MAGNETIC PARTICLE IMAGING DEVICE

Abstract

A magnetic particle imaging device comprises a detection coil (3) for detecting changes in the magnetism of magnetic particles (1), a compensating coil (4) which has a common central axis (CA) with the detection coil (3) and is connected to the detection coil (3) with opposite polarity, a first winding frame (21) for holding the detection coil (3), and a second winding frame (22) for holding the compensating coil (4). The distance between the detection coil (3) and the compensating coil (4) in one direction of the central axis (CA) is made variable by increasing or decreasing a contact section of the first winding frame (21) and the second winding frame (22).

Description

Magnetic Particle Imaging Device

[0001] The present disclosure relates to magnetic particle imaging devices.

[0002] 2. Description of the Related Art Conventionally, there has been known a configuration in which a compensation coil provided separately from a detection coil for detecting magnetism is made movable.

[0003] For example, in the magnetic sensor described in Patent Document 1, a thread is cut between the surface of the coil bobbin of the compensation coil and the inner wall of the coil bobbin of the excitation coil, and by rotating the compensation coil, the compensation coil can be moved slightly along the inside of the excitation coil.

[0004] Japanese Patent Application Publication No. 8-338864

[0005] In Patent Document 1, the compensation coil bobbin is brought into contact with the excitation coil bobbin, and the position of the compensation coil is changed while the excitation coil bobbin supports the compensation coil bobbin. Depending on the number of excitation coils, detection coils, and compensation coils, or their arrangement, it may not be possible to support the compensation coil bobbin by bringing it into contact with the excitation coil bobbin.

[0006] Therefore, an object of the present disclosure is to provide a magnetic particle imaging apparatus that can change the position of a compensation coil relative to a detection coil without the compensation coil former coming into contact with the excitation coil former.

[0007] A magnetic particle imaging device for determining the spatial distribution of magnetic particles in an inspection area of ​​an object to be inspected comprises an AC magnetic field application coil for generating an AC magnetic field that changes the magnetism of the magnetic particles, a DC magnetic field applicator for generating a region with a low magnetic field strength so as to change the magnetism of only the magnetic particles in a given region of the object to be inspected, a detection coil for detecting the change in magnetism of the magnetic particles, a compensation coil having a common central axis with the detection coil and connected with the detection coil in opposite polarity, a first bobbin for holding the detection coil, and a second bobbin for holding the compensation coil, wherein the distance between the detection coil and the compensation coil in the direction of the central axis can be changed by increasing or decreasing the contact area between the first bobbin and the second bobbin.

[0008] According to the present disclosure, the position of the compensation coil relative to the detection coil can be changed without the compensation coil bobbin coming into contact with the excitation coil bobbin.

[0009] 1A and 1B are diagrams showing the configuration of a magnetic particle imaging device according to a first embodiment. FIG. 1A is a diagram showing the AC magnetic field application coil 5, detection coil 3, and compensation coil 4 of the first embodiment as viewed from a certain direction. FIG. 1B is a diagram showing the AC magnetic field application coil 5, detection coil 3, and compensation coil 4 of the first embodiment as viewed from another direction. FIG. 1B is a diagram showing the structure of a first spool 21 and a second spool 22. FIG. 1C is a diagram showing the structure of the first spool 21 and the second spool 22. FIG. 1D is a diagram showing a state in which the first spool 21 and the second spool 22 are in contact with each other. FIG. 1E is a diagram showing the first spool 21 as viewed from another direction. FIG. 1F is a diagram showing the configuration of a magnetic particle imaging device according to a second embodiment. FIG. 1A is a diagram showing the AC magnetic field application coils 5a and 5b, detection coils 3a and 3b, and compensation coils 4a and 4b of the second embodiment as viewed from a certain direction. 1(b) is a view of the AC magnetic field applying coils 5a, 5b, the detection coils 3a, 3b, and the compensation coils 4a, 4b of embodiment 2, viewed from another direction. FIG. 1(b) is a view showing the structure of the first winding frame 42 and the second winding frame 62. FIG. 1(b) is a view showing the structure of the first winding frame 42 and the second winding frame 62. FIG. 1(b) is a view showing the state in which the first winding frame 42 and the second winding frame 62 are in contact with each other.

