Multi-slice synchronous scanning magnetic particle imaging system and method

Abstract

The invention belongs to the technical field of magnetic nanoparticle imaging, relates to a multi-slice synchronous scanning magnetic particle imaging system and method, and aims to solve the problems of narrow visual field, single imaging plane, low scanning speed and the like of existing FFL-MPI equipment. The method comprises the following steps: respectively providing excitation current and dynamic gradient current for controlling axial translation and radial rotation for an excitation module and a multi-slice gradient module; the multi-slice gradient module is composed of a plurality of FFL gradient units, the axial translation current phases of the FFL gradient units are gradually increased in sequence and are different from one another, and FFL axial rapid movement is achieved; the excitation module is used for generating an excitation magnetic field for exciting magnetic particles; and the signal detection module receives the response signal, and the response signal is transmitted to the control and processing module for algorithm reconstruction after being subjected to external signal compensation and signal processing. According to the invention, multiple radial slices can be imaged at the same time in the space, the limitation of a single imaging plane is broken through, and the axial imaging view and the scanning speed are improved.

Description

Background Art

[0002] Magnetic Particle Imaging (MPI), as a highly promising non-invasive imaging technology, has received extensive attention in the fields of biomedical imaging and others in recent years. This technology uses superparamagnetic nanoparticles as tracers, and utilizes an external high-frequency excitation magnetic field to drive these particles, enabling them to generate specific non-linear magnetic response signals. The MPI device captures these signals and, with the aid of imaging algorithms, converts them into images of the particle distribution, thereby achieving visualization of the imaging object. In the MPI device, the gradient coil module is responsible for generating a high-intensity static magnetic field, and its main function is to create a field-free point (FFP) or a field-free line (FFL) and other field-free regions; while the excitation coil module generates a high-frequency dynamic excitation magnetic field, which can move the FFP or FFL within the scanning area, thus realizing imaging of the entire area.

[0003] During the MPI imaging process, by dynamically moving the field-free region through the object to be scanned, magnetic particles can be excited to generate signals. These signals are then captured by the receiving system for reconstructing the distribution map of magnetic nanoparticles in the imaging area; among them, the FFL has unique advantages compared with the point-like FFP. The FFL refers to a line in the magnetic field along which the magnetic field strength is zero or close to zero; in an MPI device using the FFL mode (FFL-MPI), the signal response of magnetic particles is generated along this line rather than concentrated at a single point. For this reason, the FFL technology can cover a larger volume area with each excitation, greatly improving the imaging speed and becoming a key research direction for the current MPI technology in the future.

[0004] However, currently existing FFL-MPI devices generally have limitations. They all use a single field-free line for scanning. In a three-dimensional imaging scenario, the improvement of the imaging speed only depends on the scanning and rotation frequencies. However, due to the limitation of the total power consumption of the power supply, there is a bottleneck in this improvement method, making the improvement space of the imaging speed performance extremely limited. At the same time, the single imaging plane also restricts its application in imaging complex three-dimensional structures.

[0005] Therefore, an imaging system is needed that can break the dilemma of the single imaging plane and limited speed improvement of existing magnetic particle imaging devices. Summary of the Invention

[0006] To solve the above problems in the prior art, namely, the problems of narrow field of view, single imaging plane, slow scanning speed, etc. in the existing FFL-MPI device, the first aspect of the present invention proposes a magnetic particle imaging system with multi-slice synchronous scanning. The system includes a control and processing module, a signal processing module, a signal detection module, and a signal acquisition and output module. The system further includes: a multi-slice gradient module, an excitation module, and an external signal compensation module; The multi-slice gradient module includes N FFL gradient units arranged evenly at equal intervals along the length direction; the phases of the axial translation currents passed through each FFL gradient unit along the axial direction increase sequentially; each FFL gradient unit includes four gradient coils, and two mutually parallel gradient coils form a pair. The two pairs of gradient coils are arranged orthogonally in the radial direction. The two pairs of gradient coils are respectively applied with the same axial translation current and different radial rotation currents, so as to achieve the axial synchronous fast scanning and radial rotation of the FFL; the excitation module includes N groups of excitation coils arranged evenly at equal intervals along the length direction; The excitation module includes N groups of excitation coils arranged evenly at equal intervals along the length direction; The control and processing module generates the axial translation current, 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 the axial translation current and radial rotation current, generates multiple field-free lines, and controls the rotation and scanning of the field-free lines along the axial direction based on a preset control strategy; the excitation module receives the excitation current, drives the field-free lines to move quickly in the vertical direction, and further drives the magnetic particles to generate response signals; The signal detection module collects the response signals, and through the external signal compensation module and the signal processing module, obtains the particle response signals, which are returned to the control and processing module by the signal acquisition and output module, and image reconstruction is performed through a preset algorithm to achieve magnetic particle imaging.

