Magnetic particle imaging device

Abstract

This magnetic micro-particle imaging device (100) comprises: a holding unit (1) which holds a subject (S); a static magnetic field generator (2) which generates a linear nonmagnetic area (FFL) that passes the subject held by the holding unit (1); an AC magnetic field application coil (3A) which applies an AC magnetic field to the nonmagnetic field area; and a measurement coil (4) for acquiring, as a signal, magnetization variations of magnetic micro-particles within the nonmagnetic field area. The measurement coil has an axis AX4 parallel to the direction of the AC magnetic field. In a third direction (C), which is orthogonal to each of the extending direction of the axis and the extending direction of the nonmagnetic field area, the relative positions of the holding unit, the AC magnetic application coil, and the measurement coil are established. The holding unit, the AC magnetic field application coil, and the measurement coil integrally and relatively move in the third direction (C) with respect to the static magnetic field generator.

Description

[Technical field]

[0001] The present disclosure relates to a magnetic particle imaging device. [Background technology]

[0002] 2. Description of the Related Art Magnetic particle imaging (MPI: Magnetic Resonance Imaging) devices are known that image the distribution of magnetic particles (such as superparamagnetic iron oxide) injected into a subject's body.

[0003] In a magnetic particle imaging device, a linear field free line (FFL) is formed that passes through a portion of the test object, and an alternating magnetic field is applied to the field free line. If magnetic particles are present in the field free line of the test object, the magnetization of the magnetic particles fluctuates periodically due to the alternating magnetic field, and an induced electromotive force is generated in a measurement coil arranged around the test object. As a result, the presence of the magnetic particles in the field free line is detected by the measurement coil as an induced electromotive force or its change generated in the measurement coil.

[0004] In the magnetic particle imaging apparatus, one of the object to be inspected and the magnetic field-free region is moved relative to the other, so that the distribution of magnetic particles within the object to be inspected can be imaged.

[0005] A magnetic particle imaging device is known in which an object to be inspected and a measurement coil are moved (scanned) together in a magnetic field-free region and an alternating magnetic field (for example, Kenya Murase et al., Japanese Journal of Applied Physics 53, 067001 (2014) (Non-Patent Document 1)). [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Kenya Murase et al., “Development of a system for magnetic particle imaging using neodymium magnets and gradiometer”, Japanese Journal of Applied Physics 53, 067001 (2014) Summary of the Invention [Problem to be solved by the invention]

[0007] In the magnetic particle imaging device described in Non-Patent Document 1, the relative positional relationship between the test object and the measurement coil in the non-magnetic field area and the AC magnetic field changes, and the measurement sensitivity of magnetic particles changes significantly depending on these relative positional relationships. In other words, in the magnetic particle imaging device of Non-Patent Document 1, the measurement sensitivity of magnetic particles is highly position dependent.

[0008] A primary object of the present disclosure is to provide a magnetic particle imaging apparatus in which the position dependency of the measurement sensitivity of magnetic particles is reduced compared to conventional magnetic particle imaging apparatuses. [Means for solving the problem]

[0009] The magnetic particle imaging device according to the present disclosure includes a holder for holding an object to be inspected, a static magnetic field generator for generating a linear non-magnetic field region passing through the object to be inspected held in the holder, an AC magnetic field applying coil for applying an AC magnetic field to the non-magnetic field region, and a measurement coil for acquiring magnetization fluctuations of magnetic particles in the non-magnetic field region as a signal. The measurement coil has an axis parallel to the direction of the AC magnetic field. The relative positions of the holder, the AC magnetic field applying coil, and the measurement coil are determined in directions perpendicular to both the extension direction of the axis and the extension direction of the non-magnetic field region. The holder, the AC magnetic field applying coil, and the measurement coil move together relative to the static magnetic field generator in a direction perpendicular to the axis. Effect of the Invention

