JP2001340315A - Mri apparatus and mr imaging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform highly accurate tracking by automatically tracking the positional change of an imaging cross section accompanying the movement or the like of a patient to take the image of cross section and ensuring the high intensity of a position signal value detected for tracking. SOLUTION: An MRI apparatus is equipped with three position detection coils 31a-31c attached to the diagnosing region of a subject, means (12-4, 15-17) for generating MR signals in the position detection coils, receiving circuits 37a-37c and arithmetic circuits 38a-38c for operating coil attaching positions from the MR signals, a means (19) for operating the movement quantity of the imaging cross section from the coil attaching positions and means (19, 16) for correcting a pulse sequence or the like in order to perform the tracking and imaging of the imaging cross section corresponding to the movement quantity. The position detecting coils are formed by integrating microcoils and an NMR signal source. In place of the position detecting coils, a receiving coil having three orthogonal coils utilizing magnetic conversion technique may be used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an MRI (magnetic resonance imaging) apparatus and an MR imaging method for imaging the inside of a subject based on a magnetic resonance phenomenon. The present invention relates to an MRI apparatus and an MR imaging method capable of imaging an area while automatically tracking a position change of an imaging area (a two-dimensional imaging section or a three-dimensional imaging volume) in a head.

[0002]

2. Description of the Related Art In magnetic resonance imaging, a nuclear spin of a subject placed in a static magnetic field is magnetically excited by a high frequency signal of the Larmor frequency, and an image is reconstructed from an MR signal generated by the excitation. This is an imaging method.

In the field of magnetic resonance imaging, for example, an imaging method for observing a time-series change of an MR signal value generated from the same imaging section is known. Imaging methods called brain MRI and dynamic MRI are such. When this imaging is performed, accurate image data cannot be obtained due to movement of the patient, and motion artifacts and the like appear in the image, and the image quality often deteriorates. For example, in a brain function MRI, when performing an examination of a primary motor cortex or the like using a paradigm in which tasks such as finger tapping are arranged in order, even if the head is fixed, in synchronization with switching between the active mode and the rest mode. Many patients move their heads. According to this imaging method, an observation image is obtained by subtracting a pixel value for each corresponding pixel from an image in the rest mode from an image in the active mode, but in this case, if the diagnosis site moves, artifacts may occur. The activation site is shifted. Therefore, in order to obtain positionally accurate image data, it is necessary to pay considerable attention to the examination, such as the method of fixing the patient's head and understanding, cooperation, and familiarity with the examination of the patient. However, the test results are uneven, and accurate data cannot be easily obtained for every patient. Also, superimposition of the brain function image and the morphological image is a very important matter in knowing the anatomical position of the lesion, but since the imaging time for collecting each image is separated,
Patient movement during those imagings was also a problem.

[0004] Therefore, several techniques for reducing the influence of such patient movement and body movement have been proposed. 1
First, motion correction processing based on a cross-correlation method or the like is performed on the captured MR data (collected data). But,
When the motion correction is a two-dimensional data correction process, there is a problem that only the motion in the plane can be detected and corrected. In the case of three-dimensional data correction processing, three-dimensional MR
It takes a long time to collect the data itself, making it difficult to collect data at the time resolution required for brain function imaging, and furthermore, the patient's movement and body movement while collecting a set of three-dimensional data There was a problem that the influence of the system could not be ignored. For the three-dimensional data correction processing, a certain degree of time resolution can be realized by using the multi-slice EPI method, but on the other hand, there has been a conflicting situation that the spatial resolution is limited.

[0005] Therefore, based on imaging of a two-dimensional cross section capable of achieving both high time resolution and high spatial resolution, the cross section is tracked almost in real time to eliminate the influence of patient movement and body movement. A method is assumed. Specifically, the position of the imaging section is identified, and the identification information is fed back to correct the movement.

In this correction, a method of identifying the position of the imaging section is important, and several proposals have been made regarding this.

First, the marker is attached to a human body or a jig fixed to the human body so that a marker containing a substance (water, PVA, oil, or the like) which can be an NMR signal source is included in a desired imaging section. This is a technique for performing multi-slice imaging. When the imaging section to be tracked is an axial plane, a coronal plane, or a sagittal plane, only one marker may be used.
In the case of an arbitrary oblique surface, three markers are required, and each marker is positioned so that the marker appears in an image of a predetermined imaging section. However, in this marker method, the operator needs to check the image after imaging to see if the marker is included in the image each time, and if not, adjust the settings again and perform imaging again. The operation labor is very large, and there are difficulties in the operation of the operator and the patient throughput. Although a method of automatically identifying a marker is also known, it is necessary to perform an advanced and enormous amount of image processing calculations. It is not suitable for imaging such as functional imaging.

[0008] A second technique that can be used to identify an imaging section is to generate an echo signal called a navigator echo. Specifically, in a part of the imaging pulse sequence, a gradient magnetic field pulse is applied to generate a navigator echo, and information on the movement of the diagnostic site is obtained from the phase change of the navigator echo to reduce the influence of the movement. Method. However, in the case of the navigator echo method, it is basically possible to detect a parallel movement within one view, but it is not possible to detect a movement in the slice direction between encoding steps or a movement such as rotation. That is, the reference point for detecting the movement changes for each excitation, and the absolute position cannot be tracked.

A third technique which can be used for identifying an imaging section is a technique using a microcoil proposed by Dumorin et al. (Refer to the paper "'92 SMR p104"). Can be tracked. Specifically, by utilizing the fact that the sensitivity region of a micro coil having a diameter of about several millimeters is limited to a very small part of the surrounding tissue, one or a plurality of such coils are attached to a catheter, for example, as a signal source. Each microcoil is connected to an independent receiving system and a data collecting system.
Information on the position of the microcoil is obtained by performing one-dimensional Fourier transform on data collected by applying a gradient magnetic field.
The position in the three-dimensional space can be obtained by performing the operation of applying the gradient magnetic field and the one-dimensional Fourier transform in each of the three directions of the X, Y, and Z axes. Basically, since the one-dimensional Fourier transform is performed only three times, the spatial position of the coil can be tracked almost in real time (for example, about once every 20 ms). However, since this method focuses on detecting the movement of the catheter, the position of each microcoil is determined as one position in space, and cannot be used for surface detection.