[0007] 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 through 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 through the signal acquisition and output module, and the amplified excitation current is sent to the excitation module.

[0008] In some preferred embodiments, the single length of the receiving coil of the signal detection module is less than the distance between two FFLs, and the axial lengths of the multi-slice gradient module and the excitation module are the same.

[0009] In some preferred embodiments, the axial translation current is a sinusoidal current. An axial translation current for one period is applied to 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.

[0010] In some preferred embodiments, the phases of the axial translation currents applied to each FFL gradient unit increase successively from left to right along the axis by .

[0011] In some preferred embodiments, the same axial translation current and different radial rotation currents are applied to the two pairs of gradient coils in each of the FFL gradient units. The method is as follows: Currents are applied to the two pairs of gradient coils in each of the FFL gradient units respectively: ; ; where is the current of the gradient coil in the l th FFL gradient unit in the y direction, is the current of the gradient coil in the l th FFL gradient unit in the z direction, l is the serial number of the FFL gradient unit; is the frequency period of the axial translation current, controlling the scanning frequency for the FFL to move axially; is the rotation frequency of the FFL radially, is the amplitude of the dynamic current of the gradient coil, is the independent variable changing with time.

[0012] In some preferred embodiments, an excitation current is applied to the excitation coil in the excitation module to excite all magnetic particles within the field of view, and particle selection is performed through the generated FFLs; The excitation current is: ; where when applying the excitation current, and are satisfied simultaneously; is the frequency of the excitation current, controlling the rotation frequency of the FFL radially, is the amplitude of the excitation current, is the initial phase of the excitation current, is an independent variable that changes over time.

[0013] In some preferred embodiments, the non-magnetic field line is controlled to rotate and scan along the axial direction based on a preset control strategy. The method is as follows: When the scanning trajectory of the FFL is a discrete angle scanning trajectory. First, it quickly moves to the axial end of the entire magnet to complete the scanning of the whole body of the object to be measured, and then switches the angle to perform the scanning of the next angle until the 3D scanning of the object to be measured is completed; When the scanning trajectory of the FFL is a discrete translation trajectory. First, it 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 to be measured is completed; Otherwise, the FFL advances forward in a spiral trajectory until it moves to the axial end of the entire magnet to complete the 3D scanning of the object to be measured; wherein, 、 is a preset adjustment coefficient.

[0014] In some preferred embodiments, the particle response signal is subjected to image reconstruction. The method is as follows: The particle response signal is used to complete two-dimensional imaging of different imaging planes by using a system matrix or inverse Radon transform, and then a velocity compensation algorithm is used for position mapping of scans of different imaging planes to achieve three-dimensional imaging.

[0015] In the second aspect of the present invention, a magnetic particle imaging method for multi-slice synchronous scanning is proposed, which is characterized in that the method includes: S1. Pass an axial translation current through the multi-slice gradient module to generate a plurality of non-magnetic field lines along the axial direction. Among them, the phases of the axial translation currents passed through each FFL gradient unit from left to right along the axial direction increase in sequence; S2. Apply differential radial rotation currents to the two pairs of gradient coils in each FFL gradient unit, and control the non-magnetic field line to rotate and scan along the axial direction based on a preset control strategy; S3. Pass an excitation current through the excitation module to drive the non-magnetic field line to move quickly in the vertical direction, thereby driving the magnetic particles to generate a response signal; S4. Collect the response signal and suppress the interference in the response signal to obtain a particle signal; S5. Perform signal processing on the particle signal to obtain a particle response signal; S6. Based on the particle response signal, perform image reconstruction to obtain a magnetic particle three-dimensional space distribution image.

