[Gate-users] Dose Calculation interface problem?

[Theodora Kostou]

Dear GATE users, 

 I am trying to use GATE to calculate the effect of a nanoparticle on
the depth-dose curve in radiation therapy. As I was getting incorrect
results, I scaled up the problem in order to eliminate possible
nano-effects. However, even at the mm level, the problem still persists.


 It seems to me that there is a problem with geometrical interfaces. Any
help would be appreciated. 

 Here is the setup: 

 The phantom is a box of water, 20x20x20 mm3 in size. It is irradiated
by a 2x2 mm2 square source emitting monoenergetic 140.5 keV photons,
placed 2 mm outside the phantom (The small sizes of the phantom and the
source are necessary in order to achieve good statistics when a
nanoparticle is inserted in the phantom). Dose is scored in a
200x200x200 matrix. Each voxel is 0.1x0.1x0.1 mm3. 

 Then, I add a 2mm thick layer of water, placed 5 mm below the surface
of the phantom, i.e inside the phantom. The depth-dose curve now
exhibits two sharp peaks at the location of the interfaces of the water
layer and the water phantom (at 4 and 6 mm). 

 The simulations were run on the VIP platform using GATE v6.2. To narrow
down the causes I turned off all physical processes, except the Compton
effect. 

 Since physically nothing has changed - we are still dealing with a cube
of water - I suspect that the cause of the problem is the mere
introduction of a new geometrical volume. 

 Has anyone ever encountered this problem? What are the solutions? 

 Thank you, 
Theodora 
 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.opengatecollaboration.org/pipermail/gate-users/attachments/20170811/a1e207db/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Depth_Dose_With_Layer.pdf
Type: application/pdf
Size: 4115 bytes
Desc: not available
URL: <http://lists.opengatecollaboration.org/pipermail/gate-users/attachments/20170811/a1e207db/attachment-0002.pdf>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: file-2400204510890.zip
Type: application/octet-stream
Size: 6258 bytes
Desc: not available
URL: <http://lists.opengatecollaboration.org/pipermail/gate-users/attachments/20170811/a1e207db/attachment-0002.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Depth_Dose_Water_Only.pdf
Type: application/pdf
Size: 3995 bytes
Desc: not available
URL: <http://lists.opengatecollaboration.org/pipermail/gate-users/attachments/20170811/a1e207db/attachment-0003.pdf>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: file-5214221658736.zip
Type: application/octet-stream
Size: 6257 bytes
Desc: not available
URL: <http://lists.opengatecollaboration.org/pipermail/gate-users/attachments/20170811/a1e207db/attachment-0003.obj>