An active electrode system for magnetic particle magnetoacoustic tomography

Abstract

The application discloses an active electrode system for magnetic particle magneto-acoustoelectric imaging, comprising an active electrode module, an ultrasonic excitation module and an intelligent controller module. The active electrode module comprises six pairs of active electrodes, each of which is composed of an electrode sensor and a signal conditioning module; the signal conditioning module comprises a preamplification circuit, a filter circuit and a secondary amplification circuit; the intelligent controller module controls the ultrasonic excitation module to rotate around the measured object and emit ultrasonic excitation, and controls the corresponding active electrode pair to collect magnetic particle magneto-acoustoelectric signals. The application provides an active electrode system capable of improving the quality of magnetic particle magneto-acoustoelectric signals, realizing efficient and automatic multi-angle data collection, improving imaging efficiency and solving the problems of low signal-to-noise ratio of magnetic acoustic electric signal collection, insufficient adaptation of wideband and high impedance signal source in the prior art and the like.

Description

Technical Field

[0001] This invention relates to the field of biomedical imaging technology, and more specifically to an active electrode system for magnetic particle magnetoacoustic-electric imaging. Background Technology

[0002] The magneto-acousto-electrical-tomography of magnetic nanoparticles with Electrode Detection (MAET-ED) method addresses the challenges of classical magnetic particle imaging, such as excessive electromagnetic excitation from DC gradient magnetic fields and alternating magnetic fields, equipment fragility, and limited clinical application. Its principle involves using external ultrasound signals to excite magnetic nanoparticles within the tissue, causing them to vibrate and thus cutting a static magnetic field to generate an induced electromotive force. Electrodes are then used to acquire the electrical signals generated by these magnetic particles, reconstructing an image of their distribution within the tissue. [Hou X, Yan X, Chen W, et al. Magneto-Acousto-Electrical-Tomography of Magnetic Nanoparticles With Electrode Detection[J]. IEEE Transactions on Instrumentation and Measurement, 2025.]

[0003] The main characteristics of magnetoacoustic signals from magnetic particles are: signal amplitude at the μV level, frequency range of 1.8MHz to 2.7MHz, and center frequency around 2.25MHz. These signals are extremely weak and easily drowned out by environmental electromagnetic noise. Clearly, electrode detection plays a crucial role in magnetic particle magnetoacoustic imaging technology; the quality of the voltage signal detected by the electrodes directly affects the subsequent reconstruction of the magnetic particle concentration distribution image.

[0004] Currently, the electrodes described in the experimental systems of the patent applications filed by Wu Sanxi et al., "A Sector-Scanning Magnetoacoustic-Electro-Imaging Device and Method Based on Ultrasonic Excitation" (Patent No.: 202110928424.4), and Chen Xin et al., "A Magnetoacoustic-Electro-Imaging Method, System, Equipment, Medium and Product" (Patent No.: 202511756535.6), are all passive electrodes, such as Ag / AgCl electrodes and sheet electrodes. By connecting them with long wires, not only is significant transmission line parasitic capacitance introduced, reducing signal bandwidth, but the signal also suffers severe external electromagnetic interference during transmission, resulting in a sharp drop in signal-to-noise ratio (SNR), which seriously affects and restricts imaging quality.

[0005] Therefore, there is an urgent need for a tailored, parameter-specific, and immediately implementable active electrode system solution for MAET-ED technology. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an active electrode system for magnetoacoustic-electric imaging of magnetic particles. This system achieves efficient and automated multi-angle data acquisition, simplifies the operation process, and improves the practicality and efficiency of imaging. Through integrated design, it shortens the signal path, suppresses electromagnetic interference, adapts to the microvolt-level broadband signal detection requirements of MAET technology, enhances environmental adaptability, and solves problems such as low signal-to-noise ratio in magnetoacoustic-electric signal acquisition and insufficient compatibility with broadband and high-impedance signal sources in existing technologies.

