JP2007147452A - Magnetic resonator and method for measuring nuclear magnetic resonance signal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the sensitivity of a magnetic resonator on a nuclear magnetic resonance signal. <P>SOLUTION: A static magnetic field generation part 20 comprises a pair of magnets 21a and 21b fixed to a yoke 22, forming a magnetic circuit in its entirety. The generation part 20 is further equipped with a spacer 71 which is put on the magnets 21a and 21b. The spacer 71 is equipped with a dent part 71a for thereon mounting a measurement specimen 100 to shape the measurement specimen 100. A static magnetic field is formed around the generation part 20 where an equi-magnetic flux density surface exists having equal magnetic flux density. A resonance domain 100a appears in the density surface. With the measurement specimen 100 included in the measurement specimen 100 by bringing the measurement specimen 100 into line with the spacer 71, a nuclear magnetic resonance phenomenon is caused to take place over the whole of the density surface by using a transmission/reception coil 23. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic resonance apparatus and a nuclear magnetic resonance signal measurement method.

  2. Description of the Related Art Conventionally, a magnetic resonance apparatus that uses nuclear magnetic resonance phenomenon to image the distribution and concentration of a measurement sample, for example, water and fat of a human body, has been put into practical use and applied to medical fields and the like. Such a nuclear magnetic resonance phenomenon is to receive a nuclear magnetic resonance signal generated by irradiating a measurement sample with a static magnetic field and a radio wave (high-frequency magnetic field) and measure the density of a specific atom. The frequency condition of the high-frequency magnetic field for causing the resonance is expressed as f = (γ / 2π) B where B is the magnetic flux density of the static magnetic field. The value of the constant γ is determined by each atom, and is 42.56 MHz / T (Tesla) for a hydrogen atom, for example. When atoms in the measurement sample are placed in an environment that satisfies the conditions of the high-frequency magnetic field, such a magnetic resonance phenomenon occurs and a nuclear magnetic resonance signal can be received. As can be seen from this relational expression, a nuclear magnetic resonance phenomenon does not occur in a portion having a specific static magnetic flux density unless a specific frequency is applied. If the above-described distribution of magnetic flux density is known in advance, a part having a constant magnetic flux density can be specified. Therefore, a difference is provided in the magnetic flux density in the sample, and the site is specified to obtain the distribution of atomic density in the sample.

In such a magnetic resonance apparatus, an open type magnetic resonance apparatus that generates a static magnetic field on an open surface is disclosed (for example, see Patent Documents 1 and 2).
JP 2005-27763 A JP 2005-095479 A

  However, when measuring a sample whose distribution does not need to be obtained (for example, a sample having a uniform material), the intensity of the nuclear magnetic resonance signal is higher when there are more parts having a certain magnetic flux density in the sample. It is preferable in that it becomes stronger and the sensitivity becomes higher. In this regard, when measuring in a relatively thin plate-like sample, it is easy to deviate from the region where the magnetic flux density, which is generally curved, is equal because it is thin and thin. There was a problem that the resonance signal became small. In addition, since the resonance region does not coincide with the position of the specific depth, it is difficult to accurately check the state of the specific depth.

  Therefore, an object of the present invention is to improve the sensitivity of a nuclear magnetic resonance signal in a magnetic resonance apparatus.

  The present invention is configured as follows.

(1) The present invention
In a magnetic resonance apparatus provided with a static magnetic field generating means for generating a surface leakage static magnetic field on the surface of a sensor head for measuring a nuclear magnetic resonance signal of a sample,
A magnetic resonance apparatus characterized in that a sample abutting member having a surface having substantially the same shape as an isomagnetic flux surface corresponding to a magnetic flux density causing a resonance state is provided on a sensor head surface.

  In the static magnetic field generated by the static magnetic field generating means, a surface representing a region where the magnetic flux density is uniform (hereinafter referred to as “equal magnetic flux density surface”) is overlapped in layers depending on the value of the magnetic flux density. According to the present invention, the equal magnetic flux density surface which becomes the resonance region of the nuclear magnetic resonance signal by, for example, pressing the sample along the sample abutting member arranged by the sample abutting member arranging means. A sample can be put along. Therefore, a portion along the surface of the equal magnetic flux density is formed to be large, and a nuclear magnetic resonance signal can be received from the entire portion, so that reception sensitivity can be improved.

The static magnetic field generating means may have the following configuration, for example. That is, it is conceivable to have a yoke and a pair of permanent magnets, which are formed in a U shape as a whole and generate a leakage magnetic field generated around the groove or at the tip of the permanent magnet. A circular magnet and a pair of yokes having recesses for receiving the circular magnets on both sides of the magnet are formed around the gap between the yokes, a support member inserted in the gap, or the tip of the yoke It is conceivable to generate a leakage magnetic field.
(2) The present invention
The sample abutting member is characterized in that the distance between the equal magnetic flux density surface and the surface of the sample abutting member is set to a thickness that is a measurement depth of the nuclear magnetic resonance signal from the sample surface.

  When the sample abutting member is configured in this way, it is moved from the curve of the equal magnetic flux density surface at the position where the nuclear magnetic resonance signal is generated to a position retracted toward the sensor head by the measurement depth of the nuclear magnetic resonance signal. The surface of the sample contact member is provided. Therefore, the resonance point of the nuclear magnetic resonance signal can be provided at the same depth from the sample surface.

  In the present invention, “measurement depth” refers to the depth from the sample surface at the position where the sample is measured (the same applies hereinafter).

(3) The present invention
A pressing member for pressing the sample against the surface of the sample contact member is provided so that the surface of the sample is along the surface of the sample contact member.

  The present invention includes a pressing member that presses the surface of the sample contact member, and the sample can be pressed against the sample contact member by the pressing member. In this manner, the pressed sample has a larger area including the isomagnetic flux surface that becomes the resonance area of the nuclear magnetic resonance signal, and the nuclear magnetic resonance signal is received from the entire portion along the isomagnetic flux density surface. As a result, the received signal increases.

