Magnet device and magnetic resonance apparatus

Abstract

The invention relates to a magnet arrangement and a magnetic resonance apparatus. The magnetic resonance apparatus (14) comprises the magnet arrangement (11). A magnet arrangement (11) for a magnetic resonance imaging apparatus (10), the magnet arrangement (11) comprising a main magnet (12) comprising a plurality of superconducting coils (31), a reverse superconducting coil (32) and a ferromagnetic element (33), where the reverse superconducting coil (32) is arranged between two superconducting coils (31) of the plurality of superconducting coils (31), and where the ferromagnetic element (33) is arranged between the reverse superconducting coil (32) and the superconducting coils (31).

Description

Background Art

[0001] Independent of grammatical term usage, individuals with male or female gender identities are included in the term.

[0002] Conventional magnetic resonance imaging (MRI) systems used for medical diagnostics typically weigh several tons and have a footprint of at least three square meters. Such systems can only be installed where specific requirements regarding accessibility are met, as well as the load-bearing capacity of the floor or ceiling. For example, the examination room housing the MRI system must have a sufficiently high ceiling and a properly designed access path. Furthermore, the examination room floor must be able to withstand the weight of the MRI system for an extended period of time.

[0003] Smaller medical institutions and practices interested in new magnetic resonance imaging applications (such as dentistry, neurology, orthopedics) are often not equipped to transport and install conventional magnetic resonance equipment. For example, installing conventional magnetic resonance equipment in a dental practice may be difficult because the client may not accept operational interruptions due to construction or renovation work, such as opening walls or enlarging doors.

[0004] Furthermore, the adoption of new magnetic resonance imaging applications depends on the cost of the magnetic resonance apparatus, which is significantly influenced by the length of the patient bore enclosed by the main magnet of the magnetic resonance apparatus. Assuming a predetermined or constant homogeneity volume, the main magnet of the magnetic resonance apparatus generally becomes more expensive as the length of the patient bore decreases. Shorter magnets may also require custom support structures designed to withstand the unconventional distribution of (electromagnetic) forces that may result from the shortening of the patient bore. Summary of the Invention

[0005] The object of the present invention is to alleviate the disadvantages caused by reducing the length of the patient bore in a magnetic resonance apparatus.

[0006] This object is achieved by the magnet arrangement and the magnetic resonance system according to the invention. Further advantageous embodiments are described in the subsidiary aspects.

[0007] The magnet arrangement of the present invention is configured to be used in a magnetic resonance imaging apparatus.The magnet arrangement may be configured to provide a main magnetic field suitable for magnetic resonance imaging of a subject, in particular diagnostic medical imaging.

[0008] According to the present invention, a magnet arrangement includes a main magnet including a plurality of superconducting coils, an opposing superconducting coil, and a ferromagnetic element.

[0009] The magnet arrangement may include two sets of superconducting coils. In particular, the magnet arrangement may include a set of "inner coils" and a set of "outer coils".

[0010] The "inner coils" of the magnet arrangement may form the main magnet or constitute part of the main magnet. The "inner coils" may be arranged sequentially along a common axis, in particular the barrel axis or the axis of rotational symmetry of the main magnet. It is conceivable that the "inner coils" are arranged coaxially along the common axis and / or include a substantially common radius.

[0011] The main magnet may include a plurality of superconducting coils. For example, the main magnet may include five to nine superconducting coils. In a preferred embodiment, the main magnet includes five or six superconducting coils. The plurality of superconducting coils of the main magnet corresponds to the "inner coils" of the magnet arrangement.

[0012] A set of "outer coils" (or "shielding coils") of the magnet arrangement may be coaxially arranged on a larger radius than the "inner coils". The "outer coils" may be configured to actively shield the "inner coils" of the main magnet from surrounding electromagnetic fields and / or electromagnetic radiation. Depending on the embodiment, the magnet arrangement comprises two "outer coils". However, the magnet arrangement may comprise a single "outer coil" or up to five "outer coils". The "outer coils" are not considered to form part of the main magnet.

[0013] The opposing superconducting coil may form part of the "inner coil" of the magnet arrangement. In particular, the opposing superconducting coil may be arranged coaxially with the plurality of superconducting coils. For example, the axis of the opposing superconducting coil may correspond to a common axis defined by the plurality of superconducting coils. The common axis defined by the plurality of superconducting coils may correspond to the barrel axis or rotational symmetry axis of the main magnet.

[0014] The reverse superconducting coil can be characterized by a reverse current direction relative to the plurality of superconducting coils. Specifically, the reverse superconducting coil can be configured to provide a magnetic field that is oriented in a direction opposite to the magnetic field provided by the plurality of superconducting coils. Aside from the current direction, the material and / or coil structure of the reverse superconducting coil can substantially correspond to the material and / or coil structure of the plurality of superconducting coils. For example, the size and / or mass of the superconducting wire of the reverse superconducting coil can substantially correspond to the size and / or mass of the superconducting coils of the plurality of superconducting coils.

[0015] The counter-superconducting coil is arranged between two superconducting coils of the plurality of superconducting coils.

[0016] In a preferred embodiment, the counter superconducting coil is mechanically connected to at least one superconducting coil of the plurality of superconducting coils. In particular, the counter superconducting coil of the main magnet and the plurality of superconducting coils may form a cohesive structure.

[0017] The counter superconducting coil may be arranged or positioned between the first superconducting coil and the second superconducting coil.Preferably, the counter superconducting coil is mechanically connected to the first superconducting coil and / or the second superconducting coil.

[0018] According to an embodiment, one or more spacers are arranged between the counter superconducting coil and the first superconducting coil. It is also conceivable that one or more spacers are arranged between the counter superconducting coil and the second superconducting coil. In a preferred embodiment, a spacer and / or a ferromagnetic element is arranged between the counter superconducting coil and the first superconducting coil.

[0019] The inverted superconducting coil can be directly attached to the spacer, ferromagnetic element and / or superconducting coil via a form-locking connection, a force-locking connection and / or a material bond. For example, the inverted superconducting coil can be screwed, bolted and / or glued to the spacer, ferromagnetic element and / or superconducting coil.

[0020] It is conceivable that the reverse superconducting coil, the ferromagnetic element, and the plurality of superconducting coils are integrally combined.

[0021] The main magnet may include a magnet support structure configured to provide mechanical support for the main magnet. The magnet support structure may be configured to maintain a predetermined spatial arrangement of the opposing superconducting coils, the ferromagnetic element, and the plurality of superconducting coils. The magnet support structure may be configured to be mechanically connected to a support structure of the magnetic resonance apparatus, in particular an external vacuum chamber.

