JP6664911B2 - Magnetic resonance apparatus and program - Google Patents

Description

  The present invention relates to a magnetic resonance apparatus for obtaining a Z spectrum and a program applied to the magnetic resonance apparatus.

  In recent years, a CEST (Chemical Exchange Saturation Transfer) imaging method using a signal decay caused by chemical exchange has attracted attention as a method for observing a low-concentration compound (see Patent Document 1).

JP, 2012-513239, A

  In CEST imaging, a sequence is executed while changing the frequency of an RF pulse, and a Z spectrum is created based on data obtained by the sequence. The signal value of the Z spectrum attenuates near the frequency where the CEST effect appears. Therefore, by specifying at which frequency the signal is attenuated from the Z spectrum, it becomes possible to acquire information on CEST depending on the concentration of the compound and the magnetization exchange rate.

  However, in the Z spectrum, a downward peak representing the Lorentz distribution of free water is dominant near the resonance frequency of water. The peak width of this peak is proportional to the transmission magnetic field strength B1, and the value of the peak decreases to near zero. Therefore, the signal drop caused by CEST is buried in a downward peak representing the Lorentz distribution of free water, and there is a problem that it is difficult to extract information reflecting the influence of CEST from the Z spectrum.

  In addition, it is important to specify a site where CEST has occurred among the imaging sites of the subject in order to enhance image diagnostic performance. Therefore, research has been conducted to calculate various coefficient values reflecting the influence of CEST. However, as described above, since it is difficult to extract information reflecting the influence of CEST from the Z spectrum, there is also a problem that it is difficult to calculate a coefficient value reflecting the influence of CEST.

  Therefore, a technique for obtaining a spectrum suitable for acquiring CEST information and calculating a coefficient value reflecting the influence of CEST is desired.

According to a first aspect of the present invention, there is provided a magnetic resonance apparatus that performs a scan for acquiring information reflecting a transfer of magnetization caused by CEST (chemical exchange saturation transfer),
In the scan, scan means for executing a plurality of sequences having RF pulses, wherein the scan means wherein the frequency of the RF pulse is set to be different for each sequence,
Z spectrum creation means for creating a Z spectrum based on the data obtained by the plurality of sequences,
An even function including, as a variable, an offset frequency representing a deviation from the resonance frequency of water, wherein the Z function is based on an even function set so that the value of the even function becomes zero when the value of the offset frequency is zero. Spectrum conversion means for converting a spectrum into a first spectrum;
A CEST term representing a first waveform of a signal component affected by CEST, the CEST term including a first coefficient for representing a characteristic value of the first waveform, and a CEST term not being affected by CEST. Fitting means for fitting the first spectrum obtained by the spectrum converting means using an approximation formula including a baseline term representing a second waveform of the signal component to obtain a value of the first coefficient; ,
The first coefficient, a second coefficient representing the transmission magnetic field strength, and a third coefficient containing information on the magnitude of magnetization of protons contained in the CEST pool, Coefficient value calculating means for calculating the value of the coefficient of 3 in which the value calculated by the fitting means is substituted for the first coefficient of the relational expression, and the second coefficient is calculated in the sequence. Coefficient value calculating means for substituting the value of the transmission magnetic field strength of the RF pulse to be used and calculating the value of the third coefficient;
A magnetic resonance apparatus having:

According to a second aspect of the present invention, there is provided a magnetic resonance apparatus that performs a scan for acquiring information reflecting a magnetization transfer caused by a CEST (chemical exchange saturation transfer),
In the scanning, scanning means for executing a plurality of sequences having a pulse set including a plurality of RF pulses, wherein the phase of the p-th RF pulse and the phase of the (p + 1) -th RF pulse among the plurality of RF pulses Scanning means for cycling the phases of the plurality of RF pulses so that the phase difference of
Z spectrum creation means for creating a Z spectrum based on the data obtained by the plurality of sequences,
An even function including a phase difference of an RF pulse as a variable, wherein the Z spectrum is converted to a first function based on an even function set such that the value of the even function becomes zero when the value of the phase difference is zero. Spectrum conversion means for converting into a spectrum,
A CEST term representing a first waveform of a signal component affected by CEST, the CEST term including a first coefficient for representing a characteristic value of the first waveform, and a CEST term not being affected by CEST. Fitting means for fitting the first spectrum obtained by the spectrum converting means using an approximation formula including a baseline term representing a second waveform of the signal component to obtain a value of the first coefficient; ,
The first coefficient, a second coefficient representing the transmission magnetic field strength, and a third coefficient containing information on the magnitude of magnetization of protons contained in the CEST pool, Coefficient value calculating means for calculating the value of the coefficient of 3 in which the value calculated by the fitting means is substituted for the first coefficient of the relational expression, and the second coefficient is calculated in the sequence. Coefficient value calculating means for substituting the value of the transmission magnetic field strength of the RF pulse to be used and calculating the value of the third coefficient;
Is a magnetic resonance apparatus having:

A third aspect of the present invention is a magnetic resonance apparatus which executes a scan for acquiring information reflecting a magnetization transfer caused by a CEST (chemical exchange saturation transfer), and in the scan, a plurality of scans having RF pulses are provided. A program applied to a magnetic resonance apparatus having scanning means for executing a sequence of, wherein the frequency of the RF pulse is set to be different for each sequence,
Z spectrum creation processing for creating a Z spectrum based on the data obtained by the plurality of sequences;
An even function including, as a variable, an offset frequency representing a deviation from the resonance frequency of water, wherein the Z function is based on an even function set so that the value of the even function becomes zero when the value of the offset frequency is zero. A spectrum conversion process for converting the spectrum into a first spectrum;
A CEST term representing a first waveform of a signal component affected by CEST, the CEST term including a first coefficient for representing a characteristic value of the first waveform, and a CEST term not being affected by CEST. A fitting process of fitting the first spectrum obtained by the spectrum conversion process using an approximation formula including a baseline term representing a second waveform of the signal component to obtain a value of the first coefficient; ,
The first coefficient, a second coefficient representing the transmission magnetic field strength, and a third coefficient containing information on the magnitude of magnetization of protons contained in the CEST pool, A coefficient value calculation process for calculating the value of the coefficient of 3 in which the value calculated by the fitting process is substituted for the first coefficient of the relational expression, and the second coefficient is calculated in the sequence. A coefficient value calculation process of substituting the value of the transmission magnetic field strength of the RF pulse to be used and calculating the value of the third coefficient;
Is a program for causing a computer to execute.

According to a fourth aspect of the present invention, there is provided a magnetic resonance apparatus that executes a scan for acquiring information reflecting a magnetization transfer caused by CEST (chemical exchange saturation transfer). Scanning means for executing a plurality of sequences having a pulse set that includes a pulse set, wherein a phase difference between a phase of a p-th RF pulse and a phase of a (p + 1) -th RF pulse among the plurality of RF pulses is different for each of the sequences Thus, a program applied to a magnetic resonance apparatus that cycles the phases of the plurality of RF pulses,
Z spectrum creation processing for creating a Z spectrum based on the data obtained by the plurality of sequences;
An even function including a phase difference of an RF pulse as a variable, wherein the Z spectrum is converted to a first function based on an even function set such that the value of the even function becomes zero when the value of the phase difference is zero. Spectrum conversion processing for converting to a spectrum,
A CEST term representing a first waveform of a signal component affected by CEST, the CEST term including a first coefficient for representing a characteristic value of the first waveform, and a CEST term not being affected by CEST. A fitting process of fitting the first spectrum obtained by the spectrum conversion process using an approximation formula including a baseline term representing a second waveform of the signal component to obtain a value of the first coefficient; ,
The first coefficient, a second coefficient representing the transmission magnetic field strength, and a third coefficient containing information on the magnitude of magnetization of protons contained in the CEST pool, A coefficient value calculation process for calculating the value of the coefficient of 3 in which the value calculated by the fitting process is substituted for the first coefficient of the relational expression, and the second coefficient is calculated in the sequence. A coefficient value calculation process of substituting the value of the transmission magnetic field strength of the RF pulse to be used and calculating the value of the third coefficient;
Is a program for causing a computer to execute.

  By using the even function, the Z spectrum can be converted into a first spectrum suitable for acquiring CEST information. Further, based on the first spectrum, a value of a third coefficient including information on the magnitude of magnetization of protons included in the CEST pool is calculated. Therefore, the value of the coefficient reflecting the influence of CEST can be obtained.

FIG. 1 is a schematic diagram of a magnetic resonance apparatus according to a first embodiment of the present invention. FIG. 3 is an explanatory diagram of means realized by a processing device 9 in the first embodiment. FIG. 3 is an explanatory diagram of a scan executed in the first embodiment. FIG. 3 is a diagram specifically showing a sequence SE _k in the first mode. FIG. 3 is an explanatory diagram of a Z spectrum. FIG. 3 is a diagram for explaining a difference between a Z spectrum and a CPE spectrum. It is a diagram showing a flow for determining the coefficients ^{_{(M 0 b / M 0 a}} / R1 a). It is a figure which shows a Z spectrum schematically. FIG. 3 is a diagram schematically showing _a CPE spectrum F _CPE (Δω _a ). It is a figure showing the value of each coefficient calculated by fitting. FIG. 9 is a diagram showing values of coefficients (b ₀ , b ₁ , b ₂ , Δω ₀ ) calculated by fitting. It is a figure showing the value of the calculated coefficient (c ₀ , c _MT ). FIG. 4 is a diagram schematically showing _a spectrum F _{CPE_1} (Δω _a ). FIG. 9 is an explanatory diagram of a method for determining whether or not another CEST waveform is included in the CPE spectrum F _CPE (Δω _a ). It is a figure showing the value of each coefficient calculated by fitting. FIG. 9 is a diagram illustrating values of coefficients (b ₀ , b ₁ , b ₂ , Δω ₀ ) calculated by fitting when i = 2. It is a figure showing the value of the calculated coefficient (c ₀ , c _MT ). FIG. 4 is a diagram schematically showing _a spectrum F _{CPE_2} (Δω _a ). FIG. 9 is an explanatory diagram of a method for determining whether or not another CEST waveform is included in the CPE spectrum F _CPE (Δω _a ). FIG. 11 is a diagram illustrating an example in which _a difference spectrum D (Δω _a ) exceeds a threshold value TH1. It is a figure showing the value of the coefficient calculated at i = j. FIG. 9 is a diagram showing values of coefficients (b ₀ , b ₁ , b ₂ , Δω ₀ ) calculated by fitting when i = j. It is a figure showing the value of the calculated coefficient (c ₀ , c _MT ). FIG. 4 is a diagram schematically showing _a spectrum F _{CPE_i} (Δω _a ). It is a figure showing the flow of Step ST15. Step shows the values of the coefficients of the CPE spectrum obtained by recalculation F _CPE (Δω _a) of ST15. FIG. 4 is a diagram schematically illustrating values of coefficients stored in a storage unit. It is a diagram showing a flow for calculating the value of the coefficients ^{_{(M 0 b / M 0 a}} / R1 a). FIG. 3 is an explanatory diagram of a method of calculating a value of ^a coefficient (M ₀ ^b / M ₀ ^a / R1 ^a ) based on a CEST effect of an amide proton. FIG. 9 is an explanatory diagram of a method of calculating a value of ^a coefficient (M ₀ ^b / M ₀ ^a / R1 ^a ) by a CEST effect of NOE. FIG. 9 is an explanatory diagram of a scan executed in the second mode. FIG. 9 is an explanatory diagram of a processing device 9 according to the second embodiment. It is a figure showing the flow for calculating the value of a coefficient. FIG. 3 is a diagram schematically showing an M0a map and an R1a map. FIG. 9 is an explanatory diagram of a method of calculating a coefficient (M ₀ ^b / M ₀ ^a ), a coefficient (M ₀ ^b / R1 ^a ), and a value of a coefficient M ₀ ^b based on a CEST effect of an amide proton. FIG. 11 is a diagram specifically showing a sequence SE _k used in the third mode. FIG. 14 is an explanatory diagram of means realized by a processing device 9 in the fourth embodiment. FIG. 14 is a diagram specifically showing a sequence SE _k used in the fourth mode.

  Hereinafter, embodiments for carrying out the present invention will be described, but the present invention is not limited to the following embodiments.

(1) First Embodiment FIG. 1 is a schematic diagram of a magnetic resonance apparatus according to a first embodiment of the present invention.
A magnetic resonance apparatus (hereinafter, referred to as an “MR apparatus. MR: Magnetic Resonance”) 1 includes a magnet 2, a table 3, a reception RF coil (hereinafter, referred to as a “reception coil”) 4, and the like.

  The magnet 2 has an accommodation space 21 in which the subject 13 is accommodated. The magnet 2 has a superconducting coil 22, a gradient coil 23, and an RF coil 24. The superconducting coil 22 applies a static magnetic field, the gradient coil 23 applies a gradient pulse, and the RF coil 24 applies an RF pulse. Note that a permanent magnet may be used instead of the superconducting coil 22.

  The table 3 has a cradle 3a for transporting the subject 13. The subject 13 is transported to the accommodation space 21 by the cradle 3a.

  The receiving coil 4 is attached to the head of the subject 13 and receives a magnetic resonance signal from the subject 13.

  The MR device 1 further includes a control unit 5, a transmitter 6, a gradient magnetic field power supply 7, a receiver 8, a processing device 9, a storage unit 10, an operation unit 11, a display unit 12, and the like.

  The control unit 5 receives, from the processing device 9, data including waveform information of RF pulses and gradient pulses used in the sequence, application timing, and the like. Then, the control unit 5 controls the transmitter 6 based on the data of the RF pulse, and controls the gradient magnetic field power supply 7 based on the data of the gradient pulse. The control unit 5 also controls the movement of the cradle 3a. In FIG. 1, the control unit 5 controls the transmitter 6, the gradient magnetic field power supply 7, the cradle 3a, and the like. However, the control of the transmitter 6, the gradient magnetic field power supply 7, the cradle 3a, and the like is controlled by a plurality of control units. May be performed. For example, a control unit for controlling the transmitter 6 and the gradient magnetic field power supply 7 and a control unit for controlling the cradle 3a may be separately provided.

The transmitter 6 supplies a current to the RF coil 24 based on the data received from the control unit 5.
The gradient magnetic field power supply 7 supplies a current to the gradient coil 23 based on the data received from the control unit 5.

  The receiver 8 performs processing such as detection on the magnetic resonance signal received by the receiving coil 4 and outputs the processed signal to the processing device 9. A combination of the magnet 2, the receiving coil 4, the control unit 5, the transmitter 6, the gradient magnetic field power supply 7, and the receiver 8 corresponds to a scanning unit.

  The storage unit 10 stores a program executed by the control unit 5 and the like. Note that the storage unit 10 may be a non-transitory storage medium such as a hard disk or a CD-ROM. The processing device 9 reads a program stored in the storage unit 10 and operates as a processor that executes processing described in the program. The processing device 9 implements various means by executing the processing described in the program. FIG. 2 is an explanatory diagram of means realized by the processing device 9.

The image creating means 90 creates an image based on data obtained by a sequence SE ₁ to SE _r (see FIG. 4) described later.
The Z spectrum creating unit 91 creates a Z spectrum based on the image obtained by the image creating unit 90.
The spectrum converting means 92 converts the Z spectrum into a CPE spectrum F _CPE (Δω _a ) described later (for example, see FIG. 9). CPE spectrum F _CPE (Δω _a ) corresponds to the first spectrum.

The detecting means 93 detects an offset frequency at which a peak of a signal component waveform affected by CEST appears, based on the CPE spectrum.
The i value setting means 94 sets the value of i representing the number of CEST terms.

