Method for determining magnetic resonance gradient correction compensation factor, correction method and device

Abstract

The present application relates to a method for determining, correcting, and applying a magnetic resonance gradient correction compensation factor. The method comprises: acquiring axial magnetic resonance signals of a phantom when a diffusion gradient is applied by a gradient coil, and a reference magnetic resonance signal when no diffusion gradient is applied by the gradient coil; determining, based on the axial magnetic resonance signals and the reference magnetic resonance signals, a calculated diffusion coefficient of the liquid in each axial direction; and determining, based on the calculated diffusion coefficient of the liquid in each axial direction and the reference diffusion coefficient, a gradient correction compensation factor for the corresponding axis; wherein the phantom is a liquid-filled phantom, and the liquid is isotropic. This method can improve the accuracy of the obtained correction parameters and the accuracy of gradient correction, while also improving the efficiency of gradient correction.

Description

Technical Field

[0001] The present application relates to the technical field of magnetic resonance equipment, and in particular to a method for determining a magnetic resonance gradient correction compensation factor, a correction method, and a device. Background Art

[0002] Currently, magnetic resonance imaging is primarily performed using a magnetic resonance system, which generally includes a main magnet, gradient coils, radio frequency coils, an image reconstruction module, and other components. The main magnet generates a main magnetic field in the imaging space, the gradient coils generate gradient magnetic fields, the radio frequency coils generate radio frequency pulses in the imaging space, and the image reconstruction module reconstructs the received magnetic resonance signals to obtain magnetic resonance images.

[0003] During actual magnetic resonance imaging (MRI), the gradient magnetic field strength generated by the gradient coils must be calibrated to ensure the accuracy of the gradients they deliver. This is referred to as gradient calibration. In related art, this process typically involves placing a perfectly spherical water phantom precisely at the center of the main magnet. This phantom is then imaged and analyzed. The resulting image, including its geometric shape, is used to determine calibration parameters, enabling the calibration of the gradient magnetic field strength.

[0004] However, the above-mentioned technology has very strict requirements on the geometric shape and positioning of the water phantom, but it is difficult to ensure such high precision during the actual imaging process. This will make the image of the water phantom less accurate, and the correction parameters obtained will also be less accurate, so the accuracy of the gradient correction will be difficult to guarantee. Summary of the Invention

[0005] Based on this, it is necessary to provide a method for determining a magnetic resonance gradient correction compensation factor, a magnetic resonance gradient correction method, an apparatus, a magnetic resonance system, a computer-readable storage medium, and a computer program product to address the above-mentioned technical problems, which can improve the accuracy of the obtained correction parameters and the efficiency of the gradient correction process.

[0006] In a first aspect, the present application provides a method for determining a magnetic resonance gradient correction compensation factor, the method comprising:

[0007] Acquiring axial magnetic resonance signals of the phantom when a diffusion gradient is applied by the gradient coil and a reference magnetic resonance signal when no diffusion gradient is applied by the gradient coil; wherein the phantom is a phantom filled with a liquid, and the liquid is isotropic;

[0008] determining a calculated value of the diffusion coefficient of the liquid in each axial direction according to each axial magnetic resonance signal and a reference magnetic resonance signal;

[0009] The gradient correction compensation factor of the corresponding axis is determined according to the calculated diffusion coefficient value of the liquid in each axial direction and the reference diffusion coefficient.

[0010] In one embodiment, the reference diffusion coefficient is any one of the calculated diffusion coefficient values ​​along each axis; and determining the gradient correction compensation factor of the corresponding axis based on the calculated diffusion coefficient value of the liquid along each axis and the reference diffusion coefficient includes:

[0011] The other diffusion coefficient calculated values ​​are respectively calculated with the reference diffusion coefficient to obtain the gradient correction compensation factor of the corresponding axis; the above-mentioned other diffusion coefficient calculated values ​​are the diffusion coefficient calculated values ​​in each axial direction except the reference diffusion coefficient.

[0012] In one embodiment, the reference diffusion coefficient is the intrinsic diffusion coefficient of the liquid.

[0013] In one embodiment, the diffusion gradients applied to the gradient coils act on three orthogonal axes, namely, x, y, and z.

[0014] In one embodiment, the phantom is placed at any position in the linear working area of ​​the magnet.

[0015] In one embodiment, determining the gradient correction compensation factor of the corresponding axis based on the calculated diffusion coefficient of the liquid in each axial direction and the reference diffusion coefficient includes:

[0016] According to the formula Calculate the gradient correction compensation factor of the corresponding axis;

[0017] Among them, i refers to each axis; k i Refers to the gradient correction compensation factor in the corresponding axis; D i Refers to the calculated diffusion coefficient value in the corresponding axial direction; D0 refers to the reference diffusion coefficient.

[0018] In a second aspect, the present application further provides a magnetic resonance gradient correction method, which includes using the gradient correction compensation factor of the first aspect to correct the gradient of the gradient coil in the corresponding axial direction.

[0019] In a third aspect, the present application further provides a device for determining a magnetic resonance gradient correction compensation factor, the device comprising:

[0020] a signal acquisition module, configured to acquire axial magnetic resonance signals of the phantom when a diffusion gradient is applied to the gradient coil and a reference magnetic resonance signal when no diffusion gradient is applied to the gradient coil; wherein the phantom is a phantom filled with a liquid, and the liquid is isotropic;

[0021] A coefficient determination module, configured to determine a calculated value of the diffusion coefficient of the liquid in each axial direction based on each axial magnetic resonance signal and a reference magnetic resonance signal;

[0022] The compensation factor determination module is used to determine the gradient correction compensation factor of the corresponding axis according to the calculated diffusion coefficient value of the liquid in each axial direction and the reference diffusion coefficient.

