CN104685584A - Method for constructing superconducting magnet for magnetic resonance imaging - Google Patents
Method for constructing superconducting magnet for magnetic resonance imaging Download PDFInfo
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Abstract
A method for constructing a superconducting magnet for magnetic resonance imaging, includes: determining a superconducting wire material, a running current and a feasible current-carrying zone; dividing the feasible current-carrying zone into a plurality of rectangular grids, rounding off rectangular grids at the boundary, adjusting the boundary of the feasible current-carrying zone, and acquiring the number of the rectangular grids in the feasible current-carrying zone; with the centre of a magnet as an origin, establishing a coordinate system to obtain the space coordinate of the centre of each rectangular grid; with the minimal wire consumption as an optimization goal, and the field intensity of the centre, the magnetic field uniformity and the stray field as constraint conditions, programming the feasible current-carrying zone with a linear integer programming algorithm to obtain each concentrated distribution area of an initial wire of the magnet; according to the degree of influence of each concentrated distribution area on the magnetic field uniformity, and according to the degree of influence on the magnetic field uniformity in descending order, with the minimal wire consumption as the optimization goal, and the field intensity of the centre, the magnetic field uniformity and the stray field as the constraint conditions, rectangularizing each concentrated distribution area with the linear integer programming algorithm; and acquiring the parameters of a superconducting magnet coil.
Description
Method and technology field for constructing magnetic resonance image-forming superconducting magnet
The invention belongs to application superconductor technology field, more particularly to construction magnetic resonance imaging（Magnetic
Resonance Imaging, abbreviation MRI) superconducting magnet method.Background technology
Magnetic resonance imaging（MRI) it is magnetic core using organism（Mainly proton）The characteristic nmr shown in magnetic field is come the new and high technology that is imaged.Magnetic resonance imaging（MRI) equipment is mainly made up of main magnet, scanning bed, gradient coil, radio-frequency coil, spectrometer system, switch board, interactive operating desk, computer and image processor etc..
Main magnet is the main composition part of MRI equipment, for producing homogeneous static magnetic field, decides the picture quality and operating efficiency of MRI machine.Meanwhile, main magnet is also manufacturing cost maximum, operating cost highest part in MRI machine.MRI has strict demand to the intensity, the uniformity and stability in magnetic field, and this three are the most important indexs of main magnet.For permanent magnet, superconducting magnet can produce intensity, the uniformity and stability all higher magnetic field, so being used to obtain the image become apparent from.
Due to being distributed in the stray field outside superconducting magnet system detrimental effect can be brought to surrounding environment, magnetic field such as the 10 Gauss orders of magnitude is possible to cause some electronic equipment cisco unity malfunctions, and the patient with pacemaker is in peril of one's life, the magnetic field of the 100 Gauss orders of magnitude may can make computer working abnormal, therefore consider some places to the limitation of stray field, it is necessary to limit the stray magnetic field scope of superconducting magnet.
The magnetic field shielding mode of MRI main magnets includes passive screening and the class of active shield two.Take during passive screening mode, it is necessary to dispose ferromagnetic material to shield stray field around magnet, it is simple in construction, but volume and weight is all very big, and influence can also be produced on magnetic field's regularity.It is general at present to use active shield mode, i.e., the stray magnetic field outside magnet is reduced by the shielded coil of the logical reverse current of outside increase in main coil, so as to reduce the stray magnetic field scope of magnet.Simultaneously because the length of traditional MRI system is longer, a large amount of clinical trials show that patient's common manifestation in long and narrow space goes out the claustrophobia phenomenon such as anxiety, uneasiness, therefore in recent years, short cavity, self-shileding MRI system are designed to a kind of new trend.
The electromagnetic design index of high evenness magnet for magnetic resonant imaging mainly has：
(1) imaging region（Diameter Sensitive Volume, abbreviation DSV), it is general fixed
Justice is a diameter of D spheric region.
(2) central field B., refer to the magnetic induction intensity value at imaging region center point.
