A multileaf collimator includes a plurality of beam-blocking leaves of a first type and a plurality of beam-blocking leaves of a second type. The beam-blocking leaves of the first type are alternatingly arranged with the beam-blocking leaves of the second type side by side. Each of the beam-blocking leaves of the first type has a trapezoidal geometry viewed in the leaf longitudinal moving direction comprising a wider end and a narrower end with the wider end being proximal to a source. Each of the beam-blocking leaves of the second type has a trapezoidal geometry viewed in the leaf longitudinal moving direction comprising a wider end and a narrower end with the wider end being distal to the source.
