JPS63292948A - Mr imaging apparatus - Google Patents

Abstract

PURPOSE:To impart no oppressive sensation to an examine by reducing the noise emitted from the winding frame of a magnetic field coil and cooling the heat from said coil, by forming the closed space, which is provided inside a superconductive magnet and confining the inclined magnetic field coil and the winding frame of said coil, from a non-magnetic non-metallic member. CONSTITUTION:A non-magnetic non-metallic cylinder 10 is arranged between an inclined magnetic field coil 6 and an irradiation coil 7 so as to confine a static magnetic field correction coil 5 and the inclined magnetic field coil 6 and the end parts thereof are closed by the internal cylindrical end part of a cryostat 1 and an end plate to form a closed space. By this structure, since the impact sound generated from the winding frame of the coil 6 is confined in the closed space and hard to leak to the outside, noise is reduced. Therefore, possibility such that a psychological oppressive sensation or unpleasant feeling is imparted to an examinee and contamination due to incontinence and vomiting caused thereby is generated or the electrical short-circuit due to said contamination is generated in the coil 6 through which a large current flows is eliminated. Further, it is prevented that the examinee in the cylinder 10 is carelessly brought into contact with the inclined magnetic field coil.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an MR imaging apparatus, and particularly to a superconducting magnet unit suitable for reducing noise due to electromagnetic vibrations transmitted to the winding frame of a gradient magnetic field coil.

[Conventional technology]

The superconducting magnet of the MR imaging device has the shape of a cryostat, and inside it are arranged a static magnetic field correction coil made up of a cylindrical bobbin, a gradient magnetic field coil, and a high-frequency transmitting/receiving coil for NMR, and a simple cover is attached. was traditionally used.

This is shown in FIG. For this reason, no consideration was given to the noise (impact sound) vibration 9 heat generated in the winding frame due to electromagnetic vibrations generated when high-frequency pulses are applied to the gradient magnetic field coil.

[Problem that the invention seeks to solve]

In MR imaging equipment, it is necessary to provide a magnetic field gradient in order to determine the irradiation am plane. Three sets of coils are installed that generate . These coils are called gradient magnetic field generating coils. Each of these x, y, and z coils is connected to an independent dedicated power source and is excited with a controlled current (generally a maximum of 300 A with pulsed current having regular intervals).

However, since these coils are placed in a very strong static magnetic field (generally 5,000 to 20,000 Gauss), when an excitation current flows, an electromagnetic force that is determined by the direction of the static magnetic field and the direction of the current flowing through the coil acts on them. Especially when driven by a pulse power source, a strong electromagnetic force acts instantaneously, so
The coil vibrates, which is transmitted to the winding frame through the coil fixing portion and becomes a noise source (impact sound or resonance sound).

Furthermore, since a large current flows through the coil, it generates considerable heat. The purpose of this MR imaging device is to measure the human body, and the examinee is placed inside the gradient magnetic field coil, so the occurrence of these impact sounds can cause psychological pressure, which is an undesirable cause. was. Furthermore, it is difficult to remove dirt caused by incontinence, vomiting, and sweating during measurements in seriously ill patients.Furthermore, the inflow of dirt can cause a decrease in the electrical current between the gradient magnetic field coils, which poses a problem from the standpoint of patient safety. Ta.

The purpose of the present invention is to reduce the noise emitted from the winding frame of the gradient magnetic field coil, and also to cool the heat radiation from the coil, and to provide easy maintenance and safety that does not give a feeling of pressure to the person being inspected. An object of the present invention is to provide a superconducting magnet unit for an MR imaging device with high performance.

