[gate-users] record hits within block but outside crystals? attach multiple daghters to ecat crystal level?

Claude Comtat comtat at ieee.org
Wed Sep 22 13:45:42 CEST 2004

Dear Paul

1) To my understanding, if a volume is defined as a PhantomSD, like a 
detector block, you can not define its daughters, like the crystals, as 
a CrystalSD. What you can do, but this is more complex, is to defined 
your material, like the reflector, as a daughter of the block, in 
addition to the crystals, and then shape it such as it fits exactly 
between the crystals, without overlapping (the reflector and the crystal 
will be at the same level, both daughters of the block). Then, you 
can define the crystal as a crystalSD and the reflector as a phantomSD 
(in the same way as in the PET benchmark, where the septa are daughters 
of the heads (rsector) and phantomSD, and the crystals grand-daughters 
of the head and crystalSD).

Yes, with the ecat system, each logical level (block or crystal) can 
only be associated with one physical volume. Only the cylindricalPET 
system allows to have several physical volumes associated with the 
logical level "layer" (layer0, layer1, ...). If you want define two 
layers side-by-side, you can try to define them first up/down and then 
rotate the crystal. I guess it should work. As a general remark, when 
you have a geometry or a logical hierarchy that does not fit easily with 
a predefined system, it is not very difficult to define within GATE a 
new system. Of course, it requires to go inside the code, but you can 
just duplicate an already existing system (like cylindricalPET or ecat) 
and modify it. I did it for the ecat system (modification of the 
cylindricalPET system) and it did not take more than 3 days to do the 
coding, with some help from the core developers. If you want to do this, 
we can tell you which classes (files) you need to copy and modify, and 
how to add a new system.

Hope this helps,


Paul Vaska wrote:

> Hello,
> I've carefully read the well-written Users Guide, but I still have a few 
> detailed questions.
> 1) It looks like typically the crystals are assigned with 
> attachCrystalSD and phantoms with attachPhantomSD and any interactions 
> in these are recorded as hits.  What about the material outside the 
> crystals, but within the block (such as casing, reflector, ...)?  I 
> would like to keep track of any interactions here as well, but these 
> seem to fall through the cracks in your definitions?  Can I add the 
> block itself with attachCrystalSD or attachPhantomSD, or will this 
> confuse the program because the block overlaps with the crystals which 
> have already been made sensitive?
> 2) I'm trying to use the ecat system because it has convenient sinogram 
> binning functions, but my detector blocks are not symmetric enough to 
> use the cubicArray repeater.  So I divided my block into 2 sets of 
> crystals which can be created with this repeater, but I'm having trouble 
> attaching both sets to the crystal level within the ecat system - an 
> error message implies that you can't attach more than one daughter to 
> the crystal level.  If I instead use the cylindricalPET system, I 
> suppose I could use the layer0 and layer1 levels for this (even though 
> they are side-by-side and not actually layered)?   Since layer0 and 
> layer1 are at the same depth, will they be treated the same by the adder 
> module and as part of one block by the readout module?
> Thanks for any help.
> Paul
> Paul Vaska, Ph.D.
> Medical Department, Building 490
> Brookhaven National Laboratory
> Upton, NY 11973
> vaska at bnl.gov (631)344-6228 fax:(631)344-5311
> _______________________________________________
> gate-users mailing list
> gate-users at lphe1pet1.epfl.ch
> http://lphe1pet1.epfl.ch/mailman/listinfo/gate-users

Claude Comtat					comtat at ieee.org
Image acquisition and processing group		tel: +33 1 69 86 77 02
Frédéric Joliot Hospital Facility		fax: +33 1 69 86 77 49
French Atomic Energy Commission 		www-dsv.cea.fr/shfj

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