CN112515679A - Unshielded magnetocardiogram device - Google Patents
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Abstract
The present disclosure provides an unshielded magnetocardiogram apparatus that includes a scanning device, a reference array, and a control system. The scanning device comprises at least one first atomic magnetometer, the scanning device is configured to detect magnetic field information of a target to output a magnetic signal, the reference array is configured to detect environmental magnetic field information, the control system is in signal connection with the scanning device and the reference array, and the control system is configured to filter noise related to an environmental magnetic field in the magnetic signal based on the environmental magnetic field information.
Description
Technical Field
At least one embodiment of the present disclosure relates to the field of biomedical imaging, and in particular, to an unshielded magnetocardiogram apparatus.
Background
The magnetocardiogram device can detect weak magnetic fields generated in the process of heart electrophysiological activity, and has the advantages of high sensitivity, complete non-invasion, complete passivity, non-contact and the like, thereby having important application prospects in high-end medical clinical research and diagnosis applications.
However, the current magnetocardiogram apparatus has a complex structure and a large volume, which results in high cost and poor adaptability to the environment, and in addition, the current magnetocardiogram apparatus has poor processing capability to the environmental magnetic field (noise), which results in difficulty in further improving the signal-to-noise ratio.
Disclosure of Invention
At least one embodiment of the present disclosure provides an unshielded magnetocardiogram apparatus, which can solve the above technical problems.
One aspect of the present disclosure provides an unshielded magnetocardiogram apparatus including a scanning device, a reference array, and a control system. The scanning device comprises at least one first atomic magnetometer, the scanning device is configured to detect magnetic field information of a target to output a magnetic signal, the reference array is configured to detect environmental magnetic field information, the control system is in signal connection with the scanning device and the reference array, and the control system is configured to filter noise related to an environmental magnetic field in the magnetic signal based on the environmental magnetic field information.
In the scheme, the atomic magnetometer has the advantages of small volume, flexible arrangement, capability of running at room temperature, low cost and the like, and the structure of the magnetocardiogram device can be simplified by utilizing the design of scanning the target (such as the heart) by the atomic magnetometer; in addition, the scanning device and the reference array are arranged to respectively detect the magnetic field information of the target and the environmental magnetic field information, noise related to the environmental magnetic field in the magnetic signal is filtered based on the environmental magnetic field information, so that the noise influence generated by the environmental magnetic field can be eliminated without arranging magnetic field shielding equipment such as a shielding chamber (shielding cylinder) and the like, the purpose of obviously improving the signal to noise ratio is achieved, meanwhile, the structure of the magnetocardiogram equipment is further simplified and the environmental applicability is improved because the magnetic field shielding equipment such as the shielding chamber and the like is not required to be arranged.
For example, in an embodiment of the first aspect of the present disclosure, there is provided a shielding-free magnetocardiogram apparatus, wherein the at least one first atomic magnetometer of the scanning device includes a plurality of first atomic magnetometers, and the plurality of first atomic magnetometers are arranged in an array.
In the scheme, the scanning accuracy of the scanning device for the magnetic field information of the target can be improved through the plurality of first atomic magnetometers arranged in the array, and the magnetic field strengths of different areas corresponding to the target are determined.
For example, in an embodiment of the first aspect of the present disclosure, there is provided a non-shielded magnetocardiogram apparatus, wherein the scanning device includes a first scanning structure and a second scanning structure stacked on top of each other, the first scanning structure and the second scanning structure being arranged with an adjustable pitch, and the first scanning structure and the second scanning structure respectively include a plurality of first atomic magnetometers among the plurality of first atomic magnetometers.
For example, in an embodiment of the first aspect of the present disclosure, there is provided an unshielded magnetocardiogram apparatus, wherein the second scanning structure is located between the first scanning structure and the reference array, and the second scanning structure includes a plurality of through holes arranged in an array, and when a distance between the first scanning structure and the second scanning structure is zero, the first atomic magnetometer in the first scanning structure and the first atomic magnetometer in the second scanning structure are arranged in the same plane.
For example, in the unshielded magnetocardiogram apparatus provided in one embodiment of the first aspect of the present disclosure, the control system outputs a waveform diagram of a diagnosis result for a detection target after filtering out noise associated with an ambient magnetic field in the magnetic signal. The first scanning structure and the second scanning structure are adjusted to have zero space, and the oscillogram is a one-dimensional oscillogram or a two-dimensional topographic map; or the distance between the first scanning structure and the second scanning structure is adjusted to be larger than zero, and the oscillogram is a one-dimensional oscillogram, a two-dimensional topographic map or a three-dimensional source imaging map.
For example, in an unshielded magnetocardiography device provided in one embodiment of the first aspect of the present disclosure, the reference array includes at least four second atomic magnetometers, the at least four second atomic magnetometers being arranged to determine a spatial coordinate system, the ambient magnetic field information including a magnetic field strength of each of the at least four second atomic magnetometers in the spatial coordinate system.
In the scheme, the atomic magnetometer has the advantages of small volume, flexible arrangement, capability of running at room temperature, low cost and the like, and the structure of the magnetocardiogram device can be simplified by utilizing the design of detecting the environmental magnetic field by the atomic magnetometer; in addition, by arranging the second atomic magnetometer to determine a space coordinate system, the space distribution rule of the current environmental magnetic field can be determined, and noise generated by the environmental magnetic field information can be removed from the magnetic information more accurately, thereby improving the signal-to-noise ratio.
For example, in one embodiment of the first aspect of the disclosure, there is provided an unshielded magnetocardiogram apparatus, wherein a distance from a first atomic magnetometer to a target is less than a distance from a second atomic magnetometer to the target.
In the scheme, because the atomic magnetometer is not limited by external equipment (for example, the limitation of low-temperature equipment and the like is not needed), the atomic magnetometer is more flexibly arranged, so that the atomic magnetometer can be set to be close to a target, the intensity of magnetic information obtained by a scanning device is high, and the signal-to-noise ratio is favorably improved.
For example, in an embodiment of the first aspect of the present disclosure, a control system stores a reference magnetocardiogram signal and a preset threshold, and before filtering noise associated with an ambient magnetic field in the magnetic signal based on ambient magnetic field information, the control system is configured to filter a portion of the magnetic signal that differs from the reference magnetocardiogram signal by a degree greater than the preset threshold.
