Magnetic resonance coil array and self-compensating radio frequency choke

Abstract

The invention relates to a magnetic resonance coil array (30) of a magnetic resonance system having a distributed cabling realized by a self-compensating radio frequency choke (10). The magnetic resonance coil array (30) comprises a plurality of magnetic resonance receive coils (32), an input-output unit (34) and a plurality of coaxial cables (14) interconnecting the magnetic resonance receive coils (32) with the input-output unit (34). The coaxial cables (14) comprise the self-compensating radio frequency choke (10). The self-compensating radio frequency choke (10) allows replacing conventional large volume resonant radio frequency traps used in conventional magnetic resonance coil arrays and allows implementing a distributed cabling. The self-compensating radio frequency choke (10) comprises a choke housing (12) having a toroidal outer shape and a coaxial cable (14), wherein the coaxial cable (12) is wound around the choke housing (12) in a self-compensating winding pattern. The self-compensating winding pattern provides a compensation for a B1 excitation field of the magnetic resonance system and does not require the self-compensating radio frequency choke (10) to resonate with the B1 excitation field.

Description

Technical Field

[0001] This invention relates to the field of magnetic resonance (MR), and particularly to a magnetic resonance coil array having a distributed cable laying implemented by a self-compensating radio frequency choke. Background Technology

[0002] For magnetic resonance (MR) systems, and especially for magnetic resonance imaging (MRI) systems, there is a continuous effort to increase the number of radio frequency (RF) receiver coils used in order to improve image acquisition speed. It is not uncommon for MRI coil arrays to have as many as 64 RF receiver coils. The RF receiver coils are typically connected to an RF receiver via coaxial cables, which samples and digitizes the received RF signals. Due to the increasing number of RF channels, MRI system designers are under constant pressure to reduce the size of the components and subassemblies used in the RF receiver coils.

[0003] WO 2018 / 077679 A1 provides a balun suitable for use with miniature coaxial cables without requiring cable cutting for installation. A portion of each coaxial cable extending from the RF receiver coil to the RF receiver is wound multiple times around the device to form an inductor.

[0004] US Patent Application US 2012 / 0079944 relates to a wiring arrangement for a multi-resonance MRI system. A suitable resonant circuit embodiment is disclosed, comprising a loop coil conductor defining the impedance of the cable to which it is coupled. Summary of the Invention

[0005] Magnetic resonance imaging (MRI) is an imaging technique based on the principle of nuclear magnetic resonance (i.e., atomic nuclei with non-zero spin have magnetic moments). In medical MRI, the atomic nuclei with non-zero spin are typically hydrogen nuclei, which are present in the human or animal body. Radio frequency (RF) waves that form the B1 excitation field are directed at the atomic nucleus in an external magnetic field, thereby causing proton excitation and subsequent proton relaxation. Proton relaxation causes the atomic nucleus to emit RF signals, which can be detected and processed to form an image.

[0006] A typical MRI system usually includes a magnet (e.g., a superconducting electromagnet) that generates a strong static magnetic field, a gradient coil that produces a linearly varying gradient in the static magnetic field, an RF transmit coil that generates a B1 excitation field, and an RF receive coil that detects the magnetic resonance RF signals emitted by relaxed atomic nuclei. Typically, coaxial cables are used in MRI systems to control the transmission of the RF signals within the coils. Coaxial cables have an outer shield and an inner conductor separated from each other by a dielectric material. The purpose of the outer shield is to protect the inner conductor from picking up unwanted frequencies.

[0007] However, sources outside the coaxial cable can induce unwanted currents in the outer shield and thus generate unwanted magnetic fields, which can adversely affect the signal-to-noise ratio of the RF receiver coil array. For this reason, in MRI systems, RF notch filters (e.g., baluns or RF chokes) are used with the coaxial cable.

[0008] Typically, multiple RF receiver coils are used in MRI systems to form a receiver coil array. Traditional RF receiver coils and RF receiver coil arrays are often bulky and / or rigid, and are configured to remain in a fixed position relative to other RF receiver coils in the coil array and relative to the imaging subject, respectively. This bulky and inflexible configuration often prevents the RF receiver coils from coupling most effectively to the desired anatomy of the imaging subject and often makes the imaging process uncomfortable for the subject.

[0009] Increasing the number of RF receiving coils in a coil array can reduce image acquisition time. However, this increased number of RF receiving coils necessitates miniaturization of the components used with them (i.e., RF cables, RF notch filters (e.g., RF chokes), preamplifiers, and printed circuit boards (PCBs)). With the goal of miniaturizing RF receiving coil arrays, the RF receiving coils and electronics are positioned closer to the imaging object compared to conventional RF receiving coils, making the shape, size, and weight of the receiving coils and coil electronics more critical to the experience of the imaging object and the operator's handling experience. However, due to the harsh environment of MRI systems in hospitals, the RF receiving coils and components still require robust design to enable the system to withstand routine clinical operations.

