JP2007255991A - Probe for nuclear magnetic resonance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent reduction in resolution of a nuclear magnetic resonance spectrum system by adjusting the susceptibility of a bobbin being the constitutional components of the RF coil for making equal to that of atmosphere. <P>SOLUTION: The preform of bobbin 1 is constituted with e.g. quartz glass, and a metallic foil film 3, the susceptibility of which is inverted with plus and minus sign of the preform e.g. chromium (Cr) is stuck thereon. The total susceptibility per unit volume (SI unit system) of the preform and the metallic foil are made equal to the susceptibility (SI unit system) of the atmospheric matter. Thereby, the generation of erroneous magnetic field from the contact part between the bobbin 1 of the RF coil 2 is inhibited and the degradation of resolution of detection coil for detecting the nuclear magnetic resonance spectrum is prevented. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a nuclear magnetic resonance probe for detecting a nuclear magnetic resonance (NMR) signal of a sample including an atomic nucleus having a nuclear spin.

  In order to detect the NMR signal, it is necessary to apply a static magnetic field to the sample. Since the NMR signal is proportional to the magnitude of the static magnetic field, it is necessary to place a sample under a strong magnetic field in order to increase the reception sensitivity of the NMR signal. Further, in NMR measurement, it is desirable that the spectral line width when the spectral display of the NMR signal is high, that is, when the NMR signal is displayed as a spectrum, is not desired. The narrow spectral line width means that the magnetic field near the RF (radio frequency) coil that detects the sample and the NMR signal therefrom is uniform.

  In NMR measurement, it is required to increase the intensity of the magnetic field in the vicinity of the sample and the detection coil for nuclear magnetic resonance spectroscopy and to make it uniform. The demand for homogenizing the magnetic field is addressed by using a material close to the magnetic susceptibility near the RF coil for the parts near the RF coil. However, in reality, every material is different from the magnetic susceptibility of the atmosphere near the RF coil, and all the components near the RF coil cause a non-uniform magnetic field in a high magnetic field. Hereinafter, an inhomogeneous magnetic field generated by all components including the RF coil in a high magnetic field is referred to as an error magnetic field.

  In Patent Documents 1 and 2, an error magnetic field is generated by combining the paramagnetic material and the diamagnetic material at a certain ratio so that the magnetic susceptibility of the RF coil is zero or equal to the magnetic susceptibility of atmospheric air or the like. There are disclosures to suppress. That is, the generation of an error magnetic field is suppressed by using a non-magnetic material as a conductive wire of the RF coil. Further, Patent Document 3 discloses that the resolution at the time of NMR detection is increased by making the sample tube as thin as possible and suppressing the error magnetic field generated by the sample tube. That is, the generation of an error magnetic field is suppressed by reducing the volume of the material of parts necessary for NMR measurement as much as possible.

JP 2000-266828 A JP 2001-194440 A Japanese Patent Application Laid-Open No. 07-84022

  In the above prior art, the non-uniform magnetic field generated by the bobbin that is the winding axis of the RF coil depends only on the correction magnetic field of the magnetic field correction coil that cancels the non-uniform magnetic field, and no measures are taken to demagnetize the material. .

  Quartz glass is generally used as the material for the coil bobbin. Quartz glass is a diamagnetic material, and its magnetic susceptibility is -13.8 ppm. The magnetic susceptibility of air is +0.38 ppm. That is, the difference in magnetic susceptibility between quartz glass and air is about 14 ppm, and an error magnetic field of about 100 μT is generated under a magnetic field of 7 T (tesla) at the interface between the quartz glass and air. If the error magnetic field affects the RF coil sensitivity region, the magnetic field correction coil must be used to cancel the error magnetic field. However, the magnitude and shape of the correction magnetic field by the magnetic field correction coil are limited, and the shape of the bobbin depends on the output capability of the magnetic field correction coil. For example, the bobbin has a limitation that it cannot be shortened in order to avoid the influence of the error magnetic field generated at the end thereof.

  An object of the present invention is to provide a detection coil for nuclear magnetic resonance spectroscopy that counteracts the non-uniform magnetic field caused by the bobbin of the RF coil, strengthens the magnetic field in the vicinity of the RF coil, and makes it uniform. It is in.