(4) The present invention
The sample abutting member includes an exchange member in which a portion including a surface having substantially the same shape as the equal magnetic flux density surface is detachable.

  If comprised in this way, according to the measurement site | part of a sample, for example, the depth to measure, it becomes possible to attach or detach an exchange member to a sample contact member according to the surface of the substantially same shape as the said equal magnetic flux density surface. Become.

(5) The present invention
The exchange member is provided with a receiving coil for receiving the nuclear magnetic resonance signal.

  Since the sample abutting member is provided with a receiving coil for receiving the nuclear magnetic resonance signal, the interval between the sample abutting on the sample abutting member and the receiving coil can be reduced. The sensitivity of the magnetic resonance signal can be improved.

(6) The present invention
In a method of measuring a nuclear magnetic resonance signal of a sample placed in the surface leakage magnetic field by generating a surface leakage magnetic field on the sensor head surface by a static magnetic field generation means,
A sample abutting member having a surface having substantially the same shape as the isomagnetic flux surface corresponding to the magnetic flux density causing the resonance state is disposed on the sensor head surface,
A sample is disposed on the sample contact member;
The sample is sandwiched and pressed between the sample contact member and the pressing member so that the surface of the sample is along the surface of the sample contact member,
Next, a method of measuring a nuclear magnetic resonance signal is characterized by measuring a nuclear magnetic resonance signal of a sample.

  According to the present invention, the sample abutting member is disposed on the sensor head surface, the sample is disposed on the sample abutting member, and the sample is placed on the sample so that the sample surface is along the surface of the sample abutting member. The sample is sandwiched and pressed between the contact member and the pressing member. Thereby, a sample is shape | molded by the shape of the surface of the said sample contact member. Here, since the surface of the sample abutting member is formed in the same shape as the isomagnetic flux surface that becomes the resonance region of the nuclear magnetic resonance signal, the equal magnetic flux corresponding to the magnetic flux density that causes a resonance state inside the sample. The degree can be increased. In this state, since the nuclear magnetic resonance signal of the sample is measured, the nuclear magnetic resonance signal can be received from the entire surface of the equal magnetic flux density. Therefore, the receiving sensitivity of the nuclear magnetic resonance signal can be improved.

(7) The present invention
In a method of measuring a nuclear magnetic resonance signal of a sample placed in the surface leakage magnetic field by generating a surface leakage magnetic field on the sensor head surface by a static magnetic field generation means,
A sample abutting member having a surface having substantially the same shape as the isomagnetic flux surface corresponding to the magnetic flux density causing the resonance state is disposed on the sensor head surface,
Press the sample against the sample abutting member along the surface of the sample abutting member,
Next, a method of measuring a nuclear magnetic resonance signal is characterized by measuring a nuclear magnetic resonance signal of a sample.

  The present invention has the same technical idea as the method (6). Also by this method, the surface of the sample can be shaped so as to have a surface with equal magnetic flux, so that a nuclear magnetic resonance signal can be received from the entire surface with the same magnetic flux density. Therefore, the receiving sensitivity of the nuclear magnetic resonance signal can be improved.

  In the present invention, for example, by pressing a thick elastic member against the sample contact member, the molding can be performed even when the sample cannot be sandwiched as in (6). However, this example does not limit the present invention.

  According to the present invention, a nuclear magnetic resonance signal can be received from a wide area in a sample by placing the sample along an equal magnetic flux density surface where a nuclear magnetic resonance state occurs. Therefore, the receiving sensitivity of the nuclear magnetic resonance signal can be improved.

<First Embodiment>
Hereinafter, the configuration of the magnetic resonance apparatus of the first embodiment will be described with reference to FIGS. 1 and 2. This magnetic resonance apparatus has a mechanical configuration as shown in FIG. 1 and an electrical configuration as shown in FIG.

  First, the mechanical configuration of the magnetic resonance apparatus according to the present embodiment and the method of using the magnetic resonance apparatus will be described with reference to FIG.

  The configuration of the upper part of the sensor head of the magnetic resonance apparatus according to the first embodiment will be described with reference to FIGS. The main part of the mechanical configuration of the magnetic resonance apparatus of the present embodiment is a sensor head 2. The sensor head 2 includes a static magnetic field generator 20 shown in FIG. 1 (A), a spacer 71, and FIG. 1 (B). The transmitter / receiver coil 23 shown in FIG. Each will be described below.

  A static magnetic field generator 20 shown in FIG. 1A includes a metal yoke 22 and a pair of magnets 21a and 21b fixed thereon. The magnets 21a and 21b have magnetic poles in the Y-axis direction (the direction from the yoke 22 shown in FIG. 1A toward the magnets 21a and 21b). Magnets 21a and 21b have opposite magnetic poles. Thus, the yoke 22 and the magnets 21a and 21b form a one-round magnetic circuit, and the magnetic field leaks from the periphery of the gap 105 and from the upper surfaces of the magnets 21a and 21b (the surface on which the spacer 71 is provided). A static magnetic field leaking from the upper surfaces of the magnets 21a and 21b (surface on which the spacer 71 is provided) is formed on the spacer 71 on which the sample is placed. In the example of FIG. 1A, the side where the magnet 21a is in contact with the yoke is the S pole, the opposite side is the N pole, the side where the magnet 21b is in contact with the yoke is the N pole, and the opposite side is the S pole.

  The spacer 71 in FIG. 1A is made of a material that does not generate a nuclear magnetic resonance signal, such as an epoxy resin having a thickness of about 7 mm, Pyrex (registered trademark) glass, or the like, and is provided so as to cover both the magnets 21a and 21b. . The spacer 71 is provided with a recess 71a in the vicinity of the gap 105 for the purpose of improving the sensitivity of the nuclear magnetic resonance signal of the measurement sample 100 (see FIG. 1C described later) (details). Will be described in detail in FIG.

