Chemical shift encoding imaging method, device and equipment based on phase unwrapping

Abstract

The application discloses a chemical shift encoding imaging method, device and equipment based on phase unwrapping, which comprises the following steps: acquiring an initial image, determining a field map candidate solution of the initial image; performing phase conversion on the candidate field map solution, taking the correct solution and the interval between the inverse solutions of the candidate field map solution as the target within a set range, determining an intermediate field map solution based on a phase unwrapping method; determining the real phase of the intermediate field map solution, and converting the real phase to the field map candidate solution space to determine a target field map solution; determining a first chemical composition signal and a second chemical composition signal based on the target field map solution, and performing chemical shift encoding imaging based on the first chemical composition signal and / or the second chemical composition signal. By converting the problem of selecting one of the phase vectors in different chemical compositions into a phase unwrapping problem, the stability and accuracy of chemical shift component separation are ensured under the condition that the acquisition parameters do not meet specific conditions, and the chemical shift encoding imaging effect is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of image processing, and in particular to a chemical shift encoding imaging method, device and equipment based on phase unwrapping. BACKGROUND

[0002] Magnetic resonance chemical shift encoding imaging can distinguish the relative content of each component based on the resonance frequency difference of the detected object, and the most typical one is water-fat separation imaging. In water-fat separation, the most critical problem is the solution of the field, that is, how to select the appropriate solution from multiple possible candidate solutions.

[0003] In the process of implementing the present application, it is found that at least the following technical problems exist in the prior art: The existing water-fat separation method often solves the water-fat separation problem based on specific initial information, such as the region growing method based on seed points and the TREE method based on water-fat conversion region, which requires the acquired image to meet specific conditions. However, when the acquisition parameters do not meet the specific conditions, the original assumptions of the algorithm will be destroyed, and there is a lack of sufficient initial information, resulting in unstable algorithm and poor chemical shift encoding imaging effect. SUMMARY

[0004] The present application provides a chemical shift encoding imaging method, device and equipment based on phase unwrapping, to solve the technical problems of poor stability and low accuracy of chemical shift component separation when the acquisition parameters do not meet the specific conditions, and to ensure the stability and accuracy of chemical shift component separation when the acquisition parameters do not meet the specific conditions, and to improve the chemical shift encoding imaging effect.

[0005] According to one aspect of the present application, a chemical shift encoding imaging method based on phase unwrapping is provided, comprising:

[0006] Obtaining an initial image, determining the field map candidate solution of the initial image;

[0007] Taking the correct solution of the field map candidate solution and the distance between the anti-solutions within a set range as the target, performing phase conversion on the candidate field map solution, and determining the intermediate field map solution based on the phase unwrapping method;

[0008] Determining the true phase of the intermediate field map solution, and converting the true phase to the field map candidate solution space to determine the target field map solution;

[0009] Determining the first chemical component signal and the second chemical component signal based on the target field map solution, and performing chemical shift encoding imaging based on the first chemical component signal and / or the second chemical component signal.

[0010] Optionally, further, the phase conversion of the candidate field pattern solution is targeted at the correct solution and the distance between the anti-solution within a set range, comprising:

[0011] determining the intermediate variable corresponding to the correct solution and the anti-solution;

[0012] based on the variable parameter of the intermediate variable, performing phase conversion on the candidate field pattern solution, so that the phase difference between the candidate field pattern solutions is within a set range.

[0013] Optionally, further, the intermediate field pattern solution determined based on the phase unwrapping method comprises:

[0014] performing phase unwrapping on the intermediate variable to obtain a first unwrapping phase;

[0015] matching the first unwrapping phase with the original phase candidate solution, and obtaining the intermediate field pattern solution based on the matching result.

[0016] Optionally, further, the determination of the true phase of the intermediate field pattern solution comprises:

[0017] for a pixel point in the intermediate field pattern solution, matching the field pattern information of the pixel point in the intermediate field pattern solution with the original phase vector candidate solution, and determining the target field pattern information of the pixel point according to the matching result;

[0018] determining the true phase according to the target field pattern information of each pixel point.

[0019] Optionally, further, the matching of the field pattern information of the pixel point in the intermediate field pattern solution with the original phase vector candidate solution comprises:

[0020] matching the field pattern information of the pixel point in the intermediate field pattern solution with the original phase vector candidate solution through Cost(r) = min(|P w (r)-P tn (r)|,|P f (r)-P tn (r)|), wherein P t is the field pattern information of the pixel point in the intermediate field pattern solution, P tn is the original phase vector candidate solution, and r is the spatial position of the pixel point.

[0021] Optionally, further, it further comprises:

[0022] when there is phase wrapping in the candidate field pattern solution, performing phase unwrapping on the candidate field pattern solution through a second intermediate variable to obtain a second unwrapping phase;

[0023] The second unwrapping phase is phase compressed to a set range.

[0024] Optionally, the first chemical component is water, and the second chemical component is fat.

[0025] According to another aspect of the present application, there is provided a chemical shift encoding imaging device based on phase unwrapping, comprising:

[0026] A field map candidate solution determination module is configured to acquire an initial image and determine a field map candidate solution of the initial image.

[0027] An intermediate field map solution determination module is configured to perform phase conversion on the candidate field map solution with a correct solution of the field map candidate solution and a split inverse solution interval within a set range, and determine an intermediate field map solution based on a phase unwrapping method.

[0028] A target field map solution determination module is configured to determine a true phase of the intermediate field map solution, convert the true phase to a field map candidate solution space, and determine a target field map solution.

[0029] A chemical shift encoding imaging module is configured to determine a first chemical component signal and a second chemical component signal based on the target field map solution, and perform chemical shift encoding imaging based on the first chemical component signal and / or the second chemical component signal.

[0030] According to another aspect of the present application, there is provided an electronic device, comprising:

[0031] at least one processor; and

[0032] a memory connected with the at least one processor; wherein

[0033] The memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor to enable the at least one processor to perform the chemical shift encoding imaging method based on phase unwrapping according to any one of the embodiments of the present application.

[0034] According to another aspect of the present application, there is provided a computer readable storage medium storing computer instructions for enabling a processor to perform the chemical shift encoding imaging method based on phase unwrapping according to any one of the embodiments of the present application.

[0035] The technical scheme of the embodiment of the present application is: an initial image is acquired, a candidate solution of a field map of the initial image is determined; a phase conversion is performed on the candidate solution of the field map, with a correct solution and a distance between partial solutions of the candidate solution of the field map being within a set range as a target, an intermediate field map solution is determined based on a phase unwrapping method; a real phase of the intermediate field map solution is determined, and the real phase is converted to a candidate solution space of the field map to determine a target field map solution; a first chemical component signal and a second chemical component signal are determined based on the target field map solution, and chemical shift encoding imaging is performed based on the first chemical component signal and / or the second chemical component signal. By transforming the phase difference between the candidate solutions of the field map within the set range, the problem of selecting two phase vectors in different chemical components is converted into a phase unwrapping problem, and the problem of selecting two phase vectors in different chemical components can be solved by the phase unwrapping technology.

[0036] It should be understood that the content described in this part is not intended to identify key or important features of the embodiments of the present application, nor is it used to limit the scope of the present application. Other features of the present application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0038] Figure 1 is a flowchart of a chemical shift encoding imaging method based on phase unwrapping provided by an embodiment of the present application;

[0039] Figure 2 is a flowchart of a chemical shift encoding imaging method based on phase unwrapping provided by an embodiment of the present application;

[0040] Figure 3 is a process diagram of phase conversion by an intermediate variable provided by an embodiment of the present application;

[0041] Figure 4 is a field map candidate solution phase unwrapping processing diagram provided by an embodiment of the present application;

[0042] Figure 5 is a structure diagram of a chemical shift encoding imaging device based on phase unwrapping provided by an embodiment of the present application;

[0043] Figure 6 is a structure diagram of an electronic device provided by an embodiment of the present application. DETAILED DESCRIPTION

[0044] In order to better understand the technical scheme of the present application, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present application.

[0045] It should be noted that the terms "first", "second", and the like in the specification and claims of the present application and the above-described accompanying drawings are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not have to be limited to only those steps or units clearly listed, but can include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0046] Embodiment one

[0047] Figure 1 is a flowchart of a chemical shift encoding imaging method based on phase unwrapping provided by the embodiment one of the present application. The present embodiment can be applied to the case of performing chemical shift encoding imaging on separated chemical shift components, and is especially suitable for the case of performing chemical shift encoding imaging when the acquisition information does not meet certain conditions. The method can be performed by a chemical shift encoding imaging device based on phase unwrapping, which can be realized in the form of hardware and / or software, and can be configured in an electronic device. As shown in the figure, the method comprises: Figure 1

[0048] S110, acquiring an initial image, and determining a field map candidate solution of the initial image.

[0049] ​In the embodiment, the chemical shift encoding imaging is performed based on an initial image. Optionally, the initial image can be an image reconstructed based on magnetic resonance signals acquired by a magnetic resonance imaging method. It should be noted that the embodiment can realize the chemical shift encoding imaging in the case that the initial information is uncertain, and therefore, the acquisition method of the initial image and the parameters of the acquisition device (such as the magnetic field strength, the acquisition bandwidth, etc.) are not limited. Even if the initial information in the initial image reconstructed based on the acquired signals is uncertain, the signals of different chemical compositions can be stably separated.

[0050] In one implementation, the field map candidate solution of the initial image can be calculated by a conversion region extraction method or a seed point discrimination method.

[0051] Optionally, the determining the field map candidate solution of the initial image comprises: determining a fitting error of each pixel point; and taking a phase vector of the fitting error corresponding to a local minimum value as the field map candidate solution. Taking water-fat signal separation for chemical shift encoding imaging as an example, for each pixel point, the fitting error of the pixel point can be determined according to err(p) = |S-Ae|2, where err(p) is the fitting error, S is the acquired water-fat signal, p is the phase vector, and A is a parameter matrix of a multi-point Dixon signal model. The local minimum value of the fitting error err(p) can be sought in the manner of traversing (-π, π], and the phase vector of the fitting error corresponding to the local minimum value is taken as the field map candidate solution of the pixel point.

[0052] In some embodiments, before the phase conversion of the candidate field map solution, the phase unwrapping of the candidate field map solution is performed by a second intermediate variable when there is phase wrapping in the candidate field map solution, to obtain a second unwrapping phase; and the second unwrapping phase is phase compressed to be within a set range.

[0053] It is considered that there can be a correct solution of the field map or phase wrapping in the case of a positive or negative solution in the actual scenario. When one of the candidate solutions changes by 2π due to phase wrapping and the other does not, the phase unwrapping of the candidate solution of the field map (which can be P nw and P nf ) is performed first to obtain the corresponding second unwrapping phase UPw and Upf, and then the second unwrapping phase is compressed to be within the range of [-π, π], so as to simplify the problem to the case that there is no phase wrapping in the candidate solution, and the subsequent operation for chemical shift encoding imaging can be directly performed after the processing.

[0054] S120, phase conversion is performed on the candidate field pattern solution by taking the correct solution and the interval between the correct solution and the incorrect solution of the candidate field pattern solution as a target, and an intermediate field pattern solution is determined based on a phase unwrapping method.

[0055] Overall, the problem of selecting one of the phase vectors in different chemical components in the embodiment is converted into a phase unwrapping problem, and the existing phase unwrapping technology is combined to solve the problem of selecting one of the phase vectors in different chemical components.

[0056] In an embodiment of the present application, the phase conversion performed on the candidate field pattern solution by taking the correct solution and the interval between the correct solution and the incorrect solution of the candidate field pattern solution as a target comprises:

[0057] The intermediate variable corresponding to the correct solution and the incorrect solution is determined.

[0058] The phase conversion is performed on the candidate field pattern solution based on the variable parameter of the intermediate variable, so that the phase difference between the candidate field pattern solutions is within a set range.

[0059] Optionally, the phase difference between the phase vector candidate solutions can be converted into 2π through the intermediate variable, so that the problem of selecting one of the phase vectors in different chemical components is converted into a phase unwrapping problem.

[0060] First, for the correct solution and the incorrect solution of the field pattern, the following intermediate variable can be defined:

[0061] P m =p^m

[0062] Therefore, according to formula (6), the intermediate variable can be expressed as:

[0063]

[0064] When the transformation coefficient m is selected as 1 / f F ΔTE, That is, the correct solution and the incorrect solution of the phase vector are unified at this time. Based on this, the candidate field pattern solution can be memorized and phase-converted through the variable parameter of the intermediate variable, so that the phase difference between the candidate field pattern solutions is within a set range.

[0065] In an implementation, the intermediate field pattern solution determined based on the phase unwrapping method comprises:

[0066] The intermediate variable is phase-unwrapped to obtain a first unwrapping phase.

[0067] The first unwrapping phase is matched with the original phase candidate solution, and the intermediate field pattern solution is obtained based on the matching result.

[0068] Optionally, assuming that the intermediate variable P m is unwrapped, and the obtained phase is denoted as UP, a globally smooth phase can be obtained. However, when the original field map is calculated using the phase, m∠P t may be separated by an integer multiple of 2π from UP. The mismatch problem between m∠P t and UP is relatively simple, and can be solved by matching with the original phase vector candidate solution. Denote the possible candidate solution of the phase vector as The selection of n in the above formula can be determined by the following matching formula:

[0069] C(n) =∑ r min(|P w (r)-P tn (r)|,|P f (r)-P tn (r)|) where r is the spatial position of all pixel points, and P tn with the minimum cost function is the correct solution of the field map, i.e., the intermediate field map solution.

[0070] S130, determine the real phase of the intermediate field map solution, and fold the real phase to the field map candidate solution space to determine the target field map solution.

[0071] In the embodiment, after the intermediate field map solution is determined, the real phase of the intermediate field map solution needs to be folded to the field map candidate solution space to obtain the target field map solution.

[0072] In an embodiment of the present application, the determination of the real phase of the intermediate field map solution comprises: matching the field map information of a pixel point in the intermediate field map solution with the original phase vector candidate solution, and determining the target field map information of the pixel point according to the matching result; and determining the real phase according to the target field map information of each pixel point.

[0073] Optionally, the matching of the field map information of the pixel point in the intermediate field map solution with the original phase vector candidate solution comprises:

[0074] matching the field map information of the pixel point in the intermediate field map solution with the original phase vector candidate solution through Cost(r) = min(|P w (r)-P tn (r)|,|P f (r)-P tn (r)|), where P t is the field map information of the pixel point in the intermediate field map solution, P tn is the original phase vector candidate solution, and r is the spatial position of the pixel point.

[0075] The above formula can be used to verify the accuracy of the obtained field map for each pixel. Errors occurring during the unwinding process will significantly differ from the original phase vector candidate solutions, resulting in a cost function greater than 0.1. In such cases, the field map can be set to pending resolution and recalculated using spatial filtering. This process establishes a self-verification mechanism for the field map, ensuring its accuracy.

[0076] S140. Determine the first chemical component signal and the second chemical component signal based on the target field diagram, and perform chemical shift coding imaging based on the first chemical component signal and / or the second chemical component signal.

[0077] In this embodiment, after obtaining an accurate target field diagram, the separated first chemical component signal and second chemical component signal can be directly calculated based on the target field diagram. Then, the chemical shift encoding imaging result of the first chemical component is obtained based on the first chemical component signal and displayed. And / or, the chemical shift encoding imaging result of the second chemical component is obtained based on the second chemical component signal and displayed.

[0078] Optionally, the first chemical component is water, and the second chemical component is fat. Correspondingly, the first chemical component signal is a water signal, and the second chemical component signal is a fat signal, which can be obtained through [ρ...]. w ,ρ f ] T =Φ + (ψ)S separates the target water signal and the target fat signal, where ρ w For the target water signal, ρ f Let ψ be the target fat signal, Φ be the inhomogeneity of the main magnetic field, and Φ(ψ) be a function of ψ. After separating the target water signal and the target fat signal, a water signal image can be generated based on the target water signal, and a fat signal image can be generated based on the target fat signal. The water signal image and the fat signal image can then be displayed.

[0079] The technical scheme of the embodiment is characterized in that: an initial image is acquired, an initial field map of a conversion region is determined based on the initial image; the initial field map is used as initial information, local field map iteration is performed along at least two set directions, a target field map is obtained based on the local field map iteration results corresponding to each set direction; a first chemical component signal and a second chemical component signal are determined based on the target field map, and chemical shift encoding imaging is performed based on the first chemical component signal and / or the second chemical component signal. Through multi-dimensional local field map iteration, incorrect field map information is independently transmitted along different dimensions, then the multi-dimensional local field map iteration results are combined, incorrect information transmitted along different directions is excluded, correct information consistent in each dimension is retained, and the technical problem that, in the case of uncertain initial information, field map information is difficult to accurately acquire, resulting in poor stability and low accuracy of separated chemical component signals is solved, so that the separated chemical component signals are more accurate in the case of uncertain initial information, and the chemical shift encoding imaging effect is improved.

[0080] Embodiment two

[0081] The embodiment provides a preferred embodiment on the basis of the above-described embodiment.

[0082] The embodiment takes water-fat separation chemical shift encoding imaging as an example, proposes a method for determining a correct solution of a field map by combining a phase unwrapping technique, realizes a method for accurately obtaining field map information in the case that collected information does not satisfy a specific condition, and solves the problem of insufficient water-fat separation stability in this scenario.

[0083] Overall, first, the original candidate solution is converted through phase conversion, so that the distance between the correct solution of the field map and the inverse solution becomes 2π, then the real phase is determined by combining a phase unwrapping method, and is converted to the original candidate solution space to determine the correct solution of the field map. After the correct solution of the field map is obtained, the content of water and fat is calculated through matrix inverse operation, and then chemical shift encoding imaging is performed.

[0084] Figure 2 is a flowchart of a chemical shift encoding imaging method based on phase unwrapping provided by the embodiment two of the present application. Refer to Figure 2 , and the specific steps include:

[0085] In a multi-echo gradient echo sequence, when factors such as fat multi-peak and transverse relaxation attenuation are ignored, a simplified model of water-fat separation can be expressed as follows:

[0086]

[0087] Wherein, ρ w and ρ f are the contents of water and fat, f FTE is the echo time, and ψ is the inhomogeneity of the main magnetic field. n TE is the echo time, and ψ is the inhomogeneity of the main magnetic field.

[0088] The above formula can be rewritten in matrix form as

[0089] S = Φ (ψ) ρ (2)

[0090] where ρ = [ρ w , ρ f ] T and Φ (ψ) is a function of ψ:

[0091]

[0092] According to VARPRO, the field ψ can be used to uniquely represent the water and fat signals. That is:

[0093] ρ = Φ + (ψ) S (4)

[0094] Therefore, after the above steps, the key to the water-fat separation problem falls on the solution of the field map. In order to avoid the problem of phase wrapping, the concept of phase vector is introduced in document

[14] :

[0095] p = e i2πψΔTE (5)

[0096] The phase vector p can be used to equivalently represent the inhomogeneity of the main magnetic field ψ. Since the amplitude of the phase vector is fixed, it only needs to be traversed in the range of [-π, π] to find the candidate solution of the phase vector:

[0097]

[0098] Regarding the interval between the candidate solutions of the phase vector, there are relevant descriptions in the literature. For multi-point water-fat separation and two-point water-fat separation, the following formula can be obtained:

[0099]

[0100] where P t is the correct solution of the phase vector, and P a is the anti-solution of the phase vector. Let the solution with higher water content in the field map candidate solution be P w , and the solution with more fat content be P f . The present application solves the water-fat separation problem by converting the water-fat separation problem into a phase unwrapping problem and combining the existing phase unwrapping algorithm.

[0101] First, for the correct solution and the anti-solution of the field map, the following intermediate variable can be defined as the first intermediate variable:

[0102] P m =p^m (8)

[0103] Therefore, according to formula (6), the intermediate variable can be expressed as:

[0104]

[0105] When the transformation coefficient m = 1 / f is chosen F At ΔTE, That is, at this point, the correct and incorrect solutions for the phase vector are unified.

[0106] Figure 3 This is a schematic diagram illustrating a phase transformation process using an intermediate variable, as provided in Embodiment 2 of the present invention. Figure 3 As shown, by establishing an intermediate variable Pm, the difference between the correct and incorrect solutions of the phase vector is eliminated, thereby using phase solution winding and candidate solution matching to solve the water-lipid ambiguity problem.

[0107] Assume that ∠p t +2πf F ΔTE, ∠p t -2πf F ΔTE and m∠p t When both are within the range of [-π, π], we can obtain m∠p t =∠P m The correct solution for the field diagram is: where P t This is the correct solution for the phase vector, and P a This is the inverse solution of the phase vector.

[0108]

[0109] However, due to P t The phase is expanded by a factor of m, when m∠p t When the value exceeds the range of [-π, π], ∠P m For m∠p t The value corresponding to the folded-over range [-π, π], i.e.:

[0110] ∠P m =m∠P t +2kπ (11)

[0111] For intermediate variable P m By unwinding the phase and labeling the resulting phase as UP, a generally smooth phase can be obtained. However, when using this phase to calculate the original field pattern, m∠P... t The distance between UP and m∠P may be an integer multiple of 2π. tThe mismatch problem with UP is relatively simple and can be solved by matching with the original phase vector candidate solution. Let the possible candidate solution of phase vector be P tn :

[0112]

[0113] The selection of n in the above formula can be determined by the following matching formula:

[0114] C(n) =∑ r min(|P w (r)-P tn (r)|,|P f (r)-P tn (r)|) (13)

[0115] where r is the spatial position of all pixel points, and P tn is the correct solution of the field map. Let the coefficient n corresponding to the minimum cost function be N, and then the real field map solution is:

[0116]

[0117] Finally, after the field map solution P t is calculated, the P t of each pixel point is matched with the phase vector candidate solution:

[0118] Cost(r) = min(|P w (r)-P tn (r)|,|P f (r)-P tn (r)|) (15)

[0119] The difference between formula (15) and formula (13) is that formula (13) is calculated for the entire image, and the unwrapped result is matched with the original phase vector candidate solution to determine the relative relationship between them; formula (15) is calculated for each pixel point, and checks whether the obtained field map solution is correct. The part that has an error in the unwrapping process will have a large difference with the original phase vector candidate solution, and the cost function calculated by formula (15) is greater than 0.1, and the field map solution is set to pending and is calculated again by spatial filtering. Through this process, a field map self-checking mechanism is formed.

[0120] However, in practice, it is also possible that the correct solution of the field map or the anti-solution has phase wrapping. When one of the candidate solutions has a phase wrapping change of 2π and the other does not, the phase difference between the candidate solutions changes from the original 2πf F ΔTE to 2π-2πf FThe phase wrap-around of ΔTE 2π will further cause the intermediate variable P m to mutate:

[0121] Δγ = 2π m - 2kπ (16)

[0122] The range of Δγ is [-π, π]. When ΔTE = 1.5 ms, m = 1.54, then the phase mutation is Δγ = -0.92π. For this phenomenon, the phase unwrapping can be first performed on the candidate solutions P w and P f to obtain UPw and UPf. Then the unwrapped phase is compressed to the range of [-π, π], thus simplifying the problem to the case where the candidate solutions have no phase wrap-around, and thus the method described above is used to solve it. A second intermediate variable P nw and P nf is established, which has a one-to-one correspondence with UPw and UPf:

[0123]

[0124]

[0125] wherein m2 is the proportional relationship between the range of UPw and UPf and 2π, i.e.:

[0126] m2 = (ub - lb) / 2 (18)

[0127] ub and lb are the upper limit and lower limit of the union of UPw and UPf. In this process, the phase difference between the correct solution of the field map and the anti-solution becomes 2πf F ΔTE / m2, so when the intermediate variable P m is calculated, the coefficient m is m2 / f F ΔTE, not 1 / f F ΔTE. The other steps are completely consistent with the above description.

[0128] Figure 4 is a schematic diagram of phase wrap-around processing of a field map candidate solution provided in Embodiment Two of the present application. Figure 4 , (a-c) shows that when the phase wrap-around occurs in the candidate solution of the field map, it will cause the deviation of the estimated phase vector result; (d-f) by establishing a second intermediate variable Pnw and Pnf, the original phase is compressed to the range of [-π, π], thus avoiding the problem.

[0129] After obtaining the correct field map solution, the water and fat contents can be calculated by formula (4).

[0130] On the basis of the above-mentioned embodiments, the signal model in formula (1) can be changed, so that the method executed based on the changed signal model can be used for chemical shift encoding imaging methods corresponding to other chemical shift components.

[0131] The embodiment of the present application proposes a phase vector conversion method, which converts the original water-fat ambiguity problem into a phase unwrapping problem, and determines the correct phase vector through phase vector matching. By establishing an intermediate variable, the phase difference between the phase vector candidate solutions is converted into 2π, thereby converting the phase vector two-choice problem in the water-fat ambiguity into a phase unwrapping problem, and combining the existing phase unwrapping technology to solve the problem. The unwrapped phase is matched with the original phase candidate solution, so as to determine how many 2Nπ the unwrapped phase and the real phase are apart; the calculated phase vector is matched with the original phase candidate solution, forming a field map self-checking mechanism; when there is phase wrapping in the candidate solution, the original phase is compressed into the range of [-π, π] by establishing a second intermediate variable, thereby converting the problem into a case that can be handled by the method.

[0132] Embodiment three

[0133] Figure 5 is a structural schematic diagram of a chemical shift encoding imaging device based on phase unwrapping provided by the embodiment three of the present application. As shown in the figure, Figure 5 the device includes a field map candidate solution determination module 510, an intermediate field map solution determination module 520, a target field map solution determination module 530, and a chemical shift encoding imaging module 540, wherein:

[0134] The field map candidate solution determination module 510 is used to obtain an initial image, and determine a field map candidate solution of the initial image.

[0135] The intermediate field map solution determination module 520 is used to perform phase conversion on the candidate field map solution with the correct solution and the anti-solution interval of the field map candidate solution within a set range, and determine an intermediate field map solution based on a phase unwrapping method.

[0136] The target field map solution determination module 530 is used to determine a real phase of the intermediate field map solution, and convert the real phase to a field map candidate solution space to determine a target field map solution.

[0137] The chemical shift encoding imaging module 540 is used to determine a first chemical component signal and a second chemical component signal based on the target field map solution, and perform chemical shift encoding imaging based on the first chemical component signal and / or the second chemical component signal.

[0138] The technical scheme of the embodiment is characterized in that: an initial image is acquired, an initial field map of a conversion region is determined based on the initial image; the initial field map is used as initial information, local field map iteration is performed along at least two set directions, target field maps are obtained based on local field map iteration results corresponding to each set direction; first and second chemical component signals are determined based on the target field maps, and chemical shift encoding imaging is performed based on the first and / or second chemical component signals. Through multi-dimensional local field map iteration, incorrect field map information is independently transmitted along different dimensions, and then the multi-dimensional local field map iteration results are combined to exclude incorrect information transmitted along different directions and retain correct information consistent in each dimension, thereby solving the technical problem that field map information is difficult to accurately acquire in the case of uncertain initial information, resulting in poor stability and low accuracy of separated chemical component signals, and achieving more accurate separated chemical component signals and improved chemical shift encoding imaging effect in the case of uncertain initial information.

[0139] On the basis of the above-mentioned embodiment, optionally, the intermediate field map determination module 520 is specifically configured to:

[0140] determine intermediate variables corresponding to the correct solution and the inverse solution;

[0141] perform phase conversion on the candidate field maps based on variable parameters of the intermediate variables, so that phase differences between the candidate field maps are within a set range.

[0142] On the basis of the above-mentioned embodiment, optionally, the intermediate field map determination module 520 is specifically configured to:

[0143] perform phase unwrapping on the intermediate variables to obtain first unwrapping phases;

[0144] match the first unwrapping phases with original phase vector candidate solutions, and obtain the intermediate field maps based on a matching result.

[0145] On the basis of the above-mentioned embodiment, optionally, the target field map determination module 530 is specifically configured to:

[0146] for a pixel point in the intermediate field map, match field map information of the pixel point in the intermediate field map with an original phase vector candidate solution, and determine target field map information of the pixel point according to a matching result;

[0147] determine the real phase according to the target field map information of each pixel point.

[0148] On the basis of the above-mentioned embodiment, optionally, the target field map determination module 530 is specifically configured to:

[0149] match the field map information of the pixel point in the intermediate field map with the original phase vector candidate solution by Cost(r) = min(|P w (r)-P tn (r)|,|P f (r)-P tn (r)|), wherein P t is the field map information of the pixel point in the intermediate field map, P tn is the original phase vector candidate solution, and r is the spatial position of the pixel point.

[0150] On the basis of the above-mentioned embodiments, optionally, the device further comprises a phase wrapping processing module, configured to:

[0151] When there is phase wrapping in the candidate field map solution, before performing phase conversion on the candidate field map solution with the correct solution of the field map candidate solution and the interval between the partial solutions being within a set range, performing phase unwrapping on the candidate field map solution by a second intermediate variable to obtain a second unwrapped phase.

[0152] Performing phase compression on the second unwrapped phase to compress the second unwrapped phase to be within a set range.

[0153] On the basis of the above-mentioned embodiments, optionally, the first chemical component is water, and the second chemical component is fat.

[0154] The chemical shift encoding imaging device based on phase unwrapping provided in the embodiments of the present application can perform the chemical shift encoding imaging method based on phase unwrapping provided in any of the embodiments of the present application, and has the corresponding function modules and beneficial effects of the execution method.

[0155] Embodiment four

[0156] Figure 6 is a structural schematic diagram of an electronic device provided in Embodiment Four of the present application. The electronic device 10 is intended to represent various forms of digital computers, such as laptops, desktops, workstations, personal digital assistants, servers, blade servers, mainframes, and other appropriate computers. The electronic device can also represent various forms of mobile devices, such as personal digital processors, cellular telephones, smart phones, wearable devices (such as headsets, glasses, watches, etc.), and other similar computing devices. The components shown herein, their connections and relationships, and their functions, are meant to be examples only, and are not intended to limit the implementations of the present application described and / or claimed in this document.

[0157] As Figure 6As shown, the electronic device 10 includes at least one processor 11, and a memory, such as a read-only memory (ROM) 12, a random access memory (RAM) 13, etc., communicatively connected to the at least one processor 11, where the memory stores a computer program executable by the at least one processor. The processor 11 can perform various appropriate actions and processes according to the computer program stored in the read-only memory (ROM) 12 or loaded into the random access memory (RAM) 13 from the storage unit 18. In the RAM 13, various programs and data required for the operation of the electronic device 10 can also be stored. The processor 11, the ROM 12, and the RAM 13 are connected to each other through a bus 14. An input / output (I / O) interface 15 is also connected to the bus 14.

[0158] Various components in the electronic device 10 are connected to the I / O interface 15, including an input unit 16, such as a keyboard, a mouse, etc., an output unit 17, such as various types of displays, a speaker, etc., a storage unit 18, such as a magnetic disk, an optical disk, etc., and a communication unit 19, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit 19 allows the electronic device 10 to exchange information / data with other devices through a computer network, such as the Internet, and / or various telecommunication networks.

[0159] The processor 11 can be various general and / or special purpose processing components with processing and computing capabilities. Some examples of the processor 11 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various special-purpose artificial intelligence (AI) computing chips, various processors running machine learning model algorithms, a digital signal processor (DSP), and any appropriate processor, controller, microcontroller, etc. The processor 11 performs various methods and processes described above, such as the phase-unwinding-based chemical shift encoding imaging method.

[0160] In some embodiments, the phase-unwinding-based chemical shift encoding imaging method can be implemented as a computer program tangibly embodied in a computer readable storage medium, such as the storage unit 18. In some embodiments, part or all of the computer program can be loaded and / or installed onto the electronic device 10 via the ROM 12 and / or the communication unit 19. When the computer program is loaded into the RAM 13 and executed by the processor 11, one or more steps of the phase-unwinding-based chemical shift encoding imaging method described above can be performed. Alternatively, in other embodiments, the processor 11 can be configured to perform the phase-unwinding-based chemical shift encoding imaging method by any other appropriate means, such as by means of firmware.

[0161] The various embodiments of the systems and techniques described above can be implemented in digital electronic circuitry, integrated circuitry, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a system on a chip (SOC), a load programmable logic device (CPLD), computer hardware, firmware, software, and / or combinations thereof. These various embodiments can include implementation in one or more computer programs that are executable and / or interpretable on a programmable system including at least one programmable processor, which can be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device.

[0162] Computer programs implementing the phase unwrapping based chemical shift encoding imaging method of the present application can be written in any combination of one or more programming languages. These computer programs can be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the computer program running on the processor implements the functions / operations specified in the flow diagrams and / or block diagrams. The computer program can execute entirely on a machine, partly on a machine, as a stand-alone software package, partly on a machine and partly on a remote machine or entirely on a remote machine or server.

[0163] Embodiment Five

[0164] Embodiment five of the present application also provides a computer readable storage medium, which stores computer instructions for causing a processor to execute a phase unwrapping based chemical shift encoding imaging method, the method comprising:

[0165] obtaining an initial image, and determining a field map candidate solution of the initial image;

[0166] performing phase conversion on the candidate field map solution, targeting a correct solution of the candidate field map solution and an interval between the correct solution and a split solution being within a set range, and determining an intermediate field map solution based on a phase unwrapping method;

[0167] determining a true phase of the intermediate field map solution, and converting the true phase to a candidate field map solution space to determine a target field map solution;

[0168] determining a first chemical component signal and a second chemical component signal based on the target field map solution, and performing chemical shift encoding imaging based on the first chemical component signal and / or the second chemical component signal.

[0169] In the context of the present application, a computer-readable storage medium can be a tangible medium that can contain or store a computer program for use by or in connection with an instruction execution system, apparatus, or device. A computer-readable storage medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. Alternatively, a computer-readable storage medium can be a machine-readable signal medium. More specific examples of a machine-readable storage medium will include one or more lines of a program of instructions in a transitory signal, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0170] To provide for interaction with a user, the systems and techniques described here can be implemented on an electronic device 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 a pointing device (e.g., a mouse or a trackball) by which the user can provide input to the electronic device. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form, including acoustic, speech, or tactile input.

[0171] The systems and techniques described here can be implemented in a computing system that includes a back end component (e.g., as a data server), or that includes a middleware component (e.g., an application server), or that includes a front end component (e.g., a user computer having a graphical user interface or a Web browser through which a user can interact with an implementation of the systems and techniques described here), or any combination of such back end, middleware, or front end components. The components of the system can be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include a local area network (LAN), a wide area network (WAN), a blockchain network, and the Internet.

[0172] The computing system can include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. The server can be a cloud server, also known as a cloud computing server or cloud host, which is a host product in the cloud computing service system, to solve the defects of large management difficulty and weak business scalability in traditional physical host and VPS service.

[0173] It should be understood that the various forms of flow shown above can be used to reorder, add or delete steps. For example, each step described in the present application can be executed in parallel, sequentially or in a different order, as long as the desired results of the technical solutions of the present application can be achieved, which is not limited herein.

[0174] The above detailed description does not constitute a limitation on the protection scope of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A chemical shift-encoded imaging method based on phase dewinding, characterized in that, include: Obtain the initial image and determine the candidate solutions for the field map of the initial image; With the goal of ensuring that the distance between the correct solution and the inverse solution of the candidate field diagram is within a set range, the candidate field diagram is phase-transformed, and the intermediate field diagram is determined based on the phase solution winding method. Determine the true phase of the intermediate field diagram, and convert the true phase to the candidate solution space of the field diagram to determine the target field diagram; Based on the target field diagram, a first chemical component signal and a second chemical component signal are determined, and chemical shift encoding imaging is performed based on the first chemical component signal and / or the second chemical component signal.

2. The method according to claim 1, characterized in that, The step of performing a phase transformation on the candidate field diagram, with the goal of ensuring that the distance between the correct solution and the inverse solution of the candidate field diagram is within a set range, includes: Determine the intermediate variables corresponding to the correct solution and the inverse solution; Based on the variable parameters of the intermediate variable, a phase transformation is performed on the candidate field diagrams so that the phase difference between the candidate field diagrams is within a set range.

3. The method according to claim 1, characterized in that, The intermediate field diagram determined by the phase unwinding method includes: The intermediate variable is unwound in phase to obtain the first unwound phase; The first solution is wound up and matched with the original phase candidate solution, and the intermediate field diagram is obtained based on the matching result.

4. The method according to claim 1, characterized in that, Determining the true phase of the intermediate field diagram includes: For each pixel in the intermediate field diagram, the field diagram information of the pixel in the intermediate field diagram is matched with the original phase vector candidate solution, and the target field diagram information of the pixel is determined based on the matching result. The true phase is determined based on the target field map information of each pixel.

5. The method according to claim 1, characterized in that, Before performing a phase transformation on the candidate field diagram with the goal of ensuring that the distance between the correct solution and the inverse solution of the candidate field diagram is within a set range, the process further includes: When phase winding exists in the candidate field diagram, the candidate field diagram is de-wound using a second intermediate variable to obtain a second de-wound phase. The second unwinding phase is compressed to a set range.

6. The method according to claim 1, characterized in that, The first chemical component is water, and the second chemical component is fat.

7. A chemical shift-coded imaging device based on phase unwinding, characterized in that, include: The field map candidate solution determination module is used to acquire the initial image and determine the field map candidate solutions of the initial image; The intermediate field diagram determination module is used to perform phase transformation on the candidate field diagram with the goal that the distance between the correct solution and the inverse solution of the candidate field diagram is within a set range, and to determine the intermediate field diagram based on the phase solution winding method. The target field diagram determination module is used to determine the true phase of the intermediate field diagram and convert the true phase to the field diagram candidate solution space to determine the target field diagram. A chemical shift encoding imaging module is used to determine a first chemical component signal and a second chemical component signal based on the target field diagram, and to perform chemical shift encoding imaging based on the first chemical component signal and / or the second chemical component signal.

8. An electronic device, characterized in that, 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 that can be executed by the at least one processor, the computer program being executed by the at least one processor to enable the at least one processor to perform the chemical shift-coded imaging method based on phase dewinding as described in any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions that cause a processor to execute the chemical shift-coded imaging method based on phase dewinding as described in any one of claims 1-6.

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