CN115047388A - 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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- CN115047388A CN115047388A CN202110254640.5A CN202110254640A CN115047388A CN 115047388 A CN115047388 A CN 115047388A CN 202110254640 A CN202110254640 A CN 202110254640A CN 115047388 A CN115047388 A CN 115047388A
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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
Abstract
The invention discloses a manufacturing and assembling method of a magnetic resonance imaging gradient coil, which utilizes the strength of a gradient magnetic field 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 strength of the eddy current magnetic field, thereby ensuring that the relative position between the shielding coil assembly and the main coil assembly meets the requirement, eliminating the problem of larger eddy current effect caused by manufacturing error, improving the image quality of magnetic resonance imaging and further improving 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
Gradient coils are the core components of a magnetic resonance imaging apparatus and include three orthogonal coil sets for generating X, Y and Z-direction magnetic field gradients, with the X-direction magnetic field gradient being generated by an X-coil assembly, the Y-direction magnetic field gradient being generated by a Y-coil assembly, and the Z-direction magnetic field gradient being generated by a Z-coil assembly. The X-coil assembly, the Y-coil assembly and the Z-coil assembly are each comprised of a corresponding main coil for generating the required magnetic field gradient and a shielding coil for reducing eddy current effects.
The prior manufacturing method of the gradient coil adopts the processes of integrated assembly and integral casting, and the manufacturing process comprises the following steps: firstly, sequentially assembling 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 on the outer surface of a cylindrical mold, limiting the geometric positions of the coils by using positioning pins or positioning blocks in the installation process to ensure that the angular position and the axial position meet the azimuth requirement, then assembling an outer cover mold and an end cover mold, and finally pouring, curing and molding by using resin.
In the assembling process, positioning problems such as inclination and position deviation of a positioning pin or a positioning block due to machining or assembling deviation can be caused, so that the relative position of a main coil and a shielding coil deviates from a design value, and an eddy current effect is increased, for example, a relatively large eddy current zero-order component can be generated in a Z coil assembly due to the relative position deviation of 0.2mm in the axial direction, a relatively large eddy current first-order component can be generated in an X coil assembly and a Y coil assembly due to the relative position deviation of 2mm in the angular direction, and finally, the deterioration of image performance is caused, and the qualification rate of products is influenced.
Disclosure of Invention
In view of this, an object of the present invention is to provide a method for manufacturing and assembling a magnetic resonance imaging gradient coil, in which a relative position between a vortex testing device and a main coil assembly and a relative position between a shielding coil assembly and a main coil assembly are repeatedly adjusted by using a gradient magnetic field strength detected by the vortex testing device, so as to ensure that the relative position between the shielding coil assembly and the main coil assembly is reliable, reduce a vortex effect, improve image quality of magnetic resonance imaging, and improve a yield 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 a vortex testing device arranged in the main coil assembly;
judging whether the current gradient magnetic field intensity is within the range of the allowable gradient magnetic field intensity, 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;
sequentially sleeving a shielding coil assembly and a shielding barrel on the periphery of the main coil assembly;
after the shielding coil assembly and the main coil assembly are electrified in series, detecting the current eddy magnetic field intensity of the shielding barrel by using an eddy current testing device;
judging whether the current eddy magnetic field strength is within the allowable eddy 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;
after the shield barrel is removed, the main coil assembly and the shield coil assembly are fixed.
Preferably, before detecting the present gradient magnetic field strength of the main coil assembly with the eddy current testing apparatus disposed within the main coil assembly, the steps further include:
sequentially installing 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 mould;
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 (5) detaching the main die.
Preferably, before detecting the current gradient magnetic field strength of the main coil assembly by using the eddy current testing device disposed in the main coil assembly, the steps further include:
sequentially arranging 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 in a shielding mould from bottom to top;
combining shielding molds;
fixedly pouring 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 by using resin;
and (5) detaching the shielding mold.
