CN114184990B - Magnet for magnetic resonance imaging and method for optimizing iron yoke - Google Patents
Magnet for magnetic resonance imaging and method for optimizing iron yoke Download PDFInfo
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- 238000002595 magnetic resonance imaging Methods 0.000 title claims abstract description 26
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims description 72
- 229910052742 iron Inorganic materials 0.000 title claims description 36
- 238000001646 magnetic resonance method Methods 0.000 title description 2
- 238000000034 method Methods 0.000 claims abstract description 28
- 238000005457 optimization Methods 0.000 claims abstract description 13
- 108090000623 proteins and genes Proteins 0.000 claims abstract description 6
- 238000012163 sequencing technique Methods 0.000 claims abstract description 3
- 230000004907 flux Effects 0.000 claims description 20
- 239000000463 material Substances 0.000 claims description 5
- YTAHJIFKAKIKAV-XNMGPUDCSA-N [(1R)-3-morpholin-4-yl-1-phenylpropyl] N-[(3S)-2-oxo-5-phenyl-1,3-dihydro-1,4-benzodiazepin-3-yl]carbamate Chemical compound O=C1[C@H](N=C(C2=C(N1)C=CC=C2)C1=CC=CC=C1)NC(O[C@H](CCN1CCOCC1)C1=CC=CC=C1)=O YTAHJIFKAKIKAV-XNMGPUDCSA-N 0.000 claims description 2
- 238000010586 diagram Methods 0.000 description 3
- 239000000306 component Substances 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 238000003384 imaging method Methods 0.000 description 2
- 238000003759 clinical diagnosis Methods 0.000 description 1
- 239000008358 core component Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000003745 diagnosis Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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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
- G01R33/381—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field using electromagnets
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves
- A61B5/055—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
Abstract
The magnet structure optimizing method for the magnetic resonance imaging comprises the following steps: a. arranging a plurality of magnetic blocks into a magnet ring, and placing the magnet ring with small diameter inside the magnet ring with large diameter; b. sequentially numbering a plurality of magnetic blocks on each magnet ring; c. arranging the structural parameters of a plurality of magnetic blocks to obtain a plurality of groups of magnetic block structural parameters; d. coding each structural parameter variable, and dividing a certain variable value range into a plurality of equal parts; e. all the structural parameter variables form a section of gene code; f. selecting a plurality of samples, generating a plurality of groups of structure parameter optimization initial values, calculating the magnetic field generated by the samples and the magnetic field uniformity of a target area, and sequencing, wherein adjacent two sample individuals are crossed to form a new sample individual; g. calculating the magnetic field uniformity of the target area under each structural parameter; h. repeating the steps f and g for several times. The streamline yoke optimization method is that under the condition of fixed yoke width, the thickness is adjusted according to B X ＝Ф X /(d*H X ) The formula is optimized.
Description
[ field of technology ]
The invention relates to the technical field of magnetic resonance for medical diagnosis, in particular to an optimization method of a magnet and an iron yoke for magnetic resonance imaging.
[ background Art ]
Magnetic Resonance Imaging (MRI) is an imaging technique widely used in medical clinical diagnosis and medical research. When the magnetic resonance imaging system works, a human body is placed in a strong static magnetic field, and nuclei of a partial region of human tissue are excited by transmitting radio frequency pulses to the human body. After the rf field is removed, the excited nuclei radiate rf signals that are received by the antenna. Because the gradient magnetic field is added in the process, the spatial distribution information of the human body can be obtained through the radio frequency signals, so that a two-dimensional or three-dimensional image of the human body can be reconstructed.
Since the magnet and yoke are one of the core components of a magnetic resonance imaging system, they have been an important subject of investigation. MRI apparatus require a very uniform magnetic field in the imaging region, the region of the uniform magnetic field being spherical, and an image of the imaged region being captured by scanning after the region to be imaged is placed in the spherical region. Therefore, the performance of the magnet and the yoke directly relates to the magnitude and uniformity of the magnetic field of the magnetic resonance system, which determines the sharpness of the image to some extent.
