Electricity: measuring and testing – Particle precession resonance – Spectrometer components
Reexamination Certificate
2002-06-26
2003-07-08
Arana, Louis (Department: 2862)
Electricity: measuring and testing
Particle precession resonance
Spectrometer components
C439S950000
Reexamination Certificate
active
06590395
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a connector device for a sensor or actuator, particularly for surface antennas in magnetic resonance systems, of the type composed of two terminal elements releasably connected to one another, a first of those terminal elements includes a first electrical conductor that is connected to the sensor or actuator and a second of these terminal elements includes a second electrical conductor that is connectible to an evaluation unit, whereby the first and second electrical conductors are coil systems that enable signal transmission by inductive coupling given a connection of the two terminal elements.
2. Description of the Prior Art
The acquisition and forwarding of sensor signals in a radio-frequency system, such as, for example, a magnetic resonance apparatus, makes high demands as to immunity to interference and dependability of the signal transmission. Magnetic resonance tomography is a known technique for acquiring images of the inside of the body of a living examination subject. A magnetic resonance tomography apparatus has a basic field magnet for generating a uniform magnetic field for the polarization of the atomic nuclei in the body to be examined, a number of gradient coils for the location coding of the magnetic resonance signals as well as one or more radio-frequency transmission antennas that emit radio-frequency pulses for triggering the magnetic resonance signals into the body to be examined. The magnetic resonance signals that are generated are acquired via a sensor and are supplied to an evaluation unit for the calculation of the magnetic resonance images. Either the radio-frequency transmission antenna utilized for the excitation of the magnetic resonance signals, referred to as the whole body antenna, or one or more radio-frequency reception antennas not rigidly connected to the magnetic resonance tomography apparatus, referred to as surface antennas, are utilized as sensors. Magnetic resonance images having a better signal-to-noise ratio can be registered with a surface antenna. It is brought close to the body region to be examined and is connected via a connecting cable to the evaluation unit of the magnetic resonance tomography apparatus.
The connection between the surface antenna and the evaluation unit is currently designed as a galvanic plug-type connector wherein one of the two terminal elements, that are releasably connectable to one another, is connected to the surface antenna and the other is connected to the evaluation unit. These plug-type connectors have the advantage of a flexible manipulation, since the surface antennas can be removed in a simple way and replaced by other surface antennas and can be connected to the evaluation unit via the plug-type connector.
One disadvantage of the known plug-type connectors, however, is that the electrical contacts can be only inadequately disinfected due to their being freely accessible. In the medical sector, however, a regular disinfection of the examination apparatus is important. Further, the problem arises given the known plug-type connectors that undesired sheath waves propagate on the leads, which may lead to a heating of adjacent body tissue that is unpleasant for the patient.
German PS 3616389 discloses a proximity switch acting in non-contacting fashion in a different technical field that is composed of a signal-processing part, a main part and a signal-acquiring sensor part that is pluggable to the main part. The signal and energy transmission between the sensor part and the main part given this proximity switch ensues via inductive coupling on the basis of integrated core coils that lie directly opposite one another when the two parts enter into a plug-type connection.
The same principle of signal transmission by inductive coupling is also utilized in a bio-magnetometer disclosed in German Translation 69029375. With this bio-magnetometer, extremely small magnetic fields are measured, these being generated, for example, by the brain of a patient. The bio-magnetometer contains a superconducting, magnetic pick-coil that is connected to a highly sensitive magnetic signal detector, a SQUID. The entire system is accommodated in Dewar vessels for producing the temperatures required for the super-conduction. The publication proposes that the pick-up coil and the magnetic signal detector be arranged in two different Dewar vessels that are detachably connected to one another. For the signal transmission, transmission coils are situated in each Dewar vessel that are fashioned and arranged such that they are coaxially thrust inside one another given a connection between the two Dewar vessels.
The principle of signal transmission by inductive coupling utilized in these two publications, however, does not seem suitable for operation in a magnetic resonance system, since the transmission coils are exposed to high radio-frequency fields therein that disturb the signal transmission and are also influenced by it.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a connector device for a sensor or actuator, particularly for a surface antenna in a magnetic resonance system, that avoids the above disadvantages and can be unproblemmatically disinfected.
The object is achieved in a connector device according to the invention that is composed of two terminal elements releasably connectible to one another, with a first of these terminal elements includes a first electrical conductor that is connected to the sensor or actuator and a second of these terminal elements includes a second electrical conductor that is connectible to an evaluation unit. The first and second electrical conductor are coil systems that enable signal transmission by inductive coupling where the two terminal elements are connected to one another. Each of the coil systems is formed of at least two series-connected coils that have oppositely directed windings and are dimensioned such that the sum of voltages induced in the coils by a uniform electromagnetic field yields zero for each of the coil systems.
As a result of this fashioning of the connector device, the signals received by the sensor or sent to the actuator are not galvanically transmitted but are transmitted by inductive coupling between the two terminal elements of the connector device, for example of a plug-type connector. This design enables the complete hermetic sealing of the sensor or actuator with the first terminal element, so that no electrical conductors are exposed. This is especially advantageous for surface antennas that are potentially exposed to body fluids such as, for example, a prostate coil. With the inventive connector device, surface antennas that can be completely disinfected and sterilized can be achieved. In the same way, the second terminal element of the connector device, which may come into contact with the patient, can be completely hermetically sealed. As a result of a complete encapsulation, all disinfection measures can be unproblemmatically implemented, so that the inventive connector device is excellently suited for utilization in the medical field.
In the inventive connector device, reduction emission from the coupled connection, and the influence of external radio-frequency fields, are achieved by a special design of the two coil systems in the terminal elements. Each of the coil systems is formed of at least two series-connected coils that have oppositely directed windings and are dimensioned such that the sum of currents induced in the coils due to a uniform electromagnetic field yields zero for each of the coil systems. This is achieved by a suitable selection of the area and the number of turns in conjunction with the direction of the winding of the individual coils. The sum of the product of area and number of turns for all individual coils of each coil system must yield approximately zero, whereby oppositely directed numbers of turns are distinguished by opposite operational signs. Only as a result of this design is the disturbance-free uti
Reykowski Arne
Vester Markus
Arana Louis
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
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