WO2001024695A1 - Nuclear magnetic resonance imaging device and method - Google Patents

Abstract

Data for image formation including nuclear magnetic resonance signals is continuously acquired. When scanning data is collected, a plurality of sets of correction data are acquired in a predetermined cycle. A group of correction data corresponding to the acquisition time is created from the sets of correction data, and the data for image formation is corrected every corresponding acquisition time by using the group of correction data. Thus the data for image formation is corrected by the phase rotation estimate of the acquisition time, and therefore a stable MR image is generated even under an imaging condition that the phase of the signal varies with time depending on the variation of the eddy current and the saturation state of the spin.

Description

 TECHNICAL FIELD The present invention relates to a nuclear magnetic resonance imaging apparatus and method.

 The present invention measures nuclear magnetic resonance (hereinafter, referred to as “NMR”) signals from hydrogen, phosphorus, and the like in a subject, and images nuclear density distribution, relaxation time distribution, and the like. (MRI) Related to equipment. Background art

 High-speed imaging methods using MRI equipment include EPI (ecoplanar imaging) and burst sequence. These are imaging methods that measure multiple echo signals with a single excitation, and are used for three-dimensional measurement and functional measurement that continuously captures many images. There are also applications such as split EPI, which measures a set of data by dividing it into multiple shots (excitations).

 The echo signal obtained by such a high-speed imaging method is easily affected by eddy current due to the gradient magnetic field ゃ non-uniformity of the static magnetic field, etc., so the phase correction of the signal using the correction data to correct this Is generally performed (for example, JP-A-5-31095). Prior to the main measurement, such correction data is obtained by performing the same measurement (pre-scan) as in the main measurement, for example, without applying a slice encode gradient magnetic field or a phase encode gradient magnetic field. The scanned data is used. On the other hand, one of the applications of MRI is SSFP (Steady State Free).

Precession: steady free precession) SSFP measurement is a measurement in which the echo signal is continuously acquired while changing the slice-encoding gradient magnetic field or the phase-encoding gradient magnetic field with a repetition time TR that is sufficiently short compared to the longitudinal relaxation time of the subject. The detected echo is a steady precession state.

 SSFP measurement is suitable for three-dimensional measurement because it changes the application conditions of the gradient magnetic field in a short repetition time, and a method that combines this with high-speed imaging methods such as EPI (for example, SSFP-EPI) is considered. I have.

However, when the present inventors applied the above-described signal correction using the corrected scan data to SSFP-EPI, it was not possible to perform appropriate signal correction and artifacts were generated in the image. I found out. The reason is considered as follows. In other words, when correcting with prescan data, it is premised that the eddy current ゃ static magnetic field nonuniformity when the prescan data is obtained and when the image formation data (main scan data) is obtained are the same. The eddy current generated in the gradient coil has a variation due to the time constant. This variation is not a problem for measurements with long repetition times, but the variation due to this time constant is a problem for SSFP because the repetition time is short. Also, the amount of spin rotation depends on the degree of spin saturation, so SSFP-EPI can change slowly until it reaches a steady state. This change up to the steady state cannot be corrected by the conventional phase correction using the prescan data.

 Therefore, the present invention eliminates the root cause of artifacts due to physical phenomena with time variation such as eddy current of gradient magnetic field and time variation of residual magnetic field in SSFP measurement, and provides high quality MR images without artifacts. The purpose is to provide. Disclosure of the invention

 In order to solve the above problems, the MRI apparatus of the present invention performs a pre-scan for acquiring data for correcting fluctuation due to time constant of eddy current and Z or non-uniform static magnetic field prior to the main measurement scan. Based on the data obtained by the prescan, the data obtained by the main measurement scan is corrected.

 That is, the MRI apparatus of the present invention comprises: a magnetic field generating means for causing a subject to generate nuclear magnetic resonance; a detecting means for detecting a nuclear magnetic resonance signal generated from the subject; a magnetic field generating means and the detecting means. Control means for controlling; calculating means for imaging the form, function, etc. of the subject using nuclear magnetic resonance signals detected by the detecting means; and display means for displaying an image as a calculation result. In the nuclear magnetic resonance imaging apparatus, the control unit acquires a plurality of correction data at a predetermined time period, and continuously acquires image forming data between acquisitions of the respective correction data. The calculation means creates a correction data group corresponding to the acquisition time of the image formation data from the correction data, and corrects the image formation data for each corresponding acquisition time using the correction data group. Do It is characterized by the following.

Further, the MRI apparatus of the present invention comprises: a magnetic field generating means for causing the subject to cause nuclear magnetic resonance; Detecting means for detecting a nuclear magnetic resonance signal generated from the subject; control means for controlling the driving of the magnetic field generating means and the detecting means; and a nuclear magnetic resonance signal detected by the detecting means. In a nuclear magnetic resonance imaging apparatus provided with a calculation unit for imaging a form, a function, and the like of a subject, and a display unit for displaying an image as a calculation result, the control unit may include a plurality of control units for one excitation. A step of continuously executing the step of acquiring the nuclear magnetic resonance signal as the data for image formation and executing the step of acquiring a plurality of correction data at a desired interval between the successive steps; The calculating means, using the plurality of correction data acquired at the desired interval, creating a correction data group including a time variation at the interval; and the image forming data , Of the correction data group, characterized by comprising a means for using the correction data corresponding to the acquisition time.

 Further, the MRI method of the present invention comprises: a step A of acquiring image formation data comprising a plurality of nuclear magnetic resonance signals by one excitation; and the step A includes a slice encoding gradient magnetic field and / or a phase encode. Step B to be repeated while changing the gradient magnetic field; Step C to repeatedly obtain correction data at a desired interval during the period of repetition of Step A; and one correction using at least two pieces of correction data. A step D of creating correction data corresponding to the acquisition time of the image formation data acquired between the data and the correction data acquired next, and the image formation data Step E of performing phase correction using the correction data corresponding to the acquisition time of the image forming data among the correction data created in D. Here, the interval for acquiring the correction data may be the interval for acquiring one image forming data, but may be the interval for acquiring a plurality of image forming data.

 According to the MRI apparatus and method, correction data including time variation between one correction data and the next correction data is created, and a plurality of image forming data are acquired during this time. Then, the phase of each image forming data can be corrected using the correction data (estimated correction data) corresponding to the acquisition time.

The image forming data composed of a plurality of nuclear magnetic resonance signals (hereinafter, also referred to as “scan data”) is converted to a corresponding correction data group including a time variation. By making corrections using data, it is possible to perform data correction taking into account the effects of spin saturation or eddy currents in the gradient magnetic field, and physical phenomena with time changes such as the time fluctuation of the residual magnetic field. It is possible to eliminate the artifact caused by the noise.

 Each of the plurality of correction data is obtained without applying a phase encoding gradient magnetic field, or is obtained by applying a phase encoding gradient magnetic field and applying a read gradient magnetic field having a polarity different from that of the main scan data. It is desirable. When no phase-encoded gradient magnetic field is applied, the correction data consists of the same number of nuclear magnetic resonance signals as the image formation data acquired in step A. When a phase encoded gradient magnetic field is applied, the correction data is composed of the same number of nuclear magnetic resonance signals as the number of phase encodings of the image forming data. In this specification, these are collectively referred to as corrected scan data.

 In a preferred embodiment of the MRI method of the present invention, Step B is performed with a repetition time TR that is sufficiently shorter than the longitudinal relaxation time of the subject. As a result, a series of main scan data is acquired in a steady precession state.

 In this case, it is desirable that each correction scan data is performed between the preceding and following main scan data at a time interval equal to the above TR. As a result, it is retained even when the steady-state precession force corrected scan data is acquired, and the image contrast can be prevented from being lost. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic diagram showing one embodiment of the MRI method of the present invention. FIG. 2 is a flowchart showing one embodiment of the signal processing by the MRI method of the present invention. FIG. 3 is a time chart showing an EPI sequence to which the present invention is applied. FIG. 4 is a diagram showing an outline of an MRI apparatus to which the present invention is applied. FIG. 5 is a flowchart showing another embodiment of the signal processing by the MRI method of the present invention. FIG. 6 is a schematic view showing another embodiment of the MRI method of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, examples of the present invention will be described. FIG. 4 is a diagram showing a configuration of an MRI apparatus to which the present invention is applied. This MRI apparatus includes a magnet 402 for generating a static magnetic field in a space around a subject 401 as a magnetic field generating means, and an inclined surface in this space. A gradient magnetic field coil 403 for generating a magnetic field, an RF coil 404 for generating a high-frequency magnetic field in a predetermined area of the subject, and an RF probe 405 as detection means for detecting an MR signal generated by the subject 401 are provided. ing. Further, a signal processing unit 407 that performs signal processing on the detected MR signal and converts the signal into an image signal, and displays an image representing the form, function, and spectrum of the subject based on the image signal from the signal processing unit 407 The display includes a display unit 408 and a bed 412 on which the subject lies.

 The gradient magnetic field coil 403 is composed of gradient magnetic field coils in three directions of X, Y, and 、, and generates a gradient magnetic field in accordance with a signal from the gradient magnetic field power supply 409. The RF coil 404 generates a high-frequency magnetic field according to the signal of the RF transmission unit 410. The signal of the RF probe 405 is detected by the signal detection unit 406 and processed by the signal processing unit 407. The gradient magnetic field power supply 409, the RF transmitter 410, and the signal detector 406 are controlled by the controller 411 according to a control time chart called a pulse sequence.

 In the MRI apparatus according to the present embodiment, the control unit 411 executes a high-speed imaging sequence using multi-shots. That is, in order to image a predetermined region of the subject, a pulse sequence of acquiring image forming data composed of a plurality of nuclear magnetic resonance signals by one excitation is repeated, and a series of image forming data (main scan) is obtained. Data). Also, during the acquisition of the series of main scan data, the generation of the high-frequency magnetic field and the gradient magnetic field and the signal acquisition are controlled so as to acquire the corrected scan data at approximately equal time intervals (simply called equal intervals). In addition, the repetition time TR is set so that a series of scan data (main scan data and corrected scan data) is acquired in a steady precession state.

The signal processing unit 407 has a function of generating correction data including time variation using correction scan data acquired at predetermined intervals in addition to processing necessary for normal image reconstruction, and acquiring the main scan data. It has a function of correcting with time correction data. The display unit 408 displays the main scan data corrected by the correction data again. Display the composed image.

 Next, an embodiment in which the MRI method of the present invention having such a configuration is applied to a two-dimensional SSFP-EPI will be described. FIG. 1 is a diagram for explaining data acquisition and correction processing in this embodiment, and the horizontal axis is a time axis. In FIG. 1, reference numeral 13 denotes a Fourier transform in the readout direction, reference numeral 14 denotes a phase correction, and reference numeral 16 denotes a Fourier transform in the phase encoding direction. FIG. 2 is a flowchart showing the processing in the signal processing unit 407.

 In this measurement, first, the first pre-scan (scan to obtain correction data, hereinafter referred to as correction scan) is performed prior to the main measurement, and correction scan data 11 is obtained. Subsequently, the main measurement is executed to obtain the main scan data 12 (121, 122, 123, 124) (step 64). During the continuous measurement of the main scan data 12, the second and third correction scan data 11 (111, 112, 113 · · ·) are repeatedly acquired at regular time intervals (step 61). . These correction scan data 11 are used for phase correction of the main scan data described later (steps 70, 62, 63).

 Each pulse sequence in this measurement is, for example, an EPI sequence as shown in FIG. That is, a high-frequency pulse 201 is applied to a subject including a magnetic field to be detected, and at the same time, a gradient magnetic field pulse 202 for selecting a slice is applied, and a slice to be imaged is selected. Next, a pulse 203 for giving an offset of the phase code and a pulse 205 for giving an offset of the read magnetic field are applied. Thereafter, a reading gradient magnetic field pulse 206 that is continuously inverted is applied.

 The gradient pulse 206 is trapezoidal. In synchronization with the gradient magnetic field pulse 206, the phase encoder code gradient magnetic field pulse 204 is discretely applied. Within each period of the inverted readout gradient magnetic field 206, an echo signal 207 of each phase code is generated in time series, and this is sampled for each time range 208 to obtain time series data. The number n of echo signals measured here is shown to be 5 or more in FIG. 3, but may be smaller.

Assuming that the number of echo signals measured in one excitation (one shot) is n and the number of data in the phase encoding direction is N, one set is obtained by repeating the sequence shown in Figure 3 N / n times (NZn shots) 2D data can be obtained. In the correction scan, the same number of echo signals are measured without applying the phase-encoding gradient magnetic field Ge in the sequence shown in FIG. Alternatively, the polarity of the readout gradient magnetic field Gr may be inverted by applying a phase code gradient magnetic field to obtain correction scan data, and in that case, correction scan data for the same number of shots as the main measurement may be obtained. I do.

 In the embodiment shown in the figure, one set of two-dimensional data is obtained by 10 shots, and the correction scan data 11 is obtained every 10 shots. The interval between acquisitions of the corrected scan data 11 may be shorter or longer.

 The repetition time of the corrected scan data 11 and the main scan data 12 is constant and sufficiently shorter than the longitudinal relaxation time of the target spin, for example, about 10 ms.

 Next, an estimated value 19 of the phase rotation amount for each acquisition time of the main scan data is calculated based on the plurality of correction scan data periodically acquired as described above (step 70). This calculation can be performed, for example, by linear interpolation from temporally adjacent corrected scan data. In addition, a known interpolation method can be adopted. As a result, a correction data group in which the correction data is estimated for each acquisition time of the main scan data is obtained. That is, in the illustrated embodiment, the estimated correction data corresponding to each of the 10 shots of the main scan data obtained between the corrected scan data 111 and 112 is obtained.

 Next, the data arrangement of these correction data groups is inverted according to the polarity of the gradient magnetic field pulse (step 62). This is a general process of EPI.For example, in the sequence of Fig. 3, the first echo is obtained when the polarity of the gradient pulse Gr is negative, and the second echo is obtained when the polarity of the magnetic field pulse Gr is positive. Therefore, the operation is such that the signal arrangement is inverted in the time direction for the first echo with negative polarity, and not inverted for the second echo.

After the above inversion processing, the correction data is Fourier-transformed 13 in the readout direction for each echo, and this is converted into a complex data map in a two-dimensional hybrid space (spatial position in the readout direction vs. echo acquisition order) in the memory of the signal processing unit 407. (Step 63). On the other hand, for the main scan data as well as the corrected scan data, a process of inverting the data array with respect to the time in the read direction is performed for each echo according to the polarity of the read gradient magnetic field pulse at the time of acquiring the echo ( Step 65). Then for each echo, performs Fourier transform 13 into the readout direction and stored in the signal processor 40 ⁷ in the memory as a complex data map in a two-dimensional hybrid space (step 66). After that, the main scan data after the Fourier transform is corrected by the correction data after the Fourier transform. At this time, the main scan data for each shot is subjected to phase correction 14 with correction data corresponding to each acquisition time (step 67). That is, the main scan data 121 is corrected with the correction data 191 and the main scan data 122 is corrected with the correction data 192 to obtain the corrected main scan data 15.

 By this phase correction, it is possible to eliminate the influence of the inevitable adjustment of the apparatus at the time of signal acquisition, such as the residual offset component of the gradient magnetic field and the inhomogeneity of the static magnetic field due to the subject, on the signal. In particular, since the amount of phase rotation during the acquisition time of the main scan data is estimated and the main scan data is corrected using that value, the fluctuation of the phase rotation depending on the spin saturation can be corrected. In addition, even when there is a time variation of the phase due to the eddy current due to the gradient magnetic field or the non-uniformity of the static magnetic field, the phase can be accurately corrected. Finally, 10 sets of the corrected main scan data 151, 152, 153 ... are subjected to Fourier transform 16 in the phase encoding direction to obtain a two-dimensional MR image (step 68) and display it (step 69). This image is a high-quality image because the residual offset component of the gradient magnetic field and the non-uniformity of the static magnetic field due to the subject are corrected including the time variation.

 Here, since the main scan is continuously performed between the correction scans executed at predetermined time intervals, a plurality of two-dimensional MR images that are continuous in time series can be obtained. These multiple 2D MR images may be images of the same slice or images of different slices. To obtain images for different slices, in the pulse sequence of FIG. 3, the high-frequency pulse 201 and Z or the slice selection gradient magnetic field 202 are changed every 10 shots, and the echo signals 207 are measured from different slices.

When the same slice is continuously photographed, the display section 408 displays the image of the slice. Is displayed continuously. Such a continuous image can be used, for example, for observing the function of a predetermined organ. When images of different slices are obtained, images of a plurality of slices can be displayed on the display unit 408 simultaneously. In this case, a relatively wide range can be observed simultaneously. These photographing methods and display methods can be applied as appropriate. For example, while continuous imaging of the same slice is performed, imaging of a slice near or intersecting with the same slice may be performed, continuous display and simultaneous multiple display may be performed sequentially, or simultaneous multiple display may be repeated and displayed simultaneously. The images to be performed may be sequentially updated.

 In the above embodiment, a case has been described in which the phase rotation amount at each acquisition time of the main scan data is estimated based on the acquired raw correction scan data. The phase rotation amount may be estimated based on the corrected scan data after the Fourier transform. FIG. 5 shows a flow chart of the processing in that case.

 Also in the embodiment shown in FIG. 5, acquiring the corrected scan data by periodically inserting it during the acquisition of the scan data (step 61) is the same as the flow shown in FIG. 2. Here, two corrections are performed. Prior to estimating the correction data for each acquisition time of the main scan data from the scan data (step 70), the Fourier transform of the corrected scan data is performed. That is, first, the data array is inverted according to the polarity of the gradient magnetic field pulse (step 62), and then the Fourier transform in the readout direction for each echo (step 63) is performed.

 With respect to the data subjected to the Fourier transform in this way, the corresponding correction data is calculated for each acquisition time of the main scan data. This calculation can also be performed from the S interpolation of the Fourier-transformed corrected scan data obtained before and after the target time.

The correction data group obtained in this way is stored as a complex data map in a two-dimensional hybrid space, and used for phase correction M of the main scan data after the Fourier transform in the readout direction. In this case, the phase correction is also performed by sequentially correcting the main scan data with correction data corresponding to the acquisition time (step 67). As a result, as in the case of Fig. 2, it is possible to correct with high accuracy even if the conditions such as the device characteristics, the influence of the eddy current or the spin saturation change over time. Although the example in which the MRI method of the present invention is applied to two-dimensional measurement has been described above, the present invention can be applied to three-dimensional measurement in the same manner.

 FIG. 6 is a diagram showing an embodiment in which the MRI method of the present invention is applied to three-dimensional measurement. Also in this embodiment, the acquisition of the correction scan data 11 at a predetermined interval during the acquisition of the main scan data 12 and the measurement of the correction scan data and the actual measurement at the same repetition time TR are shown in FIG. Same as the example. However, in three-dimensional measurement, the steps of acquiring a series of main scan data are repeated while changing the intensity of the slice-encoding gradient magnetic field. For example, in the illustrated embodiment, the slice code is changed every time the main scan data for 10 shots is acquired.

 Also in this embodiment, the series of main scan data 12 is based on the correction data corresponding to the acquisition time in the correction data group 19 estimated from the correction scan data (for example, 111 and 112) acquired before and after the series. Is corrected. The correction data group 19, which is a set of correction data for each acquisition time of the main scan data, may be calculated by interpolation from the raw correction scan data as shown in the figure, or as shown in the flow of FIG. Alternatively, the raw correction scan data may be Fourier-transformed 13 in the readout direction, and may be calculated from the converted data. When estimation is performed from the raw correction scan data, Fourier transform 13 is performed in the readout direction for each correction data, and this is used for phase correction 14.

 The main scan data is also subjected to a Fourier transform 13 in the readout direction, and the phase is corrected based on the correction data 19 at each acquisition time to obtain corrected main scan data 15. In the three-dimensional measurement, this main scan data 15 is subjected to Fourier transform 16 for the second axis (phase encoding direction) for each data having the same slice encode gradient magnetic field strength, and the data after the Fourier transform is subjected to Fourier transform. Fourier transform 17 the three axes (slice-en code direction) to obtain a three-dimensional image. In this case, as in the case of the two-dimensional measurement, the fluctuation of the phase rotation depending on the degree of the spin saturation can be corrected. Can also be corrected.

The obtained three-dimensional image is displayed on the display unit 408 as a projection image subjected to projection processing or as a tomographic image obtained by cutting out a desired cross section. Or the actual scan data The two-dimensional images obtained by Fourier-transforming 16 in the phase encoding direction are used to continuously display the two-dimensional images in a time-series manner, as shown in the two-dimensional image capturing and displaying method shown in Fig. 1. Or they can be displayed on one screen at the same time. However, the main scan data 15 is composed of signals from a slab having a predetermined thickness, and its resolution depends on the slab thickness. Therefore, when a two-dimensional image is obtained from the main scan data 15 obtained in the three-dimensional imaging and displayed as described above, it is preferable to appropriately adjust the slab thickness.

 Note that Fig. 6 shows the case where the interval at which the corrected scan data is acquired is the same as the interval at which the slice encoding step is raised.However, these do not need to match, for example, a more accurate correction is required. In this case, a plurality of pieces of corrected scan data may be obtained within the same slice encoding step.

 In each of the embodiments described above, the multi-shot EPI has been described. However, the same can be applied to the case of the single-shot EPI. In the single-shot EPI, each of the main scan data 121, 122,... In FIG. 1 or FIG. 6 is composed of the number of echoes that make up one image, and the corrected scan data is also composed of the same number of echoes.

 Using correction scan data acquired before and after a series of main scan data acquisition, create correction data corresponding to the acquisition time of each main scan data, and perform Fourier transform 13 in the readout direction on the main scan data. The phase correction 14 using the corresponding correction data is the same as in the embodiment of FIGS. 1 and 6. However, in the single shot EPI, an image can be reconstructed by Fourier transforming the corrected main scan data 151, 152,... In the phase encoding direction. When the scan data is slice-encoded, the Fourier-transformed data in the phase-encode direction is grouped by the number of slice-encodes and Fourier-transformed in the slice-encode direction to obtain a 3D image. Data 18 can be obtained.

Although the two-dimensional or three-dimensional EPI has been described above, the present invention can be applied to any imaging sequence as long as the sequence in which the phase rotation amount has been corrected for each echo using prescan data in the past. For example, a two-dimensional or three-dimensional time-reverse multi-shot EPI sequence or a two-dimensional split type The same applies to spiral scan. It can also be applied to 3D GRSE (gradient and spin echo) sequences. It can also be applied to hybrid burst sequences. Industrial applicability

 In a phase correction sequence using the corrected scan data, the corrected scan data is periodically acquired, and is used at each acquisition time of the scan data acquired between the temporally adjacent corrected scan data. Estimation of the amount of phase rotation and correction of each scan data using the estimated amount of phase rotation, imaging in which the phase fluctuation of the signal changes every moment due to the time change of the eddy current ゃ spin saturation state, etc. Under these conditions, high-quality MR images without artifacts can be obtained.

