JP2010256220A - Apparatus and method for spin magnetic resonance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and method for spin magnetic resonance, capable of generating an arbitrary intended oscillating magnetic field while compensating a transient phenomenon without lowering its Q value, by theoretically calculating an oscillating voltage, which enables the transient phenomenon to be compensated, from a response function of a resonator. <P>SOLUTION: A means is disposed for storing reverse-distortion envelope waveform data of an oscillation voltage pulse which should be input to the resonator in order to generate an oscillation magnetic field pulse having an envelope waveform targeted by the resonator, and is previously obtained on the basis of the response function of the resonator in order to compensate such the phenomenon that an oscillation magnetic field pulse having an envelope waveform shifted from a desired waveform is applied to a prepared sample since an envelope waveform of an input oscillation voltage pulse is distorted by a transient response of the resonator. The oscillation voltage pulse having the reverse-distortion envelope waveform is generated on the basis of the stored reverse-distortion envelope waveform data and is input to the resonator. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a spin magnetic resonance apparatus such as a nuclear magnetic resonance apparatus (NMR), an electron spin resonance apparatus (ESR), a nuclear quadrupole resonance apparatus (NQR), a nuclear magnetic resonance imaging apparatus (MRI), an electron spin resonance imaging apparatus ( It belongs to the technical field of high frequency pulses used in ESRI).

  In spin magnetic resonance apparatus such as nuclear magnetic resonance apparatus (NMR), electron spin resonance apparatus (ESR), nuclear quadrupole resonance apparatus (NQR), nuclear magnetic resonance imaging apparatus (MRI), electron spin resonance imaging apparatus (ESRI) In order to efficiently irradiate a sample with a high-frequency magnetic field and to efficiently observe a high-frequency magnetic field signal (magnetic resonance signal) generated by the sample, a resonator that amplifies a high-frequency voltage is used as a place to set the sample. It has been.

  However, these resonators used for the purpose of improving the efficiency of irradiation / observation of a high-frequency magnetic field are known to cause a transient phenomenon until a steady state occurs, and to always generate a delay. This transient occurs because the resonator stores energy or the resonator releases energy. Therefore, the larger the Q value serving as an index of energy stored in the resonator, the larger the transient phenomenon. Conversely, the smaller the Q value, the smaller the transient phenomenon. Therefore, a resonator having a larger Q value has higher signal excitation and observation efficiency, but at the same time causes a large transient phenomenon.

  This transient causes problems for excitation and observation of magnetic resonance phenomena. Consider the case where an oscillating voltage is applied to a resonator to generate an oscillating magnetic field. As an example, let us consider a case where an oscillating voltage in which the envelope is a rectangular wave is applied. Such an oscillating voltage is used in many magnetic resonance phenomena and is often referred to as a pulse (excitation pulse). The pulse shape (rectangular shape) of the oscillating voltage applied to the left side of FIG. 1 is shown.

  At this time, it is expected that an oscillating magnetic field having the same shape as the applied oscillating voltage is generated, but actually, as shown on the right side of FIG. 1, the oscillating magnetic field changes its shape due to a transient phenomenon. The rise of the oscillating magnetic field becomes dull compared to the applied voltage, and the fall of the oscillating magnetic field generates an oscillating magnetic field with a tail.

  The dull rise causes a problem that the excitation region is different from what is desired. In addition, a long trailing edge means that observation cannot be performed until the tail is completely removed, and a long waiting time is required after the pulse is applied until observation is performed. If this tail leaks into the signal, it causes problems such as distorting the baseline of the observed spectrum.

  As described above, a resonator having a large Q value used in a normal spin magnetic resonance apparatus causes a transient phenomenon such as delay, dullness, and tailing, and it becomes impossible to obtain an intended oscillating magnetic field, thereby observing a signal. Also affects.

  Such a transient phenomenon occurs not only when a rectangular wave oscillating voltage is applied, but occurs for oscillating voltages of any shape and distorts the shape of the oscillating magnetic field. However, in a normal measurement, this transient phenomenon is generally ignored.

  That is, an oscillating current having the same shape as the desired oscillating magnetic field is applied, and it is neglected by approximating that there is no distortion due to a transient phenomenon. In addition, the influence of the oscillating voltage with a long tail is reduced by putting some time until the observation starts.

