A magnetic particle imaging system and method for multi-slice synchronous scanning

Abstract

The present invention belongs to the field of magnetic nanoparticle imaging technology, and relates to a multi-slice synchronous scanning magnetic particle imaging system and method, which aims to solve the problems of narrow field of view, single imaging plane, slow scanning speed, etc. of existing FFL-MPI equipment. The present invention comprises: providing an excitation current and a dynamic gradient current for controlling axial translation and radial rotation to an excitation module and a multi-slice gradient module respectively; the multi-slice gradient module is composed of a plurality of FFL gradient units, and the axial translation current phase of each FFL gradient unit increases successively and is different from each other, so as to realize the rapid axial movement of the FFL; the excitation module is used to generate an excitation magnetic field to excite magnetic particles; the signal detection module receives the response signal, and after external signal compensation and signal processing, transmits it to the control and processing module for algorithm reconstruction. The present invention can simultaneously image multiple radial slices in space, breaking through the limitations of a single imaging plane and improving the axial imaging field of view and scanning speed.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic nanoparticle imaging, and in particular relates to a multi-slice synchronous scanning magnetic particle imaging system and method. Background Art

[0002] Magnetic Particle Imaging (MPI), a highly promising non-invasive imaging technology, has garnered widespread attention in recent years in fields such as biomedical imaging. This technology uses superparamagnetic nanoparticles as tracers and utilizes an external high-frequency excitation magnetic field to drive these particles, causing them to generate specific nonlinear magnetic response signals. The MPI device captures these signals and, using imaging algorithms, converts them into images of the particle distribution, thereby visualizing the imaging subject. In an MPI device, the gradient coil module generates a high-intensity static magnetic field, primarily creating magnetic-free zones such as field-free points (FFPs) or field-free lines (FFLs). The excitation coil module, on the other hand, generates a high-frequency dynamic excitation magnetic field, which enables the FFP or FFL to move within the scanning area, thereby enabling imaging of the entire region.

[0003] During MPI imaging, by dynamically moving a magnetic field-free zone across the scanned object, magnetic particles are stimulated to generate signals. These signals are then captured by a receiving system and used to reconstruct the distribution of magnetic nanoparticles within the imaging area. FFL offers unique advantages over point-based FFP. FFL refers to a line in the magnetic field along which the magnetic field intensity is zero or near-zero. In MPI devices using FFL mode (FFL-MPI), the signal response of the magnetic particles is generated along this line rather than being concentrated at a single point. Because of this, FFL technology can cover a larger volumetric area with each excitation, significantly improving imaging speed and becoming a key research direction for future MPI technology.

[0004] However, existing FFL-MPI devices generally have limitations. They all use a single, magnetic-free line for scanning. In 3D imaging scenarios, imaging speed increases rely solely on the scanning and rotation frequencies. However, this approach faces bottlenecks due to power consumption limitations, limiting the potential for further improvements in imaging speed. Furthermore, the single imaging plane limits their application in imaging complex 3D structures.

[0005] Therefore, there is a need for an imaging system that can break the dilemma of the existing magnetic particle imaging equipment with a single imaging plane and limited speed improvement. Summary of the Invention

[0006] In order to solve the above-mentioned problems in the prior art, namely, the narrow field of view, single imaging plane, slow scanning speed and other problems of the existing FFL-MPI equipment, the first aspect of the present invention provides a multi-slice synchronous scanning magnetic particle imaging system, the system includes a control and processing module, a signal processing module, a signal detection module, a signal acquisition and output module, the system also includes: a multi-slice gradient module, an excitation module and an external signal compensation module;

[0007] The multi-slice gradient module comprises N FFL gradient units that are evenly and equidistantly arranged along the length direction; the phase of the axial translation current passed through each FFL gradient unit increases sequentially along the axial direction; each FFL gradient unit comprises four gradient coils, and two parallel gradient coils form a pair, and the two pairs of gradient coils are arranged radially orthogonally. The two pairs of gradient coils apply the same axial translation current and differentiated radial rotation current respectively, thereby achieving axial synchronous rapid scanning and radial rotation of the FFL; the excitation module comprises N groups of excitation coils that are evenly and equidistantly arranged along the length direction;

[0008] The excitation module includes N groups of excitation coils evenly and equidistantly arranged along the length direction;

[0009] The control and processing module generates the axial translation current and radial rotation current required by the multi-slice gradient module and the excitation current required by the excitation module;

[0010] The multi-slice gradient module receives an axial translation current and a radial rotation current to generate a plurality of magnetic field-free lines, and controls the magnetic field-free lines to rotate and scan in the axial direction based on a preset control strategy; the excitation module receives an excitation current to drive the magnetic field-free lines to move rapidly in the vertical direction, thereby driving the magnetic particles to generate response signals;

[0011] The signal detection module collects the response signal and obtains the particle response signal through the external signal compensation module and the signal processing module. The signal is returned to the control and processing module by the signal acquisition and output module, and image reconstruction is performed through a preset algorithm to realize magnetic particle imaging.

