Open AccessBeam energy metrics for the acceptance and quality assurance of Halcyon linear accelerator
Author(s) -
Gao Song,
Chetvertkov Mikhail A.,
Cai Bin,
Dwivedi Abhishek,
Mihailidis Dimitris,
Ray Xenia,
Netherton Tucker,
Court Laurence E.,
Simon William E.,
Balter Peter A.
Publication year - 2021
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1002/acm2.13281
Subject(s) - flatness (cosmology) , linear particle accelerator , metric (unit) , beam energy , diagonal , linear regression , energy (signal processing) , physics , beam (structure) , computational physics , mathematics , optics , statistics , geometry , operations management , cosmology , quantum mechanics , economics
Purpose Establish and compare two metrics for monitoring beam energy changes in the Halcyon platform and evaluate the accuracy of these metrics across multiple Halcyon linacs. Method The first energy metric is derived from the diagonal normalized flatness (F DN ), which is defined as the ratio of the average measurements at a fixed off‐axis equal distance along the open profiles in two diagonals to the measurement at the central axis with an ionization chamber array (ICA). The second energy metric comes from the area ratio (AR) of the quad wedge (QW) profiles measured with the QW on the top of the ICA. Beam energy is changed by adjusting the magnetron current in a non‐clinical Halcyon. With D 10cm measured in water at each beam energy, the relationships between F DN or AR energy metrics to D 10cm in water is established with linear regression across six energy settings. The coefficients from these regressions allow D 10cm (F DN ) calculation from F DN using open profiles and D 10cm (QW) calculation from AR using QW profiles. Results Five Halcyon linacs from five institutions were used to evaluate the accuracy of the D 10cm (F DN ) and the D 10cm (QW) energy metrics by comparing to the D 10cm values computed from the treatment planning system (TPS) and D 10cm measured in water. For the five linacs, the D 10cm (F DN ) reported by the ICA based on F DN from open profiles agreed with that calculated by TPS within –0.29 ± 0.23% and 0.61% maximum discrepancy; the D 10cm (QW) reported by the QW profiles agreed with that calculated by TPS within –0.82 ± 1.27% and –2.43% maximum discrepancy. Conclusion The F DN ‐based energy metric D 10cm (F DN ) can be used for acceptance testing of beam energy, and also for the verification of energy in periodic quality assurance (QA) processes.