JPH0322771B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a nuclear magnetic resonance imaging apparatus (hereinafter referred to as NMR), and particularly relates to a nuclear magnetic resonance imaging apparatus (hereinafter referred to as NMR), and in _particular , to
This invention relates to improvements in means for obtaining calculation images of T ₂ and proton density ρ.

(Prior art) Longitudinal relaxation time T ₁ , which is considered to be medically useful, has traditionally been measured using NMR imaging equipment from images measured.
There is a technique to obtain an image related to the value (T ₁ image) and an image related to the transverse relaxation time T ₂ value (T ₂ image).

(Problems to be Solved by the Invention) However, the T ₁ image and the T ₂ image have been obtained using different methods as follows.

For example, the T ₁ image is calculated as follows. The IRSE method is a combination of the inversion recovery method (hereinafter referred to as IR method) and the spin echo method (hereinafter referred to as SE method) as shown in Figure 7, and the IRSE method shown in Figure 8. The saturation recovery method (Saturation
One original image is obtained using the SRSE method, which is a combination of Recovery (hereinafter abbreviated as SR method) and SE method, and calculations are performed using these two images and an approximation formula for signal strength.

The SRSE method is a pulse sequence in which an echo signal is obtained by applying a 90° pulse and then a 180° pulse, as shown in Figure 8. The time from the 90° pulse to the center of the echo signal is T _s , 90 The time from the application of the ° pulse to the application of the 90° pulse in the next view is defined as T _r .

In addition, as shown in Figure 7, the IRSE method is a pulse sequence in which a 180° pulse for inversion recovery is applied before each 90° pulse of the SRSE method shown in Figure 8. T d is the time from the application of the 180° pulse to the application of the 90° pulse, T _s is the time from the 90° pulse to the center of the echo signal, and T _s is the time from the 90° pulse to the center of the echo signal.
The time from the application of the 180° pulse for recovery to the application of the 180° pulse for the next view is defined as T _r .

_The theoretical _{formula for} signal _{strength in the} SRSE method I _{SR is}
/2T ₁ ) + exp (-Tr/T ₁ )} In addition, the theoretical formula for signal strength in the IRSE method I _SR is I _IR = I ₀・exp (−T _s /T ₂ ) {1−2・exp (− _Td / _T1
) +2・exp(−T _r /T ₁ +T _s /2T ₁ )−exp(−T _r /
T ₁ )}.

For this theoretical formula, here, as T _r 〓T ₁
If exp(−T _r /T ₁ )=0, I _SR ≒I ₀・exp(T _s /T ₂ ) I _IR ≒I ₀・exp(−T _s /T ₂ ) {1 −2・exp (−T _d /T ₁ )} Therefore, I _IR /I _SR =1−2・exp(−T _d /T ₁ ) T ₁ =T _d /ln{2I _SR /(I _SR −I _IR )} This Find the _T1 value from the formula.

To obtain the _T2 image, for example, refer to the publication "Eizo Information (M)" June 1984 issue (Vol. 16 No. 11).
The CPMG method described on pages 570 to 576 is used to eliminate T ₁ and ρ from a plurality of echo data, and the T ₂ value is determined by the least squares method.

Note that in the CP method, which allows multiple echo data to be extracted continuously and the _T2 value obtained in one data collection, if the length of the applied pulse is incomplete, the error will cause echoes to be obtained. However, the CPMG method solves this problem by repeating a 90° pulse followed by a 180° pulse _n times, as shown in Figure 9. This is a pulse sequence that is applied to generate n echoes.

Conventional methods using such techniques have the following drawbacks.

(1) The T ₁ image and the T ₂ image are obtained separately, and the calculation images of T ₁ , T ₂ , and ρ cannot be obtained at the same time.

(2) Exact values cannot be determined because approximate formulas are used.

(3) Due to the condition of T _r 〓T ₁ , T _r must be made long, and the total scan time is long.

(4) The scan parameters of the original image are not optimized, and the best calculated image cannot be found under the given conditions.

In view of these points, an object of the present invention is to use an NMR imaging device to obtain T ₁ , T ₂ ,
NMR that accurately and simultaneously obtains ρ calculation images
The purpose of the present invention is to provide an imaging device.

Another object of the present invention is to enable accurate and simultaneous determination of T ₁ , T ₂ , and ρ calculation images using images obtained from arbitrary pulse sequences.
Our objective is to provide an NMR imaging device.

