bft_user_guide.tex

超声仿真软件

\end{tabular} 

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\headline{bft\_free\_xdc}
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\funlnk{bft_free_xdc}

Free the memory allocated for a transducer definition

\begin{tabular}[t]{lp{14cm}}  
  USAGE:& {\tt bft\_free\_xdc(xdc)}\\
  INPUT:& {\sl xdc} Pointer to the memory location returned by the
                 function \hyperlink{bft_transducer}{bft\_transducer}\\
  OUTPUT:& Nothing
\end{tabular}


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\headline{bft\_init}
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\funlnk{bft_init}

Initialize the BeamForming Toolbox. This command must be
    executed first in order to set some parameters and allocate the 
    the necessary memory
    
\begin{tabular}[t]{lp{14cm}}  
USAGE:& {\tt bft\_init}\\
INPUT:& None \\
OUTPUT:& None
\end{tabular}


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\headline{bft\_linear\_array}
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\funlnk{bft_linear_array}


 Create a linear array aperture.
 
\begin{tabular}[t]{lp{14cm}}  
 USAGE: & {\tt xdc = bft\_linear\_array(no\_elements, width, kerf)} \\
   &     {\tt xdc = bft\_linear\_array(no\_elements, pitch)} \\
 
 INPUT:& \begin{tabular}[t]{lp{11cm}}  
          {\sl no\_elements} & Number of elelements in the array \\
          {\sl pitch} & Distance between the centers of two elements [m] \\
          {\sl width} & Width in x-direction                         [m]\\
          {\sl kerf}  & Distance between two elements                [m] 
         \end{tabular} \\
          
        & The function assumes that {\sl kerf + width = pitch} \\
 OUTPUT:& {\sl xdc} - Pointer to the allocated aperture.
\end{tabular}

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\headline{bft\_no\_lines}
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\funlnk{bft_no_lines}

Set the number of lines that will be beamformed in parallel.
  After calling \hyperlink{bft_init}{bft\_init}, the number of lines 
that are beamformed in   parallel is 1. If the user wants to beamform
a whole image in one  command, he/she must set the number of lines,
and then specify the focal zones for each of the lines.

\begin{tabular}[t]{lp{14cm}}  
 
 USAGE: & {\tt bft\_no\_lines(no\_lines)}\\
 INPUT:& {\sl no\_lines}  ~~Number of lines beamformed in parallel \\
 OUTPUT: & None
\end{tabular}


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\headline{bft\_param}
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\funlnk{bft_param}

Set a parameter of the BeamForming Toolbox

\begin{tabular}[t]{lp{14cm}}  

 USAGE: & {\tt bft\_param(name, value)}\\
 
 INPUT: & \begin{tabular}[t]{lp{11cm}}  
          {\sl name} & Name of  the parameter (string). Currently supported:\\
        &  \begin{tabular}[t]{c|c|c|c}
           \hline 
            name &        Meaning       & Default value &  Unit \\
            \hline 
                  'c' & Speed of sound.       & 1540         &  m/s \\
                  'fs'& Sampling frequency    & 40,000,000   &  Hz \\
            \hline       
          \end{tabular} \\\\
         
          {\sl value} & New value for the parameter. Must be scalar. 
          \end{tabular} \\
 OUTPUT: & None
\end{tabular}


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\headline{bft\_sub\_image}
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\funlnk{bft_sub_image}

Subtract one low-res image from  high-res one.

\begin{tabular}[t]{lp{14cm}}  
 
 USAGE: & {\tt [hi\_res] = bft\_sub\_image(hi\_res, lo\_res, element, start\_time)} \\
 
 INPUT:& \begin{tabular}[t]{lp{11cm}}  
          {\sl hi\_res}  & High resolution RF image. One column per scan line.\\
          {\sl lo\_res}  & Low resolution RF image. One column per scan line.\\
          {\sl element} & Number of element, used to acquire the low resolution
                    image. \\
          {\sl start\_time}    & Arrival time of the first sample of the RF lines.
          \end{tabular} \\
 OUTPUT:& hi\_res - The high resolution image.
\end{tabular}