[0012] In some preferred embodiments, the axial translation current and radial rotation current generated by the control and processing module are sent to the gradient power amplifier for amplification via the signal acquisition and output module, and the amplified axial translation current and radial rotation current are sent to the multi-slice gradient module; the excitation current generated by the control and processing module is sent to the excitation power amplifier for amplification via the signal acquisition and output module, and the amplified excitation current is sent to the excitation module.

[0013] In some preferred embodiments, the length of a single receiving coil of the signal detection module is less than the distance between the two FFLs, and the axial length of the multi-slice gradient module is the same as the axial length of the excitation module.

[0014] In some preferred embodiments, the axial translation current is a sinusoidal current, and one cycle of axial translation current is passed through every n FFL gradient units, thereby generating two FFLs. The multi-slice gradient module generates a total of m FFLs, where , , is the total number of the FFL gradient units.

[0015] In some preferred embodiments, the phase of the axial translation current passed through each FFL gradient unit increases from left to right along the axial direction. .

[0016] In some preferred embodiments, the same axial translation current and differentiated radial rotation current are respectively supplied to the two pairs of gradient coils in each FFL gradient unit, and the method is as follows:

[0017] Current is supplied to the two pairs of gradient coils in each FFL gradient unit:

[0018] ;

[0019] ;

[0020] in, For the l FFL gradient unit y The current of the gradient coil in the direction, For the l FFL gradient unit z The current of the gradient coil in the direction, l is the serial number of the FFL gradient unit; is the frequency period of the axial translation current, controlling the scanning frequency of the FFL moving in the axial direction; is the rotation frequency of FFL in the radial direction, is the amplitude of the gradient coil dynamic current, is an independent variable that changes over time.

[0021] In some preferred embodiments, an excitation current is supplied to the excitation coil in the excitation module. , all magnetic particles within the field of view are excited and particles are selected by the generated FFL;

[0022] Excitation current for:

[0023] ;

[0024] Among them, when the excitation current is applied, and ; is the frequency of the excitation current, which controls the radial rotation frequency of the FFL. is the amplitude of the excitation current, is the initial phase of the excitation current, is an independent variable that changes over time.

[0025] In some preferred embodiments, the magnetic field-free lines are controlled to rotate and scan along the axial direction based on a preset control strategy, and the method is as follows:

[0026] when When the FFL is scanned in discrete angles, it first quickly moves to the axial end of the entire magnet to complete the whole body scan of the object, and then switches the angle to scan the next angle until the 3D scan of the object is completed.

[0027] when When , the scanning trajectory of the FFL is a discrete translation trajectory, which first completes the scanning of all two-dimensional FOVs in the current plane, and then moves to the next plane for rotation until the 3D scanning of the object is completed;

[0028] Otherwise, the FFL moves forward in a spiral trajectory until it reaches the axial end of the entire magnet, completing the 3D scanning of the object being measured;

[0029] in, 、 is a pre-set adjustment coefficient.

[0030] In some preferred embodiments, the particle response signal is image reconstructed by:

[0031] The particle response signal is subjected to two-dimensional imaging of different imaging planes using a system matrix or inverse Radon transform, and then a velocity compensation algorithm is used to perform position mapping of scanning of different imaging planes to achieve three-dimensional imaging.

[0032] A second aspect of the present invention provides a magnetic particle imaging method for multi-slice synchronous scanning, characterized in that the method comprises:

[0033] S1. Applying an axial translation current to the multi-slice gradient module to generate a plurality of magnetic field-free lines along the axial direction, wherein the phase of the axial translation current applied to each FFL gradient unit increases sequentially from left to right along the axial direction;

[0034] S2. Applying differentiated radial rotating currents to the two pairs of gradient coils in each of the FFL gradient units, and controlling the magnetic field-free lines to rotate and scan in the axial direction based on a preset control strategy;

[0035] S3, passing an excitation current into the excitation module to drive the magnetic field lines to move rapidly in a vertical direction, thereby driving the magnetic particles to generate a response signal;

[0036] S4, collecting the response signal and suppressing interference in the response signal to obtain a particle signal;

[0037] S5. performing signal processing on the particle signal to obtain a particle response signal;

[0038] S6. Perform image reconstruction based on the particle response signal to obtain a three-dimensional spatial distribution image of the magnetic particles.

