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MRI Forum
'Velocity'
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Cristobal Bertoglio

Mon. 1 Aug.16,
21:59

[Start of:
'PCMRI'
0 Reply]


 
  Category: 
General

 
PCMRI
Hi everybody

I am curious to understand a bit better what the formula that it is used in PCMRI for relating the change of phase and the velocity assume ...

As far I have unterstand that it is assumed the phase of a moving particle can be measured at two time instants, i am right? Does this not assume we can "track" the particle? Does this not "contradict" the fact that we can only compare phases that we measure at the same fixed place?

Thanks,

C.
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Pim vanOoij

Thu. 19 Mar.09,
09:58

[Reply (2 of 3) to:
'PCA aliasing problem'
started by: 'Pim vanOoij'
on Fri. 27 Feb.09]


 
  Category: 
Artifacts

 
PCA aliasing problem
This is not spatial aliasing I am talking about, but velocity aliasing. This means that when your velocity encoding parameter is set to 100 cm/s and true velocity in a certain pixel is 120 cm/s, the measured velocity will be -80 cm/s.

In my problem however, with a velocity encoding parameter of 100 cm/s, in certain pixels I measure a velocity of around -60 cm/s where an actual velocity of 40 cm/s exists, which is a real mystery to me.

I don't think increasing FOV will prevent this from happening. Maybe it has something to do with velocity aliasing in other parts of the FOV, where true flow velocity of 110-120 cm/s exists, but I wouldn't know why. Anyone? Thanks.
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Pim vanOoij

Fri. 27 Feb.09,
15:27

[Start of:
'PCA aliasing problem'
2 Replies]


 
  Category: 
Artifacts

 
PCA aliasing problem
Hi everyone,

Has anybody who reads this ever encountered aliasing in phase contrast measurements in pixels where velocity did not exceed Venc? If so, could this be due to signal leakage of surrounding vessels? Thanks for your help!

Pim
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