CN114325520A - Magnet field rising method and device - Google Patents
Magnet field rising method and device Download PDFInfo
- Publication number
- CN114325520A CN114325520A CN202011069516.3A CN202011069516A CN114325520A CN 114325520 A CN114325520 A CN 114325520A CN 202011069516 A CN202011069516 A CN 202011069516A CN 114325520 A CN114325520 A CN 114325520A
- Authority
- CN
- China
- Prior art keywords
- magnet
- frequency
- target
- field
- actual
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Abstract
The embodiment of the invention discloses a magnet field-raising method and a magnet field-raising device, which are applied to a magnetic resonance imaging system. The method comprises the following steps: setting a first target frequency of the magnet according to reflection characteristics of a radio frequency signal transmitted by a transmission channel of the magnetic resonance imaging system; calculating a first target current of the magnet according to the first target frequency of the magnet and the theoretical magnetic field rising sensitivity; calculating the actual magnetic field rising sensitivity of the magnet according to the actual field intensity frequency of the magnet without the shimming pieces and the first target current of the magnet; calculating the field intensity frequency variation brought by the magnet sticker shim; correcting the first target frequency of the magnet according to the field intensity frequency variation brought by the magnet attaching shim to obtain a second target frequency; correcting the first target current of the magnet according to the second target frequency of the magnet and the actual magnetic field rising sensitivity of the magnet to obtain a second target current of the magnet; controlling the current of the magnet to rise to a second target current of the magnet. The embodiment of the invention improves the precision and speed of the magnetic field rising.
Description
Technical Field
The invention relates to the technical field of magnetic resonance imaging, in particular to a magnet field rising method and a magnet field rising device.
Background
In the magnetic resonance imaging device, a magnet is one of the most important components, and the performance of the magnet determines the uniformity and stability of a magnetic field and directly influences the performance and imaging effect of the magnetic resonance imaging device. The center frequency of the magnet is an important feature, and for superconducting magnets, a basic requirement is to raise the magnet to a target frequency more accurately. However, it is difficult to make each magnet have an accurate field-raising sensitivity due to inevitable errors caused by the manufacturing process and the like.
In some special systems, such as low-field systems, the requirement for the resonance bandwidth is very strict, which requires the magnet to be able to perform frequency climbing more accurately, but the frequency range of the low-field system is wide, so that the frequency range of adjustment is large during frequency modulation, so that multiple adjustments are usually needed to be adjusted, the load of frequency modulation is increased, and the multiple frequency modulation also makes the system unstable.
In addition, the field strength of the magnet is attenuated due to the attenuation of the current, and the center frequency cannot meet the bandwidth requirement in a period of time. In this case, the magnetic resonance imaging cannot work at all, and it is necessary to adjust the frequency of the magnet again to reactivate the magnetic resonance imaging.
Furthermore, over a period of time, when the field strength of the magnet decays more than expected (i.e., out of specification), the frequency ramping process of the magnet needs to be repeatedly initiated.
Currently, only rough field-up sensitivity calculations can be provided based on the theoretical design of the magnet. In addition, after the magnet is manufactured, in order to make the magnetic field of the magnet uniform, shim pieces are attached to a plurality of positions of the magnet, which also affects the accuracy of the sensitivity of the magnetic field rising. If the magnet cannot be raised to the target frequency accurately, additional time (typically 2 hours) is required to repeatedly adjust the frequency of the magnet until the center frequency is within the specified range.
Disclosure of Invention
In view of this, the embodiment of the invention provides a method and a device for raising a field of a magnet, so as to improve the precision and speed of raising the field of the magnet.
The technical scheme of the embodiment of the invention is realized as follows:
a magnetic field rising method is applied to a magnetic resonance imaging system and comprises the following steps:
setting a first target frequency of the magnet according to reflection characteristics of a radio frequency signal transmitted by a transmission channel of the magnetic resonance imaging system;
calculating a first target current of the magnet according to the first target frequency of the magnet and the theoretical magnetic field rising sensitivity;
measuring the actual field intensity frequency of the magnet without the shimming pieces;
calculating the actual magnetic field rising sensitivity of the magnet according to the actual field intensity frequency of the magnet without the shimming pieces and the first target current of the magnet;
calculating the field intensity frequency variation brought by the magnet sticker shim;
correcting the first target frequency of the magnet according to the field intensity frequency variation brought by the magnet attaching shim to obtain a second target frequency;
correcting the first target current of the magnet according to the second target frequency of the magnet and the actual magnetic field rising sensitivity of the magnet to obtain a second target current of the magnet;
controlling the current of the magnet to rise to a second target current of the magnet.
