The problem of Stuck Track: potential geometry or navigation problem. Track stuck, not moving for 10 steps

Geometry, Fields and Transportation
1

Please fill out the following information to help in answering your question, and also see tips for posting code snippets. If you don’t provide this information it will take more time to help with your problem!

_Geant4 Version:_geant4-10-06-patch-03 (6-November-2020)
_Operating System:_Linux
Compiler/Version:(Ubuntu 9.4.0-1ubuntu1~20.04.2) 9.4.0
_CMake Version:_3.16.0

Hello everyone,
When I try to load a phantom in .h33 and .i33 format into GATE for simulation, I encounter the following issue. This problem occurs when I set the pixel size to 1x1x1 mm. However, if I set it to 2x2x2 mm, the issue does not occur. But my research requires the 1x1x1 mm resolution. Could anyone tell me how to solve this problem? I would be very, very grateful.

-------- WWWW ------- G4Exception-START -------- WWWW -------
*** G4Exception : GeomNav1002
issued by : G4Navigator::ComputeStep()
Stuck Track: potential geometry or navigation problem.
Track stuck, not moving for 10 steps.
Current phys volume: ‘phantom_ncat_physVol’

  • at position : (-14.34092508578862,4.707447542417131,23)
    in direction: (-0.5982347889668695,-0.7131925791212912,-0.3653374910354614)
    (local position: (0.1590749142113772,0.2074475424171309,-0.5))
    (local direction: (-0.5982347889668695,-0.7131925791212912,-0.3653374910354614)).
    Previous phys volume: ‘phantom_ncat_physVol’

Likely geometry overlap - else navigation problem !
*** Trying to get unstuck using a push - expanding step to 1e-07 (mm) … Potential overlap in geometry !

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

2

When the voxel size is reduced enough that the track experiences zero steps, a warning about a stuck track appears.

Since the problem encountered from Navigator therefore, in your GATE simulation, you can check
G4Navigator.CC and make following changes,

Step += 100*kCarTolerance;*

by

*Step += kCarTolerance*std::pow(10.,fNumberZeroSteps);

Ref.: Geant4.10: G4Navigator.cc Source File
[Look line 954.]

VRS

3

Thank you very much! I will try the method you suggested.