Self-decoupling coil array for magnetic resonance imaging

Abstract

The invention relates to a self-decoupling coil array for magnetic resonance imaging, which comprises resonance coils with detuning loops, the resonance coils are connected in series with decoupling capacitors, the two resonance coils are oppositely arranged at the positions where the decoupling capacitors are arranged so as to form decoupling units, and the multiple decoupling units are arranged in at least one direction. The decoupling units which are oppositely arranged at the position of the decoupling capacitor can enable one resonance coil to decouple the other resonance coil, and the decoupling units exist in the self-decoupling coil array in pairs, so that electric coupling does not occur in the whole self-decoupling coil array to realize self-decoupling. Compared with the prior art, the self-decoupling coil array for magnetic resonance imaging disclosed by the invention realizes decoupling between detuning resonance circuits by introducing additional electric coupling, so that the sensitivity is kept at a due level, and the imaging signal-to-noise ratio gain is more uniform.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic resonance imaging equipment, and in particular to a self-decoupling coil array for magnetic resonance imaging. Background Art

[0002] Magnetic resonance imaging is crucial in medical diagnosis, providing clear images of soft tissue morphology and function.

[0003] MRI systems are often limited by the signal-to-noise ratio when imaging small anatomical structures or when high spatial resolution is required. Studies have shown that the imaging signal-to-noise ratio can be significantly enhanced by combining wireless / wired surface coils with traditional receive coils.

[0004] However, existing wireless / wired arrays are prone to mutual interference when operating in multiple channels, resulting in sensitivity loss and uneven signal gain in wireless / wired arrays with multiple coils, which affects the signal-to-noise ratio and image quality. Summary of the invention

[0005] In order to solve the problem that the existing wireless / wired arrays are prone to mutual interference when operating in multiple channels, resulting in sensitivity loss and uneven signal gain in the wireless / wired arrays with multiple coils, the present invention proposes a self-decoupling coil array for magnetic resonance imaging.

[0006] The technical solution adopted by the present invention is a self-decoupling coil array for magnetic resonance imaging, including a resonant coil with a detuning circuit, the resonant coil is connected in series with a decoupling capacitor, two resonant coils are arranged opposite to each other at the position where the decoupling capacitor is set to form a decoupling unit, and multiple decoupling units are arranged in at least one direction.

[0007] Preferably, the resonant coil is a passive resonant coil.

[0008] Preferably, any two resonant coils do not overlap.

[0009] Preferably, the plurality of decoupling units are evenly arranged at the same distance in at least one direction.

[0010] Preferably, the plurality of decoupling units are arranged in two orthogonal directions.

[0011] Preferably, at the position where the decoupling capacitor is set, two resonant coils are arranged opposite to each other with an interval of 5 mm to form a decoupling unit, the side length of the resonant coil is 50 mm, and the size range of the decoupling capacitor is 1.4 pF to 1.9 pF.

[0012] Preferably, the decoupling unit is not bent in the length direction of any decoupling unit.

[0013] Preferably, the resonant coil is connected in series with an adjustable capacitor.

[0014] Preferably, an inductor is connected in series between the decoupling capacitor and the adjustable capacitor.

[0015] Preferably, the detuning circuit is a parallel LC circuit controlled by two pairs of bidirectional diodes.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present application discloses a self-decoupling coil array for magnetic resonance imaging, including a resonant coil with a detuning loop, the resonant coil is connected in series with a decoupling capacitor, two resonant coils are arranged oppositely at the position where the decoupling capacitor is arranged to form a decoupling unit, and a plurality of decoupling units are arranged in at least one direction. The decoupling units arranged oppositely at the position of the decoupling capacitor can make one of the resonant coils decouple the other resonant coil, and the decoupling units exist in pairs in the self-decoupling coil array, so that no electrical coupling occurs in the entire self-decoupling coil array to achieve self-decoupling.

