Multileaf collimator

A multileaf collimator (MLC) is a Collimator or beam-limiting device that is made of individual "leaves" of a high atomic numbered material, usually tungsten, that can move independently in and out of the path of a radiotherapy beam in order to shape it and vary its intensity.

Specifically, conformal radiotherapy and Intensity Modulated Radiation Therapy (IMRT) can be delivered using MLCs.

The MLC has improved rapidly since its inception and the first use of leaves to shape structures in 1965 [1] to modern day operation and use.

It was originally used as a surrogate for alloy block field shaping and is now widely used for IMRT.

Additional commissioning measurements are completed to model a MLC for treatment planning.

MLC shape of an X-MLCs
Leaves, changing shape, direct the beam to the right cancer area