JP3836424B2 - Magnetic resonance imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic resonance imaging apparatus, and more particularly, to a magnetic resonance imaging apparatus using a navigator echo.
[0002]
[Prior art]
Conventionally, in a magnetic resonance imaging apparatus, navigator echoes are acquired in the course of performing imaging, and the imaging results are corrected using the navigator echo (see, for example, Patent Document 1).
[0003]
[Patent Document 1]
JP 2001-276017 A (page 7-10, FIG. 3-7)
[0004]
[Problems to be solved by the invention]
When a profile of a subject to be imaged is created based on the navigator echo, and the respiratory phase of the target is determined based on the signal intensity of the profile at a predetermined determination point, an image of the predetermined respiratory phase is captured. Due to changes in the state over time, the initially set determination point may not be appropriate, and imaging may be inaccurate.
[0005]
Accordingly, an object of the present invention is to realize a magnetic resonance imaging apparatus that performs correct imaging regardless of changes in the respiratory state.
[0006]
[Means for Solving the Problems]
(1) One aspect of the present invention for solving the above-described problem is that a navigator echo acquisition unit that repeatedly acquires a navigator echo from an object to be imaged, and a creation unit that generates a target profile based on the navigator echo Determining means for determining whether the target respiratory phase matches a predetermined phase based on the signal intensity of the profile at a predetermined location, and the respiratory phase does not match the predetermined phase Correction means for correcting the determination part of the determination means when the frequency exceeds a predetermined limit; and imaging echo acquisition means for acquiring an imaging echo in a predetermined respiratory phase from an imaging target based on the determination; And generating means for generating an image based on the imaging echo, It is a ringing imaging apparatus.
[0007]
(2) According to another aspect of the present invention for solving the above-described problem, an acquisition unit that repeatedly acquires navigator echoes and imaging echoes, a creation unit that creates a target profile based on the navigator echoes, and an object Determining means for determining whether or not the respiratory phase matches a predetermined phase based on the signal intensity of the profile at a predetermined location, and a frequency at which the respiratory phase does not match the predetermined phase A correction unit that corrects a determination portion of the determination unit when a predetermined limit is exceeded; an adoption unit that employs an imaging echo in a predetermined respiratory phase among the imaging echoes based on the determination; Generating means for generating an image based on the obtained imaging echo, and magnetic resonance It is a shadow system.
[0008]
In the inventions according to the above aspects, the correction means corrects the determination point of the determination means when the frequency at which the respiratory phase does not match the predetermined phase exceeds a predetermined limit. The correct shooting can be performed.
[0009]
The navigator echo is preferably a spin echo from the viewpoint of obtaining an appropriate signal as the navigator echo. The imaging echo is preferably a gradient echo from the viewpoint of obtaining an appropriate signal as the imaging echo. The profile is preferably a one-dimensional profile in the body axis direction from the viewpoint of easy determination of the respiratory phase. The predetermined phase is preferably an expiratory phase from the viewpoint of photographing an expiratory phase image. The predetermined phase is preferably an intake phase from the viewpoint of capturing an image of the intake phase. The frequency is preferably the number of times or the time when the respiratory phase does not match a predetermined phase, from the viewpoint of appropriately responding to a change in the respiratory state.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiment. FIG. 1 shows a block diagram of the magnetic resonance imaging apparatus. An example of an embodiment relating to the apparatus of the present invention is shown by the configuration of the apparatus.
[0011]
As shown in the figure, this apparatus has a magnet system 100. The magnet system 100 includes a main magnetic field coil unit 102, a gradient coil unit 106, and an RF (radio frequency) coil unit 108. Each of these coil portions has a substantially cylindrical shape and is arranged coaxially with each other. A subject 1 to be imaged is mounted on a cradle 500 in a generally cylindrical inner space (bore) of the magnet system 100 and is carried in and out by a conveying means (not shown).
[0012]
The main magnetic field coil unit 102 forms a static magnetic field in the internal space of the magnet system 100. The direction of the static magnetic field is generally parallel to the direction of the body axis of the object 1. That is, a so-called horizontal magnetic field is formed. The main magnetic field coil unit 102 is configured using, for example, a superconducting coil. In addition, you may comprise using not only a superconductive coil but a normal conductive coil.
