The effect of stair-step leaf transmission on the `tongue-and-groove problem' in dynamic radiotherapy with a multileaf collimator

Abstract

When intensity-modulated fields are created using a multileaf collimator with dynamic leaf movement the potential problem for underdosage beneath the tongue-and-groove interleaf regions has been identified and a solution based on leaf-movement synchronization has been provided by Van Santvoort and Heijmen. Their first-order analysis ignored the transmission through an exposed stair-step. In this brief Note we provide the extended analysis including this contribution and show the effect on irradiation with synchronization. The result is that the synchronization approach of Van Santvoort and Heijmen solves the tongue-and-groove problem even when the transmission through the stair-step is considered, but partial synchronization is generally sufficient.