JP2001095777A - Nuclear magnetic resonance imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nuclear magnetic resonance imaging apparatus which the positioning relation of an examinee body and receiving coil can be changed even in a gantry, and the position to take picture is always situated at high sensitive picture taking position. SOLUTION: The MRI apparatus of this invention is provided with a RF coil 4 to impress magnetic field for excitement to the examinee arranged in static magnetic field space, and an gradient magnetic coil 5 to impress gradient magnetic field. The apparatus is further provided with a gantry G having a pored core part H, a signal receiving coil 20 to receive NMR signal detected from the examinee P, and the bed 10 which the examinee P can be mounted. The receiving coil 20 and the bed 10 are arranged to move each independently and relatively. More practically, the bed 10 has a top board 12 consists of the lamination of an upper top board 12a and a lower top board 12b. The linear part of the receiving coil 20 is inserted between the upper top board 12a and the lower top board 12b, and the moving possibility is secured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear magnetic resonance imaging apparatus, and more particularly to an apparatus for improving the operability of a bed and receiving means.

[0002]

2. Description of the Related Art A nuclear magnetic resonance imaging apparatus is a nuclear magnetic resonance signal (NMR signal) obtained by applying an excitation magnetic field (RF magnetic field) and a gradient magnetic field to a subject placed in a static magnetic field space. Is a device for reconstructing a nuclear magnetic resonance imaging (MRI) image (tomographic image) of the subject based on the. According to this, unlike an X-ray CT apparatus, an obtainable tomographic image is naturally limited by the installation state of an X-ray detector, but a free cross section is assumed for a subject, and the tomographic image is obtained. Has many advantages, such as the ability to obtain

[0003] As such a nuclear magnetic resonance imaging apparatus, for example, an apparatus as shown in FIG. 7 has been conventionally provided. In FIG. 7, a subject P lies on a bed 1 having a top board 1a installed so as to be capable of translating in the horizontal direction in the figure. The receiving coil 2 for receiving the above-mentioned NMR signal is installed on the top plate 1a. This receiving coil 2
Of the subject P with respect to the top plate 1a is adjusted in advance so as to coincide with a portion relating to the subject P for which a tomographic image is to be obtained. on the other hand,
A gantry G having an air core H is provided so as to face the moving direction of the top plate 1a. The gantry G has a main magnet 3 and an RF for forming a static magnetic field (polarizing magnetic field), an RF magnetic field, and a gradient magnetic field different from each other in three orthogonal axes.
The coil 4 and the gradient coil 5 each have an air core H
Are arranged concentrically with the central axis L of the same being coaxial. Note that these coils and the like are separately connected to a power supply (not shown) that can be arbitrarily controlled.

[0004] Such a nuclear magnetic resonance imaging apparatus operates as follows. The subject P and the receiving coil 2 on the top 1a are inserted into the air core H together with the top 1a,
By applying a static magnetic field to the air core portion H, the alignment of nuclear magnetic moments in the subject P and the Larmor precession of the magnetic moment around the static magnetic field direction are generated,
Applying an RF magnetic field here to absorb magnetic resonance (spin excitation)
Is generated, the NMR signal obtained at this time is received by the receiving coil 2, and a tomographic image of the subject P is formed by the image reconstruction means (not shown). In addition,
By applying the gradient magnetic field, it is possible to localize the position of the tomographic image when the tomographic image is formed.

[0005]

In a typical nuclear magnetic resonance imaging apparatus as described above,
There is a problem that the moving range of the receiving coil 2 is limited by a coil cover (not shown) which is integrally formed with the receiving coil 2 and fixes the receiving coil 2 to the top plate 1a. That is, the moving range of the receiving coil 2 is limited to the size of the coil cover. This means that, once the setting of the subject P and the receiving coil 2 on the top plate 1a has been once determined outside the air core portion H and the couch 1 has been introduced into the air core portion H, the image is easily taken. This is recognized as a problem that the position (position of the receiving coil 2) cannot be adjusted. It should be noted that such a situation also applies to a case where a receiving coil that is movable under a set of coils is employed, which is of the type laid under the subject P.

