Device and method for cardiac magnetic field imaging measurement based on diamond nv color center ensemble

Abstract

The present application relates to magnetic field imaging measurement technique, aims at providing a kind of heart magnetic field imaging measurement device and method based on diamond NV color center system.The present application proposes single-axis vector heart magnetic field imaging measurement and full-axis vector heart magnetic field imaging measurement based on the same technical principle, relies on excitation light to realize the polarization of diamond NV color center, and utilizes microwave field to control NV color center, obtains the population of NV color center spin quantum state by detecting the fluorescence signal intensity change generated by NV color center, to realize the measurement of external magnetic field intensity, realizes heart magnetic field imaging by multiple diamonds to constitute array.The present application can utilize NV color center system to non-destructively measure heart magnetic field vector field at room temperature, non-destructively, non-invasively measure and analyze heart working state;Since solid-state spin system can work in room temperature atmosphere, so that the method has the advantages of high sensitivity and robustness in practical application.

Description

Technical Field

[0001] This invention relates to magnetic field imaging measurement technology, specifically to a cardiac magnetic field imaging measurement device and method based on diamond NV color cardiac ensemble. Background Technology

[0002] The cardiac magnetic field is a direct result of the heart's electrical activity and can reflect its function and state, playing a crucial role in the diagnosis of diseases such as coronary heart disease. However, current cardiac magnetometry techniques suffer from various technical drawbacks. For example, superconducting quantum interference devices (SQUIDs) typically require cryogenic and shielded environments, and their high equipment and operating costs significantly limit their widespread application. Similarly, atomic magnetometers have gas chamber walls, restricting their proximity to the heart and causing signal attenuation.

[0003] Solid-state spin systems, benefiting from their ability to operate at room temperature and atmospheric conditions and their high sensitivity, have attracted considerable attention in recent years among various quantum systems. Thanks to the structural stability of their physical carriers, these systems possess great potential in terms of robustness. Nitrogen-Vacancy centers (NV centers), point defects in diamond, are a widely studied type of solid-state spin system. Theoretically, NV centers can achieve femtotes of sensitivity in magnetic measurements. Furthermore, NV center ensembles possess the property of enabling precise measurement of vector fields using a single sensitive unit, allowing for accurate measurement of the cardiac vector magnetic field and further analysis of the heart's condition.

[0004] Based on the above theoretical research, researchers have conducted further in-depth studies and proposed various application schemes. For example, the first published paper, "Vector magnetocardiography measurement with a compact elliptically polarized laser-pumped magnetometer," designed a compact elliptically polarized laser-pumped magnetometer to measure the total intensity of the biological magnetic field and its pseudo-vector component, and used it for experimental demonstration of vector magnetocardiography. However, this technique does not measure the true vector magnetic field of the heart, but rather a pseudo-vector magnetic field equivalent to a bias field, which still has the disadvantage of missing information compared to the true vector magnetic field. The second published paper, "Millimetre-scale magnetocardiography of living rats with thoracotomy," achieved the first measurement of the magnetic field of the mouse heart. However, this technique only measures the vector component magnetic field at a single point and cannot obtain the spatial distribution of the heart's magnetic field; and due to insufficient sensitivity, invasive measurements via thoracotomy are still required in the mice.

[0005] Therefore, it is necessary to propose new solutions for non-destructive measurement techniques of cardiac magnetic field vector fields to meet the needs of practical applications. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a cardiac magnetic field imaging measurement device and method based on diamond NV color cardiac ensemble.

[0007] To solve the above-mentioned technical problems, the solution adopted by the present invention is:

[0008] A single-axis vector cardiac magnetic field imaging measurement device based on the diamond NV color cardiac ensemble is provided. The device includes a probe array, an optical subsystem, a microwave subsystem, a signal acquisition subsystem, a noise reduction compensation coil, and a main control unit.

[0009] The probe array comprises multiple probes, each compactly arranged on a surface and constrained by non-magnetic structural components to form a whole. Each probe is equipped with a sensing unit, a gain unit, an optical adjustment unit, a fluorescence collection unit, a signal conversion and output unit, a signal input unit, and a radiating antenna. The sensing unit is a diamond sample containing NV color centers. The gain unit consists of a pair of mirror-placed cone-shaped structures made of high-permeability material, used to amplify the magnetic field in the single-axis vector direction to be measured; the sensing unit is sandwiched between the small ends of the cone-shaped structures. The optical adjustment unit illuminates the sensing unit with an excitation beam generated by the optical subsystem, exciting the NV color centers and generating a fluorescence signal. The signal conversion and output unit includes a photodiode or photomultiplier tube and its connected signal connector. The fluorescence signal is collected by the fluorescence collection unit, converted into an electrical signal by the signal conversion and output unit, and output to the signal acquisition subsystem. The signal input unit receives one or two microwave signals generated by the microwave subsystem and radiates the microwave signals to the sensing unit through the radiating antenna for manipulating the NV color centers in a single axis.

[0010] The optical subsystem includes at least one light source for generating a laser beam, and optical units that are the same number of probes in the probe array and correspond one-to-one; after the optical unit shapes and adjusts the laser beam speed, it transmits it to the corresponding optical adjustment unit in the probe array.

[0011] The microwave subsystem includes microwave units that correspond one-to-one with the number of probes. Each microwave unit includes a microwave generator and a microwave adjustment unit. The microwave generator generates one or two microwave signals. One microwave signal drives the transition from the ms=+1 level to the ms=0 level, or from the ms=-1 level to the ms=0 level, of the uniaxial NV color center. Two microwave signals simultaneously drive the transition from the ms=+1 level to the ms=0 level and from the ms=-1 level to the ms=0 level of the uniaxial NV color center. Each microwave signal contains one or three sets of microwave signals, with more sets of microwave signals used to drive the NV color center to transition between more splitting sublevels. The microwave adjustment unit adjusts each set of microwave signals to obtain an adjusted microwave field, which is then transmitted to the corresponding signal input unit in the probe array.

[0012] The signal acquisition subsystem includes acquisition units that are the same number of probes in the probe array and correspond one-to-one with the number of probes in the probe array; each acquisition unit includes a signal amplifier and a processor; the signal amplifier is connected to the corresponding signal conversion output unit in the probe array to receive the magnetic field signal to be measured on the single-axis vector component generated by it; the processor performs analog-to-digital conversion on the signal, processes, stores and transmits it, and generates signals to control the output parameters of the microwave generator.