[0010] Therefore, one object of the present invention is to provide a robust and flexible RF receiver coil array that improves the experience for both the imaging subject and the operator. Another object of the present invention is to provide an RF choke that allows for the realization of a robust and lightweight flexible RF receiver coil array.

[0011] According to the invention, this objective is achieved by the subject matter of the independent claims. Preferred embodiments of the invention are described in the dependent claims.

[0012] Therefore, according to the present invention, a radio frequency choke for a magnetic resonance system is provided, the radio frequency choke comprising a choke housing having an annular shape and a coaxial cable, wherein the coaxial cable has a first end and a second end and is configured to carry a magnetic resonance radio frequency signal of the magnetic resonance system having a B1 excitation field, wherein the portion of the coaxial cable between the first end and the second end is wound around the choke housing in a self-compensating winding pattern such that the radio frequency choke compensates for the B1 excitation field, and wherein the self-compensating winding pattern includes a first winding pattern (20) and a reverse winding pattern (22), the first winding pattern having a winding around a revolution surface of the annular shape, and the reverse winding pattern having at least one winding around a revolution axis (24) and along the outer periphery of the annular shape.

[0013] Furthermore, according to the present invention, a magnetic resonance coil array for a magnetic resonance system having a B1 excitation field is provided, the magnetic resonance coil array comprising: a plurality of magnetic resonance receiving coils, wherein the magnetic resonance receiving coils are configured to output magnetic resonance radio frequency signals; an input-output unit, wherein the input-output unit is configured to receive the magnetic resonance radio frequency signals; and a plurality of coaxial cables interconnecting the magnetic resonance receiving coils with the input-output unit, wherein the coaxial cables are configured to carry the magnetic resonance radio frequency signals and include the aforementioned radio frequency chokes.

[0014] The basic idea of ​​this invention is to use an RF choke with a self-compensating winding pattern (also referred to as a self-compensating RF choke). The self-compensating winding pattern compensates for the B1 excitation field of the MRI system and eliminates coupling with locally nearby coils. Preferably, the self-compensating winding pattern is responsible for the behavior of the self-compensating RF choke as an ideal inductor. Due to the stray capacitance of the self-compensating winding pattern, the self-compensating RF choke self-resonates at its self-resonant frequency. Typically, the self-resonant frequency of an inductor is the frequency at which the stray capacitance of the inductor resonates with the ideal inductance of the inductor, resulting in very high impedance. Therefore, the self-resonance of the self-compensating RF choke helps to increase the impedance of the self-compensating RF choke. The self-resonant frequency of the self-compensating RF choke preferably depends on the specific geometry of the choke housing, the self-compensating winding pattern, and the diameter of the coaxial cable. Even if the self-resonant frequency is not at the same frequency as or close to the frequency of the B1 excitation field of the MRI system, the self-compensating RF choke can still provide high impedance. Therefore, the signal-to-noise ratio of the MRI system is improved without requiring the RF choke to be designed with a resonant frequency equal to or close to the B1 excitation field, as is necessary for conventional resonant RF notch filters. Furthermore, conventional resonant RF notch filters require additional capacitors to achieve a high-impedance resonant notch filter due to low self-inductance.

[0015] Regarding magnetic resonance receiver coil arrays, self-compensating RF chokes allow for the replacement of conventional bulky resonant RF notch filters used in conventional receiver coil arrays, and thus allow for distributed cable routing, wherein, preferably, each magnetic resonance receiver coil is connected to the input-output unit via a coaxial cable including a self-compensating RF choke. Unlike conventional cable routing (where coaxial cables are laid along a herringbone structure, and where parallel laying of coaxial cables results in thick and inflexible cable bundles and large RF notch filters), the distributed cable routing of this invention is flexible. In other words, the coaxial cables interconnecting each magnetic resonance receiver coil to the input-output unit do not have a rigid, predefined structure, but preferably, the cable routing is flexible and therefore can be adjusted for specific situations.

[0016] A self-compensating RF choke comprises a choke housing with a toroidal shape. Mathematically, a toroidal shape is a three-dimensional object (e.g., a circle, rectangle, or square) generated by rotating the two-dimensional object in three-dimensional space about an axis of rotation coplanar with the two-dimensional object, where the axis of rotation does not contact the two-dimensional object. In other words, a toroidal shape is a three-dimensional object resembling a donut with a circular hole in the center. The axis of rotation passes through the center of the circular hole. The choke housing of a self-compensating RF choke has a toroidal shape, meaning that the shape of the choke housing is essentially toroidal. However, small deviations from the above mathematical definition are permissible; for example, the choke housing may include additional features such as holes or grooves, so that the choke housing itself does not have to be rotationally symmetric. It is also possible that the choke housing has the shape of a toroidal polyhedron, which approximates the toroidal shape through several polygonal faces.

[0017] Preferably, the two-dimensional object forming the annular shape of the choke housing is rectangular, more preferably a rectangle with rounded corners. Even more preferably, the longer side of the rectangle is parallel to the axis of rotation of the annular shape.

