Log file-based treatment efficiency analysis of TrueBeam and Halcyon delivery systems

TrueBeam (TB) and Halcyon (HC) are state-of-the-art linear accelerators (linacs) widely utilized for external beam radiotherapy. As clinical demand increases, expanding treatment capacity through new machine installations or extended operating hours remains costly and resource intensive. Retrospective analyses of treatment delivery performance can help guide machine assignment strategies that optimize machine utilization, reduce patient time alone on the treatment couch, and improve overall departmental throughput.

To introduce a trajectory log-based methodology for assessing treatment delivery efficiency on Halcyon and TrueBeam systems by quantifying gantry speed, MLC speed, and dose-rate utilization, and to integrate these machine-level parameters with beam-on time and modulation factor (MF) to guide treatment machine assignment and patient triaging.

Volumetric modulated arc therapy (VMAT) trajectory logs acquired between February 2025 and February 2026 were collected from fourteen clinical linacs across a main institution and its affiliated regional clinics. The percentages of beam-on time during which the machine operated at ≥95% of its maximum dose rate (max_DR), gantry speed (max_GS), or MLC speed (max_MLC) were quantified. Plans were categorized by procedure type and disease site, and delivery efficiencies were compared using Mann-Whitney U test.

A total of 4347 VMAT plans were included in the study. For stereotactic body radiation therapy (SBRT) plans, Halcyon had a significantly higher max_DR (0.96 ± 0.14 vs. 0.51 ± 0.39 for TrueBeam), suggesting its max dose rate might be a bottleneck for treatment efficiency. For non-SBRT plans, Halcyon demonstrated greater max_GS (0.68 ± 0.32 vs. 0.43 ± 0.22 for TrueBeam) and max_MLC (0.66 ± 0.32 vs. 0.38 ± 0.23 for TrueBeam), which is reflected in its higher MF and faster beam-on time compared to TrueBeam, saving over 50 seconds of on-table time per plan for each patient.

Halcyon demonstrates superior delivery efficiency for non-SBRT plans compared to TrueBeam through higher usage of its maximum MLC speed and gantry speed throughout treatment, especially for pelvis plans. In contrast, TrueBeam has significantly shorter beam-on time for higher-dose treatments (e.g. prostate SBRT), likely due to its higher nominal maximum dose rates at flattening filter-free energies. By linking delivery performance to underlying machine-specific limitations, this work provides a transferable framework for machine efficiency assessment that can be readily implemented at other centers using trajectory log data to guide machine assignment decisions and evaluate the potential impact of future Linac technology advancements.