[0013]
The gradient coil section 106 generates three gradient magnetic fields for giving gradients to the static magnetic field strength in the directions of three axes perpendicular to each other, that is, the slice axis, the phase axis, and the frequency axis.
[0014]
When the coordinate axes perpendicular to each other in the static magnetic field space are x, y, and z, any of the axes can be a slice axis. In that case, one of the remaining two axes is a phase axis, and the other is a frequency axis. In addition, the slice axis, the phase axis, and the frequency axis can have arbitrary inclinations with respect to the x, y, and z axes while maintaining the perpendicularity therebetween. This is also referred to as an oblique. In this device, the direction of the body axis of the target 1 is the z-axis direction.
[0015]
The gradient magnetic field in the slice axis direction is also called a slice gradient magnetic field. The gradient magnetic field in the phase axis direction is also referred to as a phase encode gradient magnetic field or a phase encode gradient magnetic field. The gradient magnetic field in the frequency axis direction is also referred to as a read out gradient magnetic field. The readout gradient magnetic field is synonymous with the frequency encoding gradient magnetic field. In order to make it possible to generate such a gradient magnetic field, the gradient coil unit 106 has three gradient coils (not shown). Hereinafter, the gradient magnetic field is also simply referred to as a gradient.
[0016]
The RF coil unit 108 forms a high-frequency magnetic field for exciting spins in the body of the target 1 in the static magnetic field space. Hereinafter, the formation of a high-frequency magnetic field is also referred to as transmission of an RF excitation signal. The RF excitation signal is also referred to as an RF pulse. An electromagnetic wave generated by the excited spin, that is, a magnetic resonance signal is received by the RF coil unit 108.
[0017]
The magnetic resonance signal is a signal in the frequency domain (Fourier) space. Since the magnetic resonance signal is encoded in two axes by the gradient in the phase axis direction and the frequency axis direction, the magnetic resonance signal is obtained as a signal in a two-dimensional Fourier space. The phase encoding gradient and readout gradient determine the sampling position of the signal in two-dimensional Fourier space. Hereinafter, the two-dimensional Fourier space is also referred to as k-space.
[0018]
A gradient driving unit 130 is connected to the gradient coil unit 106. The gradient driving unit 130 gives a driving signal to the gradient coil unit 106 to generate a gradient magnetic field. The gradient drive unit 130 has three systems of drive circuits (not shown) corresponding to the three systems of gradient coils in the gradient coil unit 106.
[0019]
An RF drive unit 140 is connected to the RF coil unit 108. The RF drive unit 140 gives a drive signal to the RF coil unit 108 and transmits an RF pulse to excite spins in the body of the subject 1.
[0020]
A data collection unit 150 is connected to the RF coil unit 108. The data collection unit 150 collects reception signals received by the RF coil unit 108 as digital data.
[0021]
A sequence control unit 160 is connected to the gradient driving unit 130, the RF driving unit 140, and the data collecting unit 150. The sequence controller 160 controls the gradient driver 130 or the data collector 150 to collect magnetic resonance signals.
[0022]
The sequence control unit 160 is configured using, for example, a computer. The sequence control unit 160 has a memory (not shown). The memory stores a program for the sequence control unit 160 and various data. The function of the sequence control unit 160 is realized by the computer executing a program stored in the memory.
[0023]
The output side of the data collection unit 150 is connected to the data processing unit 170. Data collected by the data collection unit 150 is input to the data processing unit 170. The data processing unit 170 is configured using, for example, a computer. The data processing unit 170 has a memory (not shown). The memory stores a program for the data processing unit 170 and various data.
[0024]
The data processing unit 170 is connected to the sequence control unit 160. The data processing unit 170 is above the sequence control unit 160 and controls it. The function of this apparatus is realized by the data processing unit 170 executing a program stored in the memory.
[0025]
The data processing unit 170 stores the data collected by the data collection unit 150 in a memory. A data space is formed in the memory. This data space corresponds to k-space. The data processing unit 170 reconstructs an image by performing two-dimensional inverse Fourier transform on k-space data.
