JP4711732B2 - Magnetic resonance imaging device - Google Patents

Description

  The present invention measures nuclear magnetic resonance (hereinafter referred to as `` NMR '') signals from hydrogen, phosphorus, etc. in a specimen, and visualizes nuclear density distribution, relaxation time distribution, etc. More particularly, the present invention relates to a technique for correcting body motion using navigator echoes when a subject is moved to image a wide area.

  The MRI device measures NMR signals (echo signals) generated by the spins of the subject, especially the tissues of the human body, and forms the shape and function of the head, abdomen, limbs, etc. in two or three dimensions. This is a technology for imaging. Various imaging methods for imaging based on the spin echo method and the gradient echo method have been put into practical use. In photographing, phase encoding and frequency encoding are applied to an NMR signal by a gradient magnetic field and measured as time-series data, and a two-dimensional or three-dimensional Fourier transform is performed to reconstruct one image.

In such an MRI apparatus, a method of capturing a whole body (whole body MRI imaging) while moving a bed on which a subject is placed stepwise or continuously is being performed in clinical practice. These have been reported to be effective methods for whole-body screening tests, and it has been shown that screening tests that have been performed with multiple modalities such as CT, bone scintigraphy, and PET can be performed using only MRI equipment. ing. An example of shooting while moving the bed stepwise (multi-station shooting) is disclosed in, for example, (Non-Patent Document 1). An example of imaging the whole body of a subject (moving bed imaging) while moving the bed continuously is disclosed in, for example, (Non-Patent Document 2).
Whole-Body MRI: A Simple Approach using Automatic Table Movement and Dedicated Post-Processing, ISMRM 10 (2002), M. Bock et. Al Whole Body-MRI imaging with a continuously moving table platform in de tection of metastatic disease in cancer patients First Results of a feasibility study, ISMRM 11, P.1333 (2003), NAGhanem et.

A problem in the whole-body MRI imaging is when imaging the chest and abdomen with respiratory motion.
As one method for suppressing respiratory motion artifacts, it is effective to perform imaging while holding the breath. However, when shooting in the breath-hold state in multi-station shooting, the breath-hold level is different between stations, or the breath-hold level is the same between stations, but the other stations that do not require breath-holding are used. If the slice positions are different, when the images for each station are connected to one image, a slice position shift (misregistration) occurs at the boundary between the stations, and a correct whole body image cannot be acquired.
Another method for suppressing respiratory motion artifacts is the navigator echo method, which is disclosed in, for example, (Non-patent Document 3). This navigator echo method can be imaged in a non-breath-holding state, and is particularly effective for a subject whose breath-holding is difficult.
Navigator Echoes in Cardiac Magnetic Resonance, David Firmin and Jenny Keegan: Jouranal of Cardiovascular Magnetic Resonance, 3 (3), 183-193 (2001)

When the navigator echo method is used for whole-body MRI imaging, navigator echoes are acquired from different positions of the subject as the bed moves. As a result, in addition to the original respiratory motion displacement, an offset depending on the body shape of the subject is added to the respiratory motion displacement waveform monitored by the navigator echo. As a result, respiratory movement displacement cannot be monitored correctly.
Furthermore, since the respiratory motion displacement is monitored using the correlation method and the least square method using two navigators acquired from the same position of the subject at different timings, the acquisition position of the navigator echo changes sequentially, It is necessary to acquire a navigator as a reference each time. As a result, the shooting time is extended.
That is, in multi-station imaging and moving bed imaging, it is difficult to reduce body motion artifacts because conventional respiratory echo monitoring using navigator echoes cannot accurately monitor respiratory motion.

  Therefore, an object of the present invention is to monitor respiratory motion with high accuracy when suppressing respiratory motion artifacts by monitoring respiratory motion using navigator echo in whole-body MRI imaging of multi-station imaging or moving bed imaging. It is to provide an MRI apparatus capable of this.