[0006] Further, since the moving range of the receiving coil 2 is limited as described above, there is a problem that the sensitivity unevenness in the AP direction (see FIG. 7) is observed in the imaging of the subject P. Was. That is, after the position where the receiving coil 2 and the subject P face each other is set outside the air core H, this is introduced into the air core H to start imaging. If the position is deviated from the center of the magnetic field of the RF coil 4 or the like, the adjustment is no longer possible in the related art as described above. In the latter case, there is no choice but to photograph, or as a result, the sensitivity unevenness in the AP direction is to be observed. Therefore, in the past, in order to avoid the occurrence of such sensitivity unevenness, the imaging application was limited to only the cervical spine or the spine imaging.

[0007] The present invention has been made in view of the above circumstances, and an object thereof is to make it possible to change the positional relationship between a subject and a receiving means once set within a gantry, and to perform imaging. It is an object of the present invention to provide a nuclear magnetic resonance imaging apparatus capable of always performing radiographing of a target site with high sensitivity.

[0008]

The present invention employs the following means in order to solve the above problems.

That is, a nuclear magnetic resonance imaging apparatus according to a first aspect of the present invention provides an excitation means for applying a magnetic field for excitation to a subject arranged in a static magnetic field space, and a gradient magnetic field application for applying a gradient magnetic field to the subject. A gantry having an imaging space in which the static magnetic field space is formed, a receiving means for receiving an NMR signal detected from the subject, and a receiving means for receiving the NMR signal. A nuclear magnetic resonance imaging apparatus that includes a couch having a couchtop on which the couch is placed, and that introduces the couchtop into the imaging space to capture a tomographic image of the subject. And are relatively movable.

According to a second aspect of the present invention, there is provided the nuclear magnetic resonance imaging apparatus according to the first aspect, wherein the top plate is configured by superimposing an upper top plate and a lower top plate, and a part of the receiving means is provided by the upper top plate. It has a structure sandwiched between a plate and the lower top plate.

According to a third aspect of the present invention, there is provided a nuclear magnetic resonance imaging apparatus according to the first or second aspect, wherein a part of the receiving means is provided with a sliding means at a portion where the receiving means abuts on the upper and lower top boards. Is provided.

According to a fourth aspect of the present invention, there is provided the nuclear magnetic resonance imaging apparatus according to any one of the first to third aspects, further comprising fixing means for fixing the receiving means to the gantry. Features.

According to a fifth aspect of the present invention, in the nuclear magnetic resonance imaging apparatus according to any one of the first to fourth aspects, the receiving means and / or the top plate are driven by an electric system. According to a sixth aspect of the present invention, in the nuclear magnetic resonance imaging apparatus according to any one of the first to fourth aspects, the receiving means and / or the top panel are driven by a manual method. Features.

According to a seventh aspect of the present invention, there is provided the nuclear magnetic resonance imaging apparatus according to any one of the second to sixth aspects, wherein the receiving means has a substantially elliptical cylinder having a cross section partially linear. The nuclear magnetic resonance imaging apparatus according to claim 8, wherein a part of the receiving means is the linear portion, and the nuclear magnetic resonance imaging apparatus according to claim 8 is the apparatus according to any one of claims 2 to 6. The receiving means is configured to be wrapped around the subject when used.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram schematically showing a nuclear magnetic resonance imaging apparatus according to this embodiment. In the drawings referred to in the following description, when designating an apparatus having the same configuration as that of the conventional nuclear magnetic resonance imaging apparatus described with reference to FIG. 7, the same reference numerals as those used in FIG. 7 are used. The description will be made using reference numerals.

