JP2004148024A - Quantification method for n-acetyl asparate, glutamine, and gultamate and magnetic resonance imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a quantification method for N-acetyl asparate (NAA), gultamine and gultamate (Glx) in an organism, performed simply and with good accuracy, and a magnetic resonance imaging apparatus. <P>SOLUTION: A first and second spectra including NAA and Glx of TE=25 msec are obtained, and a third and fourth spectra of only NAA of TE=60 msec are obtained. A first and second differential spectra substantially composed of Glx are obtained from a difference between the above spectra, and Marquardt fitting is performed for the second spectrum of only NAA and the first differential spectrum substantially composed of Glx to obtain the optimum fitting waveform, whereby the NAA and Glx in the inside of a subject can be quantified with high accuracy and simply. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for quantifying N-acetylaspartate, glutamine and glutamate by a spectrum obtained by a press method, and a magnetic resonance imaging apparatus.
[0002]
[Prior art]
BACKGROUND ART In recent years, quantitative evaluation of metabolites in a living body by proton spectroscopy using a magnetic resonance phenomenon has been performed. Here, for example, quantitative evaluation of N-acetylaspartate, glutamine, glutamate and the like is performed. However, since the in vivo test can be performed noninvasively, the load on the living body is light and useful. (For example, see Non-Patent Document 1).
[0003]
[Non-patent document 1]
DL Rothman et al., Localized Proton Spectra of Glutamate in the Human Brain (Localized ¹ H NMR Spectra of Glutamate in the Human Brain, "Magnetic Resonance in Medicine, USA, 1992, 25, p. 94-106)
[0004]
[Problems to be solved by the invention]
However, according to the above-mentioned conventional technology, it was not possible to simply and accurately quantify metabolites. That is, in order to quantify metabolites with high accuracy, it was necessary to lengthen the photographing time, separately prepare a special pulse sequence, analysis software, or the like.
[0005]
In particular, in the case of a plurality of metabolites having magnetic resonance frequencies close to each other, spectra overlap each other, and it is difficult to separate and extract a spectrum of only a specific metabolite from a spectrum in which the plurality of metabolites are mixed. , With difficulties.
[0006]
From these facts, it is important how to realize a method for quantifying N-acetylaspartate, glutamine and glutamate in a living body, which can be performed simply and accurately, and a magnetic resonance imaging apparatus.
[0007]
The present invention has been made to solve the above-described problems of the related art, and provides a method of quantifying N-acetylaspartate, glutamine, and glutamate in a living body, which can be simply and accurately performed, and a magnetic resonance imaging apparatus. The purpose is to:
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems and achieve the object, a method for quantifying N-acetylaspartate, glutamine and glutamate according to the first aspect of the present invention comprises a method of pulsing different TEs using a press method including water signal suppression. By the sequence, N-acetylaspartate present in the subject and in the phantom, a plurality of spectra of glutamine and glutamate are obtained, a difference between the plurality of spectra is obtained, and an optimal fitting function is obtained from the spectra and the differences, The amount of the N-acetylaspartate, the glutamine, and the glutamate in the subject is estimated based on a fitting function.
[0009]
According to the invention according to the first aspect, a plurality of spectra of N-acetylaspartate, glutamine, and glutamate present inside the subject and in the phantom are obtained by different TE pulse sequences using a press method including water signal suppression. Further, performing a difference between the plurality of spectra, determine an optimal fitting function from the spectrum and the difference, based on the fitting function, the amount of the N-acetyl aspartate, the glutamine and the glutamate in the subject is determined. Since it is to be estimated, magnetic resonance signals with N-acetylaspartate, glutamine and glutamate having resonance frequencies close to each other and having different relaxation times are separately obtained, and fitting is performed on these separated spectra. Do the accuracy Gastric quantification information can be obtained easily.