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\headline{bft\_sum\_apodization}
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\funlnk{bft_sum_apodization}

Create a summation apodization time line.
    This function is used in the case that the individual low
    resolution images must be weighted during the summation

\begin{tabular}[t]{lp{14cm}}  
 
  USAGE: & {\tt  bft\_sum\_apodization(xdc, times, values, line\_no)} \\
 
  INPUT: & \begin{tabular}[t]{lp{14cm}}  
          {\sl xdc} & Pointer to a transducer aperture.\\
          {\sl times} & Time after which the associated apodization is valid.\\
          {\sl values} & Apodization values. Matrix with one row for each
                   time value and a number of columns equal to the 
                   number of physical elements in the aperture. \\
          {\sl line\_no} & Number of line. If skipped, {\sl line\_no} is assumed
                    to be equal to '1'.
         \end{tabular}\\
  OUTPUT: & None         
\end{tabular}


\headline{bft\_sum\_images}
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\funlnk{bft_sum_images}

 Sum 2 low resolution images in 1 high resolution.

\begin{tabular}[t]{lp{14cm}}  
 
 USAGE  : {\tt [hi\_res] = bft\_sum\_images(image1, ele1, image2, ele2, time) }\\
 
 INPUT  : \begin{tabular}[t]{lp{141cm}}  
          {\sl image1} & Matrix with the RF data for the image. The number
                   of columns corresponds to the number of lines \\
          {\sl ele1}   & Number of emitting element used to obtain the image.\\ 
          {\sl image2} & Matrix with the RF data for the image. The number
                   of columns corresponding to the number of lines \\
          {\sl ele2}   & Number of emitting element used to obtain the image.\\
          {\sl time}   &  The arrival time of the first samples. The two images
                    must be aligned in time 
          \end{tabular}
 OUTPUT : hi\_res - Higher resolution image
\end{tabular}

\headline{bft\_transducer}
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\funlnk{bft_transducer}
 
 Create a new transducer definition. 
    The transducer definition is necessary for the calculation of 
    the delays.

\begin{tabular}[t]{lp{14cm}}  
 
 USAGE: &  {\tt xdc = bft\_transducer(centers)}\\
 
 INPUT: & \begin{tabular}[t]{lp{11cm}}  
            {\sl centers} & Matrix with the coordinates of the centers of 
                   the elements. It has 3 columns (x,y,z) and a
                   number of rows equal to the number of elements.
                   The coordinates are specified in [m]
         \end{tabular}\\ 
 OUTPUT: & \begin{tabular}[t]{lp{11cm}}  
          xdc & Pointer to the memory location with the transducer 
               definition. Do not alter this value !!!
          \end{tabular}
\end{tabular}

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\chapter{Examples}
\label{chap_examples}
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\section{Using Field II simulations}

\headline{Phased array B-mode image}
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\funlnk{phased_bmode}