[0026]
A display unit 180 and an operation unit 190 are connected to the data processing unit 170. The display unit 180 is configured by a graphic display or the like. The operation unit 190 includes a keyboard having a pointing device.
[0027]
The display unit 180 displays the reconstructed image and various information output from the data processing unit 170. The operation unit 190 is operated by the user and inputs various commands and information to the data processing unit 170. The user operates the apparatus interactively through the display unit 180 and the operation unit 190.
[0028]
FIG. 2 shows a block diagram of another type of magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus shown in the figure is an example of an embodiment of the present invention. An example of an embodiment relating to the apparatus of the present invention is shown by the configuration of the apparatus.
[0029]
This apparatus has a magnet system 100 ′ having a different system from the apparatus shown in FIG. Except for the magnet system 100 ′, the configuration is the same as that of the apparatus shown in FIG.
[0030]
The magnet system 100 ′ includes a main magnetic field magnet unit 102 ′, a gradient coil unit 106 ′, and an RF coil unit 108 ′. Each of the main magnetic field magnet section 102 ′ and each coil section is composed of a pair of facing each other across a space. Moreover, all have a substantially disk shape and are arranged sharing the central axis. The object 1 is mounted on the cradle 500 and carried into and out of the internal space (bore) of the magnet system 100 ′ by a conveying means (not shown).
[0031]
The main magnetic field magnet unit 102 ′ forms a static magnetic field in the internal space of the magnet system 100 ′. The direction of the static magnetic field is substantially orthogonal to the body axis direction of the target 1. That is, a so-called vertical magnetic field is formed. The main magnetic field magnet section 102 ′ is configured using, for example, a permanent magnet. In addition, you may comprise using not only a permanent magnet but a superconductive electromagnet or a normal electromagnet.
[0032]
The gradient coil section 106 ′ generates three gradient magnetic fields for giving a gradient to the static magnetic field strength in the directions of three axes perpendicular to each other, that is, the slice axis, the phase axis, and the frequency axis.
[0033]
When the coordinate axes perpendicular to each other in the static magnetic field space are x, y, and z, any of the axes can be a slice axis. In that case, one of the remaining two axes is a phase axis, and the other is a frequency axis. In addition, the slice axis, the phase axis, and the frequency axis can have an arbitrary inclination with respect to the x, y, and z axes while maintaining the perpendicularity therebetween, that is, oblique. Also in this apparatus, the direction of the body axis of the target 1 is the z-axis direction. In order to enable generation of gradient magnetic fields in the three-axis directions, the gradient coil unit 106 'has three gradient coils (not shown).
[0034]
The RF coil unit 108 ′ transmits an RF pulse for exciting the spin in the body of the subject 1 to the static magnetic field space. The electromagnetic wave generated by the excited spin, that is, the magnetic resonance signal is received by the RF coil unit 108 ′. A reception signal of the RF coil unit 108 ′ is input to the data collection unit 150.
[0035]
FIG. 3 shows an example of a pulse sequence used for magnetic resonance imaging. This pulse sequence is a pulse sequence of a spin echo (SE: Spin Echo) method.
[0036]
That is, (1) is a sequence of 90 ° pulses and 180 ° pulses for RF excitation in the SE method, and (2), (3), (4) and (5) are respectively the slice gradient Gs and the lead. This is a sequence of an out gradient Gr, a phase encode gradient Gp, and a spin echo MR. The 90 ° pulse and the 180 ° pulse are represented by center signals. The pulse sequence proceeds from left to right along the time axis t.
[0037]
As shown in the figure, 90 ° excitation of spin is performed by a 90 ° pulse. At this time, the slice gradient Gs is applied, and selective excitation for a predetermined slice is performed. After a predetermined time from the 90 ° excitation, 180 ° excitation by a 180 ° pulse, that is, spin inversion is performed. At this time, the slice gradient Gs is applied, and selective inversion is performed for the same slice.
[0038]
In the period between 90 ° excitation and spin reversal, a readout gradient Gr and a phase encode gradient Gp are applied. Spin dephase is performed by the lead-out gradient Gr. Spin phase encoding is performed by the phase encoding gradient Gp.
