System and method for shaping the intensity profile of a radiation beam incident on a target volume. Embodiments according to the present disclosure include a multi-leaf collimator (MLC) capable of sharpening (e.g., “trimming”) a proton beam, the MLC having a reduced overall weight. Leaves of the MLC according to embodiments of the present disclosure have two regions of different density, where a high density region is proximal to a radiation beam so as to block a portion of the beam, and a lower density region provides structural integrity to the leaf while reducing overall MLC weight.
