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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"><html><head> <title>Description of mriphantom</title> <meta name="keywords" content="mriphantom"> <meta name="description" content="MRIPHANTOM - simulated MRI of a Shepp Logan head phantom"> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <meta name="generator" content="m2html © 2003 Guillaume Flandin"> <meta name="robots" content="index, follow"> <link type="text/css" rel="stylesheet" href="../m2html.css"></head><body><a name="_top"></a><div><a href="../index.html">Home</a> > <a href="index.html">mri_toolbox</a> > mriphantom.m</div><!--<table width="100%"><tr><td align="left"><a href="../index.html"><img alt="<" border="0" src="../left.png"> Master index</a></td><td align="right"><a href="index.html">Index for mri_toolbox <img alt=">" border="0" src="../right.png"></a></td></tr></table>--><h1>mriphantom</h1><h2><a name="_name"></a>PURPOSE <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2><div class="box"><strong>MRIPHANTOM - simulated MRI of a Shepp Logan head phantom</strong></div><h2><a name="_synopsis"></a>SYNOPSIS <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2><div class="box"><strong>function Sk = mriphantom(kx,ky) </strong></div><h2><a name="_description"></a>DESCRIPTION <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2><div class="fragment"><pre class="comment"> MRIPHANTOM - simulated MRI of a Shepp Logan head phantom
Sk = mriphantom(kx,ky)
Creates simulated raw MRI data of a Shepp Logan head phantom
for given k space points
input is the kx and ky coordinates in the image frequency space
default values for kx and ky are for a Carthesian sampling.
Input
kx, ky Matrices with kx and ky sampling coordinates
E Optional analytical phantom data matrix as produced by
image toolbox function phantom.m (see comments below).
Data are from an analytical expression for a continuous phantom.
Core equations for this are taken form :
Rik van der Walle et al IEEE Trans Med Imag 19(12) p1160.
Note that the standard matlab function just gives the phantom
sampled in image space on a carthesian grid.
This function delivers the simulated raw MRI data sampled through
a user defined path in k-space (image frequency space)
Author : Ronald Ouwekerk Johns Hopkins University Dept. Radiology
601 N. Caroline Street Room 4250 Baltimore, MD 21287-0845 USA
rouwerke@mri.jhu.edu
Written :May 2002
Modified June 2002 : Revised to give a non-NaN result for k=0
Suppress output if nargout == 0
Added comments to explain the difference with phantom.m
Whenever this software is used for publications an acknowledgment
would be much appreciated.
RO</pre></div><!-- crossreference --><h2><a name="_cross"></a>CROSS-REFERENCE INFORMATION <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2>This function calls:<ul style="list-style-image:url(../matlabicon.gif)"></ul>This function is called by:<ul style="list-style-image:url(../matlabicon.gif)"></ul><!-- crossreference --><h2><a name="_subfunctions"></a>SUBFUNCTIONS <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2><ul style="list-style-image:url(../matlabicon.gif)"><li><a href="#_sub1" class="code">function toft=modified_shepp_logan</a></li></ul><h2><a name="_source"></a>SOURCE CODE <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2><div class="fragment"><pre>0001 <a name="_sub0" href="#_subfunctions" class="code">function Sk = mriphantom(kx,ky)</a>0002 0003 <span class="comment">% MRIPHANTOM - simulated MRI of a Shepp Logan head phantom</span>0004 <span class="comment">%</span>0005 <span class="comment">% Sk = mriphantom(kx,ky)</span>0006 <span class="comment">%</span>0007 <span class="comment">% Creates simulated raw MRI data of a Shepp Logan head phantom</span>0008 <span class="comment">% for given k space points</span>0009 <span class="comment">% input is the kx and ky coordinates in the image frequency space</span>0010 <span class="comment">% default values for kx and ky are for a Carthesian sampling.</span>0011 <span class="comment">% Input</span>0012 <span class="comment">% kx, ky Matrices with kx and ky sampling coordinates</span>0013 <span class="comment">% E Optional analytical phantom data matrix as produced by</span>0014 <span class="comment">% image toolbox function phantom.m (see comments below).