Magnetic particle imaging apparatus, magnetic particle imaging method, and storage device storing magnetic particle imaging program

Abstract

The MPI apparatus (1) generates projection data of a magnetization change based on a position of a scanning direction (Y) of the FFL region (60) and an angle of a rotating direction (R) of the FFL region (60), performs sensitivity correction on the projection data using a system function that is obtained in advance for each projection data, thereby generating corrected projection data, performs image reconstruction on the corrected projection data, and generates a magnetic nanoparticle image. In generating the system function, the control section (40) causes the linear zero magnetic field generating section (10) to form the FFL region (60) in a structure (51) that is an object and that contains magnetic nanoparticles of a predetermined particle concentration and has a predetermined size, causes the FFL region (60) to perform scanning, or rotation, or scanning and rotation, causes the excitation magnetic field applying section (20) to apply an excitation magnetic field to a magnetic field region that contains the FFL region in the structure (51), causes the detection section (30) to detect a magnetization change in the structure (51), and generates the system function for each projection data.

Description

Technical Field

[0001] This invention relates to a magnetic particle imaging apparatus, a magnetic particle imaging method, and a storage device storing a magnetic particle imaging program. Background Technology

[0002] A magnetic particle imaging (MPI) device has been proposed that injects magnetic nanoparticles, acting as a contrast agent, into the object being imaged, and images the spatial distribution of the magnetic nanoparticles within the object based on the high-order harmonic signals generated by the magnetization changes of the magnetic nanoparticles. Patent Document 1 discloses a magnetic particle imaging device that performs a process at each position along the scanning direction of a linear zero magnetic field region, "using a static magnetic field generating coil to form a linear zero magnetic field region, causing the magnetic nanoparticles present within this linear zero magnetic field region to undergo magnetization changes, and detecting the high-order harmonic signals generated at this time," thereby imaging the spatial distribution of the magnetic nanoparticles.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-96960 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In the aforementioned magnetic particle imaging apparatus, it is preferable to detect magnetization changes that occur only in magnetic nanoparticles existing within a linear zero-magnetic-field region. However, in reality, due to the influence of local magnetic fields generated in magnetic nanoparticles near (e.g., around) the outer edge of the linear zero-magnetic-field region, magnetization changes also occur in magnetic nanoparticles surrounding the linear zero-magnetic-field region. Therefore, images of magnetic nanoparticles with low spatial resolution are generated.

[0008] The purpose of this invention is to provide a magnetic particle imaging device, a magnetic particle imaging method, and a magnetic particle imaging program capable of generating images of magnetic nanoparticles with high spatial resolution.

[0009] Methods for solving problems

[0010] The magnetic particle imaging apparatus of the present invention generates an image of magnetic nanoparticles representing the spatial distribution of magnetic nanoparticles within a subject. The apparatus is characterized by comprising: a linear zero-magnetic-field generation unit that forms a linear zero-magnetic-field region within the subject and moves the linear zero-magnetic-field region along a predetermined direction; an excitation magnetic field application unit that applies an alternating excitation magnetic field to a magnetic field region containing the linear zero-magnetic-field region; a detection unit that detects the magnetization change of the magnetic nanoparticles generated by the excitation magnetic field; and a control unit.

[0011] When generating the magnetic nanoparticle image, the control unit causes the linear zero-magnetic-field generation unit to form the linear zero-magnetic-field region within the imaging object, which is the subject. The control unit then scans, rotates, or both scans and rotates the linear zero-magnetic-field region. The control unit also causes the excitation magnetic field application unit to apply the excitation magnetic field. Furthermore, the control unit causes the detection unit to detect the magnetization change. Based on the position of the linear zero-magnetic-field region in the scanning direction and the angle of the linear zero-magnetic-field region in the rotation direction, the control unit generates projection data of the magnetization change. The control unit performs sensitivity correction on the projection data using a pre-obtained system function for each projection data point, thereby generating corrected projection data. Finally, the control unit generates the magnetic nanoparticle image based on the corrected projection data.

[0012] When generating the system function, the control unit causes the linear zero magnetic field generation unit to form the linear zero magnetic field region within the structure containing magnetic nanoparticles of a predetermined particle concentration and having a predetermined size, which serves as the subject. The linear zero magnetic field region is then scanned, rotated, or both scanned and rotated. The control unit causes the excitation magnetic field application unit to apply the excitation magnetic field to the magnetic field region containing the linear zero magnetic field region within the structure. The control unit causes the detection unit to detect the magnetization change within the structure. Based on the magnetization change within the structure, the control unit generates the system function according to each projection data.

[0013] The magnetic particle imaging method of the present invention is performed by a magnetic particle imaging device, which includes: a linear zero magnetic field generating unit that forms a linear zero magnetic field region within a subject and moves the linear zero magnetic field region along a predetermined direction; an excitation magnetic field applying unit that applies an alternating excitation magnetic field to a magnetic field region containing the linear zero magnetic field region; and a detection unit that detects the magnetization change of magnetic nanoparticles generated by the excitation magnetic field. The magnetic particle imaging device generates a magnetic nanoparticle image representing the spatial distribution of magnetic nanoparticles within the subject, characterized in that...

