JP4862069B2 - Magnetic resonance diagnostic equipment - Google Patents

Description

  The present invention relates to a magnetic resonance diagnostic apparatus that obtains an MR spectrum as functional information of a living body by utilizing a magnetic resonance phenomenon.

  A magnetic resonance imaging (MRI) apparatus that is currently widely used acquires an image that reflects the concentration distribution of hydrogen nuclei in a subject (mainly contained in water molecules). Therefore, in this MRI apparatus, even if the intensity ratio in the concentration distribution of metabolites such as choline, creatine, NAA, and fat changes due to tumor, bleeding, etc., information on this tumor, bleeding, etc. cannot be obtained.

  On the other hand, a magnetic resonance spectroscopy (MRS) apparatus has been developed that can visually grasp the concentration distribution of metabolites (choline, creatine, NAA, fat, etc.) that cannot be obtained by MRI images using a complex spectrum. ing. MRS is a method for separating signals for each molecule by using a difference (chemical shift) in magnetic resonance frequency due to a difference in chemical bonding of various molecules. This chemical shift occurs because substances having different environments such as surrounding electrons even in the same nuclide sense a slightly different static magnetic field, and thus have different resonance frequencies.

  FIG. 11A shows a general MRI image, and FIG. 11B shows an MR spectrum in a region of interest (ROI) in the MRI image. By acquiring spectra of a large number of pixels simultaneously from these MRI images and MR spectra and imaging each molecule, it is possible to visually grasp the concentration distribution for each metabolite.

  Usually, when an MRI image is first displayed as an image for positioning the region of interest, and then the operator sets the region of interest 100 on the MRI image, the MR spectrum in this region of interest is displayed.

Here, in ¹ H spectroscopy, metabolites of interest (NAA, creatine, choline, lactic acid, etc.) are present approximately between the chemical shifts of water and fat, and water and fat are metabolites such as lactic acid. The signal value (signal strength) is extremely large compared to. Therefore, when water and fat signals are mixed, the peaks of lactic acid etc. are hidden and cannot be seen, or distortion is caused by the baseline of these large spectra and quantitative evaluation cannot be performed. End up. Therefore, in order to solve this problem, a method of suppressing the water signal existing in most tissues by presaturating with a frequency selective excitation pulse is usually taken.

  However, the spectral peak of lactic acid or the like to be observed exists in almost the same frequency region as the chemical shift of fat. For this reason, if the fat signal is suppressed by presaturating in the same manner as the water signal, the lactic acid signal to be observed is also suppressed together. As described above, since fat signals cannot be pre-saturated, it is necessary to set the region of interest so as not to include fat tissue as much as possible.

  However, since the region of interest displayed on the positioning image (MRI image) is based on a water signal existing in most tissues, even if the region of interest is set so as not to include adipose tissue, it is actually of interest. There is a risk of including a region containing a lot of adipose tissue in the region. This will be described in detail below.

  In general, in MRS, there are a case where one specific region is targeted and a case where spectra of a large number of pixels (voxels) are simultaneously acquired and imaged for each molecule. The former is called region selection spectroscopy or single-voxel spectroscopy. The latter is called multi-voxel spectroscopy (MRSI), magnetic resonance spectroscopy imaging (CSI), or chemical shift imaging (CSI).

  Here, in the single voxel spectroscopy, in order to limit the region where the MR signal is generated to the region of interest, a pulsed linear gradient magnetic field and a high-frequency magnetic field having a specific center frequency and band are combined to obtain this frequency. In many cases, a method of selectively exciting a corresponding region (referred to as “selective excitation method”) is used. Therefore, FIG. 12 shows a pulse sequence of region selection spectroscopy. As shown in FIG. 12, in region selection spectroscopy, gradient magnetic fields (Gx, Gy, Gz) in three directions orthogonal to X, Y, and Z are respectively applied to high-frequency pulses (RF pulses) of 90 °, 180 °, and 180 °. ) To obtain a 2nd spin echo from a rectangular parallelepiped region. This selective excitation method is the same as the method used for slice plane selection in general MRI.

On the other hand, in MRSI, spatial identification is basically performed by phase encoding and Fourier transform. In ¹ H spectroscopy, the same as in the case of region selection spectroscopy described above, in order to prevent aliasing of surrounding fat tissue signals. In some cases, the selective excitation methods are combined. FIG. 13 shows the MRSI pulse sequence. This is a spatial 2D pulse sequence combining the selective excitation method and phase encoding.

  However, when the selective excitation method such as single voxel spectroscopy or MRSI is used, a problem may occur when a region of interest is set on a positioning image. That is, since different metabolites resonate at a slightly shifted frequency due to chemical shift, MR signals of the respective metabolites are generated from different regions corresponding to the chemical shift. This will be specifically described below.

