JPH0871057A - Magnetic resonance diagnostic apparatus - Google Patents

Abstract

PURPOSE: To decrease the amt. of application of a decoupling pulse without deteriorating S/N by providing a means for applying the decoupling pulse only when data of a low frequency region on the space frequency is collected when the spectrum of a specified metabolic substance in a living body is collected. CONSTITUTION: A magnetic resonance signal received by a probe 3 is detected in a receiving part 8 and then, is sent to a computor system 10 through a data collecting part 9, wherein an image data on the density distribution of a required atomic nucleus in a subject to be inspected is reconstituted. In this case, for example, in imaging of the metabolic substance requiring a decoupling pulse as<13> C, the decoupling pulse is applied only in the low frequency region on the space frequency to make the amt. of RF application as small as possible. In addition, when points in the low frequency region are a little, the points in the low frequency region and the points in the high frequency region are alternately data-collected, and after data are collected, they are rearranged and reconstituted to obtain distribution of the spectra.

Description

Detailed Description of the Invention

[0001]

The present invention relates relates to a magnetic resonance diagnosis apparatus, the method in particular applies a decoupling pulse, and ¹³
It relates to a method of observing ¹ H J-bonded to C.

[0002]

2. Description of the Related Art In recent years, magnetic resonance diagnostic devices have been widely used as medical diagnostic devices have been developed. The magnetic resonance diagnostic apparatus is an apparatus that can image not only the distribution of water in the living body but also the distribution of metabolites. By imaging metabolites, the metabolic state in the living body can be diagnosed, which may lead to early diagnosis of diseases.

In normal metabolite imaging, M shown in FIG.
RSI (Magnetic Resonance Spectroscopic Imaging)
Use a sequence. With this sequence, the distribution of spatial two-dimensional metabolites in the living body can be imaged. A spectrum as shown in FIG. 39 is obtained for each pixel, that is, for each voxel. Each peak of the spectrum corresponds to each metabolite, and the area of the peak indicates a physical quantity related to the amount of metabolite. That is, the metabolite distribution can be imaged by determining the peak area by spectral processing such as curve fitting and then generating this distribution.

In the spectroscopy of metabolites, the situation is slightly different from the above when there is a coupling with another nucleus due to spin-spin coupling or the like. For example,
FIG. 41 shows a model diagram of the ¹³ C spectrum of ethanol when data was collected in the sequence of FIG. Although seven peaks appear in FIG. 41, this does not mean that there are seven kinds of substances. Three peaks on the right side of one ¹³ C, that is, on the high frequency side, appear, and from another ¹³ C, four peaks on the low frequency side appear.
The peak of the book appears. In other words, here, although there are only two ¹³ C in the spectrum, the respective peaks are separated by the bond with ¹ H, so that the S / N is lowered.

The decoupling method is a method for solving this problem. The sequence at this time is shown in FIG. The difference from the above sequence is the presence or absence of ¹ H RF application. At the time of data collection, by applying ¹ H RF, ¹ H and ¹³
Since it is possible to break the magnetic coupling with C, there are two peaks as shown in FIG. 43, and the S / N is improved. That is,
For example, when there is a coupling such as ¹³ C and ¹ H, it is necessary to apply a coupling pulse such as WALTZ de.

In the case of such nuclide imaging, the sequence is, for example, a normal MRSI sequence (FIG. 38) to which a decoupling pulse is added, as shown in FIG. However, in this case, since the decoupling pulse is applied, the SAR that regulates the amount of RF applied to the living body is specified.
(Surface Absorption Ratio) becomes a problem. An easily conceivable method for solving this problem is to reduce the power of the decoupling pulse. However, in this method, decoupling is incomplete, so S /
N No good spectrum can be obtained.

On the other hand, the magnetic resonance diagnostic apparatus is an apparatus capable of non-invasively imaging the distribution of water in the living body by detecting ¹ H of water, and is widely used clinically. It is a diagnostic device. However, current water distribution images can only provide morphological information.

On the other hand, by detecting, for example, ¹ H, ¹³ C or ³¹ P of the metabolite, the distribution of the metabolite can be imaged and the metabolic information in the living body can be obtained. MRSI (Magnetic Res
onance spectroscopic imaging (MRS) is a method of collecting spectra from a single pixel.
onance Spectroscopy).

[0009] Recently, ¹³ C has attracted attention in metabolite imaging. ^{Since 13} C has a low natural abundance ratio of 1.1%, it is possible to administer a substance labeled with ¹³ C to trace metabolites and obtain metabolic information different from ¹ H and ³¹ P. Is.

The greatest problem in ¹³ C detection is overcoming low sensitivity. Methods such as decoupling and polarization transfer have been developed to overcome the low sensitivity. When we focus on improving S / N, the best method is to observe J-bonded 1 ^H on ¹³ C.
¹ H observation ¹³ C-MRS or ¹ H observation ¹³ C-MRSI
Is.