[0010]
Further, the magnetic resonance imaging apparatus according to the second aspect of the present invention uses a pulse sequence using a press method including water signal suppression to convert the proton spectrum of N-acetylaspartate, glutamine and glutamate present inside the subject or in the phantom. A magnetic resonance imaging apparatus for acquiring, wherein acquiring means for acquiring a plurality of spectra having different TEs of the pulse sequence, differencing means for performing a difference between the plurality of spectra, and N-acetylas from the spectrum and the difference. Pareto, fitting means for determining an optimal fitting function of the glutamine and the glutamate, and estimating means for estimating the amount of the N-acetylaspartate, the glutamine and the glutamate in the subject from the fitting function. This The features.
[0011]
According to the invention of the second aspect, the acquisition unit acquires a plurality of spectra having different pulse sequence TEs, the difference unit performs a difference between the plurality of spectra, and the fitting unit performs N- Since the optimal fitting function of acetylaspartate, glutamine and glutamate is determined and the amount of N-acetylaspartate, glutamine and glutamate in the subject is estimated from the fitting function by the estimation means, N-acetylaspartate is used. The magnetic resonance signals of Pareto, glutamine and glutamate are separated and obtained, and fitting is performed on these separated spectra, so that highly accurate quantified information can be obtained.
[0012]
Further, in the magnetic resonance imaging apparatus according to the invention of the third aspect, the acquisition means is acquired by the pulse sequence of TE sufficiently shorter than the T2 relaxation time of the N-acetylaspartate, the glutamine and the glutamate. The phantom and the subject are provided with first and second spectra.
[0013]
According to the third aspect of the invention, the acquisition unit converts the first and second spectra of the phantom and the subject into a pulse sequence of TE that is sufficiently shorter than the T2 relaxation time of N-acetylaspartate, glutamine, and glutamate. Therefore, the spectra of N-acetylaspartate, glutamine and glutamate can be obtained with high signal intensity.
[0014]
Further, in the magnetic resonance imaging apparatus according to the invention of the fourth aspect, in the magnetic resonance imaging apparatus, the acquisition unit may be configured so that the TE of the glutamine and the glutamate is sufficiently longer than the T2 relaxation time of the N-acetylaspartate, It is characterized by comprising third and fourth spectra of the phantom and the subject acquired by a pulse sequence.
[0015]
According to the fourth aspect of the invention, the acquisition means sets the third and fourth spectra of the phantom and the subject sufficiently longer than the T2 relaxation time of glutamine and glutamate, and the T2 relaxation time of N-acetylaspartate. Since acquisition is performed using a shorter TE pulse sequence, a spectrum containing only a magnetic resonance signal of N-acetylaspartate can be acquired.
[0016]
Also, in the magnetic resonance imaging apparatus according to the invention of a fifth aspect, the difference means is configured such that the first and third and the second and fourth difference spectra are differences between the first and third and the second and fourth spectra. It is characterized by having.
[0017]
According to the fifth aspect of the invention, the difference means obtains the first and second difference spectra from the difference between the first and third and second and fourth spectra, so that glutamine is obtained. And glutamate can be largely separated from N-acetylaspartate.
[0018]
A magnetic resonance imaging apparatus according to a sixth aspect of the invention is characterized in that the fitting means is a Murcutt fitting means.
[0019]
According to the invention of the sixth aspect, since the Markat fitting means is used as the fitting means, the optimum fitting can be performed in a short time.
[0020]
Further, in the magnetic resonance imaging apparatus according to the seventh aspect of the present invention, in the magnetic resonance imaging apparatus, the Murcutt fitting means sets a peak frequency, a half width, and a peak of an N-acetyl aspartate waveform included in the fourth spectrum as initial values. It is characterized by.
[0021]
According to the seventh aspect of the invention, since the Murcutt fitting means uses the peak frequency, half-width, and peak of the N-acetylaspartate waveform included in the fourth spectrum as the initial values, The initial value approximated to the fitting function can be used.
