JPH0642878B2 - Magnetic resonance imaging equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is equipped with static magnetic field generating means, gradient magnetic field generating means, means for transmitting an excitation magnetic field and receiving an excitation signal, and The present invention relates to a magnetic resonance imaging apparatus in which a subject placement space is provided and a magnetic field is generated in the space by each of the means.

(Prior Art) A magnetic resonance (MR) phenomenon is a phenomenon in which an atomic nucleus having a non-zero spin and a magnetic moment placed in a static magnetic field resonantly absorbs and emits an electromagnetic wave of a specific frequency. , This nucleus resonates at an angular frequency ω ₀ (ω ₀ = 2πν ₀ , ν ₀ ; Larmor frequency) shown in the following formula.

ω ₀ = γH ₀ where γ is the gyromagnetic ratio peculiar to the type of nucleus,
H ₀ is the static magnetic field strength.

A device for performing a biomedical diagnosis using the above principle performs signal processing of electromagnetic waves (magnetic resonance signals: echo signals and FID signals) of the same frequency as that induced after the above-mentioned resonance absorption, to obtain nuclear density, longitudinal Relaxation time constant T1, lateral relaxation time constant T
2. Diagnostic information in which information such as flow and chemical shift is reflected, for example, a slice image of a subject is obtained non-invasively.

Further, the collection of diagnostic information by magnetic resonance is capable of exciting all the parts of the subject placed in a static magnetic field and collecting signals, but there are restrictions on the device configuration and clinical demands for imaging images. Therefore, in an actual device, excitation and signal acquisition of a specific part are performed.

In such a magnetic resonance imaging apparatus, any one of a superconducting magnet, a normal conducting magnet, and a permanent magnet or a combination thereof is used as the static magnetic field generating means. Then, a part of the static magnetic field region generated by the static magnetic field generation means can be a diagnostic possible region where the subject is placed and can be imaged. This is because the static magnetic field region of the diagnosable region is necessarily a high-intensity magnetic field of several thousand to tens of thousands of Gauss and its magnetic field homogeneity is several ppm because of the principle of the magnetic resonance phenomenon. is there.

Therefore, the static magnetic field generating means composed of any one of a superconducting magnet, a normal conducting magnet, and a permanent magnet or a combination thereof is several meters in terms of dimensions and several tons to over ten tons in terms of weight. Has become.

For example, the static magnetic field generating means consisting of a superconducting magnet is one in which a superconducting wire and a refrigerant are contained in a container in which both openings of a double cylindrical body are closed, and an axial intermediate position of the inner cylindrical space thereof, It is designed to generate a high intensity magnetic field with magnetic field homogeneity of several ppm. The axial length of the inner cylinder space is 2
It is about meters. That is, the subject is introduced along the axial direction into the inner cylindrical space having a length of 2 meters in the axial direction. The region of the subject at the axially intermediate position where the high-intensity magnetic field with the magnetic field homogeneity of several ppm in the inner cylindrical space is generated is the imageable region.

(Problems to be Solved by the Invention) In the above example, a superconducting magnet is used as the static magnetic field generating means, but in other cases as well, the subject introduction space has a length in meters. This length is extremely long as compared with an X-ray CT scanner device that is often compared as a tomographic image visualization device. This is because, for example, the necessary magnetic field is obtained as described above.

As described above, in the magnetic resonance imaging apparatus, the subject introduction space has a length of a unit of meter, so that the inside thereof is dim. Moreover, when the subject enters the area, it becomes even darker. In addition, since the scan time of the magnetic resonance imaging apparatus extends from several minutes to several tens of minutes, the subject placed in a dark space during this long scan time feels uneasy.

Therefore, an object of the present invention is to provide a magnetic resonance imaging apparatus that does not give a subject anxiety.

[Structure of the Invention] (Means for Solving the Problems) The present invention has a structure in which the following means are provided in order to solve the above problems and achieve the object. That is, the invention according to claim 1 is equipped with a static magnetic field generation means, a gradient magnetic field generation means, a means for transmitting an excitation magnetic field and a reception of an induction signal, and also provides a subject placement space in which the space is provided. In a magnetic resonance imaging apparatus configured to generate a magnetic field by each means, a light emitting means formed by scratching a clad portion of a plurality of plastic optical fibers formed in a strip shape is arranged in the space and Characterized in that it is provided with means for introducing light,
The invention according to claim 2 is characterized in that the light emitting means is colored, and the invention according to claim 3 is characterized in that at least one of a reflecting member and a diffusing member is arranged on the surface of the light emitting means. The invention according to claim 4 is characterized in that the light emitting means is sandwiched between a reflecting member and a diffusing member.