[0014] When generating the magnetic nanoparticle image, the magnetic particle imaging method includes the following steps: forming a linear zero-magnetic-field region within the object being imaged by the linear zero-magnetic-field generating unit; scanning, rotating, or both scanning and rotating the linear zero-magnetic-field region; applying the excitation magnetic field by the excitation magnetic field applying unit; detecting the magnetization change by the detection unit; generating projection data of the magnetization change based on the position of the linear zero-magnetic-field region in the scanning direction and the angle of the linear zero-magnetic-field region in the rotation direction; performing sensitivity correction on the projection data using a system function pre-obtained for each projection data, thereby generating corrected projection data; and generating the magnetic nanoparticle image based on the corrected projection data.

[0015] When generating the system function, the magnetic particle imaging method includes the following steps: forming a linear zero magnetic field region within a structure containing magnetic nanoparticles of a predetermined particle concentration and having a predetermined size, which serves as the subject, using the linear zero magnetic field generation unit; scanning, rotating, or both scanning and rotating the linear zero magnetic field region; applying the excitation magnetic field to a magnetic field region containing the linear zero magnetic field region within the structure using the excitation magnetic field application unit; detecting the magnetization change within the structure using the detection unit; and generating the system function according to each projection data based on the magnetization change within the structure.

[0016] Invention Effects

[0017] If the magnetic particle imaging device, magnetic particle imaging method and magnetic particle imaging program of the present invention are used, it is possible to generate magnetic nanoparticle images with high spatial resolution. Attached Figure Description

[0018] [ Figure 1 [Illustration] is a diagram that schematically illustrates the structure of a magnetic particle imaging apparatus according to an embodiment.

[0019] [ Figure 2 [This is a schematic diagram showing the structure of the main parts of the MPI device in an embodiment and a perspective view of a person as the subject of the photograph.]

[0020] [ Figure 3 [This is a perspective view that schematically shows the structure of the main parts of the MPI device according to the embodiment and the cylinder as the structure.]

[0021] [ Figure 4 [This is a graph showing magnetic nanoparticles of known concentration, a linear zero magnetic field region, the measured magnetic signal (i.e., the magnetic response signal), and the known magnetic response signal.]

[0022] [ Figure 5[ ] is a graph showing the relationship between the system function, the spatial distribution of magnetic nanoparticles, and the magnetic signal (measurement vector).

[0023] [ Figure 6 [Illustration 1] is a diagram illustrating an example of the hardware structure of an MPI device according to an embodiment.

[0024] [ Figure 7 [ ] is a flowchart illustrating an example of the generation process of magnetic nanoparticle images of an MPI device according to an embodiment.

[0025] [ Figure 8 [ ] is a flowchart illustrating an example of the generation process of system functions of an MPI device according to an embodiment.

[0026] [ Figure 9 ] Figure 9 (A) shows an example of projection data in the scan position / angle coordinates. Figure 9 (B) shows the waveform representing the intensity of the measured MPI signal at a certain angle and the signal obtained by performing a high-speed Fourier transform (FFT) on the measured MPI signal.

[0027] [ Figure 10 ] Figure 10 (A) shows Figure 9 The signal of (B). Figure 10 (B) shows the representation from Figure 10 The waveform of the intensity of the measured MPI signal after removing the DC component and the signal obtained by performing FFT processing on the measured MPI signal after removing the DC component.

[0028] [ Figure 11 ] Figure 11 (A) shows Figure 10 The signal of (B). Figure 11 (B) shows the waveform of the magnetic signal detected from the cylinder, which is the standard camera object, i.e., the measured MPI signal, and the signal obtained by performing FFT processing on the measured MPI signal. Figure 11 (C) shows according to Figure 11 The deconvolution coefficients calculated from (A) and (B) and the coefficients obtained by performing FFT on them.

[0029] [ Figure 12 ] Figure 12 (A) shows Figure 10 The signal of (B). Figure 12 (B) shows Figure 11 The coefficient of (C). Figure 12 (C) shows the waveform representing the strength of the corrected MPI signal, i.e., the noise-removed MPI signal, and the signal obtained by performing FFT processing on the noise-removed MPI signal.

[0030] [ Figure 13 ] Figure 13 (A) shows the corrected projection data. Figure 13 (B) shows the original projection data without correction.

[0031] [ Figure 14 ] Figure 14 (A) shows an image of magnetic nanoparticles generated by image reconstruction of corrected projection data. Figure 14 (B) shows an image of magnetic nanoparticles based on the original, uncorrected projection data. Detailed Implementation

[0032] The MPI apparatus, MPI method, and MPI program according to embodiments will now be described with reference to the accompanying drawings. The following embodiments are merely examples, and embodiments can be appropriately combined and modified.

[0033] exist Figures 1-4 To facilitate understanding of the relationships between the figures, the axes of the XYZ Cartesian coordinate system are shown. The Z-axis represents the length of the linear zero magnetic field (also known as the "Free Field Line" (FFL)) region. The Y-axis represents the scanning direction (Y direction) of the FFL region perpendicular to the Z-axis. The X-axis is the coordinate axis perpendicular to both the Z-axis and Y-axis. Figure 2 and Figure 3 In the diagram, the R direction indicates the rotation direction of the FFL region. Figure 2 and Figure 3 In the figures, the central axis of rotation in the R direction is the axis in the X direction. Furthermore, in the accompanying drawings, identical or corresponding structures are labeled with the same reference numerals.

[0034] Structure of the MPI Device

[0035] Figure 1 This is a diagram schematically illustrating the structure of the MPI apparatus 1 according to the embodiment. The MPI apparatus 1 is an apparatus for generating (also referred to as "reconstructing") an image of magnetic nanoparticles representing the spatial distribution of magnetic nanoparticles within the photographic object 50, which is the subject. Furthermore, the MPI apparatus 1 is an apparatus capable of implementing the MPI method of the embodiment. Additionally, the MPI apparatus 1 is an apparatus capable of executing the MPI program of the embodiment.

[0036] Figure 2This is a perspective view schematically showing the structure of the main parts of the MPI device 1 and the imaging subject 50. The imaging subject 50 is, for example, a person in whose body magnetic nanoparticles are injected. The imaging subject 50 can also be an object other than a person (e.g., an animal, plant, etc.). Magnetic nanoparticles are magnetic particles with diameters in the nanometer range that contain magnetic bodies. Magnetic nanoparticles are, for example, formed to have the property of concentrating in specific cells in the affected area (e.g., the brain, organs, etc.) after being injected into a person. As magnetic nanoparticles, for example, "Resovist (registered trademark)" (common name: Ferucarbotran) is known as a hydrophilic colloidal solution of superparamagnetic iron oxide coated with carboxyglucan.

[0037] like Figure 1 As shown, the MPI device 1 includes a linear zero magnetic field generating unit 10 that forms an FFL region 60, an excitation magnetic field applying unit 20 that applies an alternating excitation magnetic field, a detection unit 30 that detects (i.e. measures) the magnetization change of magnetic nanoparticles, and a control unit 40 that controls the entire device.

[0038] The linear zero magnetic field generating unit 10 forms an FFL region 60 within the subject and moves the FFL region 60 in a predetermined direction. For example, the linear zero magnetic field generating unit 10 forms the FFL region 60 within the subject and scans the FFL region 60 along a predetermined scanning direction (Y direction), or rotates the FFL region 60 along a predetermined rotation direction (R direction), or scans the FFL region 60 along the predetermined scanning direction (Y direction) and rotates it along the predetermined rotation direction (R direction). The linear zero magnetic field generating unit 10 has a linear zero magnetic field generating coil 11 as a first linear zero magnetic field generating unit and a linear zero magnetic field generating coil 12 as a second linear zero magnetic field generating unit. The linear zero magnetic field generating coils 11 and 12 are arranged on opposite sides of each other, separated by the imaging object 50, which is the subject. The linear zero magnetic field generating coils 11 and 12 are magnetic field generating coils and are powered by linear zero magnetic field power supplies 13 and 14.

[0039] The linear zero magnetic field generating section 10 causes the FFL region 60 to move along the scanning direction (e.g.) Figures 1-3 The linear zero magnetic field generating unit 10 moves the FFL region 60 linearly by a predetermined distance each time (in the Y direction). For example, the linear zero magnetic field generating unit 10 moves the position of the FFL region 60 sequentially to a plurality of predetermined positions along the scanning direction. The scanning direction is, for example, the Y direction perpendicular to the length direction (Z direction) of the FFL region 60. For example, the movement of the FFL region 60 is performed by controlling the linear zero magnetic field power supplies 13 and 14. Alternatively, the movement of the FFL region 60 can be performed by moving the camera object 50, moving the linear zero magnetic field generating unit 10, or moving both the camera object 50 and the linear zero magnetic field generating unit 10.

[0040] Furthermore, the linear zero magnetic field generating unit 10 can rotate the FFL region 60 by a predetermined rotation angle each time. The linear zero magnetic field generating unit 10 rotates the FFL region 60, for example, along the R direction parallel to the YZ plane. For example, the rotation of the FFL region 60 can be performed by controlling the linear zero magnetic field power supplies 13 and 14. Alternatively, the rotation of the FFL region 60 can also be performed by rotating the linear zero magnetic field generating coils 11 and 12 in the R and -R directions, or by rotating the camera object 50 in the R and -R directions.

[0041] The excitation magnetic field applying unit 20 includes an excitation magnetic field generating coil 21 that applies an alternating excitation magnetic field to a magnetic field region including the FFL region 60, and an excitation magnetic field power supply 22 that supplies power to the excitation magnetic field generating coil 21. Figures 1-3 As shown, the excitation magnetic field generating coil 21 is, for example, a loop coil wound along the R direction.

[0042] The detection unit 30 detects the magnetization change of the magnetic nanoparticles contained within the FFL region 60 due to the excitation magnetic field (more precisely, it detects the higher harmonic signals generated by the magnetization change as a magnetic response signal). The detection unit 30 may have one or more magnetic field detectors (e.g., magnetic field detection coils). The detection signal output from the detection unit 30 may also be amplified by an amplifier circuit. The one or more magnetic field detectors may also be semiconductor elements for magnetic field detection (e.g., Hall elements).

[0043] The control unit 40 controls the overall operation of the MPI device 1. When generating an image of magnetic nanoparticles, the control unit 40 causes the linear zero magnetic field generating unit 10 to form an FFL region 60 within the imaging object 50, scans, rotates, or both scans and rotates the FFL region 60, applies an excitation magnetic field to the excitation magnetic field applying unit 20, and detects the magnetization change to the detection unit 30. Furthermore, the control unit 40 changes the position of the FFL region 60 in the scanning direction (Y direction) and the angle of the FFL region 60 in the rotation direction R, generates projection data of the magnetization change based on the position of the FFL region 60 in the scanning direction and the angle of the FFL region 60, and performs sensitivity correction on the projection data using a system function pre-obtained for each projection data, thereby generating corrected projection data. Then, the control unit 40 uses the corrected projection data (e.g., described later) to generate corrected projection data. Figure 13 (A) generates images of magnetic nanoparticles (e.g., described later). Figure 14 (A)).

[0044] Figure 3This is a perspective view schematically showing the structure of the main parts of the MPI device 1 according to the embodiment and the structure 51 as the subject. The structure 51 is, for example, a cylinder. However, the structure 51 is not limited to a cylinder. The system function used to generate the correction projection data is generated in advance. When generating the system function, the control unit 40 causes the linear zero magnetic field generation unit 10 to form an FFL region 60 within the subject, i.e., the structure 51, which contains magnetic nanoparticles of a predetermined particle concentration and has a predetermined size. The FFL region 60 is scanned, rotated, or scanned and rotated. The excitation magnetic field application unit 20 applies an excitation magnetic field to the magnetic field region containing the FFL region 60 within the structure 51. The detection unit 30 detects the magnetization change within the structure 51. Based on the magnetization change within the structure 51, a system function is generated for each projection data. The system function is generated based on the detection sensitivity of each position in the scanning direction and each angle in the rotation direction.

[0045] Figure 4 This is a graph showing magnetic nanoparticles of known concentration, FFL region 60, measured magnetic response signal, and known magnetic response signal. Figure 4 The 8×4 circular symbols shown all represent magnetic nanoparticles of known concentration. Figure 4 The diagram shows a waveform similar to a triangular waveform, representing the sum of magnetic signals generated in and around the FFL region 60 as it moves along the Y direction. It also shows a rectangular waveform, represented by dashed lines, representing the ideal, known magnetic response characteristics (the sum of magnetic signals generated only in the FFL region 60). Magnetized magnetic nanoparticles are excited, and thus, the magnetic signal corresponding to the magnetization change (i.e., the magnetization change of the magnetic nanoparticles) is directly detected from the magnetic nanoparticles within the field of view (FOV) of the detection unit 30 via the detection unit 30.

[0046] Figure 5 This is a graph showing the relationship between the system function S, the spatial distribution c of magnetic nanoparticles in the FFL region 60, and the measured magnetic response signal u (i.e., the measurement vector). Figure 5 As shown, the measured magnetic response signal u is obtained by convolving the spatial distribution c of magnetic nanoparticles in the FFL region 60 with a system function S representing the detection sensitivity (i.e., magnetic properties).

[0047] Figure 6 This is a diagram illustrating an example of the hardware structure of the MPI device 1 according to an embodiment. (See diagram for example.) Figure 6As shown, the control unit 40 of the MPI device 1 includes, for example, a processor 41 such as a CPU (Central Processing Unit) and a memory 42 as volatile storage. The control unit 40 may also be a computer. The memory 42 is a semiconductor memory such as RAM (Random Access Memory). Furthermore, the MPI device 1 includes a storage device 70 such as a hard disk drive (HDD) or a solid-state drive (SSD). The storage device 70 may also be part of an external device capable of communicating with the MPI device 1. For example, the storage device 70 may also be the storage device of a server capable of communicating via a network.

[0048] The functions of the MPI device 1 are implemented by processing circuitry. The processing circuitry can be dedicated hardware or a processor 41 that executes a program stored in memory 42 (e.g., an MPI program that executes the MPI method of the implementation method). The processor 41 can also be any one of a processing device, an arithmetic device, a microprocessor, a microcomputer, and a DSP (Digital Signal Processor).

