[Gate-users] Overlap between scanner geometry and Voxellized phantom

[Richard Taschereau]

Hi Bosky,

Overlapping volumes is a no-no in GATE/GEANT simulations.  I know some
people have worked around that problem by splitting their phantom in smaller
parts (you can have multiple voxellized phantoms).

Richard

On 5/15/08 8:48 AM, "Simon Stute" <gate.stute at gmail.com> wrote:

> Hi Bosky,
> 
> We encountered exactly the same problem and the problem comes from Geant4. As
> I know the particles are "born" in a certain volume (here the phantom) and
> they move to a second volume only when they reach a boundary of the first one,
> so even if the particles are both in the phantom (i.e. first volume) and the
> second one (overlapping, here your scanner), they behave as they are in the
> first one. And unfortunately there is no solution ... except to resize your
> phantom if it's possible ...
> 
> Cheers,
> Simon
> 
> On Thu, May 15, 2008 at 5:14 PM, Ravindranath, Bosky <bosky at bnl.gov> wrote:
>> Hello Gate users,
>> 
>> I'm using voxellized phantoms to test my scanner performance, however due to
>> the positioning of the scanner, there is bound to be overlapping regions
>> between the scanner and the image that is read in as the phantom. The regions
>> in the phantom that overlap with the scanner has material properties set to
>> vacuum. When I run my simulations, I do not see any gamma interactions with
>> the overlapping detector regions. Is there a way to work around this? I tried
>> to define the scanner as a daughter of the phantom, GATE did not allow me to
>> do that (I set the type as parameterized box matrix), I tried defining the
>> phantom first and then the geometry, but the result was the same.
>> 
>> Any suggestions appreciated.
>> Thank you,
>> Bosky
>> 
>> _______________________________________________
>> Gate-users mailing list
>> Gate-users at lists.healthgrid.org
>> http://lists.healthgrid.org/mailman/listinfo/gate-users
> 
> 
> 
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> 


-- 
Richard Taschereau, Ph.D.
Crump Institute for Molecular Imaging
University of California Los Angeles
700 Westwood Plaza, A222
Los Angeles, CA 90095-1770
Phone: (310) 825-0697
Fax:     (310) 206-8975
email: RTaschereau at mednet.ucla.edu



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