[0022]
In the magnetic resonance imaging apparatus according to an eighth aspect of the present invention, in the magnetic resonance imaging apparatus, the Marcut fitting means starts fitting the third spectrum using the initial value, and sets parameters such as a peak frequency, a half width, and a peak value. , And the most suitable N-acetyl aspartate waveform is obtained.
[0023]
According to the eighth aspect of the invention, the Murcutt fitting means starts fitting the most suitable N-acetylaspartate waveform to the third spectrum using the initial value, and sets the peak frequency, half value as parameters. Since the value width and the peak value are determined and changed, it is possible to perform highly accurate fitting in a short time.
[0024]
Also, in the magnetic resonance imaging apparatus according to the ninth aspect of the present invention, in the magnetic resonance imaging apparatus, the Marcut fitting means fits the parameter to the second difference spectrum, and generates an N-acetyl aspartate waveform included in the second difference spectrum. Is obtained.
[0025]
According to the ninth aspect of the invention, the Murcutt fitting means fits the parameter to the second difference spectrum to determine the N-acetylaspartate waveform contained in the second difference spectrum. N-acetylaspartate contained in the difference spectrum of can be accurately evaluated.
[0026]
In a magnetic resonance imaging apparatus according to a tenth aspect, the difference means includes a glutamine and a glutamate spectrum obtained by subtracting the N-acetylaspartate waveform from the second difference spectrum.
[0027]
According to the tenth aspect, since the difference means obtains the glutamine and glutamate spectra by subtracting the N-acetylaspartate waveform from the second difference spectrum, the spectrum of only glutamine and glutamate is obtained. Can be separated and extracted.
[0028]
Further, in the magnetic resonance imaging apparatus according to the eleventh aspect of the present invention, in the magnetic resonance imaging apparatus, the Marcut fitting means performs fitting of the first difference spectrum using the glutamine and glutamate spectra, and obtains a most suitable glutamine and glutamate waveform. It is characterized by the following.
[0029]
According to the invention of the eleventh aspect, the Murcutt fitting means performs fitting of the first difference spectrum using the glutamine and glutamate spectra to determine the most suitable glutamine and glutamate waveforms, so that the accuracy is high. The amounts of glutamine and glutamate can be determined.
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a method for quantifying N-acetylaspartate, glutamine and glutamate and a magnetic resonance imaging apparatus according to the present invention will be described with reference to the accompanying drawings. Note that the present invention is not limited to this. In the following, N-acetylaspartate is abbreviated as NAA, and glutamine and glutamate are abbreviated as Glx.
[0031]
First, an overall configuration of a magnetic resonance imaging apparatus according to an embodiment of the present invention will be described. FIG. 1 is a block diagram showing an overall configuration of a magnetic resonance imaging apparatus according to Embodiment 1 of the present invention. 1, this magnetic resonance imaging apparatus includes a magnet system (magnet system) 100, a data collection unit 150, a transmission drive unit 140, a gradient drive unit 130, and a control processing unit 199.
[0032]
The magnet system 100 includes a main magnetic field coil unit 102, a gradient coil unit 106, a transmission coil unit 108, and an RF coil 110. These coil portions and coils have a substantially cylindrical shape, and are arranged coaxially with each other. A subject 1 to be imaged is mounted on a cradle 120 in a substantially cylindrical internal space (bore) of the magnet system 100, and is carried in and out by carrying means (not shown).
[0033]
The control processing unit 199 includes a scan controller (scan controller) unit 160, a data processing unit 170, a display unit 180, and an operation unit 190. Here, input of various types of control information is performed from the operation unit 190 to the data processing unit 170, and the control information is transferred to the scan controller unit 160 as a pulse sequence, and then the data is collected by the scan controller unit 160. 150, the transmission drive unit 140, and the gradient drive unit 130.
