CN109085519B - Superconducting magnet magnetic field shimming system and method - Google Patents
Superconducting magnet magnetic field shimming system and method Download PDFInfo
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- CN109085519B CN109085519B CN201810886857.6A CN201810886857A CN109085519B CN 109085519 B CN109085519 B CN 109085519B CN 201810886857 A CN201810886857 A CN 201810886857A CN 109085519 B CN109085519 B CN 109085519B
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- 230000005291 magnetic effect Effects 0.000 title claims abstract description 120
- 238000000034 method Methods 0.000 title claims abstract description 13
- 238000009434 installation Methods 0.000 claims abstract description 16
- 230000005294 ferromagnetic effect Effects 0.000 claims description 7
- 239000002245 particle Substances 0.000 claims description 4
- 239000000853 adhesive Substances 0.000 claims description 2
- 230000001070 adhesive effect Effects 0.000 claims description 2
- 238000009826 distribution Methods 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 12
- 238000002595 magnetic resonance imaging Methods 0.000 abstract description 5
- 230000006698 induction Effects 0.000 abstract description 4
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 239000002131 composite material Substances 0.000 abstract description 3
- 238000010438 heat treatment Methods 0.000 abstract description 3
- 238000011900 installation process Methods 0.000 abstract description 2
- 238000012937 correction Methods 0.000 description 16
- 238000010586 diagram Methods 0.000 description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 5
- 238000013461 design Methods 0.000 description 5
- 239000007769 metal material Substances 0.000 description 5
- 239000002989 correction material Substances 0.000 description 3
- 239000003302 ferromagnetic material Substances 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000002059 diagnostic imaging Methods 0.000 description 1
- 230000005674 electromagnetic induction Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 230000004807 localization Effects 0.000 description 1
- 230000005389 magnetism Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000005405 multipole Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
- G01R33/387—Compensation of inhomogeneities
- G01R33/3873—Compensation of inhomogeneities using ferromagnetic bodies ; Passive shimming
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- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Magnetic Resonance Imaging Apparatus (AREA)
Abstract
The invention relates to a superconducting magnet magnetic field shimming system and a method for shimming a magnetic resonance superconducting magnet (such as MRI and NMR) capable of meeting the requirements of high stability and high uniformity. The advantages are that: firstly, the requirements of high stability and high uniformity of a main magnetic field can be met; secondly, due to the use of the soft magnetic composite material, the induction flow and the heating influence of the induction flow on the shimming material in the magnetic resonance magnetic field generator are canceled or reduced, so that the temperature of the shimming material is stable, the magnetic performance stability is good, and the image quality of a magnetic resonance imaging system is further improved; thirdly, because the installation device of the soft magnetic device is modularized in a segmented way, the magnetic force born by the installation device is greatly reduced during installation, so that the mechanical structure requirement is greatly reduced, the manufacturing cost is low, and the operation safety of the installation process is improved.
Description
Technical Field
The invention relates to a superconducting magnet magnetic field shimming system and method capable of meeting the shimming requirements of a magnetic resonance superconducting magnet (such as MRI and NMR) with high stability and high uniformity, and belongs to the field of manufacturing of magnetic field correction systems.
Background
(1) In magnetic resonance medical imaging systems or other fields of application, a highly stable, high homogeneity of the main magnetic field is necessary for accurate localization of the scanned image data and for correct analysis. Meanwhile, the scanning technical means requires that a dynamic gradient magnetic field for spatially positioning a scanning object is overlapped under a main magnetic field with high stability and high uniformity.
(2) Because of different factors such as design, processing precision, assembly process, installation site structure and the like, the magnetic field of the assembled magnetic field generator cannot meet the requirement of magnetic resonance imaging, and therefore, the imaging area of the magnetic field generator needs to be corrected (shimmed) by technical means. One such shimming technique is to use special metallic materials (e.g. permanent magnet materials, ferromagnetic material pieces) placed in specific locations of the magnetic field generator (typically between the magnet interior and the volume being calibrated).
(3) When placed in a soft magnetic device, a large magnetic force is generated on the soft magnetic device due to the strong magnetic field, particularly a high magnetic field magnet, such as a 3 tesla magnetic resonance magnet. In order to reduce the harm to operators, the common method is (a) to reduce the main magnetic field firstly, to put in the shimming material, and then to adjust up the main magnetic field, resulting in long installation time and high cost, or (2) to use mechanical arm for installation, increasing the installation cost
(4) According to faraday's law of electromagnetic induction, when a metallic material is placed in a varying magnetic field, an induced current is generated in the metallic material. The induced current in turn generates joule heat on the metallic material, resulting in a temperature change of the metallic material. For a shimming material, a change in temperature causes a change in the magnetic properties of the material. Thus, the uniformity of the magnetic field will be affected. Furthermore, the gradient magnetic fields generated by the gradient coils used in the magnetic resonance scanning system are not always identical, and the magnetic field variation and the time length of the gradient magnetic fields also vary according to different scanning sequences. Resulting in a change in the magnetic properties of the shim material from one case to another. The homogeneity and stability of the main magnetic field also vary.