(Means for Solving the Problems) In order to achieve such an object, the present invention provides a nuclear magnetic resonance imaging apparatus in which at least one of the relaxation times (T ₁ , T ₂ ) or the proton density (ρ) is adjusted. 1. A nuclear magnetic resonance imaging apparatus characterized by comprising a control means having the following functions for obtaining a calculated image related to a nuclear magnetic resonance image.

Note: The optimum scan parameter for the calculated image is calculated using the law of error propagation from the theoretical formula for signal strength, the values of T ₁ , T ₂ , and ρ, and the variance of the original image, and the image is captured using the calculated scan parameter. Using this original image, directly apply the least squares method to _the theoretical formula of signal strength to obtain T ₁ , T ₂ , and ρ values.
A calculation image regarding T ₂ and ρ is obtained.

If there is an influence due to slicing, a theoretical expression including the influence of slicing is used as the theoretical expression for the signal strength.

(Example) The present invention will be explained in detail below using the drawings. FIG. 1 is a block diagram of essential parts showing an embodiment of an NMR imaging apparatus according to the present invention. In the figure, 1 is a magnet assembly, inside of which a space (hole) is provided for inserting an object, and a uniform static magnetic field H ₀ is applied to the object surrounding this space. A main magnetic field coil 2, and a gradient magnetic field coil 3 for generating a gradient magnetic field (consisting of an x gradient magnetic field coil, a y gradient magnetic field coil, and a z gradient magnetic field coil configured to be able to individually generate gradient magnetic fields). ), an RF transmitting coil 4 that provides high-frequency pulses to excite the spins of atomic nuclei within the object, and a receiving coil 5 that detects NMR signals from the object.

The main magnetic field coil is connected to the static magnetic field control circuit 15, G _x ,
G _y , G _z each gradient magnetic field coil is gradient magnetic field control circuit 1
4, the RF transmitting coil is connected to the power amplifier 18, and the NMR signal receiving coil is connected to the preamplifier 19.
are connected to each.

13 is a controller that controls the sequence of generation of gradient magnetic fields and high-frequency magnetic fields.
Performs necessary control to capture the NMR signal into the waveform memory 21.

17 is a gate modulation circuit, and 16 is a high frequency oscillator that generates a high frequency signal. Gate modulation circuit 17
appropriately modulates the high frequency signal output from the high frequency oscillator 16 using a control signal from the controller 13 to generate a high frequency pulse of a predetermined phase. This high frequency pulse is applied to the RF transmitting coil 4 through the RF power amplifier 18.

19 is a preamplifier that amplifies the NMR signal obtained from the detection coil 5; 20 is a phase detection circuit that phase-detects the NMR signal by referring to the output signal of the high-frequency oscillator; and 21 stores the phase-detected waveform signal from the preamplifier. In the waveform memory, here is A/
Contains a D converter.

11 is a computer that receives the signal from the waveform memory 21 and performs predetermined signal processing to obtain a tomographic image;
12 is a display device such as a television monitor that displays the obtained tomographic image.

Next, the procedure for creating a calculated image in such a configuration will be explained.

First, the pulse sequence and scan parameters are determined.

For example, from three original images using the SRSE method,
White matter and gray matter of the human head (T ₁ = 0.5 to 0.3 sec,
Let us take as an example the case where a calculation image centered around T ₂ =0.1 to 0.07 sec is obtained. The scan parameters are
Theoretical formula for signal strength in the SRSE method and the required T ₁ ,
From the values of T ₂ and ρ and the variance of the original image, it is selected by calculation (details of the calculation method will be described later) so as to optimize the evaluation function of the calculated image. These conditions such as pulse sequence and scan parameters are set in the controller 13. , the total scan time is about 300 seconds, and the number of views is
127, the scan parameters of the three images are determined as follows.

<> T _r =0.3sec T _s =0.022sec n=2 <> T _r =1.28sec T _s =0.025sec n=1 <> T _r =0.64sec T _s =0.109sec n=1 Here, n is Represents the average number of each sequence.

Under the control of the controller 13, a 90° pulse as shown in FIG. 2A is obtained through the gate modulation circuit 17 and applied to the RF transmitting coil 4 via the power amplifier 18 to excite the object. At this time, a gradient magnetic field G _z is also applied (FIG. 2B) to selectively excite only the spins within a specific slice plane.