  The present invention relates to a nuclear magnetic resonance probe for detecting a nuclear magnetic resonance signal of a sample, an RF coil that receives a nuclear magnetic resonance signal from a nuclear spin of the sample, a bobbin that is a winding axis of the RF coil, and the bobbin And a metal material having a polarity opposite to the magnetic susceptibility of the bobbin base material, and the bobbin has a magnetic susceptibility equal to that in the atmosphere.

  In addition, one of the RF coil and the metal material is provided inside the cylindrical bobbin and the other is provided outside the bobbin with respect to the bobbin. Alternatively, the RF coil and the metal material are provided outside the bobbin with respect to the bobbin, and an insulating material is provided between the RF coil and the metal material.

  Further, the vertical direction of the bobbin is a y-axis, the orthogonal direction is a z-axis, and a through hole is provided in the z-axis direction.

  In the present invention, when quartz glass, which is a diamagnetic material, is used for the bobbin, the magnetic susceptibility of the bobbin is made the same as the magnetic susceptibility of the atmosphere in the measurement space by thinly and evenly attaching a paramagnetic metal to the surface. I can do it.

  Also, when sapphire, ceramics mainly composed of aluminum oxide, aluminum nitride, etc. are used for the bobbin, they are diamagnetic materials, so by attaching a paramagnetic metal thinly and evenly on the bobbin surface The susceptibility of the bobbin can be made the same as the susceptibility of the atmosphere in the measurement space.

  According to the present invention, by making the bobbin non-magnetic, the generation of a non-uniform magnetic field can be brought to zero as much as possible, the magnetic field error caused by the bobbin is reduced, and the reduction in the resolution of the detection coil is suppressed. There is. Further, the degree of freedom of the shape and size of the bobbin can be increased, the bobbin can be shortened, and a through hole can be provided. The through hole makes it possible to shine light directly on the sample tube, for example.

  FIG. 1 shows an overall configuration diagram of an NMR measurement apparatus. The enlarged view of FIG. 1 is a configuration diagram of the tip portion of the probe, and shows the arrangement of the detection coil for nuclear magnetic resonance spectroscopy according to the present invention in the probe. The superconducting magnet 10 is a device that applies a strong magnetic field necessary for NMR measurement. The superconducting magnet 10 generally includes a correction coil that corrects the magnetic field uniformity near the center of the superconducting magnet on which the sample 15 is placed to about 1 ppm. The room temperature shim coil magnet 11 generates an error magnetic field that could not be corrected by the correction coil of the superconducting magnet 10 or an error magnetic field generated near the sample 14 after the probe 12 or sample 15 (sample tube 14) is inserted into the superconducting magnet. This is a device for correcting to about 1 ppb.

  The measurement console 13 and the measurement device 20 in FIG. 1 are devices for controlling the room temperature shim coil magnet 11 and the RF transmitter and the RF receiver when acquiring NMR signals. The RF coil 2 shown in the enlarged view of FIG. 1 is an apparatus for irradiating a sample with an electromagnetic wave for promoting nuclear magnetic resonance and receiving a nuclear magnetic resonance signal from the sample. The RF coil 2 is generally attached to the bobbin 1 and installed on the probe 12 via the bobbin 1.

  The RF coil 2 is electrically connected to a resonance circuit (not shown) installed in the probe 12. In general, a combination of one RF coil 2 and a resonance circuit forms a resonance circuit so that two resonances can be obtained simultaneously. That is, the NMR signals of two kinds of nuclei can be simultaneously received by one RF coil. The detection coil for nuclear magnetic resonance spectroscopy according to the present invention refers to a combination in which an RF coil is wound around or bonded to a bobbin as a winding frame.

  The specifications of the NMR measuring instrument include, for example, a nuclear magnetic resonance signal of four kinds of nuclei, hydrogen (H) nucleus, deuterium (D) nucleus, carbon 13 (C) nucleus, and nitrogen 15 (N) nucleus, as one probe. 12 is required to be measured. Therefore, when two RF coils 2a and 2b are installed like the probe 12 in the enlarged view of FIG. 1, for example, the inner RF coil 2a receives NMR signals of the H and D nuclei, and the outer RF coil 2a. The specification is such that the NMR signals of the C and N nuclei are received by the coil.

