I remember a post some time ago which tried to address the way Siemens does
interleaved acquisitions depending upon whether you have odd or even numbers
so slices. This is what I found with a quick search:
But check the follow up discussion
Hope this helps
Date: Wed, 5 Nov 2003 00:59:54 +0000
Reply-To: Daniel Kimberg <[log in to unmask]>
Sender: "SPM (Statistical Parametric Mapping)" <[log in to unmask]>
From: Daniel Kimberg <[log in to unmask]>
Subject: Re: Request for info about order of acquisition on a Siemens
Comments: To: Krish Singh <[log in to unmask]>
Krish Singh <[log in to unmask]> wrote: >Slices: 25 Axial slices.
Proscribed from inferior to superior. ... >1) Is it possible to determine
the order of slice acquisition (interleaved >etc.) from the Mosaic DICOM
files? > >2) failing that, what is the default order of acquisition for the
>epifid2d1_64 pulse sequence? Krish, hi. We had some back and forth on this
topic with the Siemens guys, and the upshot is that slice timing information
is discarded for mosaiced images. So barring some low level hacking of the
Siemens code (I can't remember when in the pipeline this information is
lost, but it was early enough that I punted on doing the hacking), you have
to fall back on option 2 (which makes me uncomfortable, but it's the best we
can do). I suspect if enough people ask, they'll patch this at some point.
They seem quite responsive and proactive about these kinds of things.
Incidentally, we have a trio here, but I believe without tremendous
justification this applies as well to other up-to-date Siemens systems.
Anyway, we checked on the slice order by acquiring non-mosaiced images via a
spin echo sequence, which someone assured us would have the same slice
order, and which are properly time stamped in the appropriate dicom fields.
Here is a list of when (ordinally) each slice is acquired, going from
inferior to superior (for axial acquisition). for odd number of slices
(example = 9) 0 2 4 6 8 1 3 5 7 for even number of slices (example = 8) 1 3
5 7 0 2 4 6 These are the ordinal indices of the slices, starting with the
most inferior. So for odd, the most inferior slice is acquired first. For
even, the most inferior slice is acquired second. Hope this helps! dan
> Dear all,
> Recently I get fMRI data from several subject. Unluckily I forgot scan
> order at that time. As for me, I have no chance to distinguish interleave
> scan from sequence scan from DICOM files.
> Thanks your help in advances
Department of Neurology [log in to unmask]
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