A radiotherapy apparatus comprises a means for producing a beam of radiation directed along a beam axis and having a width in first and second directions transverse to the beam axis, a multi-leaf collimator for selectively limiting the width of the beam in at least the first direction, a block collimator...http://www.google.ca/patents/US8090076?utm_source=gb-gplus-sharePatent US8090076 - Collimation apparatus for radiotherapy
