CN115876363A - Method and device for evaluating static stress state of shim strips in magnetic resonance system - Google Patents

Abstract

The present disclosure relates to a method for evaluating the static stress state of a shim strip in a magnetic resonance system. The shim bar has a plurality of cavities arranged along its longitudinal direction for accommodating shim pieces, and the shim bar can be inserted into the magnetic resonance system for shimming operations. The method includes: calculating the force of the shims in each chamber containing the shims in the magnetic field based on the amount of shims that need to be accommodated in each chamber of the shims for the shimming operation; Based on the stress of the shims in each chamber in the magnetic field, calculate the force on the lateral sidewall of each chamber; and determine the shim bar based on the comparison of the force on the lateral sidewall of each chamber with the corresponding threshold Static force state in a magnetic resonance system.

Description

Method and device for evaluating static stress state of shim strips in magnetic resonance system

technical field

The present disclosure relates to the field of magnetic resonance technology, in particular to a method, device, magnetic resonance system, computer-readable storage medium and computer program product for evaluating the static force state of a shim bar in a magnetic resonance system.

Background technique

Magnetic Resonance Imaging (MRI) technology plays an important role in medical diagnosis. Magnetic resonance imaging technology not only requires a high constant magnetic field, but also requires a high uniformity of the constant magnetic field. The so-called uniformity of the magnetic field refers to the uniformity of the magnetic field intensity within a certain volume range, that is, the consistency of the number of magnetic force lines passing through a unit area. In the process of magnetic resonance imaging, if the main magnetic field is not uniform, it may cause blurred images or artifacts.

However, due to the limitations of the magnet design and manufacturing process and the influence of the surrounding environment, the magnetic field of magnetic resonance may not be able to achieve the required uniformity. To improve magnetic field homogeneity, shimming of the magnetic resonance system is required to reduce the resulting image blur or artifacts. The shimming operation refers to the operation process of adjusting the uniformity of the magnetic field distribution in a certain interval of the magnetic field. Shimming methods may include passive shimming and active shimming. Passive shimming, also known as passive shimming, is to add special shims on the inner wall of the shimming hole of the magnet to deform the actual magnetic field, making the magnetic field closer to the designed magnetic field to achieve the required magnetic field uniformity. Active shimming, also known as active shimming, is to adjust the main magnetic field to improve the overall magnetic field by properly adjusting the current intensity of each coil in the shim coil array installed in the magnetic resonance system to change the local magnetic field around it. Uniformity.

The approaches described in this section are not necessarily approaches that have been previously conceived or employed. Unless otherwise indicated, it should not be assumed that any approaches described in this section are admitted to be prior art solely by virtue of their inclusion in this section. Similarly, issues mentioned in this section should not be considered to have been recognized in any prior art unless otherwise indicated.

Contents of the invention

According to an aspect of an embodiment of the present disclosure, a method for evaluating the static stress state of a shim bar in a magnetic resonance system is proposed, wherein the shim bar has a structure along its longitudinal direction for accommodating a shim a plurality of chambers of the slice, and the shim bar can be inserted into the magnetic resonance system for shimming operation, the method includes: based on each chamber of the shim bar for the shim The amount of shims that need to be accommodated in the field operation, calculate the force of the shims in the magnetic field in each chamber containing the shims; Calculating the forces on the lateral side walls of the respective chambers; and determining the force of the shim strips in the magnetic resonance system based on the comparison of the forces on the lateral side walls of the respective chambers with corresponding thresholds Static stress state.

In another aspect of the embodiments of the present disclosure, a device for evaluating the static stress state of a shim bar in a magnetic resonance system is proposed, wherein the shim bar has a structure along its longitudinal direction for accommodating a shim a plurality of chambers of the sheet, and the shimming strip can be inserted into the magnetic resonance system for shimming operation, the apparatus includes: a first computing unit configured to be based on the In each chamber of the shim bar, the amount of shims required for the shimming operation is calculated, and the force of the shims in each chamber containing the shims in the magnetic field is calculated; the second A calculation unit, the second calculation unit is configured to calculate the force on the lateral side walls of each chamber based on the force on the shims in the respective chambers in the magnetic field; and the determination unit, the The determining unit is configured to determine a static stress state of the shim bars in the magnetic resonance system based on a comparison of the stress on the lateral side walls of the respective chambers with a corresponding threshold.

According to another aspect of the embodiments of the present disclosure, a magnetic resonance system is proposed, including: a magnetic resonance system body; at least one shim bar, at least one shim bar can be inserted into the magnetic resonance system body; and electronic equipment, electronic equipment It includes: at least one processor; and a memory communicatively connected with the at least one processor; wherein, the memory stores a computer program, and the computer program implements the method according to the embodiment of the present disclosure when executed by the at least one processor.

According to another aspect of the embodiments of the present disclosure, a non-transitory computer-readable storage medium storing a computer program is provided, wherein the computer program implements the method according to the embodiments of the present disclosure when executed by a processor.

According to another aspect of the embodiments of the present disclosure, a computer program product is provided, including a computer program, wherein the computer program implements the method according to the embodiments of the present disclosure when executed by a processor.

It should be understood that what is described in this section is not intended to identify key or important features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will be readily understood through the following description.

