Apparatus and method for measuring intracorporeally generated magnetic fields

Abstract

The invention relates to an apparatus for measuring intracorporeally generated magnetic fields, comprising: a catheter, wherein an optical waveguide device is arranged within the catheter, a sensor unit for measuring magnetic fields, wherein the sensor unit is a nitrogen-vacancy centre magnetometer which has, as a sensor medium, one or more diamond crystals having a plurality of nitrogen-vacancy centres, wherein the one or more diamond crystals are arranged within the optical waveguide device, wherein the sensor unit comprises a magnetic field generating device for generating a magnetic field in the region of the sensor medium, wherein the sensor unit has an excitation light source for radiating excitation light into the optical waveguide device in order to excite the sensor medium, wherein the sensor unit comprises a microwave source for generating microwaves in order to excite the sensor medium with microwaves, and wherein the sensor unit comprises a photodetector for detecting resonance-dependent fluorescent light from the sensor medium, and an evaluation unit which is configured to determine, based on the detected fluorescent light, a magnetic field at the respective location of the one or more diamond crystals. The invention relates to a method for measuring intercorporeally generated magnetic fields, a computer program and a machine-readable storage medium.

Description

[0001] R. 412602

[0002] Description

[0003] title

[0004] Device and method for measuring intracorporeally generated magnetic fields

[0005] The invention relates to a device and a method for measuring intracorporeally generated magnetic fields, a computer program and a machine-readable storage medium.

[0006] State of the art

[0007] Various sensor technologies are known for measuring very low magnetic field strengths. One of the most sensitive sensor types is the SQU ID magnetometer (Superconducting Quantum Interference Device), which is based on superconducting components and can resolve individual magnetic flux quanta or fields down to the range of a few femtotesla (fT). However, a disadvantage of SQU ID sensors is the need for cooling below the superconducting transition temperature, which for most superconducting materials is below 77 Kelvin, i.e., below the temperature of liquid nitrogen.

[0008] Similarly, quantum-based magnetic sensors are known, for example, from DE 102018 220234 A1 or DE 10 2018214617 A1.

[0009] Patent US 10,705,163 B2 discloses a magnetic field sensor.

[0010] Disclosure of the invention

[0011] The object underlying the invention is to provide a concept for measuring intracorporeally generated magnetic fields. R. 412602

[0012] - 2 -

[0013] This problem is solved by means of the respective subject matter of the independent claims. Advantageous embodiments of the invention are the subject matter of dependent claims.

[0014] According to a first aspect, a device for measuring intracorporeally generated magnetic fields is provided, comprising: a catheter, wherein a fiber optic device is arranged within the catheter; a sensor unit for measuring magnetic fields, wherein the sensor unit is a nitrogen-vacancy center magnetometer, which has as a sensor medium one or more diamond crystals having several nitrogen-vacancy centers, wherein the one or more diamond crystals are arranged within the fiber optic device; wherein the sensor unit comprises a magnetic field generation device for generating a magnetic field in the region of the sensor medium; wherein the sensor unit comprises an excitation light source for shining excitation light into the fiber optic device in order to excite the sensor medium; and wherein the sensor unit comprises a microwave source for generating microwaves in order to excite the sensor medium with microwaves.and wherein the sensor unit comprises a photodetector for detecting resonance-dependent fluorescence light from the sensor medium and an evaluation unit which is configured to determine a magnetic field at the respective location of one or more diamond crystals based on the detected fluorescence light.

[0015] According to a second aspect, a method for measuring intracorporeally generated magnetic fields using the device according to the first aspect is provided, comprising the following steps:

[0016] Generating a magnetic field in the area of ​​the sensor medium by the magnetic field generation device,

[0017] Irradiation of excitation light into the light guide device by the excitation light source to excite the sensor medium, R. 412602

[0018] - 3 -

[0019] Generating microwaves using the microwave source to excite the sensor medium with microwaves, and

[0020] Detection of resonance-dependent fluorescence light from the sensor medium by the photodetector, and

[0021] Determination based on the detected fluorescence light of a magnetic field at the respective location of one or more diamond crystals by the evaluation unit.

[0022] According to a third aspect, a computer program is provided, comprising instructions which, when the computer program is executed by the device according to the first aspect, cause it to execute a procedure according to the second aspect.

[0023] According to a fourth aspect, a machine-readable storage medium is provided on which the computer program is stored according to the third aspect.

[0024] The invention is based on the finding and includes the fact that the above problem is solved by providing a catheter within which a fiber optic device is arranged, and within which a sensor medium of a nitrogen vacancy center magnetometer is arranged. Thus, the sensor medium can be introduced more efficiently intracorporeally via the catheter, enabling the efficient measurement of intracorporeally generated magnetic fields.

