Method and system for floating cable trap

Abstract

The present invention is entitled "Methods and Systems for Floating Cable Current Traps". The present invention provides various methods and systems for current traps. In one example, the current trap has: a helical core made of a non-conductive material, a coiled wire having a plurality of turns wound around the helical core, and one or more tuning capacitors physically attached to the helical core and electrically connected to the coiled wire to form a resonant circuit with the coiled wire.

Description

Technical Field

[0001] Embodiments of the subject matter disclosed herein relate to magnetic resonance imaging, and more particularly, to current traps for magnetic resonance imaging systems. Background Art

[0002] Magnetic resonance imaging (MRI) is a medical imaging modality that can create images of the inside of the human body without the use of X-rays or other ionizing radiation. MRI systems include superconducting magnets to generate a strong and uniform static magnetic field, B0. Exposure of the human body or a portion of the human body to the magnetic field, B0, causes polarization of hydrogen nuclear spins in tissue water. The nuclei are excited by a radio frequency signal, and upon relaxation to a rest energy state, energy is released as an RF signal that can be converted into an image.

[0003] MRI systems utilize RF coils to transmit RF excitation and / or receive MR signals. Shielded coil interface cables can be used to transmit signals between the RF coils and other aspects of the processing system of the MRI system. For example, the coil interface cable can transmit signals to control the RF coils and / or to receive signals from the RF coils. The coil interface cable can be subjected to electromagnetic fields, and therefore, common mode currents driven by the transmitter can adversely affect coil tuning, coil-to-coil coupling in a phased array coil, inhomogeneities in the generated image, and / or unpredictable component heating.

[0004] A common mode trap or balun that provides high common mode impedance can be used to reduce the effects of the transmitter drive current. Conventionally, a grounded balun can be coupled to the coil interface cable to block the induced current. However, coupling the balun to the coil interface cable can require a complex welding process. The welding process can expose the conductors in the coil interface cable to high temperatures, causing these conductors to degrade. Summary of the invention

[0005] In one embodiment, the current trap includes: a helical core made of a non-conductive material, a coiled wire having a plurality of turns wound around the helical core, and one or more tuning capacitors physically attached to the helical core and electrically connected to the coiled wire to form a resonant circuit with the coiled wire. In this way, the current trap assembly does not need to be soldered to the coil interface cables, and the current trap assembly can be located anywhere along these cables.

[0006] It should be understood that the above brief description is provided to introduce in a simplified form selected concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is solely defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The present disclosure will be better understood by reading the following description of non-limiting embodiments with reference to the accompanying drawings, in which:

[0008] Figure 1 is a block diagram of an MRI system according to an exemplary embodiment of the present disclosure.

[0009] Figure 2 is a block schematic diagram of a current trap assembly that may be implemented in an MRI system according to an exemplary embodiment of the present disclosure.

[0010] Figure 3 is a perspective view of a current trap according to an exemplary embodiment of the present disclosure, wherein a portion of a spiral core of the current trap is removed.

[0011] Figure 4 yes Figure 3 Top view of a current trap.

[0012] Figure 5 is a side view of a floating current trap assembly with a portion of the helical core removed showing the current trap coupled to a cable according to an exemplary embodiment of the present disclosure.

[0013] Figure 6 yes Figure 5 A perspective view of a floating current trap assembly.

[0014] Figure 7 is a perspective view of a floating current trap assembly according to an exemplary embodiment of the present invention.

[0015] Figure 8 yes Figure 7 Cross section of a floating current trap assembly.

[0016] Fig. 9 is a perspective view of a coiled wire assembled with a helical core according to an exemplary embodiment of the present disclosure.

[0017] Fig.10 is a perspective view of a shielded current trap according to an exemplary embodiment of the present disclosure.

[0018] Fig.11 is a high-level block diagram illustrating an example of a routine for a floating current trap assembly according to an exemplary embodiment of the present disclosure.

[0019] Fig.12 is a schematic circuit diagram of a floating current trap assembly according to an exemplary embodiment of the present disclosure.

[0020] Fig.13An example of repositioning a floating current trap assembly along a coil interface cable of an MRI system is shown according to an exemplary embodiment of the present disclosure.

[0021] Fig.14 is a detailed view of the current trap connected to the four cables.

[0022] Figures 3 to 10 Drawn approximately to scale. DETAILED DESCRIPTION

[0023] The following description relates to various embodiments of a current trap for an MRI system. Specifically, a current trap for an MRI system (such as, Figure 1 A floating spiral configuration of a current trap for an MRI system (as shown in FIG. 1 ). As used herein, a floating trap may be defined as a trap that can be removably coupled to a cable of an MRI system by mechanical engagement and without the use of an additional process (such as welding) to secure the trap to the cable. Furthermore, unlike a non-floating current trap, coupling the floating trap to the cable does not require cutting the cable, thereby allowing the position of the floating trap to be easily reconfigured along the cable. Figure 2 As shown, the current trap may be arranged along a communication cable configured to receive MR data. The current trap may be a floating trap, such as Figure 3 and Figure 4 The current trap can be assembled by joining the coiled wire to the spiral core, as shown in Fig. 9 The current trap can be configured to engage the cable of an MRI system by wrapping the cable around a helical core, as shown. Figure 5 and Figure 6 As shown. Fig.14 As shown, the current trap can be connected to up to four cables. Figure 7 shows a floating notch filter assembly, Figure 8 A cross section of the assembly is shown. When the current trap is to be positioned adjacent to the patient, the current trap may be further covered with a shield, such as Fig.10 shown. Fig.11 A routine for blocking transmission induced currents along the cables of an MRI system by implementing a floating trap is shown in FIG. Fig.12 A schematic diagram showing the circuit of a floating notch filter is shown, Fig.13 Shown is the repositioning of the floating trap along the cables of an MRI system.

