IGRT 2016 Madrid

2D vs 3D setup

2D vs 3D setup correction

Phantom test: identical Detected error in CBCT larger in all directions CBCT measurements better reproducable

Planar imaging underestimates the setup error, especially if you do it manually Deformation might contribute to this (Li et al)

Fuller et al. 2009

How flexible is the neck ?

How flexible is the neck ?

• Purple: reference CT scan

• PTV conflicts with OAR

• You cannot align all at the same time: Compromise!

• Green: daily

localization Cone Beam CT scan

• Need for choices in alignment!

How flexible is the neck ?

How flexible is the neck ?

31 patients 8 CBCT scans per patient: 249 scans evaluated 9 ROIs per patient Retrospectively: Larynx assumed as PTV

Count occurrence of ROI within certain margin

ROI:

• PTV(larynx)

• OAR (C3-C5)

Margin 0..10 mm (1 mm)

Vertebrae assumed as OAR