[0025] A nitrogen-vacancy center magnetometer advantageously exhibits very high sensitivity and can also be implemented in a compact design, allowing for a correspondingly compact catheter. This enables efficient measurement of intracorporeally generated magnetic fields even in smaller vessels or organs. Complex cooling systems, such as those required for a SQUID sensor, are unnecessary. Furthermore, a nitrogen-vacancy center magnetometer advantageously allows for inherently vectorial magnetic field measurements. R. 412602

[0026] - 4 -

[0027] Therefore, due to the high sensitivity of the nitrogen defect center magnetometer, very small magnetic field strengths can be measured.

[0028] This provides a concept for the efficient measurement of intracorporeally generated magnetic fields.

[0029] A nitrogen vacancy center magnetometer can also be called an NV magnometer. Here, "NV" stands for "nitrogen vacancy," meaning "nitrogen vacancies."

[0030] A nitrogen-vacancy center magnetometer as described thus comprises a diamond crystal or diamond crystals having nitrogen-vacancy centers as a sensor medium and is designed to detect a magnetic field strength at a measuring point by reading out a spin resonance in the sensor medium that depends on the magnetic field strength.

[0031] The NV magnetometer thus reads out several spin resonances using so-called ODM R and measures the strength and direction of the magnetic field: vector magnetic field. ODMR stands for "Optically Detected Magnetic Resonance".

[0032] The NV magnetometer utilizes optically pumped and / or optically detected magnetic resonances (ODRM). It exploits the fact that, under the influence of an external magnetic field, the energy levels of certain spin states of unpaired electrons split—the so-called Zeeman effect. This energy level splitting results in altered relaxation transitions from excited states, which can then be measured, for example, by optical excitation and frequency-dependent detection of the resulting fluorescence radiation, or by observing optical properties such as light absorption. The magnetic field strength can then be deduced from the measured optical parameters. R. 412602

[0033] - 5 -

[0034] Diamond nitrogen vacancy (NV) magnetometers are based on the detection of magnetic resonances from specific defect centers in diamond, particularly nitrogen vacancies (NV), which occur as impurities in the carbon lattice of diamond and can also be deliberately introduced. If the NV center is optically excited in its normal state without a magnetic field, for example by irradiating it with a pump laser beam of a suitable wavelength (in this case in the green wavelength range, e.g., at 532 nm for off-resonance excitation), the electrons are excited from the triplet ground state to the excited triplet state and relax, emitting fluorescence light in the red wavelength range at 637 nm. Since the probability of non-spin-conserving transitions from the spin state with spin quantum number m s If the value is greater than ±1, continuous excitation pumping ensures that the NV centers are mostly in the spin state m s= 0 hyperpolarized.

[0035] Between the m s = 0 and m s There is an energy difference of ±1 between spin states in the ground state, which in this case is approximately 2.87 GHz. Therefore, if microwave radiation is also applied to the diamond in addition to optical excitation, a dip in the red fluorescence occurs at this resonance frequency of 2.87 GHz, as the spin-polarized electrons are disturbed by the microwave field. s = 0 in the m s = ±1 -ground state can be raised and from there into the m by the pump light s = ±1 excited state. From there, however, mainly non-radiative transitions and weakly infrared fluorescence transitions occur via the singlet state, while fluorescence in the red region disappears.

[0036] If an external magnetic field is present, the so-called Zeeman effect causes the otherwise identically energetic magnetic fields to split. s= ±1 triplet levels in energetically equidistant Zeeman levels. When the fluorescence is plotted against a frequency spectrum of the microwave excitation, two dips appear in the fluorescence spectrum, the frequency separation of which is linearly proportional to the magnetic field strength of the external magnetic field. The magnetic field sensitivity is primarily defined by the minimum resolvable frequency shift and can be up to 1 pTA / Hz. R. 412602

[0037] - 6 - reach. Since the NV center in a single-crystal diamond has four possible orientations within the crystal lattice, the presence of a directed magnetic field results in the NV centers within the crystal reacting differently to the external magnetic field depending on their position within the crystal. Ideally, this allows four pairs of fluorescence minima to appear in the spectrum, from whose shape and relative position both the magnitude and direction of the external magnetic field can be uniquely determined.

[0038] The NV center magnetometer offers numerous advantages for this application. In addition to its aforementioned very high sensitivity, it can also cover a wide measurement range (> 1 Tesla). The underlying Zeeman effect is linearly dependent on the existing magnetic field and also exhibits no degradation, as the measurement is based on quantum mechanical states. Furthermore, an NV center magnetometer allows for the vectorial determination of external magnetic fields based on the various orientations present in the diamond lattice.