(Operation) According to the configuration of the invention according to claim 1 as described above, from the clad portion of the light emitting means arranged in the subject arrangement space,
Side light leakage that can be planar illumination instead of spot illumination can be obtained, and the space can be made brighter. Moreover, since the light emitting means is strip-shaped, the installation space can be small, and the subject placement space is not narrowed. . According to the invention of claim 2, when the light emitting means is colored, for example, milky white,
This is preferable because it provides a milky white planar illumination light that softens the subject's mood. Further, according to the invention of claim 3, since at least one of the reflecting member and the diffusing member is arranged on the surface of the light emitting means, it is possible to improve the light leakage directivity. Further, according to the invention of claim 4, since the light emitting means is sandwiched between the reflecting member and the diffusing member, the light leakage directivity can be further improved as compared with the invention of claim 3. it can.

(Embodiment) An embodiment of the magnetic resonance imaging apparatus according to the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a perspective view showing a configuration of a main part of the magnetic resonance imaging apparatus of this embodiment, for example, a static magnetic field generating means composed of a superconducting magnet and a light emitting means arranged in the static magnetic field generating means, and FIGS. FIG. 4 shows the details of the light emitting means of the embodiment, FIG. 2 is a perspective view of a plastic optical fiber ribbon or tape as the light emitting means, and FIG. 3 (a) is a plastic optical fiber ribbon. FIG. 3B is a view showing the occurrence of side light leakage from the side of the ribbon or tape, and FIG. 3B shows the occurrence of side light leakage from the ribbon or tape of the plastic optical fiber as seen from the end face direction of the ribbon or tape. 4 and FIG. 4 are views showing a light emitting means in which a reflecting plate and a diffusing plate are attached to the surface of a ribbon or tape of a plastic optical fiber in order to improve the light leakage directivity.

As shown in FIG. 1, the static magnetic field generating means composed of, for example, a superconducting electromagnet is a container 10 in which both openings of a double cylinder are closed, and contains a superconducting wire and a refrigerant (not shown). A high-intensity magnetic field with magnetic field homogeneity of several ppm is generated at an axially intermediate position of the inner cylindrical space 11. The axial length of the inner cylindrical space 11 is about 2 meters. That is, a subject (not shown) is introduced into the inner cylindrical space 11 having a length of 2 meters in the axial direction along the axial direction. Then, a portion of the subject (not shown) located at an intermediate position in the axial direction where a high-intensity magnetic field having a magnetic field homogeneity of several ppm is generated in the inner cylindrical space 11 becomes an imageable region.

Further, for example, two light emitting means 12 formed by forming a plurality of plastic optical fibers in a strip shape, for example, which is formed by damaging the clad portion of a ribbon or tape, are arranged in the space 11, and the two light emitting means are provided. In order to introduce light into the light guide 12, light sources 13 are provided at the light receiving ends of the light guides 15 via the light guides 15 connected to the light receiving ends. In this case, in the figure, light sources 13 are provided at both light receiving ends of one light emitting means 12 and one light guide 15, and a total of four light sources 13 are used. Further, reference numeral 14 is a subject-mounting top plate that is put in and taken out from the inner cylindrical space 11 that is a subject placement space.

Details of the light emitting means 12 will be described with reference to FIGS. As shown in FIG. 2, the light emitting means 12 can be formed in a strip shape such as a ribbon or a tape by arranging a plurality of plastic optical fibers in parallel.

Here, one of the plastic optical fibers is denoted by reference numeral 12a.
In Fig. 3 (a), the occurrence of side light leakage in the one plastic optical fiber is seen from the extending direction of the ribbon or tape, and in Fig. 3 (b) from the end face direction of the ribbon or tape. explain. That is, the plastic optical fiber 12a includes a core 12a1 and a clad 12a.
2 and by roughening a part of the surface of the clad 12a2, light is scattered on the roughened surface and the reflection angle is changed, so that light leaks to the outside and the plastic optical fiber It is known that light leakage can be obtained from the side surface of 12a.

Further, in order to improve the polarization directivity, as shown in FIG. 4, it is possible to adopt a configuration in which the reflection plate 16 and the diffusion sheet 17 are arranged on the plastic optical fiber 12a. Here, a white plate or an aluminum plate (foil) can be used as the reflection plate 16. By providing the reflection plate 16, the diffusion effect can be improved, and thus the polarization can be made efficient. Further, cellophane or the like can be used as the diffusion sheet 17. By providing this diffusing sheet 17, a diffusing effect is achieved, and thus the amount of emitted light can be made more uniform.

Of course, even if at least one of the reflection plate 16 and the diffusion sheet 17 is arranged on the plastic optical fiber 12a, the light leakage directivity can be improved to some extent.