[0018] The self-compensating RF choke also includes a coaxial cable having a first end and a second end. Preferably, the coaxial cable has an outer shield and an inner conductor separated from each other by a dielectric material. Typically, coaxial cables are used in MRI systems for controlled transmission of RF signals because the purpose of the outer shield is to protect the inner conductor from picking up unwanted frequencies. The coaxial cable has two ends—a first end and a second end. Preferably, the coaxial cable is configured to transmit the magnetic resonance RF signal from the MRI system from the first end to the second end. The portion of the coaxial cable between the first and second ends is wound around the choke housing in a self-compensating winding pattern. Wrapping the choke housing preferably means that the coaxial cable is wound along the annular shape of the choke housing. The winding of the coaxial cable in the self-compensating winding pattern preferably takes into account the characteristics of the self-compensating RF choke, i.e., the self-compensating RF choke compensates for the B1 excitation field without needing to resonate with it.

[0019] Self-compensating RF chokes are suitable for use in magnetic resonance systems, especially magnetic resonance imaging systems. Self-compensating RF chokes are preferably used in magnetic resonance coil arrays. Another preferred application of self-compensating RF chokes is in active or passive sensors within magnetic resonance imaging systems, including but not limited to radiation sensors, ultrasonic sensors, optical sensors, and / or radar sensors.

[0020] Regarding the self-compensating winding pattern of the self-compensating RF choke and according to a preferred embodiment of the invention, the self-compensating winding pattern includes a first winding pattern having a winding around a rotating surface of a ring-shaped profile, and a reverse winding pattern having at least one winding around a rotating axis and along the outer periphery of the ring-shaped profile. The first winding pattern includes a winding around a rotating surface of the ring-shaped profile. In other words, this means that the coaxial cable is wound along the rotating surface such that the windings of the first winding pattern substantially correspond in shape to the shape of the two-dimensional object used to generate the ring-shaped profile. Preferably, the first winding pattern is generated by: guiding the coaxial cable through a circular hole in the ring-shaped profile along the rotating axis in a first direction, then guiding the coaxial cable outward and away from the rotating axis and toward the outer periphery of the ring-shaped profile, then guiding the coaxial cable parallel to the rotating axis but in the opposite direction to the first direction, and then guiding the coaxial cable toward the rotating axis to begin the guiding process throughout. In this way, a spiral is formed along the rotating surface, which constitutes the first winding pattern. Preferably, the spacing between the turns of the first winding pattern is constant, and more preferably, the first winding pattern is uniformly distributed along the choke housing. This helps to maintain a constant characteristic impedance throughout the entire choke function of the self-compensating RF choke.

[0021] The self-compensating winding pattern also includes a reverse winding pattern having at least one winding around the axis of rotation and along the outer periphery of the annular shape. In other words, the reverse winding pattern has a circular shape. Preferably, the reverse winding pattern is arranged within the first winding pattern; that is, the helix of the first winding pattern is preferably formed around the reverse winding pattern. Preferably, the reverse winding pattern provides B1 excitation field compensation. More preferably, the self-compensating RF choke provides >20 dB of isolation for the shielding of the coaxial cable.

[0022] According to a preferred embodiment of the invention, and in order to facilitate constant spacing in the first winding pattern and to achieve a well-defined reverse winding pattern, the choke housing includes a first cutout structure and a second cutout structure, wherein the first cutout structure includes a plurality of cutouts for guiding the first winding pattern of the self-compensating winding pattern, wherein each cutout is located in a plane including the axis of rotation of the annular shape, and wherein the second cutout structure includes additional cutouts for guiding the reverse winding pattern of the self-compensating winding pattern, wherein the additional cutouts are located in a plane perpendicular to the axis of rotation of the annular shape and along the outer periphery of the annular shape. In other words, the choke housing does not have a flat surface, but includes cutouts in the form of grooves for guiding coaxial cables.

[0023] To guide the coaxial cable into a first winding pattern, the choke housing includes a first cut structure with multiple slits. Each slit in the first cut structure lies in a plane including the axis of rotation. The path of each slit in the first cut structure on the surface of the choke housing can correspond to a portion of the external shape of a two-dimensional object used to generate the toroidal shape. For example, if the toroidal shape is generated by rotating a rectangle about the axis of rotation (where the longer side of the rectangle is parallel to the axis of rotation), the path of the slit can correspond to a portion of the side of the rectangle. For example, the slit path on the surface can correspond to the two longer sides of the rectangle, the two shorter sides of the rectangle, or the portion where the longer and shorter sides of the rectangle connect at a corner of the rectangle. Preferably, the multiple slits of the first cut structure are evenly spaced apart from each other, and more preferably evenly distributed on the choke housing.

[0024] To guide the coaxial cable into a reverse winding pattern, the choke housing includes a second cutout structure with an additional notch. This additional notch is located in a plane perpendicular to the axis of rotation and along the outer periphery of the annular shape. In other words, the additional notch has a circular shape. When the annular shape is generated by rotating a rectangle around the axis of rotation (where one side of the rectangle is parallel to the axis of rotation), the additional notch is preferably located at half the height of this side of the rectangle.