[0039] Beneficial effects of the present invention:

[0040] The present invention can create multiple imaging planes in a three-dimensional imaging space and generate multiple magnetic field-free lines at the same time. By controlling the dynamic gradient magnetic field, the FFL can achieve rapid axial movement. Under synchronous control, multiple planes can be imaged simultaneously, and a multi-channel acquisition module is equipped to separate and reconstruct images of signals from different planes, breaking the limitation of a single imaging plane, greatly expanding the imaging range and dimension, and being able to obtain more spatial position information at one time, greatly improving imaging efficiency and the integrity of information acquisition. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Other features, objects and advantages of the present application will become more apparent upon reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0042] Figure 1 It is a structural schematic diagram of the magnetic particle imaging system for multi-slice synchronous scanning of the present invention;

[0043] Figure 2 Schematic diagram of the current phases passed to different FFL gradient units of the multi-slice gradient module in an embodiment of the present invention;

[0044] Figure 3 is a cross-sectional schematic diagram of a multi-slice gradient module and a schematic diagram of an FFL scanning field of view (FOV) in an embodiment of the present invention;

[0045] Figure 4 This is a simulation result diagram of the embodiment of the present invention in which no magnetic field lines are generated;

[0046] Figure 5 is a diagram of the axial magnetic field distribution at different times when there are no magnetic field lines in an embodiment of the present invention;

[0047] Figure 6 This is a simulation result diagram of an embodiment of the present invention when N=6 and n=6 without magnetic field line rotation scanning;

[0048] Figure 71 is a flow chart of a multi-slice synchronous scanning imaging method according to an embodiment of the present invention;

[0049] The reference numerals are as follows:

[0050] 1. Control and processing module, 2. Signal acquisition and output module, 3. Excitation power amplifier, 4. Gradient power amplifier, 5. Signal processing module, 6. Multi-slice gradient module, 610. First FFL gradient unit, 611. First coil, 612. Second coil, 613. Third coil, 614. Fourth coil, 620. Second FFL gradient unit, 621. Fifth coil, 622. Sixth coil, 623. Seventh coil, 630. Third FFL gradient unit, 631. Ninth coil, 632. Xth coil, 633. XIth coil, 640. Nth FFL gradient unit, 641. 4N-3th coil, 642. 4N-2th coil, 643. 4N-1th coil, 7. Excitation module, 8. Signal detection module, 801. First receiving coil group, 802. Second receiving coil group, 803. Third receiving coil group, 804. Nth receiving coil group, 9. External signal compensation module. DETAILED DESCRIPTION

[0051] The present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are intended only to illustrate the relevant invention and are not intended to limit the invention. It should also be noted that, for ease of description, only portions relevant to the relevant invention are shown in the accompanying drawings.

[0052] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0053] The present invention provides a slice dynamic gradient unit that dynamically constructs multiple freely rotatable and scannable magnetic field-free line gradient magnetic fields in the axial space, and by applying a sinusoidal current, the FFL is made to move rapidly and dynamically in the form of a sine wave in the axial direction, thereby achieving an improvement in the scanning speed; a high-frequency excitation magnetic field is simultaneously provided to all magnetic particles near the FFL through a multi-segment excitation module, thereby driving the magnetic particles to generate nonlinear response signals; a multi-channel detection is performed on the magnetic field response of the magnetic particles in the imaging slice, and the filtering and amplification modules are connected to the ADC converter for input to the processing computer, thereby improving the original signal data for simultaneous imaging of multiple slices, thereby achieving three-dimensional full-field synchronous and rapid imaging, and significantly improving the three-dimensional imaging speed and sensitivity.

[0054] In order to more clearly explain the magnetic particle imaging system for multi-slice synchronous scanning of the present invention, Figure 1-7The system in the embodiment of the present invention is described in detail. The system includes a control and processing module 1, an excitation power amplifier 3, a gradient power amplifier 4, a signal processing module 5, a signal detection module 8, a signal acquisition and output module 2, a multi-slice gradient module 6, an excitation module 7 and an external signal compensation module 9;

[0055] The control and processing module 1 is used to generate the axial translation current and radial rotation current required by the multi-slice gradient module 6 and the excitation current required by the excitation module 7;

[0056] The multi-slice gradient module 6 is used to receive an axial translation current and a radial rotation current, generate a gradient magnetic field and a plurality of non-magnetic field lines, and control the non-magnetic field lines to rotate and scan in the axial direction based on a preset control strategy;

[0057] The excitation module 7 is used to receive the excitation current, drive the magnetic field lines to scan in the vertical direction, and then drive the magnetic particles to generate response signals;