[0013] The noise reduction compensation coil includes at least one pair of coil groups for generating a uniform magnetic field to reduce noise; the probe array and the object under test are simultaneously located inside the noise reduction compensation coil.

[0014] The main control unit performs overall control of the processor in the signal acquisition subsystem and communicates with the host computer.

[0015] As a preferred embodiment of the present invention, the adjusted microwave field obtained by the microwave adjustment unit after adjusting the microwave signal is obtained by synthesizing one or two sets of adjusted microwave fields, totaling one to six sets. Each set of adjusted microwave fields is applied simultaneously, and each set of adjusted microwave fields is any one or more combinations of the following: single-frequency microwave field, dual-frequency microwave field synthesized from two frequencies, amplitude-modulated microwave field, frequency-modulated microwave field, phase-modulated microwave field, amplitude-shift keying (APS) modulated microwave field, frequency-shift keying (FSK) modulated microwave field, and phase-shift keying (FSK) modulated microwave field.

[0016] This invention also provides a full-axis vector cardiac magnetic field imaging measurement device based on the diamond NV color cardiac ensemble. Compared with the aforementioned single-axis vector cardiac magnetic field imaging measurement device, this full-axis vector cardiac magnetic field imaging measurement device has a basically the same structural arrangement as the former, except for the following differences:

[0017] (1) Each probe in the probe array is not equipped with a gain unit;

[0018] (2) Each microwave generator in the microwave subsystem generates four or eight microwave signals simultaneously; four microwave signals are used to drive the transitions from the ms=+1 level to the ms=0 level or from the ms=-1 level to the ms=0 level of the four principal axis NV color centers; eight microwave signals are used to drive the transitions from the ms=+1 level to the ms=0 level and from the ms=-1 level to the ms=0 level of the single axis NV color center simultaneously; each microwave signal contains one or three sets of microwave signals, and more sets of microwave signals are used to drive the NV color center to transition between more splitting sublevels;

[0019] (3) Each processor in the signal acquisition subsystem simultaneously processes the magnetic field signals to be measured in the four vector component directions generated by the NV color centers of the four principal axes.

[0020] As a preferred embodiment of the present invention, the adjusted microwave field obtained by the microwave adjustment unit after adjusting the microwave signal is obtained by synthesizing 4 to 24 sets of adjusted microwave fields from four or eight channels. The multiple adjusted microwave fields are applied sequentially in time, or simultaneously after being modulated by different frequencies. Each set of adjusted microwave fields is any one or more of the following combinations: single-frequency microwave field, dual-frequency microwave field synthesized from two frequencies, microwave field modulated by amplitude, microwave field modulated by frequency, microwave field modulated by phase, microwave field modulated by amplitude shift keying, microwave field modulated by frequency shift keying, and microwave field modulated by phase shift keying.

[0021] As a preferred embodiment of the present invention, the light source is a laser, a laser diode, or a light-emitting diode; the optical unit includes a lens, a waveplate, a beam splitter, or a combination thereof; the sensitive unit is a thin-film diamond sample with a thickness of 0.1-0.3 mm and a length and width of 1 mm, and the diamond sample is held by the gain unit in the

[110] crystal orientation; the optical adjustment unit includes a mirror, a lens, or a combination thereof and a fixing structure thereof, and the direction of the plane mirror is adjustable; the fluorescence collection unit includes a lens, an objective lens, a parabolic condenser, a mirror, a filter, or a combination thereof.

[0022] As a preferred embodiment of the present invention, the probe array further includes a bias magnet, which is a neodymium iron boron magnet, a samarium cobalt magnet, or an array composed of neodymium iron boron magnets and samarium cobalt magnets; the bias magnet is placed at the coaxial interface position of the laser incident and microwave antenna.

[0023] As a preferred embodiment of the present invention, the probe array contains at least four probes, with each group consisting of four probes. Each probe group includes four sensing units, four pairs of gain units, four optical adjustment units, four fluorescence collection units, four signal input units, four signal conversion output units, and one radiating structure antenna.

[0024] As a preferred embodiment of the present invention, the cone-shaped structure in the gain unit is made of a high permeability material, which is an iron, cobalt, or nickel metal, an iron, cobalt, or nickel alloy, or a ferrite material.

[0025] The present invention also provides a method for performing cardiac magnetic field imaging measurements using the aforementioned cardiac magnetic field imaging measurements, comprising the following steps:

[0026] (1) Start the optical subsystem, microwave subsystem, signal acquisition subsystem and main control unit to perform initialization;

[0027] (2) Diamonds containing NV centers are in a magnetic measurement state under the combined action of laser and adjusted microwave field; the NV centers are sensitive to changes in the external magnetic field and are reflected in changes in fluorescence intensity.

[0028] (3) Place the part of the organism to be tested close to the probe array;

[0029] (4) The signal acquisition subsystem obtains signals from each probe in the probe array and performs the following processing;

[0030] For a single-axis vector cardiac magnetic field imaging measurement device, each probe in its probe array is equipped with a gain unit, and the received signal is an enhanced magnetic field signal of the target magnetic field on a single-axis vector component. Based on the adjustment microwave field applied simultaneously in time, a single signal F related to fluorescence intensity is obtained. Through the pre-calibrated coefficient k, the magnetic field vector projection P = F * k is obtained. Then, through feedback gradient noise reduction processing, the magnetic field vector projection measurement results of each probe are obtained, thus realizing magnetic field imaging.

[0031] For the all-axis vector cardiac magnetic field imaging measurement device, none of the probes in its probe array are equipped with gain units; each microwave generator in the microwave subsystem simultaneously generates four or eight microwave signals, and the multi-channel adjustment microwave fields are applied sequentially in time, or simultaneously after modulation at different frequencies, to control the NV color centers of the four principal axes of the sensitive unit; the signal acquisition subsystem receives the magnetic field signal to be measured on the four-axis vector components, and each processor simultaneously processes the magnetic field signal F' to be measured, which can be distinguished in the time domain or frequency domain and contains four or eight components; then, through the pre-calibrated matrix A, the three component signals of the magnetic field (Bx, By, Bz) = F'*A are obtained; and then, through feedback gradient noise reduction processing, the measurement results of all x, y, and z components of the magnetic field vector magnetic field of each probe are obtained, thus realizing magnetic field imaging.