In the scheme, the expected parts in the magnetic signals and the environmental magnetic information can be reserved, and the interference parts are removed, so that the interference of noise is reduced, the accuracy of information processing is improved, and the signal-to-noise ratio is improved.
For example, an embodiment of the first aspect of the present disclosure provides that the unshielded magnetocardiogram apparatus further includes a distance measuring device configured to monitor distance information between the scanning device and the target in real time. The distance measuring device is connected to a control system configured to correct the magnetic signal based on the distance information as a regression factor.
In the scheme, if the distance between the scanning device and the target is changed, the strength of the magnetic signal detected by the scanning device can be changed, the distance change relation between the target and the scanning device can be detected through the distance measuring device, the adverse effect on the precision of the magnetic signal caused by the distance change is eliminated, and the signal-to-noise ratio is improved. For example, the change in distance may be caused by human respiration.
The human breath referred to above may be either the breath of the person or the breath of another person. Illustratively, in the detection process of the fetal magnetocardiogram, the position of the fetus moves along with the breathing of the mother, and correspondingly, the position of the fetal heart moves along with the breathing of the mother, so that in the detection process of the fetal magnetocardiogram, noise caused by the breathing motion of the mother on the detection of the fetal magnetocardiogram can be eliminated, and the accuracy of the fetal magnetocardiogram detection can be improved.
For example, an embodiment of the first aspect of the present disclosure provides that the unshielded magnetocardiogram apparatus further includes an electrocardiograph detection device configured to synchronously detect electrocardiograph information of the target when the scanning device detects magnetic field information of the target. The electrocardiogram detection device is connected with the control system, and the control system is configured to correct the magnetic signal based on the electrocardiogram information. The shielded magnetocardiogram device is configured to simultaneously display an electrocardiogram including said electrocardiographic information and a magnetocardiogram including said magnetic signal.
In the scheme, the magnetic signal for forming the magnetocardiogram and the electrocardio information for forming the electrocardiogram are actually acquired synchronously, so that the accuracy of correcting the magnetic signal by using the electrocardio information is ensured; in addition, the electrocardiogram and the magnetocardiogram may be displayed in synchronization, for example, as a one-dimensional waveform diagram, thereby presenting more diagnostic information about the target.
For example, one embodiment of the first aspect of the present disclosure provides that the unshielded magnetocardiogram apparatus further comprises a moveable support arm. The movable support arm is used for carrying and driving the scanning device and the reference array. For example, the drive may move the scanning device and the reference array for the movable support arm.
In this scheme, because the atomic magnetometer is not limited by external equipment (for example, the limit of low-temperature equipment and the like is not needed), the atomic magnetometer is more flexible in arrangement and can be moved, so that the scanning device and the reference array can be driven by the movable supporting arm to move to any position of the alignment target according to the requirement, the distance between the scanning device and the target and the distance between the reference array and the target can be changed according to the requirement, and the atomic magnetometer is simple and convenient to operate.
For example, one embodiment of the first aspect of the present disclosure provides that the unshielded magnetocardiogram apparatus further includes a movable host, and the control system is located within the movable host.
The current magnetocardiogram apparatus is bulky, inconvenient to move, and generally used in a private room, and also takes a long time to move, and is not suitable for emergency treatment or the like. In this scheme, because the atomic magnetometer is not limited by external equipment (for example, the limit of low-temperature equipment and the like is not needed), the atomic magnetometer is more flexible in arrangement and can be moved, and on the basis, the host including the control system can be set to be movable, so that the unshielded magnetocardiogram device is convenient to move and is not limited to be applied in a special room. For example, it may be moved for different emergency room applications depending on the process needs.
For example, one embodiment of the first aspect of the present disclosure provides that the unshielded magnetocardiogram apparatus further comprises a movable nonmagnetic bed.
In the scheme, the non-magnetic bed is arranged to be movable, so that the non-shielding magnetocardiogram device is convenient to move, a target does not need to be moved relative to the magnetocardiogram device, and the safety of the target (patient) is convenient to guarantee.
Drawings
Fig. 1 is a schematic structural diagram of an unshielded magnetocardiogram apparatus according to an embodiment of the present disclosure;
FIG. 2 is a schematic diagram of a portion of the structure of the unshielded magnetocardiogram apparatus shown in FIG. 1;
FIG. 3 is a schematic structural diagram of a scanning apparatus in an unshielded magnetocardiogram apparatus according to an embodiment of the present disclosure in one state;
FIG. 4 is a schematic view of the scanning device shown in FIG. 3 in another state;
FIG. 5 is a schematic view of the unshielded magnetocardiogram apparatus shown in FIG. 3 from one perspective;
FIG. 6 is a schematic view of the unshielded magnetocardiogram apparatus shown in FIG. 5 from another perspective;
FIG. 7 is a flow chart of a method of operation of an unshielded magnetocardiogram apparatus according to one embodiment of the present disclosure;
FIG. 8 is a flowchart of one implementation of step S320 shown in FIG. 7;
FIG. 9 is a flowchart of another implementation of step S320 shown in FIG. 7;
FIG. 10 is a flowchart of yet another implementation of step S320 shown in FIG. 7; and
fig. 11 is a flowchart of a method of operation of an unshielded magnetocardiogram apparatus according to an embodiment of the present disclosure.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Heart diseases, such as coronary heart disease, arrhythmia, and the like, are the most common health problems and are the leading cause of premature death. Although a large amount of data and experience has been accumulated clinically, the results of the electrocardiogram are not crucial as the primary examination means for suspected heart problems, and therefore patients often need further examination. However, the additional wait may be fatal for acute cardiac disease. The magnetocardiogram is a detection means with the same source as the electrocardiogram, has better diagnostic performance, for example, the sensitivity of coronary heart disease diagnosis is about twice of the electrocardiogram, and reaches about 85%, and the detection time is similar to the electrocardiogram. The advantage of magnetocardiography is that the propagation of the magnetic field is hardly affected by the medium and the sensor array density is high, so that more primitive and detailed cardiac electrophysiological activity is presented.
