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'Sampling'
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Martin Rosellen

Wed. 19 Oct.16,
15:30

[Start of:
'k space explanation'
2 Replies]


 
  Category: 
General

 
k space explanation
dear all,
I am trying to get a feel for what k-space is. So far I have not got an explanation that I understand. My idea to picture the frequencies that get emmitted from a slice as follows: - We have a box filled with still waterrn - a set of objects get dropped into the water simultaneously - every object emmits waves that are specific to its shape. To fill k space, what is measured and how? All I know is that the sampling frequency stays the same. Sorry for the ugly formatting. Did not find help on that. Thanks Martin
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peter hobden

Wed. 14 Feb.07,
15:35

[Reply (1 of 3) to:
'Geometric distortion'
started by: 'ergun ahunbay'
on Tue. 2 Jan.07]


 
  Category: 
Artifacts

 
Geometric distortion
Dear Listers,

I have some questions about the image distortions in MRI:

1) Are the magnetic field inhomogeneities the only cause of image distortions? Does RF-inhomogeneities cause distortions or just signal inaccuracies?

There are other factors that can affect the /amount/ of distortion. Run an EPI sequence and change the bandwidth and see the image change shape.

There are other causes of image distortion which are not necessarily directly related to field homogeneity.

It is a complicated question you are asking here!


2) Is it accurate to say that a spiral sequence would not have distortion due to magnetic field inhomogeneity(, but it would have blurring). Would there be image geometric distortions with a spiral imaging?


I guess you are talking about spiral filling of k-space?? The sampling time reduction will help to reduce distortion to some extent.
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