In FIG. 1, a nuclear magnetic resonance imaging apparatus is installed so as to oppose a moving direction of a top board 12 (described later) on a bed 10 and an air core portion (imaging space section) into which the top board 12 can be inserted. A gantry G having H is provided.
In the gantry G, a main magnet 3, an RF coil (excitation means) 4, and a gradient magnetic field coil (gradient magnetic field applying means) 5 are concentrically arranged with the center axis L of the air core H being coaxial. Have been.

The main magnet 3 forms a strong static magnetic field in the air core H. In the present embodiment, a permanent magnet,
Any of an electromagnet, a superconducting magnet, and the like can be applied. In particular, in the latter two cases, the main magnet 3 and the RF
The coil 4 may have an externally integrated structure. R
The F coil 4 is a coil that applies an RF magnetic field (excitation magnetic field) for causing nuclear magnetic resonance absorption in the subject P in the static magnetic field. The RF coil 4 is connected to a transmitter 4a and is driven discretely with respect to time, that is, based on a pulse signal. The gradient coil 5 has different magnetic fields (Gx, G) for each of the three orthogonal axes (x, y, z) defined in the air core H.
y, Gz). The degree of the inclination is set by the gradient magnetic field power supply system 5a. Position localization of the NMR signal obtained by the receiving coil (receiving means) 20 (described later) can be performed based on the degree of the inclination described above.

Further, the nuclear magnetic resonance imaging apparatus according to the present embodiment includes a control unit 6 for controlling the above-described components as a whole. The control unit 6 determines the pulse sequence of the sequencer 7 and, according to this,
a, operate the gradient magnetic field power supply system 5a. Accordingly, in the air core portion H in which the static magnetic field space is formed by the main magnet 3, a gradient magnetic field is applied to the subject P arranged in the static magnetic field space by the gradient magnetic field coil 5, and The application of the RF pulse by the RF coil 4 causes nuclear magnetic resonance absorption of the subject P. Then, the NMR signal generated at this time is received by the receiver 21 via the reception coil 20 and collected by the control unit 6.
The control unit 6 reconstructs an MRI image based on the collected NMR signals, and displays the MRI image on the display unit D.

Next, the configuration of the bed 10 and the receiving coil 20, which are characteristic configurations of the present embodiment, will be described. As shown in FIGS. 1 and 2, the couch 10 is configured such that a top plate 12 configured by stacking two top plates 12 a and 12 b on a base 11 is installed. It is configured. The top plate 12 is capable of translational movement in the left-right direction with respect to the base 11 as indicated by arrows in the figure. On the other hand, the receiving coil 20 is formed as a substantially elliptical cylindrical body having a partially linear portion (a bottom portion of the receiving means) 20a in cross section. Describing the straight line portion 20a in more detail, a portion where a part of the arc-shaped portion in the substantially elliptical cross section is linearly cut out over the entire axial direction of the cylindrical body corresponds to the portion (see FIG. 2). As shown in FIG. 4, the linear portion 20a faces the diagonal angle from a diagonally downward angle, and rollers (sliding means) 13 are provided at four corners of the surface.

The bed 10 and the receiving coil 20
2 means that the linear portion 20a of the receiving coil 20 is sandwiched between the upper and lower top plates 12a and 12b, In an abutting state, they are integrally incorporated.

The wall Ha of the air core H and the receiving coil 2
As shown in FIG. 2, a receiving coil fixing device (fixing means) for restricting the movement of the receiving coil 20 is provided in a gap between the receiving coil 20 and the side surface of the receiving coil 20.
30 are provided. In FIG. 2, the receiving coil fixing device 30 includes a cylinder 31, a piston 32, and a contact plate 33, of which the contact plate 33 protrudes from a wall surface Ha of the air core H. ing. The receiving coil 20 is fixed to the gantry G by the contact plate 33 pressing the outer wall surface of the receiving coil 20.