The traditional magnetic resonance system has large weight and can not meet the requirements of any department at any floor of a hospital. In order to meet the requirement of the magnetic resonance system for entering the general ward of each department, the problem of light weight of the main magnet needs to be solved first. The main factor limiting the weight of the magnet system is the iron yoke, and how to optimize the magnet and the iron yoke to realize the light weight of the equipment is a problem to be solved.
[ invention ]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for optimizing a magnet and a yoke for magnetic resonance imaging, which can maximize the magnetic flux density of the magnet by optimizing the shape of the magnet and the yoke so as to form a highly uniform magnetic field in a target region and reduce the amount of yoke material used as much as possible, thereby reducing the weight of the magnetic resonance imaging apparatus.
In order to achieve the above object, the present invention provides a method for optimizing a magnet and a yoke for magnetic resonance imaging, the method comprising the steps of:
a. arranging a plurality of magnetic blocks into magnet rings along the circumferential direction, and sequentially placing magnet rings with small diameters inside magnet rings with large diameters aiming at a plurality of magnet rings with different diameters;
b. on the upper and lower yokes, a plurality of magnet blocks are randomly distributed into a plurality of magnet rings, the magnet rings with small diameters in the magnet rings are sequentially placed in the magnet rings with large diameters, and the total number of the magnet blocks is set as n x The number of the magnet rings is set to be x, and the number of the magnet rings is n from the outermost ring to the innermost ring 1 、n 2 、n 3 ……n x The number of the magnetic blocks on the 1 st circle of the magnet ring is 1,2,3, … … and n in sequence along the clockwise or anticlockwise direction 1 The method comprises the steps of carrying out a first treatment on the surface of the A plurality of magnetic blocks on the 2 nd circle of magnet ring are numbered n in turn along the clockwise or anticlockwise direction 1 +1,n 1 +2,n 1 +3，……，n 2 And so on, a plurality of magnetic blocks on the X-th magnetic ring are numbered n in turn along the clockwise or anticlockwise direction x-1 +1,n x-1 +2,n x-1 +3,n x-1 +4,……,n x The method comprises the steps of carrying out a first treatment on the surface of the Wherein n is 1 <<n 2 <<n 3 <<n 4 <<……<<n x ；
c. The structural parameters of a plurality of magnetic blocks of a plurality of magnet rings are represented by R 1 、T 1 、b 1 、h 1 ，R 2 、T 2 、b 2 、h 2 ，R 3 、T 3 、b 3 、h 3 ……R x 、T x 、b x 、h x Representing, to obtain a plurality of groups of magnetic block structural parameters of a plurality of magnet rings, wherein R is the radius of an inner arc of a magnetic block, b is the thickness, h is the height, and T is an arc included angle;
d. coding each structural parameter variable through 3-5 bit binary codes, and dividing a certain variable value range into a plurality of equal parts;
e. all structural parameter variables are formed into a section of gene code, and the character number is 3*n x *4, wherein the first 3×4 field is the variable R of the magnetic block 1 in turn 1 ，T 1 ，b 1 ，h 1 The last field is a magnetic block n in turn x Variable R of (2) x ，T X ，b X ，h X ；
f. Selecting a plurality of structural parameter variable samples, randomly generating values of a plurality of groups of structural parameter variable samples as optimized initial values, calculating a magnetic field generated by each group of samples by a computer, calculating uniformity of a magnetic field of a target area, sequencing the samples according to the condition that the uniformity is optimal, and intersecting adjacent two sample individuals to form a new sample individual;
g. after a certain field of a newly generated sample individual is mutated with a certain probability to form a new individual group, calculating the magnetic field uniformity of a target area under each structural parameter by a computer;
h. repeating the steps f and g for several times until the magnetic block structure with the optimal uniformity is obtained, thereby obtaining the structural parameters of each magnetic block.
In the step a, the magnetic block is a sector, rectangle or trapezoid block.
In step b, the number of the magnetic blocks on each magnet ring is equal or unequal.
In step e, the number of characters encoded by the gene increases with the number of encoded bits, and when the number of encoded bits is 3, the number of characters is 3*n x *4, when the number of encoding bits is 4, the number of characters is 4*n x *4,n x The total number of the magnetic blocks.