[0010] First Embodiment Fig. 1 is a diagram showing the configuration of a magnetic particle imaging apparatus according to a first embodiment.

[0011] A magnetic particle imaging device determines the spatial distribution of magnetic particles within an object under examination in an examination region.

[0012] The magnetic particle imaging apparatus comprises an AC magnetic field applicator 11 , a DC magnetic field applicator 6 , and a magnetization distribution measuring instrument 12 .

[0013] The AC magnetic field applicator 11 applies an AC magnetic field to an imaging region in which the object 2 to be inspected is placed. The AC magnetic field changes the magnetism of the magnetic particles 1. Specifically, the AC magnetic field applicator 11 includes an AC power supply 10 and an AC magnetic field applying coil 5 connected to the AC power supply 10 for exciting the AC magnetic field.

[0014] The DC magnetic field applicator 6 generates a region having a low magnetic field strength so as to change only the magnetism of the magnetic particles 1 in a given region of the object 2 to be inspected. Specifically, the DC magnetic field applicator 6 generates a low magnetic field region such as a linear zero approximation magnetic field region FFL to change the magnetism of the magnetic particles 1 contained in the object 2 to be inspected. The DC magnetic field applicator 6 forms the linear zero approximation magnetic field region FFL in the imaging region where the object 2 to be inspected is placed. The DC magnetic field applicator 6 is composed of, for example, two permanent magnets arranged facing each other with their magnetization directions opposite each other. Alternatively, the DC magnetic field applicator 6 may be two yoke-equipped permanent magnets whose magnetizations are opposed by the yoke, or an electromagnet.

[0015] The magnetization distribution measuring instrument 12 measures the change in magnetism of the magnetic particle 1. The magnetization distribution measuring instrument 12 includes a detection coil 3, a compensation coil 4, and a measuring instrument 13.

[0016] The detection coil 3 detects magnetic changes in the magnetic particles 1. The compensation coil 4 has a common central axis with the detection coil 3 and is connected with the detection coil 3 with opposite polarity. The winding directions of the detection coil 3 and the compensation coil 4 are opposite to each other. The compensation coil 4 makes it possible to cancel out and ignore the influence of the magnetic flux generated by the AC magnetic field application coil 5.

[0017] When magnetic particle imaging is performed, the measurement position is scanned by changing the relative position of the linear zero approximation magnetic field region FFL formed by the DC magnetic field applicator 6 with respect to the object under test 2. To change the relative position, there are two methods: one is to mechanically move the DC magnetic field applicator 6, the AC magnetic field applying coil 5, the detection coil 3, and the compensation coil 4, and the other is to mechanically move the object under test 2.

[0018] The signal generated in the detection coil 3 by the AC magnetic field applicator 11 is designated AC1, and the signal generated in the compensation coil 4 by the AC magnetic field applicator 11 is designated AC2.

[0019] The signal generated in the detection coil 3 by the magnetic particle 1 is designated as M1, and the signal generated in the compensation coil 4 by the magnetic particle 1 is designated as M2.

[0020] The signal V1 generated by the detection coil 3 is expressed as follows: V1=AC1+M1 (1) The signal V2 generated by the compensation coil 4 is expressed as follows: V1=AC1+M1 (1)

[0021] V 2 = AC 2 + M 2 (2) The measuring instrument 13 outputs a signal ΔV that represents the difference between the signal V 1 generated by the detection coil 3 and the signal V 2 generated by the compensation coil 4 .

