Mammary gland MRI coil combined with passive resonant ring

Abstract

The invention discloses a mammary gland MR I coil combined with a passive resonant ring, and belongs to the technical field of magnetic resonance radio frequency, the mammary gland MR I coil comprises a shell, two groups of coil supports are oppositely arranged in the shell, the inner surface of each coil support is provided with a special-shaped birdcage coil assembly, and the inner side of each special-shaped birdcage coil assembly is detachably provided with a resonant ring part curled into a cylindrical shape; wherein the special-shaped birdcage coil assembly comprises a trumpet-shaped upper coil with an upward opening, a cylindrical lower coil is arranged below the upper coil, the upper coil and the lower coil are respectively attached and fixed on the inner surface of the coil support, and a plurality of uniformly distributed bridging capacitors are arranged between the upper coil and the lower coil. Two poles of the bridging capacitor are electrically connected with the corresponding butting ends of the upper coil and the lower coil respectively; the special-shaped birdcage coil assembly with a unique structure and the resonant ring component are matched with each other, so that the performance and the imaging quality of the radio frequency coil are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic resonance radio frequency, and particularly relates to a breast MRI coil combined with a passive resonator loop. Background Art

[0002] All along, breast cancer has been one of the malignant tumors with the highest incidence and mortality rates among the female population, seriously endangering the physical and mental health of women. With the continuous development of the medical cause, breast cancer shows good initial controllability, that is, there are relatively complete treatment plans and curative effects for early breast cancer in clinical practice. Under this background, the screening of breast cancer has become increasingly important, and the screening methods have also developed diversely. Magnetic resonance imaging (MRI) has a high differential diagnostic efficiency for both benign and malignant breast tumors due to its high sensitivity and good spatial resolution. Compared with high-field magnetic resonance systems, low-field magnetic resonance systems have lower costs. At the same time, due to the reduction of the magnetic field strength, the magnet structure of the system is more flexible, and the scanning space is more open than that of high-field systems; however, the imaging quality of low-field systems will correspondingly be discounted, so it is necessary to optimize the radio frequency coil to make up for this shortcoming by improving the sensitivity and signal-to-noise ratio of the radio frequency coil.

[0003] For breast scanning, while improving the performance of the radio frequency coil, the coil structure also needs to fit the breast tissue as much as possible. Currently, most commercial breast imaging coils are hemispherical multi-channel coils. On the one hand, the structure of such coils does not match the shape characteristics of breast tissue, so the optimization of the field uniformity and field strength in the imaging area is limited; on the other hand, in order to improve the signal-to-noise ratio, multi-channel imaging is commonly used in commercial breast imaging coils. However, due to the coupling between channels, the decoupling method between channels needs to be carefully designed during production, and the research and development process is relatively complex, greatly increasing the research and development cost. Summary of the Invention

[0004] The purpose of the present invention is to provide a breast MRI coil combined with a passive resonator loop, which uses a special-shaped birdcage coil assembly with a unique structure as a low-field breast imaging coil. Its orthogonal excitation method can ensure the signal-to-noise ratio of the coil, and at the same time its deformation is more in line with the structural characteristics of breast tissue, reducing unnecessary spatial loss; in addition, a resonator loop component is arranged on the inner circumference side of the special-shaped birdcage coil assembly, which can be coupled with the special-shaped birdcage coil assembly to achieve focusing of the magnetic field, thereby enhancing the central magnetic field strength, further improving the performance and imaging quality of the special-shaped birdcage coil assembly, and solving the problems of high cost and low imaging quality of the radio frequency coil used in low-field magnetic resonance systems proposed in the background art.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A breast MRI coil combined with a passive resonant ring comprises a shell, two groups of coil supports are arranged opposite to each other inside the shell, a special-shaped birdcage coil assembly is installed on the inner surface of the coil support, and a resonant ring component curled into a cylindrical shape is detachably arranged on the inner side of the special-shaped birdcage coil assembly; wherein the special-shaped birdcage coil assembly comprises an upper coil in a trumpet shape with an opening facing upward, a lower coil in a cylindrical shape is arranged below the upper coil, the inner wall shape of the coil support matches the upper coil and the lower coil, the upper coil and the lower coil are respectively attached and fixed to the inner surface of the coil support, a plurality of evenly distributed bridging capacitors are arranged between the upper coil and the lower coil, and the two poles of the bridging capacitors are respectively electrically connected to the corresponding butt ends of the upper coil and the lower coil.

