Magnetic field probe

Abstract

The invention relates to a magnetic field probe (1) having a capsule (3) in which an MR-active substance (5) is encapsulated. In particular, it is proposed that two coils (7, 9) are arranged in the capsule (3). Also described are advantageous methods for producing the magnetic field probe (1) and useful uses of the magnetic field probe (1) according to the invention and methods in which such a magnetic field probe (1) and an arrangement of magnetic field probes (1) are used.

Description

Technical Field

[0001] The invention relates to a magnetic field probe having a capsule in which an MR-active substance is enclosed and a first coil is provided. Background Art

[0002] Magnetic field probes having the features described in the introduction, arrangements of such magnetic field probes, the production of magnetic field probes and methods for using magnetic field probes are known in practice.

[0003] For example, a magnetic field probe having the described features is used to measure the magnetic field generated in an MR (magnetic resonance) system. This allows precise data to be determined about the magnetic field actually applied in the MR measurement range, which data can then be used to correct errors in order to thereby improve the image quality of the sectional images recorded by the MR method.

[0004] In the context of the present application, “MR” is used as an abbreviation for “magnetic resonance”, “MRT” as an abbreviation for “magnetic resonance tomography”, “NMR” as an abbreviation for “nuclear magnetic resonance”, “HF” as an abbreviation for “high frequency” and “UV” as an abbreviation for “ultraviolet”.

[0005] Therefore, if the magnetic field probe is arranged for use in an MR device, the magnetic field probe may also be referred to as an MR probe. The magnetic field probe may also be referred to as an NMR probe. When the magnetic field probe is used in an MRT device, it may also be referred to as an MRT probe. The MR device may be an MRT device or an MR device or an NMR device for spectroscopy.

[0006] The problem with currently known magnetic field probes is that they have to be reconfigured in a complex manner each time in order to measure the magnetic field in the corresponding MR system and then have to be removed again in order to carry out the actual MR measurement of the measurement object. This means that the MR-active material of the magnetic field probe constitutes a visible foreign body in the MR measurement, which can cause undesirable artifacts in the measurement image. In practice, this problem has been solved so far by using special MR-active materials whose resonance frequency deviates significantly from the actual resonance frequency of the measurement object, e.g., the MR-active material does not contain 1 H hydrogen nucleus, but contains other nuclei, such as 19 F nucleus or 2 H core. This requires additional broadband electronics and results in high costs. Summary of the invention

[0007] The object of the present invention is to improve the usability of magnetic field probes with regard to the measurement of magnetic fields generated, in particular, in MR systems.

[0008] In order to achieve this object, it is proposed according to the invention, in particular in a magnetic field probe of the type described in the introduction, that a second coil is arranged in the capsule.

[0009] The use of two coils in one magnetic field probe has many applications, wherein the various applications of such a magnetic field probe according to the invention have their own inventive aspects.

[0010] For example, the second coil can be used to change the magnetic field in the volume formed by the MR-active substance. This can be done during an MR measurement of the measurement object and / or during an excitation of the measurement object and / or during an excitation of the MR-active substance by irradiation with an RF field and / or during signal acquisition of the signals received by the first coil and / or during a period of relaxation of the longitudinal magnetization in the MR-active substance.

[0011] For example, the second coil can also be used to shift the resonance frequency of the MR-active substance during the MR measurement. The shift can be achieved by applying a low-frequency magnetic field with the aid of the second coil during the excitation of the measurement object and / or the MR-active substance and / or during the emission of the MR excitation pulse. The excitation itself can be performed in particular by irradiating an RF field. The shift can occur during the signal acquisition of the signal received by the first coil. The resonance frequency is preferably shifted in such a way that the signal of the MR-active substance falls outside the receiving bandwidth and / or the transmitting bandwidth of the MR device for the MR measurement. Furthermore, the resonance frequency is preferably shifted in such a way that the signal of the MR-active substance falls outside the measurement bandwidth of the measurement signal generated by the measurement object during the MR measurement and / or outside the emission bandwidth of the excitation pulse for the MR measurement. For example, the shift of the resonance frequency can be achieved by generating a uniform magnetic field with the second coil in the volume formed by the MR-active substance. In this case, it is only necessary that the magnetic field is formed substantially uniformly in the volume formed by the MR-active substance. The stronger the current flowing through the second coil, the stronger the shift. Preferably, the second coil is operated with a constant current. Such a resonance shift can have the advantage that interference signal components generated by the magnetic field probe during the MR measurement of the measurement object are reduced or avoided. If the MR-active substance is excited sufficiently non-resonantly due to its resonance shift, the MR measurement of the measurement object is not disturbed. If the resonance frequency of the MR-active substance lies outside the bandwidth of the receiving unit, the MR signal emitted by the MR-active substance is not effectively received. If, on the other hand, the magnetic field sample is to provide a signal, this is preferably achieved by not causing a current to flow through the second coil. This has the particular advantage, for example, that the magnetic field probe can remain in the MR system even during MR measurements of the measurement object.