[0022] ΔV=V1-V2=(AC1+M1)-(AC2+M2) (3) Figure 2(a) is a view of the AC magnetic field applying coil 5, detection coil 3, and compensation coil 4 of embodiment 1, viewed from a certain direction. Figure 2(b) is a view of the AC magnetic field applying coil 5, detection coil 3, and compensation coil 4 of embodiment 1, viewed from another direction.

[0023] The object under test 2 includes magnetic particles 1. An AC magnetic field applying coil 5 is arranged so as to sandwich the magnetic particles 1, the object under test 2, the detection coil 3, and the compensation coil 4.

[0024] The direction of the common central axis CA of the AC magnetic field application coil 5, detection coil 3, and compensation coil 4 is the X-axis direction. A magnetic particle 1 is disposed inside the detection coil 3. The direction of the line of the linear zero approximation magnetic field region FFL formed by the DC magnetic field application device 6 is the Y-axis direction.

[0025] In order to perform magnetic particle imaging, the DC magnetic field applicator 6, the AC magnetic field applying coil 5, the detection coil 3, and the compensation coil 4 are configured to be rotatable in the YZ plane so that the central axis CA of the coil and the linear zero approximation magnetic field region FFL rotate on the XY plane. Alternatively, the object 2 to be inspected containing the magnetic particles 1 may rotate in the YZ plane.

[0026] The magnetic imaging apparatus of this embodiment has a structure that allows the distance in the direction of the central axis CA between the detection coil 3 and the compensation coil 4 to be changed. Details of this will be described below.

[0027] 3 to 6 are diagrams illustrating a structure configured to enable the distance between the detection coil 3 and the compensation coil 4 in the direction of the central axis CA to be changed. FIGS. 3 and 4 are diagrams showing the structures of the first winding frame 21 and the second winding frame 22. FIG. 5 is a diagram showing a state in which the first winding frame 21 and the second winding frame 22 are in contact with each other. FIG. 6 is a diagram showing the first winding frame 21 as viewed from another direction.

[0028] The first spool 21 holds the detection coil 3. The second spool 22 holds the compensation coil 4. The first spool 21 and the second spool 22 are made of an insulating material. By increasing or decreasing the contact area between the first spool 21 and the second spool 22, the distance between the detection coil 3 and the compensation coil 4 in the direction of the central axis CA can be changed.

[0029] A more specific example configuration will be described below. The first winding frame 21 has a recess 23. The second winding frame 22 has a protrusion 24. The recess 23 and the protrusion 24 face each other. The central axis of the recess 23 and the protrusion 24 is CA. The recess 23 is formed in the direction of the central axis CA toward the second winding frame 22. The protrusion 24 is formed in the direction of the central axis CA toward the first winding frame 21. The side surfaces of the recess 23 and the side surfaces of the protrusion 24 come into contact with each other, and the degree to which the protrusion 24 enters the recess 23 can be changed, thereby increasing or decreasing the contact area between the first winding frame 21 and the second winding frame 22.

[0030] A first groove 26 is formed on the side surface of the protruding portion 24. That is, the protruding portion 24 is a male screw with a thread cut on the outer periphery. A second groove 25 is formed on the side surface of the recessed portion 23. That is, the recessed portion 23 is a female screw with a thread cut on the inner periphery.

[0031] The first groove 26 and the second groove 25 are formed in a spiral shape. With the crests of the first groove 26 and the troughs of the second groove 25 in contact with each other and the troughs of the first groove 26 and the crests of the second groove 25 in contact with each other, the convex portions 24 are pushed into the recesses 23 while rotating the convex portions 24, or pulled out of the recesses 23, thereby continuously changing the distance between the detection coil 3 and the compensation coil 4 in the direction of the central axis CA.

[0032] A viscous solid material, such as sealing tape, may be attached to the surfaces of the first groove 26 and the second groove 25. This can increase the position-retaining force.

[0033] Alternatively, one of the first winding frame 21 and the second winding frame 22 may be configured to be fixed in position, and the other may be configured to be variable in position.