[0010] According to the present disclosure, it is possible to provide a magnetic particle imaging device in which the position dependency of the measurement sensitivity of magnetic particles is reduced compared to conventional magnetic particle imaging devices. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram for explaining a magnetic particle imaging device according to a first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view taken along the line II-II in FIG. [Diagram 3] FIG. 3 is a cross-sectional view taken along the line of arrows III-III in FIG. [Figure 4] FIG. 2 is a diagram for explaining a drive mechanism of the magnetic particle imaging device according to the first embodiment. [Diagram 5] FIG. 4 is a diagram for explaining the radial sensitivity distribution of a measurement coil in the magnetic particle imaging apparatus shown in FIGS. 1 to 3. [Figure 6] FIG. 4 is a diagram for explaining the sensitivity distribution in the axial direction of a measurement coil in the magnetic particle imaging apparatus shown in FIGS. 1 to 3. [Figure 7] FIG. 11 is a cross-sectional view for explaining a magnetic particle imaging device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are given the same reference numerals and the description thereof will not be repeated. For convenience of explanation, each drawing shows an orthogonal coordinate system having a first direction A, a second direction B, and a third direction C that are mutually orthogonal.

[0013] In the present embodiment, when geometric terms and terms expressing positional and directional relationships, such as "parallel," "orthogonal," "coaxial," and "along" are used, these terms allow for manufacturing errors or slight variations.

[0014] Embodiment 1 1 to 4, a magnetic particle imaging device 100 according to the first embodiment is a device for performing magnetic particle imaging (hereinafter, also simply referred to as MPI) using a linear magnetic field free region FFL (hereinafter, also simply referred to as FFL) passing through the test subject S. In this embodiment, MPI means measuring whether or not magnetic particles (such as superparamagnetic iron oxide) are present in the magnetic field free region FFL passing through the test subject S, or imaging the distribution of magnetic particles in a specific region of the test subject S by performing the above measurement while changing the relative positional relationship of the magnetic field free region FFL with respect to the test subject S.

[0015] As shown in FIGS. 1 to 4, the magnetic particle imaging apparatus 100 includes a fixing section (holding section) 1, a static magnetic field generator 2, an AC magnetic field applicator 3, a measuring coil 4, a driving mechanism 5, a control section 6, and a measuring instrument .

[0016] The holder 1 is provided to hold the subject S. The holder 1 is, for example, a cylindrical member that houses the subject S therein. The holder 1 has a central axis AX1 extending along a first direction A. The subject S is, for example, a human or an animal.

[0017] The static magnetic field generator 2 is provided to generate a linear non-magnetic field region FFL passing through the subject S held by the holding unit 1. The non-magnetic field region FFL is ideally a region where the intensity of the static magnetic field is zero. The non-magnetic field region FFL may be a region where the static magnetic field is not saturated at least when the AC magnetic field is not applied by the AC magnetic field applicator 3. The intensity of the static magnetic field of the non-magnetic field region FFL may be greater than zero. The non-magnetic field region FFL extends along the second direction B. The linear non-magnetic field region FFL is ideally a straight non-magnetic field region, but may also be an approximately cylindrical region having a width in the radial direction relative to the extension direction.

[0018] As shown in Figs. 1 and 2, the static magnetic field generator 2 is composed of, for example, two permanent magnets arranged with the same magnetic poles facing each other. The magnetic poles of each of the two permanent magnets are oriented along the third direction C. The two permanent magnets of the static magnetic field generator 2 are arranged with a gap between them in the third direction C. The two permanent magnets are arranged to sandwich the holding unit 1, the AC magnetic field application coil 3A of the AC magnetic field applicator 3, and the measurement coil 4 in the third direction C. The two permanent magnets are arranged to generate a magnetic field-free region FFL in the center of the third direction C between the two permanent magnets.

[0019] The static magnetic field generator 2 may be composed of, for example, two electromagnets. The AC magnetic field applying device 3 includes an AC magnetic field applying coil 3A and an AC power source 3B. The AC magnetic field applying coil 3A is provided to apply an AC magnetic field to the magnetic field free region FFL. In other words, the AC magnetic field applying coil 3A is provided to vary the magnetization of the magnetic particles in the magnetic field free region FFL. The AC magnetic field applying coil 3A is connected to the AC power source 3B. The AC magnetic field applying coil 3A is provided so that the direction of the AC magnetic field is along the first direction A.

[0020] 1 and 3, the AC magnetic field applying coil 3A has a central axis AX3 extending along the first direction A. The AC magnetic field applying coil 3A is disposed outside the holding unit 1 in a radial direction relative to the central axis AX3, and is wound around the holding unit 1. The AC magnetic field applying coil 3A is disposed, for example, between two permanent magnets of the static magnetic field generator 2 in the third direction C. The AC magnetic field applying coil 3A is formed, for example, of one solenoid coil.

