JP2013111097A - Magnetic resonance spectroscopy apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic resonance spectroscopy apparats providing a spectrogram having a fixed or more level of an SN (Signal Noise) ratio.SOLUTION: An apparatus (10) includes: a reception part (150) for receiving a first nuclear magnetic resonance signal from a specific area; a storage part (172) for storing the first nuclear magnetic resonance signal received by the reception part; and an image processing part (174) for calculating a frequency spectrum, based on the first nuclear magnetic resonance signal. The apparatus also includes: an SN ratio determination part (178) for determining whether the SN ratio of a specific substance in the frequency spectrum is equal to or less than a threshold or not; and a control part (171) causing the reception part to receive a second nuclear magnetic resonance signal from the specific area when the SN ratio is equal to or less than the threshold. The image processing part calculated a frequency spectrum, based on the first nuclear magnetic resonance signal and the second nuclear magnetic resonance signal.

Description

  The present invention relates to a magnetic resonance spectroscopy apparatus. In particular, the present invention relates to an improvement in the SN ratio of a spectrogram for measuring the distribution of each metabolite.

  2. Description of the Related Art In recent years, a magnetic resonance spectroscopy (MRS) apparatus that can visually grasp the concentration distribution of a metabolite that cannot be obtained with an MRI (Magnetic Resonance Imaging) image by using a spectrum by utilizing a magnetic resonance phenomenon has been developed. Has been developed. MRS is a method of separating signals for each molecule based on a difference (chemical shift) in magnetic resonance frequency due to a difference in chemical bonds of various molecules. A chemical shift occurs when the magnetic field of a nucleus in a molecule is affected by the magnetic field created by nearby nuclei, thereby causing a difference in resonance frequency depending on the surrounding environment even in the same nucleus.

  In MRS, relative quantitative information of metabolites is important for grasping the state of a disease state. In order to obtain accurate information, the number of imaging may be increased. However, in clinical practice, the best imaging must be performed within a limited examination time. In the current MRS, information on metabolites is confirmed after imaging is completed, but quantitative information on metabolites must be examined even if the SN (Signal Noize) ratio is low at that time.

  In the apparatus of Patent Document 1, a high-resolution spectrogram is obtained by processing an edge filter on a spectrogram having a low S / N ratio.

JP 2007-301118 A

  However, processing with an edge filter may result in an inaccurate spectrogram, and the imaginary part signal may make the amount of metabolite appear more than what is actually present. Therefore, it is necessary to obtain a spectrogram that does not give a misunderstanding to the operator or doctor, that is, a spectrogram having a certain S / N ratio or more.

  Therefore, the present invention provides a magnetic resonance spectroscopy apparatus that obtains a spectrogram having a certain S / N ratio or more.

A magnetic resonance spectroscopy apparatus according to a first aspect includes a transmitter that irradiates a specific region of a subject with a high-frequency magnetic field, a receiver that receives a first nuclear magnetic resonance signal from the specific region, and a receiver that is received by the receiver. A storage unit that stores one nuclear magnetic resonance signal; and a calculation unit that calculates a frequency spectrum based on the first nuclear magnetic resonance signal. Further, the magnetic resonance spectroscopy apparatus includes an SN ratio determination unit that determines whether or not the SN ratio of a specific substance in the frequency spectrum is equal to or less than a threshold value, and when the SN ratio is equal to or less than the threshold value, the transmission unit again receives a high frequency magnetic field. And a control unit that causes the receiving unit to receive the second nuclear magnetic resonance signal from the specific region. The image processing unit calculates a frequency spectrum based on the first nuclear magnetic resonance signal and the second nuclear magnetic resonance signal.
That is, even when the SN ratio is low, in addition to the first nuclear magnetic resonance signal, the second nuclear magnetic resonance signal is obtained as many times as necessary and the frequency spectrum is calculated.

The control unit of the magnetic resonance spectroscopy apparatus according to the second aspect calculates the insufficient number of receptions reaching the threshold based on the number of receptions of the first nuclear magnetic resonance signal and the SN ratio, The nuclear magnetic resonance signal is received for the number of times of insufficient reception.
The control unit of the magnetic resonance spectroscopy apparatus of the third aspect calculates the number of receptions based on the imaging time of the second nuclear magnetic resonance signal.

