JPH04128706U - MRI machine - Google Patents

Abstract

(57) [Summary] [Purpose] The purpose is to realize an MRI device that does not require shielding of the cable leading to the RF power amplifier housing or RF coil. [Structure] An RF power amplifier 4 is installed in a photographing room 21 that accommodates a magnet assembly 1 and a table 22 and is surrounded by a shield 23 and shielded from high frequencies indoors and outdoors.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention relates to an MRI device (nuclear magnetic resonance imaging device), and in particular to the RF power of an MRI device. Concerning the installation location of the force amplifier.

0002

[Conventional technology]

When an atomic nucleus is placed in a static magnetic field, it behaves differently depending on the strength of the magnetic field and the type of nucleus. Precesses at an angular velocity proportional to a constant. The said frequency on the axis perpendicular to this static magnetic field. Magnetic resonance occurs when a high-frequency rotating magnetic field with a certain number of constants is applied, and a certain A population of atomic nuclei undergoes a transition between levels by a high-frequency magnetic field that satisfies resonance conditions, and an energy Transition to a higher energy level. The nucleus excited to a higher level after resonance is It returns to a lower level and radiates energy. The MRI machine detects this specific atomic nucleus. This is a device that observes nuclear magnetic resonance phenomena caused by nuclear magnetic resonance and captures tomographic images of a subject.

0003 An example of this MRI apparatus is shown in FIG. In the figure, 1 contains the subject inside. It has a space (hole) to allow the specimen to be examined. A static magnetic field coil that applies a constant static magnetic field and a gradient magnetic field coil that generates a gradient magnetic field. The magnetic field coil has three axes of x, y, and z. ) and of the atomic nucleus within the specimen. RF pulse transmitting coil for exciting spins and detecting NMR signals from the subject This is a magnet assembly in which receiving coils and other components are arranged. static magnetic field coil , the gradient magnetic field coil, the RF transmitter coil, and the receiver coil are each connected to a static magnetic field power supply 2, It is connected to a gradient magnetic field drive circuit 3, an RF power amplifier 4, and a preamplifier 5. S The sequence storage circuit 6 performs gate modulation in any view according to instructions from the computer 7. Operate the circuit 8 (modulate the RF output signal of the RF oscillation circuit 9 at a predetermined timing), An RF pulse signal is applied from the RF power amplifier 4 to the RF transmitting coil. Also, seek The timing storage circuit 6 is configured to use a sequence signal based on a given pulse sequence. Operate the gradient magnetic field drive circuit 3 to supply gradient magnetic fields to the three axes of x, y, and z. Ru. 10 is the received signal output of the preamplifier 5 using the output of the RF oscillation circuit 9 as a reference signal. This is a phase detector that detects the phase of force. This output signal is output to the AD converter 11. The signal is converted into a digital signal and input to the computer 7.

0004 In this MRI apparatus, the magnet assembly 1 is housed in the imaging room. The photography room is magnetically shielded to prevent external magnetic interference. Also, photography The chamber has a high frequency seal to prevent external high frequency noise from interfering with the MRI machine. has been coded.

[0005] Figure 3 shows the layout of the MRI equipment room. In the figure, the same parts as in Figure 2 have the same meaning. A code is attached. In the figure, 21 houses the magnet assembly 1 and table 22. This is an imaging room for taking tomographic images of subjects. 23 is outside the shooting room 21 Take pictures in such a way that magnetic fields do not leak into the body and the MRI machine is not interfered with by external noise. It is a shield placed around the shadow chamber. 24 is the static magnetic field of the MRI apparatus explained in Figure 2 Systems such as power supplies, gradient magnetic field drive circuits, RF oscillation circuits, gate modulation circuits, and computers A control room that houses system control and various power supply cabinets 25, and is connected to the photography room 21. A cable with a high-frequency shielded filter that relays the cable between A netration panel 26 is provided. 27 is the sequence storage circuit 6 and the operation control This is an operation room that houses a console 12, a display device 13, and the like.

