Radio Frequency (RF) Receiver System Using Active Decoupling
Patent Information
- Application Number
- JP2023540710
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2021-01-04
- Filing Date
- 2021-12-22
- Publication Date
- 2024-12-27
- Estimated Expiration
- 2041-12-22
AI Technical Summary
Modern magnetic resonance imaging (MRI) systems with high channel count coils face residual coupling issues that traditional decoupling methods cannot address, particularly in high-field applications and flexible arrays where coupling varies with patient load.
An RF receiver system with active decoupling using a compensation signal generated by a signal generator and excitation path to reduce residual coupling, utilizing a transverse communication circuit and high-speed bidirectional data bus for fast data exchange among RF receiver coil elements.
Effectively compensates for residual coupling in flexible RF receiver coils, improving image quality by reducing interference and adapting to varying patient loads.
Smart Images
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Abstract
Description
[Technical field]
[0001] The present invention relates to the field of magnetic resonance (MR) imaging. In particular, the present invention relates to a radio frequency (RF) receiver system with active decoupling. The present invention further relates to an MR imaging system, a method for active decoupling of an RF receiver system, a software package for a magnetic resonance imaging system, a software package for upgrading a magnetic resonance imaging system, and a computer program product. [Background technology]
[0002] Array coils have been used for decades in magnetic resonance imaging (MRI) to improve both image quality (signal-to-noise ratio (SNR)) and speed (e.g., by accelerated imaging, e.g., via sensitivity encoding SensE). These techniques require, at least to some extent, decoupled coil elements. The most common technique for decoupling is to use a precisely defined overlap of adjacent coil elements to null out shared magnetic flux.
[0003] Modern coils with high channel counts generally suffer from residual coupling that cannot be compensated for by traditional decoupling methods such as overlapping elements. This is mainly due to non-adjacent elements. Especially in high field applications, the coupling also depends on the patient load, which cannot be compensated for by a fixed overlap. Until now, residual coupling was considered a given, since its impact on image quality was too small to justify countermeasures.
[0004] However, nowadays, thin and flexible coil arrays are being developed and manufactured, which greatly increases the demand for compensating for residual coupling. For this type of array, the coil elements are closer to the tissue, and due to their flexibility and collapsibility, the coil coupling varies over a wide range, since it cannot be eliminated by typical static means such as overlaps, transformers, or shared capacitors. Therefore, new means are needed to compensate for residual coupling in a wide, individually adjustable range.
[0005] US Patent Application US2018 / 023978 discloses a magnetic resonance imaging system with a circuit for an RF receiver coil that uses GaN FETs to couple and decouple the receive electronics from the RF coil. In particular, an active decoupling circuit is provided to reduce inductive coupling between radio frequency coils in a multi-coil transmit / receive system. A feedback circuit is provided to couple a negative magnetic flux into the RF receiver coil that mitigates the inductive coupling effect to nearby coils. This known feedback circuit only feeds back the output of the RF receiver coil to generate a negative magnetic flux in the same RF receiver coil. Summary of the Invention [Problem to be solved by the invention]
[0006] It is an object of the present invention to provide a radio frequency (RF) receiver system in which residual coupling can be actively compensated for. [Means for solving the problem]
[0007] According to the invention, this object is addressed by the subject matter of the independent claims. Preferred embodiments of the invention are set out in the subclaims.
[0008] Therefore, according to the present invention, there is provided an RF receiver system for use in a magnetic resonance imaging system, the RF receiver system comprising at least two simultaneously used RF receiver coil elements, each RF receiver coil element comprising a signal generator for providing a compensation signal and an excitation path, the excitation path being configured to couple a compensation signal to the RF receiver coil element in order to reduce residual coupling in the RF receiver system by the compensation signal being coupled to the RF receiver coil element.