[0024] Figures 3 to 10 and Fig.14An exemplary configuration with relative positioning of various parts is shown. In at least one example, if shown as directly contacting or directly connecting each other, such elements may be referred to as directly contacting or directly connecting, respectively. Similarly, in at least one example, elements adjacent to or adjacent to each other may be adjacent to or adjacent to each other, respectively. For example, parts arranged to coplanarly contact each other may be referred to as coplanar contact. For another example, in at least one example, elements positioned to be spaced apart from each other and having only space therebetween without other parts may be described and cited as such. For another example, elements shown as being located above / below each other, located on opposite sides of each other, or located between the left / right sides of each other may be described and cited as such relative to each other. In addition, as shown in the figure, in at least one example, the topmost element or point of an element may be referred to as the "top" of a part, and the bottommost element or point of an element may be referred to as the "bottom" of a part. As used herein, top / bottom, upper / lower, above / below may be relative to the vertical axis of the figure, and may be used to describe the positioning of elements relative to each other in the figure. Thus, in one example, an element shown as being located above other elements is vertically positioned above other elements. As another example, the shapes of elements shown in the figures may be referred to as having these shapes (e.g., such as being rounded, straight, planar, curved, rounded, chamfered, angled, etc.). In addition, in at least one example, elements shown as intersecting each other may be referred to as intersecting elements or intersecting each other. In addition, in one example, an element shown as being within another element or shown as being outside another element may be described and referred to as such.

[0025] Figure 1 A magnetic resonance imaging (MRI) apparatus 10 is shown, which includes a static magnetic field magnet unit 12, a gradient coil unit 13, an RF coil unit 14, an RF body coil unit 15, a transmit / receive (T / R) switch 20, an RF driver unit 22, a gradient coil driver unit 23, a data acquisition unit 24, a controller unit 25, a bed 26, a data processing unit 31, an operation console unit 32, and a display unit 33. The MRI apparatus 10 transmits electromagnetic pulse signals to a subject 16 placed in an imaging space 18, forms a static magnetic field in the imaging space to perform scanning to obtain magnetic resonance signals from the subject 16, and reconstructs an image based on the magnetic resonance signals thus obtained by scanning.

[0026] The static magnetic field magnet unit 12 generally includes, for example, an annular superconducting magnet installed in an annular vacuum container. The magnet defines a cylindrical space around the subject 16 and generates a constant main static magnetic field.

[0027] The MRI apparatus 10 further includes a gradient coil unit 13 that forms a gradient magnetic field in an imaging space 18 so as to provide three-dimensional position information for a magnetic resonance signal received by the RF coil unit 14. The gradient coil unit 13 includes three gradient coil systems, each of which generates a gradient magnetic field that is inclined toward one of three spatial axes that are perpendicular to each other, and generates a gradient field in each of a frequency encoding direction, a phase encoding direction, and a slice selection direction according to imaging conditions.

[0028] The RF coil unit 14 is disposed, for example, to surround a region to be imaged of the subject 16. In a static magnetic field space or an imaging space 18 in which a static magnetic field is formed by the static magnetic field magnet unit 12, the RF coil unit 14 may transmit RF pulses to the subject 16 based on a control signal from the controller unit 25. This excites proton spins in the subject 16. The RF coil unit 14 may also receive magnetic resonance signals generated when the proton spins thus excited in the subject 16 return to alignment with the initial magnetization vector. The RF coil unit 14 may use the same RF coil to transmit RF excitation and receive MR signals.

[0029] The RF body coil unit 15 is provided, for example, to surround an imaging space 18, and generates RF pulses to excite nuclei within the imaging space 18. The RF body coil unit 15 is fixedly attached and connected to the MR device 10, compared to the RF coil unit 14 which can be easily disconnected from the MR device 10 and replaced with another RF coil unit.

[0030] When operating in the receive mode, the T / R switch 20 may selectively connect the RF body coil unit 15 to the data acquisition unit 24, and when operating in the transmit mode, the T / R switch 20 may selectively connect the RF body coil unit 15 to the RF driver unit 22. Similarly, when the RF coil unit 14 operates in the receive mode, the T / R switch 20 may selectively connect the RF coil unit 14 to the data acquisition unit 24, and when operating in the transmit mode, the T / R switch 20 may selectively connect the RF coil unit 14 to the RF driver unit 22. When both the RF coil unit 14 and the RF body coil unit 15 are used for a single scan, for example, if the RF coil unit 14 is configured to receive MR signals and the RF body coil unit 15 is configured to transmit RF signals, the T / R switch 20 may direct the control signal from the RF driver unit 22 to the RF body coil unit 15 while directing the received MR signal from the RF coil unit 14 to the data acquisition unit 24. The coils of the RF body coil unit 15 may be configured to operate in a transmit-only mode, a receive-only mode, or a transmit-receive mode. The coils of the local RF coil unit 14 may be configured to operate in a transmit-receive mode or a receive-only mode.

