Radio frequency receiver, medical imaging system and method

Abstract

The invention relates to a radio frequency receiver system (1) comprising: a radio frequency coil circuit (2); a preamplifier (3) configured to receive the magnetic resonance signal from the coil circuit and configured to output the amplified signal to the digitizer and control system (4); a detuning circuit (5) comprising a switch (6) configured to switch the radio frequency coil circuit between a detuning state and a tuning state based on a detuning command signal received by the detuning unit (5); and a single two-wire connection (7) configured to transmit electrical power to the preamplifier (3), to transmit the detuning command signal to the detuning circuit (5) and to carry the amplified receive signal. In this manner, a radio frequency antenna system with improved characteristics is provided.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of magnetic resonance imaging. In particular, the present invention relates to the field of radio frequency antenna systems for magnetic resonance imaging devices. The present invention further relates to a radio frequency (RF) antenna or receiver assembly comprising an RF coil loop for picking up magnetic resonance signals, a preamplifier for amplifying the magnetic resonance signals and a detuning circuit for switching the RF coil assembly between a detuned state ("off state") and a tuned state ("on state"). The detuning circuit preferably comprises a FET-based switch to switch the RF antenna assembly between the "on state" and the "off state". BACKGROUND

[0002] Part of every magnetic resonance imaging device is a radio frequency antenna system for receiving and converting magnetic resonance signals. The radio frequency antenna system comprises a radio frequency coil, a matching network, a preamplifier and an analog-to-digital converter. The preamplifier supply voltage and the amplified signal are routed between the antenna system and the system backend using a first cable connection per antenna element. In magnetic resonance imaging, the system integrated body coil generates an excitation magnetic field for the spin system, causing a pre-relaxation. The precession of the net magnetization induces a current in the radio frequency coil via electromagnetic induction. The radio frequency coil usually comprises a wire with an inductance and a coil resistance.

[0003] As with any radio frequency operating system, the radio frequency antenna system is affected by noise. Therefore, one of the most important requirements is to achieve a minimum noise figure. The lowest noise figure is achieved if the source impedance is matched to the noise impedance of the preamplifier. In particular for magnetic resonance imaging in the low field range (<1 T), the signal-to-noise ratio depends, among other things, on the patient geometry, the size of the bore and the relative position of the radio frequency coil within the bore. Additional noise sources are the modulated power supply, which can cause a further increase in noise or instability of the preamplifier, delays and gain instability, which lead to a reduction in image quality.

[0004] With the advent of lightweight digital RF coils for MRI, the coils can be equipped with smart functionality to provide a safe clinical workflow.

[0005] Magnetic resonance (MR) coils for signal reception usually have two operating states: an "on" state, also called a tuned state, which represents a low-noise receiving state for capturing very weak (down to the noise floor) nuclear signals. The other operating state is an "off state, also called a detuned state, which represents a passive state in which the coil needs to withstand strong RF pulses intended to excite the nuclei. For switching, usually PIN diode based RF switches are used. The detuning circuit needs a bias current of typically 80 mA through the diode. The supply to the detuning circuit is realized using a second feed supply cable between the individual antenna elements and the MR system. This makes the cable tree of the coil less flexible. One option would be to combine the first and second cable in a 3-conductor structure with e.g. a shared return line. But due to strong transient currents on the cable this greatly increases the risk of instability of the preamplifier of the RF coil. Furthermore, the control logic is expensive because in one of the operating phases the sum of the bias currents is several amperes in a multi-channel coil. Strong losses have to be expected and the design of the feed lines is challenging because the strong currents can disturb the B0 or gradient fields.

[0006] With the further emergence of FET (field effect transistor), FET array or MEM based switches, e.g. RF currents induced by RF transmit pulses are effectively blocked in the coil loop without the need for high detuning currents. These newer detuning circuits are fully voltage controlled, typically between 0 and 3 V, and operate almost power-free in both operating states of the coil.