In order to achieve the above object, the magnetic resonance imaging apparatus of the present invention is configured as follows. That is,
Means for generating a static magnetic field, moving means for placing a subject to move in the static magnetic field, moving the subject in the static magnetic field to monitor its body movement, and Measurement control means for acquiring echo signals for reconstructing an image, respectively, and the measurement control means outputs an echo signal for monitoring body movement of the subject in at least a part of the movement section. Acquire from the same position on the subject.

  Preferably, the measurement control unit divides the subject into a plurality of regions, and step-moves between the regions, and at least two regions, the body motion monitoring echo signal from the same position on the subject Good to get. Alternatively, the measurement control means may move the subject continuously and acquire the body motion monitoring echo signal from the same position on the subject in at least a part of the movement section.

In another preferred embodiment of the magnetic resonance imaging apparatus of the present invention, a means for generating a static magnetic field and a subject arranged in the static magnetic field are used to monitor the body movement and to replay the image. Measurement control means for acquiring echo signals for constituting each, and signal processing means for selecting only the echo signals acquired when the body movement is in a desired range and reconstructing the image of the subject. The signal processing means controls the narrowing of the range corresponding to the size of the body movement.
Preferably, the signal processing means may widen the range when photographing a part with a small body movement and narrow the range when photographing a part with a large body movement.

According to the present invention, the first effect is that the navigator echo acquisition position is fixed to a desired part of the subject, so that an offset depending on the body shape of the subject is not added to the monitored respiratory movement displacement. As a result, since gating using the monitored respiratory motion displacement can be performed accurately, respiratory motion artifacts in the image can be reduced even in whole-body MRI imaging. Further, since misregistration between slices does not occur, the quality of the entire image to be synthesized can be improved.
The second effect is that when acquiring navigator echo and monitoring the respiratory motion of the subject, the gating threshold is changed according to the magnitude of the respiratory motion of the imaging region. The extension of shooting time can be minimized. As a result, it is possible to shorten the shooting time when using the navigator echo.

Hereinafter, preferred embodiments of the MRI apparatus of the present invention will be described in detail with reference to the accompanying drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments of the invention, and the repetitive description thereof is omitted.
First, an overall outline of an MRI apparatus to which the present invention is applied will be described with reference to FIG.

  An MRI apparatus shown in FIG. 4 includes a magnet 402 that generates a static magnetic field around a specimen 401, a gradient magnetic field coil 403 that generates a gradient magnetic field in a static magnetic field space, and an RF coil 404 that generates a high-frequency magnetic field in the static magnetic field space. And an RF probe 405 for receiving an echo signal generated by the subject 401. The gradient magnetic field coil 403 is configured by gradient magnetic field coils in three directions of X, Y, and Z, and generates a gradient magnetic field in each direction in accordance with a current from the gradient magnetic field power supply 409. The RF coil 404 generates a high frequency magnetic field in response to a signal from the RF transmission unit 410. The echo signal received by the RF probe 405 is detected by the signal detection unit 406, processed by the signal processing unit 407, and converted into an image by calculation. The image is displayed on the display unit 408. The bed 412 is for the subject to lie down. The bed is driven by a bed driving unit 413. The gradient magnetic field power source 409, the RF transmission unit 410, the signal detection unit 406, the signal processing unit 407, and the bed driving unit 413 are controlled by the control unit 411, and the control time chart is generally called a pulse sequence.

  Currently, an object to be imaged by an MRI apparatus is proton, which is a main constituent material of a subject, as widely used clinically. By imaging the spatial distribution of proton density and the spatial distribution of the relaxation phenomenon in the excited state, the form or function of the human head, abdomen, limbs, etc. can be photographed two-dimensionally or three-dimensionally.

  Next, a photographing method will be described. An echo signal is detected by applying phase encoding and frequency encoding by a gradient magnetic field. This is repeated by changing the phase encoding. As the number of phase encodings, values such as 128, 256, and 512 are usually selected per image. Each echo signal is usually obtained as time-series data composed of 128, 256, 512, and 1024 sampling data. These data are two-dimensionally Fourier transformed to create one MR image. In the case of 3D, a slice encoding is further applied to the echo signal for detection, and 3D Fourier change is performed to obtain a 3D MR image.

