Magnetic resonance magnet assembly and radiation shielding assembly

Abstract

A magnetic resonance imaging (MRI) magnet assembly is disclosed herein. The magnet assembly includes a two-stage cryogenic cooling system, a primary coil, and a radiation shielding assembly. The cryogenic cooling system includes a high temperature stage and a low temperature stage. The high temperature stage is adapted to provide an upper operating temperature. The primary coil is thermally coupled to the cryogenic stage. The radiation shield assembly is thermally coupled to the high temperature stage and includes a shim coil and a radiation shield carrying the shim coil. A radiation shield is disposed in the cryostat to shield the primary coil from thermal radiation. When the shielding assembly is in thermal equilibrium with the high temperature stage, the radiation shield has an upper operating temperature, thus shielding the primary coil from thermal radiation originating from temperatures above the upper operating temperature.

Description

Technical Field

[0001] This invention relates to the field of magnetic resonance imaging systems. Specifically, this invention relates to the field of generating a uniform main magnetic field in a magnetic resonance imaging system. Background Technology

[0002] Modern magnetic resonance imaging (MRI) scanners use superconducting master magnets to generate a nearly uniform magnetic field (B0) to provide magnetic polarization in the sample being imaged. The quality of an MRI scan is strongly dependent on the uniformity of B0. Since slight manufacturing tolerances, asymmetries, and interferences in the magnet assembly are unavoidable, the magnetic field generated by the superconducting magnet must be homogenized, which means applying corrections that result in a uniform magnetic field.

[0003] B0 shimming can be achieved using static and / or dynamic correction. For static or passive shimming, shimming plates (i.e., components made of a material that locally influences the strength and / or direction of a magnetic field when applied—e.g., small shimming plates formed from ferromagnetic materials such as iron)) are fixed at various locations near the superconducting magnet. Placing steel shimming plates is a proven process, but several issues arise. Positioning all shimming plates is a time-consuming and repetitive process. Steel shimming plates are prone to thermal drift during scanning. Steel shimming plates are static. Shimming plates occupy space. This last point can be important when there is little space to integrate them, for example, in or near gradient coils.

[0004] All these problems can be overcome, at least to some extent, by adding a dynamic shimming coil to the cryostat. When supplied with a suitable current, the shimming coil generates a magnetic field that removes the B0 inhomogeneity through superposition. Therefore, the shimming coil facilitates a response to time-varying field uniformity and / or can be fine-tuned to eliminate residual inhomogeneities from existing static corrections. Typically, the shimming coil is a resistive coil, usually at room temperature, capable of generating field corrections distributed as several orders of spherical harmonics. Dynamic field correction can be automatically calibrated by observing the free induction decay (FID) signal in the absence of a field gradient and iteratively changing the supply current of the shimming coil.

[0005] The journal article “Persistent-mode high-temperature superconductor shim coils: A design concept and experimental results of a prototype Z1 high-temperature superconductor shim” published by Y. Iwasa et al. in Applied Physics Letters (103, 052607 (2013)) discloses a superconducting shim coil cut from a superconducting barium yttrium copper oxide (YBCO) strip and positioned inside a magnet assembly.

[0006] US 2022 / 171004 A1 describes a room-temperature permanent magnet assembly. Summary of the Invention

[0007] The present invention provides an MRI magnet assembly, an MRI scanner, a radiation shielding assembly, and a method for assembling an MRI magnet assembly in the independent claims. Embodiments are given in the dependent claims.

[0008] In one aspect, the present invention provides a magnetic resonance imaging (MRI) magnet assembly. The magnet assembly includes a two-stage cryostat. The cryostat includes a high-temperature stage and a low-temperature stage. The high-temperature stage is adapted to provide the upper operating temperature.

[0009] The magnet assembly also includes a primary coil that is thermally coupled to the cryogenic stage.

[0010] The magnet assembly also includes a radiation shielding assembly thermally coupled to the high-temperature stage. The radiation shielding assembly includes a shimming coil and a radiation shield carrying the shimming coil. The radiation shield is housed in a cryogenic thermostat to shield the primary coil from thermal radiation. When the shielding assembly is in thermal equilibrium with the high-temperature stage, the radiation shield has an upper operating temperature, and thus shields the primary coil from thermal radiation originating from temperatures above the upper operating temperature.