Note that the outer end face 107 and the inner end face 106 on both sides facing in the Z-axis direction in FIG. 1A are used in the description of FIGS.
Further, in the description of the magnetic field of the static magnetic field generation unit 20 of the present embodiment, the “gap 105” includes not only a literal gap but also a portion of this nonmagnetic material when a nonmagnetic material is inserted. For example, the spacer 71 shown in FIG. Even if a nonmagnetic material is inserted, it is considered that a similar magnetic field is formed.

FIG. 1B is a cross-sectional view taken along the line AA in FIG.
As shown in FIG. 1 (B), the transmitting / receiving coil 23 is an air-core coil wound with an enameled wire formed in a ring shape, and a spacer 71 is provided at the center of FIG. Or embedded in the spacer 71 as in the third embodiment described later with reference to FIG. Although details of the function will be described later with reference to FIG. 2, the transmitting / receiving coil 23 of the first embodiment has a role as a transmitting coil for generating a high-frequency magnetic field and a role as a receiving coil for receiving a nuclear magnetic resonance signal. Have both. When used as a transmission coil, nuclear magnetic resonance occurs in the measurement sample 100 when a high-frequency pulse is sent to the transmission coil so as to satisfy a relational expression between a static magnetic field and a frequency described later. When used as a receiving coil, the transmitting / receiving coil 23 converts the change in the magnetic field generated by the nuclear magnetic resonance into an electrical signal.

  Here, the coordinate system of the sensor head 2 will be described with reference to FIGS. As shown in FIGS. 1A and 1B, the direction perpendicular to the U-shaped device front surface 102 and device rear surface 103 (the surface 103 is parallel to the surface 102) is the X axis. As described above, a one-round magnetic circuit is formed along the surfaces 102 and 103, and the X axis is perpendicular thereto. Further, the direction of the lines of magnetic force in the gap 105 between the magnets 21a and 21b is the Z axis, and the direction perpendicular to the X axis and the Z axis is the Y axis described above.

  Further, the size of the static magnetic field generation unit 20, the cross-sectional shape of the spacer 71, and the transmission / reception coil 23 will be described with reference to FIG. The unit of the scale shown in FIG. 1B is [mm], and the size of the static magnetic field generator 20 is about 100 mm square. The outer end face 107 shown in FIG. 1A corresponds to a position of ± 50 mm in the X coordinate, and the inner end face 106 shown in FIG. 1A corresponds to a position of ± 10 mm in the X coordinate. As shown in FIG. 1B, the cross section of the spacer 71 is recessed in a bowl shape at the indented portion 71a, and the thickness of the spacer 71 is about 7 mm.

  Next, the usage pattern of the apparatus of this embodiment will be described with reference to FIG. When this apparatus is used, a measurement sample 100 is placed on the static magnetic field generating unit 20 shown in FIGS. 1A and 1B, and a nuclear magnetic resonance signal such as epoxy resin or Pyrex (registered trademark) glass is placed thereon. A pressing member 72 made of a material that does not generate a problem is placed, and the measurement sample 100 is sandwiched and fixed. Thereby, the measurement sample 100 is deformed by the indented portion 71a and the raised portion 72a (the reason why the measurement sample 100 is deformed will be described later in FIG. 3 and later).

Next, the internal configuration of the magnetic resonance apparatus of the first embodiment will be described with reference to FIG. FIG. 2 is an internal configuration diagram of the magnetic resonance apparatus of the first embodiment.
The high-frequency circuit system 51 in FIG. 2 generates a drive current having a specific frequency and sends a pulse current to the transmission / reception coil 23 serving as a transmission coil. The high frequency circuit system 51 includes an oscillation unit 511, a transmission unit 512, and a high frequency amplifier 513.

The oscillating unit 511 in FIG. 2 can be configured by, for example, a highly stable crystal oscillator, and sends a signal generated thereby to the transmitting unit 512.
The transmission unit 512 includes a frequency synthesizer, a frequency converter, and a pulse generator. The frequency synthesizer frequency-converts the reference signal generated by the oscillation unit 511 to generate a signal having a predetermined frequency. The frequency converter frequency-converts the signal having the predetermined frequency to generate a high-frequency signal having a predetermined frequency (hereinafter referred to as “a”). On the other hand, the pulse generator generates a pulse signal (pulse width of 1 to 20 μs, one cycle from 0.5 seconds to 1 second) separately from the high-frequency signal a (hereinafter referred to as “b”). These signals a and b are synthesized by being input to the modulator, and a high frequency signal (RF pulse) in which high frequency is intermittent is generated.
The high frequency amplifier 513 amplifies the RF pulse converted by the transmission unit 512 and sends a drive current to the magnetic circuit system 52.

  The magnetic circuit system 52 in FIG. 2 includes a static magnetic field generation unit 20 that generates a static magnetic field and a transmission / reception coil 23 as a transmission coil that generates a high-frequency magnetic field. When the above-described predetermined relationship is satisfied, a nuclear magnetic resonance signal can be received from a portion of the measurement sample 100 placed in an environment that satisfies this relationship.

The nuclear magnetic resonance signal receiving unit 53 in FIG. 2 amplifies and digitizes the nuclear magnetic resonance signal emitted from the measurement sample 100. The nuclear magnetic resonance signal receiving unit 53 includes a receiving coil 8 and an amplifying unit (not shown). The arithmetic processing system 54 includes an image reconstruction unit 541 and a data processing unit 542. The image reconstruction unit 541 converts the reception data generated by the nuclear magnetic resonance signal reception unit 53 into digital image data. The data processing unit 542 D / A converts the digital image data and sends a video output to the display. The display 55 displays the video output.
The operation unit 57 receives an operation operation of the magnetic resonance apparatus. The system control unit 56 receives an instruction from the operation unit 57 and controls the above-described units (reference numerals 51, 53, and 54).

