Permanent magnet assembly with a nonferromagnetic frame for magnetic resonance imaging

Abstract

An assembly for providing a B0 magnetic field for a magnetic resonance imaging (MRI) system, the assembly comprising: a plurality of rods extending along a common longitudinal direction and positioned to form a hole extending along the common longitudinal direction, the plurality of rods including a first rod comprising: ferromagnetic segments, each ferromagnetic segment having net magnetization in a plane substantially perpendicular to the common longitudinal direction; and non-ferromagnetic segments.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Patent Application Serial No. 62 / 946,030, filed December 10, 2019, entitled “PERMANENT MAGNET ASSEMBLY FOR MAGNETIC RESONANCE IMAGING WITH NON-FERROMAGNETIC FRAME,” filed under Title 35, Section 119(e) of the United States Code, the entire contents of which are incorporated herein by reference. Background Technology

[0003] Magnetic resonance imaging (MRI) provides an important imaging modality for many applications and is widely used in clinical and research settings to generate images of the interior of the human body. Typically, MRI is based on detecting magnetic resonance (MR) signals, which are electromagnetic waves emitted by atoms in response to state changes induced by an applied electromagnetic field. For example, nuclear magnetic resonance (NMR) techniques involve detecting MR signals emitted from the nuclei of excited atoms when the nuclear spins of atoms in an object being imaged (e.g., atoms in human tissue) are realigned or relaxed. The detected MR signals can be processed to produce images, which, in the context of medical applications, allows investigation of internal structures and / or biological processes within the body for diagnostic, therapeutic, and / or research purposes. Summary of the Invention

[0004] Some embodiments relate to an assembly for providing a B0 magnetic field for a magnetic resonance imaging (MRI) system. The assembly includes: a plurality of rods extending along a common longitudinal direction and positioned to form a hole extending along the common longitudinal direction, the plurality of rods including a first rod. The first rod includes: ferromagnetic segments, each ferromagnetic segment having net magnetization in a plane substantially perpendicular to the common longitudinal direction; and non-ferromagnetic segments.

[0005] Some embodiments relate to a method of manufacturing an assembly for providing a B0 magnetic field for an MRI system. The method includes: accessing information on the segment layout of each of a plurality of rods, the segment layout including a first layout of a first rod of the plurality of rods, the first layout indicating the positions of ferromagnetic and non-ferromagnetic segments in the first rod and the net magnetization orientation of at least some of the ferromagnetic segments; obtaining the ferromagnetic and non-ferromagnetic segments; assembling the plurality of rods using the ferromagnetic and non-ferromagnetic segments according to the information on the specified segment layout, the assembly including: orienting at least some of the ferromagnetic segments based on the net magnetization orientation; assembling the first rod using at least some of the ferromagnetic segments and at least some of the non-ferromagnetic segments according to the first layout; and assembling the plurality of rods in an arrangement in which the plurality of rods extend along a common longitudinal direction and form a hole extending along the common longitudinal direction.

[0006] Some embodiments relate to an assembly for providing a B0 magnetic field to an MRI system. The assembly includes: a non-ferromagnetic frame forming an aperture extending along a common longitudinal direction; and a plurality of at least partially cylindrical ferromagnetic segments housed within the non-ferromagnetic frame, wherein at least some of the plurality of at least partially cylindrical ferromagnetic segments have net magnetization in a plane substantially perpendicular to the common longitudinal direction.

[0007] Some embodiments relate to an assembly for providing a BO magnetic field to an MRI system. The assembly includes: a plurality of ferromagnetic segments positioned to form: a cavity extending along a common longitudinal direction; and a first gap on a first side of the cavity to accommodate at least one first gradient coil, wherein at least some of the plurality of ferromagnetic segments are positioned on one side of the first gap, and at least some of the other ferromagnetic segments are positioned on the other side of the first gap.

[0008] Some embodiments relate to an assembly for providing a B0 magnetic field to an MRI system. The assembly includes: a plurality of ferromagnetic segments positioned to form a hole extending along a common longitudinal direction; and a first gradient coil positioned on a first side of the hole, wherein at least some of the plurality of ferromagnetic segments are positioned on one side of the first gradient coil, and at least some of the other ferromagnetic segments are positioned on the other side of the first gradient coil. Attached Figure Description

[0009] Various aspects and embodiments will be described with reference to the following accompanying drawings. It should be understood that the drawings are not necessarily drawn to scale. In the drawings, the same or nearly identical components shown in the various drawings are indicated by the same reference numerals. For clarity, not every component can be labeled in every drawing.

[0010] Figure 1 Exemplary components of a magnetic resonance imaging (MRI) system according to some embodiments of the technology described herein are shown;

[0011] Figure 2A An embodiment of a rectangular magnetic assembly for providing a B0 magnetic field for an MRI system is shown, according to some embodiments of the technology described herein;

[0012] Figure 2B Some embodiments of the technology described herein are shown. Figure 2A The magnetic moment of the magnetic assembly;

[0013] Figure 2C Illustrative ferromagnetic segments are depicted according to some embodiments of the technology described herein;

[0014] Figure 3A Examples of cylindrical magnetic fittings for providing a B0 magnetic field for an MRI system are shown, according to some embodiments of the technology described herein;

[0015] Figure 3B Some embodiments of the technology described herein are shown. Figure 3A The magnetic moment of the magnetic assembly;

[0016] Figure 4A An embodiment of a rectangular magnetic fitting configured to accommodate a patient's shoulder is shown, according to some embodiments of the technology described herein;

[0017] Figures 4B to 4C Examples of cylindrical magnetic fittings configured to accommodate a patient's shoulder are shown, representing some embodiments of the technology described herein;

[0018] Figures 5A to 5C Examples of magnetic assemblies comprising magnetic segments of different sizes, according to some embodiments of the technology described herein, are shown;

[0019] Figure 6 Examples of embodiments of the technology described herein are shown, including Figure 5C MRI systems with magnetic fittings;

[0020] Figure 7 The following are examples of the use of the techniques described herein. Figure 6The MRI system was used to image the patient's head;

[0021] Figure 8 This is a flowchart illustrating a process 800 for manufacturing magnetic components according to some embodiments of the technology described herein;

[0022] Figures 9A to 9C Examples of magnetization values ​​for the x, y, and z components of magnetization along the length of a solid magnetic rod, according to some embodiments of the techniques described herein;

[0023] Figure 9D Some embodiments of the technology described herein are depicted. Figures 9A to 9C The total magnetization amplitude;

[0024] Figure 10A Examples of magnetic fittings including gaps for accommodating gradient coils are shown, representing some embodiments of the technology described herein.

[0025] Figure 10B The following are examples of the use of the techniques described herein. Figure 10A The magnetic fittings were used to image the patient's head.

[0026] Figure 10C The following illustrations show some embodiments of the technology described herein, as part of an MRI system and used for imaging a patient's head. Figure 10A Magnetic fittings;

[0027] Figure 11A An asymmetric magnetic assembly according to some embodiments of the technology described herein is shown;

[0028] Figure 11B Some embodiments of the technology described herein are shown, and their use is illustrated. Figure 11A The magnetic fittings were used to image the patient's head.

[0029] Figure 12A and Figure 12B Views are shown of another embodiment of a magnetic assembly including a gap for accommodating gradient coils, according to some embodiments of the technology described herein; and

[0030] Figure 13 An illustrative computing device is schematically depicted that can realize aspects of the technology described herein. Detailed Implementation

[0031] The vast majority of conventional magnetic resonance imaging (MRI) systems are high-field systems, particularly for medical or clinical MRI applications. The general trend in medical imaging has been the production of MRI scanners with increasingly larger field strengths, with the vast majority of clinical MRI scanners operating at 1.5T or 3T, and even higher field strengths of 7T and 9T used in research settings. As used herein, “high field” generally refers to MRI systems currently used in clinical settings, and more specifically, to MRI systems operating at a main magnetic field (i.e., the B0 field) of 1.5T or higher, although clinical systems operating between 0.5T and 1.5T are often also characterized as “high field.” In contrast, “low field” generally refers to MRI systems operating at a B0 field of less than or equal to about 0.2T, but systems with a B0 field between 0.2T and about 0.3T are sometimes characterized as low field due to the increased field strength at the higher end of the high-field regime.

[0032] Some conventional low-field MRI systems can generate a main magnetic field B0 using a magnet assembly with a steel frame and permanent magnets attached to the steel frame. However, a main magnetic field can be generated without a steel frame using an assembly of permanent magnets constructed without a ferromagnetic (e.g., steel) frame. Such a permanent magnet assembly can be constructed with a non-ferromagnetic frame and generally allows for similar field strength, performance, and accessibility with a lighter overall weight compared to assemblies with ferromagnetic frames. However, the total weight and cost of the permanent magnets in an assembly with a non-ferromagnetic frame can be twice the amount of permanent magnets used in a comparable assembly with a ferromagnetic frame. Therefore, it may be advantageous to use an assembly with a non-ferromagnetic frame when the magnet assembly fits closely around the area of ​​interest (e.g., the imaging area in an MRI scanner) and / or when the overall weight of the system is of great importance (e.g., to increase portability).

[0033] Permanent magnet assemblies with nonferromagnetic frames can be realized using Halbach dipole arrays, in which the permanent magnets form a cylindrical structure in which the magnetization rotates at twice the speed of the position rotating around the cylinder. In an ideal two-dimensional case, the cylinder is infinitely long, and the magnetization rotates continuously around the cylinder, generating a uniform field within the cylinder's cavity and a zero field outside the cylinder. The uniform field is oriented in a plane orthogonal to the longitudinal axis of the cylinder. While these properties are highly desirable, they are difficult to achieve in practice. In reality, cylinders have a finite length, and it is difficult to achieve a continuous change in the magnetization orientation around the cylinder during manufacturing. Instead, conventional Halbach arrays are manufactured by: (1) discretizing the cylinder into multiple blocks in the azimuth direction and / or along the axis of the cylinder, where each block is easier to manufacture; and (2) assembling the Halbach array using multiple blocks. However, such discretization and finite length of the resulting array affect field uniformity and / or efficiency.

[0034] The inventors have developed a novel permanent magnet assembly with a non-ferromagnetic frame, which improves the Hellbeck array by increasing the uniformity of the generated magnetic field and reducing manufacturing complexity. Specifically, the inventors have recognized that the permanent magnet assembly with a non-ferromagnetic frame can be formed from permanent magnet segments of the same shape stacked in an array together with one or more non-magnetic segments, wherein each segment has a magnetic orientation tailored to its position along the length and azimuth of the array. The magnetic orientation of the segments in the assembly with the non-ferromagnetic frame developed by the inventors differs from that of conventional continuously rotating Hellbeck dipole configurations and is not constrained by the magnetization of angular variations in the Hellbeck dipole configuration (e.g., where the rate of magnetization rotation is twice the rate of position rotation around the cylinder) to achieve magnetic field uniformity.