[0011] In another aspect, the present invention provides an MRI scanner including an MRI magnet assembly.

[0012] In another aspect, the present invention provides a radiation shielding assembly. The shielding assembly is adapted to be installed in a cryostat of an MRI magnet assembly. More specifically, the shielding assembly is adapted to be installed in a cryostat having a high-temperature stage and a low-temperature stage. The high-temperature stage of the two-stage cryostat is adapted to provide the upper operating temperature.

[0013] The MRI magnet assembly also includes a primary coil. The primary coil is thermally coupled to the cryogenic stage of a cryostat.

[0014] The radiation shielding assembly includes a shimming coil and a radiation shield carrying the shimming coil. The radiation shield is adapted to be placed in a cryogenic thermostat to shield the primary coil from thermal radiation. When the shielding assembly is in thermal equilibrium with the high-temperature stage, the radiation shield has an upper operating temperature and thus shields the primary coil from thermal radiation originating from temperatures above the upper operating temperature.

[0015] In another aspect, the present invention provides a method. The method includes providing a two-stage cryostat. The cryostat includes a high-temperature stage and a low-temperature stage. The high-temperature stage is adapted to provide an upper operating temperature.

[0016] The method also includes providing a primary coil that is thermally coupled to the cryogenic stage.

[0017] The method also includes installing a radiation shielding assembly to thermally couple it to the high-temperature stage. The radiation shielding assembly includes a shimming coil and a radiation shield carrying the shimming coil. The radiation shield is adapted to be placed in a cryogenic thermostat to shield the primary coil from thermal radiation. When the shielding assembly is in thermal equilibrium with the high-temperature stage, the radiation shield has an upper operating temperature and thus shields the primary coil from thermal radiation originating from temperatures above the upper operating temperature. Attached Figure Description

[0018] In the following description, preferred embodiments of the invention will be illustrated by way of example only and with reference to the accompanying drawings, wherein: Figure 1 It is a cross-sectional view of a medical system; Figure 2 This is another cross-sectional view of the healthcare system; Figure 3 A two-stage cryogenic cooling setup is shown; and Figure 4 A radiation shielding device carrying a shimming coil is shown. Detailed Implementation

[0019] Elements with the same number in these figures are equivalent elements or perform the same function. If the functions are equivalent, then elements already discussed will not need to be discussed in the following figures.

[0020] The example is helpful because the shimming coil is carried by a radiation shield. Therefore, the shimming coil does not consume valuable space in the aperture, i.e., the volume of the patient to be imaged, surrounded by the magnet assembly. Similarly, a dynamic shimming coil does not occupy space in the gradient encoding coil. Placing the shimming coil inside the magnet assembly without reducing the magnet's aperture effectively increases the total shimming volume. If the channels used to place the iron shimming sheet in the room temperature region remain the same size, larger inhomogeneities can be shimmed away, or the shimming channels can be made smaller, allowing for the construction of thinner gradient coils.

[0021] Furthermore, since the shimming coil is carried by the radiation shield, it can be thermally coupled to the shield. This allows the heat generated by the shimming coil to be received by the shield and transferred away to the high-temperature stage of the cryostat. In this way, the shimming coil can be effectively cooled, thus canceling out the thermal drift of the dynamic shimming coil.

[0022] In one example, the radiation shield includes an inner wall that carries a shimming coil and is surrounded by a primary coil. The inner wall of the radiation shield is relatively close to the field of view. Therefore, to obtain a specific correction field, the shimming coil can be operated with a smaller current compared to mounting the shimming coil at a greater distance from the field of view (FOV). Typically, the radiation shield can be the coolest surface closest to the patient.

[0023] In another example, the radiation shield includes an inner surface facing the primary coil and carrying the shimming coil. It may be advantageous to mount the shimming coil, or a portion thereof, on the inner surface of the radiation shield to obtain more free space outside and adjacent to the radiation shield. This free space can then be used for the magnet assembly or other components of the MRI system, which could support a more compact design for the magnet assembly.

