JPH01126956A - Magnetic resonance diagnostic apparatus - Google Patents

Abstract

PURPOSE:To bring resistance to zero, to eliminate the offset variation of a signal by voltage drop, to accurately measure the signal and to collect high accurate data, by constituting the system earth of each unit machinery constituting a system of a superconductive material and performing operation in a superconductive state. CONSTITUTION:A conductor 13 is cooled by a high temp. cooling medium 14 to hold a superconductive state. The connection part of a system earth SE', for example, the unit A thereof and the ground is formed using a conductor 16 such as a usual copper wire but the connection points 17a, 17b of the conductors 16, 13 are constituted so as to be almost cooled to the critical temp. of the conductor 13. Since said critical temp. is the temp. of liquid nitrogen being a high temp. cooling medium, the connection points 17a, 17b are easily cooled to the almost critical temp. unlike a material showing a superconductive state by liquid helium. By the above-mentioned constitution, the resistance value of the system earth SE' becomes zero and the unit A shows no offset variation of a signal by voltage drop and the signal can be accurately measured.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention provides a gradient magnetic field for excitation, which is applied to a subject placed in a static magnetic field according to a predetermined excitation/detection procedure. By applying a high frequency magnetic field, a magnetic resonance phenomenon is caused in a specific part of the subject, and the excited magnetic resonance signal is detected and signal processed. The present invention relates to a magnetic resonance diagnostic apparatus that images anatomical information and qualitative information, and particularly relates to a magnetic resonance diagnostic apparatus that can collect highly accurate data.

(Prior Art) The general configuration of this type of magnetic resonance diagnostic apparatus will be explained with reference to FIG. That is, in FIG. 2, the magnet assembly limb M forming the main body is a static magnetic field magnet 1 of a superconducting or normal conducting type, and the X-axis.

Y-axis, two-axis gradient magnetic field coil2. It has a transmitting/receiving coil 3.

Further, the static magnetic field magnet 1 is driven by a static magnetic field control system 4 including excitation control and coolant control, and is driven by an X-axis and a Y-axis.

The two-axis gradient magnetic field coils 2 each have an X-axis gradient magnetic field power supply 5,
Y-axis gradient magnetic field power supply 6. Driven by two-axis gradient magnetic field power supply 1, transmitting/receiving coil 3 is driven by transmitter 8 for excitation and by receiver 9 for detection. It is now possible to do so.

Further, the X-axis gradient magnetic field power supply 5, the Y-axis gradient magnetic field power supply 6, the two-axis gradient magnetic field power supply 1, and the transmitter 8 are controlled by the sequencer 10 to generate a predetermined pulse sequence K i! ? It is designed to be driven by The computer system 11 drives and controls the sequencer JO, introduces the magnetic resonance signal obtained from the receiver 9, performs signal processing, and generates a tomographic image of a certain slice region, which is monitored by the optical display system 12. I am trying to display it.

Here, the relationship between ground and S/N will be explained. That is, the receiver 9 and computer system 11 as a data collection system are composed of a plurality of units, and the system is grounded between them. Third
The figure is a diagram showing a connection configuration between a plurality of units connected by system ground. In other words, if the system ground SK is taken using a normal conductor such as a copper wire in order to make the ground potential between unit A and unit B the same, the power drop due to the partial voltage resistance contained in the copper wire The potential observed at A (for example, the received signal) Va
always includes the offset of Ra Ia+R (Ia+Ib).

However, Ra is the resistance value on the unit A side of the system earth SH, Ia is the current flowing in that section, Rh is the resistance value on the unit B (ill) of the system earth SE, Ib is the current flowing in that section, R is the system ground This is the resistance value on the earth side of SE.

In the above, if II, Ib, etc. have alternating current components, the ground point of unit A will fluctuate, and since magnetic resonance signals are weak in the first place, accurate signal measurement will be impossible, resulting in a decrease in S/N. I decided to invite him.

(Problem to be Solved by the Invention) In this way, in the conventional technology, although the magnetic resonance signal is weak, effective countermeasures are not taken against fluctuations in the ground potential, so it is difficult to measure the signal accurately. However, there was a problem in that it was impossible to do so, and the S/N ratio was lowered.

Therefore, an object of the present invention is to provide a magnetic resonance diagnostic apparatus that is capable of collecting highly accurate data.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems and achieve the object, the present invention has a structure that takes the following means. In a magnetic resonance diagnostic apparatus comprising an excitation system for causing a magnetic resonance phenomenon in a specimen and a detection system for detecting and signal processing the induced magnetic resonance signal, each unit constituting the system The system ground of the equipment is made of superconducting material and is configured to operate in a superconducting state.