[0034]
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 substantially parallel to the direction of the body axis of the subject 1. That is, a so-called horizontal magnetic field is formed. The main magnetic field coil unit 102 is configured using, for example, a superconducting coil. The static magnetic field strength is preferably high in order to separate and detect metabolites in the living body. For example, a magnetic field strength of 3 Tesla is used.
[0035]
The gradient coil unit 106 generates three gradient magnetic fields for giving gradients to the static magnetic field strength in directions of three axes perpendicular to each other, that is, the x-axis, the y-axis, and the z-axis.
[0036]
The transmission coil unit 108 forms a high-frequency magnetic field for exciting magnetic resonance in the body of the subject 1 in the static magnetic field space. Further, the RF coil 110 is placed on the cradle 120 and is arranged at the center of the magnet system 100 together with the subject 1. The RF coil 110 receives a magnetic resonance signal excited in the body of the subject 1 by the transmission coil unit 108.
[0037]
The gradient driving unit 130 is connected to the gradient coil unit 106. The gradient driving unit 130 supplies a driving signal to the gradient coil unit 106 to generate a gradient magnetic field. The gradient drive unit 130 has three drive circuits (not shown) corresponding to the three gradient coils in the gradient coil unit 106.
[0038]
The transmission driving unit 140 is connected to the transmission coil unit 108. The transmission drive unit 140 supplies a drive signal to the transmission coil unit 108 to transmit an RF pulse. The transmission coil unit 108 forms an RF magnetic field in the center of the magnet system 100 from the transmitted RF pulse, and To the excited state of magnetic resonance.
[0039]
The data collection unit 150 is connected to the RF coil 110. The data collection unit 150 captures a received signal received by the RF coil 110 by sampling, and collects the received signal as digital data.
[0040]
The scan controller 160 is connected to the gradient driver 130, the transmission driver 140, and the data collection unit 150. The scan controller 160, which is a reception controller, controls the gradient driver 130 or the data collector 150 to collect data.
[0041]
The output side of the data collection unit 150 is connected to the data processing unit 170. The data collected by the data collection unit 150 is input to the data processing unit 170. The data processing unit 170 is configured using, for example, a computer. The data processing unit 170 has a memory (not shown). The memory stores a program for the data processing unit 170 and various data.
[0042]
The data processing section 170 is connected to the scan controller section 160. The data processing unit 170 is above the scan controller unit 160 and controls it. The function of the present apparatus is realized by the data processing unit 170 executing a program stored in the memory.
[0043]
The data processing unit 170 stores the data collected by the data collection unit 150 in a memory. A data space is formed in the memory. This data space constitutes a one-dimensional Fourier space. The data processing unit 170 performs a one-dimensional inverse Fourier transform on the data in the one-dimensional Fourier space to generate a proton spectrum of the subject 1 or a phantom.
[0044]
The display section 180 and the operation section 190 are connected to the data processing section 170. The display unit 180 is configured by a graphic display or the like. The operation unit 190 is a pointing device (pointing device).
device).
[0045]
The display unit 180 displays the spectrum and various information output from the data processing unit 170. The operation unit 190 is operated by a user, and inputs various commands and information to the data processing unit 170. The user operates the present apparatus interactively through the display unit 180 and the operation unit 190.
[0046]
The RF coil 110 is a cylindrical coil, for example, a phased array type or a birdcage type coil.
[0047]
As the pulse sequence of the scan controller 160, a press method having a water fat suppression unit is used. FIG. 2 shows a pulse sequence of the press method according to the present embodiment. FIG. 2 is a time chart showing the operations of the transmission drive unit 140, the gradient drive unit 130, and the data collection unit 150 having a common time axis on the horizontal axis. This pulse sequence includes a first half water suppression unit and a second half press unit.
[0048]
FIG. 2A shows an RF signal waveform output from the transmission driver 140 to the RF coil 110 and a reception echo received by the data collection unit 150 from the RF coil 110. Note that what is shown here is the envelope waveform of the RF signal, which internally contains the RF signal of the magnetic resonance frequency.
