Unilateral magnetic particle imaging device and system

Abstract

The present invention discloses a unilateral magnetic particle imaging device, comprising a bracket, a Halbach array permanent magnet, an excitation coil, a ferrite core, a copper tube, a receiving coil, and a fixed housing. The bracket is disposed at the bottom of the device; the Halbach array permanent magnet surrounds and is embedded in the bracket; the excitation coil adopts a segmented "I"-shaped symmetrical structure; the ferrite core is located inside the excitation coil; the copper tube is disposed outside the excitation coil; the receiving coil comprises three parts: one part is disposed below the excitation coil and forms a receiving end using a flat spiral structure; one part is disposed inside the excitation coil and forms an intermediate end using a solenoid structure; and another part is disposed above the excitation coil and forms a compensating end using a flat spiral structure with the same specifications as the receiving end but wound in the opposite direction. The fixed housing is disposed at the top of the device. This device improves detection depth and sensitivity, while achieving higher resolution and a larger imaging field of view.

Description

Technical Field

[0001] The present invention belongs to the technical field of imaging equipment, and in particular relates to a unilateral magnetic particle imaging device and system. Background Art

[0002] Magnetic Nanoparticle Imaging (MPI) is an emerging tomographic imaging technology that can achieve fast and accurate imaging. This technology detects the nonlinear magnetization signal of magnetic nanoparticles in a changing magnetic field, and then reconstructs the concentration distribution of particles in the area to be measured. In this process, the changing magnetic field produces a moving zero-field region. When magnetic particles exist in the zero-field region, the magnetic particles are excited by the excitation signal to generate a changing harmonic signal, which can be received by the receiving device. At the same time, compared with other imaging methods, magnetic particle imaging equipment is easier to achieve high-resolution and high-sensitivity imaging, quantitative rapid dynamic scanning, and no ionizing radiation. Therefore, magnetic particle imaging equipment has broad application prospects in the fields of rapid clinical diagnosis and real-time intraoperative monitoring.

[0003] Fully enclosed magnetic particle imaging devices are primarily designed for large, fixed, small animal systems, with a maximum field of view (FOV) of only a few centimeters. Considering the small size of human lesions, adapting fully enclosed magnetic particle imaging equipment to human-scale would require a similar setup to MRI equipment, which undoubtedly increases technical difficulty and equipment cost. Therefore, fully enclosed magnetic particle imaging devices are currently not scalable to human scale and cannot be directly applied in clinical research.

[0004] Based on this, researchers have proposed magnetic particle imaging systems utilizing unilateral structures. Unilateral magnetic particle imaging, first proposed in 2008, includes unilateral magnetic particle imaging using zero magnetic field lines and miniaturized unilateral magnetic particle imaging devices that utilize zero magnetic field points to locate sentinel lymph nodes in breast cancer. In 2009, Timo F. Sattel developed a one-dimensional zero magnetic field point single-sided magnetic particle imaging scanner. This device, utilizing an asymmetric coil topology, allows for imaging of objects of unlimited size. However, its penetration depth and field of view are limited. In 2015, the University of Lübeck in Germany proposed a two-dimensional unilateral magnetic particle imaging scanner that can image within a range of approximately 10 mm from the coil. This unilateral magnetic particle imaging scanner, which uses zero magnetic field points for scanning, is not limited by the size of the scanned object. However, its penetration depth is limited, limiting examination to specific locations. Furthermore, it suffers from poor imaging resolution, uneven magnetic field intensity distribution, low magnetic field utilization, and high power consumption. By 2020, single-sided magnetic particle imaging scanners had been adapted for multidimensional imaging, achieving a penetration depth of up to 14 mm and an imaging field of 30 × 30 × 30 mm. 3In 2021, Erica E. Mason of the MIT team designed a handheld single-sided magnetic particle spectrometer that can detect magnetic particles as small as 9ug at a distance of 30mm and iron levels as low as 100ng when held close to the lower end of the device, demonstrating its ability to detect small volumes of residual tumor tissue in the breast. However, the device cannot image and requires high power, requiring a drive current of 27.9A. The heat generated by long-term operation of high current can affect the device's stable operation.