[0023] In a fourth aspect, the present application further provides a magnetic resonance gradient correction device, comprising:

[0024] a signal acquisition module, configured to acquire axial magnetic resonance signals of the phantom when a diffusion gradient is applied to the gradient coil and a reference magnetic resonance signal when no diffusion gradient is applied to the gradient coil; wherein the phantom is a phantom filled with a liquid, and the liquid is isotropic;

[0025] A coefficient determination module, configured to determine a calculated value of the diffusion coefficient of the liquid in each axial direction based on each axial magnetic resonance signal and a reference magnetic resonance signal;

[0026] A compensation factor determination module is used to determine the gradient correction compensation factor of the corresponding axis based on the calculated diffusion coefficient value of the liquid in each axial direction and the reference diffusion coefficient;

[0027] The correction module is used to correct the gradient of the gradient coil in the corresponding axial direction using each gradient correction compensation factor.

[0028] In a fifth aspect, the present application further provides a magnetic resonance system, comprising a magnetic resonance scanning device and a computer device connected to each other, wherein the magnetic resonance scanning device comprises a main magnet and a gradient coil, and the computer device comprises a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the following steps are implemented:

[0029] Acquiring axial magnetic resonance signals of the phantom when a diffusion gradient is applied by the gradient coil and a reference magnetic resonance signal when no diffusion gradient is applied by the gradient coil; wherein the phantom is a phantom filled with a liquid, and the liquid is isotropic;

[0030] determining a calculated value of the diffusion coefficient of the liquid in each axial direction according to each axial magnetic resonance signal and a reference magnetic resonance signal;

[0031] The gradient correction compensation factor of the corresponding axis is determined according to the calculated diffusion coefficient value of the liquid in each axial direction and the reference diffusion coefficient.

[0032] In a sixth aspect, the present application further provides a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the following steps are implemented:

[0033] The gradient correction compensation factor of the first aspect is used to correct the gradient of the gradient coil in the corresponding axial direction.

[0034] In a seventh aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the following steps:

[0035] Acquiring axial magnetic resonance signals of the phantom when a diffusion gradient is applied by the gradient coil and a reference magnetic resonance signal when no diffusion gradient is applied by the gradient coil; wherein the phantom is a phantom filled with a liquid, and the liquid is isotropic;

[0036] determining a calculated value of the diffusion coefficient of the liquid in each axial direction according to each axial magnetic resonance signal and a reference magnetic resonance signal;

[0037] The gradient correction compensation factor of the corresponding axis is determined according to the calculated diffusion coefficient value of the liquid in each axial direction and the reference diffusion coefficient.

[0038] In an eighth aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the following steps:

[0039] The gradient correction compensation factor of the first aspect is used to correct the gradient of the gradient coil in the corresponding axial direction.

[0040] In a ninth aspect, the present application further provides a computer program product, the computer program product comprising a computer program, which, when executed by a processor, implements the following steps:

[0041] Acquiring axial magnetic resonance signals of the phantom when a diffusion gradient is applied by the gradient coil and a reference magnetic resonance signal when no diffusion gradient is applied by the gradient coil; wherein the phantom is a phantom filled with a liquid, and the liquid is isotropic;

[0042] determining a calculated value of the diffusion coefficient of the liquid in each axial direction according to each axial magnetic resonance signal and a reference magnetic resonance signal;

[0043] The gradient correction compensation factor of the corresponding axis is determined according to the calculated diffusion coefficient value of the liquid in each axial direction and the reference diffusion coefficient.

[0044] In a tenth aspect, the present application further provides a computer program product, the computer program product comprising a computer program, which, when executed by a processor, implements the following steps:

[0045] The gradient correction compensation factor of the first aspect is used to correct the gradient of the gradient coil in the corresponding axial direction.

[0046] The above-described method for determining magnetic resonance gradient correction compensation factors, magnetic resonance gradient correction method, apparatus, magnetic resonance system, storage medium, and computer program product determine the calculated diffusion coefficient of the liquid in each axial direction based on the acquired axial magnetic resonance signals of a phantom filled with an isotropic liquid when a diffusion gradient is applied to the gradient coil, as well as the reference magnetic resonance signals when no diffusion gradient is applied. The calculated diffusion coefficient values ​​for each axial direction and the reference diffusion coefficient are then used to determine the gradient correction compensation factors for the corresponding axial direction. The gradients in each axial direction can then be corrected using the gradient correction compensation factors. In this method, because the calculated diffusion coefficient values ​​for the liquid in each axial direction can be calculated using the diffusion properties of the isotropic liquid, and the gradient correction compensation factors for each axial direction are determined using the calculated diffusion coefficient values ​​for each axial direction, the process of calculating the gradient correction compensation factors does not involve the position and size of the phantom, that is, it is independent of the position and size of the phantom. Therefore, the determined gradient correction compensation factors for each axial direction are more accurate. Consequently, when gradient correction is performed using these gradient correction compensation factors, the accuracy of the correction results obtained is also higher, thereby improving the accuracy of the gradient correction in each axial direction. In addition, since there is no need to position and size the phantom, the time for positioning and size design of the phantom can be saved, the gradient correction process can be simplified, and the efficiency of the gradient correction process can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a structural block diagram of a magnetic resonance system in one embodiment;

[0048] Figure 2 is a diagram of the internal structure of a computer device in one embodiment;

[0049] Figure 3 FIG1 is a flow chart of a method for determining a magnetic resonance gradient correction compensation factor in one embodiment;

[0050] Figure 4 FIG1 is a flow chart of a magnetic resonance gradient correction method according to an embodiment;

[0051] Figure 5 is a specific example diagram of a magnetic resonance gradient correction method in another embodiment;