Next, phase encoding is performed using the gradient magnetic field _Gy , and at the same time, a gradient magnetic field _Gx is applied (d) to prepare for observing echoes.

Next, the application of the gradient magnetic field is stopped, and a 180° pulse is applied to reverse the spin. Thereafter, as shown in Figure D, an echo signal (Figure E) generated while applying G _x is detected by the receiving coil 5 and observed. The spin echo signal detected by the receiving coil is stored in a waveform memory 21 via a preamplifier 19 and a phase detection circuit 20.

The original image (image data) is obtained from a large number of signals with different phase encoded amounts using the above method.

Apply a spatial filter to the image if necessary. That is, when the density resolution (S/N) is worse than the spatial resolution, the density resolution of the image is increased by using a spatial filter.

From the three original images obtained by the above (or) and the theoretical formula, calculation images of T ₁ , T ₂ , and ρ are obtained by the iterative correction least squares method (details will be described later).

If there is an influence due to slices, a theoretical formula including the influence of slices is used as the theoretical formula for the signal strength. This slicing effect is the effect of magnetization not tilting by 90 degrees in the slicing direction, and the details of the correction method will be described later.

By the above procedure, calculation images of T ₁ , T ₂ , and ρ can be obtained accurately and simultaneously.

() Now, the theoretical formula for signal strength and the required T ₁ ,
A method for determining scan parameters that optimize the calculated image evaluation function from T ₂ and ρ values will be explained. Here, the evaluation function is σ _T1 /T ₁ +σ _T2 /T ₂ +σ _p /ρ, where σ _T1 , σ _T2 , and σ _P are the standard deviations of T ₁ , T ₂ , and ρ.

The principle is explained as follows.
Theoretical formula F(T _r , T s , T _s ,
T ₁ , T ₂ , p) are expressed as follows.

F(T _r , T _s , T ₁ , T ₂ , p)=C _SRSE・exp(−T _s /T ₂ ) {
1-2・exp(−T _r /T ₁ +T _s /2T ₁ )+exp(−T _r /T ₁ )}・
ρ Here, C _SRSE is a coefficient representing the effect of slicing and is a function of T ₁ /T _r . For example, if a Gaussian 90° pulse is used, C _SRSE can be expressed by the following equation.

0.2<T ₁ /T _r <10.0 and C _SRSE = 8.1537E−6(T ₁ /T _r ) ⁶ −2.95086E−4(T
₁ /T _r ) ⁵ +4.27675E-3 (T ₁ /T _r ) ⁴ -3.17902E-2 (T ₁ /T _r ) ³ +1.29262E-1 (T ₁
/T _r ) ² −2.8554E−1 (T ₁ /T _r )+1.0557 The scan parameters of the three images are T _r1 ,
Assuming T _s1 , T _r2 , T _s2 , T _r3 , and T _s3 , the covariance matrix V _T1T2p of the values of T ₁ , T ₂ , and ρ calculated from the image by the least squares method is V _T1T2p = (A ^T V ^{- 1} ₁₂₃ A) ^-1 However, V ₁₂₃ is the covariance matrix of the original image, and the variance σ ² of the original image is expressed as σ ² ∝n ^-1 Ta ^-1 where the average value is n and the sampling time is Ta. is,
Also, A is becomes.

Therefore, the variance of the values of T ₁ , T ₂ , and ρ can be found as the diagonal elements of V _T1T2p .

From the above, the evaluation functions of the calculated image are T _s1 , T _s2 ,
T _s3 , T _r1 , T _r2 , T _r3 , T _a1 , T _a2 , T _a3 , n ₁ ,
It is found as a function of n ₂ and n ₃ .

Based on this principle, appropriate scan parameters are determined by the following procedure.

First, the pulse sequence to be used is determined, and a theoretical formula for signal strength is determined.

Theoretical formula, the range of T ₁ , T ₂ , and ρ you want to measure,
From the variance of the original image, the evaluation function of the calculated image is determined as a function of the scan parameter.

In the above, since the evaluation function of the calculated image was determined as a multivariable function of the scan parameters, the scan parameters T _s1 , T _s2 , T _s3 , T _r1 ,
Find T _r2 , T _r3 , T _a1 , T _a2 , T _a3 , n ₁ , n ₂ , and n ₃ .

