WO2017121532A1 - Dispositif et procédé de mesurage de signaux de résonance magnétique - Google Patents

Dispositif et procédé de mesurage de signaux de résonance magnétique Download PDF

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Publication number
WO2017121532A1
WO2017121532A1 PCT/EP2016/078936 EP2016078936W WO2017121532A1 WO 2017121532 A1 WO2017121532 A1 WO 2017121532A1 EP 2016078936 W EP2016078936 W EP 2016078936W WO 2017121532 A1 WO2017121532 A1 WO 2017121532A1
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Prior art keywords
coil
magnetic
magnetic resonance
objects
measured
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PCT/EP2016/078936
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German (de)
English (en)
Inventor
Tabea Arndt
Marijn Pieter Oomen
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Siemens Aktiengesellschaft
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Publication of WO2017121532A1 publication Critical patent/WO2017121532A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
    • G01R33/381—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field using electromagnets
    • G01R33/3815—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field using electromagnets with superconducting coils, e.g. power supply therefor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N24/00—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects
    • G01N24/08—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects by using nuclear magnetic resonance
    • G01N24/084—Detection of potentially hazardous samples, e.g. toxic samples, explosives, drugs, firearms, weapons
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/30—Sample handling arrangements, e.g. sample cells, spinning mechanisms
    • G01R33/307—Sample handling arrangements, e.g. sample cells, spinning mechanisms specially adapted for moving the sample relative to the MR system, e.g. spinning mechanisms, flow cells or means for positioning the sample inside a spectrometer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
    • G01R33/3804—Additional hardware for cooling or heating of the magnet assembly, for housing a cooled or heated part of the magnet assembly or for temperature control of the magnet assembly
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
    • G01R33/3806—Open magnet assemblies for improved access to the sample, e.g. C-type or U-type magnets
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/448—Relaxometry, i.e. quantification of relaxation times or spin density
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/46—NMR spectroscopy

Definitions

  • the present invention relates to a device for Mes ⁇ solution of magnetic resonance signals, comprising a coil means for generating a magnetic field having at least one magnetic ⁇ coil with a superconducting coil winding, wherein the coil means comprises a cooling device for dry cooling of the superconducting coil winding. Furthermore, the invention relates to a use of such a device as well as to be carried out with such a device method.
  • a magnetic resonance signal is a signal resulting from this resonant interaction, which is mostly measured by a high frequency receiver coil in response to a signal transmitted by a high frequency transmitter coil.
  • the electromagnetic signal of the measured free induction decay is typically decomposed by Fourier analysis into its individual frequency components.
  • the plot of the measured intensities to these frequency components is the so-called NMR spectrum, in which for a given type of core (for example, hydrogen or carbon 1 R 13 C) different chemical bond-making environments as different spectral bands, or
  • Spectroscopy can be used both for the structure elucidation of unknown compounds as well as for the detection of already known materials by comparison with existing spectra.
  • MR imaging magnetic resonance imaging
  • a spatially resolved signal is obtained by superimposing a location-dependent magnetic field B i on the homogeneous magnetic field Bo by one or more additional gradient coils, and then sequentially resonating the cores to be measured.
  • Such an imaging measurement is typically based not on a spectral decomposition as in spectroscopy, but on a spatially resolved determination of the signal intensities and / or the relaxation times of the spins, which affect the decay times of the measured electromagnetic signals.
  • pulse sequences for example, so-called spin-echo sequences
  • proton signals are gemes ⁇ sen, which then the different relaxation times of the hydrogen (mainly in the form of water) in the different types of tissue, as well as the different water- hydrogen content can be mapped.
  • other cores with a suitable nuclear spin can also be measured spatially resolved with regard to their frequency and chemical environment.
  • Both NMR spectroscopy and MR imaging typically require very strong Bo magnetic fields.
  • normal ⁇ conducting electromagnets or superconducting solenoids can be used for their production permanent magnets.
  • magnetic field strengths above 0.5 T predominantly superconducting magnetic coils are used.
  • the superconducting conductor such sup ⁇ ra technicallyden solenoid coil must be cooled during operation to a cryogenic temperature below its critical temperature. In order to achieve this, cooling of the superconducting material by flushing with a cryogenic liquid coolant in a bath cryostat is used in many magnetic resonance measuring devices.
  • the coolant most commonly used is liquid helium, can be achieved ⁇ rich of 4 K to the temperatures in the Be.
  • helium is limited and is becoming more expensive.
  • a further disadvantage of such cooling is that, in the event of a sudden collapse of the superconducting properties (a so-called "quench"), the entire liquid helium must be vaporized and subsequently replaced, and the cooling and commissioning of such a helium-cooled superconducting coil is altogether very time-consuming - and resource-consuming.
