Hello,
Echo spacing is the time btw. the phase encoding steps (i.e. btw. the
K-space lines). You case seems to be a bit more complicated b/c it seems
to be a multi-echo sequence, but not an EPI.
In EPI:
- Number of Phase Encoding Steps = Echo Train Length
- 1 excitation pulse/slice
- TR = time btw. volumes
The basic equation is:
ES = TR/Number of Slices/Number of Phase Encoding Steps
So I suppose, your case is:
- TR = time btw. excitation pulses
- Echo Train Length = Number of Phase Encoding Steps btw. two
excitation pulses
The equation may be:
ES = Min TR/Echo Train Length
Does that sounds correct?
Auer, Tibor M.D. Ph.D.
Biomedizinische NMR Forschungs GmbH
am Max-Planck Institut für Biophysikalische Chemie
Am Fassberg 11
37077 Göttingen
Germany
Phone/Work: +49-(0)551-201-1725
Phone/Home: +49-(0)551-387-0076
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2010.08.05. 13:59 keltezéssel, Michael Roche írta:
> Hello,
> My query is in relation to calculating the echo spacing (ES) for use
> in distortion correction of DWI images using FUGUE. I am scanning with
> a 3T Philips Achieva which does not specify the ES and neither does
> the DICOM header file. I have asked the local Physicist and he is
> unsure on how to calculate the ES. The following are my acquisition
> parameters:
> Scanning Sequence: SE
> Slice thickness: 3mm
> TE: 76.56ms
> Number of Phase Encoding Steps: 80
> Echo Train Length: 47
> Pixel Bandwidth: 3295.2Hz
> Min TR: 849ms
> Calculating the ES has been causing me major problems so any help on
> this topic would be greatly appreciated. If anyone could outline the
> steps involved in calculating the ES that would be great. Feel free to
> suggest any parameters i may need to calculate the ES.
> Thanks
> Michael
