JPH1071133A - Magnetic resonance imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic resonance imaging(MRI) device with which a high S/N can be provided while suppressing the extension of time for imaging. SOLUTION: A pulse sequence to be executed by the MRI device includes a 1st impression pattern (i) for measuring a measure signal while changing the impression strength of a phase encode gradient magnetic field through prescribed increment and a 2nd impression pattern (j) for measuring a measure signal while changing the impression strength of a phase encode gradient magnetic field through increment different from this prescribed increment at least. Concerning measured data provided by impressing such a phase encode gradient magnetic field 26 in the plural impression patterns, an image is reconstituted from raw measured data and afterwards, the image can be synthesized as well. Besides, after the raw measured data are synthesized, the image can be reconstituted from these synthetic data. Further, after raw data are interpolated, the images of raw data and interpolated data are reconstituted and the images can be synthesized later as well. In any case, the image of the high S/N can be provided near the center of the image similarly to the result arithmetically averaging data provided by repetition plural times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic resonance imaging apparatus (hereinafter, referred to as "MRI apparatus"), and more particularly to an MRI capable of imaging and image reconstruction capable of improving an S / N ratio.
Related to the device.

[0002]

2. Description of the Related Art An MRI apparatus includes a static magnetic field coil for applying a magnetic field of a constant intensity to a subject, an irradiation coil for applying a high-frequency magnetic field for causing nuclear nuclei to cause nuclei of atoms constituting a living tissue of the subject, Furthermore, a gradient magnetic field coil for providing a gradient magnetic field for obtaining positional information in space is provided. The irradiation coil and the gradient coil operate in a predetermined pulse sequence according to a signal from the sequencer.

For example, in the spin echo method, which is a typical pulse sequence, first, a 90 ° pulse, which is a high-frequency magnetic field, is applied together with a gradient magnetic field in a slice direction for selecting a measurement section, and the echo time is defined as TE. TE /
Two hours later, a 180 ° pulse is applied along with the slice gradient. As a result, an echo signal is generated from the section selected at time TE.

At this time, a linear gradient magnetic field is superimposed on the static magnetic field in order to obtain a spatial distribution of the echo signal. For example,
A phase encoding gradient magnetic field for obtaining position information in the Y direction, and a frequency encoding gradient magnetic field for obtaining position information in the X direction.

[0005] Using such a pulse sequence as a basic unit, the number of times necessary to form one image (the number of phase encodes) for each fixed repetition time TR while changing the intensity of the phase encode gradient magnetic field every time, For example, 256
Repeat several times. The relationship between the intensity Gp of the phase encoding gradient magnetic field and the application time Tp is expressed by equation (2). 2πi = γ · Gp · Tp · FOV (2) In this equation (2), γ is the gyromagnetic ratio, FOV is the field of view, and similarly, i is −prj / 2 <i ≦ prj /
2, where prj indicates the number of projections, that is, the number of phase encodings necessary to construct one image.

The spatial distribution of macroscopic magnetization is obtained by subjecting the obtained measurement data to two-dimensional inverse Fourier transform, thereby forming a photographed image.

Here, generally, the S / N ratio of a photographed image is
As shown in Expression (3), the relationship is proportional to the square root of the number of repetitions NSA of the sequence.

(Equation 1) Therefore, in order to increase the S / N ratio of a captured image, the above-described sequence is measured a plurality of times, and the arithmetic average of those data is taken.

[0008]

However, the relationship between the photographing time T and the number of repetitions NSA is proportional as shown in equation (4).

(Equation 2) If the S / N ratio of a captured image is to be doubled, the shooting time T needs to be quadrupled. In order to increase the S / N ratio in this manner, it is necessary to considerably extend the imaging time, and this imposes a long restraint time on the subject.

It is an object of the present invention to improve such a conventional MRI apparatus and to provide an MRI apparatus which realizes a high S / N ratio while suppressing an increase in imaging time.