[0031] The RF driver unit 22 may include a gate modulator (not shown), an RF power amplifier (not shown), and an RF oscillator (not shown). The RF driver unit 22 modulates the RF signal received from the RF oscillator into a signal of a predetermined timing having a predetermined envelope based on a control signal from the controller unit 25 and using the gate modulator. The RF signal modulated by the gate modulator is amplified by the RF power amplifier and then output to the RF coil unit 14.

[0032] The gradient coil driver unit 23 drives the gradient coil unit 13 based on a control signal from the controller unit 25, thereby generating a gradient magnetic field in the imaging space 18. The gradient coil driver unit 23 may include three driver circuit systems (not shown) corresponding to the three gradient coil systems included in the gradient coil unit 13.

[0033] The data acquisition unit 24 may include a preamplifier (not shown), a phase detector (not shown), and an analog / digital converter (not shown). The phase detector phase uses the output of the RF oscillator from the RF driver unit 22 as a reference signal to detect the magnetic resonance signal received from the RF coil unit 14 and amplified by the preamplifier, and outputs the phase-detected analog magnetic resonance signal to the analog / digital converter to be converted into a digital signal. The digital signal thus obtained is output to the data processing unit 31.

[0034] The MRI apparatus 10 includes a couch 26 for placing the subject 16 thereon. By moving the couch 26 based on a control signal from the controller unit 25, the subject 16 can be moved inside and outside the imaging space 18.

[0035] The controller unit 25 includes a computer and a recording medium on which a program to be executed by the computer is recorded. The program, when executed by the computer, causes the various parts of the apparatus to perform operations corresponding to MRI scanning.

[0036] The operation console unit 32 may include a user input device such as a keyboard and a mouse. The operator uses the operation console unit 32 to, for example, input such data as an imaging protocol and set a region where an imaging sequence is to be executed. Data on the imaging protocol and the imaging sequence execution region are output to the controller unit 25.

[0037] The data processing unit 31 includes a computer and a recording medium on which a program executed by the computer to perform data processing is recorded. The data processing unit 31 is connected to the controller unit 25, and performs data processing based on a control signal received from the controller unit 25. The data processing unit 31 is also connected to the data acquisition unit 24, and generates spectral data by applying various image processing operations to the magnetic resonance signal output from the data acquisition unit 24.

[0038] The display unit 33 includes a display device and displays images and / or other information on a display screen of the display device based on a control signal received from the controller unit 25. The display unit 33 displays, for example, scanning parameters. The display unit 33 also displays an MR image of the subject 16 generated by the data processing unit 31.

[0039] During scanning, a coil interface cable (not shown) may be used to transmit signals between the RF coil (e.g., the RF coil unit 14) and other aspects of the processing system (e.g., the data acquisition unit 24, the controller unit 25, etc.), for example to control the RF coil and / or receive information from the RF coil. In some embodiments, the coil interface cable is integrated into the RF coil unit 14. The coil interface cable may be disposed within the bore or imaging space 18 of the MRI device 10 and is subjected to the electromagnetic field generated and used by the MRI device 10. The cable may be subjected to common-mode current driven by the transmitter, which may cause field distortion and / or unpredictable component heating. A balun or common-mode trap providing high common-mode impedance may be used to reduce the effects of the transmitter drive current. Various embodiments of such common-mode traps and common-mode trap components are further described herein.

[0040] Figure 2 A block schematic diagram of a common mode trap assembly 200 or a balun assembly 200 is shown. The common mode trap assembly 200 can be configured, for example, as an aperture for an MRI system (such as, the MRI device 10 described above). For example, in the illustrated embodiment, the balun assembly 200 is configured as a transmission cable 201, which is configured to transmit signals between a processing unit (or controller) 250 and a receiving coil 260 of the MRI system. In some embodiments, the transmission cable 201 is integrated into and becomes part of the receiving coil 260. The receiving coil 260 also includes one or more coil elements coupled to the transmission cable, as known in the art.

[0041] In the illustrated embodiment, the transmission cable 201 (or balun assembly 200) includes a center conductor 210 and at least one balun 212. The center conductor 210 in the illustrated embodiment has a length 204 and is configured to transmit signals between an MRI receive coil 260 of an MRI system and at least one processor (e.g., processing system 250). The center conductor 210 may include, for example, one or more of a ribbon conductor, a wire, or a coaxial cable bundle.

[0042] like Figure 2As shown, the depicted balun 212 extends along at least a portion of the length 204 of the center conductor 210. In the illustrated embodiment, the balun 212 does not extend along the entire length 204. However, in other embodiments, the balun 212 may extend along the entire length 204 or substantially along the entire length 204.

[0043] The balun 212 is configured to provide impedance to the receiver transmitter drive current of the MRI system. In various embodiments, the balun 212 provides a high common mode impedance. For example, the balun 212 may include a resonant circuit and / or one or more resonant components to provide a high impedance in or near a desired frequency or target frequency range. It can be noted that the balun 212 may also be referred to as a choke by those skilled in the art.

[0044] The balun 212 may be tuned to have a resonant frequency close to the operating frequency of the MRI system. As used herein, a balun may be understood to have a resonant frequency close to the operating frequency when the resonant frequency defines or corresponds to a frequency band including the operating frequency, or when the resonant frequency is close to the operating frequency to provide blocking above the frequency, or to provide blocking impedance at the operating frequency.