[0025] According to another preferred embodiment of the invention, the choke housing includes an open cut and / or a circular hollow opening. As already mentioned, to form the first winding pattern, the coaxial cable needs to be guided through a circular hole of an annular shape, followed by several directional changes before repeating the process, thus making the winding of the coaxial cable quite cumbersome. Providing an opening in the choke housing simplifies the winding process because the directional changes can be eliminated to form the first winding pattern. The open cut is preferably located in a plane including the axis of rotation. Therefore, the open cut in the choke housing enables the use of a winding machine that automatically winds the coaxial cable around the choke housing. As an alternative to or supplement to the open cut, the choke housing may include a circular hollow opening. This is particularly advantageous when producing self-compensating RF chokes using 3D printing and / or additive manufacturing processes.

[0026] According to a preferred embodiment of the invention, the coaxial cable is a miniature coaxial cable and / or the annular shape has a diameter of 12 mm + / - 25% and a thickness of 5 mm + / - 25%. The miniature coaxial cable preferably has a diameter of less than 1 mm. The advantage of miniature coaxial cables is that the self-compensating RF choke can be made small and lightweight. Furthermore, the parasitic capacitance generated due to the proximity of the coaxial cable to other electronic components is less pronounced in miniature coaxial cables than in conventional coaxial cables. Using miniature coaxial cables also allows the choke housing to have small dimensions: preferably, the outer diameter of the annular shape is 12 mm + / - 25%, and the inner diameter is 5 mm + / - 25%. Regarding the thickness, i.e., the dimension of the annular shape parallel to the axis of rotation, the thickness is preferably 5 mm + / - 25%. Self-compensating RF chokes with these small dimensions are also referred to as self-compensating miniature RF chokes.

[0027] As already mentioned, another aspect of the invention is a magnetic resonance coil array comprising: a plurality of magnetic resonance receiving coils configured to output magnetic resonance RF signals; an input-output unit configured to receive the magnetic resonance RF signals; and a plurality of coaxial cables interconnecting the magnetic resonance receiving coils to the input-output unit, wherein the coaxial cables are configured to carry the magnetic resonance RF signals and include the self-compensating RF choke. Preferably, the plurality of magnetic resonance receiving coils (also referred to as RF receiving coils) are arranged in a two-dimensional array. Planar coils and / or thin, flexible-headed coils can be used as RF receiving coils. Furthermore, preferably, each RF receiving coil is directly connected to the input-output unit via a coaxial cable. Direct connection means that the coaxial cables are not laid along a predefined structure in which several coaxial cables are combined into a cable bundle, but preferably, each coaxial cable is laid independently from the RF receiving coil to the input-output unit. Preferably, the coaxial cable does not form a cable bundle within the area defined by the two-dimensional array of RF receiving coils. The advantage of flexible coaxial cable laying is that it can be laid around holes, openings, and / or grooves in the housing of the RF receiving coils and / or magnetic resonance coil array. These holes, openings, and / or grooves are important for the health of the imaging subject because they reduce heat generation and provide additional functionality (e.g., options for monitoring vital signs, or options for providing interventional access, such as for peripheral venous catheters for the imaging subject). The coaxial cable includes a first end and a second end, wherein either the first or second end is connected to the input-output unit, while the other end of the coaxial cable (i.e., the second or first end) is connected to the RF receiving coil. The portion of the coaxial cable between the first and second ends is wound around the choke housing in a self-compensating winding pattern to form a self-compensating RF choke. The self-compensating RF choke allows the elimination of a bulky resonant RF notch filter in the magnetic resonance coil array, thus allowing the coaxial cable interconnecting each RF receiving coil to the input-output unit to lack a rigid, predefined structure. In this way, a flexible magnetic resonance coil array is provided, which allows for more arbitrary definition of the RF receiving coils, enabling the placement and / or design of their size based on the desired anatomical coverage of the imaging subject. Therefore, the magnetic resonance coil array can be relatively easily conformally fitted to the anatomy of the imaging subject. Furthermore, the cost and weight of the magnetic resonance coil array can be significantly reduced due to the use of less material and the abandonment of conventional resonant RF notch filters including lumped capacitors. Moreover, the use of self-compensating RF chokes avoids thick cable bundles, eliminating the need for bulky and / or large-volume RF notch filters. The lightweight and highly flexible nature of the magnetic resonance coil array further improves the experience for both the imaging subject and the operator.

[0028] As already mentioned, preferably, each RF receiving coil is directly connected to the input-output unit via a coaxial cable. However, this does not preclude the possibility that the magnetic resonance coil array may include additional electronic components (e.g., RF amplifiers). These additional components can also be connected to the coaxial cable. In other words, additional electronic components can be connected to the coaxial cable between the first and second ends.