The first fitting means 95 performs fitting using Expression (16) described later, and calculates a value of a coefficient included in the CEST term. The CEST term will be described later. Note that the first fitting means 95 corresponds to fitting means for calculating the value of the first coefficient.
The CRZ spectrum creating means 96 creates a spectrum (CRZ spectrum described later) in which the CEST waveform has been removed from the Z spectrum.

The second fitting means 97 performs fitting using Expression (23) described later, and calculates the values of the coefficients (b ₀ , b ₁ , b ₂ , Δω ₀ ) included in Expression (23).
The (c ₀ , c _MT ) calculation means 98 calculates the value of the coefficient (c ₀ , c _MT ) included in the baseline term based on the value of the coefficient calculated by the second fitting means 97. The coefficients (c ₀ , c _MT ) included in the baseline term will be described later.

The spectrum calculation means 99 calculates a spectrum F _{CPE — i} (Δω _a ) described later (see Equation 24).
The determining means 100 determines whether or not the CPE spectrum F _CPE (Δω _a ) obtained by the spectrum converting means 92 includes the waveform of another signal component affected by CEST.
The spectrum estimating means 101 estimates a Z spectrum (ideal Z spectrum) represented by the sum of a baseline term and a CEST term.
The spectrum comparing unit 102 compares the ideal Z spectrum estimated by the spectrum estimating unit 101 with the Z spectrum created by the Z spectrum creating unit 91, and determines whether the Z spectrum is reproduced by the ideal Z spectrum. Determine whether or not.

The counting means 103 counts the total number TN of CEST waveforms included in the CPE spectrum F _CPE (Δω _a ).

The CEST term judging means 104 judges whether or not a CEST term of amide proton and a CEST term of NOE (Nuclear Overhauser Enhancement) described later have been obtained.
Coefficient calculating means 105 calculates the value of the coefficient to be described later _{^{(M 0 b / M 0 a}} / R1 a).

The MR device 1 includes a computer including a processing device 9. The processing device 9 realizes the image creation unit 90 to the coefficient value calculation unit 105 by reading out the program stored in the storage unit 10. In addition, the processing device 9 may realize the image creation unit 90 to the coefficient value calculation unit 105 by one processor, or realize the image creation unit 90 to the coefficient value calculation unit 105 by two or more processors. Is also good. Further, a part of the image creating unit 90 to the coefficient value calculating unit 105 may be executed by the control unit 5. The program executed by the processing device 9 may be stored in one storage unit, or may be stored separately in a plurality of storage units.
Returning to FIG. 1, the description will be continued.

The operation unit 11 is operated by an operator and inputs various information to the computer 8. The display unit 12 displays various information.
The MR device 1 is configured as described above.

FIG. 3 is an explanatory diagram of a scan executed in the first embodiment.
The upper side of FIG. 3 shows the position of the slice SL where the scan is performed. In FIG. 3, the x-axis, y-axis, and z-axis correspond to the RL direction (left-right direction), the AP direction (front-back direction), and the SI direction (head-to-tail direction) of the subject, respectively. In the first mode, the slice SL is set to cross the brain of the subject. In the first embodiment, it is assumed that only one slice SL is set for convenience of explanation. In FIG. 3, the slice SL is an axial plane, but is not limited to the axial plane, and may be a coronal plane, a sagittal plane, or an oblique plane.

The lower part of FIG. 3 shows a scan SC executed to collect data from the slice SL. In the scan SC, a sequence SE _k (k = 1 to r) for acquiring an image D _{k of the} slice SL is executed. In the first embodiment, the sequence SE _k because it is executed r times, by executing the scan SC, it is possible to obtain the r-number of the image _D 1 to D _r.

FIG. 4 is a diagram specifically showing the sequence SE _k in the first mode.
The k-th sequence SE _k includes a continuous wave RF pulse CW, a killer gradient pulse Gc for eliminating transverse magnetization, and a data acquisition segment DAQ for acquiring data by a single shot method. In this embodiment, the frequency f [Hz] of the RF pulse CW is set to f = fk. After applying the continuous wave RF pulse CW, a killer gradient pulse Gc is applied, and after applying the killer gradient pulse Gc, the data acquisition segment DAQ is executed. For fat suppression, the data collection segment can use RF pulses that selectively excite water.

The k-th sequence SE _k is configured as described above. If the frequencies of the RF pulses CW of the sequences SE ₁ , SE ₂ ,..., SE _r are represented by f1, f2,... Fr, respectively, these frequencies f1, f2,. Is set.

In the first embodiment, by executing the sequence _SE 1 _{~SE r,} it acquires an image _D 1 to D _r, based on the images _D 1 to D _r, to create a Z spectra.

FIG. 5 is an explanatory diagram of the Z spectrum.
FIG. 5A1 is a diagram schematically showing the waveform of the Z spectrum. The horizontal axis of the Z spectra are offset frequency [Delta] [omega _a representative of the deviation from the resonance frequency of water. [Delta] [omega _a is calculated by _{Δω a = 2π (f-f} w) [rad / sec]. Here, _fw is the resonance frequency of water.

As shown in FIG. 5 (a1), the Z spectra, in certain offset frequency [Delta] [omega _c, it appears the signal attenuation due to CEST. Therefore, CEST can be quantitatively evaluated by separating the waveform of the signal component affected by CEST from the Z spectrum.

  FIG. 5 (a2) shows the Z spectrum of the waveform of a signal component affected by CEST (hereinafter sometimes referred to as “CEST waveform”) P1 and the waveform of a signal component not affected by CEST (hereinafter referred to as “CEST waveform”). , P2 (which may be referred to as “baseline waveform”). Although the CEST waveform P1 actually has a downward peak at the frequency Δωc, the peak of the CEST waveform P1 is shown inverted in FIG. 5A2 for convenience of explanation.

By separating the CEST waveform P1 from the Z spectrum, CEST can be quantitatively evaluated. However, the Z spectrum includes, in addition to the signal component (CEST waveform) P1 affected by CEST, a signal component (baseline waveform) P2 not affected by CEST. Generally, the CEST waveform P1 and the baseline waveform P2 can be approximated by a Lorentz function. However, the baseline waveform P2, since having a large peak than CEST waveform P1, in the vicinity of the offset frequency [Delta] [omega _c, the ratio R of the CEST waveform P1 and the baseline waveform P2 (= P1 / P2) becomes a small value . Therefore, the peak of the CEST waveform P1 is buried in the baseline waveform P2, and it may be difficult to separate the CEST waveform P1 from the Z spectrum. Therefore, in the first embodiment, the Z spectrum is converted into a spectrum suitable for extracting a CEST waveform. Hereinafter, a method of converting a Z spectrum into a spectrum suitable for extracting a CEST waveform will be described.

The Z spectrum can be represented by the following equation (1).

Δω _a : Offset frequency indicating deviation from the resonance frequency of water
Mz ^a : magnitude of longitudinal magnetization of protons contained in the free water pool immediately before the data collection segment DAQ (see FIG. 4) of the sequence SE _k
M ₀ ^a : Magnitude of the magnetization of protons contained in the free water pool immediately before the data acquisition segment DAQ when the data acquisition segment DAQ is executed without applying the RF pulse WC and the killer gradient pulse Gc.
In addition, the suffix “a” of the letter indicates that it is caused by free water.

It has been shown by Zaiss et al. That the Z spectrum can be approximated by the following equation (2) (Zaiss M, et al. NMR Biomed 2013; 26: 507-18.).

R1ρ in equation (2) is a time constant of T1 recovery during application of an RF pulse, and is shown to be approximated by the following equation (3) by Trott et al. (Trott O, et al. J Magn Reson 2002; 154: 157-60).
Here, R ₁ ^{a is} the reciprocal of T1 (longitudinal relaxation time) of water.

Cos ² θ, sin ² θ, and Rex in Expression (3) are represented by the following expressions.

Δω _c : Offset frequency at which the peak of the signal component (CEST waveform) affected by CEST appears [radian / sec]
k _a : Time constant [Hz] of magnetization transfer from free water pool to CEST pool
k: Time constant of magnetization transfer from CEST pool to free water pool [Hz]
γ: magnetic rotation ratio B1: transmission magnetic field strength Here, the following function F (Δω _a ) representing Δω _a ² is considered.

F (Δω _a ) in the equation (4) is an even function, and when Δω _a = 0, F (Δω _a ) = 0. By substituting equation (4) into equations (3a), (3b), and (3c), the following equation is obtained.

Next, consider the spectrum 1 / Z, which is the reciprocal of the spectrum Z represented by the equation (1). From formulas (1), (2), (3), and (5c), 1 / Z can be represented by the following formula.

When the equation (6) is arranged, the following equation (7) is obtained.

Here, if the [Delta] [omega _a is sufficiently smaller than the omega _1, i.e., consider the case where the following relationship holds.

When Expression (8) holds, Expression (5a) can be approximated by the following expression.

Therefore, from equation (9a), cos θ can be approximated to the following equation.

When Expression (8) holds, Expression (5b) can be approximated by the following expression.

By rearranging equation (7) using equations (9a-1) and (9b), the following approximate equation is obtained.

When Δω _a ≫ω ₁ is satisfied (see Expression 8), an approximate expression of Expression (10) can be obtained. The first term R ₂ ^a ω ₁ ² / R ₁ ^a on the right side is a term representing the relaxation time in the free water pool. The second term on the right side is a term representing a CEST waveform (a signal component affected by CEST), and this term is hereinafter referred to as a “CEST term”. The CEST waveform represented by the CEST term is represented by a Lorentz function using coefficients a ₁ , a ₂ , and Δω _c . a ₁ / a ₂ represents the height of the peak of the CEST waveform, 2√a ₂ represents the half width of the peak of the CEST waveform, [Delta] [omega _c denotes a frequency peak appears in CEST waveform. Therefore, by using the coefficients a ₁ , a ₂ , and Δω _c , three characteristic values a ₁ / a ₂ (peak height) and 2√a ₂ (peak half width) are used as the characteristic values of the CEST waveform. , And Δω _c (the frequency at which the peak appears). It can be seen from Expression (10) that the peak of the CEST waveform can be extracted as a peak represented by the Lorentz function. Therefore, in the first embodiment, the spectrum represented by Expression (10) is referred to as a CPE (CEST Peak Extraction) spectrum.

If the CPE spectrum is F _CPE (Δω _a ), F _CPE (Δω _a ) can be represented by the following equation.

From equations (10) and (11), the CPE spectrum F _CPE (Δω _a ) can be approximated by the following equation.

The expression (3) used in the above description is based on a model of Trott or the like. The Trott et al. Model is a Two Pool model that takes into account CESTs that occur between two pools (eg, free water and NH). However, in an actual living tissue, it is necessary to consider a magnetization transfer (MT) generated between bound water and free water. Here, the spectrum representing the influence of the MT generated between the bound water and free water (magnetization transfer) and Z _MT, it is assumed that the spectrum Z _MT can be expressed by the formula minus the Lorentzian from constant. In this case, the spectrum Z _MT can be expressed by the following equation.

In equation (13), Δω ₀ represents a frequency error. The first term (b ₀ ) on the right side of Expression (13) is a constant term, and the second term on the right side is a Lorentz function term. Here, replacing Z in the right side of the equation (11) in Z _MT, further, we are assumed that expressed by Δω ₀ = ₀ Δω ₀ is sufficiently small of formula (13). In this case, the following equation is obtained using equation (11) after replacing Z with Z _MT and equation (13) after assuming that Δω ₀ = 0.

The third term on the right side of equation (14) is sufficiently small to be ignored. Therefore, equation (14) can be approximated by the following equation.

  The second term on the right side of the equation (15) is a term representing a signal component affected by MT generated between free water and combined water (hereinafter, referred to as “MT term”).

Further, in the Two pool model, only one CEST peak is considered, but a plurality of CEST peaks may appear. Then, considering n CEST terms and assuming that a linear combination is established between each CEST term and MT term, based on equations (12) and (15), the CPE spectrum F _CPE (Δω _a ) becomes , Can be represented by the following approximate expression.

However, it is Δω _a »ω _1. The sum of the first term on the right side and the second term on the right side of Expression (16) is a term representing a waveform (baseline waveform) of a signal component not affected by CEST. Hereinafter, this term will be referred to as a baseline term. Further, FL _{, i} (Δω _a ) in the third term on the right side of the equation (16) represents the i-th CEST term. The CEST waveform represented by the i-th CEST term is represented by a Lorentz function using coefficients a _{1, i} , a _{2, i} , and Δω _{c, i} . a _{1, i} / a _{2, i} represents the peak height of the CEST waveform, 2√a _{2, i} represents the half width of the peak of the CEST waveform, and Δω _{c, i} represents the frequency at which the peak of the CEST waveform appears. Represents. Therefore, from equation (16), it can be seen that the CPE spectrum F _CPE (Δω _a ) can be approximated by a function including a baseline term and n CEST terms.

The baseline term in equation (16) is represented by the sum of the constant term c ₀ and the MT term c _MT F (Δω _a ). F (Δω _a ) of the MT term is not a Lorentz function but an even function defined by Expression (4). Therefore, it can be seen that the waveform of the baseline term (baseline waveform) included in the CPE spectrum F _CPE (Δω _a ) can be approximated by an even function.

FIG. 6 is a diagram for explaining the difference between the Z spectrum and the CPE spectrum.
FIG. 6 (a1) is a schematic diagram of the waveform of the Z spectrum, and FIG. 6 (a2) is a diagram showing the Z spectrum divided into a CEST waveform P1 and a baseline waveform P2.

As described with reference to FIG. 5, the baseline waveform P2 of the Z spectrum is approximated by a Lorentz function having a large peak. Therefore, in the vicinity of the frequency Δω _c , the ratio R (= P1 / P2) between the CEST waveform P1 and the baseline waveform P2 becomes a small value, and the peak of the CEST waveform P1 is buried in the baseline waveform P2, and Z It may be difficult to separate the signal component P1 affected by CEST from the spectrum.

  On the other hand, FIG. 6B1 is a schematic diagram of the waveform of the CPE spectrum, and FIG. 6B2 is a diagram showing the CPE spectrum divided into a CEST waveform Q1 and a baseline waveform Q2.

As mentioned in the description of Equation (16), the baseline waveform of the CPE spectrum can be approximated by an even function. Thus, the base line waveform Q2 of CPE spectrum does not have a large peak due to the Lorentz function, in the vicinity of the frequency [Delta] [omega _c, is possible to increase the ratio R (= Q1 / Q2) between the CEST waveform Q1 and the baseline waveform Q2 it can. For this reason, since the CPE spectrum has a larger ratio R than the Z spectrum, the CEST waveform Q1 can be easily separated from the CPE spectrum.

  FIG. 6 shows an example in which only one CEST waveform is included in the Z spectrum for the sake of simplicity, but there are cases where a plurality of CEST waveforms are included in the Z spectrum. is there. However, even when a plurality of CEST waveforms are included in the Z spectrum, the influence of the baseline waveform can be reduced by converting the Z spectrum into a CPE spectrum. Therefore, even when a plurality of CEST waveforms are included in the Z spectrum, by converting the Z spectrum to a CPE spectrum, each of the plurality of CEST waveforms can be easily separated from the CPE spectrum.

Here, the time constant ka included in the equation (3c) is considered. The time constant ka can be represented by the following equation.
M ₀ ^b : Magnitude of proton magnetization contained in CEST pool

Therefore, when the equation (17) is substituted into the equation (10a) and rearranged using the equations (10b) and (3d), the following relational expression is obtained.

The coefficients a1, Δωc and a2 in the equation (18) can be calculated using the CPE spectrum. The coefficient B1 is a transmission magnetic field intensity generated by the RF pulse. B1 is a value determined by the RF pulse, and is a known value. 2πγ is a constant and a known value. Thus, a1, Δωc, from substituting the value of a2, and B1 in the formula ^{_{(18), M 0 b,}} M 0 a, and coefficient comprising R1 ^a of _{^{(M 0 b / M 0 a}} / R1 a) The value can be determined. In equation (18), each of the coefficients a1, a2, and Δωc corresponds to a first coefficient, B1 corresponds to a second coefficient, and (M ₀ ^b / M ₀ ^a / R1 ^a ) is a third coefficient. Corresponding to the coefficient.