[0022] The magnet assembly may further include a refrigerant vessel and / or a thermal shield. It is contemplated that the magnet assembly is circumferentially enclosed within an outer vacuum chamber. The vacuum chamber may be formed as a double-walled hollow cylindrical member comprising an outer shell and an inner shell connected by an annular end piece. The magnet assembly may be enclosed between the outer shell and the inner shell of the outer vacuum chamber. The inner shell of the outer vacuum chamber may correspond to a patient bore of a magnetic resonance device including the magnet assembly.

[0023] In conventional magnet arrangements without counter-rotating superconducting coils, the inter-coil forces, or electromagnetic forces, acting on the superconducting coils of the main magnet are generally directed toward the central symmetry plane of the main magnet. Therefore, the inter-coil forces in conventional magnet arrangements are compressive in nature and tend to pull the superconducting coils toward the central symmetry plane.

[0024] For example, in a cylindrical magnet arrangement without opposing superconducting coils, axial forces between the superconducting coils can be directed toward the central symmetry plane of the main magnet. Depending on the design of the main magnet, this axial force can result in an equivalent weight of greater than 10 tons or even greater than 100 tons acting on a single superconducting coil. Consequently, superconducting coils arranged near the central symmetry plane can experience significant compressive forces.

[0025] The counter-superconducting coil can be configured to modify the inter-coil force within the main magnet such that the electromagnetic force acting on at least one of the two superconducting coils framing the counter-superconducting coil (relative to the central symmetry plane of the main magnet) is expansionary rather than compressive. In particular, the counter-superconducting coil can be configured to reduce or reverse the electromagnetic force acting on at least one superconducting coil, particularly the end coil, compared to a conventional magnet arrangement without the counter-superconducting coil.

[0026] The inverted superconducting coils can be configured so as to allow the length of the patient bore to be reduced while maintaining a desired size of the homogeneous volume provided via the main magnet. In particular, the inverted superconducting coils can be configured to reduce the length of the main magnet to below 1.3 m, below 1.2 m, below 1.1 m, or even below 1 m without compromising the homogeneous volume provided via the main magnet.

[0027] The homogeneous volume may represent an imaging volume of a magnetic resonance device including a magnet arrangement. In particular, the homogeneous volume may correspond to a volume within a magnetic field provided by a main magnet. The homogeneity of the magnetic field within the homogeneous volume may exceed a predetermined threshold.

[0028] The goal of reducing the length of the patient bore may make the goal of providing a homogenous volume significantly more difficult. In introducing the inverted superconducting coils, multiple variables can be introduced, for example by allowing the current direction to be varied from a nominally "positive" current direction to an equally "negative" current direction, which advantageously allows solutions to be found for both goals.

[0029] From a different perspective, the sum of the individual coil harmonics of superconducting coils that are moved closer together to reduce the length of the patient bore may not allow the magnetic field homogeneity of the imaging volume to be within the desired range, as the relative harmonic ratios from only the "positive" superconducting coils may not produce the desired solution. A solution to this problem may be found when an opposing superconducting coil is introduced (e.g., by allowing for "negative" superconducting coils) that provides opposing harmonics.

[0030] According to the present invention, the ferromagnetic element is arranged between the counter-superconducting coil and the superconducting coil.

[0031] For example, the ferromagnetic element may be arranged between the opposing superconducting coil and the first superconducting coil or between the opposing superconducting coil and the second superconducting coil.

[0032] The ferromagnetic element may be directly attached to the spacer, the counter superconducting coil and / or the superconducting coil via a form-locking connection, a force-locking connection and / or a material bond.

[0033] The magnet assembly of the present invention may include a plurality of opposing superconducting coils and a plurality of ferromagnetic elements. Specifically, the number of opposing superconducting coils may correspond to the number of ferromagnetic elements. In a preferred embodiment, the magnet assembly includes two opposing superconducting coils and two ferromagnetic elements. Each ferromagnetic element may be positioned adjacent to an opposing superconducting coil.

[0034] When incorporating counter-rotating superconducting coils into a magnet arrangement, the number of design parameters that influence both the size of the main magnet and the size of the homogeneous volume can be advantageously increased. In particular, the counter-rotating superconducting coils can allow the patient bore of the main magnet to be shortened without compromising the quality of the homogeneous volume provided by the main magnet.

[0035] When incorporating counter-rotating superconducting coils into the main magnet, the absolute mass of the superconducting wire in the main magnet can be increased because the counter-rotating superconducting coils can reduce the strength of the generated magnetic field, which needs to be compensated by increasing the size of the multiple superconducting coils. In addition, as mentioned above, the counter-rotating superconducting coils can affect the inter-coil forces within the main magnet. Therefore, the size of the counter-rotating superconducting coils may need to be limited so that the electromagnetic forces acting on the superconducting coils can be adequately supported by the magnet support structure, and the total axial force on the conventional coils is essentially compressive.

[0036] When providing a magnet arrangement comprising a ferromagnetic element, the size limitations of the opposing coils can be advantageously eliminated. In particular, the ferromagnetic element can advantageously suppress or even reverse the expansive or outwardly directed electromagnetic forces acting on the superconducting coils, particularly the end coils, of the magnet arrangement.

[0037] For example, a ferromagnetic element can be magnetized by the magnetic field generated by one or more superconducting coils. Due to the magnetization, the ferromagnetic element can generate a magnetic field opposite to the magnetization field (i.e., the magnetic field generated by the one or more superconducting coils). The sum of the magnetic fields of the one or more superconducting coils and the ferromagnetic element may cause the total magnetic field to decrease in a direction away from the one or more superconducting coils (or, in the case where the superconducting coils are arranged on both sides of the ferromagnetic element, away from the majority of the superconducting coils). Therefore, the ferromagnetic element can serve as a magnetic shield.

[0038] Thus, the requirement that the magnet support structure be configured to resist expansion forces can advantageously be omitted.Furthermore, the length of the main magnet and the patient bore can advantageously be reduced without increasing the size of the support structure.

[0039] According to an embodiment of the magnet arrangement according to the invention, the ferromagnetic element is arranged between the counter superconducting coil and the superconducting coil, wherein the superconducting coil is an end coil of the main magnet.

[0040] End coils can be arranged at the outer axial ends of the main magnet. Specifically, the magnet arrangement can include two end coils that frame or confine the ferromagnetic element, the opposing superconducting element, and the superconducting coils from two opposite directions. An end coil can be understood as the first superconducting coil or starting superconducting coil of the main magnet. An end coil can also refer to the final superconducting coil or terminating superconducting coil of the main magnet. The end coils can terminate the main magnet in one direction.