A magnetic detector based on a Superconducting Quantum Interference Device (SQUID) can be applied to magnetocardiogram apparatuses. However, when the SQUID magnetic detector is used for detecting weak magnetic signals, the weak magnetic signals need to be detected in a shielding chamber (equipment with an environmental magnetic field shield), the occupied space is large, liquid helium is needed to maintain low-temperature operation, the use is inconvenient, the cost is high, and the application of the SQUID magnetic detector is severely limited.
At least one embodiment of the present disclosure provides an unshielded magnetocardiogram apparatus, which can solve the above technical problems. The unshielded magnetocardiogram apparatus includes a scanning device, a reference array, and a control system. The scanning device comprises at least one first atomic magnetometer, the scanning device is configured to detect magnetic field information of a target to output a magnetic signal, the reference array is configured to detect environmental magnetic field information, the control system is in signal connection with the scanning device and the reference array, and the control system is configured to filter noise related to an environmental magnetic field in the magnetic signal based on the environmental magnetic field information. The atomic magnetometer has the advantages of small volume, flexible arrangement, capability of running at room temperature, low cost and the like, and the structure of the magnetocardiogram device can be simplified by utilizing the design of scanning a target (such as a heart) by the atomic magnetometer; in addition, the scanning device and the reference array are arranged to respectively detect the magnetic field information of the target and the environmental magnetic field information, noise related to the environmental magnetic field in the magnetic signal is filtered based on the environmental magnetic field information, so that the noise influence generated by the environmental magnetic field can be eliminated without arranging magnetic field shielding equipment such as a shielding chamber (shielding cylinder) and the like, the purpose of obviously improving the signal to noise ratio is achieved, meanwhile, the structure of the magnetocardiogram equipment is further simplified and the environmental applicability is improved because the magnetic field shielding equipment such as the shielding chamber and the like is not required to be arranged.
The structure of an unshielded magnetocardiogram apparatus in accordance with at least one embodiment of the present disclosure is described in detail below with reference to the accompanying drawings.
As shown in fig. 1 and 2, the unshielded magnetocardiogram apparatus includes a scanning device 100, a reference array 200, and a control system (not shown, which may be located in a host 500). The scanning apparatus 100 includes a first atomic magnetometer, the scanning apparatus 100 is configured to detect magnetic field information of a target to output a magnetic signal, the reference array 200 is configured to detect environmental magnetic field information, and the control system is in signal connection with the scanning apparatus 100 and the reference array 200.
The control system includes a Central Processing Unit (CPU), which may be a single or multi-core processor or a plurality of processors for parallel processing. The control system also includes memory or memory locations (e.g., random access memory, read only memory, flash memory), electronic storage units (e.g., hard disk), communication interfaces for one or more other processing devices (e.g., network adapters), and peripherals (e.g., cache, other memory, data storage, and/or electronic display adapters). The memory, storage unit, interface and peripheral devices are configured to be in signal connection with the central processing unit via a communication bus (solid lines) such as a motherboard.
As shown in fig. 7, the operation method of the unshielded magnetocardiogram apparatus may be seen in steps 310 and S320 described below.
In step S310, magnetic field information of a target (e.g., a heart) is detected using a scanning device to output a magnetic signal, and environmental magnetic field information is detected using a reference array. For example, quadratic interpolation inference is performed using the absolute magnetic field and the gradient magnetic field of the real-time environment acquired by the reference array to calculate the environmental magnetic field at the position of each second atomic magnetometer.
For example, in the embodiment of the present disclosure, the scanning device may switch the modes of the absolute field strength and the gradient field strength, in the gradient field strength Mode, two or more first atomic magnetometers constitute one synthetic gradiometer channel, the value of which is the difference between the absolute magnetic fields measured by the two atomic magnetometers, and the Common Mode Rejection Ratio (CMRR) of the low gradient (for example, 10 petzra per centimeter time-varying magnetic field interference) can reach more than 1000, so as to further suppress the Common Mode noise.
In embodiments of the present disclosure, the source of the ambient magnetic field-corresponding noise may be various, and the ambient magnetic field-corresponding noise may have a magnetic field strength of less than about 100 nano-tesla (nT). For example, the noise of the earth's magnetic field includes a magnetic field strength of about 50 micro-tesla (μ T). The noise source may include an amplitude component, a frequency component, or a combination thereof. For example, the noise source may also include Direct Current (DC), Alternating Current (AC), or a combination of both.
In step S320, noise associated with the ambient magnetic field in the magnetic signal is filtered out based on the ambient magnetic field information. For example, the ambient magnetic field measured by the second atomic magnetometer is subtracted from the magnetic field in the magnetic signal of each first atomic magnetometer.
Next, with reference to fig. 8, an implementation of step S320 will be described by using a specific example, and specifically refer to steps S421 to S424 described below.
In step S421, the ambient magnetic field at the position of the scan array is predicted by using the absolute magnetic field and the gradient magnetic field of the real-time environment acquired by the reference array, and the corresponding value is subtracted.
For example, referring to step S421' in fig. 9, an alternative step may be to use a General Linear Model (GLM) as a regression factor for the environmental magnetic field measured by the reference array, separate a portion of the magnetic signal detected by the scanning device that is highly correlated with the environmental magnetic field, and subtract the highly correlated environmental magnetic field information from the magnetic signal.
In step S422, the scan array is adjusted to a composite gradiometer mode, where the value of each channel is the difference between the values measured by the two atomic magnetometers.
In step S423, a frequency notch filter process is performed on the 50Hz power supply frequency and its harmonics, and a low-pass filter process is performed on high frequencies of 100Hz or more. In practical applications, one of the largest sources of interference is the 50Hz power supply and its harmonic frequencies, where band-blocking digital filters are applied to reduce its interference.
In step S424, the baseline wander is corrected. For example, a baseline wander correction algorithm may be applied to the magnetocardiogram signal to attenuate the baseline wander effect.
In the embodiment of the present disclosure, the specific manner of correcting the baseline wander is not limited, and may be selected according to actual needs. For example, in one specific example of the present disclosure, the baseline wander correction may be by removing the linear wander, i.e., fitting an entire signal to a linear (first order) function, and subtracting the function from the signal. The method can be extended to polynomial function fitting, for example, fitting an optimal match by considering a function of 0-5 times, and then subtracting from the original signal. For example, in another specific example of the present disclosure, the baseline wander correction may be performed by wavelet analysis, that is, performing time-frequency domain analysis on the whole signal segment, and subtracting the corresponding main frequency within a period of time from the frequency band below, for example, 1 Hz.
