New articles published: V. 14 n. 3 (2026)

Optimization of Geometric Components of Agility Multileaf to Improve Dose Delivery Accuracy

Abstract: The Agility Multileaf Collimator (MLC) exhibits specific machining characteristics. These unique features, together with minor installation differences among various linear accelerators, produce dosimetric effects that are not accounted for by the Monaco Treatment Planning System (TPS). To address this, the manufacturer recommends that users perform post-modeling adjustments to better characterize the MLC according to the actual configuration of the clinical linear accelerator. Evidence in the literature indicates that, in techniques modulated by dynamic MLC motion, geometric positioning errors as small as 1 mm can result in dose delivery errors of 10% or more. Therefore, it is of great importance to study the behavior of the geometric factors of the MLC leaves through the concepts applied in radiation metrology. However, despite the widespread clinical use of Monaco, there is still limited literature with comprehensive information, which makes the work of medical physicists more challenging. Thus, the objectives of this study were to analyze the geometric components of the Agility MLC and to propose an efficient methodology for post-modeling—or fine-tuning—these components so that the calculated dose in the TPS is as close as possible to the dose delivered by the linear accelerator. The results showed that, with the post-modeling, for the same evaluation criteria, the calculated doses for the ExpressQA tests, TG-119 tests, and patient-specific cases were in closer agreement with the doses delivered by the linear accelerator in all situations. For the 7SegA and DMLCi fields the improvements in gamma pass rates were more than 10%. These results enable greater efficiency in dose delivery, leading to improved tumor control and reduced patient toxicity. Read full article.