[0021] The measurement coil 4 is provided to acquire the magnetization fluctuation of the magnetic particles in the non-magnetic field region FFL passing through the test subject S as a signal. The measurement coil 4 has a central axis AX4 parallel to the direction of the AC magnetic field. The central axis AX4 extends along the first direction A. The measurement coil 4 is disposed outside the holder 1 and inside the AC magnetic field applying coil 3A in the radial direction of the central axis AX4. The AC magnetic field applying coil 3A and the measurement coil 4 are disposed, for example, on the same axis. The central axis AX3 of the AC magnetic field applying coil 3A is disposed so as to overlap with the central axis AX4 of the measurement coil 4. Each of the central axis AX3 and the central axis AX4 is disposed so as to overlap with the central axis AX1 of the holder 1.

[0022] As shown in FIG. 3, the measurement coil 4 includes, for example, a first coil portion 4A and a second coil portion 4B. The first coil portion 4A and the second coil portion 4B have an electrically symmetrical structure with respect to the center of the first direction A of the AC magnetic field applying coil 3A. In other words, the first coil portion 4A and the second coil portion 4B are provided so as to remove induced electromotive force and environmental magnetic noise generated from the AC magnetic field applied to the measurement coil 4 by the AC magnetic field applying coil 3A. Specifically, the first coil portion 4A and the second coil portion 4B are, for example, electrically connected to each other in series and arranged in plane symmetry with respect to the center of the first direction A of the AC magnetic field applying coil 3A. The first coil portion 4A and the second coil portion 4B have the same configuration (number of coil turns, coil radius, etc.). Each of the first coil portion 4A and the second coil portion 4B is arranged on the same axis (center axis AX4). Each of the first coil portion 4A and the second coil portion 4B is configured as, for example, one solenoid coil.

[0023] Each of the first coil portion 4A and the second coil portion 4B of the measurement coil 4 is wound around the holding unit 1. At least a portion of the first coil portion 4A is arranged so as to overlap the test object S held by the holding unit 1 in the radial direction relative to the central axis AX4. The entirety of the second coil portion 4B is arranged so as not to overlap the test object S held by the holding unit 1 in the radial direction relative to the central axis AX4.

[0024] Each of the first coil portion 4A and the second coil portion 4B of the measurement coil 4 is disposed inside the AC magnetic field applying coil 3A. Each of the first coil portion 4A and the second coil portion 4B of the measurement coil 4 is disposed between the static magnetic field generators 2 in the third direction C.

[0025] The driving mechanism 5 drives the holding unit 1, the AC magnetic field applying coil 3A, and the measurement coil 4. The driving mechanism 5 includes a first stage 11, a second stage 12, a first driving unit 21, a second driving unit 22, and a third driving unit .

[0026] The first stage 11 supports the holding unit 1 so as to be rotatable around the central axis AX1. The holding unit 1 is supported by the first stage 11 so as to be rotatable around the central axis AX1. The first stage 11 has, for example, a first portion 11A extending along a first direction A and a pair of second portions 11B extending along a second direction B from both ends of the first portion in the first direction A. The pair of second portions 11B are provided so as to support both ends of the holding unit 1 in the first direction A. A first driving unit 21 for rotating the holding unit 1 around the central axis AX1 is fixed to at least one of the pair of second portions 11B.

[0027] The second stage 12 supports the first stage 11 so as to be movable in the first direction A. The first stage 11 is supported by the second stage 12 so as to be movable in the first direction A. The first stage 11 is provided so as to move relatively to the second stage 12 only in the first direction A. The second stage 12 has, for example, an annular portion 12A through which the first portion 11A of the first stage 11 passes. The AC magnetic field applying coil 3A and the measurement coil 4 are each fixed to the annular portion 12A of the second stage 12. A second driving unit 22 for moving the first stage 11 in the first direction A is fixed to the second stage 12.

[0028] The pedestal 13 supports the pedestal 13 so as to be movable in a third direction C. The second stage 12 is supported by the pedestal 13 so as to be movable in the third direction C. The static magnetic field generator 2 is fixed to the pedestal 13. A third drive unit 23 for moving the second stage 12 in the third direction C is fixed to the pedestal 13.