[0024] In another example, the radiation shield includes an outer surface facing away from the primary coil and carrying the shimming coil. It may be advantageous to mount the shimming coil, or a portion thereof, on the outer surface of the radiation shield to allow for more free space between the radiation shield and the primary coil. This also allows for a more compact design of the magnet assembly. Furthermore, the portion of the shimming coil mounted on the outer surface of the radiation shield can have a larger thermal generation tolerance because the thermal radiation emitted by the shimming coil in a warm state (i.e., at a temperature exceeding the upper operating temperature or the actual temperature of the radiation shield) can be captured by the radiation shield. In this way, additional thermal load on the primary coil can be reduced or avoided.

[0025] In another example, the radiation shield includes a recess that carries the shimming coil. For example, the recess can be formed by milling or another structuring technique. The recess can define the specific structure adopted by the shimming coil. This can support the assembly of the shimming coil onto the radiation shield with greater accuracy. The recess can also achieve greater structural stability of the shimming coil, making its structure less likely to be unintentionally altered, for example, during the assembly of the magnet assembly or MRI scanner by thermal or mechanical movement of the MRI scanner. The high structural accuracy of the shimming coil can also support high-quality MR images by ensuring that the magnetic field generated by the shimming coil actually corresponds to the correction magnetic field intended to be generated by the shimming coil. Furthermore, the recess can be used to spatially constrain a strip that forms the shimming coil but cannot lie flat on a surface, as it can only bend in one direction.

[0026] In another example, the radiation shielding includes an inner wall, an outer wall, and a flange. The outer wall surrounds the primary coil. The flange connects the inner wall to the outer wall and carries the shimming coil. This provides greater freedom in choosing the structure of the shimming coil. For example, the inner wall, outer wall, and flange can form a cavity in which the primary coil is disposed. The flange can shield the primary coil from thermal radiation in a direction that is neither covered by the inner wall nor by the outer wall. Thus, a shimming coil or a portion thereof mounted on the flange can be used to generate a magnetic field with an orientation that cannot be generated by a shimming coil carried solely by the inner wall and / or the outer wall. Such a flange-mounted shimming coil can, for example, be used to generate magnetic field components that differ from those generated by a portion of a shimming coil mounted on the inner wall and / or the outer wall. Therefore, greater correction flexibility and accuracy can be achieved.

[0027] In another example, the shimming coil is made of a high-temperature superconductor (HTS). In the following text, it is assumed that the HTS used to form the shimming coil is superconducting at the upper operating temperature. Therefore, a superconducting shimming coil can be obtained. The superconducting shimming coil can generate no heat during operation, or generate significantly less heat due to localized residual ohmic resistance. The current required to drive the shimming coil can be very small, for example, on the order of 10 A, compared to the typical current used to operate the primary coil. These currents can be easily maintained at the upper operating temperature using an HTS conductor of any available size. The superconducting shimming coil does not dissipate heat into the radiation shield (and cold block). Therefore, no additional thermal load can be applied to the cryostat through the shimming coil.

[0028] Superconducting shimming coils can operate in either continuous or driven mode. Therefore, because these junctions may have residual ohmic resistance, the superconductivity requirements for the superconducting shimming coils, the junctions and connections between them, can be relaxed. While the ohmic resistors forming the shimming coils can have significantly lower resistance at operating temperatures (e.g., 40 K) and thus generate less heat than when operating at room temperature, the superconducting shimming coils can further reduce the generated heat to a negligible amount due to this possible residual ohmic resistance.

[0029] In another example, the high-temperature superconductor is MgB2, Bi2Sr2Ca2Cu3O 10 One of (BSCCO) and rare earth barium copper oxide (ReBCO). These materials have high applicability for forming stable strands with processing characteristics that support the formation of shimming coils from strands on radiation shields and the operation of shimming coils at low temperatures. With a critical temperature of 39 K, MgB2 is suitable for relatively low upper operating temperatures below 39 K (e.g., 30 K) when operating at relatively low currents.