[0039] A fiber optic device as described includes, for example, one or more fiber optic cables.

[0040] An example of a fiber optic cable, as described above, is an optical fiber.

[0041] Thus, for example, it is specifically intended that the optical fiber device comprises a bundle of one or more optical fibers. For example, it is intended that the optical fiber device comprises a fiber optic bundle, i.e., a bundle of optical fibers.

[0042] An example of a fiber optic device as described is a flexible fiber optic device.

[0043] An optical fiber as described is, for example, a flexible optical fiber, in particular a flexible glass fiber. R. 412602

[0044] - 7 -

[0045] An end of an optical fiber, into which light is coupled or coupled out, can be called a facet. A corresponding end of an optical fiber can therefore be called a fiber facet, for example.

[0046] By providing a light guide device within which the sensor medium is arranged, the technical advantage is achieved, for example, that the excitation light can be efficiently directed to the sensor medium.

[0047] In one embodiment of the device, the light guide device comprises one or more light guides, within which one or more diamond crystals of the sensor unit having nitrogen vacancy centers are arranged, wherein the excitation light source is configured to shine excitation light into the one or more light guides.

[0048] This results, for example, in the technical advantage that the excitation light can efficiently irradiate the sensor medium.

[0049] In one embodiment of the device, it is provided that at least one of the diamond crystals is arranged on a facet of one of the one or more optical fibers.

[0050] This results, for example, in the technical advantage that the diamond crystal can be arranged efficiently. This type of arrangement is particularly easy to implement.

[0051] In one embodiment of the device, the light guide device comprises several separately formed light guides arranged one behind the other in the direction of light transmission, within each of which one or more diamond crystals of the sensor unit having nitrogen vacancy centers are arranged.

[0052] This results, for example, in the technical advantage of forming a compact arrangement of diamond crystals placed one behind the other. R. 412602

[0053] - 8 - In one embodiment of the device, it is provided that the magnetic field generating device comprises one or more permanent magnets which are arranged within the light guide device.

[0054] This results, for example, in the technical advantage that the magnetic field required for the measuring principle on which an NV magnetometer is based can be efficiently generated at the location of the sensor medium.

[0055] In one embodiment of the device, the magnetic field generating device comprises one or more electromagnets which are arranged within the light guide device.

[0056] This results, for example, in the technical advantage that the magnetic field required for the measuring principle on which an NV magnetometer is based can be efficiently generated at the location of the sensor medium.

[0057] In one embodiment of the device, the sensor unit comprises at least one microwave resonator connected to the microwave source, wherein the at least one microwave resonator is arranged within the light guide device.

[0058] This results, for example, in the technical advantage that the microwave field required for the measurement principle described above can be efficiently generated at the location of the sensor medium.

[0059] In one embodiment of the device, the microwave source is configured to generate microwaves that depend on the location of the one or more diamond crystals, so that the one or more diamonds are excited with different microwaves with localized amplitudes and / or modulation frequencies.

[0060] This results, for example, in the technical advantage of efficiently distinguishing which fluorescence signal belongs to which diamond crystal, thus enabling efficient spatially resolved magnetic field measurement. R. 412602

[0061] - 9 - In one embodiment of the device, it is provided that the excitation light source is configured to emit laser pulses into the fiber optic device, wherein the evaluation unit is configured to determine the magnetic field at the respective location of one or more diamond crystals based on the emitted laser pulses.

[0062] This results, for example, in the technical advantage of enabling efficient spatially resolved magnetic field measurement.

[0063] Embodiments concerning the device result analogously from embodiments concerning the method and vice versa.

[0064] Device features thus result analogously from corresponding process features and vice versa.

[0065] The device is set up, for example, to carry out all steps of the procedure.

[0066] The device is, for example, programmed to execute the computer program.

[0067] The method is, for example, a computer-implemented method.

[0068] The fiber optic device, for example, has exactly one fiber optic cable.

[0069] A light guide as described includes, for example, one or more diamond crystals of the sensor unit having nitrogen vacancy centers.

[0070] For example, a light guide as described comprises exactly one diamond crystal of the sensor unit having nitrogen-vacancy centers.

[0071] For example, the diamond crystals are designed to be arranged in an offset pattern. R. 412602

[0072] - 10 -

[0073] This makes spatially resolved magnetic field measurement advantageously possible.

[0074] The exemplary embodiments and configurations described here can be combined in any way, even if this is not explicitly described.

