RF coil with integrated vital signs detector

Abstract

An RF transmit-receive coil (1) comprising a vital sign detector (3) is proposed, wherein the vital sign detector (3) is integrated in the RF transmit-receive coil (1), wherein a pair of conductive coil elements (4) of the RF transmit-receive coil (1) forms the vital sign detector (3), wherein the vital sign detector (3) is a capacitive vital sign detector (3), and the capacitive vital sign detector (3) is suitable for receiving capacitive vital sign signals. The present invention also relates to a system for detecting vital signs of a patient in a magnetic resonance (MR) imaging system, to a method system for operating a system for detecting vital signs of a patient in a magnetic resonance (MR) imaging system, to a software package for a magnetic resonance (MR) imaging system, and to a software package for upgrading a magnetic resonance (MR) imaging system.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency (RF) transmit-receive coils for magnetic resonance (MR) imaging systems, and in particular to radio frequency (RF) transmit-receive coils with integrated vital signs detectors. The present invention also relates to a system for detecting vital signs of a patient in a magnetic resonance (MR) imaging system, a method system for operating a system for detecting vital signs of a patient in a magnetic resonance (MR) imaging system, a software package for a magnetic resonance (MR) imaging system, and a software package for upgrading a magnetic resonance (MR) imaging system. Background Art

[0002] High-quality triggering in medical imaging, especially MR, is crucial for a large number of examinations, such as cardiac, abdominal or pelvic imaging. Only with a high-quality trigger signal can the imaging sequence be performed at equal exhalation states or equal points in the cardiac cycle, resulting in excellent image quality. Typically, dedicated sensors are used to record vital signs, which are expensive and prone to errors and misplacement. Today, ECG is used to determine the heartbeat and thus trigger the imaging device. However, ECG requires additional efforts to prepare the patient (installation and connection of electrodes, connection and activation of wireless transmitter). Capacitive electrodes for evaluating human biopotentials are a very attractive alternative to conventional electrically coupled electrodes for diagnostic applications, especially when the signal has to be measured through insulating materials such as cloth, which will greatly simplify the current process.

[0003] Capacitive electrodes are able to detect biopotentials with a significant gap between the sensor and the body, even through hair and clothing. In contrast to standard conductive electrodes, the surface of these electrodes is electrically insulated and therefore stable even in long-term applications. The metal electrodes of the sensor and the body surface are capacitively coupled, forming a capacitor. In this way, the capacitive electrodes detect the so-called offset current ID postulated by JC Maxwell to account for the magnetic field around the capacitor, which is proportional to the rate of change of the electric field associated with the ECG signal.

[0004] According to document EP 2020916 A2, a wireless patient monitor for MRI is known, in which a patient supported on a movable table can be positioned outside the bore of the magnet to receive a wireless patient monitor, which receives signals from the patient via leads. The patient can then be moved into the bore of the magnet using the wireless patient monitor, allowing continuous monitoring of the patient. The wireless patient monitor can be combined with its own power supply to transmit the monitored signals from the patient to a base station positioned near the magnet but outside the bore, such as by radio transmission signals. However, the patient monitor requires additional effort to prepare the patient, such as installing and connecting electrodes and connecting a wireless transmitter. Summary of the invention

[0005] An object of the present invention is to provide a radio frequency (RF) transmit-receive coil for a magnetic resonance (MR) imaging system, which has an integrated vital sign detector for detecting the vital signs of a patient within the magnetic resonance (MR), wherein contact sensors directly connected to the patient's body are replaced by a non-contact system for monitoring the vital signs, which makes it easier to measure the patient's vital signs.

[0006] Therefore, according to the present invention, a radio frequency (RF) transmit-receive coil for a magnetic resonance (MR) imaging system is provided, the RF transmit-receive coil comprising a vital sign detector for detecting vital signs of a patient within the magnetic resonance (MR) imaging system, wherein the vital sign detector is integrated in the RF transmit-receive coil, wherein a pair of conductive coil elements of the RF transmit-receive coil forms the vital sign detector, wherein the vital sign detector is a capacitive vital sign detector adapted to receive capacitive vital sign signals. The proposed system comprises a combination of an RF transmit-receive coil and a capacitive vital sign detector for real-time vital sign monitoring and simultaneous high-resolution imaging. The capacitive vital sign detector is constituted by the conductors of the RF transmit-receive coil. Thus, the method is completely passive, as it utilizes the measurement of local electric fields modified by body motion, in particular breathing and cardiac activity. Furthermore, the combined RF coil and capacitive vital sign sensor technology provides improved signal quality using cross-correlation between the systems, an improved calibration scheme or (spatial) guidance of one system using the other. In one embodiment of the invention, the magnetic resonance (MR) imaging system may also be a MR-therapy system, such as, for example, a MR-LINAC.

