Technical Note: Improving VMAT delivery efficiency by optimizing the dynamic collimator trajectory

Abstract

Purpose To provide a method for optimizing the multileaf collimator angle trajectory in volumetric modulated arc therapy (VMAT) in order to make VMAT delivery and planning more efficient. Methods Static fluence maps are optimized at a 10‐degree spacing around the patient. Sliding window delivery time of each of these fields is computed for a large set of possible collimator orientations. An optimal trajectory, which selects a collimator angle for each field and assures that the collimator angles do not differ excessively between adjacent fields, is computed by solving a network flow model of a shortest path problem. Results For four clinical cases (two brains, an anal, and a spine), we demonstrate time reductions from 6% to 32% (average: 24%) for the optimal static angle vs the worst static angle. Further reductions from 3% to 17% (average 9%) are achievable when dynamic collimator trajectories are allowed. Conclusions Dynamic collimator trajectories, which can be computed with an efficient linear programming formulation, can improve the efficiency of VMAT delivery.

The first investigation of spot-scanning proton arc (SPArc) delivery time and accuracy with different delivery tolerance window settings

“…This result indicated that the tolerance window setting plays a crucial role in both treatment delivery and planning of the SPArc therapy. Similar conclusions can be found from the previous investigations and clinical implementations of the rotational x-ray therapy, VMAT, in which the tolerance window setting determines the allowable deviation from the ideal dose distribution, affecting the delivery accuracy and treatment efficiency (Bokrantz et al 2019). However, the perturbation effect of uncertainty on dose distribution is more pronounced than it is in photon radiotherapy.…”

“…As we recall the development of volumetric modulated arc therapy (VMAT), numerous investigations were conducted to explore the plan parameters, such as control point sampling frequency and tolerance window settings, and machine characteristics, such as the beam dose rate, gantry angular speed, multi-leaf collimators (MLC) speed with a relationship of treatment delivery accuracy and efficiency (Wang et al 2018, Bokrantz et al 2019, Pokhrel et al 2022. These investigations pave the foundation of the robust and efficient clinical implementation of VMAT, in which a tolerance for MLC positioning of 2.5 mm is recommended, and a tolerance window of 2°is recommended for prostate cancer (Hernandez et al 2015).…”

Optimization of collimator angles in dual-arc volumetric modulated arc therapy planning for whole-brain radiotherapy with hippocampus and inner ear sparing

“…Several studies showed that the VMAT optimization involving sectional optimization of collimator angle could provide delivery efficiency and dosimetric improvements 33 , 34 . Recent studies on the dynamic collimator rotation approach have shown positive results on improving the plan quality 24 , 35 – 37 .…”

Sub-arc collimator angle optimization based on the conformity index heatmap for VMAT planning of multiple brain metastases SRS treatments

“…Bokrantz et al. ( 15 ) provide an optimization method that transfers the collimator trajectory per fluence map to a trajectory per control point of the segmented VMAT plan, which may be integrated in a treatment planning system. MacDonald et al.…”