Ultra-high field magnetic resonance imaging system multi-channel sleeve monopole coil and design method

Abstract

The application discloses a multi-channel sleeve monopole coil of an ultrahigh-field magnetic resonance imaging system and a design method, belongs to the technical field of magnetic resonance imaging, and relates to radio frequency coil technology. The application establishes a multi-channel radio frequency transmitting coil unit with a segmented structure by constructing a segmented sleeve monopole antenna structure and connecting the segmented sleeve monopole antenna with multiple capacitors, effectively improves the radiation efficiency of the transmitting coil, thereby reducing the SAR value, improves the uniformity of the radio frequency field transmitted by the coil, and better meets the needs of ultrahigh-field magnetic resonance imaging application technology.

Description

Technical Field

[0001] This invention belongs to the field of magnetic resonance imaging technology, and relates to radio frequency coil technology, and particularly to a multi-channel sleeve monopole coil and its design method for a magnetic resonance imaging system under extremely high magnetic fields (greater than 10.5 Tesla). Background Technology

[0002] Magnetic resonance imaging (MRI) boasts advantages such as no ionizing radiation, safety for the human body, multi-planar imaging, multi-parameter imaging, and clear imaging, and is currently widely used in various fields including neuroscience, life sciences, neuroimaging, and cardiovascular angiography. Currently, the development of MRI technology is limited by image signal-to-noise ratio, resolution, and imaging speed. Methods to address these issues typically involve increasing the field strength of the main magnet to improve image signal-to-noise ratio and resolution, and improving the structure of the radio frequency coil to achieve multi-channel parallel imaging to increase imaging speed. When the field strength of the main magnet is increased to above 10.5 Tesla, such a system is called an extremely high field magnetic resonance imaging (UHMI) system. Currently, UHMI systems have attracted widespread attention in the field of biomedical imaging. Compared with traditional MRI systems, UHMI systems offer better image signal-to-noise ratio, shorter imaging time, and higher image resolution, providing a high-level research tool for studying brain science and the mechanisms of brain diseases.

[0003] Extremely high magnetic field (UHF) MRI offers many foreseeable advantages; however, it also presents significant challenges in radio frequency (RF) coil technology. The frequency at which atomic nuclei generate radio magnetic resonance (MMR) under extremely high magnetic fields is very high (around 500-1000 MHz). Such high frequencies induce standing wave interference in the RF coil's emission field. According to Larmor's theorem, the frequency of MMR is f = γB (where γ is the nuclear gyromagnetic ratio and B is the external magnetic field strength). As the field strength increases, the frequency increases while the wavelength decreases. When the wavelength reaches a size similar to the imaging area of ​​the human body, standing waves cause a deterioration in the amplitude and phase uniformity of the electromagnetic field, thus affecting image quality. Therefore, common coils used in traditional MRI systems, such as birdcage coils, saddle coils, and solenoid coils, are difficult to apply to UHF MRI systems.

[0004] Excessive radiofrequency deposition during magnetic resonance imaging (MRI) is a significant safety concern, potentially leading to burns from excessive electromagnetic energy absorption. Specific absorption rate (SAR) is a widely used dosimetric term describing the absorption of radiofrequency energy by a subject. In MRI, SAR is defined as the mass normalized rate at which radiofrequency energy is coupled to electrically depleted tissue, expressed in watts per kilogram (W / kg). The SAR deposition rate during an MRI scan is typically characterized as the average radiofrequency power deposition over the entire body or at exposed body parts. Both the U.S. Food and Drug Administration (FDA) and the International Electrotechnical Commission (IEC) have established SAR limits to restrict the degree of temperature rise in subject tissues across various imaging modalities. MRI scanners require estimated SAR values ​​to ensure that the SAR during the scan remains within these limits.