[0012] It may also be advantageous if the resonance shift remains within the bandwidth of the receiving unit, for example when simultaneously measuring a magnetic field and an object located in the MR system, to adjust the resonance frequency of the MR-active material in order to avoid signal interference with the signal received from the object. The bandwidth of the receiving unit can be selected to be wider than the bandwidth resulting from the bandwidth of the measured object. The resonance shift can be selected in such a way that it lies outside the measurement bandwidth of the measured object but within the bandwidth of the receiving unit.

[0013] Another application can provide that the second coil is used to dephase the signal generated by the MR-active substance. This can be achieved, for example, by generating a spatially varying magnetic field in the volume formed by the MR-active substance with the aid of the second coil. The magnetic field preferably varies linearly in the volume. In this case, it is only necessary that the magnetic field varies essentially linearly in the volume. The second coil is preferably operated with a constant or low-frequency current. The dephasing caused in this way has the advantage, for example, that the magnetic field probe can be used again to measure the magnetic field after a short time. As a result, dead times can be reduced or adapted to the measurement of the measurement object.

[0014] The magnetic field to be measured with the magnetic field probe is preferably generated by an MR system.

[0015] In the context of the invention described here, a signal is described as low-frequency if its highest frequency component is at least 10 times, preferably at least 100 times, lower than the resonant frequency of the MR-active substance in the magnetic field to be measured. In particular, a signal is low-frequency if the frequency spectrum is below 1 MHz at magnetic field strengths between 1 T and 3 T. In the context of the invention, a signal is described as high-frequency if it is at or close to the resonant frequency of the MR-active substance and / or the object being measured. Excitation pulses for resonant or non-resonant excitation of the MR-active substance and / or the object being measured are, for example, high-frequency. The signal emitted by the MR-active substance or the object being measured is also high-frequency.

[0016] An MR-active substance is a substance containing atomic nuclei whose nuclear spins can be excited to produce magnetic resonance. This is in particular a substance that can be excited in an MR device. Particularly preferably, such an MR device is an MR device that is provided for spectroscopy and / or imaging of human tissue. The MR-active substance can be excited in particular at a field strength of a uniform main magnetic field between 0.1 Tesla and 10 Tesla, preferably between 1 Tesla and 7 Tesla. The MR-active substance can contain, for example, 1 H isotope or 2 Hydrogen in the form of H isotopes, 13 C isotopic form of carbon, 19 Fluorine in the form of the F isotope, 31Phosphorus or other MR-active isotopes in the form of the P isotope. The MR-active substance may be, for example, water. At least one additive may be added to the water, for example in order to adjust its magnetic susceptibility and / or relaxation constant. For example, copper sulfate may be used as an additive.

[0017] The use of water as the MR-active substance or of an MR-active substance with hydrogen has the particular advantage that the magnetic field probe can be controlled and read out very precisely in a simple manner. For example, the magnetic field probe can be controlled by exciting the MR-active substance with a first coil and generating a magnetic field with a second coil. Since the control and readout electronics of the MR system are usually designed for hydrogen, these electronics can be used simultaneously for controlling and / or reading out the magnetic field probe. The electronics of an MR system are usually very precise. Furthermore, it is possible to control and read out the magnetic field probe and the MR system in a time-synchronous manner using the same electronics.

[0018] The MR-active substance preferably forms a volume with a diameter of less than 2 mm, particularly preferably less than 1 mm. The MR-active substance preferably forms a volume of less than 10 μl, particularly preferably less than 1 μl.

[0019] The capsules may form a body. The capsules preferably form a homogeneous body.

[0020] The capsule is further preferably made of a material having a uniform composition. The material can be a uniform mixture of a specific substance or two or more substances.

[0021] The fact that the MR active substance is encapsulated in a capsule can be understood to mean that the MR active substance is completely surrounded by the material forming the capsule. Therefore, the MR active substance has no direct contact with the area outside the capsule.

[0022] The coil may be characterized in that it forms a section of an electrical conductor. The conductor is preferably an insulated conductor. When current flows through the coil, a magnetic field is generated.