[0035] The inventors also recognized that including orientation features in the permanent magnet segments can reduce the manufacturing complexity and cost of magnetic assemblies. Orientation features on the permanent magnet segments (e.g., flat surfaces, notches, and / or pits) can be aligned with the magnetic orientation of the segments, allowing manufacturers assembling such segments into assemblies to know precisely the magnetic orientation of each permanent magnet segment. Including such orientation features also allows manufacturers to precisely rotate the permanent magnet segments to provide a wide range of potential magnetic orientations for the segments within the assembly.

[0036] The inventors have further recognized that permanent magnet assemblies with nonferromagnetic frames may include openings or other similar features configured to accommodate a patient during imaging (e.g., accommodating the patient's shoulders when imaging the patient's head in the imaging zone). Including such features can functionally increase the aspect ratio of the array while reducing the overall weight of the magnetic material used, thereby increasing field uniformity and / or strength, reducing material costs, and still allowing the patient to be comfortably positioned within the imaging zone of an MRI system using such assemblies to generate the main magnetic field.

[0037] The inventors have developed systems and methods for assembling and designing permanent magnet assemblies with non-ferromagnetic frames for providing a B0 magnetic field to an MRI system. In some embodiments, the magnet assembly includes a rod extending along a common longitudinal direction. The rod may be positioned to form a hole extending along the common longitudinal direction (e.g., a cylindrical hole, a rectangular hole, or any other suitable shape). In some embodiments, the rod may include a first rod. The first rod may include a ferromagnetic segment having net magnetization in a plane substantially perpendicular to the common longitudinal direction.

[0038] In some embodiments, the first rod may further include a non-ferromagnetic segment. Non-ferromagnetic and ferromagnetic segments may be interspersed within the first rod. For example, along the length of the rod, one or more ferromagnetic segments may be followed by one or more non-ferromagnetic segments. Additionally or alternatively, in some embodiments, one or more ferromagnetic segments may be positioned between at least two non-ferromagnetic segments (e.g., at least one non-ferromagnetic segment may be positioned on either side of one or more ferromagnetic segments). As another example, one or more ferromagnetic segments may be followed by one or more non-ferromagnetic segments, non-ferromagnetic segments may be followed by another or more ferromagnetic segments, ferromagnetic segments may be followed by another or more non-ferromagnetic segments, and so on.

[0039] In some embodiments, the first rod may include a sub-rod consisting of one or more non-ferromagnetic segments. Each end of the sub-rod may be adjacent to one of the ferromagnetic segments.

[0040] In some embodiments, the rod may be positioned to provide a substantially uniform magnetic field within the imaging region of the aperture.

[0041] In some embodiments, the ferromagnetic segments may all have substantially the same size and shape. In some embodiments, one or more non-ferromagnetic segments may have substantially the same size and shape as one of the ferromagnetic segments.

[0042] The ferromagnetic segment can have any suitable shape. For example, in some embodiments, the ferromagnetic segment can be shaped as a cylinder. In other embodiments, the ferromagnetic segment can be shaped as a truncated cylinder. The truncated cylinder can have two flat surfaces opposite each other along a common longitudinal direction. The truncated cylinder can also have a third flat surface extending from the first flat surface to the second flat surface along the common longitudinal direction. In some embodiments, the net magnetization of the ferromagnetic segment can be oriented in a direction substantially perpendicular to the common longitudinal direction. Alternatively, the net magnetization of the ferromagnetic segment can be oriented at a specified angle relative to the third flat surface of the ferromagnetic segment.

[0043] In some embodiments, all the rods may have the same length. In other embodiments, at least two of the rods may have different lengths. For example, in some embodiments, the rods may have different lengths and be positioned to receive within the perimeter of a patient's shoulder insertion hole.

[0044] In some embodiments, the rod may be positioned in a single layer surrounding the hole. In other embodiments, the rod may be positioned in multiple concentric layers surrounding the hole.

[0045] In some embodiments, the hole may have a length substantially equal to the width of the hole (e.g., an aspect ratio of 1:1). In other embodiments, the hole may have a length substantially equal to twice the width of the hole (e.g., an aspect ratio of 1:2).

[0046] In some embodiments, the weight of the magnetic assembly may be less than 120 kg. In other embodiments, the weight of the magnetic assembly may be less than 70 kg or even less than 50 kg.

[0047] In some embodiments, the rod may be at least partially cylindrical.

[0048] The inventors have also developed an MRI system with a permanent magnet assembly to provide a B0 magnetic field for the MRI system. In some embodiments, the MRI system may include a magnetic assembly as discussed herein, and a gradient coil configured to generate a magnetic field to provide spatial encoding of the emitted magnetic resonance signal. Alternatively, the MRI system may include a radio frequency (RF) transmit coil and a power system configured to power the gradient coil and the RF transmit coil. In some embodiments, the gradient coil may be positioned inside a hole formed by a rod. In other embodiments, the gradient coil may be positioned outside the hole formed by the rod. In some embodiments, the MRI system may be used to acquire at least one magnetic resonance (MR) image.

[0049] The inventors have further developed an assembly comprising a non-ferromagnetic frame for providing a B0 magnetic field for a magnetic resonance imaging (MRI) system. The assembly may include at least a partially cylindrical ferromagnetic segment housed within the non-ferromagnetic frame. In some embodiments, the non-ferromagnetic frame may form a hole extending along a common longitudinal direction, and the at least partially cylindrical ferromagnetic segment may have net magnetization oriented in a plane substantially perpendicular to the common longitudinal direction.

[0050] In some embodiments, the nonferromagnetic frame may be formed of nonferromagnetic sheets (e.g., plastic sheets and / or fiberglass sheets). The nonferromagnetic sheets may include apertures configured to accommodate at least partially cylindrical ferromagnetic segments. In some embodiments, the at least partially cylindrical ferromagnetic segments may be positioned within a plurality of nonferromagnetic sheets in rows extending along a common longitudinal direction. A row may include a region containing nonferromagnetic sheets.

[0051] In some embodiments, the at least partially cylindrical ferromagnetic segments may include two sets of segments. The first set of at least partially cylindrical ferromagnetic segments may have a first diameter, and the second set of at least partially cylindrical ferromagnetic segments may have a second diameter different from the first diameter.

[0052] In some embodiments, the at least partially cylindrical ferromagnetic segment may be shaped as a truncated cylinder having a first flat surface along a common longitudinal direction and a second flat surface opposite the first flat surface. The segment may have a third flat surface extending from the first flat surface to the second flat surface along the common longitudinal direction. In some embodiments, the net magnetization of the ferromagnetic segment may be oriented at a specified angle to the third flat surface in a direction substantially perpendicular to the common longitudinal direction.

[0053] The inventors have further developed an improved method for manufacturing magnetic assemblies for providing a B0 magnetic field to an MRI system. In some embodiments, the method may include accessing information about the segment layout of a designated rod. The segment layout may include a first layout of a first rod, and the first layout may indicate the positions of ferromagnetic and non-ferromagnetic segments in the first rod. The first layout may also specify the net magnetization orientation of at least some of the ferromagnetic segments in the first rod.

[0054] In some embodiments, the method may further include obtaining ferromagnetic segments and non-ferromagnetic segments. The obtained segments may be assembled into a rod according to information of a specified segment layout. In some embodiments, assembling the rod may include assembling a first rod using at least some of the ferromagnetic segments and at least some of the non-ferromagnetic segments according to a first layout. The ferromagnetic segments may also be oriented according to the net magnetization orientation of the segment layout. Alternatively, assembling the rod may include assembling the rod into an arrangement in which the rod extends along a common longitudinal direction. The positioned rod may form a hole extending along the common longitudinal direction.

[0055] In some embodiments, assembling the first rod may further include orienting at least some segments of the ferromagnetic segments according to net magnetization oriented in a plane substantially perpendicular to a common longitudinal direction. Orientation can be achieved by orienting the ferromagnetic segments in a direction based on their physical properties (e.g., flatness, notches, and / or pits). In some embodiments, the ferromagnetic segments may be shaped as truncated cylinders. The truncated cylinder may include a first flat surface, a second flat surface, and a third flat surface extending from the first flat surface to the second flat surface. The magnetic orientation of the ferromagnetic segments may be aligned at an angle relative to the third flat surface of the truncated cylinder.

[0056] In some embodiments, assembling the first rod may include assembling a sub-rod comprising a non-ferromagnetic segment. The sub-rod may be assembled within the first rod, with each end adjacent to a ferromagnetic segment. Alternatively, the ferromagnetic segment may be interspersed with the non-ferromagnetic segment within the first rod.

[0057] In some embodiments, the method may include determining the segment layout of the individual bars. Cone programming can be used to determine the segment layout, and the locations of ferromagnetic and non-ferromagnetic segments within the segment layout can be determined. Alternatively, the orientation of the net magnetization of the ferromagnetic segments can be determined.

[0058] Optionally and / or additionally, in some embodiments, integer programming can be used to determine the segment layout. The positions of ferromagnetic and non-ferromagnetic segments within the segment layout can be determined, and the orientation of the net magnetization of the ferromagnetic segments can be determined. The value of the net magnetization of the ferromagnetic segments can be constrained to a specific value using integer programming (e.g., using quadratic curve constraints in some embodiments). In some embodiments, determining the orientation of the net magnetization of the ferromagnetic segments can include determining that the net magnetization orientation of each segment position lies in a plane perpendicular to a common longitudinal direction.

[0059] In some embodiments, one or more methods may be used to manufacture ferromagnetic segments. One method may include placing magnetic metal alloy powder and / or a binder into a tube having a desired cross-sectional area. The method may include applying a magnetic field to the magnetic metal alloy powder while compressing the powder and the tube to align the particles of the powder. In embodiments where no binder is added to the tube, the magnetic metal alloy powder may be sintered to obtain a solid magnetic metal alloy assembly. In other embodiments, the solid magnetic metal alloy may be formed by the properties of compression and / or the binder, and may not require sintering. The solid magnetic metal alloy may be magnetized and segmented to form ferromagnetic segments.

[0060] The following is a more detailed description of various concepts and embodiments related to magnet assemblies constructed without using a ferromagnetic frame. It should be understood that the various aspects described herein can be implemented in any of a number of ways. Examples of specific implementations are provided herein for illustrative purposes only. Furthermore, the various aspects described in the following embodiments can be used alone or in any combination, and are not limited to the combinations explicitly described herein.

[0061] Figure 1 This is a block diagram of the components of the MRI system 100. Figure 1 In the illustrative example, MRI system 100 includes a computing device 104, a controller 106, a pulse sequence storage device 108, a power management system 110, and a magnetic component 120. It should be understood that system 100 is illustrative, and in addition to... Figure 1 Other than or in place of the components shown Figure 1 As shown in the diagram, an MRI system may have one or more other components of any suitable type. However, MRI systems will typically include these high-level components, although the implementation of these components may differ for a particular MRI system.