</span>0015 <span class="comment">% Data are from an analytical expression for a continuous phantom.</span>0016 <span class="comment">% Core equations for this are taken form :</span>0017 <span class="comment">% Rik van der Walle et al IEEE Trans Med Imag 19(12) p1160.</span>0018 <span class="comment">%</span>0019 <span class="comment">% Note that the standard matlab function just gives the phantom</span>0020 <span class="comment">% sampled in image space on a carthesian grid.</span>0021 <span class="comment">% This function delivers the simulated raw MRI data sampled through</span>0022 <span class="comment">% a user defined path in k-space (image frequency space)</span>0023 <span class="comment">%</span>0024 <span class="comment">% Author : Ronald Ouwekerk Johns Hopkins University Dept. Radiology</span>0025 <span class="comment">% 601 N. Caroline Street Room 4250 Baltimore, MD 21287-0845 USA</span>0026 <span class="comment">% rouwerke@mri.jhu.edu</span>0027 <span class="comment">% Written :May 2002</span>0028 <span class="comment">% Modified June 2002 : Revised to give a non-NaN result for k=0</span>0029 <span class="comment">% Suppress output if nargout == 0</span>0030 <span class="comment">% Added comments to explain the difference with phantom.m</span>0031 <span class="comment">%</span>0032 <span class="comment">% Whenever this software is used for publications an acknowledgment</span>0033 <span class="comment">% would be much appreciated.</span>0034 <span class="comment">% RO</span>0035 0036 FOV = 2; 0037 N = 64;0038 0039 <span class="keyword">if</span> nargin < 20040 <span class="comment">%=====================================================================</span>0041 <span class="comment">% Set the field of view to 24 cm (see image toolbox phantom.m)</span>0042 <span class="comment">% resolution 128x128 points</span>0043 <span class="comment">% create k-space coordinates for Carthesion sampling</span>0044 <span class="comment">% Should be equivalent to IFFT of the phantom</span>0045 <span class="comment">%=====================================================================</span>0046 FOV = 0.24;0047 res = FOV/N;0048 Kmax = 1/(2*res);0049 ky = linspace(-Kmax,Kmax, N);0050 ky = ky(ones(N,1),:);0051 kx = permute(ky, [2,1]);0052 <span class="keyword">end</span>;0053 <span class="keyword">if</span> ( (nargin < 3 ) | isempty(E) ) & (exist(<span class="string">'phantom.m'</span>)==2)0054 <span class="comment">%========================================================================</span>0055 <span class="comment">% Create 2D phantom to get defining matrix E</span>0056 <span class="comment">%========================================================================</span>0057 [P,E] = phantom;0058 <span class="keyword">elseif</span> ~(exist(<span class="string">'phantom.m'</span>)==2)0059 P = [];0060 E = <a href="#_sub1" class="code" title="subfunction toft=modified_shepp_logan">modified_shepp_logan</a>;0061 <span class="keyword">end</span>;0062 0063 <span class="comment">%========================================================================</span>0064 <span class="comment">% copy the elements of E and scale to field of view</span>0065 <span class="comment">% Matlab phantom.m default yields FOV =[-1,1]= 2</span>0066 <span class="comment">% Scale all dimensions to desired FOV (*FOV/2).</span>0067 <span class="comment">% Column 1: rho the additive intensity value of the ellipse</span>0068 <span class="comment">% Column 2: a the length of the horizontal semi-axis of the ellipse</span>0069 <span class="comment">% Column 3: b the length of the vertical semi-axis of the ellipse</span>0070 <span class="comment">% Column 4: x0 the x-coordinate of the center of the ellipse</span>0071 <span class="comment">% Column 5: y0 the y-coordinate of the center of the ellipse</span>0072 <span class="comment">% Column 6: alpha the angle (in degrees) between the horizontal semi-axis</span>0073 <span class="comment">% of the ellipse and the x-axis of the image</span>0074 <span class="comment">%========================================================================</span>0075 [me,ne] = size(E);0076 rho = E(:,1)'; ⌨️ 快捷键说明
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