[0029] The drive mechanism 5 allows each of the holder 1, static magnetic field generator 2, AC magnetic field applying coil 3A, and measurement coil 4 to move as follows.

[0030] The relative positions of the static magnetic field generator 2, the AC magnetic field applying coil 3A, and the measurement coil 4 are determined in the first direction A. The holding unit 1 moves relative to the static magnetic field generator 2, the AC magnetic field applying coil 3A, and the measurement coil 4 in the first direction A. Of the holding unit 1, the AC magnetic field applying coil 3A, and the measurement coil 4, only the holding unit 1 moves in the first direction A.

[0031] The relative positions of the holding unit 1, the AC magnetic field applying coil 3A, and the measurement coil 4 are determined in the second direction B. The relative positions of the holding unit 1, the static magnetic field generator 2, the AC magnetic field applying coil 3A, and the measurement coil 4 are determined in the second direction B.

[0032] The relative positions of the holding unit 1, the AC magnetic field applying coil 3A, and the measurement coil 4 are determined in the third direction C. The holding unit 1, the AC magnetic field applying coil 3A, and the measurement coil 4 move together with each other in the third direction C relative to the static magnetic field generator 2.

[0033] In the circumferential direction about the central axis AX1, the relative position of the measurement coil 4 with respect to the AC magnetic field applying coil 3A is fixed. Of the holding unit 1, the AC magnetic field applying coil 3A, and the measurement coil 4, only the holding unit 1 moves (rotates) in the circumferential direction about the central axis AX1.

[0034] The control unit 6 is connected to each of the first driving unit 21, the second driving unit 22, and the third driving unit 23 of the driving mechanism 5, and controls each of the first driving unit 21, the second driving unit 22, and the third driving unit 23 of the driving mechanism 5. The control unit 6 controls the relative position of the subject S with respect to the magnetic field free region FFL.

[0035] The measuring instrument 7 is connected to the measuring coil 4. The measuring instrument 7 measures the signal acquired by the measuring coil 4. The measuring instrument 7 is provided to measure whether or not magnetic particles are present in the non-magnetic field region FFL through which the test object S passes, or to perform the above measurement while changing the relative positional relationship of the non-magnetic field region FFL with respect to the test object S, thereby imaging the distribution of magnetic particles in a specific region of the test object S. The measuring instrument 7 includes, for example, a lock-in amplifier. The lock-in amplifier is connected to the AC power source 3B of the AC magnetic field applicator 3, and a reference signal having the same frequency and phase as the AC magnetic field is input to the lock-in amplifier. The lock-in amplifier extracts the signal of the magnetic particles from the measurement signal input from the measuring coil 4 based on the reference signal, and outputs the extracted signal.

[0036] <Examples of use of magnetic particle imaging device> The magnetic particle imaging device 100 is used for the above-mentioned MPI. When measuring whether or not magnetic particles are present in a linear magnetic field free region FFL passing through the specimen S, the magnetic particle imaging device 100 can be used as follows.

[0037] First, a region to be measured in the test subject S is determined. This determines the relative position that the holding part 1 should take with respect to the non-magnetic field region FFL in the first direction A and the third direction C, and the relative angle that the holding part 1 should take with respect to the non-magnetic field region FFL in the circumferential direction about the central axis AX1.

[0038] Next, the determined relative position and the determined relative angle are realized. Specifically, the holding unit 1, the AC magnetic field applying coil 3A, and the measurement coil 4 move together in the third direction C relative to the static magnetic field generator 2. The holding unit 1 moves in the first direction A relative to the static magnetic field generator 2, the AC magnetic field applying coil 3A, and the measurement coil 4, and further moves (rotates) in the circumferential direction relative to the static magnetic field generator 2, the AC magnetic field applying coil 3A, and the measurement coil 4.

[0039] Next, the above measurement is performed. Specifically, the AC magnetic field applying coil 3A is energized, and an AC magnetic field is applied to the magnetic field free region FFL. If magnetic particles exist in the magnetic field free region FFL, the magnetization of the magnetic particles is changed by the AC magnetic field, and an induced electromotive force is generated in the measurement coil 4 due to this magnetization change. On the other hand, if no magnetic particles exist in the magnetic field free region FFL, no induced electromotive force is generated in the measurement coil 4 due to the magnetization change of the magnetic particles. As a result, in the magnetic particle imaging device 100, magnetic particles existing in the magnetic field free region FFL are detected as an induced electromotive force generated in the measurement coil 4 or a change therein.

