[Gate-users] TPS Pencil Beam Source setting
张晖
zhanghui at impcas.ac.cn
Tue May 19 10:19:21 CEST 2020
Dear Gate Users:
I previously used Pencil Beam Source to simulate single-energy pencil beam for carbon-ion therapy. The features of the pencil beam source such as spot size, divergence and beam emittance were defined as follows: 3 mm spot size in both x and y directions, 4 mrad divergence and 15 mm·mrad beam emittance. The energy spread was set to 0.1% of the respective energy. Except for dipole scanning magnets,vacuum pipe and window, main and sub-dose monitors, a multi-strip ionization chamber (IC) and a mini ridge filter were modeled in my MC simulations. The source position was located before the vacuum window and a water box was located at isocenter.
#################Pencil Beam Source########################################
# SOURCE PBS
/gate/source/addSource C12 PencilBeam
#particle type
/gate/source/C12/setParticleType GenericIon
/gate/source/C12/setIonProperties 6 12 6 0
#energy spectrum
/gate/source/C12/setEnergy 2687.52 MeV
/gate/source/C12/setSigmaEnergy 2.68752 MeV
#position
/gate/source/C12/setPosition 0 0 -1.4059 m
# spot size
/gate/source/C12/setSigmaX 3 mm
/gate/source/C12/setSigmaY 3 mm
#divergence
/gate/source/C12/setSigmaTheta 4 mrad
/gate/source/C12/setSigmaPhi 4 mrad
#emittance
/gate/source/C12/setEllipseXThetaEmittance 15 mm*mrad
/gate/source/C12/setEllipseYPhiEmittance 15 mm*mrad
#positive-> converging beam; negative diverging beam
/gate/source/C12/setEllipseXThetaRotationNorm positive
/gate/source/C12/setEllipseYPhiRotationNorm positive
Now, I want to use TPS Pencil Beam Source to simulate realistic treatment plan for carbon ion therapy. In Source-properties.txt file, it contains 8 polynomial equations, each equation being a function of the energy at the nozzle entrance.
#################TPS Pencil Beam Source-Source-properties########################################
# Source properties
# Nozzle exit to Isocenter distance
1405.9
# SMX to Isocenter distance
4000
# SMY to Isocenter distance
4000
# ENERGY
# mean energy
# polynomial order
1
# polynomial parameters (highest to lowest)
1
0
# energy spread
# polynomial order
percent
1
# polynomial parameters (highest to lowest)
0.001
0
# SPOT x y theta phi
# x
# polynomial order
1
# polynomial parameters
0
3
# Theta
# polynomial order
1
# polynomial parameters
0
0.004
# y
# polynomial order
1
# polynomial parameters
0
3
# Phi
# polynomial order
1
# polynomial parameters
0
0.004
# SPOT emmittances
# x-theta emmittance
# polynomial order
1
# polynomial parameters
0
0.015
# y-phi emmittance
# polynomial order
1
# polynomial parameters
0
0.015
#################TPS Pencil Beam Source-PlanDescriptionToGate########################################
#TREATMENT-PLAN-DESCRIPTION
#PlanName
IMPT
#NumberOfFractions *** CURRENTLY THIS VALUE IS NOT USED ***
1
##FractionID *** CURRENTLY THIS VALUE IS NOT USED ***
1
##NumberOfFields
1
###FieldsID
1
#TotalMetersetWeightOfAllFields *** CURRENTLY THIS VALUE IS NOT USED ***
662421
#FIELD-DESCRIPTION
###FieldID
1
###FinalCumulativeMeterSetWeight *** CURRENTLY THIS VALUE IS NOT USED ***
336732
###GantryAngle (in degrees)
0
###PatientSupportAngle *** CURRENTLY THIS VALUE IS NOT USED ***
0
###IsocenterPosition *** CURRENTLY THIS VALUE IS NOT USED ***
0 0 0
###NumberOfControlPoints
1
#SPOTS-DESCRIPTION
####ControlPointIndex
0
####SpotTunnedID *** CURRENTLY THIS VALUE IS NOT USED ***
0
####CumulativeMetersetWeight *** CURRENTLY THIS VALUE IS NOT USED ***
0
####Energy (MeV)
2687.52
####NbOfScannedSpots
1
####X Y Weight (spot position at isocenter in mm, with weight in MU (default) or number of ions "setSpotIntensityAsNbIons true")
0 0 100
I simulated the same energy beam in my PlanDescriptionToGate.txt file and the spot position is at isocenter. However, I find that the dose distributions with these two sources in water box were different. I'm puzzled about the parameter settings in TPS Pencil Beam Source if I want to make them consistent with those in Pencil Beam Source settings. How can I do?
Best regards,
Hui Zhang
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