A 4-bank multileaf collimator provides a decomposition advantage for delivering intensity-modulated beams by step-and-shoot.

During the delivery of intensity-modulated radiation therapy (IMRT) by the multileaf collimator (MLC) step-and-shoot technique, it is required to sequence the two-dimensional intensity-modulated beams (2D IMBs) into a series of components that can be shaped with the MLC. In this paper it is shown that the use of an MLC that has four banks of leaves (in two orthogonal pairs) instead of two banks only is advantageous for this purpose.