[0052] Figure 6 is a structural block diagram of a device for determining a magnetic resonance gradient correction compensation factor in one embodiment;

[0053] Figure 7 FIG. 4 is a structural block diagram of a magnetic resonance gradient correction device in one embodiment. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0055] The method for determining the magnetic resonance gradient correction compensation factor and the magnetic resonance gradient correction method provided in the embodiments of the present application can be applied to Figure 1 The illustrated magnetic resonance system includes an interconnected magnetic resonance scanning device 102 and a computer device 104. The magnetic resonance scanning device 102 may include a main magnet, gradient coils, radio frequency coils, and other components. The main magnet can generate a main magnetic field in the imaging space, the gradient coils can generate gradient magnetic fields in the imaging space, and the radio frequency coils can generate radio frequency pulses in the imaging space. The computer device may include an image reconstruction device and a gradient correction device. The image reconstruction device primarily reconstructs received magnetic resonance signals to obtain magnetic resonance images; the gradient correction device primarily determines gradient correction compensation factors and corrects the gradients of magnetic resonance signals. Furthermore, the computer device 104 may be a terminal or a server. Terminals may include, but are not limited to, various personal computers, laptops, smartphones, tablets, IoT devices, and portable wearable devices. The server may be implemented as a standalone server or a server cluster consisting of multiple servers.

[0056] Taking the computer device 104 as a terminal as an example, its internal structure diagram can be as follows: Figure 2 As shown. The computer device includes a processor, memory, communication interface, display screen and input device connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner. The wireless manner can be achieved through WIFI, mobile cellular network, NFC (near field communication) or other technologies. When the computer program is executed by the processor, a method for determining a magnetic resonance gradient correction compensation factor and a magnetic resonance gradient correction method are implemented. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen. The input device of the computer device can be a touch layer covering the display screen, or a key, trackball or touchpad provided on the computer device housing, or an external keyboard, touchpad or mouse.

[0057] Those skilled in the art will understand that Figure 2The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement.

[0058] The following embodiment first describes a method for determining a magnetic resonance gradient correction compensation factor.

[0059] In one embodiment, Figure 3 As shown, a method for determining a magnetic resonance gradient correction compensation factor is provided, and the method is applied to Figure 2 Taking the computer device in the example as an example, the method may include the following steps:

[0060] S202 , acquiring axial magnetic resonance signals of the phantom when the gradient coil applies a diffusion gradient and a reference magnetic resonance signal when the gradient coil does not apply a diffusion gradient.

[0061] In this step, the phantom is a liquid-filled phantom. The phantom can be partially filled with liquid or completely filled with liquid. The liquid is isotropic, meaning that its properties are the same in all directions. The phantom's geometric shape can be a perfect sphere or a partial sphere, such as an ellipsoid. The liquid can be water, oil, or other liquids. Optionally, the phantom in this embodiment can be a spherical water phantom filled with liquid. Furthermore, the phantom can be placed anywhere within the linear working region of the magnet. This linear region is generally located near the center of the magnet. For example, for a 9.4T gradient field, the corresponding linear region has a spatial extent of approximately 10 cm. Due to the shape and geometric dimensions of the gradient coil, the rate of change of the gradient field intensity within the linear region is constant per unit distance. In other words, in this embodiment, there are no restrictions on the placement of the phantom within the main magnet; it can be placed within the main magnet. This lack of positioning requirements makes it easier to position the phantom during gradient correction, thereby improving the efficiency of gradient correction.

[0062] Specifically, a phantom can be pre-set and placed at any position within the linear working area of ​​the main magnet. An MRI scan can then be performed on the phantom without applying a diffusion gradient to obtain MRI signals along each axis. Because the liquid is isotropic, the MRI signals obtained along each axis without applying a diffusion gradient are identical and can therefore be recorded as reference MRI signals. After obtaining the reference MRI signals, the same diffusion gradient can be applied to the gradient coils along each axis without changing the position of the phantom. An MRI scan can then be performed on the phantom after applying the gradients to obtain MRI signals along each axis, which are recorded as the respective axial MRI signals.

[0063] The diffusion gradient refers to the gradient applied to the gradient coil during diffusion tensor imaging. Optionally, the diffusion gradient applied to the gradient coil acts separately on three orthogonal x, y, and z axes. The same diffusion gradient can be applied to the gradient coil along each of these three axes. Applying the same diffusion gradient to each axis facilitates subsequent rapid determination of the diffusion gradient correction compensation factor and rapid gradient correction.

[0064] S204 , determining a calculated value of the diffusion coefficient of the liquid in each axial direction according to each axial magnetic resonance signal and the reference magnetic resonance signal.

[0065] In this step, the set magnetic resonance parameters can be first obtained, and the preset mathematical functions are used to perform mathematical operations on the magnetic resonance parameters, each axial magnetic resonance signal and the reference magnetic resonance signal to determine the calculated diffusion coefficient value of the above-mentioned liquid in each axial direction.

[0066] The magnetic resonance parameter here can be recorded as the b-value, which is a value related to the applied diffusion gradient and the gradient action time. b is proportional to the square of the gradient size and to the cube of the time, that is, b is proportional to the square of the gradient and b is proportional to the cube of the gradient time. Before performing an MRI scan, when the MRI system sets the scan sequence, the corresponding b-value can be determined based on the set scan sequence. This b-value is the b-value when the gradient action is accurate. The actual b-value during the MRI scan is determined based on the diffusion gradient applied by the gradient coil during the actual scan. For example, if the diffusion gradient applied by the gradient coil is incorrect, then the b-value may not be the b-value set when the scan sequence was initially set.

