Physics Bucharest 2017

6/3/2017

MU efficiency and leakage

Exposure outside beam aperture

MV beam

Jaws

Head/Jaw leakage 0.1% MLC leakage 0.5% to 3%

MLC leaf

Zone I: Primary beam “ Wanted dose” to target “ Unwanted dose” to healthy tissue and OAR in the beam path Zone II: MLC/Collimator Leakage + scatter “ Unwanted dose” Zone III: Linac head leakage + scatter “ Unwanted dose”

Zone I Zone II Zone II Zone III

Zone III

75

ESTRO physics course 2017

MU efficiency and leakage

MV beam

MV beam

Jaws

Jaws

MLC leaf

MLC leaf

Open beam: 140 MU

Sliding window (1 cm): 680 MU

76

Remark: For this particular MLC device average leakage < 1% ESTRO physics course 2017