[0075] The excitation light source includes, for example, a laser. The laser radiation from the laser has, for example, a wavelength of 532 nm.

[0076] For example, it is planned that in the case of multiple optical fibers, excitation light, in particular laser radiation, is sequentially injected into the optical fibers.

[0077] This means, in particular, that laser radiation is emitted into the individual optical fibers one after the other.

[0078] An incoming radiation signal, as described, includes, for example, coupling.

[0079] A laser beam, as described, comprises, for example, one or more laser pulses.

[0080] For example, with multiple optical fibers, it is provided that laser radiation is emitted, in particular coupled, into the optical fibers in parallel, i.e., simultaneously.

[0081] The fluorescent light is coupled out, for example, from the light guide, or generally the light guide device, so that the photodetector detects the coupled-out fluorescent light.

[0082] Statements made in connection with one optical fiber apply analogously to multiple optical fibers and vice versa.

[0083] The invention is explained in more detail below with reference to preferred embodiments. Figure 412602 shows:

[0084] - 11 -

[0085] Fig. 1 shows a first device for measuring intracorporeally generated magnetic fields,

[0086] Fig. 2 shows a flowchart of a method for measuring intracorporeally generated magnetic fields,

[0087] Fig. 3 a machine-readable storage medium,

[0088] Fig. 4 shows the respective time course of two fluorescence signals,

[0089] Fig. 5 is a schematic illustration of three fluorescent NV diamond crystals,

[0090] Fig. 6 shows a cross-section of a fiber bundle,

[0091] Fig. 7 shows a minimum required time resolution plotted over a distance between the NV diamonds,

[0092] Fig. 8 shows a second device for measuring intracorporeally generated magnetic fields,

[0093] Fig. 9 shows a third device for measuring intracorporeally generated magnetic fields,

[0094] Fig. 10 shows a fourth device for measuring intracorporeally generated magnetic fields,

[0095] Fig. 11 shows a fifth device for measuring intracorporeally generated magnetic fields and a sequence of a measurement concept as it can be used within a method for measuring intracorporeally generated magnetic fields, and

[0096] Fig. 12 shows an example of a measurement concept. R. 412602

[0097] - 12 -

[0098] The same reference symbols can be used for identical features in the following.

[0099] It should be further noted that, for the sake of clarity, not all features of the devices for measuring intracorporeally generated magnetic fields described below and shown in the figures may be depicted. For example, an evaluation unit, a microwave source, or a photodetector are not always explicitly shown. However, the elements not shown in the figures are nevertheless implicitly present.

[0100] Fig. 1 shows a first device 101 for measuring intracorporeally generated magnetic fields, comprising: a catheter 103, wherein a fiber optic device 105 is arranged within the catheter 103; a sensor unit 107 for measuring magnetic fields, wherein the sensor unit 107 is a nitrogen-vacancy center magnetometer, which has as a sensor medium one or more diamond crystals 109 having several nitrogen-vacancy centers, wherein the one or more diamond crystals 109 are arranged within the fiber optic device 105; wherein the sensor unit 107 comprises a magnetic field generation device 111 for generating a magnetic field in the region of the sensor medium; wherein the sensor unit 107 comprises an excitation light source 113 for shining excitation light into the fiber optic device 105 in order to excite the sensor medium; and wherein the sensor unit 107 comprises a microwave source 115 for generating microwaves. includesto excite the sensor medium with microwaves, and wherein the sensor unit 107 comprises a photodetector 117 for detecting resonance-dependent fluorescence light from the sensor medium and an evaluation unit 119, which is configured to determine a magnetic field at the respective location of the one or more diamond crystals 109 based on the detected fluorescence light. R. 412602,

[0101] - 13 -

[0102] Fig. 2 shows a flowchart of a method for measuring intracorporeally generated magnetic fields using the device according to one of the preceding claims, comprising the following steps:

[0103] Generating a magnetic field in the area of ​​the sensor medium by the magnetic field generating device,

[0104] 203. Irradiation of excitation light into the light guide device by the excitation light source to excite the sensor medium,

[0105] Generating 205 microwaves through the microwave source to excite the sensor medium with microwaves, and

[0106] The photodetector detects 207 resonance-dependent fluorescence light from the sensor medium, and

[0107] Determine 209 based on the detected fluorescence light of a magnetic field at the respective location of one or more diamond crystals by the evaluation unit.

[0108] Fig. 3 shows a machine-readable storage medium 301 on which a computer program 303 is stored. The computer program 303 comprises instructions which, when executed by the device 101 of Fig. 1, cause the device to perform a method for measuring intracorporeally generated magnetic fields.

