[Gate-users] S-values simulation
Ashok Tiwari
tiwarias at yahoo.com
Wed Feb 10 17:59:40 CET 2021
Hi Maria,
I would check the source spectrum. I think the endpoint energy of Y90 beta is 2.28 MeV and is not listed in your source spectrum. Lanconelli et al used the decay data from the Brookhaven National Laboratory database (www.doseinfo-radar.com, RADAR), so check whether you use the same source spectrum for a fair comparison. Have you only used a beta spectrum in simulation, not photon emission x-rays, gammas, and Auger electrons? And a similar value of range or energy cuts?
Regards, Ashok On Wednesday, 10 February 2021, 10:30:50 am GMT-6, Maria Inês Ribeiro <mid.ribeiro at campus.fct.unl.pt> wrote:
Hello 陈戈飞 and Ashok,
I tried my best to implement your suggestions (thank you sooo much). I found reasonable s-values comparing to the one indicates at medphys.itFor example, my center voxel s-value is of 4.5 mGy/(MBq s) and theirs is 3 mGy/(MBq s).
However, 2 things seem a bit strange:
1) when I load the dose map at MATLAB, I get a lot of zeros in the border voxels of my kernel. I am using a 11x11x11 kernel, each with 2,21 mm. This is not supposed to be happening.
2) The values are a bit different from the reference values. Do you know if the source should have any additional spectrums that I should worry about? anyway if I add more spectrums, the dose will only increase, which is not good....
A simulates my source as follows:
/gate/source/addSource Y90Source
/gate/source/Y90Source/setActivity 1 MBq
/gate/source/Y90Source/gps/particle e-
/gate/source/Y90Source/gps/energytype Arb
/gate/source/Y90Source/gps/hist/type arb
/gate/source/Y90Source/gps/hist/point 0.0571 0.0426
/gate/source/Y90Source/gps/hist/point 0.1713 0.0518
/gate/source/Y90Source/gps/hist/point 0.2855 0.0594
/gate/source/Y90Source/gps/hist/point 0.3997 0.0649
/gate/source/Y90Source/gps/hist/point 0.5139 0.0686
/gate/source/Y90Source/gps/hist/point 0.6281 0.0708
/gate/source/Y90Source/gps/hist/point 0.7423 0.0717
/gate/source/Y90Source/gps/hist/point 0.8565 0.0715
/gate/source/Y90Source/gps/hist/point 0.9707 0.0704
/gate/source/Y90Source/gps/hist/point 1.0849 0.0685
/gate/source/Y90Source/gps/hist/point 1.1991 0.0657
/gate/source/Y90Source/gps/hist/point 1.3133 0.0619
/gate/source/Y90Source/gps/hist/point 1.4275 0.0569
/gate/source/Y90Source/gps/hist/point 1.5417 0.0507
/gate/source/Y90Source/gps/hist/point 1.6559 0.0430
/gate/source/Y90Source/gps/hist/point 1.7701 0.0342
/gate/source/Y90Source/gps/hist/point 1.8843 0.0246
/gate/source/Y90Source/gps/hist/point 1.9985 0.0150
/gate/source/Y90Source/gps/hist/point 2.1127 0.00643
/gate/source/Y90Source/gps/hist/point 2.2269 0.00113
/gate/source/Y90Source/gps/hist/inter Lin
/gate/source/Y90Source/gps/pos/type Point
/gate/source/Y90Source/gps/angtype iso
/gate/source/Y90Source/setForcedUnstableFlag true
/gate/source/Y90Source/setForcedHalfLife 230760. s
Thank you so much for your help again!
Maria
Ashok Tiwari <tiwarias at yahoo.com> escreveu no dia terça, 9/02/2021 à(s) 16:49:
Hi Maria,
You could start a simulation by setting a total number of primaries instead of time. Based on my experience with GATEv8.1, the transport of 20 million particles was found to provide sufficient statistical precision. See details in: The Impact of Tissue Type and Density on Dose Point Kernels for Patient-Specific Voxel-Wise Dosimetry: A Monte Carlo Investigation | Radiation Research | Allen Press
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The Impact of Tissue Type and Density on Dose Point Kernels for Patient-...