[0045] In conventional designs, a balun has a central opening through which a center conductor passes, and the balun is typically soldered to the center conductor. This soldering process can be complex and can expose the center conductor to high temperatures. Center conductors suitable for RF applications can be heat sensitive, and soldering the center conductor can cause degradation of the center conductor. The present disclosure describes a specific implementation of a balun that can be installed without soldering or any special complex processes. In addition, the balun can be removed and reinstalled without causing any wire degradation.

[0046] Figures 3 to 9 2 shows an exemplary embodiment of a balun 302. The balun 302 may be a balun 302 having a plurality of Figure 3 The first view 300 and Figure 4 The current trap 302 is shown in the second view 400 of the embodiment of the present invention not being coupled to any cable. Furthermore, the current trap 302 may be an unshielded current trap. A set of reference axes 301 indicating the y-axis, the x-axis and the z-axis are provided. The current trap has a central axis 303 parallel to the z-axis.

[0047] The current trap 302 may be a generally cylindrical structure formed of two parts: a spiral core 304 and a coiled wire 308. The spiral core 304 may be formed of a rigid, durable, non-conductive (e.g., insulating) material such as plastic, and provides a frame for the current trap 302. A central tube 310 of the spiral core 304 may extend along the central axis 303 along the entire length 312 of the spiral core 304. The length 312 of the spiral core 304 may vary depending on the application of the current trap 302. For example, the diameter and length of the cable to which the current trap 302 is coupled may affect the length 312 of the spiral core. For example, the length 312 of the spiral core 304 may be 3.5 cm. The inner diameter 314 of the central tube 310 may be, for example, 0.2-0.5 cm, while the outer diameter 316 of the central tube 310 may be 0.4-0.7 cm. The inner diameter 314 and the outer diameter 316 may be uniform along the length 312 of the spiral core 304. Alternatively, if Figure 8 As shown in the cross-section 800 in FIG. 1 , the inner diameter 314 can gradually narrow between the first end 802 and the second end 806 of the center tube 310 of the plastic part mold. However, in other embodiments, the inner diameter 314 can remain uniform between the first end 802 and the second end 806.

[0048] The spiral rib 318 may be disposed at an outer surface of the central tube 310, the spiral rib protruding radially outward from the central axis 303. The spiral rib 318 may provide insulation between each turn of the coiled wire 308, wherein each turn is a full 360 degree rotation around the central axis 303. In other words, each turn of the coiled wire 308 is separated from adjacent turns by the spiral rib 318, thereby electrically insulating each turn. The spiral core 304 may be made, for example, by injection molding, such that the spiral rib 318 and the central tube 310 are made as a single piece. The spiral rib 318 may have a trapezoidal cross-section, for example, when the cross-section is taken along the yz plane, as shown in FIG. Figure 4 As shown, a width 402 of the spiral rib 318 defined along the z-axis at a base 404 of the spiral rib 318 is greater than a width 406 of the spiral rib 318 at an outer edge or top 408 of the spiral rib 318 .

[0049] The height 410 of the helical rib 318 may be equal to or greater than the sum of the diameter 322 of the coiled wire 308 plus the diameter of each cable coupled to the current trap 302. Figure 8 As shown, the height 410 is equal to or greater than the sum of the diameter 322 of the coiled wire, the diameter of the first cable 716a, and the diameter of the second cable 716b. The spiral ribs 318 protrude radially outward away from the central tube 310 and are coiled around the central tube 310 to form a plurality of layers 320. The plurality of layers 320 are connected to each other, but at Figure 4 It is visible separately in the cross-sectional view.

[0050] The height 410 of the spiral ribs 318 remains substantially uniform along the length 312 of the spiral core 304. Therefore, each layer in the plurality of layers 320 is similar in shape and size. The uniform height of the spiral ribs 318 results in a cylindrical outer geometry of the spiral core 304. Figure 4 As shown, the plurality of layers 320 are evenly spaced apart along the length 312 of the spiral core 304. The distance between each of the plurality of layers 320 at the base 404 of each layer can be the pitch 412 of the spiral rib 318. The pitch 412 can be similar to, narrower than, or wider than the width 402 of the spiral rib 318 at the base 404 of the spiral rib 318.

[0051] The pitch 412 of the helical rib 318 can be configured to accommodate the winding of the coiled wire 308 such that the coiled wire 308 is inserted between each of the plurality of layers 320 at the base 404 of each of the plurality of layers 320. Thus, the pitch 412 of the helical rib 318 can be similar to or greater than the diameter 322 (in Figure 3 308). The pitch 412 of the helical rib 318 can vary depending on the thickness of the coiled wire 308. For example, if a thicker coiled wire 308 is to be inserted into the helical core 304, the pitch 412 of the helical rib 318 can be made larger. Conversely, if a thinner coiled wire 308 is to be inserted, the pitch 412 can be made smaller. If a specific pitch and a specific number of multiple layers 320 are desired, the length 312 of the helical core 304 can also be varied. In addition, as Figure 4 As shown, the helix angle α indicates the angle at which the helical rib 318 helices with respect to the y-axis.

