JP5710343B2 - Magnetic resonance imaging system - Google Patents

Description

  The present invention relates to a magnetic resonance imaging apparatus for imaging a subject.

  When imaging a subject with a magnetic resonance imaging apparatus, the imaging site of the subject is transported to the central portion of the bore of the magnet. In general, the central portion of the bore is an imageable area where a good quality image can be acquired. Therefore, a high quality image can be obtained by conveying the imaging region of the subject to the central portion of the bore of the magnet.

  However, when the imaging region is the head, the head is transported to the central portion of the bore, so that the field of view of the subject is blocked by the inner wall of the bore. Therefore, when the subject is claustrophobic, it may not be possible to photograph. Therefore, a method for reducing the pain felt by claustrophobic subjects has been proposed (see Patent Document 1).

Japanese Patent Laid-Open No. 2003-052663

By the way, when the imaging part is a leg, even if the leg is transported to the central portion of the bore, the subject's eyes may come out of the bore. In this case, the subject can see the outside of the bore, so even if the subject is claustrophobic, the feeling of obstruction felt by the subject is reduced, so no special measures should be taken May also be able to image the subject. However, when the subject's height is low, the subject's eyes may not come out of the bore even if the imaging site is a leg, so the feeling of obstruction felt by the subject is reduced so much In some cases, it is difficult to photograph the subject.
Therefore, it is desired that the subject can take an image without feeling as close as possible.

One aspect of the present invention is a magnetic resonance imaging apparatus that carries a subject into the bore from a carry-in port of a magnet bore and images the subject.
A cradle on which the subject is placed;
A cradle moving means for moving the cradle so that the imaging region of the subject is located on the carry-in side of the imageable region defined in the bore;
A magnetic resonance imaging apparatus.

  Since the imaging part is located on the side of the bore entrance in the imageable area, the subject's eyes can be brought closer to the outside of the bore, reducing the feeling of obstruction felt by the subject. It becomes.

1 is a schematic diagram of a first magnetic resonance imaging apparatus of the present invention. It is a figure which shows the setting position of a landmark. It is a figure which shows the mode after conveying an imaging | photography site | part to the imaging | photography possible area | region 28. FIG. It is a figure which shows the setting position of a landmark. It is a figure which shows the position of the imaging | photography site | part after moving the cradle 3a. It is a figure when the subject 12 is laid on the table 3. FIG. It is a figure which shows the setting position of a landmark. It is a figure which shows the position of the imaging | photography site | part after moving the cradle 3a.

  Hereinafter, although the form for inventing is demonstrated, this invention is not limited to the following forms.

(1) First Embodiment FIG. 1 is a schematic diagram of a first magnetic resonance imaging apparatus of the present invention.
A magnetic resonance imaging apparatus (hereinafter referred to as “MRI apparatus”. MRI: Magnetic Resonance Imaging) 100 includes a magnet 2, a table 3, a receiving coil 4, and the like.

  The magnet 2 has a bore 21 in which the subject 12 is accommodated. The subject 12 is carried into the bore 21 from the carry-in port 21 a of the bore 21. The magnet 2 includes a superconducting coil 22, a gradient coil 23, and an RF coil 24. The superconducting coil 22 applies a static magnetic field B0, the gradient coil 23 applies a gradient magnetic field, and the RF coil 24 transmits an RF pulse and receives a magnetic resonance signal of the subject 12. In place of the superconducting coil 22, a permanent magnet may be used.

  Further, the magnet 2 is provided with a positioning lamp 25 for setting a landmark which becomes a mark when the subject 12 is carried into the bore 21.

  The table 3 has a cradle 3a on which the subject 12 is placed. The cradle 3a is connected to a cradle moving device 30 that moves the cradle 3a. The cradle moving device 30 is configured to move in the z direction and the −z direction. When the cradle moving device 30 moves in the z direction, the cradle moving device 30 pulls the cradle 3a, and the cradle 3a moves in the z direction. When the cradle moving device 30 moves in the −z direction, the cradle moving device 30 pushes out the cradle 3a, and the cradle 3a moves in the −z direction. Therefore, the cradle moving device 30 can move the cradle 3a freely in the z direction and the −z direction.