[0049] When the processing circuit is dedicated hardware, the processing circuit may be a single circuit, a composite circuit, a programmable processor, a parallel programmable processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination of any of these circuits.

[0050] When the processing circuit is processor 41, the MPI program is implemented through software, firmware, or a combination of both. The software and firmware are described as programs and stored in memory 42. Processor 41 reads and executes the MPI program stored in memory 42, thereby implementing the functions of each part.

[0051] Alternatively, the MPI device 1 can be partially implemented using dedicated hardware and partially using software or firmware. In this way, the processing circuitry can implement its functions through hardware, software, firmware, or any combination thereof.

[0052] Actions during the generation of images of magnetic nanoparticles

[0053] Next, the operation of generating an image of magnetic nanoparticles by the MPI device 1 will be explained. The difference between the operation of generating an image of magnetic nanoparticles by the MPI device 1 and the operation described in Patent Document 1 is that a system function is used to perform correction processing on the projection data.

[0054] Figure 7 This is a flowchart illustrating an example of the generation process of an image of magnetic nanoparticles for MPI device 1. Figure 7 This example illustrates how the MPI device 1 changes both the position of the scanning direction of the FFL region 60 and the angle of the FFL region 60. However, the MPI device 1 may also change only the position of the scanning direction of the FFL region 60, or only the angle of the FFL region 60.

[0055] First, the control unit 40 controls the linear zero magnetic field generating unit 10, and the camera object 50 (in Figure 2 An FFL region 60 is formed within the area shown in the diagram, and the position of the scanning direction of the FFL region 60 is set as the initial position (step ST11). The initial position is, for example,... Figure 2 The predetermined position in the Y direction.

[0056] Next, the control unit 40 controls the linear zero magnetic field generating unit 10, setting the angle of the FFL region 60 to an initial angle (step ST12). The initial angle is, for example,... Figure 2 The predetermined angle in the R direction.

[0057] Next, the control unit 40 controls the excitation magnetic field application unit 20 to excite the magnetic nanoparticles in the FFL region 60, so that the detection unit 30 detects the magnetization change (step ST13).

[0058] Next, the control unit 40 determines whether the detection related to all predetermined angles in the R direction of the FFL region 60 at the current scanning direction position has ended. If there are angles where the detection has not ended (step ST14: No), the control unit 40 returns the process to step ST12, controls the linear zero magnetic field generation unit 10 to rotate the FFL region 60 by a certain rotation angle, sets it as the next angle (i.e., one of the predetermined angles), and returns to step ST14 after the processing of step ST13. If there are no angles where the detection has not ended at the current scanning direction position, that is, if the detection related to all angles has ended (step ST14: Yes), the control unit 40 causes the process to proceed to step ST15.

[0059] In step ST15, the control unit 40 determines whether the detection related to all predetermined multiple positions in the Y direction of the FFL region 60 (i.e., the processing in steps ST12 to ST14) has ended. If there are positions where the detection has not ended (step ST15: No), the control unit 40 returns the processing to step ST11, controls the linear zero magnetic field generating unit 10 to move the FFL region 60 a certain distance in the Y direction, thereby setting it as the next position (i.e., one of the predetermined multiple positions), and returns to the processing in step ST15 after the processing in steps ST12 to ST14. If there are no positions where the detection has not ended, that is, if the detection related to all positions has ended (step ST15: Yes), the control unit 40 causes the processing to proceed to step ST16.

[0060] In step ST16, the control unit 40 generates projection data of the magnetization change based on the position and angle of the magnetization change (e.g., the projection position and projection angle of the projection data of the detection unit 30). Here, the projection data is data obtained by projecting the detection data by the magnetic field detector of the detection unit 30 along the direction of the FFL region 60. Therefore, the projection position is the position corresponding to the position of the FFL region 60 in the scanning direction. The projection position is also called the scan position. Furthermore, the projection angle is the angle corresponding to the rotation angle of the FFL region 60 in the R direction.

[0061] In step ST17, the control unit 40 selects a system function for each projection position and projection angle from the storage device 70, performs sensitivity correction on the projection data using the selected system function, and generates corrected projection data. Alternatively, the control unit 40 can select a system function from the storage device 70, estimate a system function other than the selected one by using the position relative to the scanning direction or the angle of rotation in the linear zero magnetic field region, or both, of the selected system function, and perform sensitivity correction on the projection data using the selected system function and the estimated system function to generate corrected projection data. In this case, the number of system functions obtained beforehand can be reduced.

[0062] In step ST18, the control unit 40 generates an image of magnetic nanoparticles based on the corrected projection data.

[0063] Actions during system function generation

[0064] Figure 8 This is a flowchart illustrating an example of the generation process of system functions for MPI device 1. Figure 8This example illustrates how the MPI device 1 changes both the position of the scanning direction of the FFL region 60 and the angle of the FFL region 60. However, the MPI device 1 may also change only the position of the scanning direction of the FFL region 60, or only the angle of the FFL region 60.