[0067] Specifically, the following formula (1) can be used to calculate the diffusion coefficient of the liquid in each axial direction. Formula (1) is as follows:

[0068] D i =(lnS0-lnS i ) / b (1)

[0069] Wherein, formula (1) or its variant can be used as the mathematical function in this step; i refers to each axial direction; D i Refers to the calculated diffusion coefficient value in the corresponding axial direction; S0 refers to the reference magnetic resonance signal, S i Refers to the axial magnetic resonance signal corresponding to the axial direction.

[0070] After obtaining the axial magnetic resonance signals, the reference magnetic resonance signals, and the b value determined when setting the scanning sequence, the parameters determined here can be substituted into the above formula (1) or the modified formula of formula (1) to calculate the diffusion coefficient calculated value D in each axial direction. i .

[0071] S206 , determining a gradient correction compensation factor of the corresponding axis according to the calculated diffusion coefficient value of the liquid in each axial direction and the reference diffusion coefficient.

[0072] In this step, after determining the calculated diffusion gradient values ​​of the liquid along each axis, a preset reference diffusion coefficient can also be determined. Mathematical operations can then be performed on the calculated diffusion coefficient values ​​and the reference diffusion coefficient along each axis to obtain the corresponding gradient correction compensation factors along each axis. Examples of the mathematical operations include comparison operations, quotient operations, difference operations, square root operations, and the like.

[0073] In the above-mentioned method for determining magnetic resonance gradient correction compensation factors, calculated diffusion coefficient values ​​for the liquid in each axial direction are determined based on magnetic resonance signals obtained for a phantom filled with an isotropic liquid when a diffusion gradient is applied to the gradient coil, as well as reference magnetic resonance signals obtained when no diffusion gradient is applied. The gradient correction compensation factors for the corresponding axial directions are then determined using the calculated diffusion coefficient values ​​for each axial direction and the reference diffusion coefficient. The gradients in each axial direction can then be corrected using the gradient correction compensation factors. In this method, because the diffusion properties of the isotropic liquid can be used to calculate the calculated diffusion coefficient values ​​for the liquid in each axial direction, and the gradient correction compensation factors for each axial direction are determined using the calculated diffusion coefficient values ​​for each axial direction, the calculation of the gradient correction compensation factors does not involve the position and size of the phantom, that is, it is independent of the position and size of the phantom. Therefore, the determined gradient correction compensation factors for each axial direction are more accurate. Consequently, when gradient correction is performed using these gradient correction compensation factors, the accuracy of the correction results obtained is also more accurate, thereby improving the accuracy of the gradient correction in each axial direction. In addition, since there is no need to position and size the phantom, the time for positioning and size design of the phantom can be saved, the gradient correction process can be simplified, and the efficiency of the gradient correction process can be improved.

[0074] The above embodiment mentions that the corresponding gradient correction compensation factor can be determined for each axis. Before determining the gradient correction compensation factor, it is also possible to pre-determine whether the diffusion gradient applied in each axis is correct, and then perform gradient correction on the axis where the gradient is incorrectly applied. This process is described in detail below. In another embodiment, another method for determining the magnetic resonance gradient correction compensation factor is provided. Based on the above embodiment, the method can further include the following steps A1-A2:

[0075] Step A1: Compare the calculated diffusion coefficient value in each axial direction with the reference diffusion coefficient to obtain a comparison result.

[0076] Step A2: Determine whether the diffusion gradient applied in each axial direction of the gradient coil is correct based on the comparison result.

[0077] Here, before comparing the calculated diffusion coefficient values ​​in each axial direction with the reference diffusion coefficient, the reference diffusion coefficient may be determined in advance.

[0078] In a possible implementation, the reference diffusion coefficient may be any one of the calculated diffusion coefficient values ​​along each axial direction. That is, any one of the calculated diffusion coefficient values ​​along each axial direction may be selected as the reference diffusion coefficient. Accordingly, the above-mentioned S206 may be calculated using the following steps: calculating the other calculated diffusion coefficient values ​​and the reference diffusion coefficient respectively to obtain the gradient correction compensation factor of the corresponding axis; the other calculated diffusion coefficient values ​​are the calculated diffusion coefficient values ​​excluding the reference diffusion coefficient among the calculated diffusion coefficient values ​​along each axial direction.

[0079] In another possible embodiment, the reference diffusion coefficient may be the intrinsic diffusion coefficient of the liquid. For example, if the liquid is water, the intrinsic diffusion coefficient of water (i.e., the reference diffusion coefficient) may be 3*10 -3 mm 2 Accordingly, the above S206 can be calculated by the following steps: the calculated diffusion coefficient value in each axis is calculated with the reference diffusion coefficient to obtain the gradient correction compensation factor of the corresponding axis.

[0080] After determining the reference diffusion coefficient, the calculated diffusion coefficient values ​​for each axis can be compared with the reference diffusion coefficient to determine whether the calculated diffusion coefficient values ​​for each axis are equal to the reference diffusion coefficient. For example, the comparison process can include calculating the difference between the calculated diffusion coefficient values ​​for each axis and the reference diffusion coefficient, and comparing each calculated difference with 0. If the difference corresponding to the calculated diffusion coefficient value for a particular axis is not equal to 0, then the diffusion gradient applied for that axis is determined to be incorrect; if it is equal to 0, then the diffusion gradient applied for that axis is determined to be correct. Alternatively, the ratio of the calculated diffusion coefficient values ​​for each axis to the reference diffusion coefficient can be calculated, and each calculated ratio can be compared with 1. If the ratio corresponding to the calculated diffusion coefficient value for a particular axis is not equal to 1, then the diffusion gradient applied for that axis is determined to be incorrect; if it is equal to 1, then the diffusion gradient applied for that axis is determined to be correct. Of course, other comparison methods can also be used.