[0041] When a ferromagnetic element is positioned between the opposing superconducting coil and the superconducting coil, the electromagnetic interaction between the opposing superconducting coil and the superconducting coil can be reduced. In particular, the ferromagnetic element can provide a degree of magnetic shielding between the opposing superconducting coil and the superconducting coil. Consequently, the magnetic force, particularly the repulsive electromagnetic force, between the superconducting coil and the opposing superconducting coil can be reduced, which can advantageously facilitate the design and / or construction of the magnet support structure.

[0042] According to an embodiment of the magnet arrangement according to the invention, the ferromagnetic element is arranged in close proximity to the counter-superconducting coil and / or the superconducting coil.

[0043] The ferromagnetic element may be sandwiched between the superconducting coil and the counter-superconducting coil. Specifically, the ferromagnetic element may be constrained in two opposite directions by the superconducting coil and the counter-superconducting coil. For example, the superconducting coil may constrain the ferromagnetic element in a first direction, and the counter-superconducting coil may constrain the ferromagnetic element in a second direction opposite to the first direction.

[0044] The ferromagnetic element can be in direct mechanical contact with the superconducting coil and / or the counter-superconducting coil. In particular, the ferromagnetic element can be mechanically connected to the superconducting coil and / or the counter-superconducting coil via a form-locking connection, a force-locking connection and / or a material bond.

[0045] In another embodiment, the ferromagnetic element is arranged in close proximity to the spacer.The spacer may be mechanically connected to the superconducting coil and / or the opposing superconducting coil.

[0046] The ferromagnetic element can advantageously replace the spacers required to maintain a predetermined distance between the opposing superconducting coils. Furthermore, the ferromagnetic element directly attached to the opposing superconducting coil can advantageously improve the structural integrity of the opposing superconducting coil, which can have fewer coil windings than multiple superconducting coils.

[0047] According to an embodiment of the magnet arrangement according to the invention, the main magnet comprises at least one spacer arranged between the ferromagnetic element and the superconducting coil and / or between the ferromagnetic element and the counter superconducting coil.

[0048] It is conceivable that the ferromagnetic element is separated from the counter superconducting coil and / or the superconducting coil by at least one spacer.

[0049] Preferably, the at least one spacer is realized as a ring, a plurality of rings, a hollow cylinder, a plurality of hollow cylinders or a segment of a ring or a hollow cylinder. It is also conceivable that the at least one spacer is realized as a block or blocks of any suitable shape.

[0050] Preferably, at least one spacer comprises a thermally conductive material or is composed of a thermally conductive material. In particular, at least one spacer can be configured to transfer thermal energy between the ferromagnetic element and the superconducting coil and / or the ferromagnetic element and the reverse superconducting coil. At least one spacer can include an electrically insulating material, an electrically insulating coating or an electrically insulating layer. According to an embodiment, at least one spacer comprises a glass reinforced polymer (i.e., GRP or glass fiber) and a thermally conductive element such as an aluminum part, a copper part, etc., which is attached or glued to the superconducting coil, the ferromagnetic element and / or the reverse superconducting coil to improve the transmission of thermal energy.

[0051] The at least one spacer can be configured to fill a gap between the ferromagnetic element and the superconducting coil, and a gap between the ferromagnetic element and the opposing superconducting coil. The ferromagnetic element, the superconducting coil, the opposing superconducting coil, and the at least one spacer can form a cohesive structure. The at least one spacer can be attached to the ferromagnetic element and the superconducting coil, and to the ferromagnetic element and the opposing superconducting coil, via a force-locking connection, a form-locking connection, and / or a material bond.

[0052] In a preferred embodiment, the magnet assembly includes a first spacer disposed between the superconducting coil and the ferromagnetic element, and a second spacer disposed between the ferromagnetic element and the opposing superconducting coil. The superconducting coil, the first spacer, the ferromagnetic element, the second spacer, and the opposing superconducting coil can be integrally bonded to form a cohesive structure.

[0053] The spacers may advantageously allow the superconducting coils and the counter coils and other superconducting coils of the main magnet to be arranged at a predetermined distance from each other. When the individual superconducting coils are spaced apart, the homogeneity of the imaging volume provided by the main magnet may advantageously be improved.

[0054] If the size of the ferromagnetic element, in particular the axial length of the ferromagnetic element, is not sufficient to provide the desired distance between the counter-superconducting coil and the superconducting coil, it may be advantageous to add spacers.

[0055] Furthermore, the at least one spacer may comprise or consist of an electrically insulating material.Thus, the at least one spacer may advantageously provide electrical insulation between the ferromagnetic elements of the main magnet and the superconducting coils (including the counter superconducting coils).

[0056] In a preferred embodiment of the magnet arrangement of the present invention, the ferromagnetic element comprises the shape of a ring, a tube, a hollow cylinder or a hollow prism.

[0057] The ferromagnetic element may comprise an annular, elliptical or polygonal cross section.Preferably, the ferromagnetic element comprises the shape of a hollow cylinder.

[0058] The inner diameter of the ferromagnetic element may correspond to the inner diameter of the superconducting coils and / or the counter-superconducting coils of the main magnet. However, the inner diameter of the ferromagnetic element may also exceed the inner diameter of the superconducting coils and / or the counter-superconducting coils. It is also conceivable that the inner diameter of at least one superconducting coil of the main magnet and / or at least one superconducting coil of the counter-superconducting coil exceeds the inner diameter of the ferromagnetic element.

[0059] According to an embodiment of the magnet arrangement according to the invention, the main magnet comprises a cylindrical shape, and the ferromagnetic element is arranged coaxially to the main magnet.

[0060] The barrel axis or the axis of rotational symmetry of the ferromagnetic element may correspond to the barrel axis or the axis of rotational symmetry of the main magnet.

[0061] The ferromagnetic element according to the above described embodiments may advantageously allow a patient bore to pass through a main magnet comprising the ferromagnetic element.In a preferred embodiment, the ferromagnetic element advantageously prevents restriction of the diameter of the patient bore.

[0062] According to an embodiment of the magnet arrangement of the invention, a projection of the axial cross-sectional area of ​​the superconducting coil along the barrel axis of the main magnet and the cross-sectional area of ​​the ferromagnetic element have a non-empty intersection.

[0063] According to an embodiment, the projection of the outer circumference of the superconducting coil along the cylinder axis of the main magnet intersects the cross section of the ferromagnetic element. For example, the inner diameter of the superconducting coil may exceed the inner diameter of the ferromagnetic element, while the outer diameter of the ferromagnetic element exceeds the inner diameter of the superconducting coil.

