Radu V. Ciupa

3D Modeling of the Induced Electric Field of Transcranial Magnetic Stimulation

The objective of our study was to make use of the MQS solver available under SEMCAD-X simulation environment and the high-resolution 3D head-and-brain model available through the IT’IS Foundation, to make a full 3D analysis of the TMS procedure. The electromagnetic field induced by two typical stimulating coils has been modeled, and their efficiencies compared. The comparison was made based on the distributions of the induced electric field, the activation function and the induced current density distribution.

International Conference on Advancements of Medicine and Health Care through Technology

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Energy Efficient Coils for Magnetic Stimulation of Peripheral Nerves

The preoccupation for improving the quality of life, for persons with different handicaps, led to extended research in the area of functional stimulation. Due to its advantages compared to electrical stimulation, magnetic stimulation of the human nervous system is now a common technique in modern medicine. A difficulty of this technique is the need for accurate focal stimulation. Another one is the low efficiency of power transfer from the coil to the tissue. To address these difficulties, coils with special geometries must be designed.

Magnetic Coils Design for Focal Stimulation of the Nervous System

The technique of magnetic stimulation of nerve fibres represents a new direction of research in modern medicine. This study starts from a major limitation of the coils used for magnetic stimulation: their inability to specifically stimulate the target tissue, without activating the surrounding areas. The first goal of this study was to determine the optimal configuration of coils for some specific applications and evaluate the distribution of the electric field induced. Once the coil configuration established, we address other issues that need to be solved: achieving smaller coils, reducing power consumption (the low efficiency of power transfer from the coil to the tissue is a major drawback) and reducing coil heating.

Database Design Patterns for Healthcare Information Systems

This paper presents some general design patterns for databases in Healthcare Information Systems. The presented solutions were validated in a research project for early diagnosis and treatment of the patients with major risk of esophageal and gastric cancer. Our emphasis is on the generalization capacity of the database structure, which is able to serve other medical specializations, with no compromises for the integration of the entire system.

Magnetic Coils Design for Localized Stimulation

The technique of magnetic stimulation of nerve fibres represents a new direction of research in modern medicine. This study starts from a major limitation of the coils used for magnetic stimulation: their inability to specifically stimulate the target tissue, without activating the surrounding areas. The first goal of this study was to determine the optimal configuration of coils for some specific applications and evaluate the distribution of the electric field induced. Once the coil configuration established, we address other issues that need to be solved: achieving smaller coils, reducing power consumption (the low efficiency of power transfer from the coil to the tissue is a major drawback) and reducing coil heating.

Magnetic coil design for evaluating the response of the spinal cord during magnetic stimulation

The purpose of this paper is to evaluate the response of the spinal cord and nearby area during lumbar magnetic stimulation. One of the most important issues about magnetic stimulation of nervous tissue is the lack of precision in the stimulated region. Based on the experimental measurements performed in cooperation with the Medical University of Vienna, the figure-of-eight coil configuration was proved to be not so efficient in spinal cord stimulation (its inability to specifically stimulate the target tissue, without activating the surrounding areas). In order to obtain the best results in stimulation, the electric circuit of the magnetic stimulator must be optimized (LRC series circuit). The most important is to establish an adequate design of the inductive coil in accordance with the medical application that is used. So, starting from these considerations, the present work aims to find a suitable design of magnetic coil capable to trigger stimulation of the spinal cord.

Assessment of the electric field induced in the human tissue during magnetic stimulation of the spinal cord

Purpose – The purpose of this paper is to estimate the electrical field induced in the spinal cord and nearby area during lumbar magnetic stimulation.Design/methodology/approach – The spinal cord is modelled as a continuous cylinder, while the vertebral column is also represented by a concentric interrupted cylinder. The coil used for magnetic stimulation is a figure of eight, whose centre is placed above T12‐L1 vertebras. The electrical field is induced and its derivative is computed using the finite difference method.Findings – Preliminary results suggest that magnetic stimulation may be able to induce a sufficiently intense electric field inside the spinal cord, leading to the direct activation of spinal nerve roots.Practical implications – If the spinal cord can be stimulated directly by magnetic stimulation, this technique can facilitate functional motor activities, including standing and stepping in paralyzed people, in a non‐invasive way.Originality/value – The authors revealed the fact that functi...

Evaluating the efficiency of stimulators used in magnetic stimulation of the spinal cord

This paper aims in evaluating the efficiency of magnetic stimulators capable of stimulating neural tracts of the spinal cord in healthy subjects. Our previous preliminary tests had shown that the commercial clinical magnetic stimulator Magstim Rapid2 was unable to activate nerve structures located in the spinal cord, with its maximum deliverable energy. In this study we evaluate the characteristics of magnetic stimulators designed and tested (by modelling) for this specific application and we show that the circular commercial coil is the most efficient applicable shape, and no improvements could be gained by changing the distribution of the windings of the magnetic coils. The main conclusion of the study was that a much higher initial voltage should be loaded by the stimulators capacitor in order to achieve activation of neural tracts within the spinal cord.

Modeling the activation of a non-homogenous nerve fiber by magnetic stimulation

In this paper we present a model that combines circuit analysis with Maxwells equations of electromagnetic theory and non-linear cable theory, to explain the action of the induced electric field upon a nerve fiber. The current source and stimulating coil are modeled as a series RLC circuit. The induced electric field distribution within a homogeneous cylindrical volume conductor modeling the arm is calculated for different time courses of the current. The effect of the induced electric field upon the nerve is determined with a cable model which contains active Hodgkin-Huxley elements. The possible non-homogeneities of the nerves electrical properties are also considered, and we assess their influence on the activation of the nerve.