JP2006000247A - Magnetic resonance imaging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an MRI system which can easily set an imaging center in a manner to become the center of an imaging space without forcing pains to a subject, can improve the operability, and can shorten the operation time. <P>SOLUTION: When a target imaging area is located at a position being shifted from the central line of a top board 36 such as a crossing point C of dotted lines, the laser projector switch of a gantry operating panel is operated, and an XY laser projector direction controlling device controls a lateral motion motor gear and a motor for rotation, and the crossing point of an X-directional laser beam and a Y-directional laser beam is adjusted to an imaging position C of the subject 1 by moving an XY laser projector. A signal from the XY laser projector direction controlling device is transmitted to a top board controlling unit 39 by operating the imaging switch in the gantry operating panel. Longitudinal and lateral distances from the imaging position C to the central position of a static magnetic field space are calculated, and after moving the top board 36 by the calculated distances and directions in such a manner that the imaging position C may meet the center of the static magnetic field space, imaging is started. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetic resonance imaging (hereinafter abbreviated as MRI) apparatus that displays an image of an arbitrary cross section of a subject using a nuclear magnetic resonance phenomenon (hereinafter abbreviated as NMR), and in particular, mounts the subject. The present invention relates to a technique for controlling the movement of the top plate.

  In order to set the subject in the imaging space, the MRI apparatus is generally provided with a positioning projector at the opening of the gantry or outside. The procedure for setting the subject in the imaging space using this projector is as follows.

  That is, first, at the opening or outside of the gantry, the subject and the receiving coil are placed on the couch top, and the subject and the imaging center of the subject are positioned so that the center of the irradiation light from the positioning projector is at the center. The arrangement position of the receiving coil is determined.

  Then, the top plate is electrically or manually moved into the imaging space so that the imaging center of the subject comes to the center of the imaging space of the apparatus with the determined position of the subject and the receiving coil.

  Since the distance between the center of the irradiation light of the projector and the center of the imaging space is a predetermined fixed distance, the planned imaging center position of the subject at the determined arrangement position and the center of the imaging space of the apparatus Is equal to the fixed distance, and the imaging center of the subject can be reliably set as the center of the imaging space by moving the top plate by the fixed distance.

  In the case of the tunnel type with a gantry shape that uses the horizontal magnetic field method, the top plate moves only in the front-rear direction (static magnetic field direction). It is also possible to image a part away from the body axis center of the subject, such as a shoulder, in the left-right direction (direction perpendicular to the static magnetic field).

  Here, Patent Document 1 discloses a technique for rotating the top plate so that the imaging reference axis and the gradient magnetic field reference axis coincide with each other when the posture of the subject varies within the imaging region. .

Japanese Patent Laid-Open No. 10-248823

  However, the setting procedure as described above is not limited to a subject with a physical disability, but when a subject having a disorder at the time of examination is imaged, the position of the subject before being carried into the imaging region The decision was not taken into account.

  For example, when imaging a subject whose neck is difficult to bend or a subject whose back is bent and difficult to stretch, it is difficult to align the imaging center of the subject with the irradiation center of the projector. In some cases, it was not possible to shoot.

  Also, in this case, even if the subject can be forced to take a posture and the imaging center of the subject can be aligned with the irradiation center, the subject is forced to suffer if the subject is photographed in an impossible posture. Become.

  Therefore, there is a problem that the subject tends to move during imaging, and motion artifacts occur. Here, when the subject moves during imaging, it is conceivable to rotate the top plate as in the technique described in Patent Document 1, but the operator needs to perform troublesome operations. It is not desirable.

  The present invention has been made to solve the above-described problems, and can easily set the imaging center of the subject to be the center of the imaging space without forcing the subject to suffer. An object of the present invention is to realize an MRI apparatus that can improve the operation time and shorten the operation time.