[0007] On one hand, according to an embodiment of this application, an active electrode system for magnetoacoustic-electric imaging of magnetic particles includes: an active electrode module, an ultrasonic excitation module, and an intelligent controller module, wherein: the active electrode module is used to acquire magnetoacoustic-electric signals of magnetic particles and amplify and filter them; each pair of active electrodes is arranged in a straight line opposite each other on the surface of the object under test, and the arrangement angle between each pair of adjacent active electrodes is 30°; the ultrasonic excitation module is used to provide ultrasonic excitation to the object under test, enabling the magnetic nanoparticles to complete forced vibration; the intelligent controller module is used to control the ultrasonic excitation module to move around the object under test, while simultaneously emitting ultrasonic excitation to the object under test, and controlling the corresponding active electrode pairs to acquire magnetoacoustic-electric signals of magnetic particles.

[0008] According to one aspect of the embodiments of this application, the active electrode module includes an electrode sensor (3), a signal conditioning module (2), and a power supply module (7) for supplying power to the signal conditioning module (2); the input stage of the signal conditioning module (2) is directly electrically connected to and physically adjacent to the electrode sensor (3), and integrates a preamplifier circuit (4), a filter circuit (5), and a secondary amplification circuit module (6). Wherein: the active electrode sensor (3) contacts the test object containing magnetic particles to obtain the magnetic particle magnetoacoustic signal and transmits it to the preamplifier circuit (4); the preamplifier circuit (4) performs initial amplification processing on the magnetic particle magnetoacoustic signal collected by the active electrode sensor (3) and then transmits it to the filter circuit (5); the filter circuit (5) performs high-pass and low-pass filtering on the magnetic particle magnetoacoustic signal output by the preamplifier circuit (4) and transmits it to the secondary amplification circuit (6); the secondary amplification circuit (6) amplifies the electrical signal filtered by the filter circuit (5) to a preset multiple and then transmits it to the oscilloscope.

[0009] On the other hand, an active electrode system for magnetoacoustic-electromagnetic imaging of magnetic particles provided according to an embodiment of this application further includes a shielding housing for sealing the active electrode signal conditioning module. The interface portion of the shielding housing adopts a waterproof aviation plug, and the pins of the aviation plug are soldered one-to-one with the power supply pins and signal output pins of the signal conditioning module to prevent the insulation liquid from corroding the circuit and the system from electromagnetic interference to the circuit.

[0010] According to one aspect of the embodiments of this application, the preamplifier circuit (4) mainly includes a differential amplifier chip, a first resistor, a second resistor, a third resistor, a fourth resistor, a gain resistor, and a feedback resistor; the non-inverting input terminal of the differential amplifier chip is grounded through the second resistor and connected to the positive output terminal of the electrode sensor; the inverting input terminal of the differential amplifier chip is grounded through the first resistor and connected to the negative output terminal of the electrode sensor; the feedback pin is grounded through the gain resistor and simultaneously connected to the output terminal through the feedback resistor; the fourth resistor is connected to the output terminal of the differential amplifier chip; the resistance value of the first resistor is equal to the resistance values ​​of the second resistor and the third resistor, and is twenty times the resistance value of the fourth resistor; the resistance value of the feedback resistor is one hundred times the resistance value of the gain resistor.

[0011] According to one aspect of the embodiments of this application, the filtering circuit (4) includes a first filtering unit and a second filtering unit; the first filtering unit mainly includes a voltage feedback operation chip one, a fifth resistor, a sixth resistor, a seventh resistor, a ninth capacitor, and a tenth capacitor; the signal is input to the non-inverting input terminal of the voltage feedback operation chip one, the ninth capacitor and the tenth capacitor are connected to the non-inverting input terminal and grounded through the fifth resistor, one end of the sixth resistor is between the ninth capacitor and the tenth capacitor, and the other end is located at the output terminal of the voltage feedback operation chip one; the inverting input terminal of the voltage feedback operation chip one is connected to its own output terminal through the seventh resistor to form a feedback loop; the capacitance values ​​of the ninth capacitor and the tenth capacitor are equal, and the resistance values ​​of the fifth resistor, the sixth resistor, and the seventh resistor are unequal.