  In order to avoid the problem of this transient phenomenon, several methods have heretofore been proposed. An oscillating magnetic field with a long tail gives rise to a problem that the baseline of the spectrum is distorted due to this magnetic field leaking into the observation. In order to avoid this, it is a common practice to wait for a while before starting observation when an oscillating voltage is applied. Thereby, the influence of a long tail can be reduced.

  However, the influence cannot be completely removed, and when distortion becomes a problem, the current situation is that the observation data is cheated by applying numerical processing such as baseline correction. Further, such a process can solve only a phenomenon in which a long tail is drawn, and cannot solve any other phenomenon such as a dull rise.

  Two approaches have been proposed that more aggressively address the problem of transients. One is a method called Q dump (Non-Patent Documents 1 to 6). This is a technique to reduce the problem of transients by lowering the Q value of the resonator when applying an oscillating voltage, and to increase the Q value of the resonator when observing the signal, thereby efficiently observing the signal. .

  Thereby, the influence of the transient phenomenon of the applied oscillating voltage can be reduced, but the delay cannot be completely eliminated. In addition, since the Q value is low when the oscillating voltage is applied, the generated oscillating magnetic field becomes small and efficient signal excitation cannot be performed. Furthermore, a special device is required to switch the Q value between voltage application and signal observation, and the device becomes complicated.

  Another solution is a method of actively canceling the oscillating magnetic field with a tail by irradiating the oscillating magnetic field having an antiphase (Non-Patent Documents 7 to 9). However, since there is no clear theoretical support, trial and error is necessary. In addition, when the voltage to be applied has a complicated waveform, it is not possible to execute this because it is unclear what kind of oscillating magnetic field should be applied.

E. R. Andrew, K. Jurga, J. Magn. Reson., 73 (1987) 268. G.-Y. Li, X.-J.Xia, H.-B.Xie, Y. Liu, Rev. Sci. Instrum., 67 (1996) 704. T. N. Rudakov, V. V. Fedotov, A. V. Belyakov, V. T. Mikhal'tsevich, Instrum. Exp. Tech., 43 (2000) 78. J. B. Miller, B. H. Suits, A. N. Garroway, M. A. Hepp, Concept Magn. Reson., 12 (2000) 125. A. S. Peshkovsky, J. Forguez, L. Cerioni, D. J. Pusiol, J. Magn. Reson., 177 (2005) 67. V. A. Zabrodin, V. P. Tarasov, B. A. Shumm, L. N. Erofeev, Instrum. Exp. Tech., 50 (2007) 86. C. P. Keijzers, E. J. Reijerse, J. Schmidt, Pulsed EPR: A New Field of Applications, North Holland, Amsterdam / Oxford / Tokyo, 1989. J. L. Davis, W. B. Mims, Rev. Sci. Instrum., 52 (1981) 131. P. A. Narayama, R. J. Massoth, L. Kevan, Rev. Sci. Instrum., 53 (1982) 624. P. Styles, N. F. Soffe, C. A. Scott, D. A. Cragg, F. Row, D. J. White, P. C. J. White, J. Magn. Reson., 60 (1984) 397. P. Styles, N. F. Soffe, C. A. Scott, J. Magn. Reson., 84 (1989) 376. G. C. Liang, R. S. Withers, B. F. Cole, S. M. Garrison, M. E. Johansson, W. S. Ruby, W. G. Lyons, IEEE Trans. Appl. Supercond. 3 (1993) 3037. H. D. W. Hill, IEEE Trans. Appl. Supercond. 7 (1997) 3750. W. W. Brey, A. S. Edison, R. E. Nast, J. R. Rocca, S Saha, R. S. Withers, J. Magn. Reson., 179 (2006) 290. T. Mizuno, K. Hioka, K. Fujioka, K. Takegoshi, Rev. Sci. Instrum., 79 (2008) 044706.

  A technique for preventing a transient phenomenon from leaking into an observation signal by allowing time to start observation is widely used. There is relatively little problem when continuous observations can be made without irradiating an oscillating magnetic field during observation. However, in a method of intermittently irradiating an oscillating magnetic field and observing between the oscillating magnetic field, a sufficient waiting time cannot be taken, which is a serious problem.