  The receiving coil 4 is attached to the knee of the subject 12. The receiving coil 4 receives a magnetic resonance signal from the subject 12.

  The MRI apparatus 100 further includes a sequencer 5, a transmitter 6, a gradient magnetic field power supply 7, a receiver 8, a central processing unit 9, an operation unit 10, and a display unit 11.

  Under the control of the central processing unit 9, the sequencer 5 sends information for photographing the subject 12 to the transmitter 6 and the gradient magnetic field power supply 7.

  The transmitter 6 outputs a drive signal for driving the RF coil 24 based on the information sent from the sequencer 5.

  The gradient magnetic field power supply 7 outputs a drive signal for driving the gradient coil 23 based on the information sent from the sequencer 5.

  The receiver 8 performs signal processing on the magnetic resonance signal received by the RF coil 24 or the receiving coil 4, and outputs data obtained by the signal processing to the central processing unit 9.

  The central processing unit 9 implements various operations of the MRI apparatus 100 such as transmitting necessary information to the sequencer 5 and the display unit 11 and reconstructing an image based on data received from the receiver 8. The operation of each unit of the MRI apparatus 100 is controlled. The central processing unit 9 is constituted by a computer, for example.

The operation unit 10 is operated by the operator 13 and inputs various information to the central processing unit 9. The display unit 11 displays various information.
The MRI apparatus 100 is configured as described above.

  Next, a procedure for photographing the subject 12 using the MRI apparatus 100 will be described. Below, the case where a subject's knee is image | photographed is demonstrated.

  First, the operator 13 lays the subject 12 on the table 3 and installs the receiving coil 4. In the first mode, since the imaging region is the knee, the operator 13 installs the receiving coil 4 on the knee as shown in FIG. After installing the receiving coil 4, the operator 13 uses the light of the positioning light 25 to set a landmark that serves as a mark when the subject 12 is carried into the bore 21 (see FIG. 2).

FIG. 2 is a diagram illustrating a setting position of the landmark LM.
In the first form, the operator 13 changes the position of the landmark LM depending on whether or not the subject 12 is claustrophobic.

  FIG. 2A shows the position of the landmark LM when the subject 12 is not claustrophobic, and FIG. 2B shows the position of the landmark LM when the subject is claustrophobia. FIG.

  The operator 13 irradiates light from the positioning light 25 and sets the landmark LM. In the first form, the setting position of the landmark LM is changed according to whether or not the subject 12 is claustrophobic. When the subject 12 is not claustrophobic (see FIG. 2A), the landmark LM is set at the center position of the receiving coil 4. On the other hand, when the subject 12 is claustrophobic (see FIG. 2B), the landmark LM is set at the front end of the receiving coil 4. Comparing FIG. 2A and FIG. 2B, it can be seen that the position of the landmark LM is different.

  After setting the landmark LM, the operator 13 operates the operation unit 26 to move the cradle 3 a so that the imaging region (knee) is transported to the imageable region 28 of the bore 21. The imageable area 28 means an area where a high-quality image can be acquired. The imageable region 28 can be defined with reference to an isocenter 27 that represents the center of the gradient magnetic field, for example. In the first embodiment, a range of ± 25 cm in the z-axis direction with respect to the isocenter 27 is defined as the imageable region 28. FIG. 3 shows a state after the imaging region is transported to the imageable region 28.

  FIG. 3A shows the position of the imaging region when the subject 12 is not claustrophobia, and FIG. 3B shows the position of the imaging region when the subject 12 is claustrophobia. FIG.

  When the subject 12 is not claustrophobic (see FIG. 3A), the operator 13 operates the operation unit 26 so that the cradle 3a moves in the normal mode. The normal mode is a mode in which the cradle 3a is moved so that the position of the landmark LM in the z direction coincides with the position of the isocenter 27 in the z direction. Therefore, when a command for moving the cradle 3a in the normal mode is input from the operation unit 26, the cradle moving device 30 causes the position of the landmark LM in the z direction to coincide with the position of the isocenter 27 in the z direction. Then, the cradle 3a is moved. In this case, the imaging region is positioned substantially at the center of the imageable region 28.