[0007] Due to the required complexity, currently a two-wire connection is needed to control the coil elements. One connection is usually used for the RF signal and the DC supply of the preamplifier, while the second connection is used to route the detuning current. This increases the complexity of the acquisition and contributes to the electric field due to the two-conductor feed and acquisition. Therefore, this can lead to signal integrity issues using digital solutions. Furthermore, this usually increases the power consumption by additional digital electronics. Another requirement that has to be permanently fulfilled is patient safety by controlling the detuning function.

[0008] WO 2007 / 138547 Al describes an RF receiver assembly with a coaxial based RF coil loop with reactively coupled detuning circuits. Switching is realized by a switched supply voltage for the preamplifier. The preamplifier is directly modulated by the switched supply voltage, which can lead to instability and image artifact issues. Therefore, remote detection of faults via a single two-wire or coaxial cable or connector is still a challenge. SUMMARY

[0009] It is an object of the present invention to provide a radio frequency antenna system with improved characteristics.

[0010] According to the application, this object is solved by the subject matter of the independent claims. Preferred embodiments of the application are described in the dependent claims.

[0011] The present application relates to a radio frequency receiver system comprising a radio frequency coil circuit, a preamplifier configured to receive a magnetic resonance signal from the coil circuit and configured to output an amplified signal to a digitizer and a control system, the radio frequency receiver system further comprising a detuning circuit comprising a switch configured to switch the radio frequency coil circuit between a detuned state and a tuned state based on a detuning command signal received by a detuning unit, and a single dual-mode (e.g. twin wire) connection or coaxial connection configured to transmit electrical power to the preamplifier, to transmit the detuning command signal to the detuning circuit and to carry the amplified received signal.

[0012] According to the present application, a single dual-mode connection (e.g. twin wire or coaxial cable) is provided to provide electrical DC power to the preamplifier, to control the tuning / detuning state, and to transfer the amplified magnetic resonance (MR) signal to / from the (digital) control and reconstructor of the magnetic resonance examination system. The present application enables a reduction of the amount of wiring for data transfer, detuning control and power supply to / from the RF antenna assembly.

[0013] The present application relates to a RF receiver system for a magnetic resonance examination system. In particular, the RF receiver system comprises a RF coil circuit for picking up magnetic resonance signals of a magnetic flip. A preamplifier is provided for pre-amplifying the picked up magnetic resonance signals. For detuning / tuning the RF circuit, a detuning / tuning circuit is provided to switch the impedance of the RF coil circuit with the detuning / tuning circuit between a resonance mode and a non-resonance mode. In the resonance mode, the RF coil circuit is highly sensitive to magnetic resonance signals of a carrier frequency in the (Larmor or MR) frequency range. In the non-resonance mode, the RF coil circuit has a very low sensitivity to RF transmit signals in the Larmor frequency range, which are generated by a RF transmit function of the magnetic resonance examination system for exciting and manipulating (inverting, refocusing, etc.) the excitation transverse spins of a subject (patient to be imaged) to be examined. In the detuned mode, the non-resonant RF coil circuit shields the sensitive preamplifier from strong RF transmit fields emitted by the RF transmitter of the magnetic resonance examination system.

[0014] A single bi-modal connection is provided between (i) an RF coil circuit with pre-amplifier and detune / tune circuitry and (ii) digitizer and control circuitry. Thus, the present invention enables a reduction in the amount of wiring between the front-end and back-end of an RF receiver system, with only a single cable required in the examination zone of a magnetic resonance examination system where space is typically at a premium. While the single bi-modal connection is used to carry various signals to and from the RF coil circuit with detune circuitry, a front-end three-port network enables an electrical power signal to be passed to the pre-amplifier and the pre-amplifier to be shielded from a detune command signal. In addition, the front-end three-port network is used to apply a pre-amplified magnetic resonance signal from the pre-amplifier onto the single bi-modal connection. The single bi-modal connection also passes an electrical power signal and a detune command signal from the digitizer and control circuitry to the RF coil circuit and with the detune circuitry. The front-end three-port network is used to shield the pre-amplifier from the detune command signal. The electrical power signal and the detune command signal are passed to a power input of the pre-amplifier and control a switch of the detune circuitry, respectively.