[0034] For example, the first winding frame 21 may be fixed in position and the second winding frame 22 may be configured to be variable in position by fixing the first winding frame 21 to a winding frame (not shown) that holds the AC magnetic field applying coil 5. In this case, a moving surface of a region having a low magnetic field strength such as the linear zero approximation magnetic field region FFL is formed in the detection coil 3.

[0035] As described above, according to this embodiment, the distance between the detection coil 3 and the compensation coil 4 in the direction of the central axis CA can be changed by increasing or decreasing the contact area between the first winding frame 21 and the second winding frame 22. This makes it possible to change the position of the compensation coil 4 relative to the detection coil 3 without the second winding frame 22 that holds the compensation coil 4 coming into contact with the winding frame (not shown) that holds the AC magnetic field applying coil 5.

[0036] Modification of Embodiment 1 In the above embodiment, the first winding frame 21 has the recessed portion 23 and the second winding frame 22 has the protruding portion 24, but this is not limited to this. The first winding frame 21 may have the protruding portion 24 and the second winding frame 22 may have the recessed portion 23.

[0037] In the above embodiment, the second groove 25 is formed on the side surface of the recess 23 and the first groove 26 is formed on the side surface of the protrusion 24, but this is not limited to this. Grooves may not be formed on the side surfaces of the recess 23 and the protrusion 24, and the distance between the detection coil 3 and the compensation coil 4 in the direction of the central axis CA may be changed by inserting or removing the protrusion 24 into or from the recess 23 like a piston. This is because, even without grooves, the recess 23 and the protrusion 24 can be held in position by friction or a fixing screw to prevent displacement.

[0038] In the above embodiment, the second spiral groove 25 is formed on the side surface of the recessed portion 23, and the first spiral groove 26 is formed on the side surface of the protruding portion 24, thereby allowing the distance between the detection coil 3 and the compensation coil 4 to be continuously changed, but this is not limitative. The distance between the detection coil 3 and the compensation coil 4 may also be changed in several stages.

[0039] Embodiment 2. Figure 7 is a diagram showing the configuration of a magnetic particle imaging apparatus according to embodiment 2. The magnetic particle imaging apparatus comprises a DC magnetic field applicator 6, an AC magnetic field applicator 11A, and a magnetization distribution measuring instrument 12A.

[0040] The AC magnetic field applicator 11A applies an AC magnetic field to an imaging region in which the object to be inspected 2 is placed. The AC magnetic field applicator 11A includes an AC power supply 10 and an AC magnetic field application coil pair 51 connected to the AC power supply 10 to excite an AC magnetic field. The AC magnetic field application coil pair 51 includes AC magnetic field application coils 5a and 5b connected in series.

[0041] The magnetization distribution measuring instrument 12A measures magnetic changes of magnetic particles. The magnetization distribution measuring instrument 12A includes a detection coil pair 31, a compensation coil pair 41, and a measuring instrument 13A. The detection coil pair 31 is made up of detection coils 3a and 3b connected in series. The compensation coil pair 41 is made up of compensation coils 4a and 4b connected in series.

[0042] The detection coils 3a and 3b detect magnetic changes in the magnetic particles 1. The compensation coils 4a and 4b share a common central axis CB with the detection coils 3a and 3b and are connected with the detection coils 3a and 3b with opposite polarity. The winding directions of the detection coils 3a and 3b and the compensation coils 4a and 4b are opposite to each other. The compensation coils 4a and 4b can cancel out and ignore the influence of the magnetic flux generated by the AC magnetic field application coils 5a and 5b.

[0043] When magnetic particle imaging is performed, the measurement position is scanned by changing the relative position of the linear zero approximation magnetic field region FFL formed by the DC magnetic field applicator 6 with respect to the object under test 2. To change the relative position, there are two methods: one is to mechanically move the DC magnetic field applicator 6, the AC magnetic field applying coil pair 51, the detection coil pair 31, and the compensation coil pair 41, and the other is to mechanically move the object under test 2.

