Magnetic resonance radio frequency coil and control method thereof

Abstract

The invention discloses a magnetic resonance radio frequency coil, which is characterized in that by sampling the output voltage of a DC-DC converter and comparing the output voltage with a reference voltage, a clock signal of the DC-DC converter is switched so as to maintain the stability of the output voltage, and the feedback mechanism is beneficial to quickly responding to the change of the output voltage of the magnetic resonance radio frequency coil. And the ripple noise generated by voltage fluctuation is further reduced. A circuit configured by connecting a feedback capacitor and a feedback resistor in series is connected between the output end and the forward phase input end of the voltage comparator, so that relatively strong oscillation is prevented, and the stability of the output voltage of the magnetic resonance radio frequency coil is ensured.

Description

Technical Field

[0001] The present invention relates to the field of medical devices, and specifically to a magnetic resonance radio frequency coil and its control method. Background Art Nuclear magnetic resonance imaging equipment (hereinafter referred to as MRI equipment) is a medical imaging technology based on the principle of nuclear magnetic resonance (NMR). It uses magnetic fields and radio frequency waves to form images of human anatomy or physiological processes. MRI equipment uses very strong magnetic fields, usually with field strengths between 0.2 and 7 Tesla, which causes the hydrogen nuclei (protons) in the human body to align along the magnetic field direction. These hydrogen nuclei have spin characteristics and respond to the external magnetic field. When the equipment applies a radio frequency pulse, these hydrogen nuclei absorb energy and deviate from their original alignment direction, and this process is called resonance. After the radio frequency pulse stops, the hydrogen nuclei gradually return to their initial state, and at the same time, they release energy, which is detected by the receiver in the equipment in the form of a radio frequency signal. Through complex signal processing methods such as Fourier transform, these signals are converted into visual images, and the computer reconstructs the collected signals to generate detailed tomographic images of different cross-sections, thereby helping doctors observe and analyze the internal structure of the human body from multiple angles.

[0002] The MRI equipment mainly consists of five parts: a magnet system (main magnet), a gradient system, a radio frequency system, a control system, and an operation support system. Among them, the radio frequency system emits radio frequency pulses to make the magnetized protons absorb energy to generate resonance, and receives the energy released by the protons during the relaxation process to generate NMR signals. However, due to the instability of the power supply during the power supply process of the existing radio frequency coil, ripple noise and harmonic noise will be generated, which affect the reception and transmission of NMR signals, and further affect the magnetic resonance imaging effect. Summary of the Invention

[0003] In view of the deficiencies of the prior art, the present invention provides a magnetic resonance radio frequency coil and its control method.

[0004] To achieve the above object, the present invention provides the following technical solutions: On the one hand, a magnetic resonance radio frequency coil is provided.

[0005] A magnetic resonance radio frequency coil, which is applied to a magnetic resonance imaging device, is characterized in that the magnetic resonance radio frequency coil includes a processing circuit, and the processing circuit includes at least a radio frequency coil and a stable power supply device. The stable power supply device includes a power supply, a DC-DC converter, a first filter, and a second filter; the DC-DC converter includes a voltage divider. The radio frequency coil is used to obtain the nuclear magnetic resonance signals emitted by the human body. The output terminal of the power supply is connected to the first filter. The input and output terminals of the DC-DC converter are respectively connected to the first filter and the second filter. The stable power supply device provides stable power supply for the radio frequency coil through the output terminal of the second filter.

[0006] Preferably, the DC-DC converter at least includes a PWM controller and a feedback unit. The PWM controller is used to control the switching of the clock signal from the first clock signal to the second clock signal according to the feedback voltage from the feedback unit.

[0007] Preferably, the duty cycle of the first clock signal is less than that of the second clock signal.

[0008] Preferably, the DC-DC converter further includes a voltage divider, and the voltage divider is used to distribute the feedback voltage V1 from the feedback unit to a preset detection voltage.

