[Gate-users] Non-circular orbit in SPECT acquisition

[Gustavo COSTA]

_Hello GATErs,_ 

_ I'm trying to mimic a non-circular tomographic acquisition in GATE
meaning that I'll use the minimal detector/phantom distances that were
retrieved from real acquisitions._
_ I have 2 problems:_ 

_ 1 - Model different distances to each detector head._
_ 2 - Since I'm using a voxelized phantom from a DICOM image, it is a
cubic image and I get overlaps between the detector and the corner of
the voxel image made of air (because the detector rotates closely to the
phantom)._ 

_Any ideas how I could simulate that ?_ 
_You can see below what I have already tested and the errors I got._ 

_Thanks in advance_ 

_Problem #1_
_ - With the ring repeater it won't work because I should have different
distances for each detector head._ 
_ - The GenericRepeaterMove repeats the detector just as I need. It sets
different distances but it won't turn around the phantom (tomographic)._

_ So, my solutions for the moment is to use the genericMove with just
one detector head ( but rotating 360° instead of 180° )._ 

_Problem 2_ 
_ - Use of a tesselated volume. However, it has too many points since it
is DICOM image converted to stl. I had to kill the simulation after 4h
stuck in geometry initialization._ 
_ - Use of the hybrid navigator: the MergedVolumeActor. Surprisingly I
get a message of overlap. _ 
_   It works if using the number of particle as 100,000, but not beyond
that. Furthermore, when I use the setTimeSlice method with acquisition
values (0 s/40 s/2400 s) it doesn't work._ 
_   This is the message I get: _ 

-------- WWWW ------- G4Exception-START -------- WWWW -------
*** G4Exception : GeomNav1002
 issued by : G4Navigator::ComputeStep()
Track stuck or not moving.
 Track stuck, not moving for 10 steps
 in volume -patient_physVol- at point (-26.4331,-74.707,57.1845) (local
point (-0.0658974,0.488281,-0.94051))
 direction: (-0.761641,0.500866,0.411141) (local direction:
(-0.761641,0.500866,0.411141)).
 Potential geometry or navigation problem !
 Trying pushing it of 1e-07 mm ...Potential overlap in geometry!

*** This is just a warning message. ***
-------- WWWW -------- G4Exception-END --------- WWWW -------

 206 150 11.7 -33.8 0.208 0 1e-07 142 patient_physVol Transportation
 207 151 11.7 -34 0.208 0 0.995 143 patient_physVol Transportation
 208 152 11.7 -34.1 0.208 0 0.995 144 patient_physVol Transportation
 209 152 11.7 -34.1 0.208 0 0 144 patient_physVol Transportation
 210 152 11.7 -34.1 0.208 0 0 144 patient_physVol Transportation
 211 152 11.7 -34.1 0.208 0 0 144 patient_physVol Transportation
 212 152 11.7 -34.1 0.208 0 0 144 patient_physVol Transportation
 213 152 11.7 -34.1 0.208 0 0 144 patient_physVol Transportation
 214 152 11.7 -34.1 0.208 0 0 144 patient_physVol Transportation
 215 152 11.7 -34.1 0.208 0 0 144 patient_physVol Transportation
 216 152 11.7 -34.1 0.208 0 0 144 patient_physVol Transportation
 217 152 11.7 -34.1 0.208 0 0 144 patient_physVol Transportation

-------- WWWW ------- G4Exception-START -------- WWWW -------
*** G4Exception : GeomNav1002
 issued by : G4Navigator::ComputeStep()
Track stuck or not moving.
 Track stuck, not moving for 10 steps
 in volume -patient_physVol- at point (151.855,11.743,-34.1493) (local
point (0.488281,0.0242927,1.47574))
 direction: (0.981867,0.0434805,-0.184518) (local direction:
(0.981867,0.0434805,-0.184518)).
 Potential geometry or navigation problem !
 Trying pushing it of 1e-07 mm ...Potential overlap in geometry!

*** This is just a warning message. ***
-------- WWWW -------- G4Exception-END --------- WWWW -------

 218 152 11.7 -34.1 0.208 0 1e-07 144 patient_physVol Transportation
 219 153 11.8 -34.3 0.208 0 0.995 145 patient_physVol Transportation
 220 154 11.8 -34.5 0.208 0 0.995 146 patient_physVol Transportation
 221 154 11.8 -34.5 0.208 0 0 146 patient_physVol Transportation

              . 
              . 
              . 

_The simulations continues but, and after the 4th run the simulation is
aborted with the same message when using primary particles method with
primaries over 100,000, which is the following:_ 

terminate called after throwing an instance of 'std::out_of_range'
 what(): vector::_M_range_check: __n (which is 18446744073709551615) >=
this->size() (which is 1)
Aborted (core dumped) 

-- 
Gustavo COSTA

Doctorant
Centre de Recherches en Cancérologie de Toulouse
UMR 1037 INSERM/UPS
Team 15: Multi-resolution dosimetry for radiotherapy optimization
-------------- section suivante --------------
Une pièce jointe HTML a été nettoyée...
URL: <http://lists.opengatecollaboration.org/pipermail/gate-users/attachments/20170823/b6d3e018/attachment.html>