[0009] The essential idea is therefore to compensate for the coupling by means of a compensation signal coupled to each single RF receiver coil by an excitation path. In other words, it is proposed to feed the coil elements of the RF receiver system with an active decoupling signal generated from a linear combination of all the RF receiver coil elements in order to decouple the coil elements. The term "RF receiver coil element" in the context of the present invention refers to a single physical receiving unit, such as a loop, or to one mode of a complex resonator, such as the modes of a birdcage resonator.
[0010] The RF receiver channels communicate with each other by a transverse communication circuit, and for each RF receiver coil element (2), its compensation signal depends on the output of one or more respective other RF receiver coil elements (2) of the RF receiver system, and for each RF receiver coil element, the transverse communication circuit is configured to provide a compensation signal to a respective excitation path. The transverse communication circuit is configured as a high-speed bidirectional data bus providing correspondence between the RF receiver coil elements. The transverse communication circuit is coupled to a host that further processes the received signals from the RF receiver coil elements. Alternatively, the transverse communication circuit is configured to directly combine the controllers in the RF signal channels from the RF receiver channels to a common controller responsible for several RF receiver coils, via their respective excitation path elements to be decoupled. According to a preferred embodiment of the invention, the excitation path comprises a loop element for coupling the compensation signal to the RF receiver coil element. By means of the loop element, it is easy to couple the magnetic flux to the coil element.
[0011] Alternatively, according to another preferred embodiment, the excitation path is realized by a coupling circuit configured to couple the compensation signal to the RF receiver coil element, the coupling circuit comprising at least one lumped element or transmission line for coupling the compensation signal to the RF receiver coil element.
[0012] According to a preferred embodiment, each RF receiver coil element is provided with a matching network and the coupling circuit is incorporated into the matching network of the RF receiver coil element.
[0013] According to another preferred embodiment of the invention, the RF receiver coil element comprises a digital receive chain for digitization of the signals received by the RF receiver coil element. A digital receive chain with digitization performed directly on the RF receiver coil allows an easy decoupling of the RF receiver coil element.
[0014] According to one embodiment of the present invention, the digital receive chain of each RF receiver coil comprises a controller, which are connected by a high-speed bidirectional data bus. The existing controllers of the RF coils can be used to perform the necessary calculations for decoupling. The high-speed bidirectional data bus between the controllers of the different RF receiver coils ensures fast and easy data exchange.
[0015] In one embodiment of the present invention, the RF receiver system includes a digital-to-analog converter (DAC) for each RF receiver coil element, the DAC configured to generate a compensation signal.
[0016] According to one embodiment of the present invention, the RF receiver coil is a flexible and / or foldable and / or arbitrarily shaped RF receiver coil. The present invention relates to all kinds of array receiver coils, but especially in case of flexible coils with strong patient coupling, adaptation to load changes can be considered with the proposed RF receiver system.
[0017] The invention further relates to a magnetic resonance imaging system comprising the RF receiver system previously described.
[0018] The present invention also provides a method for active decoupling of an RF receiver system, the method comprising: providing an RF receiver system as previously described; generating a compensation signal by a signal generator of each RF receiver coil element; Compensation signal by excitation path
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[0019] According to another embodiment of the present invention, the combined complex signal vector
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[0020] According to a preferred embodiment, each RF receiver coil element comprises a digital receive chain for digitization of the signal received by the RF receiver coil element, the digital receive chain of each RF receiver coil element comprising a controller, which calculates the vector
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[0021] The present invention further provides a method for active decoupling of a radio frequency (RF) receiver system, the method comprising: Combined complex signal vector
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[0022] The invention also relates to a software package for a magnetic resonance imaging system, the software package including instructions for controlling an RF receiver system according to the method previously described.
[0023] The invention further relates to a software package for upgrading a magnetic resonance imaging system, the software package including instructions for controlling an RF receiver system according to the method previously described.
[0024] Finally, the invention relates to a computer program product comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method described above, i.e. the computer program product of the invention comprises instructions which, when executed by a computer, cause the computer to carry out the steps of the method defined in claims 11 to 13.