[0012] The second filtering unit mainly includes a voltage feedback operational chip two, an eighth resistor, a ninth resistor, a tenth resistor, a fifteenth capacitor, and a sixteenth capacitor. The signal is input to the non-inverting input terminal of the voltage feedback operational chip two. The ninth and tenth resistors are connected to the non-inverting input terminal and grounded through the sixteenth capacitor. One end of the fifteenth capacitor is between the ninth and tenth resistors, and the other end is located at the output terminal of the voltage feedback operational chip two. The inverting input terminal of the voltage feedback operational chip two is connected to its own output terminal through the eighth resistor to form a feedback loop. The resistance values ​​of the ninth and tenth resistors are equal, and the capacitance value of the fifteenth capacitor is twice that of the sixteenth capacitor. The resistance values ​​of the seventh and eighth resistors are equal.

[0013] According to one aspect of the embodiments of this application, the secondary amplification circuit (4) includes a first amplification unit and a second amplification unit; the first amplification unit mainly includes a voltage feedback operational chip three, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, and a twenty-sixth capacitor; the non-inverting input terminal of the voltage feedback operational chip three is grounded through the fifteenth resistor, and the sixteenth resistor is connected between the output terminal and the inverting input terminal of the voltage feedback operational chip three; the twenty-sixth capacitor is connected to the inverting input terminal of the voltage feedback operational chip three; the resistance values ​​of the fourteenth resistor and the fifteenth resistor are equal, and the resistance value of the sixteenth resistor is one hundred times the resistance value of the fourteenth resistor.

[0014] The second amplification unit mainly includes a voltage feedback operational chip four, an eleventh resistor, a twelfth resistor, a thirteenth resistor, and a twenty-first capacitor. The non-inverting input terminal of the voltage feedback operational chip four is grounded through the twelfth resistor, and the eleventh resistor is connected between the output terminal and the inverting input terminal of the voltage feedback operational chip four. One end of the thirteenth resistor is connected to the eleventh resistor, and the other end is connected to the inverting input terminal of the voltage feedback operational chip four. The twenty-first capacitor is connected to the non-inverting input terminal of the voltage feedback operational chip four. The resistance of the twelfth resistor is ten times that of the thirteenth resistor, and the resistance of the thirteenth resistor is approximately nine times that of the thirteenth resistor. The capacitance values ​​of the twenty-first capacitor and the twenty-sixth capacitor are equal.

[0015] According to one aspect of the embodiments of this application, the differential amplifier chip includes an AD8129 amplifier; the voltage feedback operation chip one, voltage feedback operation chip two, and voltage feedback operation chip four include an OPA842 amplifier; the total voltage gain of the magnetic particle magnetoacoustic signal acquired by the active electrode system reaches approximately 100 dB, which can effectively amplify the magnetic particle magnetoacoustic signal at the microvolt (μV) level to the volt (V) level, meeting the input range requirements of the subsequent data acquisition module.

[0016] In summary, the beneficial technologies of this application are as follows: The active electrode system of this invention enables efficient and automated multi-angle data acquisition, improving the practicality and efficiency of imaging; by deploying active electrode pairs (spaced 30° apart), in conjunction with a rotatable ultrasound excitation module, and linked with an intelligent controller, automated circular scanning is achieved. The intelligent controller only needs to control the ultrasound excitation module to rotate 30° and automatically switch to the active electrode pair connected to the corresponding angle (90° to the ultrasound excitation module) to complete the data acquisition for the next angle. This transforms complex manual electrode switching and angle alignment into simple controller commands, significantly improving the automation, repeatability, and efficiency of data acquisition, laying the foundation for rapid imaging and clinical translation.

[0017] The active electrode module of this invention integrates the preamplifier, filter, and secondary amplification circuits directly with the electrode sensor and houses them within a shielded enclosure. Simultaneously, it employs precise pin connections and a shortest-path wiring design, significantly shortening the signal path and effectively suppressing interference introduced by cables and environmental electromagnetic noise. This makes it particularly suitable for microvolt-level signal detection in MAETs, achieving a higher signal-to-noise ratio and wider signal bandwidth. Through the integrated design of signal sensing and conditioning, the modules achieve efficient collaborative operation via clearly defined pin connections, improving system reliability and convenience.

[0018] The invention’s unique immersion-compatible packaging design, combined with the waterproof aviation plug pin connection structure of the interface, enables the active electrode to work stably in special bionic environments such as insulating oil, expanding the experimental environment and application scenarios of MAET technology. Attached Figure Description

[0019] Figure 1 This is the magnetic particle magnetoacoustic-electric active electrode system of the present invention;

[0020] Figure 2 This is a block diagram of the active electrode module structure of the present invention;

[0021] Figure 3 This is a schematic diagram of the preamplifier circuit based on active electrodes of the present invention;

[0022] Figure 4 This is a schematic diagram of the filter circuit based on active electrodes according to the present invention.

