JPS6082841A - Checking method and appratus utilizing nuclear magnetic resonance - Google Patents

Abstract

PURPOSE:To shorten an operating time, by applying pulses so that magnetizing vector is aligned upward at the time the sequence of one view is finished, and making it possible to move to the next sequence immediately. CONSTITUTION:A current is made to flow to a static magnetic coil 1 from a static-magnetic-field control circuit 2. A static magnetic field is imparted to a body to be checked. A current is made to flow to a coil 3 through a gradient- magnetic-field control circuit 4 from a controller 20, and a (z) gradient magnetic-field is inputted. At this time, the direction of each magnetization M at the center of a slice surface, at the boundary of the slice surface, and at the outside of the slice surface is in the positive direction of the (z) axis (upward). A 90 deg.x pulse is applied by an RF signal, whose phase difference is 0 deg., through a gate circuit 30, and the slice surface is excited. Then the coil 3 is energized and an (x) and (y) gradient magnetic fields are applied. An NMR signal is detected by a coil 8. Similarly, measurement is performed when -180 deg.-x pulse is appled. After the measurement, a 90 deg.-x pulse is applied, than a 180 deg. pulse is further applied, and the magnetization M is aligned in the direction of +z. Thus it is possible to move to the next sequence immediately.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to nuclear magnetic resonance
ic reao-nanee) (hereinafter referred to as “NM
It is abbreviated as "R". ) Nuclear magnetism that utilizes the phenomenon to know the distribution of specific atomic nuclei inside the subject from outside the subject. = 14% regarding the testing method and testing device. In particular, it relates to improvements in NMR imaging devices suitable for medical equipment.

[Prior art]

Before explaining the present invention, the principle of NMR will first be briefly explained.

The atomic nucleus consists of protons and neutrons, which are considered to be rotating as a whole with nuclear spin angular momentum.

Figure 1 shows the hydrogen nucleus ('H)k, (r
), it consists of one proton P and rotates as expressed by the spin quantum number coefficient. Here, proton p&′i, (
As shown in (b), since it has a positive charge ef, a magnetic moment μ is generated as the atomic nucleus rotates. That is,
Each hydrogen nucleus can be thought of as a small magnet.

Figure 2 is a schematic explanatory diagram of this dot. In a ferromagnetic material such as iron, the directions of these micromagnets are aligned as shown in (A)9, and magnetization is observed as a whole. Ru. On the other hand, in the case of hydrogen, etc., the direction of the micromagnets (the direction of the magnetic moment) is random as shown in (b),
No magnetization is seen as a whole.

Here, when a static magnetic field HO in two directions is applied to such a substance, each atomic nucleus is aligned in the direction of HO. That is, the energy level of the nucleus is quantized diL in the Z direction.

Figure 3 (a) shows this situation for a hydrogen nucleus. Since the spin quantum number of a hydrogen nucleus is a coefficient,
As shown in FIG. 3(b), it is divided into two energy levels -h and 10A. The energy difference ΔE between two energy levels is expressed by the formula +11.

ΔE−γShortH,... (1) T, γ: W1 rotational ratio = h/2π h blank constant Here, a force of μ × HO is applied to each nucleus by the static magnetic field HO. So the nucleus is gold around the Z axis, (2)
It precesses at an angular velocity ω as shown in the equation.

ω=γHa (Larmor angular velocity) ・・・・・・(2)
When an electromagnetic wave (usually a radio wave) with a frequency corresponding to the angular velocity ω is applied to a system in this state, resonance occurs and the atomic nucleus (
1) It absorbs the energy that corresponds to the energy difference ΔE shown by the formula and transitions to a higher energy level. Even if several types of nuclei with nuclear spin angular momentum are mixed,
Since each atomic nucleus has a different gyromagnetic ratio γ, the resonance frequency differs, and therefore only the resonance of a specific atomic nucleus can be extracted. In addition, by measuring the total strength of the resonance, we can also determine the amount of nuclei present. After resonance, the atomic nucleus excited to a higher level returns to a lower level after a time determined by a time constant called relaxation time.

This relaxation time is the spin-lattice relaxation time (longitudinal relaxation time)
T, and spin-spin relaxation time (transverse relaxation time) T2
Data on material distribution can be obtained by observing the entire relaxation time. Generally, in solids, spins are almost fixed at fixed positions on the crystal lattice, so interactions between spins are likely to occur. Therefore, the relaxation time T2 is short, and the energy obtained by nuclear magnetic resonance is first transferred to the spin system and then to the lattice system. Therefore, the time T11'i is significantly larger than T2. On the other hand, in a liquid, molecules move freely, so the likelihood of energy exchange occurring between spins and between spins and the molecular system (lattice) is about the same. Therefore, the time T and T2 have the same value. Especially time T
1) It is a time constant that depends on the way each compound binds, and it is known that the value differs greatly between normal tissues and malignant tumors.