[0032] As a preferred embodiment of the present invention, the feedback gradient noise reduction processing includes two parts: feedback compensation and gradient noise reduction. Feedback compensation refers to using the average magnetic field value measured by one or more probes as a feedback error signal to control the coil to generate a compensation magnetic field to cancel the environmental magnetic noise. Gradient noise reduction refers to using the average magnetic field value measured by one or more probes as an environmental noise reference value, and subtracting the environmental noise reference value of the corresponding probe from the results measured by all probes to obtain the final measurement result.

[0033] Description of the invention principle:

[0034] When microwaves are applied to the spins of the NV centers in diamond, resonance occurs when the microwave frequency matches the energy difference between the NV electron spin transition levels. The resonant microwaves cause a decrease in fluorescence count; this is known as electron spin resonance (ESR) of the NV centers. Unlike traditional ESR, because NV fluorescence is spin-dependent, the paramagnetic resonance signal of NV electrons can be detected using lasers; therefore, this method is called optically detected magnetic resonance (ODMR). The resonance spectrum obtained by applying continuous laser and microwave is called CW-ODMR, or simply CW spectrum. Due to its sensitivity limit, the CW sampling method can be used to measure the static magnetic field generated by most magnetic samples.

[0035] Existing precision magnetometry techniques based on nitrogen-vacancy (NV) centers mainly rely on the polarization of NV centers by excitation light and the manipulation of NV centers using microwave fields. By detecting changes in the intensity of the fluorescence signal generated by the NV centers, the population of the spin quantum states of the NV centers can be obtained, thereby enabling the measurement of the external magnetic field strength.

[0036] To measure the cardiac magnetic field, this invention proposes two solutions based on the same technical principle: uniaxial vector cardiac magnetic field imaging measurement and full-axis vector cardiac magnetic field imaging measurement based on the diamond NV center ensemble. The former relies on excitation light to polarize the diamond NV centers and uses a microwave field to manipulate them. By detecting changes in the intensity of the fluorescence signal generated by the NV centers, the population of the spin quantum states of the NV centers is obtained, thereby enabling the measurement of the external magnetic field strength. Cardiac magnetic field imaging is achieved by using an array of multiple diamonds.

[0037] In single-axis vector cardiac magnetic field imaging measurement, to achieve magnetic field amplification, gain units with adapted shapes are fabricated from materials with high magnetic permeability (such as iron, cobalt, nickel, and their alloys), enabling amplification of the magnetic field to be measured at specific locations. By adjusting the direction of the gain unit relative to the ambient magnetic field, bias fields of varying intensities can be obtained. Therefore, this technique not only amplifies the magnetic field to be measured but also provides a suitable bias magnetic field to ensure that the NV color center resonant frequency is at its highest efficiency in the radiation structure and to remove the degeneracy of the ±1 states. Furthermore, by combining these sensing units into an array structure, the spatial distribution of the cardiac magnetic field can be measured, thus providing crucial data support for imaging.

[0038] Compared to single-axis vector cardiac magnetic field imaging measurement technology, in full-axis vector cardiac magnetic field imaging measurement technology: each probe does not contain a gain unit; each microwave generator in the microwave subsystem needs to simultaneously generate 4 or 8 microwave signals to control the NV color centers of the four principal axes in a single diamond sensing element; each processor in the signal acquisition subsystem needs to simultaneously process the magnetic field signals to be measured in four directions generated by the NV color centers of the four principal axes (while the former scheme only processes the magnetic field signal to be measured on a single vector component). Noise reduction requires the use of triaxial coils to separately process the noise reduction feedback compensation in the x, y, and z directions.

[0039] Compared with the prior art, the beneficial effects of the present invention are:

[0040] 1. This invention enables non-destructive measurement of the cardiac magnetic field vector field at room temperature using the NV color cardiac ensemble. This method allows for precise measurement of the cardiac vector magnetic field using a single sensitive unit, thereby non-destructively and non-invasively measuring and analyzing the heart's working state, providing a powerful support tool for the diagnosis of diseases such as coronary heart disease. Furthermore, because the solid-state spin system can operate at room temperature and in atmospheric conditions, this method offers advantages such as high sensitivity and robustness in practical applications.

[0041] 2. This invention has the following innovative technical advantages:

[0042] (1) Room temperature operation: Due to the inherent properties of diamond nitrogen vacancy (NV), the NV color ensemble in this invention can operate at room temperature, avoiding the need for low temperature environment and shielding facilities, and greatly improving the practicality and application range of magnetocardiography technology.

[0043] (2) High sensitivity: The NV color center has a potential femtotes of magnetic measurement sensitivity, which can more accurately detect changes in the heart's magnetic field and provide strong support for the early diagnosis of diseases such as coronary heart disease.

[0044] (3) Vector field measurement: NV color synapse can achieve accurate measurement of vector field, which helps to analyze cardiac function and status more comprehensively.

[0045] (4) Single sensitive unit: The NV color center ensemble uses a single sensitive unit to measure the vector magnetic field, which avoids errors and interference between multiple sensitive units and improves the accuracy of the measurement results.

[0046] (5) Stability of NV color centers: As a type of point defect, NV color centers have high structural stability in diamond, which helps to improve the robustness of the measurement system and make it more reliable in practical applications.

[0047] (6) Easy to integrate: The NV color cardiac ensemble can be easily integrated with other microelectromechanical and semiconductor devices, making it possible to achieve low-cost non-destructive testing of cardiac magnetic fields.

[0048] (7) High spatial resolution: The NV color heart ensemble carrier is a diamond sensitive unit that can be as close as 10 nanometers to the diamond surface, so it can be directly attached to the chest cavity and other biological tissues or organs; in contrast, the gaseous atoms of the atomic magnetometer are usually separated from the source by a millimeter-thick container wall, which reduces the spatial resolution of the system; therefore, the present invention can effectively improve the resolution of the cardiac magnetic field and is expected to provide a potential research tool for the accurate analysis of the cardiac magnetic field state.