[0010] Further, there is also known an application of the third technique. A single microcoil with a signal source is attached to the object (site), and the cross section is parallelized by controlling the RF carrier frequency when applying a slice gradient magnetic field so that the microcoil is always included in the axial cross section. This is a method of moving (Paper "'97S
MR p1927 "). This enables tracking of a cross section that always includes the target object (part). However, in the case of this application method, it is only possible to perform parallel tracking on an imaging section so that the section (object) is simply included.
Brain function imaging subtracts pixel values between an image acquired in the active state and an image acquired in the rest state, so it is not necessary that the target object be simply included in the tracking section. It is necessary to track the three-dimensional movement so as to obtain a time-series image in which the inclination of the object and the position change in the cross section of the object are taken into account.

As described above, a two-dimensional section that can ensure a high spatial resolution is used as an imaging section at an arbitrary angle (that is, not limited to an axial plane, a coronal plane, or a sagittal plane). A method has not been established that can automatically track an at-random spatial position change of a cross section almost in real time and correct a position change of an imaging target in an imaging cross section.

In view of this situation, the present applicant has disclosed in
Japanese Patent Application Laid-Open No. 84719 discloses an MRI apparatus that detects the movement of a subject and automatically tracks a desired imaging section in accordance with the movement in order to alleviate the above-described inconvenience. Specifically, three markers composed of a micro RF coil are arranged at a diagnostic site, and the movement of the subject is three-dimensionally detected by detecting the positions of the three markers. The pulse position is corrected to adjust the slice position of the imaging section (the result is that the same desired section is always sliced). In addition, the imaging data in the imaging section is corrected by correcting the acquired data according to the detection result. Adjusting the position of the object (the position change in the imaging section of the imaging object is corrected as a result) 3
This is a dimension tracking method. Each of the three markers is connected to a transmitter and a receiver, which form a part of an imaging data acquisition system, and is configured to detect a marker position using the data acquisition system.

[0013]

However, in the case of the configuration described in Japanese Patent Application Laid-Open No. H08-84719, all three markers (micro coils) forming the position detecting means are provided with a transmitter and a receiver for the data collection system. The connection cable is troublesome to operate when connected. An RF coil for imaging is also connected in parallel to the transmitter and the receiver, so especially when setting the RF coil on the patient, the number of cables that must be routed with great care is increased. To be troubled.

Further, since the imaging RF coil and the marker minute coil are connected in parallel to the transmitter and the receiver, impedance matching, prevention of RF signal wraparound, addition of drive switching means for imaging and marking, etc. However, the number of designs for parallel connection increases, and the mechanism becomes complicated.

Further, a micro coil is simply arranged as a micro coil for a marker. Since the sensitivity of the micro coil is very small, there is a problem that the intensity of the position detection signal cannot be sufficiently secured.

The present invention has been made to overcome the current situation encountered in the prior art, and uses a two-dimensional section which can ensure a high spatial resolution as an imaging section at an arbitrary angle to accompany the movement of a patient. It is possible to automatically track the at random spatial position change of the imaging section in almost real time and with high accuracy, while preventing the operability from being reduced due to the wiring of the RF coil and the like. Aim.

[0017]

In order to achieve the above object, an MRI apparatus according to the present invention comprises a motion detecting means for outputting a signal corresponding to the motion of a subject, and a motion detecting means for outputting a signal corresponding to the motion output from the motion detecting means. Movement amount calculating means for calculating a spatial movement amount of an imaging region set in the diagnosis site of the subject based on the obtained signal, and tracking the imaging region in accordance with the movement amount calculated by the movement amount calculation means. Correction means for correcting the parameters of the imaging sequence for performing the imaging.

As a preferred example, the motion detecting means includes:
An optical device that outputs an optical signal, supporting means for supporting the optical device and detachably attaching the optical device to a diagnostic site of the subject or a site in a predetermined positional relationship with the diagnostic device, and receiving the optical signal Light receiving means for outputting a signal corresponding to the movement. In this case, the optical device is, for example, a sensor that outputs the optical signal as a light source, or a sensor that reflects the light from a separately placed light source to form the optical signal.

As another preferred example, the movement detecting means includes a position sensor attached to a diagnostic part of the subject or a part having a predetermined positional relationship with the diagnostic part, and a signal generating means for generating a signal from the position sensor. And position calculating means for calculating, from a signal generated by the position sensor, position information indicating a mounting position of the position sensor as a signal corresponding to the movement. For example, a position sensor is a 3D integrated micro coil and NMR signal source.
The signal generation means is a means including a static magnetic field magnet for imaging, an RF coil, and a gradient magnetic field coil.

Further, for example, the position sensor comprises one or more receiving coil sections in which three coils are arranged orthogonally, and the signal generating means includes a transmitting coil section in which three coils are arranged orthogonally, And a driving unit for driving the unit to generate an oscillating magnetic field, wherein the transmitting coil unit is arranged so that the receiving coil unit is located in a sensitivity region of the oscillating magnetic field. In particular, RF
It is preferable to include a control unit that controls the driving unit so that the driving of the transmission coil unit is turned off during the transmission of the wave.

Further, as a preferred example, the movement amount calculating means includes reference cross section setting means for setting a cross section of the diagnostic site passing through the position sensor from the position information as a reference cross section. It is a means for obtaining a spatial movement amount of the imaging region having a spatial positional relationship.

Preferably, the correction means includes a carrier frequency of an RF excitation pulse included in the imaging sequence, an applied amount of a gradient magnetic field pulse included in the imaging sequence, and a reference signal for phase detection during reception. frequency,
And a means for correcting at least one factor of the phase of the reference signal for phase detection at the time of reception as the parameter according to the motion amount.

Further, it is preferable that the apparatus further comprises control means for executing the driving of the signal generating means, the position calculating means, the motion amount calculating means, and the correcting means immediately before or immediately after the execution of the imaging sequence. in this case,
The control means may be, for example, an R
A means for executing the driving of the signal generation means, the position calculation means, the movement amount calculation means, and the correction means every time the F excitation pulse is applied or every time when the RF excitation pulse is applied a plurality of times.

Further, according to a preferred example, the imaging region is a two-dimensional imaging section. This two-dimensional imaging section is composed of, for example, a plurality of slices.