As described above, according to the present embodiment, from the clad portion which is the side surface of the light emitting means 12 arranged in the subject arrangement space 11,
Side light leakage that can be planar illumination instead of spot illumination is obtained, and the space 11 can be made brighter and the light emitting means 1 can be used.
Since 2 is a strip shape like a ribbon or tape, the installation space can be small, which is advantageous without narrowing the subject placement space 11.

Further, it is preferable to color the light emitting means 12 into, for example, milky white because it becomes milky white planar illumination light that softens the subject's mood. The same effect is obtained by making the color of the light source 13 milky white.

Further, since at least one of the reflection plate 16 and the diffusion sheet 17 is arranged on the surface of the light emitting means 12, the light leakage directivity can be improved.

Further, since the light emitting means 12 is sandwiched between the reflection plate 16 and the diffusion sheet 17, the light leakage directivity can be further improved as compared with the above.

Of course, the subject arrangement space 11 is a magnetic field generation space and should not be mixed with noise. However, since the light emitting means 12 is a non-electrical element, it draws in noise or a noise generation source. It does not become. Further, the magnetic field is not disturbed, and the operation of the light emitting means 12 and the like does not become abnormal due to the magnetic field.

As described above, in the invention according to claim 1, the static magnetic field generating means, the gradient magnetic field generating means, the means for transmitting the excitation magnetic field and the means for receiving the induced signal are provided, and the subject arrangement space is provided. In a magnetic resonance imaging apparatus in which a magnetic field is generated in each of the means in the space, a light emitting means formed by damaging a clad portion of a plurality of plastic optical fibers formed in a stripe shape is arranged in the space. At the same time, by providing a means for introducing light to the light emitting means, side-polarized light that can be planar illumination instead of spot illumination is obtained from the clad portion of the light emitting means disposed in the subject placement space, and the section In addition, since the light emitting means is strip-shaped, the installation space can be small, and the subject placement space can be narrowed.

Further, in the invention according to claim 2, since the light emitting means is colored, when the light emitting means is colored, for example, milky white, it becomes a milky white planar illumination light that softens the subject, which is clinically preferable. Will be things.

Further, in the invention according to claim 3, since at least one of the reflecting member and the diffusing member is arranged on the surface of the light emitting means, it is possible to improve the light leakage directivity.

In the invention according to claim 4, since the light emitting means is sandwiched between the reflecting member and the diffusing member, it is possible to further improve the light leakage directivity as compared with the invention according to claim 3.

Therefore, according to the present invention, it is possible to provide a magnetic resonance imaging apparatus that does not give the subject a sense of anxiety.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a static magnetic field generating means, which is a main part of an embodiment of a magnetic resonance imaging apparatus according to the present invention, for example, a superconducting magnet, and a light emitting means arranged in the static magnetic field generating means. 2 to 4 show the details of the light emitting means of the same embodiment, and FIG. 2 is a perspective view of a ribbon or tape of a plastic optical fiber as the light emitting means,
FIG. 3 (a) is a diagram showing the occurrence of side light leakage of a ribbon or tape of a plastic optical fiber as seen from the extending direction of the ribbon or tape, and FIG. 3 (b) is a side light leakage of the ribbon or tape of the same plastic optical fiber. FIG. 4 is a view of the generation of light from the direction of the end surface of the ribbon or tape, and FIG. 4 is a light emitting means in which a reflecting plate and a diffusing plate are attached to the surface of the ribbon or tape of the plastic optical fiber to improve the light leakage directivity. FIG. 10 ... Container, 11 ... Inner cylindrical space 11, 12 ... Light emitting means, 13 ... Light source, 14 ... Subject mounting top plate, 15 ...
… Light guide, 16 …… Reflector, 17 …… Diffusion sheet.

Claims (4)

[Claims] 1. A static magnetic field generating means, a gradient magnetic field generating means,
A magnetic resonance imaging apparatus comprising: a means for transmitting an excitation magnetic field and a means for receiving an induced signal; and a subject placement space in which a magnetic field is generated by each of the means. Light emission including a light introducing part formed of a plurality of optical fibers and a light emitting part having a light leakage part disposed in the subject placement space and selectively provided along the side surface of the light introducing part. A magnetic resonance imaging apparatus comprising: a light source; and a light source that is provided outside the subject placement space and that allows light to enter at least one end of the light introducing unit. 2. The magnetic resonance imaging apparatus according to claim 1, wherein at least the light emitting portion of the light emitting means is colored. 3. A strip-shaped surface of the light emitting portion of the light emitting means,
The magnetic resonance imaging apparatus according to claim 1, wherein at least one of a reflection member and a diffusion member is arranged. 4. The magnetic resonance imaging apparatus according to claim 1, wherein the light emitting portion of the light emitting means is sandwiched between a reflecting member and a diffusing member.