  On the other hand, when the subject 12 is claustrophobic (see FIG. 3B), the operator 13 operates the operation unit 26 so that the cradle 3a moves in the claustrophobia help mode. The claustrophobic help mode is a mode in which the cradle 3a is moved so that the landmark LM coincides with the front end face 28a of the imageable region 28. Therefore, when a command for moving the cradle 3a in the claustrophobia help mode is input from the operation unit 26, the cradle moving device 30 causes the landmark LM to coincide with the front end face 28a of the imageable region 28. The cradle 3a is moved. As a result, the imaging region can be positioned on the side of the carry-in entrance 21a in the imageable region 28.

  After the cradle 3a is moved as shown in FIG. 3, scanning is performed. In the first embodiment, when a magnetic resonance signal from the subject 12 is received, the RF coil 24 of the magnet 2 is not used, but the receiving coil 4 installed in the imaging region is used. In this way, scanning is performed.

  3 (a) and 3 (b) are compared, the imaging region (knee) in FIG. 3 (b) is closer to the carry-in entrance 21a of the bore 21 by a distance ΔD than the imaging region (knee) in FIG. 3 (a). It ’s close. Therefore, in FIG. 3A, the eye of the subject 12 enters the inside of the bore 21, but in FIG. 3B, the eye of the subject 12 is moved outside the bore 21 by the distance ΔD. Can be put out. For this reason, when the subject 12 is claustrophobic (see FIG. 3B), the obstruction feeling felt by the subject 12 can be reduced. Further, even in the case of FIG. 3B, since the imaging region (the knee) has entered the imaging region 28, a sufficiently high quality image can be obtained.

  In the first embodiment, when the subject 12 is claustrophobic, the landmark LM is set at the front end of the receiving coil 4. However, the landmark LM may be set at a position different from the front end of the receiving coil 4 as long as the imaging part can be positioned on the side of the carry-in entrance 21a in the imageable region 28. .

(2) Second form In the first form, the position of the landmark LM is changed depending on whether or not the subject 12 is claustrophobic, but the position of the landmark LM may be the same. . In the second embodiment, a case where the positions of the landmarks LM are the same will be described.

  First, as shown in FIG. 1, the operator 13 places the subject 12 on the table 3 and installs the receiving coil 4. After installing the receiving coil 4, the operator 13 sets a landmark that serves as a mark when the subject 12 is carried into the bore 21 (see FIG. 4).

FIG. 4 is a diagram illustrating a landmark setting position.
In the second form, the operator 13 sets the landmark LM at the center position of the receiving coil 4 regardless of whether or not the subject 12 is claustrophobic. After setting the landmark LM, the operator 13 operates the operation unit 26 to move the cradle 3a so that the imaging region (knee) is conveyed to the imageable region 28 of the bore 21 (see FIG. 5). .

FIG. 5 is a diagram illustrating the position of the imaging region after the cradle 3a is moved.
FIG. 5A shows the position of the imaging region when the subject 12 is not claustrophobia, and FIG. 5B shows the position of the imaging region when the subject 12 is claustrophobia. FIG.

  When the subject 12 is not claustrophobia (see FIG. 5A), the operator 13 operates the operation unit 26 so that the cradle 3a moves in the normal mode. Therefore, the cradle moving device 30 moves the cradle 3a so that the position of the landmark LM in the z direction coincides with the position of the isocenter 27 in the z direction. To do.