[0016] Advantages of the present invention: The present invention can create multiple imaging planes within a three-dimensional imaging space, simultaneously generate multiple field-free lines, achieve rapid axial movement of the FFL by controlling the dynamic gradient magnetic field, perform simultaneous imaging of multiple planes under synchronous control, and is equipped with a multi-channel acquisition module to separate and reconstruct images of signals from different planes. It breaks the limitation of a single imaging plane, greatly expands the imaging range and dimension, can obtain information at more spatial positions at one time, and significantly improves the imaging efficiency and the integrity of information acquisition. Brief Description of the Drawings

[0017] Other features, objects, and advantages of the present application will become more apparent by reading the detailed description of the non-limiting embodiments with reference to the following drawings: Figure 1 is a schematic structural diagram of the magnetic particle imaging system for multi-slice synchronous scanning of the present invention; Figure 2 is a schematic diagram of the current phases applied to different FFL gradient units of the multi-slice gradient module in the embodiment of the present invention; Figure 3 is a schematic cross-sectional view of the multi-slice gradient module and a schematic diagram of the FFL scanning field of view (FOV) in the embodiment of the present invention; Figure 4 is a simulation result diagram of the generation of field-free lines in the embodiment of the present invention; Figure 5 is a schematic diagram of the axial magnetic field distribution of the field-free lines at different times in the embodiment of the present invention; Figure 6 is a simulation result diagram of the rotational scanning of the field-free lines when N = 6 and n = 6 in the embodiment of the present invention; Figure 7 is a schematic flowchart of the imaging method for multi-slice synchronous scanning in the embodiment of the present invention; The reference numerals are as follows: 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 - 3)th coil, 642. (4N - 2)th coil, 643. (4N - 1)th 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 implementation manners

[0018] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the related invention, rather than limiting the invention. In addition, it should be noted that for the convenience of description, only the parts related to the related invention are shown in the drawings.

[0019] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the drawings and embodiments.

[0020] The present invention provides a slice dynamic gradient unit to dynamically construct multiple non-magnetic field line gradient magnetic fields that can freely rotate and scan in the axial space, and make the FFL move rapidly in the axial direction in the form of a sine wave by applying a sine current, so as to improve the scanning speed; a multi-segment excitation module simultaneously provides a high-frequency excitation magnetic field to the magnetic particles near all FFLs, thereby driving the magnetic particles to generate non-linear response signals; a multi-channel detection is used to image the magnetic field response of the magnetic particles in the slice, and the signal is connected to a filtering and amplification module and then input to an ADC converter and then to a processing computer to provide original signal data for multi-slice simultaneous imaging, so as to realize three-dimensional full-field synchronous rapid imaging, and significantly improve the three-dimensional imaging speed and sensitivity.

[0021] For a clearer description of the magnetic particle imaging system for multi-slice synchronous scanning of the present invention, the following combines Figure 1-7 The system in the embodiments of the present invention will be 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; The control and processing module 1 is used to generate the axial translation current required by the multi-slice gradient module 6, the radial rotation current, and the excitation current required by the excitation module 7; The multi-slice gradient module 6 is used to receive the axial translation current and the radial rotation current, generate a gradient magnetic field and a plurality of field-free lines, and control the rotation scanning of the field-free lines along the axial direction based on a preset control strategy; The excitation module 7 is used to receive the excitation current, drive the field-free lines to scan in the vertical direction, and further drive the magnetic particles to generate a response signal; 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 it to the control and processing module by the signal acquisition and output module, and perform reconstruction through a preset algorithm to realize magnetic particle imaging; The multi-slice gradient module 6 includes N FFL gradient units arranged evenly at equal intervals along the length direction. The phases of the axial translation currents introduced into each FFL gradient unit along the axis increase sequentially. A sinusoidal current of one cycle is introduced into every n FFL gradient units, thereby generating two FFLs; each FFL gradient unit includes four gradient coils, two in a pair, and the two pairs of gradient coils are arranged orthogonally in the radial direction. The two pairs of gradient coils are respectively applied with the same axial translation current and different radial rotation currents, so as to realize the axial synchronous fast scanning and radial rotation of the FFL; The excitation module 7 includes N groups of excitation coils arranged evenly at equal intervals 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 two FFLs.