[0023] The first coil and / or the second coil can be encapsulated in the capsule. In this case, for example, a current can be generated in the first coil and / or the second coil by wireless energy transmission.

[0024] However, it is preferably provided that the electrical connections of the first coil and / or the second coil are led out of the capsule. These connections enable precise and energy-saving signal and energy transmission.

[0025] The MR active substance is preferably introduced into a capsule.

[0026] It is further preferred that the MR active substance is arranged in the center of the capsule.

[0027] It is further preferred that the first coil and the second coil are made of the same material, for example, the two coils are made of copper.

[0028] In an advantageous embodiment of the magnetic field probe, it can be provided that a third coil or a further coil is provided in the magnetic field probe. The third coil or a further coil can have the features described with reference to the first or second coil. With this embodiment, the magnetic field probe can be used more widely.

[0029] In an advantageous embodiment of the magnetic field probe, it can be provided that the capsule is spherical. The capsule can also be designed differently, for example ellipsoidally or cylindrically. However, the spherical design of the capsule has the particular advantage that the field lines are distributed evenly in the object, so that the measuring properties of the magnetic field probe are improved and it provides more precise data.

[0030] In order to improve the quality of the measurements that can be performed by the magnetic field probe, it can also be provided that the materials of the capsule, the first coil, the second coil and / or the MR-active substance are matched to one another. For example, it can be provided that the capsule is made of a material whose magnetic susceptibility is matched to the magnetic susceptibility of the material of the first coil and / or the material of the second coil. Alternatively or additionally, it can be provided that the magnetic susceptibility of the MR-active substance is matched to the magnetic susceptibility of the material of the first coil and / or the material of the capsule. In particular, they are matched to one another when the magnetic susceptibilities are identical or at least substantially identical. Slight deviations only lead to slight signal interferences, so that small deviations that do not significantly impair the signal quality of the magnetic field probe are tolerable. That is, the magnetic susceptibility differences lead to the resulting field inhomogeneities that interfere with the MR signal generated by the MR-active substance and thus reduce the measurement quality.

[0031] The magnetic susceptibility can be adapted, for example, by selecting the coil material in a suitable manner. For example, copper or an alloy with the desired magnetic susceptibility can be used. The magnetic susceptibility of the capsule material can be adjusted by selecting the material accordingly or by adding certain substances that change the magnetic susceptibility to the material. The magnetic susceptibility of the MR-active substance can also be influenced by selecting the substance, but also by adding certain additives to the substance, by doping the substance with, for example, dopants that influence the magnetic susceptibility.

[0032] In another advantageous embodiment of the magnetic field probe, it can be provided that the MR-active substance is filled in the capsule and / or in the cavity formed by the capsule. The cavity can be characterized in that it is closed to the outside.

[0033] In another advantageous embodiment of the magnetic field probe, it can be provided that the MR-active substance is in direct contact with the capsule, which preferably consists of a material of uniform composition. The MR-active substance is thus also in direct contact with the material of the capsule. Preferably, the MR-active substance is in contact with the capsule and thus with the material of the capsule over the entire surface of the MR-active substance.

[0034] In order to avoid magnetic susceptibility jumps, it is advantageous if there are no air inclusions in the capsule and / or in the MR-active substance.

[0035] In another advantageous embodiment of the magnetic field probe, it can be provided that the MR-active substance is arranged in a volume enclosed by the windings of the first coil. Alternatively or additionally, it can be provided that the MR-active substance is arranged in a volume enclosed by the windings of the second coil. As a result, the signal generated by the MR-active substance interacts particularly effectively with the coil.

[0036] In another advantageous embodiment of the invention, it can be provided that the winding of the first coil is arranged within the winding of the second coil. The windings of the first coil and the second coil and / or the magnetic fields generated by the two coils are preferably oriented orthogonally to one another. This arrangement enables a particularly compact coil winding and a particularly compact magnetic field probe.

[0037] The MR-active substance preferably fills one or both of the above-mentioned volumes. This makes it possible to increase the intensity of the generated MR signals and thus improve the measurement quality.

[0038] It can also be provided that the first coil and / or the second coil have a cylindrical winding. The coils can be used in particular with high efficiency to generate a uniform or linearly varying or otherwise spatially varying magnetic field. Furthermore, they can be manufactured in a particularly simple manner. However, other coil geometries are also possible, such as flat coils.