[0005] In summary, existing unilateral magnetic particle imaging devices suffer from low magnetic field efficiency and uneven magnetic field distribution, which limits the penetration depth that can be achieved by unilateral magnetic particle imaging, hindering its development. Furthermore, the device's sensitivity decreases dramatically as the detection depth increases. Furthermore, existing unilateral magnetic particle imaging devices generally suffer from low resolution. Summary of the Invention

[0006] In order to solve the above problems existing in the prior art, the present invention provides a unilateral magnetic particle imaging device and system. The technical problems to be solved by the present invention are achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a unilateral magnetic particle imaging device, comprising a bracket, a Halbach array permanent magnet, an excitation coil, a ferrite core, a copper tube, a receiving coil, and a fixed housing; wherein,

[0008] The bracket is arranged at the bottom of the entire device and is used to support the entire device; a through hole is provided on the bracket to facilitate the passage of the excitation coil, the ferrite core, the copper tube and the receiving coil;

[0009] The Halbach array permanent magnet surrounds and is fixed on the bracket;

[0010] The excitation coil adopts a segmented "I" symmetrical structure;

[0011] The ferrite core is located inside the excitation coil;

[0012] The copper tube is arranged outside the excitation coil;

[0013] The receiving coil comprises three parts: one part is arranged below the excitation coil and adopts a flat spiral structure to form a receiving end; one part is arranged inside the excitation coil and adopts a solenoid structure to form an intermediate end; and the other part is arranged above the excitation coil and adopts a flat spiral structure with the same specifications as the receiving end but wound in the opposite direction to form a compensation end.

[0014] The fixed shell is arranged on the top of the entire device and is used to fix the entire device.

[0015] In one embodiment of the present invention, the Halbach array permanent magnets can be set at any angle to form different FFP point positions and simultaneously change the magnitude of the gradient magnetic field there.

[0016] In one embodiment of the present invention, the excitation coil is wound with Litz wire and fixed by epoxy casting process.

[0017] In one embodiment of the present invention, the ferrite core is a cylindrical soft ferrite core having a high resistivity so as to enhance the magnetic field under a high frequency alternating magnetic field.

[0018] In one embodiment of the present invention, the bracket and the fixed shell are both made of aluminum alloy.

[0019] In one embodiment of the present invention, a water cooling tube is provided in the middle of the "I" shape of the excitation coil to maintain the temperature of the coil to the maximum extent when the device is used for high current excitation; and the water cooling tube and the excitation coil are both located inside the copper tube.

[0020] In a second aspect, the present invention provides a unilateral magnetic particle imaging system, comprising:

[0021] an imaging device, placed on one side of the subject, for generating an excitation signal and receiving a magnetic nanoparticle signal;

[0022] A data acquisition device, used to collect the received magnetic nanoparticle signals and upload them to a host computer for data processing to obtain an image of the subject's position to be imaged;

[0023] Wherein, the imaging device adopts the unilateral magnetic particle imaging device provided in the above embodiment.

[0024] Beneficial effects of the present invention:

[0025] 1. The unilateral magnetic particle imaging device provided by the present invention uses a ferrite core to enhance the unilateral excitation magnetic field, thereby increasing the detection depth of the unilateral magnetic particle imaging device. Furthermore, the structure of the excitation and receiving coils is improved, thereby increasing the detection depth while maximizing the detection sensitivity. Furthermore, a Halbach array permanent magnet is used to generate a gradient magnetic field. By changing the angle of the magnetic block, the position of the zero magnetic field point can be moved and the magnitude of the gradient magnetic field at that position can be changed. This achieves a deeper detection distance, higher resolution and sensitivity, and a larger imaging field of view, providing different options for a wider range of usage scenarios.

[0026] 2. The unilateral magnetic particle imaging system provided by the present invention places the imaging device on one side of the system, which is called a unilateral magnetic particle imaging device. This allows the subject to be unrestricted by size and has good clinical application prospects.

[0027] 3. The unilateral magnetic particle imaging device provided by the present invention has the characteristics of light weight, small size, and portability. By adding a mechanical structure to power the mobile device, it can achieve two-dimensional or even three-dimensional scanning imaging.

