Leaf shape design of multi-leaf collimator in radiotherapeutic machine for optimum conformation.

The leaf shape design of multi-leaf collimator used in 3-dimensional conformal radiation therapy was dealt with. According to the requirements of precision conformal dose delivery in radiation therapy, the focused trapezoid cross-sectional shape of the flank leaf of multi-leaf collimator is introduced, and the tongue-groove structure, which is used to minimize interleaf transmission, is determined. Genetic algorithm is utilized to optimize the leaf end shape to improve the size and uniformity of leaf-end penumbra. For several typical field sizes, the optimization is carried out. The result shows that the leaf-end penumbra keeps nearly constant in any leaf position. Optimum dose conformation can be realized by these leaf shape designs. [ABSTRACT FROM AUTHOR]