[0049] 3. The method proposed in this invention can not only play an important role in the diagnosis of heart diseases such as coronary heart disease, but can also be applied to the study of other biomagnetic fields, such as brain magnetic fields and muscle magnetic fields, bringing more breakthroughs to the biomedical field.

[0050] 4. Compared with the technical solution in Document 1 described in the background section, this invention can achieve the measurement of vector component magnetic fields using magnetic flux focusing technology, and can also achieve accurate measurement of the cardiac magnetic field using NV color ensemble four-axis vector magnetic measurement technology. Compared with existing technologies, the solid-state spin cardiac magnetic measurement technology of this invention brings great potential to the field of cardiac magnetic measurement, providing more comprehensive cardiac magnetic field information. It can play an important role in applications such as coronary heart disease diagnosis, and provide strong support for the further development of this field.

[0051] Compared with the technology in Document 2 described in the background section, the present invention is a non-destructive and non-invasive measurement, and two schemes are available: a high-sensitivity vector component magnetic field measurement scheme with enhanced magnetic flux focusing, and a four-axis vector magnetic field measurement scheme for the NV color center ensemble. Attached Figure Description

[0052] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, based on the concept of the present invention, other drawings can be obtained from these drawings without any creative effort.

[0053] Figure 1 This is a schematic diagram of the overall block diagram of the cardiac magnetic field imaging measurement device provided in Embodiment 1 of the present invention.

[0054] Figure 2 This is a schematic diagram of the probe group structure of the cardiac magnetic field imaging measurement device provided in Embodiment 1 of the present invention.

[0055] Figure 3 This is a schematic diagram of the cross-sectional structure of the probe of the cardiac magnetic field imaging measurement device provided in Embodiment 1 of the present invention.

[0056] Figure 4 This is a schematic diagram of the overall block diagram of the cardiac magnetic field imaging measurement device provided in Embodiment 2 of the present invention.

[0057] Figure 5 This is a schematic diagram of the cross-sectional structure of the probe of the cardiac magnetic field imaging measurement device provided in Embodiment 2 of the present invention. Detailed Implementation

[0058] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the design concept and embodiments of the present invention, all other embodiments obtained by those skilled in the art without departing from the principle of the present invention, and without creative effort, are within the scope of protection of the present invention.

[0059] Example 1

[0060] This embodiment provides a uniaxial vector cardiac magnetic field imaging measurement technique based on the diamond NV color cardiac ensemble, characterized by utilizing magnetic flux focusing enhancement to achieve highly sensitive biological magnetic field vector component imaging measurement.

[0061] refer to Figure 1 The diagram shown is a schematic representation of the single-axis vector cardiac magnetic field imaging measurement device provided in an embodiment of the present invention. The device includes: a probe array 100, an optical subsystem 200, a microwave subsystem 300, a signal acquisition subsystem 400, a noise reduction compensation coil 500, and a main control unit 600. The imaging device is used to perform cardiac magnetic field imaging on a living organism 700 (such as the human thoracic cavity).

[0062] The probe array 100 is an array structure containing multiple probes; as an example. Figure 1 The probe array 100 described herein contains 16 probes, arranged in groups of four, for a total of four probe groups. The structure of each probe group can be found in [reference needed]. Figure 2 , Figure 3 As shown, it includes four sensing units 101, four pairs of gain units 102, four optical adjustment units 103, four fluorescence collection units 104, four signal input units 105, four signal conversion output units 106, four excitation beams 107, a fixed substrate 108, a radiating structure antenna 109, and a mounting block 110.

[0063] All probes in the probe array must be compactly arranged on a plane to ensure that the measured magnetic field forms a spatial distribution; the probe array needs to use non-magnetic structural components to constrain the position of each probe element as a whole.

[0064] The sensitive unit 101 is sandwiched in the middle of the gain unit 102; the sensitive unit 101 is a diamond containing nitrogen-vacancy color centers as a magnetic field sensitive unit; as an example, it is a thin sheet structure with a thickness of 0.1-0.3 mm and a length and width of about 1 mm.

[0065] The gain unit 102 is made of a high-permeability material formed from iron, cobalt, nickel, and their alloys, and is processed into a specific shape, a cone-like structure with one end larger than the other. By utilizing the combination of gain units, the magnetic field at a specific location can be enhanced. By clamping the thin sheet of the sensing unit 101 between the small ends of the mirror-placed gain unit 102, amplification of the single-vector component of the magnetic field to be measured at the diamond location can be achieved.

[0066] The optical adjustment unit 103 causes the excitation beam 107 generated by the optical subsystem 200 to irradiate the sensitive unit 101, exciting the NV color center and generating a fluorescence signal, which is collected by the fluorescence collection unit 104 and converted into an electrical signal by the signal conversion and output unit 106 and output to the signal acquisition subsystem 400.

[0067] As an example, the optical adjustment unit 103 is a plane mirror and its fixing structure, and its direction is adjustable; the fluorescence collection unit 104 is a parabolic lens; the signal conversion output unit 106 is a photodiode and its connected coaxial signal connector.

[0068] The signal input unit 105 receives the microwave signal generated by the microwave subsystem 300 and radiates the microwave signal to the sensitive unit 101 through the radiating structure antenna 109.

[0069] The fixed base plate 108 and the mounting block 110 are used to support the installation and fixation of each component of the probe group.

[0070] The optical subsystem 200 is used to apply an excitation beam to the probe array 100 to excite NV color centers. The optical subsystem 200 includes a number of light sources 201 equal to the number of probes and an optical unit 202 equal to the number of probes. The light source 201 emits a light beam, which is shaped and adjusted by the optical unit 202 to form the excitation beam 107 and then transmitted to the probe array 100.

[0071] As an example, the light source 201 is a laser; the optical unit 201 is a convex lens, a waveplate, a beam splitter, or a combination thereof.

[0072] The microwave subsystem 300 is used to generate microwave signals to manipulate the NV color center. The microwave subsystem 300 includes microwave units equal to the number of probes, each microwave unit comprising a microwave generator and a microwave adjustment unit. The microwave generator and microwave adjustment unit are housed in a separate cabinet. The microwave generator generates a microwave signal, which is adjusted by the microwave adjustment unit to obtain an adjusted microwave field. This field is then connected from the microwave adjustment unit to the signal input unit 105 via a coaxial cable, and finally transmitted to the sensitive unit using the radiating antenna 109.