[0052] The coiled wire 308 is wound around the central tube 310 along the spiral rib 318. In some embodiments, the coiled wire 308 includes a first straight section 324 and a second straight section 326, and a central portion 328 of the central tube 310 positioned between the first straight section 324 and the second straight section 326 and wound around the spiral core 304. In some embodiments, the coiled wire 308 includes only the central portion 328, which forms an inductor and enables the current trap 302 to interact with the coil interface cable through electromagnetic induction. When the shielding current flows through the coil interface cable, the central portion 328 of the coiled wire 308 generates an electromagnetic field, which hinders the shielding current via the resonant circuit of the current trap 302, as further described below. The coiled wire 308 can be a conductor made of any suitable conductive material (such as, copper, aluminum, etc.) rather than a ferromagnetic material.

[0053] like Figure 4As shown, the length 416 of the center portion 328 can be similar to or shorter than the length 312 of the spiral core 304. The center portion 328 can have a number of turns that is equal to or less than the number of spaces 418 between the layers 320 of the spiral core 304. Figure 4 , the center portion 328 has six turns, corresponding to the six spaces 418 between the plurality of layers 320. However, other numbers of turns of the center portion 328 of the coiled wire 308 and the spaces 418 between the plurality of layers 320 are contemplated, such as 4, 7, 8, etc.

[0054] As described above, the central portion 328 of the coiled wire 308 contacts and wraps around the central tube 310 of the spiral core 304. The central portion 328 has a spiral configuration, and each turn of the central portion 328 is coiled around the central tube 310 of the spiral core 304 along a uniform angle relative to the y-axis, which angle may be equal to or close to the helix angle α.

[0055] Fig. 9 The coiled wire 308 is shown coupled to the helical core 304. The center portion 328 may be fed into the space 418 between the plurality of layers 320 by rotating the coiled wire 308 in the direction of rotation indicated by arrow 904. The coiled wire 308 may be rotated until all turns of the center portion 328 are engaged in the space 418. The engagement of the coiled wire 308 with the helical core 304 forces the turns of the coiled wire 308 to be spaced apart at the pitch 412 of the helical core 304.

[0056] The current trap 302 may also include one or more tuning capacitors that form a resonant circuit with the coiled wire 308 that acts as an inductor in the circuit. A printed circuit board (PCB) 702 may carry the tuning capacitors, as shown in perspective view 700 and along Figure 7 The line A-A' intercepts Figure 8 800 of the cross-sectional view of the embodiment of the present invention. The PCB 702 may carry a set of tuning capacitors 704, each of which is spaced apart from the other tuning capacitors 704 and arranged on an outward-facing surface of the PCB 702 (e.g., a surface of the PCB 702 facing away from the spiral core 304 of the current trap 302). Before the current trap assembly 703 is connected to the coil interface cable, the current trap 302 may be tuned by connecting the probe to the PCB 702 to adjust the impedance to block the target frequency, such as 127.7 MHz. In other words, the current trap assembly 703 may be pre-tuned during manufacturing and provided to the user as a tuned, ready-to-use device.

[0057] PCB 702 may be coupled to first end 802 (eg, Figure 8It should be understood that the PCB 702 may be similarly coupled to the second end 806 of the central tube 310 of the spiral core 304 without affecting the tuning capacity of the set of tuning capacitors 704. The PCB 702 may include a slot 706, such as Figure 7 303 and the like. As shown, the slot extends from the outer edge 705 of the PCB 702 toward the central axis 303 and terminates at a rounded end 710 disposed between the outer edge 705 of the PCB 702 and the central axis 303. The rounded end 710 of the slot can be aligned with the first segment 324 of the coiled wire 308 along the z-axis, thereby allowing the first segment 324 of the coiled wire 308 to extend through the rounded end 710. The rounded end 710 can be lined with a conductive material, such as a copper washer, and serves as a first electrical connection end of the set of capacitors 704. In some embodiments, the rounded end 710 is brought into contact with the first segment 324 of the coiled wire 308 via welding to electrically couple the set of tuning capacitors 704 of the PCB 702 to the coiled wire 308 at one end.

[0058] like Figure 8 As shown, the PCB 702 may also have a central hole 718 aligned with the central axis 303 and extending completely through the thickness of the PCB 702, wherein the thickness is defined along the z-axis. The bus bar serves as a second electrical connection end of the bank of capacitors 704 and passes through the central hole 718 of the PCB 702. The bus bar continues from the first end 802 through the central tube 310 to the second end 806 and contacts the second section 326 of the coiled wire 308 via welding to electrically couple the bank of tuning capacitors 704 of the PCB 702 to the coiled wire 308 at the other end.

[0059] PCB 702 may be configured as Figure 7 and Figure 8 Various conductive tracks, pads, and other features may be etched into the copper laminate, and electronic components such as the set of tuning capacitors 704 may be soldered to the PCB 702. The set of tuning capacitors 704 may be spaced apart from one another. In some embodiments, the inductor formed by the coiled wire 308 is connected to the set of capacitors 704 by connecting the two ends of the coiled wire 308 to the two ends of the capacitor set 704, respectively, as described above.

[0060] One or more cables may be wrapped around the helical core 304 and stacked on top of the coiled wire 308 to form a floating wave trap assembly. Figure 7 and Figure 8 Two cables 716 are shown wrapped around the helical core 304 and stacked on top of the coiled wire 308 . Fig.12An equivalent circuit diagram of the floating wave trap assembly is shown. The inductor 1206 (e.g., the central portion 328 of the coiled wire 308) and the tuning capacitor 704 form a resonant circuit. Cables 1202 and 1204 (e.g., coil interface cables in an MRI system) are coupled to the inductor 1206 via electromagnetic interaction. The resonant circuit has a high impedance to shield the current generated in the cables 1202 and 1204, and the shielding current can be reduced by electromagnetic coupling with the cables 1202 and 1204.