[0015] A back-end three-port network is used to pass the pre-amplified magnetic resonance signal from the single bi-modal connection to a receiver function of the digitizer and control system. In addition, the back-end three-port network is used to apply an electrical power signal and a detune command signal onto the single bi-modal connection towards the RF receiver coil circuit with detune / tune circuitry. In particular, the electrical power signal can be implemented as an RF power signal and the detune command signal can be formed as a (AM, FM or phase) modulation of the RF power signal. The back-end three-port network is used to combine the RF power signal and the detune command signal into a superimposed signal applied to the single bi-modal connection. The front-end three-port network serves to shield the pre-amplifier from the modulation representing the detune command signal.

[0016] The back-end three-port network is used to apply an injection RF signal formed as a DC power signal and a superimposed modulation representing a detune / tune signal onto the single bi-modal connection. The front-end three-port network is used to divide the modulated DC (power and detune / tune modulation) from the single bi-modal connection.

[0017] It has been found that single cable control of an MRI control loop is advantageous using a selection of a two-wire or coaxial signal to control a fully voltage controlled detune circuit. The method provides for efficient detuning of an MRI coil loop. Detection of the detune circuit is achieved via a non-linear device or by impedance switching at different frequencies.

[0018] An antenna comprises an electrical element that can typically receive and / or transmit a signal.

[0019] The digitizer and control system typically comprises a system that transforms (raw) data or further processes it into interpretable data, like image data that typically consists of two-dimensional gray scale images (also called "slices") for visualization of contrast. Thus, the digitizer and control essentially reconstructs the data that is acquired by the sensor system itself.

[0020] A duplexer typically frequency multiplexes two ports onto one port, but can multiplex more than two ports. As a passive device, a duplexer is typically reciprocal: the device does not have a concept of input or output. A duplexer typically comprises a different device than a passive combiner or splitter. The ports of a duplexer are frequency selective; the ports of a combiner are not.

[0021] Radio frequency (RF) switches, typically based on PIN diodes, are used to turn on and off the MR coil. Typically, a PIN diode typically comprises a diode with a wide, undoped intrinsic semiconductor region between a p-type and an n-type semiconductor region. The p-type and n-type regions are typically heavily doped in order to use them for ohmic contacts. The wide intrinsic region of a PIN diode contrasts with a normal p-n diode. The wide intrinsic region makes a PIN diode a poor rectifier - which is a typical function of a diode - but it makes it suitable for attenuators, fast switches, photodetectors, and high-voltage power electronics applications.

[0022] In a preferred embodiment, the radio frequency receiver system comprises a front-end duplexer that is on one side of a single twin-lead or coaxial connection pointing to the radio frequency coil circuit. Preferably, the front-end duplexer is configured to isolate the pre-amplifier from the detuning control and monitoring signal stream based on the injection radio frequency signal.

[0023] In a preferred embodiment, a back-end duplexer is on one side of a single twin-lead or coaxial cable pointing to the digitizer and control system. Preferably, the back-end duplexer is configured to isolate the digitizer and control system from other signals that are not needed by the digitizer and control system.

[0024] In a preferred embodiment, the back-end duplexer is configured to output the amplified magnetic resonance signal and to receive the injection radio frequency signal generated by the digitizer and control system. Thus, the back-end duplexer preferably outputs the amplified MR signal and receives the injection RF signal that is filtered to form a gate signal for a fully voltage controlled switch (i.e. FET) to switch the detuning circuit.

[0025] In another preferred embodiment, the front-end duplexer and the back-end duplexer are configured to isolate control signals, MR data, and electrical power. This further allows to use only a single (coaxial) cable as the main connection to the MR scanner and thus to reduce the cable connections by multiplexing different frequencies, and thus also to use different channels.