[0039]
After the spin inversion, the spin is rephased at the readout gradient Gr to generate the spin echo MR. The spin echo MR is collected as view data by the data collecting unit 150. Such a pulse sequence is repeated 64 to 512 times with a period TR (repetition time). The phase encoding gradient Gp is changed every time it is repeated, and a different phase encoding is performed each time. Thereby, view data of 64 to 512 views is obtained.
[0040]
Another example of a pulse sequence for magnetic resonance imaging is shown in FIG. This pulse sequence is a pulse sequence of a gradient echo (GRE) method.
[0041]
That is, (1) is a sequence of α ° pulses for RF excitation in the GRE method, and (2), (3), (4) and (5) are respectively slice gradient Gs, readout gradient Gr, It is a sequence of a phase encoding gradient Gp and a gradient echo MR. The α ° pulse is represented by a center signal. The pulse sequence proceeds from left to right along the time axis t.
[0042]
As shown in the figure, the α ° excitation of the spin is performed by the α ° pulse. α is 90 or less. At this time, the slice gradient Gs is applied, and selective excitation for a predetermined slice is performed.
[0043]
After the α ° excitation, spin phase encoding is performed by the phase encoding gradient Gp. Next, the spin is first dephased by the readout gradient Gr, and then the spin is rephased to generate a gradient echo MR. The gradient echo MR is collected as view data by the data collection unit 150. Such a pulse sequence is repeated 64 to 512 times with a period TR. The phase encoding gradient Gp is changed every time it is repeated, and a different phase encoding is performed each time. Thereby, view data of 64 to 512 views is obtained.
[0044]
View data obtained by the pulse sequence of FIG. 3 or 4 is collected in the memory of the data processing unit 170. Note that the pulse sequence is not limited to the SE method or the GRE method, and may be another appropriate technique such as a Fast Spin Echo (FSE) method. The data processing unit 170 reconstructs an image based on the view data collected in the memory.
[0045]
Such imaging is performed for a predetermined phase of respiration of the subject 1. That is, breathing synchronous imaging is performed. FIG. 5 shows a flow diagram of the operation of this apparatus when performing breathing synchronous imaging.
[0046]
As shown in the figure, phase designation is performed in step 501. A flow diagram for phase designation is shown in FIG. As shown in the figure, in step 601, navigator echo acquisition is performed. A pulse sequence as shown in FIG. 7 is used for navigator echo acquisition. This pulse sequence corresponds to the spin echo method pulse sequence shown in FIG. 3 with the phase encode gradient Gp set to zero.
[0047]
Using such a pulse sequence, as shown in FIG. 8, 90 ° excitation is performed on slice A of object 1, 180 ° excitation is performed on slice B, and a spin echo generated from a straight line portion C where both slices intersect is detected. Read as navigator echo. The slices A and B are set so that the straight line portion C is substantially parallel to the body axis and is offset from the body axis and extends from the lung field to the abdomen.
[0048]
Note that 90 ° excitation may be performed for slice B and 180 ° excitation may be performed for slice A. The slices A and B are basically set at positions where navigator echoes can be appropriately acquired irrespective of slices for acquiring imaging echoes described later.
[0049]
Next, in step 603, profile creation is performed. Profile creation is performed by one-dimensional inverse Fourier transform of navigator echoes. As a result, a signal intensity distribution of spins on the straight line C, that is, a one-dimensional profile is obtained.
[0050]
Next, in step 605, profile display is performed. As a result, the profile is displayed on the display unit 180. Since the straight line C is set from the lung field to the abdomen, for example, a profile as shown in FIG. 9 is obtained. This profile is greatly different in signal intensity at the middle part. The portion with low signal intensity corresponds to the lung field, the portion with high signal intensity corresponds to the abdomen, and the intermediate portion corresponds to the diaphragm.
[0051]
A portion corresponding to the diaphragm reciprocates in the body axis direction with breathing. Hereinafter, a portion corresponding to the diaphragm is also simply referred to as a diaphragm. FIG. 10 shows the displacement of the diaphragm accompanying respiration. As shown in the figure, the diaphragm moves to the abdomen during inhalation and moves to the chest during exhalation.
