http://www.k-wave.org/forum/topic/zero-matrix-computed-in-scanconversion Support for the k-Wave MATLAB toolbox en-US Fri, 15 May 2026 06:30:13 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/zero-matrix-computed-in-scanconversion#post-8309 Tue, 21 Sep 2021 03:28:58 +0000 mario7lorenzo 8309@http://www.k-wave.org/forum/ <p>Hi guys,</p> <p>I am new to this k-Wave library. My aim is to create a sector scan image using <code>scanConversion</code> method. I have the signal data for several plane wave angles with time. I have arranged the data into a matrix of sized <code>nAngles vs Time</code> as required in the documentation. I have also specified what are the scan angles used in the data, the time difference between samples, and the image size. However, somehow the result is all zero matrix. I could not think of what potential issues that happens here. Looking forward for your insights!</p> <p>Thanks!</p> <p>Btw, here is the code:<br /> <pre><code>function result = process() load(&#39;data.mat&#39;); % Compute the time delay % Reference point: The left most element as the first element dx = 10; % in mm theta = [-10 -5 0 5 10]; % in degrees na = 5; % no of steering angles c = 6300; % speed of sound in m/s thetaradian = theta * pi/180; Fs = Receive(1).decimSampleRate * 1e6; ts = 1/Fs; tStart = 0; N = Receive(1).endSample; t = tStart + (0:N-1)*ts; example = RcvData{1}(Receive(1).startSample:Receive(1).endSample, 1, 1); sz = size(example); scanLines = zeros([na sz(1)]); for j = 1:5 accumulated = RcvData{1}(Receive(j).startSample:Receive(j).endSample, 1, 1); accumulated = double(accumulated); sz = size(accumulated); dt = dx * 1e-3 * sin(thetaradian(j))/c; % time delay per elem, in s for i = 2:3 curr = RcvData{1}(Receive(j).startSample:Receive(j).endSample, i, 1); zipped = [t&#39; double(curr)]; td = (i-1) * dt; zipped(:,1) = zipped(:,1) - td; zipped = zipped(zipped(:,1) &gt;= t(1) &amp; zipped(:,1) &lt;= t(end),:); filtered = zipped(:,2); szFiltered = size(filtered); if (td &lt; 0) padded = [zeros([sz(1) - szFiltered(1) 1]); filtered]; else padded = [filtered; zeros([sz(1) - szFiltered(1) 1])]; end accumulated = accumulated + padded; end % post processing % 1. High pass filtering accumulated = highpass(accumulated, 10000, Fs); % 2. Rectification accumulated = abs(accumulated); % 3. Enveloping [accumulated, dummy] = envelope(accumulated,300,&#39;peak&#39;); scanLines(j,:) = accumulated&#39;; end % k-Wave scanConversion part image_size = [480 480]; b_mode = scanConversion(scanLines, theta, image_size, c, t(2)-t(1)); result = b_mode; end</code></pre>