  Such an observation technique is frequently seen in recent nuclear spin magnetic resonance methods. Further, in the case of a cold probe (Non-Patent Documents 10 to 15) having a Q value dramatically higher than that of a conventional probe, the transient phenomenon is very long, and the problem is serious.

  In the conventional Q dump method, a special probe is required. In addition, since the Q value when the oscillating voltage is applied is low, amplification by the resonator is reduced, resulting in a problem that the resultant oscillating magnetic field strength is reduced.

  This is an unavoidable phenomenon in the Q dump method, and in order to obtain an oscillating magnetic field strength equivalent to that of a normal device having a high Q value, it is necessary to apply a very high output oscillating current. In addition, although the transient phenomenon can be reduced by the Q dump method, the transient phenomenon always occurs as long as the resonator is used, and it is impossible in principle to completely eliminate the transient phenomenon. .

  On the other hand, in order to use a technique for compensating for a transient phenomenon by irradiating an oscillating magnetic field having an antiphase, it is necessary to know in advance the nature of the transient phenomenon caused by the resonator. However, in the past, it relied on the technique of determining the nature of the transient phenomenon by trial and error, and it was a very time-consuming measurement method. If it is a simple oscillating current of a rectangular wave, it is possible to compensate for a transient phenomenon to some extent by this approach. However, if the oscillating current has a complicated waveform, it will be completely out of hand.

  In view of the above points, the present invention theoretically calculates “oscillation voltage to be applied in order to compensate for a transient phenomenon and generate a target oscillating magnetic field” from “resonator response function”. An object of the present invention is to provide a spin magnetic resonance apparatus and method capable of compensating for a transient phenomenon without reducing the Q value and generating an arbitrary oscillating magnetic field as intended.

In order to achieve this object, a spin magnetic resonance apparatus according to the present invention includes:
In a spin magnetic resonance apparatus for inputting an oscillating voltage pulse to a resonator including a sample and applying a oscillating magnetic field pulse generated by the resonator to the sample to perform magnetic resonance measurement,
In order to compensate for the phenomenon that the envelope waveform of the input oscillating voltage pulse is distorted by the transient response of the resonator and an oscillating magnetic field pulse having an envelope waveform deviated from the desired waveform is generated and applied to the sample.
Inversely distorted envelope waveform data of an oscillating voltage pulse to be input to the resonator in order to generate an oscillating magnetic field pulse having an envelope waveform intended by the resonator, which is obtained in advance based on the response function of the resonator. A means for storing is provided, and based on the stored inverse distortion envelope waveform data, an oscillating voltage pulse having an inverse distortion envelope waveform is generated and input to the resonator.

  The response function is an exponential function with a first-order lag.

  In addition, the response function is determined based on how the rising portion of the magnetic field output from the resonator is blunted when a step signal is input to the resonator.

Further, in a spin magnetic resonance apparatus for inputting an oscillating voltage pulse to a resonator including a resonator and applying a oscillating magnetic field pulse generated by the resonator to a sample to perform magnetic resonance measurement,
Means for generating an envelope waveform signal of an oscillating magnetic field pulse to be applied to the sample;
Envelope differentiation means for differentiating the envelope waveform signal;
Adding means for adding the differential envelope signal from the envelope differential circuit to the original envelope signal at a predetermined ratio τ;
Modulation means for creating a high-frequency voltage pulse in which an envelope becomes a composite envelope obtained by the adding circuit;
And an oscillating voltage pulse obtained from the modulating means is input to the resonator.

  In the adding means, τ is variably provided.

Further, the optimum value of τ is obtained from the Q value of the resonator and the value of the frequency ν of the oscillating voltage,
τ = Q / πν
It is characterized in that it is obtained by calculation based on the following relational expression.

