[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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