JPS6365850A - Nuclear magnetic resonance imaging apparatus - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a nuclear magnetic resonance imaging device (hereinafter referred to as an MRI device) that obtains a tomographic image of a subject (human body) using nuclear magnetic resonance (NM) phenomenon. In particular, the present invention relates to an MRI apparatus that can switch the direction of irradiation and reception of high-frequency pulses depending on the region to be examined on a subject.

[Background of the invention]

In the vertical static magnetic field system, as shown in FIG. 3, when irradiation is in the X-axis direction and reception is in the Y-axis direction, the shape of the surface coil 2 on the head of the subject 10 becomes a solenoid coil wound tightly around the neck. However, if the coil cannot be divided, it will not be possible to install it. However, the head reception filter 3 has the advantage of being able to receive signals using a more sensitive solenoid coil than others.

On the other hand, if the irradiation is in the Y-axis direction and the reception is in the X-axis direction, as shown in Figure M4, a saddle-shaped coil 4 can be used as the surface coil of the neck, and the saddle 4' can be expanded as shown in Figure 5. The device can be attached to the subject 1, allowing it to be placed in close contact with the neck. However, as shown in FIG. 4, the head receiving coil 5 is a saddle-shaped coil, making it impossible to use a solenoid-shaped coil with higher sensitivity. As mentioned above, in the conventional technology, the directions of high-frequency pulse irradiation and reception were fixed.
Depending on the part of the object to be imaged, reception may not be possible with the optimally shaped coil.

[Purpose of the invention]

An object of the present invention is to provide an M-processing device that enables bidirectional irradiation with a high-frequency irradiation coil, thereby making it possible to select an optimally shaped receiving coil according to the test site of a subject.

[Summary of the invention]

An MRI apparatus is equipped with two sets of high-frequency irradiation coils at the same time, and by changing each coil by 9J, it is possible to irradiate high-frequency pulses in both directions. As a result, by switching the irradiation direction, it is possible to apply the optimum shape receiver 1] coil to an inspection site to which the optimal shape receiver 1] coil could not be applied because conventionally it could only be irradiated in one direction.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 6 is a block diagram showing the overall configuration of a nuclear magnetic resonance imaging apparatus according to the present invention. This nuclear magnetic resonance imaging apparatus obtains a tomographic image of a subject by using the nuclear magnetic resonance (NM) phenomenon, and includes a static magnetic field generating magnet 10,
It consists of a central processing unit (CPU) 11, a sequencer 12, an irradiation system 13, a magnetic field gradient generation system 14, a reception system 15, and a signal processing system 16. The static magnetic field generating magnet 10 generates a strong and uniform static magnetic field around the subject 1 in the body axis direction (horizontal direction) or in a direction perpendicular to body movement (vertical direction). Magnetic field generating means of a permanent magnet type, a normal conduction type, or a superconducting type is arranged in a surrounding space with a certain extent. The sequencer 12 operates under the control of the %CPU II and sends various commands necessary for data collection of tomographic images of the subject I to the irradiation system 13, the magnetic field gradient generation system 14, and the reception system 15.

The irradiation system 13 includes a high-frequency oscillator 17, a modulator 18, a high-frequency amplifier 19, and a high-frequency coil 20a on the irradiation side, and the modulator 18 modulates the amplitude of the high-frequency pulse output from the high-frequency oscillator 17 according to instructions from the sequencer 12. Then, this amplitude-modulated high-frequency pulse is sent to a high-frequency amplifier 1.
After being amplified in step 9, the electromagnetic waves are supplied to a high frequency coil 20a placed close to the subject 1, so that the subject IK is irradiated with electromagnetic waves. The magnetic field gradient generation system 14 is composed of gradient magnetic field coils 21 wound in the three axes of x, y, and z, and a gradient magnetic field power supply 22 that drives each coil. By driving the gradient magnetic field power supply 22 of the coil, a gradient magnetic field G
G y + G z is applied to the subject 1. Depending on how this gradient magnetic field is applied, a slice plane for the subject IK can be set. The receiving system 15 includes a solenoid-type high-frequency coil 20b on the receiving side, an amplifier 23, a quadrature phase detector 24, and an A/D converter 25. The electromagnetic wave (NMR signal) of response 1 is detected by a high frequency coil 20b placed close to the subject l, and is sent to the A/D via an amplifier 23 and a quadrature phase detector 24.
The signal is input to the D converter 25 IC and converted into a digital quantity, and further sampled by the quadrature phase detector 24 at the timing according to the command from the sequencer 12 to obtain two series of collected data, and the signal is sent to the signal processing system 16. It has become. This signal processing system 16 is.

It consists of a CPU II, a recording device such as a magnetic disk 26 and a magnetic tape 27, and a display 28 such as a CRT.Fourier transform is performed by the CPU II.

Processing such as correction coefficient calculation and image reconstruction is performed, and the signal intensity distribution of an arbitrary cross section or the distribution obtained by performing appropriate calculations on a plurality of signals is converted into an image and displayed on the display 28. In addition, in FIG. 1, the high frequency coils 20a on the irradiation side and the reception side.

20b and the gradient magnetic field coil 21 are arranged in the magnetic field space of the static magnetic field generating magnet 10 arranged in the space around the subject 1.

Here, in the present invention, the high frequency coil 20 on the irradiation side
a consists of two sets of coils. FIG. 1 shows an embodiment of a high frequency irradiation coil according to the present invention. This embodiment shows an embodiment using a saddle-shaped coil.It is made of a non-magnetic metal with low resistance to high-frequency current, such as a pipe (about φ5 to φi0) or a strip (about 20 to 40 am). The saddle-shaped coil 6 is large enough for a human body to enter from the Y-axis direction, and its WF magnetic field is formed in the X-axis direction. As long as it has the characteristic of resonating with the frequency, it is possible to connect it in series or to connect it with two or more tangents.

