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Träfflista för sökning "WFRF:(Persson Mikael 1959 ) ;pers:(Rylander Thomas 1972)"

Sökning: WFRF:(Persson Mikael 1959 ) > Rylander Thomas 1972

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  • Talcoth, Oskar, 1980-, et al. (författare)
  • Monolithic Multi-Scale Modeling of MR-Induced Pacemaker Lead Heating
  • 2011
  • Ingår i: 13th International Conference on Electromagnetics in Advanced Applications (ICEAA), 2011, Torino, 12-16 September 2011. - 978-1-61284-976-8 ; s. 599-602
  • Konferensbidrag (refereegranskat)abstract
    • Modeling of MR-induced pacemaker lead heating is complicated by, among other things, the multi-scale characteristics of the problem. In this paper, the method of moments is used to model a wide range of length scales of the problem simultaneously including the helix-shaped conducting wires present in the pacemaker lead. A cross-section area conserving meshing scheme for helices is proposed and evaluated. For a relative error of 1%, the meshing scheme reduces the number of thin wire segments needed to model a helix with a factor of roughly 3 to 6, as compared to the conventional approach. In addition, we study the relationship between the maximum induced current on the lead and the number of turns of the helices.
  • Talcoth, Oskar, 1980-, et al. (författare)
  • MR-induced heating of pacemaker leads: A parameter study of contributing factors based on multi-scale modeling
  • 2011
  • Ingår i: Proceedings of Medicinteknikdagarna 2011.
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • Magnetic resonance imaging (MRI) is a valuable tool for diagnostic imaging in healthcare and the number of examinations using this imaging modality increases each year. At the same time, pacemakers and other types of active implantable medical devices (AIMD) are getting increasingly common. Unfortunately, patients with an AIMD are currently deprived of the benefits of MRI due to the potentially harmful interactions of the implant with the electromagnetic fields present during MRI. In particular, currents induced by the radio frequency (RF) field can give rise to excessive heating near sharp corners and edges of the implant. The occurrence of such heating at the electrodes of a pacemaker lead can result in reduction or loss of the pacemaker’s pacing ability. As a consequence, there is a need for MR-safe pacemaker systems. Experiments and numerical modeling have been frequently used for investigations of the heating phenomenon. Such modeling is difficult due to the heterogeneity of the human body, the multi-scale nature of the problem, and inter-patient variations in factors like implant configuration. In this work, we model a wide range of length scales of the problem simultaneously. The modeled MRI birdcage antenna and the human-body phantom have sizes of approximately one fifth of a wavelength whereas the helix-shaped conducting wires of the bi-polar pacemaker lead vary on a length scale of roughly one thousandth of a wavelength. The model being entirely parameterized, we perform parameter studies to investigate how the heating is influenced by different factors, including the dielectric constants of the phantom material, the number of wire turns of the conductors, and the radii of the helices. Furthermore, implications of these results for the design of MR-safe pacemaker leads are discussed.
  • Talcoth, Oskar, 1980-, et al. (författare)
  • Optimal measurements in magnetic tracking for organ-positioning during radiotherapy
  • 2011
  • Ingår i: Proceedings of Medicinteknikdagarna 2011.
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • In a magnetic tracking system, the position and orientation of a coil is determined by its low frequency (LF) magnetic interactions with a coil array of known position and orientation. There are two main types of systems: (i) the coil with unknown position works as a transmitter with a receiving array of sensors, or (ii) the coil array is the transmitter and the coil with unknown position is used as sensor. As LF magnetic fields do not interact with the human body, magnetic tracking is particularly well-suited for tracking of objects in and around the human body. For example, this tracking technique has in recent years been proposed for eye tracking, tracking of tongue movements, and organ-positioning during radiotherapy. We focus on an organ-positioning system for use during radiotherapy. The system, which is of type (i) above, consists of a transmitter that is implanted near the organ of interest and an external array of sensors. Of particular interest is the spatial layout of the sensor array, since this strongly influences the performance of the tracking system. A well-designed sensor array will give good positioning accuracy whereas an ill-designed array can result in an unsolvable positioning problem. In this work, we use Fisher-information theory from the field of optimal measurements to formulate an optimization problem for the layout of the sensor array. Furthermore, we solve the optimization problem and discuss the implications of the results on the design of magnetic tracking systems.
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  • Resultat 1-5 av 5
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Lui, Hoi Shun, 1980- ... (5)
Persson, Mikael, 195 ... (5)
Talcoth, Oskar, 1980 ... (5)
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