[0007] In one embodiment of the invention, the capacitive vital sign detector is an electrocardiogram (ECG) sensor adapted to receive ECG signals.

[0008] According to an embodiment of the present invention, pairs of conductive coil elements forming an RF transmit-receive coil of a vital sign detector are covered with a material having a high dielectric constant. In order to increase the capacitance of the detector to the human body, the electrodes can be covered with a material having a high dielectric constant, such as ceramic. The electrodes are integrated into the coil cover (close to the body surface) and therefore have no galvanic contact and are galvanically isolated from the human body. The capacitance of ECG depends on several factors, but typically corresponds to a relatively small value between 0.1–10 pF. For low-frequency measurements such as ECG, such weak coupling requires a high input impedance of the sensor, since the finite input resistance will attenuate the input voltage V inVery high impedance nodes are very susceptible to any electromagnetic interference from the environment and motion induced artifacts. Therefore, in an advantageous embodiment of the invention the electrodes may be actively shielded to suppress interference.

[0009] In another preferred embodiment of the present invention, the capacitive vital sign detector and the RF transmit-receive coil are adapted to process the capacitive vital sign signal and the MRI signal acquired by the RF transmit-receive coil in different frequency spaces.

[0010] In an embodiment of the invention, the vital sign detector is arranged below the patient support of a magnetic resonance (MR) imaging system. It is advantageous to arrange the detector below the patient support because the ECG can be received particularly well here. This position is also particularly advantageous for measuring the patient's movement and position.

[0011] In another aspect of the present invention, the object is achieved by a system for detecting patient vital signs in a magnetic resonance (MR) imaging system, the system comprising: a radio frequency (RF) transmit-receive coil having a vital sign detector, the system also comprising an output preamplifier for amplifying the capacitive vital sign signal, wherein the pair of conductive coil elements are coupled to the output preamplifier, the system also comprising a digital signal processor, wherein the digital signal processor is suitable for further processing the amplified capacitive vital sign signal.

[0012] According to a preferred embodiment, the digital signal processor is a software defined radio (SDR). An SDR typically includes analog-to-digital and digital-to-analog converters, RF components for sending and / or receiving signals, an FPGA for basic filtering, signal down-conversion and up-conversion, and a two-way wireless or optical output. The software resides in a computer, which runs in the computer and sends instructions to the SDR. The received signal is amplified, for example, by a preamplifier and then returned to the radio, where it can be further amplified or attenuated. The ADC converts the signal to a digital signal, where the FPGA and digital signal processor (DSP) handle the down-conversion and filtering of the digital signal. The data stream is then returned to the computer and real-time signal processing software.

[0013] According to another embodiment of the present invention, the system includes a relaxation oscillator and / or a microcontroller for capacitive vital sign signal detection.

[0014] In another preferred embodiment of the present invention, the system comprises a multiplexer for switching between different pairs of conductive coil elements forming the RF transmit-receive coil of the vital sign detector.

[0015] In another aspect of the present invention, the object is achieved by a method for operating a system for detecting vital signs of a patient in a magnetic resonance (MR) imaging system as described above, the method comprising the following steps:

[0016] providing a radio frequency (RF) transmit-receive coil including a vital sign detector, wherein the radio frequency (RF) transmit-receive coil and the vital sign detector form a magnetic resonance (MR) imaging coil array,

[0017] receiving at least one vital sign signal from the vital sign detector,

[0018] receiving at least one MRI signal from the radio frequency (RF) transmit-receive coil,

[0019] Correction is performed on the MRI signal according to the vital sign signal.

[0020] According to an embodiment of the present invention, the step of performing correction of the MRI signal based on the vital sign signal includes correction based on a deep learning algorithm.

[0021] In yet another aspect of the present invention, the object is achieved by a magnetic resonance (MR) imaging system, which comprises the system for detecting vital signs of a patient as described above.

[0022] In another aspect of the invention, the object is achieved by a software package for a magnetic resonance (MR) imaging system, wherein the software package comprises instructions for controlling a system for detecting vital signs of a patient in a magnetic resonance (MR) imaging system according to the above method.