Factor _{^{(M 0 b / M 0 a}} / R1 a) is a factor proportional to the value of M ₀ ^b. Therefore, by determining the values of the coefficients _{^{(M 0 b / M 0 a}} / R1 a), at each position in the slice (each pixel), it is possible to know the value of the coefficient proportional to M ₀ ^b. Since M ₀ ^b represents the magnitude of the magnetization of the protons contained in the CEST pool, the coefficient (M ₀ ^b / M ₀ ^a / R1 ^a ) is obtained, so that the CEST effect appears remarkably in the slice. It is possible to know the range of the area where the image is displayed. The coefficient _{^{(M 0 b / M 0 a}} / R1 a) includes M ₀ ^b / M ₀ ^a. M ₀ ^b / M ₀ ^a represents the ratio between the magnitude of the magnetization of the protons contained in the CEST pool and the magnitude of the magnetization of the protons contained in the free water pool. Therefore, by calculating the coefficient (M ₀ ^b / M ₀ ^a / R1 ^a ), it is possible to know the range of the region where the ratio of the magnetization of protons is large (or the region where the ratio is small) in the slice. Becomes

In the first embodiment, by converting the Z spectrum CPE spectrum, using a CPE spectrum determining the values of the coefficients _{^{(M 0 b / M 0 a}} / R1 a) of formula (18). The following specifically describes how to determine the values of the coefficients _{^{(M 0 b / M 0 a}} / R1 a) using a CPE spectrum.

Figure 7 is a diagram showing a flow for determining the values of the coefficients _{^{(M 0 b / M 0 a}} / R1 a).
In step ST1, scan SC (see FIG. 4) is executed. In scan SC, sequences SE _{1 to} SE _r are executed. The control unit 5 (see FIG. 1) sends RF pulse data included in each sequence to the transmitter 6, and sends gradient pulse data included in each sequence to the gradient magnetic field power supply 7. The transmitter 6 supplies a current to the RF coil 24 based on the data received from the control unit 5, and the gradient magnetic field power supply 7 supplies a current to the gradient coil 23 based on the data received from the control unit 5. Therefore, the RF coil 24 applies an RF pulse, and the gradient coil 23 applies a gradient pulse. Each time each of the sequences SE _{1 to} SE _r is executed, an MR signal is generated from the slice SL (see FIG. 6). This MR signal is received by the receiving coil 4 (see FIG. 1). The receiving coil 4 receives the MR signal and outputs an analog signal including information of the MR signal. The receiver 8 performs signal processing such as detection on the signal received from the receiving coil 4 and outputs data obtained by the signal processing to the processing device 9.

In the processing apparatus 9, the image forming means 90 (see FIG. 2), based on the received from the receiver 8 data, to create a slice SL of the image _D 1 to D _r (see FIG. 3). Since the frequencies of the RF pulses CW of the sequences SE _{1 to} SE _r are set to mutually different values, the images D when the frequencies of the RF pulses are changed in r ways by executing the sequences SE _{1 to} SE _r. it can be obtained ₁ to D _r. After you run the sequence _SE 1 _{~SE r,} the process proceeds to step ST2.

In step ST2, the Z spectrum creating means 91 (see FIG. 2) creates a Z spectrum. FIG. 8 schematically shows the Z spectrum. Z spectrum creating means 91, the same coordinates from the image _{D 1 ~D r (x, y} ) to extract the data of the pixel located at the offset frequency [Delta] [omega _a signal value representing the deviation of the frequency from the resonance frequency of water Create a Z spectrum representing the relationship In Figure 8, Z spectrum creating means 91, the same coordinates of the image _{D 1 ~D r (x, y} ) = extract data of pixels g1 located (x1, y1), on the basis of this began out data The manner in which a Z spectrum is created is shown. Similarly, the Z spectrum creating means 91 extracts data of a pixel located at each coordinate (x, y) of the slice SL, and creates a Z spectrum at each coordinate (x, y).
After creating the Z spectrum, the process proceeds to step ST3.

In step ST3, the spectrum conversion means 92 (see FIG. 2) converts the Z spectrum into a CPE spectrum F _CPE (Δω _a ) using equation (11). FIG. 9 schematically shows the CPE spectrum F _CPE (Δω _a ). Here, it is assumed that CPE spectrum F _CPE (Δω _a ) includes peaks of the CEST waveform at offset frequencies Δω _{c, 1} and Δω _{c, 2} . The unit of the offset frequency is [rad / sec], but the unit of the offset frequency can be converted from [rad / sec] to [ppm]. Here, it is assumed that the unit of the offset frequency is converted to [ppm]. However, for convenience of explanation, even after the unit of the offset frequency is converted from [rad / sec] to [ppm], the offset frequency is represented by the symbol “Δω _a ”. After converting the Z spectrum to the CPE spectrum F _CPE (Δω _a ), the process proceeds to step ST4.

In step ST4, the detecting means 93 (see FIG. 2) detects an offset frequency at which the peak of the CEST waveform appears from the CPE spectrum F _CPE (Δω _a ). Hereinafter, an example of a method of detecting an offset frequency at which a peak of a CEST waveform appears will be described.

Since F (Δω _a ) included in the baseline term of equation (16) is represented by a quadratic function of Δω _a (see equation (4)), the baseline waveform of CPE spectrum F _CPE (Δω _a ) is It can be seen that it can be approximated by a quadratic function. Therefore, compared with the quadratic function and CPE spectrum F _CPE (Δω _a), by determining the offset frequency when the deviation between the CPE spectrum F _CPE (Δω _a) and the secondary function is increased, the peak of the CEST waveform Can be detected. Here, it is assumed that the CPE spectrum F _CPE (Δω _a ) deviates most from the quadratic function at the offset frequency Δω _{c, 1} . Therefore, the detecting means 93 detects the offset frequency Δω _{c, 1} as the offset frequency at which the peak of the CEST waveform appears. Here, it is assumed that the detected value of Δω _{c, 1} is Δω _a1 . Therefore, the detected value of Δω _{c, 1} is represented by the following equation.

After detecting the offset frequency Δω _{c, 1} = Δω _a1 , the process proceeds to step ST5.

In step ST5, the i value setting means 94 (see FIG. 2) sets the initial value 1 to i representing the number of CEST terms included in the approximate expression (16) of the CPE spectrum F _CPE (Δω _a ). When i = 1 is set, Expression (16) is represented by the following expression.

The coefficients (c ₀ , c _MT ) of the baseline term in equation (20) and the coefficients (a _1,1 , a _2,1 , Δω _c, ) of the CEST term FL _{, 1} (Δω _a ) in equation (20c) ₁ ) is an unknown coefficient. After setting i = 1, the process proceeds to step ST6.

In step ST6, the first fitting means 95 (see FIG. 2) performs fitting such that an error between the CPE spectrum F _CPE (Δω _a ) obtained by the equation (11) and the equation (20) is minimized. , The value of the coefficient (a _1,1 , a _2,1 , Δω _{c, 1} ) of the CEST term FL _{, 1} (Δω _a ) in equation (20) when the error is minimized, and the coefficient of the baseline term Calculate the value of (c ₀ , c _MT ). When performing fitting, first fitting means 95 first sets initial values of coefficients (a _1,1 , a _2,1 , Δω _{c, 1} ) and coefficients (c ₀ , c _MT ). I do. For example, the initial value of the coefficient Δω _{c, 1} is set to the value of the offset frequency Δω _{c, 1} detected in step ST4, that is, Δω _{c, 1} = Δω _a1 (see Expression 19). The initial values of the other coefficients a _1,1 , a _2,1 , c ₀ , and c _MT are obtained by using the waveform information (the maximum value and the minimum value of the CPE spectrum, etc.) of the CPE spectrum F _CPE (Δω _a ). Can be calculated. After setting the initial value of the coefficient, the first fitting means 95 changes the value of each coefficient with reference to the initial value, and obtains the CPE spectrum F _CPE (Δω _a ) obtained by the equation (11) and the equation ( 20), the value of the coefficient (a _1,1 , a _2,1 , Δω _{c, 1} ) and the value of the coefficient (c ₀ , c _MT ) when the error is minimized. FIG. 10 shows the value of each coefficient calculated by the fitting. In FIG. 10, (c ₀ , c _MT ) = (c ₀ (1), c _MT (1)), (a _1,1 , a _2,1 , Δω _{c, 1} ) = (a _1,1 (1 ), A _2,1 (1), Δω _{c, 1} (1)).

Note that, by fitting, in addition to the value of the coefficient of the CEST term FL _{, 1} (Δω _a ), the value of the coefficient (c ₀ , c _MT ) of the baseline term can also be calculated. However, the CPE spectrum F _CPE (Δω _a ) has a more suppressed baseline waveform than the Z spectrum (see FIG. 6). Therefore, if the calculated coefficients of the baseline term (c _0, c _MT) by fitting CPE spectrum F _CPE the ([Delta] [omega _a) the approximate equation (20), the estimated error of the coefficients (c _0, c _MT) is Can be large. Therefore, in the first embodiment, the coefficients (c ₀ , c _MT ) are recalculated so that the estimation error of the coefficients (c ₀ , c _MT ) is reduced. The process proceeds to step ST7 in order to recalculate the coefficients (c ₀ , c _MT ).

  Step ST7 has two steps ST71 and ST72. Hereinafter, each of steps ST71 and ST72 will be described.

In step ST71, the CRZ spectrum creating means 96 (see FIG. 2) creates a spectrum in which the CEST waveform has been removed from the Z spectrum. Hereinafter, the spectrum obtained by removing the CEST waveform from the Z spectrum will be referred to as a CRZ spectrum (CEST Removed Z-spectrum). When the CRZ spectrum is represented by “Z _CRZ ”, the CRZ spectrum Z _CRZ can be represented by the following equation using the Z spectrum.

Note that δ (Δω _a ) is a function introduced to prevent the denominator of the second term on the right side of Expression (21) from becoming zero when Δω _a = 0. Here, since i = 1, equation (21) is represented by the following equation.

Z in equation (22) is obtained in step ST2. The coefficient of F _{L, 1} of formula _{(22a) (Δω a) (} a 1,1, a 2,1, Δω c, 1) , as shown in FIG. 10, in step ST6 (a _{1, 1} , A _2,1 , Δω _{c, 1} ) = (a _1,1 (1), a _2,1 (1), Δω _{c, 1} (1)). Therefore, the CRZ spectrum Z _{CRZ from} which the signal component (CEST waveform) affected by CEST is removed can be created from Expression (22). After creating the CRZ spectrum Z _CRZ , the process proceeds to step ST72.

In step ST72, based on the CRZ spectrum Z _CRZ created in step ST71, the value of the coefficient (c ₀ , c _MT ) of the baseline term in equation (20) is calculated. Hereinafter, a method of _obtaining the values of the coefficients (c ₀ , c _MT ) will be described.

CRZ spectrum Z _CRZ represents a spectrum obtained by removing the CEST waveform from the Z spectrum. Therefore, it can be considered that the CRZ spectrum Z _CRZ mainly represents a signal component affected by MT generated between free water and bound water, not a signal component affected by CEST. Spectrum representing the signal component affected by the MT generated between the free water and the bound water is represented by the spectrum Z _MT of formula (13). Therefore, CRZ spectrum Z _CRZ can be approximated by the following equation using spectrum Z _MT .

From equation (23), it can be seen that the CRZ spectrum Z _CRZ can be approximated by a function represented by the sum of the constant term b ₀ and the term of the Lorentz function.

The second fitting means 97 (see FIG. 2) performs fitting so that the error between the CRZ spectrum Z _CRZ and the equation (23) is minimized, and the coefficient (b) of the equation (23) when the error is minimized _0, b _1, b _2, to calculate the value of [Delta] [omega _0). When performing fitting, the second fitting means 97 first calculates the initial values of the coefficients (b ₀ , b ₁ , b ₂ , Δω ₀ ). The initial values of the coefficients (b ₀ , b ₁ , b ₂ , Δω ₀ ) are, for example, the values of the baseline terms (c ₀ , c _MT ) calculated in step ST6 = (c ₀ (1), c _MT (1 )). Coefficients _{(b 0, b 1, b} 2, Δω 0) After calculating the initial value of the second fitting means 97, coefficients of the initial value to the reference _{(b 0, b 1, b} 2, Δω 0) Is changed, and the value of the coefficient (b ₀ , b ₁ , b ₂ , Δω ₀ ) when the error between the CRZ spectrum Z _CRZ and the equation (23) is minimized is calculated. FIG. 11 shows values of the coefficients (b ₀ , b ₁ , b ₂ , Δω ₀ ) calculated by the fitting. In FIG. 11, the values of the calculated coefficients (b ₀ , b ₁ , b ₂ , Δω ₀ ) are (b ₀ , b ₁ , b ₂ , Δω ₀ ) = (b ₀ (1), b ₁ (1 ), B ₂ (1), Δω ₀ (1)).

After obtaining the values of these coefficients, the (c ₀ , c _MT ) calculating means 98 (see FIG. 2) calculates (b ₀ , b ₁ ) = (b ₀ (1), b ₁ (1)) by the equation substituted into (20a), calculates the c _0. Further, the (c ₀ , c _MT ) calculation means 98 calculates c _MT by substituting b ₀ = b ₀ (1) into equation (20b). Therefore, the value of the coefficient (c ₀ , c _MT ) of the baseline term in equation (20) can be calculated. FIG. 12 shows the values of the calculated coefficients (c ₀ , c _MT ). In FIG. 12, (c ₀ , c _MT ) = (c ₀ (1) ′, c _MT (1) ′). After obtaining these values, the process proceeds to step ST8.

In step ST8, the spectrum calculation unit 99 (see FIG. 2), the spectrum F _{CPE_i} represented by the sum of the baseline term _{c 0 + c MT F (Δω} a) and CEST term _{Σ i F L, i (Δω} a) Calculate (Δω _a ). This spectrum F _{CPE_i} (Δω _a ) can be defined by the following equation.

Since i = 1 is set in step ST5, equation (24) is represented by the following equation.

The coefficients (c ₀ , c _MT ) of the baseline term in equation (25) are calculated as (c ₀ , c _MT ) = (c ₀ (1) ′, c _MT (1) ′) in step ST72. (See FIG. 12). Also, the coefficients (a _1,1 , a _2,1 , Δω _{c, 1} ) of the CEST term FL _{, 1} (Δω _a ) in the equation (25c) are _calculated as (a _1,1 , a _2,1 , Δω _{c, 1} ) = (a _1,1 (1), a _2,1 (1), Δω _{c, 1} (1)) (see FIG. 12). Therefore, spectrum F _{CPE — 1} (Δω _a ) can be calculated by substituting the values of these coefficients into equations (25) and (25c). FIG. 13 schematically shows the spectrum F _{CPE — 1} (Δω _a ). In FIG. 13, for comparison, in addition to the spectrum F _{CPE_1} (Δω _a), CPE spectrum F _CPE (Δω _a) is also shown. Spectrum F _{CPE_1} (Δω _a), in the vicinity of the offset frequency [Delta] [omega _{c, 1,} it can be seen to have a sufficiently close waveforms CPE spectrum F _CPE (Δω _a). After calculating the spectrum F _{CPE_1} (Δω _a ), the process proceeds to step ST9.

In step ST9, the determination means 100 (see FIG. 2) adds another CEST waveform F _CPE (Δω _a ) to the CEST spectrum F _{L, 1} (Δω _a ) (see equation 20c) that is different from the CEST waveform represented by the CEST term It is determined whether or not a CEST waveform is included.