[0010]

In order to achieve such an object, the present invention generally focuses on the fact that the region of interest is near the center of a captured image, and performs a normal measurement sequence to at least measure at least near the center of the image. The S / N near the center of the image is improved by adding a phase encode application pattern that can acquire data. That is, the MRI apparatus of the present invention comprises: a static magnetic field generating means for applying a static magnetic field to a subject; a gradient magnetic field generating means for applying a slice direction gradient magnetic field, a frequency encoding gradient magnetic field and a phase encoding gradient magnetic field to the subject; A transmission system that irradiates the subject with a high-frequency magnetic field that causes nuclear magnetic resonance to the nuclei of the atoms constituting the living tissue, and controls the gradient magnetic field generation unit and the transmission system,
A sequencer that repeatedly applies each gradient magnetic field and a high-frequency magnetic field in a predetermined pulse sequence, a receiving system that detects a nuclear magnetic resonance signal as a measurement signal, and a signal processing system that processes a signal detected by the receiving system and reconstructs an image. And a magnetic resonance imaging apparatus comprising a central processing system for controlling the entire apparatus, input means for inputting conditions to the central processing system, and output means for displaying and storing data processed by the signal processing system. The pulse sequence executed by the sequencer includes, at least, a first phase encoding application pattern for measuring a measurement signal while changing the applied intensity of the phase encoding gradient magnetic field in a predetermined increment, and the applied intensity of the phase encoding gradient magnetic field in a predetermined order. And a second phase encoding application pattern for measuring the measurement signal while changing the measurement signal at an increment different from the increment of A. Here, the number of applied patterns different from the first applied pattern may be two or more.

Preferably, the phase encoding gradient magnetic field is applied according to equation (5): Gp = 2πn / (γ · Tp · FOV) (5) In the first applied pattern, n = i (where i Is-
(Prj / 2) <i ≦ (prj / 2), all integers that satisfy (prj is the number of projections, the same applies hereinafter),
In the second application pattern, n = j (where j is −
(Prj / 2) <j ≦ (prj / 2) and is an integer that is an integer (m ≧ 2) times i.

In such an MRI apparatus,
In order to obtain such an image having a high S / N ratio, images are first reconstructed from raw measurement data obtained by a measurement sequence including a first application pattern and a second application pattern, and then these images are reconstructed. May be combined, and after combining the measurement data of both patterns, an image may be reconstructed from the combined data. Further, the measurement data of the smaller number of data may be combined with the other measurement data. After the interpolation, the image of the complemented data and the image of the other measurement data may be respectively reconstructed, and then the images may be combined. Note that as a specific method of synthesizing the measurement data and the image, an arithmetic average or the like can be used.

Such an MRI apparatus performs a measurement sequence including a measurement for applying a gradient magnetic field at a large increment different from the normal increment, in addition to a measurement for applying the gradient magnetic field at an increment of an applied intensity of a normal phase encoding gradient magnetic field. Run. Such a measurement sequence is implemented by repeating the same phase encoding sequence for each increment by the second application pattern while measuring while applying the voltage in the normal increment by the first application pattern. Measurement data obtained at the time of measurement (at the time of repetition) of the second application pattern has the same resolution as a normal image, and an image with a different field of view is obtained.

Specifically, when the phase encoding gradient magnetic field is applied according to the above equation (5), the step width (n) of the second applied pattern is changed to the step width (n = i) of the first applied pattern. In the second application pattern, 1 / m measurement data can be obtained, and the measurement time can be reduced to 1 / m. Therefore, the time is reduced as compared with the case where the normal measurement is repeated twice.

When the measurement data thus obtained is reconstructed as an image, an image with a standard photographing visual field is obtained from the former, and an image with a standard photographing visual field of 1 / m is obtained from the latter. This field of view will be located near the center of the standard field of view. In general, a region of interest often exists near the center, and by combining images obtained in this way, an image with a high S / N ratio can be obtained for the region of interest.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an MRI apparatus to which the present invention is applied will be described below.

