JPS5828542B2 - Sweep type nuclear magnetic resonance apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nuclear magnetic resonance apparatus (NMR apparatus) of the magnetic field or frequency sweeping type.

In a sweep type NMR device, a high frequency magnetic field is irradiated onto a sample placed in a polarized tap, and an NMR spectrum is obtained by sweeping the frequency of the magnetic field or the high frequency.

However, at this time, a phase delay or lead occurs in the signal detection system, so conventionally, a manual phase shifter was installed in the detection system.
While adjusting the phase shifter, a magnetic field or frequency sweep was actually repeated to draw an NMR spectrum, and the phase was adjusted to obtain the most ideal spectrum waveform.

Such phase adjustment not only requires skill, but also takes time to adjust the phase, and formal measurements must then be carried out, which usually lengthens the measurement time.

The present invention has been made in view of the above-mentioned conventional problems, and it is possible to achieve a The object of the present invention is to provide an NMR apparatus that can obtain an ideal NMR spectrum in one measurement.

The present invention will be explained in detail below using the drawings.

FIG. 1 shows the constituent countries of an embodiment of the present invention, and in the figure, numerals 1 and 2 are magnetic poles.

A magnetic field sweeping coil 3 and an NMR probe 4 into which a sample is inserted are arranged between the magnetic poles.

The NMR probe 4 is supplied with high frequency waves generated from an oscillator 5, and the sample is irradiated with the high frequency waves by an irradiation coil within the probe.

At the same time, the sweep circuit 6 sweeps the magnetic field, and the detection signal obtained from the detection coil of the probe is supplied to two phase detectors 8 and 9 via an amplifier 7.

The high frequency waves from the oscillator 5 are supplied to the phase detectors 8 and 9, one directly and the other via a 900 phase shifter 10, respectively.

The NMR signals obtained from the phase detectors 8 and 9 are sent to the memory 13 via A/D converters 11 and 12, and stored therein.

14 is an arithmetic device such as a microcomputer, and the arithmetic device 14 is capable of processing the two types of NMR stored in the memory 13.
Phase correction processing is performed using the signals according to a predetermined procedure to obtain two types of corrected NMR signals.

The obtained NMR signal is sent to the recorder 15 and recorded.

If the phase of the detection system is adjusted correctly in such a configuration, υ mode and U mode NMR signals such as those shown in FIG. 2 a and b can be obtained from the detectors 8 and 9 as the magnetic field is swept. .

These two types of NMR signals are nuclear magnetic resonances captured by two detection systems with 90' phase differences, and these are detected in the orthogonal X plane and This can be easily understood by thinking of it as a projection onto a plane.

In other words, the magnetization vector M of the atomic nucleus reaches a resonance point G as the magnetic field G sweeps.

If the locus of helical movement in the vicinity is represented three-dimensionally as helix L, the one projected onto the X plane is the υ mode NMR signal, and the one projected onto the Y plane is the U mode NMR signal.
This is an MR signal.

In FIG. 3, the helix L is drawn away from the G-axis for ease of viewing, but more accurately, the straight line portion of the helix L coincides with the G-axis.

Therefore, the flat portion other than the peak of the u, υ mode NMR signal has a zero level.

If there is a phase shift in the detection system at this time, X.

The X plane rotates with respect to the helix L, for example, like the X' and Y' planes shown by broken lines in FIG.

Therefore, the projection onto the X' and Y' planes is shown in Figure 2 c t d
As shown in
R signals are obtained from detectors 8 and 9.

Therefore, if we convert the two types of NMR signals obtained in the X' and Y' coordinate systems into signals seen from the X-Y coordinate system in this way, we get
Correct NMR signals as shown in FIG. 2 a v b can be obtained.

This coordinate conversion process is performed according to the procedure shown below.

Now, two types of NMR signals each contain N data (x'~ IN
-□) y (yo-y\J-□) is stored in the memory.

First of all, the arithmetic unit is A=r@n=Okara n=N-
Each gore is sequentially determined and compared, and XMt'jy, which gives the largest value AK, is determined.

The AK obtained in this way is shown in Figure 3 and the helix L in Figure 3.
As shown in Figure 4, which is projected onto the Z plane orthogonal to the X-Y and X'-Y' planes,
The point given by i, yi) corresponds to the vertex P of the spiral portion.

Therefore, if we transform the coordinates to an X-Y coordinate system such that this vertex P is on the X plane, we can obtain the correct NM as shown in Figure 2 a and b.
An R signal is obtained.

That is, as shown in Figure 4, the point Q6 (X6, yll) is the nth point when the helix L is divided into N points, and this point Qn is transformed into the X-Y coordinate system. Point Q(X,y)
Then, the following formula holds true according to the coordinate transformation formula.

are given respectively.

Therefore, first obtain xM and yI using the procedure described above, then obtain and store the value of θ, and then calculate A from memory.
, yA to the register, calculate equations (1) and (2), and obtain X.

, yn, replace the original Xn, yn with the original X6, y and store it from n=0 to n-N-1, then
Finally, the memory contains N pieces of phase-corrected data () (oM-4N-1:l) ('io-Y N-1)
will remain.

After correction, if these data are read out as appropriate and sent to the recorder 15, the NMR signal whose phase has been corrected correctly as shown in FIG. 2a, t) will be drawn on the recorder.

In addition, in the above-mentioned processing, the original data obtained by measurement (Xgyx4 1 ) y (Y'a''=YN-1
)" It is necessary to set the zero level as strictly as possible, for example, as shown below.

That is, the average value of each point in the flat part excluding the part where the spectral peak of the resonance signal is present may be determined, and the average value may be used as the reference zero level.

Furthermore, in the above-mentioned embodiment, the same phase correction was performed over the entire area of the obtained original data, but this is not the only option, and if there are multiple spectral peaks, the optimal phase correction may be performed for each individual peak. Alternatively, the phase correction may be performed by gradually changing the correction amount at a constant rate over the entire area of the original data.

As described in detail above, according to the present invention, the phases differ by 900.
Two types of NMR signals are obtained and memorized using one detection system, and phase correction is performed based on the two types of NMR signals to obtain a correct phase-matched NMR signal. An NMR signal can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, and FIGS. 2 to 4 are diagrams for explaining its operation. 3: Magnetic field sweeping coil, 4: NMR probe, 5:
Oscillator, 6: Sweep circuit, 8, 9: Phase detector, 10:9
0' phase shifter, 11, 12: A-D converter, 13: memory, 14: arithmetic unit.

Claims (1)

[Claims] 1. While irradiating a high-frequency magnetic field to a sample placed in a polarized magnetic field, the frequency of the polarized magnetic field or high frequency is swept, and a nuclear magnetic resonance signal is obtained based on a detection signal obtained from a detection coil along with the sweeping. In a swept-type nuclear magnetic resonance apparatus, two detectors with different phases are supplied with detection signals, and two types of output signals from the two detectors are
-A-D converter for D conversion, and N data (Xo'-XN-1', yO~yn- 1'), and n=0 among the N pieces of data.
-N-1, an arithmetic means for determining the set XK', tyK' with the largest value of xn" 1. A sweep type nuclear magnetic resonance apparatus, comprising a calculation means for performing coordinate transformation of the data based on the coordinate transformation of the data.