[0062] like Figure 1 As shown, the magnetic component 120 includes a B0 magnet 122, a shimming coil 124, an RF transmitting and receiving coil 126, and a gradient coil 128. The magnet 122 can be used to generate a main magnetic field B0. The magnet 122 can be any suitable type of magnetic component or combination of magnetic components capable of generating the desired main magnetic field B0. In some embodiments, the magnet 122 can be a permanent magnet, an electromagnet, a superconducting magnet, or a hybrid magnet comprising one or more permanent magnets and one or more electromagnets and / or one or more superconducting magnets. In some embodiments, the magnet 122 can be a permanent magnet with a non-ferromagnetic framework.

[0063] Gradient coil 128 can be positioned to provide a gradient field, and for example, can be positioned to generate gradients in three substantially orthogonal directions (X, Y, and Z) within the B0 field. Gradient coil 128 can be configured to encode the emitted MR signal by systematically altering the B0 field (generated by magnet 122 and / or shimming coil 124) to encode the spatial location of the received MR signal according to frequency or phase. For example, gradient coil 128 can be configured to alter the frequency or phase according to a linear function of the spatial location along a specific direction, but a more complex spatial encoding distribution can also be provided by using nonlinear gradient coils.

[0064] In some embodiments, some or all of the gradient coils 128 may be formed as portions of a laminate. The laminate may include at least one conductive layer patterned on at least one non-conductive layer to form one or more gradient coils or portions of one or more gradient coils, wherein the at least one conductive layer is capable of generating or contributing a magnetic field suitable for providing spatial encoding of the detected MR signal. For example, the laminate may include multiple laminated layers (e.g., non-conductive and conductive layers) on which gradient coils are formed. In some embodiments, the conductive layer may be patterned to form one or more X-gradient coils (or portions of X-gradient coils), one or more Y-gradient coils (or portions of Y-gradient coils), and / or one or more Z-gradient coils (or portions of Z-gradient coils).

[0065] As a non-limiting example of gradient coils being formed at least partially in a laminate, such as via one or more conductors patterned as a grid, a Z-gradient coil may be formed in one or more layers using at least a generally circular geometry, and X-gradient and Y-gradient coils may be formed in one or more layers using at least a generally rectangular geometry. The conductors for the gradient coils may be distributed across one or more layers in any combination as needed to create integrated gradient coils (with or without other magnetic components of a low-field MRI system) that share layers with other magnetic components and / or are patterned on separate layers of the laminate. In some embodiments, additional magnetic components (e.g., BO coils, shimming coils, and / or transmit / receive coils) may be patterned on additional layers of the laminate or on separate laminates. Aspects of forming gradient coil 128 using one or more laminates are described in U.S. Patent 9,817,093, filed September 4, 2015, entitled “Low Field Magnetic Resonance Imaging Methods and Apparatus”, the entire contents of which are incorporated herein by reference.

[0066] MRI is performed by exciting and detecting emitted MR signals using transmitting and receiving coils (commonly referred to as radio frequency (RF) coils). Transmitting / receiving coils may include separate coils for transmitting and receiving, multiple coils for transmitting and / or receiving, or the same coil for both transmitting and receiving. Therefore, a transmitting / receiving assembly may include one or more coils for transmitting, one or more coils for receiving, and / or one or more coils for both transmitting and receiving. Transmitting / receiving coils are also commonly referred to as Tx / Rx or Tx / Rx coils to generally refer to various configurations of the transmitting and receiving magnetic assemblies of an MRI system. These terms are used interchangeably herein. Figure 1In this configuration, the RF transmitting and receiving coil 126 includes one or more transmitting coils that can be used to generate RF pulses to induce an oscillating magnetic field B1. The transmitting coils (one or more) can be configured to generate RF pulses of any suitable type.

[0067] The power management system 110 includes electronic devices that provide operating power to one or more components of the low-field MRI system 100. For example, the power management system 110 may include one or more power supplies, gradient power components, transmit coil assemblies, and / or any other suitable power electronics required to provide appropriate operating power to excite and operate the components of the MRI system 100. Figure 1 As shown, the power management system 110 includes a power supply 112, one or more power components 114, a transmit / receive switch 116, and a thermal management component 118 (e.g., a cryogenic cooling device for a superconducting magnet). The power supply 112 includes electronics for providing operating power to the magnetic components 120 of the MRI system 100. For example, the power supply 112 may include electronics for providing operating power to one or more BO coils (e.g., BO magnet 122) to generate a main magnetic field for a low-field MRI system. The transmit / receive switch 116 can be used to select whether the RF transmit coil or the RF receive coil is being operated.

[0068] One or more power components 114 may include: one or more RF receive (Rx) preamplifiers that amplify MR signals detected by one or more RF receive coils (e.g., coil 126); one or more RF transmit (Tx) power components configured to provide power to one or more RF transmit coils (e.g., coil 126); one or more gradient power components configured to provide power to one or more gradient coils (e.g., gradient coil 128); and one or more shimming power components configured to provide power to one or more shimming coils (e.g., shimming coil 124).

[0069] like Figure 1 As shown, the MRI system 100 includes a controller 106 (also referred to as a console) having control electronics that send instructions to and receive information from a power management system 110. The controller 106 can be configured to implement one or more pulse sequences, wherein these pulse sequences are used to determine instructions sent to the power management system 110 to operate the magnetic assembly 120 in a desired sequence (e.g., parameters for operating the RF transmitting and receiving coils 126, parameters for operating the gradient coil 128, etc.). Figure 1As shown, controller 106 also interacts with computing device 104, which is programmed to process the received MR data. For example, computing device 104 can use any suitable image reconstruction process (one or more) to process the received MR data to generate one or more MR images. Controller 106 can provide computing device 104 with information relating to one or more pulse sequences for data processing by the computing device. For example, controller 106 can provide computing device 104 with information relating to one or more pulse sequences, and the computing device can perform image reconstruction processing at least in part based on the provided information.

[0070] Figure 2A A portion of a rectangular magnetic assembly 200 for providing a B0 magnetic field to an MRI system, according to some embodiments of the technology described herein, is depicted. The ferromagnetic segments 210 and non-ferromagnetic segments 220 (not shown) of the rectangular magnetic assembly 200 are arranged in... Figure 2A It is described as one-eighth of the final assembly components. Figure 2A A portion of the rectangular magnetic fitting 200 depicted may be appropriately mirrored (e.g., across the x, y, and z planes) to form a magnetic fitting with rectangular holes along a common longitudinal direction.

[0071] In some embodiments, the ferromagnetic segment 210 may be formed of a permanent magnet material. A permanent magnet is any object or material that retains its own continuous magnetic field once magnetized. Materials that can be magnetized to produce permanent magnets are referred to herein as ferromagnetic, and by way of non-limiting examples include iron, nickel, cobalt, neodymium (NdFeB) alloys, samarium cobalt (SmCo) alloys, alnicotinic (AlNiCo) alloys, strontium ferrite, barium ferrite, etc. The permanent magnet material can also retain its own internal net magnetization orientation once magnetized.

[0072] The ferromagnetic segment 210 can be manufactured using conventional methods for manufacturing permanent magnet materials. Alternatively or additionally, the ferromagnetic segment 210 can be manufactured using a forging method as described in U.S. Patent Application Publication 2019 / 0122818, filed September 28, 2018, entitled “Method of Manufacturing Permanent Magnets,” which is incorporated herein by reference in its entirety.

[0073] The permanent magnet material used can be selected based on the design requirements of the magnetic assembly. For example, according to some embodiments, the ferromagnetic segment 210 (or portions thereof) can be made of NdFeB, which, once magnetized, generates a magnetic field with a relatively high magnetic field per unit volume of material. According to some embodiments, SmCo material is used to form the ferromagnetic segment or portions thereof. While NdFeB produces a higher field strength (and is generally cheaper than SmCo), SmCo exhibits less thermal drift, thus providing a more stable magnetic field in the face of temperature fluctuations. Other types (one or more) of permanent magnet materials can also be used, and these aspects are not limited herein. Generally, the type of permanent magnet material utilized will depend at least in part on the field strength, temperature stability, field uniformity, weight, cost, and / or ease of use requirements to be achieved for a given magnet assembly.

[0074] In some embodiments, such as Figure 2A As depicted, the ferromagnetic segment 210 can be formed as a solid rod. However, in other embodiments, such as Figure 5A and Figure 5B As depicted in the example, the ferromagnetic segment 210 can be assembled from multiple rows of shorter ferromagnetic tokens. One or more ferromagnetic segments 210 and / or ferromagnetic tokens can have at least a partially cylindrical shape. For example, the ferromagnetic segments 210 and / or ferromagnetic tokens can be formed as truncated cylinders (e.g., cylinders with flat surfaces extending along a common longitudinal direction of the holes). In such embodiments, the magnetic orientation of the ferromagnetic segments 210 and / or ferromagnetic tokens can be aligned with the flat surface of the ferromagnetic segment 210. For example, the magnetic orientation can be aligned along a direction perpendicular to the flat surface. Figure 2C An example of such a ferromagnetic segment 210 is depicted, wherein the magnetization of the ferromagnetic segment 210 is aligned with a direction perpendicular to the flat surface 211. Alternatively, the magnetic orientation may be aligned along a direction parallel to the flat surface, or the magnetic orientation may be aligned along any desired angle relative to the flat surface. In some embodiments, the magnetic orientation may additionally be aligned with a plane perpendicular to the common longitudinal direction of the aperture of the rectangular magnetic fitting 200.

[0075] According to some embodiments of the technology described herein, the rectangular magnetic assembly 200 may also include a non-ferromagnetic segment 220. The non-ferromagnetic segment 220 may be formed of a non-magnetic material (e.g., plastic, glass fiber). In some embodiments, the non-ferromagnetic segment 220 may have the same size and shape as the ferromagnetic segment 210. Alternatively, the non-ferromagnetic segment 220 may have a different size and / or shape than the ferromagnetic segment 210. In some embodiments, the non-ferromagnetic segment 220 may be filled with a transparent material or may remain open to provide an opening for air. Such embodiments can reduce claustrophobia experienced by patients imaging within an MRI system and can increase patient comfort.