(Function) According to this configuration, since the grounding conductor is made of a superconducting material and is operated in a superconducting state, the resistance (impedance) is zero, and there is no signal offset fluctuation due to voltage drop. Accurate signal measurements are possible.

(Embodiment) An embodiment of the magnetic resonance diagnostic apparatus according to the present invention will be described below with reference to the drawings.In other words, this embodiment has the same overall configuration as the apparatus shown in FIG. The structure of the system ground of the data collection system receiver 9 and the computer system 11, which are composed of units, is shown in FIG.

That is, the system earth SE is made of a high-temperature superconducting material that exhibits a superconducting state at the temperature of liquid nitrogen, which is a high-temperature refrigerant 100 times higher than that of cryogenic refrigerants such as liquid helium, as conductor J3.
The conductor 13 is provided in a simple dewar 75 containing a high-temperature refrigerant 14. Here, the conductor 13
It is assumed that the wire is formed into a plate shape that is not an extremely thin wire.

With this configuration, the conductor J3 is cooled by the high temperature coolant 14 and maintained in a superconducting state. Further, a conductor J6 such as a normal copper wire is used for the connection between the unit A of the system ground SF' and the earth, and the connection point 17h between this conductor and the conductor J3 is the connection point 17h.

J7b is cooled to about the critical temperature of conductor J3. Note that cooling the connection points 11g and 17b to about the critical temperature is different from materials that exhibit a superconducting state such as liquid helium because this critical temperature is the temperature of liquid nitrogen, which is a high-temperature refrigerant. It's easy.

According to this embodiment with the above configuration, the system earth SE'
The resistance value of A is zero, and there is no signal offset fluctuation due to voltage drop in A, making accurate signal measurement possible.

Incidentally, since the magnetic resonance signal is a high frequency signal and other signals are also in a high frequency region, the system earth SE' must have a resistance value of zero and an inductance component that is suppressed. In response to this requirement, in this embodiment, the conductor J3 is formed into a plate shape that is not an extremely thin wire.
The inductance component must be a small value, and even when handling high-frequency signals as mentioned above, the impedance must be a small value.The Schnitt A does not have signal offset or fluctuation due to voltage drop, making accurate signal measurement possible. Become.

Although the application example for one unit in the data acquisition system, that is, the receiver 9 or the computer system I has been described above, a configuration in which the system earth SE' is connected between a plurality of units may also be used. Furthermore, the present invention is not limited to data collection systems, and may be applied to other units that handle weak signals.

In addition, various modifications can be made without departing from the spirit of the present invention.

[Effects of the Invention] As described above, in the present invention, the system earth of each two-layer device constituting the system is made of a superconducting material and is operated in a superconducting state. The conductor is made of superconducting material and is operated in a superconducting state, so the resistance (impedance) is zero, there is no signal offset fluctuation due to voltage drop, and accurate signal measurement is possible. A magnetic resonance diagnostic apparatus capable of collecting data can be provided.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of the main parts of an embodiment of the magnetic resonance diagnostic apparatus according to the IMK of the present invention, FIG. 2 is a diagram showing the general configuration of the magnetic resonance diagnostic apparatus, and FIG. 3 is a diagram showing the main parts of the conventional example. FIG. MA... Magneto, toe assembly, 1... Static magnetic field magnet, 2... X axis, 7461% 2-axis gradient magnetic field coil,
3... Transmission/reception coil, 4... Static magnetic field control system, 5...
・X-axis gradient magnetic field power supply, 6... Y-axis gradient magnetic field power supply, 2.
...Two-axis gradient magnetic field source, 8...Transmitter, 9...Receiver, 10...Sequence f, 11...Computer system, 12...Display system, J3... Conductor made of high temperature superconducting material, 14... High temperature refrigerant, 15... Simple dewar 116... Ordinary conductor, 17a, I 7b
...M reading mark, SE'...System earth. Applicant's agent Patent attorney Takehiko Suzue Cause 1 Figure 3

Claims (1)

[Claims] In a magnetic resonance diagnostic apparatus comprising an excitation system for causing a magnetic resonance phenomenon in a subject, and a detection system for detecting and processing the induced magnetic resonance signals, each of the systems constituting the system A magnetic resonance diagnostic apparatus characterized in that a system ground of a unit device is made of a superconducting material and is operated in a superconducting state.