For example, in the embodiment of the present disclosure, after step S421 (or step S421') is performed and before step S422 is performed, the original signal measured by the scanning device may be projected to a high-dimensional space (for example, signal space projection, independent component analysis, and the like), and then a component mainly composed of noise in the signal is separated and removed, which may be specifically referred to as step S401 in fig. 10.
For example, in an unshielded magnetocardiogram apparatus provided in at least one embodiment of the present disclosure, the at least one first atomic magnetometer of the scanning device includes a plurality of first atomic magnetometers arranged in an array. The scanning device can improve the scanning precision of the magnetic field information of the target through the first atomic magnetometers arranged in the array, and the magnetic field strengths of different areas corresponding to the target are determined. Illustratively, referring back to FIG. 1, a plurality of first atomic magnetometers are arrayed on a plane.
The scanning device is used to detect the magnetic field generated by the electrophysiological activity of the heart. Each first atomic magnetometer is internally composed of a laser light source, an optical lens, an alkali metal atom air chamber, a heater, a radio frequency coil, a compensation coil and a laser receiver. For example, the laser light source may include pump light and probe light, and the laser receiver receives the probe light. The pumping light is used for exciting alkali metal atoms, and the probe light penetrates through the atomic gas chamber and interacts with the alkali metal atoms in the gas chamber. Based on the optical-rf dual resonance phenomenon, the parameters (such as light intensity, or polarization angle) of the probe light received by the laser receiver vary according to the intensity of the external magnetic field. By acquiring these parameters, the external magnetic field strength can be deduced.
For example, in the unshielded magnetocardiogram apparatus provided in some embodiments of the present disclosure, as shown in fig. 1 and 2, the plurality of first atomic magnetometers in the scanning apparatus 100 are arranged in one layer, i.e., the plurality of first atomic magnetometers are arranged in the same plane.
For example, in the unshielded magnetocardiogram apparatus provided in some embodiments of the present disclosure, as shown in fig. 3 and 4, the scanning device 100 includes a first scanning structure 110 and a second scanning structure 120 stacked on top of each other, the first scanning structure 110 and the second scanning structure 120 are disposed with an adjustable distance therebetween, and the first scanning structure 110 and the second scanning structure 120 respectively include a set of first atomic magnetometers, that is, some first atomic magnetometers are arranged in the first scanning structure 110, and other first atomic magnetometers are arranged in the second scanning structure 120. For example, the second scanning structure 120 may be slid along the moveable support arm 400 (which may be manually adjustable) to enable adjustment of the spacing of the first scanning structure 110 and the second scanning structure 120.
For example, in the unshielded magnetocardiogram apparatus provided in the embodiments of the present disclosure, as shown in fig. 3 and 4, the second scanning structure 120 is located between the first scanning structure 110 and the reference array 200, the second scanning structure 120 includes a plurality of through holes arranged in an array, and when the distance between the first scanning structure 110 and the second scanning structure 120 is zero, the first atomic magnetometer in the first scanning structure 110 and the first atomic magnetometer in the second scanning structure 120 are arranged in the same plane.
For example, in the unshielded magnetocardiogram apparatus provided by the embodiments of the present disclosure, the control system outputs a waveform diagram of the diagnosis result of the detection target after filtering out the noise related to the ambient magnetic field in the magnetic signal. With the scanning apparatus 100 as shown in fig. 3-6, the waveform map can be output as a one-dimensional waveform map or a two-dimensional topographic map in the case where the first scanning structure 110 and the second scanning structure 120 are adjusted to have a zero pitch as shown in fig. 3. In the case where the first scanning structure 110 and the second scanning structure 120 are adjusted to have a spacing greater than zero as shown in fig. 4, the waveform map may be output as a one-dimensional waveform map, a two-dimensional topographic map, or a three-dimensional source imaging map.
In the first mode, the second scanning structure 120 is lowermost to have zero spacing from the first scanning structure 110, and all of the first atomic magnetometers are co-located in the same plane. Absolute magnetic field and gradient magnetic field information for this plane can now be obtained.
In the second mode, the second scanning structure 120 is lifted to a position (for example, 0-10 cm) above the first scanning structure 110, and the magnetic fields measured by the two arrays are interpolated in three-dimensional space, which can obtain gradient magnetic field information, i.e., the ratio of magnetic induction (for example, in pT) to different distances (for example, in cm), measured at different distances in the vertical direction, in addition to the first mode, so as to obtain gradient field distribution in three-dimensional space (the first mode can only obtain planar distribution).
The gradient magnetic field is very sensitive to a magnetic field varying in a small range of space (the magnetocardiogram is a magnetic field varying in a small range), and can suppress a large-scale spatial fluctuation or a static magnetic field (low-frequency common mode suppression). Therefore, measuring the gradient field when the disturbance of the external magnetic field is large can reduce the noise, thereby obtaining more accurate results. Although the first mode can obtain the gradient field distribution of the coronal plane, the gradient signal of the magnetocardiogram has the largest component in the direction perpendicular to the coronal plane, so the second mode has stronger detection function. In addition, since the distance (e.g., vertical distance in the direction of gravity) between the first scanning structure and the second scanning structure is variable (distance measured by gradient is variable), it is possible to find an optimal distance suitable for the current environment by scanning the signal-to-noise ratio at different vertical distances (vertical distances).
In the case where the output waveform diagram is a one-dimensional waveform diagram, the absolute magnetic field strength output by each first atomic magnetometer may be displayed as one channel, or the equivalent gradient magnetic field strength (obtained by interpolation) at the position where each first atomic magnetometer is located may be displayed as one channel. The waveform can be displayed in a differential mode and a integral mode by the aid of the absolute magnetic field and the gradient magnetic field. In addition, the magnetocardiogram signals of a plurality of heartbeat cycles can be averaged and displayed, so that a higher signal-to-noise ratio is obtained. In embodiments where acquisition is synchronized with an electrocardiogram, the signals of the magnetocardiogram and the electrocardiogram may be displayed in synchronization to obtain more comprehensive information. The magnetocardiogram is identical to the physiological origin of an electrocardiogram, i.e., the nerve currents that govern the rhythm of the heart beat. Electrocardiography detects the difference in electrical potential at different locations on the body surface caused by this current, while magnetocardiography detects the magnetic field generated by this current.
