资源分类:Matlab 工具:MATLAB 7.5 (R2007b)


CTrecon-an improved parallel data image reconstruct function

Reconstruct an image from parallel projection data using the convolution-backprojection algorithm

function [img,H] = CTrecon(prj,varargin)


for a discussion of this function including examples see:


Mathworks has created a workaround to fix the offset problem in iradon for R2010 and later users:

CTrecon will work with earlier versions and also has the other features described here.


Has the following improvements over iradon:


1. Fixes a bug in iradon that results in offsets from

 the true values in the reconstructed image. Does this by computing

 the filter transfer function as transform of direct space function

 instead of transforming a ramp in frequency.

See Ch. 3 of "Principles of Computerized Tomographic Imaging" by

A. C. Kak and Malcolm Slaney, IEEE Press, 1988.

available online at


2. Uses mex functions based on iradon_speedy to back project so it is faster


3. handles complex projections to return a complex reconstructed image - see zBackproject.c


4. regularizes the interface to ('parameter_name', parameter_value) syntax



    prj: (required) the projection data matrix of size (number of lines)X(number_of_angles)

    angles: optional = angles are equally spaced from 0 to 180 degrees but do not wrap around

                  number of angles is size(prj,2)


    interpolation: optional = 'linear', a string specifying the interpolation in the backprojection

          'linear' - linear interpolation (default)

          'nearest neighbor' - nearest neighbor interpolation

  filter_type:(optional = 'Ram-Lak') a string that specifies the filter used. Possibilities are

       'Ram-Lak' The cropped Ramachandran-Lakshimrayanan or ramp filter_type (default).

       'Shepp-Logan' The Shepp-Logan filter_type: a ramp times a sinc

       'Cosine' a ramp times cosine from 0 to the Nyquist frequency.

       'Hamming' a ramp times the Hamming filter_type.

       'Hann' a ramp times the Hann filter_type.


 freq_cutoff: (optional = 1) sets the filter to 0 starting at freq_cutoff*freq_nyquist



    img: the reconstructed image

    H: the transfer function of the filter


 The image output size is determined from the length of the projections:


     OUTPUT_SIZE = 2*floor(size(prj,1)/(2*sqrt(2)))


 Example: see for other examples


  P = phantom(128);

  R = radon(P,0:179);

  img = CTrecon(R,'filter_type','cosine','freq_cutoff',0.9);

  figure, imshow(img,[-.05 .3])

文件下载列表 (230.0KB)  
Backproject.c  CTrecon.m  P6CTrecon.m  P6CTrecon.pdf  zBackproject.c  


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