[0023] Figure 5 This is a schematic diagram of the secondary amplifier circuit based on active electrodes of the present invention.

[0024] Figure 6 This is a circuit schematic diagram of the power supply module for supplying power to the active electrode according to the present invention, wherein 06-1 is the input filtering schematic diagram, 06-2 is the DC-DC step-down schematic diagram, and 06-3 is the negative voltage conversion schematic diagram. Detailed Implementation

[0025] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.

[0026] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0027] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0028] This invention relates to electrode-based magnetoacoustic-electric imaging of magnetic particles, specifically to an active electrode system for magnetoacoustic-electric imaging of magnetic particles.

[0029] The following is combined with Figures 1 to 6 The present invention provides a detailed description of an active electrode system for magnetoacoustic imaging of magnetic particles, based on embodiments of this application.

[0030] See appendix Figure 1 The controller controls the ultrasonic transducer to perform a clockwise circumferential scan of the object under test, with each scan angle being 30°. Simultaneously, it controls a pair of corresponding active electrodes to receive magnetoacoustic signals from magnetic particles, achieving efficient and automated multi-angle data acquisition and improving the practicality and efficiency of imaging. If the ultrasonic excitation module is located at position A1, the intelligent controller controls the active electrodes at D1 and D2 to receive magnetoacoustic signals from magnetic particles; if the ultrasonic excitation module is located at position B1, the intelligent controller controls the active electrodes at E1 and E2 to receive magnetoacoustic signals from magnetic particles; if the ultrasonic excitation module is located at position C1, the intelligent controller controls the active electrodes at F1 and F2 to receive magnetoacoustic signals from magnetic particles; if the ultrasonic excitation module is located at position D1, the intelligent controller controls the active electrodes at A1 and A2 to receive magnetoacoustic signals from magnetic particles.

[0031] Referring to Figure 2, the active electrode module (1) includes the electrode sensor (3), the signal conditioning module (2) (including a preamplifier module (4), a high-pass and low-pass filter module (5) and a secondary amplification module (6)), and a power supply module (7) for supplying power to it. The specific connection relationship is as follows: The electrode sensor 3 forms a differential input terminal, and its two output solder pins are respectively soldered to the non-inverting input terminal (+IN pin) and the inverting input terminal (-IN pin) of the preamplifier module 4 to receive the magnetic particle magnetoacoustic signal; the output pin (OUT pin) of the preamplifier module (4) is soldered to the input pin of the high-pass and low-pass filter module (5) to filter noise signals other than magnetoacoustic signal; the output pin of the high-pass and low-pass filter module (5) is soldered to the input pin of the secondary amplification module (6) to amplify the filtered magnetic particle magnetoacoustic signal for better acquisition and subsequent imaging; the +5V output pin, -5V output pin and GND pin of the power supply module (7) are respectively soldered to the power supply pins (VCC+, VCC- pins) and ground pins (GND pins) of each operational amplifier and amplifier in the signal conditioning module (2) to provide stable power supply for the signal conditioning module. The active electrode module (1) is the core component for signal acquisition, and the power supply module (7) provides it with operating voltage. The components work together to achieve signal sensing, conditioning and anti-interference functions.

[0032] Referring to the circuit schematic shown in Figure 3-5, the signal conditioning module integrates a preamplifier circuit, a filter circuit, and a secondary amplifier circuit in sequence according to the signal flow. Each circuit achieves amplification of weak signals and noise suppression through precise pin connections.