The magnetic resonance spectroscopy apparatus according to the fourth aspect further includes an input unit for inputting a threshold value for the SN ratio.
A magnetic resonance spectroscopy apparatus according to a fifth aspect includes an S / N ratio calculation unit that calculates an S / N ratio, and the S / N ratio calculation unit discriminates and analyzes a frequency spectrum into a signal region and a noise region, and the peak and noise of a specific substance. The SN ratio is calculated based on the average value of the components.

In the image processing unit of the magnetic resonance spectroscopy apparatus of the sixth aspect, when calculating the frequency spectrum for each of the plurality of voxels, at least one of the plurality of voxels is set as a reference voxel, and the SN ratio determination unit In the voxel, it is determined whether or not the SN ratio is equal to or less than a threshold value.
In the magnetic resonance spectroscopy apparatus according to the seventh aspect, when the number of reference voxels is two or more, the SN ratio determination unit averages the SN ratios in the reference voxels.

  The magnetic resonance spectroscopy apparatus of the present invention can obtain a spectrogram having an S / N ratio above a certain level.

1 is a schematic configuration diagram of a magnetic resonance imaging apparatus 10. FIG. It is a calculation flowchart of the spectrum of a 1st embodiment. It is an example of spectrogram SP1 based on the 1st nuclear magnetic resonance signal. It is a figure which shows signal area SA and noise area NA of spectrogram SP1. It is an example of spectrogram SP2 based on the 1st and 2nd nuclear magnetic resonance signal. It is a calculation flowchart of the spectrogram of the second embodiment. It is the figure which showed the setting and spectrogram based on the multi-voxel of 3rd Embodiment. It is a production | generation flowchart of the spectrogram of 3rd Embodiment.

  The magnetic resonance spectroscopy apparatus (MRS: Magnetic Resonance Spectroscopy) of the first to third embodiments will be described. In the following, a magnetic resonance imaging apparatus equipped with the function of a magnetic resonance spectroscopy apparatus according to the present invention will be described as an embodiment, and the magnetic resonance imaging apparatus will be referred to as an “MRI (Magnetic Resonance Imaging) apparatus”.

<< First Embodiment >>
<Configuration of magnetic resonance imaging apparatus>
A configuration of the MRI apparatus according to the first embodiment will be described. FIG. 1 is a diagram for explaining the configuration of the MRI apparatus according to the first embodiment. The MRI apparatus according to the first embodiment is an apparatus that captures an MRI image and collects magnetic resonance spectra in a region of interest to generate a spectrum image indicating the concentration distribution intensities of a plurality of metabolites. With reference to FIG. 1, the configuration and basic operation of the magnetic resonance imaging apparatus 10 of the first embodiment will be described.

  The magnetic resonance imaging apparatus 10 includes a magnet system 100, a gradient coil drive unit 130, an RF coil drive unit 140, a data collection unit 150, a pulse sequence control unit 160, a calculation unit 170, a display unit 180, and an operation unit 190.

  The magnet system 100 includes a main magnetic field coil unit 102, a gradient coil unit 106, and an RF coil unit 108. Each of these coil portions has a substantially cylindrical shape, and is arranged coaxially with each other in a substantially columnar bore. The subject SB is placed on the bed 110 in the bore, and the bed 110 is movable in the bore in the magnet system 100 according to the imaging region.

  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 subject SB and forms a horizontal magnetic field. The main magnetic field coil unit 102 is normally configured using a superconducting coil, but may be configured using a permanent magnet or the like without being limited to the superconducting coil.

  The gradient coil unit 106 has three types of gradients for imparting gradients to the static magnetic field strength formed by the main magnetic field coil unit 102 in the three axes orthogonal to each other, that is, in the direction of the slice axis, the phase axis, and the frequency axis. Generate a 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). A gradient coil drive unit 130 is connected to the gradient coil unit 106, and the gradient coil drive unit 130 gives a drive signal to the gradient coil unit 106 to generate a gradient magnetic field. The gradient coil drive unit 130 has three drive circuits (not shown) corresponding to the three gradient coils in the gradient coil unit 106.