[0009] Preferably, the feedback unit at least includes a comparator, and determines whether to switch the clock signal by comparing the voltage detected by the voltage divider with a preset reference voltage.

[0010] Preferably, when the voltage detected by the feedback unit is higher than the reference voltage, the first clock signal is selected; otherwise, the second clock signal is selected.

[0011] Preferably, the comparator includes a feedback capacitor and a feedback resistor. The feedback capacitor and the feedback resistor are in series, and the feedback capacitor and the feedback resistor are connected between the output terminal and the non-inverting input terminal of the comparator.

[0012] Preferably, the magnetic resonance radio frequency coil further includes a compensation unit. The input terminal of the compensation unit is connected to the output terminal of the DC-DC converter, and the output terminal of the compensation unit is connected to the input terminal of the PWM controller.

[0013] Preferably, the magnetic resonance radio frequency coil stabilizes the output voltage of the magnetic resonance radio frequency coil and reduces the ripple of the output voltage by introducing the compensation unit.

[0014] On the one hand, a control method for a magnetic resonance radio frequency coil is provided.

[0015] A control method for a magnetic resonance radio frequency coil, the magnetic resonance radio frequency coil includes a processing circuit, and the processing circuit performs the following steps: Providing a stable power supply voltage for the radio frequency coil by performing first filtering at the input terminal of the DC-DC converter and second filtering at the output terminal of the DC-DC converter, and controlling the switching of the clock signal from the first clock signal to the second clock signal according to the feedback voltage at the output terminal of the processing circuit; wherein the duty cycle of the first clock signal is less than that of the second clock signal.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) The magnetic resonance radio frequency coil of the present invention uses the output voltage of the DC-DC converter to accurately control and reduce the ripple noise of the DC-DC converter, which can indirectly reduce the generation of ripple noise in the magnetic resonance radio frequency coil.

[0017] (2) The magnetic resonance radio frequency coil of the present invention samples the output voltage of the DC-DC converter and compares it with the reference voltage, thereby adjusting the clock duty cycle of the DC-DC converter to maintain the stability of the output voltage. This feedback mechanism helps to quickly respond to changes in the output voltage of the magnetic resonance radio frequency coil and further reduce the ripple noise generated by voltage fluctuations.

[0018] (3) The magnetic resonance radio frequency coil of the present invention is configured by connecting a circuit in which a feedback capacitor C2 and a feedback resistor R3 are connected in series between the output terminal and the non-inverting input terminal of the power supply comparator to prevent relatively strong oscillations and ensure the stability of the output voltage of the magnetic resonance radio frequency coil.

[0019] (4) The magnetic resonance radio frequency coil of the present invention stabilizes the control system by introducing a compensation unit and reduces the ripple of the output voltage. By adjusting the parameters of the compensation unit, the dynamic response of the control system can be optimized, and the ripple noise can be further reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of a nuclear magnetic resonance imaging device provided by the present invention; Figure 2 It is a schematic diagram of a magnetic resonance radio frequency coil provided by the present invention; Figure 3 It is another schematic diagram of a magnetic resonance radio frequency coil provided by the present invention; Figure 4 It is a circuit diagram of a device for stably supplying power to a magnetic resonance radio frequency coil provided by the present invention; Figure 5 It is another circuit diagram of a device for stably supplying power to a magnetic resonance radio frequency coil provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0022] Embodiment 1 As Figure 1As shown, this embodiment provides a magnetic resonance radio frequency coil, which includes: The MRI device 101 includes an inner cavity 102 and a wireless communication unit 108. Inside the inner cavity 102, a non-magnetic bed 103 is arranged parallel to the setting surface of the MRI device 101. The RF coil device 105 is wound around the measurement part of the subject 104 that is statically placed on the bed 103. In this way, the RF coil device 105 is arranged inside the inner cavity 102 of the MRI device 101.