The direction of the magnetic field is perpendicular to the direction of the current, as can be seen by the right hand rule. Therefore, the magnetocardiogram and the electrocardiogram are respectively more sensitive to signals in different directions (the magnetocardiogram is more sensitive to tangential current and eddy current, and the electrocardiogram is more sensitive to radial current), and the measurement can obtain complementary information.
In addition, the magnetic field propagates in the body with little influence from the medium, which means that the magnetocardiogram waveform is closer to the source signal. While the current is more likely to change waveform due to different conductivities between different tissues (e.g., muscle, fat, bone), such distortion may also provide additional information in the conduction process, such as a person's obesity. Therefore, the synchronous acquisition of the magnetocardiogram and the electrocardiogram can cross verify the etiology and also provide doctors with more comprehensive physical conditions about the testee.
Finally, the sensors of the magnetocardiogram are all located near the heart, while the electrodes of the electrocardiogram are located furthest at the extremities. The two techniques thus measure the cardiac electrophysiological signals at different spatial scales, which further enhances the complementary value of the two information.
In the case where the output oscillogram is a two-dimensional topographic map, two-dimensional spatial interpolation may be performed using discrete real values obtained by scanning the array, using a particular color table for the magnetic field strength. The two-dimensional topographic map corresponds to the magnetic field distribution of the coronal plane of the human body. The actual values may be absolute magnetic fields or gradient magnetic fields measured at different scanning device spacings. In addition, the two-dimensional topographic map may be displayed fused after registration with structural images of the subject (e.g., digital X-ray, CT, MRI, etc.). The principle of the specific registration method is as follows: the relative positions of the laser range finder and the scanning device are fixed and known, and the light spot is located at the rib feature point every time, so that the position of the rib feature point on the topographic map can be marked, for example, the point is aligned with the same corresponding point on the structural image.
In the case that the output waveform diagram is a three-dimensional source imaging diagram, because the scanning device is distributed in three orthogonal directions of space X-Y-Z in the gradient magnetic field mode, the positioning of the magnetocardiogram signal source generation position in the three-dimensional space can be realized, and the realization method can include the following steps 1-3, for example.
In step 1, a positive problem model transmission matrix (e.g., finite element model, boundary element model, etc.) is first established to specify the propagation properties of the current and the mode in which it generates the corresponding electric and magnetic fields, i.e., what current source will generate what waveform.
In step 2, a time point or time period of interest in the magnetocardiogram, such as a location of an abnormality in the waveform, is selected.
In step 3, the data for all channels within this specified time are input into the positive problem model, and then the inverse problem is solved, i.e. the spatial and intensity distribution of a current source is found, so that the signal generated through the transmission matrix has the smallest or the smallest error with the actually measured signal.
The inverse problem solving method comprises the following steps: dipole matching, minimum norm estimation, or beamforming, etc. The result of the calculation will contain the spatial distribution of the strength of the magnetocardiogram signal generating source within a specific time. Since the magnetocardiogram is homologous to the electrocardiogram, both can share the exact same positive problem model, which means that the synchronously acquired magnetocardiogram and electrocardiogram data can be imported together when solving the inverse problem. This equates to more known conditions, making the results easier to understand and more accurate.
This result is registered with a structural image (e.g., three-dimensional structural images such as CT, MRI, etc.) to display fused structural and signal source intensity information. The function has important reference value for preoperative positioning of cardiovascular operations such as cardiac ablation.
For example, in an unshielded magnetocardiogram apparatus provided in at least one embodiment of the present disclosure, the reference array includes at least four second atomic magnetometers, the at least four second atomic magnetometers being arranged to determine a spatial coordinate system, the ambient magnetic field information including magnetic field strength of each of the at least four second atomic magnetometers in the spatial coordinate system. The reference array may be used to measure ambient magnetic fields to aid in noise reduction processing of the magnetic signals, and the reference array may be used to measure absolute magnetic fields and first order gradient fields. The atomic magnetometer has the advantages of small volume, flexible arrangement, capability of running at room temperature, low cost and the like, and the structure of the magnetocardiogram device can be simplified by utilizing the design of detecting an environmental magnetic field by the atomic magnetometer; in addition, by arranging the second atomic magnetometer to determine a space coordinate system, the space distribution rule of the current environmental magnetic field can be determined, and noise generated by the environmental magnetic field information can be removed from the magnetic information more accurately, thereby improving the signal-to-noise ratio. Illustratively, referring back to FIG. 1, the reference array 200 includes four second atomic magnetometers, one second atomic magnetometer being located at the origin of the spatial coordinate system and the other three second atomic magnetometers being located on the X, Y, Z axes, respectively, in the spatial coordinate system established therewith.
For example, in an unshielded magnetocardiogram apparatus provided in at least one embodiment of the present disclosure, a distance from a first atomic magnetometer to a target is less than a distance from a second atomic magnetometer to the target. Because the atomic magnetometer is not limited by external equipment (for example, the limitation of low-temperature equipment and the like is not needed), the atomic magnetometer is more flexible in arrangement, so that the atomic magnetometer can be set to be close to a target, the intensity of magnetic information obtained by a scanning device is high, and the signal-to-noise ratio is favorably improved. Illustratively, referring back to FIG. 1, the scanning apparatus 100 (or a first atomic magnetometer it comprises) is closer to the target 10 (e.g., the heart) than the scanning array 200 (or a second atomic magnetometer it comprises).
It should be noted that, in the embodiment of the present disclosure, before the control system performs the process of filtering the noise related to the ambient magnetic field in the magnetic signal based on the ambient magnetic field information, the magnetic signal obtained by the scanning device and the ambient magnetic field information obtained by the reference array may be preprocessed to filter part of the noise, simplify the subsequent processing operation, and improve the accuracy of information processing.
