Magnetic resonance radio frequency coil automatic matching system and magnetic resonance equipment

Abstract

The invention provides an automatic matching system for a magnetic resonance radio frequency coil and magnetic resonance equipment, and the system comprises the steps: obtaining the center frequency and the matching state of a radio frequency transmitting coil of a current scanning part before the scanning of the magnetic resonance equipment, detecting whether the obtained center frequency and the matching state meet set values or not, and generating a corresponding adjustment control signal if the obtained center frequency and the matching state do not meet the set values; and dynamically adjusting parameter values of reactance elements in the matching circuit until the center frequency and the matching state of the radio frequency transmitting coil at the current scanning part meet set values, and starting scanning by the magnetic resonance equipment. The matching circuit is adjusted in real time according to different human body loads and scanning parts, radio frequency coil parameter measurement and accurate matching control are achieved, and the method is suitable for a radio frequency high-power environment.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic resonance imaging, and in particular to a magnetic resonance radio frequency coil automatic matching system and a magnetic resonance device. Background Art

[0002] Magnetic Resonance Imaging (MRI) technology has become an important means in modern medical clinical diagnosis. The radio frequency system is an important part of magnetic resonance imaging, including two parts: a radio frequency transmission link and a receiving link. Among them, the radio frequency transmission coil in the transmission link emits radio frequency pulses to the human body to excite protons in the human body, causing them to rotate and generate resonance. The transmitting coil is a device used to excite the object to be measured with a large radio frequency signal to obtain a magnetic resonance signal. Saddle coils, solenoid coils, and Helmholtz coils can all be used as body transmitting coils. As a key component in the MRI system, the performance of the birdcage coil directly affects the imaging quality. Due to its ability to generate a very uniform transverse B1 field and being suitable for operating in the orthogonal mode, it has been widely used.

[0003] During the magnetic resonance scanning process, the weight and height of each patient are different, resulting in different equivalent loads for each patient. The equivalent load of a patient with a lighter weight is smaller, and the equivalent load of a patient with a heavier weight is larger. The same patient will also have different equivalent loads due to scanning different parts, for example, the equivalent loads of parts such as the head, knees, and ankles are smaller, while the equivalent loads of the chest, abdomen, and pelvis are larger. The difference in load will cause changes in the matching transmission of the radio frequency coil, including the center frequency and reflection coefficient of the coil.

[0004] Currently, the industry usually matches the radio frequency coil to a position with a larger equivalent load. For example, it is matched to the abdominal position of a 90KG human body, and the human body loads of other weights and parts are still scanned according to this matching. However, the problem is that the excessive reflected power causes low transmission efficiency and the center frequency deviation causes non-uniformity of the transmission field. Summary of the Invention

[0005] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a magnetic resonance radio frequency coil automatic matching system and a magnetic resonance device, which are used to solve the technical problem that the radio frequency coils of existing magnetic resonance devices cannot perform radio frequency circuit matching for all human body loads and various scanned parts at the same time.

[0006] To achieve the above and other related objectives, the present invention provides an automatic matching system for a magnetic resonance radio frequency coil, which is connected to a radio frequency transmitting coil in a magnetic resonance device. The system includes: a matching circuit, a frequency and matching state detection circuit, and a control device. Among them, the frequency and matching state detection circuit is used to obtain the center frequency and matching state of the radio frequency transmitting coil of the current scanning part. The control device is connected to the frequency and matching state detection circuit and is used to detect whether the center frequency and matching state of the radio frequency transmitting coil of the current scanning part meet the set values, and generate corresponding adjustment control signals when they do not meet the set values. The matching circuit is connected to the control device and is used to dynamically adjust the parameter values of its internal reactance elements according to the adjustment control signals until the center frequency and matching state of the radio frequency transmitting coil of the detected current scanning part meet the set values.

[0007] In an embodiment of the present invention, the frequency and matching state detection circuit includes: a directional coupler, an incident processing link, a reflection processing link, an analog-to-digital conversion device, and a calculation device. Among them, the incident radio frequency signal and the reflected radio frequency signal transmitted by a port of the radio frequency transmitting coil are separated by the directional coupler, and the incident radio frequency signal and the reflected radio frequency signal are respectively input to the incident processing link and the reflection processing link to measure the power amplitude, and the output signals of the two links are converted into digital signals by the analog-to-digital conversion device. The calculation device uses the converted digital signals and the reflected radio frequency signal to calculate the matching state and the center frequency.

[0008] In an embodiment of the present invention, both the incident processing link and the reflection processing link are provided with a detector and an amplifier circuit. Among them, the power of the input radio frequency signal is converted into a DC voltage by the detector in the link, and the converted DC voltage signal is amplified by the amplifier circuit for subsequent input to the analog-to-digital conversion device.

[0009] In an embodiment of the present invention, the calculation device obtains the power amplitudes of the incident radio frequency signal and the reflected radio frequency signal based on the digital signal output by the analog-to-digital conversion device, calculates the reflection coefficient to obtain the matching state of the radio frequency transmitting coil of the current scanning part, and analyzes the reflected radio frequency signal to obtain the center frequency of the radio frequency transmitting coil of the current scanning part.