  On the other hand, when the subject 12 is claustrophobic (see FIG. 5B), the operator 13 operates the operation unit 26 so that the cradle 3a moves in the claustrophobia help mode. In the second mode, the claustrophobia help mode is a mode in which the cradle 3a is moved so that the landmark LM is displaced from the front end face 28a of the shootable area 28 to the inside of the shootable area 28 by a predetermined distance ΔV. It is. Therefore, when a command for moving the cradle 3a in the claustrophobia help mode is input from the operation unit 26, the cradle moving device 30 causes the landmark LM to be moved from the front end face 28a of the imageable area 28 by a predetermined distance ΔV. The cradle 3a is moved so as to shift to the inside of the imageable area 28. Here, ΔV is the distance between the center position of the receiving coil 4 and the front end, and is a value determined in advance depending on the type of the receiving coil 4 used. The operator 13 operates the operation unit 26 to input information on the type of the reception coil 4 before moving the cradle 3a in the claustrophobia help mode. When this information is input, the value of ΔV corresponding to the type of receiving coil 4 is determined. Therefore, even if the value of ΔV differs depending on the type of the receiving coil 4, the front end portion of the receiving coil 4 can be matched with the front end face 28 a of the imageable region 28. After the cradle 3a is moved as shown in FIG. 5, scanning is performed.

  In the second form, when the subject 12 is claustrophobic, the cradle 3a is moved so that the landmark LM is displaced from the front end face 28a of the imageable region 28 to the inside of the imageable region 28 by a predetermined distance ΔV. It is moved. Therefore, even if the landmark LM is set at the center position of the receiving coil 4, it is possible to prevent the imaging region (the knee) from protruding from the imageable region 28. Further, since the imaging region can be brought close to the carry-in port 21a of the bore 21, the eye of the subject 12 can be taken out of the bore 21, and the feeling of obstruction felt by the subject 12 can be reduced. it can.

  Furthermore, in the second embodiment, it is not necessary to change the position of the landmark LM according to whether or not the subject is claustrophobic, so that the setting operation of the landmark LM can be made common. The work burden on the operator 13 can be reduced.

  In the second embodiment, the landmark LM is set at the center position of the receiving coil 4. However, the setting position of the landmark LM is not limited to the center position of the receiving coil 4 and may be deviated from the center position of the receiving coil 4.

(3) Third Embodiment In the first and second embodiments, the example using the receiving coil 4 has been described, but in the third embodiment, a case where the receiving coil 4 is not used will be described. In the third embodiment, the case where the knee is photographed will be described as in the first and second embodiments.

First, the operator 13 lays the subject 12 on the table 3 (see FIG. 6).
FIG. 6 is a view when the subject 12 is laid on the table 3.

  In the third embodiment, since the receiving coil 4 is not used, the receiving coil 4 is not installed on the knee. After the subject 12 is laid down, the operator 13 sets a landmark that serves as a mark when the subject 12 is carried into the bore 21 (see FIG. 7).

FIG. 7 is a diagram illustrating a landmark setting position.
In the third embodiment, the landmark LM is set at the center of the imaging region regardless of whether the subject 12 is claustrophobic or not. After setting the landmark LM, the operator 13 operates the operation unit 26 to move the cradle 3a so that the imaging region (knee) is transported to the imageable region 28 of the bore 21 (see FIG. 8). .

FIG. 8 is a diagram showing the position of the imaging region after the cradle 3a is moved.
FIG. 8A is a diagram illustrating the position of the imaging region when the subject 12 is not claustrophobic, and FIG. 8B is the position of the imaging region when the subject 12 is claustrophobia. FIG.

  When the subject 12 is not claustrophobic (see FIG. 8A), the operator 13 operates the operation unit 26 so that the cradle 3a moves in the normal mode. Therefore, the cradle moving device 30 moves the cradle 3a so that the position of the landmark LM in the z direction coincides with the position of the isocenter 27 in the z direction. To do.

  On the other hand, when the subject 12 is claustrophobic (see FIG. 8B), the operator 13 operates the operation unit 26 so that the cradle 3a moves in the claustrophobia help mode. In the third mode, the claustrophobia help mode is a mode in which the cradle 3a is moved so that the landmark LM is displaced from the front end face 28a of the shootable region 28 to the inside of the shootable region 28 by a predetermined distance ΔW. It is. Therefore, when a command for moving the cradle 3a in the claustrophobia help mode is input from the operation unit 26, the cradle moving device 30 causes the landmark LM to be moved from the front end face 28a of the imageable area 28 by a predetermined distance ΔW. The cradle 3a is moved so as to shift to the inside of the imageable area 28. Here, ΔW is a value set in advance so that the imaging region of the subject is positioned on the carry-in entrance 21a side in the imageable region 28. Therefore, the imaging region can be positioned on the side of the carry-in entrance 21a in the imageable region 28. After the cradle 3 a is moved as shown in FIG. 8, scanning is performed using the RF coil 24.