Preferably, the detecting the current gradient magnetic field strength of the main coil assembly by using the eddy current testing device disposed in the main coil assembly comprises:
eight detection coils distributed at the vertex of the cube of the eddy current testing device are used for respectively detecting the corresponding positions of the main coil assembly 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 Bg 8;
obtaining the 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+ Bg 8)/(8X Gx), wherein Gx is the 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 the gradient signal intensity;
the Z-direction distance between the center of the eddy current testing device and the center of the main coil assembly is obtained according to the formula (Bg1+ Bg2+ Bg3+ Bg4+ Bg5+ Bg6+ Bg7+ Bg8)/(8 × Gz), where Gz is the gradient signal strength.
Preferentially, after the shielding coil assembly and the main coil assembly are connected in series and electrified, the current eddy magnetic field intensity of the shielding barrel is detected by using an eddy current testing device, and the method comprises the following steps:
connecting a main coil of the X coil assembly and a shielding coil of the X coil assembly in series to form an X coil assembly, connecting a main coil of the Y coil assembly and a shielding coil of the Y coil assembly in series to form a Y coil assembly, and connecting a main coil of the Z coil assembly and a shielding coil of the Z coil assembly in series to form a Z coil assembly;
eight detection coils distributed at the vertex of the cube of the eddy current testing device are used for respectively detecting corresponding positions 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 Be 8;
after the Z coil assembly is electrified, according to data obtained by all detection coils, obtaining a zeroth-order component REC-Z-B0 of the eddy current effect of the Z coil assembly according to a formula (Be1+ Be2+ Be3+ Be4+ Be5+ Be6+ Be7+ Be 8)/8; obtaining a first-order component REC-Z-X of the eddy current effect of the Z coil assembly according to a formula (Be1+ Be2+ Be5+ Be6-Be3-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 a formula (Be2+ Be3+ Be6+ Be7-Be1-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 a formula (Be1+ Be2+ Be3+ Be4-Be5-Be6-Be7-Be 8)/4;
after the current is introduced into the X coil assembly, according to data obtained by all detection coils, obtaining a zeroth-order component REC-X-B0 of the eddy current effect of the X coil assembly according to a formula (Be1+ Be2+ Be3+ Be4+ Be5+ Be6+ Be7+ Be 8)/8; obtaining a first-order component REC-X-X of the eddy current effect of the X coil assembly according to a formula (Be1+ Be2+ Be5+ Be6-Be3-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 a formula (Be2+ Be3+ Be6+ Be7-Be1-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 a formula (Be1+ Be2+ Be3+ Be4-Be5-Be6-Be7-Be 8)/4;
after the Y coil assembly is electrified, according to data obtained by all detection coils, obtaining a zeroth-order component REC-Y-B0 of the eddy current effect of the Y coil assembly according to a formula (Be1+ Be2+ Be3+ Be4+ Be5+ Be6+ Be7+ Be 8)/8; obtaining a first-order component REC-Y-X of the eddy current effect of the Y coil assembly according to a formula (Be1+ Be2+ Be5+ Be6-Be3-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 a formula (Be2+ Be3+ Be6+ Be7-Be1-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 a formula (Be1+ Be2+ Be3+ Be4-Be5-Be6-Be7-Be 8)/4;
according to the zero-order component and the first-order component of the obtained eddy current effect, the adjusting distances dx, dy and dz and the adjusting angle d theta between the shielding coil assembly and the main coil assembly are determined.
Preferably, before the current eddy magnetic field strength of the shielding barrel is detected by the eddy current testing device, 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 magnetic field intensity of the shielding barrel is detected by using an eddy current testing device; then, judging whether the current eddy magnetic field intensity is within the allowable eddy 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; and finally, removing the shielding barrel and fixing the main coil assembly and the shielding coil assembly.