FIG. 14 is an explanatory diagram of a method for determining whether or not another CEST waveform is included in the CPE spectrum F _CPE (Δω _a ).
14 shows the CPE spectrum F _CPE (Δω _a ) and the spectrum F _{CPE_1} (Δω _a ), and the lower part of FIG. 14 shows the CPE spectrum F _CPE (Δω _a ) and the spectrum F _{CPE_1} ( difference spectra D between Δω _a) (Δω _a) is shown.

First, the determination means 100 _{calculates a} difference spectrum D (Δω _a ) by subtracting the spectrum F _{CPE — 1} (Δω _a ) from the CPE spectrum F _CPE (Δω _a ).

Next, the determination means 100 determines whether or not another CEST waveform is included in the CPE spectrum F _CPE (Δω _a ) based on the difference spectrum D (Δω _a ). Hereinafter, this determination method will be described.

Spectrum F _{CPE_1} formula (25) for obtaining the ([Delta] [omega _a) includes a CEST section corresponding to the offset frequency _{Δω c, 1 F L, 1} (Δω a). Therefore, in the vicinity of the offset frequency [Delta] [omega _{c, 1} is the spectral F _{CPE_1} (Δω _a) has a sufficiently close to the CPE spectrum F _CPE (Δω _a). Therefore, the signal value of the difference spectrum D (Δω _a ) has a value close to zero near the offset frequency Δω _{c, 1} .

However, equation (25) of F _{CPE — 1} (Δω _a ) does not include a CEST term corresponding to the offset frequency Δω _{c, 2} . Therefore, near the offset frequency Δω _{c, 2} , there is a certain difference in signal value between the spectrum F _{CPE — 1} (Δω _a ) and the CPE spectrum F _CPE (Δω _a ). Therefore, a peak P2 of another CEST waveform appears near the offset frequency Δω _{c, 2 in} the difference spectrum D (Δω _a ).

Therefore, by determining whether or not the peak P2 appears in the difference spectrum D (Δω _a ), it is possible to determine whether or not another CEST waveform is included in the CPE spectrum F _CPE (Δω _a ). In the first embodiment, two thresholds TH1 and TH2 are used to determine whether the peak P2 appears in the difference spectrum D (Δω _a ). The judging means 100 compares the two thresholds TH1 and TH2 with the difference spectrum D (Δω _a ), and judges whether the difference spectrum D (Δω _a ) crosses the threshold TH1 or TH2. When the difference spectrum D (Δω _a ) crosses the threshold value TH1 or the threshold value TH2, the determining unit 100 determines that the peak P2 appears in the difference spectrum D (Δω _a ). On the other hand, when the difference spectrum D (Δω _a ) does not cross the threshold value TH1 or the threshold value TH2, the determining unit 100 determines that the peak P2 does not appear in the difference spectrum.

Referring to FIG. 14, difference spectrum D (Δω _a ) includes a peak P2 exceeding threshold value TH1 near offset frequency Δω _{c, 2} . Therefore, the judging means 100 judges that another CEST waveform is included in the CPE spectrum F _CPE (Δω _a ). When it is determined that another CEST waveform is included in the CPE spectrum F _CPE (Δω _a ), the process proceeds to step ST10.

In step ST10, the detecting means 93 detects an offset frequency Δω _{c, 2 at} which a peak of another CEST waveform of the CPE spectrum F _CPE (Δω _a ) appears. Here, it is assumed that the detected value of Δω _{c, 2} is Δω _a2 . Therefore, the detected value of Δω _{c, 2} is represented by the following equation.

After detecting the offset frequency Δω _{c, 2} = Δω _a2 , the process proceeds to step ST11.

In step ST11, the i value setting means 94 increments i representing the number of CEST terms. Therefore, i is set from i = 1 to i = 2. When i = 2, the approximate expression (16) of the CPE spectrum is represented by the following expression.

  After setting i = 2, the process returns to step ST6.

In step ST6, the first fitting means 95 performs the fitting to determine the value of the coefficient (a _1,2 , a _2,2 , Δω _{c, 2} ) of the CEST term FL _{, 2} (Δω _a ) in equation (26c_2). Is calculated. Hereinafter, a method of _obtaining the coefficients (a _1,2 , a _2,2 , Δω _{c, 2} ) will be described.

In the first embodiment, the coefficients (a _1,1 , a _2,1 , Δω _{c, 1} ) of the CEST term FL _{, 1} (Δω _a ) are already (a _1,1 (1), a _{2, 1} (1), Δω _{c, 1} (1)), and the coefficients (c ₀ , c _MT ) of the baseline terms are calculated as (c ₀ (1) ′, c _MT (1) ′). (See FIG. 12). Therefore, when these values are substituted into equation (26) and Equation (26C_1), CEST term F _{L, 2} 3 one coefficient of ([Delta] [omega _a) (a _{1, 2} of the formula _{(26c_2),} a _{2, 2} , Δω _{c, 2} ) are unknown coefficients. In this case, the error between the CPE spectrum F _CPE (Δω _a ) and the approximate expression (26) including the three unknown coefficients (a _1,2 , a _2,2 , Δω _{c, 2} ) is minimized. By fitting the CPE spectrum F _CPE (Δω _a ), the values of the three coefficients (a _1,2 , a _2,2 , Δω _{c, 2} ) can be obtained.

However, the coefficient (c ₀ , c _MT ) = (c ₀ (1) ′, c _MT (1) ′) of the baseline term includes only one CEST term (F _{L, 1} (Δω _a )). This is a value obtained based on the approximate expression (20) that is not used. On the other hand, the approximation formula (26), in addition to the CEST section F _{L, 1} ([Delta] [omega _a), new CEST terms F _{L, 2} (Δω _a) is added. Therefore, when fitting is performed with the coefficients (c ₀ , c _MT ) of the baseline term fixed at (c ₀ (1) ′, c _MT (1) ′), the CEST term FL _{, 2} (Δω _a ) The estimation error of the coefficients (a _1,2 , a _2,2 , Δω _{c, 2} ) may increase. Therefore, in the first embodiment, in order to reduce the estimation error of the coefficient (a _1,2 , a _2,2 , Δω _{c, 2} ) of the CEST term FL _{, 2} (Δω _a ), the CEST term FL _, Fitting is performed using not only the coefficients (a _1,2 , a _2,2 , Δω _{c, 2} ) of ₂ (Δω _a ) but also the coefficients (c ₀ , c _MT ) of the baseline term as unknown coefficients. Therefore, the five coefficients are unknown coefficients. The first fitting means 95 performs fitting of the CPE spectrum F _CPE (Δω _a ) using the approximate expression (26) including five unknown coefficients. When performing fitting, the first fitting means 95 first determines the initial values of the coefficients (a _1,2 , a _2,2 , Δω _{c, 2} ) of the CEST term FL _{, 2} (Δω _a ) and the baseline. Set the initial value of the coefficient of the term (c ₀ , c _MT ). The initial value of the coefficient Δω _{c, 2} is set to the value of the offset frequency Δω _{c, 2} detected in step ST10, that is, Δω _{c, 2} = Δω _a2 (see Equation 25d). Further, the initial value of the coefficient (a _1,2 , a _2,2 ) can be calculated based on the height and the half width of the peak P2 (see FIG. 14) of the difference spectrum D (Δω _a ). On the other hand, the initial values of the coefficients of the baseline term (c _0, c _MT), the value obtained when _{i = 1 (c 0, c} MT) = (c 0 (1) ', c MT (1)' ) (See FIG. 12). After setting the initial value, the first fitting means 95 changes the value of the coefficient with reference to the initial value, so that the error between the CPE spectrum F _CPE (Δω _a ) and the equation (26) is minimized. The values of the coefficients (a _1,2 , a _2,2 , Δω _{c, 2} ) and the coefficients (c ₀ , c _MT ) are calculated. FIG. 15 shows the value of each coefficient calculated by the fitting. In FIG. 15, (c ₀ , c _MT ) = (c ₀ (2), c _MT (2)), (a _1,2 , a _2,2 , Δω _{c, 2} ) = (a _1,2 (2 ), A _2,2 (2), Δω _{c, 2} (2)).

By the fitting, in addition to the coefficient (a _1,2 , a _2,2 , Δω _{c, 2} ) of the CEST term FL _{, 2} (Δω _a ), the coefficient (c ₀ , c _MT ) of the baseline term is also obtained. Is calculated. However, as described above, the value of the coefficient (c ₀ , c _MT ) of the baseline term calculated in step ST6 may have a large estimation error. Therefore, to recalculate the coefficients (c ₀ , c _MT ) of the baseline term, the process proceeds to step ST7.

In step ST7, two steps ST71 and ST72 are sequentially executed.
In step ST71, the CRZ spectrum creating means 96 creates a CRZ spectrum Z _CRZ in which the CEST waveform has been removed from the Z spectrum using Expression (21). However, since i = 2, equation (21) is represented by the following equation.

The CRZ spectrum creating means 96 creates a CRZ spectrum Z _CRZ obtained by removing the CEST waveform from the Z spectrum using Expression (27). After creating the CRZ spectrum Z _CRZ , the process proceeds to step ST72.

In step ST72, the second fitting means 97 performs fitting such that the error between the CRZ spectrum Z _CRZ created using equation (27) and equation (23) is minimized. The value of the coefficient (b ₀ , b ₁ , b ₂ , Δω ₀ ) of the equation (23) is calculated. When performing fitting, the second fitting means 97 first sets initial values of the coefficients (b ₀ , b ₁ , b ₂ , Δω ₀ ). Here, the second fitting means 97 calculates the coefficients (b ₀ , b ₁ , b ₂ , Δω ₀ ) = (b ₀ (1), b ₁ (1), b ₂ (1 ), Δω ₀ (1)) (see FIG. 12) are set as initial values of the coefficients (b ₀ , b ₁ , b ₂ , Δω ₀ ) at i = 2. i = coefficient in _{2 (b 0, b 1,} b 2, Δω 0) after setting the initial value of the second fitting means 97, coefficients of the initial value to the reference _{(b 0, b 1, b} 2 , Δω ₀ ), and the coefficients (b ₀ , b ₁ , b ₂ , Δω) when the error between the CRZ spectrum Z _CRZ created using equation (27) and equation (23) is minimized. Calculate the value of ₀ ). FIG. 16 shows values of coefficients (b ₀ , b ₁ , b ₂ , Δω ₀ ) calculated by fitting when i = 2. In FIG. 16, the values of the calculated coefficients (b ₀ , b ₁ , b ₂ , Δω ₀ ) are (b ₀ , b ₁ , b ₂ , Δω ₀ ) = (b ₀ (2), b ₁ (2 ), B ₂ (2), Δω ₀ (2)).

After obtaining the values of these coefficients, the (c ₀ , c _MT ) calculating means 98 substitutes (b ₀ , b ₁ ) = (b ₀ (2), b ₁ (2)) into the equation (26a). And calculate c ₀ . Further, the (c ₀ , c _MT ) calculating means 98 calculates c _MT by substituting b ₀ = b ₀ (2) into the equation (26b). Therefore, the value of the coefficient (c ₀ , c _MT ) of the baseline term in equation (26) can be calculated. FIG. 17 shows the values of the calculated coefficients (c ₀ , c _MT ). FIG. 17 shows (c ₀ , c _MT ) = (c ₀ (2) ′, c _MT (2) ′). After obtaining these values, the process proceeds to step ST8.

In step ST8, the spectrum calculation means 99 calculates the spectrum F _{CPE — i} (Δω _a ) using equation (24). However, since i = 2, equation (24) is represented by the following equation.

As shown in FIG. 17, the coefficient (c ₀ , c _MT ) is calculated as (c ₀ , c _MT ) = (c ₀ (2) ′, c _MT (2) ′), and the coefficient (a _{1 , 2} , a _2,2 , Δω _{c, 2} ) is (a _1,2 , a _2,2 , Δω _{c, 2} ) = (a _1,2 (2), a _2,2 (2), Δω _{c, 2} (2)). Also, as shown in FIG. 12, the coefficients (a _1,1 , a _2,1 , Δω _{c, 1} ) are (a _1,1 , a _2,1 , Δω _{c, 1} ) = (a _1,1 (1), a _2,1 (1), Δω _{c, 1} (1)). Therefore, the spectrum F _{CPE_2} (Δω _a ) can be calculated by substituting the values of these coefficients into equations (28), (28c_1), and (28c_2). FIG. 18 schematically shows the spectrum F _{CPE_2} (Δω _a ). FIG. 18 also shows _a CPE spectrum F _CPE (Δω _a ) in addition to the spectrum F _{CPE_2} (Δω _a ) for comparison. It can be _{seen that the} spectrum F _{CPE_2} (Δω _a ) has a waveform sufficiently close to the CPE spectrum F _CPE (Δω _a ) around the offset frequencies Δω _{c, 1} and Δω _{c, 2} . After calculating the spectrum F _{CPE_2} (Δω _a ), the process proceeds to step ST9.

In step ST9, the judgment means 100 sets the CEST spectrum F _CPE (Δω _a ) to the CEST waveform represented by the CEST terms FL _{, 1} (Δω _a ) and FL _{, 2} (Δω _a ) (see equations 26c_1 and 26c_2). It is determined whether or not another CEST waveform different from the above is included.

FIG. 19 is an explanatory diagram of a method for determining whether or not another CEST waveform is included in the CPE spectrum F _CPE (Δω _a ).
Determining means 100, the CPE spectrum F _CPE (Δω _a), and the difference spectrum F _{CPE_2} (Δω _a), determines the difference spectrum D ([Delta] [omega _a), the difference spectrum D and ([Delta] [omega _a) with a threshold value TH1 and TH2 Compare.

Since the difference spectrum D (Δω _a ) does not exceed the threshold _values TH1 and TH2, the spectrum F _{CPE_2} (Δω _a ) may be considered to have a waveform sufficiently close to the CPE spectrum F _CPE (Δω _a ). it can. In this case, the CEST waveform contained in the CPE spectrum F _CPE ([Delta] [omega _a), the spectrum F _{CPE_2} 2 single CEST terms contained in equation (28) _{(Δω a) F L, 1} (Δω a) and F _{L , 2} (Δω _a ). Therefore, when the difference spectrum D (Δω _a ) does not exceed the thresholds TH1 and TH2, the determination means 100 determines that the CPE spectrum F _CPE (Δω _a ) does not include another CEST waveform. If it is determined that no other CEST waveform is included, the process proceeds to step ST12.

FIG. 19 shows an example in which the difference spectrum D (Δω _a ) does not exceed the threshold values TH1 and TH2. However, the difference spectrum D (Δω _a ) may exceed the threshold value TH1 or TH2. Hereinafter, a case where the difference spectrum D (Δω _a ) exceeds the threshold value TH1 or TH2 will be described.

FIG. 20 is a diagram illustrating an example in which the difference spectrum D (Δω _a ) exceeds the threshold value TH1.
In FIG. 20, a peak P3 exceeding the threshold TH1 appears near the offset frequency Δω _{c, 3 in} the difference spectrum D (Δω _a ). Therefore, the judging means 100 judges that another CEST waveform is included in the CPE spectrum F _CPE (Δω _a ). When it is determined that another CEST waveform is included in the CPE spectrum F _CPE (Δω _a ), the process proceeds to step ST10, and the offset frequency Δω _{c, 3 at} which the peak of the other CEST waveform appears is detected. After detecting the offset frequency Δω _{c, 3} , the process proceeds to step ST11, i is incremented, and a new CEST term FL _{, 3} (Δω _a ) is added to the approximate expression (26) of the CPE spectrum F _CPE (Δω _a ). Is done. Then, steps ST6 to ST9 are executed. Accordingly, in step ST9, every time it is determined that contains other CEST waveform CPE spectrum F _CPE (Δω _a), a new CEST term is added to the approximate expression of the CPE spectrum F _CPE (Δω _a) , Steps ST6 to ST9 are executed. For example, consider the case where it is determined in step ST9 that the CPE spectrum F _CPE (Δω _a ) includes the j-th CEST waveform. In this case, since i = j is set in step ST11, the approximate expression of the CPE spectrum F _CPE (Δω _a ) is represented by the following expression.