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 1 is a schematic structural diagram of a unilateral magnetic particle imaging device provided by an embodiment of the present invention;

[0030] Figure 2 is a cross-sectional view of a unilateral magnetic particle imaging device provided by an embodiment of the present invention;

[0031] Figure 3 is a schematic structural diagram of an excitation coil provided by an embodiment of the present invention;

[0032] Figure 4 is a schematic structural diagram of a receiving coil provided in an embodiment of the present invention;

[0033] Figure 5 This is a structural block diagram of a unilateral magnetic particle imaging system provided by an embodiment of the present invention;

[0034] Description of reference numerals:

[0035] 1- bracket, 2- Halbach array permanent magnet, 3- excitation coil, 4- ferrite core, 5- copper tube, 6- receiving coil, 61- receiving end, 62- middle end, 63- compensation end, 7- fixed shell, 8- water cooling tube. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0037] Example 1

[0038] See Figure 1 , Figure 1 The figure is a schematic structural diagram of a unilateral magnetic particle imaging device provided by an embodiment of the present invention. The unilateral magnetic particle imaging device provided by this embodiment includes: a bracket 1, a Halbach array permanent magnet 2, an excitation coil 3, a ferrite core 4, a copper tube 5, a receiving coil 6, and a fixed housing 7; wherein,

[0039] The bracket 1 is provided at the bottom of the entire device to support the entire device; a through hole is provided on the bracket to facilitate the passage of the excitation coil 3, the ferrite core 4, the copper tube 5 and the receiving coil 6;

[0040] The Halbach array permanent magnet 2 surrounds and is fixed on the bracket 1;

[0041] The excitation coil 3 adopts a segmented "I" symmetrical structure;

[0042] The ferrite core 4 is located inside the excitation coil 3;

[0043] The copper tube 5 is arranged outside the excitation coil 3;

[0044] The receiving coil 6 consists of three parts: one part is arranged below the excitation coil 3 and adopts a flat spiral structure to form a receiving end 61; one part is arranged inside the excitation coil 3 and adopts a solenoid structure to form an intermediate end 62; and the other part is arranged above the excitation coil 3 and adopts a flat spiral structure with the same specifications as the receiving end but wound in the opposite direction to form a compensation end 63.

[0045] The fixed housing 7 is arranged on the top of the entire device and is used to fix the entire device.

[0046] Specifically, such as Figure 1 As shown, the top of the device is a fixed housing 7 made of aluminum alloy, which is used to fix the entire device. At the center of the device is a ferrite core 4, which is located inside the excitation coil 3. This ferrite core 4 is a cylindrical soft ferrite core with high resistivity, which can achieve magnetic field enhancement under high-frequency alternating magnetic fields.

[0047] Under the same excitation current, the magnetic field intensity generated by the excitation coil 3 with the ferrite core 4 added is significantly greater than the magnetic field intensity generated by only the excitation coil.

[0048] In addition, in order to minimize the influence of the ferrite core on the signal, the present embodiment places the ferrite core 4 at the center of the excitation coil 3, and then minimizes the harmonic influence brought by the ferrite core through the action of the compensation end 63 of the receiving coil 6.

[0049] The device designed in this embodiment effectively utilizes the free space at the center of the coil by adding a cylindrical ferrite core. Because ferromagnetic materials contain magnetic domains, in the absence of an external magnetic field, the domains are arranged in a chaotic manner, their magnetism cancels out, and they appear non-magnetic. When subjected to an external magnetic field, the magnetic domains rearrange themselves in the direction of the field, forming a strong additional magnetic field. This in turn increases the field strength of the excitation coil and, consequently, the detection capability of the receiving coil. Therefore, the addition of ferrite improves both the device's detection sensitivity and range at the same excitation current.

[0050] For further information, see Figure 2-3 , Figure 2 is a cross-sectional view of a unilateral magnetic particle imaging device provided by an embodiment of the present invention, Figure 3Schematic diagram of the structure of the excitation coil provided by the embodiment of the present invention. In this embodiment, the excitation coil 3 adopts a segmented "I" symmetrical structure, which is mainly used to generate a changing magnetic field to excite the magnetic particles.

[0051] In this embodiment, the excitation coil 3 is wound with Litz wire, with the inner layer fully wound and the outer layer only wound at both ends, and finally fixed by epoxy casting process.