In order to achieve the above object, the present invention is configured as follows.
(1) The magnetic resonance imaging apparatus of the present invention includes a static magnetic field generation source for forming a static magnetic field space, a bed having a top plate for inserting a subject into the static magnetic field space, and the static magnetic field space. A light irradiating means for generating marker light to be irradiated to the subject arranged on the top plate at an external position, and an imaging position of the subject by controlling the irradiation position of the marker light to the subject. An imaging position specifying means for specifying, a top plate control means for moving the top board based on an instruction from the imaging position specifying means, and an imaging means for imaging the imaging position based on a nuclear magnetic resonance phenomenon.
In the magnetic resonance imaging apparatus, the imaging position specifying means controls the light irradiation means so that a plurality of imaging positions and their imaging order can be specified, and the top panel control means is configured to control the plurality of imaging positions. The movement of the top plate is controlled according to the imaging sequence so that each coincides with the approximate center of the static magnetic field space.

  (2) Preferably, in the above (1), the top plate control means controls the movement of the top plate so that a line segment passing through two desired imaging positions passes through the approximate center of the static magnetic field space.

  (3) Preferably, in the above (1), the imaging position specifying means includes means for specifying a curve passing through at least two of the plurality of imaging positions, and the top panel control means is The movement of the top plate is controlled so that the curve passes through the approximate center of the static magnetic field space.

  (4) Preferably, in the above (1) and (2), a display means for displaying the tomographic image of the subject is provided, and the display screen center position of the display means is the center of the tomographic image of the subject. Image moving means for moving the tomographic image so as to be positioned is provided.

  (5) Preferably, in the above (2), the imaging means includes means for applying a gradient magnetic field having a slice gradient magnetic field, a phase encoding gradient magnetic field, and a readout gradient magnetic field to the subject, and the slice gradient Any one of the directions in which the magnetic field, the phase encoding gradient magnetic field, and the readout gradient magnetic field are applied is made to coincide with the direction of the line segment.

  (6) Preferably, in the above (1) to (5), the static magnetic field generation source is configured by vertically opposing a pair of static magnetic field generation sources with the static magnetic field space interposed therebetween. A static magnetic field is generated, and the top plate is configured to be able to move in any direction within a plane perpendicular to the static magnetic field direction in the static magnetic field space.

  According to the present invention, the MRI apparatus can easily set the imaging center of the subject to be the center of the imaging space without imposing pain on the subject, improving operability and shortening the operation time. Can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In all the drawings, components having the same function are denoted by the same reference numerals, and repeated description thereof is omitted.

  FIG. 1 is an overall schematic perspective view of an MRI apparatus in a vertical magnetic field system (open type) to which the present invention is applied.

  This MRI apparatus uses a NMR phenomenon to obtain a tomographic image of a subject, and houses various devices for inducing a NMR phenomenon in a subject and receiving NMR signals as shown in FIG. A gantry 31, a bed (table) 32 having a top plate 36 on which the subject is placed, a power supply for driving various devices in the gantry 31, a housing 33 containing various control devices, and an NMR received from the subject And a processing device 34 for processing a signal to reconstruct a tomographic image of the subject, and each is connected to a power source / signal line 35.

  The gantry 31 and the table 32 are disposed in a shield room that shields high-frequency electromagnetic waves and static magnetic fields (not shown). The housing 33 and the processing device 34 are disposed outside the shield room.

FIG. 2 is a functional block diagram of the MRI apparatus shown in FIG.
In FIG. 2, the MRI apparatus includes a static magnetic field generation system 2, a gradient magnetic field generation system 3, a transmission system 5, a reception system 6, a signal processing system 7, a sequencer 4, and a central processing unit (CPU) 8. It has.

  The static magnetic field generation system 2 generates a uniform static magnetic field in the body axis direction (horizontal magnetic field method) or the direction perpendicular to the body axis (vertical magnetic field method) in the surroundings of the subject 1. Around the subject 1, a permanent magnet type, normal conducting type or superconducting type static magnetic field generating source is arranged. This static magnetic field generation system 2 is accommodated in a gantry 31.