First, the overall configuration of such an MRI apparatus is shown in FIG. This MRI apparatus has a configuration substantially similar to that of a conventional apparatus, and includes a static magnetic field generating magnet 4 for generating a uniform static magnetic field in a space where a subject is arranged, and a subject placed in such a magnetic field. A transmission system 3 for generating a high-frequency magnetic field in order to generate nuclear magnetic resonance in a tissue, and applies a gradient magnetic field whose magnetic field strength is linearly changed independently in X, Y, and Z directions to a static magnetic field. A gradient magnetic field generation system 21, a reception system 5 for receiving a resonance signal generated from a subject by irradiation of a high-frequency magnetic field, a sequencer 2 for controlling the operation timing of each of these systems, and measurement data transmitted from the reception system 5. In addition to performing various calculations required for image reproduction, inputting imaging conditions and the like to a central processing unit (hereinafter referred to as CPU) 1 and CPU 1 for controlling the entire MRI apparatus, And a signal processing system 6 for outputting a more processed data in a variety of ways.

Specifically, the transmission system 3 includes a high-frequency oscillator 8 for generating a high-frequency signal, a modulator 9 for modulating the high-frequency signal, and a high-frequency amplifier 1 for amplifying the modulated signal.
It has an irradiation coil 11 for generating a high-frequency magnetic field according to 0 and the amplified signal.

The gradient magnetic field generating system 21 includes a gradient magnetic field coil 13 for generating a gradient magnetic field and a gradient magnetic field coil 13.
And a gradient magnetic field power supply 12 for supplying a current to the power supply.

The receiving system 5 includes a receiving coil 14 for receiving the resonance signal, an amplifier 15 connected to the receiving coil 14 for amplifying the signal, a quadrature phase detector 16 for converting the amplified signal into a two-series signal, and these components. An A / D converter 17 for converting a signal into digital quantity measurement data is provided.

The signal processing system 6 further includes a keyboard 22 as input means for inputting photographing conditions and the like to the CPU 1, a display 18 such as a CRT as output means for displaying a reconstructed image, and data processed by the CPU 1. Optical disk 19 and magnetic disk 20 as output means for storing
It has.

In the MRI apparatus having such a configuration,
After various measurement conditions are input to the CPU 1 from the keyboard 22, the CPU 1 controls and operates the entire apparatus according to these conditions.

According to a command from the CPU 1, the sequencer 2
The operation timings of the three systems of gradient magnetic field power supplies 12 are controlled, and a gradient magnetic field is applied by a gradient magnetic field coil 13 while being superimposed on a magnetic field of uniform magnetic field strength provided by the static magnetic field generating magnet 4. On the other hand, in the transmission system 3, the high-frequency signal transmitter 8
Are modulated by the modulator 9 whose operation timing is controlled by the sequencer 2, and then amplified by the amplifier 10. When this signal flows through the irradiation coil 11, a predetermined pulsed high-frequency magnetic field is applied to the subject. As described above, the sequencer 2 controlled by the CPU 1 executes a predetermined pulse sequence of the high-frequency magnetic field and the gradient magnetic field, and the A / D converter 17 collects data for each basic unit of the pulse sequence.

A resonance signal is generated from the subject irradiated with these magnetic fields, and is received by the receiving coil 14 of the receiving system 5. After the received signal is amplified by the amplifier 15,
The signal is divided into two series by the quadrature phase detector 16, and each signal is converted into digital quantity measurement data by the A / D converter 17. At this time, the timing of data collection of the A / D converter 17 is controlled by the sequencer 2. The measurement data is input to the CPU 1 and an image is reconstructed by a two-dimensional Fourier transform or the like. The reconstructed image is displayed on the display 18 of the signal processing system 6, and is stored as processing data in an external storage medium such as an optical disk 19 or a magnetic disk 20.

