Editing STIR FAQ (section)

=Projection data (aka sinograms) related FAQs=
== How to display information about projection data==
You can use '''list_projdata_info'''. run it without arguments first to see what options
are available.

== How to display projection data generated by STIR (or your scanner)? ==
STIR comes with very basic utilities called '''manip_projdata''' and '''display_projdata''' that can display sinograms or viewgram, but this
is really only useful for a quick check (or to see if STIR did read your data as expected). Your best option is
to use an external display program.

To do this, use the '''extract_segments''' utility. This will write each ''segment'' in the projection data to a different file as a 3D volume. Currently,
this is written in a version of the Interfile format. See the [[#Image related FAQs]] FAQ how to display volume.

==How are projection data organised?==
Please check the [http://stir.sourceforge.net/documentation/STIR-glossary.pdf STIR glossary, available via the STIR website] for information.

== What is the difference between default bin size and effective central bin size (e.g. in the .hs Interfile header)? ==
The "default bin size" is only used when doing arc-correction ("geometric correction" in GE language). This is normally only used when you use FBP (or when you use arc-correction with <tt>correct_projdata</tt>).

The "effective central bin size" is really only used by STIR for arc-corrected data. It is then the bin-size that will be used by the projectors, so should be the "true" bin size. (Of course, if you've asked STIR to do the arc-correction, it will normally be equal to the "default bin size", but you can ask STIR to use a different bin size for arc-correction).
 
For non-arccorrected data, the "effective central bin size" is usually a bit larger than the "default", but this is manufacturer dependent. In any case, for non-arccorrected data, its value is ignored by STIR.