  The gradient magnetic field generation system 3 includes a gradient magnetic field coil 9 wound in three axial directions of X axis, Y axis, and Z axis orthogonal to each other, and a gradient magnetic field power source 10 that drives each gradient magnetic field coil 9. . The gradient magnetic field generation system 3 drives the gradient magnetic field power supply 10 of each gradient magnetic field coil 9 according to a command from the sequencer 4 to be described later, so that the gradient magnetic field Gx in the X axis, Y axis, and Z axis directions. , Gy, Gz are applied to the subject 1.

  Specifically, a slice direction gradient magnetic field pulse (Gs) is applied in any of the X-axis, Y-axis, and Z-axis directions to set a slice plane for the subject 1, and phase encoding is performed in the remaining two axis directions. A direction gradient magnetic field pulse (Gp) and a frequency encoding direction gradient magnetic field pulse (Gf) are applied, and position information in each direction is encoded in the echo signal.

  The gradient magnetic field coil 9 is accommodated in the gantry 31, and the gradient magnetic field power supply 10 is accommodated in the housing 33.

  The sequencer 4 is a control unit that repeatedly applies a high-frequency magnetic field pulse (hereinafter referred to as an RF pulse) and a gradient magnetic field pulse in a predetermined pulse sequence. The sequencer 4 operates under the control of the CPU 8 and is necessary for collecting tomographic image data of the subject 1. These various commands are sent to the transmission system 5, the gradient magnetic field generation system 3, and the reception system 6.

  Further, in the MRI apparatus of the present invention, the sequencer 4 includes means capable of measuring while changing the output of the RF pulse. The sequencer 4 is accommodated in the housing 33.

  The transmission system 5 irradiates an RF pulse signal in order to cause nuclear magnetic resonance to occur in the nuclear spins of the atoms constituting the living tissue of the subject 1, and includes a high-frequency oscillator 11, a modulator 12, a high-frequency amplifier 13, and the like. And a high frequency coil 14a on the transmission side.

  The high frequency pulse output from the high frequency oscillator 11 is amplitude-modulated by the modulator 12 at a timing according to a command from the sequencer 4. The amplitude-modulated high-frequency pulse signal is amplified by the high-frequency amplifier 13 and then supplied to the high-frequency coil 14a disposed in the vicinity of the subject 1, and the subject 1 is irradiated with the RF pulse signal from the high-frequency coil 14a. .

  In general, the high frequency coil 14 a is accommodated in the gantry 31, and the other constituent means of the transmission system 5 is accommodated in the housing 33.

  The receiving system 6 detects an echo signal (NMR signal) emitted by nuclear magnetic resonance of nuclear spins constituting the biological tissue of the subject 1, and includes a receiving-side high-frequency coil 14b, a signal amplifier 15, A quadrature detector 16 and an A / D converter 17 are provided.

  An NMR signal from the subject 1 induced by the electromagnetic wave irradiated from the high-frequency coil 14a on the transmission side is detected by the high-frequency coil 14b arranged close to the subject 1, amplified by the signal amplifier 15, and quadrature phase It is supplied to the detector 16.

  The NMR signal is divided into two orthogonal signals by the quadrature phase detector 16 at a timing according to a command from the sequencer 4, and each signal is converted into a digital quantity by the A / D converter 17. Sent.

  Generally, the above-described device group constituting the reception system 6 is accommodated in the gantry 31.

  The signal processing system 7 includes an optical disk 19, an external storage device such as a magnetic disk 18, and a display 20 made up of a CRT or the like. When data from the receiving system 6 is input to the CPU 8, the CPU 8 executes processing such as signal processing and image reconstruction, displays the tomographic image of the subject 1 as a result on the display 20, and externally. Recording is performed on the magnetic disk 18 or the like of the storage device. The signal processing system 7 is accommodated in the processing device 34.

  In FIG. 2, the high-frequency coil 14 and the gradient magnetic field coil 9 on the transmission side are placed facing the subject 1 in the static magnetic field space of the static magnetic field generation system 2 in which the subject 1 is inserted. The high-frequency coil 14b on the receiving side is installed so as to face or surround the subject 1.