Here, we have explained hydrogen nuclei (1H), but it is possible to perform similar measurements with other atomic nuclei that have nuclear spin angular momentum. + 5 c ), sodium nucleus (25N a), fluorine nucleus (19F), oxygen nucleus (17o), etc.

In this way, NMR can measure the abundance of specific atomic nuclei and their relaxation times2, so it is possible to obtain various chemical alpha information about specific atomic nuclei within a substance, and to conduct various tests inside a subject. You can click your tongue.

Conventionally, as an examination station that utilizes this NMRi, protons in the p-section of the specimen are excited using the same principle as X-ray CT, and the NMRi corresponding to each projection is
There is a method in which R resonance signals are measured in many directions of the subject and the NMR resonance signal intensity at each position of the subject is determined by a reconstruction method.

FIG. 4 is an operational waveform diagram for fully explaining an example of an inspection method in such a conventional apparatus.

First, a two-gradient magnetic field aZ+ as shown in FIG. 4(B) and an RF pulse (9σ pulse) with a narrow frequency spectrum (f) as shown in FIG. 4(B) are applied to the subject.

In this case, protons only on the surface where the Larmor angular velocity ω = γ (Ha + ΔGz) are excited, and the magnetization Mi (Fig. 5)
Rotating coordinates rotating at an angular velocity ω as shown in a) - If shown on a thread, it would be 1 with the direction changed by 90 degrees in the y/axis direction. Next, as shown in Fig. 4 (c) and 4), an X gradient magnetic field GX and a y gradient magnetic field G7 are applied, thereby creating a two-dimensional gradient magnetic field and detecting all NMR resonance signals as shown in (e). . Therefore, the magnetization M is as shown in Figure 5 (b).
Due to the inhomogeneity of the magnetic field: 1. As the NMR resonance signal gradually decreases in the direction of the arrow within the r and 7 planes, the NMR resonance signal eventually decreases and disappears after 18 hours as shown in FIG. 4 (e). When the NMR resonance signal obtained in this manner is subjected to full Fourier transform, it becomes a projection in a direction perpendicular to the gradient magnetic field synthesized by the X gradient magnetic field Gx and the y gradient magnetic field Gy.

Thereafter, after waiting for a predetermined time Td, the next sequence is repeated in the same manner as described above. In each sequence, Gx and Gy'i are changed little by little.

This allows NMR resonance signals corresponding to each projection to be determined in numerous directions of the entire object.

By the way, in conventional devices that operate in this way,
In FIG. 4, the time Ts until the NMR resonance signal disappears is 10 to 20 m5, but the predetermined time Td until moving to the next sequence is due to the relaxation time T1.
A degree of ee is required. Therefore, if a cross section of a single object is to be reconstructed using, for example, 128 projections, the measurement requires a total time of at least 2 minutes, which is a major obstacle in achieving high speed. It is one.

[Purpose of the invention]

In view of these points, the object of the present invention is to
At the end of the sequence of ew), the entire magnetization vector must be forced upward (in the positive direction of the two axes) to remain correctly, so that the sequence of the next View can be immediately started, and the overall operation It is an object of the present invention to provide an NMR testing method and testing device that save time.

[Summary of the invention]

In the nuclear magnetic resonance testing method or apparatus thereof, the nuclear magnetic resonance testing method or apparatus comprises applying a high frequency pulse to impart nuclear magnetic resonance to the nucleus of an atom constituting a tissue of a subject, and measuring a nuclear magnetic resonance signal generated in the nucleus. When applying radio-frequency pulsed gold, there is a need to apply a first 90° pulse necessary to apply a gradient magnetic field to obtain a nuclear magnetic resonance signal, and a predetermined pulse after application of this first 90° pulse. giving a first (7) 180° pulse and a second 90° pulse at intervals and immediately following the second 90° Hals.
It is characterized in that a ° pulse is applied.

〔Example〕

The present invention will be described in detail below using the drawings. FIG. 6 is a block diagram showing the configuration of an embodiment of a device for implementing the method of the present invention. In the figure, 1 is a uniform static magnetic field H8
A static magnetic field coil 2 is a control circuit for the static magnetic field coil 1, which includes, for example, a DC stabilized power supply. The density of the magnetic flux generated by the static magnetic field coil 1 H81l'i, 0.
It is desirable that the uniformity is about 1T and the uniformity is 10-4 or more.

The 3id gradient magnetic field coil is generally shown, and 4 is a control circuit of this gradient magnetic field coil 3.