[0010] In an embodiment of the present invention, the control device includes: a judgment module, configured to judge whether the center frequency and the matching state of the radio frequency transmitting coil of the current scanning part conform to a preset center frequency and a preset matching state; an adjustment module, connected to the judgment module, configured to, in case of non - conformity, determine the parameter values of each reactance element of the matching circuit measured currently based on the center frequency and the matching state of the radio frequency transmitting coil of the current scanning part, and adjust the parameter values of the reactance elements based on the preset parameter values of each reactance element of the matching circuit corresponding to the current scanning part; wherein, the preset parameter values of each reactance element of the matching circuit corresponding to the current scanning part are the parameter values of each reactance element of the matching circuit measured when the radio frequency transmitting coil of the current scanning part is in the preset center frequency and the preset matching state.

[0011] In an embodiment of the present invention, the matching circuit includes: one or more adjustable capacitor devices and an adjustable inductor device; the matching circuit controls the adjustable capacitor device and the adjustable capacitor device to dynamically adjust the capacitance value and the inductance value according to the adjustment control signal.

[0012] In an embodiment of the present invention, each adjustable capacitor device includes: a capacitor and a PIN diode connected in series with the capacitor; each adjustable inductor device includes: an inductor and a PIN diode connected in series with the inductor; the matching circuit controls the conduction or cut - off of the PIN diode through an adjustment control signal in the form of an electrical signal sent by the control device, and determines whether the corresponding capacitor or inductor is connected to the matching circuit, so as to adjust the capacitance value and the inductance value of the matching circuit.

[0013] In an embodiment of the present invention, the center frequency and the matching state of the radio frequency transmitting coil of the current scanning part can also be obtained through a directional coupler, a spectrometer system and a power amplifier.

[0014] To achieve the above - mentioned purpose and other related purposes, the present invention provides a magnetic resonance device, which includes: a radio frequency coil system, which includes: a transmission signal source, a radio frequency transmitting coil, and the automatic matching system of the magnetic resonance radio frequency coil connected between the transmission signal source and the radio frequency transmitting coil.

[0015] In an embodiment of the present invention, the device further includes: a magnet, a gradient coil system, a receiving coil system, a control and calculation system; wherein, the control and calculation system is connected to the gradient coil system, the receiving coil system and the radio frequency coil system, and is configured to control the gradient coil system, the receiving coil system and the control and radio frequency coil system to generate a magnetic field and receive magnetic resonance signals, and process the magnetic resonance signals received from the receiving coil system to obtain a magnetic resonance image.

[0016] As described above, the present invention is an automatic matching system for a magnetic resonance radio frequency coil and a magnetic resonance device, which has the following beneficial effects: Before the magnetic resonance device scans, the central frequency and matching state of the radio frequency transmitting coil of the current scanned part are obtained, and it is detected whether the obtained central frequency and matching state meet the set values. If they do not meet the set values, corresponding adjustment control signals are generated to dynamically adjust the parameter values of the reactance elements inside the matching circuit until the central frequency and matching state of the radio frequency transmitting coil of the current scanned part meet the set values, and then the magnetic resonance device starts scanning. The present invention adjusts the matching circuit in real time according to different human loads and scanned parts, realizes the measurement of radio frequency coil parameters and precise matching control, and is applicable to a high-power radio frequency environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It shows a schematic flow diagram of the automatic matching system for a magnetic resonance radio frequency coil in an embodiment of the present invention.

[0018] Figure 2 It shows a schematic flow diagram of the automatic matching process of the magnetic resonance radio frequency coil in an embodiment of the present invention.

[0019] Figure 3 It shows a schematic diagram of impedance matching in an embodiment of the present invention.

[0020] Figure 4 It shows a schematic diagram of frequency and matching state detection in an embodiment of the present invention.

[0021] Figure 5 It shows a schematic diagram of frequency and matching state detection in an embodiment of the present invention.

[0022] Figure 6 It shows a schematic structural diagram of a magnetic resonance device in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The following specific examples illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0024] It should be noted that in the following description, with reference to the accompanying drawings, several embodiments of the present invention are described. It should be understood that other embodiments may also be used, and mechanical composition, structure, electrical, and operational changes may be made without departing from the spirit and scope of the present invention. The following detailed description should not be considered restrictive, and the scope of the embodiments of the present invention is only defined by the claims of the published patent. The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. Spatially related terms, such as "upper", "lower", "left", "right", "below", "beneath", "lower part", "above", "upper part", etc., may be used in the text to facilitate the description of the relationship between one element or feature shown in the figure and another element or feature.

[0025] Throughout the specification, when it is said that a part is "connected" to another part, this includes not only the case of "direct connection" but also the case of "indirect connection" with other elements placed therebetween. In addition, when it is said that a certain part "includes" a certain constituent element, unless there is a particularly contrary record, it does not exclude other constituent elements, but means that other constituent elements may also be included.

[0026] The first, second, and third, etc. terms mentioned therein are used to describe various parts, components, regions, layers, and / or segments, but are not limited thereto. These terms are only used to distinguish one part, component, region, layer, or segment from other parts, components, regions, layers, or segments. Therefore, the first part, component, region, layer, or segment described below may refer to the second part, component, region, layer, or segment within the scope not exceeding the present invention.

