398-399 / 3107
MV beam
MU efficiency and leakage
Jaws
MLC leaf
Zone I
Zone II
Zone II
Zone III
Zone III
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”
Head/Jaw leakage 0.1%
MLC leakage 1% to 3%
Exposure outside beam aperture
Related to beam-on time (#MU)