The setting of the first target frequency of the magnet according to the reflection characteristics of the radio frequency signals transmitted by the transmission channel of the magnetic resonance imaging system comprises:
acquiring a first frequency corresponding to the minimum reflection coefficient of a radio frequency signal transmitted by a 0-degree transmission channel of a transmitter;
acquiring a second frequency corresponding to the minimum reflection coefficient of the radio-frequency signal transmitted by a 90-degree transmission channel of the transmitter;
the mean of the first frequency and the second frequency is taken as the first target frequency of the magnet.
The calculating a first target current of the magnet according to the first target frequency and the theoretical magnetic field rising sensitivity of the magnet comprises:
and dividing the first target frequency of the magnet by the theoretical magnetic field rising sensitivity of the magnet to obtain a first target current of the magnet.
The measuring the actual field strength frequency of the magnet without the shimming pieces comprises:
and measuring the field intensity frequencies of a plurality of positions of the magnet on which the shimming sheets are not pasted, carrying out spherical harmonic decomposition on the measured field intensity frequencies of the plurality of positions, and taking the value corresponding to the zeroth order item in the decomposition result as the actual field intensity frequency of the magnet on which the shimming sheets are not pasted.
The calculating the actual magnetic field rising sensitivity of the magnet according to the actual field intensity frequency of the magnet without the shimming pieces and the first target current of the magnet comprises the following steps:
and dividing the actual field intensity frequency of the magnet without the shimming pieces by the first target current of the magnet to obtain the actual magnetic field rising sensitivity of the magnet.
The calculating of the field strength frequency variation caused by the magnet shim comprises:
and predicting the field intensity frequency of the magnet with the attached shimming pieces according to the number of the shimming pieces attached to the magnet and the positions of the shimming pieces, and subtracting the actual field intensity frequency of the magnet without the attached shimming pieces from the field intensity frequency of the magnet with the attached shimming pieces to obtain the field intensity frequency variation caused by the attachment of the shimming pieces to the magnet.
The correcting the first target frequency of the magnet according to the field intensity frequency variation brought by the magnet shim comprises:
and subtracting the field intensity frequency variation from the first target frequency of the magnet to obtain a second target frequency of the magnet.
The correcting the first target current of the magnet according to the second target frequency of the magnet and the actual magnetic field sensitivity of the magnet comprises:
and dividing the second target frequency of the magnet by the actual magnetic field rising sensitivity of the magnet to obtain a second target current of the magnet.
A magnet field-raising device comprising:
the target current calculation module is used for setting a first target frequency of the magnet according to the reflection characteristic of the radio frequency signal transmitted by a transmission channel of the magnetic resonance imaging system; calculating a first target current of the magnet according to the first target frequency of the magnet and the theoretical magnetic field rising sensitivity;
the actual magnetic field rising sensitivity calculation module is used for measuring the actual field intensity frequency of the magnet which is not pasted with the shimming piece; calculating the actual magnetic field rising sensitivity of the magnet according to the actual field intensity frequency of the magnet without the shimming pieces and the first target current of the magnet;
the target current correction module is used for calculating the field intensity frequency variation brought by the magnet sticker shim; correcting the first target frequency of the magnet according to the field intensity frequency variation brought by the magnet attaching shim to obtain a second target frequency; correcting the first target current of the magnet according to the second target frequency of the magnet and the actual magnetic field rising sensitivity of the magnet to obtain a second target current of the magnet;
and the field rising module is used for controlling the current of the magnet to rise to a second target current of the magnet.
A magnet field-raising device comprising: a memory and a processor accessible to the memory, the memory storing instructions that, when executed by the processor, cause the processor to perform the steps of the method as described in any one of the above.
In the embodiment of the invention, the first target frequency of the magnet is set according to the reflection characteristic of the radio frequency signal transmitted by the transmission channel of the magnetic resonance imaging system; calculating a first target current of the magnet according to the first target frequency of the magnet and the theoretical magnetic field rising sensitivity; calculating the actual magnetic field rising sensitivity of the magnet according to the actual field intensity frequency of the magnet without the shimming pieces and the first target current of the magnet; correcting the first target frequency of the magnet according to the field intensity frequency variation brought by the magnet attaching shim to obtain a second target frequency; correcting the first target current of the magnet according to the second target frequency of the magnet and the actual magnetic field rising sensitivity of the magnet to obtain a second target current of the magnet; the current of the magnet is controlled to rise to the second target current of the magnet, so that the target current required for successful field rising of the magnet can be accurately calculated at one time, and after the shimming pieces are installed, the overall frequency of the system after field rising meets the requirement of the first target frequency required by the system, so that the field rising of the magnet is completed at one time, and the precision and the speed of the field rising of the magnet are improved.