  The radionuclide to be imaged by the current MRI apparatus is a hydrogen nucleus (proton) that is a main constituent material of a subject as widely used clinically. Information on the spatial distribution of the proton density and the spatial distribution of the relaxation time of the excited state is imaged, thereby imaging the form or function of the human head, abdomen, limbs, etc. two-dimensionally or three-dimensionally.

A first embodiment of the present invention will be described with reference to FIGS.
FIG. 3 is a schematic perspective view of a vertical magnetic field type MRI apparatus. In this vertical magnetic field type MRI apparatus, static magnetic field generation sources are arranged to face each other vertically, and a static magnetic field space (imaging space) is formed therebetween. A subject is inserted into the imaging space so that imaging for diagnosis can be performed.

  As shown in FIG. 3, the positioning laser light from the XY laser projector 40 is irradiated in the X-axis and Y-axis directions, and the positioning laser light is irradiated from the Z laser projector 47 in the Z-axis direction. In FIG. 3, an operation panel 37 (imaging position designation means) is formed on the gantry 31, and the operator operates the operation panel 37 to set the movement operation of the top plate 36.

  Generally, the closer to the center of the static magnetic field space, the higher the static magnetic field uniformity. When the static magnetic field uniformity is lowered, artifacts accompanying image quality degradation such as image distortion, blurring, and S / N ratio decrease occur, and such artifacts are particularly prominent in recently developed high-speed imaging methods.

  For this reason, the positioning of the subject 1 is particularly important in high-speed imaging.

  FIG. 4 is an enlarged configuration diagram of the positioning XY laser projector 40 for determining the imaging position in FIG. As shown in FIG. 3, the XY laser projector 40 is installed in the A part of the gantry 31, and the projection position is controlled by the XY direction control device 41.

  Further, the XY laser projector 40 is fixed to the left-right moving rack 44 via a rotation motor 42, and the left-right moving rack 44 is connected to the left-right moving motor gear 43. The rotation motor 42 and the left / right movement motor gear 43 are connected to the XY direction control device 41 by a power source and a signal cable 45.

  A Z-direction laser projector 47 and a Z-direction control device 48 (described later) are also installed in the portion B of the gantry 31 shown in FIG. 3 with the same configuration as the XY laser projector 40.

  FIG. 5 is a configuration diagram of an operation control system of the XY laser projector 40 and the Z laser projector 47.

  In FIG. 5, the operation signal from the gantry operation panel 37 is supplied to the console 46 in the processing device 34 (in the signal processing system), and also to the XY laser projector direction control device 41 and the Z laser projector direction control device 48. Supplied. Further, an operation signal from the signal processing system operation console 46 is also supplied to the XY laser projector direction control device 41 and the Z laser projector direction control device 48.

  An XY laser projection position command signal from the XY laser projector direction control device 41 is supplied to the XY laser projector 40, and a Z laser projection position command signal from the Z laser projector direction control device 48 is supplied to the Z laser projector 47. .

  An operation signal from the gantry operation panel 37 is supplied to the top panel control unit 39 via the XY laser projector direction control device 41 or the Z laser projector direction control device 48.

  FIG. 6 is a horizontal section of the bed 32 and the receiving coil 14b portion on which the subject 1 is placed in FIG. 3, and is a view seen from the Z direction.

  In FIG. 6, the couch 32 is equipped with a couchtop control unit 39 for moving the couchtop 36 on which the subject 1 is disposed in the imaging space in the gantry 31 diagonally forward, backward, left and right by a motor or the like.

  The top panel control unit 39 controls the movement amount, speed, and the like of the top panel 36 in order to improve the riding comfort of the subject 1. The top panel control unit 39 may be installed inside the bed 32, but it may be installed outside the bed 32 with emphasis on the design and maintenance of the MRI apparatus.

  As described above, the operation panel 37 for operating the movement of the laser projector 40 and the top plate 36 is disposed on the upper side surface of the opening of the gantry 31, and is used for controlling the projection position of the laser projectors 40 and 47 in the lateral direction. A switch and an oblique direction switch are provided.