(3) uniformity of magnetic field n (peak-to-peak values）, calculation formula is：
η=leg _min x l O6 (ppm)
Bo
Wherein, Bmax and Bmi n are respectively the maximum and minimum value of magnetic induction intensity in DSV.
(4) stray magnetic field scope, refers generally to magnet and passes to the region that the 5Gs equipotential lines in produced magnetic field during operating current are surrounded.
Magnetic resonance imaging（MRI) optimization design of superconducting magnet is the basis that magnet makes, and the image quality and production cost to whole MRI machine control to play very important effect.
The method of conventional construction MRI superconducting magnets can typically be attributed to two major classes, one class is Direct Search Method, this kind of method both can be in the case where not giving magnet coil structure initial value, the overall situation is carried out preferentially to whole feas ible space, the operating current and basic loop construction of superconducting magnet can also be preselected, using the structural parameters of magnet as independent variable, uniformity of magnetic field in imaging region, stray magnetic field scope, superconducting magnet spatial volume, magnet energy etc. is constraints or object function, local optima is carried out to the structural parameters of superconducting magnet using nonlinear optimization algorithm such as simulated annealing or genetic algorithm, obtain final magnet structure.But because MRI SUPERCONDUCTING MAGNET DESIGNs are a multi-parameter, the structural optimization problems of multiple target, so that such method is computationally intensive, and it is less efficient, become apparent when especially variable is more, if when the selection of constraints and unreasonable given initial value, it will be difficult to obtain optimal solution.
The another kind of introducing for being linear programming algorithm for functional based method.First magnet structure is simplified, the rectangular mesh of division rule in the feasible current-carrying area of superconducting magnet, the equivalent being aligned plan model of MRI SUPERCONDUCTING MAGNET DESIGN problems is solved, obtain the initial current density distribution of the superconducting magnet, the basic structure and location parameter for determining magnet coil are distributed further according to initial current density, then the first quasi-nonlinear optimizing algorithm is utilized, obtain final squaring magnet coil structure but the method that magnet basic structure is determined by initial current density distribution, still there is certain subjective blindness in the selection of magnet coil number and cross sectional shape, it is not easy to seek global optimum's result.
And in the final stage of above two method; during actual coiling magnet; need to consider superconducting wire sectional dimension; coil dimension is subjected to sliding-model control; and position and radius are rounded; round with it is discrete after, the index such as uniformity of magnet, which generally has, to be decreased obviously, make design result deviate optimal solution.The content of the invention
The bright mesh purpose of book hair invention is being to be used to make magnetic magnetic in structure and resonate to shake into the square method for being imaged picture superconduction magnetic conduction magnet body for a variety of one by one in providing, , imaging is shaken into as the square method of superconduction magnetic conduction magnet body with for being resonated in the certainly existing existing magnetic magnetic having of solution solution, , real actual border around coiling magnetic magnet body constantly, , it need to need to consider that considering super superconductivity wire wire rod material cuts section face chi size cun, , line coil turn chi size little progress will be entered into the luxuriant scattered dispersionization of every trade to manage everywhere, , and and para postion is put and and half radius footpath rounded into every trade it is whole, , rounding whole and dissipating rear with luxuriant, , uniform even property of magnetic magnet body etc. refers to index mark can usually have obviously aobvious lower decline drop all, , make design meter knot result fruit wilfully luxuriant optimal excellent
The topic of asking questions of 55 solution solutions..