[0073] The adjusted microwave field is obtained by synthesizing one or two sets of adjusted microwave fields, totaling one to six sets. Each set of adjusted microwave fields is applied simultaneously. Each set of adjusted microwave fields is any one or more combinations of the following: a single-frequency microwave field, a dual-frequency microwave field synthesized from two frequencies, or a microwave field modulated by amplitude modulation, or a microwave field modulated by frequency modulation, or a microwave field modulated by phase modulation, or a microwave field modulated by amplitude shift keying, or a microwave field modulated by frequency shift keying, or a microwave field modulated by phase shift keying.

[0074] The signal acquisition subsystem 400 is used to convert analog signals into digital signals, and to process, store, and transmit the digital signals. The signal acquisition subsystem 400 includes acquisition units equal to the number of probes, each including a signal amplifier and a processor. The signal acquisition subsystem is housed in a separate cabinet. The signal amplifier receives the signal generated by the signal conversion output unit 106 via a coaxial cable and transmits it to the processor for further processing. The processor also generates signals to control the output parameters of the microwave generator.

[0075] The noise reduction compensation coil 500 is used to generate a uniform magnetic field and reduce noise through feedback. The noise reduction compensation coil 500 includes a pair of coil groups, placed in parallel, with their axes aligned with the measurement direction of the probe array; the probe array 100 and the biological object under test 700 (such as the human chest cavity) are located in the uniform region of the magnetic field generated by the noise reduction compensation coil 500 (uniformity better than 10%), so as to ensure the consistency of the bias magnetic field of each probe and achieve a better noise reduction effect;

[0076] The main control unit 600 (synchronous control system) performs overall control of all processors and communicates with the host computer.

[0077] Based on the above-described device, this embodiment also provides a method for uniaxial vector cardiac magnetic field imaging measurement based on the diamond NV color cardiac ensemble, comprising:

[0078] Step S11: Start the optical subsystem, microwave subsystem, signal acquisition subsystem and main control unit of the measuring device. After initialization, the device starts to measure the magnetic field.

[0079] Step S12: After starting the device, place the part of the organism to be measured close to the probe of the device; for example, when measuring the magnetic field of the heart, move the probe or the organism to move its chest cavity surface to the measurement surface where the probe is located.

[0080] Step S13: The signal acquisition subsystem processes the signals obtained from each probe in the probe array to obtain a signal F related to fluorescence intensity. Through the pre-calibrated coefficient k, the magnetic field vector component signal P = F * k is obtained. The measurement results of the magnetic field vector component at each probe are obtained through the feedback gradient noise reduction method, thereby realizing magnetic field imaging.

[0081] The feedback gradient noise reduction method includes a feedback compensation method and a gradient noise reduction method. The feedback compensation method uses the average magnetic field value measured by one or more probes as a feedback error signal to control a coil to generate a compensation magnetic field to cancel environmental magnetic noise. The gradient noise reduction method uses the average magnetic field value measured by one or more probes as an environmental noise reference value, and subtracts the corresponding environmental noise reference value from the results measured by all probes to obtain the final measurement result. Specific steps include:

[0082] Step S21: Assume that the 16 probes are arranged in a 4*4 pattern and denoted as Pij, where i and j are the row and column probe numbers from 1 to 4.

[0083] Step S22: Under the cardiac magnetic field measurement state, take the average value of the time-domain data of the magnetic field signals measured at P11, P14, P41, and P44, and record it as St;

[0084] Step S23: The noise reduction compensation coil generates a magnetic field of magnitude St to achieve noise feedback compensation and noise reduction at the part to be tested.

[0085] Step S24: Read the time-domain magnetic field signals measured at all Pij points, record the average value as St', and subtract St' from each data point to obtain the time-domain cardiac magnetic field data of each probe after gradient noise reduction processing.

[0086] This embodiment has the advantages of low cost and the ability to measure the spatial distribution of magnetic field of single vector components. It can obtain the distribution of cardiac current and provide a reference for the diagnosis of heart disease. It can provide a new non-invasive detection tool for medical research in the heart and expand new possibilities for the application of NV color heart in the biomedical field.

[0087] Example 2

[0088] This embodiment provides another all-axis vector cardiac magnetic field imaging measurement technique based on the diamond NV color cardiac ensemble. Its characteristic is that it utilizes diamond vector measurement technology to achieve vector magnetic field imaging measurement of biological organisms. Unlike Embodiment 1, this method measures all components of the vector magnetic field, enabling the acquisition of more spatial magnetic field information compared to Embodiment 1, and has superior potential value for cardiac condition diagnosis.

[0089] refer to Figure 4 The diagram shown is a schematic representation of the structure of the all-axis vector cardiac magnetic field imaging measurement device provided in an embodiment of the present invention, which includes: a probe array 100, an optical subsystem 200, a microwave subsystem 300, a signal acquisition subsystem 400, a noise reduction compensation coil 500, a main control unit 600, and a biological body 700.

[0090] The probe array 100 is an array structure containing multiple probes; preferably, the probe array 100 contains 16 probes, with four probes forming a group, for a total of four probe groups; each probe structure cross-section is referenced. Figure 5 As shown, it includes four sensing units 101, four optical adjustment units 103, four fluorescence collection units 104, four signal input units 105, four signal conversion output units 106, four excitation beams 107, a fixed substrate 108, a radiating structure antenna 109, and a mounting block 110.

[0091] All probes in the probe array must be compactly arranged on a surface to ensure that the measured magnetic field is a spatial distribution of a certain magnetic field; the probe array needs to use non-magnetic structural components to constrain the position of each probe element as a whole.

[0092] The sensitive unit 101 is a diamond containing nitrogen-vacancy color centers as the magnetic field sensitive unit; as an example, it is a thin sheet structure with a thickness of 0.1-0.3 mm and a length and width of about 1 mm.

[0093] The optical adjustment unit 103 causes the excitation beam 107 generated by the optical subsystem 200 to irradiate the sensitive unit 101, exciting the NV color center and generating a fluorescence signal, which is collected by the fluorescence collection unit 104 and converted into an electrical signal by the signal conversion and output unit 106 and output to the signal acquisition subsystem 400.