[0061] The cables 716 may be coil interface cables that are bent around the first end 707 of the helical rib 318 and extend through the slot 706, as shown in FIG. Figures 6 to 8 As shown. Each cable 716 may include a shield. The shield may be a common conductive layer formed of a material such as braided metal strands, a helically wound metal tape, a conductive polymer, etc., which circumferentially surrounds each of the cables 716. In this way, the shield encapsulates one or more insulated conductors, such as wires, of each of the cables 716. Implementing each of the cables 716 with a shield may reduce electrical noise that may otherwise degrade the electrical signals transmitted by the cables 716. The shield may also reduce electromagnetic radiation that may cause electromagnetic interference with other electronic devices.

[0062] The conductive nature of the shield may increase the likelihood of shield currents being generated on the cable 716, which may cause local heating of the cable 716, distortion of the MRI image, and adversely affect coil tuning. Therefore, equipping the MRI system with at least one floating notch filter assembly 703 may avoid the above problems.

[0063] The coupling of the PCB 702 to the current trap 302 allows the floating trap assembly 703 to be tuned away from and independent of the MRI system. Thus, the use of the floating trap assembly 703 can be accelerated by eliminating a time-consuming tuning process. The tuning process can be performed during the manufacture of the floating trap assembly 703, wherein the set of tuning capacitors 704 can be adjusted to provide an impedance of the floating trap assembly 703 that blocks the resonant frequency of the shielding current carried by the cable 716. Alternatively, the floating trap assembly 703 can be configured to block a range of frequencies so that the floating trap assembly 703 can be used between multiple systems having varying resonant frequencies to be blocked.

[0064] The cable 716 can pass through the spaces 418 ( Figure 4 The cables 716 may be arranged such that the cables 716 are stacked along the y-axis within each of the spaces 418. Figure 5 , Figure 6 and Figure 8 The stacking of cables 716 is shown in detail in FIG. Figure 5 Side view of 500 and Figure 6 The current trap 302 coupled to the cable 716 is shown in the perspective view 600 of FIG. Figure 3 to Figure 4 For clarity, a section of the spiral rib 318 of the spiral core 304 is removed (e.g., by Figure 3 In other examples, the diameter of the cable 716 may be similar to the diameter 322 of the coiled wire 308, or may have a diameter that is different from the coiled wire 308 or each other.

[0065] When coupled to the helical core 304, the configuration of the cable 716 can be similar to the configuration of the coiled wire 308. The first region 502 and the second region 504 of the cable 716 that are not coupled to the helical core 304 can extend away from the helical core 304 along the z-axis. The cable 716 can follow a similar geometry to the coiled wire 308, which wraps around the central portion 328 of the coiled wire 308 along the helix angle α through the spaces 418 between the plurality of layers 320, as shown in FIG. Figure 4 As shown, the first region 502 and the second region 504 extend away from the spiral core 304 in opposite directions.

[0066] The stack of cables 716 and coiled wires 308 along the helical core 304 is Figure 8 The cables 716 include a first cable 716a and a second cable 716b, as shown in the first dashed area 816. The first cable 716a is positioned directly adjacent to the coiled wire 308, between the coiled wire 308 and the second cable 716b, as shown in the first dashed area 816. Figure 6 716a and the second area 504 of the cable 716. In other words, no other cables or objects are arranged along the entire length of the coiled wire 308 between the first cable 716a and the coiled wire 308.

[0067] When the cable 716 is wound through the helical core 304, as shown in FIG. Figure 8 As shown, the relative positioning of the first cable 716a is maintained in contact with the coiled wire 308 along the length 312 of the helical core 304. Figure 8 In the first dashed area 816 of FIG. 304 , the coiled wire 308 and the cables 716 are stacked along the y-axis (e.g., along a radial direction perpendicular to the central axis 303), with the first cable 716a on top of the coiled wire 308 and the second cable 716b on top of the first cable 716a. Although the stacking of the coiled wire 308 and the cables 716 can be angled relative to the y-axis, such as along the Figure 4The helix angle α is shown, but the coiled wire 308 and the cable 716 are not aligned parallel to the central axis 303 at any point along the helical core 304.

[0068] The second dashed area 818 shows the arrangement of the coiled wire 308 and the cables 716 in the opposite side of the spiral core 304 from the first dashed area 816. The first cable 716a is positioned along the y-axis directly below the coiled wire 308, and the second cable 716b is positioned directly below the first cable 716a. Thus, the relative positioning of the first cable 716a and the second cable 716b is maintained along and around the spiral core 304.

[0069] The size of the space 418 between the plurality of layers 320 of the spiral core 304 may be configured to accommodate a cable diameter that is different than the diameter 322 of the coiled wire 308. The pitch 412 of the spiral rib 318 may be similar to the diameter 322 of the coiled wire 308. The width of the space 418 may increase along the y-axis toward the top 408 of the spiral rib 318 (which is also the top 408 of the plurality of layers 320) such that the width 820 of the space 418 is wider than the pitch 412 of the spiral core 304 at the top 408 of the space 418. The increase in width of the space 418 in the radial direction away from the central axis 303 enables the diameter 822 of each of the cables 716 (which may be larger than the diameter 322 of the coiled wire 308) to fit within the space 418. However, the width 820 of the space 418 is maintained to be less than twice the diameter 822 of the cable 716 so that the cables may not shift.