Claims

The scope of the claims 1. Magnetic field generating means for causing nuclear magnetic resonance in a subject, detecting means for detecting a nuclear magnetic resonance signal generated from the subject, and control means for controlling the driving of the magnetic field generating means and the detecting means A nuclear magnetic resonance scanner comprising: a calculation unit configured to image the form, function, and the like of the subject using a nuclear magnetic resonance signal detected by the detection unit; and a display unit configured to display an image as a calculation result. In the imaging device,  The control means continuously executes a step of acquiring a plurality of nuclear magnetic resonance signals as image forming data by one excitation, and outputs a plurality of correction data at desired intervals during the successive steps. Control to execute the step of obtaining,  The calculation means includes: means for creating a correction data group including a time variation at the interval using the plurality of correction data acquired at the desired interval; and A means for performing correction using correction data corresponding to the acquisition time of the group. 2. Acquiring image forming data consisting of a plurality of nuclear magnetic resonance signals with one excitation Step A of repeating Step A while changing the slice code gradient magnetic field and the Z or phase Encode gradient magnetic field,  Step C of repeatedly acquiring correction data at desired intervals during the period of repetition of step A;  Using at least two pieces of correction data, create correction data corresponding to the acquisition time of image formation data acquired between one piece of correction data and the subsequently acquired correction data. Step D and  A step E of correcting the phase of the image forming data using the correction data corresponding to the acquisition time of the image forming data among the correction data created in the step D. Imaging method. 3. Multiple image forming data between one correction data and the next correction data The nuclear magnetic resonance imaging according to claim 2, wherein the correction data created in step D is a group of a plurality of correction data corresponding to the plurality of image formation data. Method. 4. The nuclear magnetic resonance imaging method according to claim 2, wherein the step B is performed with a repetition time TR sufficiently shorter than the longitudinal relaxation time of the subject. 5. The nuclear magnetic resonance imaging method according to claim 2, wherein in step D, correction data is created using the raw correction data acquired in step C. 6. The method according to claim 2, wherein in the step D, the raw correction data obtained in the step C is Fourier-transformed in the reading direction, and then the correction data is created. Nuclear magnetic resonance imaging method according to the item. 7. Magnetic field generating means for causing nuclear magnetic resonance in the subject, detecting means for detecting a nuclear magnetic resonance signal generated from the subject, control means for controlling the foreground generating means and the detecting means, A nuclear magnetic resonance imaging system comprising: a calculation unit configured to image the form, function, and the like of the subject using a nuclear magnetic resonance signal detected by the detection unit; and a display unit configured to display an image as a calculation result. In one jing device,  The control unit performs a pre-scan for acquiring data for correcting fluctuation due to a time constant of the eddy current and Z or the non-uniformity of the static magnetic field prior to the main measurement scan. A nuclear magnetic resonance imaging apparatus characterized in that the data obtained in the main scan is corrected based on the obtained data. 8. The control means acquires data by not applying the phase encoding gradient magnetic field in the pre-scan or inverting the polarity of the readout gradient magnetic field in the main measurement scan, 8. The nuclear magnetic resonance according to claim 7, wherein the calculation unit creates phase data for each acquisition time of the main scan data from the pre-scan data, and corrects the phase of the main measurement scan data based on the phase data. Imaging device. 9. Magnetic field generating means for causing nuclear magnetic resonance in the subject, detecting means for detecting a nuclear magnetic resonance signal generated from the subject, control means for controlling the magnetic field generating means and the detecting means, A nuclear magnetic resonance imaging system comprising: a calculation unit configured to image the form, function, and the like of the subject using a nuclear magnetic resonance signal detected by the detection unit; and a display unit configured to display an image as a calculation result. In one jing device,  The control unit acquires a plurality of correction data at a predetermined time period, and continuously acquires image formation data between acquisitions of the respective correction data;  The calculating means creates a correction data group corresponding to the acquisition time of the image formation data from the correction data, and corrects the image formation data for each corresponding acquisition time using the correction data group. A nuclear magnetic resonance imaging apparatus characterized by the above-mentioned. 10. The nuclear magnetic resonance imaging apparatus according to claim 9, wherein said calculating means inverts the data array according to the polarity of the gradient magnetic field pulse after acquiring the image forming data. 10. The nuclear magnetic resonance imaging apparatus according to claim 9, wherein the plurality of continuous image forming data during the acquisition of each of the correction data obtained by the control means corresponds to one image. Imaging device. 12. A plurality of continuous image forming data between each of the correction data acquisitions obtained by the control means are acquired at the same slice position, and the display means The nuclear magnetic resonance imaging apparatus according to claim 11, wherein a two-dimensional image is displayed continuously. 13. Continuous between each of the correction data acquisitions obtained by the control means The nuclear magnetic resonance imaging apparatus according to claim 11, wherein a plurality of image forming data are acquired at different slice positions, and a plurality of two-dimensional images are simultaneously displayed on the display means. 14. A plurality of continuous image forming data between each of the correction data acquisitions obtained by the control means are obtained at adjacent slice positions, and a three-dimensional image is formed from two-dimensional image data by the calculation means. 12. The nuclear magnetic resonance imaging apparatus according to claim 11, wherein a three-dimensional image is displayed on said display means. 15. A nuclear magnetic resonance scanner that detects a nuclear magnetic resonance signal generated from the subject, uses the detected nuclear magnetic resonance signal to image the form and function of the subject, and displays an image as a calculation result. In the messaging method,  Acquire correction data at predetermined time intervals,  Acquiring image formation data continuously during the acquisition of the correction data, creating a correction data group corresponding to the acquisition time of the image formation data from the correction data,  A nuclear magnetic resonance imaging apparatus for correcting image forming data for each corresponding acquisition time using the correction data group. 16. continuously acquiring image forming data comprising a plurality of nuclear magnetic resonance signals while changing a slice encoding gradient magnetic field or a phase encoding gradient magnetic field;  Repeatedly acquiring correction data at a desired interval during the image formation data acquisition period;  Using at least two correction data, creating a correction data group including a time variation between one correction scan data and a subsequently acquired correction scan data; A step of correcting the phase using the correction data corresponding to the acquisition time of the image formation data in the correction data group when correcting the image formation data. Nuclear magnetic resonance imaging method comprising: