Input current optimization method based on MPI orthogonal model constant-speed rotary scanning

Abstract

The invention provides an input current optimization method based on MPI orthogonal model constant-speed rotary scanning, which aims at a rotary scanning device formed by combining two zero field line devices constructed by two groups of coils, and comprises the following steps of: controlling the input current of the two groups of coils which generate mutually vertical zero field lines to be periodic current; therefore, the fusion null field line generated by the rotary scanning device is controlled to perform periodic constant-speed rotation so as to determine the position of the fusion null field line at any moment. According to the method, the problem that the FFL of an existing selected model rotates irregularly can be solved, the effect of uniform-speed scanning is achieved, the position of the FFL is controllably observed, and the controllability of MPI is improved.

Description

Technical Field

[0001] This invention belongs to the field of medical imaging, specifically relating to an input current optimization method based on uniform rotation scanning using an MPI orthogonal model. Background Technology

[0002] Magnetic Particle Imaging (MPI) is a novel radiation-free biomedical imaging technique based on superparamagnetic iron oxide nanoparticle tracers. MPI uses a gradient magnetic field to create a magnetic field free region (FFR), which excites SPIONs to generate a nonlinear magnetization response signal to reconstruct the image. FFR morphologies are mainly divided into two types: field-free point (FFP) and field-free line (FFL). FFL, as its core magnetic field topology, employs a linear scanning method, resulting in a larger coverage area per scan and higher sensitivity, making it suitable for rapid, large-field-of-view imaging. By optimizing the morphology of the magnetic field free region, FFL significantly improves imaging sensitivity and efficiency. With its advantages of high sensitivity, radiation-free operation, and real-time imaging, MPI has broad application prospects in medical imaging, scientific research, and drug development. With advancements in nanotechnology and imaging technology, MPI is expected to become an important medical diagnostic tool.

[0003] However, MPI still faces some challenges and problems in practical applications. Its imaging quality depends on the control precision of the FFL (Field-Fluid Sensor). Only by more precise control and determination of the zero-field region can the accuracy of the reconstructed image be improved. The current optimization scheme proposed in this invention starts from a specific rotating scanning device and attempts to control the FFL produced by the rotating scanning device to scan at a uniform speed. This helps the rotating scanning device to more conveniently control and determine the position of the FFL over time during scanning, while this current also has a certain anti-interference capability. Summary of the Invention

[0004] The purpose of this invention is to propose an input current optimization method based on uniform rotation scanning of an MPI orthogonal model, which can solve the problem of irregular FFL rotation in existing selected models.

[0005] To achieve the above objectives, the technical solution of the present invention is: an input current optimization method based on MPI orthogonal model uniform rotation scanning. For a rotating scanning device composed of two zero-field line devices built by two sets of coils, the input current of the two sets of coils that generate mutually perpendicular zero-field lines is controlled to be a periodic current, thereby controlling the fused zero-field line generated by the rotating scanning device to rotate periodically at a uniform speed, so as to determine the position of the fused zero-field line at any time.

[0006] Preferably, the zero-field line device consists of four rectangular coils, and the four rectangular coils satisfy the following relative positional relationship:

[0007] For two rectangular coils on the same side, assuming the first rectangular coil is placed horizontally, the position of the second rectangular coil is obtained by translating the first rectangular coil vertically by a preset distance;

[0008] The other two rectangular coils on the same side, the third and fourth rectangular coils, are obtained by moving the first and second rectangular coils a preset distance in the horizontal direction.

[0009] Preferably, in the zero-field line device, two rectangular coils on the same side are applied with current of the same magnitude and direction, and two rectangular coils on opposite sides are applied with current of equal magnitude but opposite direction, thereby creating a zero-field line in the central region of the four rectangular coils.

[0010] Preferably, the rotating scanning device includes two zero-field line devices, and the two zero-field line devices are intersected at the same center point to generate two mutually perpendicular zero-field lines.

[0011] Preferably, the input current of the two sets of coils that generate mutually perpendicular zero-field lines is controlled to be a periodic current, as follows:

[0012]

[0013]

[0014] Where a is the amplitude of the input current, T is 1 / 8 of the input current period (T is a real number greater than zero), and t is time. and The input current for two sets of coils that generate mutually perpendicular zero-field lines within one cycle; specifically, within one current cycle. and These represent the input currents of the rectangular coils on opposite sides of one set of zero-field line devices. and These represent the input currents of the rectangular coils on the opposite side of another set of zero-field line devices.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] This invention proposes an optimization scheme for the scanning method of a rotating scanning device, making the rotational scanning of the FFL (Flexible Fluid Light) more uniform and controllable. In actual calculations, because the optimized current always maintains one current constant while the other changes, the probability of error is reduced. If the current is misaligned, the two changing currents simultaneously will cause all data to be incorrect; however, the optimized current will still contain some accurate data. Attached Figure Description

[0017] Figure 1 This is a basic flowchart of the simulation process according to an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of a zero-field line device according to an embodiment of the present invention;

[0019] Figure 3 This is a schematic diagram of a rotating scanning device according to an embodiment of the present invention;

[0020] Figure 4 This is a schematic diagram of the input current of the XFFL and YFFL according to an embodiment of the present invention;

[0021] Figure 5 This is a schematic diagram of the uniform rotation of an FFL according to an embodiment of the present invention. Detailed Implementation

[0022] The following is in conjunction with the appendix Figure 1-5 The technical solution of the present invention will be described in detail below.

[0023] This invention proposes an input current optimization method based on MPI orthogonal model uniform rotation scanning. For a rotating scanning device composed of two zero-field line devices built by two sets of coils, the input current of the two sets of coils that generate mutually perpendicular zero-field lines is controlled to be a periodic current, thereby controlling the fused zero-field line generated by the rotating scanning device to rotate periodically at a uniform speed, so as to determine the position of the fused zero-field line at any time.

[0024] In this embodiment, the zero-field line device consists of four rectangular coils, and the four rectangular coils satisfy the following relative positional relationship:

[0025] For two rectangular coils on the same side, assuming the first rectangular coil is placed horizontally, the position of the second rectangular coil is obtained by translating the first rectangular coil vertically by a preset distance;

[0026] The other two rectangular coils on the same side, the third and fourth rectangular coils, are obtained by moving the first and second rectangular coils a preset distance in the horizontal direction.

[0027] In this embodiment, in the zero-field line device, two rectangular coils on the same side are applied with current of the same magnitude and direction, and two rectangular coils on opposite sides are applied with current of equal magnitude but opposite direction, thereby creating a zero-field line in the central region of the four rectangular coils.

[0028] In this embodiment, the rotating scanning device includes two zero-field line devices, and the two zero-field line devices are intersected at the same center point to generate two mutually perpendicular zero-field lines.

[0029] In this embodiment, the input current of the two sets of coils that generate mutually perpendicular zero-field lines is controlled to be a periodic current, as follows:

[0030]

[0031]

[0032] Where a is the amplitude of the input current, T is 1 / 8 of the input current period (T is a real number greater than zero), and t is time. and The input current for two sets of coils that generate mutually perpendicular zero-field lines within one cycle; specifically, within one current cycle. and These represent the input currents of the rectangular coils on opposite sides of one set of zero-field line devices. and These represent the input currents of the rectangular coils on the opposite side of another set of zero-field line devices.

[0033] The simulation process of this invention is provided below for reference. Figure 1 This includes the following steps:

[0034] Step S1: In a simulation environment, a basic FFL generation device is built using rectangular coils.

[0035] Step S2: A fixed initial current is input to the coil in the basic FFL generating device to control the generation of a stable FFL region. The position of the FFL and the magnetic field strength around it are affected by the input current of the coil.

[0036] Step S3: Combine the two basic FFL generating devices to form a rotary scanning device that can meet the conditions for rotary scanning.

[0037] Step S4: Analyze the rotation principle of the FFL and adjust the input current of the rectangular coil to a periodic current, thereby controlling the periodic rotation of the fused FFL.

[0038] Step S5: Optimize the current parameters based on the principle to achieve a uniform scanning effect, thereby improving the controllability of MPI by making the FFL position more controllable.