  The RF coil unit 108 forms a high-frequency magnetic field for exciting spins in the body of the subject SB in the static magnetic field space. Formation of a high-frequency magnetic field is called transmission of an RF excitation signal, and the RF excitation signal is called an RF pulse. An RF coil drive unit 140 is connected to the RF coil unit 108. The RF coil drive unit 140 provides a drive signal to the RF coil unit 108, and the RF coil unit 108 transmits an RF pulse based on the drive signal. An electromagnetic wave generated by the excited spin, that is, a nuclear magnetic resonance signal is received by the RF coil unit 108. A data collection unit 150 is connected to the RF coil unit 108. The data collection unit 150 collects the nuclear magnetic resonance signals received by the RF coil unit 108 as digital data.

  A pulse sequence control unit 160 is connected to the gradient coil drive unit 130, the RF coil drive unit 140, and the data collection unit 150.

  The pulse sequence control unit 160 drives the gradient coil driving unit 130 and the RF coil driving unit 140 in accordance with the imaging conditions input by the operator, that is, the imaging protocol. More specifically, the pulse sequence control unit 160 generates “sequence information for photographing an MRI image” and “sequence information for photographing a spectrogram”. The sequence information is transmitted to the gradient coil driving unit 130 and the RF coil driving unit 140.

  The display unit 180 is configured by a graphic display or the like. The display unit 180 is connected to the calculation unit 170. The display unit 180 may display a GUI operation screen, a magnetic resonance image reconstructed based on a nuclear magnetic resonance signal for MRI image reconstruction, a spectrogram based on a nuclear magnetic resonance signal for a spectrogram, and the like. it can.

  The operation unit 190 includes a keyboard having a pointing device. The operation unit 190 is connected to the calculation unit 170. The operation unit 190 is operated by the operator via the display unit 180. The operation unit 190 may arrange a touch panel on the display unit 180 instead of a keyboard or the like.

The calculation unit 170 includes a control unit 171, a storage unit 172, an image processing unit 174, an SN ratio calculation unit 176, and an SN ratio determination unit 178.
The arithmetic unit 170 executes various data processes and programs. The control unit 171 controls the data collection unit 150, the pulse sequence control unit 160, and the like. The storage unit 172 stores various shooting protocols, various programs, and various data. The storage unit 172 stores the nuclear magnetic resonance signals collected by the data collection unit 150.

  The image processing unit 174 reconstructs a magnetic resonance image based on the nuclear magnetic resonance signal for MRI image reconstruction. Also, the image processing unit 174 performs Fourier transform on the spectrogram nuclear magnetic resonance signal to convert it into frequency space data. The image processing unit 174 plots the data in the frequency space against the frequency to generate a spectrogram.

  The SN ratio calculation unit 176 first divides this spectrogram into a signal region and a noise region. For example, by applying a discriminant analysis method, the spectrogram frequency region is divided into a region where the spectrogram signal value is larger than the reference value and a region where the signal value is smaller than the reference value. An area where the signal value is equal to or greater than the reference value is defined as a signal area, and an area where the signal value is equal to or less than the reference value is defined as a noise area. Then, the SN ratio calculation unit 176 calculates the SN ratio between the peak of the signal region and the average value of the noise region.

  The SN ratio determination unit 178 compares the SN ratio with a threshold value, and determines whether or not the SN ratio exceeds the threshold value.

<Spectrogram generation process>
FIG. 2 is a spectrogram generation flowchart of the first embodiment.
In step S11, the operator inputs a threshold value of the SN ratio required for the spectrogram. When generating a cerebral spectrogram, for example, creatine, choline, or NAA (N-Aceryl-L-aspartate) is selected as a metabolite. Depending on the site, lactic acid or citric acid may be selected as a metabolite. In the first embodiment, the operator inputs, for example, “8” as the SN ratio threshold between the peak of croatin and the average value of the noise region as a metabolite via the operation unit 190.

  Note that when the storage unit 172 of the magnetic resonance imaging apparatus 10 stores a threshold value as a default from the experience values so far, step S11 may be omitted. The SN ratio of the first embodiment will be described as a peak signal-to-noise ratio (PSNR) between the peak height of the metabolite and the average value of the noise region. However, the present invention is not limited to this, and an SN ratio between the average value of the metabolite and the average value of the noise region may be applied.

  In step S13, an initial screen for setting shooting conditions is first displayed on the display unit 180. The operator sets an imaging region in the cerebrum of the displayed subject SB and sets a voxel size. Further, the operator sets the number of receptions of spectrogram nuclear magnetic resonance signals collected by the data collection unit 150. In the first embodiment, the operator sets one voxel (single voxel), and inputs, for example, “30” as the number of receptions via the operation unit 190.