{\footnotesize\noindent
1{\tt~~~~}{\tt {\sl \%PHASED\_IMAGE~Create~phased~array~B-mode~image~with~BFT.}}\\
2{\tt~~~~}{\tt {\sl \%~~~~This~script~creates~a~B-mode~PSF~line~by~line.~Each~line~is~}}\\
3{\tt~~~~}{\tt {\sl \%~~~~calculated~using~CALC\_SCAT~and~CALC\_SCAT\_MULTY.~The~rf\_data}}\\
4{\tt~~~~}{\tt {\sl \%~~~~from~CALC\_SCAT\_MULTI~is~passed~to~~the~beamforming~toolbox,}}\\
5{\tt~~~~}{\tt {\sl \%~~~~and~in~the~end~the~results~are~compared.}}\\
6{\tt~~~~}{\tt {\sl \%}}\\
7{\tt~~~~}{\tt {\sl \%~~~~The~function~calls~XDC\_FOCUS,~and~BFT\_FOCUS~in~order~to~set~the}}\\
8{\tt~~~~}{\tt {\sl \%~~~~the~delays.~}}\\
9{\tt~~~~}{\tt }\\
10{\tt~~~}{\tt {\sl \%~VERSION~1.0,~29~Feb.~2000,~Svetoslav~Nikolov}}\\
11{\tt~~~}{\tt }\\
12{\tt~~~}{\tt f0~=~4e6;~~~~~~~~~~~~~~{\sl \%~~Central~frequency~~~~~~~~~~~~~~~~~~~~~~~[Hz]}}\\
13{\tt~~~}{\tt fs~=~100e6;~~~~~~~~~~~~{\sl \%~~Sampling~frequency~~~~~~~~~~~~~~~~~~~~~~[Hz]}}\\
14{\tt~~~}{\tt c~=~1540;~~~~~~~~~~~~~~{\sl \%~~Speed~of~sound~~~~~~~~~~~~~~~~~~~~~~~~~~[m/s]}}\\
15{\tt~~~}{\tt no\_elements~=~64;~~~~~~{\sl \%~~Number~of~elements~in~the~transducer}}\\
16{\tt~~~}{\tt }\\
17{\tt~~~}{\tt lambda~=~c~/~f0;~~~~~~~{\sl \%~Wavelength~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~[m]}}\\
18{\tt~~~}{\tt pitch~=~lambda~/~2;~~~~{\sl \%~Pitch~-~center-to-center~~~~~~~~~~~~~~~~~[m]}}\\
19{\tt~~~}{\tt width~=~.95*pitch;~~~~~{\sl \%~Width~of~the~element~~~~~~~~~~~~~~~~~~~~~[m]}}\\
20{\tt~~~}{\tt kerf~=~pitch~-~width;~~{\sl \%~Inter-element~spacing~~~~~~~~~~~~~~~~~~~~[m]}}\\
21{\tt~~~}{\tt height~=~10/1000;~~~~~~{\sl \%~Size~in~the~Y~direction~~~~~~~~~~~~~~~~~~[m]}}\\
22{\tt~~~}{\tt ~}\\
23{\tt~~~}{\tt ~}\\
24{\tt~~~}{\tt {\sl \%~~Define~the~impulse~response~of~the~transducer}}\\
25{\tt~~~}{\tt impulse\_response~=~sin(2*pi*f0*(0:1/fs:2/f0));}\\
26{\tt~~~}{\tt impulse\_response~=~impulse\_response.*hanning(length(impulse\_response))';}\\
27{\tt~~~}{\tt excitation~=~impulse\_response;}\\
28{\tt~~~}{\tt }\\
29{\tt~~~}{\tt {\sl \%~~Define~the~phantom}}\\
30{\tt~~~}{\tt }\\
31{\tt~~~}{\tt pht\_pos~=~[0~0~20;}\\
32{\tt~~~}{\tt ~~~~~~~~~~~0~0~30;}\\
33{\tt~~~}{\tt ~~~~~~~~~~~0~0~40;}\\
34{\tt~~~}{\tt ~~~~~~~~~~~0~0~50;}\\
35{\tt~~~}{\tt ~~~~~~~~~~~0~0~60;}\\
36{\tt~~~}{\tt ~~~~~~~~~~~0~0~70;}\\