[0023] In this state, the MRI device 101 emits a static magnetic field (not shown), a gradient magnetic field (not shown), and a radio frequency magnetic field 106. Then, the RF coil device 105 measures the weak NMR signal 107 generated from the subject 104 by the radio frequency magnetic field 106. The RF coil device 105 is wirelessly connected to the wireless communication unit 108 of the MRI device 101, and transmits the measurement data obtained by digitizing the measured NMR signal 107 to the MRI device 101 (or an image processing device (not shown)) through the transmission line 109. Then, the transmitted measurement data is converted into an image in the MRI device 101 (or an image processing device (not shown)).

[0024] The wireless communication unit 108 is fixed outside the MRI device 101, for example, and performs beyond-line-of-sight communication with the RF coil device 105 inside the hole 102. At this time, the wireless communication unit 108 performs wireless communication using a frequency higher than the frequency of the NMR signal 107. For example, the wireless communication unit 108 performs wireless communication using a 2.4 GHz band wireless local area network (LAN) surrounded by expected electromagnetic waves. As long as the frequency band of the wireless communication used by the wireless communication unit 108 does not overlap with the frequency band of several tens to several hundreds of MHz used by the radio frequency magnetic field 106, wireless communication using a higher frequency can also be used, such as a 5 GHz band wireless LAN. The wireless communication method of the wireless communication unit 108 is not limited to communication through a wireless LAN, and can also be wireless communication using the industrial, scientific, and medical (ISM) band, or wireless communication using sub-millimeter waves, millimeter waves, or visible light. However, when using high frequencies, the straight-line propagation ability of electromagnetic waves is enhanced. Therefore, it is best to separately arrange the wireless communication unit 108 from the MRI device 101 so that the wireless communication unit 108 can perform line-of-sight communication with the RF coil device 105.

[0025] Embodiment 2 As Figure 2 shown, this embodiment provides a schematic diagram of a magnetic resonance radio frequency coil. The magnetic resonance radio frequency coil includes a radio frequency coil 201, a low noise amplifier (LNA) 202, a low pass filter 203, an analog-to-digital conversion 204, a communication module 205, a control module 206, a battery 207, a filter 208, and a DC-DC converter 209.

[0026] The NMR signal generated by the subject 104 placed in the hole 102 by the radio frequency coil 201. Specifically, the radio frequency coil 201 includes a plurality of coils connected in parallel, and the NMR signal is obtained by measuring the change in the current value excited when the NMR signal generated by the subject 104 passes through the loops of each coil as an analog electrical signal.

[0027] The low-noise amplifier 202 performs low-noise amplification processing on the NMR signal. Here, the NMR signal is usually very weak and is interfered by various noise sources. Therefore, using a low-noise amplifier can effectively improve the signal-to-noise ratio of the MRI signal, thereby improving the quality of the NMR signal.

[0028] The low-pass filter 203 filters the NMR signal. When the MRI device is working, it is necessary to measure the response of the measured object in the radio frequency field. This process is very vulnerable to external electromagnetic noise interference. The filter only allows signals of specific frequencies to pass through, thereby effectively shielding interference signals of other frequencies, thus improving the accuracy and reliability of the measurement.

[0029] The analog-to-digital converter 204 obtains measurement data by converting the analog electrical signal corresponding to the filtered NMR signal into a digital signal. The measurement data is sent to the MRI device 101 (or an image processing device (not shown)) as a measurement result through the communication module 205.

[0030] In this embodiment, the control module 206 controls the transmission and processing process of the NMR signal. This magnetic resonance radio frequency coil is powered by the battery 207. The battery 207 is connected to the input end of the DC-DC converter 209. A filter is used at the output end of the DC-DC converter to filter out the ripple component in the output voltage.

