[Gate-users] Strange Dose Profiles

[Christopher Watanabe]

Hello Ashok,

I've attempted the corrections you suggested and am still measuring a dose
orders of magnitude above what you measured. Please take a look at the
attached code:

*1) My source file - *

#-------------------oooooOOOOO00000OOOOOooooo---------------------#

# Example of a radioactive seed within water sphere
# Output is a 3D dose distribution map (with associated
# uncertainty) and map of producted C11.

#-------------------oooooOOOOO00000OOOOOooooo---------------------#


#=====================================================
# VERBOSE and VISUALISATION
#=====================================================

# /control/execute mac/verbose.mac

# to use the visualisation :
#   - uncomment the following line
#   - use Gate --qt
#   - in the interface, type /control/execute mac/main.mac

# /control/execute mac/visu.mac


#=====================================================
# GEOMETRY
#=====================================================

/gate/geometry/setMaterialDatabase                 data/GateMaterials.db

# WORLD
/gate/world/setMaterial                      Air
/gate/world/geometry/setXLength              150 mm
/gate/world/geometry/setYLength              150 mm
/gate/world/geometry/setZLength              150 mm

# WATERSPHERE
/gate/world/daughters/name                   target
/gate/world/daughters/insert                 sphere

#/gate/target/setMaterial                     Lead
#/gate/target/setMaterial                     Tungsten
#/gate/target/setMaterial                     Copper
#/gate/target/setMaterial                     Water
#/gate/target/setMaterial                     Air
/gate/target/setMaterial                     Vacuum
/gate/target/geometry/setRmin                0 mm
/gate/target/geometry/setRmax                125 mm
/gate/target/geometry/setPhiStart            0 deg
/gate/target/geometry/setDeltaPhi            360. deg
/gate/target/geometry/setThetaStart          0 deg
/gate/target/geometry/setDeltaTheta          360. deg
/gate/target/vis/forceWireframe
/gate/target/vis/setColor                    blue

#=====================================================
# PHYSICS
#=====================================================

/gate/physics/addPhysicsList QGSP_BERT_HP_EMY
/gate/physics/addPhysicsList emstandard
/gate/physics/addProcess RadioactiveDecay

/gate/physics/addProcess Bremsstrahlung e-
/gate/physics/processes/Bremsstrahlung/setModel StandardModel e-

/gate/physics/addProcess MultipleScattering e-

/gate/physics/addProcess Compton
/gate/physics/processes/Compton/setModel StandardModel

/gate/physics/displayCuts
/gate/physics/print output/physics.txt


# ----------------------------------------------------
# the following actor stores 3D distributions of
# dose/edep/uncertainty/nbHit into files (mhd image file format)

/gate/actor/addActor                               DoseActor
doseDistribution
/gate/actor/doseDistribution/save                  output/P32_Vacuum.mhd
/gate/actor/doseDistribution/attachTo              target
/gate/actor/doseDistribution/stepHitType           random
/gate/actor/doseDistribution/setSize               250 250 250 mm
/gate/actor/doseDistribution/setPosition           0 0 0 mm
/gate/actor/doseDistribution/setVoxelSize          .5 .5 .5 mm
#/gate/actor/doseDistribution/setResolution         500 500 500        *(Note
that this Resolution line is commented out, as otherwise Gate throws an
error)       *
/gate/actor/doseDistribution/enableEdep            false
/gate/actor/doseDistribution/enableUncertaintyEdep false
/gate/actor/doseDistribution/enableDose            true
/gate/actor/doseDistribution/enableSquaredDose     false
/gate/actor/doseDistribution/enableUncertaintyDose false
/gate/actor/doseDistribution/enableNumberOfHits    true
/gate/actor/doseDistribution/saveEveryNSeconds     60


#=====================================================
# INITIALISATION
#=====================================================

/gate/run/initialize

#=====================================================
# BEAMS
#=====================================================

# Ph 32 source
/control/execute mac/betaP32.mac

#=====================================================
# START BEAMS
#=====================================================

/gate/random/setEngineName MersenneTwister
/gate/random/setEngineSeed auto
/gate/application/setTotalNumberOfPrimaries 10E5
/gate/application/start


*2) My mac file defining the P32 source as a simple mono energy beta source
(I am still rather uncertain as to how to generate a discrete source...)*

#Description of Phosphorus 32 beta source

# Add beta source

/gate/source/addSource P32_beta gps
/gate/source/P32_beta/setActivity 30000. Bq
/gate/source/P32_beta/gps/particle e-
/gate/source/P32_beta/gps/energy 1.709 MeV
/gate/source/P32_beta/gps/hist/type energy
/gate/source/P32_beta/setForcedUnstableFlag true
/gate/source/P32_beta/setForcedHalfLife 1232755 s

# /gate/source/P32_beta/gps/hist/point 0 0.0
/gate/source/P32_beta/gps/position 0 0 0 cm
/gate/source/P32_beta/gps/shape Sphere
/gate/source/P32_beta/gps/radius 0.012 mm

# Set angular distribution of beta emission
/gate/source/P32_beta/gps/angtype iso


Thank you for your assistance,

Chris


On Thu, Jan 24, 2019 at 5:01 PM Ashok Tiwari <tiwarias at yahoo.com> wrote:

> Hi Chris,
>
> First, it would be easy for us if you copy-paste the part of your macro
> instead of attaching images.
>
> Size of the dose actor is different than the size of the spherical phantom
> (say target according to your macro), but you have to set the size of actor
> (setSize parameter) is equal to size of sphere, so that you can store all
> the dose informations up to the boundary of the sphere. Therefore, diameter
> of spherical volume would be equal = Resolution of matrix * voxel size. In
> other words, setSize of dose actor = resolution * voxel size.
>
> Yes, we need to attach dose actor to the center of spherical volume. You
> did it correctly.
>
> Your dose actor seems ok. Now, you can check:
> 1. the radius of the sphere, I suggest you to put 125 mm as its radius
> (0.5*500=250, 250/2=125)
> 2. Source: use discrete spectrum of P-32 beta emitter
> 3. You may want to save your dose matrix at every 60 seconds instead 20 to
> lessen the simulation time
> 4. One more important thing: if you want to have particle interaction in
> each voxel volume (many authors defined this volume as a dosel) then set
> step size as 0.5 mm and activate the step limiter parameter.
>
> Try these things, if these does not work then send me your main macro, I
> will take a look.
>
> Thanks,
> Ashok
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