[0049]
FIGS. 2B, 2C, and 2D show gradient waveforms output from the gradient driving unit 130 in the z-axis direction, the y-axis direction, and the x-axis direction. This gradient waveform represents the magnitude of the gradient of the linear gradient magnetic field generated in the bore of the magnet system 100.
[0050]
Here, in the water suppression unit, a 90-degree pulse having a narrow frequency band and a wide time width is applied three times in order to excite only water protons in a limited manner, and the x-axis direction, the y-axis direction, and the The excitation magnetic field is dispersed by the spoiler gradient in the z-axis direction to suppress the water proton signal.
[0051]
In the press section, there are a 90-degree pulse for performing selective excitation and two 180-degree pulses. The 90-degree pulse puts a limited region in the z-axis direction into an excited state by the simultaneously output gradient magnetic field in the z-axis direction. Thereafter, the 180-degree pulse inverts the excitation magnetic field in the limited region in the x-axis direction by the simultaneously output gradient magnetic field in the x-axis direction, and further, the next 180-degree pulse outputs the simultaneously output y-axis direction. The excitation magnetic field is inverted in a limited area in the y-axis direction by the gradient magnetic field.
[0052]
Then, after a predetermined time determined by the pulse interval between the 90-degree pulse and the two 180-degree pulses, the received echo is observed. The time from the center position of the 90-degree pulse in the press section to the center position of the received echo is referred to as TE.
[0053]
Here, a functional block diagram of the data processing unit 170 is shown in FIG. The data processing unit 170 includes a spectrum acquisition unit 301, a difference unit 302, a Marquard Fitting unit 303, and an estimation unit 304.
[0054]
The spectrum obtaining means 301 obtains a spectrum of a metabolite existing in a limited region by performing an inverse Fourier transform on the received echo obtained by the pulse sequence shown in FIG. The difference means 302 performs a difference between the spectrum or the fitting waveform acquired by the spectrum acquisition means 301 to calculate a difference spectrum.
[0055]
The Marcut fitting means 303 performs fitting of the resonance waveform to the spectrum waveform using the resonance frequency, the half width, and the peak value as parameters to obtain an optimal fitting waveform. For example, a waveform error is obtained from a difference between the resonance waveform of each parameter value and the spectrum waveform at the fitting destination, and the resonance waveform of the parameter value with the least error is determined as the optimal fitting waveform.
[0056]
The estimating means 304 quantifies the spectrum information of the subject 1 by obtaining the area of the fitting waveform and comparing the area with the spectrum area information of a phantom containing a known metabolite.
[0057]
Next, the operation of quantifying NAA and Glx will be described with reference to the flowcharts of FIGS.
[0058]
First, the data processing unit 170 acquires a phantom spectrum as basic data when quantifying NAA and Glx (step S401). At this time, in the phantom, for example, a predetermined amount of NAA, Glx, and a mixture of creatine and glutamine are dissolved in a phosphate buffer adjusted to pH 7.0.
[0059]
The phantom is arranged by the operator at the position of the subject 1 in the RF coil 110 shown in FIG. 1, and acquires a received echo by a pulse sequence using the press method shown in FIG. The TE of the pulse sequence is 2 times a time sufficiently shorter than the T2 relaxation time of NAA and Glx, for example, 25 msec, and sufficiently longer than the T2 relaxation time of Glx and shorter than the T2 relaxation time of NAA, for example, 60 msec. Acquisition of a reception echo is performed by the type TE.
[0060]
Then, these received echoes are subjected to inverse Fourier transform by the spectrum obtaining means 301, and a first spectrum when TE = 25 msec and a third spectrum when TE = 60 msec are obtained. At this time, a map corresponding to the amount of NAA and Glx in the phantom and the spectrum area is simultaneously created.