FIG. 7(A) is a configuration diagram showing an example of the gradient magnetic field coil 3, in which the 2-gradient magnetic field coil 31, the y-gradient magnetic field coil 32
．． 33. Although not shown, y gradient magnetic field coil 32.33
It has the same shape as , and includes an X-gradient magnetic field coil that is rotated 90'.

This gradient magnetic field coil generates a magnetic field having a linear gradient in the X + 'f + Z axis direction in the same direction as the uniform static magnetic field Ho. The control circuit 4 is controlled by a controller 2° (details will be described later).

Reference numeral 5 denotes an excitation coil that provides an RF pulse with a narrow frequency spectrum f as an electromagnetic wave to the subject, the entire configuration of which is shown in FIG. 7 (b).

6 is the frequency corresponding to the NMR resonance condition of the atomic nucleus to be measured (for example, for protons, 42.6 MHz/T
This is an oscillator that generates a signal l, which is applied to the exciting coil g via a gate circuit 30 (details of which will be described later) and a power amplifier 7 whose opening and closing are controlled by signals from the controller 2o. 8 is NMR in the subject
This is a detection coil for detecting a resonance signal, and its configuration is the same as the excitation coil shown in FIG. Although it is desirable that this detection coil be installed as close as possible to the subject, it may also be used as an excitation coil if necessary.

9 is an NMR resonance signal (FI
D: free i'induction deca
y) f amplifying amplifier, 10 is a phase detection circuit, 11
is a wave memory circuit that stores the phase-detected waveform signal from the amplifier 9, and includes an A/D converter. 13
14 is a computer that inputs the signal from the wave memory circuit 11 through the entire transmission line 12 made up of, for example, an optical fiber and performs predetermined signal processing to obtain a tomographic image, and 14 is a television that displays the obtained tomographic image. It is a display device like a monitor. Further, necessary information is transmitted from the controller 20 to the computer 13 via a signal line 21.

The controller 20 is capable of outputting signals (analog signals) necessary for controlling all of the gradient magnetic fields Gz, GX, and Gy and control signals (digital signals) necessary for transmitting RF pulses and receiving F1D signals. It was constructed. FIG. 8 is a block diagram showing an example of such a controller, which is particularly capable of high-speed control and easy to change control sequences and analog waveforms.

In the figure, 221 is a write control circuit for writing data sent from the console 210 or the computer 13 via the console into each memory; 222, 225, 228, .
231 are x, y, given by this write control circuit.
z Waveform storage memory in which the waveform data of the gradient signal and modulation signal are stored, respectively, 223, 226, 229
．． 232 H This waveform memory mesori 222, 225.22
8. Launch circuit that temporarily holds all waveform data output from 231, 224.227°230, 233, and latch circuit 223.226.229°232, DA conversion circuit that converts the output from 232 into DA, x2 ．． y2
．． z2. M2 is the DA conversion circuit 224°227,
230.233 X, 7゜2
These are the way the gradient signal is output and the modulation signal output. 234°23
6, 238.240 is the transmitting/receiving circuit control signal, that is, A
The data of the D conversion control signal, transmission gate control signal, and reception gate control signal Waveform storage memory, 235.237.239, which is written to each control circuit 221
．． 241 is this waveform storage memory 234.236.23
8.240 A latch circuit that temporarily holds the data output from T2. S2. R2 and PS are this latch circuit 23
Each A output from 5.237.239.241
These are a D conversion control signal, a transmission gate control signal ratio, a reception gate control signal output, and a phase selection signal. 243 is each waveform storage memory 222, 225.228.231.23.
4. The contents of 236.238.240 are transferred to the latch circuit 2.
23.226.229.232゜235, 237.23
9.241 A readout control circuit 242 sets the value of the write/readout start address from the console or computer (hereinafter simply referred to as the combination unit), and performs convolution/readout control on the value of that address. A memory address register 244 sequentially adds the value +1 given from the circuit and outputs it as a write/read address, and a memory address register 244 is set with a step number given from the computer and notifies the read control circuit 243 of the end of output. An output count register 245 stores the time length (l) of one step given by the computer.
This is a one-step length pulse generation circuit that generates a pulse of l step length by setting the step length.

The operation of the circuit configured as described above is as follows.

(a) Write operation In the write operation, all waveform data sent from the computer is written to a specified address in the waveform storage memory specified by the computer. That is, first, the memory address register 24
The write start address is set to 2. The data sent from the computer along with the write command is written to the address specified by the memory address register 242 in the waveform storage memory (for example, waveform storage memory 222) selected by the write control circuit 221. After this, the write control circuit 221 automatically adds 1 to the memory address register 242 to make it the memory address for the next write. Other waveform storage memories are also sequentially loaded in the same manner as described above.