Fig. 4-1 to 5 are schematic structural views of a general superconducting magnet and a ferromagnetic shimming system. Ferromagnetic shimming systems are typically arranged between the inner wall of the magnet and the space being shimmed. According to the measured magnetic field non-uniformity and multipole component, a plurality of independent spaces of magnetic correction devices are arranged around the inner wall of the magnet
The prior art has the following defects: firstly, a correction material formed by superposing common ferromagnetic materials or iron sheets generates eddy current in a changing magnetic field, the temperature of the material is changed due to eddy current heating, the magnetic change of the correction material is caused, and finally the magnetic field uniformity is unstable; secondly, on the high magnetic field magnet, because the magnetic force of the magnetic field on the soft magnetic device acts, unsafe factors exist in the operation process when the correction device is installed, and the time for using an automatic mechanical tool is long and the cost is high.
Disclosure of Invention
The design purpose is as follows: the system and the method for correcting the superconducting and magnet magnetic field can meet the requirements of high stability and high uniformity.
The design scheme is as follows: in order to achieve the above design objective. In the system design, the shimming material adopts a soft magnetic composite material formed by pressing ferromagnetic powder particles surrounded by an electric insulation film, namely: 1. the material also substantially retains ferromagnetic properties. 2. Because the electric insulation film surrounds the iron powder particles, eddy current cannot be generated in a changing magnetic field, so that the stability of magnetism is ensured, and the stability of the magnetic field uniformity of the magnet is ensured. 3. Each independent correction device strip is formed by combining at least two sections, and when the same magnetic field non-uniformity correction system is compared, the magnetic field force born by each correction device is reduced by half when an operator installs the correction device. The same method can be applied, if necessary, for further optimization.
Fig. 2-1 and 2-3 show the structure of a magnetic correction device, typically a single strip, on which a fixing mechanism for mounting a soft magnetic device is arranged, which is pre-mounted on the strip of the device on a table outside the magnet according to the measurement results. The correction material is usually a soft iron sheet, or a ferromagnetic block formed by stacking and combining multiple layers. Each unit of the correction device is then inserted by the operator into the correction space of the magnet for magnetic field adjustment.
Technical scheme 1: a superconducting magnet magnetic field shimming system comprises a plurality of independent soft magnetic device mounting units, wherein a plurality of soft magnetic devices are distributed on each soft magnetic device mounting unit.
Technical scheme 2: a method for installing the magnetic field shimming of superconducting magnet features that a part of independent soft magnetic device is inserted and fixed from one end of magnet and another part of independent soft magnetic device is inserted and fixed from another end of magnet, or each part of independent soft magnetic device is inserted and fixed from one end of magnet.
Compared with the background technology, the invention can meet the requirements of high stability and high uniformity of the main magnetic field; secondly, due to the use of the soft magnetic composite material, the induction flow and the heating influence of the induction flow on the shimming material in the magnetic resonance magnetic field generator are canceled or reduced, so that the temperature of the shimming material is stable, the magnetic performance stability is good, and the image quality of a magnetic resonance imaging system is further improved; thirdly, because the installation device of the soft magnetic device is modularized in a segmented way, the magnetic force born by the installation device is greatly reduced during installation, so that the mechanical structure requirement is greatly reduced, the manufacturing cost is low, and the operation safety of the installation process is improved.
Drawings
FIG. 1-1 is a schematic diagram of a soft magnetic block structure.
Fig. 1-2 are schematic diagrams of rectangular soft magnetic blocks.
Fig. 1-3 are schematic diagrams of circular soft magnetic blocks.
Fig. 2-1 is a schematic structural view of the correction device.
FIG. 2-2 is a schematic diagram of a soft magnetic block without cutting.
Fig. 2-3 are schematic structural diagrams of laminations or cut soft magnetic blocks.
Fig. 3-1 is a schematic view of the installation of the correction device from both ends of the magnet, respectively.
Fig. 3-2 is a schematic view of the sectional mounting of the correction device from one end of the magnet.
Fig. 4-1 is an axial cross-sectional schematic view of a prior art magnetic field correction system.
Fig. 4-2 is a schematic side view of fig. 4-1.
Fig. 5 is a schematic diagram of a prior art magnetic field correction system installation.
Description of the embodiments
Example 1: with reference to figures 1-1 to 3-2. A superconducting magnet magnetic field shimming system comprises a plurality of independent soft magnetic device mounting units, wherein a plurality of soft magnetic devices are distributed on each soft magnetic device mounting unit. The soft magnetic device is round or rectangular formed by solidifying ferromagnetic particles and an adhesive. Each independent soft magnetic device mounting unit consists of at least two mounting soft magnetic strips and forms a whole mounting unit. Each of the correction devices (soft magnetic device mounting units, i.e., mounting soft magnetic strips) is composed of a plurality of soft magnetic devices and a long strip plate to which the soft magnetic devices are fixed, the plurality of soft magnetic devices being distributed on the long strip plate.