The bright use of book hair invention is used to make magnetic magnetic in structure and resonate to shake into imaging as the square method of superconduction magnetic conduction magnet body, bag is included：：Determine surely super superconductivity wire wire rod material, the electric electric current stream of fortune operation row with and and cocoa every trade load current-carrying stream it is trivial；；Using using the magnetic magnet Ti Zhong center hearts as origin point, set up vertical post post round one by one and sit system of coordinate mark system（（Rr, zz, aa)), its wherein middle rr be footpath radially to away from distance from, zz axles axle is high height,《《For for orientation azimuthal angle degree, magnetic magnet body axle axially to for for zz axles axle side direction to；；The cocoa every trade trivial stroke of current-carrying stream of load will be divided into for the more each and every one net grid lattice, , to cocoa every trade is carried the footpaths of the trivial Intranet grid lattice of current-carrying stream radially to count layer by layer numbers and and axle do not rounded respectively into every trade to several points of circle circle 1100 axially it is whole, , the more each and every one square rectangle shape net grid lattice must be obtained, , the whole cocoa every trade of key carries the trivial side border circle of current-carrying stream and takes cocoa every trade to carry the trivial square rectangle shape net grid lattice number number nn of current-carrying stream, , obtain to sit between absolutely empty of often each and every one square rectangle shape net grid Ge Zhong centers heart coordinate be designated as ((, ,ZZii,, aa dd ;;With with it is at least few with line line amount amount be excellent optimizationization mesh target mark, center psychological field field strength degree, the uniform evenness degree in magnetic magnetic field and and spuious end of a performance field be to constrain beam bar condition part, using algorithm method is calculated with the linear property planning of whole number number line, to being carried to cocoa every trade, current-carrying stream is trivial to carry out professional etiquette planning stroke to profit,, point distribution cloth region domain during each collection for leading wire that must obtain initially beginning at the beginning of to magnetic magnet body is concentrated；；
1155 influence sound Cheng Chengdu degree on the shadow on the uniform evenness degree in magnetic magnetic field according to according to point distribution cloth region domain in each collection concentration, , by according to according to influenceing to ring Cheng Chengdu degree on the shadow on the uniform evenness degree in magnetic magnetic field from from significantly to slight, , with with it is at least few with line line amount amount be excellent optimizationization mesh target mark, , center psychological field field strength degree, , the uniform evenness degree in magnetic magnetic field and and spuious end of a performance field be to constrain beam bar condition part, , cloth region domain is distributed into every trade square rectangle shape using in planning algorithm method to one's profit to being concentrated to each collection with the linear property rule of whole number number line points;;With and and take and obtain the ginseng parameter number of superconduction magnetic conduction magnet body line coil turn..
Book hair invention it is bright to magnetic magnet body into the excellent optimizationization of every trade design timing when, with to be that excellent optimizationization mesh target mark can be with so as to make interior interior-layer layer with least being lacked with line line amount amount
2200 magnetic magnet body line coil turns from automatic trend, inwardly contract by the compression of inside portion pressure, , using using spuious end of a performance field as constraint beam bar condition part can with so that make outer layer layer line coil turn from automatic trend outwards outside portion pressure compression contract, , draw the loads current-carrying stream square rectangle shape net grid lattice that must be obtained and can reach shape and be formed into through passing through the linear property rule planning of whole number number line and more more point be distributed cloth region domain for tightly close lead during wire collection is concentrated, , it must enough be able to can obtain to full whole design counting the optimal excellent solution solution of the global office that require asking, , if design meter knot result fruit be totally count number layer by layer and with circle circle, , in effectively avoiding exempting to know clearly all in usually square method effect ground to round whole error by mistake poor..