As an example of ¹ H observation method, MSBenda
ll et al. (MRBendall et al., J. Am.C
hem.Soc., 103,934,1981) POCE method ( ¹ H-Observed, ¹³ C-Edited NMR Spectroscopy) using J bond of ¹ H and ¹³ C
scopy). This method will be described using the sequence shown in FIG. In this sequence, ¹³ C of 180 ° pulse (hereinafter, referred to as ¹³ C-inverting pulse) ON shown in, O
FF indicates that application and non-application are alternately repeated.

[0012] First of all, by the 90 ° pulse of ¹ H, ¹ H
Defeat the spin (FIG. 46 (a)). A is ¹ H not J-bonded to ¹³ C, and B is ¹ H J-bonded to ¹³ C. It is assumed that the resonance frequency of A coincides with the frequency of the rotating coordinate system, that is, A does not move in the rotating coordinate system.

At this time, after τ = 1 / (2J), a 180 ° pulse of ¹ H is applied and B is inverted (FIG. 46).
(C), (c ')). After another 1 / (2J), FIG.
As shown in (d) and (d '), the ¹ H spin of A is also ^{1 of} B
The H spin also faces in the positive direction on the y'axis and forms an echo. Next, a case where a ¹³ C inversion pulse is applied simultaneously with a ¹ H 180 ° pulse will be described. In this case, ^{1 of 1} H
By 80 ° pulse, but B is inverted, ¹³ the rotational direction of the C-inverting pulse by the ¹ H spin that J bound to ¹³ C B reversed, not J bound to ¹³ C after 1 / (2J) A is oriented in the positive direction on the y'axis, and B which is J-coupled to ¹³ C is oriented in the negative direction on the y'axis to form echoes. Therefore, taking the difference of the spectrum when not applied as when applying a 180 ° pulse of ¹³ C, J to ¹³ C
Only the spectrum of bound B can be captured.

As the application of POCE to the metabolite imaging, the method of FIG. 47 can be easily guessed. By collecting the data when the ¹³ C inversion pulse is applied and when not applying it, and taking the difference, only the ¹ H spectrum J-bonded to ¹³ C can be edited.

As described above, in POCE, two measurements are necessary in order to take out only ¹ H J-bonded to ¹³ C. Therefore, there is a problem that the observation time is long and the load on the subject is large. Also, there is a problem that the subject is easily affected by the movement of the subject due to the long observation time.

[0016]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As shown above,
In a metabolite imaging method that requires a decoupling pulse, in a sequence in which the decoupling pulse is added to a normal MRSI sequence, the RF application amount increases by the amount of the decoupling pulse, so that the SAR standard is exceeded. was there. Further, the method of reducing the application amount of the decoupling pulse so as not to exceed the SAR standard has a problem that the S / N of the spectrum is deteriorated due to incomplete decoupling.

[0017] In the POCE method is a method of observing of ¹ H was J bound to ¹³ C, and data collected by applying a 180 ° pulse of ¹³ C the difference between the collected data without applying the pulse It had to be taken, and there was a problem that the observation time was twice as long as the usual measurement. Further, this causes a problem that the subject is easily affected by the movement of the subject.

The present invention has been made to solve such a conventional problem, and a first object thereof is to reduce the application amount of the decoupling pulse without deteriorating the S / N. A magnetic resonance diagnostic apparatus is provided.

The second object is to provide a magnetic resonance diagnostic apparatus capable of observing ¹ H J-bonded to ¹³ C in one measurement and capable of editing a spectrum in one measurement. It is to be.

[0020]

In order to achieve the above-mentioned object, the first invention of the present application is, in collecting a spectrum of a specific metabolite in a living body, another one chemically bound to the metabolite. In a magnetic resonance diagnostic apparatus for applying a decoupling pulse of an RF pulse related to a metabolite and imaging a metabolite using a pulse sequence that suppresses the influence of other metabolites, the spectrum of the specific metabolite is analyzed. When collecting, it is characterized by having a means for applying a decoupling pulse only when collecting data in the low frequency region on the spatial frequency.

In the second invention of the present application, in addition to the first invention, the data in the low frequency region to which the decoupling pulse is applied and the data in the high frequency region to which the decoupling pulse is not applied are periodically arranged. And a means for collecting and reconstructing each of the collected data.

A third invention of the present application is a magnetic resonance diagnostic apparatus for detecting an NMR signal from a second metabolite that is J-bonded to a first metabolite in a living body, wherein the first metabolite contains J. The second metabolite that binds and the second metabolite that does not J-join have a means for setting the phase difference to 180 degrees, and the phase difference encodes 0 degree and 1 degree each time the gradient magnetic field advances one step.
It is characterized by alternating to 80 degrees.