  In the third embodiment, when the subject 12 is claustrophobic, the cradle 3a is moved so that the landmark LM is displaced from the front end surface 28a of the imageable region 28 to the inside of the imageable region 28 by a predetermined distance ΔW. It is moved. Since ΔW is a value set in advance so that the imaging region of the subject is positioned on the side of the carry-in entrance 21a in the imageable region 28, the eye of the subject 12 is changed to the bore 21. The occlusion feeling felt by the subject 12 can be reduced.

  In the third embodiment, ΔW is a value set in advance, but the value of ΔW may be determined based on information on the physique (height, etc.) of the subject. Generally, the range of the imaging region varies depending on the difference in the physique of the subject. Therefore, by determining the value of ΔW based on the information on the physique of the subject, the imaging region can be imaged. It is possible not to protrude from 28.

  In the first to third embodiments, the imaging region is the subject's knee, but the imaging region is not limited to the knee. For example, the present invention is effective when imaging a calf. is there.

2 Superconducting magnet 3 Table 3a Cradle 4 Receiving coil 5 Sequencer 6 Transmitter 7 Gradient magnetic field power supply 8 Receiver 9 Central processing unit 10 Operation unit 11 Display unit 12 Subject 13 Operator 21 Bore 22 Superconducting coil 23 Gradient coil 24 RF Coil 100 MRI system

Claims (12)

A magnetic resonance imaging apparatus for carrying a subject into the bore from a carry-in port of a magnet bore and photographing the subject,
A cradle on which the subject is placed;
A cradle moving means for moving the cradle so that the imaging region of the subject is located on the carry-in side of the imageable region defined in the bore;
A magnetic resonance imaging apparatus. A positioning lamp for setting a landmark as a mark when the subject is carried into the bore;
The magnetic resonance imaging apparatus according to claim 1, wherein the cradle moving unit moves the cradle based on the landmark. Having a receiving coil installed in the imaging region of the subject;
The magnetic resonance imaging apparatus according to claim 2, wherein the landmark is set in the receiving coil. Set the landmark at the front end of the receiving coil,
The cradle moving means includes
The magnetic resonance imaging apparatus according to claim 3, wherein the cradle is moved so that the landmark coincides with a front end face of the imageable region. Set the landmark at the center position of the receiving coil,
The cradle moving means includes
The magnetic resonance imaging apparatus according to claim 3, wherein the cradle is moved so that the landmark is displaced inward of the imageable region by a predetermined distance from a front end surface of the imageable region.   The magnetic resonance imaging apparatus according to claim 5, wherein the predetermined distance is determined based on a type of the receiving coil.   The magnetic resonance imaging apparatus according to claim 5 or 6, wherein the setting position of the landmark is the same regardless of whether or not the subject has claustrophobia. The magnet has an RF coil that transmits an RF pulse and receives a magnetic resonance signal from the subject,
The magnetic resonance imaging apparatus according to claim 2, wherein the landmark is set in an imaging region of the subject. The cradle moving means includes
The magnetic resonance imaging apparatus according to claim 8, wherein the cradle is moved so that the landmark is displaced inward of the imageable region by a predetermined distance from a front end surface of the imageable region.   The magnetic resonance imaging apparatus according to claim 9, wherein the predetermined distance is determined based on information on the physique of the subject. The cradle moving means includes
If the subject is not claustrophobic, move the cradle so that the imaging region of the subject is located in the center of the imageable region,
When the subject is claustrophobia, the cradle is moved so that the imaging region of the subject is located on the side of the carry-in port in the imageable region. The magnetic resonance imaging apparatus according to any one of the above. The magnetic resonance imaging apparatus according to claim 1, wherein the imageable region is defined with reference to an isocenter representing a center of a gradient magnetic field.

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