[0030] In another example, the shimming coil is a wire or strip. A wire can have a greater thickness than a strip, which allows a given current to be transmitted at a lower current density. Furthermore, a wire can have a smaller width than a strip, which allows for defining the correction magnetic field with greater precision. A further advantage of wire is its flexibility in any direction, making it possible to construct shimming coils with high precision, which can be difficult when using strips. A beneficial wire material could be Bi2212 (Bi2Sr2CaCu2O8), which can be formed, for example, into a round wire and can function after winding, increasing the designer's freedom in constructing the shimming coil. On the other hand, for some materials, it may be easier to process them into strips than wires. Strips can also be beneficial in allowing for a stronger adhesion between the radiation shield and the shimming coil. Cutting the strip into smaller widths to improve its flexibility in the lateral direction (parallel to the shield surface) would be feasible.

[0031] In another example, the radiation shielding assembly also includes a retaining strip to secure the shimming coil to the radiation shield. The retaining strip provides improved structural stability of the shimming coil. The retaining strip can form an interface layer between the shimming coil and the radiation shield. The retaining strip can, for example, restrict movement of the shimming coil relative to the radiation shield by using an adhesive or a roughened surface to face the shimming coil. Additionally or alternatively, the retaining strip may have an adhesive surface facing the radiation shield, and / or may be secured to the radiation shield in another manner. Furthermore, the retaining strip improves thermal contact between the radiation shield and the shimming coil.

[0032] In another example, the radiation shielding assembly also includes a mold for receiving a shimming coil on the radiation shield. The mold can mechanically guide the shimming coil on the radiation shield and can secure the shimming coil within a specific structure. Compared to the groove described above, the mold can be configured as a separate component of the radiation shielding assembly. Similar to a retaining band, the mold can have an adhesive surface facing the radiation shield and / or can be otherwise secured to the radiation shield. The mold can form partial or continuous securing devices for the shimming coil, such as one or more retaining clips and / or support rails.

[0033] Figure 1 This is a cross-sectional view of medical system 100. It should be understood that, in conjunction with any other appendices disclosed herein... Figure 1 Sample, Figure 1 This is for illustrative purposes only and may contain various simplifications and omissions compared to a real medical system. Figure 1 Components not shown may include, but are not limited to, gradient coils, transmission coils, receiver coils, power supply components, cryogenic components, etc.

[0034] exist Figure 1 In a non-limiting example, the components of the medical imaging system 101 have a cylindrical geometry. Figure 1 The view is a cut through the medical system 100 in a plane containing the central axis of the cylindrical geometry. Due to the cylindrical geometry, in Figure 1 Elements with the same number at the top and bottom can represent the same parts of the medical imaging system 101, such as in Figure 2 This can be seen more clearly in the text. It should be understood that a real healthcare system may include, relative to... Figure 1 The local or global deviations in the geometry of the cylinder shown.

[0035] Medical system 100 may include medical imaging system 101 and control unit 150. Control unit 150 may be connected to medical imaging system 101 (e.g., via a bus) and may be configured to control parameters and functions of medical imaging system 101. In one example, control unit 150 may be a computer including a processor and a memory storing a set of computer-executable instructions that, when executed by the processor, cause control unit 150 to acquire medical images using medical imaging system 101.

[0036] The medical imaging system 101 may include a housing 110 surrounding a free volume referred to as an aperture 102 and a subject support 108 configured to support a subject 106 and allow the subject 106 to be placed within the aperture 102 such that a portion of the subject 106 is located within an imaging area 104. When the medical imaging system 101 is used to acquire medical images, as described above, the resulting medical images may include information representing a portion of tissue of the subject 106 located within the imaging area 104.

[0037] The housing 110 may enclose the MRI magnet assembly 111 surrounding the aperture 102. The magnet assembly 111 may include a primary coil 114 surrounded by a radiation shielding assembly, which in turn is surrounded by a cryostat 112. The cryostat 112 may be referred to as a two-stage cryostat because it encompasses different components of various stages thermally connected to the cryogenic cooling system 140, as shown in reference... Figure 1 and 3 As shown. A current can be supplied to the primary coil 114 to operate as a superconducting magnet. In operation, the primary coil 114 can generate a strong magnetic field, typically of about 1 Tesla (T) or greater, which is almost uniform, at least within the imaging region 104. The primary coil 114 may comprise a superconducting material, typically a low-temperature superconductor (LTS), such as niobium-titanium (Nb-Ti, NbTi).