The fourth invention of the present application is 90 degree RF related to ¹ H.
Pulse, 180 degree RF pulse is applied, and 90 degree RF is applied.
From pulse to (2I + 1) / 2J (I = 0, 1, 2, ...,
J is the strength of J coupling) or (2I + 1) of the echo signal
Applying 180 degree RF pulse related to ¹³ C before / 2J R
An F pulse applying means is provided, and the RF pulse applying means repeats application and non-application of the 180 degree pulse related to ¹³ C each time the encode gradient magnetic field is advanced by one step.

[0024]

According to the first and second inventions of the present invention, which are configured as described above, the total dose of decoupling pulses is reduced, and the time average of the dose is also reduced. Therefore, the safety does not exceed the SAR standard. Imaging of metabolites can be performed by irradiating with decoupling pulses.

According to the third and fourth inventions of the present application, ¹³
Phase difference of the spin echo signal C of 180 ° pulses by ¹³ C and J bonded to and ¹ H and J Unbound ¹ H 1
Since it is 80 °, 18 of ¹³ C
Application of 0 ° pulse, by repeating the non-applied and to reconstruct the data obtained, ¹ being J coupling ¹³ C
It becomes possible to separate H from ¹ H that is not J-bonded. That is, the above-described separation can be performed by one-time metabolite imaging.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a magnetic resonance diagnostic apparatus according to the first embodiment of the present invention. In the figure,
A static magnetic field magnet 1 and a gradient coil 2 and a shim coil 4 provided inside the static magnetic field magnet 1 provide a uniform static magnetic field to a subject (not shown) and a linear gradient magnetic field distribution in three directions x, y, and z orthogonal to each other in the same direction. The gradient magnetic field possessed is applied. The gradient coil 2 is driven by a gradient coil power supply 5, and the shim coil 4 is driven by a shim coil power supply 6. The probe 3 provided inside the gradient coil 2 applies a high-frequency magnetic field to the subject by being supplied with the high-frequency signal from the transmitter 7, and receives a magnetic resonance signal from the subject. The probe 3 may be used for both transmission and reception, or may be separately provided for transmission and reception. The magnetic resonance signal received by the probe 3 is detected by the receiver 8 and then transferred to the data collector 9 where it is A / D converted and then sent to the computer system 10 for data processing.

The above gradient coil power supply 5, shim coil power supply 6, receiving unit 8 and data collecting unit 9 are all controlled by the sequence control unit 12, and the sequence control unit 1 is also used.
2 is controlled by the computer system 10. The magnetic resonance signal input from the data collection unit 9 to the computer system 10 is subjected to Fourier transform or the like, and image data of the density distribution of desired nuclei in the subject is reconstructed based on the Fourier transform. This image data is sent to the image display 13,
It is displayed as an image.

In the metabolite imaging that requires a decoupling pulse such as ¹³ C, in order to make the RF application amount as small as possible, the present invention applies the decoupling pulse only in the low frequency region of the spatial frequency. , Not applied in the high frequency range. 2 and 3 show a space of spatial frequencies, that is, a so-called k space. A decoupling pulse is applied in the region a of FIG. At this time, the decoupling pulse to be applied may be a pulse train such as WALT or a continuous high frequency.

On the other hand, the decoupling pulse is not applied in the region b. In the spectrum distribution of the real space, that is, the three-dimensional space, the signal in the low frequency region of the k space becomes dominant, and the contribution of the signal in the high frequency region is small compared to this, so using the data collected by this method If reconfigured,
There is a sufficient decoupling effect. That is, a spectrum with good S / N can be obtained.

For the method of collecting data only in a limited area of k-space, see University of Calfornia San Francisc.
o AAMaudssley et al., Society of Magnetic Resona
ncein Medicine 1991 Convention (Meeting Reprint p.186)
, Said. Since their invention does not collect data in other regions of k-space, they are susceptible to cast ringing. On the other hand, in the method of the present invention, since the data of the entire region of the k-space is collected, the influence of cast ringing is reduced.

By using this method, the sum of the doses of decoupling pulses can be first reduced. In SAR, not only the sum of irradiation doses but also a specific time average becomes a problem. Therefore, the encoding application procedure must be changed from the conventional method. Since it is sufficient to make the time average of the irradiation amount as small as possible, when the number of points in both regions is the same, data collection in the low frequency region and data collection in the high frequency region of the spatial frequency may be alternately performed, for example. However, the number of points in the low frequency region and the number of points in the high frequency region are not necessarily the same, and in this case, the following is performed.