[0005] Existing research has proposed various radio frequency (RF) coil design schemes for extremely high-field magnetic resonance imaging (MRI) systems. Most RF coil designs employ multi-channel coils with parallel transmission and reception to improve the uniformity of the transmission field and the signal-to-noise ratio (SNR) of the reception. Traditional multi-channel coils typically use toroidal or microstrip coil units, but these suffer from poor RF field uniformity, low SNR, and significant difficulty in controlling SAR values. A team led by Myung Kyun Woo and Lance Dela Barre published a paper in the journal "Comparison of 16-Channel Asymmetric Sleeve Antenna and Dipole Antenna Transceiver Arrays at 10.5 Tesla MRI" disclosing a 16-channel asymmetric sleeve monopole coil for a 10.5 Tesla MRI system. This floating sleeve structure, while reducing SAR values, presents challenges in coil tuning and poor transmission field uniformity. Therefore, a novel RF coil design is needed for extremely high-field MRI to improve imaging performance and operational safety under extremely high magnetic fields. Summary of the Invention

[0006] The purpose of this invention is to provide a multi-channel sleeve monopole coil and its design method for use in extremely high field magnetic resonance imaging systems, which can effectively improve the uniformity of the radio frequency field and effectively reduce the SAR value during magnetic resonance imaging.

[0007] To achieve the above objectives, this technical solution provides a design method for a multi-channel sleeve monopole coil for extremely high field magnetic resonance imaging, comprising:

[0008] 1) Design the structure of the sleeve monopole antenna unit: The sleeve monopole antenna unit consists of a monopole antenna and a fixed sleeve. The monopole antenna adopts a segmented structure, and the disconnection is connected by a capacitor. The inner wall of the fixed sleeve is connected to the feed using a coaxial cable, and the outer conductor of the coaxial cable is connected and fixed.

[0009] 2) Setting the structure of the multi-channel sleeve monopole coil: Based on the size range of the human head, a sleeve monopole array is formed. The array consists of multiple sleeve monopole antenna elements. The array is circular, and all elements are evenly distributed on the circular array. Each sleeve monopole antenna element is fed by an independent coaxial cable, thus forming a multi-channel sleeve monopole coil.

[0010] 3) Obtain the operating frequency of the multi-channel sleeve monopole coil in the magnetic resonance imaging system;

[0011] Based on Lamour's theorem and the main magnetic field strength in the magnetic resonance imaging system, the resonance frequency of the hydrogen nucleus is determined, and the operating frequency of the multi-channel sleeve monopole coil is obtained.

[0012] 4) Determine the length of the sleeve monopole antenna element based on the size of the human head;

[0013] 5) Divide each monopole antenna element of the multi-channel sleeve monopole coil into segments, connect the disconnections with capacitors, and determine the capacitance value so that the sleeve monopole antenna element resonates at the specified operating frequency.

[0014] 6) Construct a cylindrical model with a size similar to that of a human head. Fill the interior of the model with an aqueous solution with specific dielectric parameters to form a water model, which is used for the uniformity calculation and evaluation of multi-channel sleeve monopole coils.

[0015] 7) Place the above water model at the center of the multi-channel sleeve monopole coil, and use the electromagnetic simulation software Sim4life to calculate the radio frequency field distribution generated in the target area (inside the water film);

[0016] 8) A calculation method based on radio frequency field uniformity is used to calculate the radio frequency field uniformity of the target area;

[0017] 9) The existing human digital model, Duke model, was selected for SAR value calculation and evaluation of multi-channel sleeve monopole coils;

[0018] 11) Place the head model in the Duke model at the center of the multi-channel sleeve monopole coil, and use the electromagnetic simulation software Sim4life to calculate the SAR value distribution generated by the multi-channel sleeve monopole coil in the head model.

[0019] 12) Analyze the SAR value index and assess the safety of the multi-channel sleeve monopole coil accordingly.