In the above approximation (29), FL _{, j} (Δω _a ) represents the newly added CEST term. When the CPE spectrum is represented by the approximate expression (29), the coefficient of the CEST term in the expressions (29c_1) to (29c_j-1) has already been calculated. Therefore, the five coefficients of the coefficients (c ₀ , c _MT ) and the coefficients (a _{1, j} , a _{2, j} , Δω _{c, j} ) are unknown coefficients. If i = j is set in step ST11, the process returns to step ST6. In step ST6, the first fitting means 95 calculates the values of the five coefficients (c ₀ , c _MT ) and (a _{1, j} , a _{2, j} , Δω _{c, j} ) using the approximate expression (29). calculate. FIG. 21 shows the values of the coefficients calculated when i = j.

After calculating the value of the coefficient of the CEST term, the process proceeds to step ST71. In step ST71, the CRZ spectrum creating means 96 creates a CRZ spectrum Z _CRZ in which the CEST waveform has been removed from the Z spectrum using Expression (21). Since i = j, equation (21) is represented by the following equation.

After calculating the CRZ spectrum Z _CRZ , the process proceeds to step ST72.

In step ST72, the second fitting means 97 performs fitting so that the error between the CRZ spectrum Z _CRZ created by the equation (30) and the equation (23) is minimized, and the equation when the error is minimized. The value of the coefficient (b ₀ , b ₁ , b ₂ , Δω ₀ ) of (23) is calculated. When performing fitting, the second fitting means 97 first sets initial values of the coefficients (b ₀ , b ₁ , b ₂ , Δω ₀ ). Here, the second fitting means 97 converts the value (not shown) of the coefficient (b ₀ , b ₁ , b ₂ , Δω ₀ ) calculated when i = j−1 into a coefficient at i = j (B ₀ , b ₁ , b ₂ , Δω ₀ ) are set as initial values. coefficient at _{i = j (b 0, b} 1, b 2, Δω 0) after setting the initial value of the second fitting means 97, coefficients of the initial value to the reference _{(b 0, b 1, b} 2 , Δω ₀ ), and the coefficients (b ₀ , b ₁ , b ₂ , Δω) when the error between the CRZ spectrum Z _CRZ created using equation (30) and equation (23) is minimized. Calculate the value of ₀ ). FIG. 22 shows values of coefficients (b ₀ , b ₁ , b ₂ , Δω ₀ ) calculated by fitting when i = j. In FIG. 22, (b ₀ , b ₁ , b ₂ , Δω ₀ ) = (b ₀ (j), b ₁ (j), b ₂ (j), Δω ₀ (j)).

After obtaining the values of these coefficients, the (c ₀ , c _MT ) calculating means 98 substitutes (b ₀ , b ₁ ) = (b ₀ (j), b ₁ (j)) into the equation (29a). And calculate c ₀ . The (c ₀ , c _MT ) calculating means 98 calculates c _MT by substituting b ₀ = b ₀ (j) into the equation (29b). Therefore, the value of the coefficient (c ₀ , c _MT ) of the baseline term in equation (29) can be calculated. FIG. 23 shows the values of the calculated coefficients (c ₀ , c _MT ). In FIG. 23, (c ₀ , c _MT ) = (c ₀ (j) ′, c _MT (j) ′). After calculating these values, the process proceeds to step ST8.

In step ST8, the spectrum calculation means 99 calculates the spectrum F _{CPE — i} (Δω _a ) using equation (24). However, since i = j, equation (24) is represented by the following equation.

Since the coefficients of the equation (31) have already been obtained, the spectrum F _{CPE — j} (Δω _a ) can be calculated by substituting the values of these coefficients. FIG. 24 schematically shows the spectrum F _{CPE — j} (Δω _a ). FIG. 24 also shows _a CPE spectrum F _CPE (Δω _a ) in addition to the spectrum F _{CPE — j} (Δω _a ) for comparison. After calculating the spectrum F _{CPE — j} (Δω _a ), the process proceeds to step ST9.

In step ST9, the determining means 100 determines whether or not another CEST waveform is included in the CPE spectrum F _CPE (Δω _a ). Therefore, until it is determined in step ST9 that another CEST waveform is not included in the CPE spectrum F _CPE (Δω _a ), steps ST10, ST11, ST6, ST7, ST8, and ST9 are performed. The loop is executed repeatedly. When it is determined in step ST9 that the CPE spectrum F _CPE (Δω _a ) does not include another CEST waveform, the process proceeds to step ST12.

In step ST12, the spectrum estimating means 101 (see FIG. 2) estimates a Z spectrum (hereinafter, referred to as an “ideal Z spectrum”) Zideal represented by the sum of a baseline term and a CEST term. The ideal Z spectrum Zideal can be expressed by the following equation using equations (11) and (16).

The spectrum estimating means 101 estimates an _ideal Z spectrum Z _ideal using Expression (32). After finding the _ideal Z spectrum Z _ideal , the process proceeds to step ST13.

In step ST13, the spectrum comparing means 102 (see FIG. 2) compares the ideal Z spectrum Z _ideal with the Z spectrum created in step ST2, and the Z spectrum is reproduced by the _ideal Z spectrum Z _ideal . It is determined whether or not. This determination is made as follows.

First, the spectrum comparing means 102 compares the ideal Z spectrum Z _ideal with the Z spectrum created in step ST2, and for each offset frequency, the signal value of the _ideal Z spectrum Z _ideal and the Z spectrum Find the difference from the signal value. Next, the spectrum comparing means 102 determines whether or not the sum of squares of the difference is sufficiently small. The determination of whether the sum of squares of the difference is large, for example, by previously determining a threshold for determining whether the sum of squares of the difference is large or small, and comparing the sum of squares of the difference with the threshold, It can be carried out. When the sum of squares of the difference is equal to or smaller than the threshold, the spectrum comparing unit 102 can determine that the sum of squares of the difference is small, and when the sum of squares is larger than the threshold, the sum of squares of the difference is large.

When the sum of squares of the difference is small, the spectrum comparing means 102 determines that the Z spectrum is reproduced by the _ideal Z spectrum Z _ideal . In this case, the process proceeds from step ST13 to step ST14.

On the other hand, when the sum of squares of the difference is large, the spectrum comparing unit 102 determines that the Z spectrum is not reproduced by the _ideal Z spectrum Z _ideal . In this case, the process returns to step ST7, and the baseline term is recalculated. Therefore, in step ST13, the coefficients of the baseline term are recalculated until it is determined that the Z spectrum is reproduced by the _ideal Z spectrum Z _ideal . If it is determined in step ST13 that the Z spectrum is reproduced by the _ideal Z spectrum Z _ideal , the process proceeds to step ST14.

In step ST14, the counting means 103 (see FIG. 2) counts the total number TN of CEST waveforms included in the CPE spectrum F _CPE (Δω _a ). In the first embodiment, i is incremented each time it is determined that another CEST waveform is included in the CPE spectrum F _CPE (Δω _a ) (see step ST11). _It represents the total number TN of CEST waveforms included in _CPE (Δω _a ). That is, the total number TN of CEST waveforms is TN = i. Therefore, the total number TN of the CEST waveforms included in the CPE spectrum F _CPE (Δω _a ) can be counted. Here, it is assumed that i = 2 for convenience of explanation. Therefore, the total number TN of the CEST waveforms included in the CPE spectrum F _CPE (Δω _a ) is counted as TN = 2. After counting TN = 2, the process proceeds to step ST15.

In step ST15, the coefficients (c ₀ , c _MT ) of the baseline terms used in the approximate expression (16) of the CPE spectrum F _CPE (Δω _a ) are fixed to the finally obtained coefficients of the baseline terms. And recalculate the coefficient of the CEST term. Here, since it is assumed that i = 2, the value of the coefficient of the finally obtained baseline term is a value (c ₀ (2) ′, c _MT ( 2) ') (see FIG. 17). Therefore, the value of the coefficient of the baseline term is fixed at (c ₀ , c _MT ) = (c ₀ (2) ′, c _MT (2) ′), and the coefficient of the CEST term is recalculated. Hereinafter, step ST15 will be described.

FIG. 25 is a diagram showing a flow of step ST15.
In step ST151, the i value setting means 94 sets i representing the number of CEST terms to an initial value (i = 1). After setting i = 1, the process proceeds to step ST152.

In step ST152, the first fitting means 95 sets three coefficients (a _1,1 , a _2,1 , Δω _c ) included in the CEST term FL _{, 1} (Δω _a ) of the approximate expression (20) of the CPE spectrum. _{, 1} ) is calculated. When calculating the value of the coefficient, the first fitting means 95 first calculates the coefficient (c ₀ , c _MT ) of the baseline term of the equation (20) by (c ₀ , c _MT ) = (c ₀ (2 ) ', C _MT (2)'). Therefore, in the approximate expression (20), only three coefficients (a _1,1 , a _2,1 , Δω _{c, 1} ) of the CEST term FL _{, 1} (Δω _a ) are unknown coefficients. The first fitting means 95 performs fitting so that an error between the CPE spectrum F _CPE (Δω _a ) and the approximate expression (20) including three unknown coefficients is minimized. When performing fitting, the first fitting means 95 first sets initial values of the coefficients (a _1,1 , a _2,1 , Δω _{c, 1} ) of the CEST term FL _{, 1} (Δω _a ). As the initial value of the coefficient (a _1,1 , a _2,1 , Δω _{c, 1} ) of the CEST term FL _{, 1} (Δω _a ), the value of the coefficient of the CEST term calculated in step ST6 may be used. it can. After setting the initial value, the first fitting means changes the value of the coefficient based on the initial value, and sets the CEST when the error between the CPE spectrum F _CPE (Δω _a ) and the equation (20) is minimized. The values of three coefficients (a _1,1 , a _2,1 , Δω _{c, 1} ) of the term FL _{, 1} (Δω _a ) are calculated. After calculating the values of these coefficients, the process proceeds to step ST153.

In step ST153, the spectrum calculation means 99 calculates the spectrum F _{CPE — 1} (Δω _a ) using the equations (25) and (25c).

The value of the coefficient (c ₀ , c _MT ) of the baseline term in equation (25) is fixed at (c ₀ , c _MT ) = (c ₀ (2) ′, c _MT (2) ′) ( See FIG. 17). Further, the coefficients (a _1,1 , a _2,1 , Δω _{c, 1} ) of the CEST term in equation (25c) are calculated in step ST152. Therefore, spectrum F _{CPE — 1} (Δω _a ) can be calculated by substituting the values of these coefficients into equations (25) and (25c). After calculating the spectrum F _{CPE_1} (Δω _a ), the process proceeds to step _ST154 .

In step ST154, the determining means 100 determines that the CPE spectrum F _CPE (Δω _a ) includes another CEST waveform different from the CEST waveform represented by the CEST term FL _{, 1} (Δω _a ) (see equation 20c). It is determined whether or not. If it is determined that no other CEST waveform is included, the process proceeds to step ST157. On the other hand, when it is determined that another CEST waveform is included, the process proceeds to step ST155.

In step ST155, the detecting means 93 detects an offset frequency at which a peak of another CEST waveform of the CPE spectrum F _CPE (Δω _a ) appears. After detecting the offset frequency, the process proceeds to step ST156.

In step ST156, the i value setting means 94 increments i from i = 1 to i = 2. When i = 2, the approximate expression of the CPE spectrum F _CPE (Δω _a ) is represented by Expression (26). After incrementing i, the process returns to step ST152.

Therefore, in step ST154, each time it is determined that contains other CEST waveform CPE spectrum F _CPE (Δω _a), CEST term is added to the approximate expression of the CPE spectrum F _CPE (Δω _a), add The value of the coefficient included in the obtained CEST term is calculated. Therefore, the value of the coefficient of the CEST term when the coefficient (c ₀ , c _MT ) of the baseline term is fixed to (c ₀ , c _MT ) = (c ₀ (2) ′, c _MT (2) ′) Can be calculated. If it is determined in step ST154 that the CPE spectrum F _CPE (Δω _a ) does not include another CEST waveform, the process proceeds to step ST157.

In step ST157, the counting means 103 counts the total number TN of CEST waveforms included in the CPE spectrum F _CPE (Δω _a ). After counting the total number TN of CEST waveforms, the process proceeds to step ST158.

In step ST158, the counting means 103 determines whether or not the total number TN of the CEST waveforms counted in step ST157 is equal to the total number TN (= 2) of the CEST waveforms counted in step ST14. When it is determined that the total number TN of CEST waveforms is different, it is considered that the estimation error of the coefficient of the CEST term or the coefficient of the baseline term is large. Then, when it is determined that the total number TN of the CEST waveform is different, the process returns to step ST5 (see FIG. 7). Steps ST5 to ST15 are repeatedly executed until it is determined in step ST158 that the total number of CEST waveforms is equal. Therefore, based on the CPE spectrum F _CPE (Δω _a ) obtained in step ST3, the value of the coefficient of the baseline term and the value of the coefficient of the CEST term with a small estimation error can be obtained. FIG. 26 shows the value of each coefficient of the CPE spectrum F _CPE (Δω _a ) obtained by the recalculation in step ST15. In FIG. 26, the values of the coefficients of the baseline term of the CPE spectrum F _CPE (Δω _a ) are represented by (c ₀ , c _MT ) = (c ₀ (2) ′, c _MT (2) ′). Further, the coefficient value of the CEST term FL _{, 1} (Δω _a ) of the CPE spectrum F _CPE (Δω _a ) is (a _1,1 , a _2,1 , Δω _{c, 1} ) = (a _1,1 (1 ), A _2,1 (1), Δω _{c, 1} (1)), and the coefficient value of the CEST term FL _{, 2} (Δω _a ) of the CPE spectrum F _CPE (Δω _a ) is (a _1,2 , a _2,2 , Δω _{c, 2} ) = (a _1,2 (2), a _2,2 (2), Δω _{c, 2} (2)).

FIG. 26 shows only the coefficients of the CPE spectrum F _CPE (Δω _a ) obtained at the coordinates (x1, y1). However, for the CPE spectrum F _CPE (Δω _a ) obtained at other coordinates, the values of the coefficients of the baseline term and the CEST term are similarly obtained. Therefore, the values of the coefficients of the baseline term and the CEST term are obtained for each coordinate in the slice SL. The coefficient values of the baseline term and the CEST term obtained for each coordinate in the slice SL are stored in the storage unit in association with each coordinate in the slice SL. FIG. 27 schematically shows the values of the coefficients stored in the storage unit. In FIG. 27, for convenience of explanation, the values of the coefficients associated with the coordinates (x1, y1) among the plurality of coordinates included in the slice SL are shown, but the values of the coefficients also correspond to the other coordinates. It is attached.

  As described above, by executing step ST15, each coefficient having a small estimation error can be calculated. If it is determined in step ST158 that the total number TN of CEST waveforms is equal, the process exits from step ST15 and proceeds to step ST16.

In step ST16, the coefficient value calculating means 105 (see FIG. 2) calculates the coefficient (M ₀ ^b / M ₀ ^a / R1) in equation 18 based on the coefficient values obtained in steps ST1 to ST15 (see FIG. 27). Calculate the value of ^a ). Hereinafter, a method of calculating the coefficients ^{_{(M 0 b / M 0 a}} / R1 a) will be described.