[0026] In another preferred embodiment, the digitizer and control system are configured to generate RF signals, which are modulated to control the tuning / de-tuning actor of the switch for the de-tuning circuit. Usually filtering and rectification are performed to correct the signal and obtain a signal with only a small or negligible deviation from the originally transmitted signal, as the data transmission suffers from many influences that unintentionally alter the original signal.

[0027] In another preferred embodiment, the de-tuning circuit comprises a non-linear device and / or an impedance that is switched over different frequencies. A non-linear device usually comprises an electrical component that has a characteristic response curve that is different from a linear curve. Thus, a non-linear component essentially has a response or output signal that is not simply proportional to the input signal. Impedance switching preferably comprises a change of a complex resistance (impedance). By this, a tuning or de-tuning effect can be achieved.

[0028] In another preferred embodiment, the switch of the de-tuning circuit comprises a field effect transistor. A field effect transistor (FET) is a type of transistor that uses an electric field to control and regulate the flow of electrical current in a semiconductor. A FET (JFET or MOSFET) is a device with the following three terminals: source, gate, and drain. The FET controls the flow of current by applying a voltage to the gate, which in turn alters the conductivity between the drain and source. In preferred embodiments, more than one FET is used, which allows for better switching performance. Such an array of FETs can usually be used in a single package in combination with control and / or potential monitoring logic. Single-pole single-throw (SPST) and single-pole double-throw (SPDT) are typical examples of such integrated circuits (ICs). The core switching actor can not only be a semiconductor, but also be based on other fully voltage-controlled technologies, such as MEMS (Micro-Electro-Mechanical System). SPST, SPDT, and MEMS-based devices are complex integrated circuits and can be used directly as switching actors.

[0029] In preferred embodiments, the de-tuning circuit is configured to be controlled by an external de-tuning command. This allows for external control and thus also for remote control, which is of high value in most applications. Preferably, the external de-tuning command originates from a system host.

[0030] In preferred embodiments, the de-tuning circuit comprises a boost circuit, which is used to match the requirements of the signal transmission and the tuning actor. This way, for example, the injection of RF power can be reduced. Usually, a boost circuit is a circuit that increases voltage, and it can be used as a voltage regulator that can be adjusted. The boost circuit can comprise a Zener-type circuit.

[0031] According to a further embodiment of the present application, the switch of the detuning circuit is monitored by the detection circuit. Preferably, the DC bias and / or the selection and / or control signal and / or the output of the switch is monitored by the MRI system. The respective parameters can be monitored in real time. In case of a fault, the MRI scan can be stopped.

[0032] In a preferred embodiment, the digitizer and control system comprises a digital synthesizer. The digital synthesizer is preferably a synthesizer that uses digital signal processing (DSP) technology to combine different signals and / or frequencies.

[0033] The present application also relates to a magnetic resonance imaging system comprising a processor, a memory for storing machine executable instructions and pulse sequence commands for execution by the processor, and a radio frequency receiver system that has been characterized.

[0034] The present application also relates to a method for controlling a radio frequency receiver system comprising the steps of: detecting a radio frequency signal with a radio frequency coil circuit; receiving a magnetic resonance signal from the radio frequency coil circuit with a preamplifier, the preamplifier sending an amplified signal to a digitizer and control system; switching the radio frequency coil circuit between a detuned state and a tuned state with a detuning circuit, wherein a single twin-lead or coaxial connection is used for transmitting electrical power to the preamplifier and for transmitting a detuning command signal to the detuning circuit.

[0035] The present application also relates to a method comprising the step of monitoring the detuning circuit by: (a) measuring the RF current in the shunt resonant detuning circuit, mixing the probe's signal with a pilot signal, and transmitting the mixed signal output back to the MR receiver channel's analog-to-digital converter or a separate dedicated input with a smaller dynamic range; or (b) feeding the probe's signal to the detector switch and detecting changes in frequency-selective impedance transitions during transmission at the output of the feed cable; or (c) the detector switch only grounding a DC voltage in case of a detected fault.