[0025] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter, but such embodiments do not necessarily represent the full scope of the invention, and reference is therefore made to the claims and this specification for interpreting the scope of the invention. [Brief description of the drawings]
[0026] [Figure 1] FIG. 1 illustrates a schematic diagram of a radio frequency (RF) receiver system having an RF receiver coil element and three excitation paths, according to an embodiment of the present invention. [Diagram 2]FIG. 2 illustrates a flowchart of a method for active decoupling of a radio frequency (RF) receiver system, in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] FIG. 1 shows a schematic diagram of an RF receiver system 1 with three RF receiver coil elements 2 and three excitation paths 4 according to an embodiment of the present invention. Each of the RF receiver coil elements 2 is equipped with an analog matching / detuning / preamplifier section 6 followed by an analog / digital chip 7. The excitation path 4 of each RF receiver coil element 2 is sketched in FIG. 1 by a small coupling loop 5 for coupling the magnetic flux into the RF receiver coil element 2. Alternatively, a coupling circuit comprising at least one lumped element or transmission line for coupling a compensation signal into the RF receiver coil element may also be incorporated, for example in the matching network. Furthermore, each RF receiver coil element 2 of the RF receiver system 1 comprises a signal generator 10 for providing a compensation signal. In an embodiment of the present invention, the signal generator 10 is a digital-to-analog converter (DAC). It is provided that each RF receiver coil element 2 comprises a digital receive chain 8 for digitization of the signal received by the RF receiver coil element 2. This is particularly advantageous since the digital receive chain 8 of each RF receiver coil element 2 can be equipped with a controller 11, the controllers 11 of the different RF receiver coil elements 2 being connected between each other and to a host 12 by a high speed bidirectional data bus 13. The host 12 further processes the received and digitized signals from the RF receiver coil elements 2. In one embodiment of the invention the controllers 11 may even be directly combined to a common controller or one controller 11 may be responsible for several elements. The controllers 11 of the RF receiver coil elements 2 may not only be for controlling the RF receiver coil elements 2 but may also be used to calculate the compensation of the coupling of the RF receiver coils 2 in the RF receiver system 1.
[0028] FIG. 2 shows a flow chart of a method for active decoupling of an RF receiver system 1 according to an embodiment of the present invention. The method starts in step 200, where an RF receiver system 1 is provided. The RF receiver system 1 comprises at least two simultaneously used RF receiver coil elements 2. The term "coil element" can also include system-integrated coils. Thus, in an embodiment of the present invention, the RF receiver coil elements can also be system-integrated coils, e.g. body coils and / or local receiving coils. The present invention can also be used to combine those system-integrated coils. Each RF receiver coil element 2 comprises a signal generator 10 for providing a compensation signal. The RF receiver coil element 2 further comprises an excitation path 4, which is configured to couple (input) the compensation signal to the RF receiver coil element 2. The excitation path 4 can comprise, for example, a small coupling loop 5 for coupling magnetic flux into the RF receiver coil 2, as sketched in FIG. 1. In step 210, a compensation signal is generated by the signal generator 10 of each RF receiver coil element 2. In step 220, the compensation signal generated by the signal generator 10 is coupled to the corresponding RF receiver coil element 2 by the excitation path 4. At the same time, the combined complex signal vector
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[0029] Although the present invention has been shown and described in detail in the drawings and the above description, such examples and descriptions should be considered as illustrative or exemplary, and not restrictive, and the present invention is not limited to the disclosed embodiments. Other variations of the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprises" does not exclude other elements or steps, and singular elements do not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be interpreted as limiting the scope. Moreover, for the sake of clarity, not all elements in the drawings are labeled with reference signs. [Explanation of symbols]
[0030] 1 Radio Frequency (RF) Receiver System 2 RF receiver coil elements 4. Excitation Path 5. Coupling Loop 6 Analog Matching / Detuning / Preamp Section 7 Analog / Digital Chips 8 Digital Receive Chain 9. Analog-to-Digital Converter 10 Signal Generator / Digital-to-Analog Converter 11 Controller 12 Host 13 Bidirectional Data Bus
Claims
1. 1. A radio frequency (RF) receiver system for use in a magnetic resonance imaging system, the RF receiver system comprising: two or more RF receiver coil elements and two or more RF signal channels, each RF receiver coil element coupled to a respective RF signal channel; each RF receiver coil element comprises a signal generator for providing a compensation signal and an excitation path configured to couple the compensation signal to the RF receiver coil element, each RF receiver coil element configured to reduce residual coupling in the RF receiver system by the compensation signal coupled to the RF receiver coil element; two or more RF receiver channels in communication with each other by transversely coupled communication circuits; An RF receiver system, wherein for each RF receiver coil element, its compensation signal depends on the output of one or more respective other RF receiver coil elements of the RF receiver system, and for each RF receiver coil element, the transversely coupled communication circuitry provides the compensation signal to a respective one of the excitation paths.
