Device for detecting magnetic signal generated by beating heart

Abstract

The invention relates to a device for detecting magnetic signals generated by a beating heart (M), comprising at least two nitrogen-vacancy-center, NV-, magnetometer units (S1, S2), which are arranged in a geometric arrangement relative to one another and are connected to a signal processing unit (200), wherein the device is designed to detect a magnetic field intensity (R1, R2) and a field direction (R1, R2) by means of each of the at least two NV magnetometer units (S1, S2), and determining, by means of a signal processing unit (200), at least one field vector comprising an effective magnetic field intensity and an effective field direction from the magnetic field intensities and field directions detected by means of the at least two NV magnetometer units.

Description

[0001] The present invention relates to a device for detecting magnetic signals generated by a beating heart. Background Art

[0002] In order to measure very small magnetic field strengths, quantum sensors that are optically pumped or based on NV centers in diamond are particularly suitable as sensors. DE 102022204526.2 describes a magnetometer that uses optically pumped and optically detected magnetic resonance (optically detected magnetic resonance, ODMR). What is used here is the energy level splitting of a specific spin state of unpaired electrons under the influence of an external magnetic field, the so-called Zeeman effect. By splitting the energy levels, when relaxing from the excited state, a change transition is generated, which can then be measured, for example, by optical excitation and frequency-dependent detection of the generated fluorescent radiation or by observing optical properties such as absorption of light. Then, the magnetic field strength can be inferred from the measured optical parameters. Summary of the invention

[0003] According to the invention, a device for detecting magnetic signals generated by a beating heart is provided having the features of claim 1. Advantageous embodiments are the subject matter of the dependent claims and the following description.

[0004] Magnetocardiography (abbreviated as MKG) is the recording and display of the magnetic field of the heart, which is generated by the electrophysiological activity of the myocardial cells. Within the scope of the present invention, a contactless, passive approach to long-term monitoring of the human heart with high resolution is presented. This is achieved by nitrogen-vacancy magnetometers (so-called NV magnetometers) in a geometric arrangement for vector gradient measurements.

[0005] In detail, a device for detecting a magnetic signal generated by a beating heart is now described, the device having at least two NV-magnetometer units, which are arranged in a geometric arrangement relative to each other and connected to a signal processing unit, wherein the device is configured to: detect a magnetic field strength and a field direction by means of each of the at least two NV-magnetometer units, and determine at least one field vector comprising an effective magnetic field strength and an effective field direction from the magnetic field strength and field direction detected by means of the at least two NV-magnetometer units by means of the signal processing unit. Both a wireless connection and a wired connection are provided between the sensor device and the signal processing unit. Such a device can also be referred to as a magnetocardiograph.

[0006] Diamond NV magnetometers are based on the readout of the magnetic resonance of specific vacancy centers in diamond, in particular nitrogen vacancies (NV), which occur as impurities in the carbon lattice of diamond and can also be introduced in a targeted manner. If the NV center in the ground state is optically excited, for example by irradiating a pump laser beam with a suitable wavelength (in this case in the green wavelength range, for example at 532 nm for off-resonance excitation), the electrons are raised from the triple ground state to the excited triple state and relax at 650-800 nm (637 nm = zero phonon line) while emitting fluorescence in the red wavelength range. Since the NV center with m s = ±1 spin quantum number, the possibility of non-spin-maintaining transition is relatively high, so continuous excitation pumping makes the NV-center mostly in spin state m s =0 is hyperpolarized.

[0007] In the basic state m s =0 and m s = ±1, there is an energy difference between the spin states, which in this case is approximately 2.87 GHz. Therefore, if microwave radiation is radiated into the diamond in addition to the optical excitation, then in this case a red fluorescence interference occurs at this resonance frequency of 2.87 GHz, because the spin-polarized electrons are driven from the m by the microwave field. s =0 basic status increased to m s = ±1 basis state, and from there it is pumped to m s = ±1 excited state. However, from there, firstly non-radiative transitions and weak infrared fluorescence transitions occur via the singlet state, while the fluorescence in the red range is cancelled.