Description of drawings

The drawings exemplarily illustrate the embodiment and constitute a part of the specification, and together with the text description of the specification, serve to explain the exemplary implementation of the embodiment. The illustrated embodiments are for illustrative purposes only and do not limit the scope of the claims. Throughout the drawings, like reference numbers designate similar, but not necessarily identical, elements.

Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings, so that those of ordinary skill in the art will be more aware of the above-mentioned and other features and advantages of the present disclosure. In the accompanying drawings:

FIG. 1 shows a schematic diagram of an exemplary magnetic resonance system in which various methods described herein may be implemented, according to an embodiment of the present disclosure;

2 shows a schematic diagram of exemplary shim strips and shims in which various methods described herein may be implemented, according to an embodiment of the present disclosure;

Fig. 3 shows a flow chart of a method for evaluating the static force state of a shim bar in a magnetic resonance system according to an embodiment of the present disclosure;

4 shows a schematic diagram of an exemplary shim strip in which various methods described herein may be implemented, according to an embodiment of the present disclosure; and

Fig. 5 shows a block diagram of an apparatus for evaluating a static force state of a shim bar in a magnetic resonance system according to an embodiment of the present disclosure.

Detailed ways

In order to have a clearer understanding of the technical features, purposes and effects of the present disclosure, the specific implementation manners of the present disclosure will now be described with reference to the accompanying drawings, and the same reference numerals in each of the drawings represent the same parts.

In this article, "schematic" means "serving as an example, example or illustration", and any illustration or implementation described as "schematic" should not be interpreted as a more preferred or more advantageous Technical solutions.

In order to keep the drawings concise, each drawing only schematically shows the parts related to the present disclosure, and they do not represent the actual structure of the product. In addition, to make the drawings concise and easy to understand, in some drawings, only one of the components having the same structure or function is schematically shown, or only one of them is marked.

Herein, "a" not only means "only one", but also means "more than one". In this article, "first", "second" and so on are only used to distinguish each other, not to indicate their importance and order, and the premise of mutual existence.

FIG. 1 shows a schematic diagram of an exemplary magnetic resonance system 100 in which various methods described herein may be implemented, according to an embodiment of the present disclosure.

As shown in FIG. 1 , the magnetic resonance system 100 includes a magnetic resonance system body 110 and a shim tray 120 . The magnetic resonance system body 110 can generate a magnetic field, and the magnetic field can be used, for example, for disease diagnosis and the like. The shimming strip 120 can be inserted into the shimming hole 111 on the magnetic resonance system body 110 , for example, along the arrow direction shown in the figure, so as to perform passive shimming operation on the magnetic resonance system 100 . It can be seen from FIG. 1 that the magnetic resonance system 100 is provided with a plurality of shim holes 111 distributed around its axis. Although only one shim bar 120 is shown in FIG. 1 , it should be understood that the magnetic resonance system 100 also has A plurality of shim strips 120 may be included, and the plurality of shim strips 120 may be respectively inserted into corresponding shim holes 111 on the magnetic resonance system body 110 to perform a passive shimming operation on the magnetic resonance system 100 .

FIG. 2 shows a schematic diagram of an exemplary shim strip 120 and shim sheet 130 in which various methods described herein may be implemented in accordance with an embodiment of the present disclosure.

Referring further to FIG. 2 , the shim bar 120 may be provided with a plurality of chambers 121 along its length direction, and each chamber 121 is separated by lateral side walls 122 . The cavity 121 is used to accommodate the shims 130 . For passive shimming, the parameters of the main magnetic field (ie, the magnetic field generated by the magnetic resonance system body 110 ) are obtained first, and the obtained parameters include parameters that can indicate the inhomogeneity of the magnetic field. According to the parameters, the amount of shims that need to be added in each chamber 121 can be calculated, so that after the shims 130 are placed in the corresponding chambers 121, the shims 130 can be installed 120 is inserted into the corresponding shimming hole 111 and installed and fixed to complete the passive shimming operation. The shims 130 may contain iron or silicon, for example, the shims 130 may be silicon steel sheets. When the shim strip 120 equipped with the shim 130 is inserted into the shimming hole 111, the shim 130 can attract the magnetic induction lines of the main magnetic field to move in a desired direction, thereby maintaining a uniform magnetic field distribution of the main magnetic field. Although only one shim 130 is shown in FIG. 2 , it should be understood that a plurality of shims 130 can be placed in one cavity 121 as required.

The shim 130 placed in the magnetic field will be affected by the magnetic field force, so it has a tendency to move, but because the shim 130 is accommodated in the chamber 121, its movement tendency is blocked by the lateral side wall 122 or the bottom wall, and will remain at rest in the chamber 121. However, in some cases, the amount of shims 130 that need to be added in one or several chambers 121 calculated according to the parameters may be relatively large. Under the action of , the force it acts on each wall, especially the lateral side wall 122 is correspondingly larger. Since the shim strip 120 is usually made of non-magnetic and light-weight plastic, the strength of the material may not be able to withstand a large pressure, which may cause the side wall 122 to break due to excessive force. If broken, it may cause damage to the entire shim strip 120 . Therefore, the operator needs to re-shim the system, which not only greatly wastes manpower and material resources, but also delays the normal working process of the magnetic resonance system.