Conventionally, this set of coils constituted an irradiation coil, but in the present invention, in addition to this, a coil made of the same material and shape as the coil 6 and having a larger outer diameter is installed outside the coil 6. At that time, it is installed so as to intersect lσ with the coil 6 so as to form a F magnetic field in the Y-axis direction. In this embodiment, the saddle-shaped coil 7 is installed as shown in the figure, but basically the RF magnetic field is in the direction orthogonal to the coil 6, in this case 1? Any coil formed in the t1 direction may be used. However, when coupling occurs between two sets of coils, each coil acts as a load on each other, for example, coil 6 acts as a load on coil 7. Therefore, care must be taken not to create a bond between the two. Since the coils 6 and 7 are orthogonal to each other, basically no magnetic coupling occurs. . It is necessary to increase the distance between opposing lines and prevent coupling.

The coils 6 and 7 are switched by a switch 10 according to a command from a sequencer 12 in accordance with the selection of the object to be imaged or the high-frequency receiving coil.

Now, when a high-frequency pulse is supplied to the coil 6, a high-frequency magnetic field is formed in the X-axis direction, and when it is supplied to the coil 7, a high-frequency magnetic field is formed in the Y-axis direction.
formed in the axial direction.

When the coil 7 is used, the high frequency reception direction becomes the X axis, so a saddle-shaped coil can be used as the neck surface coil 4 as shown in FIG. 4, and the solenoid coil 2 as shown in FIG. There is no need to wind the surface coil, and the problem of attaching and detaching the surface coil is solved. This is effective in applying the cervical surface coil of the vertical static magnetic field method in '19. The cervical surface coil 4 can be attached and detached by opening and closing the saddle portion 4' of the coil as shown in FIG.

However, if we consider imaging the head in this direction, we will find that the only option is to select the X-shaped saddle-shaped receiving coil 5 shown in FIG. In the case of the head, unlike the V4 section, the solenoid coil can be attached and detached as shown in Figure 3, so it is more effective to use a solenoid coil with higher reception sensitivity than the saddle type. Therefore, for imaging the @ section, the irradiation coil is switched from 7 to 6, and the reception direction is set to the Y-axis direction, making it possible to receive a high 1x degree using the solenoid type reception coil 3 as shown in Figure 3. .

As mentioned above, by providing the irradiation coil with the function of applying high-frequency pulses in both directions, it is possible to solve the problems described above and to select the optimal coil shape for high-sensitivity reception, depending on the inspection area of the subject 1. Become. Although FIG. 1 shows an example of a saddle-shaped irradiation coil, it is also possible to use a Helmholck coil as shown in FIG. Reference numerals 8 and 9 indicate Helmholtz-shaped irradiation coils arranged so as to take the X and Y axes, respectively.

〔Effect of the invention〕

As explained above, the present invention is equipped with two types of high-frequency irradiation coils that irradiate electromagnetic waves to the subject 1 at the same time.
Since high-frequency pulses can be applied in both directions, as shown in Fig. 3, an lenoid-shaped head receiving coil 3 is used for head imaging, and by switching the irradiation direction, the height of the neck can be adjusted. For resolution images, a saddle-shaped neck surface coil 4 shown in FIG. 44 can be used. Conventionally, under the certain relationship of irradiation in the X-axis direction and reception in the Y-axis direction as shown in Fig. 3, the only way to obtain high-resolution imaging of the neck was to use the solenoid-type cervical surface coil shown in Fig. 2. There was a problem with attaching and detaching it to the subject. However, according to the present invention, it is possible to solve the above-mentioned problems and to select an optimally shaped receiving coil according to the imaging region of the subject.

[Brief explanation of drawings]

FIG. 1 is a schematic BA diagram showing one embodiment of the high-frequency irradiation coil according to the present invention, FIG. 2 is an explanatory diagram showing another embodiment of the above-mentioned high-frequency coil, and FIG. FIG. 4 is an explanatory diagram of the receiving coil when YM is the irradiation direction. FIG. 5 is an explanatory diagram showing how to attach and detach the saddle-shaped surface coil to the subject. FIG. 6 is the nucleus according to the present invention. This is a block section showing the overall configuration of a magnetic resonance imaging apparatus. DESCRIPTION OF SYMBOLS 1... Subject, 2... Solenoid type neck surface coil, 3... Solenoid type receiving coil for head, 4...
Saddle-shaped neck surface coil, 4'...Saddle part, 5...Saddle-shaped receiver coil for the head, 6, 7...Saddle-shaped irradiation coil, 8.
9...Helmholtz type irradiation coil, 10...Swin? , 10... Static magnetic field generation magnet, 11... Central processing unit (CPU), 12... Controller, 13... Irradiation system, 14... Magnetic field gradient generation system, 15... Receiving system, 1
6...Signal processing system. 20a...Radiation side high frequency coil, 20b...Receiving side high frequency coil 1riJ Fig. 3 Fig. 4

Claims (1)

[Claims] 1. It has a static magnetic field generating magnet that generates a static magnetic field in the body axis direction of the subject or in a vertical direction perpendicular to this, and is placed close to the subject to irradiate the subject with electromagnetic waves, or In a nuclear magnetic resonance imaging system that has a solenoid-shaped high-frequency coil that detects electromagnetic waves emitted from a specimen, the high-frequency irradiation coil can emit high-frequency pulses in both directions, and the high-frequency reception coil can receive signals in each direction. 1. A nuclear magnetic resonance imaging apparatus characterized in that it is possible to select a receiving coil having an optimal shape depending on a part of a subject to be examined.