() Next, a calculation example using the iterative corrected least squares method will be explained.

Concerning the scan parameters T _r and T _s of the three original images, for the first image, T _r1 , T _s1 For the second image, T _r2 , T _s2 For the third image, T _r3 , T Let it be _s3 . Further, if the theoretical formula for the signal strength in the SRSE method is F (T _r , T _s , T ₁ , T ₂ , ρ), it is expressed as follows as described above.

F(T _r , T _s , T ₁ , T ₂ , ρ) = C _SRSE・exp(−T _s /T ₂ ) {1
-2・exp(−T _r /T ₁ +T _s /2T ₁ )+exp(−T _r /T ₁ )}・ρ Next, we will describe the calculation procedure with reference to the calculation process flow shown in Figure 3. . Initial approximation value〓(T ₁ ,
Taylor expansion of the theoretical formula around T ₂ , ρ),
Taking up to the first order, the signal intensities I ₁ , I ₂ , and I ₃ in each image are as follows.

I ₁ = F (T _r1 , T _s1 , 〓) + (∂F／∂T ₁ ) _Tr1Ts1 〓・ΔT
₁ + (∂F/∂T ₂ ) _Tr1 Ts1〓・ΔT ₂ + (∂F/∂ρ) _Tr1 Ts
1〓・Δρ I ₂ = F (T _r2 , T _s2 , 〓) + (∂F／∂T ₁ ) _Tr2Ts2 〓・ΔT
₁ + (∂F/∂T ₂ ) _Tr2 Ts2〓・ΔT ₂ + (∂F/∂ρ) _Tr2 Ts
2〓・Δρ I ₃ = F (T _r3 , T _s3 , 〓) + (∂F／∂T ₁ ) _Tr3Ts3 〓・ΔT
₁ + (∂F/∂T ₂ ) _Tr3 Ts3〓・ΔT ₂ + (∂F/∂ρ) _Tr3 Ts
3〓・Δρ Next, ΔT ₁ , ΔT ₂ , and Δρ are determined by the least squares method from the values of the three images and the above equation.

Next, let the new approximations for T^ ₁ , T^ ₂ , and ρ^ be T^ ₁ +ΔT^ ₁ T^ ₂ +ΔT^ ₂ ρ^+Δρ until T^ ₁ , T^ ₂ , and ρ^ converge. repeat. If convergence is not possible, change the initial value and repeat the calculation from the beginning. When it is determined that it has converged, T^ ₁ , T^ ₂ , and ρ^ at that time are the required T ₁ , T ₂ , and ρ.

() Next, a method for correcting the influence of illustrations will be explained.

The signal strength of the SRSE method is expressed as follows, when α is the angle at which the magnetization falls.

sinα・exp(−T _s /T ₂ ) {1−2exp(−T _r /
T ₁ +T _s /2T ₁ ) + exp (-T _r /T ₁ )} / 1 + cos α・exp (
−T _r /T ₁ ) ρ (1) If a Gaussian-modulated 90° pulse is used, α=π/2·exp(−z ² ) (2) in the slice direction z. By integrating Equation (1) with respect to z using Equation (2), the signal strength including the influence of the slice can be found.

The ratio of this signal strength value to the value calculated by the theoretical formula becomes a coefficient representing the influence of the slice.

Please note that the number of original images is not limited to three,
It may be more than that. The calculation is the same even if there are four or more sheets.

The method of photographing the original image may be any of the following methods.

This method sequentially captures all views using one set of scan parameters, all views using another set of scan parameters, and all views using another set of scan parameters.

A method that sequentially captures images using three sets of scan parameters for each view.

Further, in this case, it may be a mixture of three images in different pulse sequences, and the combination of pulse sequences is free.

Cases of other pulse sequences will be explained below.

In Figure 4, the application of the gradient magnetic field is omitted, but in the SRSE method, each view is
This shows the pulse sequence for the SRSE method in which 180° pulses are applied twice.
The theoretical formula for signal strength in this case _is M ₀ = C _SR2SE {1-2exp(T _r /T ₁ +T _s1 /T ₁ +T _s2 /2T ₁ ) + 2
・exp(−T _r /T ₁ +T _s1 /2T ₁ −exp(−T _r /T ₁ )}ρ, in the first echo Mo exp(−T _s1 /T ₂ ) In the second echo Mo・It is expressed as exp(T _s1 /T ₂ −T _s2 /T ₂ ). However, T _s1 is the time from the application of the 90° pulse to the peak of the first echo signal, and T _s2 is the time of the first echo signal. This is the time from the peak time to the peak time of the 32nd echo signal.

