ABSTRACT
This chapter describes how radiochromic film dosimetry techniques can be used to achieve all of the important clinical goals and thereby contribute to the ongoing quality improvement of a modulated radiotherapy program. Modulated radiotherapy treatments such as intensity-modulated radiotherapy and volumetric-modulated arc therapy involve the use of moving multileaf collimator (MLC) leaves to deliver beams with a spatially varying intensity. Before a treatment-planning or delivery system can be used for modulated radiotherapy, the system must be specifically commissioned for that purpose. The tongue-and-groove effect has been shown to produce small regions of underdosage, due to dynamic overlapping of the steps in the sides of MLC leaves, which are designed to minimize interleaf leakage when adjacent leaves are aligned. The measurements required to confirm the alignment of the MLC leaf banks with each other and with the collimator axis or rotation can also be performed effectively using radiochromic film.