[0033] Specifically, attached Figure 3In this circuit, the AD8129 operational amplifier is used as the core component of the preamplifier circuit. This amplifier features low noise, low power consumption, high input impedance, and high common-mode rejection ratio. It utilizes a differential input structure to suppress common-mode interference at the signal source end, adapting to the wide-bandwidth, high-impedance signal source requirements of MAET technology. The non-inverting input (Pin1) is grounded through a matching resistor R2 (1KΩ) and connected to the positive output of the electrode sensor; the inverting input (Pin8) is grounded through a matching resistor R1 (1KΩ) and connected to the negative output of the electrode sensor. The chip's positive power supply pin (Pin7) is connected to +5V and is equipped with a ferrite bead L2 and filter capacitors C2 (0.1μF) and C3 (10μF); the negative power supply pin (Pin2) is connected to -5V and is equipped with a ferrite bead L1 and filter capacitors C1 (0.1μF) and C4 (10μF). The enable pin PD (Pin 3) is directly connected to the positive power supply pin (Pin 7) to maintain operation; the reference pin REF (Pin 4) is directly grounded. The feedback pin FB (Pin 5) is grounded through the gain resistor Rg (10Ω) and simultaneously connected to the output terminal (Pin 6) through the feedback resistor Rf (1KΩ). The initial gain of the circuit is set to 100 times, amplifying the magnetoacoustic signal of the magnetic particles from the microvolt level to the millivolt level, while ensuring that the amplified signal does not saturate and can meet the requirements of subsequent processing. In addition, the +5V power supply line is connected to the output terminal through resistor R3 (1KΩ).

[0034] Specifically, attached Figure 4The filtering circuit includes a high-pass filter and a low-pass filter, both employing a second-order Sallen-Key structure. The core component is the OPA842 instrumentation operational amplifier, suitable for magnetoacoustic signals in the 1.8MHz–2.7MHz frequency range. Specifically: In the high-pass filter circuit, the input signal is connected to the non-inverting input (Pin 3) of the OPA842 after being connected in series with capacitors C9 (100pF) and C10 (100pF). The intermediate node between C9 and C10 is connected to the output (Pin 6) via resistor R5 (680Ω). The non-inverting input (Pin 3) is grounded via resistor R4 (1.3KΩ). The inverting input (Pin 2) is connected to its own output via resistor R6 (100Ω) to form a feedback loop. Power supply pins Pin 7 and Pin 4 are connected to ±5V and are equipped with an LC filter network (L3 / C5 / C6, L4 / C7 / C8). Low-pass filter circuit: The input signal is connected to the non-inverting input (Pin 3) of the OPA842 after being connected in series with resistors R9 (560Ω) and R8 (560Ω). The midpoint between R9 and R8 is connected to the output (Pin 6) through capacitor C15 (150pF). The non-inverting input (Pin 3) is grounded through capacitor C16 (75pF). The inverting input (Pin 2) is connected to its own output through resistor R7 (100Ω). Power supply pins Pin 7 and Pin 4 are configured with corresponding LC filter elements. The two-stage filtering unit achieves high-pass and low-pass frequency band filtering of the input signal through the buffer of the high-speed operational amplifier and the frequency gating of the RC network: the front stage takes into account both high-pass and low-pass characteristics, while the rear stage strengthens low-pass filtering. At the same time, the high-speed characteristics of the operational amplifier are used to ensure the distortion-free transmission of high-frequency signals. The power supply decoupling network improves the circuit's anti-interference capability and is suitable for conditioning high-speed analog signals. Through the cooperation of precision resistors and capacitors, the quality factor (Q value) of the filter is optimized to avoid gain spikes at the cutoff frequency.

[0035] See appendix Figure 5 The secondary amplifier circuit adopts a two-stage cascaded amplification structure to build a higher overall gain and optimize the frequency response. Both stages of the circuit are powered by a ±5V dual power supply to ensure sufficient dynamic range.

[0036] Specifically, the first-stage amplifier circuit uses the OPA847, employing an inverting amplifier structure. The signal input terminal (004) is connected to the inverting input terminal (Pin2) of the operational amplifier via a coupling capacitor C26 (0.1μF) and a resistor R14 (50Ω). The non-inverting input terminal (Pin3) of the operational amplifier is grounded via a matching resistor R15 (50Ω). A feedback resistor R16 (5kΩ) is connected between the output terminal (Pin6) and the inverting input terminal (Pin2). The power supply pins Pin7 and Pin4 are connected to +5V and are equipped with a power supply filter network consisting of ferrite beads (L9, L10) and filter capacitors (C22-C25).