[0058] The signal detection module 8 is used to collect the response signal, and obtain the particle response signal through the external signal compensation module and the signal processing module, and return the signal to the control and processing module through the signal acquisition and output module, and reconstruct it through a preset algorithm to achieve magnetic particle imaging;

[0059] The multi-slice gradient module 6 includes N FFL gradient units that are evenly and equidistantly arranged along the length direction. The phase of the axial translation current passed through each FFL gradient unit increases in sequence along the axial direction. A sinusoidal current of one cycle is passed through every n FFL gradient units, thereby generating two FFLs. Each FFL gradient unit includes four gradient coils, two of which form a pair. The two pairs of gradient coils are arranged radially orthogonally. The two pairs of gradient coils are respectively applied with the same axial translation current and differentiated radial rotation current, thereby achieving axial synchronous rapid scanning and radial rotation of the FFL.

[0060] The excitation module 7 includes N groups of excitation coils evenly and equidistantly arranged along the length direction. The axial length of the multi-slice gradient module 6 is the same as the axial length of the excitation module 7. The length of a single receiving coil of the signal detection module 8 is less than the distance between the two FFLs.

[0061] Preferably, the axial translation current and radial rotation current generated by the control and processing module 1 are sent to the gradient power amplifier 4 for amplification via the signal acquisition and output module 2, and the amplified axial translation current and radial rotation current are sent to the multi-slice gradient module 6; the excitation current generated by the control and processing module 1 is sent to the excitation power amplifier 3 for amplification via the signal acquisition and output module 2, and the amplified excitation current is sent to the excitation module 7.

[0062] Preferably, the distance between two consecutive FFLs is half the wavelength of the current passed through the FFL gradient unit. Two FFLs are generated by passing a sinusoidal current through every n FFL gradient units. The sensitive area of the receiving coil must be smaller than the distance between the two consecutive FFLs. The signal detection module 8 includes a multi-segment multi-channel receiving coil, and the length of each receiving coil segment is smaller than the distance between the two FFLs.

[0063] Preferably, the axial translation current is a sinusoidal current, and one cycle of axial translation current is passed through every n FFL gradient units, thereby generating two FFLs. The multi-slice gradient module generates a total of m FFLs, where , , is the total number of the FFL gradient units. Different FLLs move approximately linearly along the axial direction and pass through the entire body of the object being measured.

[0064] Further preferably, the phase of the axial translation current passed into each FFL gradient unit increases from left to right along the axial direction. .

[0065] Preferably, differentiated dynamic currents are applied to the two pairs of gradient coils in each FFL gradient unit, respectively. The dynamic currents include the same axial translation current and radial rotation current, specifically:

[0066] Current is supplied to the two pairs of gradient coils in each FFL gradient unit:

[0067] ;

[0068] ;

[0069] In the radial plane, each set of coils is defined according to the direction y Direction and z Direction Two pairs of coils, the magnetic field direction of each pair of coils is the same;

[0070] in, For the l FFL gradient unit y The current of the gradient coil in the direction, For the l FFL gradient unit z The current of the gradient coil in the direction, l is the serial number of the FFL gradient unit; is the frequency period of the axial translation current, controlling the scanning frequency of the FFL moving in the axial direction; is the rotation frequency of FFL in the radial direction, is the amplitude of the gradient coil dynamic current, is an independent variable that changes over time.

[0071] A sinusoidal current with increasing phases of successive coils is applied to each dynamic gradient unit coil assembly element in the axial direction, and the phase difference between adjacent elements is adjusted so that the current distribution in the axial direction is a wave spatially extended over one wavelength, so that the linearly moving sinusoidal magnetic field wave travels in this direction.

[0072] Preferably, the magnetic field-free lines are controlled to rotate and scan along the axial direction based on a preset control strategy, and the method is as follows:

[0073] when When the FFL is scanned in discrete angles, it first quickly moves to the axial end of the entire magnet to complete the whole body scan of the object, and then switches the angle to scan the next angle until the 3D scan of the object is completed.

[0074] when When , the scanning trajectory of the FFL is a discrete translation trajectory, which first completes the scanning of all two-dimensional FOVs in the current plane, and then moves to the next plane for rotation until the 3D scanning of the object is completed;

[0075] Otherwise, the FFL moves forward in a spiral trajectory until it reaches the axial end of the entire magnet, completing the 3D scanning of the object being measured;

[0076] in, 、 is the preset adjustment coefficient, To define the adjustment coefficient when the scanning frequency of the axial movement is much greater than the rotation frequency in the radial direction, This defines the adjustment factor when the scanning frequency of the axial movement is much smaller than the rotation frequency in the radial direction.