[0094] Preferably, the optical adjustment unit 103 is a plane mirror and its fixing structure, and its direction is adjustable; the fluorescence collection unit 104 is a parabolic lens; and the signal conversion output unit 106 is a photodiode and its connected coaxial signal connector.

[0095] The signal input unit 105 receives the microwave signal generated by the microwave subsystem 300 and radiates the microwave signal to the sensitive unit 101 through the radiating structure antenna 109.

[0096] The fixed base plate 108 and the mounting block 110 are used to support the installation and fixation of each component of the probe group.

[0097] The optical subsystem 200 is used to apply an excitation beam to the probe array 100 to excite NV color centers. The optical subsystem 200 includes a number of light sources 201 equal to the number of probes and an optical unit 202 equal to the number of probes. The light source 201 emits a light beam, which is shaped and adjusted by the optical unit 202 to form the excitation beam 107 and then transmitted to the probe array 100.

[0098] As an example, the light source 201 is a laser; the optical unit 201 is a convex lens, a waveplate, a beam splitter, or a combination thereof.

[0099] The microwave subsystem 300 is used to generate microwave signals to manipulate the NV color center. The microwave subsystem 300 includes microwave units equal to the number of probes, each microwave unit comprising a microwave generator and a microwave adjustment unit. The microwave generator and microwave adjustment unit are housed in a separate cabinet. The microwave generator generates a microwave signal, which is adjusted by the microwave adjustment unit to obtain an adjusted microwave field. This field is then connected from the microwave adjustment unit to the signal input unit 105 via a coaxial cable, and finally transmitted to the sensitive unit using the radiating antenna 109.

[0100] The adjusted microwave field is obtained by synthesizing 4 to 24 sets of adjusted microwave fields from four or eight channels. These multiple adjusted microwave fields are applied sequentially in time, or simultaneously after modulation at different frequencies. Each set of adjusted microwave fields is any one or more combinations of the following: a single-frequency microwave field, a dual-frequency microwave field synthesized from two frequencies, an amplitude-modulated microwave field, a frequency-modulated microwave field, a phase-modulated microwave field, an amplitude-shift keying (APS) modulated microwave field, a frequency-shift keying (FSK) modulated microwave field, or a phase-shift keying (FSK) modulated microwave field. The multiple adjusted microwave fields are applied sequentially in time, or simultaneously after modulation at different frequencies. These multiple adjusted microwave fields can excite NV color centers in different orientations, thereby achieving full-vector magnetic field measurement.

[0101] The signal acquisition subsystem 400 is used to convert analog signals into digital signals, and to process, store, and transmit the digital signals. The signal acquisition subsystem 400 includes acquisition units equal to the number of probes, each including a signal amplifier and a processor. The signal acquisition subsystem is housed in a separate cabinet. The signal amplifier receives the signal generated by the signal conversion output unit 106 via a coaxial cable and transmits it to the processor for further processing. The processor also generates signals to control the output parameters of the microwave generator.

[0102] The noise reduction compensation coil 500 is used to generate a uniform magnetic field and reduce noise through feedback. The noise reduction compensation coil 500 includes three pairs of coil groups, with the axes pointing in the XYZ directions respectively; the probe array 100 and the biological object under test 700 (such as the human chest cavity) are located in the uniform region of the magnetic field generated by the noise reduction compensation coil 500 (uniformity better than 10%), so as to ensure the consistency of the bias magnetic field of each probe and achieve a better noise reduction effect;

[0103] The main control unit 600 (synchronous control system) performs overall control of all processors and communicates with the host computer.

[0104] Accordingly, this invention also provides a method for measuring the cardiac magnetic field using full-axis vector imaging, the magnetic field imaging method comprising:

[0105] Step S11: Start the optical subsystem, microwave subsystem, signal acquisition subsystem and main control unit of the measuring device. After initialization, the device starts to measure the magnetic field.

[0106] Step S12: After starting the device, place the part of the organism to be measured close to the probe of the device; for example, when measuring the magnetic field of the heart, move the probe or the organism to move its chest cavity surface to the measurement surface where the probe is located.

[0107] Step S13: The signal acquisition subsystem processes the signals obtained from each probe in the probe array. Based on the different application times or modulation frequencies of the multi-channel adjusted microwave field, it obtains a multi-channel signal F' related to the fluorescence intensity. Through the pre-calibrated matrix A, it obtains the three component signals (Bx, By, Bz) = F'*A of the magnetic field x, y, and z. Then, through the feedback gradient noise reduction method, it obtains the measurement results of all components of the magnetic field vector x, y, and z of each probe, thus realizing magnetic field imaging.

[0108] The feedback gradient noise reduction method includes a feedback compensation method and a gradient noise reduction method. The feedback compensation method uses the average magnetic field value measured by one or more probes as a feedback error signal to control a coil to generate a compensation magnetic field to cancel environmental magnetic noise. The gradient noise reduction method uses the average magnetic field value measured by one or more probes as an environmental noise reference value, and subtracts the corresponding environmental noise reference value from the results measured by all probes to obtain the final measurement result. Specific steps include:

[0109] Step S21: Assume that the 16 probes are arranged in a 4*4 pattern and denoted as Pij, where i and j are the row and column probe numbers from 1 to 4. The magnetic field component signals measured in the x, y, and z directions are Bijx, Bijy, and Bijz, respectively.

[0110] Step S22: Under the cardiac magnetic field measurement state, take the average value of the time domain data of the magnetic field component signals in the x, y, and z directions measured at P11, P14, P41, and P44, and record them as SBxt, SByt, and SBzt.

[0111] Step S23: The noise reduction compensation coils X group generate a magnetic field of magnitude SBxt, Y group generate a magnetic field of magnitude SByt, and Z group generate a magnetic field of magnitude SBzt to achieve noise feedback compensation and noise reduction at the part to be tested.

[0112] Step S24: Read the time-domain data of the magnetic field component signals in the x, y, and z directions measured at all Pij points, and record the average values ​​as SBxt', SByt', and SBzt' respectively. Subtract SBxt', SByt', and SBzt' from the time-domain data of the magnetic field component signals in the x, y, and z directions respectively to obtain the time-domain cardiac magnetic field data of each probe after gradient noise reduction processing.