2. 2. The RF receiver system of claim 1, wherein for each RF receiver coil element, a respective transverse communication circuit generates a decoupling signal from a linear combination of all RF receiver coil elements to the RF receiver coil element of the RF receiver system.
3. The RF receiver system of claim 1 , wherein the excitation path comprises a loop element for coupling the compensation signal to the RF receiver coil element.
4. 2. The RF receiver system of claim 1, wherein the excitation path is realized by a coupling circuit that couples the compensation signal to the RF receiver coil element, the coupling circuit comprising at least one lumped element or transmission line for coupling the compensation signal to the RF receiver coil element.
5. The RF receiver system of claim 3 , wherein each RF receiver coil element comprises a matching network, and the coupling circuit is incorporated into the matching network of the RF receiver coil element.
6. 6. An RF receiver system according to claim 1, wherein for each RF receiver coil element, the RF receiver channel is configured as a digital receive chain for digitization of the signal received by the RF receiver coil element.
7. 7. The RF receiver system of claim 6, wherein the digital receive chain for each RF receiver coil element comprises at least two controllers, the at least two controllers being connected to each other by a bidirectional data bus.
8. 8. The RF receiver system of claim 1, wherein the RF receiver system comprises a digital-to-analog converter (DAC) for each RF receiver coil, the DAC generating the compensation signal.
9. 9. The RF receiver system according to any one of claims 1 to 8, wherein the RF receiver coil element is a flexible and / or foldable and / or differently shaped RF receiver coil.
10. A magnetic resonance imaging system comprising an RF receiver system according to any one of claims 1 to 9.
11. 1. A method for active decoupling of a radio frequency (RF) receiver system, the method comprising: Providing an RF receiver system according to any one of claims 1 to 9; generating a compensation signal by a signal generator in each RF receiver coil element; The compensation signal is ##EQU00021## , which is coupled to the corresponding RF receiver coil element, and a combined complex signal vector [0022] receiving, wherein [0023] is a signal vector received at the RF receiver coil elements without coupling; The combined complex signal vector ##EQU00024## and compensating for the coupling of The method comprising:
12. The combined complex signal vector [0025] The step of compensating for said coupling of For each RF receiver coil element, the vector [0026] multiplying A by a corresponding row of a matrix B and applying the result to the received signals of the RF receiver coil elements via the excitation paths, －１ −1, 1 being an identity matrix, each RF receiver coil element comprising a digital receive chain for digitizing the signal received by the RF receiver coil element, the digital receive chain of each RF receiver coil element comprising a controller, and the corresponding row of the matrix B is assigned to the vector [0027] The step of multiplying is performed on the controller.
12. The method of claim 11, having the following structure:
13. A combined complex signal vector [0028] The combination of [0029] From the left, inverse matrix A －１ 12. The method of claim 11, comprising the step of compensating by multiplying
14. A software package for a magnetic resonance imaging system, said software package including instructions for controlling a radio frequency (RF) receiver system according to the method of claims 11 to 13.
15. A software package for upgrading a magnetic resonance (MR) imaging system, said software package comprising a radio frequency (RF) receiving circuit according to the methods of claims 11 to 13. A software package that contains instructions for controlling the aircraft systems.