bft_user_guide.tex.bak

超声仿真软件

subplot(1,2,2)
imagesc([-sector/2 sector/2]*180/pi,[0 Rmax]*1000,20*log10(env_bf + 0.001));
title('Beamformed by BFT');
xlabel('Angle [deg]');
ylabel('Axial distance [mm]')
axis('image')

colorbar
colormap(gray)

clc
disp([' ' 10 10 10 10 ]);
disp([9 '*****************************************************']);
disp([9 '*                                                   *']);
disp([9 '* The image beamformed by Field II is in "env_line" *']);
disp([9 '* The image beamformed by BFT is in "env_bf"        *']);
disp([9 '*                                                   *'])
disp([9 '*****************************************************']);
disp([' ' 10 10 ]);

\end{verbatim}
}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\headline{Dynamic focusing}
%%tth:\vspace{2cm}
%%tth:\begin{html}<hr>\end{html} 
%%tth:\subsection*{Dynamic focusing}
%%tth:\begin{html}<hr>\end{html}
\funlnk{dynamic_focusing}

{\footnotesize
\begin{verbatim}
%PHASED_DYN_IMAGE Create a phased-array B-mode image, using the 
%    commands for setting a dynamic focusing

%VERSION 1.0, 29 Feb 2000, Svetoslav Nikolov

f0 = 4e6;              %  Central frequency                        [Hz]
fs = 100e6;            %  Sampling frequency                       [Hz]
c = 1540;              %  Speed of sound                           [m/s]
B = .35;               %  Relative bandwith                        [fraction]
no_elements = 64;      %  Number of elements in the transducer     

lambda = c / f0;       % Wavelength                                [m]
pitch = lambda / 2;    % Pitch - center-to-center                  [m]
width = .95*pitch;     % Width of the element                      [m]
kerf = pitch - width;  % Inter-element spacing                     [m]
height = 10/1000;      % Size in the Y direction                   [m]
 
 
%  Define the impulse response of the transducer
impulse_response = sin(2*pi*f0*(0:1/fs:2/f0));
impulse_response = impulse_response.*hanning(length(impulse_response))';
excitation = impulse_response;

%  Define the phantom

pht_pos = [0 0 20;
           0 0 30;
           0 0 40;
           0 0 50;
           0 0 60;
           0 0 70;
           0 0 80;
           0 0 90;
           ] / 1000;         %  The position of the phantom
pht_amp = 20*ones(8,1);      %  The amplitude of the back-scatter

%  Define the focus 
focus_r = [20;30;40;50;60;70;80;90] / 1000;
T = (focus_r-5/1000)/c *2;

%  Initialize the program
field_init(0);
bft_init;

%  Set some paramters
set_field('c', c);
bft_param('c', c);

set_field('fs', fs);
bft_param('fs', fs);


% Create some apertures.

xmt = xdc_linear_array(no_elements,width,height,kerf,1,1,[0 0 0]);
rcv = xdc_linear_array(no_elements,width,height,kerf,1,1,[0 0 0]);

xdc = bft_linear_array(no_elements, width, kerf);


% Set the impulse responses
xdc_impulse(rcv, impulse_response);
xdc_impulse(xmt, impulse_response);

xdc_excitation(xmt, excitation);


% Set the apodization

xdc_apodization(xmt, 0, ones(1,no_elements))
xdc_apodization(rcv, 0, ones(1,no_elements))
bft_apodization(xdc, 0 , ones(1,no_elements))

%  Define and create the image
sector = 30 * pi / 180;
no_lines = 32;
d_theta = sector / (no_lines-1);
theta = -(no_lines-1) / 2 * d_theta;