[0039] In another advantageous embodiment of the magnetic field probe according to the invention, it can be provided that the second coil is designed in such a way that a uniform magnetic field can be generated with its aid in the volume formed by the MR-active substance. It is sufficient for the magnetic field to be essentially uniform. This enables attractive applications. Some of these applications have been described above. For example, a uniform magnetic field can be generated by a solenoid coil or a Helmholtz coil or also by coils of different geometries, for example, computer simulations or optimization methods can also be used to find suitable windings.

[0040] In another advantageous embodiment of the magnetic field probe, it can be provided that the second coil is designed in such a way that a spatially varying magnetic field can be generated with its aid in the volume formed by the MR-active substance. In this case, the second coil is preferably designed in such a way that a linearly varying magnetic field can be generated with its aid in the volume formed by the MR-active substance. In this case, it is only necessary that the magnetic field varies essentially linearly in the volume. Embodiments in which the magnetic field varies spatially in a nonlinear manner are also possible and advantageous. Such a variation can have attractive applications, some of which have already been described above. The coils that generate the spatially varying magnetic field can be, for example, Maxwell coils or any other coils that generate such a varying magnetic field.

[0041] The use of a Helmholtz coil pair can be particularly advantageous because it allows, on the one hand, a uniform magnetic field to be generated, i.e. by energizing the two coils in the same direction, but also a variable, preferably linearly variable magnetic field to be generated by energizing the coils in opposite directions. Such a magnetic field probe can therefore be used in a wide range of applications. In order to ensure that the Helmholtz coil pair can be operated in the same direction and in opposite directions, it is advantageous if the coil pair is not formed by a single coil, but by two coils, each of which has a separate terminal. In this case, the magnetic field probe has at least three coils.

[0042] It can also be provided that the capsule is formed of a hardened material. The material can be hardened, for example, by electromagnetic radiation such as light or UV light. The capsule can be made, for example, of a hardened adhesive and / or polymer. The material can also be a thermoplastic that hardens by cooling. Materials that harden by heating can also be suitable.

[0043] In order to achieve the stated object, it can be provided according to the invention that the magnetic field probe has a capsule in which an MR active substance is encapsulated and a first coil is provided. Furthermore, it is provided according to the invention that the MR active substance fills the cavity formed by the capsule. The capsule is preferably made of a material with a uniform composition. It is preferably provided that the MR active substance is in direct contact with the capsule. It is particularly preferred that the MR active substance contacts the capsule with the entire surface of the MR active substance. However, the MR active substance can also, for example, contact the capsule with a first part of its surface and contact the first and / or second coil with another part of its surface, in particular the remaining part. Other variants are produced by combining the features of the variants and embodiments of the magnetic field probe already described above. In particular, the magnetic field probe can have a second coil.

[0044] In order to achieve the stated objectives, the magnetic field probes are each designed according to the invention. The magnetic field can be measured more accurately by using a plurality of magnetic field probes. For example, 16 magnetic field probes can be used, whereby the magnetic field can reach approximately 3 degrees in its multipolar expansion. Depending on the application, the arrangement can also have fewer or more magnetic field probes.

[0045] In an advantageous embodiment of the magnetic field probe arrangement, it can be provided that the first coil can be connected or is connected to receiving electronics and / or transmitting electronics, which are designed to receive signals emitted by the MR-active substance and the transmitting electronics are designed to emit HF signals. Alternatively or additionally, it can be provided that the second coil can be connected or is connected to control electronics, in particular transmitting electronics, which are designed to generate a temporally constant magnetic field and / or a low-frequency and / or high-frequency magnetic field. Such a magnetic field probe arrangement can be used flexibly. The receiving electronics and / or the control electronics are preferably the receiving electronics and / or the control electronics of an MR device, which generates the magnetic field to be measured with the magnetic field probe.

[0046] In particular, in order to achieve the above-mentioned object, it is proposed according to the invention in this production method that the first coil is arranged in a hardenable material and the hardenable material is subsequently hardened. Furthermore, it is provided according to the invention that the MR active substance is introduced into the material before the material is hardened. Thus, the MR active substance is in particular encapsulated in and by the hardenable material. The MR active substance is preferably introduced directly or immediately into the material. It is further preferred that the MR active substance is injected into the material. The injection can be carried out, for example, with the aid of a pipette or with the aid of a microfluidic printer. It is preferably provided that the introduction of the MR active substance, in particular the injection, is carried out by displacing the material. The advantage of introducing the MR active substance directly into the hardenable material (which forms the above-mentioned capsule after hardening) is that the production of the magnetic field probe is particularly simple, because, for example, the use of a glass tube (in which the MR active substance is to be introduced) can be omitted. In addition, this production method can provide a large degree of freedom for the coil structure and the capsule design.