In the first mode, the imaging site is the brain. It has been found that in the brain, as a peak of the CEST term, a peak of an amide proton and a peak of NOE (Nuclear Overhauser Enhancement) mainly appear. Therefore, here, the value of the coefficient (M ₀ ^b / M ₀ ^a / R1 ^a ) due to the CEST effect of the amide proton and the value of the coefficient (M ₀ ^b / M ₀ ^a / R1 ^a ) due to the CEST effect of the NOE are calculate. Hereinafter, a method of calculating the values of these coefficients will be described.

Coefficient calculating means 105, for each coordinate in the slice SL, the value of the coefficient due to CEST effect of the amide protons _{^{(M 0 b / M 0 a}} / R1 a), coefficient due to CEST effect of NOE (M ₀ ^b / M Calculate the value of ₀ ^a / R1 ^a ). Even in any coordinate calculation method of the value of the coefficient _{^{(M 0 b / M 0 a}} / R1 a) is the same. In the following, by taking a coordinate (x1, y1) of the plurality of coordinates included in the slice SL, how to calculate the value of the coefficients _{^{(M 0 b / M 0 a}} / R1 a) will be described.

Figure 28 is a diagram showing a flow for calculating the value of the coefficients _{^{(M 0 b / M 0 a}} / R1 a).
In step ST161, the CEST term determining means 104 (see FIG. 2) determines whether or not the CEST term of the amide proton has been obtained at the coordinates (x1, y1). This determination can be made, for example, as follows.

The CEST term determining means 104 first determines that the offset frequency Δω _{c, 1} included in the coefficient (a _1,1 , a _2,1 , Δω _{c, 1} ) of the CEST term FL _{, 1} (Δω _a ) is It is determined whether or not the frequency is at which a peak appears. Here, since Δω _{c, 1} = Δω _{c, 1} (1) (see FIG. 27), the CEST term judging means 104 determines that Δω _{c, 1} = Δω _{c, 1} (1) has an amide proton peak. It is determined whether it is a frequency.

It has been found that the peak of the amide proton appears near 3.5 ppm. Therefore, the CEST term determining means 104 determines whether or not Δω _{c, 1} (1) is a value sufficiently close to 3.5 ppm, and determines whether the value of Δω _{c, 1} (1) is sufficiently low to 3.5 ppm. If they are close to each other, it is determined that Δω _{c, 1} (1) is the frequency at which the peak of the amide proton appears. Here, when Δω _{c, 1} (1) satisfies the following equation (33), it is determined that Δω _{c, 1} (1) is a value sufficiently close to 3.5 ppm.

Here, α is a constant for determining whether Δω _{c, 1} (1) is a value sufficiently close to 3.5 ppm. α can be set to, for example, α = 0.2 ppm.

When Expression (33) holds, the CEST term determining means 104 determines that the CEST term FL _{, 1} (Δω _a ) obtained at the coordinates (x1, y1) is the CEST term of the amide proton. When Expression (33) does not hold, it is determined that the CEST term FL _{, 1} (Δω _a ) obtained at the coordinates (x1, y1) is not the CEST term of the amide proton.

When it is determined that the CEST term F _{L, 1} (Δω _a ) is the CEST term of the amide proton, the process proceeds to Step ST162.

On the other hand, when it is determined that the CEST term FL _{, 1} (Δω _a ) is not the CEST term of the amide proton, the CEST term determining means 104 determines that the other CEST term FL _{, 2} (Δω _a ) It is determined whether or not the CEST term. When determining whether or not the other CEST term FL _{, 2} (Δω _a ) is the CEST term of the amide proton, the CEST term determining means 104 first determines whether the CEST term FL _{, 2} (Δω _a ) It is determined whether or not the offset frequency Δω _{c, 2} included in the coefficients (a _1,2 , a _2,2 , Δω _{c, 2} ) is the frequency at which the peak of the amide proton appears. In this case, since Δω _{c, 2} = Δω _{c, 2} (2) (see FIG. 27), the CEST term determining means 104 indicates that Δω _{c, 2} = Δω _{c, 2} (2) has an amide proton peak. It is determined whether it is a frequency. This determination is made using the following equation (34).

When the equation (34) holds, the CEST term determining means 104 determines that the CEST term FL _{, 2} (Δω _a ) obtained at the coordinates (x1, y1) is the CEST term of the amide proton. If the equation (34) does not hold, it is determined that the CEST term FL _{, 2} (Δω _a ) obtained at the coordinates (x1, y1) is not the CEST term of the amide proton.

When it is determined that the CEST term F _{L, 2} (Δω _a ) is the CEST term of the amide proton, the process proceeds to Step ST162.

On the other hand, if not hold any formula (33) and formula (34), CEST term F _{L, 1} (Δω _a) and F _{L, 2} (Δω _a) is determined not to be a CEST section either amide protons Is done. In this case, since it is determined that the CEST term of the amide proton does not exist at the coordinates (x1, y1), the process proceeds to step ST163. In step ST163, the coefficient calculation unit 105 sets the value of the coefficient due to CEST effect of the amide protons ^{_{(M 0 b / M 0 a}} / R1 a) to zero. Then, the process proceeds to step ST164.

Here, the description is continued assuming that the equation (33) holds. Therefore, the CEST term determining means 104 determines that the CEST term FL _{, 1} (Δω _a ) obtained at the coordinates (x1, y1) is the CEST term of the amide proton. In this case, since it is determined that the CEST term of the amide proton exists at the coordinates (x1, y1), the process proceeds to step ST162.

In step ST162, the coefficient calculation unit 105, using Equation (18), to calculate the value of the coefficient due to CEST effect of the amide protons _{^{(M 0 b / M 0 a}} / R1 a). Hereinafter, a method of calculating the values of the coefficients _{^{(M 0 b / M 0 a}} / R1 a), will be described with reference to FIG. 29.

The coefficients a ₁ , a ₂ and Δω _{c on} the right side of the equation 18 correspond to the coefficients (a _1,1, a _2,1 and Δω _{c, 1} ) of the CEST term FL _{, 1} (Δω _a ) of the amide proton. . (A _1,1 , a _2,1 , Δω _{c, 1} ) is (a _1,1 , a _2,1 , Δω _{c, 1} ) = (a _1,1 (1), a _2,1 (1 ), Δω _{c, 1} (1)), which are known values. Further, B1 on the right side of Expression 18 is a known value because it is the transmission magnetic field strength determined by the RF pulse. Therefore, since a ₁ , a ₂ , Δω _c , and B _{1 on} the right side of Equation 18 are known, it is possible to calculate the value of the coefficient (M ₀ ^b / M ₀ ^a / R1 ^a ) due to the CEST effect of the amide proton. it can. After calculating the value of the coefficient due to CEST effect of the amide protons ^{_{(M 0 b / M 0 a}} / R1 a), the process proceeds to step ST164.

In step ST164, the CEST term determining means 104 determines whether or not the CEST term of NOE has been obtained at the coordinates (x1, y1). Hereinafter, this determination method will be described. In the first embodiment, since the CEST term FL _{, 1} (Δω _a ) is determined to be the CEST term of the amide proton in step ST161, the CEST term FL _{, 1} (Δω _a ) is the CEST term of the NOE. is not. Therefore, the CEST term determining means 104 does not determine whether or not the CEST term FL _{, 1} (Δω _a ) is a NOE CEST term, and determines whether the other CEST term FL _{, 2} (Δω _a ) is NOE. It is determined whether or not the CEST term.

If CEST term F _{L, 2} of ([Delta] [omega _a) to determine whether the CEST term NOE, CEST term determination unit 104, first, the coefficient of CEST section _{F L, 2 (Δω a)} (a 1, It is determined whether or not the offset frequency Δω _{c, 2} included in _{( 2} , a _2,2 , Δω _{c, 2} ) is the frequency at which the peak of the NOE appears. Here, since Δω _{c, 2} = Δω _{c, 2} (2) (see FIG. 27), the CEST term determining means 104 determines that Δω _{c, 2} = Δω _{c, 2} (2) is the frequency at which the NOE peak appears. Is determined.

It has been found that the NOE peak appears near -3.5 ppm. Therefore, the CEST term determining means 104 determines whether Δω _{c, 2} (2) is a value sufficiently close to −3.5 ppm, and sets the value of Δω _{c, 1} (2) to −3.5 ppm. If it is close enough, it is determined that Δω _{c, 2} (2) is the frequency at which the peak of the NOE appears. Here, when Δω _{c, 2} (2) satisfies the following equation (35), it is determined that Δω _{c, 2} (2) is a value sufficiently close to −3.5 ppm.

α can be set to, for example, α = 0.2 ppm. When Expression (35) holds, the CEST term determining unit 104 determines that the CEST term FL _{, 2} (Δω _a ) obtained at the coordinates (x1, y1) is the CEST term of the NOE. In this case, the process proceeds to Step ST165.

On the other hand, if the equation (35) does not hold, the CEST term determining means 104 determines that the CEST term FL _{, 2} (Δω _a ) is not the CEST term of the NOE. In this case, since it is determined that the CEST term of NOE does not exist at the coordinates (x1, y1), the process proceeds to step ST166. In step ST166, the coefficient calculation unit 105 sets the value of the coefficient ^{_{(M 0 b / M 0 a}} / R1 a) by CEST effect of NOE to zero. Then, the flow ends.

Here, it is assumed that Expression (35) holds. Therefore, the CEST term determining means 104 determines that the CEST term FL _{, 2} (Δω _a ) obtained at the coordinates (x1, y1) is the NOE CEST term. In this case, since it is determined that the CEST term of NOE exists at the coordinates (x1, y1), the process proceeds to step ST165.

In step ST165, the coefficient calculation unit 105, using Equation (18), to calculate the value of the coefficient _{^{(M 0 b / M 0 a}} / R1 a) by CEST effect of NOE. Hereinafter, a method of calculating the values of the coefficients _{^{(M 0 b / M 0 a}} / R1 a), will be described with reference to FIG. 30.

The coefficients a ₁ , a ₂ , and Δω _{c on} the right side of Expression 18 correspond to the coefficients (a _1,2, a _2,2 , Δω _{c, 2} ) of the CEST term FL _{, 2} (Δω _a ) of the NOE. (A _1,2 , a _2,2 , Δω _{c, 2} ) is (a _1,2 , a _2,2 , Δω _{c, 2} ) = (a _1,2 (2), a _2,2 (2 ), Δω _{c, 2} (2)), which are known values. Further, B1 on the right side of Expression 18 is a known value because it is the transmission magnetic field strength determined by the RF pulse. Thus, a _1, a ₂ of the right side of Formula 18, [Delta] [omega _c, and B1 because is known, it is possible to calculate the values of the coefficients ^{_{(M 0 b / M 0 a}} / R1 a) by CEST effect of NOE .

Similarly, the flow shown in FIG. 28 is executed at coordinates other than the coordinates (x1, y1) in the slice SL. Then, if it contains CEST term amide protons, the value of the coefficient due to CEST effect of the amide protons _{^{(M 0 b / M 0 a}} / R1 a) is calculated, if it contains CEST term NOE the value of the coefficient due to CEST effect of _{^{NOE (M 0 b / M 0}} a / R1 a) is calculated. Accordingly, the map of coefficients by CEST effect of the amide protons _{^{(M 0 b / M 0 a}} / R1 a) of the map (see FIG. 29), the coefficient by CEST effect of _{^{NOE (M 0 b / M 0}} a / R1 a) (See FIG. 30).

After obtaining a map of the coefficients _{^{(M 0 b / M 0 a}} / R1 a), step ST16 is completed. Thus, the flow of FIG. 7 is executed.

In the first embodiment, the Z spectrum is converted into _a CPE spectrum F _CPE (Δω _a ). The baseline waveform (signal component not affected by CEST) of the CPE spectrum F _CPE (Δω _a ) can be approximated by an even function, and therefore does not have a large peak due to the Lorentz function. Therefore, by converting the Z spectrum into the CPE spectrum F _CPE (Δω _a ), the CEST waveform can be easily separated, and the estimation error of the value of the coefficient included in the CEST term can be reduced.

  In the first embodiment, the difference between the ideal Z spectrum Zideal and the ideal Z spectrum is obtained in step ST13. If the sum of squares of the difference exceeds the threshold, the process returns to step ST7 to return to the coefficient of the baseline term. Is recalculated. Therefore, the estimation error of the coefficient of the baseline term can be further reduced.

  In the first embodiment, in step ST15, the coefficient of the baseline term is fixed, and the coefficient of the CEST term is recalculated. Therefore, the estimation error of the coefficient of the CEST term can be further reduced.

  If it is determined in step ST158 that the total number TN of the CEST waveform is different, the process returns to step ST5, and the values of the coefficient of the CEST term and the coefficient of the baseline term are recalculated. Therefore, the estimation error of the coefficients of the baseline term and the CEST term can be further reduced.

In the first embodiment, the approximate expression of the CRZ spectrum Z _CRZ (23) is represented by the sum of the term of the constant term b ₀ and Lorentzian. Since the term of the Lorentz function includes three coefficients (b ₁ , b ₂ , Δω ₀ ), the approximate expression (23) of the CRZ spectrum Z _CRZ gives a total of four coefficients (b ₀ , b ₁ , b ₂ , Δω ₀ ). On the other hand, the baseline term used in the approximate expression (16) of the CPE spectrum F _CPE (Δω _a ) is represented by the sum of the constant term c ₀ and the MT term c _MT F (Δω _a ). Since F (Δω _a ) of the MT term is not a Lorentz function but _a quadratic function of Δω _a (see Equation (4)), only one coefficient (c _MT ) is contained in the MT term. Therefore, in the approximate expression (16) of the CPE spectrum F _CPE (Δω _a ), the sum of the coefficients included in the baseline term is only two (c ₀ , c _MT ). Therefore, when the Z spectrum is converted into the CPE spectrum F _CPE (Δω _a ), the signal component (baseline waveform) that is not affected by the CEST is obtained only by calculating the values of the two coefficients (c ₀ , c _MT ). Can be specified, so that fitting accuracy can be improved.

In the first embodiment, the equation (18), it is possible to calculate the value of the coefficients _{^{(M 0 b / M 0 a}} / R1 a). Factor _{^{(M 0 b / M 0 a}} / R1 a) is a factor proportional to the value of M ₀ ^b. Since M ₀ ^b represents the magnitude of the magnetization of the protons contained in the CEST pool, the coefficient (M ₀ ^b / M ₀ ^a / R1 ^a ) is obtained, so that the CEST effect appears remarkably in the slice. It is possible to know the range of the area where the image is displayed. The coefficient _{^{(M 0 b / M 0 a}} / R1 a) includes M ₀ ^b / M ₀ ^a. M ₀ ^b / M ₀ ^a represents the ratio between the magnitude of the magnetization of the protons contained in the CEST pool and the magnitude of the magnetization of the protons contained in the free water pool. Therefore, by calculating the coefficient (M ₀ ^b / M ₀ ^a / R1 ^a ), it is possible to know the range of the region where the ratio of the magnetization of protons is large (or the region where the ratio is small) in the slice. Becomes

In the first embodiment, by using the coefficients a ₁ , a ₂ and Δω _c , three characteristic values a ₁ / a ₂ (peak height) and 2√a ₂ (peak And Δω _c (frequency at which a peak appears). However, if a CEST waveform can be obtained, the CEST term may include a coefficient for representing a characteristic value different from these three characteristic values.

In the first embodiment, in the coefficient _{^{(M 0 b / M 0 a}} / R1 a) formula for determining the value of (18), R1 ^a representative of the reciprocal of T1 is used. However, instead of R1 ^a, it may be used T1.

In the first embodiment, and calculate the value of the coefficient values and NOE coefficients amide protons _{^{(M 0 b / M 0 a}} / R1 a) (M 0 b / M 0 a / R1 a). However, the present invention can be applied to a case of calculating the value of the coefficients of the other protons causing _{^{CEST (M 0 b / M 0}} a / R1 a).

