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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
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.
How to manage uncertainties?
Can we use the PTV concept?