[0018] Compared with the prior art, the self-decoupling coil array for magnetic resonance imaging disclosed in the present application achieves decoupling between detuned resonant circuits by introducing additional electrical coupling, so that the sensitivity is maintained at an appropriate level and the imaging signal-to-noise ratio gain is more uniform, thereby optimizing the wireless array coil, improving the signal-to-noise ratio and image quality in MRI imaging, and avoiding misjudgment of lesions by doctors due to uneven signal gain. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention is described in detail below with reference to the embodiments and accompanying drawings, wherein:

[0020] Figure 1 A schematic diagram of the use of a self-decoupling coil array for magnetic resonance imaging and a structure of a 12-channel self-decoupling coil array provided in an embodiment of the present invention are shown;

[0021] Figure 2 The decoupling capacitor C obtained by electromagnetic simulation according to a self-decoupling coil array for magnetic resonance imaging provided by an embodiment of the present invention is shown. mode Capacitance value;

[0022] Figure 3 A circuit schematic diagram of a resonant coil in a self-decoupling coil array for magnetic resonance imaging provided by an embodiment of the present invention is shown;

[0023] Figure 4 The results of a water phantom imaging experiment of a self-decoupling coil array for magnetic resonance imaging provided by an embodiment of the present invention are shown;

[0024] Figure 5The results of human body imaging experiments using a self-decoupling coil array for magnetic resonance imaging provided by an embodiment of the present invention are shown;

[0025] Figure 6 A comparison diagram showing the effects of a pair of conventional coils and a pair of self-decoupling coil arrays for magnetic resonance imaging provided according to an embodiment of the present invention (C mode =1.5pF). DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings. Examples of embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar components or components with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0027] The present invention discloses a self-decoupling coil array for magnetic resonance imaging, comprising a resonant coil with a detuning loop, wherein the resonant coil is connected in series with a decoupling capacitor, and two resonant coils are arranged opposite to each other at the position where the decoupling capacitor is arranged to form a decoupling unit, and a plurality of decoupling units are arranged in at least one direction.

[0028] Decoupling units that are relatively arranged at the position of the decoupling capacitor and do not overlap can enable one resonant coil to decouple the other resonant coil, and the decoupling units exist in pairs in the self-decoupling coil array, so that no electrical coupling will occur in the entire self-decoupling coil array to achieve self-decoupling. Compared with the prior art, the self-decoupling coil array for magnetic resonance imaging disclosed in the present application achieves decoupling between detuned resonant circuits by introducing additional electrical coupling, so that the sensitivity is maintained at the proper level, the imaging signal-to-noise ratio gain is more uniform, the wireless array coil is optimized, the signal-to-noise ratio and image quality in MRI imaging are improved, and the doctor's misjudgment of the lesion due to uneven signal gain is avoided.

[0029] Specifically, the self-decoupling coil array used in the present invention has self-decoupling between the resonant coils during operation, and the current distribution of a single resonant coil is uneven. The decoupling capacitor C mode The current intensity on one side is smaller and the electric field intensity is stronger, thereby introducing additional electrical coupling between the resonant coils to achieve self-decoupling.

[0030] It should be noted that the resonant coil has a detuned state and a resonant state. The detuned state is used for detuning in the RF transmission phase, and the resonant state is used for resonating in the reception phase to enhance the signal.

[0031] Multiple decoupling units are arranged in at least one direction. The specific choice of the arrangement in several directions can be selected according to the size of the area where the magnetic resonance imaging is required. When the area is large, multiple decoupling units can be arranged in more directions. Among them, the arrangement of multiple decoupling units in at least one direction is relative to the direction on the same plane. After the multiple decoupling units are arranged on the same plane, they can be folded and bent to form other shapes, such as cylindrical, hood-shaped, etc. The resonant coil is built based on the coil, and the coil itself has a certain elastic or plastic deformation ability, so the resonant coil itself has the ability to bend.

[0032] In addition, the density of the arrangement of multiple decoupling units in any direction can also be determined according to the gain required for that position. For positions where a larger gain is required, the arrangement density at that position can be appropriately increased, that is, the distance interval between two adjacent decoupling units.

[0033] The present application does not limit the shape of the resonant coil. To achieve the purpose of decoupling, it is only necessary to arrange the two resonant coils relative to each other at the position of the decoupling capacitor.

