Hi Mark,
Thanks for the reply.
>Yep, all prelude does is unwrap phase images, it doesn't subtract them.
>Hence the input to fugue requires the two phase images so that it can
>find the difference, scale them, regularise them, etc. So the only useful
>phase maps or field maps to look at are outputs from fugue, not from
>prelude. And if you have separate phase images then they need to
>be combined before going into fugue (until I get around to allowing a
>more flexible input). Sorry for the confusion.
This still isn't quite clear to me. Our physicist wrote a program to do the following:
1. Acquire 2 gradient echos with a 10ms interval and
2. Determine how much phase has been acquired during those 10ms
As I understand it, this gives you the "phase map" and its intensity is proportional to
the inhomogeneity in the field. In fact, the output of his program looks a lot like the
phase maps that you guys have shown at the FSL course.
The input to Prelude is two images: one giving the phase and one giving absolute
values. The output is a real, unwrapped phase image.
So, why would there be two images as the input of Fugue when there is one image
as the output of Prelude? When you talk about the "two phase images", are you
referring to the two gradient echos? Is Fugue looking for real, imaginary, or complex
input as the <unwrapped phase map>?
thanks a lot,
jack
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