[0109] Fig. 4 shows a graph 401 having an abscissa 403 and an ordinate 405. Time in nanoseconds is plotted on the ordinate 403. An averaged fluorescence signal recorded by a photodetector is plotted on the abscissa 405 in detection events per millisecond, or "counts per millisecond".

[0110] Graph 401 shows two time courses of a fluorescence signal from an NV center in a diamond crystal containing NV centers. Reference 407 indicates a time course of a fluorescence signal when the NV center is in the ms = 0 state. Reference 409 indicates a time course of a fluorescence signal from an NV center when it is in the ms = 1 ground state. R. 412602

[0111] - 14 -

[0112] Reference symbols 411 and 413 mark two points on the abscissa 403 as the limits of a time interval with respect to an optimal detection duration.

[0113] The origin of the ordinate, i.e., zero, marks the time at which a laser was switched on to excite the NV center, i.e., the time at which the NV center or NV centers were irradiated with laser radiation.

[0114] Thus, the ground states at ms = 0 and ms = 1 can be distinguished by their different fluorescence signals. From this, the applied magnetic field can be deduced using the NV center ensemble average.

[0115] Fig. 5 shows a schematic illustration of three fluorescent NV diamond crystals at a distance of, for example, 1 cm.

[0116] Specifically, several optical fibers 501 are shown, arranged one behind the other in the direction of light transmission. The multiple optical fibers 501 are formed separately from each other.

[0117] The optical fibers 501 have fiber facets 502 that are opposite each other. The three diamond crystals 503 are arranged on these optical fiber facets 502. In other words, it is provided that between each pair of optical fibers 501 there is a diamond crystal 503 located on the fiber facets 502 of the optical fibers 501.

[0118] The reference symbol 505 points to a double arrow, which indicates a distance between two diamond crystals 503. This distance can be, for example, 1 cm.

[0119] Reference symbol 507 points to an arrow that points into, or is partially located within, optical fiber 501. This arrow with reference symbol 507 is intended to symbolize the laser radiation stimulating the diamond crystals 503.

[0120] The resulting fluorescent light is symbolically indicated by arrows with the reference symbol 509. Fluorescence light 509 R. 412602

[0121] - 15 - can be coupled out of these again via the optical fibers 501, for example in the direction of the direction of incidence of the exciting laser beam 507.

[0122] Below optical fiber 501, a graph 511 is shown. Graph 511 has an abscissa 513 and an ordinate 515. Time in picoseconds is plotted on the abscissa 513. A fluorescence signal in arbitrary units is plotted on the abscissa 515. Graph 511 thus shows the time course of a fluorescence light 509 detected by a photodetector. The reference symbol 516 refers to such a time course.

[0123] Arrows with the reference symbol 517 extend from the diamond crystals 503 to the time series 516 and indicate the points where the fluorescence signal increases. These increases are staggered in time, resulting from the spacing of the diamond crystals 503. Based on these time differences, the individual fluorescence yields can be assigned to the individual diamond crystals 503. This enables spatially resolved magnetic field measurements.

[0124] Fig. 6 shows a cross-section of a fiber bundle 601 comprising six optical fibers 603.

[0125] The reference symbol 605 points to a rectangle whose length corresponds to 400 pm. Thus, rectangle 605 serves as a kind of scale.

[0126] According to the concept described here, a diamond crystal 609 can, for example, be arranged on the fiber facets 607 of the optical fibers 603. The diamond crystal 609 is, for example, a diamond platelet.

[0127] A diamond crystal as described can, for example, have an edge length of 750 pm.

[0128] Fig. 7 shows a graph 701 having an abscissa 703 and an ordinate 705. The abscissa 703 represents the distance between two diamond crystals in millimeters. The ordinate 705 represents the required time resolution needed to detect two fluorescence signals resulting from two R. 412602

[0129] - 16 - to distinguish between excited diamond crystals. The unit of the ordinate 705 is picoseconds.

[0130] Thus, on the ordinate 705, the minimum required time resolution is plotted over a distance between the diamond crystals when measured directly on the rising flank in graph 401 according to Fig. 4.

[0131] Fig. 8 shows a second device 801 for measuring intracorporeally generated magnetic fields.

[0132] The device 801 comprises a catheter 803 within which a fiber optic assembly 805 is arranged. The fiber optic assembly 805 comprises several fiber optics 807, for example, optical fibers.

[0133] Furthermore, several diamond crystals 809 are provided, each arranged on a facet 811. The diamond crystals 809 are arranged offset from one another. This can be achieved, for example, by arranging the optical fibers 807 offset from one another with respect to their optical direction, as shown in Fig. 8.