[0029] Regarding miniaturization and according to a preferred embodiment of the invention, a magnetic resonance coil array is provided, wherein the self-compensating RF choke is a self-compensating miniature RF choke, and the coaxial cable is a miniature coaxial cable. As described above, the small dimensions of the self-compensating miniature RF choke and the miniature coaxial cable allow the magnetic resonance coil array to be particularly thin, flexible, and lightweight. Therefore, the comfort of the imaging subject and the operator is greatly improved. Furthermore, the miniaturization of components allows for the implementation of a larger number of RF receiving coils in the magnetic resonance coil array, thereby reducing acquisition time. In addition, the miniature coaxial cable has a smaller parasitic capacitance compared to a thick coaxial cable.

[0030] In conjunction with the high signal-to-noise ratio of the magnetic resonance coil array and according to another preferred embodiment of the invention, the coaxial cable and / or the RF choke are high impedance. In this context, high impedance means that the self-compensating RF choke provides high suppression (preferably >20 dB) of the RF current induced by the B1 excitation field in the shield of the coaxial cable. Furthermore, the high impedance of the self-compensating RF choke suppresses propagation and resonance effects along the inner conductor of the coaxial cable, thereby reducing coupling between the individual RF receiving coils in the magnetic resonance coil array.

[0031] According to another preferred embodiment of the invention, a magnetic resonance coil array is provided, the magnetic resonance coil array including a DC cable configured to carry a DC signal, wherein the DC cable includes a DC choke, and wherein the DC choke is placed inside the annular shape of the choke housing of the self-compensating RF choke. Preferably, the DC choke is placed in a circular hole in the annular shape. The DC cable (referred to as DC cable) is configured to carry a DC signal that can be used to manipulate the RF receiving coils of the magnetic resonance coil array. Preferably, each RF receiving coil is connected to the DC cable. To suppress induced RF signals on the DC cable, the DC cable includes a DC choke. Preferably, the DC choke is an inductor. However, placing the DC choke on the DC cable increases the local weight of the DC cable, making the DC cable, and therefore the magnetic resonance coil array, more susceptible to mechanical stress. By placing the DC choke inside the annular shape of the choke housing of the self-compensating RF choke, mechanical stability and robustness can be improved. Therefore, the self-compensating RF choke acts as a mechanical support and protects the DC choke and DC cable without requiring additional mechanical support components to the magnetic resonance coil array. Furthermore, by placing the RF choke inside the toroidal shape of the self-compensating RF choke, unwanted crosstalk between the self-compensating RF choke and the DC choke is reduced. This improves the signal-to-noise ratio of the magnetic resonance coil array.

[0032] In this respect, and according to a preferred embodiment of the invention, the shield of the coaxial cable configured to carry magnetic resonance RF signals can be used as a conductor in the DC circuit. In this case, the magnetic resonance coil array includes a DC cable for each RF receiving coil (including a DC choke). Therefore, preferably, a DC choke is placed inside the annular shape of the choke housing of the self-compensating RF choke.

[0033] However, it is also possible for the DC circuitry to be independent of the coaxial cable carrying the magnetic resonance RF signal. In this case, preferably, two DC cables are required for each RF receiving coil. Therefore, preferably, for each RF receiving coil, the magnetic resonance coil array includes two DC cables, wherein each DC cable includes a DC choke. In this case, preferably, the two DC chokes are placed inside the annular shape of the choke housing of the self-compensating RF choke. Furthermore, a coaxial cable can be used as the DC cable.

[0034] According to another preferred embodiment of the invention, the magnetic resonance coil array includes a flexible support structure, wherein the plurality of magnetic resonance receiving coils are arranged in a two-dimensional array on and / or within the support structure, and wherein the self-compensating RF choke and / or the coaxial cable are uniformly arranged on and / or within the support structure. Uniform arrangement preferably means that the weight of the self-compensating RF choke and / or coaxial cable, and optionally the DC cable and / or DC choke, is evenly distributed on the flexible support structure. This improves the comfort of the imaging subject. The support structure is preferably flexible clothing and / or foam. The support structure may include holes, openings, and / or cutouts to further improve the flexibility of the support structure and reduce its weight. The RF receiving coils and other electrical components (i.e., the coaxial cable, the self-compensating RF choke, the DC cable, and / or DC choke) are preferably arranged in and / or on the support structure. For example, the support structure may include several layers of clothing, and the RF receiving coils may be arranged between two layers.

[0035] Furthermore, regarding the flexibility of the self-compensating RF choke, the choke housing is preferably made of a flexible material. While many RF chokes have iron powder or ferrite cores, the choke housing of a self-compensating RF choke is preferably non-magnetic and made of a flexible, and preferably lightweight, material. This further enhances the adjustability of the magnetic resonance coil array to the shape of the imaging object.

[0036] Preferably, the magnetic resonance coil array including the support structure has a thickness of less than 20 mm. Furthermore, preferably, the weight of the magnetic resonance coil array including the support structure is less than 20 g for each RF receiving coil.