[0061]
After that, the data processing unit 170 acquires the spectrum of the subject 1 (Step S402). At this time, the subject 1 is placed in the RF coil 110 shown in FIG. 1 by an operator, and acquires a received echo by a pulse sequence using the pressing method shown in FIG. The TE of the pulse sequence is 2 times a time sufficiently shorter than the T2 relaxation time of NAA and Glx, for example, 25 msec, and sufficiently longer than the T2 relaxation time of Glx and shorter than the T2 relaxation time of NAA, for example, 60 msec. Acquisition of a reception echo is performed by the type TE.
[0062]
Then, these received echoes are subjected to inverse Fourier transform by the spectrum obtaining means 301 to obtain a second spectrum when TE = 25 msec and a fourth spectrum when TE = 60 msec.
[0063]
After that, the data processing unit 170 calculates a difference spectrum of the first to fourth spectra (Step S403). Here, the data processing unit 170 uses the difference means 302 to generate a first difference spectrum that is a difference between the first and third spectra and a second difference spectrum that is a difference between the second and fourth spectra. Is calculated.
[0064]
Here, the first to fourth spectra and the first and second difference spectra will be described with reference to the table of FIG. The spectra described in each column of the table in FIG. 6 schematically show the spectra to be obtained, and the horizontal axis of each spectrum constitutes the same frequency axis.
[0065]
The first spectrum of the phantom, acquired using a pulse sequence of TE = 25 msec, has NAA and Glx peaks because the T2 relaxation time of NAA and Glx is much longer than 25 msec. This spectrum has two peaks, NAA peak 1 and peak 2, and Glx is located close to NAA peak 2 in the middle of these peaks.
[0066]
The second spectrum of the subject 1 obtained using the pulse sequence of TE = 25 msec is substantially the same as the first spectrum, but the NAA and Glx have slightly different peak positions and peak waveforms. The half width becomes wider.
[0067]
The second spectrum of the phantom obtained using a pulse sequence of TE = 60 msec has a peak of Glx because the T2 relaxation time of NAA is sufficiently longer than 60 msec and the T2 relaxation time of Glx is sufficiently shorter than 60 msec. Without, only the NAA peak is present at the same position as the first spectrum. Note that the NAA peak value is attenuated by T2 relaxation and becomes smaller as the TE increases by 35 msec.
[0068]
The fourth spectrum of the subject 1 obtained using the pulse sequence of TE = 60 msec is substantially the same as the third spectrum, but the NAA peak position and the peak waveform are slightly different, and the half width of the peak is obtained. Becomes wider.
[0069]
In the first difference spectrum which is the difference between the first spectrum and the third spectrum of the phantom, the peak of Glx can be extracted because the NAA peak waveform almost disappears due to the difference. However, since the TEs are different, the spectrum waveforms of ΔNAA peak 1 and peak 2, which are differences in peak values due to differences in relaxation times of NAA, remain.
[0070]
The second difference spectrum, which is the difference between the second spectrum and the fourth spectrum of the subject 1, is also substantially similar to the first difference spectrum, but the Glx and ΔNAA have slightly different peak positions and peak waveforms. The half width of the peak becomes wider.
[0071]
Here, returning to FIG. 4, the data processing unit 170 measures the peak value, the half width, and the frequency of the NAA peak 2 of the fourth spectrum, and calculates the initial value of the Murcat fitting means 303 to be described below (step S404). ).
[0072]
Thereafter, the optimal fitting waveforms of NAA and Glx are obtained by the Marcut fitting means 303. First, using the initial value calculated in step S404, fitting is performed on the NAA of the third spectrum (step S405). Further, using the initial value calculated in step S404, fitting is performed on ΔNAA peak 1 of the second difference spectrum (step S406). Here, fitting can be performed on the ΔNAA peak 2, but it is preferable in terms of fitting accuracy that fitting be performed on the ΔNAA peak 1 which has a frequency greatly different from that of Glx and has few overlapping portions.
[0073]
Thereafter, the fitting waveform obtained in step S406 is similarly subtracted from the second difference spectrum (step S407). As a result, a Glx spectrum is generated.
