DEVICE, SYSTEM AND METHOD FOR OBTAINING MAGNETIC MEASUREMENTS USING PERMANENT MAGNETS - Patent application

Abstract

To provide a magnetic measurement system having a sufficient uniformity and / or stability and / or reducing the total weight.SOLUTION: A magnetic device 200 includes: a first magnet 201; a first ferromagnetic element 202 adjacent to the first magnet; a second magnet 221; a second ferromagnetic element 222 arranged for the first ferromagnetic element, the second ferromagnetic element being adjacent to the second magnet to generate a gap between the first ferromagnetic element and the second ferromagnetic element; and a third magnet 230 arranged in the gap between the first ferromagnetic element and the second ferromagnetic element.SELECTED DRAWING: Figure 1B

Description

[Technical field]

[0001] Generally, the present invention relates to magnetic devices, and more particularly, to devices, systems and methods for obtaining magnetic measurements. [Background technology]

[0002] Electromagnetic-based instruments can be used to measure the properties of a substance and / or to identify its composition. For example, electromagnetic-based instruments can be used to perform magnetic resonance spectroscopy to obtain physical, chemical and / or structural information about a substance (e.g., a molecule). Typically, to perform magnetic resonance spectroscopy and provide, for example, high-quality measurements (e.g., high-resolution images and / or image contrast) of an object / subject, it may be desirable for the magnetic field in the zone of measurement (e.g., the area in which the object to be measured is placed) to be substantially stable and / or uniform. Other applications (e.g., magnetic resonance imaging (MRI)) may also require high, stable and / or uniform magnetic field strength.

[0003] Some systems that use magnetic fields for measurement can include a magnetic coil with the application of a current to the coil to generate the magnetic field, while other systems can utilize permanent magnets, which typically do not require the application of a current, to generate the magnetic field.

[0004] One difficulty in using permanent magnet(s) to generate a sufficient (e.g., substantially stable and / or uniform) magnetic field in a measurement zone for magnetic resonance spectroscopy and / or magnetic imaging is that the magnetic field generated by the permanent magnet(s) is non-uniform and therefore can typically result in a non-uniform magnetic field in the zone of measurement.

[0005] Some current solutions for producing a uniform and / or stable magnetic field in the zone of measurement using permanent magnets are to add additional elements (e.g., coils) to the imaging device and / or increase the size of the permanent magnet. One difficulty with current solutions is that as the number of elements in a magnetic measurement device increases and / or the size of the permanent magnet increases, the weight, size and / or cost of the device can increase.

[0006] Another difficulty with current solutions is that heavy magnetic measuring devices can result in lack of mobility. For example, for magnetic measuring devices in a hospital environment (e.g., magnetic resonance imaging (MRI) devices), heavy and / or large devices can prevent hospital staff from moving the MRI. This can lead to further difficulties when imaging patients (e.g., patients on multiple life support and / or monitoring equipment) who can be difficult to move.

[0007] In another example, for magnetic measurement devices in industrial environments (e.g., nuclear magnetometry (NMR) devices that measure fluid and / or drilling mud properties in oil production facilities), heavy and / or large devices may prevent personnel from measuring the fluid / mud at various locations during the process.

[0008] Therefore, it may be desirable to achieve a desired magnetic field strength that has sufficient uniformity and / or stability and / or reduces the overall weight of the magnetic measurement system. Summary of the Invention [Means for solving the problem]

[0009] Therefore, according to some embodiments of the present invention, a magnetic field device is provided that includes a first magnet, a first ferromagnetic element disposed adjacent to the first magnet, a second magnet, a second ferromagnetic element disposed adjacent to the second magnet and relative to the first ferromagnetic element to create a gap between the first ferromagnetic element and the second ferromagnetic element, and a third magnet disposed in the gap between the first ferromagnetic element and the second ferromagnetic element.

[0010] In some embodiments, the third magnet has a first surface facing the first surface of the first ferromagnetic element and a second surface facing the first surface of the second ferromagnetic element. In some embodiments, the first surface of the third magnet abuts the first surface of the first ferromagnetic element and the second surface of the third magnet abuts the first surface of the first ferromagnetic element. In some embodiments, the third magnet has dimensions that allow the third magnet to translate between a first position and a second position, the first position being the first surface of the first ferromagnetic element and the second position being the first surface of the second ferromagnetic element.

[0011] In some embodiments, the magnetic field device further includes a fourth magnet disposed in the gap between the first ferromagnetic element and the second ferromagnetic element. In some embodiments, the fourth magnet has a first surface facing the first surface of the first ferromagnetic element and a second surface facing the first surface of the second ferromagnetic element. In some embodiments, the fourth magnet has dimensions that allow the fourth magnet to translate between a first position and a second position, the first position being the first surface of the first ferromagnetic element and the second position being the first surface of the second ferromagnetic element.

[0012] In some embodiments, the first magnet, the second magnet, and the third magnet are permanent magnets, superconducting magnets, or resistive magnets. In some embodiments, the first magnet, the second magnet, and the third magnet have dimensions based on the desired magnetic field strength, the type of subject to be imaged, or any combination thereof. In some embodiments, the first magnet, the second magnet, and the third magnet have a length between 10 and 1100 mm, a width between 10 and 300 mm, and a height between 45 and 200 mm.

[0013] In some embodiments, the gap has a dimension based on the type of subject being imaged. In some embodiments, the gap has a diameter of 190 millimeters. In some embodiments, the magnetic field device further includes at least one fifth magnet coupled to the first magnet.