[0037] Specifically, the second-stage amplifier circuit uses the OPA842, employing a non-inverting amplifier structure. The output signal of U4 is connected to the non-inverting input (Pin3) of U5 via a coupling capacitor C21 (0.1μF), which is also grounded through a bias resistor R12 (1kΩ). The inverting input (Pin2) of U5 is grounded through a resistor R13 (100Ω) and connected to the output (Pin6) through a feedback resistor R11 (910Ω). Power supply pins Pin7 and Pin4 are connected to ±5V power supplies and are equipped with ferrite beads (L7, L8) and filter capacitors (C17-C20).

[0038] Specifically, through precise pin connections and parameter settings of the two-stage amplifier circuit, the total amplification factor is approximately 1000 times. Since the preamplifier gain is 100 times, the total voltage gain of the voltage acquired by the active electrode reaches approximately 100 dB, which can effectively amplify the magnetoacoustic signal of magnetic particles at the microvolt (μV) level to the volt (V) level, meeting the input range requirements of the subsequent data acquisition module, while preserving the details of the signal for subsequent imaging.

[0039] Referring to the DC12V to ±5V schematic diagram in Figure 6, the power supply module adopts an architecture of "input filtering + DC-DC step-down + negative voltage conversion" to achieve a stable ±5V output from a 12V input, providing power to the various circuits of the signal conditioning module.

[0040] Specifically, the input filtering unit: the positive terminal of the input DC12V power supply is connected to the filter capacitor network through fuse F1 (rated current 1A). One end of fuse F1 is soldered to the positive pin of the DC12V input interface, and the other end is soldered to the common connection point of the positive terminals of capacitors C1 (22μF), C2 (22μF), C3 (4.7μF), C4 (4.7μF), and C5 (0.1μF). The negative terminals of capacitors C1, C2, C3, C4, and C5 are all soldered to GND. The subsequent stage connects capacitors C6 (10μF), C7 (10μF), and C8 (0.1μF) in parallel, with their positive terminals connected to the output terminal of the previous stage filter network and their negative terminals soldered to GND. Through the combination of capacitors with different capacitance values, the high and low frequency ripple of the 12V input power supply is filtered out (ripple rejection ratio ≥40dB), while electromagnetic interference on the power line is suppressed, providing a stable input for the subsequent DC-DC conversion.

[0041] Specifically, in the +5V step-down circuit: the input pin VIN (Pin3) of the TPS63201 is soldered to the output of the input filter unit (i.e., the positive connection point of C6, C7, and C8), receiving the filtered 12V DC voltage; the switch pin SW (Pin2) of the TPS63201 is soldered to one end of the power inductor L1 (3.3uH), and the other end of L1 is soldered to the common connection point of the positive terminals of the output filter capacitors C10 (22μF), C11 (22μF), and C12 (0.1μF), while simultaneously feeding back to the feedback pin VFB (Pin4) of the TPS63201 through capacitor C13 (20pF); the enable pin EN (Pin5) of the TPS63201 is pulled up to the 12V input voltage through resistor R1 (10kΩ) to achieve constant enable; the TPS63201... The bootstrap pin VBST (Pin1) is connected in parallel with a bootstrap capacitor C9 (0.1μF), and the other end of C9 is soldered to the SW pin (Pin2) to ensure the normal conduction of the switching transistor. The ground pin GND (Pin6) of the TPS63201 is soldered to the system GND. The feedback network consists of resistors R2 (10kΩ) and R3 (2.2kΩ). One end of R2 is soldered to the VFB pin (Pin4), and the other end is soldered to the +5V output terminal. One end of R3 is soldered to the VFB pin (Pin4), and the other end is soldered to GND. The reference voltage of this chip is 0.768V, and the output voltage is calculated by the formula Vout=0.768V×(1+R2 / R3). After substituting the parameters, the output is stable at +5V. The +5V output terminal is filtered by capacitors C10, C11, and C12 and then connected to the Pin1 pin of the power output interface.

[0042] Specifically, in the -5V conversion circuit: the input pin V+ (Pin8) of the ICL7660 is soldered to the output terminal of the +5V step-down circuit (i.e., Pin1 of the power output interface); the CAP+ pin (Pin1) of the ICL7660 is soldered to the positive terminal of the charge pump energy storage capacitor C14 (10μF), and the CAP- pin (Pin2) is soldered to the negative terminal of C14; the ground pin GND (Pin4) of the ICL7660 is soldered to the system GND; the oscillation frequency adjustment terminal OSC (Pin3) of the ICL7660 is left floating, using the internal oscillation frequency of the chip; the LV pin (Pin5) of the ICL7660 is soldered to GND, V... OUT Pin 6 serves as the -5V output terminal, with parallel filter capacitors C15 (10μF), C16 (22μF), and C17 (0.1μF) connected to GND; the -5V output terminal is connected to Pin 3 of the power output interface.