[0020] This invention also provides a multi-channel sleeve monopole coil for extremely high-field magnetic resonance imaging (MRI), comprising multiple (e.g., 8, 12, 16, etc.) sleeve monopole antenna elements and a circular array structure formed therein, designed using the multi-channel sleeve monopole coil design method for extremely high-field MRI described above. Each sleeve monopole antenna element consists of a fixed sleeve and a monopole antenna, wherein the monopole antenna is fed by a coaxial feed line connected to the inner conductor of the coaxial line, and the inner wall of the fixed sleeve structure is connected to the outer conductor of the coaxial feed line. Multiple sleeve monopole antenna elements form an array, the array shape being circular (the sleeve monopole antenna elements are evenly distributed around the circle), the diameter of the circular array being determined by the size of a human head. The multi-channel sleeve monopole coil includes: a sleeve monopole antenna structure (the monopole antenna is segmented), a multi-channel sleeve monopole coil structure (multi-channel sleeve monopole coil array), a cylindrical mold, and a water mold formed by filling the interior of the mold with an aqueous solution with specific dielectric parameters; the disconnection points after the monopole antenna is segmented are connected by capacitors.

[0021] Compared with existing technologies, this technical solution has the following characteristics and beneficial effects:

[0022] 1. A segmented transmitting coil unit structure is provided, which allows for flexible adjustment of the coil's resonant frequency. Specifically, the sleeve monopole antenna provided in this solution adopts a segmented structure and is connected by multiple capacitors. By adjusting the capacitance value, the antenna's resonant frequency can be flexibly adjusted, thereby improving tuning efficiency.

[0023] 2. A multi-channel radio frequency transmitting coil for imaging a specific region (human head) under extremely high field conditions is provided, and its unit is a sleeve monopole antenna. Compared with traditional ring array coils, the multi-channel sleeve monopole coil has a larger component perpendicular to the main magnetic field (Poynting vector), thus the transmitted field has a greater penetration depth into the subject, which can significantly improve the transmission efficiency of the coil.

[0024] 3. A method for calculating RF field uniformity is provided, which can more accurately evaluate RF field uniformity. Specifically, considering the limitations of the Sim4life electromagnetic simulation software, the RF field uniformity calculation method provided in this solution uses the 90th percentile method to process the RF field data and finally calculate a more reasonable uniformity value.

[0025] 4. The multi-channel sleeve monopole coil provided by this invention produces a lower SAR value compared to traditional multi-channel coils. The multi-channel sleeve monopole coil provided by this solution has a higher transmission efficiency than traditional multi-channel coils, therefore requiring lower transmission power to meet imaging needs, effectively reducing the SAR value and protecting the safety of the subject. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a sleeve monopole antenna structure;

[0027] In the diagram: 1- Coaxial cable for power supply; 2- Fixed sleeve structure; 3- Capacitor connecting the segmented structure; 4- Capacitor connecting the segmented structure; 5- Capacitor connecting the segmented structure; 6- Capacitor connecting the segmented structure; 7- Monopole antenna of the segmented structure.

[0028] Figure 2 This is a schematic diagram of a multi-channel sleeve monopole coil structure.

[0029] Figure 3 This is a diagram showing the reflection coefficient of a sleeve monopole antenna element.

[0030] Figure 4 This is a diagram showing the B1+ field distribution of a multi-channel sleeve monopole coil at its longitudinal center section.

[0031] Figure 5 This is a distribution map of SAR values ​​of a multi-channel sleeve monopole coil at the center section of a human head model. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0033] This solution provides a multi-channel sleeve monopole coil for magnetic resonance imaging under extremely high fields and its design method. By utilizing the novel structure of the segmented sleeve monopole antenna, the radiation efficiency of the transmitting coil can be effectively improved, thereby reducing the SAR value and improving the uniformity of the transmitted radio frequency field of the coil, thus better meeting the needs of magnetic resonance imaging technology under extremely high fields.