The roller 13 shown in FIGS.
Are provided at the four corners of the straight portion 20a for convenience.
The present invention is not limited to such an embodiment.
For example, as shown in FIG. 5, a configuration in which rollers 14 are provided on each of the upper surface and the lower surface of the linear portion 20a may be employed.
In this case, four rollers 14 are provided on the contact surface between the linear portion 20a and the upper top plate 12a, and the linear portion 20a and the lower
Eight rollers, for example, four rollers 14 are provided on the contact surface with the roller b. Furthermore,
The purpose of the present invention is to use a means that enables smooth relative movement between the top plate 12 and the receiving coil 20. Therefore, the present invention is particularly limited to a mode using a "roller" as a sliding means. is not. For example, as shown in FIG. 6, a sliding sheet (sliding means) 1 that facilitates sliding between the receiving coil 20 and the top plate 12 with respect to each other.
5 is also effective.

In the present invention, the receiving coil 20
Is not limited to the form of the receiving coil fixing device 30 using the cylinder 31 or the like as described above. For example, instead of being provided in advance as a fixed “device”, after the receiving coil 20 is introduced into the air core H, a tension spring by a known method is provided between the outer wall surface and the wall surface Ha of the receiving coil 20. For example, a means for fixing the receiving coil 20 may be adopted.

The operation and effect of the nuclear magnetic resonance imaging apparatus having such a configuration will be described below. In the following, the basic operation related to the nuclear magnetic resonance absorption phenomenon, that is, the operation mode of the RF coil 4, the gradient coil 5, the transmitter 4a, the gradient power supply system 5a, etc. in the gantry G, or the sequencer 7 Since the specific mode such as the pulse sequence does not correspond to the gist of the present invention, the description thereof will be omitted.

First, the subject P is set on the table 12 on the bed 10. Then, the position of the receiving coil 20 with respect to the bed 10 is determined so as to face (correspond to) a part of the subject P to be photographed (to obtain a tomographic image). At this time, the receiving coil 20 can easily move on the bed 10 by the roller 13 described above.

When the positional relationship between the subject P and the receiving coil 20 is determined, the top plate 12 of the bed 10 is moved and introduced into the air core H of the gantry G. When the receiving coil 20 and the main magnet 3, the RF coil 4, and the gradient coil 5 have a desired positional relationship (the receiving coil 20 is located at the center of the magnetic field of these coils and the like) in the air core portion H, The cylinder 31 of the receiving coil fixing device 30 is operated to bring the contact plate 33 into contact with the outer wall surface of the receiving coil 20. As a result, the receiving coil 20 is fixed to the gantry G.

When the setting of the subject P and the receiving coil 20 with respect to the gantry G is completed, the control unit 6
Then, the RF coil 4 and the like are operated by the sequencer 7 and the like, and a tomographic image of the part to be photographed is acquired based on the NMR signals obtained thereby.

Here, the following features can be pointed out in the present embodiment. That is, in the conventional example, as described above, once the setting position of the receiving coil 20 with respect to the subject P or the top 12 has been determined, it has not been possible to easily change the setting position. That is, the subject P
For example, when it is desired to change the part to be photographed, the bed 10 needs to be taken out of the air core H and the position of the receiving coil 20 needs to be reset. However, in the present embodiment, the receiving coil 20 can be easily moved with respect to the top 12 by the configuration shown in FIGS. Therefore, even when the part of the subject P to be imaged is changed during the imaging, the position can be easily adjusted to the optimum position, and the change can be appropriately dealt with. is there.

In such a case, since the receiving coil 20 is fixed to the gantry G by the receiving coil fixing device 30, the top plate 12 must be moved to the subject P At the same time, it may be moved with respect to the air core H. That is, the position of the subject P corresponding to the position of the receiving coil 20 is changed without changing the positional relationship of the receiving coil 20 with respect to the gantry G. In other words, the position of the subject P can be changed without changing the positional relationship between the temporarily fixed receiving coil 20 and the RF coil 4 or the like (the former is located at the center of the magnetic field of the latter). is there.