[0027] Furthermore, as used herein, the singular forms "a", "an", and "the" are also intended to include the plural forms unless the context indicates otherwise. It should be further understood that the terms "comprise", "include" indicate the presence of the stated features, operations, elements, components, items, kinds, and / or groups, but do not exclude the presence, occurrence, or addition of one or more other features, operations, elements, components, items, kinds, and / or groups. The terms "or" and "and / or" used herein are interpreted as inclusive, or meaning any one or any combination. Thus, "A, B, or C" or "A, B, and / or C" means "any one of the following: A; B; C; A and B; A and C; B and C; A, B, and C". An exception to this definition only occurs when the combination of elements, functions, or operations is inherently mutually exclusive in some way.

[0028] The present invention provides an automatic matching system for a magnetic resonance radio frequency coil. Before the magnetic resonance device scans, it acquires the center frequency and matching status of the radio frequency transmitting coil of the current scanned part, and detects whether the acquired center frequency and matching status meet the set values. If they do not meet the set values, corresponding adjustment control signals are generated to dynamically adjust the parameter values of the reactance elements inside the matching circuit until the center frequency and matching status of the radio frequency transmitting coil of the current scanned part meet the set values, and then the magnetic resonance device starts scanning. The present invention adjusts the matching circuit in real time according to different human loads and scanned parts, realizes the measurement of radio frequency coil parameters and precise matching control, and is applicable to a high-power radio frequency environment.

[0029] The following will be a detailed description of the embodiments of the present invention with reference to the accompanying drawings, so that those skilled in the technical field of the present invention can easily implement it. The present invention can be embodied in many different forms and is not limited to the embodiments described herein.

[0030] As Figure 1 shows a schematic structural diagram of an automatic matching system for a magnetic resonance radio frequency coil in an embodiment of the present invention.

[0031] The automatic matching system for a magnetic resonance radio frequency coil is connected to the radio frequency transmitting coil in the magnetic resonance device. The function of the radio frequency transmitting coil is to generate a radio frequency magnetic field and provide the necessary radio frequency excitation for magnetic resonance imaging.

[0032] The automatic matching system for a magnetic resonance radio frequency coil includes: a matching circuit 1, a frequency and matching status detection circuit 2, and a control device 3;

[0033] The frequency and matching status detection circuit 2 is connected to the radio frequency transmitting coil. Its main function is to acquire the center frequency and matching status of the radio frequency transmitting coil of the current scanned part;

[0034] The control device 3 is connected to the frequency and matching status detection circuit 2 and the matching circuit 1. It can receive the center frequency and matching status of the radio frequency transmitting coil acquired by the detection circuit, and then compare this information with the set values. If the detected center frequency and matching status do not meet the set values, the control device 3 will generate corresponding adjustment control signals. These control signals will be sent to the matching circuit 1 to direct the matching circuit 1 to adjust the parameter values of the internal reactance elements.

[0035] Matching circuit 1, connected to the RF transmitting coil; since the input port of the RF transmitting coil needs impedance matching, the purpose is to conjugate-match the input impedance of the RF transmitting coil with the output impedance of the power amplifier in the pre-stage circuit, so as to ensure maximum power transfer and minimum reflection, and improve the energy utilization efficiency of the system. Matching circuit 2 will dynamically adjust the frequency and matching state of the RF transmitting coil by changing the parameter values of internal reactance elements (such as capacitors, inductors, etc.) according to the adjustment control signal sent by the control device 4. This adjustment of the matching state is crucial, as it can ensure that the RF transmitting coil effectively transfers energy to the RF receiving system of the magnetic resonance device, minimize losses such as energy reflection, and improve the imaging quality.

[0036] Such as Figure 2 , the specific working process of this solution includes:

[0037] Before the magnetic resonance scan starts, the frequency and matching state detection circuit 2 starts to work, and it will actively obtain the center frequency and matching state information of the RF transmitting coil of the current scanned part.

[0038] After receiving the information from the detection circuit, the control device 3 will make a judgment. It will compare the detected center frequency and matching state with the preset values. The preset values are determined according to the performance requirements of the magnetic resonance device. If the detected values do not meet the preset values, the control device 3 will generate an adjustment control signal.

[0039] After receiving the adjustment control signal sent by the control device 4, the matching circuit 2 will immediately start to adjust the parameter values of its internal reactance elements. This adjustment process is dynamic and continuous. The matching circuit 2 will continuously and precisely change the parameters of the reactance elements according to the requirements of the control signal. After each adjustment is completed, the frequency and matching state detection circuit 3 will re-collect the center frequency and matching state information of the RF transmitting coil 1 of the current scanned part again, and perform detection and judgment again to determine whether it meets the preset values. If it still does not meet the preset values, the control device 4 will continue to generate adjustment control signals, and the matching circuit 2 will continue to adjust the parameters of the reactance elements, and so on, until the center frequency and matching state of the RF transmitting coil 1 fully meet the preset values and start the magnetic resonance scan, providing a stable and efficient working environment for the subsequent magnetic resonance scan.

[0040] The present invention obtains the center frequency and matching status information of the RF transmitting coil in real time through a detection circuit. The control device 3 compares it with the set value and generates an adjustment signal. The matching circuit 1 dynamically adjusts the parameters of the internal reactance elements accordingly. After each adjustment, the detection circuit re-collects the information and cyclically judges the adjustment to ensure that the RF coil always maintains a good matching state throughout the scan, improving the imaging quality and scan efficiency, and effectively solving the problem that the RF coils of existing magnetic resonance devices cannot perform RF circuit matching for all human loads and all scanned parts at the same time.