On the other hand, in order to achieve the above object, according to the MR imaging method of the present invention, a signal corresponding to the movement of the subject is detected, and a diagnosis site of the subject is detected based on the signal corresponding to the movement. And calculating a spatial movement amount of the imaging region set in (1), and correcting an imaging sequence parameter for tracking and imaging the imaging region in accordance with the movement amount.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. In the present invention, the term "diagnosis site" refers to a local site of the patient such as the head and abdomen,
The term “imaging region” refers to a scan region (specifically, a two-dimensional cross section or a three-dimensional volume) in a diagnostic site where spin excitation (magnetic resonance) is actually performed. In addition, the term “imaging target” is an object to be imaged in an imaging region (eg, brain)
I will point to.

(First Embodiment) A first embodiment will be described with reference to FIGS.

FIG. 1 shows a schematic configuration of an MRI (magnetic resonance imaging) apparatus according to this embodiment.

This MRI apparatus includes a gantry 11 for placing a patient as a subject in a static magnetic field. The gantry 11 has a static magnetic field magnet 12 composed of, for example, a superconducting magnet. A diagnostic space having a uniform static magnetic field strength is formed inside the magnet 12, and a diagnostic region of a patient is placed in the diagnostic space. When the magnet 12 is of a substantially cylindrical type, the patient is positioned inside the magnet while lying on a bed (not shown), and the diagnostic site is placed in the diagnostic space. When the magnet 12 is of the open type, the patient is located in the magnet in, for example, a sitting position or an upright position, and the diagnostic site is placed in the diagnostic space.

The magnet 12 is provided with a gradient coil 13 and an imaging RF coil 14 on a part of its wall. The gradient magnetic field coil 13 includes x, y, and z coils that generate gradient magnetic field pulses in a slice direction, a phase encode direction, and a readout direction that are superimposed on a static magnetic field based on a given pulse sequence. The unit of the gradient magnetic field coil 13 is connected to the gradient magnetic field amplifier 15. The gradient magnetic field amplifier 15 controls the gradient magnetic field in the X-axis, Y-axis, and Z-axis directions (physical axes set in the gantry 12) from the sequencer 16.
In response to SGy and SGz, application of a pulse current to be supplied to the x, y, and z coils is controlled. Thereby, the gradient magnetic fields in the slice direction, the phase encode direction, and the readout direction are controlled.

The RF coil 14 has, for example, a structure serving as both a transmission coil and a reception coil, and is connected to a transmitter 17 and a receiver 18. The transmitter 17 and the receiver 18 are also connected to the sequencer 16. The transmitter 17 receives the control signal Sf sent from the sequencer, and sends a transmission current pulse to the RF coil 14 in response to the control signal Sf. As a result, an RF magnetic field pulse is generated from the RF coil 14 and applied to a diagnostic site (for example, the head) of the patient. Since a slice gradient magnetic field is also applied in parallel with this application, a desired slice at a diagnostic site is selectively excited, and an MR signal is generated from this slice due to a magnetic resonance phenomenon.

The generated MR signal is received by the RF coil 14 and sent to the receiver 18 as a corresponding RF current signal. The receiver 18 amplifies the received RF current signal,
A predetermined reception process such as detection and digitization is performed, and the data is sent to the host computer 17 via the sequencer 14 as digital MR data.

The sequencer 16 has a CPU and a memory. At the time of scanning, the gradient magnetic field amplifier 1 is controlled based on pulse sequence information passed from the host computer 17.
5 and control signals SGx, SGy,
SGz and Sf are output. In addition, the sequencer 16 scans, that is, performs correction at an appropriate timing before or after the execution of the imaging pulse sequence,
On the basis of correction information, which will be described later, passed from the host computer 17, gradient magnetic fields Gx, Gx, X, Y, and Z directions corresponding to the slice direction, the phase encode direction, and the readout direction defined by the pulse sequence. Gy,
Gz is adjusted by the gradient magnetic field amplifier 15 by ΔGx, ΔGy, and ΔGz, and the frequency f of the transmission RF signal is transmitted to the transmitter 17 by ΔGx.
The control signal Sφ is sent to the receiver 18 to adjust the phase φ of the reference signal for phase detection in the receiver by Δφ.

The host computer 19 includes a CPU and a memory, and performs drive timing control of the entire apparatus, scan control for imaging, image reconstruction processing, control and processing for tracking an imaging area, and the like. Note that a configuration in which the image reconstruction processing is left to a dedicated processor may be employed. An input device 20, a display device 21, and a storage device 22 are connected to the host computer 19. The host computer 19 calculates pulse sequence information as scan control and passes it to the sequencer 19. Further, as image reconstruction processing, the received MR data is once arranged in a two-dimensional or three-dimensional k-space (Fourier space or frequency space), and then subjected to a two-dimensional or three-dimensional Fourier transform to perform real-space image Reconstruct into data. Further, tracking control and processing are executed as shown in FIGS.

A unit for automatically tracking an imaging area (two-dimensional section or three-dimensional volume) including an imaging target in the block configuration of FIG. 1 will be described.

The patient P placed in the diagnostic space of the static magnetic field magnet 12 or laid down has three position detecting coils 31.
a, 31b and 31c are mounted. This coil 31a,
Each of 31b and 31c is an NMR signal source (water, PV
A, oil, etc.) and a micro-coil. When the magnetization spin of the NMR signal source of the receiving element is excited by the RF signal, an MR signal is generated, and this signal is detected as a current pulse (position detection signal) by the microcoil. Although the sensitivity region of the microcoil itself is set to be very narrow, N
Since the MR signal source is always located, a position detection signal with much higher intensity can be obtained as compared with a conventional position detection coil using only a microcoil. In addition, since the sensitivity region of the microcoil can be set to be narrow by such integration, high position detection ability is maintained.

The three position detecting coils 31a, 31b, 3
1c is specifically attached by any one of the methods shown in FIGS. This attachment method is based on brain function imaging, and the patient P is imaged in a supine state, a sitting state, or a standing state, for example.

In the mounting method shown in FIG. 2, three position detecting coils 31a, 31b, 31c are individually and directly mounted on tapes 32 at appropriate positions on the head (diagnosis site). The position detecting coils 31a, 31b, 31c are independently pulled out via a coaxial cable 33 and individually connected to a receiving circuit described later. The mounting method shown in FIG. 3 uses a fixing jig 34 in the form of a headgear. The fixing jig 34 is mounted on the head, and the position detecting coil 31 is attached thereto.
a, 31b, and 31c are respectively attached. The attachment method shown in FIG. 4 uses a hair band-like attachment tool 35 such as a magic tape. Further, the mounting method shown in FIG.
The position detection coils 31a,
31b and 31c are attached respectively. Note that a liquid crystal display device may be attached to a lens portion of the glasses, and a display image of the display device may be used for visual stimulation.