As described above, according to the configuration of the nuclear magnetic resonance imaging apparatus of the present embodiment, the linear portion 20a of the receiving coil 20 is connected between the upper table 12a and the lower table 12b set on the bed 10. Between the receiving coil 2
0 itself can be freely moved with respect to the top plate 12. In other words, paying attention to the positional relationship between the receiving coil 20 and the top 12 and the gantry G, the present apparatus does not move the receiving coil 20 and
It can be said that the configuration is such that only the (subject P) can be moved. If necessary, the receiving coil 20 and the top plate 12 can be moved independently and relatively.

With such a configuration, the top plate 12 of the subject P
Alternatively, setting for the gantry G can be easily performed. Then, even if the subject P cannot be initially set to the optimum position with respect to the imaging region, the receiving coil 20 and the subject P are moved by moving only the subject P after introduction into the air core portion H. Can be substantially changed, since the opposite part of the photographing part changes. That is, according to the present embodiment, there is no need to carry out the subject P out of the air core portion H and set again as in the conventional example.

The configuration or feature of the present embodiment as described above also exerts a great effect in the following cases. That is, when performing MRI imaging over a wide range of the subject P using a contrast agent,
If the nuclear magnetic resonance imaging apparatus of the present embodiment is applied, only the subject P can be moved without moving the receiving coil 20, so that a wide range of contrast-enhanced MRA is performed using the highly sensitive receiving coil 20. It becomes possible. In other words, it is not necessary to newly provide a new receiving coil capable of capturing a wide area. Specifically, for example, when continuously photographing the lower abdomen, thighs, and lower limbs of the subject P, a coil (generally, W
B (Whole Body) coil) is required, but if the nuclear magnetic resonance imaging apparatus of the present embodiment is applied to this, a WB coil is not required. This also makes it possible to enjoy the effect of improving the S / N ratio for photographing.

In the above embodiment, the receiving coil 20 has a coil form having a substantially elliptical cross section as shown in FIG. 2, but the present invention is applied to this form. However, the present invention is not limited to this. For example, a coil wound around the body of the subject P (hereinafter referred to as a coil of a winding type) may be used. Even in this case, a part of the coil of the winding type is
It is of course possible to sandwich the coil of the winding type so as to be relatively movable with respect to the top plate 12 by sandwiching the coil between the top plate 12a and the lower top plate 12b, and providing appropriate sliding means at these contact portions. is there.

As a means for actually moving the receiving coil 20, it may be simply used manually. Even in this case, the various effects described above can be sufficiently enjoyed. Needless to say, instead of the manual operation, the manual operation is possible, and a driving means (not shown) for transmitting the driving force to the roller 13 may be separately provided. In this case, for example, an electric motor or the like may be adopted as the power source of the roller 13 or the driving unit. Further, in connection with this, after fixing the receiving coil 20 in the air core portion H,
The driving means for moving the motor 2 itself may be an electric motor or the like. In the case where the driving unit is provided for the receiving coil 20 and the top plate 12 as described above, a control unit (not shown) is provided in addition to the driving unit.
For example, it is more convenient if an instruction such as "movement by several cms" can be given.

In addition, in the above embodiment, the description is made with the nuclear magnetic resonance imaging apparatus in which the main magnet 3 and the RF coil 4 and the like are arranged concentrically about the center axis L of the air core H as an axis. However, the application of the present invention is not limited to this. For example, the present invention can be applied to the same device (not shown) having an “opposite magnet”. Of course. In this case, the “photographing space” formed between the magnets and the like facing each other.
Then, the bed 10 and the receiving coil 20 as described above are introduced.

