pmma material not found in CTDI_16cm_WaterAirPEBoneChambers.ppm

[xiaodonglu-gehc]

The "pmma" material in the ~\phantom\CTDI_16cm_WaterAirPEBoneChambers.ppm material list should be "PMMA", to match the material file name "PMMA" in the ~\material folder.
This is why the Sim_Sample_Analyic.py simulation is always broken in the Phantom_Analytic.py.
Update the CTDI_16cm_WaterAirPEBoneChambers.ppm "pmma" in the materialList to "PMMA" will solve this issue.

[MingyeWu]

Thank you for the finding!
Just fixed this issue in the repo, will update the PyPI gecatsim soon.