  • the coil means for generating the strong static magnetic fields Bo are generally designed so that the magnetic field strength in a homogeneity region corresponding approximately to the inner cavity is very strong and homogeneous, and that in the adjacent areas outside this cavity with increasing distance from the center of Device drops very quickly to very low values. In the peripheral areas of the sample room and / or in the directly adjacent areas thus occur very high field gradients.
  • the measurement objects are placed in the vicinity of the device with ferromagnetic material portions and is to be subsequently introduced into the sample compartment can in this case very high magnetic attraction forces occur, so that such metrics are greatly accelerated and can cause high dangerous ⁇ dung potential since they then similar to a bullet act.
  • the introduction of measuring objects with other metallic material fractions can be problematic because high eddy currents are induced by their movement in the region of the strong magnetic field gradients. This effect is based on the same principle as in an eddy current brake, and can restrict a desired movement of the Messob ⁇ jekts strong especially in the peripheral areas of the device.
  • the object of the invention is therefore to provide a device for measuring magnetic resonance signals, which overcomes the disadvantages mentioned.
  • a device for measuring magnetic resonance signals which overcomes the disadvantages mentioned.
  • such a device should be made available which is suitable for the
  • a further object is to benmilage- use ei ⁇ ner such a device and a method for the measurement of magnetic resonance signals with such a device.
  • the inventions dung contemporary apparatus for measuring Magnetresonanzsigna ⁇ len has a coil means for generating a magnetic field.
  • This coil device comprises at least one magnetic coil with a superconducting coil winding.
  • the coil device furthermore has a cooling device for dry cooling of the superconducting coil winding.
  • the device has a predetermined passage direction for the sequential transport of a plurality of measurement objects through the device.
  • the coil device has a NEN continuous internal cavity, which defines a continuous sample space and through which the measurement objects can be transported through ⁇ ⁇ one behind the other in the direction of passage through the device.
  • the device is designed such that it is suitable for the continuous or quasi-continuous passage of successive measurement objects.
  • the interior sample space is therefore accessible not only on one side but on both sides, and the measurement objects can be transported through it se ⁇ quentiell, the measured objects can also follow relatively close to each other, since they are not taken on the same side of the sample space on the they were introduced into the rehearsal room, but on the opposite side.
  • the measured objects may generally be persons and / or transport goods, for example bags, sacks, suitcases or boxes.
  • the sample space is thus dimensioned for the sequential passage of a large number of such measurement objects.
  • the device for screening of objects can be used for the purpose of security, for example in the range of airports, buildings or other protected at events.
  • the test objects to be examined can routinely be examined for the presence of predefined types of hazardous substances, for example of explosives or drugs.
  • the dry cooling of the superconducting coil winding has the advantage that the device for magnetic resonance measurement is much easier to handle and to put into operation, as would be the case with a liquid helium cooled coil winding.
  • the device can also be much more mobile, so easier to carry out portable, which may be important for applications in security controls.
  • a dry cooled device can also be installed for a short time (eg a few hours or days) at a destination without the equipment cost for commissioning exceeds the economic benefits of the device.
  • no supply is required for replenishing liquid coolant for dry cooling, since such a cooling device can be operated solely by supplying electrical energy.
  • a "dry cooling” should generally be understood to mean a cooling in which the superconducting coil winding is not directly surrounded by liquid coolant and is not arranged in a bath cryostat with an open coolant reservoir via a thermal coupling to a solid, low-temperature member such as the cold head of a refrigeration ⁇ machine.
  • This refrigerator can in its operation again using a liquid coolant itself, but which then is present not in an open reservoir, but in a fluidically closed coolant circuit.
  • the thermal coupling of the coil winding to the solid, cryogenic element may for example only a high heat conduction ⁇ SUC gene.
  • these thermal coupling can also be effected via a thermosiphon or a heat pump, again with a cooling medium in a closed cycle can be used.
  • the essential difference from cooling in a bath cryostat is that the coolant is present only in a fluidically closed circuit within the device and not an outwardly open reservoir.
  • Transport is possible without emptying and / or filling a helium bath cryostat.
  • Another advantage is that, in the event of breakdown of the superconductivity (for example, in the case of a sudden quench), no evaporation of the liquid coolant into the external environment takes place.
  • Such a quench results in conventional magnetic resonance coils to evaporate a very large amount of helium. It has a high hazard potential, since in this schlagar ⁇ vigen evaporation a high pressure in the cryostat arises, which can even blow up the cryostat in extreme cases. Thus, such devices are not suitable for use
  • the security control device described above is used, the measured objects being a plurality of persons and / or transport goods, which are examined with regard to the presence of predefined types of hazardous substances.