[0040] Furthermore, when imaging the distribution of magnetic particles within the test specimen S, the magnetic particle imaging device 100 can be used in a procedure basically similar to that for measuring whether or not magnetic particles are present within a linear magnetic field free region FFL passing through the test specimen S, but the above measurement is performed while changing the relative positional relationship of the magnetic field free region FFL to the test specimen S (the relative position in the first direction A and the third direction C or the relative angle in the circumferential direction).

[0041] <Effects> The strength of the alternating magnetic field applied by the alternating magnetic field applying coil to the non-magnetic field region FFL changes depending on the relative position of the non-magnetic field region FFL with respect to the alternating magnetic field applying coil. In other words, the strength of the alternating magnetic field applied by the alternating magnetic field applying coil to the non-magnetic field region FFL represents a spatial distribution. Furthermore, the measurement sensitivity of the magnetization fluctuation of the magnetic particles by the measurement coil changes depending on the relative position of the magnetic particles (non-magnetic field region FFL) with respect to the measurement coil, even if the strength of the alternating magnetic field applied by the alternating magnetic field applying coil to the non-magnetic field region FFL is uniform relative to the position of the non-magnetic field region FFL with respect to the alternating magnetic field applying coil. In other words, the above measurement sensitivity of the measurement coil also represents a spatial distribution.

[0042] Therefore, as described above, in the comparative magnetic particle imaging device in which the relative positional relationships of the test object and the measurement coil with respect to the no-magnetic field region and the AC magnetic field change, the measurement sensitivity of magnetic particles is influenced by the overlapping effects of the above-mentioned spatial portion of the AC magnetic field applying coil and the above-mentioned spatial distribution of the measurement coil, and changes depending on the relative position of the no-magnetic field region FFL with respect to each of the AC magnetic field applying coil and the measurement coil.

[0043] In contrast to this, in the magnetic particle imaging device 100, the relative positions of the holding unit 1, the AC magnetic field applying coil 3A, and the measurement coil 4 are determined in the second direction B and the third direction C. The holding unit 1, the AC magnetic field applying coil 3A, and the measurement coil 4 move together relative to the static magnetic field generator 2 in the third direction C. Therefore, in the magnetic particle imaging device 100, the position dependency of the measurement sensitivity of magnetic particles is reduced compared to the magnetic particle imaging device according to the comparative example.

[0044] In addition, in the magnetic particle imaging device according to the comparative example, when the object under test and the measurement coil move relative to the AC magnetic field applying coil, if the object under test and the measurement coil vibrate or wobble, the relative positions of the object under test and the measurement coil to the stationary AC magnetic field applying coil and the AC magnetic field change, and an induced electromotive force due to the vibration or wobble is generated in the measurement coil. Therefore, in the magnetic particle imaging device according to the comparative example, the vibration or wobble of the object under test and the measurement coil is measured as noise, making it difficult to improve the measurement accuracy.

[0045] In contrast, in the magnetic particle imaging device 100, the holder 1, the AC magnetic field applying coil 3A, and the measurement coil 4 move as a unit in the third direction C, so that even if the holder 1, the AC magnetic field applying coil 3A, and the measurement coil 4 vibrate or wobble as a unit, the relative positions of the test object S, the AC magnetic field applying coil 3A, and the measurement coil 4 do not change, and therefore no induced electromotive force due to this vibration or wobble is generated in the measurement coil 4. Therefore, in the magnetic particle imaging device 100, the vibration or wobble of the unit consisting of the test object S, the AC magnetic field applying coil 3A, and the measurement coil 4 is not measured as noise, so that the measurement accuracy of magnetic particles can be improved compared to the magnetic particle imaging device according to the comparative example.