(b) Read operation In the read operation, each memory is read in parallel. FIG. 9 shows an example of a time chart of read signal waveforms. First, the computer sets the reading start address of the waveform storage memory in the memory address register 242. Next, the number of read steps is set in the output count register 244. Also, 1 step length (time per 1 step when reading)
1 step length pulse generation circuit 245. Next, the waveform storage memory 22 at the address indicated by the memory address register 242 receives a reading start command from the computer.
2, 225.228.231.234.236.238
．． The contents of 240 are simultaneously read out, and when all the data is available, the read control circuit 243 sends the latch circuit 223.2 to the latch circuit 223.2.
26°229, 232.235.237.239.24
Outputs a latch pulse to 1 and latches the data. Next, the value Kl of the memory address register 242 is completely added. If the output count register 244 indicates completion, the read control circuit 243 sends the launch circuit 223, 226, 229
All clear pulses are output at 232, 235, 237, 239, and 241, and the read operation is completely completed. When the output count register 244 does not indicate completion, 1 is subtracted from the output count register 244, and after waiting for one step time length according to the output from the one step length pulse generation circuit 245, the next reading step is started.

By repeating the same steps, it is possible to read out the entire waveform as shown in FIG. 9, for example. X, 'y, Z gradient belief'
7 x 2 + y 2 , z 2 and modulation signal M2
Vi, the false circuit output is further converted to DA converter 224.22
7.230.233 It is an analog signal obtained by I)A conversion, the modulation signal M2 is sent to the gate circuit 30, and the X, y, Z gradient signals are sent to the control circuit 4 for gradient magnetic field.
Each will be guided by

According to such a controller, since dedicated hardware such as a waveform storage memory is used, a large amount of data can be read and output at high speed. In addition, the contents of the waveform storage memory can be rewritten as necessary, so any analog
A digital signal waveform can be output. Furthermore, it is easy to use part of the signal waveform (which is often actually used) by appropriately providing the read start address and the number of read steps.

The gate circuit 30 receives the RF multiplied signal from the oscillator 6, and generates all four types of signals whose phases differ by 90 degrees.
Based on instructions from the controller 20, one of the four types of signals is selected and further modulated with an RF modulation signal to obtain a drive signal for the excitation coil 5. The detailed configuration is shown in Fig. 10. show. In the same figure, 311 is a 90° phase shifter that can obtain two signals with a phase shift of 0° and 90° with respect to the input RF multiplied signal, 312.313 A 90° phase shifter with a phase shift of 0° and 180° with respect to the V1 input signal. It is a 180° phase shifter that can obtain two signals of 180°. 90° phaser 3 as shown
11 outputs to each of the 180° phase shifters, O', 90°, 180°, 270° for the RF multiplied signal.
A signal with a phase difference of .degree. is obtained. These signals are transmitted through high frequency switches (for example, a double balanced mixer: DBM can be used) 314 to 31, respectively.
7 are led to the combiner 321, and the four signals are added together. In this case, the high frequency switches can be individually energized by the output of the decoder driver 320, and the phase selection signal p given from the controller 20
One of the four outputs (x, y, -x, -y) of the decoder driver 320 obtained by decoding s becomes active. As a result, only the corresponding switch becomes conductive (the other three switches are non-conductive). Therefore, the result is that only one signal, Vil, is input to the coupler 321.

The output of the coupler 321 is input to the modulator 323 after passing through the amplifier 322, where the RF modulation signal (a pulse signal, whose pulse width and peak value determine the rotation angle of the magnetization M) is provided by the controller 20. modulated by
For example, it is modulated into a waveform similar to the waveform shown in FIG. 4(A) and output.

According to the gate circuit having such a configuration, it is possible to obtain RF multiplied signals exhibiting phase differences of 0°, 90°, 180°, and 270° based on one RF multiplied signal, and select a desired one from among these signals. The advantage is that it is extremely easy to select one alternative and further modulate the signal with a desired waveform at an appropriate timing.

The operation of the apparatus of the present invention thus constructed will be explained step by step with reference to FIG. 11 and Tables 1 to 3.

1) Time t.

In a state where a torrent flow is applied from the control circuit 2 to the static magnetic field coil 1 and the entire static magnetic field H8 is applied to the subject (the subject is placed in the crotch cloth within the cylinder of each coil), the controller 20 and the control circuit 4
A current is passed through the 2nd gradient magnetic field coil 31 through the 11th
As shown in Figure (b), the time point when two gradient magnetic fields Gt gold were applied.