Note that the apparatus of the first embodiment does not display the density distribution of atoms as is generally done, but the density of the entire sample, strictly speaking, a certain depth from the surface of the sample as described later. Since the atomic density of the surface is measured, the purpose of the arithmetic processing system 54 is mainly to display statistical data such as variations between the measurement samples 100.
In the apparatus according to the present embodiment, the image reconstruction unit 541 is not necessarily required, and it may be sufficient to acquire data.

  Next, functions of the magnetic resonance apparatus according to the first embodiment will be described with reference to FIGS. 1 and 2. The magnetic resonance apparatus of the present embodiment is an apparatus that measures the distribution, concentration, and the like of the measurement sample 100, for example, water or fat, with respect to the depth to be measured, using the nuclear magnetic resonance phenomenon. The nuclear magnetic resonance phenomenon is caused by applying a static magnetic field to the measurement sample 100 by the magnets 21a and 21b shown in FIG. 2 and irradiating a radio wave (high frequency magnetic field) by the transmission / reception coil 23 as a transmission coil. A magnetic resonance signal is received and the density of a specific atom is measured. The frequency condition of the high-frequency magnetic field for causing this resonance is expressed as f = (γ / 2π) B where B is the magnetic flux density of the static magnetic field, and the value of the constant γ is determined by each atom. Yes. Therefore, the nuclear magnetic resonance phenomenon occurs only at a specific frequency for a specific magnetic flux density. When a voltage of this specific frequency is applied to the transmission / reception coil 23 as a transmission coil, a nuclear magnetic resonance phenomenon occurs in a specific type of atom, and the transmission / reception coil 23 as a reception coil acquires this as an electric signal, and the nuclear magnetic field. The resonance signal receiving unit 53 amplifies and digitizes the nuclear magnetic resonance signal emitted from the measurement sample 100.

<Shape of spacer of apparatus of first embodiment>
Next, the shape of the recessed portion 71a of the spacer 71 will be described with reference to FIGS. 3 to 6 and FIGS. 1 (A) and 1 (C).

  First, the magnetic flux density around the static magnetic field generation unit 20 will be described with reference to FIG. 3A to 3C show changes in magnetic flux density with respect to the axis direction of the horizontal axis when the value of the coordinates in the square is fixed.

FIG. 3A shows _a change in magnetic flux density when the value of the Y-axis coordinate is fixed to Y = ya, the value of the Z-axis coordinate is fixed to Z = 0, and the value of the X-axis is changed. Yes. As shown in FIG. 3A, the magnetic flux density is flat from the device rear surface 103 to the device front surface 102 of the magnets 21a and 21b (see FIG. 1A). Outside that range, the magnetic flux density decreases as the X-axis coordinate moves away from the center.

  FIG. 3B shows the change in magnetic flux density when the value of the X-axis coordinate is fixed to X = 0, the value of the Z-axis coordinate is fixed to Z = 0, and the value of the Y-axis is changed. . The magnetic flux density decreases as the Y-axis coordinate moves away from the magnet.

FIG. 3C shows _a change in magnetic flux density when the value of the X-axis coordinate is fixed to X = 0 and the value of the Y-axis coordinate Y = ya and the value of the Z-axis is changed. . In the graph, when the Z coordinate is Z = 0, the value is minimum, and the value is maximum at the position of the inner end face 106 of the magnets 21a and 21b (Z = ± 10 mm in FIG. 1B). In a range where the Z-axis coordinates are outside the range between the two points, the magnetic flux density decreases as the distance from the center increases. The reason why such a tendency of the magnetic flux density occurs will be briefly described as follows. That is, depending on the position of the Z coordinate, the magnetic flux density decreases as the distance from the magnets 21a and 21b increases, but at the position of the end face 106, it is maximized by the influence of both the magnets a and b. When = 0, the magnetic flux density is slightly attenuated by moving away from the magnets a and b, and the end face 106 is considered to gradually attenuate because it gradually moves away from these magnets. Further, the degree of attenuation is further increased outside the end face 107 (point of ± 50 mm in FIG. 1B) outside the magnets 21a and 21b.

  However, the tendency of the state of the magnetic flux density in the Z-axis direction shown in FIG. 3C differs depending on the strength of the magnetic field and the gap 105 (between Z = ± 10 mm in FIG. 1B) and There may be a case where two local maximum values are overlapped and become maximum at the central portion where Z = 0 and attenuate as the distance from the center increases.

Next, how the region having the same magnetic flux density around the static magnetic field generation unit 20 is formed will be described with reference to FIG. Here, the region having the same magnetic flux density is formed as a curved surface, and the region having the same magnetic flux density is referred to as an equal magnetic flux density surface. Figure 4 is thus equal magnetic flux density radial magnetic flux density becomes a specific value B _1, represents a constant magnetic flux density lines as seen from the particular plane, FIG. 4 (A), X in the Z = 0 axis -Y axis plane, FIG. 4 (B), for an equal flux density radial magnetic flux density becomes a specific value B _2, represents a constant magnetic flux density line as viewed from the Y axis -Z-axis plane at X = 0 . In addition, each code | symbol in FIG. 4 respond | corresponds to the code | symbol of FIG. 1, FIG.

  4A is the magnetic flux density curve shown in FIGS. 3A and 3B at a plurality of positions (in the box of FIGS. 3A and 3B). 4), the X coordinate is the rear surface 103 of the static magnetic field generator 20 (shown in FIG. 1). Inside the apparatus front surface 102 (shown in FIG. 1), the equal magnetic flux density lines are substantially flat, which is substantially uniform in the X-axis direction as shown in FIG. Also, outside these planes 102 and 103, the curve representing the isomagnetic flux density plane shown in FIG. The reason why this tendency occurs will be briefly described as follows: That is, the magnetic flux density increases as the distance from the outside in the X-axis direction increases. Further, the magnetic flux density decreases as the distance from the static magnetic field generation unit 20 increases in the Y-axis direction, so that the equimagnetic flux density line as shown in FIG. The axial direction is inclined toward the magnet side.

  4B, the magnetic flux density line shown in FIG. 3B and the magnetic flux density curve shown in FIG. 3C are displayed at a plurality of positions ((FIG. 3B). (C) (by changing the value in the box), and the relationship between these is obtained.As shown in FIG. , B becomes a minimum value between the gaps 105 and reaches a maximum value at the position of the end face 106 inside the magnets 21a, b (Z = ± 10 mm point in FIG. 1B), which is the magnet 21a. 4B, the reason why the tendency as shown in FIG.4B occurs is as follows: The magnetic flux density 0 attenuates as the distance from the magnet increases in the Y-axis direction. In the distribution of the magnetic flux density on the Z axis, the minimum value is obtained at the position of Z = 0 in FIG. 3C, and the inner end face 106 (Z = ± 10). 4B, the equal magnetic flux density line shown in FIG. 4B tilts in a direction in which the Y-axis direction moves away from the magnet side as the inner end face 106 is approached.

  However, the tendency of the state of the magnetic flux density in the Z-axis direction shown in FIG. 4B differs depending on the strength of the magnetic field and the gap 105 (between Z = ± 10 mm in FIG. 1B). For example, according to the tendency of the magnetic flux density described in FIG. 3 above, the equal magnetic flux density line on the Y-axis-Z-axis plane becomes the maximum at the central portion where Z = 0 because the two maximum values overlap. In some cases, the attenuation may occur as it goes outside. In this case, it is necessary to use the apparatus of the second embodiment described later with reference to FIG. 6 instead of the embodiment shown in FIG.

  Next, returning to FIG. 1 (C), a method for forming the spacer 71 will be described based on what has been described with reference to FIGS. The resonance region 100a as shown in FIG. 1C is a portion having a magnetic flux density of a static magnetic field that satisfies the above-described relational expression, and has an equal magnetic flux density surface as shown in FIG. In the apparatus of the first embodiment, the indented portion 71a of the spacer 71 and the raised portion 72a of the pressing member 72 are formed so that the measurement sample 100 includes the curve shown in FIG. Specifically, in the Z-axis direction, as shown in FIG. 4B, between the gap 105, the equal magnetic flux density surface has a shape that is recessed downward on the Y-axis on the Y-axis-Z-axis plane. Therefore, the cross-section of the Y-axis-Z-axis plane of the shape of the recessed portion 71a is similarly formed in a recessed shape. In the X-axis direction, as shown in FIG. 4 (A), since it is flat between the apparatus rear surface 103 and the apparatus front surface 102, it is flat in the X-axis direction. Then, the measurement sample 100 is sandwiched between the recess portion 71a and the raised portion 72a, or the measurement sample 100 is pressed against the recess portion 71a to form the measurement sample 100. Thereby, the resonance region 100a in the measurement sample 100 is expanded, and the transmission / reception coil 23 can receive the nuclear magnetic resonance signal from the resonance region 100a.

  In the apparatus of the first embodiment, the purpose of the indented portion 71a is to form a portion having a uniform magnetic flux density, and the magnetic flux density value is not a problem. There is no need to mold to a value. This is because the relational expression for generating the above-described nuclear magnetic resonance signal should be satisfied. That is, a pulse having a specific frequency may be given to the transmission / reception coil 23 as a transmission coil so as to match the magnetic flux density. However, a higher magnetic flux density of the static magnetic field is preferable from the viewpoint of improving the sensitivity of the nuclear magnetic resonance signal. Further, since it is preferable to provide the transmission / reception coil 23 near the resonance region 100a, the transmission / reception coil 23 may be embedded in the spacer 71 (see the third embodiment, which will be described later, and FIG. 7).

  Further, a method for forming the recess portion 71a of the spacer 71 described with reference to FIGS. 4 and 1C will be specifically described with reference to FIG. FIG. 5 is an explanatory diagram of this molding method. FIG. 5 shows an actual measurement value of a uniform magnetic flux density surface in a Y axis-Z axis plane shape in a gap 105 (Z = ± 10 [mm]) of the static magnetic field generation unit 20, and a measurement sample 100 (in a shaded portion). (Shown)). The horizontal axis is the Z-axis direction, the vertical axis is the Y-axis direction, and the unit is [mm]. The curve of the resonance region 100a shown in FIG. 5 uses data of measured values of the equal magnetic flux density surface. The measured value data indicates that the magnetic flux density generated by the static magnetic field generation unit 20 is 0.3 [T]. When a pulse having a frequency corresponding to this is given to the transmission coil, the resonance region 100a in FIG. 5 corresponds to the resonance region 100a shown in FIG. The spacer 71 is formed in the same curve as the equal magnetic flux density surface that becomes the resonance region 100a so that the resonance region 100a that becomes the equal magnetic flux density surface enters the measurement sample 100 as much as possible, and the measurement sample 100 is placed on the spacer 71. A measurement sample 100 is formed along the same. In the example of FIG. 5, the curve of the recessed portion 71 a of the spacer 71 is formed at a position lowering from the resonance region 100 a serving as an equal magnetic flux density surface to the 0.5 mm yoke side. When the measurement sample 100 is placed along the recessed portion 71a of the spacer 71, it is 0.5 mm inside from the surface 100b (shown by a two-dot chain line) of the measurement sample 100 at an equal depth (indicated by the depth 100c). A resonance region 100a is generated at the point of entry. For example, when measuring a nuclear magnetic resonance signal of a hydrogen atom, a pulse of f = (γ / 2π) B = 42.56 [MHz / T] · 0.3 [T] = 12.8 [MHz] is used. By giving the transmission / reception coil 23 as a transmission coil, a nuclear magnetic resonance phenomenon occurs from the resonance region 100a, and a nuclear magnetic resonance signal is received from the transmission / reception coil 23 as a reception coil.

