Commissioning of the RefleXion X1 Linear Accelerator and Development of a Consensus Reference Beam Model
W Tyler Watkins1, Ray Yang2, Chunhui Han1
1Department of Radiation Oncology, City of Hope National Medical Center, Duarte, California, USA.
Medical Physics
|November 26, 2025
Summary
Commissioning the Reflexion X1 linear accelerator (linac) and Treatment Planning System (TPS) requires site-specific beam models due to machine variations. A standardized method was developed, but consensus models are not yet ideal for ensuring accurate radiation therapy delivery.
Area of Science:
- Medical Physics
- Radiation Oncology
- Radiotherapy Technology
Background:
- Ensuring accurate radiation delivery from novel systems like the Reflexion X1 linear accelerator (linac) necessitates robust commissioning.
- Initial installations provided data to develop consistent beam model commissioning methods.
Purpose of the Study:
- To establish reference commissioning, quality assurance (QA), and quality control (QC) data for the RefleXion X1 linac and Treatment Planning System (TPS).
Main Methods:
- Compared beam measurements and TPS data from seven RefleXion X1 linacs.
- Optimized beam models using static and dynamic beam geometry measurements in various phantoms.
- Generated and compared measured doses from standardized treatment plans across institutions.
Main Results:
- Static beam data (percent depth dose, profiles, output factors) showed good agreement (<2% inter-linac differences).
- Significant differences in longitudinal field widths and beam centering were observed.
- Treatment planning and delivery showed variations, necessitating unique, site-specific beam model optimization.
Conclusions:
- A systematic method for Reflexion commissioning and validation was established.
- Inter-institution variations indicate that individual, site-specific beam models are currently required.
- Improved QC at installation could enable a consensus reference dataset in the future.
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