[0034] The present invention is a self-decoupling coil array, so the use of receiving coils is not limited, and any conventional receiving coil can be used. The present invention is not limited by the type, size and dimensions of the resonant coil in the self-decoupling coil array, the number of channels of the self-decoupling coil array, or the distribution plane of the self-decoupling coil array, that is, the self-decoupling coil array can be distributed on a plane or on a cylindrical surface. In addition, the RF receiving coil and the self-decoupling coil array can be placed directly close to each other or at a certain distance.

[0035] The feasibility of this invention has been verified by experiments. Figure 4 During the water model test, it can be clearly seen that the signal-to-noise ratio on the surface has been improved by nearly 2 times. Please refer to Figure 5 In human imaging, it can be seen that when imaging the knee joint, the signal-to-noise ratio in the region of interest (ROI) is improved by up to 45%.

[0036] The working process of the self-decoupling coil array is as follows: in the RF transmission stage of the magnetic resonance imaging system, the PIN-type diode of the detuning circuit in the resonant coil of the self-decoupling coil array is turned on, so that the entire resonant coil is in a detuned state, and the response of the self-decoupling coil array to the RF transmission field is attenuated, thereby reducing the impact on the RF transmission field to a minimum; when the self-decoupling coil array is working in the receiving stage, the PIN-type diode of the detuning circuit in the resonant coil of the wireless array is not turned on, and the detuning circuit does not work, so that the signal can pass. Under Faraday's law of electromagnetic induction, the change in magnetic flux passing through the wireless array causes the self-decoupling coil array to induce an electromotive force, and the self-decoupling coil array amplifies the voltage signal by Q (the quality factor of the self-decoupling coil array) times and then is received by the RF receiving coil, thereby achieving an enhancement in the signal-to-noise ratio of the imaging signal. The present invention provides an implementation example: a 12-channel self-decoupling coil array for knee joint imaging, and its placement position diagram is shown in FIG. Figure 1 As shown, Figure 1 Reference numeral 101 is a self-decoupling coil array for magnetic resonance imaging, and reference numeral 102 is a radio frequency receiving coil (knee coil).

[0037] The debugging of the self-decoupling coil array includes tuning, detuning and decoupling; its resonant coils such as Figure 3 As shown, the unit structure of the wireless array adopts a loop structure, and its tuning is achieved through an adjustable capacitor C in a tuning loop in a resonant coil. Tune The frequency of the detuned loop in the loop is achieved by adjusting C1 and L1. The decoupling capacitor C in series with the resonant coil of the self-decoupling coil array mode , whose capacitance is very small, can introduce additional electrical coupling to offset the magnetic coupling between the relative resonant coils, thereby reducing the coupling between each unit loop. Figure 2 As shown, C mode The size of the electrical coupling will control the size of the electrical coupling, C mode The smaller the value, the greater the electrical coupling. C can be determined by electromagnetic simulation. mode The capacitance value.

[0038] It needs to be explained that Figure 6 The curves from top to bottom in the figure represent the coupling sizes of a pair of traditional coils, a pair of self-decoupling coil arrays placed normally, and a pair of self-decoupling coil arrays placed oppositely, respectively. The best decoupling effect can be obtained when they are placed oppositely.

[0039] In some embodiments, the resonant coil is a passive resonant coil.

[0040] Meanwhile, the resonant coil is a passive coil. Compared with the wired phased array coil, the manufacturing and integration process of the traditional wired phased array coil may be more expensive and complicated, and needs to be simplified to reduce the overall medical cost and improve the accessibility of the MRI system. In other embodiments, the resonant coil may also be a wired resonant coil.

[0041] In some embodiments, any two resonant coils do not overlap.

[0042] It should be noted that when the resonant coils are placed in an overlapping manner, a certain overlapping area is required to achieve overlapping decoupling. However, when faced with two adjacent resonant coils with a smaller overlapping area, decoupling cannot be achieved by overlapping. At this time, decoupling capacitors are needed to completely achieve the decoupling purpose of the self-decoupling coil array.

[0043] In some embodiments, the plurality of decoupling units are evenly arranged at the same distance in at least one direction.