2255 accompanying drawing figures are had a talk about obviously
Figure Figure 11 shown in be shown as resonating for the bright magnetic magnetic of book invention and shake into imaging and illustrate intention figure as square method that structure makes superconduction magnetic conduction magnet body applies showing for example one by one；；
Figure Figure 22 is that cocoa every trade carries the trivial signal intention figure of current-carrying stream；；
It is shown as beginning to lead distribution Butut figure in region domain point during wire collection is concentrated to be initial shown in figure Figure 33 institutes；；
Fig. 5 is the uniformity distribution in imaging area magnetic field；
Fig. 6 show the 5Gs patterns of equipotentials of magnet stray magnetic field.Embodiment
Fig. 1 show the schematic diagram of the embodiment of method one of magnetic resonance imaging construction superconducting magnet of the present invention, as shown in Figure 1：
Step 1, estimate the maximum magnitude in the feasible current-carrying area of magnet coil, minimum inside radius including feasible current-carrying area and maximum outer radius, are required, the maximum magnetic induction in space constraint and feasible current-carrying area according to Magnetic Field Design, are determined superconducting wire and are determined running current lop;
Step 2, using the center of magnet as origin, a cylindrical-coordinate system is set up（R, z,《), wherein r is radial distance, and z-axis is height,《For orientation angles, magnet axial is z-axis direction；According to the size of selected superconducting wire, feasible current-carrying zoning is divided into multiple grids, make the size in section of the physical dimension equal to selected superconducting wire of each grid, the radial direction number of plies and the axial number of turn to grid in feasible current-carrying area are rounded respectively, form multiple rectangular mesh, and accordingly adjust the border in each feasible current-carrying area, and it is (ri to obtain the rectangular mesh number n in the feasible current-carrying area of the magnet coil and the space coordinate at each rectangular mesh center, Z i, d.
Step 3, with minimum for optimization aim with line amount, center field intensity, uniformity of magnetic field and stray magnetic field are constraints, feasible current-carrying area is planned using integral linear programming algorithm, obtain each integrated distribution region of the initial wire of magnet, if distributed areas are difficult to carry out squaring, the return to step 1 of next step in the wire integrated distribution or line set of the design requirement that is not being met;
Wherein step 3 is specifically as follows：
Calculate the contribution for the magnetic field axial component put when each rectangular mesh passes to running current lop to each investigation, and each length of superconducting wire contained by rectangular mesh：
Rectangular mesh under running current lop can be equivalent to the electric current loop positioned at rectangular mesh center, its electric current is I=Iop, i.e. by the current equivalence for having cross-sectional sizes in rectangular mesh into the plain conductor in rectangular mesh center, and the wire cross-section area is zero, logical electric current is running current Iop.Then electric current loop investigate point coordinates (rj, Zj) place produce magnetic field z be to component：
Wherein,
This draws * meters/ampere)
Introducing factor e i=- l, 0,1, obtain Bzi=e^l, the formula represents to work ase iThe rectangular mesh is void when=0, i.e., to magnetic field without contribution;Whene iThe rectangular mesh is real during=l or -1, is positive or negative to field contribution, and the positive coil and reversely of superconducting magnet is corresponded to respectively
Then each magnetic field is：
Superconduction contained by each rectangular mesh;；The length of material can be by following formula meter;
L = 2k¼
N is the rectangular mesh number in feasible current-carrying area, and I is equal to running current Iop.
Wherein, in the present invention, the minimum inside radius in the feasible current-carrying area of magnet coil is limited by reserved room temperature hole Dewar structure and magnet skeleton, and reserved a certain amount is needed during design；The problems such as maximum outer radius of magnet coil and the axial length of magnet are by magnet volume, Dewar weight, Consumer's Experience is limited, they also influence whether the field quality of magnet, so as to have influence on the reasonability, practicality and economy of final optimization pass result, so rationally to be limited the two variables；
When optimizing design to magnet using this method, at least for optimization aim internal layer magnet coil can be made internally to compress automatically with line amount, outer coil can be made automatic to external compression by constraints of stray magnetic field, the current-carrying rectangular mesh obtained by integral linear programming can form distributed areas in more close line set, to carry out the optimization of next step to magnet.
