JPS6129748A - Nuclear magnetic resonance measuring method - Google Patents

Abstract

PURPOSE:To obtain nuclear spin density distribution in which a chemical shift is specified optionally by providing a surface coil and coils for magnetic field slope generation in a static magnetic field, and performing the Fourier transform of a free induction attenuation signal induced at the surface coil. CONSTITUTION:A transmitting and receiving coil (surface coil) 2 for observation and coils 3X, 3Y, 4X, and 4Y for magnetic field slope generation are arranged in the static magnetic field of a magnet 1. A high frequency signal from a transmitter 5 is supplied as high-frequency pulses to the coil 2 through a gate 6 and a power amplifier 7 and supplied as a high-frequency pulse magnetic field to an object body arranged in the coil 2 through the coil 2. The free induction attenuation signal induced at the coil 2 after high frequency pulse irradiation is led out through a gate 8, amplifier 9, and demodulating circuit 10, A/D-converted 11 and sent to a computer 12, and stored in a memory 13. The computer 12 know the position where a material having a specific chemical shift has from a two- dimensional spectrum obtained by Fourier transform.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a nuclear magnetic resonance measurement method for determining nuclear spin density distribution using nuclear magnetic resonance (NMR) phenomena, and in particular to a nuclear magnetic resonance measurement method using a Saaf S coil. Equipment (NMR equipment)
The present invention relates to a nuclear magnetic resonance measurement method that also has information on chemical shift 1- and can obtain a nuclear spin density distribution according to chemical shift.

[Prior Art] Recently, the development of an NIVR imaging device that uses the NMR phenomenon to determine the nuclear spin density distribution of a specific nucleus in a certain part of a subject has been progressing.

With such an apparatus, it would be useful to be able to obtain not only a nuclear spin density distribution in which only the nuclide is specified, but also a nuclear spin density distribution in which even chemical shifts are arbitrarily specified, so various measurement methods have been proposed. There is. The methods proposed so far can be roughly divided into two. One method uses a projection reconstruction method, and the other method uses a multi-dimensional two-dimensional conversion method, and the present invention relates to the latter method.

A measurement method using this multidimensional Fourier transform method is called “J o
urnal or tyl agnetic reso
nanceJ 56゜p, 314-317 (198
4) is introduced. Figure 11 shows the pulse sequence used therein, which is basically a spin]-Coe sequence consisting of a 90'' pulse and a 180° pulse as shown in (a), followed by a 90° pulse and a 180° pulse. Tii lift in the X direction for a period of 1× (intensity Xi)
A gradient magnetic field (intensity Yi) in the Y direction is applied at a period of time 1t and a signal is obtained in a state where the magnetic field is uniform. On the gold side, Yj was changed to dV in the rostep [1.times.the value obtained by the measurement in the rostep] - 3,000 hours based on the signal], and the conversion was performed.

[Problems to be Solved by the Invention] In the above example, the 906 pulse and the 180' pulse are used as high frequency magnetic field pulses for the subject, and as a transmitting/receiving coil for receiving echo signals. This can be applied to devices equipped with coils in which the windings are arranged opposite to each other with the test object in between, and the high-frequency magnetic field distribution in the space between the windings where the test object is placed is uniform. In the case of a so-called Nerfes coil type device that measures by applying it to the surface of the object, the high-frequency magnetic field generated by the coil is non-uniform, so the 180° pulse to obtain the signal may vary depending on the location. ° It is no longer a pulse, and the sequence of the above example cannot be applied as is.

[Configuration for Solving the Problems] The present invention has been made in view of the points mentioned in -11 above, and even in an NMR apparatus using a linear phase, nuclear spins with arbitrarily specified chemical shifts can be used. The purpose of this study is to provide a nuclear magnetic resonance measurement method that can obtain density distributions.

In order to achieve this purpose, the present invention includes (a) illuminating a measurement target placed in a uniform static magnetic field with an observation high-frequency pulse; (b) approximately i
(1) applying gradient magnetic fields in two intersecting directions in a pulsed manner to the measurement object; (2) recording and storing free induction decay signals for a time period of 12 after applying the gradient magnetic fields; (d) By systematically changing the gradient magnetic field intensities Gx and GV and repeating the above (a) to (c), 1st, data S (Gx f GV , t:2) is 1r, I (( 3) l'j is I, 2γ-ta 3 (GX
, ('N,,y,l',2)%1,2,
GV, Gx 4t, Rai (' triple-) - Li 1 variation/no thing, 1! There are some signs. Hereinafter, one embodiment of the present invention will be explained in detail using the following description.

