MECHANICAL IMPEDANCE
OF BIOLOGICAL SOFT TISSUES

General information
Measuring means
Experimental study
Spectral measurements
Single-frequency measurements
Physical models
Publications
Additional information
Phone: (7 831) 416 49 86
E-mail: eugene@appl.sci-nnov.ru
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Radiophysics in medicine
IAP RAS

GENERAL INFORMATION

Impedance characteristics of biological soft tissues are determined in experiments on touching tissues by a small, hard, vibrating indentor on the basis of measurements of indentor kinematics parameters (displacement (U), velocity (V) or acceleration (A)) and resistance force to tissue deforming (F). For the complete description of tissues behavior in these experiments one can use real and imaginary parts of any of three equal characteristics: complex stiffness K = -F/U, complex mechanical impedance Z = -F/V and complex inertia M = -F/A - or any pair of independent values, in particular, real parts of stiffness and impedance (ReK and ReZ). Studies of impedance characteristics of biologic soft tissues have been performed for a long time, but only recently they were given a new impetus owing to the development of modern computer measurement facilities and data processing. Such studies began as far back as 40-th in connection with the problem of different contact sensors matching with the human body surface. A bit later studies of dependencies of impedance characteristic on tissue conditions and development of ways of evaluation of these conditions on the basis of impedance measurements began. New trends of work within the framework of these studies are development of the method to reconstruct mechanical parameters of multi-layered tissues on the basis of spectral impedance measurements, that is to say on the basis of frequency dependencies of impedance characteristics, and development of the method of continuous monitoring of tissues viscoelastic parameters with high time resolving power on the basis of single-frequency impedance measurements. These methods offer new opportunities of tracking the changes of tissues viscoelastic characteristics, in the first place muscles, in the course of various physiological and pathological processes and in the course of the development of response to different test influences. Thereby, new opportunities are being offered for biomechanical and medical study of human neuromuscular system, for example, when studying the mechanism of the motor control or when studying an action of various drugs.

A cycle of theoretical and experimental work was performed during the several last years in IAP RAS on the interaction of vibrating indentor with biological tissues. Besides, a set of portable and computer-based devices was developed for measuring mechanical impedance of tissues, as well as a series of studies was performed of surface tissues of human body by the impedance measuring method.