The invention also provides a streamline yoke optimization method for magnetic resonance imaging, which comprises the following steps:
i. the pole plates of the magnet yoke are pole plates which are vertically symmetrical, the width of the yoke is fixed, and the thickness of the yoke is optimized;
j. the upper polar plate is divided into a plurality of parts along the magnetic field direction of the iron yoke from the center to the edge, the thickness of the upper polar plate is optimized, the iron yoke is divided into N parts, and the numbers of the iron yoke are 1,2,3,4, … … and N in sequence, and the magnetic flux of the iron yoke is phi at the position of the 1 st part of the iron yoke 1 Which represents the magnetic flux generated by all the magnet blocks directly under the 1 st iron yoke, Φ X Representing the sum of magnetic fluxes generated by all the magnet blocks right under the 1 st to the X th yokes, an optimized value phi can be determined by optimization X ；
k. The magnetic flux density standard Bx of each region is set according to the yoke material, and the magnetic flux density of each region is equal to bx=Φ X /(d*H X ) Calculating the thickness of the iron yoke according to a formula, wherein Bx is a magnetic flux density standard value of a certain area, phi X For the magnetic flux value of the selected yoke region, d is the yoke width, H X A thickness for the selected yoke region;
and when the iron yoke is divided into Y parts and the Y value is larger, the shape of the iron yoke tends to be smooth, and the iron yoke presents a soft streamline shape with small middle and high two sides, so that the polar plate optimization of the iron yoke is realized.
In step j, the iron yoke area is uniformly divided or non-uniformly divided.
The invention effectively solves the problems that the weight of the traditional magnetic resonance imaging device is large and the weight and the mobility cannot be realized due to the single magnet and iron yoke structure of the traditional magnetic resonance imaging device. According to the invention, the structural parameter variables of the plurality of magnets are coded and optimized, so that the uniformity of the magnetic field in the target area is optimal. Meanwhile, the iron yoke is formed into a streamline structure with a thin middle and gradually thickened two ends by optimizing the structure, so that the iron yoke is not only favorable for bearing, but also can reduce the use amount of iron yoke materials, thereby effectively reducing the weight of magnetic resonance imaging equipment.
[ description of the drawings ]
Fig. 1 is a schematic diagram of a magnetic structure for magnetic resonance imaging including a magnet block and a yoke.
FIG. 2 is a schematic view of a magnet ring and magnet arrangement according to the present invention.
FIG. 3 is a schematic diagram of parameters of a magnetic block according to the present invention.
Fig. 4 is a schematic diagram of example 1 of the present invention.
Fig. 5 is a schematic view of the division of the optimized region of the yoke according to the present invention.
Fig. 6 is a schematic view of the optimized yoke shape of the present invention.
[ detailed description ] of the invention
The following examples are further illustrative and explanatory of the present invention and are not intended to be limiting thereof.
The method of the present invention relates to a method for optimizing a magnet structure for magnetic resonance imaging and a method for optimizing a streamline yoke for magnetic resonance imaging, wherein the magnet 100 has a structure as shown in fig. 1 and 2, and comprises a plurality of upper magnet rings 10A, lower magnet rings 10B, upper yokes 20A, lower yokes 20B and left and right yokes 20C, 20D with different diameters arranged at intervals in a radial direction, and each of the upper magnet rings 10A, lower magnet rings 10B is composed of a plurality of magnetic blocks 11 arranged in sequence in a circumferential direction for forming a magnetic field for magnetic resonance imaging. The upper magnet ring 10A and the lower magnet ring 10B are fixed to the lower side of the upper yoke 20A and the upper side of the lower yoke 20B, respectively. The magnet structure further comprises an upper magnet protecting cover 30A arranged on the lower side of the upper magnet ring 10A, a lower magnet protecting cover 30B arranged on the upper side of the lower magnetic element, and magnet side plates 30C and 30D arranged on the inner sides of the two vertical yokes, wherein the upper yoke 20A, the lower yoke 20B, the left and right yokes 20C and 20D provided with the magnet rings are connected in a surrounding manner to form a magnetic resonance detection space. The present invention aims to optimize the magnet structure and the yoke structure. The method relates to an optimization method of a yoke structure of a magnet structure for magnetic resonance imaging.