[0074]
FIG. 7 illustrates the processing of step S406 and step S407. FIG. 7A shows a second difference spectrum, in which a fitting waveform indicated by a dotted line in FIG. FIG. 7B is a Glx spectrum obtained by subtracting the fitting waveform of ΔNAA peak 1 from the second difference spectrum of FIG. 7A. Thereby, the ΔNAA peak 1 substantially disappears, so that the fitting of the Glx spectrum can be performed with higher accuracy.
[0075]
Thereafter, the Glx spectrum obtained in step S407 is fitted to the first difference spectrum of the phantom (step S408). Then, a difference between the third spectrum and the fitting waveform in step S405 and a difference between the first difference spectrum and the fitting waveform in step S408 are obtained, and an error in the fitting waveform is calculated (step S409).
[0076]
Thereafter, it is determined whether or not to change the parameter (step S411). If the parameter is to be changed (step S411: affirmative), the peak value, half width and frequency of NAA peak 2 are newly set based on the initial value. The parameter value is changed to a suitable parameter value (step S410), and the process proceeds to the fitting of the third spectrum in step S405. When the parameter is not changed (No at Step S411), the process proceeds to the next step, and an optimal fitting waveform with the least error obtained at Step S409 is determined (Step S412). Here, whether to change the parameter is determined by, for example, whether or not the parameter has been changed a predetermined number of times or within a predetermined range.
[0077]
Thereafter, the amount of NAA and Glx inside the subject 1 is estimated and quantified from the optimal fitting waveform using the correspondence map of the third spectrum and the first difference spectrum of the phantom by the estimating means 304 (step). S413).
[0078]
As described above, in the present embodiment, the first and second spectra of NAA and Glx are acquired from the phantom and the subject 1 using the pulse sequence of TE = 25 msec, and the pulse sequence of TE = 60 msec is obtained. To obtain the third and fourth spectra of only NAA, obtain the first and second difference spectra consisting essentially of Glx from the difference between these spectra, and obtain the second and third difference spectra consisting of only NAA and substantially only Glx. With respect to the first difference spectrum, a fourth spectrum waveform of the subject 1 is used as an initial value, and a second difference spectrum from which the remaining ΔNAA spectrum is removed is used as a fitting waveform to perform a Mercut fitting to obtain an optimal fitting waveform. High accuracy and simple operation. It is possible to quantify the subject 1 of NAA and Glx on.
[0079]
Further, in the present embodiment, it has been described that the spectrum of glutamine and Glx, which is a glutamate, is one, but strictly, it is separated into two spectra. A Mercat fitting for quantification can be performed on each of these two spectra.
[0080]
Further, in the present embodiment, a single voxel (single voxel) press pulse sequence is used. However, a multi voxel (multi voxel) pulse sequence, a single voxel steam (STEAM) method, an Isis (ISIS) method, and the like are all used. Using the proton MRS.
[0081]
【The invention's effect】
As described above, according to the present invention, a plurality of spectra of N-acetylaspartate, glutamine and glutamate present inside a subject and in a phantom are obtained by different pulse sequences of TE using a press method including water signal suppression. Obtaining and further performing a difference between the plurality of spectra, obtaining an optimal fitting function from the spectra and the difference, and estimating the amounts of the N-acetylaspartate, the glutamine and the glutamate based on the fitting function. Since the resonance frequencies are close to each other, and magnetic resonance signals of N-acetylaspartate, glutamine and glutamate having different relaxation times are separately obtained, fitting is performed on these separated spectra, and accuracy is determined. High quantification information , It can be obtained in a simple manner.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an overall configuration of a magnetic resonance imaging apparatus.
FIG. 2 is a diagram showing a pulse sequence according to the embodiment.
FIG. 3 is a functional block diagram illustrating a data processing unit according to the embodiment;
FIG. 4 is a flowchart illustrating an operation of a data processing unit according to the embodiment (part 1).