That is, when there are few points in the low frequency region,
First, data in the low frequency region and data in the high frequency region may be alternately collected, and then data in the high frequency region may be collected. If there are many points in the low-frequency region, they cannot be alternated, so the data acquisition method is determined from the ratio of the number of points in the low-frequency region and the number of points in the high-frequency region. For example, in the case of 2: 1, data in the low frequency region is collected twice and then data in the high frequency region is collected once. After the data is collected by such a method, the data is rearranged and reconstructed to obtain the spectrum distribution. As a result, the method of the present invention makes it possible to obtain a spectral distribution with a sufficient decoupling effect without exceeding the SAR. The above procedure is shown in the flow chart of FIG.

Here, a method of alternately collecting data of a pulse train for decoupling and a pulse train for no decoupling is shown, but the purpose is to prevent the RF application amount from exceeding the SAR standard. Therefore, it is not always necessary to take them alternately. For example, there are many combinations such as a method in which a pulse train with decoupling is continued twice and then a pulse train without decoupling pulse is applied once. The application sequence of the pulse train with the decoupling pulse and the pulse train without the decoupling pulse is designed based on the power application time of the RF pulse to be actually irradiated and the repetition time to create a sequence.

Since the method of the present invention defines the region on the k space to which the decoupling pulse is applied and the order of data collection in the k space, it does not depend on the sequence. That is, the MRSI sequence for collecting data by FID as shown in FIG. 5 or the MRSI sequence for collecting data as SE (spin echo) as shown in FIG. 6 may be used.

A second embodiment for solving the SAR problem is as follows.
This is a method of changing the application time of the decoupling pulse for each encoding. For example, as shown in FIG. 7A, the application time of the decoupling pulse (here, 0 encoding is shown) is lengthened in the low frequency region. On the other hand, as shown in FIG. 7B, the decoupling application time is shortened in the high frequency region. In the low frequency region of the k-space, the dephase due to encoding is small, so T ₂ ^{* of the} observed signal is long. Therefore, in order to make the decoupling effective, it is necessary to lengthen the application time of the decoupling pulse. On the other hand, in the high frequency region, since the dephase due to encoding is large, T ₂ ^{* of the} observed signal
Is short. Therefore, it is not necessary to apply the decoupling pulse for a long time, and the application time can be shortened.

If the relationship between the k-space and the application time of the decoupling pulse is set as described above and the data collection order is set as described in the first embodiment, for example, the total RF application amount becomes small and the time average is also obtained. Can be made smaller.

The third embodiment is an example in which the power of the decoupling pulse is a function of time, rather than being made constant in time as in the conventional case. Basically, the power of the decoupling pulse is constant. But,
After the 90 ° RF pulse is applied, the FID is attenuated at T ₂ ^* , so not all signals contribute equally to the spectral composition.

In the FID signal of FIG. 5, as the data immediately after generation becomes dominant in the spectrum generation and attenuates, the contribution to the spectrum becomes smaller. That is, FI
Immediately after D is generated, sufficient decoupling is required, but the decoupling pulse may be weakened as it is attenuated.

In consideration of the above, the decoupling pulse may be made small in time, and for example, a method of attenuating the power with an exponential function can be considered. At this time, the MRSI sequence is as shown in FIG.

As described above, in order to control the power of the decoupling pulse with time, in the block diagram of the magnetic resonance diagnostic apparatus of FIG. 1, the computer system 10 generates an RF drive waveform which changes with time, and the sequence controller 12 To the transmitter 7.

The fourth embodiment is a method combining the first to third embodiments. That is, the length of the application time of the decoupling pulse is determined in the k-space region, whether or not to apply the decoupling pulse is determined, and the time change of the intensity of the decoupling pulse is also added. These allow effective decoupling without exceeding the SAR standard.

In the fifth embodiment, as the decoupling method and the data collection method, the method shown in the first embodiment is used. That is, decoupling is performed only in the low-frequency region of the k space, and a pulse train for decoupling and a pulse train for no decoupling are alternately collected. After collecting the data,
Rearrange in k space. The subsequent processing is the first
Different from the embodiment described above, after the rearrangement is performed, the window function processing is performed in the k space. The state of weighting in the k space at this time is shown in FIG. As the window function, a well-known function such as exponential function, Hamming, Hanning, or Gaussian function is used. By using the window function, the connection between the high frequency region to which the decoupling pulse is applied in the k space and the low frequency region to which the decoupling pulse is applied becomes smooth. After performing this process, reconfigure,
Obtain the spectral distribution. When this processing is performed, there is no possibility of waviness and interference between voxels as in cast ringing. That is, the interference between voxels in the real space becomes smooth. A flow chart showing the procedure of the fifth embodiment is shown in FIG.

In the fifth embodiment, only the window function processing on the k space is mentioned, but the window function processing by the exponential function on the time axis, which is usually performed by the NMR analyzer, is simultaneously performed. Is also good. The window function process in real time may be performed immediately after data collection, after the rearrangement, or after the window function process in the k space.