Example 1
The optimization method of the magnet structure for magnetic resonance imaging comprises the following steps:
s1, referring to fig. 1 to 3, a plurality of magnetic blocks 11 are arranged along the circumferential direction to form an upper magnet ring 10A and a lower magnet ring 10B, the upper magnet ring 10A and the lower magnet ring 10B have the same structure but different installation modes, and the upper magnet ring 10A and the lower magnet ring 10B are respectively fixed on the lower side of the upper yoke 20A and the upper side of the lower yoke 20B. For a plurality of magnet rings with different diameters, the magnet rings with small diameters are sequentially placed inside the magnet rings with large diameters, when the magnet rings with large diameters are initially optimized, the number of the magnet blocks on each magnet ring can be equal or unequal, in this embodiment, for five magnet rings with different diameters, the magnet rings with small diameters are sequentially placed inside the magnet rings with large diameters, and the number of the magnet blocks on each magnet ring is equal to form a magnet 100.
S2, for each magnet ring of the upper magnet ring 10A and the lower magnet ring 10B, sequentially placing magnet rings with small diameters inside magnet rings with large diameters, sequentially numbering five magnet rings from the outermost ring to the innermost ring as n, 2n and 3n … … n, and sequentially numbering n magnetic blocks on the magnet ring of the nth ring as 1,2,3, … … and n along the clockwise or anticlockwise direction; the n magnetic blocks on the 2 n-th circle of magnet ring are sequentially numbered n+1, n+2, n+3, … …, n+n along the clockwise or anticlockwise direction, and so on, and the n magnetic blocks on the 5 n-th circle of magnet ring are sequentially numbered 4n+1,4n+2,4n+3, … …,5n along the clockwise or anticlockwise direction, and the magnetic blocks can be sector-shaped, rectangular or trapezoid-shaped blocks.
S3, the structural parameters of 5n magnetic blocks of the five magnet rings are represented by R 1 、T 1 、b 1 、h 1 ，R 2 、T 2 、b 2 、h 2 ，R 3 、T 3 、b 3 、h 3 ……R 5n 、T 5n 、b 5n 、h 5n And obtaining five groups of magnetic block structural parameters of a plurality of magnet rings, wherein R is the radius of an inner circular arc of the magnetic block, b is the thickness, h is the height, and T is the included angle of the circular arc.
S4, coding each structural parameter variable through 3-5 bit binary coding, and dividing a certain variable value range into a plurality of equal parts by taking millimeter as a unit. In the present embodiment, a certain value range of the variable is divided into eight parts, for example, 000,001,010, … …,111, in the present embodiment, for example, h 1 The range is 1 mm-15 mm, then it is evenly divided into 8 parts of equidistant components: 13 5 7 9 11 13 15. When h 1 If the code value of (2) is 000, h is represented 1 Has a value of 1mm when h 1 If the value of (2) is 111, then h is represented 1 The value of (2) is 15mm. Other variables are similar.
S5, forming a section of gene code by all structural parameter variables, wherein the characters are 3 x 5n x 4, and the first 3 x 4 field is the variable R of the magnetic block 1 in sequence 1 ，T 1 ，b 1 ，h 1 The last field is the variable R of the magnetic block 5n in turn 5n ，T 5n ，b 5n ，h 5n 。
S6, selecting a plurality of structure parameter variable samples, wherein the number of the structure parameter variable samples is not limited, and the more the number of the structure parameter variable samples is, the more accurate the data is. In this embodiment, 20 samples are used, and 20 groups of structural parameter samples are randomly generated as optimized initial values:
1 001 010 101 110 010 100 101 101……101 110 111 101
2 001 011 101 100 010 000 011 001……101 010 111 100
3 001 110 111 101 010 001 001 101……011 011 101 110
4 101 010 111 110 001 011 101 001……011 110 111 101
……
20 100 011 101 101 100 101 011 101……101 010 111 110
then the computer calculates the magnetic field generated by each group of samples, calculates the uniformity of the magnetic field of the target area, sorts the samples according to the optimal uniformity, and crosses two adjacent sample individuals, sorts the sample individuals into 1 and 2,3 and 4, … … and 20, and forms new sample individuals.