[0052]
Next, in step 607, a phase determination point is set on the profile. The phase determination point is set by the user using the operation unit 190. Thereby, for example, one point on the body axis is set as the phase determination point P. The phase determination point P is set to a desired position between the maximum displacement position during inhalation of the diaphragm and the maximum displacement position during expiration.
[0053]
11 to 13 show three examples of setting the phase determination point P, respectively. FIG. 11 shows an example set closer to the expiration side. With this setting, the expiration phase is designated as the imaging phase. FIG. 12 shows an example set closer to the intake side. With this setting, the intake phase is designated as the imaging phase. FIG. 13 shows an example of setting between the expiration and the inspiration. This designates an intermediate phase between expiration and inspiration.
[0054]
The respiratory phase is determined based on whether or not the diaphragm is within a predetermined distance ± α centered on the phase determination point P. Hereinafter, this range is also referred to as a determination region. In the setting as shown in FIG. 11, as shown by the broken line, when the diaphragm is in the determination region, the expiration phase is determined.
[0055]
Whether the diaphragm is in the determination region is detected based on the shape of the profile in the determination region. The profile is easy to detect because the signal intensity varies greatly at the diaphragm. In the setting shown in FIG. 12, the expiration phase is determined when the diaphragm enters the determination region. In the setting shown in FIG. 13, it is determined as an intermediate phase between expiration and inspiration.
[0056]
Returning to FIG. 5, in step 505, navigator echo is acquired. Acquisition of the navigator echo is performed in the same manner as in step 601 in FIG. That is, it is acquired as a spin echo. Since the spin echo is generated by 90 ° excitation and 180 ° excitation, it is suitable as a navigator echo for obtaining a profile.
[0057]
Next, in step 507, profile creation is performed. The profile creation is performed using navigator echoes as in step 601 in FIG. As a result, a profile similar to the profile shown in FIG. 9 is obtained.
[0058]
Next, in step 511, it is determined whether or not the designated phase is reached. As described above, whether or not the phase is the designated phase is determined based on whether or not the diaphragm is included in the determination region.
[0059]
When the phase is the designated phase, imaging echo acquisition is performed in step 523. The acquisition of the imaging echo is performed by, for example, the pulse sequence shown in FIG. 3 or the pulse sequence shown in FIG. Note that the pulse sequence method of the gradient echo method shown in FIG. 4 is preferable in that an imaging echo, that is, a gradient echo can be obtained by one RF excitation. Imaging echo acquisition is performed for an appropriate number of views from one view to several views.
[0060]
Next, in step 525, it is determined whether or not all views have been acquired. If not, the process returns to step 505. Hereinafter, when the breathing phase matches the designated phase and not all views have been adopted, the operations in steps 505 to 525 are repeated. By such an operation, imaging echoes in the respiratory phase that matches the specified phase are sequentially acquired.
[0061]
If it is determined in step 511 that the phase is not the designated phase, it is determined in step 535 whether or not the mismatch frequency exceeds the limit. If it does not exceed the limit, the process returns to step 505. Thereafter, when the respiratory phase does not match the designated phase and the frequency does not exceed the limit, the operations in steps 505 to 535 are repeated. Thereby, during the phase mismatch, only navigator echoes are acquired and imaging echoes are not acquired.
[0062]
Due to the periodicity of breathing, phase mismatch occurs periodically. Therefore, an allowable limit is set for the frequency of mismatch. This limit is, for example, the number of mismatches within a certain time. Or it is good also as continuation time of mismatch.
[0063]
By repeating the operations of Steps 505 to 525 and the operations of Steps 505 to 535, an imaging echo in a period in which the respiratory phase matches the designated phase is acquired. Note that the number of mismatches or time measurement is reset every time the phases match.
[0064]
In the course of such an operation, the respiratory state may change due to sleep on the subject as time passes, and the profile may become as shown in FIG. 14 or FIG. 15, for example. FIG. 14 shows a state where the moving range of the diaphragm has moved to the intake side, and the determination region has relatively deviated from the moving range of the diaphragm. FIG. 15 shows a state in which the movement range of the diaphragm has moved to the expiration side, and the determination region has relatively deviated from the movement range of the diaphragm.
