The potential of colloidal subdomain ferrite particle suspensions (SDP) ('magnetic fluids'), exposed to an alternating magnetic field, is evaluated for hyperthermia. Power absorption measurements of different magnetic fluids are presented in comparison to multidomain ferrite particles (MDP). Variations with frequency as well as magnetic field strength have been investigated. The experimental results clearly indicate a definite superiority of even non-optimized magnetic fluids over MDP ferrites regarding their specific absorption rate (SAR). Based on the work of Shliomis et al. (1990) and Hanson (1991), a solid-state physical model is applied to explain the specific properties of magnetic fluids with respect to a possible use in hyperthermia. The experimentally determined SAR data on magnetic fluids are used to estimate the heating capabilities of a magnetic induction heating technique assuming typical human dimensions and tissue parameters. It is considered that for a moderate concentration of 5 mg ferrite per gram tumour (i.e. 0.5% w/w) and clinically acceptable magnetic fields, intratumoral power absorption is comparable to RF heating with local applicators and superior to regional RF heating (by comparison with clinical SAR measurements from regional and local hyperthermia treatments). Owing to the high particle density per volume, inductive heating by magnetic fluids can improve temperature distributions in critical regions. Furthermore, localized application of magnetic fluids in a tumour might be easier and less traumatic than interstitial implantation techniques.

No abstract

I. IntroductionNetwork simulation has become more important for EMC analysis of conducted disturbances in power electronics over the last years. However, accurate models for the EMI frequency range from 10kHz up to 30MHz are rare and in most cases it is very difficult to obtain the appropriate model parameters. Furthermore, simulation time becomes more and more critical, if EMI phenomena of the whole power electronic system have to be investigated. Therefore, a good compromise between simulation time and model accuracy need to be found. Frequency domain simulations have been established for that task because of its high simulation speed even with complex models. On the other hand nonlinear behaviour of disturbance sources cannot be modeled in frequency domain [3]. Thus, time domain simulation is advantageous for certain simulation problems.Models for induction machines as a part of the EMI noise path have been presented by different authors. Weber has presented an exact model for frequency domain simulation [5] which is a further development of a proposed model by Zhong [6]. This model applies frequency dependent parameters and has high component count which leads to extensive simulation times. Thus, it is not useful for time domain simulations even when dependencies on the frequency are neglected. High frequency models of induction machines for time domain simulations have not been developed up to a comparable accuracy or they are not suitable to simulate both common mode (CM) and

<p class="MsoNormal" style="text-align: left; margin: 0cm 0cm 0pt;" align="left"><span class="text"><span style="font-family: ";Arial";,";sans-serif";; font-size: 9pt;">In contrast to pure identification labels, passive inductive coupled RFID transponders with enhanced functionality have an increased power consumption. A nonoptimized antenna design for high power transponders may lead to a poor efficiency and high magnetic field emissions. Therefore, in this work, the energy transmission of inductive coupled systems is investigated, enabling an optimized system design. The RFID system is modeled by network elements in order to optimize the energy transmission. Next to a brief review of different methods for the antenna parameter determination, a new modification of the PEEC method is derived enabling an accelerated and accurate computation of the mutual coupling of the reader and the transponder antenna. Along with the simplification of the transformed transponder impedance and the investigation of the reader matching, consecutive design steps are deduced. The influence of the location-dependent antenna coupling on the energy transmission is characterized. Two case studies are carried out showing a successful transmission of 80mW over a distance of up to 7.6 cm by 275mW reader output power. This system demonstrates an efficient energy supply of a high power transponder while keeping the field emissions low.</span></span><span style="font-family: ";Arial";,";sans-serif";; font-size: 9pt;"></span></p>

A theoretical framework is presented for optimized heating of deep-seated tumours by phase and amplitude steering. The optimization problem for a specific tumour and perfusion case results in a functional dependency between power-level and maximum obtainable therapeutic efficiency. Different optimization criteria and strategies are outlined, which cause an increase of power or thermal dose in the tumour. Three tumour models (central pelvic tumour, eccentric abdominal tumour with or without necrosis) are analysed in detail. The simulation studies predict that appreciable parts of these tumours (50-100%) can be heated efficiently (42.5-43 degrees C) within the range of available and clinically tolerated power levels (1-5 kW/m), if tumour perfusion is less than 20-25 ml/100 g min. Some improvements are obtained by increasing the number of independent channels (from four to eight) and by the application of time-dependent (complementary) power-deposition patterns.