[Example] Figure 1 I11. A shows one embodiment of an NMR imager for carrying out the method according to the invention.
This is the kth fa Ti. Toni in that static magnetic field [
Yo? +lJ side transmitting/receiving transmitter/receiver 1a] IlFco, Sfil) 2, IL field gradient light (for G) 1'/l/3X, 3
Y, /IX, and 4Y are arranged.

Reference numeral 5 denotes an oscillator that generates a high frequency wave having the resonant frequency of the observation nucleus.The high frequency wave from this oscillator 51 is supplied as a high frequency pulse to the surface wall 2 through a gate 6 and a power amplifier 7. A high-frequency pulsed magnetic field is irradiated onto the subject placed inside the C through the C. The free induction damping signal (FID signal) induced in the surface coil 2 after this high-frequency pulse irradiation is
・8. It is taken out via the amplifier 9 and the demodulation circuit 10, and △
-D-hen 19! The J signal is converted into a digital signal by the unit 11, sent to the combination J-ri 12, and stored in the attached memory 13. 1/IX, 14Y is the coil 3X.

3Y, /1. A gradient generating circuit 15 is capable of adjusting the current supplied to X and 4Y to appropriately set and reverse the gradient magnetic field strength in both the X and Y directions; 15 is the gate 6°7, the Δ-D converter 11 and the gradient generating circuit 14X; .

This is a timing control circuit for controlling 14Y.

FIG. 2 shows the pulse sequence used in the present invention. High frequency pulse RF at J3 in Figure 2(a)
PG, desired part of the subject a;1. l; 2J) τ approximately 90
The pulse width is selected to be equal to the pulse width, as shown in (b) and (c) of the same figure. Gx and Y fj
A counter-gradient magnetic lift Gy is applied to the sample, and S! (・1.-
Time after which period 11 ends (2 niwa lko-) '(1'
ID signal is detected.

FIG. 3 is a small IJ diagram showing the signal waveforms and power lines 11'j of each part for implementing the sequence 31.

Figure 3 <a) 4 yo gate 6 0NOFI-sa 1! The timing signal g of the second router is shown in FIG.
The figure (0) shows the value of Gy generated by the gradient generating circuit 14Y. , the same figure (c) shows the timing of sampling by the A-D converter 11.

The gradient magnetic fields GX and GV applied during the period t1 are used to provide the [I] signal with phase information corresponding to the position f in the subject. The strong polishing of this gradient magnetic field is shown in Figure 3 (
b) and (c), the J, uni, and x directions 1ig are systematically varied over a total of nxm steps, with T1 steps being 5-tubes and Y directions being m stelas and ps. That l, n
At the end of X m measurements using the sequence shown in Figure 2, instead of being specified by the combination of gradient magnetic fields of n steps in the x direction and m steps in the Y direction,
The phase information of 1 n x rr points included in the desired region within the subject is included I, and 2 n x m FT D signals F
T 011 to F IOmn are obtained as shown in FIG. 4 and stored in the memory 13.

The process of processing the FTDs 11 to FIDmn thus obtained in the computer 12
, explained below.

F'1D11 to FIDln have a function C of time t2, and the combi coater 12 first performs F I Dll to F I D
Fourier transform mn with respect to t2. As a result, spectra 811 to Smn shown in FIG. 5 are obtained.

In these Subek 1 Health, the peak of a specific nucleus contained within a desired site within the subject is expanded according to Chemical Shift 1-. Also, go to each group S11-Sin, S21 with the same Gy from Subek1-! -3211,...
・For S1 to S1 to 5alrI (by λ, it can be seen in FIG. 5 that GX is taken in the direction of the arrow No. 13. Therefore:]) , by capturing the spectral data included in each group 1 in the direction of the arrow, if there are P data points for a large number of (spectrum) rules related to Qxk-, then P interfaces can be obtained for each group. Taking it as 10 grams l\, from these interfaces we can calculate grams with respect to GX, that is, 7-
Convert. Through this Fourier transformation, there are m sets of two-dimensional spectra 1 to 1 consisting of P spectra as shown in Fig. 6 (011 to 1') 1p, D 21 to [) 2p
, [) 31~D 31), ..., ()1~D
Il+)) is obtained.

Each two-dimensional spectrum is shown in Figure 6, where the chemical shift is taken on one axis and the nuclear spin density distribution in the X direction is taken on the other axis.
It can be seen that there are substances with different chemical shifts at different positions in different directions.