  • the inventive method is used for security control with a device according to the invention.
  • Magnetic resonance signals are measured at the respective measurement objects by means of the device, the type of measured magnetic resonance signals being based on the presence or absence of predefined types of hazardous substances.
  • the coil device may advantageously be designed to generate a magnetic field Bo, which along the passage ⁇ direction has a field profile, which is characterized in the interior of the hollow ⁇ space by a homogeneity region with substantially homogeneous field course and in the the
  • Homogeneity area adjacent edge areas is characterized in each case by a sloping outwards and concavely curved field profile with outwardly smaller in absolute terms field gradient.
  • a region of substantially homogeneous magnetic field Bo which may extend over part of the cavity, for example a major part of the cavity, or substantially the entire cavity.
  • the magnetic falls see field strength initially from relatively strong and takes RESIZE ⁇ SSER becoming intervals steadily becoming further, the slope of this waste always drops further to the outside - that the field profile flattens out gradually towards the outside ,
  • ⁇ with results in approximately the shape of a trapezium with concave curved sides.
  • the advantage of such a shape is that during a transport or a pre-run of the measurement objects along the passage direction, the magnetic field strength gradually increases until it reaches the maximum value Bo for performing the measurement in the sample space. In a further passage along the passing direction, the magnetic field strength decreases then all ⁇ gradually again. This gradual increase and decrease makes it possible to introduce and remove measurement objects of unknown composition, which can also have magnetic and / or electrically conductive material components.
  • the described field profile of the magnetic field Bo can have a field gradient of not more than 9 T / m in the edge regions which lie next to the homogeneity region in the direction of passage.
  • this field gradient can be below 3 T / m or even below 0.9 T / m. This ensures that the Magnetic attractions on ferromagnetic materials and the deceleration of objects with electrically conductive components are advantageously limited.
  • the maximum field gradient of 9 T / m at a mag- netic flux density of 1.4 T acts locally on a ferromagnetic Whether ⁇ ject with a volume of 1 cm 3, a magnetic force of a maximum of 10 N. With a correspondingly smaller values for the maxi ⁇ If field gradients (as well as correspondingly smaller volumes and / or magnetic flux densities) are used, the acting forces are advantageously limited to even smaller values.
  • the profile of the magnetic field Bo may be formed so that the location at which the magnetic field strength, starting from its maximum value to a
  • Fraction 1 / e has dropped, at least 50 cm - more preferably at least 2 m or even at least 5 m - is located away from the edge of the homogeneity range.
  • the magnetic attraction forces and the vortex ⁇ currents are advantageously limited in conductive objects.
  • the inner cavity of the device forming the sample space can advantageously be at least 0.5 m long in the direction of passage in order to be able to pick up persons or goods to be transported as measuring objects.
  • it can particularly advantageously have a length between 0.5 m and 3 m, in particular between 0.5 and 1.5 m.
  • the sample space may, for example, have a rectangular cross section or a circular cross section. Regardless of its exact shape, it can have a width and / or height of at least 0.5 m, in particular between 0.6 m and 2.5 m, in order to be able to pick up persons and / or transport goods as measuring objects.
  • the sample space can be arranged centrally within the coil device. This is particularly advantageous when sym ⁇ metric, especially circularly symmetric coil assemblies for generating magnetic fields particularly homogeneous.
  • the apparatus may advantageously comprise at least one acid sequence Hochfre coil for transmitting and / or receiving radio frequency signals. This can be a common coil for sending and receiving or else separate transmit and receive coils.
  • the device can be designed to record magnetic resonance spectra. In particular, they can have for this purpose a signal processing unit on ⁇ , the Fourier analysis of the frequency components of a (at separate coils by means of the RF coil: the
  • Receiving coil measured free induction decay is suitable.
  • a signal processing unit magnetic resonance spectra can be determined for the individual measurement objects in which the magnetic resonance signals are present as a function of the individual resonance frequencies, which differ slightly for the different chemical environments of the individual measured cores. These differences are also referred to as chemical shifts.
  • the spectra obtained can then be compared, for example with an analysis unit designed for this purpose, with spectra of known materials. From the comparison of the spectra can then be concluded that the presence or absence of predefined types of hazardous substances, such as certain classes of explosives or drugs.
  • the device can be designed particularly advantageously for carrying out double resonance measurements. This is Transfer spin polarization from one core type to another core type. With such a method, for some hazardous substances, detection with a particularly good signal-to-noise ratio is possible, for example for trinitrotoluene, when the transmission of the spin polarization from hydrogen to nitrogen is measured.
