Biomedical devices and em field exposure

The telecommunications sector is making great advances aimed at delivering an even stream of high tech devices, covering the significant consumer demands in this sector. EM simulation is increasingly becoming an indispensable tool in the design flow, not only on the antenna level but also on the phone and environmental levels. This article compares simulated results with measurements for several steps in the phone design chain. Read full article..

This article is concerned with the evaluation of the temperature distribution inside a human liver when a catheter is inserted. It summarises the simulations performed with the HUGO and University of L'Aquila's ALES anatomical models. The co-simulation procedure using both CST MICROWAVE STUDIO® (CST MWS) and CST EM STUDIO™ (CST EMS) is also described. With permission and courtesy of the University of L'Aquila, Italy. Read full article..

Tim Herrmann, Johannes Mallow, OvG University Magdeburg Magnetic resonance imaging (MRI) is one of the most important non-invasive examination methods in the modern medicine. To raise up examine possibilities, MRI systems with more powerful magnetic fields are constituted. The standard high-field whole body (1.5T-3T) MRI Systems (Fig. 1) are using a body coil for the excitation. MRI at ultra-high-field (UHF) requires different Tx-coils for excitation of different body parts since the construction of one large body coil, similar to those at lower fields, is to difficult. Moreover, at 7T B1 is inhomogeneous as the RF-wave length within the object is smaller than the object extensions. While in RF-coils the usable B1-field is restricted to dimensions and geometry of the RF-coil itself, with the new travelling wave concept, described by Brunner [1], the usable B1-field is restricted to the dimensions of the waveguide (RF-shield) only. Thus the MR travelling wave concept allows excitation of large volumes depending on the length of the RF-shield. For an antenna with a frequency of 297MHz the approximate wavelength is about 1m. Thus the RF-shield of the gradient coil with a diameter of 64cm can be used as a waveguide, because of the cut-off frequency. The cut-off frequency is the minimum frequency where a wave fits into the waveguide without damping. This study examines the use of the travelling wave concept as an efficient body coil replacement in UHF MRI-System with the support simulations in CST Microwave Studio 2009 and measurements. Therefore two different types of antennas have been simulated and produced. The B1-field distribution of a dipole and a patch antenna where simulated and compared with B1-field measurements in a 7T MRI System. The efficiency compared to a 1.5T body coil was investigated. Further research goals are to create biological models based on anatomical MRI-Dataset for use in field-simulation software with dynamic thermal solver for more realistic SAR calculation. However the remaining problems of exposing sensitive body parts, such as the human head by increased SAR needs to be solved for next generation UHF MRI-Systems. Read full article..

Human head models like the SAM phantom are already regularly used to test the influence on mobile phone performance as well as to check the compliance to SAR standards. However, the hand also influences the field distribution significantly. The following article shows the CST MICROWAVE STUDIO® (CST MWS) simulation results of a complete Sony Ericsson mobile phone in relation to head and hand phantoms. Read full article..

Christof Thalhammer, Berlin Ultrahigh Field Facility, Max-Delbrueck-Center At the Berlin Ultrahigh Field Facility we explore the advantages and needs of Magnetic Resonance Imaging (MRI) at 7 Tesla. Apart from the magnet and the gradient system, the radio frequency (RF) coils form an essential part of the MR system and are topic of intense research. Ultrahigh field systems are not yet in clinical use and the number of commercial coils for these systems is very limited, hence the coil design is an important part of our facility’s work. Since higher magnetic fields require higher frequencies, one has to deal with stronger interaction of the RF fields with the human tissue. Therefore conventional coil designs established at lower magnetic field strengths cannot be directly applied at 7.0 T which asks for new concepts and developments. To accelerate and streamline the design of new coils, our group recently started to use CST Studio Suite 2010. Together with detailed voxel models of human bodies (the “Virtual Family” by the ITIS Foundation), we use the CST package to simulate the distribution of the magnetic field and the RF power distribution in the patient’s body with the ultimate goal to optimize our coil designs for reasons of B1-homogeneity and local SAR distribution. Some of the first results will be shown to illustrate the application of CST Studio Suite in one of our projects, i.e. the design of a multi channel transmit/receive coil array for cardiovascular MRI at 7.0 Tesla. Read full article..

Transmitters used in vehicle environments present potential threats to the health and safety of vehicle users, in terms of both human exposure to electromagnetic fields and vehicle EMC (electromagnetic compatibility). The recently revised automotive EMC directive (2004/104/EC) now requires vehicle manufacturers to identify acceptable frequencies, powers and antenna installations that can be used on vehicles without compromising their EMC performance. The simulations presented here were performed with CST MICROSTRIPES™. Read full article..

CST MICROWAVE STUDIO® (CST MWS) was used to aid in the computational investigation of the transverse B1-field homogeneity and SAR values in a 11.7 T / 500 MHz 4-port driven RF head coil loaded with a high-resolution human model (HUGO based on the Visible Human Project®). The simulations show the expected enhancement of the B-field in the centre of the head compared with the unloaded case and no significant changes in the maximum 1g SAR values between 2-port linear and circular polarizations. This work was carried out by CEA Saclay, France and is summarised in this article with the permssion and courtesy of Xavier Hanus and his colleagues. Read full article..

A standardized spherical phantom head such as the one described in this example is commonly used for SAR investigations and measurements. Read full article..

This article demonstrates the capabilities for importing the HUGO dataset via the CST STUDIO SUITE™ Voxel Data Interface. Read full article..

The exposure of staff in the vicinity of MRI scanners to low frequency (~ 1 kHz) time-varying fields associated with gradient coils is currently of interest in view of limits prescribed in the European Union Directive 2004/40/EC (1) due to be legally enforced from April 2008. Concern has been raised regarding the likely impact that exposure limits described in (1) will have on MRI practice but currently there is little information in the literature regarding such occupational exposure. In this work we address the interactions of a switched gradient magnetic field with a human body located near to a MRI scanner. Read full article..