[0081] It should be noted that for isotropic liquids, when the diffusion gradients applied in each axial direction are the same, the calculated diffusion coefficient values ​​obtained in each axial direction should also be the same. If they are different, it means that the gradient applied in one or more axes is inaccurate, and the gradient applied in that axis needs to be corrected.

[0082] In this embodiment, the calculated diffusion coefficient values ​​along each axis are compared with the reference diffusion coefficient, and whether the diffusion gradient applied along each axis of the gradient coil is correct is determined based on the comparison results. This allows accurate and rapid identification of the axis along which the gradient is incorrectly applied, and accurate and rapid correction of the gradient along the incorrectly applied axis, thereby avoiding blind gradient correction and improving the accuracy and efficiency of gradient correction.

[0083] In the above embodiment, it is mentioned that the gradient correction compensation factor corresponding to each axis can be obtained by performing mathematical operations on the calculated diffusion coefficient value and the reference diffusion coefficient in each axis. The following describes in detail how to determine the gradient correction compensation factor corresponding to each axis. The above S206 may include the following step B:

[0084] Step B, according to formula (2) Calculate the gradient correction compensation factor of the corresponding axis; where i refers to each axis; k i Refers to the gradient correction compensation factor in the corresponding axis; D i Refers to the calculated diffusion coefficient value in the corresponding axial direction; D0 refers to the reference diffusion coefficient.

[0085] In this step, after obtaining the calculated diffusion coefficient values ​​in each axial direction and knowing the specific axial direction in which the diffusion gradient applied is incorrect, the gradient correction compensation factor in the axial direction in which the gradient is applied incorrectly can be calculated.

[0086] The following first derives the formula for calculating the gradient correction compensation factor, that is, deriving the above formula (2), the process is as follows:

[0087] Assuming that the axis to which the gradient is applied is the y-axis, we can first use formula (3) b = b n ·D y / D0 calculates the deviation of the b value, where b n The b value determined when setting the scanning sequence is a fixed value and a known quantity; D y The calculated value of the diffusion coefficient on the y-axis.

[0088] At the same time, it can be seen from the description in S204 above that b is proportional to the square of the gradient and to the cube of the time, that is, b is proportional to the square of the gradient and b is proportional to the cube of the gradient time. The relationship between b, gradient and gradient time can be expressed by the following formula (4): b = γ 2 G 2 t 3 , where γ is a constant that can be determined when setting the scanning sequence and is a known quantity; G is the gradient and t is the time.

[0089] By converting formulas (3) and (4), we can obtain formula (5)b n ·D y / D0=γ 2 G 2 t 3 , where b n , γ and t are all constants and can be simplified, so we can get formula (6)D y / D0=G 2 , take the square root of formula (6) to get formula (7) Convert the y-axis in formula (7) to any axis, that is, y Replace with D i , G is replaced by k i , we can obtain the above formula (2).

[0090] After obtaining the above formula (2), the calculated diffusion coefficient value in the axial direction where the gradient is incorrectly applied and the reference diffusion coefficient can be substituted into formula (2) for calculation to obtain the gradient correction compensation factor in the axial direction.

[0091] In this embodiment, a calculation formula for a gradient correction compensation factor including a calculated diffusion coefficient value and a reference diffusion coefficient is used to calculate a compensation factor for an axial direction in which an incorrect gradient is applied. This allows for rapid and accurate acquisition of the gradient correction compensation factor for that axial direction, thereby improving the accuracy and efficiency of obtaining the gradient correction compensation factor. Furthermore, this gradient correction compensation factor can also be used to rapidly and accurately correct that axial direction, thereby improving the accuracy and efficiency of gradient correction.

[0092] After the magnetic resonance gradient correction compensation factor is determined in the above embodiment, magnetic resonance gradient correction can be performed. The following embodiment will further illustrate the magnetic resonance gradient correction method based on the above embodiment.

[0093] In one embodiment, Figure 4 As shown, a magnetic resonance gradient correction method is provided, which is applied to Figure 2 The computer device in the embodiment is used as an example for explanation. Based on the above embodiment, the method may further include the following steps:

[0094] S302 , using each gradient correction compensation factor to correct the gradient of the gradient coil in the corresponding axial direction.

[0095] In this step, mathematical operations can be performed on each gradient correction compensation factor and the diffusion gradient in the corresponding axial direction to obtain the corrected diffusion gradient in the corresponding axial direction of the gradient coil. Specifically, each gradient correction compensation factor can be multiplied by a preset diffusion gradient in the corresponding axial direction to obtain the corrected diffusion gradient in that axial direction. A specific diffusion gradient can be preset for each axial direction and determined when setting the scanning sequence.

[0096] In this embodiment, the diffusion gradient in the corresponding axis can be corrected respectively by obtaining the gradient correction compensation factor in each axis. This can quickly and accurately correct the gradient in each axis, thereby improving the accuracy and efficiency of the gradient correction.

[0097] In order to better illustrate the technical solution of the embodiment of the present application, the technical solution of the present application is described below in conjunction with a specific embodiment. Based on the above embodiment, the method may include the following steps:

[0098] S1, acquiring axial magnetic resonance signals of a spherical phantom filled with isotropic fluid when a diffusion gradient is applied to the gradient coil, and a reference magnetic resonance signal when no diffusion gradient is applied to the gradient coil.

[0099] S2, obtain the set magnetic resonance parameters and use the preset mathematical function D i =(lnS0-lnS i) / b performs mathematical operations on the magnetic resonance parameters, each axial magnetic resonance signal and the reference magnetic resonance signal to determine the calculated diffusion coefficient value of the above-mentioned liquid in each axial direction.

[0100] S3, comparing the calculated diffusion coefficient values ​​in each axial direction with a reference diffusion coefficient to obtain a comparison result; wherein the reference diffusion coefficient is any one of the calculated diffusion coefficient values ​​in each axial direction or the intrinsic diffusion coefficient of the liquid.

[0101] S4, determining whether the diffusion gradient applied in each axial direction of the gradient coil is correct based on the comparison result.

[0102] S5, when the diffusion gradient applied in one axis is incorrect, use the formula The calculated diffusion coefficient value and the reference diffusion coefficient in the axial direction are calculated to obtain a gradient correction compensation factor in the axial direction.

[0103] S6 , multiplying the diffusion gradient in the axial direction by the gradient correction compensation factor in the axial direction to obtain a corrected diffusion gradient in the axial direction.

[0104] For details, please refer to Figure 5 As shown in the figure, magnetic resonance signals are collected when the gradient coil does not apply a diffusion gradient and when the diffusion gradient acts on the x, y, and z axes respectively. The magnitude of the diffusion gradient applied here can be changed, but the magnitude and duration of the diffusion gradient applied on the three axes need to be the same. The above calculation method can be used to calculate the calculated diffusion coefficient of the liquid (such as water) in each axis and the gradient correction compensation factor on the axis where the gradient is applied incorrectly (such as the y-axis in the figure). Gradient correction can then be performed.

[0105] It should be noted that the embodiments of the present application do not limit the manner of applying the diffusion gradient, and the dual gradient mode is not necessarily adopted. Other modes of applying the diffusion gradient may also be adopted. Figure 5 The ones shown are examples only.

[0106] It should be understood that, although the various steps in the flowcharts involved in the various embodiments described above are displayed in sequence according to the instructions of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowcharts involved in the various embodiments described above can include multiple steps or multiple stages, and these steps or stages are not necessarily executed and completed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0107] Based on the same inventive concept, embodiments of the present application further provide a device for determining a magnetic resonance gradient correction compensation factor for implementing the aforementioned method for determining a magnetic resonance gradient correction compensation factor. The solution provided by this device is similar to the solution described in the aforementioned method. Therefore, the specific limitations of one or more embodiments of the device for determining a magnetic resonance gradient correction compensation factor provided below can be found in the aforementioned method for determining a magnetic resonance gradient correction compensation factor, and are not further elaborated here.

[0108] In one embodiment, Figure 6 As shown, a device for determining a magnetic resonance gradient correction compensation factor is provided, comprising: a signal acquisition module 10, a coefficient determination module 11 and a compensation factor determination module 12, wherein:

[0109] The signal acquisition module 10 is configured to acquire axial magnetic resonance signals of the phantom when a diffusion gradient is applied to the gradient coil and a reference magnetic resonance signal when no diffusion gradient is applied to the gradient coil; wherein the phantom is a phantom filled with a liquid, and the liquid is isotropic;

[0110] The coefficient determination module 11 is used to determine the calculated value of the diffusion coefficient of the liquid in each axial direction according to each axial magnetic resonance signal and the reference magnetic resonance signal;

[0111] The compensation factor determination module 12 is used to determine the gradient correction compensation factor of the corresponding axis according to the calculated diffusion coefficient value of the liquid in each axial direction and the reference diffusion coefficient.

[0112] Optionally, the phantom is placed at any position in the linear working area of ​​the magnet.

[0113] In another embodiment, the reference diffusion coefficient is any one of the calculated diffusion coefficient values ​​along each axial direction. Based on the above embodiment, the compensation factor determination module 13 may include a compensation factor determination unit, configured to calculate other calculated diffusion coefficient values ​​and the reference diffusion coefficient respectively to obtain the gradient correction compensation factor of the corresponding axis. The other calculated diffusion coefficient values ​​are the calculated diffusion coefficient values ​​excluding the reference diffusion coefficient among the calculated diffusion coefficient values ​​along each axial direction.

[0114] Optionally, the reference diffusion coefficient is the intrinsic diffusion coefficient of the liquid.

[0115] In another embodiment, the diffusion gradients applied to the gradient coils act on three orthogonal axes, namely x, y, and z.

[0116] In another embodiment, another device for determining the magnetic resonance gradient correction compensation factor is provided. Based on the above embodiment, the compensation factor determination module 13 may include a compensation factor calculation unit, which is configured to calculate the compensation factor according to the formula Calculate the gradient correction compensation factor of the corresponding axis;

[0117] Among them, i refers to each axis; k i Refers to the gradient correction compensation factor in the corresponding axis; D i Refers to the calculated diffusion coefficient value in the corresponding axial direction; D0 refers to the reference diffusion coefficient.

[0118] In another embodiment, a magnetic resonance gradient correction device is provided. Figure 7 As shown, based on the above embodiment, the magnetic resonance gradient correction device may include: a signal acquisition module 10, a coefficient determination module 11, a compensation factor determination module 12 and a correction module 13, wherein:

[0119] The signal acquisition module 10 is used to acquire axial magnetic resonance signals of the phantom when the gradient coil applies a diffusion gradient and a reference magnetic resonance signal when the gradient coil does not apply a diffusion gradient; wherein the liquid is isotropic;

[0120] The coefficient determination module 11 is used to determine the calculated value of the diffusion coefficient of the liquid in each axial direction according to each axial magnetic resonance signal and the reference magnetic resonance signal;

[0121] A compensation factor determination module 12 is configured to determine a gradient correction compensation factor for the corresponding axis based on the calculated diffusion coefficient of the liquid in each axial direction and a reference diffusion coefficient;

[0122] The correction module 13 is used to correct the gradients of the gradient coils in the corresponding axial directions using various gradient correction compensation factors.

[0123] The aforementioned device for determining the magnetic resonance gradient correction compensation factor and each module within the magnetic resonance gradient correction device may be implemented in whole or in part via software, hardware, or a combination thereof. Each module may be embedded in or independent of a processor within a computer device in the form of hardware, or may be stored in a memory within the computer device in the form of software, so that the processor can call and execute the corresponding operations of each module.

[0124] In one embodiment, a magnetic resonance system is provided, comprising a magnetic resonance scanning device and a computer device connected to each other, wherein the magnetic resonance scanning device comprises a main magnet and gradient coils, and the computer device comprises a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the following steps are implemented:

[0125] Acquire axial magnetic resonance signals of a phantom when a diffusion gradient is applied by the gradient coil, and obtain a reference magnetic resonance signal when no diffusion gradient is applied by the gradient coil; wherein the phantom is a phantom filled with a liquid, and the liquid is isotropic; determine a calculated diffusion coefficient value of the liquid in each axial direction based on the axial magnetic resonance signals and the reference magnetic resonance signal; and determine a gradient correction compensation factor for the corresponding axis based on the calculated diffusion coefficient value of the liquid in each axial direction and the reference diffusion coefficient.

[0126] In one embodiment, when the processor executes the computer program, the processor further implements the following steps:

[0127] The other diffusion coefficient calculated values ​​are respectively calculated with the reference diffusion coefficient to obtain the gradient correction compensation factor of the corresponding axis; the above-mentioned other diffusion coefficient calculated values ​​are the diffusion coefficient calculated values ​​in each axial direction except the reference diffusion coefficient.

[0128] In one embodiment, the reference diffusion coefficient is the intrinsic diffusion coefficient of the liquid.

[0129] In one embodiment, the diffusion gradients applied to the gradient coils act on three orthogonal axes, namely, x, y, and z.

[0130] In one embodiment, the phantom is placed at any position in the linear working area of ​​the magnet.

[0131] In one embodiment, when the processor executes the computer program, the processor further implements the following steps:

[0132] According to the formula Calculate the gradient correction compensation factor of the corresponding axis; where i refers to each axis; k i Refers to the gradient correction compensation factor in the corresponding axis; D i Refers to the calculated diffusion coefficient value in the corresponding axial direction; D0 refers to the reference diffusion coefficient.

[0133] In one embodiment, a computer device is provided, including a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the following steps are implemented:

[0134] Acquire axial magnetic resonance signals of a phantom when a diffusion gradient is applied to the gradient coil, and obtain a reference magnetic resonance signal when no diffusion gradient is applied to the gradient coil; wherein the phantom is filled with a liquid, and the liquid is isotropic; determine a calculated diffusion coefficient value of the liquid in each axial direction based on the axial magnetic resonance signals and the reference magnetic resonance signal; determine a gradient correction compensation factor for the corresponding axis based on the calculated diffusion coefficient value of the liquid in each axial direction and the reference diffusion coefficient; and use each gradient correction compensation factor to correct the gradient of the gradient coil in the corresponding axial direction.

[0135] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the following steps are implemented:

[0136] Acquire axial magnetic resonance signals of a phantom when a diffusion gradient is applied by the gradient coil, and obtain a reference magnetic resonance signal when no diffusion gradient is applied by the gradient coil; wherein the phantom is a phantom filled with a liquid, and the liquid is isotropic; determine a calculated diffusion coefficient value of the liquid in each axial direction based on the axial magnetic resonance signals and the reference magnetic resonance signal; and determine a gradient correction compensation factor for the corresponding axis based on the calculated diffusion coefficient value of the liquid in each axial direction and the reference diffusion coefficient.

[0137] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0138] The other diffusion coefficient calculated values ​​are respectively calculated with the reference diffusion coefficient to obtain the gradient correction compensation factor of the corresponding axis; the above-mentioned other diffusion coefficient calculated values ​​are the diffusion coefficient calculated values ​​in each axial direction except the reference diffusion coefficient.

[0139] In one embodiment, the reference diffusion coefficient is the intrinsic diffusion coefficient of the liquid.

[0140] In one embodiment, the diffusion gradients applied to the gradient coils act on three orthogonal axes, namely, x, y, and z.

[0141] In one embodiment, the phantom is placed at any position in the linear working area of ​​the magnet.

[0142] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0143] According to the formula Calculate the gradient correction compensation factor of the corresponding axis; where i refers to each axis; k i Refers to the gradient correction compensation factor in the corresponding axis; D i Refers to the calculated diffusion coefficient value in the corresponding axial direction; D0 refers to the reference diffusion coefficient.

[0144] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the following steps are implemented:

[0145] Acquire axial magnetic resonance signals of a phantom when a diffusion gradient is applied to the gradient coil, and obtain a reference magnetic resonance signal when no diffusion gradient is applied to the gradient coil; wherein the phantom is filled with a liquid, and the liquid is isotropic; determine a calculated diffusion coefficient value of the liquid in each axial direction based on the axial magnetic resonance signals and the reference magnetic resonance signal; determine a gradient correction compensation factor for the corresponding axis based on the calculated diffusion coefficient value of the liquid in each axial direction and the reference diffusion coefficient; and use each gradient correction compensation factor to correct the gradient of the gradient coil in the corresponding axial direction.

[0146] In one embodiment, a computer program product is provided, comprising a computer program, which, when executed by a processor, implements the following steps:

[0147] Acquire axial magnetic resonance signals of a phantom when a diffusion gradient is applied by the gradient coil, and obtain a reference magnetic resonance signal when no diffusion gradient is applied by the gradient coil; wherein the phantom is a phantom filled with a liquid, and the liquid is isotropic; determine a calculated diffusion coefficient value of the liquid in each axial direction based on the axial magnetic resonance signals and the reference magnetic resonance signal; and determine a gradient correction compensation factor for the corresponding axis based on the calculated diffusion coefficient value of the liquid in each axial direction and the reference diffusion coefficient.

[0148] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0149] The other diffusion coefficient calculated values ​​are respectively calculated with the reference diffusion coefficient to obtain the gradient correction compensation factor of the corresponding axis; the above-mentioned other diffusion coefficient calculated values ​​are the diffusion coefficient calculated values ​​in each axial direction except the reference diffusion coefficient.

[0150] In one embodiment, the reference diffusion coefficient is the intrinsic diffusion coefficient of the liquid.

[0151] In one embodiment, the diffusion gradients applied to the gradient coils act on three orthogonal axes, namely, x, y, and z.

[0152] In one embodiment, the phantom is placed at any position in the linear working area of ​​the magnet.

[0153] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0154] According to the formula Calculate the gradient correction compensation factor of the corresponding axis; where i refers to each axis; k i Refers to the gradient correction compensation factor in the corresponding axis; D i Refers to the calculated diffusion coefficient value in the corresponding axial direction; D0 refers to the reference diffusion coefficient.

[0155] In one embodiment, a computer program product is provided, comprising a computer program, which, when executed by a processor, implements the following steps:

[0156] Acquire axial magnetic resonance signals of a phantom when a diffusion gradient is applied to the gradient coil, and obtain a reference magnetic resonance signal when no diffusion gradient is applied to the gradient coil; wherein the phantom is filled with a liquid, and the liquid is isotropic; determine a calculated diffusion coefficient value of the liquid in each axial direction based on the axial magnetic resonance signals and the reference magnetic resonance signal; determine a gradient correction compensation factor for the corresponding axis based on the calculated diffusion coefficient value of the liquid in each axial direction and the reference diffusion coefficient; and use each gradient correction compensation factor to correct the gradient of the gradient coil in the corresponding axial direction.

[0157] It should be noted that the data involved in this application (including but not limited to data used for analysis, stored data, displayed data, etc.) are all information and data authorized by the user or fully authorized by all parties.

[0158] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processor involved in the various embodiments provided herein may be, but are not limited to, a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic unit, a data processing logic unit based on quantum computing, and the like.

[0159] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0160] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A method for determining a magnetic resonance gradient correction compensation factor, characterized in that: The method comprises: Acquire axial magnetic resonance signals of the phantom when a diffusion gradient is applied by the gradient coil and a reference magnetic resonance signal when the gradient coil does not apply the diffusion gradient; wherein the phantom is a phantom filled with a liquid, the liquid being isotropic; and the phantom is placed at any position in the linear working area of ​​the magnet; determining a calculated value of the diffusion coefficient of the liquid in each axial direction according to each of the axial magnetic resonance signals and the reference magnetic resonance signal; The gradient correction compensation factor of the corresponding axis is determined according to the calculated diffusion coefficient value of the liquid in each axial direction and the reference diffusion coefficient.

2. The method according to claim 1, characterized in that The reference diffusion coefficient is any one of the calculated diffusion coefficient values ​​in each axial direction; determining the gradient correction compensation factor of the corresponding axis based on the calculated diffusion coefficient value of the liquid in each axial direction and the reference diffusion coefficient includes: The other diffusion coefficient calculated values ​​are respectively calculated with the reference diffusion coefficient to obtain the gradient correction compensation factor of the corresponding axis; the other diffusion coefficient calculated values ​​are the diffusion coefficient calculated values ​​in the diffusion coefficient calculated values ​​on each axis except the reference diffusion coefficient.

3. The method according to claim 1, characterized in that The reference diffusion coefficient is the intrinsic diffusion coefficient of the liquid.

4. The method according to claim 1, wherein The diffusion gradients applied to the gradient coils act on three orthogonal axes, namely, x, y, and z.

5. The method according to claim 1, wherein Determining the gradient correction compensation factor of the corresponding axis according to the calculated diffusion coefficient value of the liquid in each axial direction and the reference diffusion coefficient includes: According to the formula Calculate the gradient correction compensation factor of the corresponding axis; Among them, i refers to each axis; k i Refers to the gradient correction compensation factor in the corresponding axis; D i Refers to the calculated diffusion coefficient value in the corresponding axial direction; D0 refers to the reference diffusion coefficient.

6. A magnetic resonance gradient correction method, characterized in that: The method comprises using the gradient correction compensation factor described in any one of claims 1 to 5 to respectively correct the gradient of the gradient coil in the corresponding axial direction.

7. A device for determining a magnetic resonance gradient correction compensation factor, characterized in that: The device comprises: a signal acquisition module, configured to acquire axial magnetic resonance signals of the phantom when a diffusion gradient is applied by the gradient coil and a reference magnetic resonance signal when no diffusion gradient is applied by the gradient coil; wherein the phantom is a phantom filled with a liquid, the liquid being isotropic; and the phantom is placed at any position in the linear working area of ​​the magnet; a coefficient determination module, configured to determine a calculated value of the diffusion coefficient of the liquid in each axial direction according to each of the axial magnetic resonance signals and the reference magnetic resonance signal; The compensation factor determination module is used to determine the gradient correction compensation factor of the corresponding axis according to the calculated diffusion coefficient value of the liquid in each axial direction and the reference diffusion coefficient.

8. A magnetic resonance gradient correction device, characterized in that: The device comprises: A correction module is used to correct the gradient of the gradient coil in the corresponding axial direction using the gradient correction compensation factor according to any one of claims 1 to 5.

9. A magnetic resonance system comprising a magnetic resonance scanning device and a computer device connected to each other, wherein the magnetic resonance scanning device comprises a main magnet and gradient coils, and the computer device comprises a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 6 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

11. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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