[0043] The shielding housing is made of stainless steel with a thickness of 1.5mm. The inner wall is coated with an electromagnetic shielding layer, achieving a shielding effectiveness of 80dB@1MHz~10MHz. The housing is designed as a sealed structure, completely encapsulating the signal conditioning module and power module within it. The interface uses a waterproof aviation connector. The pins of the aviation connector are soldered one-to-one with the power pins (+5V, -5V, GND), signal output pins, and input pins of the signal conditioning module. The solder joints are sealed with waterproof sealant to ensure that insulating liquids do not seep into the housing and corrode the circuitry. Simultaneously, the metal shell of the aviation connector is reliably connected to the shielding housing, forming a complete electromagnetic shielding circuit.

[0044] The above description is merely an embodiment of the present invention and is not intended to limit the scope of the invention. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive technical essence shall fall within the protection scope of the present invention.

Claims

1. An active electrode system for magnetoacoustic-electric imaging of magnetic particles, characterized in that, include: The system comprises an active electrode module, an ultrasonic excitation module, and an intelligent controller module. The active electrode module consists of six pairs of active electrodes used to acquire magnetoacoustic signals from magnetic particles and amplify and filter these signals. Each pair of active electrodes is linearly opposed to the surface of the object under test, with an angle of 30° between adjacent pairs. The ultrasonic excitation module provides ultrasonic excitation to the object under test, enabling the magnetic nanoparticles to undergo forced vibration. The intelligent controller module controls the movement of the ultrasonic excitation module around the object under test, simultaneously emitting ultrasonic excitation towards the object and controlling the corresponding active electrode pairs to acquire the magnetoacoustic signals from the magnetic particles.

2. The active electrode system for magnetoacoustic-electromagnetic imaging of magnetic particles according to claim 1, characterized in that, The active electrode module includes an electrode sensor (3), a signal conditioning module (2), and a power supply module (7) for supplying power to the signal conditioning module (2). The input stage of the signal conditioning module (2) is directly electrically connected to and physically adjacent to the electrode sensor (3), and integrates a preamplifier circuit (4), a filter circuit (5), and a secondary amplification circuit module (6). The active electrode sensor (3) contacts the test object containing magnetic particles to obtain the magnetic particle magnetoacoustic signal and transmits it to the preamplifier circuit (4). The preamplifier circuit (4) amplifies the magnetic particle magnetoacoustic signal collected by the active electrode sensor (3) for the first time and then transmits it to the filter circuit (5). The filter circuit (5) performs high-pass and low-pass filtering on the magnetic particle magnetoacoustic signal output by the preamplifier circuit (4) and transmits it to the secondary amplification circuit (6). The secondary amplification circuit (6) amplifies the electrical signal filtered by the filter circuit (5) to a preset multiple and then transmits it to the oscilloscope.

3. The active electrode system for magnetoacoustic-electromagnetic imaging of magnetic particles according to claim 2, characterized in that, It also includes a shielding housing for sealing the active electrode signal conditioning module. The interface portion of the shielding housing adopts a waterproof aviation plug. The pins of the aviation plug are soldered one-to-one with the power pins and signal output pins of the signal conditioning module to prevent the insulation liquid from corroding the circuit and the system from causing electromagnetic interference to the circuit.

4. The active electrode signal conditioning module according to claim 2, characterized in that, The preamplifier circuit (4) mainly includes a differential amplifier chip, a first resistor, a second resistor, a third resistor, a fourth resistor, a gain resistor, and a feedback resistor; the non-inverting input terminal of the differential amplifier chip is grounded through the second resistor and connected to the positive output terminal of the electrode sensor; the inverting input terminal of the differential amplifier chip is grounded through the first resistor and connected to the negative output terminal of the electrode sensor. The feedback pin is grounded through the gain resistor and simultaneously connected to the output terminal through the feedback resistor; the fourth resistor is connected to the output terminal of the differential amplifier chip; the resistance value of the first resistor is equal to the resistance values ​​of the second resistor and the third resistor, and is twenty times the resistance value of the fourth resistor; the resistance value of the feedback resistor is one hundred times the resistance value of the gain resistor.