At this time, the center of the slice plane (90°) is the part where the magnetization M rotates correctly by 90° by applying a pulse), the slice plane boundary (the part where M rotates θ° when a 90° pulse is applied, and G2 = 0 when a 180° pulse is applied). The direction of each magnetization M outside the slice plane (the part where the application of a 90° pulse has no effect and the direction of the magnetization M is reversed by the 180° pulse) is shown in Figure 11. (to),
As shown in ()) and (g), all of the two axes are in the positive direction (upward).

2) Time t.

G2 is selected and output by the gate circuit 30 and modulated into a predetermined form with a phase difference of 0° (
For example, Gaussian type) RF multiplied signal Excites the entire surface (slice surface) of the object to be examined (gives a 90'x pulse as shown in (a) in FIG. 11). Subsequently, the X-gradient magnetic field coil and the Y-axis gradient magnetic field coil 32,33 are energized, and the magnetic fields Gx, Gyi at a predetermined angle are applied as shown in (c) and d) of Fig. 11.
Apply.

In FIG. 11(b), <G7- following G7+ is a waveform signal for completely matching the phases of NMR resonance signals from different parts of the subject, and this technique is a known technique.

If the time point at which the magnetic fields GX and Gy are applied is wot, then at this time point t, the magnetization M of each part is as shown in FIG.
), the orientation is as shown in (a).

After time t1, the first
The nuclear magnetic resonance signal (called FID signal) is detected by the detection coil 8.
The signal is guided to the phase detection circuit 10 via the amplifier 9, where it is phase detected and then stored in the wave memory circuit 11. The stored data is read at appropriate timing by the computer 13, and Fourier transformed therein to become a signal of one projection.

3) Time t2 T1 from the time t until the nuclear magnetic resonance signal disappears
After 14 hours of detection, the energization of the X gradient magnetic field coil and the Y gradient magnetic field coil is stopped, and the RF multiplied signal modulated into a rectangular shape with a phase difference of 180° is selected and output in the gate circuit 30, and the entire subject is excited. . That is, as shown in FIG. 11(a), a 180° pulse is applied to the entire subject.

4) Time t3 After applying the 180°-Evals, the same predetermined thick magnetic fields GX and Gy'i as the previous time are applied at the same time.

At this point, let it be t3 (magnetization M is shown in Fig. 11 (see),
(to).

Rotate like (e). ).

After time t3, the dispersed magnetization M begins to gather, and a second nuclear magnetic resonance signal (this signal is called a total echo signal) is output from the detection coil 8, which gradually increases as shown in FIG. 11(e).

) is detected. This echo signal is different from the first nuclear magnetic resonance signal, assuming that the GC applied before time t2 and after time t3 are the same, and the I y state of the subject does not change during that time. has a signal waveform that is symmetrical about the central time between t2 and t5.

5) Time t4 When time (t2-t,) has elapsed from time t3, the application of the magnetic fields Gx and Gy is stopped under the control of the controller 20. At this point, the total time is t4. Magnetization M is as shown.

After this point, Gz-1Gz+ is applied, and under that condition, a 90° pulse is applied to the subject using an RF multiplied signal modulated in the same manner as the first 90° pulse with a phase difference of 180'' in the gate circuit 30.
A DEG pulse is applied to re-excite the slice plane that was excited with a 90 DEG pulse of force 1. The end point of this excitation is t5
shall be. At this time, within the slice plane.

The directions of the magnetization M of the outside and the boundary, that is, all the objects to be examined, are aligned in two directions.

6) At time t6, after completely stopping the application of G-, the gate circuit 30 has a p phase difference O
The subject is excited by the RF multiplied signal modulated into a rectangular waveform at 180° (180° pulse excitation).

The end point of this excitation is assumed to be t6.

With the addition of the 180° pulse, the p magnetization amounts are aligned in the +2 direction all at once.

In this way, the starting time t is reached at time t6. It will return to the same state. However, in this method, relaxation due to spin-spin relaxation or transverse relaxation of the material remains, and the magnetization M does not completely turn upward at time t6. Therefore, a waiting time Td is provided after time t6, one sequence is completed after the magnetization M is completely turned upward, and the same sequence is repeated thereafter.

Table 1 Table 2 □ Table 3 In such a sequence, the waiting time Td is much shorter than in the conventional case. Figure 12 shows the situation.
3ms, transverse relaxation time T2 = 24.8 mS)
This is a full vertical view of the relaxed state when r is used, TB, and +TaTa2-3O. In the figure, the horizontal axis is the waiting time Td
, the vertical axis is the signal strength after reaching the equilibrium state, where curve A of the jet line is the actual value measured using the conventional method (corresponds to the theoretical value), and curve B of the solid line is the actual value measured using the method of the present invention ( (consistent with theoretical value). As is clear from the figure, the method of the present invention requires a much shorter time (T,) to obtain the same signal strength.