[0014] In some embodiments, the third magnet is positioned to provide a reduction in the magnetic field flanking the magnetic field device, in some embodiments, a first axis of the magnetic field device is defined as passing from the first ferromagnetic element to the second ferromagnetic element, the first magnet and the second magnet are positioned to provide a magnetic field with a magnetization direction along the first axis, and the third magnet is positioned to provide a magnetic field with a magnetization direction along the first axis.

[0015] In some embodiments, the magnetization direction of the third magnet is opposite to the magnetization direction of the first magnet. In some embodiments, the magnetic field device is disposed within the outer shell, and the outer shell comprises a metal alloy. In some embodiments, at least one of the first and second magnets emits a magnetic field with a predetermined magnetic field strength, and the third magnet emits a magnetic field with a predetermined magnetic field strength, and the strength of the magnetic field of at least one of the first and second magnets is substantially greater than the strength of the magnetic field of the third magnet. In some embodiments, the total magnetic field generated during operation of the magnetic field device is substantially uniform and uniform within the gap.

[0016] Therefore, according to some embodiments of the present invention, there is provided a method of directing a magnetic field into a measurement volume, the method comprising the steps of generating a first magnetic field having a first field strength in a first direction, distributing the first magnetic field into the measurement volume to produce a substantially uniform magnetic flux, and increasing the total magnetic flux into the measurement volume by directing a second magnetic field having a second field strength in a second direction, the second direction being parallel to the first direction.

[0017] In some embodiments, the method further includes directing a third magnetic field into the measurement volume in a third direction, the third direction being perpendicular to the first direction. In some embodiments, the method further includes disposing a subject within the measurement volume and performing a magnetic field analysis on the subject.

[0018] In some embodiments, at least one of the first magnetic field strength and the second magnetic field strength is between 0.5 and 1.5 Tesla. In some embodiments, the first magnetic field strength and first direction and the second magnetic field strength and second direction are based on the size of the measurement volume, the type of object being measured, or any combination thereof. In some embodiments, the total magnetic flux in the measurement volume is a substantially uniform field.

[0019] Therefore, in accordance with some embodiments of the present invention, there is provided a magnetic field device including a first magnet, a first ferromagnetic element disposed adjacent to the first magnet, a second magnet, a second ferromagnetic element disposed adjacent to the second magnet and relative to the first ferromagnetic element to create a gap between the first ferromagnetic element and the second ferromagnetic element, a third magnet disposed in the gap between the first ferromagnetic element and the second ferromagnetic element, and a shell disposed a predetermined distance from the first magnet and the second magnet to cover at least the first magnet and the second magnet, the predetermined distance being based on a desired magnetic field strength and a thickness of the shell corresponding to the predetermined distance.

[0020] Therefore, according to some embodiments of the present invention, there is provided a method of directing a magnetic field into a measurement volume, the method comprising the steps of generating a first magnetic field having a first magnetic field strength in a first direction, distributing the first magnetic field into the measurement volume to produce a substantially uniform magnetic flux, increasing the total magnetic flux into the measurement volume by directing a second magnetic field having a second magnetic field strength in a second direction, the second direction being parallel to the first direction, and determining a distance from the measurement volume at which the first and second magnetic field strengths can be generated for placing a shell based on the size of the measurement volume, wherein placing the shell at that distance from the measurement volume substantially eliminates the magnetic field outside the shell.

[0021] The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however, both as to organization and method of operation, together with its objects, features and advantages, may be understood by reference to the following detailed description when read in conjunction with the accompanying drawings.

[0022] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, dimensions of some elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. [Brief description of the drawings]

[0023] [Figure 1A] 1A and 1B illustrate schematic perspective and cross-sectional views of a magnetic field device according to an illustrative embodiment of the present invention; [Figure 1B] 1B illustrates a schematic perspective cross-sectional view of a magnetic field device having an additional magnet to the device of FIG. 1A according to an illustrative embodiment of the present invention. [Figure 2A] 1A and 1B illustrate schematic cross-sectional front and front views of a magnetic field device according to an illustrative embodiment of the present invention; [Figure 2B] 1A and 1B show schematic front and cross-sectional views of a magnetic field device with an additional magnet according to an illustrative embodiment of the present invention; [Diagram 3] 1 shows a flowchart for a method for directing a magnetic field into a measurement volume, according to an illustrative embodiment of the present invention. [Figure 4A] 1A-1D show schematic top cross-sectional views of various magnetic field devices according to illustrative embodiments of the present invention; [Figure 4B] 1A-1D show schematic top cross-sectional views of various magnetic field devices according to illustrative embodiments of the present invention; [Figure 4C] 1A-1D show schematic top cross-sectional views of various magnetic field devices according to illustrative embodiments of the present invention; [Figure 4D] 1A-1D show schematic top cross-sectional views of various magnetic field devices according to illustrative embodiments of the present invention; [Figure 4E] 1A-1D show schematic top cross-sectional views of various magnetic field devices according to illustrative embodiments of the present invention; [Figure 4F] 1A-1D show schematic top cross-sectional views of various magnetic field devices according to illustrative embodiments of the present invention; [Figure 4G] 1A-1D are schematic top cross-sectional views of various magnetic field devices according to illustrative embodiments of the present invention; 1B-1D are schematic top cross-sectional views of various magnetic field devices according to illustrative embodiments of the present invention; [Figure 4H] 1A-1D show schematic top cross-sectional views of various magnetic field devices according to illustrative embodiments of the present invention; [Figure 5A] 1A and 1B illustrate schematic cross-sectional front and front views of a magnetic field device according to an illustrative embodiment of the present invention; [Figure 5B] 1A and 1B illustrate schematic cross-sectional front and front views of a magnetic field device according to an illustrative embodiment of the present invention; [Figure 6] 1 shows a schematic front cross-sectional view of a head magnetic field device, according to an illustrative embodiment of the present invention; [Figure 7] 1 shows a graph of the fringe magnetic field as a function of distance from the magnet to the shell in accordance with an illustrative embodiment of the present invention. [Figure 8]1 shows a flowchart for a method for directing a magnetic field into a measurement volume, according to an illustrative embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] In the following detailed description, numerous specific details are presented to provide a thorough understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention.