[0064] In another embodiment, the projection of the inner circumference of the superconducting coil along the axis of the barrel of the main magnet intersects the cross section of the ferromagnetic element. For example, the outer diameter of the ferromagnetic element may exceed the outer diameter of the superconducting coil, while the outer diameter of the superconducting coil exceeds the inner diameter of the ferromagnetic element.

[0065] It is contemplated that the outer diameter of the ferromagnetic element substantially corresponds to the outer diameter of the opposing superconducting coil and / or the outer diameter of the superconducting coil. For example, the absolute deviation between the outer diameter of the ferromagnetic element and the outer diameter of the superconducting coil can be less than 5% or less than 10%. Similarly, the inner diameter of the ferromagnetic element can substantially correspond to the inner diameter of the opposing superconducting coil and / or the inner diameter of the superconducting coil.

[0066] The superconducting coil may correspond to the end coil according to the above-described embodiment.

[0067] The ferromagnetic element according to the present invention can advantageously facilitate the mechanical connection and / or bonding between the superconducting coil and the ferromagnetic element, as well as between the opposing superconducting coil and the ferromagnetic element. In particular, the ferromagnetic element according to the present invention can allow for improved mechanical stability or load-bearing capacity of the magnet arrangement.

[0068] In a preferred embodiment of the magnet arrangement, the ferromagnetic element comprises or consists of a material with high magnetic permeability.

[0069] The ferromagnetic element may include a section composed of a high-permeability material. For example, the ferromagnetic element may include an inner cylindrical member and an outer cylindrical member. The inner cylindrical member may be configured to carry and / or provide mechanical support to the outer cylindrical member. The inner cylindrical member may be mechanically coupled to the superconducting coil and / or the opposing superconducting coil. The outer cylindrical member may include or be composed of a high-permeability material.

[0070] It is also conceivable that the sections composed of a material with a high magnetic permeability are distributed at regular or irregular intervals along the inner circumference or the outer circumference of the ferromagnetic element.

[0071] According to one embodiment, the section composed of a material with high magnetic permeability is embedded in the support structure of the ferromagnetic element. However, the ferromagnetic element can also be composed of a material with high magnetic permeability.

[0072] Examples of high permeability materials are metals such as iron, cobalt or nickel, and alloys of the three metals. For example, the ferromagnetic element may include or consist of an alloy of iron, cobalt and / or nickel. Preferably, the ferromagnetic element consists of iron or an iron alloy.

[0073] The ferromagnetic element according to the present invention can advantageously be magnetically saturated by the magnetic field of the main magnet and provide a magnetic flux link between the superconducting coil and the counter superconducting coil. Thus, increased magnetic field homogeneity can be provided within the imaging volume.

[0074] According to another embodiment of the magnet arrangement, the ferromagnetic element is attached to the opposing superconducting coil and the superconducting coil.

[0075] According to the embodiments described above, the ferromagnetic element can be mechanically connected to the opposing superconducting coil and the superconducting coil. In particular, the ferromagnetic element can be attached to the opposing superconducting coil and the superconducting coil via a force-locking connection, a form-locking connection, and / or a material bond. For example, the ferromagnetic element can be attached to the opposing superconducting coil and the superconducting coil via a threaded connection, a bolted connection, and / or an adhesive connection.

[0076] A surface of the ferromagnetic element may be in direct mechanical contact with a surface of the opposing superconducting coil and / or a surface of the superconducting coil. In particular, a first axial face of the ferromagnetic element may be in direct mechanical contact with an axial face of the superconducting coil, and a second axial face of the ferromagnetic element may be in direct mechanical contact with an axial face of the opposing superconducting coil. The first axial face and the second axial face of the ferromagnetic element may represent opposite sides, in particular, opposite axial ends, of the ferromagnetic element.

[0077] In a preferred embodiment, the ferromagnetic element is attached to the opposing superconducting coils and the superconducting coils such that a cohesive structure is formed.

[0078] When attaching the ferromagnetic element to the counter superconducting coil and the superconducting coil, the mechanical stability of the main magnet may be advantageously improved.

[0079] According to an embodiment of the magnet arrangement of the present invention, the superconducting coils represent end coils. The ferromagnetic elements are configured to modify the inter-coil forces within the main magnet such that the outwardly directed forces acting on the end coils of the main magnet are reduced by at least 30%, at least 40%, at least 50%, or at least 60% compared to the case without the ferromagnetic elements.

[0080] The main magnet can be configured such that, in the absence of ferromagnetic elements, outwardly directed or expansion forces will act on the end coils. In particular, the opposing superconducting coils can influence the inter-coil forces within the main magnet such that the electromagnetic forces acting on the end coils are directed away from the central symmetry plane of the main magnet.

[0081] The ferromagnetic element can be configured to change the inter-coil force between the end coil and the opposing superconducting coil so that the expansion electromagnetic force acting on the end coil in the absence of the ferromagnetic element is reduced by at least 30%, at least 40%, at least 50% or preferably at least 60% by arranging the ferromagnetic element between the end coil and the opposing superconducting coil.

[0082] A ferromagnetic element configured to reduce outwardly directed forces acting on the end coils by at least 30% or at least 50% can exhibit a relatively small axial dimension. Furthermore, the ferromagnetic element can reduce the requirements for the magnet support structure to accommodate expansion forces. Consequently, the weight and / or cost associated with the magnet arrangement can be advantageously reduced or optimized.

[0083] According to another embodiment, the ferromagnetic element is configured to modify the inter-coil forces within the main magnet such that an inwardly directed force acts on the end coils.

[0084] As described above, the opposing superconducting coils and the end coils may be configured such that, in the absence of ferromagnetic elements, outwardly directed forces would act on the end coils.

[0085] The ferromagnetic element can be configured to modify the inter-coil force between the end coil and the opposing superconducting coil so that any expansion electromagnetic force acting on the end coil in the absence of the ferromagnetic element is canceled or reversed by arranging the ferromagnetic element between the superconducting coil and the opposing superconducting coil.

[0086] When designing a support structure for a main magnet or magnet arrangement, ferromagnetic elements configured to cancel or reverse the outwardly directed forces acting on the end coils can advantageously allow for negligible expansion electromagnetic forces. Consequently, the weight and / or cost associated with the support structure can be advantageously reduced.

[0087] According to another embodiment of the magnet arrangement of the present invention, the superconducting coils represent end coils. The ferromagnetic elements are configured to modify the inter-coil forces within the main magnet such that the inwardly directed forces acting on the end coils of the main magnet are increased by at least 10%, at least 20%, or at least 30% compared to the case without the ferromagnetic elements.

