Gregor Schaefers

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Magnetic resonance (MR) safety and compatibility are important issues for all medical implants, surgical tools, and electronic or mechatronic equipment to be used within an MR environment. MR testing of medical devices is required for device approval by regulatory agencies, such as the Food and Drug Administration (FDA) and the European Union (EU) Notified(More)
Magnetic resonance (MR) safety and image compatibility are important issues when using medical devices in the environment of magnetic resonance imaging (MRI). MR testing of medical devices is required for device approval by the FDA and the EU notified bodies. Testing methods have been established for basic issues and were published as first ASTM(More)
BACKGROUND MRI is routinely used in patients undergoing intracerebral electroencephalography (icEEG) in order to precisely locate the position of intracerebral electrodes. In contrast, fMRI has been considered unsafe due to suspected greater risk of radiofrequency-induced (RF) tissue heating at the vicinity of intracerebral electrodes. We determined the(More)
We numerically investigated power deposition and temperature rise generated due to the presence of a titanium rod placed in a phantom, located inside a 1.5 T coil. The induced power deposition and temperature rise normalized to incident tangential electric field was found to be dependent on distance to the phantom wall. The different dependence of the(More)
Radio frequency (RF) induced power deposition near straight insulated leads excited by different incident electrical field profiles was investigated. 3-D electromagnetic (EM) simulations were used to obtain implant models as well as RF-induced power depositions calculated as the integral of power loss density. For the investigated setups up to 400%(More)
The implant model obtained by 3D EM and thermal co-simulation was used to estimate power deposition and temperature rise due to the presence of bare titanium rods placed in a high permittivity medium for uniform and non-uniform 64 MHz incident electric fields. No correlation between power deposition and temperature rise were observed. Worst-case temperature(More)
Over the last decade, the number of clinical MRI studies at 7 T has increased dramatically. Since only limited information about the safety of implants/tattoos is available at 7 T, many centers either conservatively exclude all subjects with implants/tattoos or have started to perform dedicated tests for selected implants. This work presents our experience(More)
We investigated RF-induced power deposition (p) generated by insulated leads with different lengths located in proximity to two tissues. The first tissue surrounding the leads was shaped as a cylinder with diameter of 11 mm and located in a very large box filled by the second tissue. Lead electromagnetic models and p substantially depend on electrical(More)
We investigated RF-induced power deposition (p) generated by insulated leads with different lengths surrounded by lower permittivity medium (LPM). 3-D electromagnetic simulations were used to obtain p and leads electromagnetic models. Lead electromagnetic models and p substantially depend on electrical conductivity of LPM. It is impossible to define one(More)