MRI

Multiphysics Simulation Medical Applications

Multiphysics Simulation Medical Applications
This webinar will introduce the basics of bio-EM simulations, such as the available body models, the choice of numerical solver and relevant post-processing quantities, as well as advanced workflows for multi-channel systems including EM/circuit co-simulation and some HPC aspects. Finally, the tight coupling of the EM solvers with the advanced bio-heat solvers including human thermo-regulation and spin response solvers for MRI imaging will be covered. All steps will be demonstrated with state-of-the-art examples from applications areas like ultra-high-field MRI, implant safety, microwave imaging, hyperthermia, pacemakers, etc. Read full article..

Combined 3D electromagnetic and spin response simulation of MRI systems webinar

Combined 3D electromagnetic and spin response simulation of MRI systems webinar
Magnetic Resonance Imaging (MRI) systems rely on a complex interaction of different physical domains: electromagnetic fields trigger a response of nuclear spins inside the human body, while thermal heating of the body needs to be controlled. The quality of the resulting MR image depends both on the homogeneity of the underlying RF fields and on the sequence chosen to create the image. Read full article..

Combined 3D electromagnetic and spin response simulation of MRI systems

Combined 3D electromagnetic and spin response simulation of MRI systems Document type
Modern MRI systems are highly complex devices, and the interaction between the body and MRI coils introduces additional challenges into the design process. The body, with its complicated heterogeneous interior, causes major disturbance to the homogeneity of the magnetic fields, while energy absorbed by the body can cause harmful heating. Experimental measurement of these effects is often impossible, but simulation with 3D body models can help the engineer identify risks to the patient and suggest ways to reduce them. Read full article..

Applications of CST to modelling human interaction with EM fields: a metrological perspective

Applications of CST to modelling human interaction with EM fields: a metrological perspective Document type
This presentation from Benjamin Loader, National Physical Laboratory, demonstrates the use of voxel models with CST MICROWAVE STUDIO® for simulating the interaction between EM fields and the human body. Read full article..

Advanced System Simulation for Multi-Channel MRI Coils

Advanced System Simulation for Multi-Channel MRI Coils
Magnetic Resonance Imaging (MRI) has gained a lot in popularity in medical diagnoses over the past years thanks to the advantages it offers over other imaging techniques. The complex overlay of magnetic fields at frequencies from static to HF makes field simulation - even including circuit based tuning - an essential and integral part of the design and optimization process of the complete MRI system. CST STUDIO SUITE(tm), with its complete technology approach, is ideally suited to this task. Knowledge of the field distribution inside the body is crucial for the patient's safety. Since measurement of these internal fields is impossible, electromagnetic simulation can give the MRI system designer invaluable insight. Improved image quality can be achieved with the new generation of high-field MRIs, but the price of the related higher operating frequencies is that even more stringent technical challenges are introduced. These typically have to be addressed by using multi-channel coils. Using real-world examples, this webinar will give an overview of the complete MRI workflow including coil-design, circuit-based tuning, multi-channel optimization, and dedicated post-processing such as full system SAR and bio-heat evaluation. Read full article..

BioEM simulations for improved medical diagnosis and treatment

BioEM simulations for improved medical diagnosis and treatment
Interaction of the human body with electromagnetic fields is widely used in medical devices for both diagnosis and therapeutic purposes. Over the last decades there has e.g. been a continuous trend to replace X-ray-based devices in favor of EM-based ones. Additionally, wireless communication of implanted devices is gaining importance. The main challenge during the development of such devices, is the detailed understanding of the field distribution inside the body, since measurement inside living organisms is almost impossible. Here, simulation can be of great benefit. In this webinar we show that human body models have evolved to the point where both the electromagnetic radiation effects as well as macroscopic effects, such as heating, Specific Absorption Rate (SAR) distribution, etc. can be predicted with tools provided by CST. Through the appropriate selection of a body model, it is possible to personalize medical treatment plans and greatly improve diagnosis tools without the need for excessive invasive testing. Using several examples, we will show the toolbox of features related to biomedical simulations which are available to the user of CST STUDIO SUITE. These include the calculation of field distributions inside and the power absorbed by the body and thermal effects due to these fields. Read full article..

Simulation and Construction of Body Coil substitute at 7T Whole Body MRI-System with Travelling Wave Concept

Simulation and Construction of Body Coil substitute at 7T Whole Body MRI-System with Travelling Wave Concept Document type
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..

RF Coil Design for Magnetic Resonance Imaging at the Berlin Ultrahigh Field Facility

RF Coil Design for Magnetic Resonance Imaging at the Berlin Ultrahigh Field Facility Document type
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..

EM field distribution and SAR in a Human Head with MRI Coil

EM field distribution and SAR in a Human Head with MRI Coil
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..

HUGO Human Body Model

HUGO Human Body Model
This article demonstrates the capabilities for importing the HUGO dataset via the CST STUDIO SUITE® Voxel Data Interface. Read full article..

Assessment of occupational exposure of MRI workers resulting from a time-varying magnetic field associated with a cylindrical z-gradient coil

Assessment of occupational exposure of MRI workers resulting from a time-varying magnetic field associated with a cylindrical z-gradient coil Document type
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..

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