CN115047388B - Manufacturing and assembling method of magnetic resonance imaging gradient coil - Google Patents
Manufacturing and assembling method of magnetic resonance imaging gradient coil Download PDFInfo
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- CN115047388B CN115047388B CN202110254640.5A CN202110254640A CN115047388B CN 115047388 B CN115047388 B CN 115047388B CN 202110254640 A CN202110254640 A CN 202110254640A CN 115047388 B CN115047388 B CN 115047388B
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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
- G01R33/385—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field using gradient magnetic field coils
- G01R33/3858—Manufacture and installation of gradient coils, means for providing mechanical support to parts of the gradient-coil assembly
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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
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
- G01R33/022—Measuring gradient
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Abstract
The invention discloses a manufacturing and assembling method of a magnetic resonance imaging gradient coil, which utilizes the gradient magnetic field intensity detected by an eddy current testing device to repeatedly adjust the relative position between the eddy current testing device and a main coil assembly, and repeatedly adjusts the relative position between a shielding coil assembly and the main coil assembly according to the detected eddy current magnetic field intensity, so as to ensure that the relative position between the shielding coil assembly and the main coil assembly meets the requirements, eliminate the problem of overlarge eddy current effect caused by manufacturing errors, improve the image quality of magnetic resonance imaging, and further improve the qualification rate of products.
Description
Technical Field
The invention relates to the technical field of magnetic resonance imaging, in particular to a manufacturing and assembling method of a magnetic resonance imaging gradient coil.
Background
The gradient coil is a core component of the magnetic resonance imaging apparatus, and comprises three orthogonal coil sets for generating magnetic field gradients in three directions X, Y and Z, wherein the magnetic field gradients in the X direction are generated by the X coil assembly, the magnetic field gradients in the Y direction are generated by the Y coil assembly, and the magnetic field gradients in the Z direction are generated by the Z coil assembly. The X coil assembly, the Y coil assembly and the Z coil assembly are respectively composed of a corresponding main coil and a shielding coil, wherein the main coil is used for generating a required magnetic field gradient, and the shielding coil is used for reducing eddy current effect.
The current manufacturing method of the gradient coil adopts an integrated assembly and integral casting process, and the manufacturing flow is as follows: firstly, assembling the outer surface of a cylindrical die with a main coil of an X coil assembly, a main coil of a Y coil assembly, a main cooling water pipe, a main coil of a Z coil assembly, a filling material, a shielding layer water pipe, a shielding coil of the Z coil assembly, a shielding coil of the X coil assembly and a shielding coil of the Y coil assembly, limiting the geometric positions of the coils by using positioning pins or positioning blocks in the installation process to ensure that the angular positions and the axial positions meet the azimuth requirements, then assembling an outer cover die and an end cover die, and finally casting, solidifying and forming by using resin.
In the assembly process, the positioning pins or the positioning blocks can generate positioning problems such as inclination, position deviation and the like due to machining or assembly deviation, so that the relative positions of the main coil and the shielding coil deviate from a design value, eddy current effect is increased, for example, the Z coil assembly can generate a larger eddy current zero-order component due to axial relative position deviation of 0.2mm, the X coil assembly and the Y coil assembly can generate a larger eddy current first-order component due to angular relative position deviation of 2mm, and finally, image performance deterioration is caused, and the qualification rate of products is affected.
Disclosure of Invention
Therefore, the invention aims to provide a manufacturing and assembling method of a magnetic resonance imaging gradient coil, which uses the gradient magnetic field intensity detected by an eddy current testing device to repeatedly adjust the relative positions between the eddy current testing device and a main coil assembly and between a shielding coil assembly and the main coil assembly, so as to ensure the reliable relative positions between the shielding coil assembly and the main coil assembly, reduce the eddy current effect, improve the image quality of magnetic resonance imaging and improve the qualification rate of products.
The invention provides a manufacturing and assembling method of a magnetic resonance imaging gradient coil, which comprises the following steps:
after the main coil assembly is electrified, detecting the current gradient magnetic field intensity of the main coil assembly by using an eddy current testing device arranged in the main coil assembly;
judging whether the current gradient magnetic field intensity is within the allowable gradient magnetic field intensity range, if so, keeping the relative position between the eddy current testing device and the main coil assembly unchanged; if not, calibrating the relative position between the eddy current testing device and the main coil assembly;
sleeving the shielding coil assembly and the shielding barrel on the periphery of the main coil assembly in sequence;
after the shielding coil assembly and the main coil assembly are electrified in series, detecting the current eddy current magnetic field intensity of the shielding barrel by using an eddy current testing device;
judging whether the current eddy current magnetic field intensity is within the allowable eddy current magnetic field intensity range, if so, keeping the relative position between the shielding coil assembly and the main coil assembly unchanged; if not, calibrating the relative position between the shielding coil assembly and the main coil assembly;
after the shield can is removed, the main coil assembly and the shield coil assembly are secured.