[0134] The device 801 thus comprises a bundle of light guides 807 which are arranged offset from each other.

[0135] The reference numeral 813, analogous to the representation in Fig. 5, points to the excitation laser radiation, symbolized by an arrow. The laser radiation 813 is coupled into the optical fibers 807. It can be provided, for example, that the laser radiation 813 is coupled into the individual optical fibers 807 simultaneously, i.e., in parallel, or it can be provided, for example, that the laser radiation 813 is coupled into the optical fibers 807 successively or sequentially.

[0136] The coupled laser radiation 813 thus excites the diamond crystals 809. The resulting fluorescence light is indicated by arrows with the reference symbol 815. The fluorescence light 815 can be measured by the R. 412602

[0137] - 17 -

[0138] Light guide 807 is led out of the catheter 803 and can be detected by a photodetector not shown here.

[0139] The detection of the fluorescence light 805 can, for example, be carried out sequentially or in parallel, depending on the excitation.

[0140] Reference numeral 817 refers to a coil, for example made of copper. A microwave field can be generated via the coil 817 in the area of ​​the individual diamond crystals 809. The coil 817 is located inside the catheter 803. In other words, the microwave field is intended to be generated inside the catheter 803. For better illustration, the coil is also shown symbolically in coil form outside the catheter 803 (top right, referring to Fig. 8).

[0141] Reference numeral 819 refers to two permanent magnets located outside the catheter 803. When measuring intracorporeally generated magnetic fields, the permanent magnets 819 are located outside the body, whereas the catheter 803 is inserted into the body. The permanent magnets 819 generate a static magnetic field B0.

[0142] Reference numeral 821 indicates a symbolically represented electrical line for contacting one of the coils 817. Further electrical contacts are not shown for the sake of clarity.

[0143] By appropriate electrical control of the coils 817, it is possible to generate a corresponding microwave field in the respective area of ​​the diamond crystals 809.

[0144] Thus, Fig. 8 shows a multi-strand catheter setup. "Multi-strand" refers to the fiber bundle consisting of several optical fibers 807. Each optical fiber has a diamond crystal 809 at its end, i.e., at the facet 811. The fibers are surrounded by a coil 817, which generates a microwave field, the so-called B1 field. R. 412602

[0145] - 18 -

[0146] The optical fibers 807 together with the coil 817 are located inside the catheter 803. The required background magnetic field, the so-called B0 magnetic field, is generated externally via the permanent magnets 819.

[0147] An optical fiber, in particular a glass fiber, as described, has, for example, a thickness that lies, for example, in the closed interval from 50 pm to 500 pm.

[0148] Fig. 9 shows a third device 901 for measuring intracorporeally generated magnetic fields.

[0149] In contrast to the second device 801 of Fig. 8, the third device 901 has only several optical fibers 807 arranged one behind the other in the direction of light transmission, as shown by way of example in Fig. 5. Accordingly, the diamond crystals 809 are arranged between the optical fibers 807.

[0150] Thus, according to Fig. 9, no bundle of light guides is provided, but only one conductor formed from the several light guides 807, which are arranged one behind the other in the direction of the light guide.

[0151] While the fluorescence light 815 in the second device 801 according to Fig. 8 can be read out both in parallel and sequentially, the design of the third device 901 according to Fig. 9 only allows sequential readout of the fluorescence light 815. However, since a fiber bundle has been omitted, the third device 901 can be designed to be particularly compact.

[0152] Fig. 10 shows a fourth device 1001 for measuring intracorporeally generated magnetic fields.

[0153] Instead of the external permanent magnets 819, it is planned to provide several permanent magnets 1003 within the catheter 803 in the vicinity of the diamond crystals 809 in order to generate the external static magnetic field B0.

[0154] The permanent magnets 1003 can be arranged, for example, in a Hallbach configuration or in an Aubert configuration. R. 412602

[0155] - 19 -

[0156] Fig. 11 shows a fourth device 1101 for measuring intracorporeally generated magnetic fields.

[0157] Fig. 11 shows another way to generate the external magnetic field BO: according to Fig. 11 using a coil 1103. This coil 1103 surrounds the optical fiber 807. An electrical contact of the coil 1103 is indicated by the reference numeral 1105.

[0158] The possibilities for generating the external magnetic field B0 shown in Figs. 10 and 11 can also be implemented, for example, in the multi-wire catheter setup according to Fig. 8.

[0159] Fig. 12 shows an exemplary sequence of an exemplary measurement concept, as it can be used in the concept described here, in particular in a method for measuring intracorporeally generated magnetic fields. This exemplary measurement concept is the pulsed ODM R.