[0007] Furthermore, the shell is a rectangular box with an open bottom, and the top of the shell is arc-shaped.

[0008] Furthermore, the coil support is fixedly connected to the housing.

[0009] Furthermore, the top radius R of the upper coil top The bottom radius of the upper coil is 80-120mm. bottom It is 60mm.

[0010] Furthermore, the total height H of the special-shaped birdcage coil assembly is 80-90 mm; wherein the ratio of the height h1 of the cylindrical part to the height h2 of the horn part is 3:1.

[0011] Furthermore, the capacitance of the bridge capacitor is adjusted and set according to the inductance of the loop formed by the upper coil and the lower coil to ensure that the resonant frequency of the coil is always the operating frequency of the magnetic resonance system in which it is located.

[0012] Furthermore, the resonant ring component includes a soft pad, an even number of at least 4 equally spaced rectangular resonant ring components are arranged inside the soft pad; each group of rectangular resonant ring components constitutes a closed passive resonant loop.

[0013] Furthermore, the thickness of the soft pad is set to 1-10 mm.

[0014] Furthermore, the rectangular resonant ring component includes a coaxial line consisting of an outer conductor and an inner core conductor, a gap is left at both ends of the outer conductor, and a bidirectional diode is electrically connected to the two ends of the outer conductor, a resonant capacitor is arranged between the two ends of the inner core conductor, and the two ends of the inner core conductor are electrically connected to the two poles of the resonant capacitor.

[0015] Furthermore, the rectangular resonant ring component has a length of 60-67.5 mm and a width of 30 mm.

[0016] Beneficial effects:

[0017] The present invention realizes the application expansion of a special-shaped birdcage coil assembly in a low-field magnetic resonance system. Its structure is well matched with the shape of the human breast in the prone position, and while conforming to the tissue structure characteristics of the breast, it can shift the imaging area towards the chest wall end, which is more conducive to imaging of this conical tissue structure of the breast. The field generated by the special-shaped birdcage coil assembly is a stable linear field or an orthogonal circularly polarized field. On the premise of standard support structure, the coil can spontaneously be stably orthogonal to the vertical main magnetic field of the low field, reducing the radio frequency field loss. The magnetic field distribution of the special-shaped birdcage coil assembly is relatively concentrated and confined inside the coil, that is, it has good magnetic field confinement characteristics. When performing bilateral imaging, the interference between them is relatively weak, and the coupling between the bilateral special-shaped birdcage coil assemblies is well suppressed.

[0018] By detachably arranging a resonant ring component inside the special-shaped birdcage coil assembly, the present invention can improve the imaging quality of the low-field coil at a relatively low cost, and the manufacturing process is simple. The rectangular resonant ring component adopts a coaxial structure, which on the one hand reduces the negative coupling effect of the resonant ring component on the special-shaped birdcage coil assembly, and on the other hand, the flexible structure of the coaxial line can make the resonant ring component better conform to the breast tissue, occupying less space, thereby achieving a better imaging effect. Brief Description of the Drawings

[0019] The present invention will be further described below with reference to the drawings.

[0020] Figure 1 is the top view of a breast MRI coil combining a passive resonant ring according to the present invention;

[0021] Figure 2 is the three-dimensional view of a breast MRI coil combining a passive resonant ring according to the present invention after hiding the resonant ring component;

[0022] Figure 3 is the structural schematic diagram of the upper coil, lower coil and passive resonant ring arranged in cooperation according to the present invention;

[0023] Figure 4 is the front view of the upper coil and the lower coil according to the present invention;

[0024] Figure 5 is the structural schematic diagram of the soft pad according to the present invention;

[0025] Figure 6 is the structural schematic diagram of the passive resonant ring component according to the present invention;

[0026] Figure 7 is Figure 6 the partial enlarged cross-sectional view at A in

[0027] Figure 8 is the clinical use schematic diagram of a breast MRI coil combining a passive resonant ring according to the present invention;

[0028] Figure 9 It is a data comparison diagram of the central field strength before and after the soft pad component is loaded on the breast MRI coil of the present invention.