FIG. 5 is a flowchart illustrating an operation of the data processing unit according to the embodiment (part 2).
FIG. 6 is a diagram comparing spectra of the embodiment.
FIG. 7 is a diagram for obtaining a Glx spectrum from a second difference spectrum according to the embodiment.
[Explanation of symbols]
1 Subject
100 magnet system
102 Main magnetic field coil
106 gradient coil
108 Transmission coil section
110 RF coil
120 cradle
130 Gradient drive
140 Transmission driver
150 Data collection unit
160 Scan Controller
160 copies
170 Data processing unit
180 Display
190 Operation unit
199 Control processing unit
301 Spectrum acquisition means
302 Difference means
303 Mercut fitting means
304 estimation means

Claims (11)

A plurality of spectra of N-acetylaspartate, glutamine and glutamate present in the subject and in the phantom are obtained by different TE pulse sequences using a press method including water signal suppression,
Performing a difference between the plurality of spectra,
Find an optimal fitting function from the spectrum and the difference,
A method for quantifying N-acetylaspartate, glutamine, and glutamate, comprising estimating the amounts of the N-acetylaspartate, the glutamine, and the glutamate in the subject based on the fitting function. A magnetic resonance imaging apparatus for obtaining a proton spectrum of N-acetylaspartate, glutamine and glutamate present in a subject and in a phantom by a pulse sequence using a press method including water signal suppression,
An acquisition unit that acquires a plurality of spectra having different TEs of the pulse sequence, and a difference unit that performs a difference between the plurality of spectra,
A fitting means for determining an optimal fitting function of the N-acetylaspartate, the glutamine and the glutamate from the spectrum and the difference,
Estimating means for estimating the amount of the N-acetylaspartate, the glutamine and the glutamate in the subject from the fitting function,
A magnetic resonance imaging apparatus comprising: The acquisition means includes first and second spectra of the phantom and the subject acquired by the pulse sequence of TE sufficiently shorter than the T2 relaxation time of the N-acetylaspartate, the glutamine, and the glutamate. The magnetic resonance imaging apparatus according to claim 2, wherein: The acquiring means is configured to acquire the phantom and the third and the third subjects of the phantom and the subject obtained by the pulse sequence of TE sufficiently longer than the T2 relaxation time of the glutamine and the glutamate and shorter than the T2 relaxation time of the N-acetylaspartate. 4. The magnetic resonance imaging apparatus according to claim 3, comprising a fourth spectrum. 5. The magnetic resonance imaging apparatus according to claim 4, wherein the difference unit includes first and second, and first and second difference spectra that are differences between the first and third spectra and the second and fourth spectra. 6. apparatus. 3. The magnetic resonance imaging apparatus according to claim 2, wherein the fitting unit is a Murcutt fitting unit. 7. The magnetic resonance imaging according to claim 5, wherein the Murcutt fitting unit sets a peak frequency, a half width, and a peak value of an N-acetylaspartate waveform included in the fourth spectrum as initial values. apparatus. The Murcat fitting means starts fitting the third spectrum using the initial value, and changes peak frequency, half width, and peak value as parameters to obtain the most suitable N-acetyl aspartate waveform. The magnetic resonance imaging apparatus according to claim 7, wherein: 9. The magnetic resonance imaging according to claim 8, wherein the Murcutt fitting unit fits the parameter to the second difference spectrum to obtain an N-acetylaspartate waveform included in the second difference spectrum. apparatus. The magnetic resonance imaging apparatus according to claim 9, wherein the difference means includes a glutamine and a glutamate spectrum obtained by subtracting the N-acetylaspartate waveform from the second difference spectrum. 11. The magnetic resonance imaging apparatus according to claim 10, wherein the Murcutt fitting means performs fitting of the first difference spectrum using the glutamine and glutamate spectra to determine a most suitable glutamine and glutamate waveform.

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