5. The active electrode signal conditioning module according to claim 2, characterized in that, The filtering circuit (4) includes a first filtering unit and a second filtering unit; the first filtering unit mainly includes a voltage feedback operation chip, a fifth resistor, a sixth resistor, a seventh resistor, a ninth capacitor, and a tenth capacitor; the signal is input to the non-inverting input terminal of the voltage feedback operation chip, the ninth capacitor and the tenth capacitor are connected to the non-inverting input terminal and grounded through the fifth resistor, one end of the sixth resistor is between the ninth capacitor and the tenth capacitor, and the other end is located at the output terminal of the voltage feedback operation chip; the inverting input terminal of the voltage feedback operation chip is connected to its own output terminal through the seventh resistor to form a feedback loop; the capacitance values ​​of the ninth capacitor and the tenth capacitor are equal, and the resistance values ​​of the fifth resistor, the sixth resistor, and the seventh resistor are unequal; The second filtering unit mainly includes a voltage feedback operational chip two, an eighth resistor, a ninth resistor, a tenth resistor, a fifteenth capacitor, and a sixteenth capacitor. The signal is input to the non-inverting input terminal of the voltage feedback operational chip two. The ninth and tenth resistors are connected to the non-inverting input terminal and grounded through the sixteenth capacitor. One end of the fifteenth capacitor is between the ninth and tenth resistors, and the other end is located at the output terminal of the voltage feedback operational chip two. The inverting input terminal of the voltage feedback operational chip two is connected to its own output terminal through the eighth resistor to form a feedback loop. The resistance values ​​of the ninth and tenth resistors are equal, and the capacitance value of the fifteenth capacitor is twice that of the sixteenth capacitor. The resistance values ​​of the seventh and eighth resistors are equal.

6. The active electrode signal conditioning module according to claim 2, characterized in that, The secondary amplification circuit (4) includes a first amplification unit and a second amplification unit; the first amplification unit mainly includes a voltage feedback operational chip three, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, and a twenty-sixth capacitor; the non-inverting input terminal of the voltage feedback operational chip three is grounded through the fifteenth resistor, and the sixteenth resistor is connected between the output terminal and the inverting input terminal of the voltage feedback operational chip three; the twenty-sixth capacitor is connected to the inverting input terminal of the voltage feedback operational chip three; the resistance values ​​of the fourteenth and fifteenth resistors are equal, and the resistance value of the sixteenth resistor is one hundred times that of the fourteenth resistor; the second amplification unit mainly includes a voltage feedback operational chip four, The eleventh resistor, twelfth resistor, thirteenth resistor, and twenty-first capacitor; the non-inverting input terminal of the voltage feedback operational chip four is grounded through the twelfth resistor, and the eleventh resistor is connected between the output terminal and the inverting input terminal of the voltage feedback operational chip four; one end of the thirteenth resistor is connected to the eleventh resistor, and the other end is connected to the inverting input terminal of the voltage feedback operational chip four; the twenty-first capacitor is connected to the non-inverting input terminal of the voltage feedback operational chip four; the resistance of the twelfth resistor is ten times the resistance of the thirteenth resistor, and the resistance of the thirteenth resistor is approximately nine times the resistance of the thirteenth resistor; the capacitance values ​​of the twenty-first capacitor and the twenty-sixth capacitor are equal.

7. The active electrode signal conditioning module according to claims 4-6, characterized in that, The differential amplifier chip includes an AD8129 amplifier; the voltage feedback operation chip one, voltage feedback operation chip two, and voltage feedback operation chip four include an OPA842 amplifier; the voltage feedback operation chip three includes an OPA847 amplifier; the total voltage gain of the magnetic particle magnetoacoustic signal acquired by the active electrode system reaches approximately 100 dB, which can effectively amplify the microvolt (μV) level magnetic particle magnetoacoustic signal to the volt (V) level, meeting the input range requirements of the subsequent data acquisition module.

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