[0036] The detector switch is typically located between the probe or detector module and the twin-lead connection. Preferably, the detector switch comprises a FET or a semiconductor-based switch. BRIEF DESCRIPTION OF DRAWINGS

[0037] These and other aspects of the present application will become apparent upon reference to the following examples described below. Such examples do not necessarily represent the full scope of the present application, and therefore reference to the claims is necessary for determining its full scope.

[0038] In the drawings,

[0039] Figure 1A radio frequency receiver system according to a preferred embodiment of the present application is schematically depicted with a single RF loop, a single miniature coaxial cable or connector and remote RF injection for fast coil de-tuning, and

[0040] Figure 2 A second radio frequency antenna system according to a preferred embodiment of the present application is schematically depicted with individual coil elements using a single coaxial connector for fault detection.

[0041] List of reference signs:

[0042] Radio frequency receiver system 1

[0043] Radio frequency coil circuit 2

[0044] Pre-amplifier 3

[0045] Digitizer and control system 4

[0046] De-tuning circuit 5

[0047] Switch 6

[0048] Two-wire connection 7

[0049] Duplexer 8, 9

[0050] Boost circuit 10

[0051] Digital receiver / MR receive channel 11

[0052] RF de-tuning signal (Tx) 12

[0053] Blanking control 13

[0054] Detector 14

[0055] Notch filter 15

[0056] Individual coil elements 16 Detector switch 17 DETAILED DESCRIPTION

[0057] Figure 1 A radio frequency receiver system 1 according to a preferred embodiment of the present application is schematically depicted with a single radio frequency coil 2, a single miniature coaxial cable or connector 7 and remote radio frequency (RF) injection for fast coil de-tuning. As Figure 1As shown, a single coaxial connection 7 is used for the MRI preamplifier 3 and control of the detuning circuit 5. While the preamplifier 3 is supplied with a constant supply voltage (typically 9 V), the detuning circuit 5 is controlled via the injection RF signal generated by the transmitter. The RF control signal is injected into the coaxial connector via the front-end duplexer 8 and split in the radio frequency coil circuit 2 by a second duplexer, also called back-end duplexer 9. The switched RF signal is filtered and rectified to generate a DC gate voltage for the switch 6. A single radio frequency coil typically comprises a loop of wire as Figure 1 depicted. The conductor loop can also be built using a twin wire connection (like a coaxial cable) or a combination of distributed capacitors and discrete capacitors. The capacitors in the detuning circuit 5 can be local capacitors or distributed capacitors, transmission lines or any kind of device (coil, transmission line, etc.). The switching device 6 - typically a switch combined with an impedance - generates the on and off state of the coil. A voltage-step-up circuit 10, in particular a voltage multiplier of the Villard cascade, can be further applied to reduce the injection RF power, which in particular is used to match the signal transmission and the tuning of the actuator. For example, MEMS switches require high control voltages in the range of 100 V at almost zero current. Such high voltages are difficult to generate or to transmit or to duplex. The preamplifier 3 is isolated from the injection control signal via the front-end duplexer 8. A pulsed RF power of 50 mW can generate 1.58 V rms, which can be further increased using a passive voltage multiplier.

[0058] The transmitter for the RF pilot or selection signal is implemented as a digital synthesizer. The frequency, amplitude and phase can be controlled by a digital receiver 11. The digital receiver 11 typically comprises a fully integrated circuit, which contains the digital synthesizer, or the digital synthesizer is located remotely and routed to the digital receiver 11. The local digital synthesizer can be located at the digitizer and control system 4 and controlled via the digital receiver 11 or optically or galvanically by a further digital control signal. A further option is for example the use of a fixed analog signal and / or a quartz oscillator. The digitizer and control system 4 can be used to manage the tuning / detuning status timing and faults reported by the coil elements (16). Furthermore, it can be used to digitize the RX signal and generate the supply voltage for the preamplifier. The output to the right (see arrow in Figure 2 can be fed to a reconstructor (not shown). At the same time to / from a further not shown unit, it can receive control commands and synchronization signals. The signal generator 12 modulates its output according to the blank control 13. The duplexer 9 mixes the signals into one channel. In order to transmit all signals over a single twin wire connection, the DC signal control is enhanced and replaced by the coil's switching actuator from a two level DC signal (for example -5 / +5 V or 0 and 3 V) to a signal with a carrier as control demand.