For example, in an unshielded magnetocardiogram apparatus provided in at least one embodiment of the present disclosure, the control system stores a reference magnetocardiogram signal, and the control system is configured to filter out a portion of the magnetic signal that is too different from the reference magnetocardiogram signal before filtering out noise associated with the ambient magnetic field in the magnetic signal based on the ambient magnetic field information. Therefore, the expected part of the magnetic signal can be reserved, and the part with excessive interference can be removed, so that the interference degree of noise is reduced, the information processing precision is improved, and the signal-to-noise ratio is improved.
For example, as shown in fig. 11, the operation method of the unshielded magnetocardiogram apparatus may refer to steps S510, S511, and S520 described below.
In step S510, magnetic field information of a target (e.g., a heart) is detected using a scanning device to output a magnetic signal, and environmental magnetic field information is detected using a reference array. The specific implementation of step S510 can be seen in step S310 described above.
In step S511, the magnetic signal is compared with the reference magnetocardiogram signal, and a part of the magnetic signal that differs from the reference magnetocardiogram signal by more than a predetermined threshold is filtered. The preset threshold represents the degree of difference between the magnetic signal and the reference magnetocardiogram signal.
For example, the reference magnetic signal is subjected to polynomial fitting to obtain a first polynomial, which is an nth-power polynomial including N coefficients and 1 constant. And intercepting a plurality of sections from the magnetic signal, and performing polynomial fitting after performing spectrum analysis on each section in sequence to obtain a second polynomial. The first polynomial and the second polynomial are both polynomials of power N, which comprise N coefficients and 1 constant. And (4) carrying out ratio (large value is smaller than small value) on the constants of the first polynomial and the second polynomial and the coefficient of the same power, and if the number of the constants and the coefficients of which the ratio exceeds a first preset value exceeds a second preset value, discarding the section, otherwise, keeping the section.
The first preset value and the second preset value can be determined as required. For example, the first preset value may be 2, 5, 10, 15, etc. For example, the second predetermined value can be (N-1)/2, N/2, or (N +1)/2 rounded. The first and second preset values mark the degree of difference between the first and second polynomials, i.e. the preset threshold is determined by the first and second preset values.
The technical solutions in the above embodiments are explained in detail by a specific example.
Illustratively, the control system stores a reference magnetocardiogram created based on a magnetocardiogram of a healthy human body, wherein the reference magnetocardiogram may be represented as a frequency domain signal, and performs polynomial fitting, assuming that a formula corresponding to a fitting curve is a 10 th-power formula, which is specifically formula 1 below.
P1＝a1·f10+b1·f9+c1·f8+d1·f7+e1·f6+f1·f5+g1·f4+h1·f3+i1·f2+j1·f+k1
P in the formula 11Representing the magnetic field strength and f representing the frequency. Coefficient a of equation 11To j1And constant k1The number of (2) is 11.
When testing a human body, a scanning device is used for measuring magnetocardiogram signals in a specific time period (for example, 100 seconds), signals of 10-second time segments are cut out from the magnetocardiogram signals, adjacent time segments can be separated by 5 seconds, then the signals of each time segment are subjected to spectrum analysis, the signals of the time segments are converted into frequency-domain signals from time-domain signals, and then polynomial fitting is carried out on the frequency-domain signals to obtain a 10-degree formula, which is specifically shown in the following formula 2.
P2＝a2·f10+b2·f9+c2·f8+d2·f7+e2·f6+f2·f5+g2·f4+h2·f3+i2·f2+j2·f+k2
P in the equation 22Representing the magnetic field strength and f representing the frequency. Coefficient a of the equation 22To j2And constant k2The number of (2) is 11.
Comparing the coefficients of equations 1 and 2 with constants and corresponding to a comparison of coefficients to powers of the same order, e.g. a1And a2Comparison, b1And b2And (6) comparing. If the degree of difference between the coefficients and constants compared in equations 1 and 2 is more than ten times (e.g., a)1And a2Ratio of (b)1And b2The ratio of comparison, etc.) exceeds 5, the signal of the block section is regarded as a bad section to be discarded, otherwise, the signal is retained to the subsequent processing step.
In step S520, noise associated with the ambient magnetic field in the magnetic signal is filtered out based on the ambient magnetic field information. The specific implementation of step S520 can be seen in step S320.
For example, at least one embodiment of the present disclosure provides that the unshielded magnetocardiogram apparatus further includes a distance measuring device configured to monitor distance information between the scanning device and the target in real time. The distance measuring device is connected to a control system configured to correct the magnetic signal based on the distance information as a regression factor. If the distance between the scanning device and the target is changed, the strength of the magnetic signal detected by the scanning device can be changed, the distance change relation between the target and the scanning device can be detected by the distance measuring device, the adverse effect on the precision of the magnetic signal caused by the distance change is eliminated, and the signal-to-noise ratio is improved. Illustratively, as shown in FIG. 2, a ranging device 300. For example, the distance measuring device 300 may be located at the center of the scanning device 100 so that the target 10 may be aligned to improve the accuracy of obtaining information.
For example, the thoracic cavity caused by the respiratory process of the human body fluctuates according to a certain frequency, so that the distance between the thoracic cavity (and the heart therein) and the scanning device repeatedly changes according to a certain frequency, and the change of the distance can affect the magnetic field intensity of the heart measured by the scanning device, that is, the magnetic information measured by the scanning device includes a variable related to the respiratory frequency, and the distance information between the scanning device and the target is measured by the distance measuring device, so that the variable can be obtained, and thus the variable is removed in the processing process of the magnetic information, the accuracy of the magnetic information processing is improved, and the signal to noise ratio is improved.
For example, the distance measuring device may be an optical sighting distance meter. An optical sighting rangefinder may be located in the center of the scanning device, the optical sighting rangefinder being a pulsed laser transmitter and a high sampling rate laser receiver. The emitter emits laser light vertically downwards, and the light spot is projected on the surface of a human body to assist an operator to move the scanning array to be right above the heart, so that the detection results of different people have better consistency. The receiver can detect the time taken by the laser reflected from the body surface at a very high sampling rate, and thus can measure the distance of the scanning device from the body surface (or heart). By repeating this procedure at a higher frequency, the time-dependent course of the distance can be determined, with which the noise of the measured magnetocardiographic data (magnetic signals) can be further reduced.
For example, as shown in fig. 11, the operation method of the unshielded magnetocardiogram apparatus may further include the following step S530 after the step S520 is performed.