[0065] In the generation of the system function, firstly, the control unit 40 controls the linear zero magnetic field generation unit 10, in the structure 51 ( Figure 3 An FFL region 60 is generated within the area, and the position of the scanning direction of the FFL region 60 is set as the initial position (step ST21). The initial position is, for example, [example position would be inserted here]. Figure 3 The predetermined position in the Y direction.

[0066] Next, the control unit 40 controls the linear zero magnetic field generating unit 10, setting the angle of the FFL region 60 to an initial angle (step ST22). The initial angle is, for example,... Figure 3 The predetermined angle in the R direction.

[0067] Next, the control unit 40 controls the excitation magnetic field application unit 20 to excite the magnetic nanoparticles in the FFL region 60, so that the detection unit 30 detects the magnetization change (step ST23).

[0068] Next, the control unit 40 determines whether the detection related to all predetermined multiple angles in the R direction of the FFL region 60 at the current scanning direction position has ended. If there is an angle at the current scanning direction position where the detection has not ended (step ST24: No), the control unit 40 returns to step ST22, controls the linear zero magnetic field generation unit 10 to rotate the FFL region 60 by a certain rotation angle, thereby setting it as the next angle (i.e., one of the predetermined multiple angles), and returns to step ST24 after processing in step ST23. If there is no angle at the current scanning direction position where the detection has not ended, that is, if the detection related to all angles has ended (step ST24: Yes), the control unit 40 proceeds to step ST25.

[0069] In step ST25, the control unit 40 determines whether the detection related to the position of all predetermined multiple scanning directions in the Y direction of the FFL region 60 (i.e., the processing in steps ST22 to ST24) has ended. If there is a position in a scanning direction where the detection has not ended (step ST25: No), the control unit 40 returns the processing to step ST21, controls the linear zero magnetic field generation unit 10 to move the FFL region 60 a certain distance along the Y direction, thereby setting it as the position of the next scanning direction (i.e., one of the predetermined multiple scanning directions). After the processing in steps ST22 to ST24, the process returns to step ST25. If there is no position in a scanning direction where the detection has not ended, that is, if the detection related to the position of all scanning directions has ended (step ST25: Yes), the control unit 40 causes the processing to proceed to step ST26.

[0070] In step ST26, the control unit 40 generates projection data of magnetization change based on the position and angle of the magnetization change (e.g., the projection position and projection angle of the projection data of the detection unit 30).

[0071] In step ST27, the control unit 40 generates a system function representing the detection sensitivity of each combination of position and angle of the scanning direction. In step ST28, the storage device 70 stores a system function set containing multiple system functions.

[0072] Image generation from projection data

[0073] Reference Figure 9 (A) and (B) Figure 14 (A) and (B) illustrate the process of generating reconstructed images from projection data.

[0074] First, the control unit 40 extracts multiple angle MPI signals from the projection data. These multiple angles are, for example, rotational directions represented by R. Figure 9 (A) shows an example of projection data projected onto the scan position / angular coordinates. The scan position corresponds to the position of the plurality of magnetic field detectors (or detection elements) of the detection unit 30. Figure 9 In (A), the brighter the part, the stronger the measured magnetic response signal, i.e., the measured MPI signal, that is, the larger the amplitude. Figure 9 (B) shows the representation Figure 9 The waveform of the intensity of the measured MPI signal at a certain angle in (A) (Original Signal) and the signal obtained by performing high-speed Fourier transform (FFT) on the measured MPI signal (Original SignalFFT).

[0075] Next, control unit 40 from Figure 9 Remove the DC component from the signal (B). Figure 10 (A) shows Figure 9 The signal of (B). Figure 10 (B) shows the representation from Figure 10 The waveform of the intensity of the measured MPI signal after removing the DC component (Signal without DC: no DC signal) and the signal obtained by performing FFT processing on the measured MPI signal after removing the DC component (Signal without DC FFT: no DC signal FFT).

[0076] Next, the control unit 40 according to Figure 10 The deconvolution coefficients S(f) of the (B) signal and the ideal MPI signal are calculated as the system function. Figure 11 (A) shows Figure 10 The signal of (B). Figure 11 (B) shows the waveform of the magnetic signal detected from the cylinder of the reference structure 51, i.e., the ideal MPI signal m(x), and the signal M(f) obtained by performing FFT processing on the ideal MPI signal. Figure 11 (C) shows according to Figure 11 The deconvolution coefficients s(t) calculated from (A) and (B) and the deconvolution coefficients FFT obtained by processing them with FFT are S(f). Here, f represents the frequency, t represents the time, and x represents the position in the scanning direction (or the position of the magnetic field detector).

