<div>Dear Kris and Claude,</div> <div>Thanks for your reply. As of now I am simulating CTI/Siemens scanner so I should be okay with using STIR reconstruction software.</div> <div>cheers</div> <div>Vandana </div> <div>  </div> <div>On 9/12/05, Kris Thielemans <<a href="mailto:kris.thielemans@csc.mrc.ac.uk">kris.thielemans@csc.mrc.ac.uk</a>> wrote: <blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid"> Hi Claude > > > An alternative way would be to let GATE write Interfile > headers that > > STIR can understand. This shouldn't be incredibly difficult, but I > > don't know of anybody who has plans in that direction. > > For now, the sinogram outputs (raw or ecat7) are only defined > for ECAT systems as the LOR-to-SinogramBIN conversion follows > the ECAT specifications. It means, in particular, that the > sinogram radial sampling is not uniform (arc effect) and > requires reconstruction routines that handle this specific > feature. If we can keep these ECAT specifications, it is > quite straightforward to convert an ECAT7 sinogram to an > Interfile sinogram (remove the binary headers and directory > matrices and write a separate ascii header file, plus byte > swapping for the raw data if needed). > You can keep ECAT conventions without changes. As an example, STIR contains a utility ifheaders_for_ecat7 which given an ECAT7 file, it cooks up an Interfile header that points towards the binary data in the ECAT7 file. Of course, this routine can only give correct scanner dimensions if the system_type is known. So, maybe a very ugly work-around would be to let GATE write an ECAT7 file (with some junk system_type), run ifheaders_for_ecat7 on the data, and then correct the scanner dimensions etc by hand. An alternative would be to write some extra code for GATE that essentially writes only the binary data of the sinogram (just as it would have done for ECAT7), but writes in addition a fairly simple text file (with the Interfile header). Unfortunately, I'm not volunteering. [In fact, all the stuff that we say is still correct for GE scanners (to the best of my knowledge, although this is limited...). The main difference between GE VOLPET and ECAT files is the order of the data and the different axial compression scheme. In essence, VOLPET uses span=3 for segment 0, and no axial compression (span=1) for all ring differences>1.] > An alternative, valid for all PET systems, would be to have > an "exact" rebining from the LOR to the sinogram (or > projection ) space <snip> > > Kris, do you think that such an output would be useful for > STIR ? Not necessary, no. In any case, you wouldn't want that for iterative reconstructions I think. Kris </blockquote></div>