[0041] In one embodiment, the RF transmitting coil can be a birdcage coil or other parallel transmitting coils, such as dipole coils, LOOP coils, and TEM coils. Using different types of coils is suitable for different scenarios and requirements.

[0042] Taking the birdcage coil as an example, the function and principle of the matching circuit are described in detail:

[0043] The birdcage coil consists of two end metal rings, a certain number of legs in the middle, and a series of capacitors, resembling a birdcage. It can be basically divided into three categories: low-pass type, high-pass type, and high-low pass hybrid type. During magnetic resonance scanning, due to different patient weights, heights, and scanned parts, the equivalent load is different, which will cause changes in the matching transmission of the birdcage coil, specifically manifested as changes in the center frequency and reflection coefficient of the coil. The power input port of the birdcage coil is the input port of the front-stage RF power amplifier power, and impedance matching is required. The purpose is to make the input impedance of the birdcage coil conjugate-match with the output impedance of the power amplifier of the front-stage circuit to achieve maximum power transmission and minimum reflection. As Figure 3 , the meaning of conjugate is that the source impedance Z S of the voltage source E is R s + jX S , composed of the resistance R s and the reactance X S in series. The load impedance Z L is R L + jX L , composed of the resistance R L and the inductance X L . Conjugate matching requires that the source impedance and the load impedance satisfy that the real parts are equal R s = R L , and the imaginary parts cancel each other out X s + X L = 0, that is, Z S is equal to the conjugate complex number of Z L . At this time, the signal transmission reflection is the smallest, and the load can obtain the maximum power from the power supply.

[0044] The parameter values of the internal reactance elements of the matching circuit 1 have a direct impact on the center frequency and reflection coefficient of the coil. The center frequency of the coil is mainly determined by the combination of inductance and capacitance. By changing the value of the inductance or capacitance, the resonant frequency of the coil can be adjusted, and thus the center frequency can be changed. The reflection coefficient is an index to measure the impedance matching degree. When the input impedance of the coil is conjugate-matched with the output impedance of the power amplifier, the reflection coefficient is the smallest and the matching state is the best. The matching circuit changes the input impedance of the birdcage coil by adjusting the parameter values of the internal reactance elements (such as capacitors and inductors), making it conjugate-matched with the output impedance of the power amplifier, so as to adjust the center frequency and reflection coefficient of the coil.

[0045] In one embodiment, as Figure 4 , the frequency and matching state detection circuit 2 includes: a directional coupler, an incident processing link, a reflection processing link, an analog-to-digital conversion device, and a calculation device;

[0046] The directional coupler is connected to the radio frequency transmitting coil and the signal source; when the signal source emits an incident radio frequency signal, the signal enters from the input port of the directional coupler. The incident radio frequency signal coupled out by the directional coupler is then transmitted to the incident processing link for subsequent operations such as power amplitude measurement. After the incident radio frequency signal reaches the radio frequency transmitting coil, due to the possible imperfect matching between the input impedance of the radio frequency transmitting coil and the transmission line impedance, part of the signal will be reflected back. The reflected signal propagates in the opposite direction to the incident signal and returns to the through port of the directional coupler. The reflected signal will generate electromagnetic coupling inside the directional coupler again. Since the incident signal and the reflected signal propagate in opposite directions, the directional coupler can distinguish these two signals and couple the reflected signal to the coupling port without interfering with the incident signal. The coupled reflected radio frequency signal is transmitted to the reflection processing link for measuring information such as its power amplitude.

[0047] Preferably, the directional coupler is designed based on a 50Ω microstrip line, and the coupling degree can be selected from 10dB to 20dB, and can be specifically adjusted according to the signal strength. A suitable coupling degree can ensure that when separating the incident and reflected signals, it will neither cause excessive attenuation to the original signal nor accurately separate the required signal. The directivity should be better than 15dB. High directivity can ensure that the directional coupler can better distinguish the incident and reflected signals, reduce the interference between signals, and improve the detection accuracy.

[0048] The incident processing link is connected to the directional coupler and measures the power amplitude of the incident radio frequency signal separated by the directional coupler;

[0049] The reflection processing link is connected to the directional coupler and measures the power amplitude of the reflected radio frequency signal separated by the directional coupler;

[0050] An analog-to-digital conversion device, connected to the incident processing link and the reflection processing link, is configured to convert the signals processed by the incident processing link and the reflection processing link into digital signals respectively;

[0051] A calculation device, connected to the analog-to-digital conversion device, is configured to calculate the center frequency and matching status of the radio frequency transmitting coil of the current scanned part based on the digital signals converted by the analog-to-digital conversion device and the reflected radio frequency signal through a specific algorithm.