[0022] Preferably, the axial translation current and the radial rotation current generated by the control and processing module 1 are sent to the gradient power amplifier 4 through the signal acquisition and output module 2 for amplification, 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 through the signal acquisition and output module 2 for amplification, and the amplified excitation current is sent to the excitation module 7.

[0023] Preferably, the distance between two consecutive FFLs is half of the current wavelength introduced into the FFL gradient unit. A sinusoidal current of one cycle is introduced into every n FFL gradient units to generate two FFLs. The sensitive area of the receiving coil must be less than the distance between two consecutive FFLs. The signal detection module 8 includes multi-segment multi-channel receiving coils, and the length of each segment of receiving coil is less than the distance between two FFLs.

[0024] Preferably, the axial translation current is a sine current. An axial translation current for one period is applied to 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 axis and pass through the whole body of the object under test.

[0025] More preferably, the phases of the axial translation currents applied to the FFL gradient units increase sequentially from left to right along the axis .

[0026] Preferably, differential dynamic currents are applied to the two pairs of gradient coils in each of the FFL gradient units. The dynamic currents include the same axial translation current and radial rotation current. Specifically: Currents are applied to the two pairs of gradient coils in each of the FFL gradient units respectively: ; ; In the radial plane, each group of coils is defined as y direction and z direction for two pairs of coils. The magnetic field directions of each pair of coils are the same; wherein, is the current of the gradient coil in the l th FFL gradient unit y direction, is the current of the gradient coil in the l th FFL gradient unit z 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 the FFL in the radial direction, is the amplitude of the dynamic current of the gradient coil, is the independent variable changing with time.

[0027] A sine current with continuously increasing coil phase is applied to each coil group element of the dynamic gradient unit in the axial direction, and the phase difference between adjacent elements is adjusted so that the current distribution is a wave spatially extending over one wavelength along the axial direction. Therefore, a linearly moving sine magnetic field wave travels in this direction.

[0028] Preferably, the non-magnetic field lines are controlled to rotate and scan along the axial direction based on a preset control strategy. The method is: When When the scanning trajectory of the FFL is a discrete angular scanning trajectory, it first quickly moves to the axial end of the entire magnet to complete the scanning of the whole body of the object to be measured, and then switches the angle to perform the scanning of the next angle until the 3D scanning of the object to be measured is completed; When the scanning trajectory of the FFL is a discrete translation trajectory, it 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 to be measured is completed; Otherwise, the FFL advances forward in a spiral trajectory until it moves to the axial end of the entire magnet to complete the 3D scanning of the object to be measured; Among them, 、 is a preset adjustment coefficient, is the adjustment coefficient defined when the scanning frequency of the axial movement is much greater than the rotation frequency in the radial direction, is the adjustment coefficient defined when the scanning frequency of the axial movement is much less than the rotation frequency in the radial direction.

[0029] Preferably, an excitation current is applied to the excitation coil in the excitation module 7 , to excite all magnetic particles within the field of view, and particle selection is performed through the generated FFL; The excitation current is: ; Among them, is the frequency of the excitation current, controlling the rotation frequency of the FFL in the radial direction, is the amplitude of the excitation current, is the initial phase of the excitation current, is the independent variable that changes with time.

[0030] Further preferably, when applying the excitation current, both and are satisfied.

[0031] Preferably, in this embodiment, the optimal sampling rate for collecting the response signal is above 3M / s.

[0032] Preferably, the control and processing module 1 uses a system matrix or inverse Radon transform to complete the two-dimensional imaging of different imaging planes for the received and processed particle response signals, and then uses a velocity compensation algorithm for position mapping of the scans of different imaging planes to achieve three-dimensional imaging.

[0033] Preferably, the total length of the excitation coil is the same as the axial length of the gradient coil, jointly generating an axially uniform excitation magnetic field, and energizing all the excitation coils simultaneously can drive the firsti A magnetic field line scans radially within the imaging plane and drives magnetic particles on the line trajectory to generate response signals.

[0034] Further preferably, the excitation current is a multi-frequency current, which enriches the response spectrum of the particles and is beneficial to improving the resolution and sensitivity.