[0059] The frequency of the RF de-tune signal TX 12 is chosen such that the three basic signals (DC pre-amplifier supply, RF de-tune signal (TX) and MRI (RX) signal) can be easily separated.

[0060] In a very simple setup, the RF de-tune signal (TX) signal is a simple (pulse) DC voltage superimposed to the DC pre-amplifier supply voltage. The pulse signal can be provided with the help of the digital receiver 11 and the blanking control signal 13. For example, if the coil is tuned or de-tuned, depending on the implementation of the RF de-tune signal 12, the signal high corresponds to de-tuned and low (blanked) to tuned, or vice versa. In a simple implementation, the RF de-tune signal 12 is a crystal oscillator with an amplifier for the oscillator output, then blanking means not amplifying the output when it is not needed.

[0061] A modular design can be applied to different MRI field strengths or nuclei. Furthermore, the amplitude of the switching carrier is adapted to the correct and safe control of the de-tune circuit (5).

[0062] It is also possible to modulate the pilot signal to optimize the switching behavior of the rectifier circuit and to reduce the delay.

[0063] In the following, three possibilities for monitoring the de-tune circuit 5 are described. Figure 2 An individual coil element is shown for fault detection using a single coaxial connector 7. The signal of the probe is fed to a FET transistor, which is shortened via a filter at the reference plane (position at the output at the pre-amplifier 3) of the coaxial connector 7. Changes in the frequency-selective impedance transition during transmission can be detected at the output of the feed cable.

[0064] A second possibility for monitoring the de-tune circuit 5 can be realized by measuring the current in the parallel resonant de-tune circuit - especially in the framework of SAR safety monitoring. The measurement can be performed by an inductive / capacitive coupling probe. The signal of the probe is mixed (non-linear device, diode, mixer) with the selection / pilot signal, and the mixed signal output is transmitted back to the ADC of the MR receive channel 11 or a separate dedicated input with a smaller dynamic range. For this option of monitoring the de-tune circuit, the FET and the notch filter 15 are replaced by a mixer.

[0065] A third possibility for monitoring the de-tune circuit 5 is that the switch 6 or field effect transistor (FET) only grounds the applied DC voltage in the presence of a fault. The DC voltage can be easily detected via a single coaxial cable or connector.

[0066] While the application has been illustrated and described in detail in the drawings and foregoing description, such illustration and description is to be considered illustrative or exemplary and not restrictive; the application is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practising the claimed application, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality. In the claims, the term "consisting of means "including and consisting of". Although features have been described in relation to only one or several embodiments, this does not mean that they cannot be used in other embodiments. In the claims, any reference signs placed between parentheses shall not be construed as limiting the scope of the claims. Furthermore, the dimensions of the various features in the drawings can not be to scale.

