[Gate-users] How to convert Dose per Particle to Gy in Phantom Voxels

[Mery MB]

*Hi Dear Gate User*


*I simulated a medical linac and calculated dose in a voxelized phantom
(h33,i33 format of Rando Phantom) with the dose actor which I written below*

/gate/actor/addActor
DoseActor meshdose
/gate/actor/meshdose/save
output1/Randodose.hdr
/gate/actor/meshdose/attachTo                              phantom
/gate/actor/meshdose/stepHitType                         random
/gate/actor/meshdose/setSize                                652 362 872 mm
#/gate/actor/meshdose/setResolution                   326 181 436
/gate/actor/meshdose/setVoxelSize                      2 2 2 mm
/gate/actor/meshdose/enableEdep                        true
/gate/actor/meshdose/enableUncertaintyEdep     true
/gate/actor/meshdose/enableSquaredEdep         true
/gate/actor/meshdose/enableDose                       true
/gate/actor/meshdose/enableUncertaintyDose     true
/gate/actor/meshdose/enableSquaredDose         true
/gate/actor/meshdose/saveEveryNSeconds         60


*I want to convert dose in each voxel to Gy. *
*As I read in Gate Manual the dose in voxel should be in Gy.*
""The output file is a binary file (number format is 4 bytes float)
containing the absorbed dose in cGy. It has the same dimensions as the
phantom. The output module optionally writes a second binary file
containing the uncertainty on absorbed dose expressed as a fraction between
0 and 1.""

*but the numbers which I obtained for each voxel inside fields and outside
fields are in orders of 10 to power of -5 and 10 to power of -7,
respectively. based on the number it should not be in Gy!!! So I want to
convert them to Gy and compare them with the TPS result for inside fields
voxels..*

*My first question is: what is that number? Dose per incident Particle?!!!
If yes, Why they increased with increase in the number of primary particle!
even after reduce the dose uncertainty to near zero*

*           If the number of hit effect the number for each voxel, how I
should calculate them and how I should effect them in my conversion to
Gy???*

*Then: How I can convert them to Gy? *

*I found the below article and thesis for this conversion but both of them
works with EGSnrc. the number in each voxel in this code are dose per
incident voxel.*
Francescon P, Cavedon C, Reccanello S and Cora S 2000 Medical Physics
27(7), 1579–1587.
Monte Carlo Treatment Planning for Advanced Radiotherapy. Chapter 5,
Cronholm, Rickard; F. Behrens, Claus; Helt-Hansen, Jakob; E. Andersen, Claus
*I will be thankful if someone have experience in this issue and help me.*

*Best regards*

*Mery*








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