[0038] The two-stage cryostat 110 may include a high-temperature stage and a low-temperature stage, wherein the high-temperature stage is adapted to provide an upper operating temperature (e.g., 40 to 50 Kelvin (K)) and the low-temperature stage is adapted to provide a lower operating temperature (e.g., 4 K, allowing liquid helium cooling). A primary coil 114 may be thermally coupled to the low-temperature stage, and a radiation shielding assembly may be thermally coupled to the high-temperature stage. During operation, when the radiation shielding assembly is in thermal equilibrium with the high-temperature stage, the radiation shielding assembly may have the upper operating temperature and thus shield the primary coil 114 from thermal radiation originating from temperatures above the upper operating temperature.

[0039] A radiation shielding assembly may include a radiation shield 120 and one or more shimming coils 130 carried by the radiation shield 120. The radiation shield 120 may surround a primary coil 114 with several walls, such as an inner wall 122, an outer wall 124, and one or more flanges 126 connecting the inner wall 122 and the outer wall 124. The surfaces of the outer wall 124, the inner wall 122, and the flanges 126 facing the primary coil 114 are referred to as the inner surface 402 of the radiation shield 120, and the surfaces of the outer wall 124, the inner wall 122, and the flanges 126 facing away from the primary coil 114 are referred to as the outer surface 404 of the radiation shield 120. These surfaces are... Figure 4 An alternative view is used to illustrate this.

[0040] The shimming coil 130 can be formed, for example, of one or more wires or strips wound around the wall of the radiation shield 120. The structure of the shimming coil 130 can be stabilized and / or fixed relative to the radiation shield 120 using, for example, grooves, retaining strips, molds, adhesives, solder, solder joints, or combinations thereof. For example, the shimming coil 130 can be bonded to a retaining strip attached to the radiation shield 120. Similarly, the shimming coil 130 can be fixed to the radiation shield 120 by a mold, or it can be placed in a groove formed on the surface of the radiation shield 120 (thereby the radiation shield itself effectively acting as a mold). Figure 1 In one example, one or more shimming coils 130 are supported by the inner surface 402 of the inner wall 122 and the outer surface 404 of the flange 126.

[0041] In addition to mechanical contact, the shimming coil 130 may have thermal contact with the radiation shield 120. Therefore, the shimming coil 130 may be cooled by the radiation shield 120, which may be a radiation screen. Specifically, the shimming coil 130 may be formed using a superconducting material, and more specifically, using a high-temperature superconductor (HTS) that is superconducting at an upper operating temperature. Without limitation, exemplary HTS materials that appear suitable for forming the shimming coil 130 may include MgB2, Bi2Sr2Ca2Cu3O 10 (“BSCCO”) or YBa2Cu3O7 (“YBCO”).

[0042] Figure 2 This is another cross-sectional view of the medical system 100. Figure 2 The view is in Figure 1 The line shown as "II" indicates the middle and is orthogonal to the middle. Figure 1 The incision passing through the medical system 100 is within the plane of the view plane. Figure 2 In a non-limiting example, the housing 110, the walls of the cryostat 112, the outer wall 124 and inner wall 122 of the radiation shield 120, and the primary coil 114 are arranged concentrically around the aperture 102. It should be understood that real medical systems may include [the following information is missing from the original text]. Figure 2 The concentric arrangement shown may have local or global deviations. Similarly, the subject 106 and the subject support 108 may be positioned within the aperture 102 and surrounded by components enclosed by the housing 110, and a portion of the subject 106 may be located within the imaging area 104.

