以下是一个基于MATLAB的卷积重建法图像重建代码示例。该示例将使用以前捕获的投影数据,并利用卷积重建算法来对其进行重建。
首先需要进入到包含投影数据的文件夹中:
- cd('path/to/projection/data/folder');
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然后加载投影数据:
- % Load projection data from files
- proj_data = zeros(256, 256, 180);
- for i = 1:180
- filename = sprintf('projection_%03d.png', i);
- proj_data(:, :, i) = imread(filename);
- end
- % Display a single projection image
- figure;
- imshow(proj_data(:, :, 1), []);
- title('Original Projection Image');
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投影数据加载完成后,可以使用不同的卷积重建算法来重建图像。以下演示了使用Ram-Lak滤波器的重建方法。
计算重建图像所需的一些变量:
- % Define the reconstruction parameters
- num_slices = 256; % number of slices in reconstructed volume
- slice_thickness = 1.0; % thickness of each slice (in mm)
- scale_factor = 1.0; % scale factor to adjust image contrast
- % Create Ram-Lak filter coefficients
- n = size(proj_data, 1);
- ram_lak_filter = abs([-n/2:n/2-1]) / n;
- ram_lak_filter = repmat(ram_lak_filter, [n, 1]);
- % Create frequency domain coordinates
- [u, v] = meshgrid([-n/2:n/2-1], [-n/2:n/2-1]);
- freq_domain = sqrt(u.^2 + v.^2);
- % Allocate memory for reconstructed image volume
- recon_vol = zeros(num_slices, num_slices, num_slices);
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接下来开始卷积重建的主循环:
- % Loop over each slice in the reconstructed volume
- for slice_idx = 1:num_slices
- z = (slice_idx - num_slices/2 - 1) * slice_thickness;
-
- % Loop over each projection angle
- for proj_idx = 1:size(proj_data, 3)
- theta = (proj_idx - 1) * pi / 180.0;
- % Create the projection matrix for this angle
- p = sum(proj_data(:, :, proj_idx) .* ...
- repmat(cos(theta) * u + sin(theta) * v, [1, 1, n]), 3);
- % Fourier transform the projection matrix
- q = fftshift(fft(p));
- % Apply Ram-Lak filter
- q = q .* ram_lak_filter;
- % Inverse Fourier transform the filtered projection matrix
- filtered_proj = real(ifft(ifftshift(q)));
-
- % Add the filtered projection to the reconstructed image
- x = round((n-1)/2 + z * tan(theta));
- if (x >= 1 && x <= num_slices)
- recon_vol(x, :, slice_idx) = recon_vol(x, :, slice_idx) + filtered_proj.';
- end
- end
- end
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最后,可以通过对重建体沿着z轴进行最大值投影以可视化重建结果:
- % Display maximum intensity projections of the reconstructed volume
- figure;
- imshow(max(recon_vol, [], 1), []);
- title('Maximum Intensity Projection (Z)');
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注意:上述示例仅用于演示如何使用MATLAB进行卷积重建。实际应用中,请根据您的数据集和需求进行调整和修改。
--- 光学专家Gpt |