  On the other hand, when the measurement sample 100 is not molded as in the measurement sample 100d shown in FIG. 5 (conventional device), the overlapping portion between the measurement sample 100d and the resonance region 100a is small, and the measurement sample 100d is not included in the measurement sample 100d. The sensitivity is small because the resonance region is small. In addition, it is difficult to accurately check the state of a uniform depth position.

<Application of the first embodiment>
As shown in FIG. 1, the measurement sample 100 is formed only in the gap 105 (inside Z = ± 10 [mm]) of the static magnetic field generation unit 20 because the transmission / reception coil 23 as a reception coil is formed in this manner. This is because it is provided in a region and the receiving sensitivity becomes dull at a portion far from the receiving coil, and it is considered sufficient to mold the measurement sample 100 only in this region. Of course, the spacer 71 may be formed so as to form the measurement sample 100 even outside this region.

Further, the spacer 71 is not necessarily required to be a flat surface as long as a recessed portion 71 </ b> A described later can follow the sample. Any shape can be used for the spacer 71 as long as the spacer 71 is processed so as to form an equal magnetic flux density surface on the measurement sample 100. The spacer 71 covers the magnets 21a and 21b in order to support the indented portion 71a. For example, the spacer 71 can be extended and supported from both sides in the X-axis direction.
1C, the measurement sample 100 may be formed by pressing the measurement sample 100 into the recess 71a of the spacer 71 with a hand or a stand without using the pressing member 72. . For the measurement sample 100 having a thickness, the measurement sample 100 is placed on the leakage static magnetic field of the magnets 21a and 21b, and the spacer 71 is pressed against the measurement sample 100 with a hand or a stand without using the pressing member 72. May be molded.
Further, the measurement sample 100 may be pressed against the spacer 71. If the measurement sample 100 is thick and soft, it is simply placed on the spacer 71 and is pressed against the spacer 71 by its gravity, thereby forming an equal magnetic flux density surface.

  Moreover, in the apparatus of 1st Embodiment shown above, although the transmission / reception coil 23 has both a transmission coil and a reception coil, you may provide these separately.

Further, as a method of forming the recess 71a of the spacer 71, the measurement sample 100 may be fixed and the sensor head may be pressed against the sample.
In FIG. 1A, the indentation 71a extends over the entire area in the X-axis direction, but may be a part. Although it is preferable to provide the spacer 71 in the X-axis direction by the width of the sample, the effect of the present invention is not necessarily required.

The spacer 71 shown in FIG. 1 and the application example described above correspond to the “sample contact member” of the present invention.
<Second Embodiment>
Next, an external configuration diagram of a static magnetic field generation unit of the magnetic resonance apparatus of the second embodiment according to the application of the apparatus of the first embodiment is shown using FIG. FIG. 6 shows an example of the spacer 71 of the static magnetic field generation unit 20 of the apparatus of the second embodiment. Unlike the first embodiment, the spacer 71 in FIG. 6 is a raised portion 71c in that the recessed portion 71a in the vicinity of the gap 105 shown in FIG. 1 is raised. As described with reference to FIGS. 3 (C) and 4 (B), when the maximum points of the equal magnetic flux density surface generated on the inner end face 106 of the magnet 21a overlap, the Y-axis-Z-axis plane is obtained. This corresponds to the fact that the equal magnetic flux density surface rises in the positive direction of the Y axis at the center where Z = 0. In this embodiment, by providing the raised portion 71c, the resonance region 100a in the measurement sample 100 is enlarged along the equal magnetic flux density surface along the measurement sample 100 as in the embodiment shown in FIG. . In the case of this embodiment, corresponding to the raised portion 71c, the pressing member 72 is provided with a recessed portion instead of the raised portion 72a shown in FIG. In this embodiment, the curve of the equal magnetic flux density surface in the X-axis to Z-axis plane direction is substantially flat between the apparatus rear surface 103 and the apparatus front surface 102, and is formed to be approximately flat in the X-axis direction. To do.

<Third Embodiment>
Next, the apparatus of the third embodiment will be described as an application of the apparatus of the first and second embodiments with reference to FIGS. FIG. 7 is a view in which a bobbin that allows part of the spacer 71 and the transmission / reception coil 23 to be detachable is mounted. FIG. 8 is a component diagram of the bobbin. The apparatus of the third embodiment is that the bobbin that is a part of the indented portion 71a having the equal magnetic flux density surface of the spacer 71 is detachable from the spacer 71, and that the transmitter / receiver coil 23 is configured on the bobbin is the first. Different from the apparatus of the second embodiment. Hereinafter, description of the same points as those of the apparatus of the first embodiment will be omitted, and differences will be described.

  First, the shape of the bobbin will be described with reference to FIG. 8A is a component diagram of the bobbin 75, and FIG. 8B is a cross-sectional view taken along the line BB in FIG. 8A. FIG. 8C is a CC arrow view of FIG. 8B.

  The bobbin 75 shown in FIG. 8A is made of a material that cannot acquire a nuclear magnetic resonance signal from the bobbin 75. As a material of the bobbin 75, for example, an epoxy resin, Pyrex (registered trademark) glass, or the like can be used. The bobbin 75 is provided with a recess 753 as shown in FIG. The inclined portion 751 will be described later with reference to FIG.