[0043] Figure 3 This is a schematic diagram of a two-stage cryogenic cooling system 140, whose two cooling stages 302 and 306 can be used to cool corresponding stages (areas, volumes) of a cryogenic thermostat 112. The first cooling stage 302 may include a cooling device suitable for providing an upper operating temperature T1 (e.g., 40 K). The heat outlet of the first stage 302 is thermally coupled to heat exchangers 304, each of which includes a lower end thermally coupled to a corresponding thermal coupling point of a radiation shield 120 installed in the first stage of the two-stage cryogenic thermostat 112 (not shown). The second stage 302 may include another cooling device suitable for providing a lower operating temperature T2 (e.g., 4 K). The heat outlet of the second stage 306 is thermally coupled to heat exchangers 308, each of which includes a lower end thermally coupled to a corresponding thermal coupling point of a primary coil 114 installed in the second stage of the two-stage cryogenic thermostat 112. Heat exchange between cooling stages 302, 306 and primary coil 114 or (correspondingly) radiation shield 120 can be performed using heat conduction via heat exchangers 304, 308, gaseous coolant and / or working gas (e.g., helium, hydrogen, nitrogen vapor), liquid coolant (e.g., liquid helium, hydrogen, nitrogen), or combinations thereof. While the cryogenic cooling system 140 operates until thermal equilibrium is reached, radiation shield 120 may be heated at an upper operating temperature T1, and primary coil 114 may be heated at a lower operating temperature T2.

[0044] The shimming coil 130 may be disposed on the inner surface 402 and / or outer surface 404 of any wall of the radiation shield 120.

[0045] Figure 4An example of this is shown, in which an exemplary shimming coil 130 is wound around a cylindrical inner wall 122. Since the inner and outer surfaces of the wall of the radiation shield 120 are defined above relative to the primary coil 114, it can be seen that the surface of the inner wall 122 referred to as the “inner surface” 402 is located on the radially outward surface of the inner wall 122, and the surface referred to as the “outer surface” 404 is located on the radially inward surface of the inner wall 122.

[0046] As mentioned in the background section of this invention, US 2022 / 171004 A1 discloses a room-temperature permanent magnet assembly that does not include a cryostat. This enclosure facilitates accurate temperature control, but due to the absence of a cryostat, the structure with good thermal conductivity on which the shims are mounted serves only as a heat sink.

[0047] It should be understood that one or more of the foregoing examples or embodiments of the present invention can be combined, as long as the combined embodiments are not mutually exclusive.

[0048] As will be understood by those skilled in the art, aspects of the present invention can be embodied as apparatus, method, or computer program product. Therefore, aspects of the present invention can take the form of a completely hardware embodiment, a completely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, all of which are generally referred to herein as “circuit,” “module,” or “system.” Furthermore, aspects of the present invention can take the form of a computer program product embodied in one or more computer-readable media having computer-executable code thereon.

[0049] Any combination of one or more computer-readable media can be used. A computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. As used herein, "computer-readable storage medium" encompasses any tangible storage medium that can store instructions executable by a processor or computing system of a computing device. A computer-readable storage medium may be referred to as a computer-readable non-transitory storage medium. A computer-readable storage medium may also be referred to as a tangible computer-readable medium. In some embodiments, a computer-readable storage medium may also be capable of storing data accessible by a computing system of a computing device. Examples of computer-readable storage media include, but are not limited to: floppy disks, magnetic hard disk drives, solid-state drives, flash memory, USB thumb drives, random access memory (RAM), read-only memory (ROM), optical discs, magneto-optical discs, and register files of computing systems. Examples of optical discs include compact discs (CDs) and digital versatile discs (DVDs), such as CD-ROMs, CD-RWs, CD-Rs, DVD-ROMs, DVD-RWs, or DVD-R discs. The term computer-readable storage medium also refers to various types of recording media accessible by a computer device via a network or communication link. For example, data can be retrieved via a modem, via the Internet, or via a local area network. Computer-executable code embodied on a computer-readable medium may be transmitted using any suitable medium, including but not limited to wireless, wired, fiber optic cable, RF, or any suitable combination thereof.

[0050] Computer-readable signal media may include propagated data signals containing computer-executable code embodied therein, for example, in baseband or as part of a carrier wave. Such propagated signals may take any of a variety of forms, including, but not limited to, electromagnetic, optical, or any suitable combination thereof. A computer-readable signal medium may be any computer-readable medium that is not a computer-readable storage medium and may communicate, propagate, or transmit a program used by or in connection with an instruction execution system, apparatus, or device.

[0051] "Computer memory" or "memory" is an example of a computer-readable storage medium. Computer memory is any memory that can be directly accessed by a computing system. "Computer storage device" or "storage device" is another example of a computer-readable storage medium. A computer storage device is any non-volatile computer-readable storage medium. In some embodiments, a computer storage device may also be computer memory, and vice versa.