One or two sides of the soft magnetic strip are attached with a plurality of soft magnetic devices. One end of the soft magnetic strip is provided with a front end, the other end is provided with a rear end, and the front end and the rear end are different in size or different in distribution structure of the soft magnetic devices.
The eddy current is greater when the soft magnetic device is not cut as in fig. 2-2; when in a laminated structure or cut as in fig. 2-3, the eddy currents are small but the manufacturing cost is high. The shape of the magnetic device may be rectangular, circular, or other
Example 2: on the basis of the embodiment 1, the soft magnetic strips can be installed in a strip shape, a drawer shape or a single-sided or double-sided shape.
Example 3: on the basis of embodiment 1, a method for installing magnetic field shimming of a superconducting magnet is provided, wherein a part of independent soft magnetic device installation units are inserted and fixed from one end of the magnet, and the other part of independent soft magnetic device installation units are inserted and fixed from the other end of the magnet, or each part of independent soft magnetic device installation units are respectively inserted and fixed from one end of the magnet.
It should be understood that: while specific embodiments of the invention have been described above in connection with the drawings, it will be appreciated by those skilled in the art that various changes, modifications and equivalents may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be appreciated that such changes, modifications, and equivalents are intended to fall within the spirit and scope as defined by the appended claims.
Claims (3)
1. A superconducting magnet magnetic field shimming system is characterized in that: the device comprises a plurality of independent soft magnetic device mounting units, wherein a plurality of soft magnetic devices are distributed on each soft magnetic device mounting unit, each independent soft magnetic device mounting unit consists of at least two mounting soft magnetic strips and forms a whole mounting unit, and one surface or two surfaces of each mounting soft magnetic strip are attached with a plurality of soft magnetic devices; the installation method of the superconducting magnet magnetic field shimming comprises the following steps: one part of independent soft magnetic device mounting units are inserted and fixed from one end of the magnet, and the other part of independent soft magnetic device mounting units are inserted and fixed from the other end of the magnet, or each part of independent soft magnetic device mounting units are respectively inserted and fixed from one end of the magnet, so that the requirements of high stability and high uniformity of a main magnetic field are met.
2. The superconducting magnet magnetic field shimming system according to claim 1, characterized in that: the soft magnetic device is round or rectangular formed by solidifying ferromagnetic particles and an adhesive.
3. The superconducting magnet magnetic field shimming system according to claim 1, characterized in that: one end of the soft magnetic strip is provided with a front end, the other end is provided with a rear end, and the front end and the rear end are different in size or different in distribution structure of the soft magnetic devices.
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| CN201810886857.6A CN109085519B (en) | 2018-08-06 | 2018-08-06 | Superconducting magnet magnetic field shimming system and method |
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| CN201810886857.6A CN109085519B (en) | 2018-08-06 | 2018-08-06 | Superconducting magnet magnetic field shimming system and method |
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| CN109085519B true CN109085519B (en) | 2024-01-23 |
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1139499A (en) * | 1993-12-30 | 1997-01-01 | 美国3M公司 | Electrically conductive tructured sheets |
| CN101545959A (en) * | 2009-04-23 | 2009-09-30 | 苏州工业园区朗润科技有限公司 | Magnetic field regulating method and set of NMR imaging equipment |
| CN201548675U (en) * | 2009-04-23 | 2010-08-11 | 苏州工业园区朗润科技有限公司 | Field adjusting equipment of nuclear magnetic resonance imaging device |
| CN102116855A (en) * | 2010-12-31 | 2011-07-06 | 奥泰医疗系统有限责任公司 | Superconducting magnet passive shimming method |
| CN102456460A (en) * | 2010-10-21 | 2012-05-16 | 通用电气公司 | Superconducting magnet having cold iron shimming capability |
| CN204834234U (en) * | 2015-08-12 | 2015-12-02 | 上海联影医疗科技有限公司 | A superconducting magnet for magnetic resonance imaging system |
-
2018
- 2018-08-06 CN CN201810886857.6A patent/CN109085519B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1139499A (en) * | 1993-12-30 | 1997-01-01 | 美国3M公司 | Electrically conductive tructured sheets |
| CN101545959A (en) * | 2009-04-23 | 2009-09-30 | 苏州工业园区朗润科技有限公司 | Magnetic field regulating method and set of NMR imaging equipment |
| CN201548675U (en) * | 2009-04-23 | 2010-08-11 | 苏州工业园区朗润科技有限公司 | Field adjusting equipment of nuclear magnetic resonance imaging device |
| CN102456460A (en) * | 2010-10-21 | 2012-05-16 | 通用电气公司 | Superconducting magnet having cold iron shimming capability |
| CN102116855A (en) * | 2010-12-31 | 2011-07-06 | 奥泰医疗系统有限责任公司 | Superconducting magnet passive shimming method |
| CN204834234U (en) * | 2015-08-12 | 2015-12-02 | 上海联影医疗科技有限公司 | A superconducting magnet for magnetic resonance imaging system |
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