S. Seitz, and O. Dössel. Influence of body worn wireless mobile devices on implanted cardiac pacemakers. In 4th European Congress for Medical and Biomedical Engineering, vol. 22, 2008
The number of implanted cardiac pacemakers and defibrillators is constantly increasing. At the same time, more and more of those patients use wireless mobile communication devices.Aim of this work was the development of a pacemaker-electrode model and its “implantation” into a detailed anatomical correct voxel model. Additionally generic body models were examined. It consists of several layers with varying thickness and conductivity/permittivity values corresponding to different tissue types. This approach was chosen to avoid numerical errors at tilted boundaries. The excitation sources were modeled as generic dipoles and as plane waves operating at the frequency range normally used by cellular phones and wireless networks (900 to 2450 MHz). The dipoles were designed to provide maximum radiation efficiency at the frequencies of interest. Finally numerical calculation of induced fields by external signal sources were conducted. The results were then evaluated regarding the compliance to the guidelines of ICNIRP and a draft by DIN/VDE.For the Visible Man model, the computed specific absorption rate (SAR) values were well below the thresholds both for single and multi-antenna setups and for all frequencies of interest if the power did not exceed the regulatory specifications. The same results were obtained for the electrical field values determined at commonly used implantation sites for pacemakers. For some tissue configurations in the generic model, higher SAR values than allowed by regulations could be observed.
S. Seitz, G. Seemann, and O. Dössel. Influence of tissue anisotropy on the distribution of defibrillation fields. In Proc. Computers in Cardiology, pp. 489-492, 2008
The development of new devices used for defibrillation and cardioversion is often supported by numerical simulations of the induced electric potentials and current distributions. The commonly used tools incorporate isotropic models of the tissue properties present in the human torso. A comparative study was conducted to characterize the influence of anisotropic compared to isotropic tissue modeling. Defibrillation shocks with amplitudes of 1000 V and 2000 V were simulated and a set of varying conductivity values and anisotropy ratios was examined. The inclusion of tissue anisotropy produced significantly smaller values for current density compared to isotropic calculations especially in the myocardial tissue.