Course book Advanced Treatment Planning 2018

Penumbra

Lateral scattering: ➢ MCS: penumbra increases with increasing penetration depth. ➢ Exceeds penumbra of photons at some point. Presence of range shifter (combined with low energies): ➢ Substantial increase of spot size. ➢ Dose calculation accuracy for PB algorithm impaired. ➢ Reduce air gap.

Courtesy Palmans 2006

Water phantom

Low energy High energy

Courtesy Grevillot 2014