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Issues?
•
In particle therapy target alignment is only a partial solution!
•
PTV works for photons since the spatial nature of photon dose distributions is
minimally perturbed by uncertainties –(
Maleike et al PMB 2006
)
Hp: the CTV will BE 95% of the times INSIDE the PTV
→
the PTV dose distribution
How to manage uncertainties?
Can we use the PTV concept?
and DVH are the worst case scenario for the CTV
•
Patient misalignment + density heterogeneities
→
dose SHIFT+ DISTORSION
→
Particle dose distribution is significantly perturbed (DEFORMED) not only
distally or proximally, but within and outside the target volume
→
The PTV-based optimization do not consider
range uncertainties.
It considers
setup uncertainties implicitly but ignores the deformation of dose distributions
caused by them.