[0008] If an external magnetic field is present, the so-called Zeeman effect occurs: the energy m s= ±1 triplet-levels are split into Zeeman levels that are equidistant in energy. Then, when the fluorescence close to the spectrum of microwave excitation is marked, two dips are shown in the fluorescence spectrum, the frequency spacing of which is proportional to the magnetic field strength of the external magnetic field. The magnetic field sensitivity is first defined by the minimum resolvable frequency shift and can reach 1pT / √Hz or less. Since the NV-centers in single-crystal diamond have four possible arrangements in the lattice, the following situation occurs when there is an oriented magnetic field, namely: the NV-centers present in the crystal react to the external magnetic field to different degrees depending on their position in the crystal. As a result, in an ideal case, four pairs of fluorescence minima may appear in the spectrum, and from the shape and relative position of the four pairs of fluorescence minima, it is possible to clearly determine not only the magnetic field strength of the external magnetic field as a numerical value but also the direction of the external magnetic field. Therefore, in order to be able to perform vectorial magnetic field measurements, the device has a mechanism for generating a substantially uniform bias magnetic field in the region of the magnetometer unit or its sensor medium, wherein the bias magnetic fields of different NV-magnetometer units are different. This can involve a Helmholtz coil arrangement, wherein at least the sensor medium is arranged inside the Helmholtz coil arrangement (each magnetometer unit has its own bias field). Other mechanisms can also be involved, such as simple coils, elongated coils, permanent magnet solutions such as in a Halbach array, etc.

[0009] By using a certain number of vector magnetometer units in geometrical arrangement and gradient measuring instrument wiring, these magnetometer units have different orientations relative to the magnetic field of the heart. Through gradient measuring instrument wiring, that is, vector arithmetic of the parameters basically measured, the position and intensity of the magnetic field exciter (heart) can be determined. Because the significantly stronger background field in the two magnetometer units is basically the same (same intensity and orientation), it can be eliminated. Thus, the necessity of magnetic shielding is cancelled, making it possible to measure the magnetic field in the daily environment. Compared with the traditional gradient measuring instrument system with a single-dimensional magnetometer, another advantage is the compact structural form of the gradient measuring instrument system that is realized in this way, because a reference magnetometer far away is not required. The present invention is correspondingly particularly suitable for measuring weak magnetic fields without shielding. The technical details of the gradient measuring instrument solution that can also be used within the scope of the present invention are disclosed in DE102022201690.4 and should be included here together.

[0010] The heart signal has a magnetic signature with an amplitude of (still only) 1 to 2 digits of picoTesla (pT) at a distance of a few centimeters, compared to the geomagnetic field in Central Europe, for example, which is about 50 μT (microTesla), thus 10 times stronger. 6However, even such small field strengths can be resolved with high precision over long periods of time using the proposed technique.

[0011] By means of high-resolution detection of precise cardiac signals, a large number of diseases can be detected, such as, for example, persistent atrial fibrillation and paroxysmal ("burst") atrial fibrillation. As a result, myocardial infarctions and therefore strokes (especially after unrecognized myocardial infarctions) can be prevented. In addition, the present invention is suitable for the early identification of ST-elevation myocardial infarctions, other types of elevation myocardial infarctions, pulmonary embolism, AV-node-reentry-tachycardia, ventricular extrasystoles, but also very rare etiological diseases such as, for example, right ventricular tachyarrhythmias, which otherwise can only be identified by gene sequencing, can be identified at an early stage.