The position detection signals of the position detection coils 31a, 31b, 31c are sent to the receiving circuits 37a, 37b, 37c via the coaxial cable 33, respectively. Each receiving circuit includes a preamplifier, an A / D converter, and the like, and processes position detection signals detected by the respective position detection coils 31a (31b, 31c) independently and in parallel as position detection data. This digital amount of position detection data is supplied to the subsequent position information calculation circuits 38a, 38b,
38c. Each position information calculation circuit has a dedicated CPU as an example, and the input position detection data
One-dimensional Fourier transform is separately performed three times in the axial direction, the Y-axis direction, and the Z-axis direction, and the position detection coils 31a, 31
1b, 31c position information (x1, y1, z1), (x
2, y2, z2) and (x3, y3, z3).
These pieces of position information are sent to the host computer 19, and are used in tracking processing as information on the movement of the patient's diagnostic site, that is, the movement of the imaging region.

The host computer 19 performs scan control involving tracking of an imaging region (here, a two-dimensional section is handled)
The processing shown in FIG. 6 is performed. Hereinafter, this will be described in detail.

The processing shown in FIG. 3 includes an initial reference section identification process performed in the first half (steps S1 to S4) and a scan control involving identification and automatic tracking of an imaging section performed in the second half (steps S5 to S5). S13). In the latter half of the processing, the processing of the imaging section and the tracking is set to be performed immediately before the application of the imaging pulse sequence, but may be set to be performed immediately after the application of the imaging pulse sequence.

When the operation of putting the patient to sleep (to take a predetermined imaging position), setting of the positioning of the patient, and the like are completed, the host computer 19 sequentially executes the processing of each step shown in FIG. 6 based on an instruction from the operator. . First, the host computer 19 sends information on the coil position detection sequence to the sequencer 16 to execute the coil position detection sequence (step S1). FIG. 7 shows an example of a pulse sequence used in this sequence.

This coil position detection sequence is a process of applying an RF magnetic field and a gradient magnetic field pulse via the transmitter 17 and the gradient magnetic field amplifier 15 (step S1).
a) a process of instructing each of the position information calculation circuits 38a, 38b, 38c three times one-dimensional Fourier transform in the X-axis direction, the Y-axis direction, and the Z-axis direction (step S1b); , 38c obtained by the Fourier transform (x1, y1, z
1), (x2, y2, z2), (x3, y3, z3) input processing (step S1c), and the three coil positions (x1, y1, z1), (x2, y2, z)
2) Includes a process (step S1d) of calculating a cross section passing through (x3, y3, z3) simultaneously.

FIG. 7 shows the RF magnetic field pulse and the gradient magnetic field pulse.
As shown in (1), when the voltage is sequentially applied in each axial direction, the spins of the NMR signal sources of the position detection coils 31a, 31b, 31c are sequentially excited to generate an MR signal. This MR signal is detected by a microcoil of each position detection coil and sent to a receiving circuit. The MR data that has been subjected to the predetermined reception processing in each reception circuit is output to each position information calculation circuit 38a (38b,
38c).

Next, information defining the position of the section is stored using the section calculated in step S1c as an initial reference section (step S2). Further, the host computer 19
Receives the information of an arbitrary imaging section to be commanded by the operator activating the locator function via the input device 20, and determines the imaging section to be tracked (step S3). Here, it is assumed that single slice imaging is performed, and therefore, the number of imaging sections to be tracked is one. This imaging section may be located at any position within the diagnostic region, and may naturally be spatially separated from the initial reference section, or may have a different angle. When the positions of the initial reference section and the imaging section are determined in this way, the spatial relative positional relationship between the sections (parallel movement amount, rotation amount, etc.) is calculated (step S).
4).

The operations and processes up to this point are performed in a state where the head as a diagnostic site is fixed. Once the relative positional relationship is determined in this manner, the head does not need to be fixed thereafter, and can be freely moved in a predetermined space area. This movement is automatically tracked by a position detection coil attached to the head as described below, and in parallel with this, data is collected for functional brain imaging. For this reason, it is possible to collect data in an extremely natural state such as daily life.

After the identification processing of the initial reference section is completed, the host computer 19 determines whether or not to perform a scan based on information provided from the input device 20 (step S5). If the determination is YES, the scan conditions are input from the input device 20 or read from the storage device 22 which has been stored in advance (step S6), and the type of the designated pulse sequence is specified from the scan conditions (step S7). The information of this pulse sequence is passed to the sequencer 16.

When the start of scanning is determined in response to an instruction from the operator (step S8),
The above-described coil position detection sequence is executed (Step S9). By this sequence, the position detection coil 3
Since a section passing through three new positions 1a, 31b, and 31c is calculated as an updated position of the tracking imaging section (see step S1d), the amount of change in the spatial relative positional relationship between this section and the initial reference section is calculated. Calculation is performed (step S10).

Next, the host computer 19 corrects the shift in the direction and position of the slice to be sliced in the subsequent scan for imaging in accordance with the amount of change in the tracking imaging slice, and furthermore, the spatial position of the imaging target in that slice. Is corrected (step S11).

More specifically, the displacement of the slice section adjusts the carrier frequency f of the RF excitation pulse (Δf).
In addition, the slice cross section direction (ie, oblique angle or the like) is adjusted by adjusting the slice gradient magnetic field components of the X axis, the Y axis, and the Z axis (ΔGx, ΔGy, ΔGz).
It is corrected by that.

Further, the correction for the positional shift of the object to be imaged in the slice cross section is particularly important in brain functional imaging for performing subtraction between images. For this correction, the absolute position of the three position detecting coils is determined to be different from each other, and various parameters may be corrected according to the amount of the difference.
For example, regarding the positional deviation in the reading direction, the frequency of the reference signal for phase detection at the time of reception is adjusted to move off-center. Also, the displacement in the phase encoding direction is
The correction is performed by phase control of the reference signal for phase detection at the time of reception or by software processing performed until the next data collection.

By the coil position detection, the calculation of the position change amount of the tracking section, and the correction processing of the imaging parameter of the pulse sequence in the series of steps S9 to S11, the imaging section is automatically tracked at the time of the scan executed thereafter. become.