[0039] Figure 2 The FFL generation apparatus is the basis for embodiments of the present invention.

[0040] In this experimental example, step S1 specifically includes:

[0041] Step S11: In the Comsol simulation environment, a total of four square coils with a side length of 12mm are needed to form a basic FFL generating device. The device consists of two sides, with two coils on each side.

[0042] Step S12: First, introduce the left side of the device: a square coil is placed horizontally, and the position of the other coil is obtained by vertically shifting the coil 20mm upwards. These two coils are called the left coil.

[0043] Step S13: The positions of the other two coils are obtained by shifting the left coil 16mm to the right. These two coils are on the right side and are called the right coils.

[0044] In this experimental example, step S2 specifically includes:

[0045] Step S21: Apply a current of the same magnitude and direction to the two coils on the same side of the FFL generating device. The current magnitude is 1A, and the resulting magnetic fields are relatively stable after superposition.

[0046] Step S22: Currents of equal magnitude but opposite direction are passed through the coils on opposite sides of the generating device. The magnetic fields on both sides are superimposed and canceled out, and finally a straight line region with a basically zero magnetic field is generated in the central region of the four coils, which is the zero field line (FFL).

[0047] Step S23: Increase the current in all four coils by the same magnitude. The magnetic field around the FFL will also increase by the same factor. When the currents on the left and right sides are different, the FFL will shift towards the side with the lower coil current. When the shifting distance is long, the FFL will bend slightly.

[0048] In this experimental example, step S3 specifically includes:

[0049] Step S31: Place the two FFL generating devices intersecting at the same center point so that the FFLs they generate are perpendicular to each other and the coils of the two devices do not affect each other, thus obtaining a device that meets the rotation scanning conditions.

[0050] In MPI, the rotating scanning device generates a controllable zero-field region, the field-free field (FFL). Magnetic nanoparticles within this zero-field region, stimulated by an excitation signal, produce corresponding magnetization signals. By collecting the magnetization signals generated at different positions within the FFL and reconstructing these signals, a spatial distribution image of the magnetic particles can be obtained—this is the process of MPI.

[0051] Figure 3 This is a rotating scanning device according to an embodiment of the present invention.

[0052] In this experimental example, step S4 specifically includes:

[0053] Step S41: The principle of FFL rotation is that magnetic fields can be superimposed. Two FFLs that are perpendicular to each other and have different magnetic field strengths can be combined into one FFL in their intersecting plane after being superimposed.

[0054] Step S42: Changing the magnetic field strength of the two FFLs can change the angle of the fused FFL. The fused FFL rotates in the YOZ plane, and its initial position is the Y-axis. At this time, only the magnetic field of the Y-axis FFL exists, and the magnetic field of the Z-axis FFL is zero. When the magnetic fields of the two FFLs are equal, the angle between the fused FFL and its initial position is 45 degrees.

[0055] Step S43: The relationship between the two is a tan function, which means that when the overall magnetic field strength of the Y-axis FFL is cosθ and the overall magnetic field strength of the Z-axis FFL is sinθ, the angle between the merged FFL and its initial position is θ.

[0056] Step S44: Add a simple, varying periodic current to each of the two sets of coils to enable the fused FFL to rotate 180 degrees.

[0057] Furthermore, since the FFL is a straight line, rotating it 180 degrees will enable a 360-degree scan.

[0058] In this experimental example, step S5 specifically includes:

[0059] Step S51: Based on the law of fusion FFL rotation, analyze the possibility and feasibility of uniform rotation, and adjust the input current.

[0060] Step S52: The values ​​of the input current of the two sets of coils generating different FFLs within one cycle are:

[0061]

[0062] Furthermore, the two currents in the formula , These are the coil input currents that generate the corresponding FFLs, with a period of four seconds. However, the fused FFL can complete a full plane scan within two seconds. This periodically changing input current provides the energy for the uniform rotation of the FFL generated by this model.

[0063] Figure 4 The input currents of XFFL and YFFL in this embodiment of the invention are given.