In step S530, the real-time distance information measured by the distance measuring device is utilized to obtain the respiratory rhythm of the human body, and then the respiratory rhythm is used as a regression factor for processing the magnetic information, so as to suppress the gain of the respiration-related signal, thereby correcting the magnetic signal.
For example, at least one embodiment of the present disclosure provides an unshielded magnetocardiogram apparatus further comprising an electrocardiograph detection device configured to detect electrocardiographic information of a target. The electrocardiogram detection device is connected with the control system, and the control system is configured to correct the magnetic signal based on the electrocardiogram information.
For example, the electrocardiographic detection means is configured to synchronously detect electrocardiographic information of the target when the scanning means detects magnetic field information of the target, and the shielded electrocardiographic device is configured to synchronously display an electrocardiogram including the electrocardiographic information and a magnetocardiogram including the magnetic signal. In this way, the magnetic signal used to form the magnetocardiogram and the electrocardiographic information used to form the electrocardiogram are actually acquired synchronously, thereby ensuring the accuracy of correcting the magnetic signal using the electrocardiographic information; in addition, the electrocardiogram and the magnetocardiogram may be displayed in synchronization, for example, as a one-dimensional waveform diagram, thereby presenting more diagnostic information about the target.
The human breath referred to above may be either the breath of the person or the breath of another person. For example, in the case where the detection target is a fetus, the "other person" may be a mother.
For example, in one example of the embodiment of the present disclosure, the magnetocardiogram detection is performed on a detection target other than a fetus, and the human breath referred to in the scheme of the above embodiment may be the breath of the detection target itself.
For example, in one example of the disclosed embodiment, when performing magnetocardiogram detection on a fetus, the human breath referred to in the scheme of the above embodiment is maternal breath. Illustratively, during the detection of the fetal magnetocardiogram, the thoracic diaphragm of the mother moves regularly as the mother breathes, thereby pushing the position of the fetus to move along with the movement of the thoracic diaphragm. In this state, there is not only a longitudinal (in the direction from the body surface to the scanning device) movement of the fetus but also a lateral (in the direction perpendicular to the direction from the body surface to the scanning device) movement of the fetus (or the heart of the fetus) in both the lateral and longitudinal directions, which introduces noise in the magnetocardiogram signal. In this case, when the real-time distance information measured by the distance measuring device is used to obtain the respiratory rhythm of the human body and the respiratory rhythm is used as a regression factor for processing the magnetic information, noise respectively generated by movement of the fetus in the transverse direction and the longitudinal direction can be filtered, so that the effect of suppressing the gain of the respiration-related signal is achieved, and the magnetic signal is corrected.
For example, as shown in fig. 11, the operation method of the unshielded magnetocardiogram apparatus may further include the following step S540 after the step S520 is performed.
In step S540, the gain of the electrocardiographically related signal is increased using the electrocardiogram as a regression factor to correct the magnetic signal. For example, after an electrocardiogram of a human body is acquired by the electrocardiogram detection device and the magnetocardiogram, the electrocardiogram is used as a regression factor to gain a section of the magnetic signal fitting the electrocardiogram, so that the electrocardiogram detection device can play a role in increasing the gain of the electrocardiogram related signal to correct the magnetic signal.
Illustratively, the electrodes of the electrocardiogram are arranged, and the operator then moves the movable support arm so that the scanning array is aligned at the apex body surface projection (1-2 cm inside the intersection of the left mid-clavicular line and the fifth intercostal space) and at a distance of 4-5cm, and the scan can then be started, the more for 90 seconds. The magnetic signals acquired by the scanning array, the environmental magnetic field information acquired by the reference array and the electrocardiogram signals are transmitted to a control system, after being subjected to segmented spectrum analysis, the signals are compared with reference signals (such as reference magnetocardiogram signals), if the difference is larger than a certain preset threshold value, the signals are discarded as bad segments, and then the rest signals are preprocessed.
For example, at least one embodiment of the present disclosure provides that the unshielded magnetocardiogram apparatus further includes a moveable support arm. The movable support arm is used for carrying and driving the scanning device and the reference array. Because the atomic magnetometer is not limited by external equipment (for example, the atomic magnetometer is not limited by low-temperature equipment and the like), the atomic magnetometer is more flexible in arrangement and can be moved, so that the scanning device and the reference array are driven by the movable supporting arm, the scanning device and the reference array can be moved to any position of the alignment target according to the requirement, the distance between the scanning device and the target and the distance between the reference array and the target can be changed according to the requirement, and the atomic magnetometer is simple and convenient to operate.
Illustratively, referring back to FIG. 1, a moveable support arm 400 is used to move the position of the scanning apparatus 100 and the reference array 200 to align the heart, and three orthogonally oriented handles are provided to facilitate the moving operation. For example, a second atomic magnetometer of the reference array is mounted inside the handle. The scanning device 1000 and the reference array 200 are both mounted on the moveable support arm 400, the scanning device 100 and the reference array 200 are fixed in relative position, and the reference array 200 is directly above the scanning device 100. The moveable support arm 400 has three degrees of freedom, i.e., translation along the X, Y, Z axis, respectively, as shown in FIG. 1.
For example, in the unshielded magnetocardiogram apparatus provided in at least one embodiment of the present disclosure, referring back to fig. 1, the unshielded magnetocardiogram apparatus further includes a movable host 500, and the control system is located in the movable host 500. The current magnetocardiogram apparatus is bulky, inconvenient to move, and generally used in a private room, and also takes a long time to move, and is not suitable for emergency treatment or the like. Because the atomic magnetometer is not limited by external equipment (for example, the limit of low-temperature equipment and the like is not needed), the atomic magnetometer is more flexible in arrangement and can be moved, and on the basis, the host machine comprising the control system can be set to be movable, so that the unshielded magnetocardiogram device is convenient to move, and is not limited to be applied in a special room. For example, it may be moved for different emergency room applications as needed.
For example, the host computer may contain a data acquisition module, a computer, a display, data processing and visualization software, a human-computer interaction system, and the like.
For example, referring back to fig. 1, the unshielded magnetocardiogram apparatus provided by at least one embodiment of the present disclosure may further include a movable nonmagnetic bed 500. By arranging the non-magnetic bed 500 to be movable, the non-shielding magnetocardiogram apparatus is convenient to move, and the target does not need to be moved relative to the magnetocardiogram apparatus, so that the safety of the target (patient) is guaranteed. For example, rollers or the like may be disposed on the nonmagnetic bed 500 to reduce resistance (e.g., friction) during movement.
It should be noted that, in the embodiments of the present disclosure, the unshielded magnetocardiogram apparatus may present three types of diagnostic results, such as a one-dimensional waveform diagram, a two-dimensional topographic diagram, a three-dimensional dipole source location diagram, and the like.
For example, in the one-dimensional waveform map, a particular channel may be selected to exhibit time-varying magnetic and/or electric field values. For example, several channels of data can be selected for Independent Component Analysis (ICA), and the number of signal sources can be set from 2 to the number of selected channels, so as to obtain clearer magnetocardiogram and/or electrocardiographic signals. For example, feature signal extraction may be performed using signal space projection and independent component analysis algorithms. The unshielded magnetocardiogram device can automatically identify characteristic points of a waveform, such as R wave peaks, and characteristic numerical values, such as S-T intervals, heart rate variability and the like.
For example, in the two-dimensional map, all channels are displayed on one two-dimensional map, the magnitude of the magnetic field is represented by color, and the direction of the magnetic field is represented by an arrow. The regions between each channel are interpolated to estimate the value so that the image appears smoother. The number of the arrows is equal to the number of the channels, and the arrows are in one-to-one correspondence. To assist in interpretation, contours of magnetic field strength may also be added. For a two-dimensional topographic map, the unshielded magnetocardiogram device can automatically identify some characteristic values, such as dipole degree (whether only two poles appear or not and the number of all the poles appear), electric field direction at characteristic time points (for example, when R wave crest) and the like.
For example, in the three-dimensional dipole traceback localization map, the position of the electrical activity of the heart is estimated by using the measured magnetic field distribution through an inverse problem algorithm such as minimum norm estimation, beam forming or dipole matching, and the result is presented on a standardized heart model in a three-dimensional space.
For example, in embodiments of the present disclosure, the parts of the unshielded magnetocardiogram apparatus may preferably be non-ferromagnetic materials, and further preferably non-magnetic materials, to reduce noise caused by the ambient magnetic field. For example, the electrodes and leads of the electrocardiogram are made of non-magnetic materials.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and the like that are within the spirit and principle of the present invention are included in the present invention.
Claims (13)
1. An unshielded magnetocardiogram apparatus, comprising:
a scanning device including at least one first atomic magnetometer, the scanning device configured to detect magnetic field information of a target to output a magnetic signal;
a reference array configured to detect ambient magnetic field information;
and the control system is connected with the scanning device and the reference array signal and is configured to filter noise related to the environmental magnetic field in the magnetic signal based on the environmental magnetic field information.
2. The unshielded magnetocardiogram apparatus according to claim 1, wherein the at least one first atomic magnetometer comprises a plurality of first atomic magnetometers arranged in an array.
3. The unshielded magnetocardiogram apparatus according to claim 2, wherein the scanning device comprises a first scanning structure and a second scanning structure stacked on top of each other, the first scanning structure and the second scanning structure being arranged with an adjustable pitch, the first scanning structure and the second scanning structure each comprising a plurality of the first atomic magnetometers.
4. The unshielded magnetocardiogram device according to claim 3, wherein the second scanning structure is located between the first scanning structure and the reference array, and
the second scanning structure comprises a plurality of through holes arranged in an array, and when the distance between the first scanning structure and the second scanning structure is zero, the first atomic magnetometers in the first scanning structure and the first atomic magnetometers in the second scanning structure are arranged in the same plane in an array mode.
5. The unshielded magnetocardiogram apparatus according to claim 3, wherein the control system outputs a waveform map of the diagnostic result for the detected object after filtering noise associated with the ambient magnetic field in the magnetic signal, wherein,
the first scanning structure and the second scanning structure are adjusted to have zero distance, and the oscillogram is a one-dimensional oscillogram or a two-dimensional topographic map; or
The first scanning structure and the second scanning structure are adjusted to have a distance larger than zero, and the oscillogram is a one-dimensional oscillogram, a two-dimensional topographic map or a three-dimensional source imaging map.
6. The unshielded magnetocardiogram apparatus according to claim 1,
the reference array comprising at least four second atomic magnetometers, the at least four second atomic magnetometers being arranged to determine a spatial coordinate system,
the ambient magnetic field information includes a magnetic field strength of each of the at least four second atomic magnetometers in the spatial coordinate system.
7. The unshielded magnetocardiogram apparatus according to claim 1,
the distance from the first atomic magnetometer to the target is less than the distance from the second atomic magnetometer to the target.
8. The unshielded magnetocardiogram apparatus according to any one of claims 1 to 7,
the control system is used for storing a reference magnetocardiogram signal and a preset threshold value, and is configured to filter out a part of the magnetic signal, which has a difference degree with the reference magnetocardiogram signal larger than the preset threshold value, before noise related to an environmental magnetic field in the magnetic signal is filtered out based on the environmental magnetic field information.
9. The unshielded magnetocardiogram apparatus according to any of claims 1-7, further comprising:
the distance measuring device is configured to monitor the distance information between the scanning device and the target in real time;
wherein the ranging device is connected to the control system, the control system being configured to correct the magnetic signal based on the distance information as a regression factor.
10. The unshielded magnetocardiogram apparatus according to any of claims 1-7, further comprising:
the electrocardio detection device is configured to synchronously detect the electrocardio information of the target when the scanning device detects the magnetic field information of the target;
wherein the electrocardiograph detection device is connected to the control system, the control system is configured to correct the magnetic signal based on the electrocardiographic information, and the unshielded electrocardiograph device is configured to synchronously display an electrocardiogram including the electrocardiographic information and a magnetocardiogram including the magnetic signal.
11. The unshielded magnetocardiogram apparatus according to any of claims 1-7, further comprising:
a movable support arm for carrying and driving the scanning device and the reference array.
12. The unshielded magnetocardiogram apparatus according to any of claims 1-7, further comprising:
a mobile host, the control system being located within the mobile host.
13. The shieldless magnetocardiogram apparatus according to any of claims 1-7, further comprising a movable, non-magnetic bed.
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