  In step S15, the pulse sequence control unit 160 transmits a pulse sequence for imaging the spectrogram according to the imaging protocol in accordance with a command from the arithmetic unit 170.

  In step S17, the data collection unit 150 collects the first nuclear magnetic resonance signal received by the RF coil unit. The collected first nuclear magnetic resonance signal is stored in the storage unit 172. The first nuclear magnetic resonance signal stored in the storage unit 172 is stored at least until the end step of this flowchart.

  In step S19, the image processing unit 174 generates a spectrogram based on the stored first nuclear magnetic resonance signal. More specifically, the image processing unit 174 performs Fourier transform on the first nuclear magnetic resonance signal to convert it into frequency space data. The image processing unit 174 plots the data in the frequency space against the frequency to generate a spectrogram SP1. For example, FIG. 3 shows an example. The horizontal axis of FIG. 3 shows the ratio of frequency deviation from the reference substance (chemical shift amount), and the vertical axis shows the wave height of that frequency, that is, the amount of hydrogen atoms.

  In step S21, the SN ratio calculation unit 176 calculates the SN ratio between the peak of croatin as a metabolite and the average value of the noise region. Details will be described with reference to FIG. The SN ratio calculation unit 176 first divides the spectrogram SP1 displayed in FIG. 4 into a signal region and a noise region, for example, by applying a discriminant analysis method. The region of the spectrogram frequency is divided into a region where the signal value of the spectrogram SP1 is larger than the reference value ST and a region where the signal value is smaller than the reference value ST. An area where the signal value is equal to or greater than the reference value is defined as a signal area SA, and an area where the signal value is equal to or less than the reference value is defined as a noise area NA (shaded area).

  Furthermore, the SN ratio calculation unit 176 calculates the average value of the noise area NA, and calculates the peak of the signal area SA and the SN ratio with respect to the average value of the noise area NA. For example, in the first embodiment, the metabolite is croatin having a chemical shift amount of 3.02 ppm, and the SN ratio between the peak height PK1 of croatin and the average value NV1 of the noise region NA is calculated. If the metabolite is determined to be croatin, the average value of noise regions NA around croatin may be used instead of the average value of all noise regions NA. In the first embodiment, it is assumed that the SN ratio is “6”.

  In step S23, the SN ratio determination unit 178 determines whether the SN ratio is larger than the threshold set in step S11. A high SN ratio means that the operator or doctor can sufficiently determine the metabolite using the spectrogram SP1. Therefore, the generation of spectrogram SP1 ends here. If the SN ratio does not exceed the threshold value, the process proceeds to step S25. In the first embodiment, since the threshold set in step S11 is “8” and the SN ratio is “6”, the process proceeds to step S25.

  In step S25, the SN ratio calculation unit 176 further calculates the number of times of receiving nuclear magnetic resonance vibration. The spectrogram SP1 with an S / N ratio of “6” was generated with a pulse sequence of 30 receptions. Therefore, the SN ratio calculation unit 176 calculates 30 (number of receptions) × 8 (threshold) / 6 (SN ratio) −30 (number of receptions) = 10 (number of receptions for the shortage). That is, it is understood that a spectrogram having a high S / N ratio can be obtained by receiving a nuclear magnetic resonance signal for spectrogram ten times or more.

In step S27, the pulse sequence control unit 160 transmits a pulse sequence according to an imaging protocol for receiving 10 or more nuclear magnetic resonance signals.
In step S29, the data collection unit 150 collects the second nuclear magnetic resonance signal received by the RF coil unit 108. The collected second nuclear magnetic resonance signal is stored in the storage unit 172.

  In step S31, the image processing unit 174 generates a spectrogram SP2 based on the stored first nuclear magnetic resonance signal and second nuclear magnetic resonance signal. For example, FIG. 5 is an example of a spectrogram SP2 generated based on the first nuclear magnetic resonance signal and the second nuclear magnetic resonance signal. In FIG. 5, the spectrogram SP2 is drawn together with the spectrogram SP1 (dotted line). Since the spectrogram SP2 has a large S / N ratio, the operator or doctor can sufficiently determine the metabolite using the spectrogram SP2.

