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2D vs 3D setup
33 patients, 100 paired CBCT-planar images
Varian OBI
2009
2D vs 3D setup
Phantom test: identical
Detected error in CBCT is larger in all
directions
CBCT measurements better reproducible
Fuller et al. 2009
Overall Conclusion
2D vs 3D setup correction
Planar imaging underestimates the setup
error, especially if you do it manually
Deformation might contribute to this (Li et
al., Fuller et al.)
Main reason for 3D setup
But is 3D enough?
• Purple: reference CT
scan
• Green: daily
localization Cone
Beam CT scan
• Need for choices in
alignment!
How flexible is the neck ?
• PTV conflicts with OAR
• You cannot align all
at the same time:
Compromise!
How flexible is the neck ?