[gate-users] hot sources in a background activity problem

Erick Mora emoravia at yahoo.com
Fri May 12 20:17:40 CEST 2006

Hello Guys,

I am simulating phantom with similar dimensions such
as the PET Phantom-NEMA 1994. This main phantom has
three inserts, one solid and two fillable.

I want to place water in the main phantom with some
activity (to create background activity). In the two
inserts I want to fill both with water and each one
with different activities (1:3, 1:4 comparing with the
background activity).

Also I create three shells, these ones are made of
PMMA and are to create a real barrier between the
water in the main phantom and the inserts.
The main phantom is the cylinder0 who contain the
background activity. The three inserts are cylinder1,
2 and 3 (These are daughters of the main one).
Cylinders 2 and 3 have one daughter each these
daughters contain the activity in each cylinder. All
these cylinders are contained into the shells.

All shells are cylinders (regarding the example for
the NEMA-NU2 given in the user's reference material),
these cylinders are going to be replace it by the
water contained in the source inserts (the cylinders)
because these source inserts have a small radius
comparing with the shells.

My source is 131I, so I have 12 sources to simulate
the 4 main energy emissions.
All structures have been generated very well; there
are no overlaps between them. All physics is ok and
for all sources there are no overlaps againg comparing
with the cylinders.

I am using the "confine" command to confine the source
into the daughter (cylinder0,2,3) but at the end Gate
is prompting a message:

"LoopCount = 100000 

Either the source distribution >> confinement or any
confining volume may not overlap with the source
distribution or any confining volumes may not exist"
If you have set confine then this will be ignored for
this event."

Also I remove cylinder2 and 3 and I'm just keeping the
background activiy and it is working... 

I remove the background activity (I just didn't add
the sources) and keeping the cylinder2 and 3, and it
is not working....

I don't have any clue in order to see what is going

If you can give me a hand, I will really appreciate.

Best regards, 

                Erick Mora Ramirez 
Master in Medical Physics from University College London (UCL)
  Address: University College Hospital, Institute of Nuclear Medicine
                235 Euston Road, NW1 2BU, London
                United Kingdom

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