[0023] In another aspect of the present invention, the object is achieved by a software package for upgrading a magnetic resonance (MR) imaging system, wherein the software package contains instructions for controlling a radio frequency (RF) receiver system according to the method described above, the radio frequency (RF) receiver system including a vital sign detector according to the present invention.

[0024] In embodiments of the present invention, AI-based software algorithms for selecting capacitive electrodes from sensor data and for configuring, for example, filter parameters based on training data obtained using the system are foreseen. Data can be processed and filtered using, for example, Kalman or SVD filtering. Data processing can be performed remotely in the cloud, for example. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] These and other aspects of the invention will be apparent and elucidated with reference to the embodiments described herein hereinafter.Such embodiments do not necessarily represent the full scope of the invention, however, and therefore reference is made to the claims and this document to interpret the scope of the invention.

[0026] In the attached picture:

[0027] Figure 1 A system for detecting vital signs according to an embodiment of the present invention is schematically depicted, the system comprising a radio frequency (RF) transmit-receive coil having a vital sign detector,

[0028] Figure 2 A system for detecting vital signs according to another embodiment of the present invention is schematically depicted, the system comprising a radio frequency (RF) transmit-receive coil having a vital sign detector,

[0029] Figure 3 schematically depicts a portion of a system for detecting vital signs according to another embodiment of the present invention,

[0030] Figure 4 Schematically depicts a flow chart of the signal flow of a vital sign detector and an RF transmit-receive coil according to an embodiment of the present invention,

[0031] Figure 5 A flow chart showing a method for operating a system for detecting vital signs according to an embodiment of the present invention is shown.

[0032] Figure 6 A vital sign detector patch having an RF transmit-receive coil and an impedance circuit according to an embodiment of the present invention is shown.

[0033] Figure 7 An RF coil array with separate hybrid RF transmit-receive coils and vital signs detector patches according to an embodiment of the present invention is shown.

[0034] Reference numerals list

[0035] Radio frequency (RF) transmit-receive coil 1

[0036] RF Amplifier 2

[0037] Capacitive vital signs detector3

[0038] Conductive coil element 4

[0039] Capacitive Vital Sign Sensor Amplifier5

[0040] ADC for vital signs signals 6

[0041] ADC for MRI signals 7

[0042] Signal processing unit 8

[0043] Interface 9

[0044] Matching and Detuning Circuits10

[0045] Diode 11

[0046] Relaxation Oscillator 12

[0047] Microcontroller 13

[0048] Multiplexer 14

[0049] Control signal 15

[0050] Vital Signs Detector Patch 16

[0051] Impedance circuit 17

[0052] RF coil array 18 DETAILED DESCRIPTION

[0053] Figure 1 A system for detecting vital signs according to an embodiment of the present invention is schematically depicted, the system comprising a radio frequency (RF) transmit-receive coil 1 with a vital sign detector 3. The conductor 4 of the radio frequency (RF) transmit-receive coil 1 forms a coupling capacitive electrode with the body, in the order of 5-20pF. The induced ECG signal can be measured as a change in capacitance. For example, a voltage signal is measured by capacitance and amplified via a high impedance preamplifier 5. In addition, the capacitance can be modulated by the movement of the body. With an RF coil array 18, each individual measurement signal depends on the local movement and the local ECG signal. The amplified signal is further digitally processed, for example, via an FPGA unit 8. The MRI signal of the RF transmit-receive coil 1 is received by a resonant coil circuit and amplified by an RF preamplifier 2. Due to the high impedance of the ECG preamplifier 5, the RF signal is not interfered with. The RF transmit-receive coil signal is further digitized and can be used for correction and calibration of the ECG signal, for example, to remove artifacts caused by motion.

[0054] Capacitive vital sign signals and MRI signals are processed in different frequency spaces. Therefore, in an embodiment of the present invention, two separate ADC channels 6, 7 may be provided. The output of the ADC is fed to a signal processing device 8. The signal processing device 8 may be, for example, a software defined radio (SDR). The signal processing device 8 may be used, for example, to correct motion artifacts in MRI signals by means of vital sign signals. An interface 9, such as an optical interface, controls the communication between the signal processing device 8 and other components of the MRI system. Other circuit schemes may also be implemented using only one general ADC. In another embodiment of the present invention, the capacitive sensor signal may be converted (or modulated) into a pilot tone and received by an MRI receiver or by a separate receiver of a different frequency.

