Metal artifacts creation using iradon
anna
Does any one know how to produce artifacts on a constructed image using iradon function?
as an input image I tried the phantom image.
for the artifacts I am looking to generate metal artifacts (or beam hardening artifacts) which have the form of white and black streaks.
in the following code I can only generate alaising artificats which can be produced by undersampling the angle. but for the matal like artifacts, I can't see kow this can be produced thought in papers they do it easly????
Thanks for your help.
% A simple example for Radon and inverse radon transform using Matlab phantom image. this code is to generate artifacts
clc;
clear;
close all;
%Create a Shepp-Logan head phantom image.
%P = phantom(256);%phanto(n) s : the size of the phantom image.
P = phantom('Modified Shepp-Logan',200);
imshow(P)
%Compute the Radon transform of the phantom brain for three different sets of theta values. R1 has 18 projections, R2 has 36 projections, and R3 has 90 projections.
theta1 = 0:10:170; [R1,xp] = radon(P,theta1);
theta2 = 0:5:175; [R2,xp] = radon(P,theta2);
theta3 = 0:2:178; [R3,xp] = radon(P,theta3);
%Display a plot of one of the Radon transforms of the Shepp-Logan head phantom. The following figure shows R3, the transform with 90 projections.
figure, imagesc(theta3,xp,R3); colormap(hot); colorbar
xlabel('\theta'); ylabel('x\prime');
%Reconstruct the head phantom image from the projection data created in step 2 and display the results.
I1 = iradon(R1,10);
I2 = iradon(R2,5);
I3 = iradon(R3,2);
% I1 = iradon(R1,theta1);
% I2 = iradon(R2,theta2);
% I3 = iradon(R3,theta3);
max_IR = max(I3);
min_IR = min(I3);
max_IRR = max(max_IR)
min_IRR = min(min_IR)
figure, imshow(I1)
figure, imshow(I2)
figure, imshow(I3)
Titipong Kaewlek
I studied metal artifacts reduction and I created the simulation metal artifacts on Shepp-logan phatom and inserted metal on it.
I hope my code can help you, i will send into your e-mail.
Be regrad,
Titipong kaewlek
"anna " <anna.h...@gmail.com> wrote in message <j73u3d$hll$1...@newscl01ah.mathworks.com>...
Matt J
> Does any one know how to produce artifacts on a constructed image using iradon function?
> as an input image I tried the phantom image.
> for the artifacts I am looking to generate metal artifacts (or beam hardening artifacts) which have the form of white and black streaks.
>
> in the following code I can only generate alaising artificats which can be produced by undersampling the angle. but for the matal like artifacts, I can't see kow this can be produced thought in papers they do it easly????
anna, you need to do a bit more reading on the causes of x-ray beam hardening, because there is nothing in your code that simulates this. What causes beam hardening is the fact that a true x-ray beam contains multiple energies. When the image reconstruction process ignores this, beam hardening artifacts appear. More specifically, a detected signal in a CT system can be modeled something like this
Y=sum_i c_i*exp(-radon(mu_i))
where c_i is the photon flux and mu_i is the attenuation image at the i-th energy level. When reconstructing, however, people use the following simpler model, which has only a single exponential term,
Y=c*exp(-radon(mu))
It is this modeling inaccuracy that leads to beam hardening. To simulate this realistically, you will need to look up tables that give the energy dependence of the attenuation of different tissues, and also look at the energy distribution c_i of typical x-ray sources.
Another reason that you don't see metal-like artifacts is that your object contains no metal! The Shepp-Logan phantom contains only bone,water, and air-like tissue intensities. If you insert some points with much higher attenuation then what is already there, you should start to see metal-like streak artifacts (although not beam hardening artifacts necessarily).
Wanjin Jeong
I interest in metal artifact reduction. I always hope that know how to generate metal artifacts.
So, could you please send your code into my e-mail?
Wanjin Jeong
"Titipong Kaewlek" wrote in message <jer69s$bho$1...@newscl01ah.mathworks.com>...
Juan
I'm currently studying metal artifacts reduction. I implemented algorithms suggested in their papers by Mahnken as well as by Watzke & Kalender. However, I'm having a resolution loss through both algorithms and a delay of several minutes due to the necessary increase in reconstruction angles. Can you please send me the code you are using (or developed)? I will be giving you the credit if used forward.
Best regards,
Juan
Titipong Kaewlek
Thanks you for you interesting my code. You can download my simulation metal artifacts code on this link: http://www.mathworks.com/matlabcentral/fileexchange/34589-created-metal-artifact-of-computed-tomography
I hope it can help you , and if you have any inquire please feel free to contact me.
Titipong Kaewlek
Titipong Kaewlek
I want to know detail and discuss on you work, but I don't know your e-mail. please give me your e- mail.
Best regards,
Titipong Kaewlek
"Juan" wrote in message <jf6mpp$2fd$1...@newscl01ah.mathworks.com>...
rsriddh...@gmail.com
i am working on removal of metal artifacts from dental images.
i am also interested to know how to add artifacts in ct images. i have some ct reconstructed image (without arifacts images)
i want to design such algorithm which is worked on the bases of non statistical manner. for that i used fft.
will you send me your code regarding this.
thank you
rsriddh...@gmail.com
Titipong Kaewlek
You can download my file at http://www.mathworks.com/matlabcentral/fileexchange/34589-created-metal-artifact-of-computed-tomography
thanks
titipong