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IMRT: arbitrary sharp dose gradients
concave dose distributions
New photon technology
IGRT/gating/tracking: reducing PTV-margins
reducing surrounding dose
Adaptive/painting: reducing CTV (sub)volumes
reducing surrounding dose
Is the best tool to explore new clinical directions*
Technology development much faster for photons
Advantage of photons consolidated by faster upgrading
*Early recurrence, immunogenic/vascular cancercell death, synchronous and metachronous
painting, (oligo)metastatic disease, elective nodal instead of elective compartmental irradiation
Fundamental disadvantage of protons
Degradation of lateral penumbra in depth
Gradient near PTV, nearby small or sensitive OAR
Loss of the Bragg peak using small pencils
Fine painting
Small targets
Improves treatment in existing clinical indications