Now, in addition to the main magnetic field B ₀ is applied a linear gradient G _X in the X direction of the space, the resonant frequency F of the metabolites of a chemical shift σ at that time, when the gyromagnetic ratio and gamma, (1) formula become that way.
[Equation 1]
F = (γ / 2π) (1-σ) (B ₀ + G _X · X)
= (Γ / 2π) B ₀ + (γ / 2π) G _X · X
-(Γ / 2π) σB _0- (γ / 2π) σG _X · X (1)

Here, the fourth term is sufficiently smaller than the other terms and can be ignored. Therefore, the frequency f observed after setting the center frequency to (γ / 2π) B ₀ and detecting is expressed by the equation (2).
[Equation 2]
_{f = (γ / 2π) (} G X · X-σB 0) ...... (2)

Therefore, using this equation (2), the relationship shown in FIG. 14 is established when the chemical shift is expressed by the resonance frequencies of the two metabolites A and B of σ _A and σ _B , respectively, and the excited region. That is, MR signals excited from the metabolites A and B are generated from different regions with a shift corresponding to the chemical shift.

  Further, an example will be given of how much this area shift is on the actual MRI screen.

The selective excitation RF pulse band is Δf, the gradient magnetic field strength is G, the size of one side of the region of interest is L, the chemical shift between water and fat is σ, the resonance frequency of the target nuclide is f ₀ , and the water and fat are misaligned. When D is D, it is expressed as shown in equations (3) and (4).
[Equation 3]
G = Δf / L (3)
[Equation 4]
D = (σ · f ₀ ) / G (4)

  Here, considering the case where it is necessary to increase the value of Δf, in order to obtain the same flip angle, it is necessary to increase the peak value of RF, so the performance of hardware that outputs RF pulses, the human body is irradiated. It is limited by the upper limit of the RF power and the withstand voltage of the RF coil. Accordingly, the value of Δf cannot be increased unnecessarily.

Consider the case of region selection spectroscopy in which the RF pulse band is 2000 [Hz]. When the voxel size is 2 [cm] per side, the gradient magnetic field strength to be added is 2000/2 = 1000 [Hz / cm] from the above equation (3). The chemical shift between water and fat is about 3.5 [ppm], and the Larmor frequency at a static magnetic field strength of 1.5 [T] is 63.9 × 10 ⁶ [Hz]. The resonance frequency at T] is 3.5 × 10 ⁻⁶ × 63.9 × 10 ⁶ = 224 [Hz]. Accordingly, the displacement between the positions of water and fat is 224/1000 = 0.22 [cm] from the equation (4).

  Next, consider the case of MRSI. In this method, it is necessary to selectively excite a wide region including a plurality of voxels as compared with the case of single voxel spectroscopy. However, for the above reason, it is practically difficult to widen the band of the high-frequency pulse in accordance with this, and therefore, a method of actually reducing the intensity of the gradient magnetic field pulse has been taken. Here, if the selected region of MRSI is 8 [cm] per side, the strength of the gradient magnetic field is ¼ that in the above case, so that the misalignment between the water signal and the fat signal is 0.9 [cm It also becomes. That is, when the maximum output amplitude of the RF pulse is constant, the chemical shift position shift increases as the slice thickness increases.

  However, the region of interest displayed on the positioning image is based on the water signal present in most tissues as described above. For this reason, when the position where the water signal and the fat signal are excited as described above is shifted, the operator intends to set the region of interest while avoiding the region containing a lot of fat tissue. A region including many is included in the region of interest. As a result, surrounding adipose tissue is excited and mixed in MR spectrum data. In particular, as described above, in the case of MRSI, the displacement between the position of water and fat is as high as 0.9 [cm], and therefore this displacement is ignored when positioning the region of interest on the MRI image. I can't. Here, how much the positional deviation actually becomes will be described by taking a human head as an example.

  FIG. 15 shows an MRI image (positioning image) of the human head. The adipose tissue 103 of the head exists mainly under the scalp. Therefore, the operator needs to locate the region of interest while avoiding the adipose tissue 103. However, as shown by the solid line 101, even if the operator intends to locate the region of interest while avoiding the fat tissue 103, the position of the region where the water signal and the fat signal are excited is shifted as described above. Indicates that the region indicated by the dotted line 102 has been positioned. In this case, since the fat tissue is excited and mixed in the spectrum data, it is meaningless to position the fat tissue away from the fat tissue.

  By the way, the direction in which the position shift of the region where the fat signal is excited with respect to the water signal occurs depends on the polarity of the gradient magnetic field at the time of selective excitation. That is, as shown in FIG. 16A, when a gradient magnetic field in the positive direction is applied to the coordinate axis of the system, the region where fat is excited always shifts in the positive direction of the coordinate axis of the system. On the other hand, as shown in FIG. 16B, when the polarity of the gradient magnetic field is reversed, the system shifts in the negative direction of the coordinate axis of the system. However, in the positioning operation using an actual MRI image, the operator cannot know the polarity to which the gradient magnetic field is applied, and therefore cannot know the region where fat is excited.

  From the above, in the conventional MRS apparatus, even if the operator knows the fact that the position of the region where the fat signal is excited shifts with respect to the water signal, how much (in which direction and how much) it shifts. Since the fat tissue around the region of interest is excited and mixed in a large amount of MR spectrum data, the concentration distribution of metabolites other than water and fat cannot be clearly grasped visually. There was a problem that there was a case.

  The present invention has been made in view of the above-described circumstances. When a region of interest is set on a positioning image (MRI image) in order to obtain an MR spectrum, the set region of interest includes a portion containing a large amount of adipose tissue. The purpose of this is to make it possible to visually grasp the concentration distribution of metabolites other than water and fat so as not to contain as much as possible.