Embodiments of the present disclosure provide a method, device, system, computer-readable storage medium, and computer program product for evaluating a static stress state of a shim bar in a magnetic resonance system.

Fig. 3 shows a flowchart of a method 300 for evaluating a static force state of a shim bar in a magnetic resonance system according to an embodiment of the present disclosure.

As shown in FIG. 3 , the method 300 includes step S310 to step S330.

In step S310, based on the amount of shims that need to be accommodated in each chamber of the shim for the shimming operation, the force of the shims in each chamber containing the shims in the magnetic field is calculated;

In step S320, based on the force of the shims in each chamber in the magnetic field, calculate the force of the lateral side walls of each chamber; and

In step S330, based on the comparison between the force on the lateral side walls of the respective chambers and the corresponding threshold, determine the static force state of the shim bars in the magnetic resonance system.

Further, in some embodiments, the method 300 not only includes calculating the force on the lateral side walls of the respective chambers, but also includes calculating the force on the fixed ends of the shim strips for fixing them to the magnetic resonance system. Force, that is, method 300 includes:

Based on the amount of shims that need to be accommodated in each chamber of the shims for the shimming operation, the force of the shims in each chamber containing the shims in the magnetic field is calculated;

Based on the force of the shims in each chamber in the magnetic field, the force of the lateral side walls of each chamber and the force of the shim bars for fixing them to the fixed ends of the magnetic resonance system are calculated. force; and

Based on the comparison of the forces on the lateral side walls of the respective chambers and the forces on the fixed ends with corresponding thresholds, the static force states of the shim strips in the magnetic resonance system are determined.

By calculating the force on the transverse sidewall 122 of each chamber, if necessary, also calculate the fixed end 123 of the shim bar 120 along its longitudinal direction for fixing it to the magnetic resonance system (in FIG. 1), and comparing them with corresponding thresholds, the static stress state of the shim strip 120 can be determined. Therefore, after determining the amount of shim strips 130 that need to be configured in each chamber 121 for the shimming operation, the static stress state of the shim strips 120 under the configuration can be evaluated first through the method 300, Therefore, it is possible to timely identify the possible situation that the shim strip 120 is under too much force, so as to determine whether a part or the whole of the shim strip 120 may be broken before inserting the shim strip 120 into the shim hole 111 . Therefore, damage to the shim strip 120 can be avoided, which not only saves manpower and material resources, but also ensures the normal working process of the magnetic resonance system.

Wherein, in step S310, the amount of the shims to be accommodated may be the volume of the shims to be accommodated. For shims of the same material, their magnetic permeability is the same, the larger the total volume of the shim, the greater the influence of the shim on the main magnetic field, and the greater the magnetic field force on the shim. big. In some embodiments, the shims 130 are shims with different size specifications. For example, a group of shims 130 can be a group of shims with the same length and width and different thicknesses, and the length and width of the shims 130 can correspond to the length and width of the chamber 121 for convenience. The shims 130 are accommodated in the chamber 121 in such a manner. Therefore, the amount of shims 130 that need to be accommodated may be the total thickness of the shims 130 that need to be accommodated in each chamber of the shim bar for the shimming operation.

In addition, in step S310 , calculating the force of the shims 130 in the magnetic field in each chamber 121 containing the shims includes calculating the magnetic field force in each direction experienced by the shims 130 . For example, based on the known magnetic field strength (or magnetic induction) of the main magnetic field, the magnetic permeability of the shims 130, and the volume of the shims 130 in each chamber 121, the calculation of the shims 130 in each The direction of the magnetic field force. Furthermore, the magnetic field force received in each direction can be converted into the resultant force in the radial direction and the axial direction, and the next step of calculation can be performed based on the resultant force in the axial direction or the resultant force in the radial direction, respectively. Wherein, the axial direction refers to the direction parallel to the central axis of the magnetic resonance system 100 ; the radial direction refers to the direction perpendicular to the central axis of the magnetic resonance system 100 .

The method 300 will be further described below with reference to FIG. 4 . Since the strength of the transverse sidewall 122 between each chamber 121 is generally weaker than that of other parts of the chamber 121 (such as the bottom wall or the sidewall extending along the length direction of the shim bar), therefore, in the following example calculation process In , only the resultant force of the shims in the axial direction is considered, and the resultant force of the shims in the radial direction is not considered.

FIG. 4 shows a schematic diagram of an exemplary shim strip 420 in which various methods described herein may be implemented, according to an embodiment of the present disclosure. Wherein, P01 to P10 represent 10 pockets distributed along the length direction of the shim bar 420 , and each pocket is separated by nine transverse sidewalls (walls) W01 to W09 . In addition, W00 represents the lateral sidewall of the shim bar 420 at the head end (the side close to the fixed end); W10 represents the lateral sidewall of the shim bar 420 tail end (the side away from the fixed end). In one or more of the chambers P01 to P10, one or more shims may be accommodated (the shims are not shown in FIG. 4 for simplicity of illustration).

In some embodiments, in step S310, calculating the force of the shims in the magnetic field in each chamber containing the shims includes: calculating the force of the shims in the magnetic field generated by the magnetic resonance system 100 .