Drawings
The foregoing and other features and advantages of the invention will become more apparent to those skilled in the art to which the invention relates upon consideration of the following detailed description of a preferred embodiment of the invention with reference to the accompanying drawings, in which:
fig. 1 is a flowchart of a magnet field-up method in a magnetic resonance imaging system according to an embodiment of the present invention;
fig. 2 is a flowchart of a magnet field-up method in a magnetic resonance imaging system according to another embodiment of the present invention;
fig. 3 is a schematic diagram of reflection characteristics of radio frequency signals transmitted by two transmission channels BC0 and BC90 of a transmitter of a magnetic resonance imaging system;
FIG. 4 is a schematic illustration of a hysteresis loop;
fig. 5 is a schematic structural diagram of a magnetic field-increasing device according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of a magnetic field-increasing device according to another embodiment of the present invention.
Wherein the reference numbers are as follows:
| reference numerals | Means of |
| 101-108 | Step (ii) of |
| 201-208 | Step (ii) of |
| 31 | Reflection characteristic curve of radio frequency signal emitted by emission channel BC0 |
| 32 | Reflection characteristic curve of radio frequency signal emitted by emission channel BC90 |
| 50 | The embodiment of the invention provides a magnet field- |
| 51 | Target |
| 52 | Actual magnetic field rising |
| 53 | Target |
| 54 | Field- |
| 60 | The magnet field-raising device provided by the second embodiment of the |
| 61 | |
| 62 | Processor with a memory having a plurality of memory cells |
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail by referring to the following examples.
Fig. 1 is a flowchart of a magnet field-raising method in a magnetic resonance imaging system according to an embodiment of the present invention, which includes the following specific steps:
step 101: a first target frequency of the magnet is set based on a reflection characteristic of a radio frequency signal transmitted by a transmit channel of the magnetic resonance imaging system.
In an optional embodiment, the step 101 specifically includes: acquiring a first frequency corresponding to the minimum reflection coefficient of a radio frequency signal transmitted by a 0-degree transmission channel of a transmitter; acquiring a second frequency corresponding to the minimum reflection coefficient of the radio-frequency signal transmitted by a 90-degree transmission channel of the transmitter; the mean of the first frequency and the second frequency is taken as the first target frequency of the magnet.
Step 102: a first target current of the magnet is calculated based on the first target frequency of the magnet and the theoretical magnetic field-up sensitivity.
In an optional embodiment, the step 102 specifically includes: and dividing the first target frequency of the magnet by the theoretical magnetic field rising sensitivity of the magnet to obtain a first target current of the magnet.
Step 103: the actual field strength frequency of the magnet with no shim attached is measured.
In an optional embodiment, the step 103 specifically includes: and measuring the field intensity frequencies of a plurality of positions of the magnet to which the shimming sheets are not attached, carrying out spherical harmonic decomposition on the measured field intensity frequencies of the plurality of positions, and taking the value corresponding to the zero-order term in the decomposition result as the actual field intensity frequency of the magnet to which the shimming sheets are not attached.
Step 104: and calculating the actual magnetic field rising sensitivity of the magnet according to the actual field intensity frequency of the magnet without the shimming pieces and the first target current of the magnet.
In an optional embodiment, this step 104 specifically includes: and dividing the actual field intensity frequency of the magnet without the shimming pieces by the first target current of the magnet to obtain the actual magnetic field rising sensitivity of the magnet.
Step 105: and calculating the field intensity frequency variation caused by the magnet attaching shim.
In an optional embodiment, the step 105 specifically includes: and predicting the field intensity frequency of the magnet with the attached shimming pieces according to the number of the shimming pieces attached to the magnet and the positions of the shimming pieces, and subtracting the actual field intensity frequency of the magnet without the attached shimming pieces from the field intensity frequency of the magnet with the attached shimming pieces to obtain the field intensity frequency variation caused by the attachment of the shimming pieces to the magnet.
Step 106: and correcting the first target frequency of the magnet according to the field intensity frequency variation brought by the magnet attaching shim to obtain a second target frequency.
In an optional embodiment, the step 106 specifically includes: and subtracting the field intensity frequency variation from the first target frequency of the magnet to obtain a second target frequency of the magnet.
Step 107: and correcting the first target current of the magnet according to the second target frequency of the magnet and the actual magnetic field rising sensitivity of the magnet to obtain a second target current of the magnet.
In an optional embodiment, this step 107 specifically includes: and dividing the second target frequency of the magnet by the actual magnetic field rising sensitivity of the magnet to obtain a second target current of the magnet.
Step 108: controlling the current of the magnet to rise to a second target current of the magnet.
In the above embodiment, the first target frequency of the magnet is first set according to the reflection characteristics of the radio frequency signal emitted by the transmission channel of the magnetic resonance imaging system; then calculating a first target current of the magnet according to the first target frequency of the magnet and the sensitivity of the theoretical magnetic field rising; calculating the actual magnetic field rising sensitivity of the magnet according to the actual field intensity frequency of the magnet without the shimming pieces and the first target current of the magnet; then, according to the field intensity frequency variation brought by the magnet attaching shim, correcting the first target frequency of the magnet to obtain a second target frequency; correcting the first target current of the magnet according to the second target frequency of the magnet and the actual magnetic field rising sensitivity of the magnet to obtain a second target current of the magnet; and finally, controlling the current of the magnet to rise to a second target current of the magnet, so that the target current required for successful field rising of the magnet can be accurately calculated at one time, and after the shimming pieces are loaded, the overall frequency of the system after field rising meets the requirement of the first target frequency required by the system, thereby finishing the field rising of the magnet at one time and improving the precision and the speed of the field rising of the magnet.
Fig. 2 is a flowchart of a magnet field-up method in a magnetic resonance imaging system according to another embodiment of the present invention, which includes the following specific steps:
step 201: obtaining a frequency f corresponding to a minimum reflection coefficient of a radio frequency signal transmitted by a 0 DEG transmission channel of a transmitter of a magnetic resonance imaging systemBC0Obtaining the frequency f corresponding to the minimum reflection coefficient of the radio frequency signal transmitted by the 0-degree transmission channel of the transmitterBC90。
Fig. 3 is a schematic diagram of reflection characteristics of radio frequency signals transmitted by two transmission channels BC0 and BC90 of a transmitter of a magnetic resonance imaging system, BC0 is a 0 ° transmission channel, BC90 is a 90 ° transmission channel, the horizontal axis in the diagram represents frequency, and the vertical axis represents reflection coefficient, where a curve 31 is the reflection characteristic of the radio frequency signal transmitted by the transmission channel BC0, a curve 32 is the reflection characteristic of the radio frequency signal transmitted by the transmission channel BC90, and a frequency corresponding to the minimum reflection coefficient of the radio frequency signal transmitted by each channel is the optimal frequency f of the channelBC0、fBC90。
Step 202: calculating a first target frequency f of the magnetBC：fBC＝(fBC0+fBC90)/2。
fBC、fBC0、fBC90All three may be in Hz (hertz).
Step 203: calculating a first target current C of the magnetmag：Cmag＝fBC/Smag0Wherein S ismag0Is the theoretical magnetic field rise sensitivity of the magnet, Smag0Given by the designer of the magnet and calibrated at the time of shipment.
CmagMay have units of A (ampere), Smag0May be in units of Hz/a (hertz/ampere).
Smag0Can be obtained by the following calculation process:
Smag0B/I, and B ═ μ0H, H ═ N · I/L, then:
Smag0＝μ0·N·I/(L·I)＝μ0·N/L
wherein B is the theoretical magnetic induction of the magnet, H is the field strength of the magnet, mu0For magnetic permeability, N is the number of turns of the wound coil in the magnet, L is the length of the unwinding of the wound coil in the magnet, and I is the current of the magnet.
Step 204: measuring the field intensity frequencies of a plurality of positions of the magnet without the shimming pieces attached, carrying out spherical harmonic decomposition on the measured field intensity frequencies of the plurality of positions, and taking the value corresponding to the zero-order term in the decomposition result as the actual field intensity frequency of the magnet without the shimming pieces attachedfMag。
For example: the field strength frequencies of n positions of the magnet without the shimming pieces are measured respectively
The n field strength frequencies are respectively expressed by spherical harmonics, and then:
the n expressions form an equation set, and the equation set is solved to obtain
Actual field strength frequency f of magnet as non-shimMag. Wherein the content of the first and second substances,
in a polar coordinate system for n measurement positions respectively
The lower theta is equal to the lower theta,
the value of the coordinates is selected from the group,
is the coefficient of spherical harmonic function, l and m are positive integers, and m is less than or equal to l,
is a Legendre polynomial coefficient
fMagThe unit of (d) may be Hz.