[0113] This embodiment has the advantages of low cost and the ability to measure the spatial distribution of the full-vector three-component magnetic field. It can obtain the cardiac current distribution more accurately and provide a reference for the diagnosis of heart disease. It provides a new non-invasive detection tool for medical research in the heart and expands new possibilities for the application of NV color heart in the biomedical field.

[0114] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A uniaxial vector cardiac magnetic field imaging measurement device based on the diamond NV color cardiac ensemble, characterized in that, The device includes a probe array, an optical subsystem, a microwave subsystem, a signal acquisition subsystem, a noise reduction compensation coil, and a main control unit; among which, The probe array comprises multiple probes, each compactly arranged on a surface and constrained by non-magnetic structural components to form a whole. Each probe is equipped with a sensing unit, a gain unit, an optical adjustment unit, a fluorescence collection unit, a signal conversion and output unit, a signal input unit, and a radiating antenna. The sensing unit is a diamond sample containing NV color centers. The gain unit consists of a pair of mirror-placed cone-shaped structures made of high-permeability material, used to amplify the magnetic field in the single-axis vector direction to be measured; the sensing unit is sandwiched between the small ends of the cone-shaped structures. The optical adjustment unit illuminates the sensing unit with an excitation beam generated by the optical subsystem, exciting the NV color centers and generating a fluorescence signal. The signal conversion and output unit includes a photodiode or photomultiplier tube and its connected signal connector. The fluorescence signal is collected by the fluorescence collection unit, converted into an electrical signal by the signal conversion and output unit, and output to the signal acquisition subsystem. The signal input unit receives one or two microwave signals generated by the microwave subsystem and radiates the microwave signals to the sensing unit through the radiating antenna for manipulating the NV color centers in a single axis. The optical subsystem includes at least one light source for generating a laser beam, and optical units that are the same number of probes in the probe array and correspond one-to-one; after the optical unit shapes and adjusts the laser beam speed, it transmits it to the corresponding optical adjustment unit in the probe array. The microwave subsystem includes microwave units that correspond one-to-one with the number of probes. Each microwave unit includes a microwave generator and a microwave adjustment unit. The microwave generator generates two microwave signals. These two microwave signals simultaneously drive the transitions of the uniaxial NV color center from the ms=+1 level to the ms=0 level, and from the ms=-1 level to the ms=0 level. Each microwave signal contains three sets of microwave signals, which drive the NV color center to transition between more splitting sublevels. The microwave adjustment unit adjusts each set of microwave signals to obtain an adjusted microwave field, which is then transmitted to the corresponding signal input unit in the probe array. The adjusted microwave field is obtained by synthesizing six sets of adjusted microwave fields from two sources. Each set of adjusted microwave fields is applied simultaneously. Each set of adjusted microwave fields is any one or more of the following combinations: a single-frequency microwave field, a dual-frequency microwave field synthesized from two frequencies, an amplitude-modulated microwave field, a frequency-modulated microwave field, a phase-modulated microwave field, an amplitude-shift keying (APS) modulated microwave field, a frequency-shift keying (FSK) modulated microwave field, and a phase-shift keying (PSK) modulated microwave field. The signal acquisition subsystem includes acquisition units that are the same number of probes in the probe array and correspond one-to-one with the number of probes in the probe array; each acquisition unit includes a signal amplifier and a processor; the signal amplifier is connected to the corresponding signal conversion output unit in the probe array to receive the magnetic field signal to be measured on the single-axis vector component generated by it; the processor performs analog-to-digital conversion on the signal, processes, stores and transmits it, and generates signals to control the output parameters of the microwave generator. The noise reduction compensation coil includes at least one pair of coil groups for generating a uniform magnetic field to reduce noise; the probe array and the object under test are simultaneously located inside the noise reduction compensation coil. The main control unit performs overall control of the processor in the signal acquisition subsystem and communicates with the host computer.

2. The single-axis vector cardiac magnetic field imaging measurement device according to claim 1, characterized in that, The cone-shaped structure in the gain unit is made of a high-permeability material, which is an iron, cobalt, or nickel metal, an iron, cobalt, or nickel alloy, or a ferrite material.

3. The single-axis vector cardiac magnetic field imaging measurement device according to claim 1, characterized in that, The light source is a laser, a laser diode, or a light-emitting diode; the optical unit includes a lens, a waveplate, a beam splitter, or a combination thereof; the sensitive unit is a thin diamond sample with a thickness of 0.1–0.3 mm and a length and width of 1 mm, and the diamond sample is held by the gain unit in the [110] crystal orientation; the optical adjustment unit includes a mirror, a lens, or a combination thereof and a fixing structure thereof, and the direction of the mirror is adjustable; the fluorescence collection unit includes a lens, an objective lens, a parabolic condenser, a mirror, a filter, or a combination thereof.

4. The single-axis vector cardiac magnetic field imaging measurement device according to claim 1, characterized in that, The probe array contains at least four probes, with each group consisting of four probes. Each probe group includes four sensing units, four pairs of gain units, four optical adjustment units, four fluorescence collection units, four signal input units, four signal conversion output units, and one radiating structure antenna.