  • the device for measuring spin-spin relaxation times can be set up.
  • it may have a transmitting device, by means of which a plurality of high-frequency excitation coils in the form of spin-echo sequences can be emitted. It may further comprise a processing unit with which from the measured via a receiving coil high-frequency
  • Pulse responses a relaxation time can be determined.
  • the presence of particular substances can advantageously be determined without having to record a whole magnetic resonance spectrum.
  • the presence of hydrogen peroxide detected ⁇ the by proton with a chemical shift that is, a resonance frequency
  • the input of the echo time flow in a spin-echo sequence on the measured relaxation time is determined. For example, about determining the ratio of two to different
  • Echo times measured relaxation times are concluded with a very short measurement time on the presence of hydrogen peroxide.
  • Hydrogen peroxide is a key ingredient in some explosives.
  • ⁇ terhin may include a gradient coil for generating a location-dependent magnetic field within the sample space, so that by means of the device a spatially resolved measurement magneti ⁇ shear resonance is possible.
  • the device can be designed for magnetic resonance imaging, so that an image of the test objects to be examined is possible. becomes light.
  • Such a mapping may be in the form slaughterdimensio ⁇ tional sectional images or projections as well as in the form of a three-dimensional tomographic image data set.
  • the coil device can be designed so that it can be used to generate a magnetic field Bo, which runs essentially perpendicular to the direction of passage.
  • Words can run within the sample space, a main direction of the magnetic field Bo perpendicular to the direction of passage.
  • the passage direction can generally run substantially parallel to the earth's surface, ie horizontally.
  • the main direction of the magnetic field BO can then be, for example, either vertically in space or it can also be horizontal, but perpendicular to the direction of passage. However, it can also assume other oblique orientations perpendicular to the direction of passage.
  • this main direction of Bo is an advantage of a vertical orientation to the passage direction is that the measuring objects are not accelerated by ferromagnetic Mate ⁇ rialkomponenten along the direction of passage (but only perpendicular thereto). In this case, the magnetic field is advantageously oriented downwards.
  • Any ferro ⁇ magnetic components then pull the measurement object in the direction in which it already rests due to gravity anyway. Thus, movements of the DUT are avoided. In the other directions perpendicular to the direction of the measurement objects, however, can be more easily fixed against such magnetic ⁇ table caused movements, since they in these directions in space to run does not have to be mobile.
  • the coil device can also be designed so that it can be used to generate a magnetic field B o which runs essentially parallel to the passage direction.
  • Such parallel magnetic field can be generated with the example of a circular cylindrical magnet coil, which has a circular cylindrical cavity as a sample space in its interior ⁇ example.
  • the coil device may have either only one or more magnetic coils.
  • This plurality of magnetic coils can be arranged symmetrically around the sample space, or they can also assume an asymmetrical arrangement which generates an approximately homo ⁇ nes magnetic field B o in the interior of the sample chamber. Is Wesent ⁇ Lich that (in ⁇ By running direction) a homogeneity range is present at least over a part of the length of the sample space in which the magnetic field strength is substantially kon ⁇ constant.
  • the coil means may comprise a plurality of circular cylindrical superconducting coils, which are stacked in the axial direction to generate a homogeneous magnetic ⁇ field inside the resulting hollow cylinder.
  • the dimensions of the homogeneity region should generally correspond at least to the expected dimensions of the objects to be measured.
  • the device can generally advantageously have a conveying device with which the measuring objects can be transported through the cavity of the magnetic coil in succession in a continuous or quasi-continuous process.
  • Such a conveying device may be an automatic conveying device and comprise, for example, a conveyor belt, a roller conveyor, a chain conveyor or a similarly acting conveying means.
  • the conveying device may also comprise receiving means for receiving the measurement ⁇ objects, such as containers such as plates, Kis ⁇ th or baskets, can also be arranged in groups in which the individual measurement objects or.
  • the various forms of such a conveying device have in common that with it the individual measuring objects can be moved one after the other in the direction of passage at the same time.
  • a run is to be understood in the context of the present invention generally, in which a plurality of sequential objects to be measured are simultaneously moved continuously in the region of the device.
  • a similar run process is understood to be a quasi-continu ⁇ ous process in which the lead but for the duration of each measurement briefly - for example, for a few seconds - is stopped. This brief pause can either concern only the object to be measured, while the others
  • Objects in front and behind continue to run. Or, in particular, if the measurement objects follow one another very closely on or in the conveying means, the forward flow can also be measured simultaneously for all objects located in the area of the device for the duration of the measurement
  • Essential for the continuous or quasi-continuous feed is that all at the same time move up the measurement objects in the device.