[0077] Preferably, an excitation current is supplied to the excitation coil in the excitation module 7. , all magnetic particles within the field of view are excited and particles are selected by the generated FFL;

[0078] Excitation current for:

[0079] ;

[0080] in, is the frequency of the excitation current, which controls the radial rotation frequency of the FFL. is the amplitude of the excitation current, is the initial phase of the excitation current, is an independent variable that changes over time.

[0081] Further preferably, when the excitation current is applied, and .

[0082] Preferably, in this embodiment, the optimal sampling rate for collecting the response signal is above 3M / s.

[0083] Preferably, the control and processing module 1 uses a system matrix or inverse Radon transform to complete two-dimensional imaging of different imaging planes for the received processed particle response signals, and then uses a velocity compensation algorithm to perform position mapping of scanning of different imaging planes to achieve three-dimensional imaging.

[0084] Preferably, the total length of the excitation coil is the same as the axial length of the gradient coil, and together they generate an axially uniform excitation magnetic field. Simultaneously energizing all the excitation coils can drive the first and second excitation coils simultaneously. i A magnetic field-free line scans radially in the imaging plane and drives the magnetic particles on the line track to generate response signals.

[0085] Further preferably, the excitation current is a multi-frequency current, which enriches the response spectrum of the particles and is conducive to improving resolution and sensitivity.

[0086] The signal detection module 8 and external compensation module 9 consist of a set of receiving coils and a set of external excitation receiving pairs. The compensated signal is input into the control and processing module 1 through the signal processing unit. By analyzing the magnetic particle signals in response to the excitation magnetic field applied to different slices, the harmonic signal values corresponding to different fundamental frequencies in the signal spectrum can be separated due to the different applied frequencies. This completes signal mapping for different slices and uses a predetermined reconstruction algorithm to achieve image reconstruction of different regions.

[0087] Preferably, in this embodiment, Figure 2 As shown, the multi-slice gradient module 6 includes a first FFL gradient unit 610, a second FFL gradient unit 620, a third FFL gradient unit 630...Nth FFL gradient unit 640, each group of units is respectively fed into a continuous coil phase increase The sinusoidal current will generate an FFL at each zero-crossing point of the magnetic field, generating a total of m FFLs, where ,and .

[0088] More preferably, n≥3 can form the simplest dynamic gradient coil array.

[0089] That is, in the axial direction, a sinusoidal current of one cycle is supplied to each of the N dynamic gradient coil units (the phase difference is , so the phase of the nth unit is Same as the first one, for one cycle), so every n dynamic gradient coil units generate two FFLs, and the distance between two consecutive FFLs is approximately To obtain signals from only one FFL at a time, the sensitive area of the receiving coil must be smaller than the distance between two consecutive FFLs, that is, smaller than The distance between the dynamic gradient coils.

[0090] Preferably, if Figure 3 As shown, the first FFL gradient unit 610 includes two pairs of gradient coils, the first coil 611 and the third coil 613 constitute a first gradient coil pair, and the second coil 612 and the fourth coil 614 constitute a second gradient coil pair; the two coils of the gradient coil pair are coaxially arranged in parallel, and the axes of the two coil pairs are orthogonal; the axis of the excitation coil passes through the orthogonal point of the axes of the two coil pairs, and the third axis is perpendicular to the plane formed by the axes of the two coil pairs. In the second FFL gradient unit 620, the fifth coil 621 and the seventh coil 623 constitute a third gradient coil pair, and the sixth coil 622 and the eighth coil constitute a fourth gradient coil pair. In the third FFL gradient unit 630, the ninth coil 631 and the XIth coil 633 constitute a fifth gradient coil pair, and the Xth coil 632 and the XIIth coil constitute a sixth gradient coil pair. In the NFFL gradient unit 640, the 4Nth coil 641 and the 4N-3th coil 643 constitute a 2N-1th gradient coil pair, and the 4N-1th coil 642 and the 4N coil constitute a 2Nth gradient coil pair.

[0091] The first coil 611 and the third coil 613 are supplied with current in the same direction. , the second coil 612 and the fourth coil 614 are supplied with current in the same direction , and The phase difference is 90° and the rotation frequency is and the second FFL gradient unit 620, the The dynamic gradient units 640 work together to generate the FFL in the axial center, and the current is continuously switched (frequency is )FFL also moves dynamically along the axial direction. At the same time, the excitation current is fed into the excitation magnetic field coil module. , all magnetic particles within the field of view are excited, and particles are selected through the generated FFL. The signal detection module 8 includes a first receiving coil group 801, a second receiving coil group 802, a third receiving coil group 803, and an Nth receiving coil group 804, which respectively detect the response signals of the magnetic particles excited by each FLL area.