[0052] In one embodiment, as Figure 4 , both the incident processing link and the reflection processing link are provided with a detector and an amplifier circuit; the detector is the core component for realizing the radio frequency signal power measurement in these two links. When the incident radio frequency signal and the reflected radio frequency signal enter the incident processing link and the reflection processing link respectively, the detector will convert their power into a DC voltage. When the detector converts the radio frequency signal power into a DC voltage, it needs to satisfy the square-law detection characteristic, that is, the voltage is proportional to the power. This characteristic has important practical significance, which ensures the accuracy and linearity of the measurement results. In practical applications, when the radio frequency signal power changes, according to the square-law detection characteristic, the output DC voltage will also change in proportion accordingly, so that the change of the radio frequency signal power can be accurately reflected, providing a reliable basis for subsequent circuit adjustment and status analysis. The detector can use the integrated detection chip AD8307 as the detector. AD8307 is a logarithmic detector, which can directly output a voltage proportional to the logarithm of the power. The logarithmic relationship has unique advantages in signal processing. It can compress a large range of power changes into a relatively small voltage range, which is convenient for the subsequent processing and analysis of the circuit.

[0053] After the detector converts the radio frequency signal power into a DC voltage, the converted DC voltage signal is usually very weak and difficult to be directly input into the analog-to-digital conversion device for processing. At this time, the amplifier circuit comes into play. It amplifies the converted DC voltage signal to make it reach the voltage range suitable for the input of the analog-to-digital conversion device. The amplifier circuit works in cooperation with the detector to ensure that the measurement signal can be accurately and effectively transmitted to the subsequent circuit, providing a guarantee for the normal operation of the entire detection circuit.

[0054] In one embodiment, the ways for the calculation device to obtain the matching status of the radio frequency transmitting coil of the current scanned part include:

[0055] First, receive the digital signals output by the analog-to-digital conversion device. The analog-to-digital conversion device converts the analog signals output by the incident processing link and the reflection processing link (where the radio frequency signal power has been converted into a DC voltage by the detector and amplified by the amplifier circuit) into digital signals. The calculation device analyzes and processes these digital signals to obtain the power amplitudes of the incident radio frequency signal and the reflected radio frequency signal. The power amplitude of the incident radio frequency signal reflects the magnitude of the energy input from the radio frequency power amplifier to the radio frequency transmitting coil, while the power amplitude of the reflected radio frequency signal reflects the magnitude of the energy reflected back due to impedance mismatch and other reasons during the transmission process. According to the obtained power amplitudes of the incident radio frequency signal and the reflected radio frequency signal, calculate the reflection coefficient to obtain the matching state of the radio frequency transmitting coil at the current scanned site.

[0056] The calculation device, based on the obtained power amplitude P of the incident radio frequency signal in and the power amplitude P of the reflected radio frequency signal ref , uses the formula: to calculate the reflection coefficient |S|. The reflection coefficient is a complex number, but in practical applications, usually its modulus value is concerned, and the modulus value range is between 0 and 1. When the reflection coefficient is close to 0, it indicates that almost all of the incident signal is absorbed by the radio frequency transmitting coil, and the reflected signal is very small, indicating that the matching state between the radio frequency transmitting coil and the previous-stage radio frequency power amplifier is good, and the energy transmission efficiency is high. On the contrary, when the modulus value of the reflection coefficient is close to 1, it means that most of the incident signal is reflected back, the matching state is poor, the energy transmission efficiency is low, and the matching circuit needs to be adjusted.

[0057] The center frequency of the radio frequency transmitting coil refers to its resonant frequency. At this frequency, the impedance characteristics of the coil are the best, and the energy transmission efficiency is the highest. When the frequency of the radio frequency signal deviates from the center frequency of the coil, the impedance of the coil will change, resulting in changes in the power amplitude and phase of the reflected signal. The ways for the calculation device to obtain the center frequency of the radio frequency transmitting coil at the current scanned site include: the calculation device performs a Fourier transform on the reflected radio frequency signal, converts it from the time domain to the frequency domain, and obtains the spectrum diagram of the reflected signal. In the spectrum diagram, the power distribution of the reflected signal can be observed, and the frequency point with the maximum power is the center frequency of the current radio frequency transmitting coil.

[0058] In one embodiment, the control device 3 includes:

[0059] A judgment module, used to judge whether the center frequency and the matching state of the radio frequency transmitting coil at the current scanned site meet the preset center frequency and the preset matching state; wherein, the preset center frequency and the preset matching state are determined according to factors such as the design requirements of the radio frequency transmitting coil, the application scenario, and the system performance indicators.

[0060] An adjustment module, connected to the judgment module, is configured to, when the judgment module determines that the center frequency and matching state of the radio frequency transmitting coil of the current scanned part do not conform to the preset values, first determine the parameter values of each reactance element (such as capacitors, inductors, etc.) of the matching circuit 1 measured currently based on the center frequency and matching state of the radio frequency transmitting coil of the current scanned part. The parameter values of these reactance elements directly affect the impedance characteristics of the radio frequency transmitting coil, and thus affect the center frequency and matching state. After determining the current reactance element parameter values, the adjustment module will compare them with the preset parameter values of each reactance element of the matching circuit corresponding to the current scanned part.

[0061] Since different human body parts (such as the head, chest, abdomen, etc.) have different tissue structures and electrical properties (such as dielectric constant, conductivity, etc.), these properties will affect the impedance of the radio frequency transmitting coil. By presetting parameter values for each scanned part, it can be ensured that the radio frequency transmitting coil can achieve the best matching state in different parts, thereby improving the imaging quality and efficiency. The impedance characteristics of the transmitting coil at the preset center frequency and preset matching state in different scanned parts are obtained through measurement. According to the measured impedance characteristics, combined with the topological structure of the matching circuit 1, the parameter values of each reactance element (inductor and capacitor) in the matching network are calculated using circuit theory, and then the preset parameter values of each reactance element of the matching circuit corresponding to the current scanned part are obtained.

