There are lots of tungsten alloy leaves on a tungsten heavy alloy multi-leaf collimator. Tungsten alloy multi-leaf collimator, as an important part of the medical electronic linear accelerator, and is a new design to replace traditional lead block. You know, lead is toxic and its radiation shielding performance is not so ideal when it is compared with tungsten alloy. So, the volume of lead block is larger than tungsten alloy leaves, which is not a choice for applications of small device.
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The multi-leaf collimator is mainly used as a three-stage collimator of the linear accelerator. The secondary collimator moves in an arc-shaped trajectory to reduce penumbra. While as each tungsten alloy leaf can be driven independently, the end face design of these tungsten alloy leaves cannot adopt the arc-shaped trajectory, but arc surface design. So, these leaves can move to any position, as long as it moves along the vertical direction of the central axis of the beam, and the rays can be tangent to the end surface. Also, the design increases the penumbra of the irradiation field. As long as the position of these leaves away from the central axis of the beam changes, the blade penumbra will change as well.
