Monte Carlo based suggestion of the best choice for material of a Multileaf Collimator (MLC) and the required thickness

Abstract

Due to intensive use of multileaf collimators in clinics, determination of an optimum design and material for the leaves become essential. Although Tungsten is the popular material for MLC leaf fabrication, other suitable options should be taken into consideration as well. In this study, we characterized the multileaf collimator (MLC) dosimetric parameters for a MLC with a proposed design which gathers the useful properties of Varian, Elekta and Siemens systems. The study was done using MCNP4c code. It was assumed that the MLC was mounted on a Varian accelerator and with a similar thickness as Varian's and the same distance from the source. Then regular characteristics of the MLC such as leakage radiation, beam hardening, MLC transmissions and penumbra width were calculated for four different materials. Considering the obtained results and the maximum allowable leakage, guide us through determination of required thickness for Lead alloy. Comparison between Depleted Uranium, Tungsten heavy and Tantalum alloys with a 6 cm thickness with Lead alloy leaf having 10 cm thickness shows better characteristics in addition to lower cost and a bit lighter leaves for a leaded leaf. Although leaded leaf shows almost wider penumbra in comparison with other materials, taking into account a more curved motion path for the leaves, providing double focusing design will solve the problem. © 2009 Springer-Verlag.