[Means for solving problems]

The above problem consists of a superconducting magnet with a cylindrical inner surface, a cylindrical static magnetic field correction coil provided inside the superconducting magnet, and a cylindrical coil provided inside the static magnetic field correction coil located on the NMR signal. A gradient magnetic field coil that imparts information and a pulsed electromagnetic wave provided inside the gradient magnetic field coil are applied to perform NMR.
An MR imaging apparatus comprising a high-frequency NMR transmitting/receiving coil for receiving signals, wherein a cylinder made of a non-metallic and non-magnetic material is provided between the gradient magnetic field coil and the NMR high-frequency transmitting/receiving coil. Solved by an MR imaging device in which each end of the superconducting magnet is joined with an end corresponding to each end inside the superconducting magnet to form a closed space, or the space is filled with cooled oil. be done.

[Effect]

When a gradient magnetic field coil is driven by a pulsed power source, a strong electromagnetic force acts instantaneously, causing the coil to vibrate, and this vibration is transmitted to the winding frame through the coil fixing part, causing noise (as if it were hitting the winding frame). (percussion sound or resonance sound) or vibration.・
A cylinder made of a non-metallic, non-magnetic material is provided between the gradient magnetic field coil and the NMR high-frequency transmitter/receiver coil, and each end of this cylinder is connected to an end corresponding to each end inside the superconducting magnet. By joining the end plates to form a closed space and sealing the static magnetic field correction coil and the gradient magnetic field coil within the closed space, the noise and vibrations generated from the winding frame of the gradient magnetic field coil are confined within the closed space and released to the outside. Furthermore, the space is filled with cooled oil to attenuate the noise and vibration and remove the heat generated by the gradient coil.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 shows a first embodiment of the invention. The superconducting magnet is formed by a cryotat 1, inside which a conductor N2 container 2 and a liquid He container 3 are formed inside the container 2 in a cylindrical shape. The superconducting wire 4 is housed in a liquid He container 4, and is excited from the outside by a magnetizing power source (not shown) to generate a static magnetic field. Since this cryostat 1 is for measuring the human body, its interior is hollow and cylindrical. A cylindrical static magnetic field correction coil 5 for correcting the uniformity of the static magnetic field is disposed within this, and X and Y coils are located inside the coil.

A gradient magnetic field coil 6 that generates an arbitrary gradient magnetic field in each direction of Z is arranged, and an irradiation coil 7 and a reception coil 8 for transmitting and receiving high frequency NMR waves are arranged inside the coil 6. The structure is such that any tomographic image placed at the center of the magnet is affected. For this reason, when an excitation current from a pulse power source flows through the gradient magnetic field coil 6, a strong electromagnetic force acts on the coil instantaneously, causing the coil to vibrate, which is transmitted to the winding frame through the coil fixing part and generates noise. This is directly transmitted to the patient inside, creating a psychological feeling of pressure and discomfort. This embodiment uses a non-magnetic device to confine the static magnetic field correction coil 5 and the gradient magnetic field coil 6, as shown in FIG. 1, in the conventional device.

A nonmetallic material 10 is disposed between the gradient magnetic field coil 6 and the irradiation coil 7, and each end thereof is joined to the inner cylindrical end of the cryostat 1 by an end plate to form a closed space. As a result, the impact sound generated by the winding frame of the gradient magnetic field coil 6 is confined within the closed space and is less likely to leak outside, thereby reducing noise. Therefore, there is no fear of contamination due to incontinence, vomiting, etc. that gives the patient psychological pressure and discomfort, and of electric shorts occurring in the gradient magnetic field coil 6 through which a large current flows due to the contamination. Furthermore, patients entering the room do not inadvertently touch the gradient magnetic field coils, allowing for safe and comfortable measurements.

FIG. 2 shows a second embodiment of the invention. In this embodiment, a vacuum pump unit 11 is installed in order to bring the closed space formed by the non-magnetic, non-metallic cylinder 10 into a vacuum state as described in the first embodiment. The sound generated by the winding frame of the magnetic field coil 6 is not propagated outside the closed space, and the noise is reduced, and the conduction of heat generated by the gradient magnetic field coil 6 is also reduced.