Further, in a spin magnetic resonance method in which an oscillating voltage pulse is input to a resonator including a sample, and an oscillating magnetic field pulse generated by the resonator is applied to the sample to perform magnetic resonance measurement.
In order to compensate for the phenomenon that the envelope waveform of the input oscillating voltage pulse is distorted by the transient response of the resonator and an oscillating magnetic field pulse having an envelope waveform deviated from the desired waveform is generated and applied to the sample.
A first step of determining a response function of the resonator;
A second step of obtaining an inverse distortion envelope waveform of an oscillating voltage pulse to be input to the resonator in order to generate an oscillating magnetic field pulse having the desired envelope waveform based on the obtained response function; ,
A third step of generating an oscillating voltage pulse having an inverse distortion envelope waveform based on the inverse distortion envelope waveform obtained in the second step and inputting the oscillation voltage pulse to the resonator is provided.

  The first step detects an oscillating magnetic field generated by the resonator by a pickup coil installed in the vicinity of the resonator, and based on the detected output and an input signal to the resonator, the resonator It is characterized by obtaining the response function of.

  The response function is an exponential function with a first-order lag.

  According to the spin magnetic resonance apparatus and method of the present invention, an arbitrary oscillating magnetic field can be generated without lowering the Q value. Transient phenomena generated by the resonator are actively compensated by the back-calculated oscillating voltage. This brings about the following effects.

  (1) Since there is no need to actively change the Q value, a normal magnetic resonance apparatus can be used as it is or with a slight modification.

  (2) When an oscillating magnetic field is applied, a certain blank period is usually provided before the signal is observed. This blank period is provided to wait for the transient phenomenon caused by the resonator to settle, but if the transient phenomenon is actively suppressed according to the present invention, it is not necessary to provide this blank period. Thereby, the distortion of the baseline of the spin magnetic resonance spectrum is removed, and a high-quality spectrum can be observed. This is particularly effective when the spectrum width is wide. Also, in the case of an experiment in which a signal is observed between a plurality of oscillating magnetic fields (referred to as a multi-pulse experiment), the effect of the oscillating magnetic field due to the transient phenomenon can be minimized. Function.

  (3) Cooling coil probes (commercially available under the names of cryoprobes, cold probes, etc.) with a very high Q value developed to improve signal measurement sensitivity are greatly affected by transient phenomena. Therefore, it is particularly effective for such a probe.

  (4) Since an oscillating magnetic field as intended can be generated, it effectively functions for an observation method in which an oscillating magnetic field having a complicated shape is applied. This is very effective in a method of applying a complex oscillating magnetic field that has been developed in recent years in nuclear spin magnetic resonance.

  (5) When an oscillating magnetic field with a very short time width is irradiated, the transient phenomenon is large, and the shape of the oscillating magnetic field is greatly changed. Application of an oscillating magnetic field as described above becomes possible. This feature functions effectively in a microcoil apparatus that irradiates a very short oscillating magnetic field that has recently begun to be used in a nuclear spin magnetic resonance apparatus.

  (6) By knowing the response function, it is possible to appropriately compensate for the input voltage distortion of any waveform. Especially in the case of a first-order delay, any waveform can be obtained with only one parameter τ (resonator time constant). Can be compensated for. In other words, the parameters may be adjusted for one waveform. As a result, any waveform can be compensated using the same parameters.

It is a figure which shows an example of the conventional magnetic resonance pulse. It is a figure which shows the concept of the generation method of the magnetic resonance pulse concerning this invention. It is another figure which shows the concept of the generation method of the magnetic resonance pulse concerning this invention. It is a figure which shows the concept of the method of obtaining an impulse response function from the magnetic resonance pulse concerning this invention.

[Background theory]
First, the theory behind the present invention will be described. In the present invention, distortion of the waveform of the oscillating magnetic field pulse, that is, distortion of the envelope waveform becomes a problem. First, it is assumed that the impulse response function of the resonator of the spin magnetic resonance apparatus that causes distortion of the oscillating magnetic field pulse is h (t). At this time, if the envelope of the oscillating voltage input to the resonator is a (t), the envelope b (t) of the oscillating magnetic field output as a result is

It is calculated by. Here, a (t) is a desired envelope waveform, and b (t) is an undesirable envelope waveform that is output from the resonator.

  From this relational expression, the envelope waveform b (t) output from the resonator is obtained by convolving and integrating the impulse response function h (t) and the envelope waveform a (t) of the oscillating voltage pulse input to the resonator. It turns out that it is a value. When the impulse response function h (t) is known in advance, it can be seen that the shape of the resulting oscillating magnetic field is obtained from the shape of the oscillating voltage to be applied.