[0029] In the attached drawings, the list of components represented by each reference numeral is as follows:

[0030] 1. Housing; 2. Coil bracket; 3. Special-shaped birdcage coil assembly; 301. Upper coil; 302. Lower coil; 303. Bridging capacitor; 4. Resonant ring component; 401. Soft pad; 402. Rectangular resonant ring assembly; 4021. Outer conductor; 4022. Inner core conductor; 4023. Bidirectional diode; 4024. Resonant capacitor. Specific embodiments

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] Please refer to Figures 1-7 As shown, the present invention provides a breast MRI coil combined with a passive resonant ring, including a housing 1. Two groups of coil brackets 2 are oppositely arranged inside the housing 1. A special-shaped birdcage coil assembly 3 is installed on the inner surface of the coil bracket 2. A resonant ring component 4 curled into a cylindrical shape is detachably arranged inside the special-shaped birdcage coil assembly 3; among them, the special-shaped birdcage coil assembly 3 includes an upper coil 301 in the shape of a horn with an upward opening. A lower coil 302 in the shape of a cylinder is arranged below the upper coil 301. The inner wall shape of the coil bracket 2 matches the upper coil 301 and the lower coil 302. The upper coil 301 and the lower coil 302 are respectively attached and fixed to the inner surface of the coil bracket 2. A number of evenly distributed bridging capacitors 303 are arranged between the upper coil 301 and the lower coil 302. The two poles of the bridging capacitor 303 are electrically connected to the corresponding docking ends of the upper coil 301 and the lower coil 302 respectively to form a complete circuit.

[0033] Based on the fact that the main magnetic field direction (vertically up and down) of the low-field magnetic resonance system is different from that of the high-field system (horizontally axial), the birdcage coil standing upright in the low-field magnet spontaneously meets the requirement of the perpendicularity between the coil radiofrequency field and the main magnetic field, and the birdcage coil has natural advantages compared with the conventional coil; on this premise, the present invention deforms the structure of the traditional birdcage coil, combines the traditional cylindrical birdcage structure with the horn-shaped birdcage structure into a new special-shaped birdcage coil assembly 3, making the overall special-shaped birdcage coil assembly 3 look like a "flower pot", so that the central imaging area is closer to the chest wall position of the human body in the prone state, thereby achieving good imaging of the mammary gland tissue in the hanging state and the chest wall nearby; during magnetic resonance imaging, the resonant ring component 4 is located between the special-shaped birdcage coil assembly 3 and the mammary gland tissue, and uses the coupling with the special-shaped birdcage coil assembly 3 to focus the low field, so that the signal received by the special-shaped birdcage coil assembly 3 is enhanced, thereby improving the signal-to-noise ratio of the image.

[0034] Further, the housing 1 is a rectangular box with an open bottom, and the top of the housing 1 is arc-shaped, matching the contour of the human chest wall, improving the use comfort.

[0035] Further, the coil bracket 2 is fixedly connected to the housing 1, and the coil bracket 2 can be obtained by 3D printing, having the advantages of low cost and simple operation.

[0036] Further, the top radius Rtop of the upper coil 301 is 80 - 120 mm. Specifically, the top radius Rtop of the upper coil 301 can be 80 mm, 90 mm, 100 mm, 110 mm, and 120 mm, and the bottom radius Rbottom of the upper coil 301 is 60 mm; through simulation verification, the present invention finds that by scaling the flared end of the upper coil 301, the central imaging area of the special-shaped birdcage coil assembly 3 will shift significantly upward, and the larger the ratio of the diameters of the upper and lower ports, the greater the field offset.

[0037] Further, the total height H of the special-shaped birdcage coil assembly 3 is 80 - 90 mm; specifically, the total height H of the special-shaped birdcage coil can be 80 mm and 90 mm; among them, the height ratio of the cylindrical part to the horn part is h1:h2 = 3:1. The lower half-cylindrical structure is the main target imaging area, and the upper half mainly plays the role of field offset and improving the average field operation. Therefore, the present invention sets the optimal height ratio of the cylindrical part to the horn part to 3:1.

[0038] Further, according to the calculation formula of the coil resonance frequency:

[0039]

[0040] where, f 0Let \(f_0\) be the operating frequency of the magnetic resonance system (for example, the operating frequency of the 035 system is 14.9 MHz), \(L\) be the inductance value of the loop formed by the upper coil 301 and the lower coil 302, and \(C\) be the capacitance value of the bridging capacitor 303. From the above calculation formula, it can be seen that when the coil structure and size change, the inductance value \(L\) is greatly affected. To ensure that \(f_0\) is always the operating frequency of the magnetic resonance system, the capacitance value \(C\) of the bridging capacitor 303 needs to be adjusted accordingly.