[0046] Furthermore, in the magnetic particle imaging device 100, the holder 1, the AC magnetic field applying coil 3A, and the measurement coil 4 are arranged to move as a unit in the third direction C, but not as a unit in the first direction A. Therefore, in the magnetic particle imaging device 100, the position dependency of the measurement sensitivity of the magnetic particles is reduced compared to a magnetic particle imaging device in which the holder 1, the AC magnetic field applying coil 3A, and the measurement coil 4 are arranged to move as a unit in each of the first direction A and the third direction C. The reason for this will be explained below with reference to Figs. 5 and 6.

[0047] FIG. 5 is a diagram for explaining the sensitivity distribution of the measurement coil 4 in the radial direction relative to the central axis AX4 of the measurement coil 4. The upper part of FIG. 5 shows a cross section perpendicular to the central axis AX4 of the measurement coil 4. The lower part of FIG. 5 shows the distribution of the sensitivity of the measurement coil 4 to the magnetic particles in the non-magnetic field region FFL at each position when the radial position of the non-magnetic field region FFL relative to the measurement coil 4 is changed in the upper cross section of FIG. 5. FIG. 6 is a diagram for explaining the sensitivity distribution of the measurement coil 4 in the direction along the central axis AX4 of the measurement coil 4. The upper part of FIG. 6 shows a cross section along the central axis AX4 of the measurement coil 4. The lower part of FIG. 6 shows the distribution of the sensitivity of the measurement coil 4 to the magnetic particles in the non-magnetic field region FFL at each position when the axial position of the non-magnetic field region FFL relative to the measurement coil 4 is changed in the upper cross section of FIG. 6. The sensitivity distribution of the measurement coil 4 shown in FIG. 5 and FIG. 6 can be obtained by analysis or experiment.

[0048] As shown in FIG. 5, even if the radial position of the non-magnetic field area FFL with respect to the measurement coil 4 is changed, the sensitivity of the measurement coil 4 does not change significantly. In other words, the rate of change of the radial sensitivity distribution of the measurement coil 4 is relatively low. In contrast, as shown in FIG. 6, when the axial position of the non-magnetic field area FFL with respect to the measurement coil 4 is changed, the sensitivity of the measurement coil 4 changes significantly. This is because the measurement coil 4 has a first coil portion 4A and a second coil portion 4B, and the sensitivity of the measurement coil 4 is inverted at the midpoint between the first coil portion 4A and the second coil portion 4B in the axial direction. In other words, the rate of change of the axial sensitivity distribution of the measurement coil 4 is higher than the rate of change of the radial sensitivity distribution of the measurement coil 4.

[0049] Therefore, in the magnetic particle imaging device 100, the holding unit 1, the AC magnetic field applying coil 3A, and the measurement coil 4 move as a whole in the third direction C relative to the magnetic field free region FFL, but do not move as a whole in the first direction A relative to the magnetic field free region FFL, so the position dependence of the measurement sensitivity of magnetic particles is reduced compared to a magnetic particle imaging device in which the holding unit 1, the AC magnetic field applying coil 3A, and the measurement coil 4 are arranged to move as a whole in each of the first direction A and the third direction C.

[0050] As described above, the sensitivity distribution of the measurement coil 4 shown in FIG. 5 and FIG. 6 can be obtained analytically or experimentally once the relative positions of the measurement coil 4 and the non-magnetic field region FFL are determined. From the sensitivity distribution of the measurement coil 4 obtained analytically or experimentally, the ratio of increase or decrease in the intensity of the signal acquired by the measurement coil 4 due to the sensitivity distribution can be calculated. In the magnetic particle imaging device 100, the measuring device 7 can normalize the intensity of the signal acquired by the measurement coil 4 based on the increase or decrease ratio calculated as described above. As a result, the spatial distribution of magnetic particles in the test object S can be quantitatively evaluated by using the magnetic particle imaging device 100. In other words, the magnetic particle imaging device 100 is excellent in quantitative performance.

[0051] In the magnetic particle imaging device 100, the central axis AX4 of the measurement coil 4 is perpendicular to the linear magnetic field free region FFL. Therefore, in the magnetic particle imaging device 100, the holding unit 1, the AC magnetic field applying coil 3A, and the measurement coil 4 are moved together relative to the magnetic field free region FFL in the third direction C, without moving each of them in the second direction B in which the magnetic field free region FFL extends, and only the holding unit 1 is moved in the first direction A and rotated in the circumferential direction, so that the position of the test object S relative to the magnetic field free region FFL can be easily controlled.