[0034] In the first embodiment of this solution, a design method for a multi-channel sleeve monopole coil for extremely high field magnetic resonance imaging is provided, including the following steps:

[0035] 1) Design of the sleeve monopole antenna unit structure: The sleeve monopole antenna consists of a monopole antenna and a fixed sleeve. The monopole antenna adopts a segmented structure, and the disconnection is connected by a capacitor. The inner wall of the fixed sleeve is connected to the outer conductor of the coaxial cable used for feeding and is fixed.

[0036] 2) Setting up a multi-channel sleeve monopole coil structure: Based on the size range of the human head, a sleeve monopole array is formed. The array consists of multiple sleeve monopole antennas, and each monopole antenna element is fed by an independent coaxial cable.

[0037] 3) Based on Lamour's theorem and the magnetic field strength of magnetic resonance imaging, the resonance frequency of the hydrogen nucleus is determined, and the operating frequency of the transmitting coil is obtained;

[0038] 4) Determine the length of the sleeve monopole antenna element based on the size of the human head;

[0039] 5) Divide the monopole antenna into segments, connect the breaks with capacitors, and determine the capacitance value so that the antenna resonates at the specified operating frequency.

[0040] 6) Multiple sleeve monopole antenna elements form an array, which is circular in shape and its diameter is determined according to the size of the human head;

[0041] 7) Construct a cylindrical model with a size similar to that of a human head. Fill the interior of the model with an aqueous solution with specific dielectric parameters to form a water model, which is used for the uniformity calculation and evaluation of multi-channel sleeve monopole coils.

[0042] 8) Place the above water model at the center of the array of multi-channel sleeve monopole coils, and use the electromagnetic simulation software Sim4life to calculate the radio frequency field distribution generated in the target area;

[0043] 9) Calculation of radio frequency field uniformity in the target area is performed using a calculation method based on radio frequency field uniformity.

[0044] 10) The existing human digital model, Duke model, was selected for SAR value calculation and evaluation of multi-channel sleeve monopole coils;

[0045] 11) Place the head model in the Duke model at the center of the array of multi-channel sleeve monopole coils, and use the electromagnetic simulation software Sim4life to calculate the SAR value distribution generated by the multi-channel sleeve monopole coils in the head model.

[0046] 12) Analyze the SAR value index and assess the safety of the multi-channel sleeve monopole coil accordingly.

[0047] like Figure 1As shown, the transmitting coil unit of this scheme is designed as a segmented sleeve monopole antenna structure, consisting of a monopole antenna and a fixed sleeve. The monopole antenna is a segmented structure, with a length set between 230mm and 270mm and a diameter of 2.4mm. Unlike the floating sleeve used in existing schemes, the sleeve monopole antenna in this scheme uses a fixed sleeve structure. The floating sleeve is a double-conductor structure, and the transmitted field it produces is the superposition of two transmitted fields, resulting in poor uniformity of the superimposed field at the center; the fixed sleeve structure is a single-conductor structure, which produces a more uniform transmitted field. The sleeve length is set between 70mm and 90mm, and the diameter is set between 25mm and 28mm.

[0048] In step 1), the monopole antenna in this scheme has a segmented structure, with the disconnections connected by capacitors. If the monopole antenna has too many segments, it will increase structural complexity and make tuning more difficult; if it has too few segments, it will reduce the tuning frequency range and may not be able to tune to the required operating frequency. In this embodiment, the monopole antenna structure is evenly divided into 5 segments, with the disconnections connected by capacitors.

[0049] In step 2), the multi-channel sleeve monopole coil of this scheme is composed of multiple (e.g., 8, 12, 16, etc.) sleeve monopole antenna elements. If too many antenna elements are selected, it will lead to severe inter-element coupling problems, requiring the design of a complex decoupling network; if too few antenna elements are selected, it will result in poor uniformity of the superimposed transmission field. In this embodiment, 16 sleeve monopole antennas are selected to form an array, constituting a multi-channel sleeve monopole coil, such as... Figure 2 As shown. The amplitude of the power supply to each cell is equal, and the phase difference between the power supplies to adjacent cells is 22.5°.

