1. GATE activities @ Creatis, Lyon
Opengate meeting 2017 – Marseille, France
GATE activities @ Creatis, Lyon
D. Sarrut
Thursday, 30th November 2017

2. Projects @ CREATIS, Lyon
Gate RT Ion (Medaustron)
OpenDose (Toulouse)
Still working on VRT
Fast simulation combining determinist and stochastic methods
Fast low energy photon dose [Baldacci et al. zMedPhys 2015]
Faster low energy photon dose [Smekens et al. PMB 2014]
Fast X-ray FFD simulation [Arbor et al, PMB 2015]
Fast Prompt-Gamma emission [Huisman et al. PMB 2016]
Fast SPECT FFD+ARF simulation [Cajgfinger et al. PMB, 2018]
neutronTLE Arbor
Currently working on 3D SPECT simulation
Next project: Compton Camera module For proton dose monitoring For nuclear medicine with high E radioisotope
Hermann
Maxime
Nothing new
Still future

3. Back to basis
the DoseActor

4. DoseActor: back to basis
Uncertainty
Conventional “batch method”: simulations, mean, standard deviation
“History by history” estimation [Walters2002]
k =pixel
/gate/actor/addActor DoseActor da
/gate/actor/da/save output/dose_map.mhd
/gate/actor/da/attachTo phantom
/gate/actor/da/setVoxelSize mm
/gate/actor/da/enableEdep true
/gate/actor/da/enableDose true
/gate/actor/da/enableUncertaintyDose true
i = event

5. DoseActor: “uncertainty trick”
Compute the squared dose, by event i
Brute force approach:
Take the square after each events, for all voxels
Slow !
Approach in Gate [Walters2002]:
Store id of the last event in every voxel
Only take the square when the event change
Need a final loop over all voxels before final output writing
Fast. Small memory increase.

6. What if need output for a region ?
CT (Hounsfield Unit)
Image of labels

7. What if need output for a region ?
ROI: group of voxels
e.g. image of labels
For the edep/dose: easy
Also sum over k
Consider mass per voxel
For the uncertainty ?
The squared edep in ROI by event i is not available
This is not the SD of dk in the region
Need a new option !

8. DoseActor by regions With Maxime Chauvin Macros
Label image must have the same size/spacing than phantom
Output is a txt file
/gate/actor/addActor DoseActor da
/gate/actor/da/save output/dose_map.mhd
/gate/actor/da/attachTo phantom
/gate/actor/da/setVoxelSize mm
/gate/actor/da/enableEdep true
/gate/actor/da/enableDose true
/gate/actor/da/enableUncertaintyDose true
/gate/actor/da/inputDoseByRegions data/label.mhd
/gate/actor/da/outputDoseByRegions output/dose_regions.txt

9. DoseActor by regions Example of output (TODO: add a column for mass)
(TODO: change column name)
#id vol(mm3) edep(MeV) std_edep sq_edep dose(Gy) std_dose sq_dose n_hit n_event_roi
e e
e e e …
e e e
e e e
Volume in mm3
edep & dose
Nb of hits / last event id

10. How does it work ? Manage a map of label - region statistic
std::map<label, regionStat>
label: integer
regionStat: data structure with: edep, dose, squared values, last_event_id, nb_hits
At each step:
Get label at current voxel (same index than phantom)
Get region statistics thanks to the map
Update statistics, use similar “trick”
Also need final loop before writing output

11. What if group of regions ?
Want edep+uncertainty in user-defined regions composed of several labels ?
/gate/actor/addActor DoseActor da
/gate/actor/da/save output/dose_map.mhd
/gate/actor/da/attachTo phantom
/gate/actor/da/setVoxelSize mm
/gate/actor/da/enableEdep true
/gate/actor/da/enableDose true
/gate/actor/da/enableUncertaintyDose true
/gate/actor/da/inputDoseByRegions data/label.mhd
/gate/actor/da/outputDoseByRegions output/dose_regions.txt
/gate/actor/da/addRegion :

12. Aggregated region labels
Compute a map of vector
To each label associate a vector of regions
std::map<label, std::vector<regionStat>>
Vector contains:
The region with unique label
All other “aggregated regions” that contain the label
Update all regions
Need to build this map during initialization (closure)
Flexible
Timing:
DoseActor cost: ~14% additional time
DoseActor with region: ~1% additional time

13. Conclusion on DoseActor
GateDoseActor is a very used/old tool
introduced in ~2006
… still alive !!
Improvements:
edep, dose, uncertainty, nb of hits
dose_to_water vs dose_to_medium [Grevillot2012,Simon/Fuchs2017]
Adaptation to large CT voxels [Deschler, Arbor2015]
Adaptation to regions [Chauvin, Sarrut2017]
Need finalize code, documentation, example
Will be included in next Gate release
Code in github
Docs in the wiki
Example in GateContrib
DoseActor

14. That’s it ! Thanks for your attention
Acknowledgements:
Laurent Guigues
Simon Rit
Thibault Frisson
Jean-Michel Létang
Maxime Chauvin
Herman Fuchs
Adrien Halty
Loic Grevillot
Thomas Baudier
Luc Simon
Jean-Noel Badel
Thomas Deschler
Thomas Cajgfinger
Nicolas Arbor