[0076] In some embodiments, the ferromagnetic segment 210 and the non-ferromagnetic segment 220 may be positioned within a rod having a length along a common longitudinal direction. The rod may be positioned to provide a substantially uniform magnetic field of desired intensity in the central region of the aperture (e.g., the field of view (FOV) or imaging region). Additionally, the positions of the ferromagnetic segment 210 and the non-ferromagnetic segment 220 within the respective rods may be positioned to provide a magnetic field of desired intensity and uniformity in the central region of the aperture. For example, the BO magnetic field may have a uniformity of 500 ppm over a volume having a diameter of approximately 20 cm (or any other diameter in the range of 15-25 cm). Alternatively, the BO magnetic field may have uniformity in the range of 10 ppm to 1000 ppm, 100 ppm to 500 ppm, 500 ppm to 1000 ppm, 200 ppm to 800 ppm, or any other suitable range within the aforementioned ranges over a volume having a diameter of approximately 20 cm (or any other diameter in the range of 15-25 cm). In some embodiments, the BO magnetic field within the central region of the aperture of the rectangular magnetic fitting 200 may have an intensity ranging from 0.05T to 0.2T. Alternatively or additionally, the BO magnetic field may have an intensity ranging from 0.05T to 0.1T (e.g., 0.064T).

[0077] In some embodiments, the aperture of the rectangular magnetic fitting 200 may have a square cross-section, the width and height of which are selected to accommodate the patient's torso. For example, the aperture of the rectangular magnetic fitting 200 may have a square cross-section with a width and height of 70 cm. In such embodiments, the length of the rectangular magnetic fitting 200 may be less than or equal to 1 m. For such a size, the rectangular magnetic fitting 200 may include approximately 350 kg of permanent magnet material. Alternatively, for fittings of other sizes, the weight of the permanent magnet material may range from 300 kg to 400 kg or from 275 kg to 425 kg. In some embodiments, the weight of the permanent magnet material may be reduced by introducing steel at appropriate locations on the sides of the rectangular magnetic fitting 200 to increase the DC field efficiency of the rectangular magnetic fitting 200.

[0078] According to some embodiments of the technology described herein, the rectangular shape of the rectangular magnetic assembly 200 allows for the placement of gradient coils (e.g., gradient coil 128) of the MRI system within the apertures of the rectangular magnetic assembly 200. Placing the gradient coils within the apertures of the magnetic assembly positions them closer to the FOV of the MRI system, thereby reducing the power required to supply the gradient magnetic field during MR imaging procedures.

[0079] Figure 2B Some embodiments of the technology described herein are depicted. Figure 2A The magnetic moment 222 of the ferromagnetic segment 210 (not shown) of the rectangular magnetic assembly 200. The magnetic moment 222 can have an orientation that varies based on its position within the rectangular magnetic assembly 200. Figure 2B In the example, the orientation of the magnetic moment 222 is unrestricted and can vary along three directions. In other embodiments, the magnetic moment 222 can be constrained to vary along two directions (e.g., the orientation of the magnetic moment 222 can be constrained to lie in a plane). In some embodiments, the orientation of the magnetic moment 222 can be constrained to lie in a plane perpendicular to the common longitudinal direction of the hole.

[0080] In some embodiments, computational optimization processes can be used to determine the orientation and position of the magnetic moment 222, and examples of computational optimization processes are provided herein. Figure 2B Control point 230 is shown, depicting a point on the surface of a spherical field of view (FOV) within the aperture of the rectangular magnetic assembly 200. Control point 230 can be used during computational optimization to set the desired magnetic field strength and uniformity of the rectangular magnetic assembly 200.

[0081] Figure 3A A portion of a cylindrical magnetic assembly 300 for providing a B0 magnetic field to an MRI system, according to some embodiments of the technology described herein, is depicted. For one-eighth of the total assembly, in Figure 3A The arrangement of the ferromagnetic section 210 and the non-ferromagnetic section 220 (not shown) of the cylindrical magnetic assembly 300 is depicted. Figure 3A A portion of the cylindrical magnetic fitting 300 depicted in the figure can be appropriately mirrored (e.g., across the x, y, and z planes) to form a magnetic fitting with cylindrical holes along a common longitudinal direction.

[0082] In some embodiments, it may be advantageous to make the cylindrical magnetic assembly 300 smaller and fit more closely to the patient and the field of view (FOV). In such embodiments, the gradient coils of the MRI system (e.g., gradient coil 128) can be positioned outside the cylindrical magnetic assembly 300, rather than inside as in the case of the rectangular magnetic assembly 200. Although the gradient coils can be positioned further away from the FOV, thus requiring more power to provide the same gradient field strength within the FOV, this also removes the gradient coils from the effects of the BO magnetic field, which can reduce the acoustic output level resulting from the operation of the gradient coils.

[0083] Figure 3B Some embodiments of the technology described herein are depicted. Figure 3A The magnetic moment 222 of the ferromagnetic segment 210 (not shown) of the cylindrical magnetic fitting 300. Figure 3B Control point 230 is shown, which depicts a point on the surface of a spherical FOV within the hole of the magnetic fitting 300.

[0084] Alternatively, the magnetic fitting can be configured to improve accessibility to the FOV of the MRI system. For example, the magnetic fitting can be configured to accommodate the patient's shoulder when imaging the patient's head. Figure 4A Examples of rectangular magnetic fittings 400a, including an opening 430 configured to receive a patient’s shoulder, are depicted according to some embodiments of the technology described herein. Figures 4B to 4C Examples of cylindrical magnetic fittings 400b according to some embodiments of the technology described herein are depicted, wherein the cylindrical magnetic fittings 400b are configured with an S-shaped shoulder opening to accommodate the shoulder of a patient 410.

[0085] In some embodiments, such openings can reduce the overall weight of magnetic fittings 400a, 400b. The openings can functionally increase the length of the magnetic fitting relative to its width, while still allowing comfortable patient access to the FOV of the MRI system. Increasing the length of the magnetic fitting can improve magnetic field uniformity and efficiency, and can reduce the amount of permanent magnet material required to form the magnetic fitting. For example, a magnetic fitting (e.g., cylindrical magnetic fitting 400b) having a 320mm diameter hole, a 450mm length, and a 200mm length shoulder opening can be composed of 60-70kg of permanent magnet material to provide a 65mT magnetic field with the magnetization of the ferromagnetic segments confined to a plane perpendicular to the common longitudinal direction. Comparatively, a cylindrical magnetic fitting (e.g., cylindrical magnetic fitting 300) with the same width and length (e.g., a 1:1 aspect ratio) and an inner diameter of 320mm can be composed of approximately 150kg of permanent magnet material to provide the same magnetic field and uniformity.

[0086] Figure 5A A magnetic assembly 500a, comprising a first ferromagnetic segment 510 and a second ferromagnetic segment 512 positioned to form a hole extending along a common longitudinal direction, is depicted according to some embodiments of the technology described herein. The first ferromagnetic segment 510 and the second ferromagnetic segment 512 may be made of... Figures 2A to 2B The ferromagnetic segment 210 is formed of the same material and can be made of the same material as the ferromagnetic segment 210. Figures 2A to 2B The first ferromagnetic segment 510 is shaped in the same manner as the second ferromagnetic segment 512. However, the first ferromagnetic segment 510 may have a different size than the second ferromagnetic segment 512, such that the first ferromagnetic segment 510 has a larger magnetic moment than the second ferromagnetic segment 512. For example, the first ferromagnetic segment 510 may have a larger diameter than the second ferromagnetic segment 512 (e.g., more than two, three, four, five times, etc.). In some embodiments, the first ferromagnetic segment 510 may have a diameter of approximately 30-42 mm (e.g., 36 mm), while the second ferromagnetic segment 512 may have a diameter of approximately 8-20 mm (e.g., 14 mm).

[0087] The magnetic fitting 500a may also include non-ferromagnetic segments at spaces 520, 522 (the non-ferromagnetic segments entering these spaces are not shown in the figures themselves). In some embodiments, the non-ferromagnetic segments in spaces 520, 522 may be spacers formed of any suitable non-ferromagnetic material (e.g., plastic, fiberglass). The spacers may have the same size and shape as the first ferromagnetic segment 510 and the second ferromagnetic segment 512, respectively, and may be interspersed with ferromagnetic segments. For example, along the length of the rod, one or more ferromagnetic segments may be followed by one or more non-ferromagnetic segments. Additionally or alternatively, in some embodiments, one or more ferromagnetic segments may be positioned between at least two non-ferromagnetic segments (e.g., at least one non-ferromagnetic segment may be positioned on either side of one or more ferromagnetic segments). In some embodiments, instead of non-ferromagnetic segments, the spaces (e.g., 520, 522) may be left open to provide increased accessibility to the openings and / or reduce claustrophobia and increase patient comfort.

[0088] In other embodiments, the non-ferromagnetic segments in spaces 520, 522 may be provided by a non-ferromagnetic frame configured to accommodate the first ferromagnetic segment 510 and the second ferromagnetic segment 512. For example, as Figure 5B As depicted in the example, the non-ferromagnetic segment can be formed as a non-ferromagnetic sheet 530 configured to accommodate a first ferromagnetic segment 510 and a second ferromagnetic segment 512. The non-ferromagnetic sheet 530 can be formed as an annular and / or semi-annular slice having a hollow cylinder extending along a hole in the magnetic fitting 500. The non-ferromagnetic sheets 530 can be glued together to form the magnetic fitting 500b. Alternatively or additionally, the non-ferromagnetic sheets 530 can be secured together using threaded rods and suitable nuts to form the magnetic fitting 500b.

[0089] In some embodiments, the non-ferromagnetic sheet 530 may include a aperture configured to receive a first ferromagnetic segment 510 and a second ferromagnetic segment 512. The aperture may be machined to indicate the orientation of the first ferromagnetic segment 510 and the second ferromagnetic segment 512 (e.g., the aperture may include a flat surface that is a mirror image of the flat surface of the ferromagnetic segment). Figure 5C An exploded view of the magnetic assembly 500b, showing these machined narrow holes, is shown.

[0090] Using the techniques described herein, the inventors have developed a portable, low-power MRI system that can be brought to patients to provide affordable and widely deployable MRI wherever needed. Figure 6 Examples of embodiments of the technology described herein are shown, including Figure 4C An example of a portable low-field MRI system 600 with magnetic fitting 400b. Magnetic fitting 400b can be supported by a base 610. The base 610 can accommodate and integrate... Figure 1The discussion includes power components and / or electronic devices (including power components configured to operate the MRI system 600).

[0091] According to some embodiments of the technology described herein, the base 610 may also include one or more transport mechanisms 620 that enable the MRI system 600 to be used at a point of care. Figure 6 In the example, the transport mechanism 620 is depicted as a wheel, but other transport mechanisms may be used. In some embodiments, the transport mechanism 620 may include a motor component 625, which may be configured to allow the MRI system 600 to be driven from one position to another, for example, using controls such as a joystick or other control mechanisms located on or off the MRI system 600. In this way, as Figure 7 As shown, the MRI system 600 can be transported to the patient and manipulated to the bedside for imaging.

[0092] Figure 7 The use of some embodiments of the technology described herein is depicted. Figure 6 A portable MRI system is used to perform brain scans on patients. During the brain scan, the MRI system 600 can be used to acquire at least one magnetic resonance image of the patient for clinical use.