[0037] According to another embodiment of the invention, the plurality of RF receiving coils, the self-compensating RF choke, and / or the coaxial cable are fixed to the support structure by stitching, gluing, clamping, and / or additive printing processes. To further improve the flexibility of the magnetic resonance coil array and further reduce its weight, the RF receiving coils and other electrical components (i.e., the coaxial cable, the self-compensating RF choke, the DC cable, and / or the DC choke) can also be attached to the support structure in a lightweight and flexible manner. This requirement can be met by attaching components using gluing, stitching, and / or additive printing processes.

[0038] In this respect, and according to another preferred embodiment of the invention, the way the self-compensating RF choke is fixed to the support structure allows the self-compensating RF choke to rotate and / or angle with respect to the support structure. In this way, a flexible magnetic resonance coil array can be provided, which allows for more arbitrary positioning of the self-compensating RF choke, thereby allowing placement based on specific circumstances (e.g., the contour of the imaging object). Preferably, the way the self-compensating RF choke is fixed allows the self-compensating RF choke to rotate and / or angle with respect to the support structure by + / - 30 degrees. Attached Figure Description

[0039] These and other aspects of the invention will become apparent from the embodiments described below. However, such embodiments do not necessarily represent the full scope of the invention, and therefore the scope of the invention is to be interpreted with reference to the claims and this document.

[0040] In the attached diagram:

[0041] Figure 1 A magnetic resonance receiving coil array is schematically depicted, wherein the cable laying has a fishbone structure known in the prior art;

[0042] Figure 2 A magnetic resonance coil array according to a possible embodiment of the present invention is schematically depicted, wherein multiple coaxial cables interconnect the magnetic resonance receiving coil with the input-output unit, and wherein the coaxial cables include radio frequency chokes;

[0043] Figure 3 The diagram schematically depicts one magnetic resonance receiving coil and one coaxial cable in a magnetic resonance receiving coil configuration, including... Figure 2 RF choke coil;

[0044] Figure 4 A choke housing of a radio frequency choke according to a possible embodiment of the present invention is schematically depicted;

[0045] Figure 5 A cross-section of a radio frequency choke coil of a magnetic resonance coil array according to another possible embodiment of the invention is schematically depicted;

[0046] Figure 6 A cross-section of a magnetic resonance coil array according to another possible embodiment of the invention is schematically depicted.

[0047] List of reference numerals

[0048] 1. Receiver coil array (prior art)

[0049] 2. Receiver coil (Prior art)

[0050] 3-resonance RF notch filter (existing technology)

[0051] 4. Coaxial cable (existing technology)

[0052] 5. Fishbone structure (existing technology)

[0053] 6-Input-Output Unit (Prior Art)

[0054] 10 self-compensating RF choke coils

[0055] 12 Choke housing

[0056] 14 coaxial cable

[0057] 16 First End

[0058] 18 Second End

[0059] 20 First winding pattern

[0060] 22 Reverse winding mode

[0061] 24 around the axis of rotation

[0062] 26 First incision structure

[0063] 28 Second incision structure

[0064] 30 magnetic resonance coil array

[0065] 32 receiving coils

[0066] 34 Input-Output Units

[0067] 36 DC cable

[0068] 38 DC choke coil

[0069] 40 Support Structure

[0070] 42 Imaging Objects

[0071] 44 small holes

[0072] 46 spacing

[0073] 48mm thickness Detailed Implementation

[0074] Figure 1A known prior art magnetic resonance receiving coil array 1 is schematically depicted. The receiving coil array 1 comprises a plurality of receiving coils 2 arranged in a two-dimensional array. Each receiving coil 2 is connected to a coaxial cable 4, which interconnects the receiving coil 2 with an input-output unit 6. The individual coaxial cables 4 of the plurality of receiving coils 2 are bundled together and laid to the input-output unit 6 in a herringbone structure 5. A plurality of bulky resonant RF notch filters 3 are connected to the cable bundle, resulting in a non-flexible magnetic resonance receiving coil array 1 with high weight.

[0075] Figure 2 A magnetic resonance coil array 30 according to a preferred embodiment of the present invention is schematically depicted. The magnetic resonance coil array 30 includes a plurality of RF receiving coils 32 arranged in a two-dimensional array. Each RF receiving coil 32 is connected to a coaxial cable 14, which interconnects an RF receiving coil 34 with an input-output unit 34. The individual coaxial cables 14 connect the RF receiving coil 32 to the input-output unit 34 in a direct manner, meaning that the coaxial cables 14 are not bundled together but form a cable bundle within the area defined by the two-dimensional array of the plurality of RF receiving coils 32. Furthermore, the coaxial cables 14 include self-compensating RF chokes 10. The coaxial cables 14 and the self-compensating RF chokes 10 are uniformly arranged within the area defined by the two-dimensional array, i.e., the weight of the coaxial cables 14 and the self-compensating RF chokes 10 is substantially uniformly distributed within the area defined by the two-dimensional array.

