spot parameters which are the most effective from the point of view noninvasive diagnostics of biological mediums. Dependence of local impulsive shear strains and processes of their relaxation on the viscoelastic properties of a tissue is theoretically explored. It proved, that the simultaneous analysis of the shape of relaxation curves and amplitudes of shear strain, induced to local pressure of a focused ultrasonic waves pressure, gives necessary data for quantitative assessment of viscosities and a shear modulus of a tissue which are defined from the received functional relation of shear displacement from these parameters. During framework of study new opportunities for reconstruction of a spatial distribution of the viscoelastic properties in a examined tissue were established, the best diagnostic attributes and additional diagnostic opportunities of the Doppler methods of diagnostic are spotted. New methods of reconstruction of a spatial distribution of the viscoelastic properties of biological mediums, inconvertible against noises and speckles - hums, are important for the further development of a ultrasonic Doppler method of medical diagnostic. The procedure of a calibration of a method of the remote ultrasonic palpation, new methods and algorithm for separate reconstruct of elasticity and viscosity of a tissue is offered. The method of mapping of viscoelastic properties is offered and implemented. It is shown also, that spectral characteristics of curves of a relaxation depend on local viscosity of tissues andcan be used for visualization of its allocation. For the first time body height of quantity of shear strains with an increase of temperature in samples of biological tissues in vitro and ultrasonic phantoms of tissues is explored. It is shown, that a method of a ultrasonic palpation with the help of force of radiation pressure and ultrasonic Doppler intubation give the key opportunity noninvasive testing of actual time of process ultrasonic thermodestruction tissues. It fixed, that presence of fluctuation character of amplitude of induced local displacements is the indicator of first-order phase transition in explored area of biological object, that are bound with the beginning thermodestruction of albuminous globules. On this basis new method of a testing ultrasonic hyperthermia of the soft tissues at which thermodestruction it is implemented with the help of the same beam waves which create radiation force is offered. Pilot experiments which confirm the key opportunity of use ultrasonic Doppler method for diagnostic of a state of skeletal muscles by the analysis of local vibratory motions of muscular tissues at their isometric loading are carried out. The analysis of amplitude-frequency characteristics of fluctuation oscillations of muscular fibers in a load condition and a unload condition indicate on dependence of a vibration amplitude on quantity of an exterior load and about increasing of the contribution high-frequency component with exterior loading. The fluctuation nature and spectral characteristics of total displacements in different conditions are bound to stochastic character mechanochemical processes which proceed at muscular contraction. Product Description popup.authors popup.nrat_date 2020-04-02 Close