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- Persson, Mikael, 1959, et al.
(författare)
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Advances in Neuro Diagnostic based on Microwave Technology, Transcranial Magnetic Stimulation and EEG source localization
- 2011
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Ingår i: Asia Pacific Microwave Conference, (APMC 2011;Melbourne, VIC; 5 - 8 December 2011). - 9780858259744 ; , s. 469-472
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Konferensbidrag (refereegranskat)abstract
- Advances in neuro diagnostics based on microwave antenna system in terms of a helmet including a set of broad band patch antennas is presented. It is shown that classification algorithms can be used to detect internal bleeding in stroke patients. Transcranial magnetic stimulation has traditionally been used for brain mapping and treatment of depression. In this paper we discuss the use of the method for neuro diagnostics with the help of integrated image guidance. Surgical therapy has become an important therapeutic alternative for some patients with medically intractable epilepsy. Electroencephalography and the associated model based diagnostics as a non-invasive diagnostic tool is also discussed.
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| 4. |
- Shirvany, Yazdan, 1980, et al.
(författare)
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Investigation of brain tissue segmentation error and its effect on EEG source localization
- 2012
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Ingår i: Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS. - 1557-170X. ; , s. 1522-1525
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Konferensbidrag (refereegranskat)abstract
- Surgical therapy has become an important therapeutic alternative for patients with medically intractable epilepsy. Correct and anatomically precise localization of the epileptic focus, preferably with non-invasive methods, is the main goal of the pre-surgical epilepsy diagnosis to decide if resection of brain tissue is possible. For evaluating the performance of the source localization algorithms in an actual clinical situation, realistic patient-specific human head models that incorporate the heterogeneity nature of brain tissues is required. In this paper, performance of two of the most widely used software packages for brain segmentation, namely FSL and FreeSurfer has been analyzed. Then a segmented head model from a package with better performance is used to investigate the effects of brain tissue segmentation in EEG source localization.
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| 5. |
- Talcoth, Oskar, 1980, et al.
(författare)
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Monolithic Multi-Scale Modeling of MR-Induced Pacemaker Lead Heating
- 2011
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Ingår i: 13th International Conference on Electromagnetics in Advanced Applications (ICEAA), 2011, Torino, 12-16 September 2011. - 9781612849768 ; , s. 599 - 602
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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.
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| 6. |
- Talcoth, Oskar, 1980, et al.
(författare)
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MR-induced heating of pacemaker leads: A parameter study of contributing factors based on multi-scale modeling
- 2011
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Ingår i: Proceedings of Medicinteknikdagarna 2011. ; , s. 52-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Magnetic resonance imaging (MRI) is a valuable tool for diagnostic imaging inhealthcare 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 currentlydeprived of the benefits of MRI due to the potentially harmful interactions of the implant withthe electromagnetic fields present during MRI. In particular, currents induced by the radiofrequency (RF) field can give rise to excessive heating near sharp corners and edges of theimplant. The occurrence of such heating at the electrodes of a pacemaker lead can result inreduction or loss of the pacemaker’s pacing ability.As a consequence, there is a need for MR-safe pacemaker systems. Experiments andnumerical 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 natureof 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. Themodeled MRI birdcage antenna and the human-body phantom have sizes of approximatelyone fifth of a wavelength whereas the helix-shaped conducting wires of the bi-polarpacemaker lead vary on a length scale of roughly one thousandth of a wavelength. The modelbeing entirely parameterized, we perform parameter studies to investigate how the heating isinfluenced by different factors, including the dielectric constants of the phantom material, thenumber of wire turns of the conductors, and the radii of the helices. Furthermore, implicationsof these results for the design of MR-safe pacemaker leads are discussed.
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| 8. |
- Talcoth, Oskar, 1980, et al.
(författare)
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Optimal measurements in magnetic tracking for organ-positioning during radiotherapy
- 2011
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Ingår i: Proceedings of Medicinteknikdagarna 2011. ; , s. 79-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)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 isthe transmitter and the coil with unknown position is used as sensor. As LF magnetic fields do not interact withthe human body, magnetic tracking is particularly well-suited for tracking of objects in and around the humanbody. For example, this tracking technique has in recent years been proposed for eye tracking, tracking of tonguemovements, 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 particularinterest is the spatial layout of the sensor array, since this strongly influences the performance of the trackingsystem. A well-designed sensor array will give good positioning accuracy whereas an ill-designed array canresult in an unsolvable positioning problem.In this work, we use Fisher-information theory from the field of optimal measurements to formulate anoptimization problem for the layout of the sensor array. Furthermore, we solve the optimization problem anddiscuss the implications of the results on the design of magnetic tracking systems.
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