[0062] The adjustment module will adjust the parameter values of the reactance elements in the matching circuit 1 according to the comparison result. The adjustment methods may include replacing reactance elements of different specifications, using adjustable reactance elements for adjustment, etc. After the adjustment is completed, the center frequency and matching state of the radio frequency transmitting coil of the current scanned part are obtained again through the frequency and matching state detection circuit 2. Then, the judgment module will make a judgment again. If it still does not conform to the set value, the adjustment module will continue to adjust the parameters according to the new measurement results, and so on in a loop until the center frequency and matching state of the radio frequency transmitting coil of the current scanned part meet the set values.

[0063] In an embodiment, the matching circuit 1 is composed of one or more adjustable capacitor devices and adjustable inductor devices, and the matching circuit is one of an L-type network, a T-type network, and a π-type network. The adjustable capacitor device and the adjustable inductor device can adjust the capacitance value and inductance value through mechanical, electronic and other means. For example, a mechanical variable capacitor changes the capacitance value by changing the distance or area between the plates, while an electronic variable capacitor can change its capacitance characteristics by controlling the voltage; a variable inductor can usually adjust the inductance value by changing the number of turns of the coil, the position of the magnetic core, etc. The matching circuit 1 controls the adjustable capacitor device and the adjustable inductor device according to the control signal to dynamically adjust the capacitance value and inductance value.

[0064] In one embodiment, since conventional electrically tunable inductors or capacitors do not support the operating state under high RF power, in order to achieve support for the operating state under high RF power, each adjustable capacitor device in this solution consists of a capacitor and a PIN diode connected in series with the capacitor. Each adjustable inductor device consists of an inductor and a PIN diode connected in series with the inductor. The PIN diode has unique electrical characteristics. When reverse-biased, it presents a high impedance, equivalent to an open circuit, and at this time the capacitor or inductor is not connected to the circuit; when forward-biased, it presents a low impedance, equivalent to a short circuit, and the capacitor or inductor is connected to the circuit. In this way, the PIN diode can be used to control whether the capacitor or inductor is connected to the matching circuit 1. The matching circuit 1 controls the conduction or cutoff of the PIN diode through an adjustment control signal in the form of an electrical signal sent by the control device 3.

[0065] In this solution, for each capacitor or inductor that needs to be transformed, an array form is adopted, and each inductor and capacitor are individually controlled by diodes. When it is necessary to increase the inductor or capacitor value, it is achieved by increasing the number of conducting PIN diodes. Similarly, when it is necessary to decrease the inductor or capacitor value, it is achieved by decreasing the number of conducting PIN diodes.

[0066] Taking the π-type impedance matching as an example, the π-type impedance matching circuit consists of a series inductor and two parallel capacitors. In the π-type matching circuit that supports high RF power operation, both the series inductor and the two parallel capacitors adopt the structures of the above-mentioned adjustable inductor device and adjustable capacitor device. Assume that in the initial state, some PIN diodes are conducting, so that the series inductor and the parallel capacitors have a certain amount of connection, and the circuit is in a preliminary matching state. When impedance mismatch is detected, the control device calculates the inductor and capacitor values that need to be adjusted according to the impedance measurement results. Then, by sending corresponding control signals, the conduction state of the PIN diodes is changed. If it is necessary to increase the series inductor value, the number of conducting PIN diodes in series with the series inductor is increased; if it is necessary to decrease the value of a certain parallel capacitor, the number of conducting PIN diodes in series with the parallel capacitor is decreased. By continuously adjusting the conduction state of the PIN diodes, the impedance of the matching circuit gradually approaches the target value, achieving good impedance matching.

[0067] In one embodiment, as Figure 5 , the center frequency and matching state of the RF transmitting coil at the current scanning site can also be obtained through a directional coupler, a power amplifier, and a spectrometer system; the directional coupler is connected to the transmission line between the power amplifier and the RF transmitting coil. The spectrometer system is connected to the power amplifier.

[0068] The spectrometer system comes with its own RF transmission and reception system. During the magnetic resonance scanning process, the spectrometer transmitter board emits a small RF signal of a specific frequency. This small RF signal is the starting signal for the entire detection process, and its frequency range and characteristics are preset according to the requirements of magnetic resonance scanning. Since the power of the small RF signal emitted by the spectrometer transmitter board is relatively low and cannot directly drive the RF transmitter coil to generate an RF magnetic field of sufficient intensity, it needs to be amplified by a power amplifier. The power amplifier can boost the power of the small RF signal to an appropriate level to meet the operating requirements of the RF transmitter coil. The amplified RF signal has sufficient energy to effectively excite the RF transmitter coil. The directional coupler can accurately separate the incident RF signal output from the power amplifier to the RF transmitter coil and the reflected RF signal reflected back from the RF transmitter coil. The incident signal and the reflected signal separated by the directional coupler are transmitted to the spectrometer receiver board. The spectrometer receiver board has high-precision signal acquisition capabilities and can accurately collect the power amplitudes of the incident signal and the reflected signal and calculate the center frequency and matching status of the RF transmitter coil at the current scanned location.