[0050] In step 3), the resonant frequency of the hydrogen nucleus is obtained based on the magnitude of the main magnetic field. This frequency is the operating frequency of the coil. In this embodiment, 14 Tesla is selected as the magnetic field magnitude of the main magnetic field for extremely high field magnetic resonance imaging. According to Larmor's theorem, the resonant frequency of the hydrogen nucleus is calculated to be 598 MHz, which is the operating frequency of the transmitting coil.

[0051] In step 4), the length of the sleeve monopole antenna element is determined based on the size of the human head. The length of most human heads is in the range of 18cm-25cm. Considering the need for imaging the human head, the coil length should cover the length of the human head as much as possible. In this embodiment, the length of the sleeve monopole antenna element is 250mm.

[0052] In step 5), the coil is tuned to the operating frequency by setting the capacitor values, and verified using the electromagnetic simulation software Sim4life. In this embodiment, the monopole antenna is divided into 5 segments, requiring four capacitors for connection. The values ​​of the four capacitors are set so that the sleeve monopole antenna unit can resonate at the specified operating frequency. The final selected capacitor values ​​are all 3pF, and the results are verified using the electromagnetic simulation software Sim4life as follows. Figure 3 As shown, the coil resonates at 598MHz, at which point the reflection coefficient is -16dB, which meets the requirements for extremely high field magnetic resonance imaging.

[0053] In step 6), considering the size of the human head and compatibility with hardware in other magnetic resonance imaging systems, a suitable diameter for the circular antenna array is determined. In this embodiment, the diameter of the circular array formed by the multi-channel sleeve monopole antenna elements is 280 mm.

[0054] In step 7), a cylindrical phantom with dimensions similar to a human head is constructed. The phantom is filled with an aqueous solution with specific dielectric parameters to form a water phantom, which is used for the uniformity calculation and evaluation of the multi-channel sleeve monopole coil. In this embodiment, the size of the water phantom is determined based on the size of the human head, and the dielectric parameters of the water phantom are determined based on the frequency variation characteristics of the dielectric parameters within the human head. Specifically, considering the requirements for imaging the human head, the cylindrical water phantom is selected with a diameter of 20 cm and a height of 20 cm. Based on the frequency variation law of the dielectric parameters of each medium within the human head, the relative permittivity of the water film at 598 MHz is determined to be 42.28, and the conductivity is 0.88 S / m.

[0055] In step 8), the cylindrical water model constructed above is placed at the center of the array of multi-channel sleeve monopole coils, and the B1+ field distribution generated by the transmitting coil in the target area is calculated using the electromagnetic simulation software Sim4life. Figure 4 The figure shows the B1+ field distribution at the longitudinal center section of a multi-channel sleeve monopole coil.

[0056] When meshing a model in the electromagnetic simulation software Sim4life, the mesh can only be created along the coordinate axes of a Cartesian coordinate system. This can lead to unnecessary singularities when meshing models composed of curved surfaces, surfaces of revolution, and irregular surfaces. This is determined by the algorithm of the electromagnetic simulation software itself, which can cause some singularities in the simulation results and affect the correct assessment of the uniformity of the radio frequency field distribution.

[0057] The method for calculating the radio frequency field uniformity in this scheme is as follows:

[0058]

[0059] Where Hom represents uniformity, represent The maximum value of the modulus, represent The minimum value of the modulus.

[0060] In step 9), the B1+ field data obtained in step 8) is organized, and the uniformity of the radio frequency field is calculated after data processing. In this embodiment, considering the limitations of electromagnetic simulation software in mesh generation, the data is post-processed to eliminate singularities. Specifically, the 90-quantile method is used to process the obtained B1+ field data, that is, 5% of the maximum and 5% of the minimum data are eliminated, and the uniformity of the radio frequency field is calculated using the remaining data. These processes are all implemented using Matlab software, and the calculated uniformity of the longitudinal central cross-section (diameter of 180mm) is 50%.