[0044] Specifically, in order to make the gain obtained at each location of the self-decoupling coil array for magnetic resonance imaging the same in at least one direction, multiple decoupling units are evenly arranged at the same distance in at least one direction. When installing the self-decoupling coil array in this direction, there is no need to consider the impact of misalignment on imaging. In addition, multiple decoupling units are evenly arranged at the same distance in at least one direction, so that during the magnetic resonance imaging process, it is possible to visually observe whether the gain at each location is at the same level. When a decoupling unit in the self-decoupling coil array is damaged and cannot work normally, this can be used as a marker to quickly determine the damaged location.

[0045] In some specific embodiments, a plurality of decoupling units are arranged in two orthogonal directions.

[0046] It should be noted that multiple decoupling units are arranged in two orthogonal directions, which makes it easier to calculate the gain of each position of the self-decoupling coil array. At the same time, arranging them in two orthogonal directions can adapt to most application scenarios and facilitate the processing and layout of the self-decoupling coil array.

[0047] In some more specific embodiments, two resonant coils are arranged relative to each other with a spacing of 5 mm at the position where the decoupling capacitor is set to form a decoupling unit, the side length of the resonant coil is 50 mm, and the size of the decoupling capacitor ranges from 1.4 pF to 1.9 pF.

[0048] It should be explained that the decoupling capacitor C connected in series with the resonant coil of the self-decoupling coil array mode , whose capacitance is very small, can introduce additional electrical coupling to offset the magnetic coupling between the relative resonant coils, thereby reducing the coupling between each unit loop. Figure 2 As shown, C mode The size of the electrical coupling will control the size of the electrical coupling, C mode The smaller the value, the greater the electrical coupling. C can be determined by electromagnetic simulation. mode The capacitance value.

[0049] The decoupling capacitor size range of the self-decoupling coil array manufactured using the above parameters is 1.4 pF to 1.9 pF, which is used for imaging the knee joint to obtain the best decoupling effect. The preferred value is 1.65 pF, please refer to Figure 2 , at this time, the coupling coefficient between the self-decoupling coil arrays is smaller, and the decoupling effect is better. Preferably, the decoupling capacitor C mode The capacitive reactance value is greater than 200Ω, achieving high-quality decoupling between wireless array channels.

[0050] In some more specific embodiments, the resonant coil is in a square shape.

[0051] The sides of the squares are the same length, so that in two orthogonal directions, the distances between any two adjacent detuned resonant loops are the same, so that for some self-decoupling coil arrays that need to be bent and have different bending degrees at different locations, the bending degree is the only parameter that affects the gain strength, so it is easy to adjust the bending degree and the position of the required high gain. In other embodiments, the shape of the resonant coil can also be other polygons.

[0052] In some embodiments, the decoupling unit is not bent in the length direction of any decoupling unit.

[0053] Specifically, the length direction of the decoupling unit refers to the connection direction of the two decoupling capacitors. In order to avoid changes in the distance between the two decoupling capacitors in the unified decoupling unit during the bending process, bending in the connection direction of the two decoupling capacitors should be avoided, thereby obtaining a better decoupling effect.

[0054] In some embodiments, the decoupling units are all disposed on the flexible structure.

[0055] The flexible structure may be a flexible structure such as cloth or felt, and the decoupled wireless array may be more convenient to use by setting the flexible structure.

[0056] In some specific embodiments, a bonding structure is provided on the flexible structure, and the size of the imaging area enclosed by the flexible structure can be adjusted through the bonding structure. The flexible structure is connected to a shielding structure, and the shielding structure can shield the remaining decoupling units that do not enclose the imaging area, so as not to affect the normal operation of the enclosed imaging area.

[0057] In some specific embodiments, the flexible structure has at least two detachable structures, so that the operator can adjust the appropriate size according to the size of the required imaging area.

[0058] In some embodiments, the resonant coil is connected in series with an adjustable capacitor.

[0059] In order to further optimize the resonant coil structure and reduce the manufacturing cost of the self-decoupling coil array, the present application connects an adjustable capacitor in series in the resonant coil to achieve a tuning state. It should be noted that the detuning loop and the tuning loop do not emphasize having two different loops. In some embodiments, the detuning loop and the tuning loop have a common circuit.

