k-Wave User Forum » Topic: Why is 3D TR reconstruction in heterogeneous medium so bad?

k-Wave User Forum » Topic: Why is 3D TR reconstruction in heterogeneous medium so bad? http://www.k-wave.org/forum/topic/why-is-3d-tr-reconstruction-in-heterogeneous-medium-so-bad Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 02:33:20 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://www.k-wave.org/forum/search.php wang mengxiao on "Why is 3D TR reconstruction in heterogeneous medium so bad?" http://www.k-wave.org/forum/topic/why-is-3d-tr-reconstruction-in-heterogeneous-medium-so-bad#post-6503 Mon, 25 Jun 2018 16:59:06 +0000 wang mengxiao 6503@http://www.k-wave.org/forum/ Hi Foufour, Thanks for your reply. I tried image reconstruction in a homogeneous medium, it is just better than reconstruction in heterogeneous medium. But it's still not good enough,especially many slices in the middle. so if you have any other comments/suggestions. Thank you very much. Sincerely, Mengxiao Foufour on "Why is 3D TR reconstruction in heterogeneous medium so bad?" http://www.k-wave.org/forum/topic/why-is-3d-tr-reconstruction-in-heterogeneous-medium-so-bad#post-6495 Thu, 21 Jun 2018 17:28:52 +0000 Foufour 6495@http://www.k-wave.org/forum/ Dear Mengxiao, what I definitely expect to be a problem for image reconstruction is the limited view of your planar detector. (You can read about the limited view problem in the k-Wave online documentation) Or did you get better results in a homogeneous medium (since you were referring to heterogeneities)? Cheers, Foufour wang mengxiao on "Why is 3D TR reconstruction in heterogeneous medium so bad?" http://www.k-wave.org/forum/topic/why-is-3d-tr-reconstruction-in-heterogeneous-medium-so-bad#post-6494 Wed, 20 Jun 2018 19:25:11 +0000 wang mengxiao 6494@http://www.k-wave.org/forum/ Hi, About above-mentioned code , there are four medium:soundspeed1=1480,tissdst1=920; soundspeed2=1540, tissdst2=1040;soundspeed3=3200,tissdst1=2000; soundspeed4=1500,tissdst1=1000; The soundspeed and tissue density were set according to the structure of the pelvic cavity. Thank you so much. Sincerely, Mengxiao wang mengxiao on "Why is 3D TR reconstruction in heterogeneous medium so bad?" http://www.k-wave.org/forum/topic/why-is-3d-tr-reconstruction-in-heterogeneous-medium-so-bad#post-6493 Wed, 20 Jun 2018 19:02:19 +0000 wang mengxiao 6493@http://www.k-wave.org/forum/ Hi, I reconstructed initial pressure using 3D Time Reversal Reconstruction For A Planar Sensor in heterogeneous medium. But i can not get good reconstructed images.The codes I use are as following: %% create the computational grid PML_size = 10; % size of the PML in grid points % Nx = 64 * scale - 2 * PML_size; % number of grid points in the x direction % Ny = 64 * scale - 2 * PML_size; % number of grid points in the y direction % Nz = 32 * scale - 2 * PML_size; % number of grid points in the z direction Nx = 190 - 2 * PML_size; % number of grid points in the x direction Ny = 270 - 2 * PML_size; % number of grid points in the y direction Nz = 126 - 2 * PML_size; % number of grid points in the z direction dx = 1.25e-3/2 ; % grid point spacing in the x direction [m] dy = 1.25e-3/2; % grid point spacing in the y direction [m] dz = 1.25e-3/2; % grid point spacing in the z direction [m] kgrid = kWaveGrid(Nx, dx, Ny, dy, Nz, dz); %% load the speed of sound and the tissue density and the initial pressure distribution from an image and scale soundspeed=importdata('C:\Users\WANG MENG XIAO\Desktop\project\XACT\code_and_results\work3_06152018\a_segmentation\mat\soundspeed_160_240_96.mat'); tissdst=importdata('C:\Users\WANG MENG XIAO\Desktop\project\XACT\code_and_results\work3_06152018\a_segmentation\mat\tissdst_160_240_96.mat'); p0=importdata('C:\Users\WANG MENG XIAO\Desktop\project\XACT\code_and_results\work3_06152018\b_initial_pressure\mat\initial_dose_160_240_53.mat'); %% get the size of soundspeed [r,c,h]=size(soundspeed); %% define the speed of sound(m/s) for k=1:h for i=1:r for j=1:c if soundspeed(i,j,k)<=343 soundspeed(i,j,k)=1500; end end end end %% define the tissue density(kg/m3) for k=1:h for i=1:r for j=1:c if tissdst(i,j,k)<=1.2 tissdst(i,j,k)=1000; end end end end p0_binary=zeros(Nx,Ny,Nz); p0_binary(6:165,6:245,6:58)=p0; % p0_binary=zeros(Nx,Ny,Nz); % p0_binary(1:32,1:32,5)=im; % smooth the initial pressure distribution and restore the magnitude % p0 = smooth(kgrid, p0_binary, true); p0=p0_binary; %% assign to the source structure source.p0 = p0; %% define the properties of the propagation medium sound_speed=ones(Nx,Ny,Nz)*1500; sound_speed(6:165,6:245,6:101)=soundspeed; medium.sound_speed = sound_speed; % [m/s] density=ones(Nx,Ny,Nz)*1000; density(6:165,6:245,6:101)=tissdst; medium.density=density; % [kg/m3] % medium.alpha_coeff = 0.75; % power law absorption prefactor [dB/(MHz^y*cm)] % medium.alpha_power = 1.5; % power law absorption exponent %% define a binary planar sensor sensor.mask = zeros(kgrid.Nx, kgrid.Ny, kgrid.Nz); sensor.mask(6:2:165,6:2:245,102) = 1; % sensor.mask(1:32, 1:32,1) = 1; %% define frequence and bandwidth of sensor center_freq =1e6; %!!!!!!定义探测器的中心频率 bandwidth = 100; %带宽100% sensor.frequency_response = [center_freq, bandwidth]; %定义传感器完整参数，包括中心频率和带宽 %% create the time array kgrid.makeTime(medium.sound_speed); %% set the input arguements input_args = {'PMLSize', PML_size, 'PMLInside', false, ... 'PlotPML', false, 'Smooth', false, 'DataCast', 'single'}; %% run the simulation sensor_data = kspaceFirstOrder3D(kgrid, medium, source, sensor, input_args{:}); %% reset the initial pressure source.p0 = 0; %% assign the time reversal data sensor.time_reversal_boundary_data = sensor_data; %% run the time-reversal reconstruction p0_recon = kspaceFirstOrder3D(kgrid, medium, source, sensor, input_args{:}); %% add first order compensation for only recording over a half plane p0_recon = 2 * p0_recon; %% apply a positivity condition p0_recon(p0_recon < 0) = 0; Thank you very much. Sincerely, Mengxiao