When the magnetic field intensity (or magnetic induction intensity) of the magnetic field generated by the magnetic resonance system 100 is known, the permeability of the shims, and the amount of the shims in each chamber (such as the thickness of the shims) , based on equations (1) to (3), the force of the shims in the magnetic field generated by the magnetic resonance system 100 can be calculated.

For equation (1):

表示匀场条的每个腔室中单位厚度的匀场片在磁共振系统100自身磁体所产生的磁场中的受力，其单位是牛顿/毫米(N/mm)；in,

Represents the force of the shims per unit thickness in each chamber of the shims in the magnetic field generated by the magnetic resonance system 100 itself, and its unit is Newton/millimeter (N/mm);

n represents the number of chambers in the shim strip, in the embodiment shown in Figure 4, n=10;

a ₁₁ to a _nn represent the force of the shims per unit thickness in each chamber in the magnetic field generated by the magnetic resonance system 100 itself, where the values of a ₁₁ to a _nn are related to the corresponding chambers in the magnetic field The magnetic field strength at the position and the magnetic permeability of the shims contained therein are related;

可以表示成如等式(1)的矩阵形式。Therefore, for a shim strip containing n chambers,

can be expressed in matrix form as in equation (1).

For equation (2):

Wherein, _HP represents the thickness of the shim sheet in each chamber of the shim bar, and its unit is millimeter (mm);

n represents the number of chambers in the shim strip, in the embodiment shown in Figure 4, n=10;

For a shim strip containing n chambers, H _P can be expressed in the matrix form of equation (2), where h ₁ to h _n represent the shims contained in the 1st to nth chambers respectively Total thickness.

Further, the force of the shims in each chamber in the magnetic field generated by the magnetic resonance system 100 can be calculated by equation (3), and the unit is Newton (N):

For example, when a certain element (eg h ₁ ) in the matrix H _P is 0, it means that no shim is accommodated in the chamber (eg chamber P01 ). Then the calculated magnetic force of the shim in the magnetic field generated by the magnetic resonance system 100 for the chamber P01 is zero.

Through the above equation, the force of the shims in each chamber containing the shims in the magnetic field generated by the magnetic resonance system 100 can be calculated.

In some embodiments, in step S310, calculating the force of the shims in the magnetic field in each chamber containing the shims further includes: calculating the force of the shims 130 in at least one adjacent chamber 121 The force in the magnetic field generated by the shim.

Since the shims 130 contain magnetizable substances such as iron and silicon, when the shims are actually inserted into the magnetic resonance system 100, the magnetic field of the magnetic resonance system 100 will place the shims therein Magnetization, so that the shim 130 itself also generates a magnetic field. The magnetic field generated by the shim 130 will also have a magnetic effect on other shims in the nearby chamber. Therefore, taking into account the magnetic field generated by the shims in at least one adjacent chamber 121 , the magnetic field force on the shims 130 can be evaluated more accurately.

In some embodiments, the force of the shims of unit thickness in the magnetic field generated by the shims of unit thickness in at least one adjacent chamber can be calculated according to, for example, equation (4):

Among them, G _{P to P} represents the force of the magnetic field generated by the shim of unit thickness in the i-th chamber on the shim of unit thickness in the j-th chamber, and its unit is Newton/mm (N/mm ² ) ; n represents the number of chambers in the shim strip, in the embodiment shown in FIG. 4 , n=10.

For a specific chamber, the magnetic field generated by the shims in the two adjacent chambers along the longitudinal direction of the shim bar has a greater force on the shims in the specific chamber, and the farther apart the chamber The magnetic field generated by the shims in , exerts less force on the shims in that particular chamber.

In equation (4), b _1,2 to b _n-1,n represent the shims of unit thickness in each chamber and the shims of unit thickness in the first adjacent chamber in front of it the magnetic force experienced in the resulting magnetic field;

b _2,1 to b _n,n-1 represent the shims of unit thickness in each chamber that are subjected to the magnetic field generated by the shims of unit thickness in the first adjacent chamber behind it magnetic force;

c _{1, 3} to c _{n-2, n} represent that the shims of unit thickness in each chamber are subjected to the magnetic field generated by the shims of unit thickness in the second adjacent chamber in front of it magnetism; and

c _3,1 to c _n,n-2 represent the shims of unit thickness in each chamber are subjected to the magnetic field generated by the shims of unit thickness in the second adjacent chamber magnetic force.

Similarly, Z _{1, n} represents the magnetic force experienced by the shims of unit thickness in each chamber in the magnetic field generated by the shims of unit thickness in the adjacent nth chamber in front of it; and

Similarly, z _n,1 represents the magnetic force experienced by the shims of unit thickness in each chamber in the magnetic field generated by the shims of unit thickness in the adjacent nth chamber behind it.

Among them, b _1,2 to b _n-1,n , b _2,1 to b _n,n-1 , c _1,3 to c _n-2,n , c _3,1 to c _n,n-2 , The values of z _n,1 and z _1,n are related to the magnetic field intensity at the position of the corresponding chamber in the magnetic field and the magnetic permeability of the shims accommodated therein.

Therefore, for a shim bar containing n chambers, G _{P to P} can be expressed in a matrix form as in equation (4).