[0160] In this process, the NV centers in the diamond crystals are initialized using a laser pulse 1201. The laser pulse has a duration of less than 1 ms; for example, the duration of the laser pulse 1201 is 30 ps. The wavelength of the laser pulse 1201 is, for example, 532 nm.

[0161] The laser pulse 1201 is followed by a microwave pulse 1203, which, for example, has a duration of less than 0.2 ms. For instance, microwave pulse 1203 has a duration of 100 ps. The duration of microwave pulse 1203 is symbolically indicated by a double arrow with the reference symbol 1204.

[0162] This means that the laser pulse 1201 is followed by a microwave pulse 1203 at a frequency f that is resonant with the ground state transition from ms = 0 to ms = 1. R. 412602

[0163] - 20 -

[0164] Following the microwave pulse 1203, a further laser pulse 1205 is emitted, which can be used, for example, for both readout and initialization. This further laser pulse 1205 can also be used, for example, solely for readout. During the duration of this further laser pulse 1205, the fluorescence of the diamond crystals can be measured via the optical fiber for any readout time that is less than or equal to the laser pulse duration. The fluorescence signal can be measured, for example, in parallel using multiple photodetectors for the multi-wire catheter variant according to Fig. 8, or sequentially with a time offset by a single photodetector in the case of sequential readout according to the setup shown in Fig. 9.

[0165] For example, it is planned that after the readout pulse 1205, which has a length of, for example, 4 ps, an initialization pulse 1201 follows, which has a length of, for example, 30 ps. Both pulses, i.e., the initialization pulse 1201 and the readout pulse 1205, can be combined into a total pulse of, for example, 34 ps, in which these two processes, i.e., initialization and readout, take place.

[0166] The fact that two impulses are required, one for reading and another for initialization, has the physical basis that reading does not occur without a change in state, but in turn leads to a change in state.

[0167] The total duration of a pulsed measurement, as shown by way of example in Fig. 12, can therefore be a maximum of 143.6 ps, for example.

[0168] A photodetector, as described, is for example a photodiode.

[0169] In summary, the concept described here is based in particular on arranging one or more optical fibers within a catheter, wherein the diamond crystals of a nitrogen-vacancy center magnetometer are also located within the catheter: for example, within an optical fiber or, for example, at a facet of an optical fiber. For example, several optical fibers are provided, arranged one after the other in the direction of light transmission (R. 412602).

[0170] - 21 - are arranged so that several diamond crystals can be arranged like a string of pearls, positioned on the facets of the series of optical fibers. For example, a diamond crystal is bonded to a facet.

[0171] Excitation light, for example green light or laser radiation with a wavelength of 532 nm, is introduced into the diamond crystals via the optical fiber(s). The fluorescence of the diamond crystals can then be measured, detected, or recorded, for example, via reflection from the same optical fiber. To detect the magnetic field using the ODMR concept or measurement method, microwave radiation is also required, which is generated by the microwave source.

[0172] The assignment of the fluorescence signals to the individual diamond crystals can be achieved, for example, via different microwave excitations with localized amplitudes and modulation frequencies.

[0173] The assignment of the fluorescence signals to the individual diamond crystals can be achieved, for example, by means of pulsed measurements via the precise temporal detection of the fluorescence signals.

[0174] The required background magnetic field BO can be generated from the outside, i.e., outside the body, i.e., extracorporeally, for example, on the chest.

[0175] Due to the strong miniaturization made possible by the concept described here, especially down to a diameter of 5 pm, particularly small vessels can be examined or the catheter can be inserted into such small vessels.

[0176] A necessary microwave radiation, the so-called B1 field, can be brought to each diamond crystal, for example, by means of appropriate cables and resonators.

[0177] For example, microwave radiation can be generated extracorporeally. R. 412602

[0178] - 22 -

[0179] The necessary offset magnetic field, the so-called BO field, can be introduced from the outside and / or from the inside, for example by permanent magnets and / or by a magnetic field coil, i.e. by electrical conductors inside the catheter.

[0180] The concept described here has the advantage that the setup can be efficiently adapted to the size of the vessels being examined, so that optimal fluorescence yields can be achieved.

[0181] The concept described here thus advantageously enables, in particular, the construction of cost-effective magnetometer arrays or other types of flexible multi-magnetometers. The catheter can, for example, be a cardiac catheter, which can be used, for instance, in magnetocardiography.

[0182] The catheter could, for example, be an esophageal catheter, i.e., a catheter such as those used for transesophageal magnetocardiography.

