Breast
Exact match of field edges using ‘half’ beams
couch always at 0
AP-field: only use upper
half
of collimator
tangential fields: only use lower
half
of collimator
in junction plane exact match, defined by sides of leaves
(independent of leaf calibrations)
junction plane
through isocenter
focus
cranial
edge
central
axis
‘half’ beam
Simple geometry, complex dosimetry