Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2001-09-18
2004-03-23
Layno, Carl (Department: 3762)
Surgery
Diagnostic testing
Cardiovascular
Reexamination Certificate
active
06711434
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a physiological sensor system for recording electrical measurement signals in an environment which impairs this recording, particularly in a magnetic resonance instrument, having a plurality of measurement electrodes as well as a signal amplifier device, a power supply, and an electronic device for signal conversion and transmission to an external signal processing and/or control instrument.
Such a physiological sensor system is used for the in situ recording of physiological measurement values, for example, during an examination of a patient using a magnetic resonance instrument. By using such a sensor system, it is, for example, possible to record an ECG during the examination so that, on the one hand, the heart activity can be registered continuously and, on the other hand, the imaging of the magnetic resonance instrument can be controlled by continuously registering the heart's position. If the magnetic resonance images show, for example, the heart in a certain valve position, then the moment at which the heart is in the desired valve position can be registered exactly through the ECG signals, and the imaging can be triggered as a result of this information.
2. Description of the Related Art
Such a physiological sensor system is known from U.S. Pat. Nos. 5,782,241 and 6,052,614. In this sensor system, there are a number of measurement electrodes which are applied directly to the patient's skin. The electrodes are arranged at the lower end of a shielded casing. The casing further contains radio frequency filter devices to each of which an electrode is allocated, as well as a differential amplifier unit, a low pass filter, an electro-optical transducer for converting the measurement signals into optical signals that are given through an optical data line to an external processing and display device, as well as a power source in the form of a battery.
All of the elements relevant to the operations of recording and preprocessing the measurement signals are hence arranged together in the casing, which is applied to the patient. However, this is disadvantageous because of the considerable structural size and the simultaneous integration of the measurement electrodes—the sensor system has to be positioned close to the heart. Moreover, this entails the risk that this sensor system lies at least partially in the imaging region, i.e., in the region from which the magnetic resonance image is intended to be recorded. The latter is thereby at least impaired.
European patent document EP 0 173 130 A1 discloses a device for nuclear spin tomography, in which the electrodes are connected through a cable link to an amplifier device located externally to the nuclear spin tomography device. From this amplifier device, which is arranged together with the nuclear spin tomography device in an RF cabin, the measurement signals are given through an optical waveguide with a connection to a processing device located externally to the cabin. German patent document DE 33 27 731 A1 describes a device for obtaining an ECG signal in a nuclear spin tomograph, in which the nuclear spin tomograph is likewise arranged in an RF cabin, the recorded signals being fed through a shielded connection, which is set to the electrical potential of the RF cabin, in order to avoid interference with the NMR image. German patent document DE 198 17 094 describes a method and a device for deriving an electroencephalogram in the nuclear spin tomograph, while U.S. Pat. No. 4,737,712 describes an isolated power source which can operate in a strong magnetic field and an RF field, as may be found, e.g., in an NMR instrument. Lastly, U.S. Pat. No. 5,052,398 describes a filter suitable to be used in an NMR instrument for real-time heart representation, while German patent document DE 41 38 702 A1 describes a method and a device for diagnosis and quantitative analysis of apnoea and for simultaneous identification of other diseases. Lastly, German patent document DE 41 23 578 A1 describes a non-invasive method for spatial registering of local heart potentials.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a physiological sensor system which affects the imaging as little as possible, yet allows minimally distorted recording of the measurement signals.
To achieve this object, in a physiological sensor system of the type mentioned previously, according to the invention, the measurement electrodes and the signal amplifier device are arranged in or on a shielded first sensor casing to be arranged close to the patient, and the power supply and the electronic device are arranged in a second shielded casing to be arranged close to the patient, the signal amplifier device being connected or connectable to the electronic device and the power supply through a shielded and/or twisted-wire cable connection.
The sensor system according to the invention comprises two shielded casings, which are constructed in the manner of a Faraday cage, and which contain the components needed for the measurement value recording and pre-processing. Only the measurement electrodes and the signal amplifier device are present in the shielded first sensor casing. This first sensor casing is applied directly to the patient, in the region near the heart in the case of recording an ECG. Since only the measurement electrodes—generally three—and the signal amplifier device are integrated in this sensor casing, it is very small so that it can be positioned in such a way that exact measurement value recording is possible, although because of its size it does not substantially affect the imaging.
The recorded measurement signals are given through a shielded or twisted-wire cable connection to the second shielded casing, and there to the electronic device and the power supply. The shielded or twisted-wire cable connection ensures that the analog and amplified measurement signals can be transmitted substantially unaffected by the strong magnetic fields which exist during the operation of a magnetic resonance instrument. This means that the signal-to-noise ratio is virtually unchanged. The second casing can then be positioned fully out of the image-relevant examination region. The length of the cable connection should expediently be in the range between 20-30 cm, although it may be greater.
The signal amplifier device should expediently be arranged in immediate proximity to the measurement electrodes so as to minimize the admission of noise signals. If a plurality of measurement electrodes are arranged in the sensor casing, then a common signal amplifier device can be allocated to them. Alternatively, each measurement electrode can be provided with its own amplifier.
Besides a system configuration having one first sensor casing and one second shielded casing, it is also possible for the system to comprise a plurality of sensor casings, each with a plurality of measurement electrodes and an allocated signal amplifier device, different measurement signals being recordable by the measurement electrodes of a respective sensor casing, and each signal amplifier device being connected or connectable to the common electronic device and the common power supply through a separate shielded or twisted-wire cable connection. In this multifunctional sensor system, for example, one first sensor casing can be used to record ECG measurement signals and the other sensor casing can be used to record EEG measurement signals. Both are very small, since they only contain the electrodes and the amplifier device, and the common signal preparation takes place in the common second shielded casing.
It is particularly expedient for the signal amplifier device, in the case of measurement electrodes intended to record ECG measurement signals, to be designed just to amplify the measurement signals. As an alternative to this, it is possible for the amplifier device also to be designed to form leadoff-specific differential signals. In the scope of an ECG measurement, which corresponds to the extremit
Kramer Michael
Maerzendorfer Walter
Schaetzle Ulrich
Layno Carl
Schiff & Hardin LLP
Siemens Aktiengesellschaft
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