[0092] There are three types of scanning strategies for FFL rotation and translation:

[0093] 1. Discrete angle scanning trajectory, that is , the speed of FFL moving in the axial direction is much greater than the rotational speed. FFL will first quickly move to the axial end of the entire magnet to complete the whole body scan of the object, and then switch the angle to scan the next angle, and finally complete the whole body 3D scan;

[0094] 2. Spiral scanning trajectory, i.e. and When the difference is not large, the radial rotation speed of the FFL is close to the axial movement speed, and the FFL moves forward in a spiral trajectory;

[0095] 3. Discrete translation trajectory, i.e. , the radial rotation speed of the FFL must be greater than or equal to the axial movement speed, that is, the FFL first completes the scanning of all two-dimensional FOVs in the current plane, and then moves to the next plane for rotation. The frequency ratio can be calibrated through actual measurement to achieve the optimal scanning speed and imaging effect.

[0096] Preferably, the gradient coil in the FFL gradient unit is annular, and the excitation coil is cylindrical, but the shapes are not limited to the above-mentioned shapes. The shapes of the above-mentioned coils are only used as examples. On the premise of meeting the structural layout of the present invention, other shapes can be used.

[0097] Further preferably, in this embodiment, an example of the multi-slice magnet structure of the present invention is a simulation diagram of two magnetic field line-free imaging planes generated by 6 groups of FFL gradient units, wherein the total number of axial units N=6, the total number of units in one axial scanning cycle n=6, and the coil winding directions of adjacent units are opposite.

[0098] Each unit inputs the same amplitude and phase difference The sinusoidal current of one cycle is just equal to the total axial length of the gradient coil unit. Therefore, at least The FFLs (i.e., the zero-crossing point of the x-direction magnetic field) correspond to the current between the positive coil and the negative coil. As time increases, the current amplitude of each coil changes according to the sine wave law, and the positions of the two FFLs also change accordingly (moving along the x-axis in the direction of the sine wave).

[0099] Preferably, in this example, there are three control strategies:

[0100] ① Discrete angle scanning trajectory, that is , if , ;

[0101] ②Spiral scanning trajectory, that is and If the difference is not big, , ;

[0102] ③ Discrete translation trajectory, that is , if , .

[0103] like Figure 5 As shown in FIG, based on the above specific embodiment, the simulation results of the distribution of magnetic field intensity along the x-axis at different times are as follows:

[0104] The magnetic field is at 0 point in the figure, which is the plane where the FFL is located. The simulation sets up 5 instances at different times (from time 0 to Start to , time interval , is the axial scanning frequency The corresponding scanning period) is independent of the magnet structure and only depends on the system sampling frequency. About (i.e. ). The axial length of the magnet coil is , it can be seen from arrive Moved to the right after 0 o'clock , and the FFL moves rapidly in the axial direction over time, and after a complete cycle T, the FFL returns to In addition, it can be found that in this example, the phases of all axial coils are within one cycle, and the number of FFLs generated is 2. Therefore, it is actually only necessary to complete the axial scanning of all positions. Reducing N can generate more FFLs. As mentioned above, the number of FFLs can be , so the scanning period corresponds to .

[0105] like Figure 6 As shown in FIG, based on the above specific embodiment, the magnetic field distribution effect diagram of multiple FFLs rotating simultaneously is achieved by controlling the current difference of two pairs of orthogonal coils in the same group of dynamic gradient units. Figure 3 The shown i The current flowing through the coil pair in the y direction is The current flowing through the coil in the x direction is , the other structural parameters of the coil are Figure 4 Same, eventually Figure 6 Shown is The imaging results at the moment produce two radial rotations Corner FFL.

[0106] Preferably, the signal detection module 8 is disposed inside the multi-slice gradient module 6 and is coaxial with the multi-slice gradient module 6 .

[0107] It should be noted that the multi-slice synchronous scanning magnetic particle imaging system provided in the above embodiment is merely illustrated by the division of the above functional modules. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the modules or steps in the embodiments of the present invention can be further decomposed or combined. For example, the modules in the above embodiment can be combined into one module or further divided into multiple sub-modules to complete all or part of the functions described above. The names of the modules and steps involved in the embodiments of the present invention are merely for the purpose of distinguishing the modules or steps and are not to be considered as improper limitations of the present invention.