FIG. 11 is a diagram for explaining the sixth embodiment.
It was shown to. In this embodiment, the power of the decoupling pulse is a function of ki (i = x, y, z) as shown in this figure. The idea is the same as in the first embodiment, and a sufficient decoupling pulse is applied in the low frequency region of the k space, and the power of the decoupling pulse is reduced as the frequency advances to the high frequency region. For the data collection, for example, a method of alternately applying a pulse train that sufficiently applies the power of the decoupling pulse and a pulse train that applies a small power is used. After data collection, rearrangement is performed by rearranging in k-space.

The seventh embodiment is an application of the above method to multi-slice. The basic idea is the same as the idea of the method described above, and is based on the idea that the decoupling pulse is applied in the low frequency region of the k space and not applied in the high frequency region. Figure 12 shows the sequence.
Each slice plane (here, an example of 3 slices is shown)
The subject corresponding to is shown in FIG. As shown here, the time average of the irradiation amount of the decoupling pulse can be lowered by changing the encoding step for each slice plane. By this method, the problem of SAR can be avoided.

In the case of multi-slice MRSI, only an example in which it is combined with the first embodiment has been described, but in combination with the second embodiment, that is, the decoupling pulse is not applied in the high frequency region, but the application time May be used, or may be combined with the decoupling pulse application method shown in the third to sixth embodiments.

The metabolite imaging method requiring decoupling has been described above. This nuclide is not limited to ¹ H decoupling during ¹³ C detection. For example, ¹
There is also an example of ¹³ C decoupling during H detection. In this regard, the detected and decoupled nuclei are summarized in Table 1 below.

[0048]

[Table 1] Further, in the above-mentioned sequence for explaining the application of the decoupling pulse, the sequence in which the decoupling pulse is irradiated immediately after the encode gradient magnetic field has fallen is shown, but the time of applying the RF that matches the resonance frequency of the nucleus to be detected. Therefore, the irradiation of the decoupling pulse has a greater effect of the decoupling and the S / N is also improved. Further, since the decoupling pulse is applied not before the RF irradiation of the nucleus to be detected but before the irradiation, the RF irradiation amount can be reduced. This embodiment is shown in FIG. This decoupling irradiation method can be applied to all the embodiments described in the present invention.

As described above, regarding the metabolite imaging method that requires decoupling, a method for preventing the SAR standard from being exceeded has been shown.

Next, an eighth embodiment relating to claims 3 and 4 of the present invention will be described. In the eighth embodiment of the present invention, a two-dimensional metabolite imaging method will be described for simplification. The sequence is shown in FIG. This method and Fig. 4
The difference from the POCE method shown in FIG. 7 is that the data collected in FIG. 47A of the sequence in which the POCE method applies a 180 pulse of ¹³ C and the sequence of FIG.
While the difference from the data collected in (b) is taken to edit the ¹ H that is J-bonded to ¹³ C, in the present invention, a 180 ° pulse of ¹³ C is applied or not applied each time the encoding is advanced. Since the application is repeated, the observation time is half that of the POCE method.

[0051] In the sequence of FIG. 15, the application of ¹³ C inversion pulse every time the encoding advanced by 1, 2n → ON shown next to the ¹³ C inversion pulse repeating the non-application, 2
It is indicated by n + 1 → OFF. The timing of applying the ¹³ C inversion pulse is from the 90 pulse of ¹ H to (2I +
1) / (2J) later (I = 0, 1, 2, 3, ...).

For example, consider the case where the application and non-application of the ¹³ C inversion pulse are repeated each time kx advances by one step as shown in FIG. In this case, ON and OFF can be expressed in k space as shown in FIG. ¹³ C inversion pulse ON, O
By FF, only ¹ H J-bonded to ¹³ C is 0 ° and 18
Since it is inverted at 0 °, reconstructing the data collected by the sequence of FIG. 15 produces two data in the x direction, as in FIG. The central area a is ¹³ C at J
Shows A ¹ H Unbound shows ¹ H of region b of the end are J coupled to ¹³ C. That is, in the method of the present invention, ¹ H that is J-bonded to ¹³ C and other ¹ H can be separated by a ^single metabolite imaging sequence. This method
The spectrum is edited by adding not only the frequency axis direction but also the x, y, z spatial coordinate axis directions.

Although FIG. 15 shows the sequence for the spatial two-dimensional metabolite imaging method, the spatial three-dimensional sequence can be similarly shown as in FIG.