Claims

1. A radio frequency receiver system (1), comprising: Radio frequency coil circuit (2), a digitizer and control system (4) comprising a digital receiver (9), a single dual-mode connection (7) extending between a front-end three-port network (8) on the side of the single dual-mode connection (7) directed toward the radio frequency coil circuit (2) and a back-end three-port network (9) on the side of the single dual-mode cable directed toward the digitizer and control system (4); a preamplifier (3) configured to receive a magnetic resonance signal from the radio frequency coil circuit (2) and coupled between the radio frequency coil circuit (2) and the front-end three-port network (8), A detuning circuit (5) comprising a switch (6) configured to switch the radio frequency coil circuit between a detuned state and a tuned state based on a detuning command signal from a digital receiver received by the detuning unit (5), wherein The front-end three-port network is configured to: receive an amplified magnetic resonance signal from the preamplifier, apply the amplified magnetic resonance signal to the single dual-mode connection, receive the detuning command signal superimposed on the power signal from the single dual-mode connection, and forward the detuning command signal toward the detuning circuit, The back-end three-port network is configured to: receive the pre-amplified magnetic resonance signal from the single dual-mode connection and apply the amplified magnetic resonance signal to the digital receiver, receive the detuning control signal from the digitizer and control system (4) and apply the detuning command signal superimposed on the power signal to the single dual-mode connection (7), such that: The single dual-mode connection (7) is configured to transmit the electrical power carried by the power signal to the preamplifier (3), transmit the detuning command signal to the detuning circuit (5), and carry the amplified receive signal, and The front-end three-port network (8) is further configured to isolate the preamplifier (3) from the detuning control signal, The back-end three-port network (9) is further configured to output the amplified magnetic resonance signal towards the digital receiver and forward the detuning control signal towards the front-end in the form of an injection radio frequency signal generated by the digitizer and control system (4).

2. The radio frequency receiver system (1) according to claim 1, wherein The front-end three-port network and the back-end three-port network are configured as a duplexer (8).

3. The radio frequency receiver system (1) according to claim 1, wherein: The radio frequency receiver system (1) according to claim 2, wherein the front-end three-port network and the back-end three-port network are configured as a bias T circuit (8).

4. The radio frequency receiver system (1) according to claim 1, wherein: The front-end three-port network (8) and the back-end three-port network are configured to isolate control signals, MR data, and electrical power.

5. The radio frequency receiver system (1) according to any one of the preceding claims, wherein The digitizer and control system (4) is configured to generate an RF signal that is modulated to control a tuning / detuning actuator for the switch (6) of the detuning circuit.

6. The radio frequency receiver system (1) according to any one of the preceding claims, wherein The detuning circuit (6) comprises a non-linear device and / or an impedance that switches at different frequencies.

7. The radio frequency receiver system (1) according to any one of the preceding claims, wherein The switch (6) of the detuning circuit (5) comprises at least one field effect transistor.

8. The radio frequency receiver system (1) according to any one of the preceding claims, wherein The detuning circuit (6) is configured to be controlled by an external detuning command.

9. The radio frequency receiver system (1) according to any one of the preceding claims, wherein The detuning circuit (6) includes a voltage boost circuit (10) for matching signal transmission and tuning actuator requirements.

10. The radio frequency receiver system (1) according to any one of the preceding claims, wherein The digitizer and control system (4) includes a digital synthesizer.

11. A magnetic resonance imaging system comprising: processor, a memory for storing machine-executable instructions and pulse sequence commands for execution by the processor, and A radio frequency receiver system (1) according to any one of the preceding claims.

12. A method for controlling a radio frequency receiver system (1), comprising the following steps: Utilizing a radio frequency coil circuit (2) to detect radio frequency signals, receiving magnetic resonance signals from the radio frequency coil circuit (2) using a preamplifier (3), which sends the amplified signals to a digitizer and control system (4), The radio frequency coil circuit (2) is switched between a detuned state and a tuned state using a detuning circuit (5), wherein A single dual-mode connection (7) extends between a front-end three-port network (8) on the side of the single dual-mode connection (7) directed toward the radio frequency coil circuit (2) and a back-end three-port network (9) on the side of the single dual-mode cable directed toward the digitizer and control system (4); The single dual-mode connection is used to transmit electrical power to the preamplifier (3) and to transmit a detuning command signal to the detuning circuit (5).

13. The method of claim 12, comprising the step of monitoring the detuning circuit by: (a) Measure the RF current in the parallel resonant detuned circuit, mixing the probe signal with the pilot signal; and Transmitting the mixed signal output back to the analog-to-digital converter of the MR receiving channel (11) or a separate dedicated input section with a smaller dynamic range; or (b) feeding said signal from said probe to a detector switch (17), and detecting a change in a frequency selective impedance transition during transmission at an output of the feeder cable; or (c) The detector switch (17) connects the DC voltage to ground only when a fault is detected.

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