Rank: 4779 based on 20 downloads (last 30 days) and 1 file submitted
photo

Cheng Guan Koay

E-mail

Personal Profile:

http://sites.google.com/site/cgkoay/pr


 

Watch this Author's files

 

Files Posted by Cheng Guan Koay
Updated   File Tags Downloads
(last 30 days)
Comments Rating
26 Oct 2008 Three Dimensional Analytical Magnetic Resonance Imaging Phantom in the Fourier Domain This software contains 2D and 3D Shepp-Logan phantoms in both the image and Fourier domains. Author: Cheng Guan Koay image generation, shepplogan 3d analyti..., shepplogan 3d analyti..., 3d fourier domain pha..., shepplogan 2d analyti..., 2d fourier domain pha... 20 6
  • 5.0
5.0 | 3 ratings
Comments and Ratings by Cheng Guan Koay View all
Updated File Comments Rating
27 Apr 2010 Three Dimensional Analytical Magnetic Resonance Imaging Phantom in the Fourier Domain This software contains 2D and 3D Shepp-Logan phantoms in both the image and Fourier domains. Author: Cheng Guan Koay

Sorry, I had problems with the comment submission. I accidentally deleted an earlier message that contained my explanations.

I shall try to explain it again here.

The first thing I should point out is that the field-of-view (FOV) in the image domain is fixed. Each FOV in each dimension is two units (arbitrary unit) from -1 to 1. Therefore, the resolution along the x-axis, denoted as del_x, in the image domain is determined by the number of samples, N, and it is given by del_x = FOV/N.

The resolution along the k-axis, denoted as del_kx, in the Fourier domain is determined by the FOV, and it is given by del_kx = 1/FOV.

The main thing is to know how wide one should sample the k-space or Fourier domain. The magnitude of k_max, i.e., |k_max| is given by del_kx * N/2 . Note that it is assumed that the negative and the positive regions are sampled equally.

So, "K<0.002" should not be the problem. Hope this helps. If not, feel free to email.

27 Apr 2010 Three Dimensional Analytical Magnetic Resonance Imaging Phantom in the Fourier Domain This software contains 2D and 3D Shepp-Logan phantoms in both the image and Fourier domains. Author: Cheng Guan Koay

I forgot to say that there is no problem with K<0.002. :)

12 Aug 2009 Three Dimensional Analytical Magnetic Resonance Imaging Phantom in the Fourier Domain This software contains 2D and 3D Shepp-Logan phantoms in both the image and Fourier domains. Author: Cheng Guan Koay

In the revised SampleTest.m, I used imtool and please make sure that you click on a menu that allows you to change contrast. min=0.0 and max=3.0 should be fine and these values should be applied to both imtool panels.

11 Aug 2009 Three Dimensional Analytical Magnetic Resonance Imaging Phantom in the Fourier Domain This software contains 2D and 3D Shepp-Logan phantoms in both the image and Fourier domains. Author: Cheng Guan Koay

Due the inconvenience of updating and commenting on the site, I have decided to only update the site with major releases.

The MATLAB codes that illustrate the steps needed to perform FFT on the k-space signals of the 3D Shepp-Logan phantom can be found in a revised version of SampleTest.m, which is located on my google site: http://sites.google.com/site/hispeedpackets/Home/shepplogan

Comments and Ratings on Cheng Guan Koay's Files View all
Updated File Comment by Comments Rating
27 Apr 2010 Three Dimensional Analytical Magnetic Resonance Imaging Phantom in the Fourier Domain This software contains 2D and 3D Shepp-Logan phantoms in both the image and Fourier domains. Author: Cheng Guan Koay Cheng Guan Koay

Sorry, I had problems with the comment submission. I accidentally deleted an earlier message that contained my explanations.

I shall try to explain it again here.

The first thing I should point out is that the field-of-view (FOV) in the image domain is fixed. Each FOV in each dimension is two units (arbitrary unit) from -1 to 1. Therefore, the resolution along the x-axis, denoted as del_x, in the image domain is determined by the number of samples, N, and it is given by del_x = FOV/N.

The resolution along the k-axis, denoted as del_kx, in the Fourier domain is determined by the FOV, and it is given by del_kx = 1/FOV.

The main thing is to know how wide one should sample the k-space or Fourier domain. The magnitude of k_max, i.e., |k_max| is given by del_kx * N/2 . Note that it is assumed that the negative and the positive regions are sampled equally.

So, "K<0.002" should not be the problem. Hope this helps. If not, feel free to email.

27 Apr 2010 Three Dimensional Analytical Magnetic Resonance Imaging Phantom in the Fourier Domain This software contains 2D and 3D Shepp-Logan phantoms in both the image and Fourier domains. Author: Cheng Guan Koay Cheng Guan Koay

I forgot to say that there is no problem with K<0.002. :)

27 Apr 2010 Three Dimensional Analytical Magnetic Resonance Imaging Phantom in the Fourier Domain This software contains 2D and 3D Shepp-Logan phantoms in both the image and Fourier domains. Author: Cheng Guan Koay Giuseppe

First of all really nice work!!! I have just a question the package work well for an image resolution equal or higher 128x128X128, for lower resolution the signal in kspace is not numerically unstable.......to avoid this problem is it sufficient to change the condition on K<0.002, or i have to do something else???

Thank you

12 Aug 2009 Three Dimensional Analytical Magnetic Resonance Imaging Phantom in the Fourier Domain This software contains 2D and 3D Shepp-Logan phantoms in both the image and Fourier domains. Author: Cheng Guan Koay Cheng Guan Koay

In the revised SampleTest.m, I used imtool and please make sure that you click on a menu that allows you to change contrast. min=0.0 and max=3.0 should be fine and these values should be applied to both imtool panels.

11 Aug 2009 Three Dimensional Analytical Magnetic Resonance Imaging Phantom in the Fourier Domain This software contains 2D and 3D Shepp-Logan phantoms in both the image and Fourier domains. Author: Cheng Guan Koay Cheng Guan Koay

Due the inconvenience of updating and commenting on the site, I have decided to only update the site with major releases.

The MATLAB codes that illustrate the steps needed to perform FFT on the k-space signals of the 3D Shepp-Logan phantom can be found in a revised version of SampleTest.m, which is located on my google site: http://sites.google.com/site/hispeedpackets/Home/shepplogan

Contact us