Step 5, according to influence degree of each integrated distribution region to uniformity of magnetic field, according to magnetic
The influence degree of field uniformity is from big to small, with minimum for optimization aim with line amount, center field intensity, uniformity of magnetic field and stray magnetic field are constraints, squaring to each integrated distribution region progress using integral linear programming algorithm, to obtain with the minimum magnet structure of line amount；
Wherein, squaring is that each integrated distribution region is planned using integral linear programming algorithm.Each integrated distribution region can be to the decision procedure of the influence degree of uniformity of magnetic field：Investigate in the initial line set of magnet that process -1-0-1 integral linear programmings are obtained in distributed areas, influence degree of each integrated distribution region of each separation to uniformity of magnetic field, find influence degree most strong one, then other integrated distribution regions are fixed constant, the integrated distribution region is carried out squaring；It is met after the result of condition, then next integrated distribution region is carried out using same method squaring;At the end of squaring, the final cross section parameter of superconducting magnet coil is obtained, the optimization design of magnet is completed；More excellent one kind is selected, consider the initial each integrated distribution region of wire of gained, the shape in each integrated distribution region close to the degree and its influence degree to uniformity of magnetic field of rectangle, each integrated distribution region is carried out in order it is squaring, to obtain with the minimum magnet structure of line amount：
Judge whether not yet to carry out each integrated distribution region of the initial wire of the squaring magnet, if completed, perform the cross section parameter that step obtains superconducting magnet coil, otherwise return and squaring step is carried out to each integrated distribution region；
It is to the algorithm of realizing that each integrated distribution region carries out squaring step：
Each integrated distribution region under the running current is subjected to rectangular mesh division again, the new feasible current-carrying area in the feasible current-carrying area is determined according to each integrated distribution region, and the radial direction number of plies and the axial number of turn of grid in new feasible current-carrying area are rounded respectively, the border in the new feasible current-carrying area of adjustment and obtain each rectangular mesh center space coordinate and new feasible current-carrying area in total rectangular mesh number nl, the plurality of rectangular mesh is equivalent to the electric current loop positioned at rectangular mesh center, the electric current of the electric current loop is equal to the running current, electric current loop is investigating point coordinates（rj,Z j, the axial z-component in magnetic field for locating to produce is：
B-. =
Wherein,
X 10" 7T 2
Factor ei is -1,0 or 1, whene iWhen=0 the integrated distribution region to magnetic field without contribution；The integrated distribution region is the just positive coil of correspondence superconducting magnet to field contribution during ei=l,eiThe integrated distribution region is negative, the reverse winding of correspondence superconducting magnet to field contribution during=- i；Then the magnetic field z of each investigation point is to component：
The length of superconducting wire is by following formula meter contained by each integrated distribution region;
L; = 2k¼
( 7 )
Magnet is used：Then it is expressed as
Wherein, nl is total grid number in new feasible current-carrying area, and I is equal to the running current.
Step 6, whether judge the parameter of final design Project Realization and can meet superconducting wire
JC (B) characteristic, optimizes if meeting and terminates, return to step 1 if being unsatisfactory for.
Step 7, output parameter and associated arguments are calculated, including：The scope of Distribution of Magnetic Field and equipotential line of the structure chart, magnetic field of output winding in homogeneity range, the maximum field in magnet current-carrying area and 5 gaussian lines.
Below in conjunction with the accompanying drawings 1 and foregoing construction magnetic resonance image-forming superconducting magnet method, to further illustrate the principle and specific embodiment of the present invention.
As shown in figure 1, its basic step can be as follows：
Step 1. sets the feasible current-carrying area of short cavity self-shileding superconducting magnet coil according to Magnetic Field Design requirement and space constraint, selects suitable superconducting wire and determines running current Iop.
Fig. 2 is feasible current-carrying area schematic diagram.Magnet is symmetrical on Z axis, and symmetrical on Z=0 plane, so part shown in Fig. 2 is 1/4 section in feasible current-carrying area.Feasible current-carrying area inside radius the RfO m, outer radius R of magnet coil2The 645m of=0. 92m, length L=0..The section of superconducting wire used
Size is the 20mm of 1. 80 X 1.2, running current is 400A.
Feasible current-carrying zoning is divided into multiple rectangular mesh by step 2..
According to the size of selected superconducting wire, feasible current-carrying zoning is divided into multiple rectangular mesh, the physical dimension of rectangular mesh is set to be equal to selected superconducting wire size, the border in feasible current-carrying area is rounded and accordingly adjusted to rectangular mesh, the rectangular mesh number n in the feasible current-carrying area of magnet coil is obtained, it is then determined that the space coordinate at each rectangular mesh center.