An example of the inversion of the phase of the NMR signal in imaging is the invention of Norbert Joseph Berg (Japanese Patent Laid-Open No. 61-142448). This method is a method of inverting the phase of the NMR signal by inverting the phase of the 90 ° pulse in the sequence of FIG. 19 and separating the baseline error component which is an artifact and the image component. The difference between the method of JP-A-61-242448 and the method of the present invention is that JP-A-61-124444 is used.
While the method of No. 8 has only the effect of removing the unwanted signal from the desired signal, this method separates the two desired signals of the ¹ H signal coupled to ¹³ C and the other ¹ H signal and separates them. It has the effect that the spectrum can be easily edited. Moreover, the baseline error component is no longer a problem due to the development of digital transmission / reception systems in recent years,
The method of JP-A-61-244448 is no longer necessary. In contrast, the method of the present invention is still useful.

Next, C for suppressing the water signal is added to the prepulse.
FIG. 20 shows a locally excited ¹ H observation sequence in which a HESS pulse is applied. FIG. 20 shows an example in which the application position of the ¹³ C inversion pulse is (2I + 1) / (2J) before the third echo signal, but it may be after (2I + 1) / (2J) of the 90 ° pulse. It may be before (2I + 1) / (2J) or after (2I + 1) / (2J) of two echoes. Applies the ¹³ C inversion pulse encoding each time advanced by one, if to repeat the non-application, to separate and ¹ H and the other of the ¹ H which is J-coupling in the same manner as ¹³ C in the case of FIG. 15 You can

Further, by using the present invention, it is possible to separate two or more metabolites. FIG. 21 shows a sequence for separating ¹ H which is J-bonded with ¹³ C and spin-spin coupling constants J ₁ and J ₂ , respectively. In this case, it is necessary to use a frequency selective excitation pulse as the ¹³ C inversion pulse. The ¹³ C inversion pulse A applied 1/2 J ₁ after the 90 ° pulse is
An inversion pulse that selectively excites only ¹³ C that is J-coupled with the spin-spin coupling constant J ₁ is used. Similarly, as the ¹³ C inversion pulse applied 1/2 J ₂ of the 90 ° pulse, an inversion pulse that selectively excites only ¹³ C that is J-coupled with the spin-spin coupling constant J ₂ is used. FIG. 22 shows the order of application and non-application of the ¹³ C inversion pulse A. In this way, the pulse A is repeatedly applied and not applied every time it advances in the kx direction, and is not changed in the ky direction. On the other hand, the pulse B is repeatedly applied and not applied every time the step advances in the ky direction, and does not change in the kx direction. As a result,
Like the metabolites image 23, the x-direction the separated ¹ H spin-spin coupling with ¹³ C and J _1, the y-direction ¹³ C
And J ₂ spin-spin-coupled ¹ H is separated.

In the above-mentioned separated imaging, the area (FO
V) is required, but a method of performing 0 filing on the spatial frequency data in order to make this one image worth is also conceivable.
In this case, for example, data of matrix size 16 × 16 is collected and 32 × 32 is obtained by 0 filing.
It may be reconfigured after setting the data size to. As a result, it is possible to obtain the FOV required for separation imaging in a short observation time.

Next, an example in which the present method is applied to one dimension will be shown. The sequence is shown in FIG. This data is shown in Figure 25-
Two-dimensional data of 2 in the t-axis direction as in A is 2
When subjected to dimensional Fourier transform, ¹ H and J that J bound to ¹³ C
Unbound ¹ H can be separated. (Fig. 2
5 (B)).

Further, the present invention can be used in the case of a method of editing a spectrum by taking a difference by utilizing phase inversion other than the POCE method.

As one example of this, there is a method of editing lactic acid by utilizing J bonds between ¹ H's. This method is shown in FIG.
Shown in This method is described by CJ Hardy et al. In Magnetic
Resonance in Medicine, Vol.5, p.58-p.66, 1987. This method uses TE1 = 136 ms and TE2
This is a method of obtaining a lactic acid signal by removing the water signal and the fat signal by taking the difference between the signals of = 272 ms. Even with this method, the signal S of 136 ms as shown in FIG.
The lactic acid spectrum and the water and fat spectrum can be separated by arranging the 1 and 272 ms signals S2 in the t-axis direction × 2 and performing two-dimensional Fourier transform. The method described above may be applied to the method of converting lactic acid into pixels, and the sequence is as shown in FIG. In this sequence, the encoding step of 272 ms is advanced by 1 for the encoding step of 136 ms (FIG. 29). By performing this encoding step in the kx direction as shown in FIG. 29, it is possible to separate an image of a substance, such as water and fat, in which ¹ H is not J-bonded, from an image of lactic acid (FIG. 30).