Therefore, the invention can repeatedly adjust the relative position between the shielding coil assembly and the main coil assembly by utilizing the gradient magnetic field intensity detected by the eddy current testing device, ensure the relative position between the shielding coil assembly and the main coil assembly to be reliable, reduce the eddy current effect, eliminate the problem of larger 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 used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a simplified flow diagram of a method of manufacturing and assembling a magnetic resonance imaging gradient coil according to an embodiment of the present invention;
fig. 2 is a simplified overall flowchart of a method for manufacturing and assembling a magnetic resonance imaging gradient coil according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view of a main coil assembly in a method for fabricating and assembling a magnetic resonance imaging gradient coil according to an embodiment of the present invention;
FIG. 4a is a block diagram of a main 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 main coil of the Z-coil assembly;
FIG. 5 is a cross-sectional view of a shield coil assembly in a method of manufacturing an assembly gradient magnetic resonance imaging coil in accordance with an 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 the shield coil of the Y-coil assembly;
FIG. 6c is a block diagram of the shield coil of the Z-coil assembly;
fig. 7 is an assembled cross-sectional view of a main coil assembly, a shield coil assembly and a shield barrel in a method for manufacturing and assembling a magnetic resonance imaging gradient coil according to an embodiment of the present invention;
fig. 8 is a state diagram in alignment of the scribes of both the main coil assembly and the shield coil assembly.
The reference numbers 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 mark 106, and the first 90-degree scale mark 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 mark 206 and the second 90-degree scale mark 207.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order that those skilled in the art will better understand the disclosure, a more detailed description of the disclosure is given below along with the accompanying drawings and specific examples.
Referring to fig. 1 to 8, fig. 1 is a simplified flowchart of 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 flowchart of a method for manufacturing and assembling a magnetic resonance imaging gradient coil according to an embodiment of the present invention; FIG. 3 is a cross-sectional view of a main coil assembly in a method for fabricating and assembling a magnetic resonance imaging gradient coil according to an 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 main 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 an 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 the shield coil of the Y-coil assembly; FIG. 6c is a block diagram of the shield coil of the Z-coil assembly; fig. 7 is an assembled cross-sectional view of the main coil assembly, the shielding coil assembly and the shielding barrel in the method for manufacturing and assembling the mri gradient coil according to an embodiment of the present invention; fig. 8 is a state diagram in alignment of the scribes of both the main coil assembly and the shield coil assembly.
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 is as follows: 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 powered on, 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, 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, fixing a main coil 101 of the X coil assembly, a main coil 102 of the Y coil assembly, a main cooling water pipe 104 and a main coil 103 of the Z coil assembly by resin casting; finally, the main mold 105 is removed, and the assembled main coil assembly 1 is shown in fig. 3.
One or more shim coils may be included in the main coil assembly 1. 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 90 degrees different from the main coil 101 of the X-coil assembly, 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 cross section, and is made of nylon or a copper pipe with good heat conductivity. Of course, the main cooling water pipe 104 may be coiled in a serpentine shape.
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 a Z coil assembly, a shielding coil 201 of an X coil assembly and a shielding coil 202 of a Y coil assembly are sequentially arranged in a shielding mould 205 from bottom to top; wherein, the structure of the shielding mold 205 is the same as that of the main mold 105; secondly, the shielding mold 205 is assembled; then, 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 fixed by resin casting; finally, the shielding mold 205 is removed and the assembled shielded coil assembly 2 is shown in fig. 4.
Wherein the shield coil 201 of the X-coil assembly consists of saddle coils, symmetrical about the yz-plane, as shown in fig. 6 a; the shield coil 202 of the Y-coil assembly consists of saddle coils, symmetrical about the xz-plane, the shield coil 202 of the Y-coil assembly being circumferentially 90 degrees different from the shield coil 201 of the X-coil assembly, as shown in fig. 6 b; the shield 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 a copper pipe with good heat conductivity. Of course, the shield cooling water pipe 204 may be coiled in a serpentine shape.