5. A full-axis vector cardiac magnetic field imaging measurement device based on the diamond NV color cardiac ensemble, characterized in that, The device includes a probe array, an optical subsystem, a microwave subsystem, a signal acquisition subsystem, a noise reduction compensation coil, and a main control unit; among which, The probe array comprises multiple probes, each compactly arranged on a surface and constrained by non-magnetic structural components to form a whole. Each probe is equipped with a sensitive unit, an optical adjustment unit, a fluorescence collection unit, a signal conversion and output unit, a signal input unit, and a radiating antenna. The sensitive unit is a diamond sample containing NV centers. The optical adjustment unit illuminates the sensitive unit with an excitation beam generated by the optical subsystem, exciting the NV centers and generating a fluorescence signal. The signal conversion and output unit includes a photodiode or photomultiplier tube and its connected signal connector. The fluorescence signal is collected by the fluorescence collection unit, converted into an electrical signal by the signal conversion and output unit, and then output to the signal acquisition subsystem. The signal input unit receives one or two microwave signals generated by the microwave subsystem and radiates these signals to the sensitive unit via the radiating antenna for manipulating uniaxial NV centers. The optical subsystem includes at least one light source for generating a laser beam, and optical units that are the same number of probes in the probe array and correspond one-to-one; after the optical unit shapes and adjusts the laser beam speed, it transmits it to the corresponding optical adjustment unit in the probe array. The microwave subsystem comprises microwave units, one-to-one with the number of probes. Each microwave unit includes a microwave generator and a microwave adjustment unit. Each microwave generator simultaneously generates four or eight microwave signals. The four microwave signals drive transitions from the ms=+1 to ms=0 level, or from the ms=-1 to ms=0 level, of the four principal axis NV color centers. The eight microwave signals simultaneously drive transitions from the ms=+1 to ms=0 level, and from the ms=-1 to ms=0 level, of a single axis NV color center. Each microwave signal contains three sets of microwave signals, which are used to drive the NV color center at more splitting energy levels. A transition occurs between stages; the microwave adjustment unit adjusts each group of microwave signals to obtain an adjusted microwave field, which is then transmitted to the corresponding signal input unit in the probe array; the adjusted microwave field is obtained by synthesizing 4 to 24 groups of adjusted microwave fields from four or eight channels, and multiple adjusted microwave fields are applied sequentially in time, or simultaneously after modulation at different frequencies; each group of adjusted microwave fields is any one or more of the following combinations: single-frequency microwave field, dual-frequency microwave field synthesized from two frequencies, microwave field modulated by amplitude, microwave field modulated by frequency, microwave field modulated by phase, microwave field modulated by amplitude shift keying, microwave field modulated by frequency shift keying, and microwave field modulated by phase shift keying; The signal acquisition subsystem includes acquisition units that correspond one-to-one with the number of probes in the probe array; each acquisition unit includes a signal amplifier and a processor; the signal amplifier is connected to the corresponding signal conversion output unit in the probe array to receive the magnetic field signal to be measured on the single-axis vector component generated by it; the processor performs analog-to-digital conversion on the signal, processes, stores and transmits it, and generates signals to control the output parameters of the microwave generator; each processor simultaneously processes the magnetic field signal to be measured in the four vector component directions generated by the NV color centers of the four principal axes. The noise reduction compensation coil includes at least one pair of coil groups for generating a uniform magnetic field to reduce noise; the probe array and the object under test are simultaneously located inside the noise reduction compensation coil. The main control unit performs overall control of the processor in the signal acquisition subsystem and communicates with the host computer.

6. The all-axis vector cardiac magnetic field imaging measurement device according to claim 5, characterized in that, The light source is a laser, a laser diode, or a light-emitting diode; the optical unit includes a lens, a waveplate, a beam splitter, or a combination thereof; the sensing unit is a thin diamond sample with a thickness of 0.1–0.3 mm and a length and width of 1 mm; the optical adjustment unit includes a mirror, a lens, or a combination thereof and a fixing structure thereof, and the direction of the mirror is adjustable; the fluorescence collection unit includes a lens, an objective lens, a parabolic condenser, a mirror, a filter, or a combination thereof.

7. The all-axis vector cardiac magnetic field imaging measurement device according to claim 5, characterized in that, The probe array contains at least four probes, with each group consisting of four probes. Each probe group includes four sensing units, four optical adjustment units, four fluorescence collection units, four signal input units, four signal conversion and output units, and one radiating structure antenna.

8. The vector cardiac magnetic field imaging measurement device according to claim 1 or 5, characterized in that, The probe array also includes a bias magnet, which is a neodymium iron boron magnet, a samarium cobalt magnet, or an array composed of neodymium iron boron magnets and samarium cobalt magnets; the bias magnet is placed at the coaxial interface of the laser incident and microwave antenna.

9. A method for cardiac magnetic field imaging measurement using the vector cardiac magnetic field imaging measurement device according to claim 1 or 5, characterized in that, Includes the following steps: (1) Start the optical subsystem, microwave subsystem, signal acquisition subsystem and main control unit to perform initialization; (2) Diamonds containing NV centers are in a magnetic measurement state under the combined action of laser and adjusted microwave field; NV centers are sensitive to changes in the external magnetic field and this is reflected in changes in fluorescence intensity. (3) Place the part of the organism to be tested close to the probe array; (4) The signal acquisition subsystem obtains signals from each probe in the probe array and performs the following processing; For a single-axis vector cardiac magnetic field imaging measurement device, each probe in its probe array is equipped with a gain unit, and the received signal is an enhanced magnetic field signal of the target magnetic field on a single-axis vector component. Based on the adjustment microwave field applied simultaneously in time, a single signal F related to fluorescence intensity is obtained. Through the pre-calibrated coefficient k, the magnetic field vector projection P=F×k is obtained. Then, through feedback gradient noise reduction processing, the magnetic field vector projection measurement results of each probe are obtained, thus realizing magnetic field imaging. For the all-axis vector cardiac magnetic field imaging measurement device, none of the probes in its probe array are equipped with gain units; each microwave generator in the microwave subsystem simultaneously generates four or eight microwave signals, and the multi-channel adjustment microwave fields are applied sequentially in time, or simultaneously after modulation at different frequencies, to control the NV color centers of the four principal axes of the sensitive unit; the signal acquisition subsystem receives the magnetic field signal to be measured on the four-axis vector components, and each processor simultaneously processes the magnetic field signal F' to be measured, which can be distinguished in the time domain or frequency domain and contains four or eight components; then, through the pre-calibrated matrix A, the three component signals of the magnetic field (Bx, By, Bz) = F' × A are obtained; and then, through feedback gradient noise reduction processing, the measurement results of all x, y, and z components of the magnetic field vector magnetic field of each probe are obtained, thus realizing magnetic field imaging.

10. The method according to claim 9, characterized in that, The feedback gradient noise reduction process includes two parts: feedback compensation and gradient noise reduction. Feedback compensation refers to using the average magnetic field value measured by one or more probes as a feedback error signal to control the coil to generate a compensation magnetic field to cancel out the environmental magnetic noise. Gradient noise reduction refers to using the average magnetic field value measured by one or more probes as an environmental noise reference value, and subtracting the environmental noise reference value of the corresponding probe from the results measured by all probes to obtain the final measurement result.

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