Longitudinal Assessment of Daily QA Measurements In Elekta Harmony Linear Accelerator
Abstract
Purpose
To evaluate the longitudinal dosimetric and mechanical performance of the Elekta Harmony LINAC over its first year of clinical use in our center.
Methods
We evaluated the mechanical and dosimetry performance of the Harmony LINAC with daily QA testing. The metrics evaluated include output constancy, energy checks, flatness and symmetry, and mechanical jaw positioning. Daily QA metrics were acquired using the Sun Nuclear DailyQA device and logged into the TotalQA database. The data were analyzed to determine deviations from baseline values. Event dates were tracked to facilitate root cause analysis of system performance.
Results
For daily photon output constancy, the mean value is <1.25% ± 0.4% across all energy. The maximum deviation recorded was -2.41% (for 6X FFF), with 95th Percentile (P95) ~ 2%. Electron output constancy showed a mean of <1% ± 0.3% with P95 of 1.2% for all energies. The maximum deviation was −1.680% for 6 MeV. The energy constancy averaged 0.83% (-4.2% max.) and 0.97% (-5.12% max.) for electron and photon respectively. Absolute deviations for mechanical shifts and field sizes across all photon and electron energies were < 0.2 cm. Also, the flatness and symmetry (radial and transverse) were <1% for all photon and electron energies. Overall, electrons demonstrated greater stability than photons, with daily electron constancy (absolute) mean deviations within 0.56%–0.91% compared with 0.71%–1.24% for photons.
Conclusion
The Elekta Harmony LINAC demonstrated dosimetric and mechanical stability during its initial year of clinical operation in our center. Overall performance remained stable, with maximum deviations consistently within TG-142 and our institutional clinical protocols. Future study will be to extend the longitudinal tracking to improve QA efficiency, aid in proactive service scheduling, and minimize downtime while maintaining high-quality clinical delivery. Outliner data (near 100% deviation) was excluded from analysis to ensure accurate stability tracking.