Claims

R. 412602 - 23 - Claims 1. Device (101, 801, 901, 1001, 1101) for measuring intracorporeally generated magnetic fields, comprising: a catheter (103, 803) wherein a fiber optic device (105, 805) is arranged within the catheter (103, 803), a sensor unit (107) for measuring magnetic fields, wherein the sensor unit (107) is a nitrogen-vacancy center magnetometer, which has as a sensor medium one or more diamond crystals (109, 503, 809) having several nitrogen-vacancy centers, wherein the one or more diamond crystals (109, 503, 809) are arranged within the fiber optic device (105, 805), wherein the sensor unit (107) includes a magnetic field generation device (111, 819, 1003, 1103) for generating a magnetic field in the area of ​​the sensor medium, wherein the sensor unit (107) comprises an excitation light source (113) for shining excitation light (507, 813) into the light guide device (105, 805) to excite the sensor medium,wherein the sensor unit (107) comprises a microwave source (115, 817) for generating microwaves to excite the sensor medium with microwaves, and wherein the sensor unit (107) comprises a photodetector (117) for detecting resonance-dependent fluorescence light (509, 815) from the sensor medium and an evaluation unit (119) which is configured to determine a magnetic field at the respective location of the one or more diamond crystals (109, 503, 809) based on the detected fluorescence light (509, 815).

2. Device (101, 801, 901, 1001, 1101) according to claim 1, wherein the light guide device (105, 805) comprises one or more light guides (807) within which one or more nitrogen vacancy centers are located. R. 412602 - 24 - having diamond crystals (109, 503, 809) of the sensor unit (107) are arranged, wherein the excitation light source (113) is configured to shine excitation light (507, 813) into one or more light guides (807).

3. Device (101 , 801 , 901, 1001 , 1101) according to claim 2, wherein at least one of the diamond crystals (109, 503, 809) is arranged on a facet (502, 811) of one of the one or more optical fibers (807).

4. Device (101, 801, 901, 1001, 1101) according to claim 2 or 3, wherein the light guide device (105, 805) comprises several separately formed light guides (807) arranged one behind the other in the direction of light transmission, within each of which one or more diamond crystals (109, 503, 809) of the sensor unit (107) having nitrogen vacancy centers are arranged, 5. Device (101 , 801 , 901, 1001 , 1101) according to one of the preceding claims, wherein the magnetic field generating device (111 , 819, 1003, 1103) comprises one or more permanent magnets (1003) which are arranged within the light guide device (105, 805).

6. Device (101 , 801 , 901, 1001 , 1101) according to one of the preceding claims, wherein the magnetic field generating device (111 , 819, 1003, 1103) comprises one or more electromagnets (1103) which are arranged within the light guide device (105, 805).

7. Device (101 , 801 , 901, 1001 , 1101) according to one of the preceding claims, wherein the sensor unit (107) comprises at least one microwave resonator (817) connected to the microwave source (115, 817), wherein the at least one microwave resonator is arranged within the optical fiber device (105, 805).

8. Device (101, 801, 901, 1001, 1101) according to one of the preceding claims, wherein the microwave source (115, 817) is configured to generate microwaves dependent on the respective location of one or more diamond crystals (109, 503, 809), such that one or more R. 412602 - 25 - Diamonds are excited with different microwaves with localized amplitudes and / or modulation frequencies.

9. Device (101 , 801 , 901, 1001 , 1101) according to one of the preceding claims, wherein the excitation light source (113) is configured to emit laser pulses into the optical fiber device (105, 805), wherein the evaluation unit (119) is configured to determine the magnetic field at the respective location of one or more diamond crystals (109, 503, 809) based on the emitted laser pulses.

10. Method for measuring intracorporeally generated magnetic fields using the device (101, 801, 901, 1001, 1101) according to any one of the preceding claims, comprising the following steps: Generating (201) a magnetic field in the area of ​​the sensor medium by the magnetic field generating device (111 , 819, 1003, 1103), Illumination (203) of excitation light (507, 813) into the light guide device (105, 805) by the excitation light source (113) to excite the sensor medium, generation (205) of microwaves by the microwave source (115, 817) to excite the sensor medium with microwaves, and Detection (207) of resonance-dependent fluorescence light (509, 815) from the sensor medium by the photodetector (117), and Determine (209) based on the detected fluorescence light (509, 815) a magnetic field at the respective location of the one or more diamond crystals (109, 503, 809) by the evaluation unit (119).

11. Computer program (303) comprising instructions which, when the computer program (303) is executed by the device (101 , 801 , 901 , 1001, 1101) according to any one of claims 1 to 9, cause it to execute a method according to claim 10.

12. Machine-readable storage medium (301) on which the computer program (303) according to claim 11 is stored.

Images