In this way, according to the present invention, it is possible to proceed to the next sequence with a much shorter waiting time than in the past, so that the time required to scan all views can be completely shortened.

The method of reconstructing an image based on the sequence of the above embodiment is the so-called two-dimensional PR (ProjectionRec+
This is a method called the +natruction) method.

In addition, in the example, in one sequence, the total RF pulse applied is 90°-180°-x-90'x-180
However, the feature of the method of the present invention is that the second 90° pulse directs all the magnetization Mi downward, and the 90°x-
isoy-90° engineering/180°-x (180°yRF
A variety of phase relationships can be used, such as applying pulses (pulses are generated using RF multiplied signals with a phase difference of 90°). (Also applicable to the methods listed below)
.

Further, the present invention is not limited to the above-mentioned embodiments, but can also be applied to the following methods and systems.

1) Instead of the first nuclear magnetic resonance signal (FID signal),
Using only the second nuclear magnetic resonance signal (echo signal), its Fourier transform is taken as one projection,
How to reconstruct images.

2) A method of completely improving the S/N ratio by averaging the first nuclear magnetic resonance signal (FID signal) and the second nuclear magnetic resonance signal (echo signal), and reconstructing an image using the signal. However, 1. FI
The D signal and the echo signal are averaged taking into account that they are symmetrical about the central time between t2 and t3 as described above.

Furthermore, in the RF pulse sequence of 90° x - 180°, -90° - 180°, the phases of the FID signal and the echo signal are 180° opposite, so this method is used to take all of this into account and average them.

3) By obtaining images separately from the first nuclear magnetic resonance signal (FID signal) and the second nuclear magnetic resonance signal (echo signal) and performing calculations between the two images, T2 (Method for imaging spin-spin relaxation time, i.e. ζ
Since the echo signal is relaxed with a time constant of T2 compared to the FID signal, T200 million can be obtained from each image.

4) So-called spin warp method in which a magnetic field GXI Gy* Gz k is applied as shown in FIG. In this case, the NMR signal is observed not in the form of FID but in the form of spin echo.

5) Magnetic field Gz+ Gy+ Gz'! r So-called two-dimensional Fourier method in which the voltage is applied as shown in Fig. 14.

6) So-called selective excitation line method using magnetic fields GX, Gy, G2 and RF Hals excitation as shown in FIG.

7) As shown in Figure 16, the PR method described above (Figure 11)
Also, the sequence in each of the above methods 1) to 2) (within the dotted line frame in the figure, the figure exemplifies the PR method) includes all steps of inversion recovery. That is, in each method, the subject is excited with a 180° pulse modulated in a rectangular waveform for 17 hours (as appropriate) prior to 90° Hals excitation, and after this 180° pulse, 180°
° Homogenity spoiler to eliminate all negative lateral effects caused by pulse inaccuracy
Added in common to GXI Gy+ Gz. however,
The application of the homogeneity spoil pulse is not necessarily required and can be omitted if the adverse effect in the lateral direction does not occur or can be ignored.

8) In order to prevent the generation of extra signals caused by errors in the excitation pulse size, spoil pulses (their application points are indicated by 1 period 'rHs1 to H84) are applied at various points in the sequence as shown in Figure 17. ).

In FIG. 17, if the first 180" pulse is inaccurate, a component of the magnetization vector is generated, which becomes a noise signal, so 1 (32 spoil pulses (GX, Gy,
Common to G2) Apply after the 18σ pulse of Kinoshi 1 to erase the components of the magnetization vector.

In the absence of Hs2, the NMR signal ((e) in the same figure) appears as a dotted line.

In addition, since the movement of the magnetization vector is disturbed when H52 is inserted, as shown in the figure, H8, (same thickness, same time width aX, ay, c,) w 180" pulse (7)
Add before. H82 and H,l are always used as a pair.

Furthermore, Hs3'c is added after the 90° pulse in order to eliminate components of the magnetization vector that are magnetized due to inaccuracy of the 90° pulse or other causes.

In order to eliminate the component of the magnetization vector that is magnetized due to the inaccuracy of the second 180° pulse or other causes, and also to break the correlation between the beams and enable correct observation, the second 180° pulse is After 18o° pulse ■ (Put in all 84.

Note that H8, Hs2, H83, and HB4 are not limited to the combination shown in the figure, but may be a combination of one or any two of them.

9) Method of shortening T or Ta2.

FIG. 18 illustrates the case where Ta2 is completely shortened.

