Andrzej Krawczyk

Simulation of magnetic stimulation of the brain

The paper presents a computer simulation of the transcranial magnetic stimulation of the brain with a low-frequency magnetic field, a technique which is proposed to replace the electroconvulsive treatment in psychiatry. The field model is based on the T-/spl Omega/ formulation, that, by the low electric conductivity and constant magnetic permeability of the human tissue, allows us to build a finite-element model of the head only.

Comparison of numerical and measurement methods of SAR of ellipsoidal phantoms with muscle tissue electrical parameters

Purpose – The assessing of the specific absorption rate (SAR) of living organisms or phantoms is difficult to realize and this paper seeks to do this. SAR much more precisely describes the energy absorbed by biological objects than values of electric field strength (E [V/m]) or power density (S [W/m2]) measured at the point of exposition. However, for living objects the assessing of SAR is not an easy task by measuring methods or even in calculation evaluations. Numerical techniques, especially the finite‐difference time‐domain method (FDTD), offer different possibilities of calculations. The important problem with FDTD method introduced to lossy objects with complex shapes is that this method is not verified with the measuring data.Design/methodology/approach – In this work the results of calculations and measuring data of ellipsoidal phantoms filled with specimen of electrical parameters like muscle tissue are presented. The calculations of SAR have been realized for two cases, e.g. for plane wave incid...

A numerical evaluation of eddy currents distribution in the human knee with metallic implant

Purpose – The purpose of this paper is to use numerical methods and modelling to estimate the effect of a passive, metallic (conducting) implant on eddy currents distribution in a human knee model. There exists a concern among wearers of such implants that they alter electromagnetic field (eddy currents) significantly and there is a need for standardization of that problem.Design/methodology/approach – The numerical model of a human knee has been built on the base of Visual Human Project and electromagnetic field calculations were carried out using Meep FDTD engine. In total, two scenarios have been considered: the knee model with and without a metallic implant. The knee implant model has been prepared as the knee model with overestimated electrical parameters of bone tissues by titanium metal. Alternating eddy current distribution has then been evaluated for both models using FDTD low frequency algorithm.Findings – The highest values of eddy currents occurred on the interface between skin and muscle tiss...

Mathematical modelling of electrobiological interaction

The paper shows how biological structures (membranes) are modelled when subjected to electromagnetic field. A short explanation of what such an interaction is for is given. The electromagnetic features of a biological cell are given and then, on the basis of it, the mathematical model is presented. The numerical approach is shown and some relevant conclusions are quoted.

Computer modelling of magnetotherapy in orthopedic treatments

Purpose – The paper aims to clarify the method/methodology of establishing a computer model of the electromagnetic therapy connected with some knee joint problems. Two cases are considered: the arthritis of the knee and the fracture of bone. In both cases the analysis of eddy current distribution in the knee is made. It gives results which can be helpful in the planning of treatment. The paper presents the exemplary results of eddy current distribution inside a bone. A short discussion on the safety aspect of magnetotherapy has been carried out.Design/methodology/approach – In order to calculate the eddy current distribution in human knee joint the low frequency finite‐difference time‐domain algorithm has been applied. The numerical model of the leg was based on US Air Force Research Laboratory data and the electrical properties of tissues were modeled using 4‐Cole‐Cole approximation with parameters taken from Gabriels.Findings – The paper presents the general methodology which can be used in magnetothera...

SAR calculations for titanium bar-implant subjected to microwave radiation

The paper describes the assessment of exposure of a six-year-old male patient with a titanium bar implanted after Nuss procedure to microwave radiation with frequency of 2.45 GHz. The local SAR concentrations inside the boys trunk for two variants of plane wave polarizations with regard to the titanium implant have been considered. It was demonstrated that an analyzed concave bar-implant poses no danger during occupational and environmental exposures according to current safety standards.

The investigation of electromagnetic field influence generated by mobile phones on cardiac pacemakers with the anatomically based human model

Purpose – The aim of this paper is to investigate the coupling model which describes the relationship between the electromagnetic (EM) field emitted by a field source, in this case the mobile phone, and the interfering voltage at a cardiac pacemaker which is digitally implanted into the human body model.Design/methodology/approach – The research was carried out using two kinds of numerical phantoms with various configurations, i.e. the mobile placed in front of a trunk and the mobile placed near the human ear (totally 12 configurations). Moreover, the simplified homogeneous human model with numerically implanted cardiac pacemaker is considered (two configurations). The simulations are carried out using the finite difference time domain method according to international standards.Findings – From the investigation it was found that the interfering voltage at the cardiac pacemaker (for each of the considered models) was much smaller than the one proposed by IEC standard. A practical conclusion that can be dr...

The Comparison of Phantom Model And Simulation Results in SAR Analysis

The Specific Absorption Rate (SAR) is the coefficient which determines the thermal effect on the biological tissue subjected to the electromagnetic field. Thermal effect is especially important when the radio-frequency electromagnetic field is considered. The paper presents the analytical method for computational SAR analysis. The biological model is prolate spheroid. The illumination is a uniform plane wave with the magnetic field vector polarized along the z axis. The simulation results are compared with the measurement carried out on the phantom.

Magnetic stimulation of knee - mathematical model

Arthritis, the illness of the bones, is one of the diseases which especially attack the knee joint. Magnetic stimulation is a very promising treatment, although not very clear as to its physical background. Deals with the mathematical simulation of the therapeutical technique, i.e. the magnetic stimulation method. Considers the low‐frequency magnetic field. To consider eddy currents one uses the pair of potentials: electric vector potential T→ and magnetic scalar potential Ω . Since the problem is of low frequency and the electric conductivity of biological tissues is very small, consideration of electric vector potential only is quite satisfactory.

Modelling of eddy currents induced in human brain by transcranial magnetic stimulation

Deals with the problems of interactions between the electromagnetic field and the human brain. In particular, the problem of eddy currents in brain tissue induced for medical purposes is discussed. The mathematical modelling of the phenomenon is presented.