[0025] 1A is a schematic cross-sectional perspective view of a magnetic field device 100 according to an illustrative embodiment of the present invention. The magnetic field device 100 may include an outer shell 111, a first magnet 101 (e.g., a first permanent magnet), a first ferromagnetic element 102 (e.g., a first pole piece), and a second magnet 121 (e.g., a second permanent magnet) and a second ferromagnetic element 122 (e.g., a second pole piece). In some embodiments, the first magnet 101 and the first ferromagnetic element 102 and / or the second magnet 121 and the second ferromagnetic element 122 may be assembled together as a single unit (e.g., as an assembly).

[0026] The first ferromagnetic element 102 can be coupled to and / or disposed adjacent to the first magnet 101. The second ferromagnetic element 122 can be coupled to and / or disposed adjacent to the second magnet 121. In some embodiments, the magnetic field device 100 can include a third magnet 130 disposed between the first ferromagnetic element 102 and the second ferromagnetic element 122.

[0027] The first and second ferromagnetic elements 102, 122 can be coupled to and positioned adjacent to corresponding first and second magnets 101, 121 such that the first and second ferromagnetic elements 102, 122 can be proximal to a gap 150 (e.g., a zone of measurement) of the magnetic field device 100. The first magnet 101 and the second magnet 121 can be distal to the gap 150 of the magnetic field device 100. The magnetization direction of the first magnet 101 can be parallel to the magnetization direction of the second magnet 121 along a second axis (denoted as "X" in FIG. 1A), and the first and second ferromagnetic elements 102, 122 can face each other, creating a gap 150 between them.

[0028] In various embodiments, the dimensions of gap 150 (and therefore the placement of elements 102, 122, 101, 121 thereon) can depend on the subject / object being measured. For example, if the subject being measured is an adult human head, gap 150 can have dimensions that comfortably accommodate an adult human head. In another example, if the subject being measured is a mouse, gap 150 can accommodate a mouse. It will be apparent to one of skill in the art that other subjects / objects can be measured and that these are examples.

[0029] 1B is a schematic cross-sectional perspective view of a magnetic field device 200 having an additional magnet to the device of FIG. 1A according to an illustrative embodiment of the present invention. The magnetic field device 200 can include an outer shell 211, a first magnet 201, a first ferromagnetic element 202 (e.g., a first pole piece), a second magnet 221, a third magnet 230, a fourth magnet 240, a first ferromagnetic element 202, and a second ferromagnetic element 222 (e.g., a second pole piece). The first ferromagnetic element 202 can be coupled to and / or disposed adjacent to the first magnet 201. The second ferromagnetic element 222 can be coupled to and / or disposed adjacent to the second magnet 221.

[0030] In some embodiments, the magnetic field device 200 can include additional magnets, such as magnets 103, 123 in Figure 1A or magnets 203, 223 in Figure 1B. In some embodiments, magnets 103, 123 in Figure 1A are not present.

[0031] The first and second ferromagnetic elements 202, 222 can be coupled to and positioned adjacent to their corresponding first and second magnets 201, 221 such that the first and second ferromagnetic elements 202, 222 can be proximal to a gap 250 (e.g., a zone of measurement) of the magnetic field device 200. The first magnet 201 and the second magnet 221 can be distal to the gap 250 of the magnetic field device 200. The magnetization direction of the first magnet 201 can be parallel to the magnetization direction of the second magnet 221 along a second axis (denoted as "X" in FIG. 1B), and the first and second ferromagnetic elements 202, 222 can face each other, creating a gap 250 between them.

[0032] The third magnet 230 may be coupled to and disposed between the first ferromagnetic element 202 and the second ferromagnetic element 222 .

[0033] The third magnet 230 can have a first surface 231 facing the first surface 204 of the first ferromagnetic element 202 and a second surface 232 facing the first surface 224 of the second ferromagnetic element 222. The first surface 231 of the third magnet 230 can abut the first surface 204 of the first ferromagnetic element 202 and the second surface 232 of the third magnet 230 can abut the first surface 224 of the first ferromagnetic element 220. In some embodiments, the third magnet 230 can have dimensions that allow the third magnet 230 to translate between a first position and a second position, where the first position is the first surface 204 of the first ferromagnetic element 202 and the second position is the first surface 224 of the second ferromagnetic element 222.

[0034] A fourth magnet 240 can be disposed in the gap 250 between the first ferromagnetic element 202 and the second ferromagnetic element 222. The fourth magnet 240 can have a first surface 241 facing the first surface 204 of the first ferromagnetic element 202 and a second surface 242 facing the first surface 224 of the second ferromagnetic element 222. The fourth magnet 240 can have dimensions that allow the fourth magnet 240 to translate between a first position and a second position, where the first position is the first surface 204 of the first ferromagnetic element 202 and the second position is the first surface 224 of the second ferromagnetic element 222.

[0035] As will be appreciated by those skilled in the art, magnetic gradient coils (which generate a magnetic field through the application of an electrical current) can be utilized in the gap to provide a magnetic gradient, however, certain embodiments of the present invention use permanent magnets without the need for magnetic gradient coils.