Next, ¹³ C will be described. Although the decoupling pulse for making the spectrum easy to see is not applied in the above-mentioned embodiments, this application is possible for all the sequences regarding ¹³ C described. For example, an example in which a decoupling pulse is applied to the sequence of FIG. 15 is shown in FIG. By applying a ¹³ C decoupling pulse during the data collection period as described above, the J bond between ¹³ C and ¹ H can be eliminated, and the spectrum can be made easier to see. The decoupling pulse application start time is
In order to make the spin phases split by the J coupling match, t _l (2l + 1) / 2J (l
= 0, 1, 2, ...). Similarly, FIG.
By applying a decoupling pulse during the data acquisition period of the sequence of FIGS.

Next, another embodiment of ¹ H observation ¹³ C-MRSI will be described.

This example is described by A. Bax et al.
f Magnetic Resonance, vol.55, p.301,1983, HMQC (Heteronuclezr multiple quantum coh)
erence) method or by Bodenhausen et al.
This is a method that applies the SQC (Single quantum coherence) method introduced in hysics Letters, vol.69, p.185, 1980. 32 shows an application example of the HMQC method, and FIG. 33 shows SQC.
An application example of the method is shown. These examples allow the separation of ¹ H bound to ¹³ C and ¹ H other than that.
FIG. 34 shows an example of a sequence using stimulated echo. In this example, three CHES are included in the water signal suppression pulse.
An example using the S pulse is shown. The water signal suppression pulse can be used in the sequence described so far.

FIG. 35 shows a sequence which can bring ¹ H bound to ¹³ C to the center of the image. This can also be achieved by changing the phase of reception to 0 ° and 90 ° each time the sequence proceeds, without changing the phase of ¹ H RF.

Further, in the sequence as shown in FIG. 20, if the ¹³ C inversion pulse is applied or not applied in the order as shown in FIG. 36, the separated image can be obtained as shown in FIG.

[0066]

As described above, according to the first and second inventions of the present application, the metabolism using the decoupling pulse is performed without increasing the RF irradiation dose or the time average value, that is, without exceeding the SAR standard. It becomes possible to perform object imaging.

According to the third and fourth inventions of the present application, P
In metabolite imaging in which the desired signal and the other signals are separated in phase, and then the desired signal is separated by the difference like the OCE method, conventionally, the desired signal and the other signals have the same phase. It was necessary to acquire the image and the image whose phase is shifted by π, but according to the present invention, the separated image can be obtained at one time. Also, in spectrum editing, a desired signal can be separated without using the difference.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a magnetic resonance diagnostic apparatus.

FIG. 2 is a diagram showing a region irradiated with a decoupling pulse and a region not irradiated with it in a k-space.

FIG. 3 is a diagram showing a region to be irradiated with a decoupling pulse and a region not to be irradiated in the k space.

FIG. 4 is a flow chart diagram for explaining an embodiment of the present invention.

FIG. 5 is a pulse sequence diagram for explaining an embodiment of the present invention.

FIG. 6 is a pulse sequence diagram for explaining an embodiment of the present invention.

FIG. 7 (a) is a diagram illustrating a decoupling pulse emitted in a low frequency region on k space. (B) It is a figure explaining the decoupling pulse irradiated in a high frequency area | region in k space.

FIG. 8 is a diagram showing an example of a decoupling pulse for irradiation.

FIG. 9 is a diagram showing a function for weighting the collected and rearranged data on the k space.

FIG. 10 is a flowchart showing a procedure from data collection when weighting in k-space.

FIG. 11 is an explanatory diagram showing a function when the power of the decoupling pulse is changed in the k space.

FIG. 12 is a pulse sequence diagram showing irradiation of a decoupling pulse in multi-slice MRSI.

13 is a diagram showing a slice plane that is selectively excited in the sequence of FIG.

FIG. 14 is a pulse sequence diagram for explaining an example of the present invention.

FIG. 15. ¹ H J-linked to ¹³ C in a single metabolite imaging.
FIG. 7 is a pulse sequence diagram for separating ¹ H and the other ¹ H.

16 is an explanatory diagram showing the order of application and non-application of the ¹³ C inversion pulse on the k space in FIG.

17 is an explanatory diagram showing an image obtained by performing a Fourier transform on the data collected by the sequence of FIG.

FIG. 18 is a diagram showing an example in which the spatial two-dimensional sequence of FIG. 15 is applied to a spatial three-dimensional sequence.

FIG. 19 is a pulse sequence diagram for removing a baseline error component from an image.

FIG. 20: ¹ by water signal suppression pulse and local excitation method
It is a pulse sequence diagram of H observation ¹³ C-MRSI method.

FIG. 21 is a pulse sequence diagram for separating ¹ H that is J-bonded with ¹³ C by a coupling constant J ₁ , ¹ H that is bonded by a coupling constant J ₂ and ¹ H other than that.

22 is an explanatory diagram showing the order of application and non-application of ¹³ C inversion pulses A and B in the sequence shown in FIG. 21. FIG.