Thereafter, the host computer 19 operates in the sequencer 1
6 is instructed to sequentially execute one excitation of the imaging pulse sequence (step S12). Thus, for example, in response to a pulse sequence based on the SE method (see FIG. 8), echo data for a certain phase encoding amount is collected from the tracked imaging section. As shown in FIGS. 8 and 9, the correction parameters such as the gradient magnetic field pulse and the carrier frequency of the RF excitation pulse in this pulse sequence are, for each excitation and immediately before the excitation, the position change amount of the tracking imaging section from the previous RF excitation. Has been corrected by the amount corresponding to.

Thereafter, if the amount to be phase-encoded still remains (step S13, NO), the processing of steps S9 to S12 is repeated until all excitations are completed and data collection for all phase-encoded amounts is completed. Be executed.

By the above-described tracking control and imaging, even if the patient pulls his chin from the stationary state of FIG. 10A and the head tilts as shown in FIG.
Since ma is automatically tracked in real time, it does not affect imaging such as brain function imaging. In addition,
In FIG. 10, a cross section CSref indicates a reference cross section passing through the coil position. Both cross sections CSima and CSref
The relative positional relationship between them is always constant.

Also, as compared with the device described in Japanese Patent Application Laid-Open No. Hei 8-84719, the position detecting coils 31a, 31b and 31c constituting the position detecting means are not physically connected to the data collection system. When setting a patient or the like, the trouble of routing the connection cable is greatly reduced. Further, the position detection coils 31a, 3
1b, 31c and the imaging RF coil 14 are electrically separate systems, so the imaging RF coil 14
There is no effect on impedance matching and prevention of RF signal wraparound. Further, the position detection coils 31a,
Since the 31b and 31c have an integrated NMR signal source, even if the sensitivity region of the microcoil is very small, a high-intensity position detection signal can be collected and the tracking accuracy can be improved.

A modification of the first embodiment will be described below.

FIG. 11 shows a first modification. This modification is a high-speed SE (FSE) as a pulse sequence.
1 shows a form in which imaging is performed by a multi-slice method using the method. Also in this case, for each excitation unit, the coil position detection sequence is activated as described above, and the imaging parameters are corrected according to the amount of change in the coil position obtained by the activation of this sequence, that is, the reference cross-sectional position. Thus, the motion of the diagnostic site can be detected for each excitation unit, and a highly accurate tracking operation can be performed.

The second modification shown in FIG. 12 shows a case where two slice sections that are substantially orthogonal to each other are imaged by the EPI method. Also at this time, the coil position sequence is activated before excitation for each slice cross section, and correction is performed to reflect the coil position detection result as motion information to the imaging parameter.

The third modification shown in FIG. 13 shows a time relationship between a tracking operation and an imaging operation when a three-dimensional volume area is set as an imaging area and this is imaged by the EPI method. Also in this case, the coil position detection sequence and the correction processing are executed for each excitation unit, that is, for each slice encoding. The area to be cross-sectionally tracked may be three-dimensional as described above, and is effective when the time resolution is moderately restricted.

In the above-described embodiment and its modifications, the coil position detection sequence and the correction processing are set to be performed for each RF excitation. However, the coil position detection sequence and the correction processing need not always be performed for each excitation. The tracking accuracy may be appropriately thinned out within an allowable range.

The three position detecting coils 31a, 31
The three receiving circuits individually connected to b and 31c are one equipped with a high-speed A / D converter, and this one receiving circuit and three position detecting coils are connected via a multiplexer. Configurations are also possible. It is not necessary to independently install the position information calculation circuit provided at the subsequent stage of the reception circuit for each detection coil, and it is a circuit having a processing speed capable of substantially completing the calculation before the next coil signal detection. For example, one arithmetic circuit common to the three circuits may be used, and this may be configured to be driven in a time-division manner.

Furthermore, the tracking method (coil position detection sequence and correction processing) of the present invention
The present invention can be applied to normal imaging that does not matter. In particular, it is effective for patients who are apt to move during imaging, such as elderly people, children, and severely injured patients, and can capture high-quality morphological images with reduced artifacts.

(Second Embodiment) An MRI apparatus according to a second embodiment of the present invention will be described with reference to FIGS. In this embodiment, the same or equivalent components as those of the MRI apparatus of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted or simplified.

The overall configuration of the MRI apparatus according to the second embodiment is substantially the same as that described above, but differs in the signal form of the detecting means for detecting the movement of the patient. In the case of the first embodiment, the MR signal is collected by the detection coil attached to the diagnosis site. However, in the case of the present embodiment, a magnetic conversion technique is used.

The motion detecting means based on the magnetic conversion technique includes a set of a transmitting coil unit 41 having three orthogonal coils, a set of a receiving coil unit 42 having three orthogonal coils, And a driver 43 for generating an oscillating magnetic field of about 10 kHz in the coil section 41. The oscillating magnetic field transmitted from the transmission coil unit 41 is
Are detected by the three orthogonal coils 42x, 42y, and 42z (see FIG. 15), and the detection signal of each of the orthogonal coils is sent to the position information calculator 44.

If the diagnostic site is the head, the receiving coil unit 42 is attached to an arbitrary position on the head as shown in FIG. As shown in FIG. 16, for example, the transmission coil unit 41
The RF coil 14 is attached to the inner wall position (i) of the cover or a predetermined position (ii) of the bed. The mounting position is determined so that the receiving coil unit 42 is located within the sensitivity region of the oscillating magnetic field generated by the coil unit 41.

The position information calculator 44 receives the detection signals of the three orthogonal coils 42x, 42y, and 42z in a time-division manner, and receives the three-dimensional absolute coordinate values of x, y, and z of the receiving coil unit 42, pitch, yaw, and roll. And a total of six degrees of freedom of the Euler angles are calculated, and this calculated value is output to the host computer 19. The host computer 19 uniquely determines a cross section passing through the receiving coil unit 42 from the six calculated values. Therefore, as in the first embodiment, a section passing through the receiving coil section 42 is used as a reference section, and an arbitrary imaging section can be tracked based on this reference section.

The driver 43 operates according to a drive control signal from the host computer 19. Therefore, when performing imaging, the host computer 19 gates the driver 43 and controls the drive timing so that the captured image is not deteriorated by the magnetic field from the transmission coil unit 41.

