The SimSET header does not contain the ring radius used for the binning. 
This is why we need to pass the scanner name to th eSTIR conversion routines. 
This is underdesirable (or even dangerous) however as
it relies on the user having match the SimSET and STIR scanner. 
We could get the ring radius from phg.rec.

The correspondence between the coordinate system between the SimSET scanner 
definition and STIR image needs to be documented better (currently only 
via the example files) image. The SimSET input image is constructed 
using coordinates obtained by list_image_info. Scanner
coordinates have currently to be set by hand. 
It needs to be tested what happens with non-standard number of planes in 
the image etc. (Definitely not the same as STIR which shifts to centre of image)