[0012] A particular advantage of NV sensors is the directional or vector information. Compared to other technologies, this is inherently generated for NV sensors. Therefore, it is not necessary to introduce interferences by modulation techniques or to use more unfavorable projections, nor is it necessary to use a plurality of individual sensors. As a result, one has vector and gradient measurement information at exactly the same position (diamond size, i.e. single-digit mm). ∧ 3 and below) and not separated by a few centimeters or more as in other technologies. With NV magnetometer units that can determine not only the field strength but also the direction of the magnetic field, an improved suppression of the background field can be achieved and thus a better detection of signals that are strongly superimposed by interference signals can be achieved. This is based on two mechanisms of action: firstly, the signal is not easily influenced by the tilt of the sensors relative to one another (in standard gradiometer applications, the tilt of the 1D magnetometer leads to different projections of the measurement field or the interference field) and can be compensated for, which is important for non-rigid obstructions, especially in combination with positioning, for example in the relevant mattress. Secondly, the interference field can have a different spatial direction than the field to be measured. This makes it easier to separate the signal from the background.

[0013] In particular, if a gradient measuring instrument system consisting of at least two NV-magnetometer units with different main extension planes is used, the direction information can be used to record a channel equivalent to an EKG channel. Here, the vector and / or scalar difference of different NV-magnetometer units of a device can be formed in order to detect or eliminate background noise. The formation of the time derivative of the signal can also be used. Vector information allows accurate (not only projected, but directly) correction / separation of background signals / interference signals. This especially eliminates the following problem, that is, for traditional gradient measuring instruments consisting of single-dimensional magnetic field sensors, these gradient measuring instruments must be very accurately coordinated with each other in terms of angle. With vector information, this is no longer necessary because the interference field is completely known.

[0014] It is also possible to use the directional differences or different vector signals or both of the gradient measurements in order to generate information equivalent to different EKG channels (direction- and position-resolved signals from the heart). In one embodiment, the signal processing unit is configured to determine a plurality of field vectors, each comprising a magnetic field strength and a field direction, from the magnetic field strength and field direction detected by means of the at least two NV magnetometer units.

[0015] In particular, spatial resolution of the heart can be achieved by a plurality of individual magnetometer units of the device near the heart, wherein a straight projection of the heart onto the device covers a plurality of NV magnetometer units. In this way, the 3D distribution of the magnetic field of the heart is spatially detected (a plurality of field vectors). According to embodiments, actual 2D and 3D images of the heart are thus obtained, and a much more in-depth analysis than previously possible can thus be performed.

[0016] After the data has been processed, the signal is analyzed. In particular, attention is paid to specific items that are indicators for specific problem signals or for healthy signals. Specific deviations of these indicators from the standard may, for example, result in the output of an interference signal that can, for example, trigger an alarm or forward a signal to a doctor.

[0017] Only the accurate resolution of the heart signal can realize this detection of symptoms. That is to say, when the signal is seriously polluted by noise or poorly resolved, the displacement of different PQRST complexes of the heart relative to each other or over time, the fluctuation, deformation or small interference in its amplitude cannot be detected. However, this resolution of these standards is an important factor, because the above-mentioned problems may cause confusion of complexes (such as the T wave of the increased and offset is interpreted as the R wave, but this often occurs on the "healthy" heart) and cause false alarms. In particular, vector information also allows the positioning of the heart position, and thus also allows the source to be determined and the data from the correct direction to be clearly evaluated. This can also be used in particular to measure the various parts of the heart or other objects and assign the signal specifically to these parts. Thus, the information content is higher than that of EKG, because the heart is spatially resolved and thus different abnormalities can be specifically assigned to physical areas. This allows for a more accurate diagnosis. In addition, there are signals that can only be seen in the MKG but not in the EKG, especially in those directional signals that provide additional information, such as when one ventricle is "claudication behind" the other. The MKG signal is particularly instructive here, because artifacts can occur separately in different directions or locations and can thus be accurately identified.

[0018] Another advantage of NV sensor systems is their size, in particular the size of the sensor medium. For such applications, the active measurement volume should be small relative to the object to be measured (the heart), because otherwise the signal would be integrated over a large part of the surface coverage and the signal could disappear because the integral is zero. The smaller the active measurement volume is compared to the heart, the better the signal detection. NV sensor systems have a very small active sensor volume. In addition, this miniaturization allows the use of sensors in geometric arrangements. In particular, arrangements with very high resolution through a very small active sensor volume are possible.