[0052] As used herein, "computing system" encompasses electronic components capable of executing programs or machine-executable instructions or computer-executable code. References to computing systems, including examples of "computing systems," should be interpreted as potentially including more than one computing system or processing core. A computing system can, for example, be a multi-core processor. A computing system can also refer to a collection of computing systems within a single computer system or distributed across multiple computer systems. The term computing system should also be interpreted as potentially referring to a collection or network of computing devices, each including a processor or computing system. Machine-executable code or instructions can be executed by multiple computing systems or processors that may be located within the same computing device or even distributed across multiple computing devices.

[0053] Machine-executable instructions or computer-executable code may include instructions or programs that cause a processor or other computing system to perform aspects of the invention. Computer-executable code for performing the operations of aspects of the invention may be written in any combination of one or more programming languages, including object-oriented programming languages ​​(such as Java, Smalltalk, C++, etc.) and conventional procedural programming languages ​​(such as the "C" programming language or similar programming languages), and compiled into machine-executable instructions. In some cases, the computer-executable code may be in a high-level language form or a pre-compiled form, and may be used in conjunction with an interpreter that generates machine-executable instructions on the spot. In other cases, the machine-executable instructions or computer-executable code may be in a programmable gate array (GNA) form.

[0054] Computer executable code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer can be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computer (e.g., via the Internet provided by an Internet service provider).

[0055] Aspects of the invention are described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It should be understood that each block or portion of a block in a flowchart, illustration, and / or block diagram may be implemented, where applicable, by computer program instructions in the form of computer-executable code. It should also be understood that combinations of blocks in different flowchart illustrations, illustrations, and / or block diagrams may be combined without mutual exclusion. These computer program instructions may be provided to a computing system of a general-purpose computer, special-purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, executable via the computing system of the computer or other programmable data processing apparatus, create means for implementing the functions / actions specified in one or more blocks of the flowchart and / or block diagram.

[0056] These machine-executable instructions or computer program instructions may also be stored in a computer-readable medium that directs a computer, other programmable data processing apparatus or other device to operate in a particular manner, such that the instructions stored in the computer-readable medium produce an article of writing comprising instructions that implement the functions / actions specified in one or more boxes of a flowchart and / or block diagram.

[0057] Machine-executable instructions or computer program instructions may also be loaded onto a computer, other programmable data processing apparatus or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide a process for implementing the functions / actions specified in one or more boxes of a flowchart and / or block diagram.

[0058] The term "user interface" as used herein refers to an interface that allows a user or operator to interact with a computer or computer system. A "user interface" may also be referred to as a "human-machine interface device." A user interface can provide information or data to and / or receive information or data from an operator. A user interface enables input from an operator to be received by the computer and provides output from the computer to the user. In other words, a user interface allows an operator to control or manipulate a computer, and the interface allows the computer to indicate the effects of the operator's control or manipulation. Displaying data or information on a monitor or graphical user interface is an example of providing information to an operator. Receiving data via a keyboard, mouse, trackball, touchpad, joystick, graphical tablet, joystick, game controller, webcam, head-mounted device, pedal, wired gloves, remote control, and accelerometer are all examples of user interface components capable of receiving information or data from an operator.

[0059] As used herein, "hardware interface" encompasses the interfaces that enable a computer system to interact with and / or control external computing devices and / or devices. A hardware interface allows the computing system to send control signals or instructions to external computing devices and / or devices. A hardware interface also enables the computing system to exchange data with external computing devices and / or devices. Examples of hardware interfaces include, but are not limited to: Universal Serial Bus (USB), IEEE 1394 port, parallel port, IEEE 1284 port, serial port, RS-232 port, IEEE-488 port, Bluetooth connectivity, wireless LAN connectivity, TCP / IP connectivity, Ethernet connectivity, control voltage interface, MIDI interface, analog input interface, and digital input interface.

[0060] As used herein, “display” or “display device” encompasses an output device or user interface suitable for displaying images or data. Displays may output visual, audio, and / or tactile data. Examples of displays include, but are not limited to: computer monitors, television screens, touchscreens, tactile electronic displays, Braille screens, cathode ray tubes (CRTs), memory tubes, bistable displays, electronic paper, vector displays, flat panel displays, vacuum fluorescent displays (VFs), light-emitting diode (LED) displays, electroluminescent displays (ELDs), plasma display panels (PDPs), liquid crystal displays (LCDs), organic light-emitting diode (OLED) displays, projectors, and head-mounted displays.