Preferably, before detecting the current gradient magnetic field strength of the main coil assembly with the eddy current testing device disposed within the main coil assembly, the steps further comprise:
sequentially arranging a main coil of an X coil assembly, a main coil of a Y coil assembly, a main cooling water pipe and a main coil of a Z coil assembly in a main die from bottom to top;
assembling a main die;
the main coil of the X coil assembly, the main coil of the Y coil assembly, the main cooling water pipe and the main coil of the Z coil assembly are fixed by resin casting;
and (5) detaching the main die.
Preferably, before detecting the current gradient magnetic field strength of the main coil assembly with the eddy current testing device disposed within the main coil assembly, the steps further comprise:
the shielding cooling water pipe, the shielding coil of the Z coil assembly, the shielding coil of the X coil assembly and the shielding coil of the Y coil assembly are sequentially arranged in a shielding mold from bottom to top;
combining shielding molds;
resin is used for casting and fixing a shielding cooling water pipe, a shielding coil of a Z coil assembly, a shielding coil of an X coil assembly and a shielding coil of a Y coil assembly;
and (5) removing the shielding mold.
Preferentially, detecting the current gradient magnetic field strength of the main coil assembly with the eddy current testing device disposed within the main coil assembly comprises:
the method comprises the steps of respectively detecting corresponding positions of a main coil assembly by utilizing eight detection coils distributed at the vertexes of a cube of an eddy current testing device to obtain a first gradient magnetic field Bg1, a second gradient magnetic field Bg2, a third gradient magnetic field Bg3, a fourth gradient magnetic field Bg4, a fifth gradient magnetic field Bg5, a sixth gradient magnetic field Bg6, a seventh gradient magnetic field Bg7 and an eighth gradient magnetic field Bg8;
obtaining an X-direction distance between the center of the eddy current testing device and the center of the main coil assembly according to a formula (Bg1+Bg2+Bg3+Bg4+Bg5+Bg6+Bg7+Bg8)/(8X Gx), wherein Gx is gradient signal intensity;
obtaining a Y-direction distance between the center of the eddy current testing device and the center of the main coil assembly according to a formula (Bg1+Bg2+Bg3+Bg4+Bg5+Bg6+Bg7+Bg8)/(8 x Gy), wherein Gy is gradient signal intensity;
and obtaining the Z-direction distance between the center of the eddy current testing device and the center of the main coil assembly according to a formula (Bg1+Bg2+Bg3+Bg4+Bg5+Bg6+Bg7+Bg8)/(8 x Gz), wherein Gz is the gradient signal intensity.
Preferentially, after the shielding coil assembly and the main coil assembly are electrified in series, the current eddy current magnetic field intensity of the shielding barrel is detected by using the eddy current testing device, and the method comprises the following steps of:
the method comprises the steps of connecting a main coil of an X coil assembly and a shielding coil of the X coil assembly in series to form the X coil assembly, connecting a main coil of a Y coil assembly and a shielding coil of the Y coil assembly in series to form the Y coil assembly, and connecting a main coil of a Z coil assembly and a shielding coil of the Z coil assembly in series to form the Z coil assembly;
the method comprises the steps of respectively detecting corresponding positions by using eight detection coils distributed at the vertexes of a cube of an eddy current testing device to obtain a first eddy current magnetic field Be1, a second eddy current magnetic field Be2, a third eddy current magnetic field Be3, a fourth eddy current magnetic field Be4, a fifth eddy current magnetic field Be5, a sixth eddy current magnetic field Be6, a seventh eddy current magnetic field Be7 and an eighth eddy current magnetic field Be8;
after the Z coil component is electrified, according to the data obtained by all detection coils, a zero-order component REC-Z-B0 of the eddy current effect of the Z coil component is obtained according to the formula (Be1+Be2+Be3+Be4+Be5+Be6+Be7+Be8)/8; obtaining a first-order component REC-Z-X of the eddy current effect of the Z coil assembly according to the formula (Be1+Be2+Be5+Be6-Be 3-Be4-Be7-Be 8)/4; obtaining a first-order component REC-Z-Y of the eddy current effect of the Z coil assembly according to the formula (Be2+Be3+Be6+Be7-Be 1-Be4-Be5-Be 8)/4; obtaining a first-order component REC-Z-Z of the eddy current effect of the Z coil assembly according to the formula (Be1+Be2+Be3+Be4-Be 5-Be6-Be7-Be 8)/4;
after the X coil assembly is electrified, according to data obtained by all detection coils, a zero-order component REC-X-B0 of an eddy current effect of the X coil assembly is obtained according to a formula (Be1+Be2+Be3+Be4+Be5+Be6+Be7+Be8)/8; obtaining a first-order component REC-X-X of the eddy current effect of the X coil assembly according to the formula (Be1+Be2+Be5+Be6-Be 3-Be4-Be7-Be 8)/4; obtaining a first-order component REC-X-Y of the eddy current effect of the X coil assembly according to the formula (Be2+Be3+Be6+Be7-Be 1-Be4-Be5-Be 8)/4; obtaining a first-order component REC-X-Z of the eddy current effect of the X coil assembly according to the formula (Be1+Be2+Be3+Be4-Be 5-Be6-Be7-Be 8)/4;
after the Y coil assembly is electrified, according to the data obtained by all detection coils, a zero-order component REC-Y-B0 of an eddy current effect of the Y coil assembly is obtained according to a formula (Be1+Be2+Be3+Be4+Be5+Be6+Be7+Be8)/8; obtaining a first-order component REC-Y-X of the eddy current effect of the Y coil assembly according to the formula (Be1+Be2+Be5+Be6-Be 3-Be4-Be7-Be 8)/4; obtaining a first-order component REC-Y-Y of the eddy current effect of the Y coil assembly according to the formula (Be2+Be3+Be6+Be7-Be 1-Be4-Be5-Be 8)/4; obtaining a first-order component REC-Y-Z of the eddy current effect of the Y coil assembly according to the formula (Be1+Be2+Be3+Be4-Be 5-Be6-Be7-Be 8)/4;
the adjustment distances dx, dy, and dz and the adjustment angle dθ between the shield coil assembly and the main coil assembly are determined based on the zero-order component and the first-order component of the obtained eddy current effect.