[0044] The signal generated by the AC magnetic field applicator 11A in the detection coil pair 31 is designated AC1, and the signal generated by the AC magnetic field applicator 11A in the compensation coil pair 41 is designated AC2.

[0045] A signal generated in the detection coil pair 31 by the magnetic particle 1 is designated as M1, and a signal generated in the compensation coil pair 41 by the magnetic particle 1 is designated as M2.

[0046] A signal V1 generated by the detection coil pair 31 is expressed as follows: V1=AC1+M1 (1) A signal V2 generated by the compensation coil pair 41 is expressed as follows: V1=AC1+M1 (1)

[0047] V 2 = AC 2 + M 2 (2) The measuring instrument 13 A outputs a signal ΔV that represents the difference between the signal V 1 generated by the detection coil pair 31 and the signal V 2 generated by the compensation coil pair 41 .

[0048] ΔV=V1-V2=(AC1+M1)-(AC2+M2) (3) Fig. 8(a) is a view showing the AC magnetic field applying coils 5a, 5b, detection coils 3a, 3b, and compensation coils 4a, 4b of embodiment 2 as viewed from a certain direction. Fig. 8(b) is a view showing the AC magnetic field applying coils 5a, 5b, detection coils 3a, 3b, and compensation coils 4a, 4b of embodiment 2 as viewed from another direction.

[0049] A detection coil pair 31 is arranged to sandwich the magnetic particle 1 and the test object 2 containing the magnetic particle 1. The detection coil pair 31 includes detection coils 3a and 3b. The detection coil 3a and the detection coil 3b sandwich the magnetic particle 1 and the test object 2.

[0050] A compensation coil pair 41 is arranged to sandwich the magnetic particle 1, the object to be inspected 2, and the detection coil pair 31. The compensation coil pair 41 includes compensation coils 4a and 4b. The compensation coil 4a and the compensation coil 4b sandwich the magnetic particle 1, the object to be inspected 2, the detection coil 3a, and the detection coil 3b.

[0051] An AC magnetic field application coil pair 51 is arranged to sandwich the magnetic particle 1, the object 2, the detection coil pair 31, and the compensation coil pair 41. The AC magnetic field application coil pair 51 includes AC magnetic field application coils 5a and 5b. The AC magnetic field application coil 5a and the AC magnetic field application coil 5b sandwich the magnetic particle 1, the object 2, the detection coil 3a, the detection coil 3b, the compensation coil 4a, and the compensation coil 4b.

[0052] The AC magnetic field application coil pair 51, the detection coil pair 31, and the compensation coil pair 41 share a common central axis CB. The direction of the AC magnetic field is the first direction (X-axis direction). Axes perpendicular to the X-axis are the Y-axis and the Z-axis.

[0053] The line direction of the linear zero approximation magnetic field region FFL formed by the DC magnetic field applicator 6 can be approximately parallel to the first direction (X-axis direction). That is, the angle between the line direction of the linear zero approximation magnetic field region FFL and the first direction (X-axis direction) can be in the range of ±5°. More preferably, the line direction of the linear zero approximation magnetic field region FFL may be the first direction (X-axis direction). Furthermore, the basic position of the linear zero approximation magnetic field region FFL overlaps with the common central axis CB.

[0054] The distance between the AC magnetic field applying coil 5a and the AC magnetic field applying coil 5b is D1. The distance between the compensation coil 4a and the compensation coil 4b is D2. The distance between the detection coil 3a and the detection coil 3b is D3, where D1 > D2 > D3. The coil radius of the AC magnetic field applying coil 5a and the AC magnetic field applying coil 5b is R1. The coil radius of the compensation coil 4a and the compensation coil 4b is R2. The coil radius of the detection coil 3a and the detection coil 3b is R3, where R1 > R2 = R3.