Next, the combination 1-12 is the m obtained in this way.
Two-dimensional spectrum of gl (D11 to D1p.

D21-D2p, D31-D3p, ・---, Dm
l~Dmp), specify 1 for a specific chemical shift 1~IIR where a peak exists, for example, and specify 1 for the spectrum [)lk, [)2 at the position of K1, ..., [
)mk are extracted and arranged in order to create one data matrix as shown in FIG. In this data matrix, the nuclear spin density distribution in the X direction is plotted on one axis, and the change in Gy of the density distribution is plotted on the other axis. Therefore, the computer 12 regards these deumas 1 to RIX as n interferograms in the GVh direction, and performs a Fourier transform on these interferograms with respect to Gy. Through this Fourier transformation, a two-dimensional spectrum as shown in FIG. 8 is obtained. In this two-dimensional spectrum, the nuclear spin density distribution in the X direction is taken on one axis, and the nuclear spin density distribution in the Y Jj direction is taken on the other axis. It is possible to know the location and can of the substance W1 with .

Figure 9 shows a two-dimensional spectrum (~) obtained in exactly the same way by specifying 2 as the chemical git value where another peak exists for the two-dimensional spectrum r in Figure 6. , a substance W2 with a specific chemical shift of 1 to 2
It is possible to know the density distribution of the location where it exists. Moreover, if FIG. 8 and FIG. 9 are combined and displayed, a substance W1 with a chemical shift of 1 and a substance W2 with a chemical shift of 1 to 2 exist inside the specimen as shown in FIG. 10. It is possible to know something. Figure 11 shows the transmitting/receiving coil 2 and the substance W1.
．． It is a diagram showing the actual positional relationship of W2.

In addition, if we change the magnetic field gradient in exactly the same way in the seven directions orthogonal to the X and Y directions and perform one more Fourier transform, we can obtain the nuclear spin density distribution in three-dimensional space. It goes without saying that this is a big deal.

To specify the chemical shift, the 2'1 amp coater automatically determines the value at which the peak exists and determines 1) 1 J: Sea urchin (
), or the A node may specify it at any time.

[Effects of the Invention] As detailed above, according to the present invention, even with an NMR apparatus using a V-face coil, it is possible to obtain a nuclear spin density b for which a chemical shift is arbitrarily specified. A magnetic resonance measurement method is realized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an NMR imaging apparatus for implementing the method according to the present invention, FIG. 2 is a diagram showing a pulse sequence used in the present invention, and FIG. A diagram showing the signal waveforms and intensity values of each part for implementing the sequence, FIG.
Figures 5 to 7 are diagrams for explaining the data processing process, and Figures 8 and 9 are diagrams for explaining the storage state of data D11 to FID mn. Fig. 1 shows the nuclear spin density distribution obtained by combining Fig. 8 and Fig. 9, and Fig. 10 shows the spin density distribution of the material W1 and material W2 simultaneously. Figure 12 showing the actual positional relationship between the file and the substances W1 and W2.
The figure shows a pulse sequence conventionally used in iK. 1: 11 stone 2: Observation transmission/reception 4 = ``+ i'le 3X, 3Y, 4X, /IY: l field gradient oscillation -1il j): oscillator 6, B nige -1 ~ ゛10: fear tone Circuit '11: Δ-1) = Converter 12: 2] P1--Ta 13: Mels 14 X, 14 Y: Gradient fit times 1i'!
f155: Timing control circuit fr rlOne person who came out [I Moku Denryo Co., Ltd. 1 Representative Iju -jin 14--→t2 Fig. 3 -m=→Y -11-→Y Fig. 10

Claims (2)

[Claims] (1) (a) Irradiating a measurement target placed in a uniform static magnetic field with a high-frequency pulse for observation; (b) After irradiating the high-frequency pulse, apply gradient magnetic fields in two substantially orthogonal directions to the measurement target in a pulsed manner. (c) obtaining and storing a free induction decay signal for a time t2 after applying the gradient magnetic field; (d) systematically varying the intensities Gx and Gy of the gradient magnetic field as described in (a) to (c) above; By repeating , data S(
(e) obtain the obtained data S(Gx, Gy, t2) with respect to t2, Gy, Gx.
A nuclear magnetic resonance measurement method consisting of multiple Fourier transform. (2) The nuclear magnetic resonance measurement method according to claim 1, wherein the observation high-frequency pulse is irradiated by a single coil placed close to the measurement target.