Step 205: calculating the actual magnetic field rising sensitivity S of the magnetMag：SMag＝fMag/Cmag。
Step 206: predicting the field intensity frequency f of the magnet after the shimming pieces are pasted according to the number of the shimming pieces pasted on the magnet and the positions of the shimming piecespredictCalculating the field intensity frequency variation delta f caused by the magnet attaching shimming piece: f ═ fpredict-fMag。
For a magnetic resonance imaging system, in order to improve the uniformity of a magnetic field, shim pieces need to be attached to a magnet.
Step 207: according to the delta f to the first target frequency fBCCorrected to obtain f'BC：f'BC＝fBC-Δf。
Step 208: according to f'BCAnd SMagCalculating post shim magnet to f'BCRequired second target Current C'mag：C'mag＝f'BC/SMag。
Step 209: controlling the magnet's Current to rise to C'mag。
When the field intensity H of the magnetic field changes, the magnetic induction intensity B has a magnetic saturation phenomenon, so that after the shimming piece is attached and the field intensity of the shimming piece is increased to a certain degree, the magnetic induction intensity B is saturated, and the magnetic field is stable.
The hysteresis loop represents the closed magnetization curve of the hysteresis of the magnet when the field strength of the magnetic field varies periodically. It shows the relationship between the magnetic induction B and the field strength H of the magnetic field during the repeated magnetization of the magnet. Fig. 4 is a schematic diagram of a hysteresis loop, as shown in fig. 4, the magnetic induction strength of the magnet starts from B being 0, the magnetic field strength H of the magnet is gradually increased, and the magnetic induction strength B is increased along the OAC curve in fig. 4 until the magnetic saturation state C is reached. At this point, H is increased and the magnetization state of the magnet will remain substantially unchanged. When the magnetic induction reaches the saturation value B0, the corresponding field strength H is represented by H0. The OAC curve is called the initial magnetization curve.
If the field strength H is reduced thereafter, the magnetization curve does not return from point C along the original initial magnetization curve, which means that the change in the magnetic induction B lags behind the change in H, a phenomenon known as hysteresis. If the magnitude of the reverse field strength continues to increase to-H0, the magnet will be magnetized in the reverse direction to saturation E, corresponding to a saturation value of-B0. Points E and C are symmetric with respect to the origin.
If the field strength in the reverse direction is reduced to 0, then it increases again in the positive direction. The magnet magnetization state will return to the forward saturation magnetization state C along the curve EFC. The EFC and CDE curves are also symmetric about the origin O. It can thus be seen that as the field strength changes from H0 to-H0 and then from-H0 to H0 repeatedly, the change in the magnetization state of the magnet undergoes a cyclic process described by the CDEFC closed loop. The curve CDEFC is called the hysteresis loop.
Fig. 5 is a schematic structural diagram of a magnetic field-increasing device 50 according to an embodiment of the present invention, which mainly includes:
a target current calculation module 51 for setting a first target frequency of the magnet according to a reflection characteristic of a radio frequency signal transmitted by a transmission channel of the magnetic resonance imaging system; calculating a first target current of the magnet according to the first target frequency of the magnet and the theoretical magnetic field rising sensitivity;
an actual magnetic field rising sensitivity calculation module 52, configured to measure an actual field strength frequency of the magnet to which no shim is attached; calculating the actual magnetic field rising sensitivity of the magnet according to the actual field intensity frequency of the magnet without the shimming pieces and the first target current of the magnet calculated by the target current calculating module 51;
a target current correction module 53, configured to calculate a field intensity frequency variation caused by the magnet shim; according to the field intensity frequency variation caused by the magnet attaching shim, the first target frequency of the magnet set by the target current calculation module 51 is corrected to obtain a second target frequency; correcting the first target current of the magnet according to the second target frequency of the magnet and the actual magnetic field sensitivity of the magnet calculated by the actual magnetic field sensitivity-increasing calculation module 52 to obtain a second target current of the magnet;
and a field raising module 54 for controlling the current of the magnet to rise to the second target current of the magnet calculated by the target current correction module 53.