FIG. 3 shows a third embodiment of the invention. In this embodiment, the closed space formed by the non-magnetic, non-metallic cylinder 10 described in the first embodiment is filled with insulating oil 12, the oil 12 is circulated by an external oil pump, and the oil 12 is further circulated by an external oil pump. 1
2 is configured to be cooled by a cooling unit 14. According to this, the impact sound generated by the gradient magnetic field coil 6 is attenuated by the oil 12, and the noise and vibrations are also attenuated. Furthermore, since the heat generated from the gradient magnetic field coil 6 can be cooled by the external cooling unit 14, the performance of the gradient magnetic field coil 6 is improved.

FIG. 4 shows a fourth embodiment of the present invention. In this embodiment, the closed space formed by the non-magnetic, non-metallic cylinder 102 explained in the first embodiment is filled with a sound absorbing material and a cushioning material 15. It is. According to this, the noise generated by the gradient magnetic field coil 6 can be absorbed and attenuated, and vibrations can also be attenuated. In addition, the sound absorbing material and buffer material 15 are poor conductors of heat, so they can be insulated against the heat generated from the gradient magnetic field coil 6, making the superconducting magnet quiet, vibration-free, and safe with little heat generation. unit can be provided.

〔Effect of the invention〕

According to the present invention, it is provided inside the superconducting magnet, and the noise and
By forming the closed space that confines the gradient magnetic field coil and the coil winding frame, which are the sources of vibration, with non-magnetic and non-metallic members, the noise and vibration can be removed from the closed space without adversely affecting the performance of the MR imaging apparatus. We provide a highly safe device that can greatly attenuate propagation from the space to the outside and do not give a feeling of pressure to the person being inspected.Furthermore, the closed space is filled with cooling oil, and in addition to the above effects, the gradient coil It has an excellent effect of removing heat generation.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a first embodiment of the invention, FIG. 2 is a sectional view showing a second embodiment of the invention, and FIG. 3 is a sectional view showing the invention. Third
FIG. 4 is a sectional view showing a fourth embodiment of the present invention, and FIG. 5 is a sectional view of a conventional device. 11. , superconducting magnet, 5...static magnetic field correction coil, 6.
... Gradient magnetic field coil, 7... Irradiation coil, 8... Receiving coil, 10... Cylinder, 12... Oil, 13...
・Oil pump 1, Meishincho coil 7 8 history name carp 1
Around 61 4? rJo Pressure Receptacle Coil Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. A superconducting magnet whose inside is cylindrical, a cylindrical static magnetic field correction coil provided inside the superconducting magnet, and a cylindrical NMR provided inside the static magnetic field correction coil. An MR imaging apparatus comprising: a gradient magnetic field coil that adds position information to a signal; and an NMR high-frequency transmitting/receiving coil that is provided inside the gradient magnetic field coil and transmits a pulsed electromagnetic wave and receives an NMR signal. Gradient magnetic field coil and the NM
A non-metallic, non-magnetic tube is provided between the R high-frequency transmitting and receiving coil, and each end of the tube is joined to an end corresponding to each end inside the superconducting magnet with an end plate. An MR imaging device characterized by forming a closed space. 2. The device according to claim 1, wherein the closed space has a pressure lower than atmospheric pressure. 3. The device according to claim 1, wherein the closed space is filled with a sound and vibration damping material. 4. A superconducting magnet with a cylindrical shape on the inside, a cylindrical static magnetic field correction coil provided inside the superconducting magnet, and a cylindrical shape provided inside the static magnetic field correction coil to give position information to the NMR signal. An MR imaging apparatus comprising a gradient magnetic field coil that transmits a pulsed magnetic field, and a high frequency transmitting/receiving coil for NMR that is provided inside the gradient magnetic field coil and transmits a pulsed electromagnetic wave and receives an NMR signal.
A non-metallic, non-magnetic tube is provided between the R high-frequency transmitting and receiving coil, and each end of the tube is joined to an end corresponding to each end inside the superconducting magnet with an end plate. An MR imaging apparatus characterized in that a closed space is formed, the closed space is filled with oil, and a pump for circulating the oil and a cooling unit for cooling the oil are provided outside the closed space.