  In order to solve the above problems, the invention according to claim 1 of the present invention relates to the polarity of a gradient magnetic field in a magnetic resonance diagnostic apparatus capable of displaying spectral data indicating the concentration distribution of each metabolite in a region of interest. Setting means for setting information by an operator, information indicating the region of interest, and information indicating a region where fat is excited based on information regarding the polarity of the set gradient magnetic field are displayed on the positioning image. And a display means for making it possible.

  Here, the region where fat is excited may be displayed separately from the set region of interest, and the display mode (for example, line, figure, symbol) of the region where fat is excited and the set region of interest is set. , Patterns, colors, etc.) may be the same. Further, the area where fat is excited may be blinked and displayed. Furthermore, the region where fat is excited and the set region of interest may be displayed separately on different display screens.

  According to a second aspect of the present invention, the display means displays, on the positioning image, information indicating a region where the fat is excited based on a shift amount of the region where the fat is excited with respect to water in the region of interest. It is characterized by being displayed.

  Furthermore, the invention according to claim 3 is characterized in that the positioning image is an MRI image.

  Furthermore, the invention according to claim 4 is a magnetic resonance diagnostic apparatus capable of displaying spectral data indicating a concentration distribution for each metabolite in a region of interest, and a setting means for setting the region of interest; An MRI image includes information indicating a region where fat is excited when water is excited in the region, a region of interest set by the setting unit, and a region where fat is determined determined by the calculation unit. It is characterized by comprising display means for displaying above.

On the other hand, in order to solve the above-mentioned problems, the invention according to claim 5 is a region of interest by controlling each part of the magnetic resonance diagnostic apparatus based on information inputted from the input means. In the magnetic resonance spectroscopic imaging method for displaying spectral data indicating the concentration distribution for each metabolite in the display means, a positioning image is displayed on the display means, and on the positioning screen based on information input from the input means Information on the polarity of the region of interest is set and displayed on the display means, and information indicating the region of interest and information indicating a region where fat is excited based on the set information on the polarity of the gradient magnetic field are positioned. A magnetic resonance spectroscopy imaging method characterized by displaying on an image.

The invention according to claim 6 displays spectral data indicating the concentration distribution of each metabolite in the region of interest by controlling each part of the magnetic resonance diagnostic apparatus based on information input from the input means. In the magnetic resonance spectroscopy imaging method displayed on the means, a positioning image is displayed on the display means, the region of interest is displayed on the display means based on information input from the input means, and water is excited in the region of interest. A magnetic resonance spectroscopic imaging method comprising: calculating a first fat excitation region where fat is excited when displayed, and displaying the first fat excitation region on the positioning image.

Further, in the invention according to claim 7 , when the information for reversing the polarity of the gradient magnetic field is received following the step of displaying the first fat excitation region on the positioning image, water in the region of interest A magnetic resonance spectroscopic imaging method comprising: calculating a second fat excitation region where fat is excited when excited, and displaying the second fat excitation region on the positioning image.

The invention according to claim 8 collects the spectrum data using a gradient magnetic field having a polarity for exciting the second fat excitation region, and displays the collected spectrum data on the display means. This is a magnetic resonance spectroscopy imaging method.

On the other hand, in order to solve the above-mentioned problem, among the present inventions, the invention according to claim 9 is a magnetic resonance diagnostic apparatus capable of displaying spectral data indicating a concentration distribution for each metabolite in a region of interest. The setting means for the operator to set information on the polarity of the information, the information indicating the region of interest, and the information indicating the chemical shift based on the information on the polarity of the set gradient magnetic field are displayed on the positioning image. And a display means.

  According to the magnetic resonance diagnostic apparatus of the present invention, when the region of interest for obtaining the MRS image is positioned and the information regarding the polarity of the gradient magnetic field is changed, the fat region follows, and the set region of interest represents the fat tissue. Since it is possible to avoid as many portions as possible, the concentration distribution of metabolites other than water and fat can be clearly seen visually.

The functional block diagram which shows an example of a structure of the MRS apparatus which concerns on embodiment of this invention. The figure which shows the positioning image (MRI image) of the MRS apparatus which concerns on embodiment of this invention. The flowchart until the setting of the region of interest which is the characteristic part of the 1st Embodiment of this invention is completed. The figure which showed the predefined gradient magnetic field polarity which is the characteristic part of the 2nd Embodiment of this invention. The flowchart until the setting of the region of interest which is the characteristic part of the 2nd Embodiment of this invention is completed. The figure which shows the positioning image (MRI image) used as a premise explaining the 3rd Embodiment of this invention. The figure which shows the positioning image (MRI image) used as a premise explaining the 3rd Embodiment of this invention. The flowchart until the setting of the region of interest which is the characteristic part of the 3rd Embodiment of this invention is completed. The flowchart until the setting of the region of interest which is the characteristic part of the 4th Embodiment of this invention is completed. The flowchart until the setting of the region of interest which is the characteristic part of the 5th Embodiment of this invention is completed. The figure which shows a general MRI image and MR spectrum. The figure which shows the pulse sequence of the single voxel spectroscopy used conventionally. The figure which shows the pulse sequence of MRSI method of the space 2D (two dimensions) which combined the selective excitation method and phase encoding conventionally used. The figure which shows the shift | offset | difference of the slice position by a chemical shift. The figure which shows the conventional positioning image (The dotted-line square 102 is not actually displayed). The figure which shows the shift | offset | difference of the slice position by the difference in the polarity of the gradient magnetic field in the case of selective excitation.