[0070] The height 410 of the helical rib 318 may be equal to or greater than the sum of the diameter 322 of the coiled wire 308 and the diameter 822 of the cable 716. In addition, the height 410 may be varied to accommodate Figures 5 to 7 More cables 716 are shown. The current trap 302 can be configured to be coupled to up to four cables 716, which are stacked in a radial direction perpendicular to the central axis 303 in a manner similar to the first cable 716a and the second cable 716b, as shown in FIG. Figure 8 shown. Fig.14 An example of a current trap coupled to four cables is shown in FIG.

[0071] Fig.14 A detailed view 1400 of a section of a current trap 1402 is shown having a spiral core 1404 that is similarly configured as Figures 3 to 9 The helical core 304 is shown. The spaces 1406 between adjacent threads 1408 of the helical core 1404 receive a coiled wire 1410 and four cables 1412. The cables 1412 are stacked on top of the coiled wire 1410 and on top of each other with respect to the y-axis.

[0072] The floating trap assembly 703 may have several advantages over conventional baluns (e.g., non-floating baluns). The coil interface cable of the MRI system may be wrapped around the helical core of the floating trap assembly without cutting the cable. Thus, there is no need to solder the floating trap assembly to the cable, thereby reducing the risk of exposing the cable to high temperatures. Since the floating trap assembly is a portable unit that is not anchored to any other structure, the floating trap assembly may be positioned at any location along the cable without cutting the cable, and may therefore be placed in convenient locations along the cable that allow the floating trap assembly to be easily accessible.

[0073] Fig.13 An example of how a floating trap assembly may be reconfigured along at least one coil interface cable is shown in the schematic diagram 1300 in FIG. A current trap 1302 may be coupled to a cable 1304 extending between a processing unit 1306 and a receive coil 1308 of an MRI system. The current trap 1302 may be arranged at a first position 1310, closer to the processing unit 1306 than the receive coil 1308, and connected to the cable 1304 by wrapping the cable 1304 around a helical core of the floating trap assembly 1302 on top of the coiled wire of the current trap 1302.

[0074] By unwinding the cable 1304 from the helical core of the current trap 1302 and moving the current trap 1302 along the cable, the floating trap assembly can be repositioned to a second location 1312 along the cable 1304, closer to the receiving coil 1308. The current trap 1302 can be coupled to the cable 1304 by wrapping the cable 1304 around the helical core of the current trap 1302. Furthermore, the floating trap assembly can be easily repositioned to any point along the cable 1304 between the processing unit 1306 and the receiving coil 1308.

[0075] See also Fig.10 , a shielded current trap 1002 is shown in perspective view 1000. Similar to Figure 3 to Figure 4 Unlike the unshielded current trap shown, the shielded current trap 1002 may have a coiled wire 1004 coupled to a bus 1014 that serves as an electrical connection end for a tuning capacitor. Additionally, the shielded current trap 1002 may be configured as a floating current trap. It should be appreciated that although Fig.10 The bus 1014 is not shown in the figure for the sake of simplicity. Figures 3 to 9 , but bus 1014 may be similarly coupled to Figures 3 to 9 The current trap 302 is provided.

[0076] In addition to the components of the unshielded current trap, the shielded current trap 1002 also includes a shield 1020 that encapsulates the cable 1018. The shield 1020 is a hollow cylinder that encapsulates the spiral core, the coiled wire, and the cable. The shield 1020 can be formed of an electromagnetic insulating material such as a plastic coated with an outer layer of copper tape. In addition, the shield 1020 can be provided as a sheet of electromagnetic insulating material having a mechanism for coupling parallel edges of the sheet to each other. In this way, the cable 1018 can first be coiled around the spiral core, and then the shield 1020 can be wrapped around the spiral core and maintained in a cylindrical geometry around the spiral core by fastening the parallel edges of the shield 1020 to each other. Implementing the shielded current trap 1002 with the shield 1020 can reduce the risk of patient exposure to electromagnetic radiation.

[0077] Fig.11 is a high-level block diagram illustrating an exemplary method 1100 for providing a floating wave trap assembly (such as, Figure 7 and Figure 8 The floating trap assembly 703 of the embodiment of the present invention is used to block the transmission induced current on one or more center conductors (e.g., coil interface cables). Prior to engagement with the center conductors, the floating trap assembly can be tuned to a resonant frequency equal to or close to the operating frequency of the MRI system via a tuning capacitor coupled to a printed circuit board of the floating trap assembly. The one or more center conductors can be continuously wrapped around the floating trap assembly, such as Figures 5 to 8 shown.

[0078] Method 1100 begins at 1102. At 1102, RF energy generated at a body coil of an MRI system is transmitted to a center conductor. At 1104, the signal transmission generates a shield current carried by a shield along the center conductor. At 1106, a floating trap assembly traps the RF current at the center conductor. For example, the high impedance of the floating trap assembly, where the resonant frequency is pre-set (e.g., tuned) to the operating frequency of the MRI system, reduces the shield current.

[0079] A technical effect of the present disclosure may include improved performance of an MRI system due to reduced interaction between a transmission cable and coil elements. Another technical effect of the present disclosure may include achieving a desired impedance of a floating wave trap assembly by a single floating wave trap. Yet another technical effect of the present disclosure may include positioning the floating wave trap assembly at any position along the transmission cable. Yet another technical effect of the present disclosure may include reducing the temperature of the coil surface relative to a feed board of the MRI system.