The second step is that: judging whether the current gradient magnetic field intensity is within the range of the allowable gradient magnetic field intensity, 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 a gradient magnetic field strength corresponding to the minimum relative positional deviation between the eddy current testing device 3 and the main coil assembly 1 within a 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 vertex of the cube of the eddy current testing device 3 are firstly utilized to respectively detect the corresponding positions of the main coil assembly 1, so as 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 Bg 8; then obtaining the 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+ Bg 8)/(8X Gx), wherein Gx is the gradient signal intensity; next, the Y-direction distance between the center of the eddy current testing apparatus 3 and the center of the main coil block 1 is obtained according to the formula (Bg1+ Bg2+ Bg3+ Bg4+ Bg5+ Bg6+ Bg7+ Bg8)/(8 × Gy), where Gy is the gradient signal intensity; finally, the Z-direction distance between the center of the eddy current testing apparatus 3 and the center of the main coil assembly 1 is obtained according to the formula (Bg1+ Bg2+ Bg3+ Bg4+ Bg5+ Bg6+ Bg7+ Bg8)/(8 × Gz), where Gz is the gradient signal strength.
And continuously adjusting the position of the eddy current testing device 3 according to the X-direction distance, the Y-direction distance and the Z-direction distance 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 an allowable range. Of course, the eddy current testing device 3 may also consist of six, twelve or more search coils.
The third step: sequentially sleeving a shielding coil assembly 2 and a shielding barrel 4 on the periphery of a main coil assembly 1; specifically, firstly, the shielding coil assembly 2 is 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 barrel 4 may be an aluminum barrel, or an aluminum alloy. The size of the shielding barrel 4 can be determined according to the size of a heat radiation screen of the superconducting magnet matched with the corresponding gradient coil.
Before the relative position between the shielding coil assembly 2 and the main coil assembly 1 is accurately adjusted by using the eddy current effect, coarse adjustment may be performed by using a scribing method. Specifically, a first zero-degree scale mark and a first 90-degree scale mark are marked at 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 shield coil assembly 2 is rotated relative to the main coil assembly 1 until the first zero degree scale mark is aligned with the second zero degree scale mark and the first 90 degree scale mark is aligned with the second 90 degree scale mark, so that the main coil 101 of the X coil assembly and the shield coil 201 of the X coil assembly are consistent in orientation, and the main coil 102 of the Y coil assembly and the shield coil 202 of the Y coil assembly are consistent in orientation.
The fourth step: after the shielding coil assembly 2 and the main coil assembly 1 are electrified in series, detecting the current eddy magnetic field intensity of the shielding barrel 4 by using the eddy current testing device 3;
the main coil assembly 2 and the main coil assembly 1 are connected in series, specifically, the main coil 101 of the X coil assembly and the shielding coil 201 of the X coil assembly are connected in series to form the X coil assembly, the main coil 102 of the Y coil assembly and the shielding coil 202 of the Y coil assembly are connected in series to form the Y coil assembly, and the main coil 103 of the Z coil assembly and the shielding coil 203 of the Z coil assembly are connected in series to form the Z coil assembly.
The current eddy current magnetic field strength of the shielding barrel 4 is detected by the eddy current testing device 3, and specifically, the eight detection coils distributed at the vertex of the cube of the eddy current testing device 3 are used for respectively detecting corresponding positions 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 Be 8.