37{\tt~~~}{\tt ~~~~~~~~~~~0~0~80;}\\
38{\tt~~~}{\tt ~~~~~~~~~~~0~0~90;}\\
39{\tt~~~}{\tt ~~~~~~~~~~~]~/~1000;~~~~~~~~~{\sl \%~~The~position~of~the~phantom}}\\
40{\tt~~~}{\tt pht\_amp~=~20*ones(8,1);~~~~~~{\sl \%~~The~amplitude~of~the~back-scatter}}\\
41{\tt~~~}{\tt }\\
42{\tt~~~}{\tt }\\
43{\tt~~~}{\tt }\\
44{\tt~~~}{\tt {\sl \%~~Define~the~focus~}}\\
45{\tt~~~}{\tt focus\_r~=~[20;30;40;50;60;70;80;90]~/~1000;}\\
46{\tt~~~}{\tt T~=~(focus\_r-5/1000)/c~*2;}\\
47{\tt~~~}{\tt }\\
48{\tt~~~}{\tt }\\
49{\tt~~~}{\tt {\sl \%~~Initialize~the~program}}\\
50{\tt~~~}{\tt field\_init(0);}\\
51{\tt~~~}{\tt bft\_init;}\\
52{\tt~~~}{\tt }\\
53{\tt~~~}{\tt }\\
54{\tt~~~}{\tt {\sl \%~~Set~some~paramters}}\\
55{\tt~~~}{\tt set\_field('c',~c);}\\
56{\tt~~~}{\tt bft\_param('c',~c);}\\
57{\tt~~~}{\tt }\\
58{\tt~~~}{\tt set\_field('fs',~fs);}\\
59{\tt~~~}{\tt bft\_param('fs',~fs);}\\
60{\tt~~~}{\tt }\\
61{\tt~~~}{\tt }\\
62{\tt~~~}{\tt }\\
63{\tt~~~}{\tt {\sl \%~Create~some~apertures.}}\\
64{\tt~~~}{\tt }\\
65{\tt~~~}{\tt xmt~=~xdc\_linear\_array(no\_elements,width,height,kerf,1,1,[0~0~0]);}\\
66{\tt~~~}{\tt rcv~=~xdc\_linear\_array(no\_elements,width,height,kerf,1,1,[0~0~0]);}\\
67{\tt~~~}{\tt }\\
68{\tt~~~}{\tt xdc~=~bft\_linear\_array(no\_elements,~width,~kerf);}\\
69{\tt~~~}{\tt }\\
70{\tt~~~}{\tt }\\
71{\tt~~~}{\tt {\sl \%~Set~the~impulse~responses}}\\
72{\tt~~~}{\tt xdc\_impulse(rcv,~impulse\_response);}\\
73{\tt~~~}{\tt xdc\_impulse(xmt,~impulse\_response);}\\
74{\tt~~~}{\tt }\\
75{\tt~~~}{\tt xdc\_excitation(xmt,~excitation);}\\
76{\tt~~~}{\tt }\\
77{\tt~~~}{\tt }\\
78{\tt~~~}{\tt }\\
79{\tt~~~}{\tt {\sl \%~~Define~and~create~the~image}}\\
80{\tt~~~}{\tt sector~=~30~*~pi~/~180;}\\
81{\tt~~~}{\tt no\_lines~=~32;}\\
82{\tt~~~}{\tt d\_theta~=~sector~/~(no\_lines-1);}\\
83{\tt~~~}{\tt theta~=~-(no\_lines-1)~/~2~*~d\_theta;}\\
84{\tt~~~}{\tt }\\
85{\tt~~~}{\tt Rmax~=~max(sqrt(pht\_pos(:,1).\^~2~+~pht\_pos(:,2).\^~2~~+~pht\_pos(:,3).\^~2))~+~15/1000;}\\
86{\tt~~~}{\tt }\\
87{\tt~~~}{\tt no\_rf\_samples~=~ceil(2*Rmax/c~*~fs);}\\
88{\tt~~~}{\tt rf\_line~=~zeros(no\_rf\_samples,~1);}\\
89{\tt~~~}{\tt bf\_line~=~zeros(no\_rf\_samples,~1);}\\
90{\tt~~~}{\tt }\\
91{\tt~~~}{\tt env\_line~=~zeros(no\_rf\_samples,~no\_lines);}\\