  Next, whole body MRI imaging provided in the MRI apparatus will be described. This whole body MRI imaging is controlled by the control unit 411. First, the outline of multi-station shooting will be described with reference to FIGS. In the example of FIG. 1, the image from the head to the lower limb is imaged in 6 steps (6 stations), and the imaging plane is set as 101 to 106 in each station (the example in the figure is a COR cross section). The bed moves between shots and is stationary at each station during the shot. When images of 6 stations from the head to the lower limb are acquired in order from 101 to 106, all are connected to create one image. If necessary, move the shooting position in the A-P direction, and then acquire 6 station images again. For example, as shown in FIG. 2, when images for 6 stations are acquired at the position 201, the position 202 and the position 203 are sequentially changed, and the bed is moved in the HF direction each time. Repeat and acquire images for the necessary area. Images of 6 stations acquired at positions 201, 202, and 203 are also connected to form one image.

  Next, an outline of moving bed shooting will be described with reference to FIG. Usually, moving bed imaging is performed with an axial section (transverse section: TRS, coronal section: COR, sagittal section: SAG), and a sectional image in the other direction is reformatted from a sectional image in one direction. The figure shows an example of taking a whole body with a TRS cross-section while continuously moving the bed and reformatting it into a COR cross-section. A COR image 303 is created from the TRS image of the head and neck region 301, and a COR image 304 is created from the TRS image of the chest region 302. A similar operation is performed in the whole body region, and all the COR images are connected to create one image (305). Similarly, it is also possible to create a SAG image by photographing a TRS cross section.

  The problem with the conventional technique of whole body MRI imaging is when imaging the chest and abdomen with respiratory motion. In order to facilitate understanding of the operational effects of the MRI apparatus of the present invention, this problem will be described before the description of the embodiment of the MRI apparatus of the present invention. FIG. 5 shows an example in which breath holding imaging is performed in order to suppress respiratory motion artifacts when imaging the chest and abdomen. FIG. 5 shows a case where a COR section is imaged by multi-station imaging. If you hold your breath at the chest and abdominal sections, the levels of both breath-holds are exactly the same (501, 502), and other slices (head and lower limbs) that do not require breath-holding If it matches with the position where the image is acquired, there is no problem even if all the images are finally joined together. However, when both breath-hold levels are different (503, 504), or when both breath-hold levels are the same, but different from the position where another slice (head or leg) that does not require breath-holding is acquired (505, 506) Even when connected to one image, a slice position shift (misregistration) occurs at the boundary portion of the station, and a correct whole body image cannot be acquired. In this example, the cause of misregistration is respiratory movement in the AP direction of the chest and abdomen.

  Next, problems of the navigator echo method in the prior art will be described in order to facilitate understanding of the navigator echo method provided in the MRI apparatus and the effects of the MRI imaging of the present invention. Imaging using the navigator echo method is controlled by the control unit 411.

  First, FIG. 6 shows an example in which the navigator echo method is used for multi-station imaging. When the bed position is A, the abdominal region is photographed at the COR section 602. At this time, the navigator echo is acquired at the position 601 and the respiratory motion in the AP direction of the abdominal wall is monitored. During shooting, the bed is stationary and 601 is also stationary. The respiratory movement displacement monitored at 601 during imaging corresponds to the portion 607 of the respiratory movement displacement waveform 606. 605 is a range called a gate window. If the displacement monitored by the navigator echo is within 605, measurement data is used for image reconstruction. If it is outside 605, measurement data is not used for image reconstruction. It is used for measurement data acquisition judgment (gating), such as discarding. When the image 602 is acquired, the bed is moved in the direction of the arrow in the figure, and the image 604 is taken. At this time, the navigator echo is acquired from 603, and the monitored respiratory movement displacement corresponds to 608 of 606. Here, the navigator echo acquisition position 603 is the position of the subject different from 601 as the bed moves. As a result, an offset (Δx) depending on the body shape of the subject is added to the monitored respiratory motion displacement waveform 606 in addition to the original respiratory motion displacement. When gating is performed in such a state, gating cannot be performed because the gate window 605 set first is moved away from the gate window 605. This is a problem when the conventional navigator echo method is used for multi-station imaging.