  • the device can also be designed for the automatic movement of the measuring objects through the sample space.
  • the measured objects can be persons who run in a continuous or quasi-continuous sequence in a row one behind the other through the sample space. This is particularly advantageous for the security of per ⁇ sonen, for example, in airports or at events to control many people within a short time.
  • the apparatus may comprise at least one retaining means to me ⁇ mechanically to fix the object to be measured in each case in the region of the sample space.
  • the holding means may be a holding pad, such as a blowable on ⁇ holding pads, for example.
  • One or more holding means can be used, so that the objects can be fixed against movements in different spatial directions for each to be measured Whether ⁇ ject. Special attention should be fixing in direction of the main direction of the magnetic Bo to avoid the risk of possibly occurring defects ⁇ trend (in From ⁇ dependence on the composition of the object) strong accelerations.
  • the object to be measured in each case can be fixed along the passage path at the position intended for the measurement. Above all, in the case of inanimate measurement objects in which high proportions of ferromagnetic components may possibly also be expected, even a relatively strong fixation can be effected with the holding means (or the holding means) in order to limit deviations from the predetermined pass path as far as possible.
  • the motion ⁇ freedom can be as restricted to a few mm or a few cm ⁇ to.
  • the device can be set up to perform magnetic resonance measurements on measurement objects with a measurement time between 1 second and 1 minute, in particular between 1 second and 30 seconds per sample.
  • the conveyor device can then be set up so that each measurement object remains within the sample space for at least the stated time period. As described, this can be achieved either via a continuous pass through a suitable speed with which the measurement objects arranged one after the other move simultaneously. Or the object to be measured is stopped for this period, as previously described for the quasi-continuous process.
  • the superconducting coil winding of the device can advantageously have a high-temperature oxide superconductor and / or magnesium diboride as conductor material. Such Sup ⁇ raleiter have higher critical temperatures than conventional metallic low-temperature superconductor and may be cooled more easily dry so German lent. Furthermore, with
  • High-temperature superconductors are also easier particularly high magnetic field strengths can be achieved, since they can be operated at temperatures well below their critical temperature and then the upper critical magnetic field strengths are particularly high.
  • Conductors can be present for example in the form of superconducting wires or in the form of flat strip conductors.
  • Particularly suitable for processing in strip conductors are compounds of the type REBa 2 Cu30 x (REBCO for short), where RE stands for a rare earth element or a mixture of such elements.
  • RE stands for a rare earth element or a mixture of such elements.
  • Magnesium diboride has a transition temperature of about 39 K and thus is considered as a high-temperature superconductor, but the transition temperature is rather low compared to other high-temperature superconducting materials.
  • the advantages of this material compared to oxide-ceramic high-temperature superconductors lie in its easy and thus inexpensive manufacturability.
  • the cooling device may comprise a refrigerating machine having a heat conductive ⁇ coupled to the superconducting coil winding cold head, wherein the cooling unit is designed to be operated with a closed coolant circuit.
  • the device does not completely free of FLÜS ⁇ Sigem coolant, in particular also not be free of liquid helium.
  • the liquid coolant is within the refrigerator in a closed circuit and therefore can not evaporate from the device.
  • the refrigerator can be for example a pulse tube cooler or a Kompressi ⁇ onshimltemaschine after the Gifford-McMahon principle. It can advantageously be a two-stage or multi-stage refrigerator, with which particularly low temperatures can be achieved without requiring direct cooling of the superconductor with liquid helium.
  • the coil device can generally be advantageously designed to generate a magnetic field B o with a maximum field strength in the sample space between 0.25 T and 4 T.
  • Such magnetic field strengths are well suited for substance detection by NMR spectroscopy. They are also suitable for optional magnetic resonance imaging on the DUTs.
  • the coil device for generating the magnetic field B o can generally advantageously have a maximum weight of 1000 kg, in particular ⁇ sondere a maximum of 250 kg.
  • the definition of the weight of the coil device should be such that the weight of the cooling device, which is part of the coil device, is included.
  • the entire Spulenein ⁇ direction is so easily executed that it is suitable for mobile appli ⁇ tions.
  • the device has a cryostatic container within which the at least one superconducting coil winding is arranged.
  • This container may for example be a single-walled vacuum container, so that the coil winding (s) can be arranged within this container in an evacuated space. It may in particular be a hollow cylindrical container, wherein the walled inner cylinder wall to the container for the coil winding ⁇ (s) separates from the sample space.
  • the at least one coil winding can be thermally insulated by a super insulation against the external environment.
  • the at least one magnetic coil of the coil device can be operated according to an advantageous embodiment in the so-called continuous short-circuit current mode.