[0076] In this embodiment, the magnetic resonance coil array 30 also includes a support structure 40, which, in this implementation, is a flexible garment that not only covers the area defined by the two-dimensional array of multiple RF receiving coils 32, but also overlaps with the area symmetrically. Outside the area defined by the two-dimensional array but still within the area of ​​the support structure, multiple coaxial cables 14 are bundled together to form a cable bundle leading to the input-output unit 34. In this embodiment, the magnetic resonance coil array 30 serves as the receiving coil array 30 of a magnetic resonance imaging system with a B1 excitation field.

[0077] Figure 3 schematically depicted Figure 2 One of the RF receiving coils in the RF receiving coil 32 and one of the coaxial cables in the coaxial cable 14, including a self-compensating RF choke 10. Figure 3 As can be seen, the coaxial cable 14 includes a first end 16 and a second end 18 connected to the RF receiving coil 32. The portion of the coaxial cable 14 between the first end 16 and the second end 18 is wound with a choke housing 12 having an annular shape (e.g., Figure 4(as depicted in the diagram) to form a self-compensating RF choke 10. The coaxial cable 14 is wound around the choke housing 12 in a self-compensating winding pattern, such that the self-compensating RF choke 10 compensates for the B1 excitation field of the magnetic resonance system.

[0078] Figure 4 A choke housing 12 of a self-compensating RF choke 10 according to another possible embodiment of the invention is schematically depicted. The choke housing 12 has an annular shape, which in this embodiment is formed by a rectangle with rounded corners rotating around an axis of rotation 24, wherein the longer side of the rectangle is parallel to the axis of rotation 24. As already mentioned, the coaxial cable 14 is wound around the choke housing 12 in a self-compensating winding pattern. To guide the winding of the coaxial cable 14 around the choke housing 12, the choke housing 12 includes a first cut structure 26 and a second cut structure 28. The first cut structure 26 includes a plurality of cuts 26a, 26b, 26c, which are used to guide a first winding pattern 20 of the self-compensating winding pattern (e.g., ...). Figure 5 (As depicted), wherein each cut 26a, 26b, 26c is located in a plane including the annular shape about the axis of rotation 24. In this embodiment, the cuts 26a, 26b, 26c of the first cut structure 26 are located on the surface of the annular shape corresponding to the two longer sides of the rectangle. Regarding the second cut structure 28, the second cut structure 28 includes additional cuts 28 for guiding the reverse winding pattern 22 of the self-compensating winding pattern (e.g., Figure 5 (As depicted), wherein an additional cut 28 is located in a plane perpendicular to the axis of rotation 24 of the annular shape and along the outer periphery of the annular shape. From Figure 4 It can also be seen that the choke housing 12 also includes three small holes 44 to guide the coaxial cable 14 from the first winding mode 20 to the reverse winding mode 22.

[0079] Figure 5 A cross-section of a self-compensating RF choke 10 of a magnetic resonance coil array 30 according to another possible embodiment of the invention is schematically depicted. From Figure 5As can be seen, the self-compensating winding pattern includes a first winding pattern 20 and a reverse winding pattern 22. The first winding pattern 20 has a winding around a rotating surface of an annular shape, and the reverse winding pattern 22 has a winding around a rotation axis 24 and along the outer periphery of the annular shape. The first winding pattern 20 is generated by guiding the coaxial cable 14 through a circular hole in the annular shape along the rotation axis 24 in a first direction, then guiding the coaxial cable 14 outward and away from the rotation axis 24 and towards the outer periphery of the annular shape, then guiding the coaxial cable 14 parallel to the rotation axis 24 but in the opposite direction to the first direction, and then guiding the coaxial cable 14 towards the rotation axis 24 to begin guiding the process throughout. In this way, a spiral is formed along the rotating surface, which constitutes the first winding pattern 20. Figure 5 As can be seen, the spacing 46 between the turns in the first winding pattern 20 remains constant throughout the entire winding pattern 20. Regarding the reverse winding pattern 22, Figure 5 As shown, in this embodiment of the invention, the reverse winding pattern 22 is arranged within the first winding pattern 20 and is located at half the height of the longer side of the rectangle.

[0080] from Figure 5 It can also be seen that, in this embodiment of the magnetic resonance coil array 30, the magnetic resonance coil array 30 also includes a DC cable 36. The DC cable 36 is configured to carry a DC signal and includes a DC choke 38. The DC choke 38 (in this case, an inductor) is placed inside the annular shape of the choke housing 12 of the self-compensating RF choke 10.

[0081] Figure 6 A cross-section of a magnetic resonance coil array 30 according to another possible embodiment of the invention is schematically depicted. Figure 6 As can be seen, the magnetic resonance coil array 30 is positioned close to the imaging object 42 to perform magnetic resonance imaging. Also, Figure 2 As depicted, a possible embodiment of the magnetic resonance coil array 30 includes a support structure 40. Figure 6 In the illustrated embodiment, the support structure 40 is made of flexible foam and has a double-layer structure. The RF receiving coil 32 of the magnetic resonance coil array 30 is arranged between the two layers of foam. The self-compensating RF choke 10 is arranged in the foam layer away from the imaging object. In this embodiment, the RF receiving coil 32, the self-compensating RF choke 10, and the coaxial cable 14 (not shown) are attached to the foam of the support structure 40 by stitching. The self-compensating RF choke 10 is stitched to the support structure 40 in a loose manner that allows the self-compensating RF choke 10 to rotate and be angled about + / -30 degrees with respect to the support structure 40. In this embodiment, the thickness 48 of the magnetic resonance coil array 30 is 12 mm.