  Next, FIG. 7 shows an example in which the navigator echo method is used for moving bed photography. In the example of FIG. 7, the TRS cross section is photographed while moving the bed continuously in the direction shown in the figure. Photographing is performed while monitoring respiratory movements in the AP direction of the abdominal wall using navigator echo. The imaging slice position and navigator echo acquisition position are fixed at the magnetic field center. In this case, the navigator echo is acquired from different positions of the subject such as 701, 703, and 705 as the bed moves. As a result, an offset (Δx) depending on the body shape of the subject is added to the monitored respiratory motion displacement waveform 708 in addition to the original respiratory motion displacement. If the above-described gating is performed in such a state, gating cannot be performed because 708 moves away from the initially set range (gate window) 707. This is a problem when the conventional navigator echo method is used for moving bed imaging, which is the same as in the case of multi-station imaging described above.

  Furthermore, monitoring of respiratory motion displacement by navigator echo is usually performed using a correlation method or a least square method using two navigators acquired from the same position at different timings. Therefore, when the navigator echo acquisition position sequentially changes as shown in FIGS. 6 and 7, it is necessary to acquire a reference navigator each time. Therefore, the shooting time is extended. The problem of extending the shooting time in this conventional technique occurs in both multi-station shooting and moving bed shooting.

Based on the above description, each embodiment relating to a body motion monitor using navigator echo at the time of whole body MRI imaging in the MRI apparatus of the present invention will be described below.
(First embodiment)
First, a first embodiment of the MRI apparatus of the present invention will be described. In the present embodiment, navigator echoes are acquired from a fixed position of a subject in order to accurately monitor respiratory motion using navigator echoes in whole body MRI imaging.

  As Example 1-1 of this embodiment, an example in which navigator echoes are acquired from a fixed position of a subject in multi-station imaging is shown in FIG. FIG. 8 shows a case where there are imaging slices in the abdomen and chest affected by respiratory motion in whole body imaging. First, an abdominal COR section 802 is taken at bed position A. Photographing is performed while navigator echoes are acquired from the position indicated by 801 and respiratory movement in the AP direction is monitored. When the photographing at 802 is completed, the bed is moved so that the chest becomes the center of the magnetic field, and the COR section 804 of the chest is photographed at the bed position B. When shooting 804, the respiratory motion in the AP direction is continuously monitored by navigator echo. Here, although the imaging section 804 has moved from 802 as much as the moving distance of the bed, the navigator echo acquisition position 803 is fixed on the subject and is not moved from the position 801. That is, the positions 801 and 803 where the navigator echo is acquired are set to the same position on the subject. As a result, the waveform of monitoring respiratory motion is also constant as shown by 806, and between the displacement measured at bed position A and the displacement measured at bed position B as in the conventional example shown in FIG. There is no offset depending on the figure (807,808). As a result, gating using the same gate window 805 is possible when shooting at the bed position A and when shooting at the bed position B.

  Fixing the navigator echo on the subject means that the excitation position of the navigator moves together with the bed when viewed from the apparatus coordinate system. That is, the irradiation frequency of the excitation RF pulse for acquiring navigator echo is changed by the frequency corresponding to the bed moving distance in accordance with the bed moving distance between the stations.

  Another characteristic of gating shooting using navigator echo is that the shooting time is extended. This is an extension due to the time for acquiring the navigator echo or the time for re-acquisition when the measurement data is discarded from the result of gating. For this reason, the imaging range in which the navigator echo is used together can be limited to the portion (chest and abdomen) affected by respiratory motion, so that the extension of the imaging time can be minimized. This limitation may be specified directly by the operator, or may be automatically determined from the amplitude of the body movement indicated by the navigator echo acquired by changing the position on a trial basis.