[0055] Detecting movement, for example by breathing or heartbeat, is one application of the vital sign detector 3. Additionally, the capacitive vital sign signal may be simultaneously processed by other vital sign detectors such as cameras or radar sensors.

[0056] Figure 2 A system for detecting vital signs according to another embodiment of the present invention is schematically depicted, the system comprising a radio frequency (RF) transmit-receive coil 1 having a vital sign detector 3. Figure 2 In FIG. 1 , an RF transmit-receive coil 1 is shown with four capacitive conductors 4 forming a capacitive vital sign detector 3. The conductors 4 increase the capacitance of the ECG signal, while the MRI coil resonance is determined by the ring conductors and the lumped capacitors. The MRI signal is received by the conductive coil elements of the RF transmit-receive coil 1 and fed to a matching and detuning circuit 11, amplified by an RF amplifier 2 and further fed to an analog-to-digital converter (ADC) 7. The capacitive vital sign signal is received by the capacitive conductors and fed to a relaxation oscillator 12 or a microcontroller via two diodes 11 to detect the capacitive vital sign signal.

[0057] Figure 3 Schematically depicted is a part of a system for detecting vital signs according to another embodiment of the invention. In an embodiment of the invention, several conductive coil elements 4 forming an RF transmit-receive coil 1 of a vital sign detector 3 are foreseen. In order to be able to switch between different vital sign detectors 3, a multiplexer 14 is provided, which is controlled by a control signal 15, for example by a microcontroller 13. Furthermore, in this embodiment, a relaxation oscillator 12 can be provided to detect the vital sign signal.

[0058] Figure 4 A flow chart schematically depicts the signal flow of a vital sign detector and an RF transmit-receive coil 1 according to an embodiment of the present invention. In step 400, the vital sign signal from the vital sign detector 3 is analyzed. In step 410, the MRI signal from the RF transmit-receive coil 1 is analyzed. In step 420, the best signal is identified from the vital sign detector 3 or the RF transmit-receive coil 1. Thereafter, in step 430, a signal processing device 8, such as a software defined radio (SDR), is used to generate a correlation of the signals. An improved trigger signal can then be generated based on the vital sign signal 450 for improving the control of the MRI signal in step 470, for example using the correlation of the two signals. The vital sign signal can also be used to improve the MRI signal 440. For example, the overall signal quality can be improved by setting a range of interest, which also improves the MRI reconstruction in step 460.

[0059] Figure 5 A flow chart of a method for operating a system for detecting vital signs according to an embodiment of the present invention is shown.

[0060] The method starts at step 500, where a radio frequency (RF) transmit-receive coil 1 including a vital sign detector 3 is provided, wherein the radio frequency (RF) transmit-receive coil 1 and the vital sign detector 3 form a magnetic resonance (MR) imaging coil array.

[0061] In step 510 , at least one vital sign signal is received from the vital sign detector 3 .

[0062] In step 520 , at least one MRI signal is received from a radio frequency (RF) transmit-receive coil 1 .

[0063] In step 530 , correction of the MRI signal based on the vital sign signal is performed.

[0064] Figure 6 A vital sign detector patch 16 having an RF transmit-receive coil 1 and an impedance circuit 17 according to an embodiment of the present invention is shown. In order to increase the capacitance, the additional conductive coil elements 4 forming the vital sign detector 3 can be formed as a patch 16 and combined with the RF transmit-receive coil 1. The patch can be, for example, an ECG patch with electrocardiogram (ECG) sensors that are suitable for receiving ECG signals. Several patches 16 can be located within the circumference of the coil or partially under the coil. The patches 16 are separated from each other to prevent B1 shielding effects of the excitation field from the MR body transmit coil. The individual patches 16 are connected by an impedance circuit 17. The impedance circuit 17 can be an RF choke or a parallel resonant circuit with high impedance at MRI frequencies and low impedance at ECG and respiratory frequencies. In Figure 6 In the embodiment, the signals are amplified and processed by different optimized amplifiers 2, 5, such as low noise amplifiers (LNA).

[0065] Figure 7 An RF coil array 18 with individual hybrid RF transmit-receive coils 1 and vital sign detector patches 16 according to an embodiment of the invention is shown. Each coil 1 views an individual part of the human body. Individual signals of the vital sign detector patches 16 may be selected, for example, using a multiplexer.