Rmax = max(sqrt(pht_pos(:,1).^2 + pht_pos(:,2).^2  + pht_pos(:,3).^2)) + 15/1000;

no_rf_samples = ceil(2*Rmax/c * fs);
rf_line = zeros(no_rf_samples, 1);
bf_line = zeros(no_rf_samples, 1);

env_line = zeros(no_rf_samples, no_lines);
env_bf =  zeros(no_rf_samples, no_lines);


xmt_r = (max(focus_r) + min(focus_r) )/2;

for i = 1 : no_lines
  rf_line(:) = 0;  
  theta
  
  xmt_f = [sin(theta)*xmt_r, zeros(length(xmt_r),1), cos(theta)*xmt_r];
  xdc_center_focus(xmt,[0 0 0])
  xdc_center_focus(rcv,[0 0 0])
  bft_center_focus([0 0 0]);
  
  xdc_focus(xmt, 0, xmt_f);
  xdc_dynamic_focus(rcv, 0, theta, 0);
  
  %  Beamform with Field II
  [rf_temp, t(i)] = calc_scat(xmt,rcv, pht_pos, pht_amp);
  
  %  Beamform with BFT
  bft_dynamic_focus(xdc, theta,0)
  xdc_focus_times(rcv, 0, zeros(1,no_elements));
  [rf_data, start_t] = calc_scat_multi(xmt,rcv, pht_pos, pht_amp);
  
  rf_data = [zeros(300,no_elements); rf_data; zeros(300,no_elements)];

  start_t = start_t - 300  / fs;
  bf_temp = bft_beamform(start_t, rf_data);
  
  start_sample = t(i)*fs; no_temp_samples = length(rf_temp);
  
  rf_line(start_sample:start_sample+no_temp_samples-1) = rf_temp(1:no_temp_samples);
  env_line(:,i) = abs(hilbert(rf_line(:)));

  start_sample = floor(start_t*fs); no_temp_samples = length(bf_temp);
  bf_line(start_sample:start_sample+no_temp_samples-1) = bf_temp(1:no_temp_samples);
  env_bf(:,i) = abs(hilbert(bf_line(:)));
  theta = theta + d_theta;

end

%  Release the allocated memory

field_end
bft_end
env_line = env_line / max(max(abs(env_line)));
env_bf = env_bf / max(max(abs(env_bf)));

figure;
subplot(1,2,1)
imagesc([-sector/2 sector/2]*180/pi,[0 Rmax]*1000,20*log10(env_line + 0.001))
axis('image')
xlabel('Angle [deg]');
ylabel('Axial distance [mm]')
title('Beamformed by Field II ');

subplot(1,2,2)
imagesc([-sector/2 sector/2]*180/pi,[0 Rmax]*1000,20*log10(env_bf + 0.001));
title('Beamformed by BFT');
xlabel('Angle [deg]');
ylabel('Axial distance [mm]')
axis('image')

colorbar
colormap(gray)

clc
disp([' ' 10 10 10 10 ]);
disp([9 '*****************************************************']);
disp([9 '*                                                   *']);
disp([9 '* The image beamformed by Field II is in "env_line" *']);
disp([9 '* The image beamformed by BFT is in "env_bf"        *']);
disp([9 '*                                                   *'])
disp([9 '*****************************************************']);
disp([' ' 10 10 ]);


\end{verbatim}
}

\headline{Synthetic Aperture Focusing}
%%tth:\vspace{2cm}
%%tth:\begin{html}<hr>\end{html} 
%%tth:\subsection*{Synthetic Aperture Focusing}
%%tth:\begin{html}<hr>\end{html}
\funlnk{sar_focusing}

{\footnotesize
\begin{verbatim}
%SYNTHETIC Synthetic aperture beamforming with BFT
% 


f0 = 4e6;              %  Central frequency
fs = 100e6;            %  Sampling frequency
c = 1540;              %  Speed of sound
no_elements = 74;      %  Number of elements in the transducer

lambda = c / f0;       % Wavelength
pitch = lambda / 2;    % Pitch - center-to-center
width = .95*pitch;     % Width of the element
kerf = pitch - width;  % Inter-element spacing
height = 10/1000;      % Size in the Y direction
 
 
%  Define the impulse response of the transducer
impulse_response = sin(3*pi*f0*(0:1/fs:2/f0));
impulse_response = impulse_response.*hanning(length(impulse_response))';
excitation = sin(2*pi*f0*(0:1/fs:3/f0));