  Next, as Example 1-2 of this embodiment, an example in which navigator echoes are acquired from a fixed position of a subject in moving bed imaging is shown in FIG. FIG. 9 shows a case where there is an imaging slice from the abdomen to the chest that is affected by respiratory motion in whole body imaging. First, using the navigator echo, the TRS cross section 902 is imaged while monitoring the respiratory motion in the AP direction at the position indicated by 901 at the bed position A. The imaging slice moves from the abdomen to the chest as indicated by 902 (bed position A), 904 (bed position B), and 906 (bed position C) in accordance with continuous bed movement. When photographing 904 and 906, respiratory motion is monitored by navigator echo in the same way as in 902. Here, as described above, the imaging slice moves in accordance with the bed movement, but the acquisition position of the navigator echo is fixed to the subject and has not moved from 901. That is, the navigator echo acquisition positions 901, 903, and 905 at the bed positions are the same on the subject. Therefore, the waveform of monitoring respiratory motion is also constant as shown in 908, and the body shape of the subject is changed during each displacement measured at bed positions A, B, and C as in the conventional example shown in FIG. No dependent offset occurs (909, 910, 911). As a result, gating using the same gate window 907 is possible in any of the cases of shooting at bed positions A, B, and C. In order to fix the navigator echo acquisition position on the subject, the frequency of the irradiation RF pulse of the navigator is sequentially changed according to the bed moving distance in the same manner as in Example 1-1.

Here, in normal moving bed photography, the bed moving speed is constant as 1001 in FIG. However, when gating shooting using navigator echo is performed on a moving bed, measurement data may be discarded without being used for image reconstruction from the result of gating. When it is discarded, it is necessary to remeasure the data corresponding to the measurement data discarded at the same position, so the bed must stop during that time. Therefore, for example, a section (1004) in which the bed is moved at a constant speed, such as 1002, and a section (1003) to be stopped are repeated.
Further, as described in Example 1-1, when the navigator echo is used together, the photographing time is extended. Therefore, it is possible to minimize the extension of the imaging time by limiting the imaging range in which the navigator is used together to the part where the respiratory motion is affected. This limitation may be directly designated by the operator as in the case of Example 1-1, or may be automatically determined from the amplitude of body movement indicated by the navigator echo acquired by changing the position on a trial basis. .

In Examples 1-1 and 1-2 described above, the calculation of the respiratory movement displacement using the navigator echo is performed by the least square method or the correlation method using the two navigator echoes acquired at the same position. Therefore, when navigator echoes are continuously taken at the same position of the subject as shown in FIGS. 8 and 9, the navigator echo obtained first can be used as the reference navigator echo until the end of the measurement, and the navigator echo that becomes the reference is obtained on the way. There is no need to fix it.
In the examples of FIGS. 8 and 9, the respiratory motion in the AP direction is monitored by navigator echo, but this is not a limitation. For example, the navigator echo acquisition position is fixed to the diaphragm, and gating can be performed while performing respiratory motion monitoring in the HF direction.

  As described above, according to the present embodiment, in whole body MRI imaging, since the navigator echo acquisition position is fixed to a desired part of the subject, an offset depending on the body shape of the subject is added to the monitored respiratory movement displacement. There is nothing. As a result, since the gating using the monitored respiratory motion displacement can be performed accurately, respiratory motion artifacts in the image can be reduced even in whole-body MRI imaging. In addition, since misregistration between slices does not occur, the quality of the overall image to be synthesized can be improved.

(Second Embodiment)
Next, a second embodiment of the MRI apparatus of the present invention will be described. In the present embodiment, the imaging time is shortened by controlling the gate window in accordance with the magnitude of the respiratory motion displacement.
As described in the description of Examples 1-1 and 1-2 above, the shooting time is extended when gating shooting is performed. In gating shooting, measurement data for image reconstruction is acquired only when the displacement is within the gate window, and the measurement data is discarded when the displacement is outside the gate window. Therefore, if the gate window is narrowed, the effect of suppressing artifacts due to respiratory motion is enhanced, but the data acquisition efficiency is lowered, so that the imaging time is extended. On the contrary, if the gate window is widened, the effect of suppressing respiratory motion artifacts is reduced, but the data acquisition efficiency is increased and the imaging time is not extended.