  As shown in FIGS. 8B and 8C, the bobbin 75 has a concave portion 752, and a coil is wound around the concave portion 752 to form the transmission / reception coil 23 (see FIG. 1). In this way, as shown in FIG. 7A, the distance between the measurement sample 100 placed on the indented portion 753 and the transmission / reception coil 23 can be shortened. Therefore, the bobbin 75 is mounted and the nuclear magnetism as shown in FIG. If a resonance signal is received, the sensitivity can be improved. The inclined portion 751 shown in FIG. 8 is provided so that the measurement sample 100 can be easily placed when the bobbin 75 is mounted as shown in FIG.

  Next, the mounting of the bobbin 75 will be described with reference to FIG. FIG. 7A is a view in which the bobbin 75 is mounted, and FIG. 7B is a cross-sectional view taken along the line AA in FIG. 7A. The bobbin 75 shown in FIG. 7A is detachable from the spacer 71. If it does so, multiple can be prepared and replaced | exchanged according to the shape of the equal magnetic flux density surface of the part to measure of the measurement sample 100. FIG.

  As shown in FIG. 7B, a recess 753 similar to the recess 71a shown in FIG. 1 is formed at the center of the bobbin 75. The measurement sample 100 is placed on this portion, and the measurement sample 100 The measurement sample 100 is formed along the recessed portion 753. In this way, as shown in FIG. 7B, the indented portion 753 can be formed to have an equal magnetic flux density surface as shown in FIG. And it becomes possible to make the measurement sample 100 follow the hollow part 753 on this, and there exists an effect similar to the apparatus of 1st Embodiment mentioned above in FIGS.

  In addition, in the static magnetic field generating unit 20 of the apparatus of the third embodiment shown in FIG. 7A, a bobbin 75 is provided, and a recessed portion 71a is provided in the entire X-axis direction of the spacer 710 as shown in FIG. Although this is not considered, this is in consideration of the reception sensitivity of the transmission / reception coil 23. That is, since the reception sensitivity is originally low at the portion far from the transmission / reception coil 23, it does not significantly affect the improvement of the reception sensitivity of the entire apparatus, so the necessity of providing the recess 71a is low. However, the bobbin 75 may be formed longer in the X-axis direction than shown in FIG.

<Fourth Embodiment>
Next, the mechanical configuration of the magnetic resonance apparatus of the fourth embodiment according to the application of the first to third embodiments will be described with reference to FIG. FIG. 9 is an external configuration diagram of the apparatus of the fourth embodiment, and the basic configuration is the same as that of the apparatus described in Patent Document 1. Although the static magnetic field generator 20 is different from the apparatus of the above embodiment, the rest is the same, and the description of FIG. 1 and FIG. 2 is applied mutatis mutandis, and redundant description is omitted. Hereinafter, the sensor head 2 will be described with emphasis. As will be described below, the spacer 71, the pressing member 72, and the bobbin 75 shown in FIG. 7 can be applied almost as they are in the apparatus of the fourth embodiment (details are described in detail). (It will be described later.)

Hereinafter, the configuration and function of the sensor head 2 of the magnetic resonance apparatus of FIG. 9 will be described.
The sensor head 2 of the apparatus of FIG. 9 includes a static magnetic field generation unit 20, a transmission / reception coil 23, and a spacer 710 corresponding to the spacer 71 described in FIG.
9 (corresponding to FIG. 2 of the apparatus of the first embodiment. A permanent magnet 21c on a columnar shape fixed to a rotating shaft 28 rotatably supported, and this permanent magnet 21c. The peripheral surface of the magnet 20 is provided with a pair of yokes 22a and 22b disposed opposite to each other via upper and lower nonmagnetic materials 27a and 27b, and a motor 26 that rotates the permanent magnet 21c.
The permanent magnet 21c has a pair of magnetic poles in the circumferential direction. The rotation of the motor 26 can reduce magnetic field leakage when not in use.

As shown in FIG. 9, the pair of yokes 22a and 22b has a recess for storing a part of the circumference of the permanent magnet, and the permanent magnet 21c, the nonmagnetic bodies 27a and 27b, and the pair of yokes 22a and 22b. The gap is made very small so that the amount of leakage magnetic flux in this portion does not increase.
For the motor 26, for example, a stepping motor is used so that the rotation angle of the permanent magnet 21c can be accurately controlled. Also, use a high torque one that can rotate rapidly. The motor 26 is controlled using a motor drive unit (not shown), and the angle of the permanent magnet 21c is precisely controlled.

  As described above, by configuring the static magnetic field generation unit 20 of the apparatus of the fourth embodiment, a magnetic circuit is formed by the loop of the yoke 22a, the permanent magnet 21c, the yoke 22b, the nonmagnetic material 27a, and the yoke 22a. The In this apparatus, the magnetic field leaks from the periphery of the non-magnetic material 27a located on the upper surface of the sensor head 2 and the upper surfaces of the magnets 21a and 21b (the surface on which the spacer 71 is provided) above the permanent magnet 21c. A static magnetic field leaking from the upper surfaces of the yokes 22a and 22b is formed on the spacer 71 on which the sample is placed. A high-frequency magnetic field that satisfies the above-described predetermined relationship is applied to the static magnetic field from the transmission / reception coil 22. Thereby, a nuclear magnetic resonance signal is generated.

  As shown in FIG. 9, a transmitting / receiving coil 23 as a transmitting coil for receiving a resonance signal is disposed in the vicinity of the non-magnetic material 27a. In the apparatus according to the fourth embodiment, the transmitter / receiver coil 23, the recessed portion 71a and the raised portion 71c shown in FIG. 1 are provided in the vicinity of the nonmagnetic material 27a. Further, a replaceable bobbin as described in FIG. 7 may be provided.

  It is considered that the static leakage magnetic field as shown in FIG. 3 is also generated in the vicinity of the nonmagnetic material 27b in the yokes 22a and 22b and the yoke 22b of the apparatus of the fourth embodiment described above. The concave portion 71a can be provided, and the measurement sample 100 is placed along the surface of the equal magnetic flux density shown in FIGS. Further, depending on the shape of the isomagnetic flux surface, the raised portion 71c described with reference to FIG. 6 may be provided so that the measurement sample 100 is along the isomagnetic flux density surface.