  Equation (1) shows that the envelope a (t) of the input oscillating voltage is transformed into an envelope b (t) of the oscillating magnetic field due to the transient phenomenon h (t). In the present invention, the envelope waveform of the input oscillating voltage that can compensate for this transient phenomenon is obtained by back calculation from the impulse response function. However, since equation (1) includes an integration process, the envelope waveform a (t) of the input oscillating voltage that can compensate for the transient phenomenon cannot be obtained by simple division.

Therefore, by performing Laplace transform on both sides of the equation (1) and replacing the function of the time parameter t with a function of a certain parameter s different from the time t,
A (s) = B (s) / H (s) (2)
And Equation (1) are converted. The introduction of the Laplace transform is a mathematical technique that enables the division of equation (1) independently of integration. As a result, the function B (s) related to the envelope waveform output from the resonator can be divided by the impulse response function H (s) to obtain the function A (s) related to the envelope of the applied vibration voltage. Become.

  here,

It is.

  B (s) is obtained from the desired envelope waveform, and the function A (s) of the parameter s regarding the envelope waveform of the oscillating voltage pulse obtained by the equation (2), that is, the function of the parameter s represented by the equation (2) is obtained. If inverse Laplace transform is performed, the function of the parameter s can be returned to the function of time t again, and the envelope waveform a (t) of the input oscillating voltage that can compensate for the transient phenomenon, that is, the oscillating voltage to be input. Can be obtained.

  If this relational expression is used, the envelope waveform a (t) of the oscillating voltage to be applied to generate the envelope waveform b (t) of the target oscillating magnetic field can be obtained by back calculation from the impulse response function. . What is important here is that the envelope waveform a (t) of the oscillating voltage to be applied can be calculated backward only by the impulse response function, and can be calculated for any oscillating magnetic field.

  Many recent nuclear spin magnetic resonance apparatuses can generate an oscillating voltage of an arbitrary shape as well as a rectangular wave. In the case of such a device, it is possible to compensate for a transient phenomenon by obtaining an oscillation voltage to be applied in advance from the response function of the resonator and inputting it beforehand into the device.

  For example, assuming a first-order lag as a response function, the vibration voltage to be applied can be obtained by calculation. The shape of the target oscillating voltage envelope was a Gaussian shape. The oscillating voltage was applied using an arbitrary waveform generator. FIG. 2 (a) shows the oscillating voltage when transient compensation is not considered. It is normally expected that the envelope waveform of the applied oscillating voltage becomes the envelope waveform of the oscillating magnetic field as it is.

  However, when a pick-up coil is installed in the oscillating magnetic field generator of the resonator and the actually generated oscillating magnetic field is monitored, the rise is dull as shown in FIG. An oscillating magnetic field is observed. In this way, when the oscillating magnetic field is distorted from the intended shape, there is an adverse effect such as the excitation band of the signal deviating from the intended range. In addition, the signal cannot be observed until the influence of the oscillating magnetic field with a long tail is settled.

  Therefore, based on the method of the present invention, an oscillating voltage pre-distorted so as to actively compensate for the transient phenomenon was calculated. The calculated oscillating voltage is shown in FIG. It was experimentally confirmed using a pickup coil that an oscillating magnetic field as shown in FIG. The observed waveform completely coincides with the originally intended waveform of FIG. In this way, if an oscillating voltage that actively compensates for a transient phenomenon according to the present invention is applied in advance, the transient phenomenon is compensated and an oscillating magnetic field as intended can be realized.

An exponential equation with a simple first-order lag whose impulse response function is
h (t) = C · exp (−t / τ) (4)
, The inverse Laplace transform of equation (2) can be performed analytically. Here, τ is a time constant of the resonator.

Solving equation (2) including equation (4) as a component by Laplace transform and inverse Laplace transform, the following equation:
a (t) ∝b (t) + τ (d / dt) b (t) (5)
Is obtained. From this equation (5), the envelope waveform a (t) of the oscillating voltage to be applied to the resonator is changed from the envelope waveform b (t) of the target oscillating magnetic field to the transient compensation term τ (d / dt ) B (t) is added as a form.