[0041] Further, the resonant ring component 4 includes a soft pad 401 with a certain thickness. Inside the soft pad 401, there are an even number of at least 4 rectangular resonant ring assemblies 402 distributed at equal intervals; each group of rectangular resonant ring assemblies 402 forms a closed passive resonant circuit; when the resonant ring component 4 is curled into a cylindrical shape, the rectangular resonant ring assemblies 402 are opposite to each other in the soft pad 401 and surround the breast tissue.

[0042] Further, the thickness of the soft pad 401 is set to 1 - 10 mm to ensure a spacing between the rectangular resonant ring assemblies 402 and the special-shaped birdcage coil assembly 3. The purpose of this setting is: on the one hand, to ensure comfort, and on the other hand, to reduce the coupling effect of the rectangular resonant ring assemblies 402 on the special-shaped birdcage coil assembly 3.

[0043] Further, the rectangular resonant ring assembly 402 includes a coaxial line composed of an outer conductor 4021 and an inner core conductor 4022. There are gaps at both ends of the outer conductor 4021, and bidirectional diodes 4023 are electrically connected to both ends of the outer conductor 4021. A resonant capacitor 4024 is arranged between both ends of the inner core conductor 4022, and both ends of the inner core conductor 4022 are electrically connected to the two poles of the resonant capacitor 4024. In the present invention, a coaxial line is used as the conductor to form a high-impedance circuit. While the inner core conductor 4022 realizes magnetic field focusing through coupling, the outer conductor 4021 generates a reverse induced current to suppress the external coupling effect of the circuit.

[0044] Further, the length of the rectangular resonant ring assembly 402 is 60 mm and the width is 30 mm; specifically, the size of the rectangular resonant ring assembly 402 can also be adaptively adjusted according to the size of the special-shaped birdcage coil assembly 3.

[0045] Embodiment 1

[0046] This embodiment provides a breast MRI coil combined with a passive resonant ring, including a housing 1. The housing 1 is a rectangular box with an open bottom end, and the top end of the housing 1 is arc-shaped and matches the contour of the human chest wall. Inside the housing 1, two groups of coil brackets 2 obtained by 3D printing are oppositely arranged. The coil brackets 2 are fixedly connected to the housing 1. The inner surface of the coil brackets 2 is equipped with a special-shaped birdcage coil assembly 3, and a resonant ring component 4 curled into a cylindrical shape is detachably arranged inside the special-shaped birdcage coil assembly 3;

[0047] The special-shaped birdcage coil assembly 3 includes an upper coil 301 in a horn shape with an upward opening. Below the upper coil 301, there is a lower coil 302 in a cylindrical shape. The inner wall shape of the coil bracket 2 matches that of the upper coil 301 and the lower coil 302. The upper coil 301 and the lower coil 302 are respectively attached and fixed to the inner surface of the coil bracket 2. The top radius Rtop of the upper coil 301 is 80 mm, and the bottom radius Rbottom is 60 mm. Between the upper coil 301 and the lower coil 302, there are several evenly distributed bridging capacitors 303. The two poles of the bridging capacitor 303 are respectively electrically connected to the corresponding docking ends of the upper coil 301 and the lower coil 302 to form a complete circuit. The total height H of the special-shaped birdcage coil assembly 3 is 80 mm. Among them, the height ratio of the cylindrical part h1 to the horn-shaped part h2 is 3:1, that is, h1 = 60 mm and h2 = 20 mm. The special-shaped birdcage coil assembly 3 operates in the 035 system;

[0048] The resonant ring component 4 includes a soft pad 401 with a thickness of 10 mm. Inside the soft pad 401, there are 4 equally spaced rectangular resonant ring assemblies 402. Each group of rectangular resonant ring assemblies 402 forms a closed passive resonant circuit. The rectangular resonant ring assembly 402 includes a coaxial cable composed of an outer conductor 4021 and an inner core conductor 4022. There are gaps at both ends of the outer conductor 4021, and bidirectional diodes 4023 are electrically connected to both ends of the outer conductor 4021. A resonant capacitor 4024 is arranged between the two ends of the inner core conductor 4022, and the two ends of the inner core conductor 4022 are electrically connected to the two poles of the resonant capacitor 4024. The length of the rectangular resonant ring assembly 402 is 60 mm, and the width is 30 mm.