92{\tt~~~}{\tt env\_bf~=~~zeros(no\_rf\_samples,~no\_lines);}\\
93{\tt~~~}{\tt }\\
94{\tt~~~}{\tt }\\
95{\tt~~~}{\tt xmt\_r~=~(max(focus\_r)~+~min(focus\_r)~)/2;}\\
96{\tt~~~}{\tt }\\
97{\tt~~~}{\tt for~i~=~1~:~no\_lines}\\
98{\tt~~~}{\tt ~~rf\_line(:)~=~0;~~}\\
99{\tt~~~}{\tt ~~disp(['Line~no~'~num2str(i)])}\\
100{\tt~~}{\tt ~~}\\
101{\tt~~}{\tt ~~focus~=~[sin(theta)*focus\_r,~zeros(length(focus\_r),1),~cos(theta)*focus\_r];}\\
102{\tt~~}{\tt ~~xmt\_f~=~[sin(theta)*xmt\_r,~zeros(length(xmt\_r),1),~cos(theta)*xmt\_r];}\\
103{\tt~~}{\tt ~~xdc\_center\_focus(xmt,[0~0~0])}\\
104{\tt~~}{\tt ~~xdc\_center\_focus(rcv,[0~0~0])}\\
105{\tt~~}{\tt ~~bft\_center\_focus([0~0~0]);}\\
106{\tt~~}{\tt ~~}\\
107{\tt~~}{\tt ~~xdc\_focus(xmt,~0,~xmt\_f);}\\
108{\tt~~}{\tt ~~xdc\_focus(rcv,~T,~focus);}\\
109{\tt~~}{\tt ~~bft\_focus(xdc,~T,~focus);}\\
110{\tt~~}{\tt ~~}\\
111{\tt~~}{\tt ~~{\sl \%~~Beamform~with~Field~II}}\\
112{\tt~~}{\tt ~~[rf\_temp,~t(i)]~=~calc\_scat(xmt,rcv,~pht\_pos,~pht\_amp);}\\
113{\tt~~}{\tt ~~}\\
114{\tt~~}{\tt ~~{\sl \%~~Beamform~with~BFT}}\\
115{\tt~~}{\tt ~~xdc\_focus\_times(rcv,~0,~zeros(1,no\_elements));}\\
116{\tt~~}{\tt ~~[rf\_data,~start\_t]~=~calc\_scat\_multi(xmt,rcv,~pht\_pos,~pht\_amp);}\\
117{\tt~~}{\tt ~~rf\_data~=~[zeros(300,no\_elements);~rf\_data;~zeros(300,no\_elements)];}\\
118{\tt~~}{\tt }\\
119{\tt~~}{\tt ~~start\_t~=~start\_t~-~300~~/~fs;}\\
120{\tt~~}{\tt ~~bf\_temp~=~bft\_beamform(start\_t,~rf\_data);}\\
121{\tt~~}{\tt ~~}\\
122{\tt~~}{\tt ~~start\_sample~=~t(i)*fs;~no\_temp\_samples~=~length(rf\_temp);}\\
123{\tt~~}{\tt ~~}\\
124{\tt~~}{\tt ~~rf\_line(start\_sample:start\_sample+no\_temp\_samples-1)~=~rf\_temp(1:no\_temp\_samples);}\\
125{\tt~~}{\tt ~~env\_line(:,i)~=~abs(hilbert(rf\_line(:)));}\\
126{\tt~~}{\tt }\\
127{\tt~~}{\tt ~~start\_sample~=~floor(start\_t*fs);~no\_temp\_samples~=~length(bf\_temp);}\\
128{\tt~~}{\tt ~~bf\_line(start\_sample:start\_sample+no\_temp\_samples-1)~=~bf\_temp(1:no\_temp\_samples);}\\
129{\tt~~}{\tt ~~env\_bf(:,i)~=~abs(hilbert(bf\_line(:)));}\\
130{\tt~~}{\tt ~~theta~=~theta~+~d\_theta;}\\
131{\tt~~}{\tt }\\
132{\tt~~}{\tt end}\\
133{\tt~~}{\tt }\\
134{\tt~~}{\tt {\sl \%~~Release~the~allocated~memory}}\\
135{\tt~~}{\tt }\\