[0064] Step S53: The fused FFL generated under this current condition moves in the plane at a rate of [per second]. By rotating at a constant speed, the position of the fused FFL can be determined at any given moment. This allows us to identify the source of the magnetization signal at any given time, improving the accuracy of the reconstructed image.

[0065] Figure 5 This is an image of an FFL rotating at a constant speed, representing an embodiment of the present invention.

[0066] Furthermore, the white area in the diagram represents the zero magnetic field region at the corresponding moment, and the black line represents the position at the corresponding angle. The two almost overlap, indicating that the FFL indeed achieved uniform rotation.

[0067] In summary, this invention proposes an optimization scheme for the scanning method of the rotating scanning device, making the rotational scanning of the FFL more uniform and controllable. In actual calculations, since one current remains constant while the other changes in each cycle after optimization, the probability of error is reduced. If the current is misaligned, the two changing currents simultaneously will cause all data to be incorrect; however, the optimized current still contains some accurate data. Specifically:

[0068] Since the amplitude of the DC signal input current remains constant, it does not produce errors such as crosstalk that only occur with changing currents. Therefore, the probability of error is lower than with changing current signals. Because the optimized current in this application involves one current remaining constant while the other changes, the probability of error is reduced compared to two changing currents.

[0069] Furthermore, if both input currents are variable currents, as long as the phase of one of the signals changes, the actual position of the fused FFL will deviate from the expected position at all times. However, with the current optimized in this application, if one input current experiences a phase shift while the other remains unchanged, because the input current that causes the shift contains a DC component, the phase shift will not affect a portion of the DC signal. The fused FFL position generated in this portion remains accurate. Ideally, the phase deviation can be inferred from this accurate region and the input signal can be adjusted accordingly.

[0070] Specifically, deviations only occur at all times when the phase deviation is 1 / 4 period or 3 / 4 period.

[0071] The above are preferred embodiments of the present invention. Any changes made to the technical solution of the present invention that do not exceed the scope of the technical solution of the present invention shall fall within the protection scope of the present invention.

Claims

1. An input current optimization method based on uniform rotational scanning using an MPI orthogonal model, characterized in that, For a rotating scanning device composed of two zero-field line devices built by two sets of coils, the input current of the two sets of coils that generate mutually perpendicular zero-field lines is controlled to be a periodic current, thereby controlling the fused zero-field line generated by the rotating scanning device to rotate periodically at a uniform speed, so as to determine the position of the fused zero-field line at any time.

2. The input current optimization method based on uniform rotation scanning of an MPI orthogonal model according to claim 1, characterized in that, The zero-field line device consists of four rectangular coils, and the four rectangular coils satisfy the following relative positional relationship: For two rectangular coils on the same side, assuming the first rectangular coil is placed horizontally, the position of the second rectangular coil is obtained by translating the first rectangular coil vertically by a preset distance; The other two rectangular coils on the same side, the third and fourth rectangular coils, are obtained by moving the first and second rectangular coils a preset distance in the horizontal direction.

3. The input current optimization method based on uniform rotation scanning of an MPI orthogonal model according to claim 2, characterized in that, In the zero-field line device, two rectangular coils on the same side are applied with current of the same magnitude and direction, and two rectangular coils on opposite sides are applied with current of equal magnitude but opposite direction, thereby creating a zero-field line in the central region of the four rectangular coils.

4. The input current optimization method based on uniform rotation scanning of an MPI orthogonal model according to claim 3, characterized in that, The rotating scanning device includes two zero-field line devices, which are intersected at the same center point to generate two mutually perpendicular zero-field lines.

5. The input current optimization method based on uniform rotation scanning of an MPI orthogonal model according to claim 4, characterized in that, By controlling the input current of the two sets of coils that generate mutually perpendicular zero-field lines to be periodic currents, as follows: Where a is the amplitude of the input current, T is 1 / 8 of the input current period (T is a real number greater than zero), and t is time. and The input current for two sets of coils that generate mutually perpendicular zero-field lines within one cycle; specifically, within one current cycle. and These represent the input currents of the rectangular coils on opposite sides of one set of zero-field line devices. and These represent the input currents of the rectangular coils on the opposite side of another set of zero-field line devices.

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