[0036] In some embodiments, the first magnet 201, the second magnet 221, and the third magnet 230 are permanent magnets and / or superconducting magnets and / or resistive magnets. The first magnet 201, the second magnet 221, and the third magnet 230 can have dimensions based on the desired magnetic field strength, the type of subject to be imaged, or any combination thereof.

[0037] In some embodiments, at least one of the first magnet 201, the second magnet 221 and the third magnet 230 has a length between 10 and 1100 millimeters, a width between 10 and 300 millimeters, and a height between 45 and 200 millimeters.

[0038] Each magnet in the magnetic field device 200 has a direction of magnetization and produces a magnetic field. The dashed arrows in Figure 1B indicate the direction of magnetization of the particular magnet over which the arrow is labeled.

[0039] The first magnet 201 and the second magnet 221 can have the same magnetization direction along a first axis (denoted as “Y” in FIG. 1B), for example, a horizontal axis of the magnetic field device 200.

[0040] The magnetization direction of the third magnet 230 may be opposite to the magnetization direction of the first and second magnets 201, 221, for example along the first axis (denoted as "Y" in FIG. 1B).

[0041] In some embodiments, the first ferromagnetic element 202 and the second ferromagnetic element 222 can spread and direct the magnetic field generated by the corresponding first magnet 201 and second magnet 221 and / or reduce noise from outside the magnetic field device 200.

[0042] 2A and 2B are schematic front and cross-sectional views of a magnetic field device 200 and a magnetic field device 200 with an additional magnet, respectively, according to an illustrative embodiment of the present invention.

[0043] In some embodiments, the magnetic field device 200 can include additional magnets. For example, referring to FIG. 2B, the magnetic field device 200 can include a fifth magnet 203 and a sixth magnet 223. In some embodiments, at least one of the fifth magnet 203 and the sixth magnet 223 is a permanent magnet.

[0044] In some embodiments, the magnetic field device 200 can include additional magnets 203, 223 while a third magnet 230 can be coupled to the first and second ferromagnetic elements 202, 222.

[0045] In various embodiments, the fifth and sixth magnets 203, 223 are disposed around the first and second magnets 201, 221, respectively, with the sixth magnet 223 being disposed around the second magnet 221, as an example.

[0046] The fifth and sixth magnets 203, 223 can have a magnetization direction perpendicular to the magnetization direction of the first magnet 201 along a second axis (denoted as "X" in FIG. 2B) perpendicular to the first axis, e.g., the longitudinal axis of the magnetic field device 200. According to some embodiments, the magnetization direction of the at least one fifth magnet 203 can be away from the first magnet 201 and the magnetization direction of the at least one sixth magnet 223 can be toward the second magnet 221.

[0047] As will be apparent to one of ordinary skill in the art, additional magnets can be included in the magnetic field device 200. For example, in some embodiments, additional third magnets, fifth magnets and / or the first magnet can be used.

[0048] In some embodiments, the exterior shell 211 can include a metal alloy, allowing the magnetic field generated by the magnets of the magnetic field device 200 to be contained (or substantially contained) within the exterior shell 211. In this manner, there can be zero and / or negligible presence of the magnetic field outside the exterior shell 211. For example, if a device susceptible to magnetic fields (e.g., a cell phone, a pacemaker, etc.) is placed outside the device 200 adjacent to the exterior shell 211, the effect that the magnetic field at that location may have on the device is negligible. In some embodiments, the exterior shell 111 can also have an opening to provide access to the gap 250.

[0049] In various embodiments, the third magnet 230 and / or the fourth magnet 240 can have a hollow structure and surround the gap 250 between the first and second ferromagnetic elements 202, 222. In various embodiments, the third magnet 230 and / or the fourth magnet 240 can be provided in various shapes and sizes, for example, cylindrical or triangular in shape and size.

[0050] In the case where the magnetic field device 200 is used for magnetic resonant imaging, additional electromagnetic elements such as a radio frequency (RF) generator or a field sensor can be included. For example, to prevent radiation leakage from the additional electromagnetic elements, e.g., an RF generator in the magnetic resonance device, the third magnet 230 can be configured to surround the gap 250 between the first and second ferromagnetic elements 202, 222. For example, the third magnet 230 can be in the shape of a hollow cube or hollow cylinder surrounding the gap 250 to prevent radiation leakage from the additional electromagnetic elements outside the third magnet 230.

[0051] The third magnet 230 can contribute to making the overall magnetic field uniform and / or homogeneous in the area of ​​measurement for the magnetic field device 200. The third magnet 230 can, for example, allow for a reduction in size, weight, and / or magnetic field strength of the first and / or second magnets 201, 221 and / or the fifth and / or sixth magnets 203, 223 due to the contribution of the third magnet 230 to the overall magnetic field strength in the gap. The reduction in size of the first and / or second magnets 201, 221 and / or the fifth and / or sixth magnets 203, 223 can, for example, allow for a magnetic field device with substantially the same field strength to have a lower weight compared to a magnetic field device that does not include the third magnet 230.

[0052] In some embodiments, the magnetic field device 200 includes two fifth magnets 203 and also includes two sixth magnets 223. In these embodiments, the ability to reduce the size of the magnets, for example due to the third magnet 230, can provide even further weight reduction of the magnetic field device.

[0053] In some embodiments, at least one of the first and second magnets 201, 221 can emit a magnetic field having a predetermined magnetic field strength, and the third magnet 230 can emit a magnetic field having a predetermined magnetic field strength, and the magnetic field strength of at least one of the first and second magnets 201, 221 can be substantially greater than the magnetic field strength of the third magnet 230.