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Also, I recommend using ~1 keV energy cuts in dose point kernel simulations. Cuts can be set by using:
/gate/physics/Gamma/SetCutInRegion world ... mm/gate/physics/Electron/SetCutInRegion world ... mm
/gate/physics/Gamma/SetCutInRegion my_phantom ... mm /gate/physics/Electron/SetCutInRegion my_phantom .. mm
Another important thing is an steplimiter, you could set it by using:
/gate/physics/SetMaxStepSizeInRegion my_phantom ... mm/gate/physics/ActivateStepLimiter e-
All other infos are described in the paper.
Regards,Ashok
On Tuesday, 9 February 2021, 09:19:23 am GMT-6, Maria Inês Ribeiro <mid.ribeiro at campus.fct.unl.pt> wrote:
Thank you so much.
It was supposed to be 100000 s. I just killed the simulation because it was taking too long. I swapped to the normal ion source definition since fastY90 can't be used for dosimetry.
Do you recommend decreasing cut energy for photons and electrons?
Kind regards, Maria
陈戈飞 <xiaofeizaina at 126.com> escreveu no dia terça, 9/02/2021 à(s) 15:13:
Hi maria
The total time of your simulations is 10000s，right? If so, you only need to multiply by 1000(Gy->mGy) and divide 10000(time to 1s).
And I recommend setting cut energy for beta and photon. Default is 10 mm.
You'd better recheck the definition of fastY90. It can't be used for dose purposes.
Thank you
| | 陈戈飞 邮箱：xiaofeizaina at 126.com |
签名由 网易邮箱大师 定制
On 02/09/2021 22:38, Maria Inês Ribeiro wrote:
Hi everyone,
I am attempting to compute a dose point kernel in soft tissue for a point source of Y90. I am using the fastY90 with an activity of 1 MBq. I then ran 40.000 slices of 1 second and stored the dose.
My question is how do I convert my dose map (Gy) into the s values (mGy/(MBq.s)) for each voxel?
Here is my could in case it could help to support my question:
#===============================================================================
# GEOMETRY
#===============================================================================
/gate/geometry/setMaterialDatabase data/GateMaterials.db
#WORLD ======================================
/gate/world/setMaterial Air
/gate/world/geometry/setXLength 50 mm
/gate/world/geometry/setYLength 50 mm
/gate/world/geometry/setZLength 50 mm
#LIVER ======================================
/gate/world/daughters/name liverPhantom
/gate/world/daughters/insert box
/gate/liverPhantom/setMaterial Liver
/gate/liverPhantom/geometry/setXLength 24.31 mm
/gate/liverPhantom/geometry/setYLength 24.31 mm
/gate/liverPhantom/geometry/setZLength 24.31 mm
#===============================================================================
# PHYSICS
#===============================================================================
/gate/physics/addPhysicsList emstandard_opt3
#===============================================================================
# DETECTORS
#===============================================================================
#DOSE ACTOR ==============================
#builds 3D images of:
# - the energy deposited (edep in MeV)
# - dose deposited (Gy)
# - the number of hits in a volume
/gate/actor/addActor DoseActor VSV
/gate/actor/VSV/attachTo liverPhantom
/gate/actor/VSV/stepHitType random
/gate/actor/VSV/setSize 24.31 24.31 24.31 mm
/gate/actor/VSV/setPosition 0 0 0 cm
/gate/actor/VSV/setResolution 11 11 11
/gate/actor/VSV/enableEdep true
/gate/actor/VSV/enableUncertaintyEdep true
/gate/actor/VSV/enableSquaredEdep true
/gate/actor/VSV/enableDose true
/gate/actor/VSV/enableUncertaintyDose true
/gate/actor/VSV/enableSquaredDose true
/gate/actor/VSV/enableNumberOfHits true
/gate/actor/VSV/save output/VSV.mhd
#SIMULATION STATISTIC =====================
#this actos counts the number of steps, tracks, events, runs in the simulation
/gate/actor/addActor SimulationStatisticActor stat
/gate/actor/stat/save output/stat-VSV.txt
/gate/actor/stat/saveEveryNSeconds 60
#===============================================================================
# INITIALISATION
#===============================================================================
/gate/run/initialize
/gate/random/setEngineName MersenneTwister
/gate/random/setEngineSeed auto
#===========================================================
# SOURCE
#===========================================================
# fastY90
/gate/source/addSource y90 fastY90
/gate/source/y90/setActivity 1. MBq
#=====================================================
# START
#=====================================================
/gate/application/setTimeSlice 1. s
/gate/application/setTimeStart 0. s
/gate/application/setTimeStop 1000000. s
/gate/application/start
Thanks a lot for your attention,
Maria Inês
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