[0082] Although the invention has been illustrated and described in detail in the accompanying drawings and the foregoing description, such illustrations and descriptions should be considered illustrative or exemplary, not restrictive; the invention is not limited to the disclosed embodiments. Those skilled in the art, through studying the drawings, the disclosure, and the claims, will understand and implement other variations of the disclosed embodiments in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the words "a" or "an" do not exclude a plurality. Although certain measures are recited in dissimilar dependent claims, this does not indicate that combinations of these measures cannot be advantageously used. No reference numerals in the claims should be construed as limiting the scope. Furthermore, for clarity, not all elements in the drawings are provided with reference numerals.

Claims

1. A radio frequency choke (10) for a magnetic resonance system, comprising: The choke housing (12) has an annular shape, and A coaxial cable (14), wherein the coaxial cable (14) has a first end (16) and a second end (18) and is configured to carry the magnetic resonance radio frequency signal of the magnetic resonance system having a B1 excitation field. The portion of the coaxial cable (14) between the first end (16) and the second end (18) is wound around the choke housing (12) in a self-compensating winding pattern, such that the radio frequency choke (10) compensates for the B1 excitation field. The self-compensating winding pattern includes a first winding pattern (20) and a reverse winding pattern (22). The first winding pattern has a winding around the rotating surface of the annular shape, and the reverse winding pattern has at least one winding around the rotating axis (24) and along the outer periphery of the annular shape.

2. The radio frequency choke (10) according to claim 1, wherein, The choke housing (12) includes a first cut structure (26) and a second cut structure (28). The first cut structure (26) includes a plurality of cuts (26a, 26b, 26c) for guiding the first winding pattern (20) of the self-compensating winding pattern, wherein each cut (26a, 26b, 26c) is located in a plane including the rotation axis (24) of the annular shape. The second cut structure (28) includes an additional cut for guiding the reverse winding pattern (22) of the self-compensating winding pattern, wherein the additional cut is located in a plane perpendicular to the axis of rotation (24) of the annular shape and along the outer periphery of the annular shape.

3. The radio frequency choke (10) according to claim 1 or 2, wherein, The choke housing (12) includes an open cutout and / or a circular hollow opening.

4. The radio frequency choke (10) according to claim 1 or 2, wherein, The coaxial cable (14) is a miniature coaxial cable and / or the annular shape has a diameter of 12 mm + / - 25% and a thickness of 5 mm + / - 25%.

5. A magnetic resonance coil array (30) for a magnetic resonance system having a B1 excitation field, comprising: Multiple magnetic resonance receiving coils (32), wherein the magnetic resonance receiving coils (32) are configured to output magnetic resonance radio frequency signals. Input-output unit (34), wherein the input-output unit (34) is configured to receive the magnetic resonance radio frequency signal, and Multiple coaxial cables (14) interconnect the magnetic resonance receiving coil (32) with the input-output unit (34), wherein the coaxial cables (14) are configured to carry the magnetic resonance radio frequency signal and include a radio frequency choke (10) according to any one of claims 1 to 4.

6. The magnetic resonance coil array (30) according to claim 5, wherein, The radio frequency choke (10) is a miniature radio frequency choke (10), and the coaxial cable (14) is a miniature coaxial cable (14).

7. The magnetic resonance coil array (30) according to claim 5 or 6, wherein, The coaxial cable (14) and / or the radio frequency choke (10) are high impedance.

8. The magnetic resonance coil array (30) according to claim 5 or 6, comprising a DC cable (36) configured to carry a DC signal, wherein, The DC cable (36) includes a DC choke (38), wherein the DC choke (38) is placed inside the annular shape of the choke housing (12) of the radio frequency choke (10).

9. The magnetic resonance coil array (30) according to claim 5 or 6, comprising a flexible support structure (40), wherein, The plurality of magnetic resonance receiving coils (32) are arranged in a two-dimensional array on and / or in the flexible support structure (40), and wherein the RF choke (10) and / or the coaxial cable (14) are uniformly arranged on and / or in the flexible support structure (40) such that the weight of the self-compensating RF choke and / or the coaxial cable and optionally the DC cable and / or the DC choke is uniformly distributed on the flexible support structure.

10. The magnetic resonance coil array (30) according to claim 9, wherein, The plurality of magnetic resonance receiving coils (32), the radio frequency choke (10) and / or the coaxial cable (14) are fixed to the flexible support structure (40) by stitching, gluing, clamping and / or additive printing processes.

11. The magnetic resonance coil array (30) according to claim 9, wherein, The radio frequency choke (10) is fixed to the flexible support structure (40) so that the radio frequency choke (10) can rotate and / or tilt about the flexible support structure (40).

Images