The fifth step: judging whether the current eddy magnetic field strength is within the allowable eddy magnetic field strength 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, a current of 10A is introduced into the Z coil assembly, and a zeroth-order component REC-Z-B0 of the eddy current effect of the Z coil assembly is obtained according to a formula (Be1+ Be2+ Be3+ Be4+ Be5+ Be6+ Be7+ Be8)/8 according to data obtained by all the search coils; obtaining a first-order component REC-Z-X of the eddy current effect of the Z coil assembly according to a formula (Be1+ Be2+ Be5+ Be6-Be3-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 a formula (Be2+ Be3+ Be6+ Be7-Be1-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 a formula (Be1+ Be2+ Be3+ Be4-Be5-Be6-Be7-Be 8)/4;
a current of 10A is introduced into the X coil assembly, and according to data obtained by all the detection coils, a zeroth order component REC-X-B0 of the eddy current effect of the X coil assembly is obtained according to a formula (Be1+ Be2+ Be3+ Be4+ Be5+ Be6+ Be7+ Be 8)/8; obtaining a first-order component REC-X-X of the eddy current effect of the X coil assembly according to a formula (Be1+ Be2+ Be5+ Be6-Be3-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 a formula (Be2+ Be3+ Be6+ Be7-Be1-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 a formula (Be1+ Be2+ Be3+ Be4-Be5-Be6-Be7-Be 8)/4;
a current of 10A is introduced into the Y coil assembly, and according to data obtained by all the detection coils, a zeroth-order component REC-Y-B0 of the eddy current effect of the Y coil assembly is obtained according to a formula (Be1+ Be2+ Be3+ Be4+ Be5+ Be6+ Be7+ Be 8)/8; obtaining a first-order component REC-Y-X of the eddy current effect of the Y coil assembly according to a formula (Be1+ Be2+ Be5+ Be6-Be3-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 a formula (Be2+ Be3+ Be6+ Be7-Be1-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 a formula (Be1+ Be2+ Be3+ Be4-Be5-Be6-Be7-Be 8)/4;
then, according to the signal strength of the zero-order components REC-X-B0, REC-Y-B0, REC-Z-B0 and the corresponding zero-order components, the adjusting distances dx, dy and dz of the shielding coil assembly 2 are determined; and determining an adjusting angle d theta 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 performing corresponding translation and rotation adjustment on the shielding coil assembly 2 according to the measured adjusting amplitude dx, dy, dz and d theta, and repeating the steps for a plurality of times until the current eddy current magnetic field intensity is within the allowable range of the eddy current magnetic field intensity. The allowable range of the eddy current magnetic field strength refers to the corresponding eddy current magnetic field strength when the relative position between the shielding coil assembly 2 and the main coil assembly 1 reaches the optimal range. When the current eddy magnetic field strength of the shield can 4 reaches a minimum, the relative position between the shield coil assembly 2 and the main coil assembly 1 reaches an optimum.
Of course, the signal intensity of the zeroth order component and the signal intensity of the first order component can be obtained through computer simulation, and can also be obtained through a test means.
And a sixth step: after the shield can 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, and the resin can provide sufficient adhesive strength and support rigidity after curing and molding, so that the relative positional relationship between the main coil assembly 1 and the shield coil assembly 2 can be ensured. The filling resin may be a resin cured at normal temperature or a resin cured by heating. Of course, inorganic materials such as silica can be added into the filling resin to increase the rigidity of the resin, which is beneficial to improving the noise characteristic 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, the manufacturing and assembling method of the magnetic resonance imaging gradient coil provided by the invention can repeatedly adjust the relative position between the shielding coil assembly and the main coil assembly by using the strength of the gradient magnetic field detected by the eddy current testing device, ensure the relative position between the shielding coil assembly and the main coil assembly to be reliable, reduce the eddy current effect, eliminate the problem of large eddy current effect caused by manufacturing errors, improve the image quality of magnetic resonance imaging, and further improve the qualification rate of products.
The method for manufacturing and assembling the magnetic resonance imaging gradient coil provided by the invention is described in detail, and the principle and the embodiment of the invention are explained by applying specific examples, and the description of the above examples is only used for helping to understand the method of the invention and the core idea thereof; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
Claims (6)
1. A method of manufacturing and assembling a magnetic resonance imaging gradient coil, comprising the steps of:
after the main coil assembly is electrified, detecting the current gradient magnetic field intensity of the main coil assembly by using a vortex testing device arranged in the main coil assembly;
judging whether the current gradient magnetic field strength is within an allowable gradient magnetic field strength 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;
sequentially sleeving the shielding coil assembly and the shielding barrel on the periphery of the main coil assembly;
after the shielding coil assembly and the main coil assembly are electrified in series, detecting the current eddy magnetic field intensity of the shielding barrel by using the eddy current testing device;
judging whether the current eddy magnetic field strength is within an allowable eddy 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;
after removing the shielding barrel, fixing the main coil assembly and the shielding coil assembly.