[0093] The inventors have further developed methods for manufacturing magnetic assemblies (e.g., magnetic assemblies 200, 300, 400a, 400b and / or 500). Figure 8 This is a flowchart illustrating a process 800 for manufacturing magnetic components according to some embodiments of the technology described herein.

[0094] Processing 800 begins with action 802, where information about the segment layout of one or more specified bars can be accessed. This information can be accessed from any suitable source and can be in any suitable format; the aspects of the technique described herein are not limited thereto.

[0095] In some embodiments, the information accessed at action 802 may include a first layout of a first rod among a plurality of rods. The first layout may indicate the position of ferromagnetic and non-ferromagnetic segments in the first rod. The first layout may also indicate the orientation of the net magnetization of at least some of the ferromagnetic segments in the first rod.

[0096] Next, at action 804, multiple ferromagnetic segments and multiple non-ferromagnetic segments can be obtained. The ferromagnetic segments can be any type of ferromagnetic segment described herein (e.g., ferromagnetic segments 210, 510, and / or 512). The non-ferromagnetic segments can be any type of non-ferromagnetic segment described herein (e.g., non-ferromagnetic segments 220, 520, and / or 522).

[0097] Next, at action 806, multiple rods may be assembled. Assembling multiple rods may include assembling rods from multiple ferromagnetic segments and multiple non-ferromagnetic segments obtained in action 804. Assembling multiple rods may also include assembling rods according to information specifying a segment layout. For example, assembling multiple rods may include placing ferromagnetic and non-ferromagnetic segments at specific segment locations along the rods (e.g., locations specified by information accessed at action 802). Placing ferromagnetic segments may additionally include orienting at least some of the ferromagnetic segments such that the magnetic moments of at least some of the ferromagnetic segments are aligned along a specified direction provided by the information specifying the segment layout.

[0098] Next, at action 808, the plurality of rods can be assembled to form an arrangement of magnetic fittings (e.g., any one of magnetic fittings 200, 300, 400a, 400b, or 500 as described herein). The plurality of rods can be positioned to extend along a common longitudinal direction and form a hole extending along the common longitudinal direction. In some embodiments, the hole may be cylindrical in shape. In other embodiments, the hole may be rectangular in shape.

[0099] In some embodiments, computational optimization methods can be used to generate information about the layout of a specified segment. Such computational optimization methods can be performed using any suitable computing environment that executes appropriate optimization software.

[0100] In some embodiments, cone planning can be used to generate information for a specified segment layout. In such embodiments, the magnetic field generated by ferromagnetic segments having a specified shape, size, and magnetization (components along one or more of the x, y, and z directions) can be calculated. For example, for each segment location i, the density variable X can be used. i To determine the magnitude of magnetization, the range is from 0 to 1. For each position, a set of three variables can be defined. (The value of the variable is between -1 and 1). Density variable X i These variables can be constrained according to the following expression:

[0101]

[0102] This constraint ensures that the mixing of the three magnetization orientations results in a magnetization vector with a smaller magnitude (magn de) than the density variable.

[0103] In some embodiments, a set of control points (e.g., control point 230) can be defined, evenly distributed on the surface of the sphere surrounding the FOV. The field strength at each control point can be set and defined as the sum of the effects of magnetization of various types and orientations at each segment location. This constraint can be written as:

[0104]

[0105] The electric field strength and homogeneity are defined as equivalent to the constraints of setting the boundaries to the values ​​just defined. Finally, the question is:

[0106]

[0107] Make:

[0108]

[0109]

[0110] 0≤X i ≤1

[0111]

[0112] Where P is the number of narrow holes, and V i Let be the volume of the block at position i, b0 be the desired electric field strength, and δ be the electric field strength. b It is the maximum expected offset of the field from b0 among all control points. This problem can be solved using cone programming (an extension of linear programming), and the segment positions can be determined.

[0113] However, the problem described above allows the total magnetization vector magnitude at each location to take fractional values ​​between 0 and 1. Since this implies partial magnetization of the segment, this may be undesirable. One solution could be to reduce the size of the block. Alternatively, to simplify assembly and manufacturing, it might be desirable to restrict the magnetization of the segment to 0 or 1 and use integer programming, reformulating the problem as follows:

[0114]

[0115] Make:

[0116]

[0117]

[0118] 0≤X i ≤1

[0119]

[0120] In this case, all density variables can be integers. The L1 property of the cost function allows M to be... i The variable is driven to its limit, resulting in very few segment locations being partially magnetized.

[0121] In some embodiments, it may also be desirable to include additional constraints. For example, it may be desirable to constrain the field strength outside the magnetic assembly (e.g., to constrain the edge magnetic field and reduce the radius of the 5 Gaussian line). In this way, the orientation of the magnetic moment within the assembly can be selected to reduce the magnetic field strength outside the assembly.

[0122] According to some embodiments of the technology described herein, the above-described cone planning method generates information that can be provided to manufacturers of ferromagnetic segments, enabling them to produce segments for constructing permanent magnet assemblies with non-ferromagnetic frames.

[0123] In other embodiments, the permanent magnet assembly with a non-ferromagnetic frame may be assembled from multiple solid rods rather than from multiple ferromagnetic and non-ferromagnetic segments. For example, as described in U.S. Patent Application Publication 2019 / 0122818, filed September 28, 2018, entitled "Method of Manufacturing Permanent Magnets," the entire contents of which are incorporated herein by reference. In such embodiments, magnetic alloy powder may be placed in a hollow tube having a desired cross-sectional shape (e.g., circular, square, trapezoidal, etc.). The tube and magnetic alloy powder may then be forged to form a solid magnetic rod, and the solid magnetic rod may be magnetized along one or more desired directions. In some embodiments, bonding may include sintering the magnetic alloy powder. Alternatively, the magnetic alloy powder may be forged only and may not be sintered. In other embodiments, bonding may include mixing the magnetic alloy powder with a binder prior to forging. In such embodiments, the magnetic alloy powder may not be sintered. In some embodiments, the tube may be removed or partially removed (e.g., etched or abraded) from the solid magnetic material before the magnetic fitting is assembled.

[0124] In such embodiments, a solid rod can be produced using programmable pre-magnetization, while forging creates a variable magnetization orientation within the solid rod. For example, these methods can be used to magnetize the first region of the solid rod with an orientation different from that of the second region, with the first and second regions located at different positions along the length of the solid rod.

[0125] Alternatively, in some embodiments, the magnetic alloy powder can be diluted in a programmatic manner with a binder to achieve variable effective magnetization along the solid rod. For example, a third region of the solid magnetic rod may have a magnetic moment twice the magnitude of a fourth region of the solid magnetic rod. In some embodiments, a fifth region of the solid magnetic rod may have a substantially zero magnetic moment.

[0126] To produce such solid magnetic rods, these rods can be formed, for example, using a specific sequence of currents driven along the x, y, and z axes in a pre-magnetizing coil. Pre-magnetization can occur during the drawing and forging of the rod. Figures 9A to 9C An example of the desired magnetization of the seven base rods of a 26-bar magnetic assembly in all three directions is shown. The entire assembly can be obtained by appropriate mirroring (e.g., across the x, y, and z planes). In some embodiments, these desired magnetization patterns can be used to calculate the desired angles of the pre-magnetization field at various points along the length of the rods. These desired angles can be converted into waveforms of the pre-magnetization coils.

[0127] Figure 9D It shows the basis Figures 9A to 9C An example of the total magnetization curve of the magnetization pattern is shown. The total magnetization curve illustrates the dilution of the magnetic alloy powder along the length of the rod (e.g., variation between regions of 100% magnetic alloy powder and 100% non-magnetic powder). Alternatively, an integer solution can be considered for this calculation, which would yield a solid magnetic rod consisting of a first region of magnetic material and a second region of non-magnetic material.

[0128] Figure 10A A magnetic assembly 1000 is depicted including a gap for accommodating one or more gradient coils. For example, in some embodiments, the gap accommodates the insertion of one or more panels 1030 on which gradient coils are formed. In some embodiments, the panel 1030 may include one or more additional magnetic components fabricated thereon. For example, in addition to or instead of gradient coils, the panel 1030 may include transmitting / receiving coils and / or shimming coils fabricated thereon as described herein. Figure 10B The image shown is an image of a patient’s head using a magnetic fitting 1000, according to some embodiments of the technology described herein.

[0129] In some embodiments, the magnetic assembly 1000 may be formed by the arrangement of ferromagnetic segments 1010. For example... Figure 10A As shown in the example, the ferromagnetic segment 1010 can be positioned to form a cylindrical aperture extending along a common longitudinal direction A. In some embodiments, the ferromagnetic segment 1010 can also be positioned such that the ferromagnetic segment 1010 forms two separate portions. The space between the two separate portions can be shaped to provide space for portions of the patient's constituent structures (e.g., the shoulder) during MR imaging.

[0130] In some embodiments, the ferromagnetic segment 1010 may also be positioned to form gaps configured to accommodate an insertion of the panel 1030. The positioning of the ferromagnetic segment 1010 to form these gaps can be achieved using computational optimization processing, examples of which are provided herein. To form these gaps using computational optimization processing, the placement of the ferromagnetic segment within the gap area can be prevented, such that the position of the ferromagnetic segment is determined solely by computational optimization processing to be outside the gap.

[0131] In some embodiments, the ferromagnetic segment 1010 may be a rectangular or cubic block or rod. As incorporated herein by reference... Figures 2A to 2C As described in the ferromagnetic segment 210, the ferromagnetic segment 1010 can be formed of a permanent magnet material. For example, the ferromagnetic segment 1010 can be formed from one of the following non-limiting examples: iron, nickel, cobalt, neodymium (NdFeB) alloy, samarium cobalt (SmCo) alloy, alnicotinic (AlNiCo) alloy, strontium ferrite, barium ferrite, etc.

[0132] The ferromagnetic segment 1010 can be manufactured using conventional methods for manufacturing permanent magnet materials. Alternatively or additionally, the ferromagnetic segment 1010 can be manufactured using a forging method as described in U.S. Patent Application Publication 2019 / 0122818, filed September 28, 2018, entitled “Method of Manufacturing Permanent Magnets,” which is incorporated herein by reference in its entirety.

[0133] According to some embodiments of the technology described herein, the magnetic assembly 1000 may also include a non-ferromagnetic segment (not shown). (As in conjunction with...) Figures 2A to 2C As described in nonferromagnetic segment 220, the nonferromagnetic segment can be formed of a nonmagnetic material (e.g., plastic, glass fiber). In some embodiments, the nonferromagnetic segment can have the same size and shape as the ferromagnetic segment 1010. Alternatively, the nonferromagnetic segment can have a different size and / or shape than the ferromagnetic segment 1010. In some embodiments, the nonferromagnetic segment can be filled with a transparent material or can remain open to provide a hole for airflow.