[0080] As used herein, the elements or steps listed in the singular and beginning with the word "one" or "a kind of" should be understood as not excluding a plurality of the elements or steps, unless such exclusion is explicitly stated. In addition, the reference to "an embodiment" of the present invention is not intended to be interpreted as excluding the existence of additional embodiments that also include the cited features. In addition, unless explicitly stated to the contrary, the embodiment of "including", "comprising" or "having" an element or multiple elements with a specific characteristic may include additional such elements without the characteristic. The terms "including" and "in..." are used as the concise language equivalents of the corresponding terms "including" and "wherein". In addition, the terms "first", "second" and "third" etc. are only used as marks, and are not intended to impose numerical requirements or specific positional order on their objects.

[0081] This written description uses examples to disclose the invention, including the best mode, and also to enable a person skilled in the relevant art to practice the invention, including making and using any devices or systems and performing any included methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to a person skilled in the art. Such other examples are intended to fall within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insignificant differences from the literal language of the claims.

Claims

1. A current trap, comprising: A spiral core, wherein the spiral core is made of a non-conductive material; a coiled wire having a plurality of turns wound around the helical core; and one or more tuning capacitors physically attached to the helical core and electrically connected to the coiled wire to form a resonant circuit with the coiled wire, One or more cables are wound around the helical core and stacked on the coiled wire, wherein the resonant circuit has a high impedance to common mode currents carried by the one or more cables.

2. The current trap of claim 1, wherein the spiral core comprises a central tube and spiral ribs protruding from the central tube, the spiral ribs forming a plurality of spaces, each of the plurality of spaces being used to receive one of the plurality of turns of the coiled wire. 3 . The current trap of claim 2 , further comprising a printed circuit board attached to the helical core, wherein the one or more tuning capacitors are carried by the printed circuit board.

4. The current trap of claim 3, wherein the printed circuit board is secured to the spiral core by an adhesive.

5. The current trap of claim 3, wherein a first electrical connection end for the one or more tuning capacitors is formed on the printed circuit board and electrically connected to the first end of the coiled wire.

6. The current trap of claim 5, wherein the second electrical connection end for the one or more tuning capacitors is a bus bar that passes through the central tube and is electrically connected to the second end of the coiled wire.

7. The current trap of claim 1, wherein the spiral core is made of plastic.

8. The current trap of claim 1, wherein the coiled wire is made of a non-ferromagnetic conductive material.

9. A floating current trap assembly, the floating current trap assembly comprising: A current trap, the current trap comprising: A spiral core, wherein the spiral core is made of a non-conductive material; a coiled wire having a plurality of turns wound around the helical core; and one or more tuning capacitors electrically connected to the coiled wire to form a resonant circuit with the coiled wire; and One or more cables are wrapped around the helical core and stacked on the coiled wire, wherein the resonant circuit has a high impedance to common mode currents carried by the one or more cables.

10. The floating current trap assembly of claim 9, wherein the one or more cables are coupled to the coiled wire by an electromagnetic coupling.

11. The floating current trap assembly of claim 9, wherein the position of the current trap relative to the one or more cables is reconfigurable.

12. The floating current trap assembly of claim 11, wherein the position of the current trap is reconfigured by unwinding the one or more cables from the helical core at a first position and rewinding the one or more cables onto the helical core at a second position.

13. The floating current trap assembly of claim 9, wherein the spiral core comprises a central tube and spiral ribs protruding from the central tube, the spiral ribs forming a plurality of spaces, each of the plurality of spaces being used to receive one of the plurality of turns of the coiled wire and the one or more cables.

14. The floating current trap assembly of claim 13, further comprising a printed circuit board attached to the helical core, wherein the one or more tuning capacitors are carried by the printed circuit board.

15. The floating current trap assembly of claim 14, wherein a first electrical connection end for the one or more tuning capacitors is formed on the printed circuit board and electrically connected to a first end of the coiled wire, and wherein a second electrical connection end for the one or more tuning capacitors is a bus bar passing through the center tube and electrically connected to a second end of the coiled wire.

16. A radio frequency coil unit for magnetic resonance imaging, the radio frequency coil unit comprising: one or more radio frequency coil elements; a coil interface cable electrically coupled to the one or more radio frequency coil elements; and A current trap, the current trap comprising: A spiral core, wherein the spiral core is made of a non-conductive material; a coiled wire having a plurality of turns wound around the helical core; and one or more tuning capacitors electrically connected to the coiled wire to form a resonant circuit with the coiled wire, Wherein the coil interface cable is wrapped around the helical core and stacked on the coiled wire.

17. The radio frequency coil unit according to claim 16, wherein the coiled wire is made of a non-ferromagnetic conductive material.

18. The radio frequency coil unit of claim 16, wherein the coil interface cable is coupled to the coiled wire by an electromagnetic coupling, and wherein the resonant circuit provides a high impedance to common mode currents carried by the coil interface cable.

19. The radio frequency coil unit of claim 16, wherein the position of the current trap relative to the coil interface cable is reconfigurable.

20. The radio frequency coil unit of claim 19, wherein the position of the current trap is reconfigured by unwinding the coil interface cable from the helical core at a first position and rewinding the coil interface cable onto the helical core at a second position.

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