[0054] According to some embodiments, the outer shell 211 may constitute a majority of the weight of the magnetic field device 200. The addition of the third magnet 230 may provide a uniform and homogeneous magnetic field as well as reduce the weight of other components, making it possible to utilize an outer shell with reduced weight. In some embodiments, the overall weight of the magnetic field device 200 may be reduced, for example, by at least 20 percent, compared to a device without the third magnet. In some embodiments, the magnetic field strength may be increased, for example, by at least 30 percent, compared to a device without the third magnet but having substantially the same overall weight as the magnetic field device 200. The third magnet 230 may allow for a stronger magnetic field and / or a lower overall magnet weight to be obtained.

[0055] In some embodiments, the area of ​​the fringe field from the center of the gap can be reduced, for example, the area can be reduced to substantially 100 millimeters for a field limit of about 1 Gauss (sometimes called the 1G line). The reduction in the fringe field can therefore reduce the dimensions of the outer shell 211, for example, from substantially 860×1032 millimeters to substantially 786×894 millimeters. The reduction in the outer shell 211 can accordingly result in a reduction in the overall weight of the magnetic field device 200.

[0056] The total weight of the magnetic field device can be reduced, for example, by more than 10% increase in the ratio of magnetic field strength to the total weight of at least the combination of the first and second magnets and at least one third magnet. In some embodiments, the increase in magnetic field provided by the third magnet can be greater than the increase that can be achieved by correspondingly enlarging the first and second magnets (without the third magnet). This is due to the alignment of the third permanent magnet, and also due to the scalability of the weight savings, such that the addition of magnets can result in a reduction in weight.

[0057] In some embodiments, the outer shell 211 may also have a smaller surface area compared to commercially available magnetic resonance devices due to a reduction in the fringe weight of the outer shell and / or due to a reduction in the fringe fields. Such a reduction may occur because the addition of the third magnet 230 may increase the magnetic field in the gap 250 between the first and second ferromagnetic elements 202, 222, and therefore reduce the fringe fields of the magnetic field device 200, so that the outer shell 211 no longer needs to be as heavy and large in surface area as, for example, a commercially available magnetic resonance device.

[0058] In some embodiments, additional materials including, for example, iron, can be added to the magnetic field device 200 to further confine and manipulate the magnetic field in the gap. In some embodiments, additional materials including, for example, iron and / or titanium can be added adjacent to the at least one magnet 201 and / or adjacent to the at least one ferromagnetic element 202.

[0059] It will be appreciated that regions of high magnetic flux density resulting in external fringing fields may occur adjacent to magnet connections, for example, as shown by dashed lines in Figure 4 A. In some embodiments, an external shell (or covering), typically comprising iron, surrounds the magnetic resonance device to reduce magnetic flux.

[0060] In some embodiments, the third magnet 230 can prevent at least a portion of the magnetic flux from exiting the gap (e.g., the area where the magnetic field is directed). The magnetic field device 200 can be utilized to provide a strong magnetic field while providing reduced device weight, for example, for magnetic resonant imaging, or other devices where a strong magnetic field may be essential. It will be appreciated that the addition of a third magnet can oppose the magnetic flux, for example, in the area shown by the dashed lines in FIG. 4A, to reduce, for example, fringe fields.

[0061] According to some embodiments, an existing magnetic field system including two magnets, neither of which includes a third magnet, can be modified, for example, by inserting at least one third magnet between the two magnets to increase the magnetic field in the gap and / or reduce fringe fields. For example, a comparison between three systems: a first system "A" without a third magnet, a second system "B" provided with at least one third magnet, and a third system "C" modified by adding at least one third magnet. In this example, in weight comparison with the first system "A", the second system "B" can have a reduced weight of about 5.5%, while the third system "C" can have a weight increase of about 6.5%. In this example, in comparison of field strength in the gap with the first system "A", the second system "B" can have an increase of about 15% and the third system "C" can have an increase of about 13%. In this example, in comparison to the first system "A" in fringe field reduction, the second system "B" may have about a 55% reduction and the third system "C" may have about a 16% reduction. Thus, proper placement of the third magnet can provide various advantages to new systems as well as existing systems that can be modified. It will be apparent to one skilled in the art that the examples given above provide exemplary weight reduction values ​​for illustrative purposes and that other comparative weight configurations are within the scope of the present invention.

[0062] Reference is now made to FIG. 3, which illustrates a flow chart for a method of directing a magnetic field into a measurement volume, according to some embodiments of the present invention.

[0063] The method includes generating a first magnetic field having a first field strength in a first direction, step 301. For example, first and second magnets 201 and 221 as previously described in FIG. 1B can direct the first magnetic field having the first field strength in a first direction.

[0064] The method may further include distributing a first magnetic field into the measurement volume to produce a substantially uniform magnetic flux (step 302). For example, the first ferromagnetic element 202 and / or the second ferromagnetic element 222, as previously described in FIG. 1B, may distribute the first magnetic field into the measurement volume.

[0065] The method may further include increasing the total magnetic flux into the measurement volume by directing a second magnetic field having a second magnetic field strength in a second direction, the second direction being parallel to the first direction (step 303). For example, a third magnet 230 as previously described in FIG. 1 may direct the second magnetic field having the second magnetic field strength in the second direction. In some embodiments, the method may include directing a third magnetic field having a third magnetic field strength in a third direction, the third direction being perpendicular to the first direction. For example, a fifth magnet 203 and / or a sixth magnet 223 as previously described in FIG. 2 may direct the third magnetic field having the third magnetic field strength in the third direction.