Here, C _SR2SE is a coefficient representing the influence of slicing and is a function of T ₁ /T _r . For example, Gaussian
Using a 90° pulse, C _SR2SE can be expressed as:

C _SR2SE = −2.4203E−5( _{T 1 /} T _{r )} ⁵ +5.6861E−4(T ₁
/T _r ) ⁴ -3.6523E-3 (T ₁ /T _r ) ³ -1.0071E-2 (T ₁ /T _r ) ² +3.2162E-2 (T ₁ /T _r )
+0.9178 Then, one image is captured using the SRSE method and two images are captured using the SR2SE method (two images are obtained in one scan).
Assuming that the calculated image is obtained from the three images,
The scan parameters at this time should be determined as follows, assuming that the total scan time is approximately 300 seconds and the number of views is 127.

<> For the SRSE method, T _r = 0.34 sec T _s = 0.031 sec n = 2 <> For the SR2SE method, T _r = 1.38 sec T = 0.021 sec T = 0.09 sec n = 1 The number of images and the imaging method are as described in the above embodiment. The same is true in the case of

In this method of combining SRSE method and SR2SE method,
In addition to the effect of using only the SRSE method, since multiple echoes are used, multiple images can be obtained in one scan, which has the effect of shortening the total scan time.

FIG. 5 is a diagram showing another pulse sequence. The diagram omits the application of gradient magnetism, but after applying the 180° pulse,
This is a pulse sequence that shortens the waiting time between applying a 90° pulse and moving on to the next sequence (called the FRSE method). The theoretical formula in this case is exp(−T _s1 /T ₂ )1−exp(−T _d
/T ₁ )/1−exp(−T _d /T ₁ −T _s1 /T ₂ −T _s2 /T ₂ )ρ. However, T _s1 is the time from 90° pulse application to the peak of the echo signal, and T _s2 is the time from the peak of the echo signal to 90° for fast recovery.
The time to pulse application, T _d is the time from this 90° pulse to the next sequence of 90° pulses.

Then, a calculated image is obtained from the three images, and the scan parameters at this time are preferably determined as follows, assuming that the total scan time is approximately 300 seconds and the number of views is 127.

<> T _r =0.14sec T _s1 =T _s2 =0.023sec n=4 <> T _r =0.74sec T _s1 =T _s2 =0.016sec n=1 <> T _r =1.18sec T _s1 =0.099sec T _s2 =0.031sec n=1 The number of images and the imaging method are the same as in the previous embodiment.

In addition, Figure 10 is a diagram showing still another pulse sequence, which is the FR2SE method in which one more 180° pulse is added for each view in the FRSE method shown in Figure 5, making it possible to collect two sets of echo signals each. It is. The calculation images are two images obtained by this FR2SE method, and
It is determined from one image using the FRSE method shown in Figure 5.

The theoretical formula for the signal strength of the FR2SE method is M _{0 =} 1-exp(-T _d /T ₁ )/1-e
As xp−(−T _d /T ₁ −T _s1 /T ₂ −T _s2 /T ₂ −T _s3 /T ₂ )ρ, for the first echo, Mo・exp(−T _s1 /T ₂ ) for the second echo Then, it is expressed as Mo・exp(−T _s1 /T ₂ −T _s2 /T ₂ ).

The scan parameters when calculating a calculated image from one image using the FRSE method and two images using the FR2SE method are as follows: total scan time is approximately 300 seconds, and the number of views is approximately 300 seconds.
127, it would be better to define it as follows.

<> For FRSE method, T _r =0.14sec T _s1 =0.026sec T _s2 =0.026sec n=4 <> For FR2SE method, T _r =1.62sec T _s1 =0.021sec T _s2 =0.081sec T _s3 =0.031sec n= 1 In addition, two images obtained by the SR2SE method shown in Fig. 4,
The case where a calculated image is obtained from one image using the IRSE method shown in FIG. 7 will be described next.