[0134] In some embodiments, the ferromagnetic segment 1010 may be positioned along a common longitudinal direction A. The ferromagnetic segment 1010 may be positioned to provide a substantially uniform magnetic field of desired intensity in the central region of the aperture (e.g., the field of view (FOV) or imaging region). Alternatively, the positions of the ferromagnetic segment 1010 and non-ferromagnetic segments within the respective rods may be positioned to provide a magnetic field of desired intensity and uniformity in the central region of the aperture. For example, the BO magnetic field may have a uniformity of 500 ppm over a volume having a diameter of approximately 20 cm (or any other diameter in the range of 15-25 cm). Alternatively, the BO magnetic field may have uniformity in the range of 10 ppm to 1000 ppm, 100 ppm to 500 ppm, 500 ppm to 1000 ppm, 200 ppm to 800 ppm, or any other suitable range within the aforementioned ranges over a volume having a diameter of approximately 20 cm (or any other diameter in the range of 15-25 cm). In some embodiments, the BO magnetic field within the central region of the aperture of the rectangular magnetic fitting 1000 may have an intensity in the range of 0.05T to 0.2T. Alternatively or additionally, the BO magnetic field may have an intensity in the range of 0.05T to 0.1T (e.g., 0.064T).

[0135] In some embodiments, the opening of the magnetic fitting 1000 may have a circular cross-section with a width and height selected to accommodate a patient's head, arms, legs, hands, and / or feet. For example, to accommodate a patient's head, the opening of the magnetic fitting 1000 may have a circular cross-section with a width and height of 36 cm. In such embodiments, the length of the circular magnetic fitting 1000 may be less than or equal to 45 cm, and the gap between the portions of the circular magnetic fitting 1000 on opposite sides of the opening may have a height of approximately 15 cm. For such a size, the magnetic fitting 1000 may comprise approximately 90 kg or less of permanent magnet material. Alternatively, for fittings of other sizes (e.g., to accommodate different parts of a patient's anatomy), the weight of the permanent magnet material may range from 40 kg to 120 kg, from 60 kg to 80 kg, or any range within these ranges. Alternatively, the height of the gap between the portions of the magnetic fitting may range from 10 cm to 70 cm.

[0136] In some embodiments, panel 1030 or other substantially planar components may be positioned within a gap formed between the ferromagnetic segments 1010 of magnetic assembly 1000. Positioning panel 1030 within such a gap allows additional magnetic components to be placed closer to the imaging area without requiring the fabrication of complex, curved magnetic components configured to fit within cylindrical apertures. Therefore, maintaining the use of a substantially planar panel 1030 can reduce the manufacturing cost of other magnetic components in the MRI system. In some embodiments, panel 1030 may have a thickness of approximately 6 mm, or a thickness ranging from 4 mm to 12 mm, from 5 mm to 10 mm, and / or from 6 mm to 8 mm, or any thickness within these ranges.

[0137] like Figure 10A As shown in the example, panels 1030 can be positioned substantially parallel to each other and on opposite sides of the opening. In some embodiments, panels 1030 can be positioned such that layers of the ferromagnetic assembly 1010 are positioned between the respective panels 1030 and the opening. It should be understood that Figure 10A The symmetrical arrangement of panel 1030 shown in the example is not required in all embodiments, and some embodiments may have only one panel 1030, more than two panels 1030, or asymmetrical positioning of panel 1030.

[0138] In some embodiments, panel 1030 may include a laminate on which magnetic components are formed. Panel 1030 may include one or more BO coils, one or more gradient coils, one or more transmit / receive coils and / or one or more shimming coils, or any desired portion or combination thereof may be fabricated on a single laminate or distributed among multiple laminates.

[0139] For example, panel 1030 may include multiple non-conductive layers and multiple conductive layers formed between the non-conductive layers. Connections between the conductive layers can be achieved by forming holes (e.g., electroplated through holes) filled with conductive material in the intermediate non-conductive layers. Depending on the desired design, any number of non-conductive and conductive layers can be used to implement the laminate.

[0140] Alternatively, it should be understood that multiple conductive layers can be provided for each non-conductive layer (e.g., a non-conductive layer having conductive layers laminated to both sides). The multilayer laminate can be attached using one or more adhesive layers. These adhesive layers can be any suitable adhesive or combination of materials (such as prepreg, dry adhesive, epoxy, and / or any other suitable layer or combination of layers), wherein the adhesive layers bond the multilayer laminate together when activated (e.g., via heat and / or pressure). It should be understood that any configuration of conductive and non-conductive layers, adhesives, etc., using any one or combination of lamination techniques can be used to produce the desired laminate.

[0141] As described above, the layers of a laminate can be electrically connected using a desired arrangement of vias formed through appropriate layers in the laminate. In some embodiments, conductive traces can be formed by patterning copper conductors on a non-conductive material, and vias between layers can be used to connect the conductive traces. The copper conductors can be patterned in any desired geometry and configured to form desired circuitry corresponding to one or more magnetic components (or portions of magnetic components) and / or any supporting electronics, control electronics, etc., of an MRI system. Vias (such as plated through-holes) can be used to electrically connect copper conductors on different layers. It should be understood that vias can be formed throughout the entire laminate or can be formed through a subset of the layers of the laminate (including connecting adjacent layers or multiple adjacent layers). The laminated layers of the laminate can contain multiple vias arranged to connect to different layers of the laminate. For example, layers having multiple components or portions of multiple components can be electrically isolated from each other and independently connected to conductors patterned on other layers. Conductors patterned on the layers of a laminate can be connected in any desired manner, and one or more layers may not include vias at all, thus maintaining electrical isolation from other layers of the laminate.

[0142] As discussed in further detail below, multiple components of an MRI system can be integrated on a single panel or distributed among multiple panels to facilitate the fabrication of components according to a desired configuration. For example, panel 1030 may include multiple BO layers on which one or more BO coils are formed. BO coils can be configured to generate at least a portion of a BO field for the MRI system when an appropriate current is applied to (one or more) the coils. In some embodiments, each BO layer includes one or more conductive trace turns patterned on a conductive layer to generate a portion of the desired BO field. BO coils can be patterned according to any desired geometry. For example, BO coils can be patterned according to a generally circular geometry having one or more conductive trace turns.

[0143] As described above, panel 1030 may further include at least one conductive layer (patterned to form one or more gradient coils, or portions thereof) capable of generating or contributing a magnetic field suitable for providing spatial encoding of the detected MR signal when operated in a low-field MRI system. For example, panel 1030 may include multiple laminated layers on which gradient coils are formed. One or more layers may include conductive traces patterned to form all or part of a Z-gradient coil, conductive traces patterned to form all or part of a Y-gradient coil, and / or conductive traces patterned to form all or part of an X-gradient coil. The gradient coils may be formed using any suitable geometry, with any number and configuration of layers, to provide one or more desired gradient coils.

[0144] As a non-limiting example of gradient coils being at least partially formed in a laminate (e.g., panel 1030), the Z-gradient coil may be formed in one or more layers using at least partially a generally circular geometry, and the X-gradient coil and Y-gradient coil may be formed in one or more layers using at least partially a generally rectangular geometry (such as via one or more conductors patterned as a grid). Conductors for the gradient coils may be distributed across one or more layers in any combination as needed to produce integrated gradient coils (with or without other magnetic components of a low-field MRI system) that share layers with other magnetic components and / or are patterned on separate layers of the laminate.

[0145] As described above, the laminate may also include at least one conductive layer (patterned to form one or more transmit and / or receive coils, or portions thereof), wherein the at least one conductive layer is configured to stimulate an MR response (emission) and / or receive emitted MR signals (reception) by generating a B1 excitation field when operated in conjunction with coils configured to generate a B0 field and a corresponding gradient field. Such a laminate may contain a single transmit coil and / or receive coil (or portions thereof) or multiple transmit coils and / or receive coils (or portions thereof) for performing single-channel or parallel MRI.

[0146] Any suitable geometry can be used to pattern transmit / receive coils or assemblies of transmit / receive coils. For example, in some embodiments, a helical conductor can be patterned in one or more layers to form one or more transmit / receive coils (or portions thereof). According to some embodiments, lamination techniques can be used to fabricate one or more transmit and / or receive coils using substantially rectangular geometries. According to some embodiments where different coils are used for transmitting and receiving, the transmit and receive coils can be formed in one or more layers using different corresponding geometries. In some embodiments, multiple layers and / or multiple laminates can be used to collectively form transmit / receive coils and / or assemblies of transmit / receive coils for use in a low-field MRI system. It should be understood that one or more transmit / receive coils fabricated using lamination techniques can be used in combination with one or more other magnetic components fabricated using lamination techniques (e.g., by integrating one or more other magnetic components in a shared or separate laminate), or can be used as part of a low-field MRI system in combination with one or more other magnetic components fabricated using conventional techniques.

[0147] The shimming coils, arranged to facilitate the generation of a desired magnetic field, can also be patterned on one or more layers of the laminate (e.g., panel 1030). According to some embodiments, the laminate may include at least one conductive layer patterned to form one or more shimming coils or portions thereof, arranged to generate or contribute (one or more) a magnetic field and adapted to improve the uniformity of the B0 field generated by one or more B0 coils, or otherwise improve the B0 field within a given field of view and / or counteract other magnetic fields that negatively affect the B0 field. For example, panel 1030 may include (one or more) layers on which one or more shimming coils (or portions thereof) are formed. For embodiments including a laminate with at least one B0 coil and at least one shimming coil, the at least one shimming coil may be formed from a conductive layer shared (but electrically isolated) with the at least one B0 coil (or a portion of the B0 coil), or may be formed in one or more conductive layers separate from the at least one B0 coil (or a portion of the B0 coil). As with other magnetic components discussed, the shimming coil fabricated using lamination techniques can be utilized together with other components fabricated using lamination techniques (e.g., by integrating the shimming coil in a shared or separate laminate), or together with other components manufactured using conventional techniques, as part of a low-field MRI system.

[0148] As described above, multiple low-field MRI components (or portions thereof) can be formed on a single layer (i.e., a single laminate) of a laminate (e.g., plate 1030). That is, multiple magnetic components or portions thereof can be patterned on the same conductive layer of a single laminate. For example, the conductive layer of a single laminate can be patterned to form one or more B0 coils (forming or contributing to a complete B0 magnet) and one or more gradient coils or portions thereof. Aspects of forming such magnetic components using one or more laminates are described in U.S. Patent 9,817,093, filed September 4, 2015, entitled “Low Field Magnetic Resonance Imaging Methods and Apparatus,” which is incorporated herein by reference in its entirety.

[0149] In some embodiments of the technology described herein, such as Figure 10C As illustrated in the example, the ferromagnetic segment 1010 may be surrounded by a housing structure and incorporated into an MRI system, wherein the MRI system 1050 is depicted for imaging a patient's head. The MRI system 1050 may include the ferromagnetic segment 1010 (not shown) housed within a housing assembly 1040, wherein a panel 1030 is inserted on the opposite side of the aperture. In some embodiments, additional magnetic components (e.g., shimming coils, transmit / receive coils) may be incorporated into the panel 1030, or may be included as separate components within the aperture of the MRI system 1050.