[First Embodiment]
A first embodiment of the present invention will be described below mainly based on FIGS. FIG. 1 is a schematic diagram of an MRS apparatus according to an embodiment to which the present invention is applied. This MRS apparatus includes a bed unit on which a patient P as a subject is placed, a static magnetic field generation unit for generating a static magnetic field, a gradient magnetic field generation unit for adding position information to the static magnetic field, and transmission and reception for transmitting and receiving RF signals. Functionally includes a control unit, a control / computation unit responsible for overall system control and image reconstruction, and an electrocardiogram measurement unit that measures an ECG (electrocardiogram) signal as a signal representing the cardiac phase of the patient P .

The static magnetic field generation unit includes, for example, a superconducting magnet 1 and a static magnetic field power supply 2 that supplies current to the magnet 1, and a longitudinal axis of a cylindrical opening (diagnostic space) into which the subject P is loosely inserted. generating a static magnetic field H ₀ in the direction (Z axis direction). In addition, the shim coil 14 is provided in this magnet part. The shim coil 14 is supplied with a current for homogenizing the static magnetic field from the shim coil power supply 15 under the control of the host computer 6 described later. The couch portion can removably insert the top plate on which the subject P is placed into the opening of the magnet 1.

  The gradient magnetic field generator includes a gradient magnetic field coil unit 3 incorporated in the magnet 1. The gradient coil unit 3 includes three sets (types) of x, y, and z coils 3x to 3z for generating gradient magnetic fields in the X, Y, and Z axis directions orthogonal to each other. The gradient magnetic field unit further includes a gradient magnetic field power supply 4 that supplies current to the x, y, z coils 3x to 3z. This gradient magnetic field power supply 4 supplies a pulse current for generating a gradient magnetic field to the x, y, z coils 3x to 3z under the control of a sequencer described later.

By controlling the pulse current supplied from the gradient magnetic field power source 4 to the x, y, z coils 3x to 3z, the gradient magnetic fields in the three-axis X, Y, Z directions are synthesized, and the slice gradient along the Z axis Each direction of the magnetic field, the first phase encoding gradient magnetic field along the X axis, and the second phase encoding gradient magnetic field along the Y axis direction can be arbitrarily set and changed. Slice direction, gradient magnetic fields of the first and second phase-encoding direction is superimposed on the static magnetic field H _0.

  The transmission / reception unit includes an RF coil 7 disposed in the vicinity of the patient P in the imaging space in the magnet 1, and a transmitter 8T and a receiver 8R connected to the RF coil 7. Under the control of a sequencer described later, the transmitter 8T supplies an RF current pulse having a Larmor frequency for exciting magnetic resonance (NMR) to the RF coil 7, while the receiver 8R receives the RF coil 7. The received MR signal (high frequency signal) is received, and various received signal processing is performed on the received signal to form corresponding digital data.

  The control / arithmetic unit further includes a sequencer (also referred to as a “sequence controller”) 5, a host computer 6, an arithmetic unit 10, a storage unit 11, a display device 12, and an input device 13. Among these, the host computer 6 has a function of commanding the pulse sequence information to the sequencer 5 according to the stored software procedure and overseeing the operation of the entire apparatus including the sequencer 5.

  The sequencer 5 includes a CPU and a memory, stores pulse sequence information sent from the host computer 6, and controls a series of operations of the gradient magnetic field power source 4, the transmitter 8T, and the receiver 8R according to this information. . Here, the pulse sequence information is all information necessary for operating the gradient magnetic field power source 4, the transmitter 8T, and the receiver 8R according to a series of pulse sequences, for example, x, y, z coils 3x to 3z. Includes information on the intensity, application time, application timing, and the like of the pulse current applied to. In addition, the sequencer 5 inputs digital data (MR signal) output from the receiver 8 </ b> R and transfers this data to the arithmetic unit 10.

  The arithmetic unit 10 inputs the digital data of the MR signal sent from the receiver 8R through the sequencer 5 and inputs the original data (also referred to as “raw data”) to the Fourier space (also referred to as k space or frequency space). And a two-dimensional or three-dimensional Fourier transform process for reconstructing the original data into a real space image, while performing an image data synthesis process. This image data is transmitted to the display 12 and displayed as an MRI image or an MRS image. The Fourier transform process may be assigned to the host computer 6.

  In addition to the above-described functions, the arithmetic unit 10 has the following as functions that bear the features of the present invention. That is, the arithmetic unit 10 can recognize the position on the MRI image of the region of interest (region where the water signal is excited) set by the input unit 13. Further, based on the above equations (3) and (4), the shift amount of the region where the fat signal is excited with respect to the water signal is calculated, and the fat is excited on the MRI image separately from the region of interest. A region (for example, an outer frame of the region is indicated by a dotted line) can be displayed. Furthermore, when the operator changes the setting of the size or position of the region of interest using the input device 13, the region excited with fat can also be changed and displayed.

