Electricity: measuring and testing – Particle precession resonance – Spectrometer components
Reexamination Certificate
2001-02-02
2001-10-16
Arana, Louis (Department: 2862)
Electricity: measuring and testing
Particle precession resonance
Spectrometer components
C324S318000
Reexamination Certificate
active
06304085
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an auxiliary apparatus for a control device for a magnetic resonance tomography apparatus, the control device being of the type which emits an output signal via a transmission output and an Input signal produced by the output signal is fed into the control device via a reception input, and wherein the output signal exhibits an initial frequency and the input signal can be properly processed by the control device only when it exhibits the initial frequency.
2. Description of the Prior Art
Magnetic resonance tomography devices and their control devices are generally known. Normally, the control devices can only emit a prescribed frequency via the transmission output. The Input signal usually can be properly processed only when it (within the bandwidth of a sequence) exhibits this frequency. The frequency normally corresponds to the Larmor frequency of a hydrogen nucleus, which is for example 8.25 MHZ. The bandwidth is ±300 kHz, for example.
Control devices for magnetic resonance tomography systems, wherein the primary frequency is variable, are also known. These control devices, however, are very expensive.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an economic way to operate a magnetic resonance tomography apparatus with at least two frequencies.
This object is achieved in an auxiliary apparatus for a magnetic resonance tomography apparatus control device of the type initially described, wherein the output signal is supplied to the auxiliary apparatus, and the output signal is modified by the auxiliary apparatus such that it has a second frequency that is different from the initial frequency. The auxiliary apparatus supplies the modified output signal to a transmission element as a transmission signal. A reception signal received by a reception element and produced by the transmission signal has the second frequency. The reception signal is supplied to the auxiliary apparatus, and the reception signal is modified by the auxiliary apparatus such that it exhibits the initial frequency. The auxiliary apparatus supplies the modified reception signal to the reception input as an input signal.
The magnetic resonance tomography apparatus and the control device can remain unmodified as a result of the invention. The conversion to the second frequency and back occurs in the auxiliary apparatus. Another frequency other than the actual measuring frequency is generated separately from the control device. It is not necessary to adapt the system control, the image calculation software or the other user software.
The second frequency can be prescribed or can be modifiable in steps or continuously. Normally, the second frequency is fixed, or is variable in relatively large steps of 1 MHZ, for example.
The frequency transfer from the primary frequency to the second frequency and back is particularly simple when the auxiliary apparatus has an auxiliary oscillator, which emits an auxiliary oscillator signal, which exhibits an auxiliary oscillator frequency. The auxiliary oscillator signal and the output signal can be supplied to an output signal frequency mixer, which emits the modified output signal, and the auxiliary oscillator signal and the reception signal can be supplied to a reception signal frequency mixer, which emits the modified reception signal.
An output signal filter can follow the output signal frequency mixer, or a reception signal filter can precede the reception signal frequency mixer, so that frequencies that could cause a phantom signal are filtered out.
The auxiliary oscillator frequency can be generated and stabilized in a simple way when the control device, via a reference output, can emit a reference signal exhibiting a reference frequency, and the reference signal can be supplied to the auxiliary oscillator. The auxiliary oscillator derives the auxiliary oscillator frequency from the reference frequency.
The transmission signal is supplied to the transmission element via a transmission amplifier. The transmission amplifier can be optionally arranged in the auxiliary apparatus or can be allocated to the magnetic resonance tomography apparatus.
A particularly simple and compact structure of the unit formed by the auxiliary apparatus and the transmission/reception element is achieved in an embodiment wherein the transmission element and the reception element are combined to form a common transmission/reception element and wherein the auxiliary apparatus is arranged at the common transmission/reception element.
A gradient signal can be emitted by the control device via at least one gradient output. The gradient signal can be supplied to the auxiliary apparatus and when the auxiliary apparatus can amplify the gradient signal by an amplification factor. The amplification factor is equal to the ratio of initial frequency to second frequency, so that the same allocation of location to transmission/reception frequency results for a nucleus having a different gyromagnetic ratio as would occur without the auxiliary apparatus for the basic nucleus (primarily hydrogen).
The auxiliary apparatus can be connected to the control devices via switches, which allows the auxiliary apparatus to be connected to the control device in a fast and simple manner. The switches can be operated together, allowing the auxiliary apparatus to be particularly simply switched on.
REFERENCES:
patent: 4446431 (1984-05-01), McKay
patent: 4691163 (1987-09-01), Blass et al.
patent: 4873486 (1989-10-01), Kuhn et al.
patent: 5250944 (1993-10-01), Urbas et al.
patent: 5442292 (1995-08-01), Kolem et al.
patent: 5483158 (1996-01-01), van Heteren et al.
Kuth Rainer
Vester Markus
Arana Louis
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
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