[0035] The signal detection module 8 and the external compensation module 9 are composed of a set of receiving coils and a set of external excitation-receiving pairs. The compensated signal is input to the control and processing module 1 through the signal processing unit. By analyzing the magnetic particle signals corresponding to the excitation magnetic fields applied to different slices respectively, since the applied frequencies are different, the harmonic signal values corresponding to different fundamental frequencies can be separated in the signal spectrum, completing the signal mapping of different slices, and realizing the image reconstruction of different regions through a predetermined reconstruction algorithm.

[0036] Preferably, in this embodiment, as Figure 2 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... an Nth FFL gradient unit 640. Each group of units is respectively fed with a sinusoidal current with a continuously increasing coil phase . An FFL is generated at each zero crossing of the magnetic field, and a total of m FFLs are generated, where , and .

[0037] Further preferably, n≥3 is required to form the simplest dynamic gradient coil array.

[0038] That is, axially, a sinusoidal current with a period is fed to N dynamic gradient coil units respectively (the phase difference is , so the phase of the nth unit is , which is the same as the first one and is a cycle). Therefore, two FFLs are generated by every n dynamic gradient coil units. In addition, the distance between two consecutive FFLs is approximately times the distance of the dynamic gradient coils. In order to obtain signals from only one FFL at a time, the sensitive area of the receiving coil must be less than the distance between two consecutive FFLs, that is, less than times the distance of the dynamic gradient coils.

[0039] Preferably, as Figure 3As shown, the first FFL gradient unit 610 includes two pairs of gradient coils. The first coil 611 and the third coil 613 form the first gradient coil pair, and the second coil 612 and the fourth coil 614 form the second gradient coil pair. The two coils of the gradient coil pair are coaxially and parallelly arranged, and the axes of the two coil pairs are orthogonal. The axis of the excitation coil passes through the orthocenter 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 form the third gradient coil pair, and the sixth coil 622 and the eighth coil form the fourth gradient coil pair. In the third FFL gradient unit 630, the ninth coil 631 and the XIth coil 633 form the fifth gradient coil pair, and the Xth coil 632 and the XIIth coil form the sixth gradient coil pair. In the Nth FFL gradient unit 640, the 4Nth coil 641 and the 4N - 3th coil 643 form the 2N - 1th gradient coil pair, and the 4N - 1th coil 642 and the 4Nth coil form the 2Nth gradient coil pair.

[0040] The first coil 611 and the third coil 613 are passed with currents in the same direction , and the second coil 612 and the fourth coil 614 are passed with currents in the same direction , and have a phase difference of 90° and a rotation frequency of , and jointly act with the second FFL gradient unit 620 and the Nth dynamic gradient unit 640 to generate the FFL at the axial center, and the current is continuously switched (the frequency is ), and the FFL also moves dynamically along the axis. At the same time, the excitation magnetic field coil module is passed with an excitation current , to excite all magnetic particles within the field of view, and perform particle selection 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 to respectively detect the response signals of the excited magnetic particles in each FLL region.

[0041] There are three types in the scanning strategy of the FFL rotation and translation: 1. Discrete angle scanning trajectory, that is , the moving speed of the FFL in the axial direction is much greater than the rotation speed. The FFL will first quickly move to the axial end of the entire magnet to complete the scanning of the whole body of the object to be measured, then switch the angle to perform the scanning of the next angle, and finally complete the whole body 3D scanning; 2. Spiral scanning trajectory, that is and When they are not much different, the rotational speed of the FFL in the radial direction is close to the axial movement speed, and the FFL advances forward in a spiral trajectory; 3. Discrete translation trajectory, that is , the rotational speed of the FFL in the radial direction should 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. This frequency ratio can be calibrated through actual measurement to achieve the optimal scanning speed and imaging effect.

[0042] Preferably, the gradient coil in the FFL gradient unit is annular, and the excitation coil is cylindrical, but its shape is not limited to the above shape setting. Only the shapes of the above coils are used as examples. Under the premise of meeting the structural layout of the present invention, it can be other shapes.

[0043] Further preferably, in this embodiment, an example of the multi-slice magnet structure in the present invention is a simulation diagram of two field-free line imaging planes generated by 6 groups of FFL gradient units, where the total number of axial units N = 6, the total number of units n = 6 in one axial scanning cycle, and the winding directions of the coils of adjacent units are opposite.