  The input device 13 can input information such as parameter information for selecting the synchronization timing desired by the operator, scan conditions, pulse sequences, image composition methods, and the like to the host computer 6.

  The storage unit 11 can store not only the original data and the reconstructed image data but also the image data that has been subjected to the above-described combining process. The storage unit 11 stores a program for executing an algorithm described later, and is read and executed by the arithmetic unit 10.

  When obtaining an MRI image, the x, y and z coils 3x to 3z are used to generate a slice direction gradient magnetic field, a phase encode direction gradient magnetic field, and a readout direction (frequency encode direction) gradient magnetic field, respectively.

  Subsequently, the operation of the MRS apparatus in the present embodiment will be described mainly with reference to FIGS.

  First, before displaying the MR spectrum, it is necessary to display a positioning image (MRI image) of the region of interest on the display 12. Since the pulse sequence for displaying the MRI image has been conventionally used as disclosed in Japanese Patent Application Laid-Open No. 4-227232 and the like, description thereof is omitted here.

This pulse sequence, x, y, z coils 3x~3z overlaps each slice direction gradient magnetic field, a phase encode direction gradient magnetic field, a readout direction (frequency encode direction) gradient magnetic field on the static magnetic field H _0. During this time, the RF pulse is applied from the RF coil 7 to the patient P by the RF current pulse supplied from the transmitter 8T to excite magnetic resonance. On the other hand, the receiver 8R receives the excited MR signal and performs various signal processing on the received signal to form corresponding digital data. This digital data is sent to the arithmetic unit 10 via the sequencer 5.

  The arithmetic unit 10 performs the two-dimensional or three-dimensional Fourier transform processing for reconstructing the original data in the Fourier space and reconstructing the original data into a real space image, while performing the image data synthesis processing. The image data that has been combined by the arithmetic unit 10 is displayed on the display 12 as an MRI image.

  Next, the region-of-interest positioning operation, which is a feature of the present invention, is started. This positioning operation is performed by the following processing based on the algorithm shown in FIG. In this embodiment, an MRI image of the human head is used as an example of the positioning image.

  First, as shown in FIG. 2, when an operator sets a region of interest (solid square 21) on the positioning image using the input device 13 (step S1), what is the solid rectangle 21 representing the region of interest? Separately, a region where fat is excited is represented by a dotted square 22 (step S2). Thereby, the operator can recognize whether the area | region where fat is excited includes the scalp part 23 or not.

  Here, when the dotted rectangle 22 is displayed so as to include the scalp portion 23 (step S3), the operator again determines the region of interest so that the dotted rectangle 22 does not include the scalp portion 23. Is set again (step S4), and the setting of the region of interest is completed. On the other hand, when the dotted rectangle 22 does not include the scalp portion 23 (step S3), the setting of the region of interest is completed at this point.

  When the setting of the region of interest is completed, the operator performs an operation for displaying the MR spectrum by the input device 13. This operation is performed, for example, by pressing a switch (not shown) provided in the input device 13. As a result, the MR spectrum is displayed on the display 13 based on the pulse sequence shown in FIGS.

  As described above, in this embodiment, when an operator sets a region of interest (a region where water is excited) on an MRI image, it is possible to simultaneously display a region where fat is excited. Therefore, even if the region where fat is excited includes a portion containing a lot of fat in the human body, the operator can easily make the region of interest so that the region where fat is excited does not include a portion containing a lot of fat tissue. Can be set again. As a result, the adipose tissue can be prevented from being excited and mixed in the MR spectrum data, and the concentration distribution of metabolites other than water and fat can be clearly grasped visually.

  In the above example, only the two directions X and Y are displayed. However, the present invention is not limited to this. In the case where a sagittal section or a coronal section is displayed as an MRI image, a region where a fat signal is excited. Similarly, in the Z direction, fat-excited regions are displayed at the same time.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described mainly based on FIG. 1, FIG. 4, and FIG. Here, the present embodiment is the same as the first embodiment except for the function of displaying the region where fat is excited, which is a characteristic part of the first embodiment. The description will be omitted using reference numerals.

  As described above in the section of “Prior Art”, the direction in which the fat position shift occurs with respect to water depends on the polarity of the gradient magnetic field at the time of selective excitation, but an actual MRI image is used. When performing the positioning operation, the operator cannot know the polarity to which the gradient magnetic field is applied. Therefore, the operator cannot know in which direction the region where fat is excited is located with respect to the region of interest.

However, the main target of ¹ H spectroscopy is the brain, and fat in the head to avoid contamination is mainly present in the scalp, that is, in the periphery of the region of interest (in the direction outward from the center of the static magnetic field). I know that.

  Therefore, in the present embodiment, based on this known fact, the polarity of the gradient magnetic field is automatically set with a predetermined setting according to a certain rule as shown below, and the polarity of the gradient magnetic field (magnetic field gradient) is automatically set. This is a function in which a function for changing (positive / negative) is added to the arithmetic unit 10. For convenience of explanation, only one dimension in the X direction will be described below.