Therefore, even with the motion detecting means of the present embodiment, the motion of the patient's diagnostic site can be accurately detected, and the imaging area can be tracked with high accuracy, as in the first embodiment. In addition, since there is no need to share the transmission / reception system with the imaging system, independent independent design with a high degree of freedom can be achieved, and the simultaneous measurement performance is higher than in the configuration of the first embodiment.

In the second embodiment, only one receiving coil section 42 is attached to the diagnosis site.
Instead of this, for example, three receiving coil units can be attached to achieve more accurate position detection. A configuration is also possible in which a gradient magnetic field is used instead of the transmission coil unit, and gradient magnetic field pulses in the X, Y, and Z directions are sequentially applied to identify the position of the reception coil unit, and positional information in each axis direction is obtained. It is possible.

(Modification of Motion Detecting Means) The means for detecting the motion of the diagnostic part of the subject applicable to the first and second embodiments described above uses an optical signal as follows. The present invention can be implemented in various forms.

First, three or more light emitting devices (eg, LEDs)
May be attached to a diagnostic site, the light emitting device may be photographed by at least three cameras, the mounting position of the light emitting device may be determined from the captured image, and the amount of movement of the diagnostic site may be calculated from the change in the mounting position. .

Further, as another motion detecting means using an optical signal, means having the structure shown in FIGS. 17 to 26 is provided.

The movement detecting means shown in FIG. 17 includes a band 51 wrapped around the head, which is a part to be diagnosed of the subject P at the time of diagnosis, and a light source mounted at three different positions around the band 51. Laser pointers 52A to 52C
And a CCD panel 53 for receiving beams emitted from the laser pointers 52A to 52C. The three laser pointers 52A to 52C are in the Z-axis direction (the longitudinal direction of the bed top).
Beams are emitted in parallel to the CCD panel 5
Light is incident on three different positions. The CCD panel 53 is a CCD
This is a light receiving element in which elements are arranged two-dimensionally. CCD
The light receiving signals obtained by the panel 53 receiving the three beams are sent to a processing device (not shown) to obtain position information of the light receiving beams, and the position information is sent to the host computer 19. Therefore, when the head of the subject P moves, the beam position incident on the CCD panel 53 changes according to the movement,
The position information obtained in response to the position change is sent to the host computer 19. This makes it possible to detect the movement of the subject's head, and to perform the same control of correcting the imaging pulse sequence as in the above-described embodiment. In the case of this detection means, the detection sensitivity in the Z-axis direction is low, but the movement in the case of the head is more remarkable in the XY plane than in the Z-axis direction. Can work effectively.

The motion detecting means shown in FIG. 18 uses three laser pointers 54A to 54C as light sources at predetermined three different positions of the band 51 similar to the above.
Is standing. However, this laser pointer 54A
The light exits at the tips of .about.54C are bent as shown. This bending angle is set so that the emitted beam propagates at an angle deeper than the Z-axis direction. Therefore, the three outgoing beams are narrowed by the lens system 55 and further imaged by the CCD imaging device 56. As a result, FIG.
As in the case of the motion detecting means, the motion of the head of the subject can be detected, and the parameters of the imaging pulse sequence can be changed based on the detected information.

In the motion detecting means shown in FIGS. 17 and 18, three beam pointers 52A installed separately are provided.
52C or 54A to 54C, these beam pointers can be integrated as one pointer 57 as shown in FIG. This facilitates attachment of the pointer 57 to the belt 51.

Although three laser light sources are individually provided inside the beam pointer 57, one light source is provided.
The light from this light source may be split using a beam splitter to finally generate three beams.

The pointer 57 may be composed of only a beam exit port, and may guide light from a separately provided light source through an optical fiber (not shown).

Further, the movement detecting means shown in FIG. 20 comprises three lasers as light sources, which are set up at three different positions on the band 51 wound around the patient's head in the same manner as described above. It has pointers 58A to 58C. The laser pointers 58A to 58C emit laser beams radially substantially along the XY plane orthogonal to the Z-axis direction, unlike the above-described various detection means. To receive this,
As a part of such a motion detecting means, CCD panels 59A to 59C are arranged on the inner wall surface of the gantry in correspondence with the respective laser pointers. For this reason, the movement of the subject's head P _HEAD can be detected with high sensitivity, especially in the Z-axis direction.

Further, the motion detecting means shown in FIG. 21 combines the configurations shown in FIGS. 17 and 20 to form X, Y, Z
The motion component can be detected with high sensitivity in all directions of the axis. More specifically, this detection means has three laser pointers 60A to 60C as light sources, which are erected at predetermined three different positions on the band 51 wound around the patient's head. This laser pointer 60
Each of A to 60C is configured to emit a laser beam in a Z-axis direction and a radial direction along the XY plane. The three laser beams in the Z-axis direction are the CCD panel 5
3 while receiving light in the radial direction 3 along the XY plane.
This laser beam is installed along the inner wall of the gantry.
The light is received by the CD panel 61. In accordance with the detection signals from the two CCD panels 53 and 61, the motion components can be detected with high sensitivity in the three directions of the X, Y and Z axes.

Further, the laser pointers 60A to 60A
As shown in FIG. 22, each of 60C includes laser pointers 62A to 62C for emitting a beam in the Z-axis direction and a laser pointer 6 for emitting a beam in a radial direction along the XY plane.
3A to 63C, each may be configured separately.

The laser pointer described above is a light source that emits a laser beam by itself.
As shown in FIG. 7, a laser light source 64 is provided separately, and laser pointers 62A to 62A to
Light may be guided to 62C and 63A to 63C.

Further, another structure of the motion detecting means is shown in FIG.
This will be described with reference to FIGS. FIG. 24 shows that this detecting means
Here is an overview. According to this, the head rest is placed on the bed top plate TP.
A strike RT is installed, and the head of the subject is
Part P_HEADIs located. Head P_HEADHas a band 5
One is wound. The band 51 has different surroundings.
Pillars 66A to 66C are fixed from three predetermined positions
It is erected in a state. These pillars 66A to 66C are vans
Head 51, so that the head P _HEAD
Moves, the tip positions of the pillars 66A to 66C are adjusted accordingly.
Will also move spatially.