[0052] In the magnetic particle imaging device 100, the measurement coil 4 includes a first coil portion 4A and a second coil portion 4B that are arranged at a distance from each other in the first direction A, and the first coil portion 4A and the second coil portion 4B have an electrically symmetrical structure with respect to the center of the first direction A of the AC magnetic field applying coil 3A, so that it is possible to eliminate the induced electromotive force generated in the measurement coil 4 by the AC magnetic field generated by the AC magnetic field applying coil 3A, and environmental magnetic noise.

[0053] The static magnetic field generator 2 includes two permanent magnets arranged with the same magnetic poles facing each other. A magnetic field free area formed by an electromagnet or the like may vary due to the influence of current flow conditions or the like. A magnetic field free area FFL formed by a permanent magnet is less likely to vary compared to a magnetic field free area formed by an electromagnet or the like. Therefore, when the static magnetic field generator 2 includes two permanent magnets, the effect of the magnetic particle imaging device 100 described above is significantly achieved.

[0054] In the magnetic particle imaging device 100, only the holding unit 1 moves (rotates) in the circumferential direction, so that the structure of the driving mechanism 5 is simpler than when the holding unit 1 rotates in the circumferential direction integrally with at least one of the AC magnetic field applying coil 3A and the measurement coil 4, and the occurrence of problems such as tangling of the wiring connected to each of the AC magnetic field applying coil 3A and the measurement coil 4 can be suppressed.

[0055] Embodiment 2 7, the magnetic particle imaging device 101 according to the second embodiment has a basically similar configuration to the magnetic particle imaging device 100 according to the first embodiment, but differs from the magnetic particle imaging device 100 in that the AC magnetic field applying coil 3A is configured as a Helmholtz coil. The following mainly describes the differences between the magnetic particle imaging device 101 and the magnetic particle imaging device 100.

[0056] The AC magnetic field applying coil 3A has a first coil 3A1 and a second coil 3A2 that are identical in configuration (number of coil turns, coil radius, etc.) and are arranged coaxially. The radii R of the first coil 3A1 and the second coil 3A2 are equal to each other and are equal to the distance D between the first coil 3A1 and the second coil 3A2. This makes the intensity of the AC magnetic field near the center of the space sandwiched between the first coil 3A1 and the second coil 3A2 uniform.

[0057] The first coil 3A1 and the second coil 3A2 of the AC magnetic field applying coil 3A are positioned with respect to the measurement coil 4 so that the center in the first direction A between the first coil 3A1 and the second coil 3A2 overlaps with the center in the first direction A between the first coil portion 4A and the second coil portion 4B of the measurement coil 4. Therefore, the position dependency of the signal intensity of magnetic particles acquired by the measurement coil 4 in the magnetic particle imaging device 101, which is caused by the intensity distribution of the AC magnetic field, can be reduced compared to that of the signal intensity of magnetic particles acquired by the measurement coil 4 in the magnetic particle imaging device 100.

[0058] <Modification> When the magnetic particle imaging devices 100, 101 are used only to measure whether or not magnetic particles exist in a magnetic field free region FFL through which the subject S passes, the holder 1 may not be rotatable around the central axis AX1. Even in this case, if the holder 1, the AC magnetic field applying coil 3A, and the measurement coil 4 are movable as a whole relative to the static magnetic field generator 2 in the third direction C, the position dependency of the measurement sensitivity of the magnetic particles can be reduced compared to conventional magnetic particle imaging devices.

[0059] In the magnetic particle imaging devices 100, 101, the holding unit 1, the AC magnetic field applying coil 3A, and the measurement coil 4 may be fixed as a single unit, and the static magnetic field generator 2 may be provided so as to move relative to the unit of the holding unit 1, the AC magnetic field applying coil 3A, and the measurement coil 4 in the third direction C. The holding unit 1 is movable, for example, in the first direction A and rotatable around the central axis AX1. As described above, the holding unit 1 may not be rotatable around the central axis AX1.

[0060] Although the embodiment of the present disclosure has been described above, the above-mentioned embodiment can be modified in various ways. The scope of the present disclosure is not limited to the above-mentioned embodiment. The scope of the present disclosure is defined by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims. [Explanation of symbols]

[0061] 1 holding unit, 2 static magnetic field generator, 3 AC magnetic field applicator, 3A AC magnetic field application coil, 3A1 first coil, 3A2 second coil, 3B AC power supply, 4 measurement coil, 4A first coil portion, 4B second coil portion, 5 driving mechanism, 6 control unit, 7 measuring instrument, 11 first stage, 11A first portion, 11B second portion, 12 second stage, 12A annular portion, 13 stand, 21 first driving unit, 22 second driving unit, 23 third driving unit, 100, 101 magnetic particle imaging device.

Claims

1. A magnetic particle imaging apparatus for measuring magnetic particles in a subject, comprising: a holder for holding the test object; a static magnetic field generator that generates a linear magnetic field free region passing through the test subject held by the holding unit; An AC magnetic field applying coil that applies an AC magnetic field to the non-magnetic field region; a measurement coil for acquiring a magnetization variation of the magnetic nanoparticles in the non-magnetic field region as a signal, the measurement coil has an axis parallel to the direction of the alternating magnetic field; a relative position of each of the holding unit, the AC magnetic field applying coil, and the measurement coil is determined in a direction perpendicular to each of an extension direction of the axis and an extension direction of the magnetic field free region, A magnetic particle imaging apparatus, wherein the holding unit, the AC magnetic field applying coil, and the measurement coil move together in the orthogonal direction relative to the static magnetic field generator.

2. a relative position of the measurement coil with respect to the AC magnetic field application coil is determined in a circumferential direction with respect to the axis; 2. The magnetic particle imaging apparatus according to claim 1, wherein among said holding unit, said AC magnetic field applying coil, and said measurement coil, only said holding unit moves in said circumferential direction.

3. A magnetic particle imaging apparatus for measuring magnetic particles in a subject, comprising: a holder for holding the test object; a static magnetic field generator that generates a linear magnetic field free region passing through the test subject held by the holding unit; An AC magnetic field applying coil that applies an AC magnetic field to the non-magnetic field region; a measurement coil for acquiring a magnetization variation of the magnetic nanoparticles in the non-magnetic field region as a signal, the measurement coil has an axis parallel to the direction of the alternating magnetic field; a relative position of the measurement coil with respect to the AC magnetic field application coil is determined in a circumferential direction with respect to the axis; A magnetic particle imaging apparatus, wherein, of said holding unit, said AC magnetic field applying coil, and said measurement coil, only said holding unit moves in said circumferential direction.

4. a relative position of each of the holding unit, the AC magnetic field applying coil, and the measurement coil is determined in a direction perpendicular to each of an extension direction of the axis and an extension direction of the magnetic field free region, 4. The magnetic particle imaging apparatus according to claim 3, wherein said holding unit, said AC magnetic field applying coil, and said measurement coil move together in the direction perpendicular to said static magnetic field generator.

5. A first drive unit for moving only the holding unit in the circumferential direction; A second drive unit for moving only the holding unit in the extending direction of the shaft; a third driving unit for moving the holding unit, the first driving unit, the AC magnetic field applying coil, and the measurement coil as a whole in the orthogonal direction; 5. The magnetic particle imaging apparatus according to claim 2, further comprising a control section that independently controls each of said first driving section, said second driving section, and said third driving section.

6. 6. The magnetic particle imaging apparatus according to claim 1, wherein the AC magnetic field applying coil and the measuring coil are arranged coaxially.

7. 7. The magnetic particle imaging device according to claim 6, wherein said axis is perpendicular to said magnetic field free region.

8. the measurement coil includes a plurality of coil portions spaced apart in an extension direction of the axis, 8. The magnetic particle imaging device according to claim 1, wherein said plurality of coil portions have a structure electrically symmetrical to each other with respect to the center of said AC magnetic field applying coil.

9. 9. The magnetic particle imaging apparatus according to claim 1, wherein the AC magnetic field applying coil is a Helmholtz coil.

10. The magnetic particle imaging device according to any one of claims 1 to 9, further comprising an image generator that corrects the intensity of the signal acquired by the measurement coil based on the sensitivity distribution of the measurement coil, and generates an image from the corrected signal.

11. 11. The magnetic particle imaging apparatus according to claim 1, wherein said static magnetic field generator includes two permanent magnets arranged with the same magnetic poles facing each other.

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