In some embodiments, calculating the force experienced by the shims of unit thickness in the magnetic field generated by the shims of unit thickness in at least one adjacent chamber may include: calculating the force of the shims of unit thickness along the The force in the magnetic field generated by the shims of unit thickness in each of the two chambers adjacent to each other in the longitudinal direction of the shims. That is, parameters other than parameter b and parameter c among parameters b to z in equation (4) may be set to 0.

It should be understood that although in the above calculation process, the calculation of the shims of unit thickness in the magnetic field generated by the shims of unit thickness in the two chambers adjacent to each other along the longitudinal direction of the shim bar However, in some embodiments, the shims of unit thickness can also be calculated in the magnetic field generated by the shims of unit thickness in each chamber adjacent to each other along the longitudinal direction of the shim bar subjected to magnetic force. In some other embodiments, the shims of unit thickness produced by the shims of unit thickness in three (or more) chambers adjacent to each other along the longitudinal direction of the shim bar can also be calculated. The magnetic force in the magnetic field is used to further accurately calculate the magnetic force of the shims, which will not be repeated here.

Further, the force of the shims per unit thickness in the magnetic field generated by the shims in at least one chamber adjacent to it can be calculated according to, for example, expression (5), and its unit is Newton/mm (N/ mm):

H _P · I _P ^T · G _{P to P} (5)

Wherein, _HP represents the thickness of the shim sheet in each chamber of the shim bar, and its unit is millimeter (mm), and its meaning is the same as in equation (2); the expression (6) of _IP is as follows As shown, it is an identity matrix, which is convenient for matrix operations.

Further, the expression (5) is multiplied by _HP to obtain the equation (7), which is used to calculate the shims in each chamber in at least one adjacent chamber. The force in a magnetic field in Newtons (N):

F _P″ ＝[H _P ·I _P ^T ·G _{P to P} ]·H _P (7)

In some embodiments, the static force of the shim can be calculated by the following equation (8):

Therefore, when evaluating the static stress of the shims, not only the stress of the shims in the magnetic field generated by the magnetic resonance system, but also the force of the shims in at least one adjacent chamber The force in the magnetic field generated by the shim. A linear matrix operator is used to simplify the force calculation of the shims in the magnetic field, and the linear matrix operator is related to the magnetic field parameters, which shortens the calculation time within an acceptable error range.

In some other embodiments, when evaluating the static force of the shims, only the force of the shims in the magnetic field generated by the magnetic resonance system can be calculated, without considering the shims in at least one adjacent The force in the magnetic field generated by the shims in the chamber.

In step S320, based on the force of the shims in the magnetic field in the chambers containing the shims, the forces on the lateral side walls of these chambers can be calculated.

The static force of the shims accommodated in each chamber has been calculated through the above equation. Based on this, the force on the side walls of each chamber can be calculated by the following equation (9):

Wherein, F _Wt represents the force of the tth lateral sidewall; t represents the sequential numbering of the lateral sidewalls along the shim bar from the head end to the tail end; and wherein, F _Pt represents the tth The force of the shims in the chamber in the magnetic field, F _Pt+1 represents the force of the shims in the t+1th chamber in the magnetic field.

For example, as shown in FIG. 4 , the static forces of the shims accommodated in P01 to P10 can be calculated, and the magnetic field forces received are F _P01 to F _P10 respectively.

As shown in Figure 4, for the lateral side wall W05 between the chamber P05 and the chamber P06, the force on the lateral side wall W05 can be the shims in the chamber P05 and the shims in the chamber P06 The resultant force acting on the lateral sidewall W05. For example, the force on the lateral sidewall W05 can be calculated based on equation (9).

With reference to the direction shown in Figure 4, according to equation (9), when the shims in the chamber P05 are subjected to the magnetic force F P05 in the magnetic field generated by the magnetic resonance system 100, the direction of the magnetic force F _P05 is towards the end of the tail, and the chamber P06 When the direction of the magnetic force F _P06 suffered by the shims in the magnetic field generated by the magnetic resonance system 100 is toward the end of the head, F _W05 is the vector sum of F _P05 and F _P06 ; when the shims in the chamber P05 The direction of the magnetic force F _P05 in the magnetic field generated by the magnetic resonance system 100 is towards the end of the tail, and the direction of the magnetic force F P06 that the shims in the chamber _P06 are subjected to in the magnetic field generated by the magnetic resonance system 100 is also towards At the tail end, F _W05 is F _P05 ; when the magnetic force F _P05 of the shim in the chamber P05 in the magnetic field generated by the magnetic resonance system 100 is directed toward the head end, and the shim in the chamber P06 When the direction of the magnetic force F _P06 that the field sheet receives in the magnetic field generated by the magnetic resonance system 100 is also toward the end of the head, F _W05 is F _P06 ; When the direction of the magnetic force F _P05 in the magnetic field is towards the end of the head, and the direction of the magnetic force F _P06 of the shim in the chamber P06 is towards the end of the tail in the magnetic field generated by the magnetic resonance system 100, F _W05 is 0.