  • a continuous current flows through an annular closed superconducting circuit, which almost does not decay over a very long period of time due to the vanishing resistance of the superconducting coil winding.
  • coils can be operated with low temperature superconductors over several years in this short circuit current mode, without the decay of the magnetic field, the magnetic resonance measurement ⁇ substantially impaired.
  • To enable such an operation should form a ringför ⁇ -shaped circuit with continuous superconducting properties of the superconducting coil. Any required connections should have a contact resistance of no more than 1 fOhm.
  • a superconducting permanent current switch can be advantageously provided within the winding in this embodiment.
  • the superconducting permanent current switch is part of the current ⁇ circle of the coil and is for feeding an external Power from an external power source, for example, by heating in an ohmic conductive state. After switching off the heating and cooling down to the operating temperature, this part of the coil also becomes superconductive again.
  • a operated in the short circuit current mode coil be ⁇ Sonders advantageous for magnetic applications in which the device is operated at least for several months at a FES th place.
  • the magnetic field generated by such a coil is particularly constant over time, since it is not influenced by the network fluctuations of an additional current source.
  • the coil means comprises a current source which is connected in series with the superconducting conductor of the magnetic coil.
  • Such a permanently powered solenoid consumed due to the low electrical losses in the coil winding still little electrical power, and they can be taken relatively quickly and a ⁇ times in operation and / or are turned off again.
  • the operating current of the magnetic coil can be reset daily in order to restart the device for the measurements planned for the respective day.
  • a magnetic resonance spectrum can be determined by Fourier analysis. This magnetic resonance spectrum can then be compared with spectra of known materials, it being concluded from the comparison of the spectra on the presence or absence of predefined types of hazardous substances.
  • the magnetic resonance signals can be advantageous ⁇ adhesive obtained by a double-resonance measurement.
  • ⁇ can be carried out drive to spectrally resolved measurement principle a spatially resolved measurement of the magnetic resonance signals by the nacheinan ⁇ be brought in magnetic resonance with a stimulating radio frequency field by means of at least one gradient coil different locations within the sample space.
  • FIG. 1 shows a schematic longitudinal section through a device according to a first exemplary embodiment
  • Figure 2 shows a schematic longitudinal section through a device according to a second embodiment and Figure 3 shows a field strength profile of the magnetic field B0 for a
  • Coil means of such a device shows.
  • FIG. 1 shows a device 1 for measuring magnetic resonance signals according to a first exemplary embodiment of the invention in a schematic longitudinal section, cut along the passage direction x through the device. Along this passage direction x measuring objects 9 can be transported through the device one behind the other.
  • the device 1 has a conveying means, which comprises such measuring objects in the form of
  • the conveyor 13 comprises in the example shown a conveyor belt 15, on which individual delivery containers are attached.
  • objects 9 to be measured can be arranged individually and / or bundled together in order to be driven through the sample space 11 in succession in a continuous or quasi-continuous process.
  • magnetic resonance signals are measured within the sample chamber 11 then to the depending position ⁇ wells there measurement objects.
  • the delivery containers 17 may advantageously have a material which contributes comparatively little to this measured signal.
  • the measurement objects may also be loose on the conveyor belt or a similar suitable one
  • one or more holding means may be provided, in the example shown in FIG. 1 this is for the delivery container 17a shown by way of example on the right side of the illustration an arrangement of a plurality of inflatable holding cushions 21, with which the measurement object 9a within this container 17a fi ⁇ xed is.
  • a lid 19 may be provided for the delivery container 17a.
  • the device 1 has a coil device 3 for generating a strong, static and within the sample chamber 11 is substantially homo ⁇ gene magnetic field Bo.
  • This coil device 3 has one or more superconducting magnetic coils 5 with windings of superconducting conductor materials.
  • Fig. 1 exemplarily shown two Magnetspu ⁇ len 5a and 5b, one above and one of which is arranged Below the sample compartment 11. With them, a strong magnetic field Bo can be generated, which is perpendicular to the passage direction x. In the example shown, this is the vertical spatial direction with geodesic orientation downwards. In principle, however, the magnetic field BO can also have other orientations.
  • the superconducting conductor materials of the solenoids 5a and 5b may be advantageous high-temperature superconductor having a transition temperature above 25 K and can therefore be cooled more easily than low temperature superconductor with a refrigerating machine without being immersed himself in a bath of flüssi ⁇ according helium.
  • the superconducting conductors of these coil windings may be formed as a band conductor with a layer of the type REBa 2 Cu30 x . Such materials have a particularly high transition temperature.
  • the device 1 In order to cool the superconducting coil windings to an operating temperature below the transition temperature of the superconductor, the device 1 has a cooling device 7, which is designed to cool the coil winding dry - ie without direct embedding of the windings in a liquid coolant.