Preferably, before detecting the current eddy current magnetic field strength of the shielding tub using the eddy current testing apparatus, the steps include:
marking a first zero degree scale mark and a first 90 degree scale mark on the top end of the main coil assembly;
marking a second zero degree scale mark and a second 90 degree scale mark on the top end of the shielding coil assembly;
the shield coil assembly is rotated relative to the main coil assembly until the first zero degree tick mark is aligned with the second zero degree tick mark and the first 90 degree tick mark is aligned with the second 90 degree tick mark.
Compared with the background art, the manufacturing and assembling method of the magnetic resonance imaging gradient coil provided by the invention comprises the following steps: firstly, placing an eddy current testing device in the center of a main coil assembly, electrifying the main coil assembly, and detecting the current gradient magnetic field intensity of the main coil assembly by using the eddy current testing device; secondly, judging whether the current gradient magnetic field intensity is within the allowable gradient magnetic field intensity range, if so, keeping the relative position between the eddy current testing device and the main coil assembly unchanged; if not, calibrating the relative position between the eddy current testing device and the main coil assembly; then, firstly sleeving the shielding coil assembly on the periphery of the main coil assembly, and then sleeving the shielding barrel on the periphery of the shielding coil assembly; then, the shielding coil assembly and the main coil assembly are electrified in series, and the current eddy current magnetic field intensity of the shielding barrel is detected by using an eddy current testing device; then judging whether the current eddy current magnetic field intensity is within the range of the allowable eddy current magnetic field intensity, if so, keeping the relative position between the shielding coil assembly and the main coil assembly unchanged; if not, calibrating the relative position between the shielding coil assembly and the main coil assembly; finally, the shielding barrel is removed, and the main coil assembly and the shielding coil assembly are fixed.
From the above, the invention can repeatedly adjust the relative position between the shielding coil assembly and the main coil assembly by using the gradient magnetic field intensity detected by the eddy current testing device, ensure the reliable relative position between the shielding coil assembly and the main coil assembly, reduce the eddy current effect, eliminate the problem of overlarge eddy current effect caused by manufacturing errors, improve the image quality of magnetic resonance imaging, and further improve the qualification rate of products.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method of manufacturing and assembling a magnetic resonance imaging gradient coil in accordance with an embodiment of the present invention;
fig. 2 is a simplified overall flow diagram of a method of fabricating and assembling a magnetic resonance imaging gradient coil in accordance with one embodiment of the present invention.
FIG. 3 is a cross-sectional view of a main coil assembly in a method of manufacturing and assembling a magnetic resonance imaging gradient coil in accordance with one embodiment of the present invention;
FIG. 4a is a block diagram of a primary coil of an X coil assembly;
FIG. 4b is a block diagram of the main coil of the Y coil assembly;
FIG. 4c is a block diagram of the primary coil of the Z-coil assembly;
FIG. 5 is a cross-sectional view of a shield coil assembly in a method of manufacturing and assembling a magnetic resonance imaging gradient coil in accordance with one embodiment of the present invention;
FIG. 6a is a block diagram of a shield coil of the X coil assembly;
FIG. 6b is a block diagram of a shield coil of the Y coil assembly;
FIG. 6c is a block diagram of a shield coil of the Z coil assembly;
FIG. 7 is a cross-sectional view of an assembly of a main coil assembly, a shielding coil assembly and a shielding barrel in a method of manufacturing and assembling a magnetic resonance imaging gradient coil according to an embodiment of the present invention;
fig. 8 is a state diagram of the main coil assembly and the shield coil assembly when scribe lines are aligned.
The reference numerals are as follows:
the main coil 101 of the X coil assembly, the main coil 102 of the Y coil assembly, the main coil 103 of the Z coil assembly, the main cooling water pipe 104, the main mold 105, the first zero degree scale line 106 and the first 90 degree scale line 107;
the shielding coil 201 of the X coil assembly, the shielding coil 202 of the Y coil assembly, the shielding coil 203 of the Z coil assembly, the shielding cooling water pipe 204, the shielding mold 205, the second zero degree scale line 206, and the second 90 degree scale line 207.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In order that those skilled in the art will better understand the present invention, the following description will be given in detail with reference to the accompanying drawings and specific embodiments.
Referring to fig. 1 to 8, fig. 1 is a schematic flow diagram illustrating a method for manufacturing and assembling a magnetic resonance imaging gradient coil according to an embodiment of the present invention; FIG. 2 is a simplified overall flow chart of a method of manufacturing and assembling a magnetic resonance imaging gradient coil in accordance with one embodiment of the present invention; FIG. 3 is a cross-sectional view of a main coil assembly in a method of manufacturing and assembling a magnetic resonance imaging gradient coil in accordance with one embodiment of the present invention; FIG. 4a is a block diagram of a primary coil of an X coil assembly; FIG. 4b is a block diagram of the main coil of the Y coil assembly; FIG. 4c is a block diagram of the primary coil of the Z-coil assembly; FIG. 5 is a cross-sectional view of a shield coil assembly in a method of manufacturing and assembling a magnetic resonance imaging gradient coil in accordance with one embodiment of the present invention; FIG. 6a is a block diagram of a shield coil of the X coil assembly; FIG. 6b is a block diagram of a shield coil of the Y coil assembly; FIG. 6c is a block diagram of a shield coil of the Z coil assembly; FIG. 7 is a cross-sectional view of an assembly of a main coil assembly, a shielding coil assembly and a shielding barrel in a method of manufacturing and assembling a magnetic resonance imaging gradient coil according to an embodiment of the present invention; fig. 8 is a state diagram of the main coil assembly and the shield coil assembly when scribe lines are aligned.
The embodiment of the invention discloses a manufacturing and assembling method of a magnetic resonance imaging gradient coil, which comprises the following steps:
the first step: firstly, placing an eddy current testing device 3 in the center of a main coil assembly 1, electrifying the main coil assembly 1, and detecting the current gradient magnetic field intensity of the main coil assembly 1 by using the eddy current testing device 3;
before the main coil assembly 1 is electrified, the main coil assembly 1 is assembled, firstly, the main coil 101 of the X coil assembly, the main coil 102 of the Y coil assembly, the main cooling water pipe 104 and the main coil 103 of the Z coil assembly are sequentially arranged in a main die 105 from bottom to top, wherein the main die 105 comprises an upper end cover, a positioning cylinder and a lower end cover, firstly, the main coil 101 of the X coil assembly, the main coil 102 of the Y coil assembly, the main cooling water pipe 104 and the main coil 103 of the Z coil assembly are sequentially stacked on the upper end cover from bottom to top, then the positioning cylinder is sleeved, and finally, the lower end cover is covered on the positioning cylinder. Next, the main mold 105 is assembled. Then, the main coil 101 of the X coil assembly, the main coil 102 of the Y coil assembly, the main cooling water pipe 104, and the main coil 103 of the Z coil assembly are fixed by resin casting; finally, the main mold 105 is removed and the assembled main coil assembly 1 is shown in fig. 3.
Wherein the main coil assembly 1 may comprise one or more shim coils. The main coil 101 of the X-coil assembly consists of saddle coils, symmetrical about the yz plane, as shown in fig. 4 a. The main coil 102 of the Y coil assembly consists of saddle coils, symmetrical about the xz plane, the main coil 102 of the Y coil assembly being circumferentially different from the main coil 101 of the X coil assembly by 90 degrees, as shown in fig. 4 b. The main coil 103 of the Z-coil assembly consists of a solenoid coil, symmetrical about the xy-plane, as shown in fig. 4 c. The main cooling water pipe 104 is formed by spirally winding a hollow water pipe with a circular section, and is made of nylon or copper pipe with good heat conduction performance. Of course, the main cooling water pipe 104 may be serpentine coiled.
Before the main coil assembly 1 is electrified, the shielding coil assembly 2 is assembled, firstly, a shielding cooling water pipe 204, a shielding coil 203 of the Z coil assembly, a shielding coil 201 of the X coil assembly and a shielding coil 202 of the Y coil assembly are sequentially arranged in a shielding mold 205 from bottom to top; wherein the structure of the shielding mold 205 is the same as that of the main mold 105; next, the shielding mold 205 is assembled; then, the shield cooling water pipe 204, the shield coil 203 of the Z coil assembly, the shield coil 201 of the X coil assembly, and the shield coil 202 of the Y coil assembly are fixed by resin casting; finally, the shielding mold 205 is removed, and the assembled shielding coil assembly 2 is shown in fig. 4.
Wherein the shielding coil 201 of the X-coil assembly consists of saddle coils, symmetrical about the yz plane, as shown in fig. 6 a; the shielding coil 202 of the Y coil assembly consists of saddle coils, symmetrical about the xz plane, the shielding coil 202 of the Y coil assembly being circumferentially different by 90 degrees from the shielding coil 201 of the X coil assembly, as shown in fig. 6 b; the shielding coil 203 of the Z-coil assembly consists of a solenoid coil, symmetrical about the xy-plane, as shown in fig. 6 c. The shielding cooling water pipe 204 is formed by spirally winding a hollow water pipe with a circular cross section, and is made of nylon or copper pipe with good heat conducting performance. Of course, the shielded cooling water pipe 204 may also be serpentine coiled.
And a second step of: judging whether the current gradient magnetic field intensity is within the allowable gradient magnetic field intensity range, if so, keeping the relative position between the eddy current testing device 3 and the main coil assembly 1 unchanged; if not, calibrating the relative position between the eddy current testing device 3 and the main coil assembly 1;
the allowable gradient magnetic field strength range refers to the gradient magnetic field strength corresponding to the minimum time when the relative positional deviation between the eddy current testing device 3 and the main coil assembly 1 is in the range of 1 mm.
Specifically, the eddy current testing device 3 is composed of eight detection coils, and the eight detection coils distributed at the vertexes of the cube of the eddy current testing device 3 are utilized to respectively detect the corresponding positions of the main coil assembly 1 to obtain a first gradient magnetic field Bg1, a second gradient magnetic field Bg2, a third gradient magnetic field Bg3, a fourth gradient magnetic field Bg4, a fifth gradient magnetic field Bg5, a sixth gradient magnetic field Bg6, a seventh gradient magnetic field Bg7 and an eighth gradient magnetic field Bg8; obtaining an X-direction distance between the center of the eddy current testing device 3 and the center of the main coil assembly 1 according to a formula (Bg1+Bg2+Bg3+Bg4+Bg5+Bg6+Bg7+Bg8)/(8X Gx), wherein Gx is gradient signal intensity; then, according to the formula (bg1+bg2+bg3+bg4+bg5+bg6+bg7+bg8)/(8×gy), the Y-direction distance between the center of the eddy current testing device 3 and the center of the main coil assembly 1 is obtained, wherein Gy is the gradient signal intensity; finally, according to the formula (bg1+bg2+bg3+bg4+bg5+bg6+bg7+bg8)/(8×gz), the Z-direction distance between the center of the eddy current testing device 3 and the center of the main coil assembly 1 is obtained, wherein Gz is the gradient signal intensity.
According to the X-direction distance, the Y-direction distance and the Z-direction distance, the position of the vortex testing device 3 is continuously adjusted to reduce the X-direction distance, the Y-direction distance and the Z-direction distance until the X-direction distance, the Y-direction distance and the Z-direction distance are within the allowable range. Of course, the eddy current testing device 3 may also consist of six, twelve or more detection coils.
And a third step of: the shielding coil assembly 2 and the shielding barrel 4 are sequentially sleeved on the periphery of the main coil assembly 1; specifically, the shielding coil assembly 2 is first sleeved on the main coil assembly 1, and then the shielding barrel 4 is sleeved on the periphery of the shielding coil assembly 2. The shielding tub 4 may be an aluminum tub, and of course, may be an aluminum alloy. The size of the shielding tub 4 may be determined according to the size of the heat radiation screen of the superconducting magnet matched to the corresponding gradient coil.
Rough adjustment may be performed by scribing before the relative position between the shield coil assembly 2 and the main coil assembly 1 is precisely adjusted by using the eddy current effect. Specifically, a first zero degree scale mark and a first 90 degree scale mark are firstly marked on the top end of the main coil assembly 1; marking a second zero degree scale mark and a second 90 degree scale mark on the top end of the shielding coil assembly 2; the shielding coil assembly 2 is rotated relative to the main coil assembly 1 until the first zero degree graduation line is aligned with the second zero degree graduation line and the first 90 degree graduation line is aligned with the second 90 degree graduation line, so that the main coil 101 of the X coil assembly is ensured to be consistent with the shielding coil 201 of the X coil assembly in azimuth, and the main coil 102 of the Y coil assembly is ensured to be consistent with the shielding coil 202 of the Y coil assembly in azimuth.
Fourth step: after the shielding coil assembly 2 and the main coil assembly 1 are electrified in series, detecting the current eddy current magnetic field intensity of the shielding barrel 4 by using the eddy current testing device 3;
the series connection of the shielding coil assembly 2 and the main coil assembly 1, specifically, the series connection of the main coil 101 of the X coil assembly and the shielding coil 201 of the X coil assembly forms the X coil assembly, the series connection of the main coil 102 of the Y coil assembly and the shielding coil 202 of the Y coil assembly forms the Y coil assembly, and the series connection of the main coil 103 of the Z coil assembly and the shielding coil 203 of the Z coil assembly forms the Z coil assembly.
The current eddy current magnetic field intensity of the shielding barrel 4 is detected by the eddy current testing device 3, specifically, the corresponding positions are detected by eight detection coils distributed at the vertex of the cube of the eddy current testing device 3 to obtain a first eddy current magnetic field Be1, a second eddy current magnetic field Be2, a third eddy current magnetic field Be3, a fourth eddy current magnetic field Be4, a fifth eddy current magnetic field Be5, a sixth eddy current magnetic field Be6, a seventh eddy current magnetic field Be7 and an eighth eddy current magnetic field Be8.
Fifth step: judging whether the current eddy current magnetic field intensity is within the allowable eddy current magnetic field intensity range, if so, keeping the relative position between the shielding coil assembly 2 and the main coil assembly 1 unchanged; if not, calibrating the relative position between the shielding coil assembly 2 and the main coil assembly 1;
specifically, 10A current is supplied to the Z coil assembly, and a zero-order component REC-Z-B0 of the eddy current effect of the Z coil assembly is obtained according to the data obtained by all the detection coils and according to the formula (Be1+Be2+Be3+Be4+Be5+Be6+Be7+Be8)/8; obtaining a first-order component REC-Z-X of the eddy current effect of the Z coil assembly according to the formula (Be1+Be2+Be5+Be6-Be 3-Be4-Be7-Be 8)/4; obtaining a first-order component REC-Z-Y of the eddy current effect of the Z coil assembly according to the formula (Be2+Be3+Be6+Be7-Be 1-Be4-Be5-Be 8)/4; obtaining a first-order component REC-Z-Z of the eddy current effect of the Z coil assembly according to the formula (Be1+Be2+Be3+Be4-Be 5-Be6-Be7-Be 8)/4;
charging 10A current into the X coil assembly, and obtaining a zero-order component REC-X-B0 of the eddy current effect of the X coil assembly according to the data obtained by all the detection coils and the formula (Be1+Be2+Be3+Be4+Be5+Be6+Be7+Be8)/8; obtaining a first-order component REC-X-X of the eddy current effect of the X coil assembly according to the formula (Be1+Be2+Be5+Be6-Be 3-Be4-Be7-Be 8)/4; obtaining a first-order component REC-X-Y of the eddy current effect of the X coil assembly according to the formula (Be2+Be3+Be6+Be7-Be 1-Be4-Be5-Be 8)/4; obtaining a first-order component REC-X-Z of the eddy current effect of the X coil assembly according to the formula (Be1+Be2+Be3+Be4-Be 5-Be6-Be7-Be 8)/4;
charging 10A current into the Y coil assembly, and obtaining a zero-order component REC-Y-B0 of the eddy current effect of the Y coil assembly according to the data obtained by all the detection coils and the formula (Be1+Be2+Be3+Be4+Be5+Be6+Be7+Be8)/8; obtaining a first-order component REC-Y-X of the eddy current effect of the Y coil assembly according to the formula (Be1+Be2+Be5+Be6-Be 3-Be4-Be7-Be 8)/4; obtaining a first-order component REC-Y-Y of the eddy current effect of the Y coil assembly according to the formula (Be2+Be3+Be6+Be7-Be 1-Be4-Be5-Be 8)/4; obtaining a first-order component REC-Y-Z of the eddy current effect of the Y coil assembly according to the formula (Be1+Be2+Be3+Be4-Be 5-Be6-Be7-Be 8)/4;
then, the adjustment distances dx, dy and dz of the shielding coil assembly 2 are determined according to the signal intensities of the zero-order components REC-X-B0, REC-Y-B0, REC-Z-B0 and the corresponding zero-order components; and then determining an adjustment angle dθ of the shielding coil assembly 2 according to the first-order component REC-X-Y, REC-Y-X of the eddy current and the signal intensity of the corresponding first-order component, and finally carrying out corresponding translational and rotational adjustment on the shielding coil assembly 2 according to the measured adjustment amplitudes dx, dy, dz and dθ, and repeating for a plurality of times until the current eddy current magnetic field intensity is within the allowable eddy current magnetic field intensity range. The allowable eddy current magnetic field intensity range refers to the eddy current magnetic field intensity corresponding to the optimum range of the relative position between the shield coil assembly 2 and the main coil assembly 1. When the current eddy current magnetic field strength of the shield can 4 is minimized, the relative position between the shield coil assembly 2 and the main coil assembly 1 is optimized.
Of course, the signal intensity of the zero-order component and the signal intensity of the first-order component can be obtained through computer simulation, and also can be obtained through a testing means.
Sixth step: after the shield tub 4 is removed, the main coil assembly 1 and the shield coil assembly 2 are fixed. Specifically, the gap 5 between the main coil assembly 1 and the shield coil assembly 2 is filled with an adhesive material such as resin, which can provide sufficient adhesive strength and supporting rigidity after curing and molding, and can ensure the relative positional relationship of the main coil assembly 1 and the shield coil assembly 2. The filler resin may be a resin curable at normal temperature or a resin curable by heating. Of course, inorganic materials such as silica can be added to the filling resin to increase the rigidity of the resin, which is beneficial to improving the noise characteristics of the gradient coil. In addition, it is necessary to ensure that the relative position between the main coil assembly 1 and the shield coil assembly 2 does not change during the casting process.