Step 3. calculates contribution and contained superconducting wire length of each rectangular mesh to magnetic field.
Each rectangular mesh is equivalent to the electric current loop of position at its center, its running current is I=Iop, the space coordinate at each rectangular mesh center is（ri, Z i, calculate each electric current loop and investigate point in each magnetic field（rj, Zj, the magnetic field z of generation is to component.
Superconducting wire length contained by each rectangular mesh is then calculated by following formula：
4. = 2
Wherein, if it is considered that quadrant is symmetrical on z=o planes, then superconducting wire length contained by each rectangular mesh can then be calculated by following formula：
4. = 4^.
Step 4. use -1-0-1 integral linear programmings method optimizes calculating to the wire integrated distribution of magnet.
Using at least with line amount as optimization aim, central field, imaging area uniformity of magnetic field and stray magnetic field scope etc. are constraints, calculating is optimized to the wire integrated distribution of magnet using -1-0-1 integral linear programmings method, Fig. 3 show regional distribution chart in initial line set, wherein, it is positive coil, the i.e. factor that black box 1,2,3 and 4 bodies, which represent electric current,ei, e2, e3And e4For 1, it is reverse winding, factor e that white framework 5,6 and 7, which represents electric current,5、 e6And e7For -1.
Step 5. is squaring to the progress of wire concentrated area, obtains the final optimization pass result of magnet.Fig. 4 be it is squaring after magnet structure schematic diagram, wherein, it is forward direction coil, i.e. factor e that black box 1,2,3 and 4 bodies, which represent electric current,2, e3And e4For 1, it is reverse winding, factor e that white framework 5,6 and 7, which represents electric current,5、 e6And e7For -1.
Magnet length is 1. 29m, and superconducting wire overall length used is 63. 6km, and table 1 designs the coil parameter completed for the implementation case.
Table 1
Sorrowful edge axis in internal diameter
Radius/m is to the number of plies heart away from/m to the number of turn
0. 5
18 0 16
030
0. 5
20 30 ffl 2Line 000
0. 5
32 0. 2972 41 ffl 3Line 000
0. 5
76 0. 5614 46 ffl 4Line 000
0. 5
6 O 0. 2171 12 ffl 5Line 010
0. 5 cun
o
24 0. 4375 37 ffl 6Line 000
0. 9
m 7 m 18 0. 4414 101
000 step 6, whether can Project Realization and meet JC (B) characteristic of superconducting wire, optimize if meeting and terminate if judging the parameter of final design, return to step 1 if being unsatisfactory for.
Fig. 5 is the uniformity distribution in imaging area magnetic field, the 5T of the magnet center B0 of gained in the present embodiment=1., the 07T of the maximum field Bmax in magnet current-carrying area=6., and the uniformity of magnetic field distribution of imaging area is as shown in figure 5, unit is rice（M), it can be seen that in a diameter of 50cm spheric region, the design objective that the uniformity is less than lOppm is met.The 5Gs patterns of equipotentials of magnet stray magnetic field are illustrated in figure 6, unit is rice（M), distance of the 5Gs equipotential lines away from magnet center, radially less than 3. 5m, is axially less than 4m.
Rapid 7. output parameters of Walk simultaneously calculate associated arguments, including：The scope of Distribution of Magnetic Field and equipotential line of the structure chart, magnetic field of output winding in homogeneity range, the maximum field in magnet current-carrying area and 5 gaussian lines.
