Multi-Institutional Experience In Varian Halcyon Commissioning
Abstract
Purpose
The Varian Halcyon linear accelerator, featuring a ring-gantry design and dual-layer multileaf collimator (MLC), has gained increasing clinical adoption due to its streamlined workflow and operational efficiency. Unlike conventional C-arm linacs, Halcyon commissioning is centered on verification of vendor-provided Golden Beam data rather than independent beam modeling. However, published guidance on acceptable commissioning methodologies remains limited. This study presents a multi-institutional comparison of Halcyon commissioning practices and results.
Methods
Commissioning reports from nine Varian Halcyon systems across five medical centers (three community institutions and two academic institutions) were retrospectively reviewed, including four version 2.0 systems and five version 3.0 systems. Evaluations focused on dosimetric parameters that remain consistent across Halcyon versions, including reference dosimetry, percent depth dose (PDD), output factors, beam profiles, and delivery validation. A range of detectors, phantoms, and measurement workflows were employed across institutions. All measured data were compared against Varian Golden Beam data and relevant task group references.
Results
Across all institutions, commissioning measurements demonstrated excellent agreement with Varian Golden Beam data. For reference dosimetry, calibration accuracy was evaluated using available independent IROC validations, which showed a mean deviation of 0.93% and confirmed accurate output calibration. Percent depth doses (PDDs), output factors, and beam profiles exhibited minimal inter-institutional variability and closely agreed with reference values within established tolerances. Available VMAT delivery validation results, including TG-119 tests and IROC lung phantom irradiations, further confirmed stable geometric and dosimetric performance of the systems.
Conclusion
This multi-institutional study demonstrates that Halcyon commissioning results are highly reproducible across diverse clinical settings. Despite variations in commissioning methodologies, appropriate measurement strategies consistently verified agreement with Golden Beam data. These findings provide practical guidance and reference benchmarks for clinical medical physicists and may serve as a valuable resource for institutions undertaking Halcyon commissioning.