[0088] The opposing superconducting coils and end coils of a magnet arrangement can be configured such that, in the absence of ferromagnetic elements, inwardly directed forces act on the end coils. Specifically, the opposing superconducting coils can influence the inter-coil forces within the main magnet, such that the electromagnetic forces acting on the end coils are compressive. However, the compressive forces acting on the end coils can be less than those in conventional magnet arrangements without opposing superconducting coils.

[0089] The ferromagnetic elements may be configured to modify the inter-coil forces at the axial ends of the main magnet such that the compressive electromagnetic forces that would act on the end coils in the absence of the ferromagnetic elements are increased by arranging the ferromagnetic elements between the end coils and the opposing superconducting coils.

[0090] Ferromagnetic elements configured to increase the inwardly directed electromagnetic forces acting on the end coils may advantageously allow for further reductions in weight and / or cost of the magnet support structure.

[0091] According to another embodiment, the magnet arrangement comprises a first ferromagnetic element and a second ferromagnetic element.

[0092] The first ferromagnetic element and the second ferromagnetic element may correspond to the embodiments of the ferromagnetic elements described above.

[0093] According to the present invention, the first ferromagnetic element is arranged between the first opposing superconducting coil and the first superconducting coil, and the second ferromagnetic element is arranged between the second opposing superconducting coil and the second superconducting coil.

[0094] The first superconducting coil may correspond to an end coil disposed at a first end of the main magnet. The second superconducting coil may correspond to an end coil disposed at a second end of the main magnet. The first end and the second end of the main magnet may represent axial ends of the main magnet. In particular, the first end and the second end of the main magnet may represent opposite ends of the main magnet.

[0095] According to an embodiment, the first superconducting coil, the first ferromagnetic element and the first counter superconducting coil are arranged symmetrically to the second superconducting coil, the second ferromagnetic element and the second counter superconducting coil with respect to a central symmetry plane of the main magnet.

[0096] It is also conceivable that the first superconducting coil and the second superconducting coil represent dispersed coils. For example, the first superconducting coil may be arranged at a predetermined distance from the first end coil, and the second superconducting coil may be arranged at a predetermined distance from the second end coil.

[0097] When providing a magnet arrangement comprising at least two opposing superconducting coils and at least two ferromagnetic elements arranged symmetrically with respect to a central symmetry plane of the main magnet, the homogeneity of the magnetic field may advantageously be improved compared to conventional magnet arrangements of similar dimensions.

[0098] The magnetic resonance apparatus of the present invention is configured to acquire magnetic resonance data of a subject positioned within an imaging region of the magnetic resonance apparatus.

[0099] Preferably, the magnetic resonance apparatus is configured to acquire magnetic resonance image data, in particular diagnostic magnetic resonance image data, from an object positioned in an imaging region. The object may be a patient, in particular a human or an animal.

[0100] The magnetic resonance apparatus of the present invention may represent a closed-bore scanner. The closed-bore scanner may include a generally cylindrical bore that circumferentially encloses an imaging region. The main magnet of the closed-bore scanner may include one or more solenoid superconducting coils that circumferentially enclose the imaging region along the axial direction or rotational symmetry axis of the cylindrical bore. The one or more superconducting coils may include a wire having negligible resistance at (or below) the superconducting temperature. The direction of the main magnetic field provided by the main magnet may be oriented to be generally parallel to the direction in which the object enters the imaging region and / or the axial direction of the cylindrical bore.

[0101] The magnetic resonance system comprises a magnet arrangement according to the embodiments described above.

[0102] The magnetic resonance apparatus may include other components necessary for the proper operation of the magnetic resonance apparatus. For example, the magnetic resonance apparatus may include an outer vacuum chamber, a magnet support structure, a thermal shield, and a cryocooler. In some embodiments, the magnetic resonance apparatus includes a cryogen vessel.

[0103] The cryogen vessel can be configured to store or pre-store a fluid, in particular a cryogen, at a predetermined temperature level. Preferably, the fluid or cryogen, such as argon, nitrogen, neon, helium, etc., exhibits a low boiling point. The predetermined temperature level can substantially correspond to the superconducting temperature of the main magnet.

[0104] The refrigerator can be configured to maintain the main magnet at a temperature level close to the superconducting temperature of the superconducting coils. The main magnet, thermal shield, magnet support structure and / or cryogen vessel can be thermally connected to the refrigerator via solid thermal conductors, convection loops and / or thermal pipes.

[0105] The magnetic resonance apparatus of the present invention may represent a "dry" system, comprising minimal or no refrigerant. For example, the magnetic resonance apparatus of the present invention may include one or more small refrigerant vessels thermally connected to the main magnet via a solid thermal conductor. The one or more small refrigerant vessels may hold a refrigerant volume of less than 10 liters, less than 5 liters, or less than 1 liter. In some embodiments of the magnetic resonance apparatus of the present invention, the refrigerant vessels are omitted. Thus, the main magnet can be cooled entirely via thermal conduction.

[0106] In an alternative embodiment, the magnetic resonance apparatus represents a "wet" system. A "wet" system may comprise at least one refrigerated container having a volume greater than 10 1 or greater than 100 1. Preferably, the main magnet is housed in a cryogen vessel and is cooled directly by the cryogen.

[0107] The magnetic resonance system has the advantages of the magnet arrangement according to the invention according to the embodiments described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0108] Further advantages and details of the present invention can be seen from the following description of the embodiments and the accompanying drawings. The drawings show:

[0109] Figure 1 is a schematic diagram of an embodiment of a magnetic resonance apparatus according to the present invention,

[0110] Figure 2 is a schematic diagram of an embodiment of a magnet arrangement,

[0111] Figure 3 is a schematic diagram of an embodiment of a magnet arrangement,

[0112] Figure 4 is a schematic diagram of an embodiment of a magnet device of the present invention,

[0113] Figure 5 is a schematic diagram of an embodiment of a magnet device of the present invention,

[0114] Figure 6 is a schematic diagram of an embodiment of a magnet device of the present invention,

[0115] Figure 7 is a schematic diagram of an embodiment of a magnet device of the present invention,

[0116] Figure 8 is a schematic diagram of an embodiment of a magnet device of the present invention,

[0117] Figure 9 Schematic diagram of an embodiment of a magnetic resonance apparatus according to the present invention. DETAILED DESCRIPTION

[0118] Figure 1 An embodiment of a magnetic resonance apparatus 10 according to the present invention is shown. In the illustrated example, the magnetic resonance apparatus 10 includes a static field magnet or main magnet 12 configured to provide a homogeneous, static magnetic field 13 (B0 field) that includes an imaging volume (not shown). The static magnetic field 13 passes through an imaging region 14 configured to receive an imaging subject, such as a patient 15. The imaging region 14 may correspond to a patient bore configured to accommodate the patient 15 during a magnetic resonance measurement. The imaging region 14 is surrounded circumferentially by the main magnet 12.

