Physics Bucharest 2017

Interplay - Dynamic IMRT

→ If motion mitigation is not applied during IMRT to a moving target

CTV under/over-dosage

• Fractionation 1fx → 20% dose variation 30fx → <2% dose variation Bortfeld PMB (47) 2002 - Jiang PMB (48) 2003 - … • Multiple fields → statistical averaging over the beam reduces the overall dose error • Avoid low MU segments (few s delivery) Seco et al. Med Phys(34) 2007

Bortfeld PMB (47) 2002

→ Delivery time comparable to breathing period → Segment size comparable to breathing amplitude