[0077] Next, the control unit 40 according to Figure 10 The signal of (B) and Figure 11 The deconvolution coefficients (i.e., system function) of (C) are used to calculate the noise-removed MPI signal m(x) and the signal after Fourier transform of it M(f). Figure 12 (A) shows Figure 10 The signal of (B). Figure 12 (B) shows Figure 11 The deconvolution coefficients of (C). Figure 12 (C) shows the waveform representing the intensity of the noise-removed MPI signal m(x) as the corrected MPI signal and the signal M(f) obtained by performing FFT processing on the noise-removed MPI signal.

[0078] pass Figure 9 (A) and (B) Figure 12 The processes shown in (A) to (C) can be based on Figure 9 (B) shows the signal generation based on the original projection data. Figure 12The noise-removed MPI signal is shown in (C).

[0079] Effects of the Implementation Method

[0080] Figure 13 (A) shows the corrected projection data generated by the control unit 40 of the MPI device 1 in the embodiment. Figure 13 (B) shows the original, uncorrected projection data (comparative example). For example... Figure 13 As shown in (A), regarding the corrected projection data generated by the control unit 40 of the MPI device 1 of the embodiment, the boundary between the area where magnetic nanoparticles are present (white area) and the area where magnetic nanoparticles are not present (black area) becomes a clear straight line. Thus, if the MPI device 1 of the embodiment is used, it is possible to generate a magnetic nanoparticle image with high spatial resolution.

[0081] Figure 14 (A) shows an image of magnetic nanoparticles generated by image reconstruction of the corrected projection data of the MPI device 1 of the embodiment. Figure 14 (B) shows an image of magnetic nanoparticles based on the original, uncorrected projection data (comparative example). Figure 14 As shown in (B), when reconstructing an image using uncorrected projection data, the boundaries between the areas where magnetic nanoparticles are present (white areas) and the areas where magnetic nanoparticles are absent (black areas) are unclear. Furthermore, in Figure 14 In (B), the large outer circle is an artifact. In contrast, as... Figure 14 As shown in (A), regarding the corrected projection data generated by the MPI device 1 of the embodiment, the boundary between the area where magnetic nanoparticles are present (white area) and the area where magnetic nanoparticles are not present (black area) becomes a clearly defined circle. Thus, by using the MPI device 1 of the embodiment, it is possible to generate magnetic nanoparticle images with high spatial resolution.

[0082] Label Explanation

[0083] 1: MPI device; 10: Linear zero magnetic field generating unit; 11, 12: Linear zero magnetic field generating coil; 13, 14: Power supply for linear zero magnetic field; 20: Excitation magnetic field applying unit; 21: Excitation magnetic field generating coil; 22: Excitation magnetic field power supply; 30: Detection unit; 40: Control unit; 50: Imaging object (subject); 51: Structure (subject); 60: FFL area; 70: Storage device; R: Rotation direction.

Claims

1. A magnetic particle imaging device, which generates an image of magnetic nanoparticles representing the spatial distribution of magnetic nanoparticles within a subject, characterized in that, The magnetic particle imaging device has the following features: A linear zero magnetic field generating unit forms a linear zero magnetic field region within the subject, and moves the linear zero magnetic field region along a predetermined direction; An excitation magnetic field applying unit applies an alternating excitation magnetic field to a magnetic field region containing the linear zero magnetic field region; The detection unit detects the magnetization change of the magnetic nanoparticles generated by the excitation magnetic field; and Control Department When generating the image of the magnetic nanoparticles The control unit causes the linear zero magnetic field generating unit to form the linear zero magnetic field region within the imaging object, which is the subject, and causes the linear zero magnetic field region to be scanned, rotated, or both scanned and rotated. The control unit causes the excitation magnetic field application unit to apply the excitation magnetic field. The control unit causes the detection unit to detect the magnetization change. The control unit generates projection data of the magnetization change based on the position of the linear zero magnetic field region in the scanning direction and the angle of the linear zero magnetic field region in the rotation direction. The control unit uses a pre-obtained system function according to each projection data to perform sensitivity correction on the projection data, thereby generating corrected projection data. The control unit generates the image of the magnetic nanoparticles based on the corrected projection data. When generating the system function The control unit causes the linear zero-magnetic-field generation unit to form the linear zero-magnetic-field region within a structure containing magnetic nanoparticles of a predetermined particle concentration and having a predetermined size, which serves as the subject. The control unit then scans, rotates, or both scans and rotates the linear zero-magnetic-field region. The control unit causes the excitation magnetic field application unit to apply the excitation magnetic field to the magnetic field region containing the linear zero magnetic field region within the structure. The control unit causes the detection unit to detect the magnetization change within the structure. The control unit generates the system function according to each projection data based on the magnetization change within the structure.

2. The magnetic particle imaging device according to claim 1, characterized in that, During the scanning process, the linear zero magnetic field generating unit causes the linear zero magnetic field region to move a predetermined distance in a straight line along the scanning direction each time.

3. The magnetic particle imaging device according to claim 1 or 2, characterized in that, The scanning direction is perpendicular to the length direction of the linear zero magnetic field region.