[0108] A second embodiment of the present invention provides a multi-slice synchronous scanning magnetic particle imaging method, characterized in that the steps include:

[0109] S1. Applying an axial translation current to the multi-slice gradient module 6 to generate a plurality of magnetic field-free lines along the axial direction, wherein the phase of the axial translation current applied to each FFL gradient unit increases sequentially from left to right along the axial direction;

[0110] S2. Applying differentiated radial rotating currents to the two pairs of gradient coils in each of the FFL gradient units, and controlling the magnetic field-free lines to rotate and scan in the axial direction based on a preset control strategy;

[0111] S3, passing an excitation current into the excitation module 7, driving the magnetic field lines to scan in the radial plane along the vertical direction of the FFL, and exciting the magnetic particles in the area to generate a response signal, thereby completing the excitation in one direction;

[0112] S4, collecting the response signal and suppressing interference in the response signal to obtain a particle signal;

[0113] S5, the collected response signal is sent to the external signal compensation module 9 and the signal processing module 5 in sequence for signal processing to obtain the particle response signal;

[0114] S6. Perform image reconstruction based on the particle response signal to obtain a three-dimensional spatial distribution image of the magnetic particles.

[0115] Although the various steps in the above embodiment are described in the above-mentioned order, those skilled in the art will understand that in order to achieve the effect of this embodiment, different steps do not have to be executed in such an order. They can be executed simultaneously (in parallel) or in a reverse order. These simple changes are within the scope of protection of the present invention.

[0116] The system of the present invention can simultaneously image magnetic particle tracers in multiple planes under synchronous control, and use a multi-channel acquisition module to separate signals from different planes and reconstruct images, thereby realizing imaging of multiple radial slices.

[0117] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working process and related instructions of the above-described method can refer to the corresponding process in the aforementioned system embodiment and will not be repeated here.

[0118] An electronic device according to a third embodiment of the present invention includes:

[0119] at least one processor; and

[0120] a memory communicatively connected to at least one of the processors; wherein,

[0121] The memory stores instructions that can be executed by the processor, and the instructions are used to be executed by the processor to implement the above-mentioned multi-slice synchronous scanning magnetic particle imaging method.

[0122] A fourth embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer instructions, and the computer instructions are configured to be executed by the computer to implement the above-mentioned multi-slice synchronous scanning magnetic particle imaging method.

[0123] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes and related instructions of the electronic device and computer-readable storage medium described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0124] Those skilled in the art should be able to appreciate that the modules and method steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two, and the programs corresponding to the software modules and method steps can be placed in random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium known in the art. In order to clearly illustrate the interchangeability of electronic hardware and software, the above description has generally described the components and steps of each example according to their functions. Whether these functions are performed in electronic hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0125] Computer program code for performing the operations of the present application may be written in one or more programming languages, or a combination thereof, including object-oriented programming languages such as Java, Smalltalk, C++, and conventional procedural programming languages such as "C" or similar programming languages. The program code may be executed entirely on the user's computer, partially on the user's computer, as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., through the Internet using an Internet service provider).

[0126] The flow charts and block diagrams in the accompanying drawings illustrate the possible architecture, functions and operations of the systems, methods and computer program products according to various embodiments of the present application. In this regard, each box in the flow chart or block diagram can represent a module, program segment or a part of code, and the module, program segment or a part of code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order than that marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flow chart, and the combination of the boxes in the block diagram and / or flow chart can be implemented by a dedicated hardware-based system that performs the specified function or operation, or can be implemented by a combination of dedicated hardware and computer instructions.

[0127] The terms "first", "second", etc. are used to distinguish similar objects, rather than to describe or indicate a particular order or sequence.

[0128] The term "comprise" or any other similar term is intended to cover non-exclusive inclusion such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0129] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

Claims

1. A magnetic particle imaging system for multi-slice synchronous scanning, comprising a control and processing module, a signal processing module, a signal detection module, and a signal acquisition and output module, characterized in that: The system further comprises: a multi-slice gradient module, an excitation module and an external signal compensation module; The multi-slice gradient module comprises N FFL gradient units that are evenly and equidistantly arranged along the length direction; the phase of the axial translation current passed through each FFL gradient unit increases sequentially along the axial direction; each FFL gradient unit comprises four gradient coils, and two parallel gradient coils form a pair, and the two pairs of gradient coils are arranged radially orthogonally. The two pairs of gradient coils apply the same axial translation current and differentiated radial rotation current respectively, thereby achieving axial synchronous rapid scanning and radial rotation of the FFL; the excitation module comprises N groups of excitation coils that are evenly and equidistantly arranged along the length direction; The control and processing module generates the axial translation current and radial rotation current required by the multi-slice gradient module and the excitation current required by the excitation module; The multi-slice gradient module receives an axial translation current and a radial rotation current to generate a plurality of magnetic field-free lines, and controls the magnetic field-free lines to rotate and scan in the axial direction based on a preset control strategy; the excitation module receives an excitation current to drive the magnetic field-free lines to move rapidly in a vertical direction, thereby driving the magnetic particles to generate a response signal; the length of a single receiving coil of the signal detection module is less than the spacing between the two FFLs, and the axial length of the multi-slice gradient module is the same as the axial length of the excitation module; The signal detection module collects the response signal and obtains the particle response signal through the external signal compensation module and the signal processing module. The signal is returned to the control and processing module by the signal acquisition and output module, and image reconstruction is performed through a preset algorithm to realize magnetic particle imaging.