[0119] The magnetic resonance apparatus 10 may include a patient positioning device 16 configured to transport a patient 15 into the imaging region 14. The patient support 16 may be configured to transport a diagnostically relevant body region of the patient 15 into the imaging volume or isocenter of the magnetic resonance apparatus 10. The main magnet 12 and other components of a field generating unit (not shown) of the magnetic resonance apparatus 10 may be concealed in a housing 30.

[0120] The magnetic resonance apparatus 10 may include a gradient system comprising one or more gradient coils 18. The one or more gradient coils may be configured to generate gradient magnetic fields in different spatial directions, preferably in orthogonal spatial directions. The gradient magnetic fields may be used to spatially encode magnetic resonance signals acquired during a magnetic resonance measurement. The one or more gradient coils 18 may be activated or controlled via appropriate current signals provided by a gradient control unit 19.

[0121] The magnetic resonance apparatus 10 may include an integrated radio frequency antenna 20 (i.e., a body coil). The radio frequency antenna 20 may be activated or controlled via a radio frequency control unit 21. The radio frequency control unit 21 may be configured to control the radio frequency antenna 20 to generate a high-frequency magnetic field and transmit radio frequency excitation pulses into the imaging region 14. The magnetic resonance apparatus 10 may also include a local coil 26. The local coil 26 may be positioned on or near a diagnostically relevant region of the patient 15. The local coil 26 may be configured to transmit radio frequency excitation pulses into the patient 15 and / or receive magnetic resonance signals from the patient 15. It is contemplated that the local coil 26 is controlled via the radio frequency controller 21.

[0122] Preferably, the magnetic resonance apparatus 10 includes a control unit 22 configured to control the magnetic resonance apparatus 10. The control unit 22 may include a processing unit 28 configured to process magnetic resonance signals and reconstruct magnetic resonance images. The processing unit 28 may also be configured to process input from a user of the magnetic resonance apparatus 10 and / or provide output to the user. To this end, the processing unit 28 and / or the control unit 22 may be connected to a display unit 24 and an input unit 25 via suitable signal connections. In preparation for the magnetic resonance measurement, preparation information, such as imaging parameters or patient information, may be provided to the user via the display unit 24. The input unit 25 may be configured to receive information and / or imaging parameters from the user.

[0123] Of course, the magnetic resonance apparatus 10 may include other components and / or functions commonly found in magnetic resonance apparatuses. The general operation of the magnetic resonance apparatus 10 is known to those skilled in the art, and therefore a more detailed description is omitted.

[0124] Figure 2 An embodiment of the magnet arrangement 11 of the present invention is shown without the ferromagnetic element 33. In the depicted example, the magnet arrangement 11 includes five superconducting coils 31a, 31b, 31c, 31d, 31e (31a to 31e) and two counter-superconducting coils 32a and 32b (32a to 32b) that constitute the main magnet 12. The magnet arrangement 11 also includes two outer coils or shielding coils 34a and 34b (34a to 34b) that are configured to shield the main magnet 12 from electromagnetic radiation. The superconducting coils 31a and 31e are arranged at the axial ends of the main magnet 12 and constitute the end coils of the magnet arrangement 11.

[0125] In the depicted example, the opposing superconducting coil 32a is arranged between the two superconducting coils 31a and 31b. Likewise, the opposing superconducting coil 32b is arranged between the two superconducting coils 31d and 31e.

[0126] Figure 3 Shown through Figure 2 Schematic diagram of a cross section of a section of the magnet arrangement 11 depicted in FIG. In the depicted example, the superconducting coil 31 forms an end coil of the magnet arrangement 11. The counter superconducting coil 32 is arranged adjacent to the end coil 31. It is conceivable that the end coil 31 and the counter superconducting coil 32 are separated by a spacer 42 (not shown). For example, as Figure 6 or Figure 7 As shown in FIG, spacers 42 may be disposed between the end coils 31 and the counter superconducting coils 32. As shown in FIG.

[0127] Without the ferromagnetic element 33 , the electromagnetic force F2 acting on the opposing superconducting coils 32 may be directed toward the central symmetry plane 40 of the magnet arrangement 11 , while the electromagnetic force F1 acting on the end coils 31 may be directed away from the central symmetry plane 40 .

[0128] In some embodiments, the electromagnetic force F2 can cause an equivalent weight of 19.1 tons to act on the reverse superconducting coil 32. The electromagnetic force F1 can cause an equivalent weight of 11.4 tons to act on the end coil 31. Figure 2 and Figure 3 The magnet arrangement 11 requires a dedicated support structure (not shown) that is configured to accommodate the electromagnetic forces F1 and F2 and to hold the main magnet 12, in particular the end coils 31a and 31e, in a predetermined spatial arrangement relative to the counter superconducting coils 32a to 32b and the superconducting coils 31b to 31d.

[0129] Depending on the design of the main magnet 12, such as the number of superconducting coils 31, the number of counter-superconducting coils 32, the diameters of the superconducting coils 31 and 32, the axial dimensions of the superconducting coils 31 and 32, and the number of windings of superconducting wire forming the superconducting coils 31 and 32, the electromagnetic force F1 can cause an equivalent weight greater than 11.4 tons to act on the end coils 31. It is also conceivable that the equivalent weight is less than 11.4 tons. In some embodiments, the electromagnetic force F1 acting on the end coils 31 can be directed toward the central symmetry plane 40 of the main magnet 11.

[0130] Figure 4 An embodiment of the magnet apparatus 11 of the present invention is shown, including ferromagnetic elements 33a and 33b (33a-33b). Ferromagnetic element 33a is arranged between opposing superconducting coil 32a and superconducting coil 31a. Similarly, ferromagnetic element 33b is arranged between opposing superconducting coil 32b and superconducting coil 31e. Superconducting coils 31a and 31e may represent end coils of magnet apparatus 11.

[0131] In some embodiments, the opposing superconducting coil 32a and the ferromagnetic element 33a may be positioned a distance from the end coils. For example, the opposing superconducting coil 32a and the ferromagnetic element 33a may be positioned between the superconducting coils 31b and 31c. Similarly, the opposing superconducting coil 32b and the ferromagnetic element 33b may be positioned between the superconducting coils 31c and 31d.

[0132] The magnet arrangement 11 of the present invention may include more than five superconducting coils 31 and / or more than two opposing superconducting coils 32. However, it is conceivable that the magnet arrangement 11 of the present invention includes fewer than five superconducting coils 31.