  • a refrigerant ⁇ machine 23 which works in the illustrated example on the basis of a two-step ⁇ Gifford-McMahon cooler compression with a closed helium circuit.
  • This chiller 23 comprises a cold head 25, which is thermally connected to the magnetic coils 5a and 5b here for cooling the windings by high heat conduction materials.
  • these coils 5a and 5b are arranged inside a cryostatic vessel 27, which is designed here as a single-walled vacuum vessel.
  • the Coils 5a and 5b are thus arranged within a vacuum space V on ⁇ .
  • vacuum space V may be either the hollow cylindrical about a common vacuum chamber, within which are both solenoids 5a and 5b angeord ⁇ net. Alternatively, it may also be separate sub-arrangements with separate vacuum spaces V above and below the sample space 11.
  • the sample space 11 is an internal cavity within the device 1, through which the measurement objects 9 can be transported in succession. This cavity may be circular-cylindrical or may have other cross-sectional geometries, for example a rectangular cross-section. It can be arranged centrally or else decentrally within the device. It is only important that it forms a continuous bore in the passage direction x and that it is sufficiently large to receive the objects 9 to be measured.
  • the magnetic field B0 generated by the coil device 3 has a homogeneity range in which the field strength is substantially constant.
  • the length of this homogeneity region is indicated in FIG. 1 by h .
  • the length l ⁇ h at least as large as the to be expected ⁇ tend maximum length l m of the measuring objects 9.
  • the strength of magnetic field B0 for example, be between 0.25 T and 4 T.
  • Such a static magnetic field is the basis for the magnetic resonance measurements to be carried out with the device 1.
  • the device 1 can additionally have one or more radiofrequency coils, not shown here for the sake of clarity, with which high-frequency electromagnetic signals (for example pulses) can be transmitted and / or received.
  • Magnetic resonance spectra and / or spin relaxation times can be measured with such a device.
  • the device may additionally comprise one or more gradient coils, to enable spatially resolved measurements.
  • the device may have a processing unit, likewise not shown here, in order to amplify and process the measured signals and to determine the desired NMR spectra, relaxation times and / or images.
  • the thus measured NMR spectra, relaxation times and / or images can be used to perform security checks on the objects 9 to be measured. These objects - regardless of whether they are transported goods or persons - can be examined for example with regard to explosives, drugs or other hazardous substances.
  • FIG. 2 shows a further apparatus 1 for measuring magnetic resonance signals according to a second exemplary embodiment of the invention.
  • a schematic longitudinal section along the direction of passage x of the device is shown.
  • persons 9b are examined here with regard to potentially present hazardous substances. These persons each run themselves on a track 22 through the sample space 11 of the device. Alternatively, these persons 9b can also be moved automatically by a conveyor belt similar to the example of FIG. 1 for the transported goods.
  • the device 1 is similar in structure to the device of FIG. 1, the cooling device 7 constructed in a similar way not being shown here for the sake of clarity, and the radio-frequency coils and the processing unit again are not shown.
  • the coil device 3 for generating the static magnetic field Bo is constructed somewhat in ⁇ DERS in the second embodiment: Namely, here is an arrangement of several ⁇ ren annular magnetic coils 5 in front of which are each disposed in an annular plane perpendicular to the direction x. Each magnetic coil 5 surrounds the inner cavity as keptbil ⁇ Deten sample chamber 11 so annularly. By way of example, an arrangement of five such axially stacked magnetic coils is shown here. len 5, wherein the exact number can also be larger or smaller. In principle, the measurement also works only with a single annular magnetic coil 5. Overall, a static magnetic field Bo is generated here by the coil device 3, which is parallel to the passage direction x of the objects to be measured.
  • the magnetic coils 5 of the second embodiment may have a circular cylindrical cross-section and thus surround a circular cylindrical inner cavity 11 symmetrically.
  • a circular cylindrical cross-section may surround a circular cylindrical inner cavity 11 symmetrically.
  • particularly homogeneous magnetic fields BO can be generated.
  • other, in particular rectangular cross-sectional geometries are possible.
  • the spatial extent of the sample space may be the same or different in width and height. In the example application with passing persons, it is advantageous if the sample space is significantly higher than it is wide. When measuring Transportgü ⁇ tern, for example suitcases, boxes, bags or other better lying to be transported objects this may be reversed.
  • FIG. 1 The structure of the magnetic coils and the orientation of the magnetic field in Figures 1 and 2 is to be understood only by way of example.
  • a device for examining persons with a coil device 3 can be equipped similarly as in FIG. 1, and a device for examining transported goods can also be equipped with a coil device 3 similar to that shown in FIG.