[0061] Although the invention has been described and illustrated in detail in the accompanying drawings and the foregoing description, such description and illustration are to be regarded as illustrative or exemplary rather than restrictive; the invention is not limited to the disclosed embodiments.

[0062] By studying the accompanying drawings, the disclosure, and the appended claims, those skilled in the art can understand and implement other variations of the disclosed embodiments. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude multiple. A single processor or other unit can perform the functions of several items recited in the claims. The mere fact that some measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used advantageously. Computer programs may be stored / distributed on suitable media, such as optical storage media or solid-state media supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems. Any reference numerals in the claims should not be construed as limiting the scope.

Claims

1. A magnetic resonance imaging (MRI) magnet assembly, comprising: A two-stage cryogenic cooling system (140) includes: Low temperature stage; and High temperature grade, suitable for providing upper operating temperatures; Low-temperature thermostat, which includes: The primary coil (114), which is thermally coupled to the cryogenic stage; and A radiation shielding assembly, which is thermally coupled to the high-temperature stage; The radiation shielding assembly includes a radiation shield (120) carrying at least one shimming coil, the radiation shield being configured to shield the primary coil from thermal radiation originating from a temperature higher than the operating temperature when the radiation shielding assembly and the high-temperature stage are in thermal equilibrium.

2. The MRI magnet assembly according to claim 1, wherein, The radiation shielding includes an inner wall (122) surrounded by the primary coil, the inner wall carrying the shimming coil.

3. The MRI magnet assembly according to claim 1 or 2, wherein, The radiation shielding includes an inner surface (402) facing the primary coil and carrying the shimming coil.

4. The MRI magnet assembly according to any one of the preceding claims, wherein, The radiation shielding includes an outer surface (404) facing away from the primary coil and carrying the shimming coil.

5. The MRI magnet assembly according to any one of the preceding claims, wherein, The radiation shielding component includes a groove for supporting the shimming coil.

6. The MRI magnet assembly according to claim 1, wherein, The radiation shielding includes an inner wall (122), an outer wall (124) surrounding the primary coil, and a flange (126) connecting the inner wall to the outer wall and carrying the shimming coil.

7. The MRI magnet assembly according to any one of the preceding claims, wherein, The shimming coil includes a high-temperature superconductor.

8. The MRI magnet assembly according to claim 7, wherein, The high-temperature superconductor is MgB2, Bi2Sr2Ca2Cu3O 10 It is one of the rare earth barium copper oxides.

9. The MRI magnet assembly according to any one of the preceding claims, wherein, The shimming coil is a line or a strip.

10. The MRI magnet assembly according to any one of the preceding claims, wherein, The radiation shielding assembly also includes a retaining strip for securing the shimming coil to the radiation shield.

11. The MRI magnet assembly according to any one of the preceding claims, wherein, The radiation shielding assembly also includes a mold for receiving the shimming coil on the radiation shielding member.

12. The MRI magnet assembly according to any one of the preceding claims, wherein, The cryogenic thermostat is a two-stage cryogenic thermostat.

13. A magnetic resonance imaging scanner comprising an MRI magnet assembly according to any one of the preceding claims.

14. A radiation shielding assembly adapted to be installed in a magnetic resonance imaging magnet assembly according to any one of claims 1 to 13.

15. A method for assembling a magnetic resonance imaging magnet assembly, comprising: A two-stage cryogenic cooling system (140) is provided, which includes: Low temperature stage; and High temperature grade, suitable for providing upper operating temperatures; A primary coil (114) is provided that is thermally coupled to the cryogenic stage. A radiation shielding assembly is installed to thermally couple with the high-temperature stage. The radiation shielding assembly includes a radiation shield (120) carrying at least one shimming coil (130). The radiation shield is disposed in a cryostat to shield the primary coil from thermal radiation originating from temperatures above the operating temperature when the radiation shielding assembly and the high-temperature stage are in thermal equilibrium.

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