Updating the Imaging and Radiation Oncology Core (IROC) Houston QA Center’s Reference Dosimetry Dataset for Elekta Linear Accelerators
Abstract
Purpose
To identify and consolidate contemporary dosimetric performance data for Elekta linear accelerators including specialized beams such as flattening-filter free (FFF) beams, which were not included in the original IROC reference dosimetry dataset.
Methods
All measured dosimetric data for Elekta linear accelerators were obtained from IROC’s on-site dosimetry audits conducted from 2010 to 2025. The collected data were point measurements of several dosimetric parameters acquired at multiple locations in a water phantom, with the source-to-surface distance set to 100 cm. These data reflect highly consistent measurements of important beam characteristics, including depth dose, output factor, and off-axis factor characteristics. Model-specific dosimetric properties were summarized using descriptive statistics, and comparisons among model types were evaluated using analysis of variance (ANOVA) with Tukey’s honest significant difference post hoc test.
Results
Elekta linear accelerators were grouped by model type, and the reference dosimetric characteristics were described for each group. Three linear accelerator models (VersaHD, Infinity, Synergy) equipped with the Agility head configuration were independently evaluated for each energy. Measurements of beam characteristics were compiled for beam energies 6, 6FFF, 10, 10FFF, 15, and 18 MV. Most factors exhibited consistent dosimetric performance (within ± 2%). In contrast, wedge transmission factors frequently showed markedly larger variations for up to ± 10%.
Conclusion
Assessing the dosimetric performance of Elekta linear accelerators strengthens IROC’s ability to provide accurate and targeted feedback to institutions receiving both on-site and virtual dosimetry review audits. In addition, the updated reference dosimetry dataset for Elekta linear accelerators will provide institutions with a valuable quality assurance resource for independent dose verification of their clinical treatment systems. Caution is required when evaluating wedge factors as these show highly variable values.