[0061] In step 10), the existing human digital model, the Duke model, is selected for SAR value calculation and evaluation of the multi-channel sleeve monopole coil. The Duke model is a human digital model designed based on Duke, a 34-year-old German man, with a height of 1.77m and a weight of 70.2kg. It can be used in the electromagnetic simulation software Sim4life to simulate the dielectric parameters and other characteristics of an adult male. In this embodiment, since the multi-channel sleeve monopole coil in this design is used for magnetic resonance imaging of the human head under extremely high fields, the head model from the Duke model is selected for SAR value calculation and evaluation.

[0062] In step 11), the head model in the Duke model is placed at the center of the array of multi-channel sleeve monopole coils, and the SAR value distribution generated by the multi-channel sleeve monopole coils in the head model is calculated using the electromagnetic simulation software Sim4life. Figure 5 The figure shows the SAR value distribution of the multi-channel sleeve monopole coil at the center section of the human head model.

[0063] In step 12), the normalized 10g peak SAR value is calculated and used to evaluate the safety of the transmitting coil. In this embodiment, with a normalized power of 1W, the calculated 10g peak SAR value generated by the multi-channel sleeve monopole coil is 0.2347W / kg. The 10g peak SAR is the maximum value of the average SAR value within any 10g tissue. The team represented by Myung Kyun Woo, Lance DelaBarre et al., in their paper "Comparison of 16-Channel Asymmetric Sleeve Antenna and Dipole Antenna Transceiver Arrays at 10.5TeslaMRI," published in the journal, reported a 10g peak SAR value of 0.31W / kg (normalized 1W power) generated by a 16-channel asymmetric sleeve monopole coil for a 10.5 Tesla MRI system. This value is greater than the 10g peak SAR value generated by the multi-channel sleeve monopole coil in this design, indicating that the transmitting coil of this invention has better safety.

[0064] It should be noted that the purpose of disclosing the embodiments is to help further understand the present invention. However, those skilled in the art will understand that various substitutions and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the scope of protection of the present invention is defined by the scope of the claims.

Claims

1. A method for designing a multi-channel sleeve monopole coil of an ultra-high field magnetic resonance imaging system, comprising: 1) designing a structure of a sleeve monopole antenna unit: the sleeve monopole antenna unit comprises a monopole antenna and a fixed sleeve, wherein each monopole antenna is segmented, the segmented structure is adopted, and the disconnected part is connected by a capacitor; the fixed sleeve has a single-conductor structure; the inner wall of the fixed sleeve is connected with a feed by a coaxial cable, and the outer conductors of the coaxial cable are connected and fixed; 2) setting a structure of the multi-channel sleeve monopole coil: a sleeve monopole array is formed by a plurality of sleeve monopole antenna units; the sleeve monopole antenna units are uniformly distributed on the sleeve monopole array, wherein each sleeve monopole antenna unit is fed by an independent coaxial cable, thereby forming the multi-channel sleeve monopole coil; 3) obtaining a working frequency of the multi-channel sleeve monopole coil in the magnetic resonance imaging system; 4) determining a length of the sleeve monopole antenna unit; 5) determining a size of a capacitor value at the disconnected part of the segmented monopole antenna, so that the sleeve monopole antenna unit resonates at the specified working frequency; 6) constructing a cylindrical phantom, filling the inside of the phantom with an aqueous solution having specific dielectric parameters to form a water phantom for calculating and evaluating the uniformity of the multi-channel sleeve monopole coil; 7) placing the water phantom at the center of the multi-channel sleeve monopole coil, taking the inside of the water phantom as a target region, and obtaining a radio frequency field distribution generated in the target region through electromagnetic simulation calculation; 8) calculating the radio frequency field uniformity of the target region; 9) selecting a human digital model to calculate and evaluate a specific absorption rate (SAR) value of the multi-channel sleeve monopole coil; 10) placing a head model in the human digital model at the center of the multi-channel sleeve monopole coil, and obtaining a SAR value distribution generated by the multi-channel sleeve monopole coil in the human head model through electromagnetic simulation calculation; 11) analyzing the SAR value and evaluating the safety of the multi-channel sleeve monopole coil; The design of the multi-channel sleeve monopole coil of the ultra-high field magnetic resonance imaging system is realized.