The band 51 and the pillars 66A to 66C
Together with the frame 6
7 and detection boxes 68A to 68C.
The frame 67 is arranged in an arch shape at a predetermined distance around the band 51 of the head P _HEAD , and both ends thereof are fixed on the top plate TP. Detection boxes 68A to 68
Each of C has an open bottom and a hollow interior, and receives the distal ends of pillars 66A (〜66C) rising from below in its internal space. That is, when the subject head P _HEAD moves, the pillar 66A is moved.
The tip of (-66C) moves in the inner space of the detection box.

FIG. 2 shows an example of the detection boxes 68A to 68C.
It is shown in FIG. That is, each detection box includes a box-shaped housing 69 having an open bottom, and CCD panels 70 to 72 mounted on three orthogonal sides of the housing 69.

Each of the pillars 66A (to 66C) has a laser pointer configuration as a light source therein. In addition, an optical system 66OP using a half mirror or the like is installed at the tip of the optical system 66OP.
The three laser beams are emitted in three orthogonal directions. For this reason, laser beams are emitted toward the CCD panels 70 to 72 in three directions from the distal ends of the pillars 66A (to 66C) inserted from the bottom into the internal space of the housing 69, respectively.

Therefore, when the subject's head P _HEAD moves,
The tips of the pillars 66A to 66C also move in the internal spaces of the detection boxes 68A to 68C. This movement amount
The movement of the head P _HEAD can be detected three-dimensionally as the change amount of the output signals of the three CCD panels 70 to 72.

FIG. 26 shows detection boxes 68A to 68A-6.
8C shows another configuration example of 8C. In this configuration, the pillar 66
A (-66C) functions as a light shielding means, and as shown in FIG. 3C, a light shielding body 66α along the pillar axis direction.
And a light-shielding body 66β protruding in a direction orthogonal to the axial direction.
And In each detection box 68A (Ａ68C), three pairs of linear light sources and linear light receiving elements, that is,
73A, 73B pairs, 74A, 74B pairs, and 75
The pair of A and 75B are installed so as to be orthogonal to each other.

Specifically, the linear light beam OP1 emitted from the linear light source 73A is applied to the linear light receiving element 73B.
And one of the light shields 66α is interposed in the middle of the transmission. In addition, the linear light beam OP2 emitted from another linear light source 74A propagates to the linear light receiving element 74B, and the above-described light shield 66α similarly intervenes in the middle thereof. Further, the linear light beam OP3 emitted from the remaining linear light source 75A is
B and the other light shield 6
6β is interposed.

Therefore, when the head P _HEAD of the subject P moves, the light shields 66α and 66β move together, so that the light shielding position in the light receiving signals of the linear light receiving elements 73B, 74B and 75B also changes. Based on this change amount, the subject's head P
The motion amount of the _HEAD is calculated, and the imaging pulse sequence is corrected according to the motion amount.

Further, although not particularly shown, in the above-described modified embodiment, reflecting mirrors are attached to three places of the band wound around the diagnosis site of the subject, and each of the reflecting mirrors is irradiated with a laser beam from a laser pointer. The reflected beam may be received by the light receiving panel.
The laser beam and the light receiving panel are mounted, for example, on the inner wall of the gantry. In this configuration, the jig to be attached to the band only needs to be the mirror, so that the equipment to be attached to the subject is simplified.

Further, the target site to which the present invention can be applied is not limited to the head, but may be any site.

[0094]

As described above, according to the MRI apparatus and the MR imaging method of the present invention, even when the diagnosis site of the patient moves, the imaging section during the imaging can be automatically tracked in real time, and the influence of the movement can be avoided. For example, functional brain imaging can be performed, and a high-quality image with few artifacts can be provided, and an image excellent in time resolution, spatial resolution, and anatomical position accuracy can be provided.

Also, in particular, when performing a brain function test, it is originally desirable that the body part such as the head can be freely moved. However, conventionally, in order to reduce the influence of such movement, the head must be moved. Although the method had to be fixed to a rigid body, the method according to the present invention allows the inspection to be performed while freely moving the head. That is, since the patient can be examined in a natural state where it should be, the reliability of the examination can be improved and the accuracy can be improved. For example, when used in conjunction with an open MRI system that can be tested in a sitting or standing position, it is now possible to perform brain function tests while performing natural activities, which was almost difficult with conventional imaging. In addition, it is possible to provide an imaging method in which the problem of the conventional brain function test is greatly improved.

Further, the imaging method of the present invention can be applied to normal imaging for obtaining morphological information, and provides a high-quality morphological image with few artifacts to easily move patients such as elderly patients, children and seriously injured patients. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of an MRI apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of an arrangement of a position detection coil.

FIG. 3 is a view for explaining another example of the arrangement of the position detection coils.

FIG. 4 is a view for explaining still another example of the arrangement of the position detection coils.

FIG. 5 is a view for explaining still another example of the arrangement of the position detection coils.

FIG. 6 is a flowchart illustrating an outline of a process related to automatic tracking of an imaging section executed by a host computer.

FIG. 7 is a pulse sequence used in a coil position detection sequence.

FIG. 8 is a diagram illustrating a coil position detection sequence, an execution timing of correction processing, and an imaging pulse sequence in the case of one imaging section.

FIG. 9 is a diagram illustrating a time relationship between the execution timing of a coil position detection sequence and a correction process and the execution timing of an imaging pulse sequence.

FIG. 10 is a diagram schematically illustrating an initial reference section and an imaging section to be automatically tracked.

FIG. 11 is a diagram illustrating a coil position detection sequence, an execution timing of a correction process, and an imaging pulse sequence when a plurality of imaging sections (multi-slice method) are used, according to a modification.

FIG. 12 is a diagram illustrating a coil position detection sequence, an execution timing of a correction process, and an imaging pulse sequence in the case of two imaging slices (multi-slice method) according to another modification.

FIG. 13 is a diagram illustrating a coil position detection sequence, a correction processing execution timing, and an imaging pulse sequence in the case of a three-dimensional imaging volume according to another modification.

FIG. 14 is a block diagram showing a schematic configuration of an MRI apparatus according to a second embodiment of the present invention.

FIG. 15 is a schematic diagram showing an outline of a three-dimensional magnetic sensor as a position detecting means.

FIG. 16 is a diagram showing an example of the arrangement of a three-dimensional magnetic sensor.

FIG. 17 is a view for explaining an example according to a modification of the motion detection means.

FIG. 18 is a view for explaining another example according to a modification of the motion detection means.