The theoretical formula for the signal strength of the IRSE method is C _IRSE・exp(−T _s /T ₂ ){1−2・exp(−T _d /T ₁ )
+2·exp(T _r /T ₁ +T _s /2T ₁ )−exp(T _r /T ₁ )}·ρ.

Here, C _IRSE is a coefficient representing the influence of slicing, and is a function of T ₁ /T _r , and C _IRSE = C _SR2SE .

The scan parameters when calculating a calculated image from one image using the IRSE method and two images using the SR2SE method are as follows: the total scan time is approximately 300 seconds, and the number of views is approximately 300 seconds.
127, it would be better to define it as follows.

<> For the FRSE method, T _r = 1.2 sec T _d = 0.23 sec T _s = 0.031 sec n = 1 <> For the SR2SE method, T _r = 0.6 sec T _s1 = 0.018 sec T _s2 = 0.089 sec n = 2 The scan parameters when calculating a calculated image from one image according to the method and two images according to the FR2SE method should be determined as follows, assuming that the total scan time is about 300 seconds and the number of views is 127.

<> For the IRSE method, T _r = 1.16 sec T _d = 0.221 sec T _s = 0.031 sec n = 1 <> For the FR2SE method, T _r = 0.82 sec T _s1 = 0.018 sec T _s2 = 0.092 sec T _s3 = 0.031 sec n = 2 This method using the pulse sequence of the IRSE method has the advantage that the standard deviation of T ₁ can be particularly reduced because the IRSE method is used.

In the manner described above, relaxation time images and proton density images can be obtained accurately.

(Effects of the Invention) As explained above, the present invention has the following effects.

Since no approximation formula is used, accurate values can be obtained.

T ₁ , T ₂ , ρ can be calculated without eliminating them by calculating the theoretical formulas, so T ₁ , T ₂ , ρ
calculation images can be obtained at the same time.

The optimum scan parameters are determined from the evaluation of the calculated image, and the best calculated image can be obtained under the given conditions (total scan time).

By increasing the number of images used, the dispersion can be reduced over a wide range of T ₁ and T ₂ .

[Brief explanation of drawings]

FIG. 1 is a block diagram of main parts showing an embodiment of an NMR imaging device according to the present invention, FIG. 2 and FIGS. 4 to 9 are diagrams showing an example of a pulse sequence, and FIG.
The figure is a diagram showing the flow of calculation processing. DESCRIPTION OF SYMBOLS 1... Magnet assembly, 2... Main magnetic field coil, 3... Gradient magnetic field coil, 4... RF transmitting coil, 5... Receiving coil, 11... Computer, 12... Display, 13... Controller ,1
4... Gradient magnetic field control circuit, 15... Static magnetic field control circuit, 16... High frequency oscillator, 17... Gate modulation circuit, 18... Power amplifier, 19... Preamplifier, 20... Phase detection circuit, 21... Waveform memory.

Claims (1)

