JPH0630165Y2 - Receiver coil for nuclear magnetic resonance imaging - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a high-frequency receiver coil for an NMR imaging apparatus that visualizes a desired portion of a subject using nuclear magnetic resonance (hereinafter abbreviated as NMR). It is a thing.

[Conventional technology]

In the NMR imaging apparatus, the atomic nuclei are excited by being irradiated with a high frequency wave, and a high frequency signal (this is called an NMR signal) emitted from the resonated atomic nuclei is detected. A coil is usually used to detect a high frequency signal, and various types of coils such as a saddle type coil, a solenoid type coil, and modifications thereof are considered. The S / N of the image in which the sensitivity of this detection coil is reconstructed
Many research improvements have been made because they directly affect the ratio.

In the case of the vertical magnetic field type NMR imaging apparatus, a solenoid coil having high sensitivity can be used as the receiving coil. Also, D.I. I. Hoult and R.H. E. Richards S /
According to the formula representing the N ratio, it is said that the S / N ratio is improved by reducing the size (diameter) of the high frequency receiving coil, which is also confirmed in the experiment.

When the receiving coil is attached to the subject, it is desirable that the coil can be divided to improve the usability. In addition, a small-diameter coil cannot be attached unless it can be divided at the cervical vertebra or the like. Therefore, the conventional device is Japanese Patent Application No. 63-1.
As described in No. 52341, the receiving coil is made of a flexible material, part of which can be attached and detached using a connector,
The structure is such that the length of the receiving coil can be changed according to the inspection part of the subject so as to be in close contact with the subject.

[Problems to be solved by the device]

In the above-mentioned prior art, since a general connector is used for the receiving coil, the influence of the magnetic material contained in the connector material or the mat is not taken into consideration, which disturbs the uniformity of the static magnetic field. However, there is a problem that the obtained image is distorted. Therefore, the receiving coil and the connecting connector must be mounted apart from the subject to the extent that magnetic distortion does not affect them, resulting in a large receiving coil diameter and a decrease in S / N ratio. It was

The present invention has been made to solve the above-described problems, and an object thereof is to provide a high-frequency receiver coil for an NMR imaging apparatus that can obtain a high-quality image with a high S / N ratio without magnetic distortion. And

[Means for Solving the Problems]

The above-mentioned problem is caused by the fact that the connector used for the receiving coil uses a magnetic substance. Therefore, it is recommended that the connector contact material be made of an alloy that does not contain a magnetic material and has properties such that it can be used as a contact such as phosphor bronze, and that gold plating is applied to improve the reliability of the contact part. I chose

Here, in general gold plating, nickel plating must be performed as a base in order to stabilize the plating surface such as prevention of peeling. However, nickel is a magnetic substance, which hinders demagnetization. Therefore, copper plating or silver plating is applied as a base of the gold plating to obtain a non-magnetic plating. Also,
When silver plating is applied, a small amount of nickel is generally mixed and used as an alloy to prevent sulfurization, but pure silver is used because it also prevents demagnetization.

In this way, by making the connector used for the receiving coil the magnetic material from the material and plating material, it is possible to obtain an image without magnetic distortion even when the receiving coil is brought into close contact with the subject. It will be possible.

[Action]

To use the receiving coil in close contact with the subject by configuring the connector used for the receiving coil for the NMR imaging device with a non-magnetic material including the plating material and eliminating the influence on the uniformity of the static magnetic field. Is possible and S without distortion
It becomes possible to obtain a high-quality image with a high / N ratio.