2. The method of designing a multi-channel sleeve solenoid for an ultra-high field magnetic resonance imaging system as claimed in claim 1, wherein, The shape of the sleeve monopole array is circular; the diameter of the sleeve monopole circular array is determined according to the size of the human head.

3. The method of designing a multi-channel sleeve solenoid for an ultra-high field magnetic resonance imaging system as claimed in claim 1, wherein, The monopole antenna is segmented into five segments; the diameter of the sleeve monopole circular array is 280 mm.

4. The method of designing a multi-channel sleeve solenoid for an ultra-high field magnetic resonance imaging system as claimed in claim 1, wherein, The length of the sleeve monopole antenna unit is determined according to the size of the human head; the length of the monopole antenna unit is 230-270 mm, and the diameter is 2.4 mm.

5. The method of designing a multi-channel sleeve monopole coil for a very high field magnetic resonance imaging system as claimed in claim 1, wherein, The length of the fixed sleeve is 70-90 mm; the diameter is 25-28 mm.

6. The method of designing a multi-channel sleeve solenoid for a very high field magnetic resonance imaging system as claimed in claim 1, wherein, The array is composed of 16 sleeve monopole antenna units to form the multi-channel sleeve monopole coil; the amplitudes of the feed of each sleeve monopole antenna unit are equal, and the phases of the feed of adjacent units differ by 22.5°.

7. The method of designing a multi-channel sleeve monopole coil for a very high field magnetic resonance imaging system as claimed in claim 1, wherein, Step 3) Based on the Larmor theorem and the main magnetic field strength in the magnetic resonance imaging system, the resonance frequency of the hydrogen nucleus is determined, and the working frequency of the transmit coil of the radio frequency coil in the magnetic resonance imaging system is obtained.

8. The method of designing a multi-channel sleeve monopole coil for a very high field magnetic resonance imaging system as claimed in claim 1, wherein, The size of the constructed cylindrical phantom is similar to the size of a human head; the cylindrical water phantom has a diameter of 20 cm and a height of 20 cm; the relative permittivity of the water film at 598 MHz is 42.28, and the conductivity is 0.88 s / m; The resonance frequency of the hydrogen nucleus is obtained according to the size of the main magnetic field, specifically, 14 Tesla is selected as the magnetic field size of the main magnetic field of the high-field magnetic resonance imaging, and the resonance frequency of the hydrogen nucleus is calculated according to the Larmor theorem, that is, the working frequency of the transmitting coil.

9. The method of designing a multi-channel sleeve monopole coil for a very high field magnetic resonance imaging system as claimed in claim 1, wherein, The human digital model is specifically the Duke model; electromagnetic simulation software Sim4life is used for electromagnetic simulation calculation; The method for calculating the uniformity of the radio frequency field is: The obtained B1+ field data is processed by using the 90th percentile method to eliminate singular points, and then the remaining data is used to calculate the uniformity of the radio frequency field.

10. A multi-channel sleeve monopole coil for a very high field magnetic resonance imaging system obtained using the design method of claim 1, characterized by, The sleeve monopole antenna unit and the circular array structure composed of a plurality of sleeve monopole antenna units are included. The sleeve monopole antenna unit is composed of a fixed sleeve and a monopole antenna, wherein the monopole antenna is fed by a coaxial feeder and connected with the inner conductor of the coaxial line; the inner wall of the fixed sleeve is connected with the outer conductor of the coaxial feeder; The plurality of sleeve monopole antenna units form an array, and the array shape is circular; the sleeve monopole antenna units are uniformly distributed around the circle.

Images