Here, the following relationship needs to hold.

gxjotml: gx2°tm2 gy1°tm1″gy'2 ”m, 1m, , 1m2: Magnetic field application time gz1 +
gz2 ' Gx Magnetic field strength gyl 9gy2 ”
By reducing the strength of the y magnetic field Tl12k, it is possible to reduce the negative effect # of the T2 value of the material (transverse relaxation of the magnetization vector due to T2).

20) Complete sequence of the example diagram shown in FIG. 11,
TiI4. Ta2. A method in which a plurality of images are obtained by varying at least one of Td, and then an inter-image calculation is performed to obtain all images of T, image, T2 image, spin density image, or a combination thereof.

11) The so-called multi-slice method uses the waiting time of Td to excite other planes and obtain that information.

FIG. 20 is a diagram showing the sequence, and here is an example of the case where it is applied to a two-dimensional PR method. For each view, n slice planes are excited, and the first
As shown in Fig. 9, the entire n slice planes of AA-W are excited for the sample OBJ in the first view, and the next n slice planes adjacent to the slice plane are excited in the next second view. It is a method of going.

This makes it possible to increase the apparent operating speed.

12) The G7 gradient magnetic field applied when applying a 90° pulse is
As shown in Figure 21, the magnetic field is oscillated in positive and negative directions at high speed to create a square wave-shaped magnetic field.

As a result, disturbance of the magnetization vector (phase mismatch in two directions) does not occur, so 7 aes (re-phase)
is not necessary, and the FID signal can be observed immediately after applying the 90° pulse.

13) A method in which each of the 90' pulse and 180° pulse is composed of a plurality of pulses.

For example, in place of 180°-epulse, 90°a, 180°
”-E.

Use a combination of three pulses at 90°A or three pulses at 90°-7, 180°-E, and 90°-7.
For ``Apulse'', three pulses are used: 90°, 180°A, 9Q'' or 90°-E, 180°A, 90°-
A combination of three pulses is used. Figure 22 is 18
90″ machining for 0′a’s p.

This is a diagram showing the direction of the magnetization vector when three pulses of 180°A and 90°D are used, where (A) to (A) are vectors inside the slice plane, and (E) to (G) are vectors outside the slice plane. All are shown individually. As is clear from the figure, since the rotation of the longitudinal component is performed accurately, the movement of the magnetization vector especially out of plane can be made correct.

Also, for example, instead of 90°Evals, υ is 45'y.

The magnetization vector can be accurately rotated using four pulses: 90°, 90'a, and 45°.

〔Effect of the invention〕

As explained above, according to the present invention, the magnetization vector is forcibly directed in the positive direction of the two axes at the end of the sequence of one view and one minute, so it is possible to immediately shift to the sequence of the next view. This makes it possible to shorten operating time.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the spin density image of a hydrogen atom, Figure 2 is a diagram illustrating the magnetic moment of a hydrogen atom, Figure 3 is a diagram explaining the state in which the nuclei of hydrogen atoms are aligned in the direction of the magnetic field, and Figure 4
The figure shows an example of the test pulse waveform by NMR.
6 is a configuration diagram of the device according to the embodiment of the present invention, FIG. 7 is a configuration diagram showing an example of a magnetic field coil, and FIG. 8 is a detailed configuration diagram of the controller 20. ,
FIG. 9 is a diagram for explaining the operation of the controller 20,
FIG. 10 is a configuration diagram of the gate circuit 30, FIG. 11 is a diagram of operation waveforms and magnetization vectors for explaining the sequence according to the present invention, FIG. 12 is a diagram showing the relationship between waiting time and signal strength, and FIG. Figures 13 to 18 and Figures 20 and 21
The figure is an operation waveform diagram showing another embodiment of the present invention, Figure 19 is a diagram for explaining the entire multi-slice method, and Figure 22 is a diagram showing 18
It is a figure which shows the state of the movement of the magnetization vector in the case of applying a 90°, 180°, and 90° pulse instead of applying a 0° pulse. 1... Static magnetic field coil, 2.4... Control circuit, 3.
... Gradient magnetic field coil, 5... Excitation coil, 6...
Oscillator, 8...Detection coil, 10...Phase detection circuit, Jl...Wave memory circuit, 13...Computer, 20...Controller, 30...Gate circuit. apnlllldwy 1DIJ5! S

Claims (1)