[0052] For further information, please refer to Figure 1 、 Figure 2 and Figure 4 , Figure 4 Schematic diagram of the structure of the receiving coil provided by the embodiment of the present invention; wherein the receiving coil 6 also adopts a symmetrical structure, which mainly includes three parts, the receiving end 61 of the receiving coil 6 is below the excitation coil 3, as shown Figure 4 As shown, this coil is different from a conventional solenoid coil. It is a flat spiral structure specially designed based on the characteristics of unilateral magnetic particle imaging. It has a higher detection sensitivity for magnetic particles placed outside the device. Correspondingly, there is a spiral compensation end 63 with the same specifications but reverse winding on its upper part. The middle part of the receiving coil 6 is set inside the excitation coil 3, and the middle end is formed by a solenoid structure. In this embodiment, as shown in FIG. Figure 4 As shown, the middle end 63 is divided into two sections, one section is adjacent to the receiving end and its winding direction is the same as the winding direction of the receiving end coil, and the other section is adjacent to the compensation end and its winding direction is the same as the winding direction of the compensation end coil.

[0053] In view of the characteristics of unilateral equipment, this embodiment uses a segmented excitation coil to enhance the unilateral excitation magnetic field. The segmented excitation increases the number of coil turns at both ends on the basis of the original whole-segment excitation, thereby increasing the intensity of the excitation magnetic field. The spiral receiving coil is used to minimize the distance from the object to be measured, further improving the detection sensitivity of unilateral magnetic particles.

[0054] For further information, please see Figure 1 and Figure 2 In this embodiment, a Halbach array of permanent magnets surrounds the coil structure, secured by an aluminum alloy bracket 1. The Halbach array of permanent magnets 2 is located at the bottom of the device, outside the copper tube 5, creating a gradient magnetic field. The permanent magnets are secured within the aluminum alloy bracket 1.

[0055] In this embodiment, the Halbach array permanent magnet 2 can be set at any angle to form different FFP point positions and simultaneously change the magnitude of the gradient magnetic field at the position.

[0056] Specifically, the permanent magnet can be rotated at different angles θ to move the FFP point and change the magnitude of the gradient magnetic field at the same time. Figure 2 Indicated by the white arrow in the middle.

[0057] The unilateral magnetic particle imaging device proposed in this embodiment utilizes a Halbach array magnet to generate a zero magnetic field point. By varying the rotation angle θ of the permanent magnet block, the location of the zero magnetic field point and the magnitude of the magnetic field gradient there can be moved, achieving a variable gradient field. Furthermore, by adding a mechanical scanning structure, a deeper detection distance can be achieved, enabling high-resolution scanning imaging with a large imaging field of view.

[0058] Optionally, as an implementation method, this embodiment also includes a water cooling tube 8 located in the middle of the "I" shape of the excitation coil 3 to maintain the coil temperature to the greatest extent possible when the device is used for high-current excitation. Both the water cooling tube 8 and the excitation coil 3 are located inside the copper tube 5. The copper tube 5 is made of pure copper to reduce interference from complex external electromagnetic environments.

[0059] The unilateral magnetic particle imaging device provided by the present invention utilizes a ferrite core to enhance the unilateral excitation magnetic field, thereby increasing the device's detection depth. Furthermore, it improves the structure of the excitation and receiving coils, increasing detection depth while maximizing detection sensitivity. Furthermore, it utilizes a Halbach array permanent magnet to generate a gradient magnetic field. By varying the angle of the magnetic block, the zero magnetic field point can be moved and the magnitude of the gradient magnetic field at that location can be altered. This achieves a deeper detection distance, higher resolution and sensitivity, and a larger imaging field of view, providing diverse options for a wide range of applications. Furthermore, the device is lightweight, compact, and portable. By incorporating a mechanical structure to power the mobile device, it can achieve two-dimensional and even three-dimensional scanning imaging.

[0060] Example 2

[0061] Based on the above embodiment 1, this embodiment provides a unilateral magnetic particle imaging system. Figure 5 , Figure 5 : is a structural block diagram of a unilateral magnetic particle imaging system provided by an embodiment of the present invention, which includes:

[0062] an imaging device, placed on one side of the subject, for generating an excitation signal and receiving a magnetic nanoparticle signal;

[0063] A data acquisition device is used to collect the received magnetic nanoparticle signals and upload them to a host computer for data processing to obtain an image of the subject's position to be imaged;

[0064] The imaging device adopts the unilateral magnetic particle imaging device provided in the first embodiment.