[0037]

As described above, according to the nuclear magnetic resonance imaging apparatus of the present invention, since the receiving means is configured to be independently and relatively movable with respect to the tabletop, the subject and the receiving apparatus can be moved. Even after the means is once positioned and introduced into the gantry, the photographing position can be easily changed, and high-sensitivity photographing can be performed at the optimum position. In addition, it is also possible to apply a coil of a winding type as a receiving means. Further, the configuration according to the present invention is also effective for contrast MRA, for example. In other words, in this case, it is not necessary to provide a receiving means capable of specially wide-area photographing, and it is also possible to improve the S / N ratio for photographing.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration example of a nuclear magnetic resonance imaging apparatus according to an embodiment.

FIG. 2 is a transverse sectional view showing a configuration example of a receiving coil and a bed in the device shown in FIG.

FIG. 3 is an enlarged longitudinal sectional view showing a configuration example of a linear portion of a receiving coil sandwiched between an upper top plate and a lower top plate and rollers provided in the linear portion in the device shown in FIG.

FIG. 4 is a schematic diagram showing rollers provided on a linear portion of a receiving coil.

FIG. 5 is a schematic diagram showing a configuration example of a conventional nuclear magnetic resonance imaging apparatus.

FIG. 6 shows an example of a configuration different from that of FIG. 3 in a linear portion of a receiving coil sandwiched between an upper top plate and a lower top plate and a roller provided in the linear portion in the device shown in FIG. It is a longitudinal section enlarged view.

7 is a configuration example of a linear portion of a receiving coil sandwiched between an upper top plate and a lower top plate, and a sliding sheet provided on the upper and lower top plates and the linear portion in the apparatus shown in FIG. FIG.

[Explanation of symbols]

 Reference Signs List 10, 1 bed 11 base 12, 1a top plate 12a upper top plate 12b lower top plate 13, 14 roller (sliding means) 15 sliding sheet (sliding means) 20, 2 receiving coil (receiving means) 20a linear portion 21 receiver Reference Signs List 30 receiving coil fixing device (fixing means) 3 main magnet 4 RF coil (excitation means) 4a transmitter 5 gradient magnetic field coil (gradient magnetic field applying means) 5a gradient magnetic field power supply system 6 control unit 7 sequencer G gantry H air core part (photographing Space) Ha Wall L Central axis P Subject

Claims (8)

[Claims] 1. An apparatus comprising: excitation means for applying an excitation magnetic field to an object placed in a static magnetic field space; and gradient magnetic field applying means for applying a gradient magnetic field to the object. A gantry having an imaging space section, receiving means for receiving an NMR signal detected from the subject, a bed having the receiving means and a couch having a top plate for directly placing the subject, In a nuclear magnetic resonance imaging apparatus that introduces a top plate into the imaging space and captures a tomographic image of the subject, the receiving unit and the top plate are configured to be independently and relatively movable. A nuclear magnetic resonance imaging apparatus characterized by the above-mentioned. 2. The apparatus according to claim 1, wherein the top plate is configured by stacking an upper top plate and a lower top plate, and has a structure in which a part of the receiving unit is sandwiched between the upper top plate and the lower top plate. Item 7. A nuclear magnetic resonance imaging apparatus according to Item 1. 3. The nuclear magnetic resonance imaging according to claim 1, wherein a sliding unit is provided at a portion where a part of the receiving unit contacts the upper and lower top plates. apparatus. 4. The nuclear magnetic resonance imaging apparatus according to claim 1, further comprising fixing means for fixing the receiving means to the gantry. 5. The nuclear magnetic resonance imaging apparatus according to claim 1, wherein the receiving unit and / or the top board are driven by an electric system. 6. The nuclear magnetic resonance imaging apparatus according to claim 1, wherein the receiving unit and / or the top board are driven by a manual method. 7. The receiving means is a substantially elliptical cylindrical body having a cross section partially having a straight part, and a part of the receiving means is the straight part. 7. The nuclear magnetic resonance imaging apparatus according to any one of items 1 to 6. 8. The apparatus according to claim 2, wherein the receiving means is configured to be used by being wound around the subject.
7. The nuclear magnetic resonance imaging apparatus according to any one of items 1 to 6.