FIG. 19 is a view for explaining still another example according to a modification of the motion detection means.

FIG. 20 is a view for explaining still another example according to a modification of the motion detection means.

FIG. 21 is a view for explaining still another example according to a modification of the motion detection means.

FIG. 22 is a view for explaining still another example according to a modification of the motion detection means.

FIG. 23 is a view for explaining still another example according to a modification of the motion detection means.

FIG. 24 is a view for explaining still another example according to a modification of the motion detection means.

FIG. 25 is a schematic view showing an example of a detection box.

FIG. 26 is a schematic plan view, a schematic sectional view, and a pillar external view showing another example of the detection box.

[Explanation of symbols]

Reference Signs List 11 Gantry 12 Static magnetic field magnet (motion detecting means / signal generating means) 13 Gradient magnetic field coil (motion detecting means / signal generating means) 14 RF coil (motion detecting means / signal generating means) 15 Gradient magnetic field amplifier (motion detecting means / signal) Generating means) 16 Sequencer (motion detecting means / signal generating means / correcting means) 17 Transmitter (motion detecting means / signal generating means / correcting means) 18 Receiver (correcting means) 19 Host computer (motion amount calculating means / correcting means) 31a-31c Position detecting coil (motion detecting means / position sensor) 37a-37c Receiving circuit (motion detecting means / position calculating means) 38a-38c Position information calculating circuit (motion detecting means / position calculating means) 41 Transmission coil section ( (Motion detecting means / Signal generating means) 42 Receiving coil unit (Motion detecting means / Position sensor) 43 Driver 44 Position information Information calculator (motion detecting means / position calculating means) 51 band (motion detecting means) 52A to 52C, 54A to 54C, 57, 58A to 58
C, 60A-60C, 62A-62C, 63A-63C
Laser pointer (motion detection means) 53, 59A to 59C, 61 CCD panel (motion detection means) 55 Lens system (motion detection means) 56 CCD imaging device (motion detection means) 64 Laser light source (motion detection means) 65 Optical fiber ( Motion detection means) 66A to 66C Pillar (motion detection means) 67 frames (motion detection means) 68A to 68C Detection box (motion detection means)

Claims (15)

[Claims] 1. A motion detecting means for outputting a signal corresponding to a motion of a subject, and a spatial detection means for detecting a signal corresponding to the motion outputted by the motion detecting means, wherein a spatial region of an imaging region set at a diagnosis site of the subject is detected. Motion amount calculating means for calculating an appropriate amount of motion, and correcting means for correcting parameters of an imaging sequence for tracking and imaging the imaging area in accordance with the amount of motion calculated by the motion amount calculating means. MR characterized by
I device. 2. The MRI apparatus according to claim 1, wherein the motion detection unit outputs an optical signal,
Supporting means for supporting the optical device and detachably attaching the optical device to a diagnostic site of the subject or a site in a predetermined positional relationship with the diagnostic site, and receiving the optical signal and transmitting a signal corresponding to the movement; An MRI apparatus, comprising: a light receiving unit for outputting. 3. The MRI apparatus according to claim 2, wherein the optical device is a sensor that outputs the optical signal as a light source. 4. The MRI apparatus according to claim 2, wherein the optical device is a sensor that reflects the light from a separately placed light source to form the optical signal. 5. The MRI apparatus according to claim 1, wherein the movement detecting means includes a position sensor attached to a diagnostic part of the subject or a part having a predetermined positional relationship with the diagnostic part.
Signal generating means for generating a signal from the position sensor; and position calculating means for calculating position information indicating an attachment position of the position sensor from the signal generated by the position sensor as a signal corresponding to the movement. Characteristic MR
I device. 6. The MRI apparatus according to claim 5, wherein said position sensor comprises three or more position detection coils in which a microcoil and an NMR signal source are integrated, and said signal generating means is a static imaging sensor. M means comprising a magnetic field magnet, an RF coil, and a gradient coil.
RI equipment. 7. The MRI apparatus according to claim 5, wherein the position sensor includes one or more receiving coil units in which three coils are arranged orthogonally, and the signal generating unit includes a three-coil receiving unit.
A transmission coil unit in which three coils are arranged orthogonally, and a driving unit that drives the transmission coil unit to generate an oscillating magnetic field, wherein the transmission coil unit is located in a sensitivity region of the oscillating magnetic field. An MRI apparatus characterized by being arranged as follows. 8. The MRI apparatus according to claim 7, further comprising control means for controlling said driving means so that driving of said transmission coil unit is turned off during transmission of an RF wave. MRI equipment. 9. The MRI apparatus according to claim 6, wherein the movement amount calculating unit includes a reference cross section setting unit that sets a cross section of the diagnosis site passing through the position sensor from the position information as a reference cross section, An MRI apparatus, which is means for calculating a spatial motion amount of the imaging region having a desired spatial positional relationship from the reference cross section. 10. The MRI apparatus according to claim 6, wherein the correction unit includes a carrier frequency of an RF excitation pulse included in the imaging sequence, an application amount of a gradient magnetic field pulse included in the imaging sequence, An MRI apparatus for correcting at least one factor of a frequency of a phase detection reference signal and a phase of the phase detection reference signal at the time of reception as the parameter in accordance with the amount of motion. . 11. The MRI apparatus according to claim 6, wherein the driving of the signal generation unit, the position calculation unit, the movement amount calculation unit, and the correction unit is performed immediately before or immediately after the execution of the imaging sequence. An MRI apparatus comprising a control unit for executing the MRI apparatus. 12. The MRI apparatus according to claim 11, wherein the control unit controls the signal generation unit each time an RF excitation pulse included in the imaging sequence is applied or when the RF excitation pulse is applied a plurality of times. An MRI apparatus characterized in that the MRI apparatus is a means for driving the position calculating means, the movement amount calculating means, and the correcting means. 13. The MRI apparatus according to claim 6, wherein the imaging region is a two-dimensional imaging section. 14. The MRI apparatus according to claim 13, wherein the two-dimensional imaging section includes a plurality of slices. 15. A signal corresponding to the movement of the subject is detected,
A spatial motion amount of an imaging region set at the diagnostic site of the subject is calculated based on a signal corresponding to the motion, and an imaging sequence for tracking and imaging the imaging region according to the motion amount is calculated. An MR imaging method comprising correcting a parameter.