[0047] In one embodiment of the production method, it can be provided that the second coil is arranged in the material before the material hardens. As a result, the magnetic field probe according to the invention having the above-mentioned features can be produced in a particularly simple manner.

[0048] In order to achieve the stated object, according to the invention, in a production method for producing a magnetic field probe, alternatively or additionally, it is provided that an MR-active substance is introduced, in particular injected, into an inner volume enclosed by an outer surface of a hardenable material and the material is subsequently hardened, wherein the first coil is arranged in the inner volume before the material hardens. According to the invention, it is further provided that the second coil is arranged in the material before the material hardens. The production method thus allows the production of a magnetic field probe, in particular of the above-described design. Preferably, the MR-active substance is introduced into the material by introduction, in particular injection.

[0049] The above-described production methods can also be combined with one another. Variants of the production method are produced by changing the sequence of the individual production steps required for producing the magnetic field probe. Preferably, provision is made that first the first and / or second coil is positioned and in a next step the hardenable material is applied to the already positioned coil and then the MR-active substance is introduced into the interior volume and / or injected into the material. As an alternative, for example, the hardenable material can also be placed first and then the first and / or second coil is positioned in the material and in a third step the MR-active substance is added.

[0050] Preferably, the MR-active substance is arranged, as described above, in the volume enclosed by the windings of the first coil and / or in the volume enclosed by the windings of the second coil.

[0051] As mentioned above, it is further preferred that the winding of the first coil is arranged within the winding of the second coil, the windings of the first coil and the second coil and / or the magnetic fields generated by the two coils being preferably oriented orthogonally to one another.

[0052] Preferably, the hardenable material and / or the above-mentioned inner volume and / or the MR-active substance form droplets.

[0053] In an advantageous embodiment of the manufacturing method, it can be provided that the material is hardened by electromagnetic radiation such as light, ultraviolet rays, X-rays or infrared radiation and / or by temperature changes such as, in particular, by heating and / or cooling and / or catalysis such as by using a two-component epoxy resin. Therefore, the material can be, in particular, an adhesive preferably hardened by ultraviolet light and / or a light-hardened polymer and / or a thermoplastic. Therefore, the capsule already described above can be made of a hardenable material, which is a thermoplastic and / or a material hardened by electromagnetic radiation. The use of such a material and a hardening method can simplify and improve the manufacture of the magnetic field probe and the performance of the manufactured magnetic field probe.

[0054] The first and / or second coil is preferably arranged in such a way that their electrical connections each protrude outwardly from the inner volume and / or from the hardenable material.

[0055] In another advantageous embodiment of the manufacturing method, it can be provided that a quantity of hardenable material is first placed on the working surface and then hardened. The working surface is preferably a flat working surface. For example, the placement can be carried out by placing a drop of hardenable material on the working surface. After the material has hardened, the hardened quantity is turned over, in particular rotated 180° perpendicular to its axis of symmetry, and the quantity is then used as a base for further production of a magnetic field probe using the above-described manufacturing steps. This embodiment of the manufacturing method has the advantage that the positioning of the first and / or second coil and the MR-active substance at the desired position in the capsule is simplified thereby.

[0056] In another advantageous embodiment of the production method, it can be provided that the capsule of the magnetic field probe is produced by repeatedly applying layers of new material that have not yet hardened and hardening the last applied layer. As a result, the shape of the capsule can be produced in a controlled manner so that it obtains a desired shape, such as a spherical shape.

[0057] In another advantageous embodiment of the production method, it can be provided that the viscosity of the hardenable material is greater than the viscosity of the MR-active substance. This has the advantage that the MR-active substance can be introduced more easily into the material.

[0058] Alternatively, it can be provided that the viscosity of the hardenable material is lower than the viscosity of the MR-active substance. This has the advantage of preventing air inclusions.

[0059] In order to adjust the viscosity of the MR active substance, it can contain in particular at least one additive that influences the viscosity. For example, the MR active substance can contain a gelling additive such as agarose. The MR active substance can contain or consist of water and such an additive and optionally further additives.

[0060] In another advantageous embodiment of the invention, it can be provided that the material properties of the MR-active substance and the hardenable material are selected such that the MR-active substance assumes an ellipsoidal, preferably spherical, geometry after introduction into the material. Ellipsoidal or even spherical geometries are firstly particularly compact and secondly the signals emitted from such geometries provide particularly precise information about the magnetic field properties to be measured.

[0061] The surface tension, viscosity and density of the MR-active substance and the hardenable material are preferably selected such that the MR-active substance assumes an ellipsoidal, preferably spherical, geometry after introduction into the material.