[0044] Each unit is passed through a sinusoidal current with the same amplitude and a phase difference of . The coil units corresponding to one cycle are just equal to the total axial length of the gradient coil units. Therefore, at least FFLs (that is, the zero points of the x-direction magnetic field) are generated within one cycle, corresponding to between the positive coil current and the negative coil current. As time increases, the current amplitude of each coil changes according to the sine wave law, and the positions of the 2 FFLs also change accordingly (advancing along the X-axis in the direction of the sine wave movement).

[0045] Preferably, in this example, there are three control strategies: ① Discrete angle scanning trajectory, that is , such as setting , ; ② Spiral scanning trajectory, that is When it is not much different from , such as setting , ; ③ Discrete translation trajectory, that is , such as setting , .

[0046] As Figure 5 shows, based on the above specific embodiments, the simulation results of the magnetic field strength distribution along the x-axis direction at different times: The point where the magnetic field in the figure is 0 is the plane where the FFL is located. Five instances at different times are set in the simulation (starting from time 0 to , with a time interval , being the axial scanning frequency corresponding scanning period). This time interval has nothing to do with the magnet structure and is only related to the system sampling frequency (i.e., ). Denote the axial length of the magnet coil part as . It can be seen that from to it has moved to the right by past the 0 point, and with the passage of time, the FFL realizes a rapid axial movement. After a complete cycle T, the FFL also returns to point to complete a cycle of scanning. In addition, it can also be found that in this instance, since the phases of all axial coils are within one cycle, the number of FFLs generated is 2. Therefore, actually only is required to scan all positions axially. Reducing N can generate more FFLs. As known from the previous text, the number of FFLs , so the corresponding scanning period is .

[0047] As Figure 6 shown, based on the above specific embodiments, the magnetic field distribution effect diagram of multiple FFLs rotating simultaneously is realized by controlling the current difference between two pairs of orthogonal coils in the same group of dynamic gradient units. In this instance, for the coil pair in the y direction in the Figure 3 shown i group of coils, the current passed is , and for the coil pair in the x direction, the current passed is . The other structural parameters of the coil are the same as Figure 4 . Finally Figure 6 shows the imaging result at time, respectively generating two FFLs rotating radially by angles.

[0048] Preferably, the signal detection module 8 is arranged inside the multi-slice gradient module 6 and is coaxial with the multi-slice gradient module 6.

[0049] It should be noted that the magnetic particle imaging system for multi-slice synchronous scanning provided in the above embodiments is only illustrated by dividing the above functional modules. In practical applications, the above functions can be assigned to different functional modules according to needs, 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 embodiments can be merged into one module, or further split 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 only used to distinguish each module or step, and are not regarded as an improper limitation of the present invention.

[0050] A magnetic particle imaging method for multi-slice synchronous scanning according to the second embodiment of the present invention is characterized in that the steps include: S1. Apply an axial translation current to the multi-slice gradient module 6 to generate a plurality of magnetic field-free lines along the axis. Among them, the phase of the axial translation current applied to each FFL gradient unit increases sequentially from left to right along the axis; S2. Apply differential radial rotation currents to the two pairs of gradient coils in each FFL gradient unit respectively, and control the magnetic field-free lines to rotate and scan along the axial direction based on a preset control strategy; S3. Apply an excitation current to the excitation module 7 to drive the magnetic field-free lines to scan along the direction perpendicular to the FFL in the radial plane, and excite the magnetic particles in this area to generate a response signal, completing the excitation in one direction; S4. Collect the response signal and suppress the interference in the response signal to obtain a particle signal; S5. The collected response signals are sequentially sent to the external signal compensation module 9 and the signal processing module 5 for signal processing 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 magnetic particles.

[0051] Although the above steps are described in the above order in the above embodiments, those skilled in the art can understand that in order to achieve the effects 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 reversed order, and these simple changes are all within the protection scope of the present invention.

[0052] The system of the present invention can simultaneously image magnetic particle tracers on multiple planes under synchronous control, and at the same time use a multi-channel acquisition module to separate and reconstruct the signals on different planes, so as to realize imaging of multiple radial slices.