  However, if there is an imaging slice in a part where respiratory movement is large, it is necessary to set the gate window narrow. However, in the part where the respiratory movement displacement is small, the influence of the respiratory movement displacement on the image quality is originally small. Shooting efficiency can be increased.

  Accordingly, FIG. 11 shows Example 2-1 of the present embodiment in which the gate window is controlled according to the magnitude of respiratory motion. FIG. 11 shows an example in which multi-slices are imaged in multi-station imaging combined with the navigator echo method. Here, multi-slice imaging means that a plurality of slices are captured one by one. At the bed position A, the slices indicated by 1102, 1103, and 1104 are sequentially photographed. When photographing any slice, gating is performed using navigator echo acquired from a position 1101 fixed on the subject. The respiratory movement displacement at each slice position is largest at 1102 close to the abdominal wall, and decreases in the order of 1103 and 1104. In this case, if the gate window is kept constant for all slices as before, the result is as shown in Fig. 11 (b), and data is acquired only in the portion of the respiratory motion amplitude (1114) within the gate window (1110). Is called. Normally, 1114 is about 10-15 mm and 1110 is about 3-5 mm, so the data acquisition efficiency is about 1/3. On the other hand, when the method of widening the gate window is used when the respiratory movement displacement is small, the result is as shown in FIG. When shooting 1102 with large respiratory motion displacement, set a narrow gate window 1120 (about 1/3 of the respiratory motion amplitude), and then when shooting 1103, gate window (respiratory motion amplitude about 1120 times). In the case where 1121 is set and 1104 is shot at the end, a gate window 1122 having the same width as the respiratory motion amplitude is set. By such control, the shooting time can be shortened by 1/3 in the example of FIG. The relationship between the navigator echo acquisition position (= abdominal wall) and the imaging slice shown in the example of FIG. 11 and the gate window is a proportional relationship 1201 as shown in FIG. 12 (a), but is not limited thereto. For example, as shown in FIG. 12B, it is possible to narrow the gate window to the same level as 1102 when shooting 1103 and to widen only when shooting 1104 (1202).

  Next, Example 2-2 of this embodiment is shown in FIG. FIG. 13 shows an example of shooting a multi-slice in moving bed shooting combined with the navigator echo method. The slice 1302 is photographed at the bed position A, the slice 1304 is photographed at the bed position B, and the slice 1306 is photographed at the bed position C. The respiratory movement displacement at each slice position is largest at the abdominal center 1306 and decreases in the order of 1304 and 1302 as it goes to the lower abdomen. In this case, if the gate window is kept constant for all slices as usual, the result is as shown in Fig. 13 (b), and data is acquired only in the part within the gate window (1310) of the respiratory motion amplitude (1311). Is called. As described in Example 2-1, since 1311 is about 10-15 mm and 1310 is about 3-5 mm, the data acquisition efficiency is about 1/3. On the other hand, when the method of widening the gate window is used when the respiratory movement displacement is small, the result is as shown in FIG. When shooting 1302 with a small respiratory motion displacement, set a wide gate window 1320 (approximately the same as the respiratory motion amplitude), then narrow down to about 2/3 of the respiratory motion amplitude when shooting 1304 (1321) Finally, when shooting 1302, the gate window is narrowed to about 1/3 of the respiratory motion amplitude (1322). By such control, the shooting time can be shortened by 1/3 in the example of FIG. Similarly to Example 2-1, the relationship between the navigator echo acquisition position (= abdominal wall) shown in the example of FIG. 13 to the imaging slice and the gate window is, for example, linear (1201) shown in FIG. ) And non-linear (1202).

  In the above two examples, the navigator echo method is applied to whole body MRI imaging. However, the present embodiment is not limited to whole body MRI imaging, and also when imaging a subject at a fixed position. It is possible to apply.

  As described above, according to the present embodiment, when the navigator echo is acquired and the respiratory motion of the subject is monitored, the gating threshold is changed according to the magnitude of the respiratory motion displacement of the imaging region. In this way, it is possible to minimize the extension of the shooting time during gating shooting. As a result, it is possible to shorten the shooting time when using the navigator echo.