[0066] In some embodiments, the method includes placing a subject within a measurement volume and performing a magnetic field analysis on the subject (eg, by using the magnetic device 200 in an NMR device and / or an MRI device).

[0067] In some embodiments, the first, second and third magnetic fields are oriented to achieve a desired magnetic field strength. The desired magnetic field strength can be based on the particular device performing the measurement and / or the subject being measured. For example, the desired magnetic field strength can be between 0.5-1.5 T for magnetic resonance imaging of human biological tissue. As will be apparent to one of skill in the art, the desired magnetic field strengths shown are for illustrative purposes only and the desired magnetic field strength can vary based on the subject / application of the magnetic field.

[0068] In some embodiments, the first magnetic field strength and first direction and the second magnetic field strength and second direction are based on a size of the measurement volume and / or a type of object being measured, and / or any combination thereof. In some embodiments, the total magnetic flux in the measurement volume can be a substantially uniform field.

[0069] Reference is now made to FIGS. 4A-4H, which diagrammatically illustrate top cross-sectional views of some exemplary configurations for the magnetic components of a magnetic field device (e.g., magnetic field device 200) according to some embodiments of the present invention. FIG. 4A diagrammatically illustrates a first exemplary configuration, in which at least one third magnet 430 (similar to third magnet 230, as shown in FIGS. 1-2) can be disposed adjacent to, e.g., vertically, a first magnet 401 (similar to first magnet 201, as shown in FIGS. 1-2). Such an arrangement can be utilized to at least partially surround and / or cover a gap 450 (similar to gap 250, as shown in FIGS. 1-2). In some embodiments, multiple third magnets 430 can be utilized, with each second magnet 430 (e.g., primary magnet) having a different size and / or shape. In some embodiments, the fifth and sixth magnets can be positioned such that they are not in physical contact with the third magnet.

[0070] 4B illustrates a first exemplary configuration in which at least one first intermediate magnet 432 (e.g., a main magnet) can be disposed between two adjacent third magnets 430. FIGURE 4C illustrates a first exemplary configuration in which at least one second intermediate magnet 434 (e.g., a main magnet) can be disposed between adjacent third magnets 430 and the first intermediate magnet 432. In some embodiments, at least one of the first intermediate magnet 432 and / or the second intermediate magnet 434 can be a permanent magnet.

[0071] According to some embodiments, a subject (or test subject) can be introduced into the gap (or measurement region) from any one of four possible directions, e.g., due to the symmetry of the system, e.g., to adjust elements therein. In some embodiments, access can also be provided for introducing cameras, air conditioning, and / or other equipment adjacent to the gap.

[0072] FIG. 4D illustrates a first exemplary configuration, in which at least one first intermediate magnet 442 can be positioned between two adjacent third magnets 440 and at least one second intermediate magnet 444 can be positioned between two adjacent third magnets 440. Different sizes and / or shapes of the at least one first intermediate magnet 442 and the at least one second intermediate magnet 444 can allow for magnet differentiation, e.g., providing smaller magnets of different shapes at specific locations instead of a single large magnet, to allow for a desired magnetic flux in the gap 450. In cases where the shape symmetry about an axis through the center of the third magnet is broken, e.g., for magnetic field shimming and / or to create an opening that allows access to the gap, other elements (e.g., permanent magnets) can be modified to maintain a predetermined magnetic field. In some embodiments, for example, breaking the symmetry of the magnet shape may also require modification of the outer shell.

[0073] 4E illustrates a first exemplary configuration in which at least one first intermediate magnet 442 can be positioned a predetermined distance from the center of the first magnet 401 based on a predetermined magnetic field strength to allow a desired magnetic flux in the gap 450. FIG. 4F illustrates a first exemplary configuration in which at least one first intermediate magnet 442 can be positioned between two adjacent third magnets 440 and at least one second intermediate magnet 444 can be positioned between two adjacent third magnets 440. In some embodiments, the addition of at least one first intermediate magnet 442 can be configured to further support the structure of the system and / or create an at least partial magnetic cage in the gap 450.

[0074] Figure 4G illustrates a first exemplary configuration in which a ring-shaped third magnet 460 may surround the gap 450. Figure 4H illustrates a first exemplary configuration in which a hexagonal-shaped third magnet 470 may surround the gap 450. In some embodiments, an opening may be provided in the third magnet surrounding the gap 450 to allow for insertion of a subject therein.

[0075] Reference is now made to Figures 5A-5B, which illustrate a magnetic field device 500 (e.g., magnetic field device 200 as previously described in Figure 2) including a support element. Figure 5A illustrates a schematic front cross-sectional view of magnetic field device 500 having a first support element 511, according to some embodiments of the present invention. It will be appreciated that magnetic field device 500 can include all of the elements of magnetic field device 200 (e.g., as shown in Figures 1-2), with the addition of at least one first support element 511 between first ferromagnetic element 202 and second ferromagnetic element 222.

[0076] According to some embodiments, at least one third magnet 530 can be added to the first support element 511 so as to create at least one air gap (not shown) between the third magnet 530 and the first and / or second magnet 201, 221. In some embodiments, instead of an air gap, a gap of diamagnetic material can be formed therein.

[0077] FIG. 5B is a schematic diagram showing a front cross-sectional view of a magnetic field device 500 having a second support element 513 according to some embodiments of the present invention. It will be appreciated that the magnetic field device 500 can include all elements of the magnetic field device 200 (e.g., as shown in FIGS. 1-2) with the addition of at least one second support element 513. In some embodiments, the outer shell 211 (or the covering) can contact at least one third magnet 230 by at least one second support element 513 to support the placement of the third magnet 230. It will be appreciated that such support of the third magnet 230 can counter the magnetic attraction acting on the third magnet 230 so that the third magnet 230 can remain in a desired position. In some embodiments, the at least one second support element 513 can couple the third magnet 230 to the outer shell 211 and at least one of the first and second ferromagnetic elements 202, 222.