For the lateral side wall W00, when the direction of the magnetic force F _P01 of the shim in the cavity P01 in the magnetic field generated by the magnetic resonance system 100 is towards the end of the head, F _W00 is F _P01 ; when the cavity When the direction of the magnetic force F _P01 that the shims in P01 are subjected to in the magnetic field generated by the magnetic resonance system 100 is toward the end of the tail, F _W00 is 0.

For the lateral sidewall W10 (i.e., the tail end), when the magnetic force F _P10 of the shim in the chamber P10 in the magnetic field generated by the magnetic resonance system 100 is directed toward the head end, F _W10 is 0; when the magnetic force F P10 of the shim in the chamber P10 in the magnetic field generated by the magnetic resonance system 100 is directed towards the end of the tail, _{F W10 is} F _P10 .

Similarly, the forces on the lateral side walls of each chamber can be calculated.

In addition, in some embodiments, the end of the shim bar includes a fixed end 423-1 (or 123-1 in FIG. 2 ) for fixing the shim bar 420 into the magnetic resonance system 100, the shim bar The force on the fixed end along its longitudinal direction is equal to the superposition of the forces on the shims in the magnetic field in each chamber.

For example, the force F _H on the fixed end 423-1 of the shim bar can be calculated based on equation (10), in Newton (N):

For the example in Figure 4, n=10. Therefore, the resultant force on the fixed end may be the superposition of the force on the shims in the ten chambers in the first to tenth chambers in the magnetic field. Since the fixed end is used to fix the shim bar to the MRI system, the fixed end usually includes a structure for fixing (such as a threaded structure), so it is also very important to evaluate the force situation at the fixed end to evaluate in time Damage to the fixed end may occur.

In some embodiments, the method 300 also includes:

In response to determining that the force on the lateral sidewall of any of the chambers housing the shims or the force on the fixed end of the shim bar exceeds a corresponding threshold, indicating that the shim bar is inserted into the magnetic resonance system Previously, the amount of shims needed to be accommodated in the chamber was reconfigured.

For example, when the calculated force of the lateral side wall W05 (for example, the magnitude is 500 Newton, and the direction is toward the tail end) exceeds a corresponding threshold (for example, the magnitude is 400 Newton), the lateral sidewall of the shim bar 120 can be determined W05 may break. Thus, prior to insertion of the shim strips into the magnetic resonance system, a reconfiguration of the amount of shims that needs to be accommodated in the chamber may be indicated. For example, it can be instructed to reconfigure the thickness of the shims that need to be accommodated in one or several chambers, so as to avoid the occurrence of damage to the lateral side walls when the shims are inserted, thereby ensuring magnetic resonance The normal work flow of the system and save manpower and material resources.

Similarly, when the calculated force F _H of the fixed end (for example, the magnitude is 600 Newtons, and the direction is towards the tail end) exceeds the corresponding threshold (for example, the magnitude is 500 Newtons), it can be determined that the shim bar is in the magnetic resonance The static stress state in the system is the first state. For this first state, it may indicate that the fixed end of the shim strip 120 may be broken. Thus, prior to insertion of the shim strips into the magnetic resonance system, a reconfiguration of the amount of shims that needs to be accommodated in the chamber may be indicated. For example, it can be instructed to reconfigure the thickness of the shims that need to be accommodated in one or several chambers, so as to avoid damage to the fixed end when the shims are inserted, thereby ensuring magnetic resonance The normal work flow of the system and save manpower and material resources.

In some embodiments, the method 300 also includes:

In response to determining that neither the force on the respective chamber lateral sidewall housing the shims nor the force on the fixed end of the shim bar exceeds a respective threshold, permission to insert the shim bar into the magnetic resonance system is indicated.

For example, when the calculated forces on the lateral sidewalls W00 to W10 and the calculated force F _H on the fixed end do not exceed the corresponding threshold, it can be determined that a part or the whole of the shim strip 120 is inserted into the magnetic resonance system 100 In the middle, there is no risk of damage, and therefore, it may be indicated that the insertion of the shim strip 120 into the magnetic resonance system 100 is permitted.

Thus, after the configuration of the shims is completed and before the shims configured with the shims are inserted into the magnetic resonance system, the static stress state of the shims in the magnetic resonance system can be evaluated, which can be preliminarily Determine if inserting shim strips will overstress parts or the whole of the shim strips and cause damage. Instructions for reconfiguring the shims are given in response to potential risks, thereby ensuring the normal workflow of the magnetic resonance system and improving efficiency and safety.

According to another aspect of the embodiments of the present disclosure, a device for evaluating a static force state of a shim bar in a magnetic resonance system is provided.

Fig. 5 shows a block diagram of an apparatus 500 for evaluating a static force state of a shim bar in a magnetic resonance system according to an embodiment of the present disclosure, wherein the shim bar has a shim bar arranged along its longitudinal direction for accommodating a shim sheet multiple chambers, and shim strips can be inserted into the magnetic resonance system for shimming operations. Device 500 includes:

The first calculation unit 510, the first calculation unit is configured to calculate the amount of shims in each chamber containing the shims based on the amount of shims that need to be accommodated in each chamber of the shim bar for the shimming operation. The force of the shim in the magnetic field;

The second calculation unit 520, the second calculation unit is configured to calculate the force on the lateral side walls of each chamber based on the force on the shims in the respective chambers in the magnetic field; and

A determination unit 530, the determination unit is configured to determine the static stress state of the shim strips in the magnetic resonance system based on the comparison of the stress on the lateral side walls of the respective chambers with the corresponding threshold.