[Scope of Claims] 1. A nuclear magnetic resonance imaging apparatus that applies high-frequency pulses and a magnetic field to an object to generate nuclear magnetic resonance signals, and uses these signals to obtain an image of the tissue of the object, comprising at least A nucleus characterized by being equipped with a control means having the following functions (a) to (g) for obtaining a calculated image regarding either relaxation time (T ₁ , T ₂ ) or proton density (ρ) Magnetic resonance imaging device. (a) Determine the pulse sequence to be used and obtain the theoretical formula for the signal strength in that pulse sequence. (b) From the theoretical formula for the signal strength, scan parameters, relaxation times (T ₁ , T ₂ ), proton density (ρ), and original image variance, calculate the variance or standard deviation of the calculated image or their weighted values. An evaluation function defined by the sum of the scan parameters is obtained as a function of the scan parameters using the law of error propagation. (c) Newly find scan parameters that give the best evaluation function for the calculated image found in (b) above. (d) Imaging is performed using the new scan parameters determined in (c) above. (e) Obtain a new original image from the signal obtained in imaging in (d) above. (F) Using the new original image obtained in (E) above and the theoretical formula for the signal strength of each image related to the scan conditions, it is calculated according to the type of image to be imaged using the iteratively corrected least squares method. to find the value of relaxation time (T ₁ , T ₂ ) or proton density (ρ). (g) From the values obtained in (f) above, at least T ₁ ,
A calculation image regarding either T ₂ or ρ is obtained. 2. When obtaining T ₁ , T ₂ , and ρ calculation images from the three images in the SRSE method, the control means uses the following formula and value as the theoretical formula for signal strength and the value of the scan parameter applied to imaging. The nuclear magnetic resonance imaging apparatus according to claim 1, characterized in that: Note: The theoretical formula is C _SRSE・exp(−T _s /T ₂ ) × {1−2・exp(−T _r /T ₁ +T _s /(2T ₁ )) +exp(−T _r /T ₁ )}・ρ C _SRSE is a coefficient representing the influence of slices. As scan parameters: (1) T _r = 0.3 sec T _s = 0.022 sec (2) T _r = 1.28 sec T _s = 0.025 sec (3) T _r = 0.64 sec T _s = 0.109 Average sec (1), (2), and (3) at a ratio of 1.4:1:1. However, T _r : Time between one view T _s : Time from the 90° pulse to the center of the echo signal. 3. When obtaining the T ₁ , T ₂ , and ρ calculation images from the three images in the SRSE method and the SR2SE method, the control means uses the following formula and value as the theoretical formula for signal strength and the value of the scan parameter applied to imaging. 2. The nuclear magnetic resonance imaging apparatus according to claim 1, wherein the nuclear magnetic resonance imaging apparatus is used as a nuclear magnetic resonance imaging apparatus. As a theoretical formula, in the SRSE method, C _SRSE・exp(−T _s /T ₂ )×{1−2・exp(−T _r /T ₁ +T _s /(2T ₁ )) +exp(−T _r /T ₁ ) }・ρ In the SR2SE method, M ₀ =C _SR2SE {1−2・exp(−T _r /T ₁ +T _s1 /T ₁ +T _s2 /(2T ₁ )) +2exp(−T _r /T ₁ +T _s1 /(2T ₁ ) −exp(−T _r /T ₁ )}・ρ, and for the first echo, M ₀ exp(−T _s1 /T ₂ −T _s2 /T ₂ ) However, C _SRSE and C _SR2SE are affected by the slice. A coefficient representing the scan parameters: (1) For the SRSE method, T _r = 0.34 sec T _s = 0.031 sec (2) For the SR2SE method, T _r = 1.38 sec T _s1 = 0.021 sec T _s2 = 0.09 sec (1), (2 ) at a ratio of 1.8:1. However, T _r : Time between 1 views T _s1 : Time from application of 90° pulse to the peak of the first echo signal. T _s2 : Time of the first echo signal The time from the peak time to the peak time of the second echo signal. 4. The control means applies the theoretical formula of signal strength and imaging when obtaining T ₁ , T ₂ , and ρ calculation images from three images in the FRSE method. The nuclear magnetic resonance imaging apparatus according to claim 1, characterized in that the following formula and value are used as the value of the scan parameter.The theoretical formula is exp( _-Ts1 / _T2 ) x {1- exp(−T _d /T ₁ )}ρ/{1 −exp(−T _d /T ₁ −T _s1 /T ₂ −T _s2 /T ₂ )} As scan parameter (1) T _r =0.14sec T _s1 T = _s2 = 0.023sec (2) Tr = 0.74sec T _s1 = T _s2 = 0.016sec (3) _Tr = 1.18sec T _s1 = 0.099sec T _s2 = 0.031sec (1), (2), (3) are averaged at a ratio of 3.4:1:1. However, T _r : Time between 1 views T _s1 : Time from 90° pulse application to the peak of the first echo signal. T _s2 : First echo signal from the peak time of the second echo signal to the peak time of the second echo signal. 5. When obtaining the T ₁ , T ₂ , and ρ calculation images from the three images in the FRSE method and the FR2SE method, the control means uses the theoretical formula of the signal strength and 2. The nuclear magnetic resonance imaging apparatus according to claim 1, wherein the following equation and value are used as values of scan parameters applied to imaging. As a theoretical formula, in the FRSE method, exp(−T _s1 /T ₂ ) × {1−exp(−T _d /T ₁ )}ρ/{1 −exp(T _d /T ₁ −T _s1 /T ₂ −T _s2 /T ₂ )} In the FR2SE method, M ₀ = {1−exp(−T _d /T ₁ )}/{1 −exp(−T _d /T ₁ −T _s1 /T ₂ −T _s2 /T ₂ − T _s3 /T ₂ )}, for the first echo M ₀ exp (−T _s1 /T ₂ ) and for the second echo M ₀ exp (−T _s1 /T ₂ −T _s2 /T ₂ ) as scan parameters. (1) For the FRSE method, T _r = 0.16 sec T _s1 = T _s2 = 0.026 sec (2) For the FR2SE method, T _r = 1.62 sec T _s1 = 0.021 sec T _s2 = 0.081 sec T _s3 = 0.031 sec (1), ( 2) is averaged at a ratio of 3.8:1. However, T _r : Time between 1 views T _s1 : Time from application of 90° pulse to the peak of the first echo signal. T _s2 : Time from the peak of the first echo signal to the peak of the second echo signal T _s3 : Time from the peak of the second echo signal to the peak of the second echo signal
Time to 90° pulse. 6. When obtaining the T ₁ , T ₂ , and ρ calculation images from the three images in the IRSE method and the SR2SE method, the control means uses the following formula and value as the theoretical formula for signal strength and the value of the scan parameter applied to imaging. The nuclear magnetic resonance imaging apparatus according to claim 1, wherein the nuclear magnetic resonance imaging apparatus is used as a nuclear magnetic resonance imaging apparatus. As a theoretical formula, in the IRSE method, C _IRSE・exp(−T _s /T ₂ ) × {1−2・exp(−T _d /T ₁ +2exp(−T _r /T ₁ +T _s /(2T ₁ )) − exp(−T _r /T ₁ )}・ρ In the SR2SE method, M ₀ =C _SR2SE {1−2・exp(−T _r /T ₁ +T _s1 /T ₁ +T _s2 /(2T ₁ )) +2exp(−T _r / T ₁ + T _s1 / (2T ₁ ) −exp (−T _r /T ₁ )}・ρ, for the first echo M ₀ exp (−T _s1 /T ₂ ) for the second echo M ₀ exp (−T _s1 /T ₂ −T _s2 /T ₂ ) However, C _IRSE and C _SR2SE are coefficients representing the influence of slices. As scan parameters, (1) In the IRSE method, T _r = 1.2 sec T _d = 0.23 sec T _s = 0.031sec (2) In the SR2SE method, T _r = 0.6 sec T _s1 = 0.018 sec T _s2 = 0.089 sec (1) and (2) are averaged at a ratio of 1:1.9. However, T _r : Time between 1 view T _d : Time from application of inversion recovery pulse to 90° pulse T _s : Time from application of 90° pulse to peak of echo signal T _S1 : Time from application of 90° pulse to peak of first echo signal Time T _S2 : Time from the peak time of the first echo signal to the peak time of the second echo signal. 7 The control means calculates the T ₁ , T ₂ , and ρ calculation images from the three images in the IRSE method and the FR2SE method. 2. The nuclear magnetic resonance imaging apparatus according to claim 1, wherein the following formula and value are used as the theoretical formula for the signal intensity and the value of the scan parameter applied to imaging when calculating. In the IRSE method, _CIRSE・exp(−T _s /T ₂ ) × {1−2・exp(−T _d /T ₁ +2exp(−T _r /T ₁ +T _s /(2T ₁ )) −exp(−T _r /T ₁ )}・ρ In the FR2SE method, M ₀ = {1−exp(−T _d /T ₁ }ρ/{1 −exp(−T _d /T ₁ −T _s1 /T ₂ −T _s2 /T ₂ −T _s3 /T ₂ )}, the first echo is M ₀ exp (−T _s1 /T ₂ ) and the second echo is M ₀ exp (−T _s1 /T ₂ −T _s2 /T ₂ ) scan. The parameters are (1) In the IRSE method, T _r = 1.16 sec T _d = 0.221 sec T _s = 0.031 sec (2) In the FR2SE method, T _r = 0.82 sec T _s1 = 0.018 sec T _s2 = 0.092 sec T _s3 = 0.031 sec ( Average 1) and (2) at a ratio of 1:1.4. However, T _r : Time between 1 views T _d : Time from application of inversion recovery pulse to 90° pulse T _S1 : Time from application of 90° pulse to the peak of the first echo signal T _S2 : First Time from the peak of the second echo signal to the peak of the second echo signal T _S3 : Time from the peak of the second echo signal to the peak of the second echo signal
Time to 90° pulse.