[0066] Although the present invention has been illustrated and described in detail in the drawings and the foregoing description, such illustrations and descriptions should be considered illustrative or exemplary, rather than restrictive. The present invention is not limited to the disclosed embodiments. Those skilled in the art can understand and implement other variations of the disclosed embodiments when practicing the claimed invention by studying the drawings, the disclosure, and the claims. In the claims, the word "comprising" does not exclude other elements or steps, and the words "one" or "an" do not exclude multiple. Although specific measures are described in mutually different dependent claims, this does not indicate that a combination of these measures cannot be used to advantage. Any figure marks in the claims should not be interpreted as limiting the scope. In addition, for the sake of clarity, figure marks may not be provided on all elements in the drawings.

Claims

1. A radio frequency (RF) transmit-receive coil for a magnetic resonance (MR) imaging system, the RF transmit-receive coil comprising a vital sign detector (3) for detecting vital signs of a patient in the magnetic resonance (MR) imaging system, wherein: The vital sign detector (3) is integrated in the RF transmit-receive coil (1), wherein a pair of conductive coil elements (4) of the RF transmit-receive coil (1) forms the vital sign detector (3), wherein the vital sign detector (3) is a capacitive vital sign detector, the capacitive vital sign detector is suitable for receiving capacitive vital sign signals, wherein the vital sign detector is configured to measure breathing and / or cardiac activity, and wherein the capacitive vital sign detector is an electrocardiogram (ECG) sensor suitable for receiving ECG signals.

2. The radio frequency (RF) transmit-receive coil according to claim 1, wherein: The pair of conductive coil elements (4) forming the RF transmit-receive coil (1) of the vital sign detector (3) is covered with a material having a high dielectric constant.

3. A radio frequency (RF) transmit-receive coil according to any one of the preceding claims, wherein The capacitive vital sign detector and the RF transmit-receive coil (1) are suitable for processing the capacitive vital sign signal and the MRI signal collected by the RF transmit-receive coil (1) in different frequency spaces.

4. The radio frequency (RF) transmit-receive coil according to any one of claims 1 to 2, wherein: The vital sign detector (3) is arranged below a patient support of a magnetic resonance (MR) imaging system.

5. A system for detecting vital signs of a patient in a magnetic resonance (MR) imaging system, the system comprising: A radio frequency (RF) transmit-receive coil according to any one of claims 1 to 4, the radio frequency (RF) transmit-receive coil comprising a vital sign detector (3), the system further comprising an output preamplifier (5) for amplifying the capacitive vital sign signal, wherein the pair of conductive coil elements (4) are coupled to the output preamplifier (5), the system further comprising a digital signal processor (8), wherein the digital signal processor (8) is adapted to further process the amplified capacitive vital sign signal.

6. The system according to claim 5, wherein: The digital signal processor (8) is a software defined radio (SDR).

7. The system according to claim 5 or 6, comprising a relaxation oscillator (12) and / or a microcontroller (13) for the capacitive vital sign signal detection.

8. The system according to any one of claims 5 to 6, comprising a multiplexer for switching between different pairs of conductive coil elements (4) forming the RF transmit-receive coil (1) of the vital sign detector (3).

9. A method of operating a system for detecting vital signs of a patient in a magnetic resonance (MR) imaging system according to claim 5, comprising the steps of: A radio frequency (RF) transmit-receive coil (1) including a vital sign detector (3) is provided, wherein the radio frequency (RF) transmit-receive coil (1) and the vital sign detector (3) form a magnetic resonance (MR) imaging coil array, receiving at least one vital sign signal from the vital sign detector (3), receiving at least one MRI signal from the radio frequency (RF) transmit-receive coil (1), Correction is performed on the MRI signal based on the vital sign signal.

10. The method according to claim 9, characterized in that The step of performing correction on the MRI signal based on the vital sign signal includes correction based on a deep learning algorithm.

11. A magnetic resonance (MR) imaging system comprising a radio frequency (RF) transmit-receive coil according to any one of claims 1 to 4 or a system according to any one of claims 5 to 8.

12. A software package for a magnetic resonance (MR) imaging system, wherein: The software package comprises instructions for controlling a system for detecting vital signs of a patient within a magnetic resonance (MR) imaging system according to the method of any one of claims 9 to 10.

13. A software package for upgrading a magnetic resonance (MR) imaging system, wherein: The software package contains instructions for controlling a radio frequency (RF) transmit-receive coil (1) including a vital sign detector (3) according to the method of any one of claims 9 to 10.

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