For example:
the original individuals are:
1 001 010 101 110 010 100 101 101……101 110 111 101
2 001 011 101 100 010 000 011 001……101 010 111 100
after crossing at the box positions, 2 new sample individuals are formed:
1 001 010 101 110 010 100 11 101……101 110 111 101
2 001 011 101 100 010 000 01 001……101 010 111 100
s7, a field of the newly generated sample individual changes with a certain probability, that is, from 1 to 0, or 0 to 0, for example, 0 in the first new individual becomes 1 (represented by a box):
1 001 010 11 110 010 100 111 101……101 110 111 101
after the new population is formed, the computer calculates the magnetic field uniformity of the target region under each structural parameter.
S8, repeating the steps of S6, S7 and S8 for a plurality of times until the magnetic block structure with the optimal uniformity is obtained, thereby obtaining the structural parameters of each magnetic block.
The optimization result enables the uniformity of the magnetic field in the target area to be optimal.
Example 2
The streamline yoke optimization method for magnetic resonance imaging comprises the following steps:
s9, referring to fig. 5 and 6, the method for optimizing the magnet structure for magnetic resonance imaging of the present invention comprises the following steps: the thickness of the yoke is optimized when the width of the yoke is fixed, and the yoke is a plate-shaped body with a thin middle and thick two ends and streamline upper and lower surfaces.
S10, dividing the iron yoke into a plurality of areas of 1,2 and 3 … … N from the middle to the two sides, wherein the areas can be uniformly divided or unevenly divided, and the magnetic flux density of the iron yoke is gradually increased from the middle to the two sides in the embodiment.
S11, the magnetic flux density of each region is according to B X ＝Ф X /(d*H X ) Formula calculation, wherein B X For a certain area of magnetic flux density, phi X D is the width of the iron yoke, H X The thickness of the yoke in this region is a variable in the above formula. In this embodiment, taking area 1 as an example, when the optimized parameters of the magnet 11 are determined, Φ 1 Is determined in order to make B 1 Approximately equal to the magnetic flux standard value, H 1 ≈B 1 *d/Ф 1 . When the yoke is divided into N parts, and the parts are larger, for example, 100, 1000, etc., the shape of the yoke becomes smoother and smoother, and the yoke presents a soft streamline shape with small middle and high sides. The same is true for the optimization of the side panels.
S12, the magnetic flux density of each region calculated according to the above formula is gradually increased from the middle to the two sides along with the increase of the thickness of the iron yoke, so that the thickness of the iron yoke is smoothly transited from the middle to the two sides. The optimized result is favorable for bearing, and the using amount of iron yoke materials can be reduced, so that the weight of the magnetic resonance imaging equipment is effectively reduced.
Although the present invention has been disclosed by the above embodiments, the scope of the present invention is not limited thereto, and modifications, substitutions, etc. made to the above components will fall within the scope of the claims of the present invention without departing from the spirit of the present invention.