  Here, a method of compensating for a transient phenomenon at the same time as applying an oscillating voltage to a resonator will be described, not a method of making a (t) by back calculation. First, the differential component (d / dt) b (t), which is the compensation term of Equation (5), can be generated by electrically differentiating b (t) using an operational amplifier or the like.

  That is, in this embodiment, as shown in FIG. 3, first, in the first step, the envelope waveform b (t) of the oscillating magnetic field pulse to be applied is extracted. For this purpose, the envelope waveform may be extracted from the oscillating magnetic field pulse, or the envelope waveform may be directly electrically synthesized instead of being extracted from the oscillating magnetic field pulse. Next, in the second step, the envelope waveform b (t) is electrically differentiated by a differentiation circuit. Next, in the third step, while changing the weighting factor τ of the differential waveform (d / dt) b (t) of the envelope obtained by electrical differentiation, the original envelope waveform b (t ).

  This operation is an operation for adjusting the magnitude of τ as the weighting factor of the differential waveform (d / dt) b (t) included in the equation (5) to the time constant τ of the actual resonator. For example, an original waveform b (t is obtained by installing a pickup coil in the vicinity of a resonator and monitoring an envelope waveform of an oscillating magnetic field actually generated by receiving a transient phenomenon so as to have a desired shape without distortion. ) And the differential waveform (d / dt) b (t) weight ratio τ is brought to an optimum place.

  Alternatively, instead of using a pickup coil to monitor, the intensity of a specific peak of the magnetic resonance spectrum obtained by irradiating an oscillating magnetic field pulse that wants to know the shape of the envelope to an off-resonance position deviated from the resonance frequency by a predetermined offset frequency. This measurement may be repeated by changing the offset frequency little by little, and the obtained offset frequency-peak intensity data may be subjected to inverse Fourier transform. In this method, the waveform obtained after the inverse Fourier transform takes the form of an envelope of the irradiated oscillating magnetic field pulse that one wanted to know. Therefore, according to this method, for example, if the waveform after the inverse Fourier transform becomes a Gaussian waveform, it can be verified that the irradiated oscillating magnetic field pulse is a Gaussian waveform pulse. What is necessary is just to use (tau) at that time.

In these operations, since the value of τ can be easily changed, adjustment is easy. More generally, an equation representing a damped vibration can be used to derive the relationship between the Q value of the resonator and the transient attenuation. When a step function having an angular velocity ω ₀ is input, an equation to be solved and initial conditions are as follows.

and,

The solution to this equation is given by

The attenuation component after the second term is a component due to a transient phenomenon. The time constant τ of the resonator is determined by using the Q value of the resonator and the angular velocity ω _{0 of the} oscillating voltage.

It is expressed by the following relational expression. The angular velocity ω ₀ and the frequency ν of the oscillating voltage are
ω ₀ = 2πν ………… (10)
As a result, the time constant τ of the resonator can be obtained as long as the Q value of the resonator in which the sample is set and the value of the frequency ν of the vibration voltage are known.
τ = Q / πν ………… (11)
It can be easily obtained by calculation using the following relational expression.

  Finally, in the fourth step, if the envelope waveform a (t) represented by the expression (5) thus completed is multiplied by a high frequency of a desired frequency by a multiplier, the envelope to be applied to the resonator A high-frequency oscillating voltage pulse having a line waveform a (t) can be obtained.

  In this approach, only an electric envelope differentiating circuit capable of differentiating the envelope a (t) needs to be mounted. Then, if the user of the apparatus applies an oscillating voltage b (t) having the same waveform as the desired oscillating magnetic field as shown in FIG. 3, the oscillating voltage (in which the envelope is differentiated in hardware) d / dt) b (t) and a high-frequency oscillating voltage pulse a (t) consisting of the sum of the oscillating voltage b (t) having the same shape as the waveform of the desired oscillating magnetic field are obtained, and the desired oscillating magnetic field is supplied to the resonator. b (t) is generated.

  In the present invention, it is very important to set the impulse response function appropriately. In the case of many resonators, the impulse response function takes the form of an exponential function with a first order lag. At this time, as shown in the second embodiment, handling becomes very simple. However, if the time constant of the resonator is unknown even if it is a first-order lag impulse response function, it is necessary to investigate the time constant.