[0055] In order to perform magnetic particle imaging, the DC magnetic field applicator 6, the AC magnetic field applying coil pair 51, the detection coil pair 31, and the compensation coil pair 41 are configured to be rotatable within the XZ plane so that the central axis CB, the direction of the AC magnetic field, and the linear zero approximation magnetic field region FFL rotate on the XZ plane. Alternatively, the object 2 to be inspected containing the magnetic particles 1 may rotate within the XZ plane.

[0056] To perform magnetic particle imaging, the DC magnetic field applicator 6 is moved so that the linear zero approximation magnetic field region FFL not only rotates but also translates left and right about the basic position.

[0057] The magnetic imaging apparatus of this embodiment has a structure that allows the distance between the detection coil 3a and the compensation coil 4a in the direction of the central axis CB to be changed, as will be described in detail below.

[0058] 9 to 11 are diagrams illustrating a structure configured to enable the distance between the detection coil 3a and the compensation coil 4a in the direction of the central axis CB to be changed. Figures 9 and 10 are diagrams illustrating the structures of the first winding frame 42 and the second winding frame 62. Figure 11 is a diagram illustrating a state in which the first winding frame 42 and the second winding frame 62 are in contact with each other.

[0059] The first winding frame 42 holds the detection coil 3a, the detection coil 3b, and the compensation coil 4b. The second winding frame 62 holds the compensation coil 4a. The first winding frame 42 and the second winding frame 62 are made of an insulating material. The first winding frame 42 has a protrusion 34. The second winding frame 62 has a recess 33. The protrusion 34 and the recess 33 face each other. The central axes of the recess 33 and the protrusion 34 are CB. The protrusion 34 is formed in the direction of the central axis CB toward the second winding frame 62. The recess 33 is formed in the direction of the central axis CB toward the first winding frame 42. The side surfaces of the protrusion 34 and the side surfaces of the recess 33 come into contact with each other, and the degree of penetration of the protrusion 34 into the recess 33 is variable, so that the contact area between the first winding frame 42 and the second winding frame 62 can be increased or decreased.

[0060] A first groove 36 is formed on the side surface of the protruding portion 34. That is, the protruding portion 34 is a male screw with a thread cut on the outer periphery. A second groove 35 is formed on the side surface of the recessed portion 33. That is, the recessed portion 33 is a female screw with a thread cut on the inner periphery. The first groove 36 and the second groove 35 are formed in a spiral shape.

[0061] With the crests of the first grooves 36 and the valleys of the second grooves 35 in contact and the valleys of the first grooves 36 and the crests of the second grooves 35 in contact, the convex portions 34 are rotated and pushed into or pulled out of the recesses 33, thereby continuously changing the distance between the detection coil 3a and the compensation coil 4a in the direction of the central axis CB. The distance between the detection coil 3b and the compensation coil 4a in the direction of the central axis CB and the distance between the compensation coils 4a and 4b in the direction of the central axis CB also continuously changes.

[0062] A viscous solid material, such as sealing tape, may be attached to the surfaces of the first groove 36 and the second groove 35. This can increase the position-retaining force.

[0063] Alternatively, one of the first reel 42 and the second reel 62 may be configured to be fixed in position, while the other may be configured to be variable in position.

[0064] For example, the position of the first winding frame 42 may be fixed, and the position of the second winding frame 62 may be configured to be variable. In this case, a moving surface of a region having a low magnetic field strength such as a linear zero approximation magnetic field region FFL is formed in the detection coils 3 a, 3 b.

[0065] As described above, according to this embodiment, the distance between the detection coil 3a and the compensation coil 4a in the direction of the central axis CB can be changed by increasing or decreasing the contact area between the first winding frame 42 and the second winding frame 62. This makes it possible to change the position of the compensation coil 4a relative to the detection coil 3a without the second winding frame 62 that holds the compensation coil 4a coming into contact with the winding frames (not shown) that hold the AC magnetic field application coils 5a and 5b.