  The above description is a case where two RF coils 2 and bobbins 1, that is, detection coils for nuclear magnetic resonance spectroscopy are installed in one probe 12. In some cases, one detection coil for nuclear magnetic resonance spectroscopy is installed in one probe 12. When the present invention is applied to one nuclear magnetic resonance spectroscopy detection coil or to two coils, the effect of suppressing the generation of an error magnetic field is the same. Hereinafter, in order to simplify the description, a single detection coil for nuclear magnetic resonance spectroscopy will be described.

  FIG. 2 shows Example 1 of a detection coil for nuclear magnetic resonance spectroscopy provided with a non-magnetized bobbin according to the present invention. The detection coil for nuclear magnetic resonance spectroscopy of this embodiment is composed of a bobbin 1, an RF coil 2, and a metal thin film 3 bonded to the bobbin 1.

  The atmosphere of the detection coil for nuclear magnetic resonance spectroscopy is a gas such as air or a vacuum, and the magnetic susceptibility of the atmosphere refers to the magnetic susceptibility thereof. As the material of the bobbin 1, glass, quartz, sapphire, ceramics, or the like is used. The bobbin 1 has a cylindrical shape with a diameter of about 5 mm to 20 mm and a thickness of about 100 μm to 2 mm. The coil 2 is configured by bonding a superconductive or normal conductive material having good electrical conductivity and another metal material so as to be equal to the magnetic susceptibility of the atmosphere. Alternatively, the bobbin 1 is provided with the metal thin film 2 by a method such as vapor deposition, sputtering, or electroless plating. The metal thin film 3 is selected from a material whose polarity is opposite to the magnetic susceptibility of the bobbin 1 material.

The thickness d (metal thin film) of the metal thin film 3 is
d (metal thin film) = d (bobbin) × χ (bobbin) / χ (metal thin film)
It is requested from. Here, d (bobbin) is the thickness of the bobbin 2, χ (bobbin) is the magnetic susceptibility (SI unit system) of the material of the bobbin 2, and χ (metal thin film) is the magnetic susceptibility (SI of the metal thin film 3). Unit system).

  FIG. 3 shows an example of dimensions in the configuration of the detection coil shown in FIG. The bobbin 1 is a cylindrical shape of 10Φ quartz glass, and the vertical direction of the bobbin cylinder is the y-axis, and the direction perpendicular thereto is the z-axis. The coil 2 is made of a metal material having a thickness of 50 μm and is attached to the inside of the bobbin 1. The metal thin film 3 is affixed with a chromium material having a positive and negative polarity opposite to the magnetic susceptibility of the material of the bobbin 1 to a thickness of 14.44 μm to sufficiently cover the coil 2.

  It is assumed that a magnetic field of 7 T (Tesla) is applied along the z axis of this detection coil. The RF coil 2 is corrected by the metal thin film 3 so that the magnetic susceptibility is the same as the magnetic susceptibility of the atmosphere, and no error magnetic field is generated.

  FIG. 4 shows the magnitude of the error magnetic field appearing on the cylindrical central axis of the coil. FIG. 4 shows error magnetic fields when the metal thin film 3 for compensating the magnetic susceptibility of the bobbin is present (solid line) and when there is no metal thin film 3 (dotted line) in the detection coil of FIG.

  The dotted line is obtained by numerical calculation of the error magnetic field on the central axis of the cylinder generated when the bobbin 1 is only the base material. In the case where no compensation of the magnetic susceptibility of the bobbin 1 is performed, an error magnetic field of about 0.7 μT at maximum is generated. On the other hand, when the magnetic susceptibility of the bobbin 1 is compensated by the metal thin film 3, it can be seen that almost no error magnetic field is generated. In other words, the detection coil for nuclear magnetic resonance spectroscopy in which a metal foil is provided on the opposite side of the bobbin around which the coil is wound compensates for the magnetic susceptibility of the bobbin and suppresses the generation of an error magnetic field, thus ensuring the resolution of the NMR signal. There is.

  FIG. 5 is a diagram for explaining the second embodiment. The difference from the first embodiment is that the metal thin film 3 for compensating the magnetic susceptibility is arranged inside the bobbin 1. The RF coil 2 is attached to the outside of the bobbin 1 to prevent the RF coil 3 from making electrical contact with the metal thin film 2.

  Here, the bobbin compensated for the magnetic susceptibility is considered as a cylinder composed of an inner material and an outer material. Then, the difference between attaching the metal thin film 3 to the inside of the bobbin 1 or attaching it to the outside only changes the positive / negative relationship between the magnetic susceptibility of the material on the inside and the material on the outside. That is, if the magnetic susceptibility of the bobbin is compensated by the metal thin film, there is no essential difference between the inside of the metal thin film and the outside of the metal thin film. By suppressing the occurrence of this, the effect of ensuring the resolution of the NMR signal can be obtained.

  FIG. 6 is a diagram for explaining the third embodiment. The feature of the third embodiment is that a metal thin film 3 is pasted on the outer surface of the bobbin 1 to correct the magnetic susceptibility, and then an insulation film such as polyimide is used to insulate the RF coil 2 and the metal film 3 to be pasted. 4 is applied. The insulating film 4 allows the RF coil 2 and the metal thin film 3 to be attached to the outside of the bobbin. As in the first and second embodiments, it is difficult to attach the coil or the metal thin film to the inside of the bobbin. There is no.

  The insulating film 4 prevents the metal thin film 3 from coming into contact with air. Therefore, the metal film 3 is easily oxidized and it is possible to prevent the ability of correcting the magnetic susceptibility from being lowered due to the oxidation.

  FIG. 7 is a diagram for explaining the fourth embodiment. The feature of the fourth embodiment is similar to that of the third embodiment, and is a structure in which the insulating film 4 is applied to the RF coil 2c. Since the RF coil 2c and the metal thin film 4 are attached to the outside of the bobbin 1 as in the third embodiment, assembly is facilitated.

  FIG. 8 is a diagram for explaining a modification of the fourth embodiment. The difference between FIG. 7 and FIG. 8 is that the shape of the wire of the RF coil 2c in FIG. 7 is a thin film shape, whereas the wire of the RF coil 2d in FIG.

  Next, another embodiment of the present invention will be described. FIG. 9 is an example showing a configuration in which a through hole is provided in a bobbin. The through hole 8 has a diameter of about 5 mm, for example, and the bobbin 1 is made of quartz glass. The metal thin film 3 that corrects the magnetic susceptibility of the bobbin 1 is chromium. The through hole 8 provided in the bobbin 1 faces the z-axis direction.

  FIG. 10 shows the magnitude of the error magnetic field that appears on the cylindrical central axis of the coil when a magnetic field of 7 T (Tesla) is applied along the z-axis of the detection coil of FIG. The error magnetic field is shown when there is a metal thin film 3 that compensates the magnetic susceptibility of the bobbin 1 (solid line) and when there is no metal thin film 3 (dotted line). When the metal thin film 3 is not provided, an error magnetic field represented by a size of 10 μT is generated when a through hole having a diameter of 5 mm is formed in the bobbin 1. On the other hand, when the magnetic susceptibility of the bobbin 1 is compensated by the metal thin film 3, an error magnetic field is hardly generated even when a through hole having a diameter of 5 mm is formed, and there is an effect that the resolution of the NMR signal can be secured.

  FIG. 11 is a configuration diagram illustrating an application example of the fifth embodiment. The sample tube 14 is irradiated with light or the like through the through hole 8 of the bobbin 1 and directly receives transmitted light and scattered light from the sample 15. In this configuration, there is nothing that blocks light from the light emitting unit to the sample tube 14 or from the sample tube 14 to the light receiving unit. Therefore, when the sample 15 is irradiated with radio waves or light such as terahertz waves, infrared rays, visible rays, ultraviolet rays, X-rays, laser rays, maser rays, etc., and the transmitted light or scattered light is received, the NMR signal is simultaneously received. This is an effective structure for receiving.