[0062] Particularly preferably, the choice of surface tension leads to a phase separation which itself can withstand mechanical influences. Thus, for example, the MR-active substance can be positioned more easily.

[0063] The correct viscosity is particularly important so that when the MR active substance is introduced into the hardenable material the droplets break apart and the MR active substance remains in the material before the capsule hardens.

[0064] This can determine the upper limit of the viscosity. On the other hand, a high viscosity can be advantageous because the mobility of the MR-active substance is limited even before the material hardens and the MR-active substance can be positioned more easily. The density of the material must not deviate too much from the density of the MR-active substance, otherwise the MR-active substance may float or sink.

[0065] In order to achieve the above-mentioned object, a measuring method for measuring magnetic field characteristics can also be provided according to the invention. The characteristic to be measured can be in particular the magnetic field strength and / or its change over time at the position of the magnetic field probe. In order to achieve the above-mentioned object, in this measuring method, it is in particular provided according to the invention that a magnetic field probe designed according to the invention is used. Preferably, the magnetic field is generated by an MR device. It is further preferred that before, after or during the measurement of the magnetic field characteristics, an MR measurement is performed on the measurement object with the MR device, wherein the magnetic field probe remains in the MR device.

[0066] In order to achieve the object, it is provided according to the invention that the magnetic field probe is designed according to the invention. Preferably, the signal of the MR-active substance is received by the first coil and a temporally constant magnetic field is generated by the second coil. Alternatively or additionally, a low-frequency magnetic field is generated by the second coil. Furthermore, alternatively or additionally, a high-frequency magnetic field is generated by the second coil. Attractive extensions and applications of this method have already been described above.

[0067] Particularly preferably, the signals received by the first coil are further processed by the receiving electronics of the MR system. Furthermore, preferably, the second coil is controlled by the control electronics of the MR system. The magnetic field probe is preferably arranged in the MR system.

[0068] Further embodiments of the method for operating a magnetic field probe have already been described above in conjunction with certain applications of the magnetic field probe. The method described there is also a development according to the invention of the above method, regardless of the specifically described application.

[0069] In another advantageous embodiment of the method, it can be provided that the MR active substance has a resonance shift relative to the resonance frequency of the substance of the measurement object arranged in the MR device. The substance is especially water. The resonance shift can be achieved by appropriately arranging the MR active substance, for example by selecting suitable molecules for the MR active substance and / or by adding additives. Alternatively or additionally, in particular as described above, the second coil can be designed to generate a uniform magnetic field and operate with a constant current to achieve the resonance shift. The shifted resonance frequency is preferably located outside the bandwidth for measuring the measurement object. As an alternative, the second coil can be operated with a low-frequency alternating current. As a result, the resonance frequency of the MR active substance can be divided into a plurality of frequencies, which allows the MR active substance to be excited simultaneously without interference and the signal generated by the MR active substance to be read out. The HF transmitting coil of the MR device can be used to excite the measurement object and / or the MR active substance. As an alternative, the first coil can be used to excite the MR active substance. For this purpose, a third coil arranged in the magnetic field probe can also be used. In this way, it is possible to measure the characteristics of the magnetic field by the magnetic field probe while simultaneously performing MR measurements on the measurement object, without the signal generated by the MR active substance interfering with the signal generated by the measurement object during the signal reception process. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] The invention is now explained in detail with reference to several embodiments, but the invention is not limited to these embodiments. Other inventive variants and embodiments are generated by combining the features of the invention with each other and / or with single or multiple features of the previously described variants of the embodiments and / or the device and method according to the invention. The drawings are as follows:

[0071] Figure 1 An embodiment of a magnetic field probe according to the present invention is shown;

[0072] Figure 2 The method for manufacturing the Figure 1 An embodiment of a method for manufacturing a magnetic field probe;

[0073] Figure 3 The method for manufacturing the Figure 1 An alternative embodiment of a method for manufacturing a magnetic field probe. DETAILED DESCRIPTION

[0074] In the following description of different exemplary embodiments of the invention, functionally identical elements are provided with the same reference numerals even if their design or shape differs.

[0075] Figure 1 The magnetic field probe 1 shown has a capsule 3 made of a material 19 hardened by UV light. The capsule 3 is spherical. The capsule 3 is solid and closed to the outside. The surface 25 forms a closed surface, and the terminals 35 and 37 for the first coil 7 and the second coil 9 embedded in the capsule 3 protrude from the capsule 3 only at four points. A cavity 11 is formed in the center of the capsule 3, which is completely filled with an MR-active substance 5, which in the embodiment described here consists essentially of water, which is doped with a substance that makes the magnetic susceptibility of the MR-active substance 5 equal to the magnetic susceptibility of the capsule 3 material 19 and the magnetic susceptibility of the first coil 7 and the second coil 9 made of copper wire.