In summary, according to the method for manufacturing and assembling the magnetic resonance imaging gradient coil provided by the invention, the relative position between the shielding coil assembly and the main coil assembly can be repeatedly adjusted by utilizing the gradient magnetic field intensity detected by the eddy current testing device, so that the reliability of the relative position between the shielding coil assembly and the main coil assembly is ensured, the eddy current effect is reduced, the problem of overlarge eddy current effect caused by manufacturing errors is eliminated, the image quality of magnetic resonance imaging is improved, and the qualification rate of products is further improved.
The above description is made in detail of the method for manufacturing and assembling a magnetic resonance imaging gradient coil provided by the present invention, and specific examples are applied herein to illustrate the principles and embodiments of the present invention, and the above examples are only used to help understand the method and core ideas of the present invention; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in accordance with the ideas of the present invention, the present description should not be construed as limiting the present invention in view of the above.
Claims (6)
1. A method of manufacturing and assembling a magnetic resonance imaging gradient coil, comprising the steps of:
detecting the current gradient magnetic field intensity of the main coil assembly by using an eddy current testing device arranged in the main coil assembly after the main coil assembly is electrified;
judging whether the current gradient magnetic field intensity is within an allowable gradient magnetic field intensity range, if so, keeping the relative position between the eddy current testing device and the main coil assembly unchanged; if not, calibrating the relative position between the eddy current testing device and the main coil assembly;
sleeving a shielding coil assembly and a shielding barrel on the periphery of the main coil assembly in sequence;
detecting the current eddy current magnetic field intensity of the shielding barrel by using the eddy current testing device after the shielding coil assembly and the main coil assembly are electrified in series;
judging whether the current eddy current magnetic field intensity is within an allowable eddy current magnetic field intensity range, if so, keeping the relative position between the shielding coil assembly and the main coil assembly unchanged; if not, calibrating the relative position between the shielding coil assembly and the main coil assembly;
after removing the shielding tub, the main coil assembly and the shielding coil assembly are fixed.
2. The method of manufacturing and assembling a magnetic resonance imaging gradient coil according to claim 1, wherein the step of, prior to detecting the current gradient magnetic field strength of the main coil assembly with an eddy current testing device disposed within the main coil assembly, further comprises:
sequentially arranging a main coil of an X coil assembly, a main coil of a Y coil assembly, a main cooling water pipe and a main coil of a Z coil assembly in a main die from bottom to top;
combining the main molds;
fixing the main coil of the X coil assembly, the main coil of the Y coil assembly, the main cooling water pipe and the main coil of the Z coil assembly by resin casting;
and detaching the main die.
3. The method of manufacturing and assembling a magnetic resonance imaging gradient coil according to claim 1, wherein the step of, prior to detecting the current gradient magnetic field strength of the main coil assembly with an eddy current testing device disposed within the main coil assembly, further comprises:
the shielding cooling water pipe, the shielding coil of the Z coil assembly, the shielding coil of the X coil assembly and the shielding coil of the Y coil assembly are sequentially arranged in a shielding mold from bottom to top;
combining the shielding mold;
the shielding cooling water pipe, the shielding coil of the Z coil assembly, the shielding coil of the X coil assembly and the shielding coil of the Y coil assembly are fixed by resin casting;
and removing the shielding mold.
4. A method of manufacturing and assembling a magnetic resonance imaging gradient coil according to any one of claims 1 to 3, wherein the detecting the current gradient magnetic field strength of the main coil assembly with an eddy current testing device disposed within the main coil assembly comprises:
the method comprises the steps of respectively detecting corresponding positions of a main coil assembly by utilizing eight detection coils distributed at the vertexes of a cube of an eddy current testing device to obtain a first gradient magnetic field Bg1, a second gradient magnetic field Bg2, a third gradient magnetic field Bg3, a fourth gradient magnetic field Bg4, a fifth gradient magnetic field Bg5, a sixth gradient magnetic field Bg6, a seventh gradient magnetic field Bg7 and an eighth gradient magnetic field Bg8;
obtaining an X-direction distance between the center of the eddy current testing device and the center of the main coil assembly according to a formula (Bg1+Bg2+Bg3+Bg4+Bg5+Bg6+Bg7+Bg8)/(8X Gx), wherein Gx is X-direction gradient signal intensity;
obtaining a Y-direction distance between the center of the eddy current testing device and the center of the main coil assembly according to a formula (Bg1+Bg2+Bg3+Bg4+Bg5+Bg6+Bg7+Bg8)/(8 x Gy), wherein Gy is Y-direction gradient signal intensity;
and obtaining the Z-direction distance between the center of the eddy current testing device and the center of the main coil assembly according to a formula (Bg1+Bg2+Bg3+Bg4+Bg5+Bg6+Bg7+Bg8)/(8 x Gz), wherein Gz is the Z-direction gradient signal intensity.