2. The multi-slice synchronous scanning magnetic particle imaging system according to claim 1, characterized in that: The axial translation current and radial rotation current generated by the control and processing module are sent to the gradient power amplifier for amplification via the signal acquisition and output module, and the amplified axial translation current and radial rotation current are sent to the multi-slice gradient module; the excitation current generated by the control and processing module is sent to the excitation power amplifier for amplification via the signal acquisition and output module, and the amplified excitation current is sent to the excitation module.

3. The multi-slice synchronous scanning magnetic particle imaging system according to claim 1, characterized in that: The axial translation current is a sinusoidal current. One cycle of axial translation current is passed through every n FFL gradient units, thereby generating two FFLs. The multi-slice gradient module generates a total of m FFLs, where , , N is the total number of the FFL gradient units.

4. The multi-slice synchronous scanning magnetic particle imaging system according to claim 3, characterized in that: The phase of the axial translation current introduced into each FFL gradient unit increases from left to right along the axial direction. .

5. The multi-slice synchronous scanning magnetic particle imaging system according to claim 3, characterized in that: The same axial translation current and differentiated radial rotation current are respectively passed through the two pairs of gradient coils in each FFL gradient unit, and the method is as follows: Current is supplied to the two pairs of gradient coils in each FFL gradient unit: ； ； in, For the l FFL gradient unit y The current of the gradient coil in the direction, For the l FFL gradient unit z The current of the gradient coil in the direction, l is the serial number of the FFL gradient unit; is the frequency period of the axial translation current, controlling the scanning frequency of the FFL moving in the axial direction; is the rotation frequency of FFL in the radial direction, is the amplitude of the gradient coil dynamic current, is an independent variable that changes over time.

6. The multi-slice synchronous scanning magnetic particle imaging system according to claim 3, characterized in that: The excitation current is supplied to the excitation coil in the excitation module , all magnetic particles within the field of view are excited and particles are selected by the generated FFL; Excitation current for: ； Among them, when the excitation current is applied, and ; is the frequency of the excitation current, which controls the radial rotation frequency of the FFL. is the amplitude of the excitation current, is the initial phase of the excitation current, is an independent variable that changes over time.

7. A multi-slice synchronous scanning magnetic particle imaging system according to any one of claims 1 to 6, characterized in that: Based on the preset control strategy, the magnetic field-free lines are controlled to rotate and scan along the axial direction. The method is as follows: when When the FFL is scanned in discrete angles, it first quickly moves to the axial end of the entire magnet to complete the whole body scan of the object, and then switches the angle to scan the next angle until the 3D scan of the object is completed. when When , the scanning trajectory of the FFL is a discrete translation trajectory, which first completes the scanning of all two-dimensional FOVs in the current plane, and then moves to the next plane for rotation until the 3D scanning of the object is completed; Otherwise, the FFL moves forward in a spiral trajectory until it reaches the axial end of the entire magnet, completing the 3D scanning of the object being measured; in, 、 is a pre-set adjustment coefficient.

8. The multi-slice synchronous scanning magnetic particle imaging system according to claim 7, characterized in that: Performing image reconstruction on the particle response signal, the method is as follows: The particle response signal is subjected to two-dimensional imaging of different imaging planes using a system matrix or inverse Radon transform, and then a velocity compensation algorithm is used to perform position mapping of scanning of different imaging planes to achieve three-dimensional imaging.

9. A multi-slice synchronous scanning magnetic particle imaging method, based on a multi-slice synchronous scanning magnetic particle imaging system according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: S1. Applying an axial translation current to the multi-slice gradient module to generate a plurality of magnetic field-free lines along the axial direction, wherein the phase of the axial translation current applied to each FFL gradient unit increases sequentially from left to right along the axial direction; S2. Applying differentiated radial rotating currents to the two pairs of gradient coils in each of the FFL gradient units, and controlling the magnetic field-free lines to rotate and scan in the axial direction based on a preset control strategy; S3, passing an excitation current into the excitation module to drive the magnetic field lines to move rapidly in a vertical direction, thereby driving the magnetic particles to generate a response signal; S4, collecting the response signal and suppressing interference in the response signal to obtain a particle signal; S5. performing signal processing on the particle signal to obtain a particle response signal; S6. Perform image reconstruction based on the particle response signal to obtain a three-dimensional spatial distribution image of the magnetic particles.

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