Assuming that the magnetic field strength at position X is B _X , the static magnetic field strength is B 0, and the X coordinate of the center of the region of interest is X _R , the predefined definitions according to a certain rule are expressed by equations (5) and (6). The
[Equation 5]
B _X = B ₀ −G _X · X (X _R ≧ 0) (5)
B _X = B ₀ + G _X · X (X _R <0) (6)

The (5) and (6), for example, as shown in FIG. 4 (a), the center X _R in the region of interest, with respect to the center of the magnet 1, when in the positive side of the X coordinate axis of the system The sequencer 5 outputs a pulse that gives a negative magnetic field gradient. That is, a pulse having a polarity with which the static magnetic field strength decreases with increasing spatially in the positive direction of the X coordinate is output. On the other hand, as shown in FIG. 4 (b), the center X _R in the region of interest, with respect to the center of the magnet 1, when in the negative side of the X coordinate axis of the system, to provide a positive magnetic field gradient from the sequencer 5 Output a simple pulse. That is, a pulse having a polarity in which the static magnetic field strength increases with respect to the increase in the positive direction of the X coordinate spatially is output.

  Needless to say, the Y direction and the Z direction have the same predefined settings as the X direction.

  Next, the operation of this embodiment will be described with reference to FIG. Since the operation up to the positioning of the region of interest is the same as that of the first embodiment, the description thereof will be omitted and the region of interest positioning operation will be described. This positioning operation is performed by the following processing based on the algorithm shown in FIG.

First, the operator sets a region of interest on the positioning image using the input device 13 (step S11). Then, the arithmetic unit 10, or the center X _R of the set region of interest is in or the negative side is the positive side of the X coordinate axis of the system with respect to the center of the magnet 1 is determined (step S12). The arithmetic unit 10, the center X _R in the region of interest, if it is determined that the positive side of the X coordinate axis of the system with respect to the center of the magnet 1, the gradient magnetic field provided by the transmitter 8T is negative magnetic field It changes so that it may become polarity (step S13). On the other hand, the arithmetic unit 10, the center X _R in the region of interest, if it is determined that the negative side of the X coordinate axis of the system with respect to the center of the magnet 1, the gradient magnetic field provided by the transmitter 8T is positive (Step S14). Thereby, the setting of the region of interest is completed. Since the subsequent steps are the same as those in the first embodiment, description thereof is omitted.

  As described above, in the present embodiment, the positive and negative magnetic field gradients are changed according to the set position of the region of interest on the positioning image, so that the region where fat is excited is excited by water. The region always shifts toward the center of the static magnetic field. As a result, the same effects as those of the first embodiment can be obtained, and further, the operator can save the trouble of resetting the region of interest, so that smoother diagnosis can be performed.

[Third Embodiment]
In the following, a third embodiment of the present invention will be described mainly based on FIGS. In summary, the present embodiment is inclined according to the function of displaying the region excited by fat, which is a characteristic part of the first embodiment, and the set position of the region of interest, which is a characteristic part of the second embodiment. It combines functions to control the polarity of the magnetic field. Thus, since this embodiment is the structure which combined 1st and 2nd embodiment, the description is abbreviate | omitted using the same code | symbol for the same component. Further, since the operation up to the positioning of the region of interest is the same as that of the first embodiment, the description thereof is omitted.

  First, the necessity (meaning) of this embodiment will be described.

In the third embodiment, the main target of ¹ H spectroscopy is the brain, and the fat of the head to avoid contamination is mainly the scalp, that is, the peripheral part of the region of interest (from the center of the static magnetic field to the outside) This is a preferable setting when it is assumed to exist in the direction). Therefore, for example, when the MRS image is obtained by the same method as described above when the center of the head is greatly deviated from the center of the static magnetic field, a situation in which the region of interest includes fat tissue occurs. This will be described in more detail below.

An example in which the center of the head is greatly deviated from the center of the static magnetic field is shown in FIG. FIG 6 shows a case center X _R of the region of interest is in the negative direction (left) when referenced to the center of the head, in the static magnetic field when relative to the center of the (system) normal direction (right side) ing. In such a case, when the polarity of the gradient magnetic field is controlled as in the second embodiment, the region where fat is excited is further in the negative direction (left side), and more adipose tissue is excited and becomes spectral data. It will be mixed.

  Therefore, in this embodiment, as shown in FIG. 7, in addition to the second embodiment, the feature of the first embodiment is that “a region where fat is excited is indicated by a dotted line. The function of “display with rectangle 22” is used.

  Needless to say, in the present embodiment, as in the second embodiment, the Y direction and the Z direction have the same predefined settings as in the X direction.

  Next, the operation of this embodiment will be described with reference to FIG. Since the operation up to the positioning of the region of interest is the same as that of the first embodiment, the description thereof will be omitted and the region of interest positioning operation will be described. This positioning operation is performed by the following processing based on the algorithm shown in FIG.

  First, the operator sets a region of interest on the positioning image using the input device 13 (step S21). Then, as in the second embodiment, the calculation unit 10 determines whether the center of the set region of interest is on the positive side or the negative side of the system X coordinate axis with respect to the center of the magnet 1. Determination is made (step S22). When the arithmetic unit 10 determines that the center of the region of interest is on the positive side of the X coordinate axis of the system with respect to the center of the magnet 1, the gradient magnetic field provided by the transmitter 8T has a negative magnetic field polarity. (Step S23). On the other hand, when the arithmetic unit 10 determines that the center of the region of interest is on the negative side of the X coordinate axis of the system with respect to the center of the magnet 1, the gradient magnetic field provided by the transmitter 8T is a positive magnetic field. It changes so that it may become a gradient (step S24).