Fig. 6 is a schematic structural diagram of a magnetic field-increasing device 60 according to another embodiment of the present invention, which mainly includes: a memory 61 and a processor 62 having access to the memory 61, the memory 61 storing instructions that, when executed by the processor 62, cause the processor 62 to perform the steps of the method as described in steps 101 and 108, or steps 201 and 208.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A magnetic field lifting method is applied to a magnetic resonance imaging system and is characterized by comprising the following steps:
setting a first target frequency of the magnet according to reflection characteristics of a radio frequency signal transmitted by a transmission channel of the magnetic resonance imaging system;
calculating a first target current of the magnet according to the first target frequency of the magnet and the theoretical magnetic field rising sensitivity;
measuring the actual field intensity frequency of the magnet without the shimming pieces;
calculating the actual magnetic field rising sensitivity of the magnet according to the actual field intensity frequency of the magnet without the shimming pieces and the first target current of the magnet;
calculating the field intensity frequency variation brought by the magnet sticker shim;
correcting the first target frequency of the magnet according to the field intensity frequency variation brought by the magnet attaching shim to obtain a second target frequency;
correcting the first target current of the magnet according to the second target frequency of the magnet and the actual magnetic field rising sensitivity of the magnet to obtain a second target current of the magnet;
controlling the current of the magnet to rise to a second target current of the magnet.
2. The method of claim 1, wherein setting the first target frequency of the magnet according to the reflection characteristics of the radio frequency signals transmitted by the transmit channel of the magnetic resonance imaging system comprises:
acquiring a first frequency corresponding to the minimum reflection coefficient of a radio frequency signal transmitted by a 0-degree transmission channel of a transmitter;
acquiring a second frequency corresponding to the minimum reflection coefficient of the radio-frequency signal transmitted by a 90-degree transmission channel of the transmitter;
the mean of the first frequency and the second frequency is taken as the first target frequency of the magnet.
3. The method of claim 1, wherein calculating the first target current of the magnet based on the first target frequency and the theoretical magnetic field rise sensitivity of the magnet comprises:
and dividing the first target frequency of the magnet by the theoretical magnetic field rising sensitivity of the magnet to obtain a first target current of the magnet.
4. The method of claim 1, wherein said measuring an actual field strength frequency of an unstitched magnet comprises:
and measuring the field intensity frequencies of a plurality of positions of the magnet on which the shimming sheets are not pasted, carrying out spherical harmonic decomposition on the measured field intensity frequencies of the plurality of positions, and taking the value corresponding to the zeroth order item in the decomposition result as the actual field intensity frequency of the magnet on which the shimming sheets are not pasted.
5. The method of claim 1, wherein calculating the actual field rise sensitivity of the magnet based on the actual field strength frequency of the un-shimmed magnet and the first target current of the magnet comprises:
and dividing the actual field intensity frequency of the magnet without the shimming pieces by the first target current of the magnet to obtain the actual magnetic field rising sensitivity of the magnet.
6. The method of claim 1, wherein calculating the frequency change in field strength due to the magnet shim comprises:
and predicting the field intensity frequency of the magnet with the attached shimming pieces according to the number of the shimming pieces attached to the magnet and the positions of the shimming pieces, and subtracting the actual field intensity frequency of the magnet without the attached shimming pieces from the field intensity frequency of the magnet with the attached shimming pieces to obtain the field intensity frequency variation caused by the attachment of the shimming pieces to the magnet.
7. The method of claim 1, wherein the modifying the first target frequency of the magnet based on the amount of field strength frequency change due to the magnet shim comprises:
and subtracting the field intensity frequency variation from the first target frequency of the magnet to obtain a second target frequency of the magnet.
8. The method of claim 7, wherein the modifying the first target current of the magnet based on the second target frequency of the magnet and the actual field-up sensitivity of the magnet comprises:
and dividing the second target frequency of the magnet by the actual magnetic field rising sensitivity of the magnet to obtain a second target current of the magnet.