[0031] As Figure 3 shown, this embodiment provides another schematic diagram of a magnetic resonance radio frequency coil. The magnetic resonance radio frequency coil includes a radio frequency coil 301, a low-noise amplifier (LNA) 302, a low-pass filter 303, an analog-to-digital conversion 304, a communication module 305, a control module 306, a battery 307, a first filter 308, a DC-DC converter 309, and a second filter 310. In this embodiment, the components 301-307 have the same functions as the components 201-207. The difference is that a second filter 310 is added to the input end of the DC-DC converter 309, that is, filters are connected to both the input end and the output end of the DC-DC converter 309, thereby filtering out the ripple component in the output voltage and minimizing the ripple component in the output voltage as much as possible.

[0032] Embodiment 3 As Figure 4As shown, it is the circuit diagram of the stable power supply device for the magnetic resonance radio frequency coil provided by the present invention. The stable power supply device includes a first filter 401, a DC-DC converter 402, and a second filter 403. The input end of the first filter is connected to the input voltage Vin. The input end of the DC-DC converter 402 is connected to the first filter 401. The output end of the DC-DC converter 402 is connected to the second filter 403. The voltage of the magnetic resonance radio frequency coil power supply device is output as Vo through the second filter 403.

[0033] In order to be able to provide stable power supply for the magnetic resonance radio frequency coil, in this embodiment, the DC-DC converter 402 is improved. A feedback mechanism is introduced into the DC-DC converter 402, that is, the output voltage V1 is sampled at the output end of the DC-DC converter 402, and then the voltage Va after voltage division is input to the positive-phase input end of the voltage comparator CMP1 through the voltage divider 404. The reverse-phase input end of CMP1 is connected to the reference voltage Vref. The output end of the voltage comparator CMP1 is connected to the clock selector 406. The output end of the clock selector 406 is connected to the PWM controller, and the PWM controller controls the conduction of the field effect transistor P1.

[0034] Specifically, the voltage divider 404 distributes the feedback voltage V1 from the feedback unit 405 to the preset detection voltage Va. The voltage divider 404 consists of two resistors, and the distribution ratio of the feedback is: the voltage V1 is appropriately set in advance. For example, at the initial drive, the detection voltage Va is set to be lower than the reference voltage Vref of the subsequent voltage comparator CMP1. After the initial drive, the detection voltage Va is determined by the voltage comparator CMP1, and the voltage distribution ratio is set to be higher than the reference voltage Vref.

[0035] Then, the voltage comparator CMP1 compares the voltage Va detected by the voltage divider 404 with the preset reference voltage Vref to determine whether the drive is initial and outputs a comparison result signal. For example, when the detection voltage Va is lower than the reference voltage Vref, a low level is output, while when the detection voltage Va is higher than the reference voltage Vref, a high level is output.

[0036] The clock selector 406 can be configured to convert one of the first clock signal and the second clock signal according to the comparison result signal of the comparator CMP1 and select one of the clock signals to output to the PWM controller 407.

[0037] The PWM controller supplies a pulse-width modulation signal to the boost circuit 408. In the high-level case, when the detected voltage Va is higher than the reference voltage Vref, that is, when the feedback voltage V1 is higher than the preset internal reference voltage, the duty cycle is reduced according to the voltage difference, and the duty cycle of the pulse-width modulation signal is further reduced. The duty cycle of the pulse-width modulation signal acts on the boost circuit 408 to reduce the input voltage Vin to the preset voltage. Otherwise, in the low-level case, when the detected voltage Va is lower than the reference voltage Vref, that is, when the feedback voltage V1 is lower than the preset value, the duty cycle is increased according to the voltage difference, and the duty cycle of the pulse-width modulation signal is further increased. The PMOS transistor is turned off, and the pulse-width modulation signal acts on the boost circuit 408 to increase the input voltage Vin to the preset voltage.

[0038] In this embodiment, the DC-DC converter samples the output voltage V1 and compares it with the reference voltage Vref, thereby adjusting the clock signal of the DC-DC converter to maintain the stability of the output voltage. This feedback mechanism using the output voltage control of the DC-DC converter helps to quickly respond to changes in the output voltage and further reduce the ripple noise generated by voltage fluctuations.

[0039] In addition, the positive input terminal and the output terminal of the voltage comparator of the feedback unit 405 in this embodiment are connected by a feedback resistor R3 and a feedback capacitor C3 in series, which can form a filter circuit. According to the values of the resistor and the capacitor and their positions, a high-pass filter / low-pass filter circuit can be formed respectively. Adding such a filter circuit at the input terminal or the output terminal of the comparator can filter out unnecessary frequency components. The circuit configured by connecting the feedback capacitor C2 and the feedback resistor R3 in series is connected between the output terminal and the positive input terminal of the comparator, which helps to prevent the comparator from generating oscillations or instability phenomena under high-frequency signals and improves the performance of the power supply circuit.

[0040] In this embodiment, a control method for a magnetic resonance radio frequency coil is also provided. The magnetic resonance radio frequency coil includes a processing circuit as follows Figure 4 The processing circuit performs the following steps: Provide a stable power supply voltage for the radio frequency coil by performing first filtering 401 and second filtering 403 at the input and output of the DC-DC converter 402 respectively. When the detected voltage Va is lower than the reference voltage Vref, control the clock signal to switch from the first clock signal to the second clock signal; the duty cycle of the first clock signal is less than the duty cycle of the second clock signal.

[0041] Embodiment 4 As Figure 5 shown, Figure 5Another circuit diagram of the power supply device for stabilizing the magnetic resonance radio frequency coil provided by the present invention. In order to provide stable power supply for the magnetic resonance radio frequency coil, in this embodiment, the DC-DC converter is improved, and a compensation mechanism is introduced into the DC-DC converter, that is, a compensation unit 508 is introduced at the output end of the DC-DC converter. The compensation unit 508 includes a voltage boosting circuit 511, a PWM controller 510, a compensator 512, and a power supply unit 514 of the compensation unit. The output voltage Vo generates the input voltage V3 of the compensation unit according to the voltage division of resistors R8 and R9. The comparator CMP3 detects the voltage V3. When V3 > Vref1 and V3 > Vref2, both the voltage comparator CMP3 and the second comparator CMP4 output low levels, the PMOS transistor ST1 conducts, and the NMOS transistor ST2 cuts off. The power supply unit 514 enters the charging state, and the charging current is output to the feedback voltage V4 node, which is the inverting input node of the operational amplifier of the compensator 512. Due to the influence of the error voltage Ve of the compensator 512, the feedback voltage of the DC-DC converter drops significantly, so as to quickly output the output voltage Vo, which drops and enters the steady state. When V3 < Vref1 and V3 < Vref2, both the voltage comparator CMP3 and the second comparator CMP4 output high levels, the PMOS transistor ST1 cuts off, and the NMOS transistor ST2 conducts. The power supply unit 514 enters the discharging state, and the discharging current is output to the feedback voltage V4 node of the compensator 512, and the error voltage of the compensator 512 is reduced, Ve increases significantly, and the DC-DC converter performs feedback through the error voltage Ve, so that the output voltage Vo increases rapidly and enters the normal state.

[0042] The PWM controller 513 receives the error voltage Ve and generates a pulse width modulation signal. The PWM controller acts on the boost circuit 509 with the pulse width modulation signal to extend the discharge time of the capacitor C2 and further increase the output voltage. In this embodiment, by introducing the compensation unit 508, the output voltage is stably controlled and the ripple of the output voltage is reduced. By adjusting the parameters of the compensation unit, specifically, the values of the capacitor C4, the resistors R4, R6, and R7 can be adjusted to optimize the dynamic response of the control system and further reduce the ripple noise.

[0043] In summary, a magnetic resonance radio frequency coil proposed by the present invention samples the output voltage of a DC-DC converter and compares it with a reference voltage, thereby adjusting the clock duty cycle of the DC-DC converter to maintain the stability of the output voltage. This feedback mechanism helps to quickly respond to changes in the output voltage of the magnetic resonance radio frequency coil and further reduces the ripple noise generated by voltage fluctuations. A circuit configured by connecting a feedback capacitor and a feedback resistor in series is connected between the output terminal and the positive-phase input terminal of a power comparator to prevent strong oscillations and ensure the stability of the output voltage of the magnetic resonance radio frequency coil. The magnetic resonance radio frequency coil of the present invention stabilizes the control system by introducing a compensation unit and reduces the ripple of the output voltage. By adjusting the parameters of the compensation unit, the dynamic response of the control system can be optimized and the ripple noise can be further reduced.

[0044] It should be noted that the technical features in the above embodiments can be combined arbitrarily, and the combined technical solutions all fall within the protection scope of this application. And in this article, terms such as "including", "comprising" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, article or device including the said element.

[0045] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A magnetic resonance radio frequency coil, which is applied to a magnetic resonance imaging device, characterized in that: The magnetic resonance radio frequency coil includes a processing circuit, the processing circuit includes at least a radio frequency coil and a stable power supply device, the stable power supply device includes a power supply, a DC-DC converter, a first filter and a second filter; the DC-DC converter includes a voltage divider; The radio frequency coil is used to obtain nuclear magnetic resonance signals emitted by the human body; The output end of the power supply is connected to the first filter, the input and output ends of the DC-DC converter are respectively connected to the first filter and the second filter, and the stable power supply device provides stable power supply to the radio frequency coil through the output end of the second filter.

2. The magnetic resonance radio frequency coil according to claim 1, characterized in that The DC-DC converter at least includes a PWM controller and a feedback unit, wherein the PWM controller is used to control the clock signal to switch from a first clock signal to a second clock signal according to a feedback voltage from the feedback unit.

3. The magnetic resonance radio frequency coil according to claim 2, characterized in that The duty cycle of the first clock signal is smaller than the duty cycle of the second clock signal.

4. The magnetic resonance radio frequency coil according to claim 2, characterized in that The DC-DC converter further includes a voltage divider, which is used to divide the feedback voltage V1 from the feedback unit into a preset detection voltage.

5. The magnetic resonance radio frequency coil according to claim 4, characterized in that The feedback unit at least includes a comparator, which determines whether to switch the clock signal by comparing the voltage detected by the voltage divider with a preset reference voltage.

6. The magnetic resonance radio frequency coil according to claim 4, characterized in that When the voltage detected by the feedback unit is higher than the reference voltage, the first clock signal is selected; otherwise, the second clock signal is selected.

7. The magnetic resonance radio frequency coil according to claim 2, characterized in that: The comparator includes a feedback capacitor and a feedback resistor, the feedback capacitor and the feedback resistor are connected in series, and the feedback capacitor and the feedback resistor are connected between the output terminal and the non-inverting input terminal of the comparator.

8. The magnetic resonance radio frequency coil according to claim 2, characterized in that: The magnetic resonance radio frequency coil further includes a compensation unit, an input end of the compensation unit is connected to an output end of a DC-DC converter, and an output end of the compensation unit is connected to an input end of a PWM controller.

9. The magnetic resonance radio frequency coil according to claim 8, characterized in that The magnetic resonance radio frequency coil stabilizes the output voltage of the magnetic resonance radio frequency coil and reduces the ripple of the output voltage by introducing the compensation unit.

10. A method for controlling a magnetic resonance radio frequency coil, the magnetic resonance radio frequency coil comprising a processing circuit, the processing circuit performing the following steps: Providing a stable supply voltage for the radio frequency coil by performing a first filtering at the input end of the DC-DC converter and a second filtering at the output end of the DC-DC converter; When the detection voltage Va is lower than the reference voltage Vref, the control clock signal is switched from the first clock signal to the second clock signal; The duty cycle of the first clock signal is smaller than the duty cycle of the second clock signal.

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