[0150] According to some embodiments of the technology described herein Figure 11A An embodiment of the asymmetric magnetic assembly 1100 is shown. Figure 11B Imaging of a patient's head is shown using an asymmetric magnetic assembly 1100. The asymmetric magnetic assembly 1100 can be formed by an asymmetric arrangement of ferromagnetic segments 1010. The ferromagnetic segments 1010 can be combined with... Figures 10A to 10C The example magnetic fittings 1000 are the same as those described.

[0151] In some embodiments, the ferromagnetic segment 1010 of the asymmetric magnetic fitting 1100 may be positioned to form a hole along a common longitudinal direction A. The ferromagnetic segment 1010 may be positioned in two asymmetric portions 1100a and 1100b on opposite sides of the hole. The asymmetric portions 1100a and 1100b may have different arrangements of the ferromagnetic segment 1010. For example, portion 1100a may be shaped to provide a curved inner surface adjacent to the hole (e.g., similar to a cylindrical hole), while portion 1100b may be shaped to provide a substantially flat inner surface adjacent to the hole. The curved inner surface of portion 1100a may provide space to accommodate components of the patient to be imaged (e.g., the patient's head, legs, arms, feet, and / or hands), while the flat inner surface of portion 1100b may provide support for adjacent portions of that portion or the patient's anatomical structures.

[0152] In some embodiments, the ferromagnetic segment 1010 may be positioned to provide a substantially uniform magnetic field of desired strength in the central region of the aperture (e.g., the field of view (FOV) or imaging region). Alternatively, the ferromagnetic segment 1010 and the non-ferromagnetic segment (not shown) within the asymmetric magnetic assembly 1100 may be positioned to provide a magnetic field of desired strength and uniformity in the central region of the aperture. For example, the BO magnetic field may have a uniformity of 500 ppm over a volume having a diameter of approximately 20 cm (or any other diameter in the range of 15-25 cm). Alternatively, the BO magnetic field may have uniformity in the range of 10 ppm to 1000 ppm, 100 ppm to 500 ppm, 500 ppm to 1000 ppm, 200 ppm to 800 ppm, or any other suitable range within the aforementioned ranges over a volume having a diameter of approximately 20 cm (or any other diameter in the range of 15-25 cm). In some embodiments, the BO magnetic field within the central region of the aperture of the rectangular magnetic fitting 1000 may have an intensity in the range of 0.05T to 0.2T. Alternatively or additionally, the BO magnetic field may have an intensity in the range of 0.05T to 0.1T (e.g., 0.064T).

[0153] In some embodiments, such as in combination Figures 10A to 10C As described, the ferromagnetic segment 1010 of portion 1100a can be positioned to form a gap, wherein the gap is configured to receive the insertion of panel 1030 (not shown) to provide additional magnetic components for the MRI system. In some embodiments, the opposing panel 1030 can be positioned on a substantially flat surface of portion 1100b of the asymmetric magnetic assembly 1100.

[0154] In some embodiments, the aperture of the asymmetric magnetic fitting 1100 may have an asymmetric cross-section with a width and height selected to accommodate a patient's head, arms, legs, hands, and / or feet. For example, to accommodate a patient's head, the aperture of the asymmetric magnetic fitting 1100 may have a partial or semi-circular cross-section with a radius of 18 cm on one side and a rectangular cross-section (36 cm wide, located 14 cm from the center of the semi-circular portion of the aperture) on the other side. In such embodiments, the length of the asymmetric magnetic fitting 1100 may be less than or equal to 45 cm. For such a size, the asymmetric magnetic fitting 1100 may comprise approximately 85 kg or less of permanent magnet material, or 100 kg or less of permanent magnet material, or 120 kg or less of permanent magnet material. Alternatively, for fittings of other sizes (e.g., to accommodate smaller portions of a patient's constituent structures), the weight of the permanent magnet material may range from 50 kg to 120 kg, from 60 kg to 90 kg, or any range within these ranges.

[0155] Figure 12A and Figure 12B A diagram illustrates a magnetic fitting 1200, comprising a gap for insertion into one or more panels, according to some embodiments of the technology described herein. The magnetic fitting 1200 can be configured in a manner similar to a coupling. Figures 5A to 5C The magnetic fittings 500a, 500b, and 500c are described in a manner that allows for assembly. In some embodiments, the magnetic fitting 1200 may include a ferromagnetic segment 1210 positioned to form a hole extending along a common longitudinal direction. The ferromagnetic segment 1210 may be composed of... Figures 2A to 2B The ferromagnetic segment 210 is formed of the same material and can be made of the same material as the ferromagnetic segment 210. Figures 2A to 2B The ferromagnetic segment 210 is formed in the same way.

[0156] In some embodiments, the magnetic assembly 1200 may include a non-ferromagnetic sheet 1230. The non-ferromagnetic frame segment 1230 may be composed of... Figures 5B to 5C The non-ferromagnetic sheet 1230 is made of the same material or formed in the same manner as the ferromagnetic segment 1210. The non-ferromagnetic sheet 1230 can be configured to accommodate the ferromagnetic segment 1210 and can be formed as annular and / or semi-annular slices of a hollow cylinder extending along the holes of the magnetic fitting 1200. The non-ferromagnetic sheets 1230 can be glued together to form the magnetic fitting 1200. Alternatively or additionally, the non-ferromagnetic sheets 1230 can be secured together using threaded rods and suitable nuts to form the magnetic fitting 1200.

[0157] In some embodiments, such as in combination Figures 10A to 10CAs described in the embodiments, the ferromagnetic segment 1210 can be positioned to accommodate a panel 1030 or other substantially planar component inserted into a corresponding gap. Alternatively, a non-ferromagnetic sheet 1230 can be formed to provide space for the panel 1030 in the gap. For example, the non-ferromagnetic sheet 1230 can be formed as an annular ring and then cut to create a gap configured to accommodate the panel 1030. Alternatively, the non-ferromagnetic sheet 1230 can be formed as discrete segments and then assembled to leave gaps between corresponding portions of the assembly to accommodate the panel 1030 (e.g., secured in place using external fasteners).

[0158] exist Figure 13 In the illustrated embodiment, computer 1300 includes a processing unit 1301 having one or more processors and a non-transitory computer-readable storage medium 1302 that may include, for example, volatile and / or non-volatile memory. Memory 1302 may store one or more instructions to program the processing unit 1301 to perform any of the functions described herein. In addition to system memory 1302, computer 1300 may also include other types of non-transitory computer-readable media (such as storage device 1305 (e.g., one or more disk drives)). Storage device 1305 may also store one or more applications that can be loaded into memory 1302 and / or resources (e.g., software libraries) that are used by the applications.

[0159] Computer 1300 may have one or more input devices and / or output devices (such as...) Figure 13 (See devices 1306 and 1307, etc.). Furthermore, these devices can be used, in particular, to present a user interface. Examples of output devices that can be used to provide a user interface include a printer or display screen for visual presentation of output and a speaker or other sound-generating device for audible presentation of output. Examples of input devices that can be used for a user interface include keyboards and pointing devices (such as mice, touchpads, and digitizing tablets). As another example, input device 1307 may include a microphone for capturing audio signals, and output device 1306 may include a display screen for visually presenting recognized text and / or a speaker for audibly presenting recognized text. As another example, input device 1307 may include a sensor (e.g., electrodes in a pacemaker), and output device 1306 may include means configured to interpret and / or present signals collected by the sensor (e.g., means configured to generate an electrocardiogram based on signals collected by electrodes in a pacemaker).

[0160] like Figure 13As shown, computer 1300 may also include one or more network interfaces (e.g., network interface 1310) to enable communication via various networks (e.g., network 1320). Examples of networks include local area networks (LANs) or wide area networks (WANs) (such as corporate networks or the Internet). Such networks can be based on any suitable technology and can operate according to any suitable protocol, and may include wireless networks, wired networks, or fiber optic networks. Such networks may include analog and / or digital networks.

[0161] Since several aspects of at least one embodiment of the technology have been described so far, it should be understood that various changes, modifications and improvements will be readily apparent to those skilled in the art.

[0162] The embodiments of the technology described herein can be implemented in any of a number of ways. For example, the embodiments can be implemented using hardware, software, or a combination thereof. When implemented in software, the software code can be executed on any suitable processor or set of processors, whether the software is located in a single computer or distributed among multiple computers. Such a processor can be implemented as an integrated circuit, with one or more processors in an integrated circuit assembly (including commercially available integrated circuit assemblies known in the art, such as those called CPU chips, GPU chips, microprocessors, microcontrollers, or coprocessors). Alternatively, the processor can be implemented in custom circuitry (such as ASICs) or in a semi-custom circuitry obtained by configuring programmable logic devices. As yet another alternative, the processor can be part of a larger circuit or semiconductor device, whether commercially available, semi-custom, or custom. As a specific example, some commercially available microprocessors have multiple cores, such that one or a subset of these cores can constitute a processor. However, the processor can be implemented using circuitry of any suitable format.

[0163] Furthermore, the various methods or processes outlined herein can be encoded as software executable on one or more processors running any of a variety of operating systems or platforms. Such software can be written using any of a number of suitable programming languages ​​and / or programming tools, including scripting languages ​​and / or scripting tools. In some instances, such software can be compiled into executable machine language code or intermediate code that executes on a framework or virtual machine. Additionally or alternatively, such software can be interpreted.

[0164] The techniques disclosed herein can be embodied in a non-transitory computer-readable medium (or multiple computer-readable media) (e.g., computer memory, one or more floppy disks, compact disks, optical disks, magnetic tapes, flash memory, circuit configurations in field-programmable gate arrays or other semiconductor devices, or other non-transitory tangible computer storage media) encoding one or more programs, which, when executed on one or more processors, perform methods for implementing the various embodiments of this disclosure described above. The computer-readable medium or media can be transportable, such that one or more programs stored on the computer-readable medium or media can be loaded onto one or more different computers or other processors to implement the various aspects of this disclosure as described above.

[0165] As used herein, the terms "program" or "software" refer to any type of computer code or set of computer executable instructions (which can be used to program one or more processors to implement the various aspects of this disclosure as described above). Furthermore, it should be understood that, according to one aspect of this embodiment, one or more computer programs (that perform the methods of this disclosure when executed) do not need to reside on a single computer or processor, but can be distributed in a modular manner among multiple different computers or processors to implement the various aspects of this disclosure.

[0166] The various aspects of the technology described herein can be used alone, in combination, or in various arrangements not specifically described in the foregoing embodiments, and therefore their application is not limited to the details and arrangements of the components set forth in the foregoing specification or shown in the figures. For example, an aspect described in one embodiment can be combined in any manner with aspects described in other embodiments.