[0078] Reference is now made to FIG. 6, which shows a schematic front cross-sectional view of a head magnetic field device 600 according to some embodiments of the present invention. The head magnetic field device 600 includes a first magnet 201 and a first ferromagnetic element 202 coupled to the first magnet 201, and a second magnet 221 and a second ferromagnetic element 222 coupled to the second magnet 221. The first magnet 201 and the second magnet 221 can be arranged to create a gap 250 therebetween, and adjacent to the gap 250, the first ferromagnetic element 202 and the second ferromagnetic element 222 are arranged between the gap 250 and the first magnet 201 and the second magnet 221, respectively. The head magnetic field device 600 can also include an opening 650, which is configured to allow, for example, at least partial accommodation of the patient's head 610 in the gap 250 (or measurement volume). In some embodiments, the head magnetic field device 600 can also include at least one third magnet 230. Although the patient's head 610 is described here, it will be appreciated that other body parts, such as an arm or leg, may similarly be introduced into the gap 250 for examination.

[0079] In some embodiments, a magnetic resonance imaging element (e.g., an RF coil) can be coupled to the head magnetic field device 600 to allow imaging of the patient's head 610 in the gap 250. In an exemplary embodiment, the magnetic field strength of such a head magnet is greater than or about 4900 Gauss. In an exemplary embodiment, the field of view for MRI imaging in the gap 250 is a sphere with a diameter of about 190 millimeters. In an exemplary embodiment, the diameter of the opening 650 into the gap 250 is greater than or about 660 millimeters. In an exemplary embodiment, the dimensions for the head permanent magnet are 1226 x 1226 x 866 millimeters.

[0080] According to some embodiments, the distance between the outer shell and the magnet can be modified to achieve a modified magnetic field, hi some embodiments, the thickness of the outer shell can be modified according to the change in the distance between the outer shell and the magnet.

[0081] Reference is now made to Figure 7, which shows a graph of the fringe magnetic field as a function of distance from the magnet to the shell, according to some embodiments of the present invention. The change in the fringe magnetic field as a function of distance of the shell from the magnet (encased by the shell) is shown for constant and varying thickness of the shell, for example shell 211 as shown in Figure 1B. In some embodiments, the thickness of the shell can be varied so that the overall weight of the magnetic field device (including the shell and magnet) can be reduced.

[0082] In some embodiments, the shell can be positioned a predetermined distance from the magnet, and the predetermined distance can be based on a desired magnetic field strength. In some embodiments, the thickness of the shell corresponds to the predetermined distance. It will be appreciated that varying the distance between the shell and the magnet can also reduce fringe fields.

[0083] In some embodiments, the thickness of the shell corresponds to the inverse of the predetermined distance such that the thickness decreases with increasing distance between the shell and the magnet. In some embodiments, the thickness of the shell is based on the predetermined distance exceeding a predetermined threshold. In some embodiments, the predetermined distance is also based on the weight of the at least one magnet. In some embodiments, the predetermined distance is 50 millimeters.

[0084] The first curve 701 corresponds to a constant thickness of the shell and varies with distance relative to the fringe field along the "Y" axis as shown in FIG. 1B. The total weight of the magnetic field device can be maintained by reducing the thickness of the outer shell to a given thickness while increasing the distance of the shell from the magnet. The second curve 702 corresponds to a varying thickness of the shell and varies with distance relative to the fringe field along the "Y" axis as shown in FIG. 1B. The third curve 711 corresponds to a constant thickness of the shell and varies with distance relative to the fringe field along the "X" axis as shown in FIG. 1B. The fourth curve 712 corresponds to a varying thickness of the shell and varies with distance relative to the fringe field along the "X" axis as shown in FIG. 1B.

[0085] As can be appreciated by one skilled in the art, the fringe fields are reduced by moving the outer shell away, and at a distance of about 50 millimeters, the fringe fields are substantially reduced for all curves. Thus, reduced fringe fields can be achieved by varying the distance between the shell and the magnet.

[0086] According to some embodiments, the magnetic field within the measurement volume is substantially unaffected by the reduction in fringe fields brought about by an increase in the distance between the shell and the magnet.

[0087] Reference is now made to FIG. 8, which illustrates a flow chart for a method of directing a magnetic field into a measurement volume, according to some embodiments of the present invention.

[0088] The method includes generating a first magnetic field having a first field strength in a first direction, step 801. For example, first and second magnets 201 and 221 as previously described in FIG. 1B can direct the first magnetic field having the first field strength in a first direction.

[0089] The method may further include distributing a first magnetic field in the measurement volume to produce a substantially uniform magnetic flux (step 802). For example, the first ferromagnetic element 202 and / or the second ferromagnetic element 222, as previously described in FIG. 1B, may distribute the first magnetic field in the measurement volume.

[0090] The method may further include increasing the total magnetic flux into the measurement volume by directing a second magnetic field having a second magnetic field strength in a second direction, the second direction being parallel to the first direction (step 803). For example, a third magnet 230 as previously described in FIG. 1 may direct the second magnetic field having the second magnetic field strength in the second direction. In some embodiments, the method may include directing a third magnetic field having a third magnetic field strength in a third direction, the third direction being perpendicular to the first direction. For example, a fifth magnet 203 and / or a sixth magnet 223 as previously described in FIG. 2 may direct the third magnetic field having the third magnetic field strength in the third direction.