[0006]

[Problem that the idea aims to solve]

As mentioned above, the imaging room 21 is equipped with a shield 23 to prevent magnetic fields from leaking outside. It is also protected from external high frequency noise.

[0007] In addition, the system control in the control room 24 and the RF power supply in the various power supply cabinets 25 are From the force amplifier 4, R is used to prevent radio wave interference due to unnecessary radio wave radiation to the outside. The casing of F power amplifier 4 is high frequency shielded, which increases the cost. ing. Also, the case between the RF power amplifier 4 and the RF coil may be damaged due to load mismatch. If there are standing waves in the cable, radiation from the cable will also become a problem, so the cable should also be shielded. This will further increase the cost.

[0008] The present invention was made in view of the above points, and its purpose is to M that does not require shielding of the cable connected to the force amplifier 4 housing or RF coil The objective is to realize an RI device.

[0009]

[Means to solve the problem]

The present invention solves the above problems and includes a magnet assembly and a table. RF in a shooting room that is surrounded by a shield and shielded from high frequencies indoors and outdoors. It is characterized by the installation of a power amplifier.

0010

[Effect]

Unnecessary radio waves are radiated from the RF power amplifier, but there is a shield installed around the outside of the photography room. Due to security restrictions, they do not go outside the shooting room. Also, a cable connecting the RF power amplifier and the RF coil. The camera is also located inside the shooting room, so it does not go outside.

[0011]

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

0012 FIG. 1 is a layout diagram of an MRI apparatus according to an embodiment of the present invention. In figure, figure 2, figure The same parts as in 3 are given the same reference numerals. RF power amplifier in control room 24 4 is placed in the photographing room 21. RF oscillation circuit 9 has little high frequency power, so there is concern about EMI. Since there is no one, it will be installed in the control room 24 as it is. RF amplifier 4 and RF amplifier 4 The radiation from the cable that connects the RF coil in magnet assembly 1 is The shield 23 provided around the shadow chamber 21 greatly attenuates the radiation to the outside. 70dB or more), so there is no need to worry about EMI.

[0013] As explained above, according to this embodiment, the RF power amplifier 4 is Since it is installed inside the shadow room 21, there is no need to shield the casing of the RF power amplifier 4. It's gone. A weak drive signal is sent from the RF oscillation circuit 9 to the RF power amplifier 4. There is no need to worry about EMI even if it is placed in the control room 24 because it will only be exposed to electricity. Shooting room 21 The shield 23 provided around the magnet assembly installed in the photography room 21 This is necessary to prevent external noise from interfering with the RF power amplifier. It is not necessary to install a shield to prevent radiation to the There is no cost increase. Also, the cable leading to the RF coil is in the same room, so it is short. In this way, it is expected that the loss of high frequency signals due to cables will be reduced.

[0014] Note that the present invention is not limited to the above embodiments. For example, RF power amplifier When using a switching power supply as the power source, the noise may adversely affect MR images. There is a risk that it will occur. Therefore, the power source is placed outside the photography room and only the RF power amplifier is photographed. It is best to install it indoors.

[0015]

[Effect of the idea]

As explained in detail above, according to the present invention, the shield of the RF power amplifier housing It is no longer necessary to shield the cable leading to the RF coil, making it practical. The above effect is significant.

[Brief explanation of drawings]

FIG. 1 is a layout diagram of an MRI apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram of an example of an MRI apparatus.

FIG. 3 is a layout diagram of a conventional MRI apparatus.

[Explanation of symbols]

1 Magnet assembly 4 RF power amplifier 21 Photography room 22 table 23 Shield

Claims (1)

[Scope of utility model registration request] 1. A photographing room (21) that houses a magnet assembly (1) and a table (22) and is surrounded by a shield (23) to shield the interior and exterior from high frequencies.
M characterized in that an RF power amplifier (4) is installed in the
RI device.