IMRT

PAROTID GLANDS – shrinkage and CT density 84 pts, (Fiorino et al , RO,2012), parotid reduced during IMRT parotid deformation and average Hounsfield number changes evaluated through MVCT or kVCT diagnostic at treatment start individual ∆ HU highly correlated with degree of local deformation in terms of volume change and with neck thickness variation

Risk of density variation <-11 HU (kVCT data)

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1

individual assessment of density changes reliable with kVCT

% risk

density changes to score toxicity?

4 4,5 5 5,5 6 6,5 7 7,5 8 8,5 9 9,5 Initial neck half-thickness (cm)

no or moderately deforming parotids

Largely deforming parotids