〔Example〕

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

FIG. 3 is a block diagram showing the overall configuration of the NMR imaging apparatus according to the present invention. This NMR imaging apparatus obtains a tomographic image of the subject 6 by utilizing a nuclear magnetic resonance (NMR) phenomenon, and includes a static magnetic field generating magnet 10, a central processing unit (hereinafter referred to as CPU) 11, and a sequencer 12.
, Transmission system 13, magnetic field gradient generation system 14, and reception system 15
And a signal processing system 16. The static magnetic field generating magnet 1
0 is for generating a strong and uniform static magnetic field around the subject 6 in a direction orthogonal to the body axis thereof. The permanent magnet system, the normal conducting system, or the normal conduction system in a space with a certain space around the subject 6 is used. A superconducting magnetic field generating means is arranged. The sequencer 12 operates under the control of the CPU 11 and sends various commands necessary for collecting tomographic image data of the subject 6 to the transmission system 13, the magnetic field gradient generation system 14, and the reception system 1.
To send to 5. The transmission system 13 includes a high frequency generator 17, a modulator 18, a high frequency amplifier 19, and a high frequency coil 20a on the transmission side. The high frequency pulse output from the high frequency generator 17 is modulated by a sequencer 12 in accordance with a command. The electromagnetic wave is applied to the subject 6 by amplitude-modulating 18 and amplifying the amplitude-modulated high-frequency pulse by a high-frequency amplifier 19 and then supplying the amplified high-frequency pulse to a high-frequency coil 20a arranged close to the subject 6. It is becoming like this. The magnetic field gradient generation system 14 is composed of a gradient magnetic field coil 21 wound in three directions of X, Y, and Z, and a gradient magnetic field power source 22 for driving each coil, and according to a command from the sequencer 12. By driving the gradient magnetic field power source 22 of each coil, the gradient magnetic fields G _X , G _Y , and G _Z in the triaxial directions of _X , _Y , and _Z are applied to the subject 6. The slice plane for the subject 6 can be set by the method of applying the gradient magnetic field. The reception system 15 includes a high frequency coil 20b on the reception side, an amplifier 23, a quadrature phase detector 24, and an A / D converter 25, and the response of the subject 6 to the electromagnetic wave emitted from the high frequency coil 20a on the transmission side. Of the electromagnetic wave (NMR signal) is detected by the high-frequency coil 20b arranged close to the subject 6, is input to the A / D converter 25 via the amplifier 23 and the quadrature phase detector 24, and is converted into a digital amount. , And the quadrature detector 2 at the timing according to the command from the sequencer
The collected data of two systems sampled by 4 are sent, and the signals thereof are sent to the signal processing system 16. The signal processing system 16 includes a CPU 11, a recording device such as a magnetic disk 26 and a magnetic tape 27, and a display 28 such as a CRT. The CPU 11 performs processing such as Fourier transform and correction coefficient calculation image reconstruction. The signal intensity distribution of an arbitrary cross section or the distribution obtained by performing an appropriate calculation on a plurality of signals is imaged to display 28
It is supposed to be displayed in.

In FIG. 3, the high frequency coils 20a and 20b and the gradient magnetic field coil 21 on the transmitting side and the receiving side are arranged in the magnetic field space of the static magnetic field generating magnet 10 arranged in the space around the subject 6. .

An embodiment of the high frequency coil 20b according to the present invention is shown in FIGS. FIG. 1 is a diagram showing the overall configuration of a high frequency receiving coil. The coil wire 30 is a flexible material, and has connectors 31, 32, a tuning circuit 33 for tuning to the NMR signal frequency, and an output connector 34 for connecting to a preamplifier attached thereto.

FIG. 2 is an explanatory diagram of a usage example. High frequency receiving coil 20
At the time of imaging, b, first, winds the coil wire 30 along the inspection site of the subject, and then connects the connectors 31 and 32. At this time, since the connector 32 for the connector 31 is attached at a plurality of positions on the coil wire, the structure is such that it can be appropriately selected according to the peripheral length of the inspection site. FIG. 2 (a) shows the case where the inspection site is large, and FIG. 2 (b) shows the case where it is small.

As described above, since the present receiving coil has a structure capable of being brought into close contact with the subject, all its constituent members must be non-magnetic materials. Therefore, phosphor bronze is used as a material for the contact portions of the connectors 31 and 32 and the output connector 34, and the plating treatment for surface stabilization is made non-magnetic as gold plating with the copper plating as a base.

Conventionally, since a general connector is used here, there is a problem in that the uniform magnetic field is disturbed by the influence of the magnetic substance and distortion occurs on the reconstructed image. According to the present invention, this problem can be solved, and it becomes possible to use a receiving coil having a shape suitable for the examination site of the subject, and a high-quality image with a high S / N ratio can be obtained.

[Effect of device]

As described above, the present invention can solve the problem of magnetic distortion by demagnetizing the connector used for the high-frequency receiving coil in the NMR imaging apparatus, and enables the installation close to the subject. There is an effect that a high-quality image having a high / N ratio can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the overall structure of a high frequency receiving coil according to an embodiment of the present invention, FIG. 2 is an explanatory view showing a usage state of the high frequency receiving coil, and FIG. 3 is an NMR imaging apparatus according to the present invention. It is a block diagram which shows the whole structure. 6 ... Subject, 20b ... High frequency receiving coil, 30 ... Coil wire, 31, 32 ... Connector, 33 ... Tuning circuit, 34 ...
Output connector.

Claims (1)

[Scope of utility model registration request] 1. A means for generating a static magnetic field, a means for generating a gradient magnetic field, a means for generating a high-frequency pulse for causing nuclear magnetic resonance in atomic nuclei of atoms constituting a tissue of a subject, and the nucleus. A high frequency receiving coil which is the signal detecting means of the nuclear magnetic resonance imaging apparatus, which comprises a nuclear magnetic resonance signal detecting means for detecting a signal by magnetic resonance and an arithmetic means for performing image reconstruction using the nuclear magnetic resonance signal. The mounting of this high-frequency receiving coil on the subject is
In a receiving coil for a nuclear magnetic resonance imaging apparatus which is capable of closely contacting by connecting a connector, the connector is made of a material containing no magnetic substance, and a plating containing no magnetic substance is applied. Receiver coil for magnetic resonance imaging.