  Subsequently, as in the first embodiment, as shown in FIG. 2, a region where fat is excited is represented by a dotted rectangle 22 apart from the solid rectangle 21 representing the region of interest (step S25). ). Thereby, the operator can recognize whether the area | region where fat is excited includes the scalp part 23 or not.

  Here, when the dotted rectangle 22 is displayed so as to include the scalp portion 23 (step S26), the operator again selects the region of interest so that the dotted rectangle 22 does not include the scalp portion 23. Is set again (step S27a), and the setting of the region of interest is completed. On the other hand, when the dotted rectangle 22 does not include the scalp portion 23 (step S26), the setting of the region of interest is completed at this point. Since the subsequent steps are the same as those in the first embodiment, description thereof is omitted.

  As described above, in the present embodiment, when the center of the head is not greatly deviated from the center of the static magnetic field, it is possible to save the operator from re-setting the region of interest as in the first embodiment. Only when the center of the part is greatly deviated from the center of the static magnetic field, the operator only has to reset the region of interest. Thus, in any case, the fatty tissue can be prevented from being excited and mixed into the data, and the concentration distribution of metabolites other than water and fat can be clearly grasped visually.

[Fourth Embodiment]
Hereinafter, a fourth embodiment of the present invention will be described mainly based on FIG. In the third embodiment, when the center of the head is greatly deviated from the center of the static magnetic field, the region of interest on the positioning image is reset, but in this embodiment, the region of interest is set. The operator can manually reverse the polarity of the gradient magnetic field that has been automatically performed in the second embodiment. Therefore, in this embodiment, the input device 13 is provided with a switch mechanism (not shown) for reversing the polarity of the gradient magnetic field in the three orthogonal directions of the region of interest. Thus, this embodiment is one of the modifications of the third embodiment, and has the same configuration as the third embodiment except for the switch mechanism that reverses the polarity of the gradient magnetic field. The description is omitted.

  Next, the operation of the present embodiment will be described with reference to FIG. Note that the positioning operation is processed based on the algorithm shown in FIG. 9, but the processing up to step S26 is the same as that in the third embodiment, and hence the subsequent processing will be described.

  As described above, when the dotted rectangle 22 is displayed so as to include the scalp portion 23 (step 26), the operator manually operates the polarity of the gradient magnetic field (magnetic field gradient) by the switch mechanism of the input device 13. Are reversed (step S27b). On the other hand, when the dotted rectangle 23 does not include the scalp portion 23 (step S26), the setting of the region of interest is completed at this point. Since the subsequent steps are the same as those in the first embodiment, description thereof is omitted.

  As described above, in this embodiment, when the center of the head is not greatly deviated from the center of the static magnetic field, it is possible to save the operator from having to reset the region of interest as in the first embodiment. Only when the center of the magnetic field is greatly deviated from the center of the static magnetic field, the operator needs to reverse the polarity of the gradient magnetic field. Thus, as in the third embodiment, it is possible to prevent the adipose tissue from being excited and mixed into the data in all cases, and to visually clarify the concentration distribution of metabolites other than water and fat. Can be caught.

[Fifth Embodiment]
The fifth embodiment of the present invention will be described below mainly based on FIG. In the fourth embodiment, the polarity of the gradient magnetic field is reversed by the switch mechanism of the input device 13, but in this embodiment, the dotted rectangle 22 indicating the region where fat is excited is moved on the positioning screen. In response to this, the function is such that the polarity of the gradient magnetic field is automatically reversed.

  That is, in the present embodiment, the dotted square 22 indicating the region where fat is excited shown in FIG. 2 can be independently moved to the solid square 21 indicating the region of interest, and the operator can When the quadrangle 22 is moved, the function of changing the polarity of the gradient magnetic field in accordance with this is obtained.

  Specifically, the position of the dotted square 22 moved by the input device 13 is recognized by the host computer 6, and based on this, the pulse sequence information sent to the sequencer 5 is changed. This changed pulse sequence information reverses the polarity of the gradient magnetic field applied by the transmitter 8T.

  Note that a mechanism for moving the dotted-line rectangle 22 may be newly provided in the input device 13, or a mechanism used when setting a region of interest (solid-line rectangle 23) may be used.

  As described above, this embodiment is one of the modifications of the third embodiment, except that when the dotted quadrilateral 22 is moved, the polarity of the gradient magnetic field changes accordingly. Since the configuration is the same as that of the third embodiment, the description thereof is omitted.

  Next, the operation of the present embodiment will be described with reference to FIG. The positioning operation is processed based on the algorithm shown in FIG. 10, but the process up to step S <b> 26 is the same as that in the third embodiment, and will be described from the subsequent processing.

  As described above, when the dotted rectangle 22 is displayed so as to include the scalp portion 23 (step 26), the operator manually inputs the dotted rectangle 22 shown in FIG. When moving away from 23, the magnetic field gradient of the gradient magnetic field is automatically reversed (step S27c). On the other hand, when the dotted rectangle 23 does not include the scalp portion 23 (step S26), the setting of the region of interest is completed at this point. Since the subsequent steps are the same as those in the first embodiment, description thereof is omitted.

  As described above, according to the present embodiment, since the dotted quadrilateral 22 which is a region where fat is excited is directly moved on the positioning screen, it is more intuitive and more intuitive than the third and fourth embodiments. Visual movement can be performed.

  In each of the above embodiments, the set region of interest (the region where the water signal is excited) is represented by a solid line, and the region where the fat signal is excited is represented by a dotted line. However, the present invention is not limited to this. As long as the region where fat is excited is distinguished and displayed, both may be represented by a solid line. These differences may be displayed in any manner as long as the display mode is different. Here, as examples in which the display modes are different, for example, these differences are represented by differences in color of color display, are represented by being distinguished from thick lines and thin lines, and are represented by being distinguished from solid lines and wavy lines. Furthermore, by operating the input device 13, the region of interest and the region where fat is excited may be switched and displayed on one positioning image (MRI image), or each may be displayed independently on two positioning images. .

  In each of the above embodiments, the center frequency is adjusted to the water signal, and the region where water is excited is set as the region of interest. However, the present invention is not limited to this, and the measurement target exists between the resonance frequencies of water and fat. May be tailored to specific metabolites. Further, the intermediate frequency may be adjusted to a position between water and fat.

  As described above, according to the present invention, when the region of interest for obtaining the MRS image is positioned, the set region of interest can contain as little as possible a portion containing adipose tissue. There is an effect that the concentration distribution of metabolites other than water and fat can be clearly grasped visually.

DESCRIPTION OF SYMBOLS 1 Magnet 2 Static magnetic field power supply 3 Gradient magnetic field coil unit 4 Gradient magnetic field power supply 5 Sequencer 6 Controller 7 RF coil 8T Transmitter 8R Receiver 10 Arithmetic unit 11 Storage unit 12 Display 13 Input device 16 Sound generator 17 ECG sensor 18 ECG unit

Claims (9)

In the magnetic resonance diagnostic apparatus capable of displaying spectral data indicating the concentration distribution of each metabolite in the region of interest,
Setting means for the operator to set information regarding the polarity of the gradient magnetic field;
Display means for displaying information indicating the region of interest and information indicating a region where fat is excited based on information on the polarity of the set gradient magnetic field on a positioning image;
A magnetic resonance diagnostic apparatus comprising: The display means displays information indicating the region where fat is excited on the positioning image based on a shift amount of the region where fat is excited with respect to water in the region of interest. The magnetic resonance diagnostic apparatus described. 3. The magnetic resonance diagnostic apparatus according to claim 1, wherein the positioning image is an MRI image. In the magnetic resonance diagnostic apparatus capable of displaying spectral data indicating the concentration distribution of each metabolite in the region of interest,
Setting means for setting the region of interest;
A computing means for determining a region where fat is excited when water is excited in the region of interest;
A magnetic resonance diagnostic apparatus comprising: a display unit configured to display, on an MRI image, information indicating a region of interest set by the setting unit and a region in which fat obtained by the calculation unit is excited. Magnetic resonance spectroscopy imaging method for displaying spectral data indicating concentration distribution of each metabolite in the region of interest on the display means by controlling each part of the magnetic resonance diagnostic apparatus based on information input from the input means In
Displaying a positioning image on the display means;
Based on the information input from the input means, set information on the polarity of the region of interest on the positioning image and display on the display means,
A magnetic resonance spectroscopic imaging method, comprising: displaying information indicating the region of interest and information indicating a region where fat is excited based on the set information regarding the polarity of the gradient magnetic field on a positioning image. Magnetic resonance spectroscopy imaging method for displaying spectrum data indicating concentration distribution for each metabolite in the region of interest on the display means by controlling each part of the magnetic resonance diagnostic apparatus based on information input from the input means In
Displaying a positioning image on the display means;
Displaying the region of interest on the display means based on the information input from the input means;
Calculating a first fat excitation region where fat is excited when water is excited in the region of interest;
A magnetic resonance spectroscopic imaging method, wherein the first fat excitation region is displayed on the positioning image. Following the step of displaying the first fat excitation region on the positioning image,
Calculating a second fat excitation region where fat is excited when water is excited in the region of interest when receiving information for reversing the polarity of the gradient magnetic field;
The magnetic resonance spectroscopy imaging method according to claim 6 , wherein the second fat excitation region is displayed on the positioning image. Collecting the spectral data using a polar gradient magnetic field to excite the second fat excitation region;
8. The magnetic resonance spectroscopy imaging method according to claim 7 , wherein the collected spectrum data is displayed on the display means. In the magnetic resonance diagnostic apparatus capable of displaying spectral data indicating the concentration distribution of each metabolite in the region of interest,
Setting means for the operator to set information regarding the polarity of the gradient magnetic field;
Display means for displaying information indicating the region of interest and information indicating a chemical shift based on information on the polarity of the set gradient magnetic field on a positioning image;
A magnetic resonance diagnostic apparatus comprising:

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