http://www.k-wave.org/forum/topic/time-reversal-reconstruction-in-1d Support for the k-Wave MATLAB toolbox en-US Tue, 12 May 2026 23:39:45 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/time-reversal-reconstruction-in-1d#post-288 Sat, 04 Feb 2012 02:27:05 +0000 Bradley Treeby 288@http://www.k-wave.org/forum/ <p>Hi Chao,</p> <p>Do you mean, why do you see the extra peaks on either side of the reconstructed initial pressure? These occur because the time reversal algorithm only correctly reconstructs the pressure distribution on the interior of the measurement surface. In 1D, this means in between your two measurement points. If you truncate your field of view based on the measurement positions, the reconstructed image should agree. </p> <p>If you leave plotting on and try setting:</p> <p><code>&#39;DisplayMask&#39;, cart2grid(kgrid, sensor.mask), &#39;PlotFreq&#39;, 1</code></p> <p>you can visualise what's happening.</p> <p>Note, if you use a Cartesian sensor mask, you might also notice a small numerical discrepancy when doing your comparison. This is because linear interpolation is used to calculate the pressures in the forward case, while these are enforced at the nearest grid point in the reconstruction.</p> <p>We haven't played with 1D that much, so if you notice any strange behaviour, please let us know!</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/time-reversal-reconstruction-in-1d#post-287 Sat, 04 Feb 2012 00:54:05 +0000 huangchao 287@http://www.k-wave.org/forum/ <p>Hi, Dr. Cox and Dr. Treeby,</p> <p>I found that I cannot use time-reversal algorithm to exactly reconstruct images in 1D. The codes I used are as following:</p> <p>clear<br /> Nx = 128;<br /> dx = 0.05e-3;<br /> kgrid = makeGrid(Nx, dx);</p> <p>medium.sound_speed = 1500*ones(Nx, 1);<br /> medium.density = 1000*ones(Nx, 1);</p> <p>x_pos = 54;<br /> width = 20;<br /> height = 1;<br /> in = 0:pi/(width/2):2*pi;<br /> source.p0 = [zeros(x_pos,1); ((height/2)*sin(in-pi/2)+(height/2)).'; zeros(Nx - x_pos - width - 1, 1)];</p> <p>sensor.mask = [-1e-3 1e-3];</p> <p>[kgrid.t_array, dt] = makeTime(kgrid, medium.sound_speed);</p> <p>pd = kspaceFirstOrder1D(kgrid, medium, source, sensor, 'PMLSize', 20, 'PlotSim', false, 'Smooth', false);</p> <p>source.p0 = 0;<br /> sensor.time_reversal_boundary_data = pd;</p> <p>r = kspaceFirstOrder1D(kgrid, medium, source, sensor, 'PMLSize', 20, 'PlotSim', false, 'Smooth', false);</p> <p>Do you have idea why it's like this?</p> <p>Thank you very much!</p> <p>Best,<br /> Chao </p>