Biomedical Engineering

The potentials of multichannel methods of precordial electrical impedance mapping for monitoring cardiac activity indicators are considered. This review addresses the possibility of constructing models of blood in the heart allowing solution of the inverse impedancemetry problem to be used to determine the volume characteristics of heart activity and displacement of the boundaries of the heart, as well as movement of the center of mass of the blood in the heart during the cardiac cycle. Pilot studies of three healthy volunteers in comparison with MRI data were conducted.

Among the instrumented methods for assessing the volume characteristics of cardiac activity, ultrasound, MRI, and CT with contrast are well known. Conventional methods do not provide for measurement of the parameters of central hemodynamics and respiration in monitoring conditions. The possibility of multichannel electrical impedance technology allows the stroke volume and fractional output of the heart to be determined and the displacement of the ventricular walls to be visualized in real time with an accuracy no worse than 1-2 mm. This article considers questions of the implementation of techniques for computing stroke and minute volumes of the circulation and displacements of the heart chamber by solving the electrical impedance measurement problem. Results of mathematical and physical modeling of cardiac activity based on precordial measurements are presented.

The specifics of using tetrapolar electrode systems for a wide class of electrical impedance measurements are discussed. The key factors affecting the error in solving the inverse electrical impedance problem using a tetrapolar electrode system are determined.

Current endovascular surgical technology requires the development and introduction of new methods allowing the drawbacks of existing technologies to be overcome. These methods include combined approaches to recanalization of arteries and prevention of instent restenosis, which can be achieved by combining minimally invasive techniques. It is proposed that the reliability and efficacy of these methods, increasing comfort and radiation safety of the surgeon, can be ensured by introducing new robotic systems into endovascular surgery.

Preliminary research into the application of spectrophotometry for localizing and identifying neurovascular structures, such as large arteries, veins, and nerve stems, in the process of neurosurgical navigation was carried out. The results of preliminary in vivo and in situ experiments confirm the possibility of developing appropriate quantitative criteria on the basis of measured spectrophotometric parameters and calculated optical and physio-logical parameters of the investigated biological tissue volume. Further verification of the obtained data is required. The results obtained in this work can be used in designing a system for the automated intraoperative detection and identification of neurovascular structures.

The possibility of analyzing the structure and the developmental stage of small parasites as exemplified by Demodex mites is considered. The analysis is based on the method of hyperspectral holography in the near infrared region. It is shown that the optical density of the mite structure can be registered in the wavelength range ≥0.7 μm. The amplitude–phase distribution of the structure in the short wavelength spectral region is obtained. Registration of the amplitude–phase information in the shorter wavelength range is complicated by the diffuse structure of the integument, which leads to image speckling.

Problems associated with changes in the shape and size of red blood cells in patients with atherosclerosis are considered. The applicability of physical optics techniques (in particular, holography) for the examination of red blood cells is discussed. An interferographic technique for analyzing the shape of red blood cells and estimating quantitatively their cross section and size is suggested. Experimental data on the comparative characteristics of red blood cells in normal and pathological states are presented.

A series of polyurethanes with low modulus of elasticity for soft tissue implantation was synthesized. Polyurethane samples were implanted into mice for seven days, after which histological studies of capsule formation were carried out. The mechanical properties of polyurethane were found to affect the organism’s immune response at sites close to implants at which specific conditions concentrating biomechanical stress in tissues, particularly around the ends of polyurethane films, occur. Softer polyurethane with a modulus of elasticity close to the modulus of elasticity of tissues produced essentially no reaction to biomechanical stress, though reactions to the foreign surface of the implant remained.

We present results from the first stage of numerical modeling of implanted rotary blood pumps which can be used in pediatric heart surgery in patients undergoing the Fontan procedure. Two three-dimensional models of pumps − the centrifugal and axial types − were constructed. Head pressure-flow characteristics were obtained for each model and the effects of pump geometry on blood flow at an operating point of 2.5 L/min were evaluated. Stagnation zones were identified by quantitative assessment of the volume of fluid with flow rates of 0-0.1 m/s. The distribution of flow lines was used to identify vortex zones. Numerical modeling of fluid flow in pumps was run in Fluent ANSYS 19.0 computational fluid dynamics software.