The present invention is used for the method for constructing magnetic resonance image-forming superconducting magnet by the feasible current-carrying Division grid magnet coil, and the physical dimension of grid is selected ribbon dimension, is considered with line amount, magnetic
The indexs such as induction, uniformity of magnetic field, stray magnetic field scope, obtain area distribution in the initial line set of magnet coil using -1-0-1 integral linear programming algorithms, then distributed areas in the initial line set of magnet are carried out squaring obtaining final optimization pass result in certain sequence.The above-mentioned method for being used to construct magnetic resonance image-forming superconducting magnet can not only carry out traditional MRI SUPERCONDUCTING MAGNET DESIGNs, it is also applied for internal layer and MRI SUPERCONDUCTING MAGNET DESIGNs of short cavity MRI SUPERCONDUCTING MAGNET DESIGNs, asymmetric solenoid coil system and open biplane coil system of reverse current coil etc. is distributed with, in addition, can flexibly it be configured according to the foundation of specific design coordinate system and symmetric relation, for example, for above-mentioned MRI SUPERCONDUCTING MAGNET DESIGNs if unsymmetric structure, then coordinate system is not required to symmetrical on Z=0 plane.The above embodiment of the present invention is by taking -1-0-1 integral linear programming algorithms as an example, such as 0-1 integral linear programmings algorithm can also actually be used, because realization principle is similar to the above embodiments, those skilled in the art refer to above-described embodiment realization, therefore will not be described here.
In summary, when optimizing design to magnet in the present invention, at least for optimization aim internal layer magnet coil can be made internally to compress automatically with line amount, outer coil can be made automatic to external compression by constraints of stray magnetic field, the current-carrying rectangular mesh obtained by integral linear programming can form distributed areas in more close line set, the globally optimal solution of design requirement can be met, design result is integer layer and circle, efficiently avoid the round-off error in usual method.
Although exemplary embodiment describing the present invention with reference to several, it is to be understood that, term used is explanation and exemplary and nonrestrictive term.Because the present invention can be embodied without departing from the spiritual or substantive of the present invention in a variety of forms, it is to be understood that, above-described embodiment is not limited to any foregoing details, and should widely be explained in the spirit and scope that appended claims are limited, therefore the whole changes fallen into claim or its equivalent scope and remodeling all should be appended claims and covered.
Claims (1)
- Claim1. a kind of method for constructing magnetic resonance image-forming superconducting magnet, it is characterised in that including：Determine superconducting wire, running current and feasible current-carrying area；Using the center of magnet as origin, a cylindrical-coordinate system is set up（R, z,《), wherein r is radial distance, and z-axis is height,《For orientation angles, magnet axial is z-axis direction, the feasible current-carrying zoning is divided into multiple grids, the radial direction number of plies and the axial number of turn to grid in feasible current-carrying area are rounded respectively, obtain multiple rectangular mesh, adjust the border in feasible current-carrying area and obtain the rectangular mesh number n in feasible current-carrying area, obtain the space coordinate at each rectangular mesh center for (Z i, a d ;So that with line amount, at least for optimization aim, center field intensity, uniformity of magnetic field and stray magnetic field are constraints, and feasible current-carrying area is planned using integral linear programming algorithm, each integrated distribution region of the initial wire of magnet is obtained；According to influence degree of each integrated distribution region to uniformity of magnetic field, according to the influence degree to uniformity of magnetic field from big to small, with minimum for optimization aim with line amount, center field intensity, uniformity of magnetic field and stray magnetic field are constraints, each integrated distribution region are carried out using integral linear programming algorithm squaring;And obtain the parameter of superconducting magnet coil.2. the method as described in claim 1, it is characterised in that the feasible current-carrying area is symmetrical on Z axis, and symmetrical on Z=0 plane.3. the method as described in claim 1, it is characterised in that the integral linear programming algorithm is -1-0-1 integral linear programming algorithms.4. method as claimed in claim 3, it is characterised in that so that, at least for optimization aim, center field intensity, uniformity of magnetic field and stray magnetic field are constraints, are planned using integral linear programming algorithm feasible current-carrying area, realize that algorithm is with line amount：The plurality of rectangular mesh is equivalent to the electric current loop positioned at rectangular mesh center, the electric current of the electric current loop is equal to the running current, electric current loop investigate point coordinates (,Zj, place produce magnetic field axial direction z components be：Wherein,μ0 = 4π X 10 7Τ m/A, (2)i \ - k sin( 5 )Factor ei is -1,0 or 1, as ei=0 rectangular mesh to magnetic field without contribution；Work as ei=The rectangular mesh is the just positive coil of correspondence superconducting magnet to field contribution during l, and as ei=_ l, the rectangular mesh is negative, the reverse winding of correspondence superconducting magnet to field contribution；Then each component is： The length of superconducting wire is calculated by following formula contained by each rectangular mesh：4 = .|^. ( 7 )For：Wherein, i is the rectangular mesh number in feasible current-carrying area, and I is equal to the running current,（4) formula is the first ellptic integral,（5) formula is the second ellptic integral.5. the method as described in claim 1, it is characterised in that planning is carried out to each integrated distribution region using integral linear programming algorithm and specifically included：Squaring step is carried out to each integrated distribution region, including：Calculate influence degree of each integrated distribution region to uniformity of magnetic field of the initial wire of the magnet obtained by the integral linear programming, find influence degree most strong one, then other integrated distribution regions are fixed constant, the integrated distribution region is carried out squaring；Judge whether not yet to carry out each integrated distribution region of the initial wire of the squaring magnet, if completed, perform the cross section parameter that step obtains superconducting magnet coil, otherwise return and squaring step is carried out to each integrated distribution region.6. method as claimed in claim 5, it is characterised in that be to the algorithm of realizing that each integrated distribution region carries out squaring step：Each integrated distribution region under the running current is subjected to rectangular mesh division again, the new feasible current-carrying area in the feasible current-carrying area is determined according to each integrated distribution region, and in new feasible current-carrying area The radial direction number of plies of grid and the axial number of turn are rounded respectively, the border in the new feasible current-carrying area of adjustment and obtain each rectangular mesh center space coordinate and new feasible current-carrying area in total rectangular mesh number nl, the plurality of rectangular mesh is equivalent to the electric current loop positioned at rectangular mesh center, the electric current of the electric current loop is equal to the running current, electric current loop investigate point coordinates (Zj, the axial z-component in magnetic field for locating to produce is：B = e^.IWhereinμο 4π 10 7T m/A, (2)( 5 )Factor ei is -1,0 or 1, as ei=0 the integrated distribution region to magnetic field without contribution；Work as ei=The l integrated distribution regions to field contribution for just, the positive coil of correspondence superconducting magnet, as ei=_ l, distributed areas be negative to field contribution in this, correspond to the reverse winding of superconducting magnet；Then the magnetic field z of each investigation point is to component：n\=∑e' (6) each the length of superconducting wire is calculated by following formula contained by the integrated distribution region：4 = .|^. (7)Magnet is then expressed as with line total amount：Wherein, 11 for the new feasible current-carrying area total grid number, I is equal to the running current.7. the method as described in claim 1, it is characterized in that, also include after the final cross section parameter for obtaining superconducting magnet coil, whether judge the parameter of final design Project Realization and can meet the characteristic of superconducting wire, design and complete if meeting, the step of determination superconducting wire, running current and feasible current-carrying area are returned to if being unsatisfactory for, and adjust superconducting wire, running current and feasible current-carrying area.8. the method as described in claim 1, it is characterised in that the cross section parameter includes：The scope of Distribution of Magnetic Field and equipotential line of the structure chart, magnetic field of output winding in homogeneity range, the maximum field in magnet current-carrying area and 5 gaussian lines.9. the method as described in claim 1, it is characterized in that, if distributed areas are difficult to carry out the squaring of next step in the wire integrated distribution or line set of the design requirement that is not being met, the step of determining superconducting wire, running current and feasible current-carrying area is then returned, and adjusts superconducting wire, running current and feasible current-carrying area.10. the method as described in claim 1, characterized in that, the short cavity MRI SUPERCONDUCTING MAGNET DESIGNs and asymmetric solenoid coil system of reverse current coil and the MRI SUPERCONDUCTING MAGNET DESIGNs of open biplane coil system is distributed with suitable for internal layer in the method for construction magnetic resonance image-forming superconducting magnet.
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