[0167] Furthermore, the techniques described in this article can be embodied as methods, including references. Figure 8 Examples of methods are provided. The actions performed as part of a method can be ordered in any suitable manner. Thus, embodiments can be constructed that perform actions in a different order than that shown, wherein the embodiments may include some actions performed simultaneously, even if they are shown as sequential actions in the illustrative embodiments.

[0168] The use of ordinal terms such as “first,” “second,” and “third” to modify a claim element does not imply any priority, order, or sequence of action of one claim element relative to another, or the chronological order of the method actions. Rather, it serves only as a marker to distinguish one claim element with a specific name from another element with the same name (but using ordinal terms) to differentiate claim elements.

[0169] Furthermore, the wording and terminology used herein are for descriptive purposes and should not be considered restrictive. The use of “including,” “comprising,” or “having,” “containing,” “involving,” and variations thereof in this document is intended to cover the items listed thereafter and their equivalents, as well as any additional items.

[0170] The terms "approximately," "substantially," and "about" may be used in some embodiments to indicate within ±20% of the target value, in some embodiments to indicate within ±10% of the target value, in some embodiments to indicate within ±5% of the target value, and in some embodiments to indicate within ±2% of the target value. The terms "approximately," "substantially," and "about" may include the target value.

Claims

1. An assembly for providing a B0 magnetic field for an MRI system, said assembly comprising: A plurality of rods extending along a common longitudinal direction and positioned to form holes extending along the common longitudinal direction, the plurality of rods including a first rod comprising: Ferromagnetic segments, wherein each ferromagnetic segment has net magnetization in a plane substantially perpendicular to the common longitudinal direction; and Non-ferromagnetic segment The rods of the plurality of rods have different lengths and are positioned such that the assembly, when used as part of an MRI system, accommodates the patient’s shoulder inserted into the perimeter of the opening.

2. The assembly according to claim 1, wherein, The non-ferromagnetic segment and the ferromagnetic segment are interspersed within the first rod.

3. The assembly according to claim 1, wherein, The first rod includes a sub-rod composed of one or more of the nonferromagnetic segments, and each end of the sub-rod is adjacent to one of the ferromagnetic segments.

4. The assembly according to claim 1, wherein, The plurality of rods are positioned to provide a substantially uniform magnetic field within the imaging area of ​​the aperture.

5. The assembly according to claim 1, wherein, The ferromagnetic segments are essentially all the same size and shape.

6. The assembly according to claim 5, wherein, The first non-ferromagnetic segment in the non-ferromagnetic segment has substantially the same size and shape as the first ferromagnetic segment in the ferromagnetic segment.

7. The assembly according to claim 1, wherein, The first ferromagnetic segment in the ferromagnetic segment is cylindrical.

8. The assembly according to claim 1, wherein, The first ferromagnetic segment of the ferromagnetic segment is shaped into a truncated cylinder, the truncated cylinder having a first flat surface along the common longitudinal direction and a second flat surface opposite to the first flat surface.

9. The assembly according to claim 8, wherein, The first ferromagnetic segment of the ferromagnetic segment has a third flat surface extending from the first flat surface to the second flat surface along the common longitudinal direction.

10. The assembly according to claim 9, wherein, The net magnetization of the first ferromagnetic segment in the ferromagnetic segment is oriented at a specified angle to the third flat surface in a direction substantially perpendicular to the common longitudinal direction.

11. The assembly according to claim 1, wherein, The hole is a cylindrical hole.

12. The assembly according to claim 1, wherein, The hole is a rectangular hole.

13. The assembly according to claim 1, wherein, Each of the plurality of rods has the same length.

14. The assembly according to claim 1, wherein, The plurality of rods includes a first set of rods having a first length and a second set of rods having a second length shorter than the first length, the second set of rods being positioned on opposite lateral sides of the hole to form a shoulder opening, and the first set of rods being positioned to extend longitudinally beyond the shoulder opening.

15. The assembly according to claim 1, wherein, The plurality of rods are positioned to form a shoulder opening with an S-shaped profile at the proximal end of the hole.

16. The assembly according to claim 1, wherein, The rods of the plurality of rods are positioned in a single layer around the hole.

17. The assembly according to claim 1, wherein, The rods of the plurality of rods are positioned in multiple concentric layers around the hole.

18. The assembly according to claim 1, wherein, The length of the hole along the common longitudinal direction is substantially equal to the width of the hole.

19. The assembly according to claim 1, wherein, The length of the hole along the common longitudinal direction is substantially equal to twice the width of the hole.

20. The assembly according to claim 1, wherein, The weight of the assembly is less than 120 kg.

21. The assembly according to claim 1, wherein, The weight of the assembly is less than 70 kg.

22. The assembly according to claim 1, wherein, The plurality of rods are housed within a non-ferromagnetic frame.

23. The assembly according to claim 1, wherein, The plurality of rods includes a first portion and a second portion, wherein the first portion includes a rod arrangement different from that of the second portion.

24. The assembly according to claim 23, wherein, The first part and the second part are separated by a gap.

25. The assembly according to claim 1, wherein, The plurality of rods includes a plurality of rods that are at least partially cylindrical.

26. An MRI system, comprising: Assembly according to any one of claims 1 to 25; Gradient coil; At least one radio frequency transmitting coil; as well as A power system configured to provide power to the gradient coil and the at least one radio frequency transmitting coil.

27. The MRI system according to claim 26, wherein, One of the multiple rods is positioned such that, when the assembly is part of the MRI system, the assembly accommodates the insertion of a laminate at a location within the assembly and outside the opening.

28. The MRI system according to claim 27, wherein, The laminate has at least one gradient coil among the gradient coils patterned on the laminate.

29. The MRI system according to claim 27, wherein, One of the plurality of rods is positioned such that, when the assembly is part of the MRI system, the assembly accommodates the insertion of a first laminating plate into a first gap on a first side of the aperture and the insertion of a second laminating plate into a second gap on a second side of the aperture opposite to the first side of the aperture.

30. The MRI system according to claim 26, wherein, The gradient coil is positioned inside the hole formed by the plurality of rods.

31. The MRI system according to claim 26, wherein, The gradient coil is positioned outside the hole formed by the plurality of rods.

32. A method for acquiring magnetic resonance images, comprising: At least one magnetic resonance image is captured using the MRI system according to any one of claims 26 to 31.

33. A method of manufacturing an assembly for providing a B0 magnetic field for an MRI system, the method comprising: Access information on the segment layout of each of a plurality of bars, the segment layout including a first layout of a first bar of the plurality of bars, the first layout indicating the positions of ferromagnetic and non-ferromagnetic segments in the first bar and the net magnetization orientation of at least some of the ferromagnetic segments; Obtain ferromagnetic and nonferromagnetic segments; Based on the information regarding the specified segment layout, the plurality of rods are assembled using the ferromagnetic segments and the non-ferromagnetic segments, the assembly comprising: The first rod is assembled according to the first arrangement by orienting at least some of the ferromagnetic segments based on the net magnetization orientation, using at least some of the ferromagnetic segments and at least some of the non-ferromagnetic segments; and The plurality of rods are assembled in an arrangement in which the plurality of rods extend along a common longitudinal direction and form a hole extending along the common longitudinal direction. The assembly of the plurality of rods also includes assembling rods of different lengths and positioning the rods such that the assembly, when used as part of an MRI system, accommodates the patient’s shoulder inserted into the perimeter of the opening.

34. The method according to claim 33, wherein, Assembling the plurality of rods into the arrangement also includes assembling the plurality of rods such that, when the assembly is part of the MRI system, the assembly accommodates the insertion of a laminate at a location within the assembly and outside the opening.

35. The method according to claim 34, wherein, Assembling the plurality of rods into the arrangement further includes assembling a rod of the plurality of rods such that, when the assembly is part of the MRI system, the assembly accommodates insertion of the laminate at a position outside the aperture, with a first laminate of the laminate inserted at a first position within the assembly and on one side of the aperture, and a second laminate of the laminate inserted at a second position within the assembly and on the opposite side of the aperture.

36. The method according to claim 33, wherein, Assembling the plurality of rods into the arrangement further includes arranging the plurality of rods into a first part and a second part, the first part comprising a rod arrangement different from that of the second part.

37. The method of claim 36, wherein, Arranging the plurality of rods into the first portion and the second portion includes arranging the first portion and the second portion such that the hole is positioned between the first portion and the second portion, and the first portion and the second portion are separated by a gap.

38. The method according to claim 33, wherein, Assembling the first rod also includes: At least some of the ferromagnetic segments are oriented according to their net magnetization orientation in a plane substantially perpendicular to the common longitudinal direction.

39. The method according to claim 33, wherein, Orienting at least some of the ferromagnetic segments further includes: Orient at least some of the ferromagnetic segments in a direction determined based on the physical properties of each of the at least some of the ferromagnetic segments.

40. The method according to claim 39, wherein, The ferromagnetic segment includes a first ferromagnetic segment, which is shaped as a truncated cylinder and has a first flat surface, a second flat surface parallel to the first flat surface, and a third flat surface extending from the first flat surface to the second flat surface, wherein the physical properties of the first ferromagnetic segment include the third flat surface.

41. The method according to claim 33, wherein, Assembling the first rod includes: Assemble the first rod to include: Sub-stem, comprising one or more of the said nonferromagnetic segments; and One of the ferromagnetic segments, which is adjacent to each end of the sub-rod.

42. The method according to claim 41, wherein, Assembling the first rod includes: This causes the ferromagnetic segment to be mixed with the non-ferromagnetic segment.

43. The method of claim 38, further comprising: Determine the segment layout of each of the plurality of rods.

44. The method according to claim 43, wherein, Determining the segment layout includes: Cone programming is used to determine the positions of ferromagnetic and non-ferromagnetic segments among a plurality of segment locations, as well as the net magnetization orientation of at least some of the ferromagnetic segments.

45. The method according to claim 44, wherein, Determining the segment layout includes: Integer programming and cone constraints are used to determine the positions of ferromagnetic and non-ferromagnetic segments in a plurality of segment locations, as well as the net magnetization orientation of at least some of the ferromagnetic segments.

46. ​​The method according to claim 45, wherein, Determining the segment layout also includes: The orientation of net magnetization at each segment position is determined to be located in a plane perpendicular to the common longitudinal direction.

47. The method of claim 33, further comprising manufacturing the ferromagnetic segment at least in part by: Magnetic metal alloy powder is placed into a tube with a desired cross-sectional area; A magnetic field is applied to the magnetic metal alloy powder while pressing the magnetic metal alloy powder and the tube together; The magnetic metal alloy powder is solidified to obtain a solid magnetic metal alloy; Magnetize the solid magnetic metal alloy; The solid magnetic metal alloy is segmented to form ferromagnetic segments.

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