[0065]
In such a case, the diaphragm does not enter the determination region even though breathing continues, and therefore it is always determined that the phases do not match. For this reason, the number of mismatches or the mismatch time eventually exceeds the limit.
[0066]
If the limit is exceeded, phase decision point correction is performed at step 537. The correction of the phase determination point is automatically performed by the data processing unit 170. That is, for example, as shown in FIG. 16, the maximum displacement position p1 at the time of inhalation of the diaphragm and the maximum displacement position p2 at the time of expiration are based on a threshold value TH having an intermediate value between the signal intensity of the abdomen and the signal intensity of the lung field. Each is obtained, and a new phase determination point P ′ is determined between these two positions. Thereby, for example, the determination of the expiration phase can be resumed. For the determination of the inspiration phase and the determination of the intermediate phase between expiration and inspiration, a new phase determination point P ′ is determined as shown in FIGS.
[0067]
By correcting the phase determination point in this way, it is possible to correctly determine the phase regardless of the change in the respiratory state. Therefore, it is possible to acquire imaging echoes for all views in the respiratory phase that matches the specified phase.
[0068]
When all views have been acquired, image reconstruction is performed in step 527. Since all the imaging echoes are acquired at the designated phase, the reconstructed image is of high quality. The reconstructed image is displayed and stored at step 529.
[0069]
FIG. 19 shows a functional block diagram of this apparatus. As shown in the figure, the apparatus includes a navigator echo acquisition unit 702, a profile creation unit 704, a phase determination unit 706, an imaging echo acquisition unit 708, a determination point correction unit 710, and an image generation unit 712.
[0070]
The navigator echo acquisition unit 702 acquires navigator echoes and inputs them to the profile creation unit 704. The profile creation unit 704 creates a profile from the navigator echo and inputs it to the phase determination unit 706. The phase determination unit 706 determines the respiratory phase from the profile, and inputs the determination result to the imaging echo acquisition unit 708 and the determination point correction unit 710. The determination point correction unit 710 corrects the phase determination point of the phase determination unit 706 when the frequency of phase mismatch exceeds the limit.
[0071]
The imaging echo acquisition unit 708 acquires an imaging echo having a predetermined phase based on the phase determination result and inputs the acquired imaging echo to the image generation unit 712. The image generation unit 712 generates an image based on the input imaging echo.
[0072]
The navigator echo acquisition unit 702 corresponds to the function of step 505 in the flowchart of FIG. The navigator echo acquisition unit 702 is an example of an embodiment of navigator echo acquisition means in the present invention. The profile creation unit 704 corresponds to the function of step 507 in the flowchart of FIG. The profile creation unit 704 is an example of an embodiment of creation means in the present invention.
[0073]
The phase determination unit 706 corresponds to the function of step 511 in the flowchart of FIG. The phase determination unit 706 is an example of an embodiment of determination means in the present invention. The imaging echo acquisition unit 708 corresponds to the function of step 523 in the flowchart of FIG. The imaging echo acquisition unit 708 is an example of an embodiment of the imaging echo acquisition means in the present invention.
[0074]
The decision point correction unit 710 corresponds to the functions of steps 535 and 537 in the flowchart of FIG. The determination point correction unit 710 is an example of an embodiment of the correction means in the present invention. The image generation unit 712 corresponds to the function of step 527 in the flowchart of FIG. The image generation unit 712 is an example of an embodiment of generation means in the present invention.
[0075]
FIG. 20 shows a flowchart of another operation of the present apparatus. In this figure, the same operations as those shown in FIG. As shown in the figure, navigator echoes and imaging echoes are acquired in step 505 ′. Acquisition of the navigator echo is performed in the same manner as in step 601 in FIG. The acquisition of the imaging echo is performed by, for example, the pulse sequence shown in FIG. 3 or the pulse sequence shown in FIG.
[0076]
FIG. 21 shows a time chart for acquiring navigator echoes and imaging echoes. As shown in the figure, a navigator echo is first acquired, and then an imaging echo is acquired. Such echo acquisition is repeated periodically. Thereby, for example, imaging echoes of 64 to 512 views are sequentially acquired. A plurality of imaging echoes may be acquired each time one navigator echo is acquired.