[0065] Specifically, in this embodiment, the imaging device is equipped with a power supply module, which primarily utilizes a signal generator to generate a 25kHz excitation signal. This signal is then applied to the excitation coil of the unilateral magnetic particle imaging device via a power amplifier to generate magnetic nanoparticles oscillating at the FFP position. The receiving coil of the unilateral magnetic particle imaging device collects the third harmonic of the oscillating particles, i.e., the 75kHz signal. The symmetrical structure of the excitation and receiving coils compensates for the fundamental frequency signal, preventing direct feedthrough of the excitation magnetic field. Simultaneously, the position of the ferrite core is fine-tuned to minimize the harmonic effects it brings. Before being collected, the magnetic nanoparticle signal passes through a high-pass filter, a low-noise amplifier, and a phase-locked amplifier, focusing only on the 75kHz signal. Finally, it is connected to a data acquisition device, i.e., an acquisition card, to collect the signal data and upload it to a host computer. The acquisition card has a sampling rate of 625kHz / s.

[0066] The unilateral magnetic particle imaging system provided by the present invention places the imaging device on one side of the system, which is called a unilateral magnetic particle imaging device. This allows the subject to be unrestricted by size and has good clinical application prospects.

[0067] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0068] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0069] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0070] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A unilateral magnetic particle imaging device, characterized in that: It comprises a bracket (1), a Halbach array permanent magnet (2), an excitation coil (3), a ferrite core (4), a copper tube (5), a receiving coil (6) and a fixed housing (7); wherein, The bracket (1) is arranged at the bottom of the entire device and is used to support the entire device; a through hole is provided on the bracket to facilitate the passage of the excitation coil (3), the ferrite core (4), the copper tube (5) and the receiving coil (6); The Halbach array permanent magnet (2) surrounds and is embedded in the bracket (1); The excitation coil (3) adopts a segmented "I"-shaped symmetrical structure; The ferrite core (4) is located inside the excitation coil (3); The copper tube (5) is arranged outside the excitation coil (3); The receiving coil (6) includes three parts, one part is arranged below the excitation coil (3) and adopts a flat spiral structure to form a receiving end (61); one part is arranged inside the excitation coil (3) and adopts a solenoid structure to form an intermediate end (62); and another part is arranged above the excitation coil (3) and adopts a flat spiral structure with the same specifications as the receiving end but wound in the opposite direction to form a compensation end (63); The fixed shell (7) is arranged on the top of the entire device and is used to fix the entire device.

2. The unilateral magnetic particle imaging device according to claim 1, characterized in that: The Halbach array permanent magnet (2) can be set at any angle to form different FFP point positions and simultaneously change the magnitude of the gradient magnetic field at the position.

3. The unilateral magnetic particle imaging device according to claim 1, characterized in that: The excitation coil (3) is wound with Litz wire, with the inner layer fully wound and the outer layer only wound at both ends, and fixed by epoxy casting process.

4. The unilateral magnetic particle imaging device according to claim 1, characterized in that: The ferrite core (4) is a soft ferrite core with a cylindrical structure.

5. The unilateral magnetic particle imaging device according to claim 1, characterized in that: The bracket (1) and the fixed housing (7) are both made of aluminum alloy.

6. The unilateral magnetic particle imaging device according to claim 1, characterized in that: A water cooling pipe (8) is provided in the middle of the "I" shape of the excitation coil (3) to maintain the temperature of the coil to the maximum extent possible when the device is used for high current excitation; and the water cooling pipe (8) and the excitation coil (3) are both located inside the copper tube (5).

7. A unilateral magnetic particle imaging system, characterized in that: include: an imaging device, placed on one side of the subject, for generating an excitation signal and receiving a magnetic nanoparticle signal; A data acquisition device, used to collect the received magnetic nanoparticle signals and upload them to a host computer for data processing to obtain an image of the subject's position to be imaged; Wherein, the imaging device adopts the unilateral magnetic particle imaging device described in any one of claims 1-6.

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