[Scope of Claims] (1) A step of applying a first 90° pulse of gold to impart nuclear magnetic resonance to the nuclei of atoms constituting the tissue of the subject, and subsequently a first nuclear magnetism generated in the nuclei. Measuring a resonance signal and T81 after applying the first 90° pulse
A step of applying a first 180° gold pulse to the atomic nucleus after a lapse of time, a step of measuring all of the second nuclear magnetic resonance signals generated in the atomic nucleus, and a step of applying a first 180° pulse of gold to the atomic nucleus. sequentially applying a second 90° pulse and a second 180° pulse to the nucleus after a period of time;
After this step, the sequence including a waiting time step is repeated after T1 time has elapsed before proceeding to the next step, and an image related to the tissue of the subject is regenerated based on the nuclear magnetic resonance signal. An inspection method using nuclear magnetic resonance characterized by consisting of the following steps. (2) A patent characterized in that in the step of configuring the image, the image is reconstructed using at least one of the first nuclear magnetic resonance signal and the second nuclear magnetic resonance signal. An examination method using nuclear magnetic resonance according to claim 1. (3) In the step of configuring the image, the first nuclear magnetic resonance signal and the second nuclear magnetic resonance signal are averaged, and the image is reconstructed using the data thus obtained. An examination method by nuclear magnetic resonance according to claim 1, characterized in that: (4) In the step of composing the image, the first nuclear magnetic resonance signal and the second nuclear magnetic resonance signal are used to image the spin-spin relaxation time through arithmetic processing. An examination method using nuclear magnetic resonance according to claim 1. (5) The first 90° pulse and the first 180° bar/l
The phase relationship between the second 90° pulse and the second 180° pulse is expressed as 90°, 180″-e, 90°-x,
Claim 1 characterized in that the angle is 180°.
Inspection method using nuclear magnetic resonance as described in section. (6) The phase relationship between the first 90° pulse, the first 180° pulse, the second 90' pulse, and the second 180° pulse is 90°, 180°, 90'', 180°
- D. An examination method using nuclear magnetic resonance according to claim 1, characterized in that: - D. (Force In the step of measuring the nuclear magnetic resonance signal, the gradient magnetic field GX, Gyi to be applied is determined as appropriate, and the two-dimensional PR
Nuclear magnetism according to claim 1, characterized in that image reconstruction can be performed by any one of the method, the spin warp method, the two-dimensional Fourier method, or the selective excitation line method. Inspection method using resonance. (8) In the step of applying the first 90° pulse, apply the 180° pulse for inversion recovery to the first
2. The nuclear magnetic resonance testing method according to claim 1, wherein the 90° pulse is applied prior to the 90° pulse. (9) In the step of applying the first 180° pulse, a spoil pulse sound is applied before and after applying the first 180° pulse. An examination method using nuclear magnetic resonance. H In the step of fully applying the second 90° angle (the second 180° angle), this 90° angle and the second 180° angle
2. The nuclear magnetic resonance testing method according to claim 1, wherein a spoil noculus is generated between the ° pulse and the pulse. aυ The second 90° angle and the second 180° angle (
2. The nuclear magnetic resonance inspection method according to claim 1, wherein in the step of applying the las, the entire spoil pulse is applied after the 180[deg.] las is applied. The nuclear magnetic resonance inspection method according to claim 1, characterized in that either the time Ts or T82 of α is shortened while maintaining a predetermined relationship. (Lta) At least one of the times Tg11, T!l., and Td is changed so that a plurality of original images for arranging various images can be obtained by inter-image calculation. A nuclear magnetic resonance inspection method as set forth in claim 1.
Inspection method using nuclear magnetic resonance as described in section. The nuclear magnetic resonance inspection method according to claim 1, characterized in that during the waiting time step, all steps other than the waiting time are performed on other slice planes. Oe Inspection by nuclear magnetic resonance according to claim 1, characterized in that in the step of applying the first 90° pulse, the gradient magnetic field G2 is applied in all positive and negative directions in a manner of oscillation many times. Method. Q7) In an examination apparatus using nuclear magnetic resonance, which is equipped with means for applying high-frequency pulses for imparting nuclear magnetic resonance to the nuclei of atoms constituting the tissue of a subject, and means for measuring all the nuclear magnetic resonance signals generated in the nuclei. , the means for applying the radio frequency pulse applies a gradient magnetic field after applying the first 90° pulse so that a nuclear magnetic resonance signal is obtained, and at a predetermined time interval after applying the first 90°/cycle. Then, the first 180° angle and the second 90° angle (the entire russ is given and the second 90°) <the second 1 immediately after the russian
The device is configured to apply an 80° pulse and wait a predetermined time after applying the second 180° pulse before proceeding to the next sequence, and the means for measuring all the nuclear magnetic resonance signals is configured to apply the first 90° pulse. At least one of the first nuclear magnetic resonance signal generated after the pulse is applied and the second nuclear magnetic resonance signal generated after the first 180° pulse is fully measured to obtain an image related to the tissue of the subject. A nuclear magnetic resonance examination apparatus characterized in that it is constructed so that PM is included in the reconstruction.