(2) Second Embodiment In the first embodiment, the value of the coefficient (M ₀ ^b / M ₀ ^a / R1 ^a ) is obtained by using Expression (18). In the second embodiment, the coefficient (M ₀ the other values of ^{_{b / M 0 a / R1 a}} ), for further example of obtaining the value of another coefficient will be described.

First, consider moving the R1 ^a of the left side of the equation (18) to the right side. Moving the R1 ^a to the right side, the equation (36) below is obtained.

Equation (36) is an equation for calculating a value of ^a coefficient (M ₀ ^b / M ₀ ^a ) including M ₀ ^b and M ₀ ^a . In Expression (36), the coefficient _{^{(M 0 b / M 0 a}} ) corresponds to the third factor, the coefficient R1 ^a is equivalent to the coefficient of the fourth.

Next, consider moving the left side of the M ₀ ^a of formula (18) to the right side. By moving M ₀ ^a to the right side, the following equation (37) is obtained.

Equation (37) is an equation for calculating ^a value of ^a coefficient (M ₀ ^b / R 1 ^a ) including M ₀ ^b and R1 ^a . In Expression (37), the coefficient (M ₀ ^b / R1 ^a) corresponds to the third factor, the coefficient M ₀ ^a corresponds to the coefficients of the fifth.

Further, consider moving the left side of the M ₀ ^a and R1 ^a of formula (18) to the right side. By moving M ₀ ^a and R 1 ^a to the right side, the following equation (38) is obtained.

Equation (38) is an equation for ^calculating the value of the coefficient M ₀ ^b . In Expression (38), the coefficient M ₀ ^b corresponds to the third factor, the coefficient R1 ^a is equivalent to the coefficient of the fourth, the coefficient M ₀ ^a corresponds to the coefficients of the fifth.

In the second embodiment, in addition to the coefficients _{^{(M 0 b / M 0 a}} / R1 a), coefficients _{^{(M 0 b / M 0 a}} ), coefficients _{^{(M 0 b / R1 a)}} , and the coefficient M ₀ ^b of The value is calculated. However, in order to calculate the values of the coefficient (M ₀ ^b / M ₀ ^a ), the coefficient (M ₀ ^b / R1 ^a ), and the coefficient M ₀ ^b , the values of a ₁ , a ₂ , Δω _c , and B1 In addition, the values of M ₀ ^a and R ¹ a need to be determined. a ₁ , a ₂ , and Δω _c are obtained from the data obtained by the scan SC, and B 1 is obtained by the RF pulse used in the sequence, but the values of M ₀ ^a and R 1 ^a cannot be obtained. Therefore, in the second embodiment, and performs a scan for obtaining the M ₀ ^a and R1 ^a. Next, a scan executed in the second embodiment will be described.

FIG. 31 is an explanatory diagram of a scan executed in the second mode.
In the second mode, scans SC and SC1 are executed. The scan SC is the same as the scan SC executed in the first embodiment, and a description thereof will be omitted.

Scan SC1 is a scan for obtaining a value of M ₀ ^a and R1 ^a. In scan SC1, the sequence is repeatedly executed while changing the TR of the sequence using the SE method or the like. By executing the sequence while changing TR, the magnitude Mz of the longitudinal magnetization at each value of TR can be measured. On the other hand, the TR and Mz, between the M ₀ ^a and R1 ^a, the following relationship holds.

As described above, by executing scan SC1, Mz at each value of TR is measured. Therefore, the value of the measured Mz by fitting the formula (39) can calculate the value of M ₀ ^a and R1 ^a included in the formula (39). Therefore, by substituting the calculated value of M ₀ ^a into equations (37) and (38) and substituting the calculated value of R ¹ a into equations (36) and (38), the coefficient (M _{0 a} ^b / M ₀ ^a), it is possible to calculate the value of the coefficients ^{_{(M 0 b / R1 a)}} , and the coefficient M ₀ ^b.

  Next, an MR apparatus according to a second embodiment will be described. It should be noted that the MR device of the second embodiment differs from the MR device of the first embodiment in the processing device 9 but has the same other configuration. Therefore, in the MR device of the second embodiment, the processing device 9 will be mainly described.

FIG. 32 is an explanatory diagram of the processing device 9 according to the second embodiment.
The processing device 9 in the second embodiment is different from the processing device 9 in the first embodiment (see FIG. 2) in that the coefficient value calculating means 105 is different, but the other means are the same. Therefore, in the processing device 9 according to the second embodiment, the description of the image creation unit 90 to the CEST item determination unit 104 will be omitted, and the coefficient value calculation unit 105 will be described.

In the second embodiment, the coefficient value calculator 105 has a first coefficient value calculator 105a and a second coefficient value calculator 105b. The first coefficient value calculation unit 105a calculates the value of the coefficient M0a and the value of the coefficient R1a based on the data obtained by the scan SC1. Second coefficient value calculation unit 105b, the coefficient _{^{(M 0 b / M 0 a}} / R1 a) in addition to the coefficients _{^{(M 0 b / M 0 a}} ), coefficients _{^{(M 0 b / R1 a)}} , and the coefficient Calculate the value of M ₀ ^b .

  The coefficient value calculation means 105 is configured as described above.

In the second embodiment, perform a scan SC and SC1, based on data obtained by scanning SC and SC1, in addition to the coefficients _{^{(M 0 b / M 0 a}} / R1 a), coefficients (M ₀ ^b / M ₀ ^a ), the coefficient (M ₀ ^b / R1 ^a ), and the coefficient M ₀ ^b are obtained. Hereinafter, a flow for calculating the values of these coefficients will be described.

FIG. 33 is a diagram showing a flow for calculating the value of the coefficient.
In step ST1, scans SC and SC1 (see FIG. 31) are executed. After executing the scans SC and SC1, the process proceeds to step ST2.

Steps ST2 to ST16 are the same as in the first embodiment, and a description thereof will be omitted. In step ST16, the map of coefficients by CEST effect of the amide protons _{^{(M 0 b / M 0 a}} / R1 a) ( see FIG. 29) and the coefficient by CEST effect of _{^{NOE (M 0 b / M 0}} a / R1 a) (See FIG. 30). In the second embodiment, the second coefficient value calculation unit 105b calculates the value of the coefficient _{^{(M 0 b / M 0 a}} / R1 a). After obtaining these maps, the process proceeds to step ST17.

In step ST17, the first coefficient value calculation unit 105a calculates the value of the coefficient M0a and the value of the coefficient R1a for each coordinate in the slice SL based on the data obtained by the scan SC1, and calculates the M0a map. And find the R1a map. FIG. 34 is a diagram schematically showing the M0a map and the R1a map. As described above, by executing scan SC1, Mz at each value of TR is measured. First coefficient value calculation unit 105a, the value of the measured Mz by fitting the formula (39), to calculate the value of M ₀ ^a and R1 ^a. Therefore, the value of the coefficient M0a and the value of the coefficient R1a can be calculated for each coordinate in the slice SL. In FIG. 34, for convenience of explanation, M ₀ ^a value at the coordinates (x1, y1) of the plurality of coordinates included in the slice ^{_{SL (M 0 a = M 0}} a _1) and R1 ^a value (R1 ^a = R1 ^a _1) Although only are shown, in other coordinates, the value of M ₀ ^a and R1 ^a are calculated. Thus, M ₀ ^a map and R1 ^a map is obtained. The values of M ₀ ^a and R 1 ^a are stored in the storage unit in association with each coordinate. After obtaining the M ₀ ^a map and R1 ^a map, the process proceeds to step ST18.

In step ST18, the second coefficient value calculation section 105b is, for each coordinate in the slice SL, coefficient due CEST effect of the amide protons _{^{(M 0 b / M 0 a}} ), coefficients _{^{(M 0 b / R1 a)}} , and Calculate the value of the coefficient M ₀ ^b . Hereinafter, the coefficient _{^{(M 0 b / M 0 a}} ), coefficients _{^{(M 0 b / R1 a)}} , and calculation of the value of the coefficient M ₀ ^b will be described.

Even in any coordinate, factor _{^{(M 0 b / M 0 a}} ), coefficients _{^{(M 0 b / R1 a)}} , and calculation of the value of the coefficient M ₀ ^b are the same. In the following, by taking a coordinate (x1, y1) of the plurality of coordinates included in the slice SL, coefficients _{^{(M 0 b / M 0 a}} ), coefficients _{^{(M 0 b / R1 a)}} , and the coefficient M described ₀ ^b calculation method of values.

Figure 35 is a coefficient _{^{(M 0 b / M 0 a}} ) by CEST effect of the amide protons, it is an illustration of the coefficient _{^{(M 0 b / R1 a)}} , and the coefficient M ₀ ^b calculation method of values.
The second coefficient value calculation unit 105b calculates the coefficients of the CEST term FL _{, 1} (Δω _a ) in a ₁ , a ₂ , and Δω _c of Expressions (36), (37), and (38). (See FIG. 29), and the value of the transmission magnetic field intensity generated by the RF pulse is substituted for B1. The second coefficient value calculation unit 105b, the M ₀ ^a of formula (37) and (38), by substituting _{^{M 0 a = M 0 a _1}} , formula (36) and (38) R1 to ^a, to substitute the R1 ^a = R1 ^a _1. Therefore, coefficient due CEST effect of the amide protons _{^{(M 0 b / M 0 a}} ), it is possible to calculate the value of the coefficients _{^{(M 0 b / R1 a)}} , and the coefficient M ₀ ^b.

Similarly, in other coordinates other than the coordinates in the slice SL (x1, y1), coefficient due to CEST effect of the amide protons _{^{(M 0 b / M 0 a}} ), coefficients _{^{(M 0 b / R1 a)}} , and The value of the coefficient M ₀ ^b is calculated. Therefore, coefficient due CEST effect of the amide protons _{^{(M 0 b / M 0 a}} ), coefficients _{^{(M 0 b / R1 a)}} , and can be determined map of coefficients M ₀ ^b.
After creating a map based on the CEST effect of amide protons, the process proceeds to step ST19.

In step ST19, the second coefficient value calculation section 105b is, for each coordinate in the slice SL, coefficient due CEST effect of ^{_{NOE (M 0 b / M 0}} a), coefficients ^{_{(M 0 b / R1 a)}} , and the coefficient Calculate the value of M ₀ ^b .

When calculating the value of the coefficient due to the CEST effect of the NOE, in FIG. 35, instead of the value of the coefficient of FL _{, 1} (Δω _a ), the value of the coefficient of FL _{, 2} (Δω _a ) is a ₁ , a ₂ and Δω _c . Therefore, coefficient due CEST effect of ^{_{NOE (M 0 b / M 0}} a), coefficients ^{_{(M 0 b / R1 a)}} , and can be determined map of coefficients M ₀ ^b.
After obtaining these maps, the flow ends.

In the second embodiment, based on data obtained by performing a scan SC1, the value of M ₀ ^a and R1 ^a are determined. Therefore, in addition to the coefficients ^{_{(M 0 b / M 0 a}} / R1 a), coefficients ^{_{(M 0 b / M 0 a}} ), to calculate the value of the coefficient ^{_{(M 0 b / R1 a)}} , and the coefficient M ₀ ^b Therefore, the range of the region where the CEST effect is remarkably exhibited can be more specifically specified.

(3) Third Embodiment In the first and second embodiments, an example using a sequence having a continuous wave RF pulse has been described. In the third embodiment, an example using a sequence having a plurality of preparation pulses is used. Will be described.
The MR device according to the third embodiment is the same as the MR device according to the first or second embodiment.

Figure 36 is a diagram showing a sequence SE _k in the third embodiment in detail.
The k-th sequence SE _k has m preparation pulses and a data acquisition segment DAQ. Each preparation pulse includes an RF pulse X and a killer gradient pulse Gc for bringing the longitudinal magnetization into a steady state. The frequency f of the RF pulse X is set to f = fk. The preparation pulse is repeatedly executed, and after the m-th preparation pulse is executed, a data acquisition segment DAQ for acquiring data by the single-shot method is executed.

Even when the sequence shown in FIG. 36 is used, similarly to the sequence using continuous wave RF (see FIG. 4), the coefficient (M ₀ ^b / M ₀ ^a / R1 ^a ) and the coefficient (M ₀ ^b / M ₀₎ ^a ), the coefficient (M ₀ ^b / R1 ^a ), and the value of the coefficient M ₀ ^b can be calculated. Therefore, in the third embodiment, the same effect as in the first or second embodiment can be obtained.

(4) Fourth Embodiment In a fourth embodiment, an example will be described in which a sequence for collecting data by a phase cycling method that cycles the phase of an RF pulse is used.

  The MR device of the fourth embodiment differs from the MR device 1 of the first embodiment in the means realized by the processing device 9, but the hardware configuration is the same as that of the MR device 1 of the first embodiment. Is the same as Therefore, in describing the MR device of the fourth embodiment, the description of the hardware configuration is omitted, and the processing device 9 is mainly described.

FIG. 37 is an explanatory diagram of means realized by the processing device 9 in the fourth embodiment.
The processing device 9 according to the fourth embodiment differs from the processing device 9 according to the first embodiment in the following points (1) and (2).

(1) The Z spectrum creating means 91 creates a Z spectrum. However, in the first embodiment, the horizontal axis of the Z spectrum is the offset frequency, but in the fourth embodiment, the horizontal axis of the Z spectrum is a phase difference described later.
(2) In the fourth embodiment, the processing device 9 has the frequency conversion unit 106. The frequency conversion means 106 converts the phase difference into a frequency.

In other respects, the processing device 9 in the fourth embodiment is the same as the processing device 9 in the first embodiment, and a description thereof will not be repeated. The processing device 9 reads out a program stored in the storage unit 10 and implements means 90 to 106 for executing processing described in the program.
Next, a sequence used in the fourth embodiment will be described.

Figure 38 is a diagram showing a sequence SE _k used in the fourth embodiment in detail.
The k-th sequence SE _k has first to m-th pulse sets Set1 to Setm, a killer gradient pulse Gc, and a data acquisition segment DAQ. Hereinafter, first, the first to m-th pulse sets Set1 to Setm will be described. Since the first to m-th pulse sets Set1 to Setm have the same configuration, the first to m-th pulse sets Set1 to Setm will be described by taking the first pulse set Set1 as a representative. .

FIG. 38 shows the first pulse set Set1 in an enlarged manner.
The first pulse set Set1 has r RF pulses X1 to Xr. The RF pulses X1 to Xr are configured such that positive RF pulses and negative RF pulses alternately appear. The RF pulses X1 to Xr are applied at time intervals T_iter. “Φ1” to “φr” described below the symbols “X1” to “Xr” represent the phases of the RF pulses.

Next, the phases φ1 to φr of the r RF pulses X1 to Xr will be described. First, among the r RF pulses X1 to Xr, a p-th RF pulse Xp and a (p + 1) -th RF pulse Xp + 1 will be considered (p is 1 ≦ p ≦ r−1). The p-th phase of the RF pulses Xp represented by ".phi.p", to represent the p + 1-th RF pulses Xp + 1 phase in ".phi.p + 1", k-th RF pulse in the sequence SE _k phase difference [Delta] [phi (k ) = Φp + 1−φp is set so as to satisfy the following expression.

  From equation (40), it can be seen that the phase difference Δφ (k) is set to change according to the value of k.

  Although FIG. 38 illustrates the first pulse set Set1, the second to m-th pulse sets Set2 to Setm also have the same configuration as the first pulse set Set1. Therefore, each pulse set has r RF pulses X1 to Xr, and the phase difference Δφ (k) of the RF pulses is set to satisfy Expression (40).

  After applying the first to m-th pulse sets Set1 to Setm, a killer gradient pulse Gc for eliminating transverse magnetization is applied. Then, after applying the killer gradient pulse Gc, a data acquisition segment DAQ for acquiring data is executed. Here, it is assumed that the data collection segment DAQ collects data by the single shot method.