[0133] In a preferred embodiment of the magnet arrangement 11 of the present invention, the ferromagnetic element 33 arranged adjacent to the opposing superconducting coil 32 defines a side or surface of the opposing superconducting coil 32 facing the nearer axial end of the magnet arrangement 11 .

[0134] Figure 5 Shown through Figure 4 Schematic diagram of a cross section of a section of the inventive magnet arrangement 11 depicted in FIG. In the depicted example, a ferromagnetic element 33 is arranged between the superconducting coil 31 and the counter superconducting coil 32 .

[0135] The ferromagnetic element 33 comprises a ring or short barrel shape. In the depicted example, the ferromagnetic element 33 is arranged coaxially with the main magnet 12 along the barrel axis 41 of the main magnet 12. The ferromagnetic element 33 is arranged so that a projection 50 of the axial cross-sectional area of ​​the superconducting coil 31 along the barrel axis 41 of the main magnet 12 and the cross-sectional area of ​​the ferromagnetic element 33 have a non-empty intersection.

[0136] exist Figure 5 In the embodiment shown in FIG, the inner circumference of the superconducting coil 31, along a projection 50 b of the barrel axis 41 of the main magnet 12, intersects with the cross section of the ferromagnetic element 33. Furthermore, the outer circumference of the superconducting coil 31, along a projection 50 a of the barrel axis 41 of the main magnet 12, intersects with the cross section of the ferromagnetic element 33. In other words, the outer diameter of the ferromagnetic element 33 exceeds the outer diameter of the superconducting coil 31, while the inner diameter of the superconducting coil 31 exceeds the inner diameter of the ferromagnetic element 33.

[0137] The ferromagnetic element 33 preferably comprises iron or an iron alloy. In particular, the ferromagnetic element 33 can be magnetically saturated so that the ferromagnetic element 33 changes the inter-coil force in the main magnet 12. Figure 5 In the embodiment depicted in FIG, the ferromagnetic element 33 changes the inter-coil force at the end section of the main magnet 12 so that Figure 3 The embodiment depicted in FIG. 1 reduces the electromagnetic force F1 by more than 70%.

[0138] For example, the equivalent weight acting on the superconducting coil 31 caused by the electromagnetic force F1 can reach 5.4t. Figure 5 In the embodiment of the present invention, the electromagnetic force F1 still points away from the central symmetry plane 40, but is reduced to such an extent that the magnet support structure (not shown) configured to maintain the superconducting coil 31 in a predetermined spatial arrangement relative to the other superconducting coils 31 of the main magnet 12 can be manufactured in a more cost-effective manner. In addition, the ferromagnetic element 33 changes the inter-coil force within the main magnet 12 so that the equivalent weight acting on the opposing superconducting coil 32 due to the electromagnetic force F2 is increased to approximately 17.3 tons.

[0139] Figure 6Another embodiment of the magnet arrangement 11 of the present invention is shown. In the depicted example, the ferromagnetic element 33 is configured to modify the inter-coil forces within the main magnet 12 such that the electromagnetic force F1 acting on the superconducting coils 31 is substantially canceled or reduced to zero.

[0140] The inner circumference or inner diameter of the superconducting coil 31 exceeds the inner circumference or inner diameter of the ferromagnetic element 33 so that a projection 50 b of the inner circumference of the superconducting coil 31 along the barrel axis 41 of the main magnet 12 intersects a cross section of the ferromagnetic element 33 .

[0141] exist Figure 6 In the embodiment depicted in FIG, spacer 42a is disposed between superconducting coil 31 and ferromagnetic element 33, and spacer 42b is disposed between ferromagnetic element 33 and counter-superconducting coil 32. Spacers 42a and 42b (42a-42b) may include or be constructed of a rigid material, such as a metal, metal alloy, plastic, and / or composite material. Preferably, the material of spacers 42a-42b is configured to withstand the (compressive) inter-coil forces within main magnet 12.

[0142] According to an embodiment, the spacers 42a-42b are glued or bonded to the superconducting coil 31, the ferromagnetic element 33, and the counter-superconducting coil 32 to form an integrally bonded or cohesive structure. Preferably, the adhesive that provides the material bond between the spacers 42a-42b, the ferromagnetic element 33, the superconducting coil 31, and / or the counter-coil 33 is thermally conductive.

[0143] In an alternative embodiment, the ferromagnetic element 33 may be arranged in close proximity to the superconducting coil 31 and / or the counter-superconducting coil 32 (see Figure 8 For example, the ferromagnetic element 33 may directly contact the superconducting coil 31 and / or the counter superconducting coil 32. In particular, the axial surface or axial side of the ferromagnetic element 33 may be glued or bonded to the axial surface of the superconducting coil 31 and / or the axial surface of the counter superconducting coil 32.

[0144] Figure 7 Another embodiment of the magnet arrangement 11 of the present invention is shown. In the depicted example, the ferromagnetic element 33 is configured to change the inter-coil force in the main magnet 12 so that Figure 3 Compared to the embodiment depicted in FIG, the electromagnetic force F1 acting on the superconducting coil 31 is reversed. Specifically, the ferromagnetic element 33 is configured to change the inter-coil force within the main magnet 12 so that an inwardly directed force F1 acts on the superconducting coil 31. For example, the equivalent weight acting on the superconducting coil 31 due to the electromagnetic force F1 can reach approximately 5.5 tons.

[0145] In this example, the outer circumference of the ferromagnetic element 33 exceeds the outer circumference of the superconducting coil 31, so that the projection 50a of the outer circumference of the superconducting coil 31 along the barrel axis 41 of the main magnet 12 intersects with the cross section of the ferromagnetic element 33. The inner circumference of the ferromagnetic element 33 can correspond to the inner circumference of the superconducting coil 31 and / or the inner circumference of the counter-superconducting coil 32. It is also conceivable that the inner circumference of the ferromagnetic element 33 exceeds the inner circumference of the superconducting coil 31 and / or the inner circumference of the counter-superconducting coil 32.

[0146] exist Figure 8 In the embodiment of the magnet apparatus 11 of the present invention depicted in FIG, the ferromagnetic element 33 is directly mechanically connected to the superconducting coil 31 and the counter-superconducting coil 32. In particular, a first axial face of the ferromagnetic element 33 is in contact with an axial face of the superconducting coil 31, and a second axial face of the ferromagnetic element 33 is in contact with an axial face of the counter-superconducting coil 32.

