Blood vessel selection artery spin marking coding method and device based on signal modulation

Abstract

The invention relates to the technical field of medical images, in particular to a blood vessel selection artery spin mark coding method and device based on signal modulation, and the method comprises the steps: generating a plurality of mark signal modulation graphs on a mark plane, obtaining the number of to-be-coded blood vessels and the spatial positions of the to-be-coded blood vessels on the mark plane, determining a plurality of groups of alternative coding mode combinations, selecting a mark signal modulation graph of each coding mode of each group of alternative coding mode combinations, identifying corresponding parameter combinations and blood vessel mark signal values in the mark signal modulation graph to form a blood vessel mark signal value matrix corresponding to each group of alternative coding mode combinations, and calculating loss values of each group of alternative coding mode combinations, a target coding mode combination is selected according to the loss value and fed back to the magnetic resonance scanner, and the magnetic resonance scanner conducts coding and scanning of the blood vessel coding artery spin mark on the to-be-coded blood vessel. Therefore, the problems of low universality, low coding accuracy and the like due to the fact that a signal modulation curve is required to be a cosine function in related technologies are solved.

Description

Technical Field

[0001] The present application relates to the field of medical imaging technology, and in particular to a method and device for encoding blood vessel-selective arterial spin labeling based on signal modulation. Background Art

[0002] ASL (Arterial Spin Labeling) MRI (Magnetic Resonance Imaging) is a blood perfusion imaging method that plays an important role in CBF (Cerebral Blood Flow) quantification and collateral circulation assessment. Due to its advantages of being completely non-invasive and repeatable, it has been widely used in clinical work such as brain tumors, stroke, and neurodegenerative diseases. PCASL (pseudo-continuous ASL) has a good signal-to-noise ratio and high labeling efficiency. It is currently the most widely used ASL perfusion imaging method in clinical practice. Its imaging principle is mainly based on the use of a longer pulse array, such as Figure 1 As shown, a special phase control is performed on the arterial blood downstream of the neck to reverse the flowing blood signal. The arterial blood is used as an endogenous tracer. After a period of PLD (Post Labeling Delay), the perfusion process of arterial blood flowing into the static brain tissue can be directly observed.

[0003] Vascular blood supply area is another important concept in blood perfusion assessment. Obtaining the supply area of ​​a certain blood vessel in the brain tissue is very important information in tumor blood supply tracing, collateral circulation and other assessments. VEASL (Vessel-Encoded ASL) is the earliest vascular selection imaging method based on PCASL to achieve simultaneous division of the blood supply areas of multiple vessels. Figure 2 As shown, this method applies a magnetic field gradient in the xy plane, that is, Figure 2 Gx and Gy in a generate periodic “signal modulation” on the marking plane, that is, periodic marking stripes along a specific direction, such as Figure 2 As shown in b, specific labeling of blood vessels at different locations is achieved, such as Figure 2 As shown in c, the signal patterns of different blood vessel blood supply areas can be distinguished and information about different blood vessel blood supply areas can be obtained. By changing the direction and magnitude of the magnetic field gradient applied in the xy plane and the phase of the radio frequency signal, different marking patterns can be generated on the marking plane. In order to simultaneously obtain the blood supply areas of multiple blood vessels, VEASL needs to collect image data under multiple marking modes.

[0004] Designing the vascular coding pattern is one of the most critical steps in VEASL blood supply area division. Current vascular coding technologies all assume that the signal modulation generated by VEASL is approximately a cosine function, that is, the switching between the marking band and the control band is relatively smooth and has similar widths. This assumption is only valid under specific PCASL parameters, thus limiting the optional range of PCASL parameters in the VEASL sequence, and the marking pattern of some blood vessels may deviate from the preset value, making it difficult to ensure the accuracy of the coding; in addition, these methods are limited to treating the blood vessel as a single point on the marking plane, without considering the size of the blood vessel on the marking plane. Summary of the invention

[0005] The present application provides a method and device for blood vessel selection arterial spin labeling encoding based on signal modulation to solve the problem of low encoding accuracy in related technologies.

[0006] In a first aspect, the present application provides a blood vessel selection arterial spin labeling encoding method based on signal modulation, comprising the following steps: generating multiple labeling signal modulation images on a labeling plane; obtaining the number of blood vessels to be encoded and the spatial position of the blood vessels to be encoded on the labeling plane; determining multiple groups of candidate coding mode combinations according to the blood vessels to be encoded, and selecting the labeling signal modulation image of each coding mode of each group of candidate coding mode combinations from the multiple labeling signal modulation images based on the spatial position; identifying the parameter combination and blood vessel labeling signal value corresponding to the labeling signal modulation image of each coding mode of each group of candidate coding mode combinations, forming a blood vessel labeling signal value matrix corresponding to each group of candidate coding mode combinations, and calculating the loss value of each group of candidate coding mode combinations according to the parameter combination and the blood vessel labeling signal value matrix; selecting a target coding mode combination from the multiple groups of candidate coding mode combinations according to the loss value, and feeding back the parameter combination corresponding to each coding mode in the target coding mode combination to a magnetic resonance scanner, and the magnetic resonance scanner performs blood vessel encoding and scanning of the blood vessel to be encoded arterial spin labeling based on the parameter combination corresponding to each coding mode in the target coding mode combination.

[0007] Optionally, the parameter combination includes angle, wavelength, and relative magnet center offset.

[0008] Optionally, multiple marker signal modulation diagrams on the marker plane are generated, including: abstracting the marker plane into a first matrix and determining the representation dimension of the first matrix; given a parameter combination of the angle, wavelength, and offset of the signal modulation stripes relative to the center of the magnet, calculating the signal intensity at each spatial position on the marker plane according to the signal modulation curve under specific pseudo-continuous arterial spin labeling parameters; for each set of parameter combinations, generating a marker signal modulation diagram according to the representation dimension of the first matrix and the signal intensity at each spatial position.

[0009] Optionally, multiple groups of candidate coding mode combinations are determined according to the blood vessels to be encoded, including: determining a second matrix of a target order according to the number of blood vessels to be encoded; removing a column of the second matrix of the target order, randomly selecting multiple columns from the remaining columns, and forming a group of candidate coding modes based on the randomly selected multiple columns.

[0010] Optionally, a marker signal modulation map of each coding mode in each group of alternative coding mode combinations is selected from a plurality of marker signal modulation maps based on spatial position, including: for any marker signal modulation map, taking out the signal value at the position where the blood vessel to be encoded is located; calculating the total value of the marker signal modulation map according to the signal value and the marker value in the coding mode; and traversing all marker signal modulation maps to find the marker signal modulation map with the highest total value.

[0011] Optionally, the loss value of the alternative coding mode combination is calculated as:

[0012]

[0013] Among them, C is the condition number of the matrix; min(λ) is the shortest wavelength; motion is the preset motion displacement tolerance, which is used to control the sensitivity to motion.

[0014] Optionally, encoding of the vessel to be encoded by vascular coded arterial spin labeling includes: setting the vascular encoding gradient and radio frequency phase of the imaging sequence according to the angle, wavelength and offset to the center of the magnet corresponding to the encoding mode, so that a specific labeling signal is generated at the location of the vessel to be encoded.

[0015] In a second aspect, the present application provides a blood vessel selection arterial spin labeling encoding device based on signal modulation, comprising: a generation module, used to generate multiple label signal modulation diagrams on a labeling plane; an acquisition module, used to acquire the number of blood vessels to be encoded and the spatial position of the blood vessels to be encoded on the labeling plane; a determination module, used to determine multiple groups of candidate coding mode combinations according to the blood vessels to be encoded, and select the label signal modulation diagram of each coding mode of each group of candidate coding mode combinations from the multiple label signal modulation diagrams based on the spatial position; an identification module, used to identify the parameter combination and blood vessel label signal value corresponding to the label signal modulation diagram of each coding mode of each group of candidate coding mode combinations, to form a blood vessel label signal value matrix corresponding to each group of candidate coding mode combinations, and calculate the loss value of each group of candidate coding mode combinations according to the parameter combination and the blood vessel label signal value matrix; a selection module, used to select a target coding mode combination from the multiple groups of candidate coding mode combinations according to the loss value, and the parameter combination corresponding to each coding mode in the target coding mode combination is fed back to the magnetic resonance scanner, and the magnetic resonance scanner performs blood vessel encoding arterial spin labeling encoding and scanning on the blood vessels to be encoded based on the parameter combination corresponding to each coding mode in the target coding mode combination.

[0016] The third aspect of the present application provides a medical device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the blood vessel selection arterial spin labeling encoding method based on signal modulation of the first aspect.

[0017] A fourth aspect of the present application provides a computer-readable storage medium having a computer program stored thereon, the program being executed by a processor to implement the blood vessel selection arterial spin labeling encoding method based on signal modulation according to the first aspect.

[0018] Therefore, this application includes the following beneficial effects:

[0019] The embodiment of the present application generates multiple marker signal modulation diagrams on the marking plane, obtains the number of blood vessels to be encoded and the spatial position of the blood vessels to be encoded on the marking plane, determines multiple groups of alternative coding mode combinations, selects the marker signal modulation diagram of each group of alternative coding mode combinations from the multiple marker signal modulation diagrams based on the spatial position, identifies the corresponding parameter combination and the blood vessel marker signal value matrix, calculates the loss value of each group of alternative coding mode combinations based on the two, selects the target coding mode combination from the multiple groups of alternative coding mode combinations based on the loss value, and feeds back to the magnetic resonance scanner, which encodes the blood vessel to be encoded by the vascular coded arterial spin labeling, is compatible with a wider range of PCASL sequence parameters, makes full use of the signal modulation of VEASL, and considers the size of the blood vessel, thereby improving the accuracy of the encoding. Therefore, the problems of the related technical requirement that the signal modulation curve is a cosine function, low versatility, low coding accuracy, and low accuracy are solved.

[0020] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0022] Figure 1 A schematic diagram of a pseudo-continuous arterial spin labeling perfusion imaging sequence provided for related technologies;

[0023] Figure 2 Schematic diagram of vascular coded arterial spin labeling imaging sequence and typical labeling signal modulation diagram provided for related technologies;

[0024] Figure 3 A schematic diagram of the basic principle of the random encoding method provided for the related art;

[0025] Figure 4A schematic diagram of the basic principle of a vascular coding pattern design method through an optimized coding strategy provided for related technologies;

[0026] Figure 5 A flowchart of a blood vessel selection arterial spin labeling encoding method based on signal modulation according to an embodiment of the present application;

[0027] Figure 6 is a marker signal modulation curve under different PCASL parameters and flow rates provided according to one embodiment of the present application;

[0028] Figure 7 A typical marking signal modulation diagram on a marking plane provided by an embodiment of the present application;

[0029] Figure 8 A flowchart for determining a marking mode combination and a parameter combination provided in an embodiment of the present application;

[0030] Fig. 9 This is an example diagram of a blood vessel selection artery spin labeling encoding device based on signal modulation according to an embodiment of the present application;

[0031] Fig.10 It is a schematic diagram of the structure of a medical device provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0032] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0033] In the related art, the RE (Random Encoding) method is to correlate the collected VEASL signal with the simulation signal within a certain range of the marking plane through 60 randomly generated paired coding patterns, so as to trace the potential blood supply artery source, such as Figure 3 As shown in A, all the blood vessel positions that can be effectively encoded on the marking plane are Figure 3 As shown in D in the figure, the 60 coding modes corresponding to the traced blood vessel positions are the coding matrix referenced by the VEASL blood supply area division. This method is completely data-driven and can resist the interference caused by off-resonance to a certain extent, such as Figure 3 As shown in B and C, it does not need to know the exact location of each blood vessel, so it can deal with more complex blood vessel distribution, such as the area above the Willis circle. However, RE currently has the following disadvantages:

[0034] (1) For imaging sequences with slow single coding modes, such as vascular imaging, the scanning time of 60 coding modes is unacceptable. (2) In the step of simulating the signal of the marker plane, the signal is potentially debugged by default to be close to the cosine function, which limits the parameter setting of PCASL. (3) Although it is not necessary to accurately obtain the coordinate information of each blood vessel, the freedom of placement of the marker plane is given. However, if the marker plane is completely parallel to a certain blood vessel segment or does not contain the blood vessel segment, it still cannot be correctly decoded. (4) The signal-to-noise ratio of VEASL is not the optimal strategy.

[0035] OES (Optimized Encoding Scheme) is a Fourier transform-based vascular coding pattern design method. For a given vascular coordinate and an ideal vascular coding pattern (some blood vessels are in the marked state, the signal value is -1, and some blood vessels are in the control state, the signal value is 1), OES constructs an ideal coding pattern diagram, such as Figure 4 As shown in a; the Fourier transform of this matrix is ​​as follows Figure 4 As shown in b, the low-frequency part is weighted, and then the pixel with the largest amplitude in weighted Fourier space is found, such as Figure 4 As shown in c, the optimal VEASL sequence design for the vascular encoding mode (including the phase of the RF pulse, the direction and magnitude of the gradient) is inferred based on the coordinates of the value on the complex plane, as shown in Figure 4 As shown in (d) in the figure. Because OES takes into account the vascular coordinate information, the number of vascular coding modes is greatly reduced; and given the vascular coordinates and coding mode, the coding strategy with the optimal signal-to-noise ratio can be designed completely automatically. In addition, because the low-frequency Fourier space is weighted, OES can resist the error caused by head movement to a certain extent. In addition, OES can also take the influence of off-resonance into account in the coding design, which is theoretically feasible for any number and distribution of blood vessels.

[0036] In addition, OES can also take the influence of off-resonance into account in the coding design, which is theoretically feasible for any number and distribution of blood vessels. However, OES also has obvious disadvantages: (1) This method relies on Fourier transform, that is, it assumes that the signal modulation should be a perfect cosine function, which is only valid under specific PCASL sequence parameter settings; (2) This method only gives a strategy for optimal signal-to-noise ratio under a certain fixed coding mode, but it cannot obtain how to obtain a set of optimal coding combinations under the premise of given blood vessel coordinates, and it is impossible to design a coding matrix with optimal signal-to-noise ratio efficiency; (3) This method assumes that the blood vessel is just a point on the marking plane, and does not consider the influence of the blood vessel geometry.

[0037] Based on the above-mentioned defects of the prior art, the present application proposes a blood vessel selection artery spin labeling encoding method and device based on signal modulation. The blood vessel selection artery spin labeling encoding method and device based on signal modulation of the present application are described below with reference to the accompanying drawings. Specifically, Figure 5 A schematic flow chart of a blood vessel selection arterial spin labeling encoding method based on signal modulation provided in an embodiment of the present application.

[0038] like Figure 5 As shown, the blood vessel selection artery spin labeling encoding method based on signal modulation includes the following steps:

[0039] In step S101, a plurality of marker signal modulation patterns on a marker plane are generated.

[0040] The labeling plane refers to the spatial position where the arterial blood is labeled during the arterial spin labeling process; the generation of the labeling signal modulation map will be described in detail below and will not be repeated here.

[0041] In an embodiment of the present application, multiple marker signal modulation diagrams are generated on a marker plane, including: abstracting the marker plane into a first matrix and determining the representation dimension of the first matrix; given a parameter combination of the angle, wavelength, and offset of the signal modulation stripes relative to the center of the magnet, calculating the signal intensity of each spatial position on the marker plane according to the signal modulation curve under specific pseudo-continuous arterial spin labeling parameters; for each set of parameter combinations, generating a marker signal modulation diagram according to the representation dimension of the first matrix and the signal intensity of each spatial position.

[0042] Among them, the first matrix is ​​a two-dimensional matrix; the parameter combination will be described in detail below and will not be repeated here; the shape of the signal modulation curve under specific pseudo-continuous arterial spin labeling parameters is determined by the pseudo-continuous arterial spin labeling parameters and blood flow velocity used in the vascular encoded arterial spin labeling imaging sequence, and the signal modulation curve is not affected by the parameter combination offset, but the position of the signal modulation curve can be determined based on the offset of the parameter combination. For example, the angle determines how much the curve should be rotated on the two-dimensional plane, the wavelength determines how large the spatial distance each cycle actually corresponds to, and the offset determines the offset of the curve on the two-dimensional plane. Regardless of the pseudo-continuous arterial spin labeling parameter setting, the signal modulation curve can be taken into account, thereby achieving the goal of not forcing the signal modulation curve to be a cosine function and allowing more flexible pseudo-continuous arterial spin labeling parameter settings.

[0043] It can be understood that the embodiment of the present application generates multiple marker signal modulation graphs on the marker plane. First, the marker plane is abstracted as a two-dimensional matrix, namely the first matrix. Given a set of parameter combinations, combined with the signal modulation curve under specific pseudo-continuous arterial spin labeling parameters, the signal intensity of each spatial position on the marker plane is calculated, and for each set of parameter combinations, a marker signal modulation graph is generated according to the representation dimension of the first matrix and the signal intensity of each spatial position, so that by setting the parameter combination, marker signal modulation graphs under multiple different parameter combinations are generated, and a marker signal modulation graph dictionary is constructed.

[0044] In the embodiment of the present application, the parameter combination includes angle, wavelength and relative magnet center offset.

[0045] The relative magnet center offset represents the displacement of the marker signal modulation pattern relative to the center position of the magnetic resonance imaging device.

[0046] In step S102, the number of blood vessels to be encoded and the spatial positions of the blood vessels to be encoded on the marking plane are obtained.

[0047] It is understandable that the embodiment of the present application first needs to obtain the number of blood vessels to be encoded and the spatial positions of these blood vessels on the marking plane, so as to determine the generation and optimization of the signal modulation diagram.

[0048] In step S103, multiple groups of candidate coding mode combinations are determined according to the blood vessels to be encoded, and a marker signal modulation map of each coding mode of each group of candidate coding mode combinations is selected from multiple marker signal modulation maps based on spatial positions.

[0049] It can be understood that the embodiments of the present application can determine multiple groups of alternative coding mode combinations through the blood vessels to be encoded. The determination method will be described in detail below and will not be repeated here; and by utilizing the spatial position, the marker signal modulation diagram of each coding mode of each group of alternative coding mode combinations is selected from multiple marker signal modulation diagrams.

[0050] In an embodiment of the present application, multiple groups of candidate coding mode combinations are determined according to the blood vessels to be encoded, including: determining a second matrix of a target order according to the number of blood vessels to be encoded; removing a column of all ones in the second matrix of the target order, randomly selecting multiple columns from the remaining columns, and forming a group of candidate coding modes according to the randomly selected multiple columns.

[0051] The second matrix is ​​a Hadamard matrix; the target order of the second matrix is ​​determined according to the number of blood vessels to be encoded, and the method is: if the number of blood vessels to be encoded is N, the target order of the second matrix is ​​at least N+1.

[0052] It can be understood that in the embodiment of the present application, the number of blood vessels to be encoded is N, and it is determined that the target order of the second matrix is ​​at least N+1. After the target order of the second matrix is ​​determined, a column of all ones in the second matrix is ​​removed, and multiple columns are randomly selected from the remaining columns to form a group of alternative coding modes. In this way, multiple groups of alternative coding modes can be obtained.

[0053] In an embodiment of the present application, each coding mode marker signal modulation map in each group of candidate coding mode combinations is selected from multiple marker signal modulation maps based on spatial position, including: for any marker signal modulation map, taking out the signal value at the position of the blood vessel to be encoded; calculating the total value of the marker signal modulation map according to the signal value and the marker value in the coding mode; traversing all marker signal modulation maps to find the marker signal modulation map with the highest total value.

[0054] The total value of the marker signal modulation map is calculated according to the combination of the signal value and the marker value in the alternative coding mode. The method is to multiply the signal value at the position of the blood vessel to be encoded by the marker value in the coding mode, that is, +1 or -1 in the matrix, one by one, and then add all the blood vessels to obtain the total value of the marker signal modulation map.

[0055] It can be understood that the embodiment of the present application selects a marker signal modulation diagram for each group of alternative coding mode combinations from multiple marker signal modulation diagrams, firstly, for any marker signal modulation diagram, according to the spatial position of the blood vessel to be encoded, the signal value at the position is extracted, then these signal values ​​are multiplied with the marker values ​​in the alternative coding mode combination at the corresponding position, and the results of all blood vessel positions to be encoded are summed to obtain a total value, which is repeated for each marker signal modulation diagram, and all possible marker signal modulation diagrams are traversed until the diagram with the highest total value is found, that is, the marker signal modulation diagram that best represents the current alternative coding mode.

[0056] In step S104, the parameter combination and the vascular marker signal value corresponding to the marker signal modulation diagram of each coding mode of each group of alternative coding mode combinations are identified, a vascular marker signal value matrix corresponding to each group of alternative coding mode combinations is constructed, and the loss value of each group of alternative coding mode combinations is calculated according to the parameter combination and the vascular marker signal value matrix.

[0057] It can be understood that the embodiment of the present application utilizes the parameter combination and the blood vessel marker signal value corresponding to the marker signal modulation diagram of each coding mode of each group of alternative coding mode combinations to form a blood vessel marker signal value matrix corresponding to each group of alternative coding mode combinations, and calculates the loss value of the group of alternative coding mode combinations according to a specific formula. The formula will be described in detail below and will not be repeated here. The lower the loss value, the better the performance of the group of coding modes under the influence of noise and head movement.

[0058] In the embodiment of the present application, the calculation formula of the loss value of the candidate coding mode combination is:

[0059]

[0060] Among them, C is the condition number of the matrix; min(λ) is the shortest wavelength; motion is the preset motion displacement tolerance, which is used to control the sensitivity to motion.

[0061] In step S105, a target coding mode combination is selected from multiple groups of alternative coding mode combinations according to the loss value, and the parameter combination corresponding to each coding mode in the target coding mode combination is fed back to the magnetic resonance scanner. The magnetic resonance scanner encodes and scans the coded blood vessels by vascular coded arterial spin labeling based on the parameter combination corresponding to each coding mode in the target coding mode combination.

[0062] It can be understood that the embodiment of the present application evaluates the performance of each group of alternative coding modes by calculating the loss value of the alternative coding modes. The group with the lowest loss value is the target coding mode combination. Then, the parameter combination corresponding to each coding mode in the target coding mode combination, including the angle, wavelength and relative magnet center offset, is fed back to the magnetic resonance scanner. The magnetic resonance scanner encodes the vascular coded arterial spin labeling of the coded blood vessels based on this set of optimized parameter combinations to achieve high-precision vascular perfusion imaging.

[0063] In an embodiment of the present application, the coding of the vascular coded arterial spin labeling for the coded blood vessel includes: setting the vascular coding gradient and radio frequency phase of the imaging sequence according to the angle, wavelength and offset to the center of the magnet corresponding to the coding mode, so that a specific labeling signal is generated at the location of the coded blood vessel.

[0064] It can be understood that the embodiment of the present application feeds back the parameter combination corresponding to each coding mode in the target coding mode combination, including the angle, wavelength and relative magnet center offset, to the magnetic resonance scanner. The magnetic resonance scanner sets the vascular coding gradient and radio frequency phase of the imaging sequence based on these parameters so that a marking signal is generated at the location of the blood vessel to be encoded.

[0065] According to the signal modulation-based blood vessel selection arterial spin labeling encoding method proposed in the embodiment of the present application, by generating multiple marker signal modulation graphs on the labeling plane, and obtaining the number of blood vessels to be encoded and the spatial position of the blood vessels to be encoded on the labeling plane, multiple groups of alternative coding mode combinations are determined, and the marker signal modulation graph of each group of alternative coding mode combinations is selected from the multiple marker signal modulation graphs based on the spatial position, and the corresponding parameter combination and blood vessel marker signal value matrix are identified. The loss value of each group of alternative coding mode combinations is calculated based on the two, and the target coding mode combination is selected from the multiple groups of alternative coding mode combinations based on the loss value, and the target coding mode combination is fed back to the magnetic resonance scanner. The magnetic resonance scanner encodes the blood vessels to be encoded by vascular coded arterial spin labeling, is compatible with a wider range of PCASL sequence parameters, makes full use of the signal modulation of VEASL, and takes into account the size of the blood vessels, thereby improving the accuracy of encoding.

[0066] The following is a further description of the arterial spin labeling encoding method for vascular selection based on signal modulation through a specific embodiment. The new encoding method (MOdulation-Guided Encoding, MOGEN) proposed in this embodiment is similar to the OES method, but abandons the assumption that the signal modulation is a cosine function, allowing the use of a more general signal modulation function that is closer to the actual situation. Figure 6 The following are the signal modulation curves in one cycle obtained by theoretical calculation under two different sets of PCASL sequence parameters and different flow rates. As an example, the signal modulation curve under a flow rate of 30 cm / s is selected for MOGEN design. The following is the specific implementation of MOGEN:

[0067] (I) MOGEN uses the following method to generate the marker signal modulation diagram on the marker plane: First, the marker plane is abstracted into a 1024×1024 matrix, and the two dimensions of the matrix are represented by x and y. Given a combination (α, λ, ε) of the angle (α), wavelength (λ), and offset (ε) of a signal modulation stripe relative to the center of the magnet, the signal strength at each position on the marker plane is calculated in combination with the above signal modulation curve to obtain a marker signal modulation diagram, such as Figure 7 As shown in the figure, the curve is a one-dimensional marker signal modulation curve under a specific PCASL sequence parameter setting. According to actual needs, the range and step size of α, λ and ε are set, and the marker signal modulation graph under all combinations is calculated, thereby constructing a marker signal modulation graph dictionary.

[0068] (II) Given the number of blood vessels to be encoded and their spatial positions on the above-mentioned marking plane, we need to select several combinations from the above-mentioned (α, λ, ε) combinations based on a certain method and apply them to the VEASL sequence scanning. The specific implementation method is as follows: (1) According to the number of blood vessels to be encoded N, determine the minimum order Hadamard matrix. As an example, Figure 8 (a) is an 8th-order Hadamard matrix, which can be used for VEASL imaging of no more than 7 blood vessels; (2) remove a column of all 1s in the Hadamard matrix, and randomly select N columns from the remaining columns to form a set of candidate coding patterns, such as Figure 8 (b); (3) For any one of a set of alternative coding modes, find a best-matching graph in the above-mentioned marker signal modulation graph dictionary to obtain the best-matching (α, λ, ε) combination. The specific implementation method is: for any marker signal modulation graph, take out the signal value at the location of the blood vessel to be encoded, multiply it by the ideal marker value (i.e. +1 or -1) set in the coding mode one by one, and then add all blood vessels to obtain a total value. Traverse all marker signal modulation graphs, and the signal modulation graph with the highest total value is the best-matching marker signal modulation graph, and the corresponding (α, λ, ε) is the best-matching combination; (4) Based on the method (3), obtain a set of (α, θ, ε) combinations corresponding to a set of alternative coding modes in (2) and the corresponding blood vessel marker signal value matrix, as shown in FIG. Figure 8 (c) as shown; (5) as shown Figure 8 As shown, in order to select the best one from the multiple groups of candidate coding modes randomly generated in (2), the loss value of each group of candidate coding modes is calculated using the following formula:

[0069]

[0070] Where C is the condition number of the above-mentioned vascular marker signal value matrix, min(λ) is the minimum value of all wavelengths θ in this group of marker modes, and motion is the preset motion displacement tolerance, which is used to control the sensitivity to motion. The lower the above loss value, the stronger the resistance of MOGEN-based VEASL imaging to noise and head movement. The group of selected coding modes with the lowest loss value is the final selected coding mode combination, and its corresponding (α, λ, ε) combination will be fed back to the magnetic resonance scanner to determine the vascular coding gradient (size and direction) and radio frequency phase of VEASL.

[0071] MOGEN also uses the following methods to improve imaging and computational effects: (1) To further avoid the impact of head movement on encoding accuracy, an exponentially decaying smoothing kernel can be used to smooth the signal modulation map in the ε dimension; (2) When MOGEN generates the above signal modulation map, it can use either a point or a ROI of a certain shape to represent a blood vessel. For the latter, it is only necessary to use multiple points on the marking plane to represent a blood vessel, and then optimize the search for the best matching signal modulation map ( Figure 8 (c)), consider the sum of the products of the ideal coding values ​​and the simulated signal values ​​of all vascular points. This design can improve the difference in labeling patterns between blood vessels when the distance between the coded blood vessels is small; (3) In actual calculation, in order to speed up the calculation speed, the above signal strength is only calculated for the position (x, y) of the blood vessel to form a signal modulation dictionary; (4) In the above step (ii), in order to ensure the best set of candidate coding modes, MOGEN randomly selects the column combinations of the Hadamard matrix a sufficient number of times; another method is to traverse all possible column combinations; (5) In order to improve the calculation effect, MOGEN will temporarily store the results of the processed coding mode during the calculation process to avoid repeated calculations in subsequent searches.

[0072] Next, a blood vessel selective arterial spin labeling encoding device based on signal modulation according to an embodiment of the present application will be described with reference to the accompanying drawings.

[0073] Fig. 9 It is a block diagram of a blood vessel selective arterial spin labeling encoding device based on signal modulation according to an embodiment of the present application.

[0074] like Fig. 9 As shown, the blood vessel selective arterial spin label encoding device 10 based on signal modulation includes: a generation module 201 , an acquisition module 202 , a determination module 203 , an identification module 204 and a selection module 205 .

[0075] The generating module 201 is used to generate a plurality of marker signal modulation diagrams on the marking plane; the acquiring module 202 is used to acquire the number of the blood vessels to be encoded and the spatial position of the blood vessels to be encoded on the marking plane; the determining module 203 is used to determine a plurality of groups of candidate coding mode combinations according to the blood vessels to be encoded, and select the marker signal modulation diagram of each coding mode in each group of candidate coding mode combinations from the plurality of marker signal modulation diagrams based on the spatial position; the identifying module 204 is used to identify the parameter combination and the blood vessel marker signal value corresponding to the marker signal modulation diagram of each coding mode in each group of candidate coding mode combinations, and form a blood vessel marker signal value matrix corresponding to each group of candidate coding mode combinations, and calculate the loss value of each group of candidate coding mode combinations according to the parameter combination and the blood vessel marker signal value matrix; the selecting module 205 is used to select a target coding mode combination from the plurality of groups of candidate coding mode combinations according to the loss value, and the parameter combination corresponding to each coding mode in the target coding mode combination is fed back to the magnetic resonance scanner, and the magnetic resonance scanner performs vascular coded arterial spin labeling encoding and scanning on the blood vessels to be encoded based on the parameter combination corresponding to each coding mode in the target coding mode combination.

[0076] In the embodiment of the present application, the parameter combination includes angle, wavelength and relative magnet center offset.

[0077] In an embodiment of the present application, multiple marker signal modulation diagrams are generated on the marker plane, and the generation module 201 is further used to: abstract the marker plane into a first matrix and determine the representation dimension of the first matrix; given a parameter combination of the angle, wavelength, and offset of the signal modulation stripes relative to the center of the magnet, calculate the signal intensity of each spatial position on the marker plane according to the signal modulation curve under specific pseudo-continuous arterial spin labeling parameters; for each set of parameter combinations, generate a marker signal modulation diagram according to the representation dimension of the first matrix and the signal intensity of each spatial position.

[0078] In the embodiment of the present application, multiple groups of candidate coding mode combinations are determined according to the blood vessels to be encoded, and the determination module 203 is further used to: determine a second matrix of a target order according to the number of blood vessels to be encoded; remove a column in the second matrix of the target order, randomly select multiple columns from the remaining columns, and form a group of candidate coding modes according to the randomly selected multiple columns.

[0079] In the embodiment of the present application, based on the spatial position, a marker signal modulation map of each coding mode in each group of alternative coding mode combinations is selected from multiple marker signal modulation maps, and the determination module 203 is further used to: for any marker signal modulation map, take out the signal value at the position of the blood vessel to be encoded; calculate the total value of the marker signal modulation map according to the signal value and the marker value in the alternative coding mode combination; traverse all marker signal modulation maps to find the marker signal modulation map with the highest total value.

[0080] In the embodiment of the present application, the calculation formula of the loss value of the candidate coding mode combination is:

[0081]

[0082] Among them, C is the condition number of the matrix; min(λ) is the shortest wavelength; motion is the preset motion displacement tolerance, which is used to control the sensitivity to motion.

[0083] In the embodiment of the present application, the selection module 205 is further used to: encode the blood vessel to be encoded by vascular coded arterial spin labeling, including: setting the blood vessel encoding gradient and radio frequency phase of the imaging sequence according to the angle, wavelength and offset to the center of the magnet corresponding to the encoding mode, so that a specific marking signal is generated at the location of the blood vessel to be encoded.

[0084] It should be noted that the above explanation of the embodiment of the blood vessel selective artery spin labeling encoding method based on signal modulation is also applicable to the blood vessel selective artery spin labeling encoding device based on signal modulation in this embodiment, which will not be repeated here.

[0085] According to the signal modulation-based blood vessel selection arterial spin labeling encoding device proposed in the embodiment of the present application, by generating multiple marker signal modulation graphs on the labeling plane, and obtaining the number of blood vessels to be encoded and the spatial position of the blood vessels to be encoded on the labeling plane, multiple groups of alternative coding mode combinations are determined, and the marker signal modulation graph of each group of alternative coding mode combinations is selected from the multiple marker signal modulation graphs based on the spatial position, and the corresponding parameter combination and blood vessel marker signal value matrix are identified. The loss value of each group of alternative coding mode combinations is calculated based on the two, and the target coding mode combination is selected from the multiple groups of alternative coding mode combinations based on the loss value, and the target coding mode combination is fed back to the magnetic resonance scanner. The magnetic resonance scanner encodes the blood vessels to be encoded by vascular coded arterial spin labeling, is compatible with a wider range of PCASL sequence parameters, makes full use of the signal modulation of VEASL, and takes into account the size of the blood vessels, thereby improving the accuracy of encoding.

[0086] Fig.10 A schematic diagram of the structure of a medical device provided in an embodiment of the present application. The medical device may include:

[0087] A memory 301 , a processor 302 , and a computer program stored in the memory 301 and executable on the processor 302 .

[0088] When the processor 302 executes the program, the blood vessel selection arterial spin labeling encoding method based on signal modulation provided in the above embodiment is implemented.

[0089] Furthermore, the medical device also includes:

[0090] The communication interface 303 is used for communication between the memory 301 and the processor 302 .

[0091] The memory 301 is used to store computer programs that can be run on the processor 302 .

[0092] The memory 301 may include a high-speed RAM (Random Access Memory) memory, and may also include a non-volatile memory, such as at least one disk memory.

[0093] If the memory 301, the processor 302 and the communication interface 303 are implemented independently, the communication interface 303, the memory 301 and the processor 302 can be connected to each other through a bus and communicate with each other. The bus can be an ISA (Industry Standard Architecture) bus, a PCI (Peripheral Component Interconnect) bus or an EISA (Extended Industry Standard Architecture) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Fig.10 Only one thick line is used in the diagram, but this does not mean that there is only one bus or only one type of bus.

[0094] Optionally, in a specific implementation, if the memory 301, the processor 302 and the communication interface 303 are integrated on a chip, the memory 301, the processor 302 and the communication interface 303 can communicate with each other through an internal interface.

[0095] The processor 302 may be a CPU (Central Processing Unit), or an ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement the embodiments of the present application.

[0096] The embodiment of the present application further provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-mentioned blood vessel selection arterial spin labeling encoding method based on signal modulation.

[0097] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0098] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0099] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or N executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0100] It should be understood that the various parts of the present application can be implemented in hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, the steps or methods can be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array, a field programmable gate array, etc.

[0101] A person of ordinary skill in the art may understand that all or part of the steps carried by the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the above-mentioned program may be stored in a computer-readable storage medium, which, when executed, includes one of the steps of the method embodiment or a combination thereof.

[0102] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in the field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A blood vessel selective arterial spin labeling encoding method based on signal modulation, characterized in that: The following steps are involved: generating a plurality of marker signal modulation images on a marker plane; Acquire the number of blood vessels to be encoded and the spatial positions of the blood vessels to be encoded on the marking plane; Determine a plurality of groups of candidate coding mode combinations according to the blood vessel to be coded, and select a marker signal modulation diagram of each coding mode of each group of candidate coding mode combinations from the plurality of marker signal modulation diagrams based on the spatial position; Identify a parameter combination and a blood vessel marker signal value corresponding to a marker signal modulation diagram of each coding mode of each group of candidate coding mode combinations, form a blood vessel marker signal value matrix corresponding to each group of candidate coding mode combinations, and calculate a loss value of each group of candidate coding mode combinations according to the parameter combination and the blood vessel marker signal value matrix; A target coding mode combination is selected from the multiple groups of alternative coding mode combinations according to the loss value, and a parameter combination corresponding to each coding mode in the target coding mode combination is fed back to a magnetic resonance scanner. The magnetic resonance scanner encodes and scans the blood vessel to be encoded by vascular coded arterial spin labeling based on the parameter combination corresponding to each coding mode in the target coding mode combination.

2. The method for blood vessel selection arterial spin labeling encoding based on signal modulation according to claim 1, characterized in that: The parameter combination includes angle, wavelength, and relative magnet center offset.

3. The method for blood vessel selection arterial spin labeling encoding based on signal modulation according to claim 1, characterized in that: The generating of a plurality of marker signal modulation diagrams on the marker plane comprises: Abstracting the marking plane into a first matrix, and determining a representation dimension of the first matrix; Given a parameter combination of the angle, wavelength, and offset of the signal modulation stripes relative to the center of the magnet, the signal intensity at each spatial position on the labeling plane is calculated according to the signal modulation curve under specific pseudo-continuous arterial spin labeling parameters; For each set of parameter combinations, a marker signal modulation diagram is generated according to the representation dimension of the first matrix and the signal strength of each spatial position.

4. The method for blood vessel selection arterial spin labeling encoding based on signal modulation according to claim 1, characterized in that: The step of determining a plurality of groups of candidate coding mode combinations according to the blood vessels to be coded includes: A second matrix of target order is determined according to the number of blood vessels to be encoded; A column in the second matrix of the target order is removed, multiple columns are randomly selected from the remaining columns, and a group of candidate coding modes is formed according to the randomly selected multiple columns.

5. The method for blood vessel selection arterial spin labeling encoding based on signal modulation according to claim 1, characterized in that: The selecting, based on the spatial position, a marker signal modulation graph of each coding mode in each group of candidate coding mode combinations from the multiple marker signal modulation graphs comprises: For any marker signal modulation diagram, the signal value at the position of the blood vessel to be encoded is obtained; Calculate the total value of the modulation diagram of the marker signal according to the signal value and the marker value in the coding mode; Traverse all marker signal modulation graphs and find the marker signal modulation graph with the highest total value.

6. The method for blood vessel selection arterial spin labeling encoding based on signal modulation according to claim 1, characterized in that: The calculation formula for the loss value of the alternative coding mode combination is: Where C is the condition number of the matrix; min(λ) is the shortest wavelength; motion is the preset motion displacement tolerance, which is used to control the sensitivity to motion.

7. The method for blood vessel selection arterial spin labeling encoding based on signal modulation according to claim 1, characterized in that: The encoding of the to-be-encoded blood vessel by vascular coded arterial spin labeling comprises: According to the angle, wavelength and offset to the center of the magnet corresponding to the encoding mode, the blood vessel encoding gradient and radio frequency phase of the imaging sequence are set so that a specific marking signal is generated at the location of the blood vessel to be encoded.

8. A blood vessel selective arterial spin labeling encoding device based on signal modulation, characterized in that: include: A generating module, used for generating a plurality of marker signal modulation diagrams on a marker plane; An acquisition module, used for acquiring the number of blood vessels to be encoded and the spatial positions of the blood vessels to be encoded on the marking plane; a determination module, configured to determine a plurality of groups of candidate coding mode combinations according to the blood vessel to be coded, and select a marker signal modulation diagram of each coding mode in each group of candidate coding mode combinations from the plurality of marker signal modulation diagrams based on the spatial position; an identification module, configured to identify a parameter combination and a blood vessel marker signal value corresponding to a marker signal modulation diagram of each coding mode in each group of candidate coding mode combinations, and to form a blood vessel marker signal value matrix corresponding to each group of candidate coding mode combinations, and to calculate a loss value of each group of candidate coding mode combinations according to the parameter combination and the blood vessel marker signal value matrix; A selection module is used to select a target coding mode combination from the multiple groups of alternative coding mode combinations according to the loss value, and feed back a parameter combination corresponding to each coding mode in the target coding mode combination to a magnetic resonance scanner, and the magnetic resonance scanner encodes and scans the blood vessel to be encoded by vascular coded arterial spin labeling based on the parameter combination corresponding to each coding mode in the target coding mode combination.

9. A medical device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the blood vessel selection arterial spin labeling encoding method based on signal modulation according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program or instruction stored thereon, characterized in that: When the computer program or instruction is executed, the blood vessel selection artery spin labeling encoding method based on signal modulation according to any one of claims 1 to 7 is implemented.

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