[0060] In some embodiments, an inductor is connected in series between the decoupling capacitor and the adjustable capacitor.

[0061] Specifically, on the one hand, in order to prevent the normal tuning of the resonant coil from being affected when a too small decoupling capacitor is selected, an inductor is connected in series between the decoupling capacitor and the adjustable capacitor; on the other hand, in order to further enhance the decoupling effect of the self-decoupling coil array and prevent the mutual influence between the decoupling capacitor and the adjustable capacitor, an inductor is connected in series between the decoupling capacitor and the adjustable capacitor.

[0062] In some embodiments, the detuning circuit is a parallel LC circuit controlled by two pairs of bidirectional diodes.

[0063] This embodiment uses a parallel LC circuit controlled by two pairs of bidirectional diodes to achieve detuning. Other methods can also be used to achieve detuning in the detuning circuit, such as introducing a new detuning circuit.

[0064] In the description of this specification, if the terms "embodiment one", "this embodiment", "in an embodiment" and the like appear, it means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in the invention or at least one embodiment or example of the invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example; moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in an appropriate manner.

[0065] In the description of this specification, the terms "connect", "install", "fix", "set", "have", etc. are all understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0066] In the description of this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0067] The above description of the embodiments is to facilitate ordinary technicians in the technical field to understand and apply the technology of this case. People familiar with the technology in this field can obviously easily make various modifications to these examples and apply the general principles described here to other embodiments without creative work. Therefore, this case is not limited to the above embodiments. Modifications to the following situations should all be within the scope of protection of this case: ① A new technical solution implemented based on the technical solution of the present invention and combined with existing common knowledge, the technical effect produced by the new technical solution does not exceed the technical effect of the present invention; ② The equivalent replacement of some features of the technical solution of the present invention by using known technology, the technical effect produced is the same as the technical effect of the present invention; ③ The technical solution of the present invention can be expanded, and the substantive content of the expanded technical solution does not exceed the technical solution of the present invention; ④ The equivalent transformation made by using the contents of the description and drawings of the present invention is directly or indirectly applied to other related technical fields.

Claims

1. A self-decoupling coil array for magnetic resonance imaging, characterized in that: It comprises a resonant coil with a detuning circuit, wherein the resonant coil is connected in series with a decoupling capacitor, and two resonant coils are arranged opposite to each other at the position where the decoupling capacitor is arranged to form a decoupling unit, and a plurality of the decoupling units are arranged in at least one direction.

2. A self-decoupling coil array for magnetic resonance imaging according to claim 1, characterized in that: The resonant coil is a passive resonant coil.

3. A self-decoupling coil array for magnetic resonance imaging according to claim 1, characterized in that: Any two of the resonant coils do not overlap.

4. A self-decoupling coil array for magnetic resonance imaging according to claim 3, characterized in that: The plurality of decoupling units are evenly arranged at the same distance in at least one direction.

5. A self-decoupling coil array for magnetic resonance imaging according to claim 4, characterized in that: The multiple decoupling units are arranged in two orthogonal directions.

6. A self-decoupling coil array for magnetic resonance imaging according to claim 5, characterized in that: At the position where the decoupling capacitor is set, the two resonant coils are arranged opposite to each other with an interval of 5 mm to form a decoupling unit. The side length of the resonant coil is 50 mm, and the size of the decoupling capacitor ranges from 1.4 pF to 1.9 pF.

7. A self-decoupling coil array for magnetic resonance imaging according to claim 1, characterized in that: In the length direction of any one of the decoupling units, the decoupling unit is not bent.

8. A self-decoupling coil array for magnetic resonance imaging according to any one of claims 1 to 7, characterized in that: The resonant coil is connected in series with an adjustable capacitor.

9. A self-decoupling coil array for magnetic resonance imaging according to claim 8, characterized in that: An inductor is connected in series between the decoupling capacitor and the adjustable capacitor.

10. A self-decoupling coil array for magnetic resonance imaging according to any one of claims 1 to 7, characterized in that: The detuning circuit is a parallel LC circuit controlled by two pairs of bidirectional diodes.

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