9. A magnet field-raising device (50), comprising:
a target current calculation module (51) for setting a first target frequency of the magnet according to a reflection characteristic of a radio frequency signal transmitted by a transmission channel of the magnetic resonance imaging system; calculating a first target current of the magnet according to the first target frequency of the magnet and the theoretical magnetic field rising sensitivity;
an actual magnetic field rising sensitivity calculation module (52) for measuring the actual field intensity frequency of the magnet to which no shim is attached; calculating the actual magnetic field rising sensitivity of the magnet according to the actual field intensity frequency of the magnet without the shimming pieces and the first target current of the magnet;
the target current correction module (53) is used for calculating the field intensity frequency variation brought by the magnet sticker shim; correcting the first target frequency of the magnet according to the field intensity frequency variation brought by the magnet attaching shim to obtain a second target frequency; correcting the first target current of the magnet according to the second target frequency of the magnet and the actual magnetic field rising sensitivity of the magnet to obtain a second target current of the magnet;
a field-up module (54) for controlling the current of the magnet to rise to a second target current of the magnet.
10. A magnet field-raising device (60), comprising: a memory (61) and a processor (62) accessible to the memory (61), the memory (61) storing instructions which, when executed by the processor (62), cause the processor (62) to perform the steps of the method according to any one of claims 1 to 8.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011069516.3A CN114325520A (en) | 2020-09-30 | 2020-09-30 | Magnet field rising method and device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011069516.3A CN114325520A (en) | 2020-09-30 | 2020-09-30 | Magnet field rising method and device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN114325520A true CN114325520A (en) | 2022-04-12 |
Family
ID=81031852
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202011069516.3A Pending CN114325520A (en) | 2020-09-30 | 2020-09-30 | Magnet field rising method and device |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114325520A (en) |
Citations (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4680551A (en) * | 1985-10-07 | 1987-07-14 | General Electric Company | Method for homogenizing a static magnetic field over an arbitrary volume |
| CN1934458A (en) * | 2004-03-17 | 2007-03-21 | 皇家飞利浦电子股份有限公司 | Dynamic shimset calibration for B0 offset |
| US20110137589A1 (en) * | 2009-12-02 | 2011-06-09 | Nanalysis Corp. | Method and apparatus for producing homogeneous magnetic fields |
| CN102680930A (en) * | 2011-03-17 | 2012-09-19 | 西门子公司 | Method to adjust shim current and RF center frequency and magnetic resonance apparatus |
| CN102955140A (en) * | 2011-08-16 | 2013-03-06 | 西门子公司 | Local coil arrangement for magnetic resonance system, has return line that is arranged away from marginal area and conductor |
| JP2013105384A (en) * | 2011-11-15 | 2013-05-30 | Nippon Hoso Kyokai <Nhk> | Attention degree estimating device and program thereof |
| CN103454605A (en) * | 2012-05-30 | 2013-12-18 | 西门子(深圳)磁共振有限公司 | Shimming regulation device for superconducting magnets |
| US20140327440A1 (en) * | 2012-01-11 | 2014-11-06 | Hitachi Medical Corporation | Magnetic resonance imaging apparatus and region-imaging method |
| CN105652225A (en) * | 2015-12-28 | 2016-06-08 | 沈阳东软医疗系统有限公司 | Field uniforming method and field uniforming device of magnetic resonance system |
| CN108387857A (en) * | 2017-12-25 | 2018-08-10 | 深圳先进技术研究院 | A kind of local shimming system and method for shimming for magnetic resonance imaging |
| CN109765509A (en) * | 2017-11-09 | 2019-05-17 | 西门子(深圳)磁共振有限公司 | The method for shimming of superconducting magnetic resonance imaging equipment |
| KR20190078757A (en) * | 2017-12-27 | 2019-07-05 | 한국기초과학지원연구원 | method for shimming superconductor magnet apparatus and structure of the same |
| CN110632541A (en) * | 2018-06-22 | 2019-12-31 | 上海尚磁机电科技有限公司 | Shimming method and device of magnetic resonance system |
| US20200064425A1 (en) * | 2018-08-21 | 2020-02-27 | Siemens Healthcare Gmbh | Operating an mri apparatus |
-
2020
- 2020-09-30 CN CN202011069516.3A patent/CN114325520A/en active Pending
Patent Citations (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4680551A (en) * | 1985-10-07 | 1987-07-14 | General Electric Company | Method for homogenizing a static magnetic field over an arbitrary volume |