23 is a diagram showing an image obtained by performing a Fourier transform on the data collected by the sequence of FIG. 21.

FIG. 24 is a pulse sequence diagram according to a method for collecting one-dimensional data.

FIG. 25 is a diagram showing the arrangement of data obtained in FIG. 24;
It is a figure showing the result of reconstructing.

FIG. 26 is a signal of TE = 136 ms and TE = 272 ms.
FIG. 6 is a pulse sequence diagram showing a method of extracting only the lactate signal by taking the difference from the signal of FIG.

27 is a diagram showing a result of reconstructing the data obtained in FIG. 26. FIG.

FIG. 28 is a pulse sequence diagram showing a procedure for imaging a signal of lactic acid.

FIG. 29: TE 136 ms and TE = 27 on k-space
It is explanatory drawing which showed the order of 2 ms data collection.

[Figure 30] Water is an explanatory view showing a state in which imaging was separated by ¹ H of the ¹ H and lactic fat.

FIG. 31 is a graph showing ¹³ C during the data collection period of the sequence of FIG.
It is a pulse sequence diagram which applied the decoupling pulse.

FIG. 32 is a pulse sequence diagram in which the present invention is applied to the HMQC method.

FIG. 33 is a pulse sequence diagram in which the present invention is applied to the SQC method.

FIG. 34 is a pulse sequence diagram in which the present invention is applied to the stimulated echo method.

FIG. 35 is a pulse sequence diagram for moving ¹ H coupled to ¹³ C to the center of an image.

FIG. 36 is an explanatory diagram showing another method for performing of the ¹ H and the other of the ¹ H bonded to ¹³ C separation imaging.

37 is a diagram showing an image obtained by reconstructing data collected using the sequence of FIG. 35.

FIG. 38 is a conventional MRSI pulse sequence diagram.

FIG. 39 is an explanatory diagram showing a spectral distribution obtained by an MRSI sequence.

FIG. 40 is an explanatory diagram showing data obtained in a sequence without a tecoupling pulse.

41 is an explanatory diagram showing a spectrum obtained by the sequence of FIG. 40. FIG.

FIG. 42 is a pulse sequence diagram for irradiating a decoupling pulse.

43 is an explanatory diagram showing spectra obtained by the sequence of FIG. 42. FIG.

FIG. 44: Conventional MR irradiating decoupling pulse
It is an SI sequence.

FIG. 45 is a pulse sequence diagram of the POCE method which is a conventional ¹ H observation ¹³ C spectroscopy method.

FIG. 46 is an explanatory diagram showing a behavior of spin in the POCE method.

FIG. 47 is an explanatory diagram showing an example in which the POCE method is applied to a metabolite imaging method.

[Explanation of symbols]

 1 Static Magnetic Field Magnet 2 Gradient Coil 3 Probe 4 Shim Coil 5 Gradient Coil 6 Shim Coil Power Supply 7 Transmitter 8 Receiver 9 Data Acquisition 10 Computer System 11 Console 12 Sequence Controller 13 Image Display

Claims (4)

[Claims] 1. When collecting a spectrum of a specific metabolite in a living body, an RF pulse relating to the other metabolite chemically bound to the metabolite is applied as a decoupling pulse, and the other metabolite is applied. In a magnetic resonance diagnostic apparatus that images a metabolite using a pulse sequence that suppresses the influence of the above, when collecting the spectrum of the specific metabolite, decoupling is performed only when data in a low frequency region on a spatial frequency is collected. A magnetic resonance diagnostic apparatus comprising means for applying a pulse. 2. A unit for periodically switching and collecting data in the low frequency region to which the decoupling pulse is applied and data in the high frequency region to which the decoupling pulse is not applied, and rearranging each of the collected data. 2. The magnetic resonance diagnostic apparatus according to claim 1, further comprising: 3. A second J-bond to a first metabolite in vivo.
Is a magnetic resonance diagnostic apparatus for detecting an NMR signal from a metabolite of the first metabolite, wherein the phase difference between the second metabolite J-bonded to the first metabolite and the second metabolite J-unbonded to the first metabolite is 180. A magnetic resonance diagnostic apparatus, characterized in that it has a means for setting the phase difference and alternately switches the phase difference between 0 degree and 180 degrees each time the encoding gradient magnetic field is advanced by one step. 4. A 90 degree RF pulse and a 180 degree RF pulse related to ¹ H are applied, and (2I
¹³ C after +1) / 2J (I = 0,1,2, ..., J is the strength of the J coupling) or before (2I + 1) / 2J of the echo signal
The RF pulse applying means for applying the 180-degree RF pulse according to 1), the RF pulse applying means repeats application and non-application of the 180-degree pulse according to ¹³ C each time the encode gradient magnetic field is advanced by one step. A characteristic magnetic resonance diagnostic apparatus.