In some embodiments, the second calculation unit 520 is further configured to calculate the force on the fixed end of the shim bar based on the force on the shims in the respective chambers in the magnetic field, and accordingly, determine The unit 530 is further configured to determine the static force state of the shim bar in the magnetic resonance system based on the comparison of the force on the fixed end of the shim bar with the corresponding threshold.

According to another aspect of the embodiments of the present disclosure, a magnetic resonance system 100 is proposed, including: a magnetic resonance system body 110; at least one shim strip 120, at least one shim strip 120 can be inserted into the magnetic resonance system body 110; and An electronic device, the electronic device includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein, the memory stores a computer program, and when the computer program is executed by the at least one processor, the method according to an embodiment of the present disclosure is implemented. A method 300 for evaluating the static force state of a shim bar in a magnetic resonance system.

According to another aspect of the embodiments of the present disclosure, there is provided a non-transitory computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the method for evaluating magnetic resonance according to an embodiment of the present disclosure is implemented. A method 300 for the static force state of the shim bar in the system.

According to another aspect of the embodiments of the present disclosure, a computer program product is provided, including a computer program, wherein, when the computer program is executed by a processor, the method for evaluating shimming in a magnetic resonance system according to an embodiment of the present disclosure is provided. Method 300 for Static Stress Conditions.

Various implementations of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chips Implemented in a system of systems (SOC), load programmable logic device (CPLD), computer hardware, firmware, software, and/or combinations thereof. These various embodiments may include being implemented in one or more computer programs executable and/or interpreted on a programmable system including at least one programmable processor, the programmable processor Can be special-purpose or general-purpose programmable processor, can receive data and instruction from storage system, at least one input device, and at least one output device, and transmit data and instruction to this storage system, this at least one input device, and this at least one output device an output device.

Program codes for implementing the methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general-purpose computer, a special purpose computer, or other programmable data processing devices, so that the program codes, when executed by the processor or controller, make the functions/functions specified in the flow diagrams and/or block diagrams Action is implemented. The program code may execute entirely on the machine, partly on the machine, as a stand-alone software package partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of the present disclosure, a computer-readable storage medium may be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, apparatus, or device. The computer readable storage medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of extreme readable storage media would include one or more wire-based electrical connections, portable computer disks, hard disks, random access memory (RAM), read only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, compact disc read only memory (CD-ROM), optical storage, magnetic storage, or any suitable combination of the foregoing.

To provide for interaction with the user, the systems and techniques described herein can be implemented on a computer having a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user. ); and a keyboard and pointing device (eg, a mouse or a trackball) through which a user can provide input to the computer. Other kinds of devices can also be used to provide interaction with the user; for example, the feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and can be in any form (including Acoustic input, speech input or, tactile input) to receive input from the user.

The systems and techniques described herein can be implemented in a computing system that includes back-end components (e.g., as a data server), or a computing system that includes middleware components (e.g., an application server), or a computing system that includes front-end components (e.g., as a a user computer having a graphical user interface or web browser through which a user can interact with embodiments of the systems and techniques described herein), or including such backend components, middleware components, Or any combination of front-end components in a computing system. The components of the system can be interconnected by any form or medium of digital data communication, eg, a communication network. Examples of communication networks include: Local Area Network (LAN), Wide Area Network (WAN) and the Internet.

It should be understood that steps may be reordered, added or deleted using the various forms of flow shown above. For example, each step described in the present disclosure may be executed in parallel, sequentially or in a different order, as long as the desired result of the technical solution disclosed in the present disclosure can be achieved, no limitation is imposed herein.

Although the embodiments or examples of the present disclosure have been described with reference to the accompanying drawings, it should be understood that the above-mentioned methods, systems and devices are merely exemplary embodiments or examples, and the scope of the present invention is not limited by these embodiments or examples, but It is limited only by the appended claims and their equivalents. Various elements in the embodiments or examples may be omitted or replaced by equivalent elements thereof. Also, steps may be performed in an order different from that described in the present disclosure. Further, various elements in the embodiments or examples can be combined in various ways. Importantly, as technology advances, many of the elements described herein may be replaced by equivalent elements appearing after this disclosure.

Claims (15)

1. A method for assessing a shim bar in a static state of force in a magnetic resonance system, wherein the shim bar has a plurality of chambers arranged along its longitudinal direction for accommodating shims, and the The shimming strips can be inserted into the magnetic resonance system for shimming operations, the method comprising: Based on the amount of shims that need to be accommodated in each chamber of the shim bar for the shimming operation, calculating the force of the shims in each chamber containing the shims in the magnetic field; calculating the forces on the lateral sidewalls of the respective chambers based on the forces on the shims in the respective chambers in the magnetic field; and Based on the comparison of the force on the lateral side walls of the respective chambers with the corresponding threshold, the static force state of the shim bar in the magnetic resonance system is determined. 2. The method of claim 1, wherein the shim strip has fixed ends for fixing it into the magnetic resonance system, the method further comprising: calculating the force on the fixed ends of the shim strips based on the force on the shims in the respective chambers in the magnetic field; and, Based on the comparison between the force on the fixed end of the shim bar and the corresponding threshold, the static force bearing state of the shim bar in the magnetic resonance system is determined. 3. The method according to claim 1 or 2, wherein calculating the stress of the shims in the magnetic fields in the respective chambers containing the shims comprises: Calculating the force of the shims in the magnetic field generated by the magnetic resonance system. 4. The method according to claim 3, wherein calculating the stress of the shims in the magnetic field in each chamber containing the shims also includes: Calculating the force of the shim in the magnetic field generated by the shim in at least one chamber adjacent to it. 5. The method according to claim 3, wherein the stress of the shims in the magnetic field produced by the magnetic resonance system is calculated by the following equation:

in:

Represents the force of the shims per unit thickness in each chamber of the shim strip in the magnetic field generated by the magnetic resonance system, wherein n represents the number of chambers in the shim strip, a ₁₁ to a _nn represent the stresses of the shims per unit thickness in the corresponding chambers of the shim strips in the magnetic field generated by the magnetic resonance system, wherein the values of a ₁₁ to a _nn are the same as those of the corresponding chambers in The magnetic field intensity at the position in the magnetic field generated by the magnetic resonance system is related to the magnetic permeability of the shims contained in the corresponding chamber; as well as

_HP denotes the thickness of the shims in each chamber of the shim strip. 6. The method according to claim 4, wherein the stress of the shim in the magnetic field generated by the shim in at least one chamber adjacent to it is calculated by the following equation: F _P″ ＝[H _P ·I _P ^T ·G _PtoP ]·H _P in:

Among them, G _PtoP represents the force of the magnetic field generated by the shim of unit thickness in the i-th chamber to the shim of unit thickness in the j-th chamber, and n represents the number of chambers in the shim, where b _1,2 to b _n-1,n , b _2,1 to b _n,n-1 , c _1,3 to c _n-2,n , c _3,1 to c _n,n-2 , z The values of _n,1 and z1 _,n are related to the magnetic field strength of the magnetic resonance system at the corresponding chamber and the magnetic permeability of the shims contained in the corresponding chamber;

_HP represents the thickness of the shims in each chamber of the shim strip; and _IP is the identity matrix. 7. The method according to claim 1 or 2, wherein the force on the lateral side walls of each chamber is calculated according to the following equation:

Wherein, F _Wt represents the force of the tth lateral sidewall; t represents the sequential numbering of the lateral sidewalls along the shim bar from the head end to the tail end; and wherein, F _Pt represents the tth The force of the shims in the chamber in the magnetic field, F _Pt+1 represents the force of the shims in the t+1th chamber in the magnetic field. 8. The method according to claim 2, wherein the force on the fixed end of the shim strip is equal to the superposition of the force on the shims in each chamber in the magnetic field. 9. The method of claim 2, wherein, In response to determining that the force on the lateral sidewall of any of the respective chambers or the force on the fixed end exceeds a respective threshold, indicating prior to insertion of the shim strips into the magnetic resonance system, The amount of shims to be accommodated in each chamber of the shim bar is reconfigured. 10. The method of claim 2, wherein, In response to determining that neither the force on the lateral sidewall of each of the respective chambers nor the force on the fixed end exceeds a respective threshold, indicating that insertion of the shim strip into the magnetic resonance system is permitted middle. 11. The method according to claim 1 or 2, wherein the amount of shims to be accommodated in each chamber of the shim bar for the shimming operation comprises: The total thickness of the shims that need to be accommodated in each cavity of the shim bar for the shimming operation. 12. A device for evaluating the static stress state of a shim bar in a magnetic resonance system, wherein the shim bar has a plurality of chambers arranged along its longitudinal direction for accommodating shims, and the The shimming strips can be inserted into the magnetic resonance system for shimming operations, the device comprising: A first calculation unit, the first calculation unit is configured to calculate the amount of shims in each cavity of the shim bar for the shimming operation, and calculate the shims containing the shims. The force of the shims in the chamber in the magnetic field; A second calculation unit configured to calculate the forces on the lateral side walls of the respective chambers based on the forces on the shims in the respective chambers in the magnetic field; and A determining unit configured to determine a static force-bearing state of the shim bars in the magnetic resonance system based on a comparison between the forces on the lateral side walls of the respective chambers and corresponding thresholds. 13. The apparatus of claim 12, wherein, The second calculation unit is further configured to calculate the force on the fixed end of the shim bar based on the force on the shims in the respective chambers in the magnetic field, and wherein, The determining unit is further configured to determine a static stress state of the shim bar in the magnetic resonance system based on a comparison of the force on the fixed end of the shim bar with a corresponding threshold. 14. A magnetic resonance system comprising: Magnetic resonance system body; at least one shim strip insertable into the magnetic resonance system body; and Electronic equipment, said electronic equipment including: at least one processor; and memory communicatively coupled to the at least one processor; Wherein the memory stores a computer program which, when executed by the at least one processor, implements the method according to any one of claims 1-11. 15. A computer program product comprising a computer program, wherein said computer program, when executed by a processor, implements the method according to any one of claims 1-11.

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