[0069] The present invention provides a magnetic resonance device. This magnetic resonance device focuses on the optimization of the RF coil system. By integrating a magnetic resonance RF coil automatic matching system, it effectively solves the problem that it is difficult for the RF coil in traditional devices to achieve precise RF circuit matching for different human loads and scanned locations, and improves the quality and efficiency of magnetic resonance imaging.

[0070] The RF coil system includes:

[0071] A transmission signal source responsible for generating small RF signals of specific frequencies, amplitudes, and phases. These signals are the basis of magnetic resonance imaging, and their frequency range is set according to the requirements of magnetic resonance scanning.

[0072] A magnetic resonance RF coil automatic matching system, which includes key components such as an RF transmitter coil, a frequency and matching status detection circuit, a control device, and a matching circuit, which are the same as those in the above embodiments.

[0073] To better describe the magnetic resonance device, the following embodiments are now used for illustration.

[0074] As Figure 6 , the magnetic resonance device includes:

[0075] A magnet 101, which is a static magnetic field magnet designed in the shape of a hollow cylinder, and a uniform static magnetic field is generated in its internal space; the static magnetic field magnet can be configured by using, for example, a permanent magnet or a superconducting magnet.

[0076] Gradient coil system, comprising: a gradient coil 102 and a gradient power supply 103 connected to the gradient coil; the gradient coil 102 also forms a hollow cylindrical shape and is installed inside the magnet 101. The gradient coil 103 receives power supply through the gradient power supply 103 and generates a gradient magnetic field on the basis of the static magnetic field.

[0077] Radio frequency coil system, comprising: a signal transmitter 104, a radio frequency transmitting coil 105, and an automatic matching system 106 for magnetic resonance radio frequency coils; wherein, the automatic matching system 106 for magnetic resonance radio frequency coils is connected between the signal transmitter 104 and the radio frequency transmitting coil 05; the radio frequency transmitting coil 105 is placed on the inner wall of the gradient coil 102, and its function is to amplify the radio frequency small signal generated by the signal transmitter 104 and convert it into a radio frequency magnetic field. The automatic matching system 106 for magnetic resonance radio frequency coils is consistent with the above embodiment, that is, it performs automatic matching of radio frequency coils, so it will not be elaborated here.

[0078] Receiving coil system, comprising: a receiving coil 107 and a receiving unit 108; the receiving coil 107 is a local receiving coil, and the local receiving coil is placed inside the radio frequency coil 105 to form an aperture for the patient to enter, so that the coil is placed on the human body surface for receiving magnetic resonance (MR) signals emitted by the patient. The receiving unit 107 is connected to the receiving coil 107 and is responsible for amplifying, filtering, and digitizing the received magnetic resonance signals. The receiving unit 107 converts the analog magnetic resonance signals into digital signals and transmits them to the control and computing system 109 for further processing.

[0079] The control and computing system 109 is connected to the gradient power supply 103, the signal transmitter 104, and the receiving unit 108, and has control functions and image processing functions; wherein, the control functions include controlling the operation of the gradient 103, the radio frequency transmitting coil 105, and the receiving coil gradient power supply 103, the signal transmitter 104, and the receiving unit 108. By precisely controlling the output of the gradient power supply 103, the generation and switching of the gradient magnetic field are realized; by controlling the parameters of the signal transmitter 104 and the working state of the radio frequency transmitting coil 105, the generation and adjustment of the radio frequency magnetic field are realized; by controlling the operation of the receiving unit 108, the accurate reception and processing of the magnetic resonance signals are realized. The image processing functions include: processing the magnetic resonance signals received from the receiving unit 108, including operations such as signal reconstruction, filtering, and correction. By applying specific algorithms and mathematical models, the received magnetic resonance signals are converted into visual magnetic resonance images.

[0080] The specific working process of the magnetic resonance device includes:

[0081] The patient lies flat on the hospital bed, and the hospital bed slowly sends the patient into the aperture of the receiving coil 107. Before magnetic resonance scanning, the radio frequency transmitting coil is first controlled for matching through the automatic matching system of the magnetic resonance radio frequency coil, and magnetic resonance scanning starts after the center frequency and matching status of the radio frequency transmitting coil meet the set values. The control and calculation system 109 controls the gradient power source 103 to generate a gradient magnetic field and the signal transmitting source 104 to generate a radio frequency small signal according to the preset scanning sequence and parameters, and converts it into a radio frequency magnetic field through the radio frequency transmitting coil 105 to excite hydrogen protons in the human tissue to generate magnetic resonance signals. The receiving coil 107 receives the magnetic resonance signals emitted by the human body and transmits them to the receiving unit 108 for processing. The receiving unit 108 transmits the processed digital signals to the control and calculation system 109. The control and calculation system 109 performs image reconstruction and processing on the received magnetic resonance signals, generates the final magnetic resonance image, and displays it on the computer screen for doctors to diagnose and analyze.

[0082] In summary, for the automatic matching system of the magnetic resonance radio frequency coil and the magnetic resonance device of the present invention, before the magnetic resonance device scans, the center frequency and matching status of the radio frequency transmitting coil of the current scanning part are obtained, and it is detected whether the obtained center frequency and matching status meet the set values. If not, a corresponding adjustment control signal is generated to dynamically adjust the parameter values of the reactance elements inside the matching circuit until the center frequency and matching status of the radio frequency transmitting coil of the current scanning part meet the set values, and then the magnetic resonance device starts scanning. The present invention adjusts the matching circuit in real time according to different human loads and scanning parts, realizes parameter measurement and precise matching control of the radio frequency coil, and is applicable to the radio frequency high-power environment. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0083] The above embodiments are only used to exemplarily illustrate the principles and effects of the present invention, rather than to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. An automatic matching system for a magnetic resonance radio frequency coil, characterized in that, Connected to the radio frequency (RF) transmitting coil in a magnetic resonance device, the system includes: a matching circuit, a frequency and matching state detection circuit, and a control device; Among them, the frequency and matching state detection circuit is used to obtain the center frequency and matching state of the RF transmitting coil of the current scanned part; The control device, connected to the frequency and matching state detection circuit, is used to detect whether the center frequency and matching state of the RF transmitting coil of the current scanned part meet the set values, and generate corresponding adjustment control signals when they do not meet the set values; The matching circuit, connected to the control device, is used to dynamically adjust the parameter values of its internal reactance elements according to the adjustment control signal until the adjusted center frequency and matching state of the RF transmitting coil of the current scanned part meet the set values.

2. The automatic matching system for a magnetic resonance radio frequency coil according to claim 1, wherein The frequency and matching state detection circuit includes: a directional coupler, an incident processing link, a reflection processing link, an analog-to-digital conversion device, and a calculation device; Among them, the directional coupler separates the incident RF signal and the reflected RF signal transmitted by a port of the RF transmitting coil, and inputs the incident RF signal and the reflected RF signal into the incident processing link and the reflection processing link respectively to measure the power amplitude, and converts the output signals of the two links into digital signals through the analog-to-digital conversion device. The calculation device uses the converted digital signals and the reflected RF signal to calculate the matching state and the center frequency.

3. The automatic matching system of a magnetic resonance radio frequency coil according to claim 2, wherein Both the incident processing link and the reflection processing link are provided with a detector and an amplifier circuit; wherein, the link converts the power of the input RF signal into a DC voltage through the detector, and amplifies the converted DC voltage signal through the amplifier circuit for subsequent input to the analog-to-digital conversion device.

4. The automatic matching system for a magnetic resonance radio frequency coil according to claim 2, wherein The calculation device obtains the power amplitudes of the incident RF signal and the reflected RF signal based on the digital signal output by the analog-to-digital conversion device, and calculates the reflection coefficient to obtain the matching state of the RF transmitting coil of the current scanned part; at the same time, analyzes the reflected RF signal to obtain the center frequency of the RF transmitting coil of the current scanned part.

5. The automatic matching system of the magnetic resonance radio frequency coil according to claim 1, characterized in that The control device includes: A judgment module, used to judge whether the center frequency and matching state of the RF transmitting coil of the current scanned part conform to the preset center frequency and preset matching state; An adjustment module, connected to the judgment module, is used to, in case of non-conformity, determine the parameter values of each reactance element of the current measured matching circuit based on the center frequency and matching state of the RF transmitting coil of the current scanned part, and adjust the parameter values of the reactance elements based on the preset parameter values of each reactance element of the matching circuit corresponding to the current scanned part; wherein, the preset parameter values of each reactance element of the matching circuit corresponding to the current scanned part are the parameter values of each reactance element of the matching circuit measured when the RF transmitting coil of the current scanned part is in the preset center frequency and preset matching state.

6. The automatic matching system for a magnetic resonance radio frequency coil according to claim 1, wherein The matching circuit includes: one or more adjustable capacitor devices and adjustable inductor devices; the matching circuit controls the adjustable capacitor device and the adjustable capacitor device to dynamically adjust the capacitance value and the inductance value according to the adjustment control signal.

7. The automatic matching system for a magnetic resonance radio frequency coil according to claim 6, wherein Each adjustable capacitance device includes: a capacitance and a PIN diode connected in series with the capacitance; each adjustable inductance device includes: an inductance and a PIN diode connected in series with the inductance; the matching circuit controls the conduction or cutoff of the PIN diode through an adjustment control signal in the form of an electrical signal sent by the control device, and determines whether the corresponding capacitance or inductance is connected to the matching circuit to adjust the capacitance value and inductance value of the matching circuit.

8. The automatic matching system for a magnetic resonance radio frequency coil according to claim 1, wherein The center frequency and matching state of the radio frequency transmit coil at the current scanning site can also be obtained through a directional coupler, a spectrometer system, and a power amplifier.

9. A magnetic resonance device, characterized in that, The device includes: a radio frequency coil system, which includes: a transmit signal source, a radio frequency transmit coil, and a magnetic resonance radio frequency coil automatic matching system as described in any one of claims 1 to 8 connected between the transmit signal source and the radio frequency transmit coil.

10. The magnetic resonance device according to claim 9, characterized in that, The device further includes: a magnet, a gradient coil system, a receive coil system, a control and calculation system; wherein, the control and calculation system is connected to the gradient coil system, the receive coil system, and the radio frequency coil system, and is used to control the gradient coil system, the receive coil system, and the control and radio frequency coil system to generate a magnetic field and receive magnetic resonance signals, and to process the magnetic resonance signals received from the receive coil system to obtain magnetic resonance images.

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