Next, a pulse sequence executed in the MRI apparatus of the present invention will be described. FIG. 3 shows a case where the present invention is applied to the spin echo method. First, after a high-frequency magnetic field is applied as a 90 ° pulse 23, and the echo time is TE, a 180 ° pulse 24 is applied after TE / 2. Is added. As a result, time T
At E, an echo signal is obtained. Simultaneously with the 90 ° pulse 23 and the 180 ° pulse 24, a slice-direction gradient magnetic field 25, which is a gradient magnetic field in the Z direction, is applied to excite the selected cross section. Further, a phase encoding gradient magnetic field 26 and a frequency encoding gradient magnetic field 27 are applied between the 90 ° pulse 23 and the 180 ° pulse 24 in order to provide two-dimensional position information.

These pulses 23 and 24 and gradient magnetic fields 25 to
Numeral 27 is repeatedly applied at a timing controlled by the sequencer 2 at every predetermined repetition time TR, and an echo signal is repeatedly measured. At this time, the applied intensity of the phase encoding gradient magnetic field 26 is changed in a predetermined increment.

In the MRI apparatus according to the present embodiment, unlike the related art, not only is measured once for each intensity while changing the intensity of the phase encoding gradient magnetic field 26, but also, as shown by a thick line in FIG. In the encoding step (even number step as shown), measurement is performed by repeating the basic sequence (FIG. 3) twice.

FIG. 1 shows the application pattern of the phase encoding gradient magnetic field 26 in more detail. This application pattern can be expressed by the following equation (6): Gp = 2πn / (γ · Tp · FOV) ( 6) Here, n is ...- 3, -2, -2, -1, 0,
It is a sequence of integers represented by 0, 1, 2, 2, 3, 4, 4,. In FIG. 1A, the symbols i and j are used to distinguish between the case of measuring once and the case of measuring twice for the same magnetic field strength. That is, the symbol i represents an integer, the symbol j represents a multiple of 2, and is measured twice with a magnetic field having an intensity corresponding to the symbol j.

This applied pattern is shown in FIG. 1 (b) showing the phase encoding gradient magnetic field 26 corresponding to the symbol i and the symbol j.
FIG. 1 showing a phase encoding gradient magnetic field 26 corresponding to FIG.
It can be decomposed into (c). As can be seen from FIG. 1 (b), the applied pattern corresponding to the symbol i is the same as the conventional phase encoding gradient magnetic field shown by the equation (2). On the other hand, as can be seen from FIG. 1C, the applied pattern indicated by the symbol j has a step width twice as large as the standard when the phase encoding step width in FIG. 1B is standardized.

Therefore, the measurement sequence of the present embodiment includes a normal measurement sequence (first application pattern) for measuring while changing the applied intensity of the phase encoding gradient magnetic field in one basic increment, and a measurement sequence of the phase encoding gradient magnetic field. This can be grasped as a combination of a measurement sequence (second application pattern) that measures while changing the applied intensity in double increments.

By adopting such an application pattern, the photographing time can be reduced as compared with the case where the conventional method is repeated twice.

In this example, the measurement is performed twice at the same intensity every other change in the intensity of the phase encoding magnetic field, that is, the case where the step width of the second application pattern is twice is shown. In general, m is 2
If the integer is equal to or more than 2, the same intensity is set to 2 every m changes in intensity.
The step width may be measured and the step width may be multiplied by m.

In consideration of the above, when the symbol n of the equation (6) representing the phase encoding gradient magnetic field strength Gp is represented in a general form, in the case of the first application pattern (n = i), i
Are all integers that satisfy − (prj / 2) <i ≦ (prj / 2), and in the case of the second applied pattern (n = j), j is − (prj / 2) <j ≦ ( prj / 2) are all multiples of an integer m of 2 or more. Note that the number of projections prj is the number of phase encodes for the first application pattern having a normal step width, for example, 256,
512 and the like.

Next, a method of processing the measurement data obtained by such an application pattern in the signal processing system 6 will be described.

The measurement data obtained when the phase encoding gradient magnetic field 26 is applied by the first application pattern as shown in FIG. 1 and the measurement data obtained when the phase encoding gradient magnetic field 26 is applied by the second application pattern are respectively shown in FIG. R
When i (x, y) and Rj (x, y) are represented, the k-space arrangement when these are two-dimensionally Fourier transformed is shown in FIG.
As shown in (b), they are arranged symmetrically around i = 0 and j = 0, respectively.

FIGS. 4C and 4D show images obtained by reconstructing images of these measurement data by two-dimensional Fourier transform.
It was shown to. As can be seen from FIG. 4, the measurement data Ri (x, y) at the time of applying the first application pattern has the same application pattern of the phase encoding gradient magnetic field 26 as that of the related art.
The obtained image Ii (x, y) has the same visual field as the conventional one.
On the other hand, in the second application pattern, since the increment of the phase encoding step is doubled, the image Ij (x, y) obtained from the measurement data Rj (x, y) according to the equation (2) is the image Ii.
The field of view becomes 1/2 of (x, y), and this image Ij (x, y)
Is near the center.

The image data Ii (x,
y) and the image data Ij (x, y) have different visual fields but the same spatial resolution as described above, and can be synthesized by arithmetically averaging the overlapping parts of the visual fields.
A composite image If (x, y) as shown in (e) is obtained. That is, in the case of-(prj / 2) / m <y ≦ (prj / 2) / m, that is, in the vicinity of the center of the image, the image data can be expressed by Expression (7). If (x, y) = (Ii (x, y) + Ij (x, y)) / 2 (7) In other cases, that is, near the upper and lower ends of the image, Expression (8), If (x, y) = Ii (x, y) (8) By combining the images in this manner, only the vicinity of the center of the image is averaged by the two measurement data, so that the S / N ratio can be improved for this portion.

Next, measurement data Ri (x, acquired by applying the phase encode gradient magnetic field 26 of two patterns.
y) and another processing method of Rj (x, y) will be described with reference to FIG. FIGS. 5A and 5B show the k-space arrangement of measurement data represented by Ri (x, y) and Rj (x, y), respectively, as in the above-described example. In this process, first, the measurement data Ri (x, y) and the measurement data Rj (x, y) are combined.
Since the measurement data Ri (x, y) and the measurement data Rj (x, y) have different numbers of data, data obtained by applying the same phase encoding gradient magnetic field are arithmetically averaged, and are shown in FIG. The composite data Rf (x, y) having such a k-space arrangement is obtained. When the value of y in the k-space is a multiple of the integer m, the composite data Rf (x, y) can be obtained by an arithmetic average as shown in Expression (9). Rf (x, y) = (Ri (x, y) + Rj (x, y)) / 2 (9) On the other hand, in cases other than the above, Rf (x, y) = Ri (x, y) (10) The measurement data according to the first application pattern is used as it is. When Rf (x, y) thus obtained is subjected to image reconstruction by two-dimensional Fourier transform, an image If (x, y) as shown in FIG. 5D is obtained. In this case, the portion where Rf (x, y) is obtained by averaging the measurement data according to equation (9) corresponds to the vicinity of the center of the image, and therefore, as in the example of FIG. High images can be obtained.