2. The method for manufacturing and assembling a magnetic resonance imaging gradient coil as set forth in 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 installing 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 mold;
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 for manufacturing and assembling a magnetic resonance imaging gradient coil as set forth in 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 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 in a shielding mould from bottom to top;
assembling the shielding mold;
fixing the shielding cooling water pipe, the shielding coil of the Z coil component, the shielding coil of the X coil component and the shielding coil of the Y coil component by resin casting;
and removing the shielding mould.
4. The method for manufacturing and assembling a magnetic resonance imaging gradient coil according to any one of claims 1 to 3, wherein the detecting a current gradient magnetic field strength of the main coil assembly with an eddy current testing device disposed within the main coil assembly comprises:
eight detection coils distributed at the vertex of the cube of the eddy current testing device are used for respectively detecting the corresponding positions of the main coil assembly 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 Bg 8;
obtaining the 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+ Bg 8)/(8X Gx), wherein Gx is the 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 × Gy), wherein Gy is the gradient signal intensity;
obtaining the Z-direction distance between the center of the eddy current testing device and the center of the main coil assembly according to the formula (Bg1+ Bg2+ Bg3+ Bg4+ Bg5+ Bg6+ Bg7+ Bg8)/(8 x Gz), wherein the Gz is the gradient signal intensity.
5. The method for manufacturing and assembling a magnetic resonance imaging gradient coil according to any one of claims 1 to 3, wherein the current eddy magnetic field strength of the shielding barrel is detected by the eddy current testing device after the shielding coil assembly and the main coil assembly are electrified in series, and the steps include:
connecting a main coil of the X coil assembly and a shielding coil of the X coil assembly in series to form an X coil assembly, connecting a main coil of the Y coil assembly and a shielding coil of the Y coil assembly in series to form a Y coil assembly, and connecting a main coil of the Z coil assembly and a shielding coil of the Z coil assembly in series to form a Z coil assembly;
eight detection coils distributed at the vertex of the cube of the eddy current testing device are used for respectively detecting corresponding positions 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 Be 8;
after the Z coil assembly is electrified, according to data obtained by all the detection coils, obtaining a zeroth-order component REC-Z-B0 of the eddy current effect of the Z coil assembly according to a formula (Be1+ Be2+ Be3+ Be4+ Be5+ Be6+ Be7+ Be 8)/8; obtaining a first-order component REC-Z-X of the eddy current effect of the Z coil assembly according to a formula (Be1+ Be2+ Be5+ Be6-Be3-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 a formula (Be2+ Be3+ Be6+ Be7-Be1-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 a formula (Be1+ Be2+ Be3+ Be4-Be5-Be6-Be7-Be 8)/4;
after the current is introduced into the X coil assembly, according to data obtained by all the detection coils, obtaining a zero-order component REC-X-B0 of the eddy current effect of the X coil assembly according to a formula (Be1+ Be2+ Be3+ Be4+ Be5+ Be6+ Be7+ Be 8)/8; obtaining a first-order component REC-X-X of the eddy current effect of the X coil assembly according to a formula (Be1+ Be2+ Be5+ Be6-Be3-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 a formula (Be2+ Be3+ Be6+ Be7-Be1-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 a formula (Be1+ Be2+ Be3+ Be4-Be5-Be6-Be7-Be 8)/4;
after the Y coil assembly is electrified, according to data obtained by all the detection coils, obtaining a zeroth-order component REC-Y-B0 of the eddy current effect of the Y coil assembly according to a formula (Be1+ Be2+ Be3+ Be4+ Be5+ Be6+ Be7+ Be 8)/8; obtaining a first-order component REC-Y-X of the eddy current effect of the Y coil assembly according to a formula (Be1+ Be2+ Be5+ Be6-Be3-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 a formula (Be2+ Be3+ Be6+ Be7-Be1-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 a formula (Be1+ Be2+ Be3+ Be4-Be5-Be6-Be7-Be 8)/4;
and determining the adjusting distances dx, dy and dz and the adjusting angle d theta 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. The method for manufacturing and assembling a magnetic resonance imaging gradient coil according to any one of claims 1 to 3, wherein before the detecting the current eddy magnetic field strength of the shielding barrel by 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;
rotating the shield coil assembly relative to the primary 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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