  The above is an explanation of each embodiment in which body motion correction is performed using navigator echoes when imaging a wide area while placing the subject and moving the bed in the MRI apparatus of the present invention. However, the MRI apparatus of the present invention is not limited to the contents disclosed in the description of the above embodiment, and may take other forms based on the gist of the present invention.

For example, in the above description, the case where the subject is imaged by moving the subject to the F side in the HF direction has been described, but the present invention can be similarly applied to the case of moving to the H side. Alternatively, the present invention can be similarly applied to a case where the subject is moved to any side in the RL direction or a combination of a plurality of movements in these directions.
Furthermore, although the case of the respiratory motion as the body motion has been described, the present invention can be applied not only to the respiratory motion but also to other body motions, for example, the case where the motion of the joint is photographed while moving the hands and feet. .

Multi-station shooting example (conventional example). Multi-station shooting example (conventional example). Moving bed shooting example (conventional example). An MRI apparatus to which the present invention is applied. Problems when taking non-breathtaking shots. Problems with moving bed photography with navigator. Problems with multi-station shooting with navigator. Example of the present invention (Example 1-1). Example of the present invention (Example 2-2). Example of controlling bed moving speed (Example 1-2). Example of the present invention (Example 2-1). Relationship between gate window and slice position (Example 2-1). Example of the present invention (Example 2-2).

Explanation of symbols

  401 subject, 402 static magnetic field magnet, 403 gradient coil, 404 RF coil, 405 RF probe, 406 signal detection unit, 407 signal processing unit, 408 display unit, 409 gradient magnetic field power supply, 410 RF transmission unit, 411 control unit, 412 beds

Claims (6)

Means for generating a static magnetic field, moving means for placing a subject to move in the static magnetic field, moving the subject in the static magnetic field to monitor its body movement, and In a magnetic resonance imaging apparatus comprising: a measurement control unit that acquires an echo signal for reconstructing an image,
The magnetic resonance imaging apparatus characterized in that the measurement control means acquires an echo signal for monitoring the body movement of the subject from the same position on the subject in at least a part of the movement section. The magnetic resonance imaging apparatus according to claim 1.
The measurement control unit divides the subject into a plurality of regions, moves the step between the regions, and acquires the body motion monitoring echo signal from the same position on the subject in at least two regions. A magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus according to claim 1.
The measurement control means moves the subject continuously and acquires the body motion monitoring echo signal from the same position on the subject in at least a part of the movement section. Shooting device. The magnetic resonance imaging apparatus according to claim 1.
Comprising signal processing means for reconstructing an image of the subject by selecting only echo signals acquired when the body movement is in a desired range;
The magnetic resonance imaging apparatus characterized in that the signal processing means expands the range as the imaging slice position moves away from the position for acquiring the body motion monitoring echo signal . The magnetic resonance imaging apparatus according to claim 1,
Comprising signal processing means for reconstructing an image of the subject by selecting only echo signals acquired when the body movement is in a desired range;
The signal processing means sets g1 as the range when imaging the region where the body motion displacement is δ1, and g2 as the range when imaging the region where the body motion displacement is δ2, and satisfies δ1 <δ2. In this case, the magnetic resonance imaging apparatus controls the range of each part so that g1> g2 . Means for generating a static magnetic field, measurement control means for acquiring echo signals for monitoring the body movement and reconstructing the image from the subject arranged in the static magnetic field, and In a magnetic resonance imaging apparatus comprising: signal processing means for reconstructing an image of the subject by selecting only echo signals acquired when the body movement is in a desired range;
The measurement control means acquires an echo signal for monitoring the body movement from the same position on the subject,
The signal processing means sets g1 as the range when imaging the region where the body motion displacement is δ1, and g2 as the range when imaging the region where the body motion displacement is δ2, and satisfies δ1 <δ2. In this case, the magnetic resonance imaging apparatus controls the range of each part so that g1> g2 .

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