[0066] The above-described embodiments can be combined as appropriate. The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0067] 1 magnetic particle, 2 object to be inspected, 3, 3a, 3b detection coil, 4, 4a, 4b compensation coil, 5, 5a, 5b AC magnetic field application coil, 6 DC magnetic field applicator, 10 AC power supply, 11, 11A AC magnetic field applicator, 12, 12A magnetization distribution measuring instrument, 13, 13A measuring instrument, 21, 42 first winding frame, 22, 62 second winding frame, 23, 33 recess, 24, 34 protrusion, 25, 35 second groove, 26, 36 first groove, 31 detection coil pair, 41 compensation coil pair, 51 AC magnetic field application coil pair, CA, CB central axis, FFL linear zero approximation magnetic field region.

Claims

1. A magnetic particle imaging device for determining the spatial distribution of magnetic particles in an inspection area within an object to be inspected, comprising: an AC magnetic field application coil for generating an AC magnetic field that changes the magnetism of the magnetic particles; a DC magnetic field applicator that generates a region with a low magnetic field strength so as to change only the magnetism of the magnetic particles in any region of the object to be inspected; a detection coil for detecting the magnetic change of the magnetic particles; a compensation coil having a common central axis with the detection coil and connected with opposite polarity to the detection coil; a first winding frame that holds the detection coil; and a second winding frame that holds the compensation coil, wherein the magnetic particle imaging device is configured to be able to change the distance between the detection coil and the compensation coil in the direction of the central axis by increasing or decreasing the contact area between the first winding frame and the second winding frame.

2. A magnetic particle imaging device as described in claim 1, wherein one of the first and second winding frames has a convex portion, and the other of the first and second winding frames has a concave portion, the side of the convex portion contacts the side of the concave portion, and the degree to which the convex portion penetrates into the concave portion is changeable.

3. A magnetic particle imaging device according to claim 2, wherein a first groove is formed on a side surface of said convex portion, and a second groove is formed on a side surface of said concave portion.

4. A magnetic particle imaging device according to claim 3, wherein said first groove and said second groove are formed in a spiral shape.

5. A magnetic particle imaging apparatus according to claim 3 or 4, wherein a viscous solid material is attached to the surfaces of said first groove and said second groove.

6. A magnetic particle imaging device according to any one of claims 2 to 5, wherein one of the first and second winding frames is fixed in position, and the other is configured to be variable in position.

7. A magnetic particle imaging apparatus according to claim 6, wherein the position of said first spool is fixed and the position of said second spool is variable.

8. A magnetic particle imaging apparatus as claimed in claim 7, wherein said detection coil defines a moving surface of an area having low magnetic field strength.

9. A magnetic particle imaging apparatus according to any one of claims 1 to 8, further comprising a measuring instrument which outputs a signal representing the difference between a signal measured by the detection coil and a signal measured by the compensation coil.

10. A magnetic field applying device comprising: a first AC magnetic field applying coil and a second AC magnetic field applying coil; a first detection coil and a second detection coil connected in series as the detection coils; and a first compensation coil and a second compensation coil connected in series as the compensation coils; the first detection coil, the second detection coil, the first compensation coil, and the second compensation coil have a common central axis; the first detection coil and the second detection coil are arranged so as to sandwich the magnetic particle; the first compensation coil and the second compensation coil are arranged so as to sandwich the magnetic particle and the first detection coil and the second detection coil; the first AC magnetic field applying coil and the second AC magnetic field applying coil are arranged so as to sandwich the magnetic particle, the first detection coil, the second detection coil, the first compensation coil, and the second compensation coil; the first spool holds the first detection coil, the second detection coil, and the second compensation coil; 2. The magnetic particle imaging device according to claim 1, wherein the second winding form holds the first compensation coil, and the distance between the first detection coil and the first compensation coil in the direction of the central axis is changed by increasing or decreasing the contact area between the first winding form and the second winding form.

11. A magnetic particle imaging device as described in claim 10, comprising a measuring instrument that outputs a signal representing the difference between a signal measured by the first detection coil and the second detection coil and a signal measured by the first compensation coil and the second compensation coil.

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