  • FIG. 3 shows an advantageous field profile 31 of the magnetic field Bo generated by the coil devices 3 as a function of the passage direction x, as may be present within the device of the first and / or second exemplary embodiment.
  • the field profile 31 has a homogeneity ⁇ region 33 of length l to h, which advantageously extends over the largest possible part of the sample room 11, and within which the magnetic field strength Bo at the essential is constant and at a maximum value B max .
  • This homogeneity region is flanked by two edge areas 35, in which the field strength from the value B max to we ⁇ sentlich lower values decreases. For example, this waste can be approximately exponential.
  • edge region 35 of the area may for example be considered where the field strength of Bmax to a fraction 1 / e of B / max from ⁇ falls.
  • the dots 39 in which this fraction is achieved can be beneficial ge ⁇ separated at least by a distance 41 of at least 2 m from the edges of the homogeneity range 33rd
  • Such a spatially extended waste of the magnetic field Bo is much more gradual than in the typically used today magnetic resonance imaging apparatus in which the magnet coils to reduce the stray field preferably be so incorporated ⁇ oriented such that a steep drop as possible is achieved.
  • the gradual decay shown has for the dung OF INVENTION ⁇ intended use but the advantage that the lower to the sample chamber 11 passing through the measurement objects 11 are exposed to magnetic attraction forces, since the maximum field gradient 37 are limited to lower values.

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Abstract

L'invention concerne un dispositif (1) de mesurage de signaux de résonance magnétique, qui comprend un dispositif à bobines (3) pour la génération d'un champ magnétique (B0) à l'aide d'au moins une bobine magnétique (5, 5a, 5b) dotée d'un enroulement de bobine supraconducteur. Le dispositif à bobines (5) comprend un dispositif de refroidissement (7) pour le refroidissement sec de l'enroulement de bobine supraconducteur. Le dispositif (1) présente une direction de déplacement (x) prédéfinie pour le transport séquentiel d'une pluralité d'objets à mesurer (9) à travers le dispositif (1). Le dispositif à bobines (5) comprend en outre un espace creux intérieur continu qui définit un espace d'échantillon (11) continu et à travers lequel les objets à mesurer (9) peuvent être transportés les uns derrière les autres le long de la direction de déplacement (x) à travers le dispositif (1). L'invention concerne en outre une utilisation d'un tel dispositif pour le contrôle de la sécurité, les objets à mesurer (9) étant une pluralité de produits à transporter (9a) et/ou de personnes (9b) qui sont examinés en termes de la présence de types prédéfinis de substances dangereuses. En outre, l'invention concerne un procédé de contrôle de la sécurité à l'aide d'un tel dispositif.
PCT/EP2016/078936 2016-01-14 2016-11-28 Dispositif et procédé de mesurage de signaux de résonance magnétique WO2017121532A1 (fr)

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Citations (5)

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Publication number Priority date Publication date Assignee Title
JPH07198636A (ja) * 1993-12-29 1995-08-01 Yamamoto Mfg Co Ltd 果実の品質評価装置
JP2000004708A (ja) * 1998-06-23 2000-01-11 Kobe Steel Ltd 魚の雌雄判別装置および判別方法
US20110112395A1 (en) * 2008-07-08 2011-05-12 Kyushu University Measurement device and measurement method
GB2517654A (en) * 1989-06-21 2015-03-04 Marconi Uk Intellectual Prop Inspection Apparatus
WO2015189786A1 (fr) * 2014-06-11 2015-12-17 Victoria Link Ltd Système d'imagerie à résonance magnétique transportable

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GB2517654A (en) * 1989-06-21 2015-03-04 Marconi Uk Intellectual Prop Inspection Apparatus
JPH07198636A (ja) * 1993-12-29 1995-08-01 Yamamoto Mfg Co Ltd 果実の品質評価装置
JP2000004708A (ja) * 1998-06-23 2000-01-11 Kobe Steel Ltd 魚の雌雄判別装置および判別方法
US20110112395A1 (en) * 2008-07-08 2011-05-12 Kyushu University Measurement device and measurement method
WO2015189786A1 (fr) * 2014-06-11 2015-12-17 Victoria Link Ltd Système d'imagerie à résonance magnétique transportable

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J. D. KING ET AL: "Development and evaluation of magnetic resonance technologies, particularly NMR, for detection of explosives", APPLIED MAGNETIC RESONANCE, vol. 25, no. 3-4, 1 September 2004 (2004-09-01), pages 535 - 565, XP055176704, ISSN: 0937-9347, DOI: 10.1007/BF03166547 *

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