<< Second Embodiment >>
<Spectrogram generation process>
FIG. 6 is a flowchart of spectrogram generation according to the second embodiment. In the second embodiment, a shooting time condition is added to the flowchart of the first embodiment. Steps S11, S13, S25, and S27 are different from the generation flowchart of the first embodiment. For this reason, only new steps S11R, S13R, S25R and S27R will be described. The configuration of the magnetic resonance imaging apparatus is the same as that of the first embodiment.

  In step S11R, the operator inputs a threshold value of the S / N ratio required for the spectrogram. Also in the second embodiment, the operator inputs “8” as the threshold value of the SN ratio between the peak of croatin and the average value of the noise region as a metabolite. Furthermore, the operator inputs an upper limit shooting time. For example, the operator sets the upper limit of the imaging time to 5 minutes in consideration of the physical condition of the subject SB.

  In step S13R, the operator sets one imaging region in the cerebrum of the displayed subject SB, and sets the voxel size and the number of reception times of the nuclear magnetic resonance signal for the spectrogram. Thereby, the arithmetic unit 170 calculates the time from the transmission of the pulse sequence (start of imaging) to the display of the spectrogram on the display unit 180 (end of imaging). For example, in the second embodiment, since the operator inputs, for example, “30” as the number of receptions via the operation unit 190, the shooting time is calculated as 4 minutes.

  In step S25R, the SN ratio calculation unit 176 further calculates the number of times of receiving nuclear magnetic resonance vibration. The spectrogram SP1 with an S / N ratio of “6” was generated with a pulse sequence of 30 receptions. Therefore, the SN ratio calculation unit 176 calculates 30 (number of receptions) × 8 (threshold) / 6 (SN ratio) −30 (number of receptions) = 10 (number of receptions for the shortage). That is, it is understood that a spectrogram having a high S / N ratio can be obtained by receiving a nuclear magnetic resonance signal for spectrogram ten times or more.

  On the other hand, the calculation unit 170 calculates an imaging time for receiving the spectrogram nuclear magnetic resonance signal for 10 times. For example, the calculation unit 170 calculates that it takes 2 minutes from the transmission of the pulse sequence (start of imaging) to the display of the spectrogram on the display unit 180 (end of imaging). Since the imaging time has already passed from step S15 to step S23, if the nuclear magnetic resonance signal for the spectrogram is received 10 times, the total imaging time becomes 6 minutes. In this case, the upper limit photographing time set in step S11R exceeds 5 minutes. Therefore, the calculation unit 170 instructs the pulse sequence control unit 160 to obtain a pulse sequence that can be obtained in the remaining imaging time of 1 minute. For example, the pulse sequence can receive five nuclear magnetic resonance signals for the spectrogram.

  In step S27R, the pulse sequence control unit 160 transmits a pulse sequence according to an imaging protocol for receiving five nuclear magnetic resonance signals.

  In the second embodiment, the operator or doctor can determine the metabolite using the spectrogram SP2 in which the SN ratio is sufficiently improved within the range allowed by the physical condition of the subject SB.

<< Third Embodiment >>
In the first embodiment and the second embodiment, the case where a nuclear magnetic resonance signal is collected a plurality of times when a single voxel is set has been described. In the third embodiment, an example in which multi-voxels are set will be described.

  FIG. 7A is a diagram illustrating a state in which the operator sets a multi-voxel shooting area on the initial screen for setting shooting conditions. FIG. 7B shows a spectrogram of each voxel size.

<Spectrogram generation process>
FIG. 8 is a spectrogram generation flowchart of the third embodiment. Steps S13 and S21 are different from the generation flowchart of the first embodiment. Therefore, only new steps S13T and S21T will be described. The configuration of the magnetic resonance imaging apparatus is the same as that of the first embodiment.

  In step S13T, an initial screen for setting shooting conditions as shown in FIG. 7A is displayed on the display unit 180 first. The operator sets an imaging region in the cerebrum of the displayed subject SB, and sets the voxel size and the number of voxels. In FIG. 7A, nine voxels VX (VX1 to VX9) are set. Similarly to the first and second embodiments, the operator sets the number of receptions of the nuclear magnetic resonance signal for the spectrogram collected by the data collection unit 150.