[0076] The first coil 7 has a winding 13. The winding 13 is designed in such a way that the coil 7 forms a solenoid coil. The second coil 9 also has a winding 15. In the embodiment described here, the coil 9 also forms a solenoid coil. The inner diameter of the first coil 7 corresponds to the outer diameter of the volume 17 occupied by the MR active substance. The first coil 7 is arranged in the volume enclosed by the second coil 9. The first coil 7 and the second coil 9 are oriented orthogonally to each other.

[0077] The MR active substance 5 is encapsulated in the capsule 3 . The MR active substance 5 is enclosed in the capsule 3 .

[0078] The MR-active substance 5 is arranged in an inner volume 27 which, in the exemplary embodiment described here, occupies the volume enclosed by the outer surface 25 of the hardened material 19 .

[0079] When a potential difference is applied to the terminals 37 of the second coil 9 and a current thus flows through the second coil 9 , the solenoid-shaped second coil 9 generates a uniform magnetic field in the volume 17 formed by the MR-active substance 5 .

[0080] If the second coil 9 is operated with a constant current, the magnetic field strength thus varies uniformly in the volume 27 of the MR-active substance 5, so that the nuclear spin resonance frequency 5 of the hydrogen nuclei contained in the MR-active substance shifts by a value that depends on the current strength. Some technical effects and practical applications of this have already been described above.

[0081] In alternative embodiments not shown here, the first coil 7 and / or the second coil 9 are designed differently, so that, for example, the second coil 9 does not generate a uniform magnetic field but a spatially varying magnetic field, such as a linearly varying magnetic field. Some variants have been described above.

[0082] Figure 2 From top to bottom it shows the Figure 1The method of producing a magnetic field probe 1 comprises several steps. In a first method step 100, the first coil 7 and the second coil 9 are positioned side by side. Then in a second method step 102, a drop of hardenable material 19 is applied, which forms the capsule 3 of the magnetic field probe 1 after hardening, so that the first coil 7 and the second coil 9 are arranged in the center of the material 19. The terminals 35 and 37 of the first coil 7 and the second coil 9 protrude from the material 19.

[0083] In a third method step 104, a small drop of the MR-active substance 5 is then injected into the hardenable material 19 by means of the pipette 41. This takes place in the volume enclosed by the first coil 7. The introduction of the MR-active substance 5 into the material 19 displaces the material 19 at this location. The MR-active substance 5 forms a spherical geometry, whose spherical surface is completely encapsulated in the material 19 and is encapsulated by the material. In the exemplary embodiment shown here, the diameter of the volume 17 occupied by the MR-active substance 5 corresponds to the inner diameter of the first coil 7. The inner diameter of the first coil 7 can be, for example, 1 mm and its outer diameter can be, for example, 1.4 mm. In an alternative exemplary embodiment, the inner diameter of the first coil 7 is greater than the diameter of the volume occupied by the MR-active substance 5.

[0084] In the next method step 106, the first coil 7 is pushed together with the MR-active substance 5 into the second coil 9 so that the winding 13 of the coil 7 is surrounded by the winding 15 of the second coil 9. The second coil 7 can have, for example, an inner diameter of 1.8 mm and an outer diameter of 2.2 mm. In the exemplary embodiment described here, the two coils 7, 9 are wound from enameled copper wire. After this method step, the winding 13 of the first coil 7 and the winding 15 of the second coil 9 both surround the volume 17 filled with the MR-active substance 5. The first coil 7, the second coil 9 and the MR-active substance 5 are moved in such a way that they are arranged exactly in the center of the material 19. At this point, the material 19 has not yet hardened. Before the material 19 hardens, Figure 2 as well as Figure 3 The material 19 in FIG. 1 additionally has the reference numeral 21 and is shown in a dark grey tone.

[0085] In the final production step 108, the uncured material 19, 21 is then irradiated with UV light, causing the material 19 to cure. After curing, the material 19 Figure 2 as well as Figure 3 2 and 3. In the figure, it is additionally provided with the reference numeral 23 and is illustrated in light grey.

[0086] exist Figure 3 A method for Figure 1 An alternative manufacturing method of the magnetic field probe 1.