  Even in the prior art, it is possible to provide a through-hole in the bobbin, but since an error magnetic field is generated, the resolution of the NMR signal is lowered. However, since the detection coil of the present invention corrects the magnetic susceptibility of the bobbin by the metal thin film, the resolution of the NMR signal is kept high, and at the same time, the sample can be irradiated with strong light. Thereby, simultaneous measurement of NMR measurement and measurement by light becomes possible.

  FIG. 12 is an explanatory diagram of sample temperature management according to another embodiment of the present invention. In NMR measurement, temperature management of the sample 15 is important, and the temperature of the sample 15 is adjusted by flowing the temperature control gas 30. The temperature control gas 30 flows in 30a from a plurality of holes 8 formed in the bobbin 1, and flows out 30b downward or upward.

  When the NMR signal observed from the sample has temperature dependence, if a temperature gradient occurs in the vertical direction of the sample, the NMR spectrum spreads and the resolution decreases. For this reason, when performing temperature control of the sample 15, it is necessary not to generate a temperature gradient in the vertical direction of the sample.

  FIG. 13 shows an example of a conventional technique in which the correction of the magnetic susceptibility of the bobbin is not performed, and the temperature control gas 30 is flowed upward from below. The temperature control gas 30 is discharged upward while exchanging heat with the sample tube 14 and the sample 15. At this time, if the sample 15 is in a condition that does not cause convection, the sample has a thermal gradient in the vertical direction.

  However, in the case of the present embodiment, the temperature control gas 30 is simultaneously released from the plurality of holes 8 formed in the bobbin 1 to the sample tube 14. Therefore, the temperature gradient is not generated in the sample 15 or the sample tube 14 as compared with the case of FIG.

  FIG. 14 is a diagram for explaining still another embodiment of the present invention, and shows the wiring of the lead wire of the RF coil. As shown in the overall configuration diagram of FIG. 1, the RF coil 2 of this embodiment is located on the inner side 2 a and the outer side 2 b with the sample tube 14 as an axis. In this case, if the lead wire 40 is wired near the sample 15 or the sample tube 14, the sensitivity and resolution of the NMR signal may be affected. This is because the lead wire 40 picks up an unnecessary signal of the sample 15 and the error magnetic field generated by the lead wire affects the sample 15. Moreover, it is better to make the lead wire as short as possible so as not to reduce the sensitivity.

  In FIG. 14, the lead wire 40 of the RF coil 2a is wired through the hole 9 formed in the bobbin 1b of the RF coil 2b. In order to allow the lead wire 40 to pass through the bobbin 1b, naturally, a hole 9 having a size through which the lead wire 40 passes through the bobbin 1b is required. When the magnetic susceptibility of the bobbin 1b is not corrected, providing such a hole 9 causes the generation of an error magnetic field, which lowers the resolution of the NMR signal.

  However, in the present embodiment, since the metal thin film 3 for correcting the magnetic susceptibility of the bobbin 1b is provided, the generation of the error magnetic field can be suppressed even if the hole 9 is provided. In other words, the configuration in which the magnetic susceptibility of the bobbin 1 is corrected has an effect of preventing influence on the sensitivity and resolution of the NMR signal by passing the lead wire 40 through the hole provided in the outer bobbin.

The block diagram of the NMR measuring device with which this invention is applied. Sectional drawing of the detection coil of Example 1 which concerns on this invention. FIG. 3 is a detailed view of an example of a detection coil according to the first embodiment. The graph which shows the magnetic field error of Example 1 and a prior art. Sectional drawing of the detection coil of Example 2 which concerns on this invention. Sectional drawing of the detection coil of Example 3 which concerns on this invention. Sectional drawing of the detection coil of Example 4 which concerns on this invention. Sectional drawing of the detection coil by the modification of Example 4. FIG. FIG. 10 is a detailed cross-sectional view of a detection coil according to a fifth embodiment of the present invention. The graph which shows the magnetic field error of Example 5 and a prior art. FIG. 10 is an explanatory diagram illustrating one application example of the fifth embodiment. The block diagram of the detection coil and temperature control of Example 6 which concerns on this invention. The block diagram of the conventional detection coil and temperature control. The block diagram of the detection coil and leader line of Example 6 which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Bobbin, 2 ... RF coil, 3 ... Metal thin film, 4 ... Insulating film, 5 ... Quartz glass, 6 ... Chrome thin film, 8 ... Through-hole, 9 ... Hole, 10 ... Superconducting magnet, 11 ... Room temperature shim coil magnet, DESCRIPTION OF SYMBOLS 12 ... Probe, 13 ... Measurement console, 14 ... Sample tube, 15 ... Sample, 20 ... Measuring instrument, 30 ... Flow of temperature control gas, 40 ... Lead line.

Claims (10)

In a nuclear magnetic resonance probe that detects a nuclear magnetic resonance signal of a sample,
An RF coil that receives a nuclear magnetic resonance signal from a nuclear spin of a sample, a bobbin that is a winding axis of the RF coil, and a metal material that is provided on the bobbin and has a polarity opposite to the magnetic susceptibility of the bobbin base material A nuclear magnetic resonance probe characterized in that the bobbin has a magnetic susceptibility equal to that in the atmosphere.   2. The nuclear magnetic resonance probe according to claim 1, wherein one of the RF coil and the metal material is provided inside the cylindrical bobbin and the other is provided outside the bobbin with respect to the bobbin.   2. The nuclear magnetic resonance probe according to claim 1, wherein the RF coil and the metal material are provided outside the bobbin with respect to the bobbin, and an insulating material is applied between the RF coil and the metal material.   4. The nuclear magnetic resonance probe according to claim 1, wherein the metal material is a metal thin film, and the RF coil is a metal thin film or a wire.   5. The nuclear magnetic resonance probe according to claim 1, wherein a vertical direction of the bobbin is a y-axis and a direction perpendicular thereto is a z-axis, and a through hole is provided in the z-axis direction.   6. The nuclear magnetic resonance probe according to claim 1, wherein the bobbin is made of quartz glass and the metal material is made of chromium (Cr). In a nuclear magnetic resonance probe that detects a nuclear magnetic resonance signal of a sample,
An RF coil that receives a nuclear magnetic resonance signal from a nuclear spin of a sample, a bobbin that is a winding axis of the RF coil, and a metal material that is provided on the bobbin and has a polarity opposite to the magnetic susceptibility of the bobbin base material The bobbin has a magnetic susceptibility equal to that in the atmosphere,
The vertical direction of the bobbin is the y-axis, the orthogonal direction is the z-axis, a through hole is provided in the z-axis direction, a light emitting part is provided on one side of the through hole, and a light receiving part is provided on the other side. A probe for nuclear magnetic resonance.   8. The nuclear magnetic resonance probe according to claim 7, wherein the light emitting unit irradiates the sample with terahertz waves, infrared rays, visible rays, ultraviolet rays, X-rays, laser rays, or maser rays. In a nuclear magnetic resonance probe that arranges a sample tube in a detection coil and detects a nuclear magnetic resonance signal of the sample,
An RF coil that receives a nuclear magnetic resonance signal from a nuclear spin of a sample, a bobbin that is a winding axis of the RF coil, and a metal material that is provided on the bobbin and has a polarity opposite to the magnetic susceptibility of the bobbin base material The bobbin has a magnetic susceptibility equal to that in the atmosphere,
The vertical direction of the bobbin is the y-axis, the orthogonal direction is the z-axis, a plurality of through holes are provided in the z-axis direction, and the temperature adjusting fluid is allowed to flow through the plurality of through holes for temperature adjustment of the sample tube. A probe for nuclear magnetic resonance characterized in that it is configured. In a nuclear magnetic resonance probe that arranges a sample tube in a detection coil and detects a nuclear magnetic resonance signal of the sample,
The detection coil has an RF coil that receives a nuclear magnetic resonance signal from a nuclear spin of a sample, a bobbin that is a winding axis of the RF coil, and a polarity opposite to a magnetic susceptibility of a bobbin base material provided on the bobbin. A metal material, and configured such that the magnetic susceptibility of the bobbin is equal to the magnetic susceptibility in the atmosphere,
A nuclear magnetic resonance characterized in that the detection coil configured in this manner is doubled with respect to the sample tube, and the lead wire of the inner RF coil is pulled out through a hole formed in the outer bobbin. Probe.

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