| CN1934458A (en) * | 2004-03-17 | 2007-03-21 | 皇家飞利浦电子股份有限公司 | Dynamic shimset calibration for B0 offset |
| US20110137589A1 (en) * | 2009-12-02 | 2011-06-09 | Nanalysis Corp. | Method and apparatus for producing homogeneous magnetic fields |
| CN102680930A (en) * | 2011-03-17 | 2012-09-19 | 西门子公司 | Method to adjust shim current and RF center frequency and magnetic resonance apparatus |
| CN102955140A (en) * | 2011-08-16 | 2013-03-06 | 西门子公司 | Local coil arrangement for magnetic resonance system, has return line that is arranged away from marginal area and conductor |
| JP2013105384A (en) * | 2011-11-15 | 2013-05-30 | Nippon Hoso Kyokai <Nhk> | Attention degree estimating device and program thereof |
| US20140327440A1 (en) * | 2012-01-11 | 2014-11-06 | Hitachi Medical Corporation | Magnetic resonance imaging apparatus and region-imaging method |
| CN103454605A (en) * | 2012-05-30 | 2013-12-18 | 西门子(深圳)磁共振有限公司 | Shimming regulation device for superconducting magnets |
| CN105652225A (en) * | 2015-12-28 | 2016-06-08 | 沈阳东软医疗系统有限公司 | Field uniforming method and field uniforming device of magnetic resonance system |
| CN109765509A (en) * | 2017-11-09 | 2019-05-17 | 西门子(深圳)磁共振有限公司 | The method for shimming of superconducting magnetic resonance imaging equipment |
| CN108387857A (en) * | 2017-12-25 | 2018-08-10 | 深圳先进技术研究院 | A kind of local shimming system and method for shimming for magnetic resonance imaging |
| KR20190078757A (en) * | 2017-12-27 | 2019-07-05 | 한국기초과학지원연구원 | method for shimming superconductor magnet apparatus and structure of the same |
| CN110632541A (en) * | 2018-06-22 | 2019-12-31 | 上海尚磁机电科技有限公司 | Shimming method and device of magnetic resonance system |
| US20200064425A1 (en) * | 2018-08-21 | 2020-02-27 | Siemens Healthcare Gmbh | Operating an mri apparatus |
Non-Patent Citations (2)
| Title |
|---|
| 刘畅 等: "磁共振成像系统中匀场电源参数优化设计", 《电力电子技术》, vol. 53, no. 2, pages 74 - 78 * |
| 武海澄;周荷琴;刘正敏;: "有源匀场电流优化算法研究", 北京生物医学工程, no. 05, pages 20 - 23 * |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN113447699B (en) | Tunnel magnetoresistance annular array current sensor and current measuring method | |
| US5165269A (en) | Electronic flux gate compass calibration technique | |
| CN103454461B (en) | The heteropical method of armoured magnetic field coil is compensated by winding | |
| CN108776356A (en) | The design method of Transient electromagnetic measure device | |
| CN109407022B (en) | Method and device for controlling magnetic field drift and storage medium | |
| CN114325520A (en) | Magnet field rising method and device | |
| CN109597137B (en) | Overhauser magnetometer tracking and tuning method based on semiconductor magnetic sensor | |
| US9666343B2 (en) | Magnetic field control | |
| CN109765509A (en) | The method for shimming of superconducting magnetic resonance imaging equipment | |
| JP2011152348A (en) | Magnetic resonance imaging apparatus | |
| CN109782196B (en) | Interference magnetic field compensation method | |
| CN106026971B (en) | A kind of accurate program controlled step attenuator frequency response bearing calibration and system | |
| CN111913007B (en) | Accelerometer calibration method and calibration device | |
| CN112730944B (en) | Current measuring method and device based on Rogowski coil | |
| CN108896945B (en) | Sensitivity index calibration method of high-sensitivity atomic magnetometer | |
| US7167002B2 (en) | Stabilizer for stabilizing NMR magnetic field and method of the same | |
| CN116505947B (en) | Analog-to-digital converter calibration method, device, storage medium and chip | |
| Shifrin et al. | Experimental estimation of the accuracy of modern scalar quantum magnetometers in measurements of the Earth's magnetic field | |
| CN114814675B (en) | Method and system for calibrating magnetic moment of magnetic torquer, storage medium and electronic equipment | |
| CN112584136B (en) | Position calibration module, calibration method, electronic device, calibration apparatus, and storage medium | |
| Wang et al. | Design of Magnet Measurement System Based on Multi-Hall Sensor | |
| US20210396822A1 (en) | Power control apparatus for radio-frequency power amplifier and radio-frequency transmission system for mri system | |
| CN111312469B (en) | Magnet capable of inhibiting ripples and parameter determination method thereof | |
| CN114646790B (en) | Current measuring device based on giant magnetoresistance effect | |
| AU2021102140A4 (en) | In-orbit Real-time Calibration System and Method of Vector Magnetometer |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |