Method for correcting velocity field for particle image velocity measurement of ultrasonic cardiogram
A particle image velocimetry, echocardiography technology, applied in image enhancement, image analysis, image data processing and other directions, can solve the problem of anisotropic diffusion noise reduction algorithm difficulty, loss of details, blurred images and other problems
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specific Embodiment approach 1
[0018] Specific implementation mode one: (please refer to the attached figure 1 ) A method for modifying the velocity field of an echocardiographic particle image velocimetry according to the present embodiment is performed according to the following steps:
[0019] Step 1: Use an ultrasonic instrument to detect the echocardiogram, and then read in the initial velocity field of the echocardiogram at time t measured by Particle Image Velocimetry The initial velocity field u 1 Consists of m×n grids, each grid has a velocity vector Among them, 1≤i≤m, 1≤j≤n; use k to represent the number of cycles, K is the maximum value of the number of cycles, and K is 3 to 5; initialize k=1;
[0020] Step 2: Calculate the initial velocity field Each velocity vector of 2≤i≤m-1 and 2≤j≤n-1 in The corresponding covariance matrix S c ,in, S c = ψ xx ...
specific Embodiment approach 2
[0030] Embodiment 2: This embodiment differs from Embodiment 1 in that the sorting rule of velocity vectors in the median filtering in step 4 is edge median method or vector median method; the others are the same as Embodiment 1.
[0031]In this embodiment, the edge median method is a new vector obtained by taking the median value of each component after comparing and sorting each component of the velocity vector; and the vector median method is to calculate the Euclidean formula of each vector in the vector and its 3×3 neighborhood. Distance, sorted according to the size of the Euclidean distance. The purpose of performing median filtering is to reduce the local error caused by the anisotropic diffusion of the velocity vector in step 3.
specific Embodiment approach 3
[0032] Specific implementation mode three: the difference between this implementation mode and specific implementation mode one or two is: the method for shifting flow calculation in step five is as follows:
[0033] The diagram of the displacement calculation is shown in figure 2 As shown, the velocity vector of grid a at the current moment is Calculate the position of the velocity vector before the time Δt as point b, and use the bilinear interpolation method to calculate the value of the velocity vector at point b then Assigned to the velocity vector in the grid of a, namely
[0034] The method of calculating the value of the velocity vector at point b by bilinear interpolation is as follows:
[0035] Bilinear interpolation diagram as image 3 As shown, the four velocity vectors u around point b A , u B , u C and u D The points where they are connected form a square, and the four vertices are represented by A, B, C and D respectively, where f x =AP / AB,f y =F...
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