  A receiving coil 14 b for receiving an NMR signal emitted from the subject 1 is attached to the imaging part of the subject 1. The closer the receiving coil 14b is to the imaging region of the subject 1, the higher the S / N ratio of the NMR signal emitted from the subject 1.

  In addition, when the sensitivity center of the receiving coil 14b is matched with the center of the imaging part, an image with a high S / N ratio without sensitivity unevenness can be obtained. For this reason, when imaging the head of the subject 1, there are a large number of receiving coils fitted to each imaging region, such as a receiving coil for the head, a receiving coil for the cervical spine for the cervical spine, and a receiving coil for the lumbar spine for the lumbar spine. Have been prepared.

  Since the sensitivity center of the receiving coil 14b and the center of the imaging region of the subject 1 are normally matched, the top plate is used to match the sensitivity center of the receiving coil 14b with the center of the static magnetic field space (the center of the imaging space). By sending 36 into the imaging space, the setting of the subject 1 is completed.

  The subject 1 and the receiving coil 14 b are arranged on the top plate 36 of the bed 32 at the opening of the gantry 31 or outside. Next, the irradiation light from the laser projectors 40 and 47 is aligned with the three axes of the X direction, the Y direction, and the Z direction in accordance with the body shape of the subject 1 at the target imaging region.

  Then, the top plate 36 is electrically moved so that the imaging center of the subject 1 comes to the center of the imaging space of the MRI apparatus.

  The distance between the center (intersection) of the irradiation light from the laser projectors 40 and 47 and the center of the imaging space can be calculated by the position control device, that is, the CPU 8, so the imaging center of the subject 1 and the MRI apparatus The distance in the front-rear and left-right directions from the center of the imaging space is also automatically calculated.

  The subject 1 can be reliably set in the imaging space by moving the top 32 by the calculated distance and direction.

  Specifically, when the target imaging region is at a position deviated from the center line of the top plate 36 as shown by the intersection C of the dotted line shown in FIG. 6, the laser projector switch on the gantry operation panel 37 is operated. As a result, the XY laser projector direction control device 41 controls the left / right motor gear 43 and the rotation motor 42 to move the XY laser projector 40, and the intersection of the X direction laser light and the Y direction laser light is detected. Align with the imaging position C of the specimen 1.

  Next, by operating the imaging switch in the gantry operation panel 37 or the imaging switch of the console 46 in the signal processing system, a signal from the XY laser projector direction control device 41 is sent to the top panel control unit 39.

  The top panel control unit 39 calculates the distance between the imaging position C and the front / rear / left / right direction to the center position of the static magnetic field space, and calculates the distance of the top panel 36 so that the imaging position C matches the center of the static magnetic field space. And move in the direction. Then, imaging is started after the imaging position C and the center of the static magnetic field space are matched.

  The longitudinal distance from the laser projector 40 attached to the opening of the gantry 31 to the center of the static magnetic field space is a fixed length determined by the structure of the gantry 31. For this reason, the amount of movement in the front-rear direction of the top plate 36 for sending the top plate 36 to the center of the static magnetic field space is an amount obtained by adding the laser light intersection point and the interval length of the laser projector 40 to the fixed length. Therefore, the fixed length is set in the top panel control unit 39 in advance. The interval length is calculated and calculated by the top panel control unit 39 each time.

  When the imaging is finished and the subject 1 is pulled out of the gantry 31, the operation panel 37 is operated to instruct the top plate 36 to move out of the gantry 31. A position information signal indicating the position of the imaging position C is transmitted from the signal processing system console 46 to the top panel control unit 39. The top board control unit 39 calculates a movement amount for moving the top board 36 out of the gantry 31 from the transmitted position information, controls the movement quantity and movement speed, and the top board 36 before insertion. Return to a predetermined position on the bed 32.

  As described above, in the first embodiment of the present invention, instead of moving the subject 1 to the imaging target position of the subject arranged on the top plate 36, the intersection of the laser beams from the laser projector. Move position to match. Then, the front / rear / left / right direction distance between the intersection position matched with the scheduled imaging position and the center position of the static magnetic field space is calculated, and the top plate 36 is moved by the calculated distance to move the planned imaging position and the center of the static magnetic field space. Match the position and start imaging.

  Therefore, according to the first embodiment of the present invention, it is possible to easily set the imaging center of the subject to be the center of the imaging space without causing pain to the subject, thereby improving operability. An MRI apparatus that can shorten the operation time can be realized.

  FIG. 7 is an explanatory diagram of the second embodiment of the present invention. The basic configuration of the second embodiment and the first embodiment is the same, and therefore illustration and detailed description thereof are omitted.

  In the first embodiment described above, the imaging region of the subject 1 is imaged at one location. However, in the second embodiment, the imaging region of the subject 1 is a plurality of locations, and these multiple locations. It is an example in the case of image-capturing continuously.

  In FIG. 7, the operation panel 37 is operated in the same manner as in the first embodiment so that the first imaging region C1 and the intersection of the XY direction laser beams coincide. And after making the 1st imaging region C1 and the intersection of XY direction laser light correspond, the position is memorize | stored in a memory | storage means (not shown) as 1st imaging position information with the operation panel 37. FIG.

  Subsequently, in the same manner as the position setting of the first imaging region C1 described above, the operation panel 37 is operated so that the second imaging region C2 coincides with the intersection of the XY direction laser beams. Then, after matching the second imaging region C2 and the intersection of the XY direction laser beams, the position is stored in the storage means as second imaging position information by the operation panel 37.

  Next, by operating the imaging switch in the gantry operation panel 37 or the imaging switch of the console 46 in the signal processing system, a signal from the XY laser projector direction control device 41 is sent to the top panel control unit 39.

  The top panel control unit 39 calculates the distance between the imaging position C1 and the front / rear / left / right direction to the center position of the static magnetic field space, and calculates the distance of the top panel 36 so that the imaging position C1 matches the center of the static magnetic field space. And move in the direction. Then, imaging is started after the imaging position C1 and the center of the static magnetic field space are matched.

  Next, the top panel control unit 39 calculates the distance between the imaging position C2 and the center position of the static magnetic field space in the front-rear and left-right directions, and moves the top plate 36 so that the imaging position C2 matches the center of the static magnetic field space. Move to the calculated distance and direction. Then, after the imaging position C2 and the center of the static magnetic field space are matched, imaging is started.

  When the imaging is finished and the subject 1 is pulled out of the gantry 31, the operation panel 37 is operated to instruct the top plate 36 to move out of the gantry 31. A position information signal indicating the position of the imaging position C2 is transmitted from the signal processing system console 46 to the top panel control unit 39. The top board control unit 39 calculates a movement amount for moving the top board 36 out of the gantry 31 from the transmitted position information, controls the movement quantity and movement speed, and the top board 36 before insertion. Return to a predetermined position on the bed 32.

  As described above, according to the second embodiment of the present invention, a plurality of imaging centers are set on the subject without causing pain to the subject, and the plurality of imaging centers are continuously set in the imaging space. The MRI apparatus can be realized that can control the movement of the top plate so as to be at the center, improve the operability and shorten the operation time.

  Here, in the first and second embodiments described above, the imaging position C (C1, C2) of the subject 1 is not necessarily along the body axis of the subject 1. For this reason, since the tomographic image displayed on the display (display unit) 20 of the subject 1 has the imaging center C as the center of the screen, as a whole, the tomographic image is biased toward the display 20 as indicated by a broken line 49b in FIG. It is displayed in the state.

  Therefore, in the present invention, as shown in FIG. 8, since the initial intersection position P of the XY direction laser light is determined in advance, the initial intersection position P and the set imaging position, that is, the static magnetic field center C The CPU 8 (image moving means) calculates the offset amount S with respect to the position.

  Then, the CPU 8 calculates the screen movement amount corresponding to the calculated offset amount S, moves the tomographic image by the screen movement amount, and displays the tomographic image at the center of the display 20 (solid line image 49a).

  In this way, if the tomographic image is displayed in the center of the display 20, the observer can observe the image without feeling uncomfortable.

  In addition, as described above, the imaging position C (C1, C2) of the subject 1 is not necessarily along the body axis of the subject 1, and may be an oblique image.

  Therefore, in the present invention, as shown in FIG. 9, since the initial intersection direction of the XY direction laser light is determined in advance, the amount of oblique m between this initial direction and the direction of the XY laser light at the set imaging position. Is calculated by the CPU 8 (image correction means).

  In the case of the example shown in FIG. 9, for example, the oblique can be performed so that any one of the slice axis, the phase encode axis, and the readout axis is assigned in parallel to the dotted line shown in the figure.

  As a result, an axial plane can be set perpendicular to the dotted line shown in FIG. 9, or a sagittal plane can be set parallel to the dotted line.

  As shown in FIG. 9, an image 50a (solid line) is displayed on the display 20 instead of the oblique image 50b (broken line) as shown in FIG. 9 by obliterating the gradient magnetic field by an amount corresponding to the calculated amount of oblique m. The

  In this way, if the tomographic image is displayed on the display 20, the observer can observe the image without feeling uncomfortable.

  Even in the case of intentionally making the oblique, the display image can be an image viewed from the body axis direction.

FIG. 10 is an operation flowchart for executing the example shown in FIGS.
In step 100 of FIG. 10, the subject 1 is placed on the top board 36. Next, in step 101, the imaging part of the subject 1 arranged on the top board 36 is set by the operation panel 37 using laser light. In step 102, shooting conditions are set such as when oblique or continuous shooting is performed at a plurality of locations.

  Next, in steps 103 and 104, imaging of the subject 1 is started, and the image is reconstructed and displayed on the display 20. Here, when the image is shifted as shown in FIG. 8 or when the image is corrected as shown in FIG. 9, the frequency shift corresponding to the off-center in the frequency encoding direction and the phase rotation corresponding to the phase encoding direction oblique. Or oblique field gradients.

  Then, in step 105, it is determined whether or not imaging has been completed, that is, whether or not other parts are to be continuously imaged. If imaging is not terminated, the process returns to step 102.

  If the imaging is to be terminated in step 105, the process proceeds to step 106, and the subject 1 on the top board 32 is taken out from the imaging space.

  In the second embodiment described above, two positions C1 and C2 are shown as a plurality of imaging positions. However, the number is not limited to two, and the number of imaging positions can be three or more. When there are three or more shooting positions, it is possible to specify the shooting order as well as the shooting position. For example, it is possible to specify the shooting order of C3 from the positions C1 to C2, and further other positions, or C2,... Following the positions C1 to C3.

  That is, the top plate can be set to move randomly in any of the front, rear, left and right directions. This is particularly useful when an imaging location is designated according to the path through which the contrast agent flows during angiography.

  Two points are designated with C1 as the imaging start position and C2 as the imaging end position, and the top plate is moved so that the straight line passing through the positions C1 and C2 always passes through the center of the static magnetic field. Move the top plate intermittently and take pictures as necessary. This is useful in whole body photography.

  In this case, the imaging start position C1 and the movement direction of the top board are designated by the XY laser, and the movement amount of the top board is designated by the operation panel 37 or the console 46, whereby the direction designated from the imaging start position C1. The top plate is moved continuously or intermittently up to the amount of movement specified in, and images are taken as necessary.

  In addition, a desired curve from the imaging start position C1 to the imaging end position C2 is designated with the XY laser, and the top board is continuously or intermittently moved so that the curve is always at the center of the static magnetic field, and as necessary. To shoot. For example, the curve can be designated by providing a joystick on the operation panel 37 and operating the joystick.

1 is an overall schematic perspective view of an MRI apparatus in a vertical magnetic field system to which the present invention is applied. It is a functional block diagram of the MRI apparatus shown in FIG. 1 is a schematic perspective view of a vertical magnetic field type MRI apparatus to which the present invention is applied. FIG. 4 is an enlarged configuration diagram of a positioning XY laser projector that determines an imaging position in FIG. 3. It is a block diagram of the operation control system of an XY laser projector and a Z laser projector. FIG. 4 is a horizontal cross section of a bed on which a subject in FIG. 3 is placed and a receiving coil unit. It is explanatory drawing of the 2nd Embodiment of this invention. It is explanatory drawing of the offset amount setting of the initial intersection position P and the static magnetic field center C. It is explanatory drawing of the amount of oblique setting of an initial intersection direction and the direction of an XY laser beam. FIG. 10 is an operation flowchart for executing the example shown in FIGS. 8 and 9. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Subject 2 Static magnetic field generation system 3 Gradient magnetic field generation system 4 Sequencer 5 Transmission system 6 Reception system 7 Signal processing system 8 Central processing unit (CPU)
DESCRIPTION OF SYMBOLS 9 Gradient magnetic field coil 10 Gradient magnetic field power supply 11 High frequency oscillator 12 Modulator 13 High frequency amplifier 14a, 14b High frequency coil 15 Signal amplifier 16 Quadrature phase detector 17 A / D converter 18 Magnetic disk 19 Optical disk 20 Display 31 Gantry 32 Bed 33 Case 34 Processing Device 35 Power Signal Line 36 Top Plate 37 Operation Panel 39 Top Plate Control Unit 40, 47 Laser Projector 41 XY Laser Projector Direction Control Device 48 Z Laser Projector Direction Control Device

Claims (6)

A static magnetic field generation source for forming a static magnetic field space, a bed having a top plate for inserting a subject into the static magnetic field space, and the above-mentioned plate placed on the top plate at an external position of the static magnetic field space A light irradiating means for generating marker light applied to the subject; an imaging position specifying means for controlling the irradiation position of the marker light on the subject to specify the imaging position of the subject; and In a magnetic resonance imaging apparatus comprising: a top plate control means for moving the top board based on an instruction from the means; and an imaging means for imaging the imaging position based on a nuclear magnetic resonance phenomenon.
The photographing position specifying means controls the light irradiation means so that a plurality of photographing positions and their photographing order can be designated,
The magnetic resonance imaging apparatus, wherein the top plate control means controls the movement of the top plate according to the photographing order so that each of the plurality of photographing positions coincides with a substantially center of the static magnetic field space. The magnetic resonance imaging apparatus according to claim 1.
The magnetic resonance imaging apparatus, wherein the top plate control means controls the movement of the top plate so that a line segment passing through two desired imaging positions passes through a substantially center of the static magnetic field space. The magnetic resonance imaging apparatus according to claim 1.
The shooting position specifying means has means for specifying a curve passing through at least two of the plurality of shooting positions,
The magnetic resonance imaging apparatus, wherein the top plate control means controls the movement of the top plate so that the curve passes through a substantially center of the static magnetic field space.   3. The magnetic resonance imaging apparatus according to claim 1, further comprising display means for displaying a tomographic image of the subject, wherein a center position of a display screen of the display means is a center position of the tomographic image of the subject. A magnetic resonance imaging apparatus comprising image moving means for moving the tomographic image. The magnetic resonance imaging apparatus according to claim 2.
The imaging means includes means for applying a gradient magnetic field having a slice gradient magnetic field, a phase encoding gradient magnetic field, and a readout gradient magnetic field to the subject,
A magnetic resonance imaging apparatus characterized in that any one of the directions in which the slice gradient magnetic field, the phase encoding gradient magnetic field, and the readout gradient magnetic field are applied coincides with the direction of the line segment. The magnetic resonance imaging apparatus according to any one of claims 1 to 5,
The static magnetic field generation source is configured to vertically oppose a pair of static magnetic field generation sources across the static magnetic field space, and generates a static magnetic field in the vertical direction,
2. The magnetic resonance imaging apparatus according to claim 1, wherein the top plate is configured to move in the static magnetic field space in an arbitrary direction within a plane perpendicular to the static magnetic field direction.

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