5. A method of manufacturing and assembling a magnetic resonance imaging gradient coil according to any one of claims 1 to 3, wherein the step of detecting the current eddy current magnetic field strength of the shield can with the eddy current testing device after the shield coil assembly is energized in series with the main coil assembly comprises:
the method comprises the steps of connecting a main coil of an X coil assembly and a shielding coil of the X coil assembly in series to form the X coil assembly, connecting a main coil of a Y coil assembly and a shielding coil of the Y coil assembly in series to form the Y coil assembly, and connecting a main coil of a Z coil assembly and a shielding coil of the Z coil assembly in series to form the Z coil assembly;
the method comprises the steps of respectively detecting corresponding positions by using eight detection coils distributed at the vertexes of a cube of an eddy current testing device to obtain a first eddy current magnetic field Be1, a second eddy current magnetic field Be2, a third eddy current magnetic field Be3, a fourth eddy current magnetic field Be4, a fifth eddy current magnetic field Be5, a sixth eddy current magnetic field Be6, a seventh eddy current magnetic field Be7 and an eighth eddy current magnetic field Be8;
judging whether the current eddy current magnetic field strength is within an allowable eddy current magnetic field strength range, if so, keeping the relative position between the shielding coil assembly and the main coil assembly unchanged; if not, calibrating the relative position between the shielding coil assembly and the main coil assembly, wherein the steps comprise:
after the Z coil component is electrified, according to the data obtained by all the detection coils, a zero-order component REC-Z-B0 of the eddy current effect of the Z coil component is obtained according to the formula (Be1+Be2+Be3+Be4+Be5+Be6+Be7+Be8)/8; obtaining a first-order component REC-Z-X of the eddy current effect of the Z coil assembly according to the formula (Be1+Be2+Be5+Be6-Be 3-Be4-Be7-Be 8)/4; obtaining a first-order component REC-Z-Y of the eddy current effect of the Z coil assembly according to the formula (Be2+Be3+Be6+Be7-Be 1-Be4-Be5-Be 8)/4; obtaining a first-order component REC-Z-Z of the eddy current effect of the Z coil assembly according to the formula (Be1+Be2+Be3+Be4-Be 5-Be6-Be7-Be 8)/4;
after the X coil component is electrified, according to the data obtained by all the detection coils, a zero-order component REC-X-B0 of the eddy current effect of the X coil component is obtained according to the formula (Be1+Be2+Be3+Be4+Be5+Be6+Be7+Be8)/8; obtaining a first-order component REC-X-X of the eddy current effect of the X coil assembly according to the formula (Be1+Be2+Be5+Be6-Be 3-Be4-Be7-Be 8)/4; obtaining a first-order component REC-X-Y of the eddy current effect of the X coil assembly according to the formula (Be2+Be3+Be6+Be7-Be 1-Be4-Be5-Be 8)/4; obtaining a first-order component REC-X-Z of the eddy current effect of the X coil assembly according to the formula (Be1+Be2+Be3+Be4-Be 5-Be6-Be7-Be 8)/4;
after the Y coil assembly is electrified, according to the data obtained by all the detection coils, a zero-order component REC-Y-B0 of an eddy current effect of the Y coil assembly is obtained according to the formula (Be1+Be2+Be3+Be4+Be5+Be6+Be7+Be8)/8; obtaining a first-order component REC-Y-X of the eddy current effect of the Y coil assembly according to the formula (Be1+Be2+Be5+Be6-Be 3-Be4-Be7-Be 8)/4; obtaining a first-order component REC-Y-Y of the eddy current effect of the Y coil assembly according to the formula (Be2+Be3+Be6+Be7-Be 1-Be4-Be5-Be 8)/4; obtaining a first-order component REC-Y-Z of the eddy current effect of the Y coil assembly according to the formula (Be1+Be2+Be3+Be4-Be 5-Be6-Be7-Be 8)/4;
and determining adjustment distances dx, dy and dz and an adjustment angle dθ between the shielding coil assembly and the main coil assembly according to the zero-order component and the first-order component of the obtained eddy current effect.
6. A method of manufacturing and assembling a magnetic resonance imaging gradient coil according to any one of claims 1 to 3, wherein prior to said detecting the current eddy current magnetic field strength of the shielding bucket with the eddy current testing device, the steps comprise:
marking a first zero-degree scale mark and a first 90-degree scale mark on the top end of the main coil assembly;
marking a second zero-degree scale mark and a second 90-degree scale mark on the top end of the shielding coil assembly;
the shield coil assembly is rotated relative to the main coil assembly until the first zero degree tick mark is aligned with the second zero degree tick mark and the first 90 degree tick mark is aligned with the second 90 degree tick mark.
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