Patient-specific bolus positioning with AlignRT

Laurence Delombaerde
PhD
Medical Physicist
University Hospitals Leuven
Belgium

1. Patient specific bolus
positioning with AlignRT
Laurence Delombaerde
Bertrand Dewit
Truus Reynders
Tom Depuydt

2. The departmentof Radiotherapy-Oncologyis a referencesite for
VisionRTandVarianMedicalSystems
Conflictsof Interest

3. The issues withgel bolus…
Conventional(cut) Superflab Bolus in TPS
…ifincludedin scan
→howtopositionpatientwithAlignRT?
… ifnotincludedin scan
→howtoexactlypositionflap duringRT?

4. The issues withgel bolus…
Conventionalbolus
TPS bolus
(treatment planning system)
•Geometrydoes notmatch
•Consequence→differencein deliveredvs. planneddose!

5. Developa methodforpatient-specificbolusses
Goals
→Decreasetheair gap totheskin/mask
→Cover difficultregions(vulva, groin, scalp, nose, cheek, etc)
→Complete freedomforthedosimetrist(shape, thickness, location)
Afterintroductionin theclinic:
→UsePosturalVideo of AlignRTforcheck/positioning
(thispresentationdoes notfocus on thedevelopment but thecurrentworkflow)
Orfit5 mm sheets

6. •Externalcontour needstobeverified
•Dosimetristcreatesthebolus (150 HU)
•Afterphysicsreview →export with
C# Eclipsescript
3D bolus workflow
TPS
Treatment
Bolus
creation
AlignRT
import
+ createa copy of thebolus (AlignBolus) as a ‘true’ structure
+ RTPlanandRTStructtoAlignRT
̴ 5 min

7. •Script generatesmoldfrombolus
•Print themold
3D bolus workflow
TPS
Treatment
Bolus
creation
AlignRT
import
Orientationautomaticallycorrectedin thescript
Includespatientnr. andbolus volume
Using toolboxin Blender
Raise3D N+ printers
FusedDepositionModellingwithPLA
̴ 1 min

8. •Fillmoldwithtwo-component silicone
•Cut open moldwithplastersaw
3D bolus workflow
TPS
Treatment
Bolus
creation
AlignRT
import
Eurosil8 (Shore A 8)
Remainsliquid for15 min, sets in 2 hours
Partiallyopaque→limitsAlignRTuse
Addskintonepigment (<0.1%)
̴ 20min

9. •QualityControl
3D bolus workflow
TPS
Treatment
Bolus
creation
AlignRT
import
The script performsa random selectionof patientsforQA (1/3)
Acquirea CT scan of thebolus tocheck for:
-Air bubbles
-ShapecongruencewithTPS bolus structure
̴ 15 min

10. •Export RTPlanandRTStructtoAlignRT
•Draw ROI on body contour
•Draw ROI on AlignBolus
3D bolus workflow
TPS
Treatment
Bolus
creation
AlignRT
import
Select theBODYandAlignBolusstructure
Follow theusualprocedure
Selectiondoes notmatter, as we willuse
PosturalVideo forpositioning
̴ 5 min

11. •PositionpatientusingBODY contour
•Switch totheAlignBolussurface
3D bolus workflow
TPS
Treatment
Bolus
creation
AlignRT
import
*

12. 3D bolus workflow
TPS
Treatment
Bolus
creation
AlignRT
import
Bolusseson masksare contouredtoalloweasy positioning fromfraction2 onwards…

13. A selectionof results… H&N
Bolus on maskare generallytheeasiest…

14. A selectionof results… hygienicbreast
gel flap
Alignbolus

15. A selectionof results… hygienicbreast

16. A selectionof results… extremities

17. Toconclude…
We startedfromthis…
… andnowwe canachievethis.

18. Thankyouforyourattention!