[0147] The ferromagnetic element 33 may include an electrically insulating layer configured to prevent current from passing through the ferromagnetic element 33. For example, the first axial face and / or the second axial face of the ferromagnetic element 33 may be clad, laminated, coated, or otherwise provided with an electrically insulating material. Preferably, the electrically insulating material is thermally conductive. In accordance with an embodiment, the adhesive providing the material bond between the ferromagnetic element 33 and the superconducting coil 31 and between the ferromagnetic element 33 and the counter-coil 33 is thermally conductive but electrically insulating.

[0148] Figure 9 A further embodiment of a magnetic resonance system 10 according to the invention is shown. Figure 9 The functions and components of the magnetic resonance system 10 shown in FIG. 1 may correspond to Figure 1 The functions and components of the magnetic resonance apparatus 10 are depicted in FIG.

[0149] For example, the magnetic resonance apparatus 10 can be configured to perform a magnetic resonance examination of the jaw region and / or eye region of the patient 15. The magnetic resonance apparatus 10 of the present invention can also be configured to perform cardiac imaging, mammography imaging, neurological imaging, urological imaging, orthopedic imaging, prostate imaging or other parts of the patient's body. In particular, the magnetic resonance apparatus 10 can represent a special scanner that is designed to perform magnetic resonance imaging of the jaw region and / or head region of a standing or sitting patient 15. Compared with conventional cylindrical (or closed-bore) magnetic resonance apparatus, the magnetic resonance apparatus 10 can be significantly shorter along the Z axis. Therefore, the magnetic resonance apparatus 10 of the present invention can be advantageously transported to and / or installed in smaller medical facilities or practices via conventional or standardized access routes, and can not interrupt operation due to construction sites or renovation work.

[0150] exist Figure 9In the example shown in , the magnetic resonance device 10 is supported via a mounting member 31. The mounting member 31 is configured to carry the magnet arrangement 11 and to maintain the magnet arrangement 11 at a predetermined distance from the floor 71 of the examination room 70. It is conceivable that the mounting member 31 has a positioning unit (not shown) designed to position and / or align the magnet arrangement 11 relative to a diagnostically relevant body region of the patient 15. For example, the positioning unit may include a rotating joint designed to rotate the magnet arrangement 11 along a direction of rotation. The mounting member 31 may also include a telescopic guide and / or a rail system configured to adjust the spatial position of the magnet arrangement 11 along the Y direction and / or the Z direction.

[0151] It is conceivable that if Figure 1 As shown in FIG, the magnetic resonance apparatus 10 comprises a patient positioning apparatus 16 and / or a patient table 17. The patient positioning apparatus 16 and / or the patient table 17 may be configured to position a diagnostically relevant body region of the patient 15 in the imaging region 14.

[0152] As Figure 9 As an alternative to the embodiment shown in , the mount 31 may be configured to attach the magnetic resonance apparatus 10 or the magnet arrangement 11 to a wall and / or ceiling of the examination room 70 .

[0153] The embodiments described herein are to be regarded as examples. It will be understood that, if not otherwise stated, each embodiment may be expanded by features of other embodiments or combined with features of other embodiments. Figures 1 to 9 The embodiments depicted in the drawings are illustrations that are not necessarily drawn to scale.

Claims

1. A magnet arrangement (11), the magnet arrangement (11) being used in a magnetic resonance imaging device (10), the magnet arrangement (11) comprising a main magnet (12), the main magnet (12) comprising a plurality of superconducting coils (31), an inverted superconducting coil (32) and a ferromagnetic element (33), wherein: The reverse superconducting coil (32) is arranged between two superconducting coils (31) of the plurality of superconducting coils (31), and wherein the ferromagnetic element (33) is arranged between the reverse superconducting coil (32) and the superconducting coil (31).

2. The magnet arrangement (11) according to claim 1, wherein The superconducting coil (31) is an end coil of the main magnet (12).

3. The magnet arrangement (11) according to one of the preceding claims, wherein The ferromagnetic element (33) is arranged in close proximity to the reverse superconducting coil (32) and / or the superconducting coil (31).

4. The magnet arrangement (11) according to claim 1 or 2, wherein: The main magnet (12) includes at least one spacer (42) arranged between the ferromagnetic element (33) and the superconducting coil (31) and / or between the ferromagnetic element (33) and the counter superconducting coil (32).

5. The magnet arrangement (11) according to one of the preceding claims, wherein The ferromagnetic element (33) comprises a shape of a ring, a tube, a hollow cylinder or a hollow prism.

6. The magnet arrangement (11) according to claim 5, wherein The main magnet (12) comprises a cylindrical shape, and wherein the ferromagnetic element (33) is arranged coaxially with the main magnet (12).

7. The magnet arrangement (11) according to claim 6, wherein A projection (50) of the axial cross-sectional area of ​​the superconducting coil (31) along the cylinder axis (41) of the main magnet (12) has a non-empty intersection with the cross-sectional area of ​​the ferromagnetic element (33).

8. The magnet arrangement (11) according to one of the preceding claims, wherein The ferromagnetic element (33) comprises or consists of a material with high magnetic permeability.

9. The magnet arrangement (11) according to one of the preceding claims, wherein The ferromagnetic element (33) is attached to the reverse superconducting coil (32) and the superconducting coil (31).

10. The magnet arrangement (11) according to one of the preceding claims, wherein The superconducting coils (31) represent end coils, and wherein the ferromagnetic elements (33) are configured to alter the inter-coil forces within the main magnet (12) such that the outwardly directed forces acting on the end coils of the main magnet (12) in the absence of the ferromagnetic elements (33) are reduced by at least 30%, at least 40%, at least 50% or at least 60%.

11. The magnet arrangement (11) according to claim 10, wherein The ferromagnetic element (33) is configured to change the inter-coil force within the main magnet (12) so that an inwardly directed force acts on the superconducting coil (31).

12. The magnet arrangement (11) according to one of claims 1 to 9, wherein The superconducting coils (31) represent end coils, and wherein the ferromagnetic elements (33) are configured to alter the inter-coil forces within the main magnet (12) such that the inwardly directed forces acting on the end coils in the absence of the ferromagnetic elements (33) are increased by at least 10%, at least 20%, or at least 30%.

13. The magnet arrangement (11) according to one of the preceding claims, comprising a first ferromagnetic element (33a) and a second ferromagnetic element (33b), wherein The first ferromagnetic element (33a) is arranged between the first reverse superconducting coil (32) and the first superconducting coil (31a), and the second ferromagnetic element (33b) is arranged between the second reverse superconducting coil (32b) and the second superconducting coil (31e).

14. A magnetic resonance apparatus (10) for acquiring magnetic resonance data of an object positioned in an imaging region (14) of the magnetic resonance apparatus (10), the magnetic resonance apparatus (10) comprising a magnet arrangement (11) according to one of the preceding claims.

Images