[0091] The method may further include determining a distance from the measurement volume at which the first magnetic field strength and the second magnetic field strength can be generated based on a size of the measurement volume for placing the shell, such that placing the shell at that distance from the measurement volume substantially eliminates the magnetic field outside the shell (step 804). For example, determining the distance from the measurement volume for placing the shell such that the magnetic field outside the shell is below a predetermined threshold.

[0092] In some embodiments, the method may further include reducing a thickness of the shell if the predetermined distance exceeds a predetermined threshold. In some embodiments, the method may further include reducing a weight of the at least one magnet if the predetermined distance exceeds a predetermined threshold and maintaining a desired magnetic field strength. In some embodiments, the predetermined distance is also based on the strength of the fringe magnetic fields.

[0093] Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or chronological order in time. In addition, some of the elements of the described methods may be omitted or repeated during the sequence of operations of the method.

[0094] Various embodiments have been presented, each of which can, of course, include features from the other embodiments presented, and embodiments not specifically described can include various features described herein.

Claims

1. 1. A magnetic field device, comprising: A first magnet, a first ferromagnetic element disposed adjacent to the first magnet; A second magnet; a second ferromagnetic element disposed adjacent to the second magnet and relative to the first ferromagnetic element to create a gap between the first ferromagnetic element and the second ferromagnetic element; a third magnet disposed at least partially between the first ferromagnetic element and the second ferromagnetic element and at least partially within the gap; and a fourth magnet disposed around the first magnet; a first axis of the magnetic field device is defined as passing through the first magnet, the first ferromagnetic element, the second ferromagnetic element and the second magnet, and a second axis of the magnetic field device is perpendicular to the first axis; the first magnet, the second magnet, and the third magnet each have a magnetization direction parallel to the first axis, the first magnet and the second magnet have the same magnetization direction, and the third magnet has a magnetization direction opposite to the magnetization direction of the first magnet and the second magnet; The fourth magnet has a magnetization direction parallel to the second axis. Magnetic field device.

2. The magnetic field device of claim 1 , wherein the third magnet has a first surface facing the first surface of the first ferromagnetic element and a second surface facing the first surface of the second ferromagnetic element.

3. 3. The magnetic field device of claim 2, wherein the first surface of the third magnet is adjacent to the first surface of the first ferromagnetic element and the second surface of the third magnet is adjacent to the first surface of the second ferromagnetic element.

4. 3. The magnetic field device of claim 2, wherein the third magnet has dimensions that allow the third magnet to translate between a first position and a second position, the first position being the first surface of the first ferromagnetic element and the second position being the first surface of the second ferromagnetic element.

5. The magnetic field device of claim 1 , wherein the first magnet, the second magnet, and the third magnet are permanent magnets, superconducting magnets, or resistive magnets.

6. The magnetic field device of claim 1 , wherein the gap has a diameter of 190 millimeters.

7. The magnetic field device of claim 1 , wherein the third magnet is positioned to provide a fringe magnetic field reduction to the magnetic field device.

8. The magnetic field device of claim 1 , wherein the magnetic field device is disposed within an exterior shell, the exterior shell comprising a metal alloy.

9. The magnetic field device of claim 1 , wherein a magnetic field strength of at least one of the first magnet and the second magnet is substantially greater than a magnetic field strength of the third magnet.

10. The magnetic field device of claim 1 , wherein a total magnetic field generated during operation of the magnetic field device is substantially uniform and homogeneous within the gap.

11. 2. The magnetic field device of claim 1, further comprising a fifth magnet disposed around the second magnet, the fifth magnet having a magnetization direction parallel to the second axis and opposite to the magnetization direction of the fourth magnet.

12. The magnetic field device of claim 1 , wherein the third magnet at least partially surrounds the gap.

13. The magnetic field device of claim 12 , wherein the third magnet comprises a plurality of magnets.

14. The magnetic field device of claim 12 , wherein the third magnet is cylindrical or triangular.

15. The magnetic field device of claim 12 , wherein the third magnet is in the shape of a hollow cube or a hollow cylinder.

16. The magnetic field device of claim 13 , wherein the third magnet comprises four magnets located at corners of the gap.

17. 17. The magnetic field device of claim 16, further comprising at least one intermediate magnet disposed between two of the four magnets of the third magnet.

18. 12. The magnetic field device of claim 11, wherein the fourth magnet comprises two magnets and the fifth magnet comprises two magnets.

19. 12. The magnetic field device of claim 11, wherein the magnetization direction of the fourth magnet is away from the first magnet and the magnetization direction of the fifth magnet is toward the second magnet.

20. The magnetic field device of claim 11 , wherein the fourth magnet and the fifth magnet are not in physical contact with the third magnet.

21. The magnetic field device of claim 1 , further comprising at least one first support element disposed between the first ferromagnetic element and the second ferromagnetic element.

22. 22. The magnetic field device of claim 21, further comprising an air gap between the third magnet and the first ferromagnetic element.

23. 22. The magnetic field device of claim 21, further comprising an air gap between the third magnet and the second ferromagnetic element.

24. 22. The magnetic field device of claim 21, further comprising an air gap between the third magnet and the first ferromagnetic element, and an air gap between the third magnet and the second ferromagnetic element.

25. an outer shell covering the magnetic field device; The magnetic field device of claim 1 , further comprising: at least one second support element disposed between the third magnet and the outer shell.

26. 26. The magnetic field device of claim 25, wherein the second support element supports the placement of the third magnet within the magnetic field device.

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