Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1998-11-12
2001-04-17
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S425000, C600S426000, C324S318000, C324S322000
Reexamination Certificate
active
06219570
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrical device with an electrical line for operation in the examination volume of a nuclear spin tomography device wherein a sheath wave trap tuned to the operating frequency of the nuclear tomography device is installed in the line.
2. Description of the Prior Art
In nuclear spin tomography devices it is occasionally necessary to lead lines to devices which lie within the examination volume of the nuclear spin tomography device. Problems arise therein particularly when lines are located in the region of transmitting antennas. During the transmission phase there are high electromagnetic fields in the examination volume. Coupling events result between the typically shielded lines and the transmitting antenna of the nuclear spin tomography device via the cable shielding by what are known as sheath waves.
The coupling of the antenna field occurs magnetically (inductively) and electrically (capacitively). This coupling can lead to considerable disturbances of not only the image quality but also the electronic components. An even more serious problem is that local field overelevations of the high frequency field can occur due to such couplings. If electrical lines lie too close to a patient, such field overelevations also lead to a sharp increase of the HF power in the neighboring tissue.
Previously, the problem of electrical lines in the transmission field of a nuclear spin tomograph was solved only for passive components. For the present case, this means local coils and sensors such as for EKG, EEG or breathing signals, in particular. In U.S. Pat. No. 5,065,760, primarily two measures were proposed for avoiding the coupling problem. First, the leading of a cable in a shielded cable channel that is arranged in a zone of low HF field strength, and optimally short “free” cable leading to an apparatus arranged at the patient via a plug connector at a patient bed. Second, the installation of a sheath wave filter in the plug connector.
In EKG and EEG sensors, the problem has been further solved in that lines with relatively high electrical resistance are employed which sharply attenuate a HF coupling. For active electrical devices, particularly video displays, sound converters, manually operable control devices and the like, there has been no satisfactory solution until now. Such devices, therefore, usually have not been employed in the transmission field of the nuclear spin tomography device. This can be achieved by transmission with a local coil instead of a whole-body antenna, for example. Such a limitation is unsatisfactory, however, since a more homogenous irradiation of the HF field is achieved with a whole-body antenna than with a local coil.
The known solution for local coils with a sheath wave trap in the plug connector is not, however, sufficient for the use of the abovementioned active electrical devices, since greater line lengths are typically necessary therein and the danger is greater that a cable lies immediately adjacent to the patient. On the other hand, in local coils a lateral connection is typically provided via which a line can be connected to the plug connector without there being a danger that the line lies directly on the patient.
Accordingly, it is an object of the present invention to construct an active electrical device of the abovementioned type such that HF interference is largely avoided when the line lies in the transmission range of a nuclear spin tomography device.
SUMMARY OF THE INVENTION
This object is inventively achieved in that at least one sheath wave trap that is tuned to the operating frequency of the nuclear spin tomography device is built into the line of the electrical device of the present invention. HF interferences between the transmitting antenna and the line are thus largely avoided. Thus, active electrical devices also can be operated in the transmission range of a nuclear spin tomography device without extreme field overelevations arising in the region of the lines and causing increased HF load and image artefacts.
Accordingly, in an embodiment of the present invention, an active electrical device for operation in the examination volume of a nuclear spin tomography device is provided which includes an electrical line attached to the active electrical device, and a first sheath wave trap installed in the line wherein the first sheath wave trap is tuned to the operating frequency of the nuclear tomography device.
In an embodiment, an electrical outer insulation which is at least 5 mm thick surrounds the electrical line wherein the electrical outer insulation guarantees a corresponding spacing between supporting surfaces of the electrical line and electrical conductors of the electrical line.
In a further embodiment of the present invention, an active electrical device for operation in the examination volume of a nuclear spin tomography device is provided which includes an electrical line attached to the active electrical device, and an electrical outer insulation which surrounds the electrical line wherein the electrical outer insulation guarantees a corresponding spacing between supporting surfaces of the electrical line and electrical conductors of the electrical line.
In an embodiment, the active electrical device further includes a plug connector on the electrical line wherein a length of the electrical line extends from a site of the active electrical device to a plug counter part arranged in an area of a patient bed.
In an embodiment, a second sheath wave trap is installed in the plug connector.
In an embodiment, a second sheath wave trap is installed in the electrical device itself.
In an embodiment, the active electrical device further includes a video display.
In an embodiment, the active electrical device further includes a sound generator.
Additional features and advantages of the present invention are described in, and will be apparent from, the Detailed Description of the Preferred Embodiments and the Drawings.
REFERENCES:
patent: 4922204 (1990-05-01), Duerr et al.
patent: 5065760 (1991-11-01), Krause et al.
patent: 5477147 (1995-12-01), Friedrich et al.
patent: 5855553 (1999-01-01), Tajima et al.
Mueller Edgar
Wicklow Karsten
Lateef Marvin M.
Lin Jeoyuh
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
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