%  Define the phantom

pht_pos = [0 0 40] / 1000;   %  The position of the phantom

[m n] = size(pht_pos);
pht_amp = 20*ones(m,1);      %  The amplitude of the back-scatter


%  Define the focus 

focus_r = [1:max(sqrt(pht_pos(:,1).^2 + pht_pos(:,2).^2 + pht_pos(:,3).^2))*1000]' / 1000;
T = (focus_r-.5/1000)/c *2;



%  Initialize the program
field_init(0);
bft_init;

%  Set some paramters
set_field('c', c);
bft_param('c', c);

set_field('fs', fs);
bft_param('fs', fs);


% Create some apertures.

xmt = xdc_linear_array(no_elements,width,height,kerf,1,1,[0 0 0]);
rcv = xdc_linear_array(no_elements,width,height,kerf,1,1,[0 0 0]);

xdc = bft_linear_array(no_elements, width, kerf);


% Set the impulse responses
xdc_impulse(rcv, impulse_response);
xdc_impulse(xmt, impulse_response);

xdc_excitation(xmt, excitation);


%  Define and create the image
sector = 60 * pi / 180;
no_lines = 64;
d_theta = sector / (no_lines-1);
theta = -(no_lines-1) / 2 * d_theta;

%  Set the delays for one whole image
%
bft_no_lines(no_lines);
for i = 1 : no_lines
  bft_apodization(xdc,0,hanning(no_elements)',i);
  bft_sum_apodization(xdc,0,ones(1,no_elements),i);
  focus = [sin(theta)*focus_r, zeros(length(focus_r),1), cos(theta)*focus_r];
  bft_center_focus([0 0 0],i);
  bft_focus(xdc, T, focus,i);
  theta = theta + d_theta;
end


%
%  Allocate memory for the image
%
Rmax = max(sqrt(pht_pos(:,1).^2 + pht_pos(:,2).^2  + pht_pos(:,3).^2)) + 10/1000;
Rmin = min(sqrt(pht_pos(:,1).^2 + pht_pos(:,2).^2  + pht_pos(:,3).^2)) - 10/1000;
if (Rmin < 0) Rmin = 0; end;
Tmin = 2*Rmin / c; Tmax = 2*Rmax / c;
Smin = floor(Tmin * fs); Smax = ceil(Tmax * fs);

no_rf_samples = Smax - Smin + 1;

bf_image = zeros(no_rf_samples, no_lines);

%
% Make one low-resolution image at a time and sum them
%

xdc_focus_times(xmt,0,zeros(1,no_elements)); 
xdc_focus_times(rcv,0,zeros(1,no_elements));
for emission_no = 1:no_elements
  disp(['emission no: ' num2str(emission_no)]);  
  xdc_apodization(xmt,0,[zeros(1,emission_no-1) 1 zeros(1, no_elements - emission_no)]);

  [scat, start_time] = calc_scat_multi (xmt, rcv, pht_pos, pht_amp);

  start_sample = floor(start_time * fs + 0.5);
  end_sample = start_sample + max(size(scat))-1;
  
  scat = [zeros(start_sample - Smin, no_elements); scat; zeros(Smax - end_sample,no_elements)];
 
  start_time = Tmin;
  beamformed = bft_beamform(start_time,scat);
  bf_image = bft_add_image(bf_image, beamformed, emission_no, start_time);
  
end



%  Release the allocated memory

field_end
bft_end



%
%  Dispplay the image
%

bf_image = abs(hilbert(bf_image));                  % Envelope detection
bf_image = bf_image / max(max(bf_image));

figure;
imagesc([-sector/2 sector/2]*180/pi,[0 Rmax]*1000,20*log10(bf_image + 0.001))
axis('image')
xlabel('Angle [deg]');
ylabel('Axial distance [mm]')
title('Beamformed by Field II ');
clc
disp([' ' 10 10 10 10 ]);
disp([9 '*****************************************************']);
disp([9 '*                                                   *']);
disp([9 '* The image beamformed by BFT is in "bf_image"      *']);
disp([9 '*                                                   *'])
disp([9 '*****************************************************']);
disp([' ' 10 10 ]);

\end{verbatim}
}


\end{document}