  Further, the operator sets one reference voxel SVX from the voxels VX (VX1 to VX9). For example, the voxel VX5 is set as the reference voxel SVX. When calculating the SN ratio between the peak height of the metabolite and the average value of the noise region, if there are nine voxels VX (VX1 to VX9), the respective SN ratios are different due to differences in imaging regions. Therefore, one reference voxel SVX is set in the case of a multi-voxel imaging region.

  In step S21T, the SN ratio calculation unit 176 calculates the SN ratio between the peak of the metabolite in the voxel VX5 which is the reference voxel SVX and the average value of the noise region.

  Note that, as an application example of the third embodiment, it may be applied to set two or more reference voxels SVX. For example, consider a case in which it is desired to set the reference voxel SVX to two voxels VX5 and VX6 in step S13T. In this case, in step S21T, the SN ratio calculation unit 176 calculates the SN ratio between the peak of the metabolite in the voxel VX5 and the average value of the noise region, and the average of the peak of the metabolite in the voxel VX6 and the noise region. The signal-to-noise ratio with the value is calculated. Then, the SN ratio calculation unit 176 averages the SN ratio of the voxel VX5 and the SN ratio of the voxel VX6. The SN ratio determination unit 178 may determine whether the averaged SN ratio is larger than the threshold value.

DESCRIPTION OF SYMBOLS 10 ... Magnetic resonance imaging apparatus 100 ... Magnet system 102 ... Main magnetic field coil part 106 ... Gradient coil part 108 ... RF coil part 110 ... Bed 130 ... Gradient coil drive part 140 ... RF coil drive part 150 ... Data acquisition part 160 ... Pulse sequence Control unit 170 ... Calculation unit 171 ... Control unit 172 ... Storage unit 174 ... Image processing unit 176 ... SN ratio calculation unit 178 ... SN ratio determination unit 180 ... Display unit 190 ... Operation unit NA ... Noise region NV1 ... Average value PK1 ... Wave height SA ... Signal region SB ... Subject SP1 ... Spectrogram SP2 ... Spectrogram ST ... Reference value SVX ... Reference voxel VX ... Voxel

Claims (8)

A transmitter that irradiates a specific region of the subject with a high-frequency magnetic field;
A receiver for receiving a first nuclear magnetic resonance signal from the specific region;
A storage unit for storing the first nuclear magnetic resonance signal received by the reception unit;
A calculation unit for calculating a frequency spectrum based on the first nuclear magnetic resonance signal;
An SN ratio determination unit that determines whether an SN ratio of a specific substance in the frequency spectrum is equal to or less than a threshold;
A control unit that, when the SN ratio is equal to or less than a threshold value, causes the transmission unit to irradiate a high-frequency magnetic field again and causes the reception unit to receive a second nuclear magnetic resonance signal from the specific region;
The image processing unit is a magnetic resonance spectroscopy apparatus that calculates a frequency spectrum based on the first nuclear magnetic resonance signal and the second nuclear magnetic resonance signal.   The control unit calculates an insufficient number of receptions that reach the threshold based on the number of receptions of the first nuclear magnetic resonance signal and the SN ratio, and sends the second nuclear magnetic resonance signal to the reception unit. The magnetic resonance spectroscopy apparatus according to claim 1, wherein reception is performed for an insufficient number of receptions.   The magnetic resonance spectroscopy apparatus according to claim 2, wherein the control unit calculates the number of receptions based on an imaging time of the second nuclear magnetic resonance signal.   The magnetic resonance spectroscopy apparatus according to claim 1, further comprising an input unit that inputs a threshold value for the SN ratio. An SN ratio calculation unit for calculating the SN ratio;
The SN ratio calculation unit discriminates and analyzes the frequency spectrum into a signal region and a noise region, and calculates the SN ratio based on a peak of the specific substance and an average value of the noise component. 5. The magnetic resonance spectroscopy apparatus according to any one of 4 above. When the image processing unit calculates the frequency spectrum for each of a plurality of voxels, at least one of the plurality of voxels is set as a reference voxel,
The magnetic resonance spectroscopy apparatus according to any one of claims 1 to 5, wherein the SN ratio determination unit determines whether the SN ratio is equal to or less than a threshold value in the reference voxel.   The magnetic resonance spectroscopy apparatus according to claim 6, wherein when the number of reference voxels is two or more, the SN ratio determination unit averages the SN ratio in the reference voxels. The magnetic resonance spectroscopy apparatus according to claim 1, further comprising a display unit that displays the calculated frequency spectrum in a graph.