The k-th sequence SE _k is configured as described above. In the fourth mode, the sequence SE _k is executed r times. Note that, as the number r of executed sequences increases, a Z spectrum having a higher frequency resolution is obtained. Therefore, it is desirable that r has a somewhat large value. Generally, it is conceivable to set r = 16 to 32.

Here, F (Δω _a ) (see equation (4)) in the case of using the sequence of the phase cycling method will be considered.

Represents a time interval of the RF pulses in T_iter, to represent the phase difference between the RF pulse in [Delta] [phi _a, [Delta] [omega _a is a Miyoshi etc., have been shown to be replaced by a periodic function of the following (Miyoshi M, et al. , Proceedings of ISMRM2014, # 3299).

Therefore, in the equation (4), replacing the [Delta] [omega _a ² 2 in _{(1-cosΔφ a) / T} iter 2, the following equation is obtained.

F (Δφ _a ) defined by the equation (42) is an even function like F (Δω _a ) defined by the equation (4). Therefore, even if equation (42) is used instead of equation (4), a CPE spectrum suitable for separating the CEST waveform can be obtained.

When the phase cycle is used, the i-th CEST term can be expressed by the following equation.

The CEST waveform represented by the i-th CEST term is represented by a Lorentz function using coefficients a _{1, i} , a _{2, i} , and Δφ _{c, i} . a _{1, i} / a _{2, i} represents the height of the peak of the CEST waveform, 2√a _{2, i} represents the half width of the peak of the CEST waveform, and Δφ _{c, i} is the phase difference at which the peak of the CEST waveform appears Is represented.

In the first embodiment, by using an expression containing the frequency [Delta] [omega _a and [Delta] [omega _{c, i} as a variable, various spectra are required. However, in the fourth embodiment, since the phase difference is used instead of the frequency, it is necessary to obtain each spectrum (such as a CPE spectrum) using an expression in which the frequency is replaced with the phase difference. Specifically, the frequency [Delta] [omega _a and [Delta] [omega _{c, i,} respectively, the following phase difference [Delta] [phi _a and [Delta] [phi _c, may be replaced to _i.

The phase differences Δφ _a and Δφ _{c, i} are represented by the following equations.

  In the MR device according to the fourth embodiment, the processing device 9 includes a frequency conversion unit 106 (see FIG. 37) that converts a phase difference into a frequency. The frequency conversion means 106 can convert the phase difference into a frequency based on the equations (44) and (45). Therefore, it can be seen that even when the phase cycle method is used, the phase difference of each spectrum can be converted into a frequency.

Reference Signs List 1 MR device 2 Magnet 3 Table 3a Cradle 4 Receiving coil 5 Control unit 6 Transmitter 7 Gradient magnetic field power supply 8 Receiver 9 Processing device 10 Storage unit 11 Operation unit 12 Display unit 13 Subject 21 Storage space 22 Superconducting coil 23 Gradient coil 24 RF coil 21 accommodation space 90 image creating means 91 Z spectrum creating means 92 spectrum converting means 93 detecting means 94 i value setting means 95 first fitting means 96 CRZ spectrum creating means 97 second fitting means 98 (c ₀ , c _MT ) calculation means 99 spectrum calculation means 100 judgment means 101 spectrum estimation means 102 spectrum comparison means 103 counting means 104 CEST term judgment means 105 coefficient value calculation means 106 frequency conversion means

Claims (22)

A magnetic resonance apparatus for performing a scan for acquiring information reflecting a magnetization transfer caused by CEST (chemical exchange saturation transfer),
In the scan, scan means for executing a plurality of sequences having RF pulses, wherein the scan means wherein the frequency of the RF pulse is set to be different for each sequence,
Z spectrum creation means for creating a Z spectrum based on the data obtained by the plurality of sequences,
An even function including, as a variable, an offset frequency representing a deviation from the resonance frequency of water, wherein the Z function is based on an even function set so that the value of the even function becomes zero when the value of the offset frequency is zero. Spectrum conversion means for converting a spectrum into a first spectrum;
A CEST term representing a first waveform of a signal component affected by CEST, the CEST term including a first coefficient for representing a characteristic value of the first waveform, and a CEST term not being affected by CEST. Fitting means for fitting the first spectrum obtained by the spectrum converting means using an approximation formula including a baseline term representing a second waveform of the signal component to obtain a value of the first coefficient; ,
The first coefficient, a second coefficient representing the transmission magnetic field strength, and a third coefficient containing information on the magnitude of magnetization of protons contained in the CEST pool, Coefficient value calculating means for calculating the value of the coefficient of 3 in which the value calculated by the fitting means is substituted for the first coefficient of the relational expression, and the second coefficient is calculated in the sequence. Coefficient value calculating means for substituting the value of the transmission magnetic field strength of the RF pulse to be used and calculating the value of the third coefficient;
A magnetic resonance apparatus comprising: Represents the offset frequency [Delta] [omega _a, when representing the even function in F (Δω _a),
The magnetic resonance apparatus according to claim 1, wherein the CEST term is represented by using the even function F (Δω _a ).   The magnetic resonance apparatus according to claim 2, wherein the characteristic value of the first waveform includes a peak height of the first waveform, a half width of the peak, and a frequency at which the peak appears. The approximate expression has n CEST terms,
The i-th CEST term of the n CEST terms includes three coefficients a _{1, i} , a _{2, i} and Δω _{c, i} as the first coefficient,
4. The method according to claim 3, wherein a _{1, i} / a _{2, i} represents the height of the peak, 2√a _{2, i} represents the half-width of the peak, and Δω _{c, i} represents the frequency at which the peak appears. The magnetic resonance apparatus according to claim 1. 5. The i-th CEST term is represented by the following equation using the three coefficients a _{1, i} , a _{2, i} , Δω _{c, i} and the even function F (Δω _a ). 6. The magnetic resonance apparatus according to claim 1.
Here, F _{L, i} (Δω _a ): the i-th CEST term
_{F (Δω a -Δω c, i} ): function obtained by replacing the [Delta] [omega _a of the even function _{F (Δω a) Δω a -Δω} c, the _i A magnetic resonance apparatus for performing a scan for acquiring information reflecting a magnetization transfer caused by CEST (chemical exchange saturation transfer),
In the scanning, scanning means for executing a plurality of sequences having a pulse set including a plurality of RF pulses, wherein the phase of the p-th RF pulse and the phase of the (p + 1) -th RF pulse among the plurality of RF pulses Scanning means for cycling the phases of the plurality of RF pulses so that the phase difference of
Z spectrum creation means for creating a Z spectrum based on the data obtained by the plurality of sequences,
An even function including a phase difference of an RF pulse as a variable, wherein the Z spectrum is converted to a first function based on an even function set such that the value of the even function becomes zero when the value of the phase difference is zero. Spectrum conversion means for converting into a spectrum,
A CEST term representing a first waveform of a signal component affected by CEST, the CEST term including a first coefficient for representing a characteristic value of the first waveform, and a CEST term not being affected by CEST. Fitting means for fitting the first spectrum obtained by the spectrum converting means using an approximation formula including a baseline term representing a second waveform of the signal component to obtain a value of the first coefficient; ,
The first coefficient, a second coefficient representing the transmission magnetic field strength, and a third coefficient containing information on the magnitude of magnetization of protons contained in the CEST pool, Coefficient value calculating means for calculating the value of the coefficient of 3 in which the value calculated by the fitting means is substituted for the first coefficient of the relational expression, and the second coefficient is calculated in the sequence. Coefficient value calculating means for substituting the value of the transmission magnetic field strength of the RF pulse to be used and calculating the value of the third coefficient;
A magnetic resonance apparatus having: Represents the phase difference [Delta] [phi _a, when representing the even function in F (Δφ _a),
The magnetic resonance apparatus according to claim 6, wherein the CEST term is represented by an equation using the even function F (Δφ _a ). The magnetic resonance apparatus according to claim 7 , wherein the characteristic value of the first waveform includes a height of a peak of the first waveform, a half-value width of the peak, and a phase difference at which the peak appears. The approximate expression has n CEST terms,
The i-th CEST term of the n CEST terms includes three coefficients a _{1, i} , a _{2, i} and Δφ _{c, i} as the first coefficient,
9. The method according to claim 8, wherein a _{1, i} / a _{2, i} represents the height of the peak, 2√a _{2, i} represents the half width of the peak, and Δφ _{c, i} represents a phase difference at which the peak appears. 6. The magnetic resonance apparatus according to claim 1. 10. The i-th CEST term is represented by the following equation using the three coefficients a _{1, i} , a _{2, i} , Δφ _{c, i} and the even function F (Δφ _a ). 6. The magnetic resonance apparatus according to claim 1.
Here, FL _{, i} (Δφ _a ): the i-th CEST term
_{F (Δφ a -Δφ c, i} ): function obtained by replacing the [Delta] [phi _a of the even function _{F (Δφ a) Δφ a -Δφ} c, the _i The third coefficient is
11. A coefficient including the magnitude of magnetization of protons contained in the CEST pool, the magnitude of magnetization of protons contained in the free water pool, and the longitudinal relaxation time of water or the reciprocal of the longitudinal relaxation time of water. The magnetic resonance apparatus according to claim 1. The third coefficient is a coefficient including the magnitude of the magnetization of the protons contained in the CEST pool and the magnitude of the magnetization of the protons contained in the free water pool,
The relational expression includes a fourth coefficient representing a longitudinal relaxation time of water or a reciprocal of a longitudinal relaxation time of water,
The scanning means performs another scan to determine the value of the fourth coefficient,
11. The apparatus according to claim 1, wherein the coefficient value calculation unit includes a first coefficient value calculation unit that calculates a value of the fourth coefficient based on data obtained by the another scan. Item 7. The magnetic resonance apparatus according to Item 1. The coefficient value calculation unit includes a second coefficient value calculation unit that calculates a value of the third coefficient based on the relational expression,
The second coefficient value calculation unit substitutes the value of the fourth coefficient calculated by the first coefficient value calculation unit for the fourth coefficient of the relational expression, and calculates the third coefficient The magnetic resonance apparatus according to claim 12, which calculates a value. The third coefficient is a coefficient including the magnitude of magnetization of protons contained in the CEST pool and the longitudinal relaxation time of water or the reciprocal of the longitudinal relaxation time of water,
The relational expression includes a fifth coefficient representing the magnitude of magnetization of protons contained in the free water pool,
The scanning means performs another scan to determine the value of the fifth coefficient,
11. The apparatus according to claim 1, wherein the coefficient value calculation unit includes a first coefficient value calculation unit that calculates a value of the fifth coefficient based on data obtained by the another scan. Item 7. The magnetic resonance apparatus according to Item 1. The coefficient value calculation unit includes a second coefficient value calculation unit that calculates a value of the third coefficient based on the relational expression,
The second coefficient value calculation unit substitutes a value of the fifth coefficient calculated by the first coefficient value calculation unit for the fifth coefficient of the relational expression, and calculates a value of the third coefficient. The magnetic resonance apparatus according to claim 14, which calculates a value. The third coefficient is a coefficient representing the magnitude of magnetization of protons contained in the CEST pool,
The relational expression includes a fourth coefficient representing the longitudinal relaxation time of water or the reciprocal of the longitudinal relaxation time of water, and a fifth coefficient representing the magnitude of magnetization of protons contained in the free water pool,
The scanning means performs another scan to determine the value of the fourth coefficient and the value of the fifth coefficient,
2. The coefficient value calculation unit includes a first coefficient value calculation unit that calculates a value of the fourth coefficient and a value of the fifth coefficient based on data obtained by the another scan. 3. The magnetic resonance apparatus according to any one of claims 10 to 10. The coefficient value calculation unit includes a second coefficient value calculation unit that calculates a value of the third coefficient based on the relational expression,
The second coefficient value calculation unit substitutes the value of the fourth coefficient calculated by the first coefficient value calculation unit for the fourth coefficient of the relational expression, and 17. The magnetic resonance apparatus according to claim 16, wherein the value of the fifth coefficient calculated by the first coefficient value calculation unit is substituted for a fifth coefficient, and the value of the third coefficient is calculated.   The magnetic resonance apparatus according to any one of claims 6 to 10, further comprising frequency conversion means for converting the phase difference into a frequency.   The magnetic resonance apparatus according to claim 1, wherein the RF pulse is a continuous wave RF pulse. The sequence has a plurality of preparation pulses,
The magnetic resonance apparatus according to any one of claims 1 to 5, wherein each of the plurality of preparation pulses includes the RF pulse and a killer gradient pulse for setting longitudinal magnetization to a steady state. What is claimed is: 1. A magnetic resonance apparatus which executes a scan for acquiring information reflecting a magnetization transfer caused by a CEST (chemical exchange saturation transfer), comprising: a scan unit which executes a plurality of sequences having RF pulses in the scan. A program applied to a magnetic resonance apparatus in which the frequency of the RF pulse is set to be different for each sequence,
Z spectrum creation processing for creating a Z spectrum based on the data obtained by the plurality of sequences;
An even function including, as a variable, an offset frequency representing a deviation from the resonance frequency of water, wherein the Z function is based on an even function set so that the value of the even function becomes zero when the value of the offset frequency is zero. A spectrum conversion process for converting the spectrum into a first spectrum;
A CEST term representing a first waveform of a signal component affected by CEST, the CEST term including a first coefficient for representing a characteristic value of the first waveform, and a CEST term not being affected by CEST. A fitting process of fitting the first spectrum obtained by the spectrum conversion process using an approximation formula including a baseline term representing a second waveform of the signal component to obtain a value of the first coefficient; ,
The first coefficient, a second coefficient representing the transmission magnetic field strength, and a third coefficient containing information on the magnitude of magnetization of protons contained in the CEST pool, A coefficient value calculation process for calculating the value of the coefficient of 3 in which the value calculated by the fitting process is substituted for the first coefficient of the relational expression, and the second coefficient is calculated in the sequence. A coefficient value calculation process of substituting the value of the transmission magnetic field strength of the RF pulse to be used and calculating the value of the third coefficient;
A program for causing a computer to execute. What is claimed is: 1. A magnetic resonance apparatus for performing a scan for acquiring information reflecting a magnetization transfer caused by a CEST (chemical exchange saturation transfer), comprising: performing a plurality of sequences including a pulse set including a plurality of RF pulses in the scan. Scanning means for performing the scanning, wherein the phase difference between the phase of the p-th RF pulse and the phase of the (p + 1) -th RF pulse of the plurality of RF pulses is different for each of the sequences. A program applied to a magnetic resonance apparatus that cycles a phase,
Z spectrum creation processing for creating a Z spectrum based on the data obtained by the plurality of sequences;
An even function including a phase difference of an RF pulse as a variable, wherein the Z spectrum is converted to a first function based on an even function set such that the value of the even function becomes zero when the value of the phase difference is zero. Spectrum conversion processing for converting to a spectrum,
A CEST term representing a first waveform of a signal component affected by CEST, the CEST term including a first coefficient for representing a characteristic value of the first waveform, and a CEST term not being affected by CEST. A fitting process of fitting the first spectrum obtained by the spectrum conversion process using an approximation formula including a baseline term representing a second waveform of the signal component to obtain a value of the first coefficient; ,
The first coefficient, a second coefficient representing the transmission magnetic field strength, and a third coefficient containing information on the magnitude of magnetization of protons contained in the CEST pool, A coefficient value calculation process for calculating the value of the coefficient of 3 in which the value calculated by the fitting process is substituted for the first coefficient of the relational expression, and the second coefficient is calculated in the sequence. A coefficient value calculation process of substituting the value of the transmission magnetic field strength of the RF pulse to be used and calculating the value of the third coefficient;
A program for causing a computer to execute.