Claims (6)
1. A method of optimizing a magnet structure for magnetic resonance imaging, the method comprising the steps of:
a. arranging a plurality of magnetic blocks into magnet rings along the circumferential direction, and sequentially placing magnet rings with small diameters inside magnet rings with large diameters aiming at a plurality of magnet rings with different diameters;
b. on the upper and lower yokes, a plurality of magnet blocks are randomly distributed into a plurality of magnet rings, the magnet rings with small diameters in the magnet rings are sequentially placed in the magnet rings with large diameters, and the total number of the magnet blocks is set as n x The number of the magnet rings is set to be x, and the number of the magnet rings is n from the outermost ring to the innermost ring 1 、n 2 、n 3 ……n x The number of the magnetic blocks on the 1 st circle of the magnet ring is 1,2,3, … … and n in sequence along the clockwise or anticlockwise direction 1 The method comprises the steps of carrying out a first treatment on the surface of the A plurality of magnetic blocks on the 2 nd circle of magnet ring are numbered n in turn along the clockwise or anticlockwise direction 1 +1,n 1 +2,n 1 +3，……，n 2 And so on, a plurality of magnetic blocks on the xth magnetic ring are numbered n in turn along the clockwise or anticlockwise direction x-1 +1,n x-1 +2,n x-1 +3,n x-1 +4,……,n x The method comprises the steps of carrying out a first treatment on the surface of the Wherein n is 1 <<n 2 <<n 3 <<n 4 <<……<<n x ；
c. The structural parameters of a plurality of magnetic blocks of a plurality of magnet rings are represented by R 1 、T 1 、b 1 、h 1 ，R 2 、T 2 、b 2 、h 2 ，R 3 、T 3 、b 3 、h 3 ……R x 、T x 、b x 、h x Representing, to obtain a plurality of groups of magnetic block structural parameters of a plurality of magnet rings, wherein R is the radius of an inner arc of a magnetic block, b is the thickness, h is the height, and T is an arc included angle;
d. coding each structural parameter variable through 3-5 bit binary codes, and dividing a certain variable value range into a plurality of equal parts;
e. all structural parameter variables are formed into a section of gene code, and the character number is 3*n x *4, wherein the first 3×4 field is the variable R of the magnetic block 1 in turn 1 ，T 1 ，b 1 ，h 1 The last field is a magnetic block n in turn x Variable R of (2) x ，T X ，b X ，h X ；
f. Selecting a plurality of structural parameter variable samples, randomly generating values of a plurality of groups of structural parameter variable samples as optimized initial values, calculating a magnetic field generated by each group of samples by a computer, calculating uniformity of a magnetic field of a target area, sequencing the samples according to the condition that the uniformity is optimal, and intersecting adjacent two sample individuals to form a new sample individual;
g. after a certain field of a newly generated sample individual is mutated with a certain probability to form a new individual group, calculating the magnetic field uniformity of a target area under each structural parameter by a computer;
h. repeating the steps f and g for several times until the magnetic block structure with the optimal uniformity is obtained, thereby obtaining the structural parameters of each magnetic block.
2. The method of claim 1, wherein in step b, the number of magnets on each magnet ring is equal or unequal.
3. The method of claim 1, wherein in step e, the number of characters encoded by the gene increases with increasing number of encoded bits, and the number of characters is 3*n when the number of encoded bits is 3 x *4, when the number of encoding bits is 4, the number of characters is 4*n x *4,n x The total number of the magnetic blocks.
4. The method of claim 1, wherein in step a, the magnet is a sector, rectangle, or trapezoid block.
5. A method for optimizing a streamlined yoke for magnetic resonance imaging, the method comprising the steps of:
i. the pole plates of the magnet yoke are pole plates which are vertically symmetrical, the width of the yoke is fixed, and the thickness of the yoke is optimized;
j. the upper polar plate is divided into a plurality of parts along the magnetic field direction of the iron yoke from the center to the edge, the thickness of the upper polar plate is optimized, the iron yoke is divided into N parts, and the N parts are numbered 1,2,3 and … … N in sequence, then the 1 st partThe position of the iron yoke, the magnetic flux of which is phi 1 Which represents the magnetic flux generated by all the magnet blocks directly under the 1 st iron yoke, Φ X Representing the sum of magnetic fluxes generated by all the magnet blocks right under the 1 st to the X th yokes, an optimized value phi can be determined by optimization X ；
k. The magnetic flux density standard Bx of each region is set according to the yoke material, and the magnetic flux density of each region is equal to bx=Φ X Calculating the thickness of the iron yoke according to the formula (d) Hx, wherein Bx is a standard value of magnetic flux density in a certain area, and phi X For the magnetic flux value of the selected yoke region, d is the yoke width, H X A thickness for the selected yoke region;
and when the iron yoke is divided into Y parts and the Y value is larger, the shape of the iron yoke tends to be smooth, and the iron yoke presents a soft streamline shape with small middle and high two sides, so that the polar plate optimization of the iron yoke is realized.
6. The method of claim 5, wherein in step j, the yoke region is uniformly divided or non-uniformly divided.
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| DE102018214213A1 (en) * | 2018-08-22 | 2020-02-27 | Bruker Biospin Gmbh | Permanent magnet arrangement for generating a homogeneous field ("3D Halbach") |
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