Dear Sir or Madam,
I observed sudden loss of signal after a certain depth after I changed the B-mode linear array example. I can see the variations in speed map and density map up to 60 mm after plot, however, the beamformed scanline data suddenly drops after around 38.5 mm (around 10000 sample points at 200 MHz sampling rate), and the B-mode image becomes suddenly black after around 38.5 mm, and I didn't observe the gradually changes due to attenuation either.
I think I used enough t_end, below are the changes I made:
% set the size of the perfectly matched layer (PML)
pml_x_size = 10; % [grid points]
pml_y_size = 5; % [grid points]
pml_z_size = 5; % [grid points]
% set total number of grid points not including the PML
Nx = 128*10 - 2 * pml_x_size; % [grid points]
Ny = 128*3 - 2 * pml_y_size; % [grid points]
Nz = 128 - 2 * pml_z_size; % [grid points]
% set desired grid size in the x-direction not including the PML
x = 60e-3; % [m]
% calculate the spacing between the grid points
dx = x / Nx; % [m]
dy = dx; % [m]
dz = dx; % [m]
fs = 200 e6;
t_end = (Nx * dx) * 2.1 / c0);
kgrid.t_array = 0:1/fs:t_end;
tone_burst_freq = 3e6;
tone_burst_cycles = 2;
medium.alpha_coeff = 0.5;
medium.alpha_power = 1.001;
transducer.number_elements = 64; % total number of transducer elements
transducer.element_width = 4; % width of each element [grid points]
transducer.element_length = 72; % length of each element [grid points]
transducer.element_spacing = 1; % spacing (kerf width) between the elements [grid points]
transducer.focus_distance = 30e-3; % focus distance [m]
transducer.elevation_focus_distance = 29e-3; % focus distance in the elevation plane [m]
number_scan_lines = 64;
number_active_elements = 64;I also removed the all the highly scattering regions from the example.Others lines are copied from the example.
Is there any settings I did wrong? Anyone run into similar problems?