[0087] In a first method step 200, a drop of a not yet hardened material 19, 21 is applied to a flat working surface 31. The material 19, 21 is then irradiated with UV light 39, so that the material 19 hardens and forms hardened material 19, 23. This takes place in step 202. A portion of a capsule 3 is thereby produced.

[0088] In the next method step 204, the hardened material 19, 23 is turned over on the working surface 31 so that the surface of the material 19, 23 that was originally in contact with the flat working surface 31 forms a base 33, which is flat. The further method steps 206 to 214 for producing the magnetic field probe 1 are then carried out on this base 33. The method steps 206 to 214 correspond to the method steps already described in Figure 2 The method steps 100 to 108 described in the foregoing description are simpler to position the first coil 7 and the second coil 9 in the center of the material 19, because a portion of the capsule 3 has already hardened and the first coil 7 and the second coil 9 can therefore be positioned directly on the base 33. More material 19, 21 that has not yet hardened is applied to the base 33 in this way and then in a plurality of Figure 3 The base 33 is applied in layers not explicitly shown (hardening layer by layer after each application) so that overall a spherical capsule 3 is produced. The base 33 forms part of the capsule 3.

[0089] In summary, a magnetic field probe 1 is described which has a capsule 3 in which an MR-active substance 5 is encapsulated. In particular, it is proposed that two coils 7, 9 are arranged in the capsule 3. Also described are advantageous methods for producing the magnetic field probe 1 and useful uses of the magnetic field probe 1 according to the invention as well as methods for using such a magnetic field probe 1 and a system for arranging a magnetic field probe 1.

[0090] Reference numerals list

[0091] 1 Magnetic field probe

[0092] 3 capsules

[0093] 5MR active substances

[0094] 7First coil

[0095] 9 Second coil

[0096] 11 Cavity

[0097] 13 Winding of the first coil 7

[0098] 15 Winding of the second coil 9

[0099] 17 Volume

[0100] 19 Materials

[0101] 21 Material before hardening 19

[0102] 23 Hardened material 19

[0103] 25 Surface

[0104] 27 Internal volume

[0105] Quantification of 29 Materials 19

[0106] 31 working surface

[0107] 33 base

[0108] 35 terminal

[0109] 37 terminal

[0110] 39UV light

[0111] 41 pipette

Claims

1. A magnetic field probe (1) comprising a capsule (3) in which an MR-active substance (5) is encapsulated and a first coil (7) is provided, characterized in that: A second coil (9) is arranged in the capsule (3), and the winding (13) of the first coil (7) is arranged in the winding (15) of the second coil (9).

2. The magnetic field probe (1) according to claim 1, characterized in that The MR active substance (5) fills the cavity (11) formed by the capsule (3).

3. The magnetic field probe (1) according to claim 1, characterized in that The capsule (3) is spherical in shape.

4. The magnetic field probe (1) according to claim 1, characterized in that The capsule (3) is made of a material (19) with uniform composition.

5. The magnetic field probe (1) according to claim 4, characterized in that The MR active substance (5) is in contact with the material (19) of the capsule (3).

6. The magnetic field probe (1) according to claim 1, characterized in that The windings of the first coil (7) and the second coil (9) and / or the magnetic fields generated by the first coil (7) and the second coil (9) are oriented orthogonally to each other.

7. The magnetic field probe (1) according to any one of claims 1 to 6, characterized in that The second coil (9) is designed in such a way that a homogeneous magnetic field can be generated by means of the second coil in a volume (17) formed by the MR-active substance (5).

8. The magnetic field probe (1) according to any one of claims 1 to 6, characterized in that The second coil (9) is designed in such a way that a spatially varying magnetic field can be generated by means of the second coil in a volume (17) formed by the MR-active substance (5).

9. The magnetic field probe (1) according to any one of claims 1 to 6, characterized in that The second coil (9) is designed in such a way that a spatially linearly varying magnetic field can be generated by means of the second coil in a volume (17) formed by the MR-active substance (5).

10. A magnetic field probe (1) comprising a capsule (3) in which an MR-active substance (5) is encapsulated and a first coil (7) is provided, wherein: The first coil can be used to receive signals from the MR-active substance or to excite the MR-active substance. The MR active substance (5) fills the cavity (11) formed by the capsule (3). The cavity is closed to the outside, and The MR active substance is in direct contact with the capsule.

11. The magnetic field probe (1) according to claim 10, characterized in that The capsule (3) is spherical in shape.

12. The magnetic field probe (1) according to claim 10, characterized in that The capsule (3) is made of a material (19) with uniform composition.

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