Surgery – Diagnostic testing – Structure of body-contacting electrode or electrode inserted...
Reexamination Certificate
1998-06-04
2001-03-13
Dvorak, Linda C. M. (Department: 3739)
Surgery
Diagnostic testing
Structure of body-contacting electrode or electrode inserted...
C600S393000, C600S411000, C128S901000
Reexamination Certificate
active
06201981
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an electrode for measuring a biomedical signal and an electrode support device for measuring a biomedical signal which are preferably used in a medical measuring apparatus for measuring vital information, such as an electroencephalograph or an electrocardiograph.
2. Related art
Conventionally, in MRI (Magnetic Resonance Instrument) diagnosis, an electroencephalogram or an electrocardiogram is measured.
FIG. 10
is a view diagrammatically showing the configuration of MRI.
The case where an electroencephalogram or an electrocardiogram is to be obtained in MRI will be considered. In a strong magnetic field formed in MRI magnet of the MRI, a movement of the body of the subject causes a voltage in conformance to Faraday's law of electromagnetic induction to appear in lead wires of electrodes of an electroencephalograph or an electrocardiograph. Such a voltage functions as noises, and produces a problem in that the measurement cannot be correctly performed. This problem is produced also by a minute movement of the body of the subject caused by the heartbeat. Therefore, it is requested to develop a countermeasure to the problem as soon as possible.
FIG. 11
shows an electrocardiogram and the waveform of noises. From the figure, it will be seen that noises appear in synchronization with the electrocardiogram. The noise level varies depending on the site to which an electrode is attached and the manner of drawing out a lead wire therefrom, and is in proportion to the number of crossing magnetic fluxes.
SUMMARY OF THE INVENTION
Conventionally, in order to solve this problem, the arrangement direction of lead wires of electrodes is made coincident with the direction of the line of magnetic force so that the opening area with respect to the line of magnetic force is reduced, or a filter is disposed in a signal processing circuit. However, such countermeasures are insufficient for suppressing noises.
Therefore, it is an object of the invention to provide an electrode for measuring a biomedical signal and an electrode support device for measuring a biomedical signal which, when used in a magnetic field, can suppress noises generated in lead wires connected to electrodes of an electroencephalograph or an electrocardiograph, to a low level.
In order to attain the object, according to the present invention, there is provided the electrode for measuring a biomedical signal including a plurality of electrodes for taking out a biomedical signal; lead wires respectively connected to the electrodes; and a support member which supports the electrodes and the lead wires, and which is made of a flexible and insulative material such as plastic or rubber, and the lead wires are tightly twisted in the support member and the twisted lead wires are disposed in a straight line.
According to this configuration, the lead wires respectively connected to the electrodes are tightly twisted in the support member. Consequently, even when the electrode is placed in a magnetic field, there is little opening area with respect to the line of magnetic force. As a result, even when the electrode is used together with an apparatus such as MRI which produces a strong magnetic field, a voltage induced in each lead wire is very low in level, and hence an electrocardiogram or an electroencephalogram can be correctly measured.
The electrode for measuring a biomedical signal of the invention comprises: a plurality of electrodes for taking out a biomedical signal; lead wires respectively connected to the electrodes; and a support member which is made of a flexible and insulative material such as plastic or rubber, and in which the electrodes are stacked so as not to overlap one another and the lead wires are stacked so as to overlap one another in a noncontact state.
According to this configuration, the electrodes are stacked so as not to overlap one another and the lead wires are stacked so as to overlap one another in a noncontact state. Therefore, the opening area of each lead wire with respect to the line of magnetic force is reduced. As a result, even when the electrode is used together with an apparatus such as MRI which produces a strong magnetic field, a voltage induced in each lead wire is very low in level, and hence an electrocardiogram or an electroencephalogram can be correctly measured.
Furthermore, a sensor which, when placed in a magnetic field, generates a current corresponding to the number of crossing magnetic fluxes may be disposed in the support member. For example, the sensor is configured by disposing a conductive wire in the support member, in a shape of a loop.
The electrode support device for measuring a biomedical signal of the invention comprises: a plurality of housing portions which are made of a flexible and insulative material such as plastic, or rubber, and which respectively house a plurality of electrodes for taking out a biomedical signal; and a groove through which lead wires respectively connected to the electrodes are drawn out in a straight line to an outside.
According to this structure, the lead wires can be linearly fixed, and hence the opening area with respect to the line of magnetic force in the stack direction can be reduced. As a result, even when the electrode support device is used together with an apparatus such as MRI which produces a strong magnetic field, a voltage induced in each lead wire is very low in level, and hence an electrocardiogram or an electroencephalogram can be correctly measured.
The electrode support device may further comprise an accommodating portion which accommodates a sensor which generates a current corresponding to the number of crossing magnetic fluxes.
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Wolf et al. “Student Reference Manual for Electronic Instrumentation Laboratories”, Prentice Hall Pub. 1990.
Catalog For An Electrode Located In The Cranium, AD-Tech Medical Instrument Corporation; Nihon Kohden; catalog No. 930-850.
Dvorak Linda C. M.
Nihon Kohden Corporation
Ruddy David M.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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