[0053] Those skilled in the art can clearly understand that for the convenience and conciseness of description, the specific working processes and related descriptions of the methods described above can refer to the corresponding processes in the foregoing system embodiments, and will not be repeated here.

[0054] An electronic device according to a third embodiment of the present invention includes: At least one processor; and A memory communicatively connected to at least one of the processors; wherein, The memory stores instructions executable 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.

[0055] A computer-readable storage medium according to a fourth embodiment of the present invention, the computer-readable storage medium stores computer instructions, and the computer instructions are used to be executed by the computer to implement the above-mentioned multi-slice synchronous scanning magnetic particle imaging method.

[0056] Those skilled in the art can clearly understand that for the convenience and conciseness of description, the specific working processes and related descriptions of the above-mentioned electronic device and computer-readable storage medium can refer to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0057] Those skilled in the art should be able to realize that the modules and method steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. The programs corresponding to the software modules and method steps can be placed in a random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium well-known in the art. To clearly illustrate the interchangeability of electronic hardware and software, the components and steps of each example have been generally described according to their functions in the above description. Whether these functions are executed in the form of electronic hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0058] Computer program code for performing the operations of this application can be written in one or more programming languages or combinations thereof. The above-mentioned programming languages include object-oriented programming languages such as Java, Smalltalk, C++, and also include conventional procedural programming languages such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, executed 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 the case of a remote computer, the remote computer can be connected to the user's computer through any kind of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computer (for example, by using an Internet service provider to connect through the Internet).

[0059] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in the flowchart or block diagram may represent a module, a program segment, or a part of code that contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than that marked in the accompanying drawings. For example, two consecutive blocks shown may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, and the combination of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system for performing the specified functions or operations, or can be implemented by a combination of dedicated hardware and computer instructions.

[0060] The terms "first", "second", etc. are used to distinguish similar objects and not to describe or represent a specific order or sequence.

[0061] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that comprises a series of elements includes not only those elements but also other elements not expressly listed, or also includes elements inherent to those process, method, article, or apparatus / device.

[0062] So far, the technical solution of the present invention has been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easily understood by those skilled in the art that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of the present invention.

Claims

1. A magnetic particle imaging system for multi-slice synchronous scanning, the system comprising a control and processing module, a signal processing module, a signal detection module, a signal acquisition and output module, characterized in that: The system also includes: 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 into each FFL gradient unit increases in sequence along the axial direction; each FFL gradient unit comprises four gradient coils, and two gradient coils that are parallel to each other form a pair, and the two pairs of gradient coils are radially orthogonally arranged, and the two pairs of gradient coils respectively apply the same axial translation current and differentiated radial rotation current, so as to realize 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, generates 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, drives the magnetic field-free lines to move rapidly in a vertical direction, and then drives the magnetic particles to generate a response signal; 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, and returns the signal to the control and processing module through the signal acquisition and output module, and performs image reconstruction through a preset algorithm to realize magnetic particle imaging.

2. A magnetic particle imaging system for multi-slice synchronous scanning 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 magnetic particle imaging system for multi-slice synchronous scanning according to claim 1, characterized in that: The single length of the receiving coil of the signal detection module is smaller 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.

4. The magnetic particle imaging system for multi-slice synchronous scanning 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.

5. The magnetic particle imaging system for multi-slice synchronous scanning according to claim 4, 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. .

6. The magnetic particle imaging system for multi-slice synchronous scanning according to claim 4, 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 of the FFL gradient units, and the method is as follows: Current is supplied to the two pairs of gradient coils in each of the FFL gradient units: ； ； 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 dynamic current of the gradient coil, is an independent variable that changes over time.

7. The magnetic particle imaging system for multi-slice synchronous scanning according to claim 4, characterized in that: The excitation current is supplied to the excitation coil in the excitation module. , all magnetic particles in the field of view are excited and particles are selected through 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.

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

9. The multi-slice synchronous scanning magnetic particle imaging system according to claim 8, characterized in that: The particle response signal is image reconstructed by: 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.

10. A magnetic particle imaging method for multi-slice synchronous scanning, based on a magnetic particle imaging system for multi-slice synchronous scanning according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: S1, passing an axial translation current into 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 passed into each FFL gradient unit increases in sequence 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-free 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 the 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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