[0019] For the application described, a sampling rate higher than the heart signal, in particular greater than 50 Hz, is required in order to resolve the heart signal. Here, a range of 200 Hz to 400 Hz is considered to be particularly advantageous. A higher range is always better for resolution, but increases the requirements on sensitivity.

[0020] Further advantages and embodiments of the invention are apparent from the description and the drawings.

[0021] The invention is schematically illustrated in the drawings on the basis of exemplary embodiments and is described below with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1The main components of an NV center magnetometer as can be used within the scope of the present invention are shown in a schematic block diagram.

[0023] Figure 2 In the various illustrations a) to c), a possible geometrical arrangement of an NV magnetometer unit of a device for detecting magnetic signals according to one embodiment is shown in each case in the form of a schematic block diagram.

[0024] Figure 3 The measuring principle of NV vector gradiometric determination, as can be used in one embodiment of the present invention, is shown in a schematic block diagram. DETAILED DESCRIPTION

[0025] Figure 1 The main components of the NV center magnetometer are schematically shown. Here, as the sensor medium, there is first a diamond 110 with nitrogen vacancies (NV). The optical excitation of the NV center can be achieved by a suitable light source 120, such as an LED or a pump laser. Here, for example, a frequency-doubled Nd:YAG laser or a semiconductor laser in the green range of, for example, 510-532 nm, such as 532 nm, is suitable for off-resonance excitation. As an alternative, an LED in a suitable wavelength range can also be used. Depending on the layout, the light of the light source 120 can be radiated into the diamond 110 through suitable optical elements 122, such as, for example, reflectors, beam splitters, focusing mirrors, such as lenses, and if necessary, through fiber-optic elements. In addition, the excitation light can be radiated continuously or pulsed by a laser, so as to, for example, retain a time window for interference-free fluorescence measurement.

[0026] In addition, the magnetometer can include a microwave source 150, which can generate an electromagnetic field in the sensor medium, that is, in the region of the NV center of the diamond 110, within the bandwidth covering the desired resonance frequency. A microwave resonator structure can be used to uniformly distribute the generated microwaves in the space of the measurement range in the diamond. The resonator structure or microwave source 150 is preferably matched to the frequency of the electron spin resonance. In order to achieve vector magnetometry, an additional static bias magnetic field 140 is generated. As a result, the measurement becomes intrinsic vector. For this purpose, different spatial directions in the crystal structure are used. For example, Helmholtz coils are suitable for generating such a magnetic field 140, for which a substantially uniform magnetic field in a restricted range can be generated by means of a coil pair.

[0027] The generated fluorescence 112 from the diamond 110 can be guided to the first photodetector 130 by suitable optical elements 134, such as optical filters, beam splitters, lenses and / or fiber optic elements, which are sensitive at least in the range of the fluorescence wavelength. The first photodetector 130 can also be arranged directly on the diamond 110. The second photodetector 132 is arranged so that it can detect at least a part of the excitation light of the light source 120, which can be coupled out by beam splitters, filters or partially transparent elements. This detector signal 132 of the excitation light can be used as a reference signal, so as to eliminate background signals and highlight the resonance signal of interest, for example, by means of a phase-locked amplifier through modulation of the excitation light. As a supplement or alternative, this reference signal can be used to take into account the fluctuations of the excitation light. Corresponding circuits 160, such as preamplifiers, logarithmic amplifiers, phase-locked amplifiers, signal filters or other circuits are thus provided for obtaining the signals of the first and second photodetectors and preprocessing the signals in a suitable manner for further evaluation. Finally, the preprocessed fluorescence signal can be evaluated by a signal processing unit 170 , for example using a suitable microcontroller or processor, in order to derive from the signal desired parameters of the detected magnetic field, in particular the magnetic field strength and direction of the magnetic field.

[0028] It goes without saying that such a device can also have further units (not shown), such as a communication unit or an interface for outputting measurement results. Such a device can also be advantageously integrated into an ASIC or FPGA.

[0029] In order to be able to use in everyday environments, magnetic fields that do not originate from the expected weak sources, especially those at 10 -5 The Earth's magnetic field in the range of a few microteslas is eliminated as much as possible from the measurement. In contrast, the heart's magnetic field is in the range of 10-100 times 10 -12 Fluctuates within the range of Tesla (picotesla).

[0030] The elimination of the background magnetic field can be achieved during the measurement of the magnetic field according to an exemplary embodiment by means of a gradiometer system. In principle, a gradiometer is a sensor unit that can detect both the field strength and the gradient of the field.

[0031] For this purpose, at least two individual magnetometer units S1, S2, ..., Sn, S11, S21, ..., Sn1, S12, S22, ..., Sn2, S1m, ..., SnmS11, S21, ..., Sn1, S12, S22, ..., Sn2, S1m, ..., Snm can be used, which are arranged at different positions in space. As an example, the following is combined with Figure 2 A sensor unit is described which uses two or more NV-center-magnetometers in a gradiometer system.

[0032] Figure 2 In different illustrations a) to c), possible geometric arrangements of NV-magnetometer units of a device for detecting magnetic signals according to a design are shown. FIG. a) shows in a side view the arrangement of at least two NV-magnetometer units S1, S2, ..., Sn in an arbitrary arrangement relative to each other in one plane (the plane is perpendicular to the illustrated plane, that is, only the first row can be seen). FIG. b) shows in a side view two NV-magnetometer units S1, S2, whose sensor media are segments of the same diamond crystal 110. FIG. c) shows in a side view a certain number (n times m) of NV-magnetometer units S11, S21, ..., Sn1, S12, S22, ..., Sn2, S1m, ..., Snm in an arbitrary three-dimensional arrangement. Here, other (not shown) layers are adjacent behind the illustrated plane, so that a cubic grid is formed as a whole. Here, at least one NV magnetometer unit (not shown), for example located in one of the later layers, is not arranged in the following level (illustrated level): the level in which other NV magnetometer units S11, S21, ..., Sn1, S12, S22, ..., Sn2, S1m, ..., Snm are arranged.

[0033] Furthermore, M denotes a signal source, here the heart, and O denotes an optional surface, in particular the body skin, which limits the accessibility or reachability of the magnetic field source M.

[0034] In a design of the invention, more than two (but at least two) NV magnetometer units can be combined to form a gradiometer. With each additional NV magnetometer unit, the background field can be better determined and the position and intensity of the actuator can be better separated from the background.

[0035] In other embodiments of the invention, always two NV-magnetometer units can also form a gradiometer, wherein a plurality of gradiometers are then formed overall according to the number of NV-magnetometer units and detect the signal of interest. A valid measurement signal can then be formed therefrom, in particular by a signal processing unit, for example by averaging, summing, etc.

[0036] The distance d between two NV magnetometer units S1, S2, ... or more precisely their sensor media corresponds to the distance between the following positions at which the magnetic field measurement is carried out simultaneously. If the distance between the measurement positions is relatively small, it can be assumed that the additional background magnetic field B envThe intensity of the magnetic field B is approximately the same at both locations. In contrast, the weak magnetic field B of interest decreases significantly with increasing distance from the magnetic field source M. In addition, the different orientations of the magnetic field of an exciter (e.g., the heart) allow a clear separation from the background field even at small distances.

[0037] Therefore, by arranging two NV-magnetometer units at a spacing and angle different from the source or heart, the background field can be eliminated or determined by vector arithmetic, and the small magnetic field of interest is determined thereby, and its source is characterized (position and orientation). This can be further improved by a far-away magnetometer, which is so far away that the weak magnetic field of interest falls below the detection threshold. With such a configuration, local changes in the background field can be compensated by the at least two nearby magnetometers. For this purpose, two NV-magnetometer units can be arranged up and down, for example, in an axial gradient meter configuration, so that an NV-magnetometer unit of the first layer forms a gradient meter with an NV-magnetometer unit of the second layer below it, respectively. The background field can also be determined by another NV-magnetometer unit arranged at a larger spacing, such as at least 1m, relative to the two NV-magnetometer units.

[0038] A kind of concept of the present invention is to measure the field in a vectorial manner and from different positions simultaneously using multiple NV-magnetometer units. As long as this arrangement is near the signal source M that should be measured, then use each vector sensor to measure the field of the signal source in different directions. This distribution of the measured field vector is characteristic and allows to infer the source about intensity, position and orientation. In order to detect weak signals in comparison with the background, the assumption of a uniform background field within the range of the geometric arrangement consisting of the NV-magnetometer units (usually this should be assumed here, because the spacing between the source of the interference and the sensor medium should be assumed to be much larger than the spacing between the signal to be measured and the sensor medium) allows to calculate individual field vectors, because the vector of the interference field can be assumed to be the same, and thus simple vector arithmetic is sufficient for extracting the signal vector. If a geometric arrangement is used, then it is also possible to compensate for the inhomogeneity in the background.

[0039] As in Figure 3As shown in , different measuring positions of the NV-magnetometer units S1, S2 determine the field vector in different directions. Since the background field Z1 is the same for both NV-magnetometer units, this allows the strength and orientation of the source to be deduced. By measuring the signal / field in different directions (the field of the source depends on the position of the individual sensors relative to the source in terms of amplitude and orientation), the noise in the background field can be further suppressed (fluctuations orthogonal to the measurement signal are suppressed). This allows for noise suppression that is superior to conventional gradient determination schemes.

[0040] For example, M1 to Mn is at least one magnetic field component and Z1 to Zn is at least one interference component (such as the Earth's magnetic field), which can be static or variable in time. Figure 1 (To expand) measure the synthetic components R1 to Rn containing the interference signal. Here, the NV-magnetometer unit S1 measures the component R1 composed of the first interference Z1 and the signal M1 at the position of S1, and the NV-magnetometer unit S2 measures the component R2 composed of the second interference Z2 and the signal M2 at the position of S2, etc. A signal that is slow to react relative to the interference component can be determined from this by vector arithmetic.

[0041] Figure 3 The measuring principle of NV vector gradiometric determination, as can be used in one embodiment of the present invention, is shown in a schematic block diagram for two NV magnetometer units S1 and S2. The evaluation can be performed as follows:

[0042] Two vector-valued signals R1 and R2 are measured. These signals contain signal components M1 and M1' as well as interference components Z1 and Z2=Z1, which are in particular identical for the measurement range. The gradiometer then measures the signal according to: To produce.

[0045] As equation (1) indicates, the signal no longer contains interference components, if these are identical for the measuring range. Furthermore, the measuring signal is vectorial, which allows, for example, the assignment of direction ("where does the signal come from?"), the differentiation of different signals and the correlation of multiple signals from different sensors in a system (imaging methods).

[0046] The result in equation 1 can be expressed in terms of magnitude and direction. This is particularly advantageous when the source is between the magnetometer units (or in a plane extending through the center of two magnetometer units) and thus the magnetic fields are opposite.

[0047] By using three or more magnetometer units (geometrical arrangement), it is possible to construct a system of equations which allows the respective magnetic field at the magnetometer units to be determined.

[0048] Another advantage is that, for conventional gradiometers, the difference of two scalar sensors connected in series is measured. The performance here depends on the fact that the sensors measure only the background field (the measured values ​​(scalars) are simply subtracted from each other). Furthermore, in this case, the difference of the sensors is always smaller than the actual measurement size (<M). The approach described here makes it possible to determine the measurement signal at different angles relative to the background signal by arranging it in different spatial angles (also projected onto one plane). Thus, the signal-to-noise ratio and thus the sensitivity are increased (in the ideal case of symmetry, the magnetic fields for the two sensors are exactly opposite).

[0049] Another advantage of vector gradiometers is that they can be made significantly smaller than conventional gradiometers. Here, the reference sensor is arranged so that its spacing relative to the signal source is so large that the signal is significantly smaller at the reference sensor. This requires that the spacing between the sensors is significantly larger than the spacing between the source and the measuring sensor. By using the vector information, all magnetometer units can be placed near the source, and no reference sensors far away are required.

[0050] By means of calibration, assumptions about the distance to the signal source or reference sensors that characterize the background field at a distance from the source, a kind of "card" can be generated, that is, a spatial resolution (3D) of the measurement signal. In this case, a 2D resolution is inherently generated by the sensor array. If the sensor array is not used in one plane, a 2D resolution can thus be achieved.

[0051] The spacing d of the sensor heads inside the gradiometer unit, that is to say the spacing of the two sensor diamonds in this case, can be in the range of millimeters to several centimeters, for example between 0.5 cm and 2 cm. For values ​​in this order of magnitude, good results can be obtained, for example, for measuring biomagnetic fields in the range of picoteslas. However, as long as sufficient independence of the signal from the background field is achieved, it is also possible to use larger or smaller spacings or other gradiometer configurations, such as sensors arranged side by side. In the case of too large a spacing between the individual sensor heads, especially for local background fields (wires, etc.), the background field can no longer be the same at two locations; in contrast, in the case of too small a spacing between the sensor heads, the difference between the field strengths of the magnetic field to be measured between the two locations may be too small. The selection of a suitable spacing between the two sensors of the gradiometer unit is thus preferably also dependent on the type and orientation of the magnetic field source of interest and on the expected field strength. The spacing of the sensor unit from the magnetic field source can likewise be in the range of millimeters to centimeters.

[0052] The signal processing for this case has the task of being independent of external magnetic field disturbances. Wherever charges move or magnetic or magnetizable materials move, the ambient noise changes. This must be separated from the signal by appropriate signal processing in order to make the signal measurable.

[0053] Furthermore, particularly good signal processing allows for an improved signal resolution and thus the detection of relatively rare or relatively difficult to detect artifacts and the symptoms associated therewith.

[0054] Many environmental signals occur at specific frequencies. Signals can be seen through the power grid, in particular for harmonics such as 50 Hz or 60 Hz and higher. Filtering of these typical frequencies is of great benefit, since a lot of noise is reduced thereby. In particular, the performance of the gradient measuring unit can be significantly improved thereby. In this case, for example, for the frequency of the AC supply (such as 50 Hz) and / or harmonics (such as 100 Hz, 150 Hz, etc.), a band stop filter or a narrow stop band filter (English: Notch filter) is used in order to filter the measured signal.

[0055] Furthermore, it can be advantageous to use a high-pass filter to filter out particularly low frequencies, for example less than 1 Hz, from the measured signal and / or to use a low-pass filter to filter out particularly high frequencies, for example greater than 200 Hz, from the measured signal. “Particularly high and particularly low” are relative to frequencies such as typically occur in a heart signal, i.e. typically approximately 60 to 180 Hz.

[0056] In addition, other special filters can be introduced, which filter out interference frequencies, such as field frequencies or field patterns that typically occur in technical equipment, in a manner adapted to the specific environment. This can also be different for different fields of application. For example, interference frequencies in a hospital are different from interference frequencies in a private home.

Claims

1. A device for detecting magnetic signals generated by a beating heart (M), having at least two nitrogen-vacancy-center-, NV-, magnetometer units (S1, S2, ..., Sn, S11, S21, ..., Sn1, S12, S22, ..., Sn2, S1m, ..., Snm), which are arranged in a geometrical arrangement relative to one another and are connected to a signal processing unit (170, 200), The device is configured to: detecting a magnetic field strength (R1, R2) and a field direction (R1, R2) by means of each of the at least two NV-magnetometer units (S1, S2, ..., Sn, S11, S21, ..., Sn1, S12, S22, ..., Sn2, S1m, ..., Snm), and With the aid of the signal processing unit (170, 200), at least one field vector including an effective magnetic field intensity and an effective field direction is determined from the magnetic field intensity and field direction detected with the aid of the at least two NV-magnetometer units (S1, S2, ..., Sn, S11, S21, ..., Sn1, S12, S22, ..., Sn2, S1m, ..., Snm).

2. The device according to claim 1, wherein the geometric layout is a two-dimensional layout, wherein the at least two NV-magnetometer units (S1, S2, ..., Sn, S11, S21, ..., Sn1, S12, S22, ..., Sn2, S1m, ..., Snm) are arranged in one plane.

3. An apparatus according to claim 1, wherein the at least two NV-magnetometer units (S1, S2, ..., Sn, S11, S21, ..., Sn1, S12, S22, ..., Sn2, S1m, ..., Snm) include at least four NV-magnetometer units, and wherein the geometric layout is a three-dimensional layout, wherein at least one of the at least four NV-magnetometer units is not arranged in the following layer: at least three other NV-magnetometer units of the at least four NV-magnetometer units are arranged in the layer.

4. A device according to any of the preceding claims, wherein each of the at least two NV magnetometer units (S1, S2, ..., Sn, S11, S21, ..., Sn1, S12, S22, ..., Sn2, S1m, ..., Snm) has a diamond crystal or a segment of a diamond crystal with nitrogen-vacancy centers as a sensor medium (110), wherein the device is configured to detect the magnetic field strength and field direction by reading out a spin resonance in the sensor medium (110) that depends on the magnetic field strength.

5. The device according to claim 4 also has at least one excitation light source (120) for inputting light (124) radiation into the sensor medium (110), at least one microwave source (150) for generating a resonance field in the sensor medium, and at least one photodetector (130) for detecting resonance-dependent fluorescence (112) from the sensor medium (110).

6. The device according to claim 5, wherein the at least two NV-magnetometer units (S1, S2, ..., Sn, S11, S21, ..., Sn1, S12, S22, ..., Sn2, S1m, ..., Snm) are assigned the same excitation light source (120) and / or the same microwave source (150).

7. A device according to any one of claims 4 to 6, wherein the sensor medium of the at least two NV-magnetometer units (S1, S2, ..., Sn, S11, S21, ..., Sn1, S12, S22, ..., Sn2, S1m, ..., Snm) respectively has a segment of the same diamond crystal (110).

8. A device according to any one of claims 4 to 7, wherein the spacing (d) between the sensor media (110) of the at least two NV-magnetometer units (S1, S2, ..., Sn, S11, S21, ..., Sn1, S12, S22, ..., Sn2, S1m, ..., Snm) is between 1 and 30 mm, preferably between 5 and 20 mm.

9. The device according to any one of claims 4 to 8 also has at least one mechanism (140) for generating a substantially uniform bias magnetic field at the position of the sensor medium (110) of the at least two NV-magnetometer units (S1, S2, ..., Sn, S11, S21, ..., Sn1, S12, S22, ..., Sn2, S1m, ..., Snm), wherein the bias magnetic fields of different NV-magnetometer units (S1, S2, ..., Sn, S11, S21, ..., Sn1, S12, S22, ..., Sn2, S1m, ..., Snm) are different.

10. The device according to any of the preceding claims further comprises a band-stop filter or a narrow band-stop filter, the filtering frequency of which is the frequency of the AC power supply or its harmonics; and / or a low-pass filter and / or a high-pass filter for filtering the detected signal.

11. An apparatus according to any one of the preceding claims, wherein the signal processing unit (170, 200) is configured to determine a plurality of field vectors each including a magnetic field strength and a field direction from the magnetic field strength and field direction detected by means of the at least two NV-magnetometer units (S1, S2, ..., Sn, S11, S21, ..., Sn1, S12, S22, ..., Sn2, S1m, ..., Snm).

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