[0049] Example 2

[0050] Compared with Example 1, the difference in this example is that the top radius Rtop of the upper coil 301 is 100 mm, the total height H of the special-shaped birdcage coil assembly 3 is 86 mm, and the length of the rectangular resonant ring assembly 402 is 64.5 mm. The rest of the structures and parameters are the same.

[0051] Example 3

[0052] Compared with Example 1, the difference in this example is that the top radius Rtop of the upper coil 301 is 120 mm, the total height H of the special-shaped birdcage coil assembly 3 is 90 mm, and the length of the rectangular resonant ring assembly 402 is 67.5 mm. The rest of the structures and parameters are the same.

[0053] Comparative Example 1

[0054] Compared with Example 1, the difference in this comparative example is that the resonant ring component 4 curled into a cylindrical shape is not provided inside the special-shaped birdcage coil assembly 3, and the rest of the structures are the same.

[0055] The breast MRI coil of Example 1 is applied to the actual clinical scanning position. It can be seen that Figure 8 the female human body model lies prone on the breast MRI coil, and the breast MRI coil has a good match with the breast tissue in terms of structure.

[0056] The central field strength of the breast MRI coils of Example 1 and Comparative Example 1 is simulated. It can be seen that Figure 9 after the resonant ring component 4 is loaded, the central field strength of the breast MRI coil is significantly enhanced.

[0057] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0058] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A breast MRI coil combined with a passive resonant ring, characterized in that: The invention comprises a shell (1), wherein two groups of coil supports (2) are arranged opposite to each other inside the shell (1), a special-shaped birdcage coil assembly (3) is installed on the inner surface of the coil support (2), and a resonant ring component (4) curled into a cylindrical shape is detachably arranged on the inner side of the special-shaped birdcage coil assembly (3); wherein the special-shaped birdcage coil assembly (3) comprises an upper coil (301) in a trumpet shape and opening upward, a lower coil (302) in a cylindrical shape is arranged below the upper coil (301), the upper coil (301) and the lower coil (302) are respectively attached and fixed to the inner surface of the coil support (2), a plurality of evenly distributed bridge capacitors (303) are arranged between the upper coil (301) and the lower coil (302), and the two poles of the bridge capacitor (303) are respectively electrically connected to the corresponding butt ends of the upper coil (301) and the lower coil (302).

2. The breast MRI coil combined with a passive resonant ring according to claim 1, characterized in that: The shell (1) is a rectangular box with an open bottom, and the top of the shell (1) is arc-shaped.

3. The breast MRI coil combined with a passive resonant ring according to claim 1, characterized in that: The coil support (2) is fixedly connected to the housing (1).

4. The breast MRI coil combined with a passive resonant ring according to claim 1, characterized in that: The top radius of the upper coil (301) is 80-120 mm, and the bottom radius of the upper coil (301) is 60 mm.

5. The breast MRI coil combined with a passive resonant ring according to claim 1, characterized in that: The total height of the special-shaped birdcage coil assembly (3) is 80-90 mm, wherein the ratio of the height of the cylindrical part to the height of the horn part is 3:

1.

6. The breast MRI coil combined with a passive resonant ring according to claim 1, characterized in that: The capacitance of the bridge capacitor (303) is adjusted and set according to the inductance of the loop formed by the upper coil (301) and the lower coil (302) to ensure that the coil resonance frequency is always the operating frequency of the magnetic resonance system in which it is located.

7. The breast MRI coil combined with a passive resonant ring according to claim 1, characterized in that: The resonant ring component (4) comprises a soft pad (401), an even number of at least four equally spaced rectangular resonant ring components (402) being arranged inside the soft pad (401); each group of rectangular resonant ring components (402) constitutes a closed passive resonant loop.

8. The breast MRI coil combined with a passive resonant ring according to claim 7, characterized in that: The thickness of the soft pad (401) is set to 1-10 mm.

9. The breast MRI coil combined with a passive resonant ring according to claim 7, characterized in that: The rectangular resonant ring component (402) comprises a coaxial line consisting of an outer conductor (4021) and an inner conductor (4022), a gap is left at both ends of the outer conductor (4021), and a bidirectional diode (4023) is electrically connected to both ends of the outer conductor (4021), a resonant capacitor (4024) is arranged between the two ends of the inner conductor (4022), and the two ends of the inner conductor (4022) are electrically connected to the two poles of the resonant capacitor (4024).

10. The breast MRI coil combined with a passive resonant ring according to claim 7, characterized in that: The rectangular resonant ring component (402) has a length of 60-67.5 mm and a width of 30 mm.

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