  In this embodiment, a method for determining an impulse response function by observing an oscillating magnetic field generated when an oscillating voltage is applied to the resonator will be described. FIG. 4 shows the basic principle of this embodiment. As an input, a step input that suddenly changes from 0 to 1 is adopted as an oscillating current. Then, the oscillating magnetic field generated in the resonator generates an exponential delay in rising. The impulse response function (the value of the time constant τ when the impulse response function is an exponential function with a first-order lag) is determined by mathematically analyzing the resulting bluntness at the rise from 0 to 1. be able to.

  Can be widely used in spin magnetic resonance apparatus.

Claims (9)

In a spin magnetic resonance apparatus for inputting an oscillating voltage pulse to a resonator including a sample and applying a oscillating magnetic field pulse generated by the resonator to the sample to perform magnetic resonance measurement,
In order to compensate for the phenomenon that the envelope waveform of the input oscillating voltage pulse is distorted by the transient response of the resonator and an oscillating magnetic field pulse having an envelope waveform deviated from the desired waveform is generated and applied to the sample.
Inversely distorted envelope waveform data of an oscillating voltage pulse to be input to the resonator in order to generate an oscillating magnetic field pulse having an envelope waveform intended by the resonator, which is obtained in advance based on the response function of the resonator. A spin magnetic resonance apparatus characterized in that a means for storing is provided and an oscillating voltage pulse having an inverse distortion envelope waveform is generated based on the stored inverse distortion envelope waveform data and input to the resonator. 2. The spin magnetic resonance apparatus according to claim 1, wherein the response function is an exponential function having a first-order lag. 3. The response function according to claim 1, wherein a step signal is input to the resonator, and the response function is determined based on how the rising portion of the magnetic field output from the resonator is blunted. Spin magnetic resonance apparatus. In a spin magnetic resonance apparatus for performing magnetic resonance measurement by inputting an oscillating voltage pulse to a resonator including a resonator and applying an oscillating magnetic field pulse generated by the resonator to a sample.
Means for generating an envelope waveform signal of an oscillating magnetic field pulse to be applied to the sample;
Envelope differentiation means for differentiating the envelope waveform signal;
Adding means for adding the differential envelope signal from the envelope differential circuit to the original envelope signal at a predetermined ratio τ;
Modulation means for creating a high-frequency voltage pulse in which an envelope becomes a composite envelope obtained by the adding circuit;
And a oscillating voltage pulse obtained from the modulating means is input to the resonator. 5. The spin magnetic resonance apparatus according to claim 4, wherein τ is variably provided in the adding means. The optimal value of τ is determined from the Q value of the resonator and the frequency ν of the oscillating voltage.
τ = Q / πν
5. The spin magnetic resonance apparatus according to claim 4, wherein the spin magnetic resonance apparatus is obtained by calculation based on the following relational expression. In a spin magnetic resonance method in which an oscillating voltage pulse is input to a resonator including a sample, and an oscillating magnetic field pulse generated by the resonator is applied to the sample to perform magnetic resonance measurement.
In order to compensate for the phenomenon that the envelope waveform of the input oscillating voltage pulse is distorted by the transient response of the resonator and an oscillating magnetic field pulse having an envelope waveform deviated from the desired waveform is generated and applied to the sample.
A first step of determining a response function of the resonator;
A second step of obtaining an inverse distortion envelope waveform of an oscillating voltage pulse to be input to the resonator in order to generate an oscillating magnetic field pulse having the desired envelope waveform based on the obtained response function; ,
A spin comprising: a third step of generating an oscillating voltage pulse having an inverse distortion envelope waveform based on the inverse distortion envelope waveform obtained in the second step and inputting the oscillation voltage pulse to the resonator. Magnetic resonance measurement method. In the first step, an oscillating magnetic field generated by the resonator is detected by a pickup coil installed in the vicinity of the resonator, and the response of the resonator is based on the detected output and an input signal to the resonator. 8. The spin magnetic resonance measuring method according to claim 7, wherein a function is obtained. 9. The spin magnetic resonance measuring method according to claim 7, wherein the response function is an exponential function with a first-order lag.

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