[0077]
In this way, when the imaging echo acquired as a pair with the navigator echo matches the designated phase according to the phase determination at step 511, the imaging echo is adopted at step 523 ′, and when it does not match, the step is adopted. At 533, the imaging echo is not adopted.
[0078]
By such an operation, among the imaging echoes acquired in step 505 ′, the imaging echo acquired at the respiratory phase that matches the specified phase is adopted as a signal for image reconstruction and acquired at the respiratory phase that does not match the specified phase. Things are not adopted. Note that the imaging echoes of the views that have not been adopted are reacquired together with the navigator echoes.
[0079]
If not adopted, i.e., phase mismatch, it is determined in step 525 whether or not the mismatch frequency has exceeded the limit, and if not exceeded, the process returns to step 505 ′. The phase determination point is corrected. The phase determination point correction is performed in the same manner as described above. As a result, it is possible to continue imaging at a predetermined phase regardless of the change in the respiratory state, and it is possible to acquire data of all views at a specified phase in combination with re-acquisition of imaging echoes of views that have not been adopted.
[0080]
FIG. 22 shows a functional block diagram of this apparatus. As shown in the figure, the apparatus includes a signal acquisition unit 702 ′, a profile creation unit 704, a phase determination unit 706, a signal adoption unit 708 ′, a determination point correction unit 710 ′, and an image generation unit 712. In the figure, the same parts as those shown in FIG.
[0081]
The signal acquisition unit 702 ′ acquires navigator echoes and imaging echoes, inputs the navigator echoes to the profile creation unit 704, and inputs the imaging echoes to the signal adoption unit 708 ′.
[0082]
The profile creation unit 704 creates a profile from the navigator echo and inputs it to the phase determination unit 706. The phase determination unit 706 determines the respiratory phase from the profile, and inputs the determination result to the signal adoption unit 708 ′ and the determination point correction unit 710.
[0083]
The signal adopting unit 708 ′ determines whether or not to adopt the imaging echo according to the respiratory phase, and inputs the adopted imaging echo to the image generating unit 712. The determination point correction unit 710 ′ corrects the phase determination point of the phase determination unit 706 when the frequency of phase mismatch exceeds the limit. The image generation unit 712 generates an image based on the adopted imaging echo.
[0084]
The signal acquisition unit 702 ′ corresponds to the function of step 505 ′ in the flowchart of FIG. The signal acquisition unit 702 ′ is an example of an embodiment of acquisition means in the present invention. The profile creation unit 704 corresponds to the function of step 507 in the flowchart of FIG. The profile creation unit 704 is an example of an embodiment of creation means in the present invention.
[0085]
The phase determination unit 706 corresponds to the function of step 511 in the flowchart of FIG. The phase determination unit 706 is an example of an embodiment of determination means in the present invention. The signal adoption unit 708 ′ corresponds to the functions of steps 523 ′ and 533 in the flowchart of FIG. The signal adopting unit 708 ′ is an example of an embodiment of the adopting means in the present invention.
[0086]
The determination point correction unit 710 ′ corresponds to the function of steps 525 and 537 in the flowchart of FIG. The determination point correction unit 710 ′ is an example of an embodiment of correction means in the present invention. The image generation unit 712 corresponds to the function of step 527 in the flowchart of FIG. The image generation unit 712 is an example of an embodiment of generation means in the present invention.
[0087]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to realize a magnetic resonance imaging apparatus that performs correct imaging regardless of changes in the respiratory state.
[Brief description of the drawings]
FIG. 1 is a block diagram of an exemplary apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram of an exemplary apparatus according to an embodiment of the present invention.
FIG. 3 is a diagram showing an example of a pulse sequence executed by an example apparatus according to an embodiment of the present invention.
FIG. 4 is a diagram showing an example of a pulse sequence executed by an example apparatus according to an embodiment of the present invention.
FIG. 5 is a flowchart of the operation of the apparatus according to the embodiment of the present invention.
6 is a detailed view of a portion of the flow diagram of FIG.
FIG. 7 is a diagram showing an example of a pulse sequence for navigator echo acquisition.
FIG. 8 is a diagram illustrating an example of slice selection for navigator echo acquisition;
FIG. 9 is a diagram showing a profile.
FIG. 10 is a diagram showing a profile.
FIG. 11 is a diagram illustrating an example of phase determination point setting.
FIG. 12 is a diagram illustrating an example of phase determination point setting.
FIG. 13 is a diagram illustrating an example of phase determination point setting.
FIG. 14 is a diagram showing a relative shift of phase determination points.
FIG. 15 is a diagram showing a relative shift of phase determination points.
FIG. 16 is a diagram illustrating correction of a phase determination point.
FIG. 17 is a diagram illustrating correction of a phase determination point.
FIG. 18 is a diagram illustrating correction of a phase determination point.
FIG. 19 is a functional block diagram of an exemplary apparatus according to an embodiment of the present invention.
FIG. 20 is a flowchart of the operation of the apparatus according to the example of the embodiment of the present invention.
FIG. 21 is a diagram illustrating a time chart of acquisition of navigator echoes and imaging echoes.
FIG. 22 is a functional block diagram of an exemplary apparatus according to an embodiment of the present invention.
[Explanation of symbols]
1 Target 100, 100 'Magnet system 102 Main magnetic field coil unit 102' Main magnetic field magnet unit 106, 106 'Gradient coil unit 108, 108' RF coil unit 130 Gradient drive unit 140 RF drive unit 150 Data collection unit 160 Sequence control unit 170 Data processing unit 180 Display unit 190 Operation unit 500 Cradle 702 Navigator echo acquisition unit 704 Profile creation unit 706 Phase determination unit 708 Imaging echo acquisition unit 710, 710 ′ Determination point correction unit 712 Image generation unit 702 ′ Signal acquisition unit 708 ′ Signal adoption Part

Claims (9)

Navigator echo acquisition means for repeatedly acquiring navigator echo from the subject of shooting;
Creating means for creating a target profile based on the navigator echo;
Determining means for determining whether or not the breathing phase of the subject matches a predetermined phase based on the signal intensity of the profile at a predetermined location;
Correction means for correcting the determination location of the determination means when the frequency at which the respiratory phase does not match a predetermined phase exceeds a predetermined limit;
An imaging echo acquisition means for acquiring an imaging echo in a predetermined respiratory phase from an imaging target based on the determination;
Generating means for generating an image based on the imaging echo;
A magnetic resonance imaging apparatus comprising: An acquisition means for repeatedly acquiring navigator echoes and imaging echoes;
Creating means for creating a target profile based on the navigator echo;
Determining means for determining whether or not the breathing phase of the subject matches a predetermined phase based on the signal intensity of the profile at a predetermined location;
Correction means for correcting the determination location of the determination means when the frequency at which the respiratory phase does not match a predetermined phase exceeds a predetermined limit;
Adopting means for adopting an imaging echo in a predetermined respiratory phase among the imaging echoes based on the determination;
Generating means for generating an image based on the employed imaging echo;
A magnetic resonance imaging apparatus comprising: The navigator echo is a spin echo,
3. The magnetic resonance imaging apparatus according to claim 1, wherein the magnetic resonance imaging apparatus is a magnetic resonance imaging apparatus. The imaging echo is a gradient echo,
The magnetic resonance imaging apparatus according to claim 1, wherein the magnetic resonance imaging apparatus is a magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus according to claim 1, wherein the profile is a one-dimensional profile in a body axis direction. The predetermined phase is an expiration phase;
6. The magnetic resonance imaging apparatus according to claim 1, wherein the magnetic resonance imaging apparatus is a magnetic resonance imaging apparatus. The predetermined phase is an intake phase;
6. The magnetic resonance imaging apparatus according to claim 1, wherein the magnetic resonance imaging apparatus is a magnetic resonance imaging apparatus. The frequency is the number of times the breathing phase does not match a predetermined phase.
The magnetic resonance imaging apparatus according to claim 1, wherein the magnetic resonance imaging apparatus is a magnetic resonance imaging apparatus. The frequency is the time when the respiratory phase does not match a predetermined phase,
The magnetic resonance imaging apparatus according to claim 1, wherein the magnetic resonance imaging apparatus is a magnetic resonance imaging apparatus.

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