Another processing method for the measurement data Ri (x, y) and Rj (x, y) will be described with reference to FIG. FIG.
(A) and (b) are Ri (x,
y) and k-space arrangement of measurement data represented by Rj (x, y). In this process, first, the measurement data Rj (x, y) acquired at the time of application of the second application pattern with a small number of data items
The missing data is supplemented by using the measurement data Ri (x, y) acquired when the first application pattern is applied, and FIG.
The complementary data Rj '(x, y) as shown in (c) is created. That is, when the value of y in the k-space is a multiple of m, the complementary data Rj ′ (x, y) is expressed as Rj ′ (x, y) = Rj (x, y) (11) In other cases, Rj ′ (x, y) = Ri (x, y) (12) as in equation (12). After complementing the data in this way, the measurement data Ri (x, y) and the complement data Rj ′ (x, y) acquired at the time of applying the first application pattern are respectively subjected to two-dimensional Fourier transform, and FIG. , (E) image Ii (x, y)
And an image Ij (x, y). These are the same image data in both the field of view and the spatial resolution.
Create If (x, y) = (Ii (x, y) + Ij (x, y)) / 2 (13) The composite image If (x, y) thus obtained has two measurement data, Rj ( (x, y), that is, an image with a high S / N ratio near the center of the image.

Although the above embodiment has been described using the spin echo method as the pulse sequence, the present invention can be applied to other pulse sequences, for example, the gradient echo method.

Also, only the case where the measurement is performed twice with the phase encoding gradient magnetic field strength corresponding to the second application pattern has been described, but the measurement may be performed any number of times as long as it is 2 degrees or more. In this case, as the number of times of measurement increases, the S / N ratio near the center of the image improves. Also, only the case where the width of the phase encoding step in the second application pattern is doubled (m = 2) has been described, but the width may be any multiple of twice or more. Thus, the field of view differs, and when the step width is increased by m (> 2), the field of view becomes 1 / m. Accordingly, m can be arbitrarily selected according to the size of the region of interest or the like, and the S / N of the region of interest can be increased.

In the present invention, in addition to the standard first application pattern, a plurality of application patterns having different step widths can be combined. For example, it is also possible to use a second application pattern having a double step width and a third application pattern having a triple step width. By freely selecting the application pattern in this way, it is possible to improve the S / N ratio of the image of the region of interest while minimizing the extension of the imaging time.

Although the two-dimensional Fourier transform has been described as a method of image reconversion, the present invention can be similarly applied to other image reconstitution methods.

Further, in the above embodiment, as a combination of the first applied pattern and the second applied pattern, both patterns are executed in such a manner that the one having the same phase gradient magnetic field intensity is repeated in a series of measurement sequences. Although the description has been given only of the case where the first application pattern and the second application pattern are sequentially arranged, the same effect can be obtained and the same effect can be obtained. That is, first, a series of measurement sequences based on the first application pattern is executed,
A series of measurement sequences based on the application pattern can be executed. As described above, when a plurality of application patterns are sequentially arranged, the present invention can be applied to an echo planar method, a spiral scan, and the like, which are difficult to repeatedly measure with the same phase encoding.

[0045]

As described above, the MRI apparatus of the present invention comprises at least a first phase encode application pattern for measuring a measurement signal while changing the applied intensity of the phase encode gradient magnetic field in a predetermined increment, A phase encoding gradient magnetic field is applied by a pulse sequence combining a second phase encoding application pattern for measuring a measurement signal while changing the applied strength of the gradient magnetic field at an increment different from the predetermined increment. By adding an application pattern composed of different phase encode step increments as described above, it is possible to reduce the photographing time as compared with a case where the pattern is repeated a plurality of times with a fixed pattern.

In addition, the measurement data obtained by increasing the increment of the phase encoding step has a narrower field of view after image reconstruction, but maintains the resolution of the image for that part, and the position in the k-space is generally higher. Since this corresponds to the vicinity of the center of the image, which is the region of interest of the captured image, an image having a high S / N ratio can be obtained in the main part.

As described above, the MRI apparatus of the present invention can realize a high S / N ratio while suppressing an increase in imaging time.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an application pattern of a phase encoding gradient magnetic field by the MRI apparatus of the present invention.

FIG. 2 is a block diagram of the MRI apparatus of the present invention.

FIG. 3 is a diagram showing an example of a pulse sequence in the MRI apparatus of the present invention.