4. The magnetic particle imaging device according to any one of claims 1 to 3, characterized in that, The linear zero magnetic field generating unit causes the linear zero magnetic field region to rotate by a predetermined rotation angle each time it rotates during the rotation.

5. The magnetic particle imaging device according to any one of claims 1 to 4, characterized in that, When generating the system function, the control unit generates a system function representing the detection sensitivity of each combination of the position and the angle, and the storage device stores a system function set containing multiple system functions.

6. The magnetic particle imaging device according to claim 5, characterized in that, When generating the magnetic nanoparticle image, the control unit selects the system function from the storage device, uses the selected system function to perform sensitivity correction on the projection data, and generates the corrected projection data.

7. The magnetic particle imaging device according to claim 5, characterized in that, When generating the magnetic nanoparticle image, the control unit selects the system function from the storage device, estimates a system function other than the selected system function by interpolating the selected system function, performs sensitivity correction on the projection data using the selected system function and the estimated system function, and generates the corrected projection data.

8. The magnetic particle imaging device according to any one of claims 5 to 7, characterized in that, The magnetic particle imaging device also has the storage device for storing the system function set.

9. A magnetic particle imaging method, performed by a magnetic particle imaging device, the magnetic particle imaging device comprising: a linear zero magnetic field generating unit that forms a linear zero magnetic field region within a subject and moves the linear zero magnetic field region along a predetermined direction; an excitation magnetic field applying unit that applies an alternating excitation magnetic field to a magnetic field region containing the linear zero magnetic field region; and a detection unit that detects magnetization changes of magnetic nanoparticles generated by the excitation magnetic field, the magnetic particle imaging device generating a magnetic nanoparticle image representing the spatial distribution of magnetic nanoparticles within the subject, characterized in that... The magnetic particle imaging method comprises the following steps in generating the image of the magnetic nanoparticles: The linear zero magnetic field generating part forms the linear zero magnetic field region within the camera object, and the linear zero magnetic field region is scanned, rotated, or scanned and rotated. The excitation magnetic field is applied by the excitation magnetic field application unit; The detection unit detects the magnetization change; The projection data of the magnetization change is generated based on the position of the linear zero magnetic field region in the scanning direction and the angle of the linear zero magnetic field region in the rotation direction. Sensitivity correction is performed on the projection data using a system function pre-obtained for each projection data, thereby generating corrected projection data; and The magnetic nanoparticle image is generated based on the corrected projection data. The magnetic particle imaging method comprises the following steps in generating the system function: The linear zero magnetic field generating part forms the linear zero magnetic field region within a structure containing magnetic nanoparticles of a predetermined particle concentration and having a predetermined size, which serves as the subject, and the linear zero magnetic field region is scanned, rotated, or scanned and rotated. The excitation magnetic field applying part applies the excitation magnetic field to the magnetic field region containing the linear zero magnetic field region within the structure. The detection unit detects the magnetization change within the structure. as well as The system function is generated according to each of the projection data based on the magnetization changes within the structure.

10. A storage device storing a magnetic particle imaging program, the magnetic particle imaging program being executed by a magnetic particle imaging apparatus, the magnetic particle imaging apparatus comprising: a linear zero magnetic field generating unit that forms a linear zero magnetic field region within a subject and moves the linear zero magnetic field region along a predetermined direction; an excitation magnetic field applying unit that applies an alternating excitation magnetic field to a magnetic field region containing the linear zero magnetic field region; and a detection unit that detects magnetization changes of magnetic nanoparticles generated by the excitation magnetic field, the magnetic particle imaging apparatus generating a magnetic nanoparticle image representing the spatial distribution of magnetic nanoparticles within the subject being photographed, characterized in that... In generating the image of the magnetic nanoparticles, the magnetic particle imaging procedure causes the magnetic particle imaging device to perform the following steps: The linear zero magnetic field generating part forms the linear zero magnetic field region within the camera object, and the linear zero magnetic field region is scanned, rotated, or scanned and rotated. The excitation magnetic field is applied by the excitation magnetic field application unit; The detection unit detects the magnetization change; The projection data of the magnetization change is generated based on the position of the linear zero magnetic field region in the scanning direction and the angle of the linear zero magnetic field region in the rotation direction. Sensitivity correction is performed on the projection data using a system function pre-obtained for each projection data, thereby generating corrected projection data; and The magnetic nanoparticle image is generated based on the corrected projection data. When generating the system function, the magnetic particle imaging procedure causes the magnetic particle imaging device to perform the following steps: The linear zero magnetic field generating part forms the linear zero magnetic field region within a structure containing magnetic nanoparticles of a predetermined particle concentration and having a predetermined size, which serves as the subject, and the linear zero magnetic field region is scanned, rotated, or scanned and rotated. The excitation magnetic field applying part applies the excitation magnetic field to the magnetic field region containing the linear zero magnetic field region within the structure. The detection unit detects the magnetization change within the structure. as well as The system function is generated according to each of the projection data based on the magnetization changes within the structure.

Images