  If the sample is measured in this manner, the same operation as the apparatus of the embodiment shown in FIGS. 1 to 8 occurs, and the effect can be exhibited. Therefore, the description of FIGS. 1 to 8 applies mutatis mutandis to the description of the configuration of the apparatus of the fourth embodiment. The correspondence in this case is as follows. That is, the spacer 710 corresponds to the spacer 71, the yoke 22a and the yoke 22b correspond to the magnets 21a and 21b in FIG. 1, respectively, and the nonmagnetic material 27a corresponds to the gap 105 between the magnets 21a and 21b in FIG. To do. The transmission / reception coil 23 in FIG. 9 corresponds to the transmission / reception coil 23 in FIG. 1.

The static magnetic field generation unit 20 shown in FIG. 9 corresponds to “static magnetic field generation means” of the present invention.
Moreover, the numerical value and shape shown by the above embodiment are examples, and do not limit the content of this invention.

1 is an external configuration diagram of a magnetic resonance apparatus according to a first embodiment and a method of using the magnetic resonance apparatus. 1 is an internal configuration diagram of a magnetic resonance apparatus of a first embodiment. When the value of a specific coordinate is fixed, the change of the magnetic flux density with respect to the axial direction indicated by the horizontal axis is shown. The graph which looked at the equal magnetic flux density surface from which a magnetic flux density becomes a specific value from the specific plane is shown. The explanatory view showing the method of concretely forming spacer 71 using the actual measurement value of the equal magnetic flux density surface is shown. The external appearance block diagram of the static magnetic field generation | occurrence | production part of the magnetic resonance apparatus of 2nd Embodiment which concerns on the application of the apparatus of 1st Embodiment is shown. The figure which mounted the bobbin which attaches and detaches a part of spacer of the magnetic resonance apparatus of 3rd Embodiment which concerns on the application of the apparatus of 1st, 2nd Embodiment, and a transmission / reception coil is shown. FIG. 6 shows a part diagram of a bobbin that allows a part of a spacer and a transmission / reception coil to be attached / detached in a magnetic resonance apparatus of a third embodiment. The external appearance block diagram of the apparatus of 4th Embodiment which concerns on the application of 1st-3rd embodiment is shown.

Explanation of symbols

2-sensor head 20-static magnetic field generator 21a-magnet, 21b-magnet, 21c-magnet 22-yoke 22a-yoke 22b-yoke 23-transmission / reception coil 24-sensor head support 25-guide rail 26-magnet rotation motor 27a 27b-Non-magnetic material 28-Rotating shaft 51-High frequency circuit system 511-Oscillation unit 512-Transmission unit 513-High frequency amplifier 52-Magnetic circuit system 53-Nuclear magnetic resonance signal reception unit 54-Operation processing system 541-Image reconstruction Unit 542-data processing unit 55-display unit 56-system control unit 57-operation unit 71-spacer 71a-indentation unit 71c-bulging unit 710-spacer 72-pressing member 72a-bulging unit 75-bobbin 751-inclined unit 752- Concave portion 753-recessed portion 100-measurement sample 100a-resonance region 100b-surface 100c-depth 100d-Measurement sample 102-Device front surface 103-Device rear surface 105-Gap 106-Inner end surface 107-Outer end surface

Claims (7)

In a magnetic resonance apparatus provided with a static magnetic field generating means for generating a surface leakage static magnetic field on the surface of a sensor head for measuring a nuclear magnetic resonance signal of a sample,
A magnetic resonance apparatus characterized in that a sample contact member having a surface having substantially the same shape as an isomagnetic flux surface corresponding to a magnetic flux density that causes a resonance state is provided on a sensor head surface.   The sample abutting member is characterized in that the distance between the isomagnetic flux density surface and the surface of the sample abutting member is set to a thickness that is a measurement depth of the nuclear magnetic resonance signal from the sample surface. The magnetic resonance apparatus according to 1.   3. The magnetic resonance apparatus according to claim 1, further comprising a pressing member that presses the sample against the surface of the sample contact member so that the surface of the sample is along the surface of the sample contact member.   The magnetic resonance apparatus according to claim 1, wherein the sample abutting member includes an exchange member that allows a portion including a surface having substantially the same shape as the isomagnetic flux density surface to be detachable.   The magnetic resonance apparatus according to claim 4, wherein the exchange member is provided with a receiving coil that receives the nuclear magnetic resonance signal. In a method of measuring a nuclear magnetic resonance signal of a sample placed in the surface leakage magnetic field by generating a surface leakage magnetic field on the sensor head surface by a static magnetic field generation means,
A sample abutting member having a surface having substantially the same shape as the isomagnetic flux surface corresponding to the magnetic flux density causing the resonance state is disposed on the sensor head surface,
A sample is disposed on the sample contact member;
The sample is sandwiched and pressed between the sample contact member and the pressing member so that the surface of the sample is along the surface of the sample contact member,
Next, a method of measuring a nuclear magnetic resonance signal, comprising measuring a nuclear magnetic resonance signal of a sample. In a method of measuring a nuclear magnetic resonance signal of a sample placed in the surface leakage magnetic field by generating a surface leakage magnetic field on the sensor head surface by a static magnetic field generation means,
A sample abutting member having a surface having substantially the same shape as the isomagnetic flux surface corresponding to the magnetic flux density causing the resonance state is disposed on the sensor head surface,
A sample is disposed on the sample contact member;
Press the sample against the sample abutting member along the surface of the sample abutting member,
Next, a method of measuring a nuclear magnetic resonance signal, comprising measuring a nuclear magnetic resonance signal of a sample.

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