FIG. 4 is a diagram showing an embodiment of image acquisition by the MRI apparatus of the present invention.

FIG. 5 is a view showing a second embodiment of image acquisition by the MRI apparatus of the present invention.

FIG. 6 is a diagram showing a third embodiment of image acquisition by the MRI apparatus of the present invention.

[Explanation of symbols]

 Reference Signs List 1 central processing system (CPU) 2 sequencer 3 transmission system 4 static magnetic field generating means 5 receiving system 12, 13, 21 gradient magnetic field generating means 6 signal processing system 26 phase encoding gradient magnetic field i first phase encoding applied pattern j second Phase encoding applied pattern Ri (x, y), Rj (x, y) Measurement data Ii (x, y), Ij (x, y) Image If Synthesized image Rf (x, y) Synthesized data Rj '(x, y ) Supplementary data

Claims (5)

[Claims] 1. A static magnetic field generating means for applying a static magnetic field to a subject, a gradient magnetic field generating means for applying a slice direction gradient magnetic field, a frequency encoding gradient magnetic field and a phase encoding gradient magnetic field to the subject, and a living tissue of the subject A transmission system that irradiates the subject with a high-frequency magnetic field that causes nuclear magnetic resonance in the nuclei of the atoms that constitute the object, the gradient magnetic field generation unit and the transmission system are controlled, and each of the gradient magnetic field and the high-frequency magnetic field is a predetermined pulse A sequencer that repeatedly applies in a sequence, a receiving system that detects a nuclear magnetic resonance signal as a measurement signal, a signal processing system that processes a signal detected by the receiving system and reconstructs an image, and a central processing unit that controls the entire device. Magnetic resonance, comprising: a system, input means for inputting conditions to the central processing system, and output means for displaying and storing data processed by the signal processing system. In the imaging apparatus, the pulse sequence executed by the sequencer includes at least a first phase encode application pattern for measuring the measurement signal while changing the applied intensity of the phase encode gradient magnetic field in a predetermined increment, and a phase encode gradient magnetic field. A second phase encode application pattern for measuring the measurement signal while changing the applied intensity at an increment different from the predetermined increment. 2. The phase encoding gradient magnetic field is applied according to the following equation (1): Gp = 2πn / (γ · Tp · FOV) (1) where Gp is the phase encoding gradient magnetic field intensity, γ is the gyromagnetic ratio, Tp is the phase encoding gradient magnetic field application time, FOV
Is the field of view, and in the first phase encoding applied pattern, in the above equation (1), n = i (where i is − (prj / 2) <i ≦ (pr
j / 2), and prj is the number of projections, the same applies hereinafter. In the second phase encoding application pattern, n = j (where j is − ( (prj / 2) <j ≦ (pr
j / 2), and an integer that is an integer (m ≧ 2) times i.
The magnetic resonance imaging apparatus according to claim 1, wherein 3. The image processing system according to claim 1, wherein the signal processing system uses the measurement data obtained by the measurement using the first phase encoding application pattern and the measurement data obtained by the measurement using the second phase encoding application pattern, respectively. 3. A magnetic resonance imaging apparatus according to claim 1, wherein said magnetic resonance imaging apparatus comprises means for combining these images. 4. The signal processing system according to claim 1, further comprising: a unit configured to combine measurement data acquired by measurement using the first phase encoding application pattern and measurement data acquired by measurement using the second phase encoding application pattern. 3. The magnetic resonance imaging apparatus according to claim 1, further comprising: reconstructing an image of the combined data. 5. A deficient portion of measurement data obtained by measurement using the second phase encoding application pattern, using the measurement data obtained by measurement using the first phase encoding application pattern. Means for reconstructing an image from each of the complemented data and the measurement data obtained by the measurement using the first phase encoding application pattern, and means for synthesizing these images. The magnetic resonance imaging apparatus according to claim 1 or 2, wherein: