Independent Quality Control to Improve Stability and Reduce Calibration Time In Elekta Linear Accelerators
Abstract
Purpose
To reduce the frequency of calibration and adjustment of Elekta linear accelerator components, including MLCs, jaws, mechanical isocenter, beam spot position, symmetry, and flatness.
Methods
Independent quality control (QC) procedures were developed to assess Elekta linear accelerator performance. These procedures were independent of, yet aligned with, manufacturer calibration methodologies to minimize false-positive action levels and unnecessary recalibrations. In-house scripts were developed for data analysis, and all procedures and scripts are publicly available.
Results
Twelve beam matched Elekta linear accelerators were evaluated over a five-year period. Tolerance and action levels were established to meet published guidelines while maximizing machine performance and limiting calibration and adjustment time to ≤1 h/month. MLC and jaw field size and field center stability were within 0.3 mm and 0.5 mm, respectively. Beam spot position remained within 0.5 mm at gantry 0 and 1.0 mm at non-zero gantry angles. Beam symmetry and flatness were stable within 0.5% at gantry 0 and 1.0% at non-zero gantry angles. mechanical sag, CBCT flexmap and isocenter deviations from month to month were ≤0.5 mm. End-to-end testing was done on 3 units with hexapod couch and demonstrated stability within 0.6 mm for two units and1.3 mm for the other unit.
Conclusion
This framework allows Elekta linear accelerator users to independently verify machine performance at no cost, exceed manufacturer specifications, and maintain calibration and adjustment time below one hour per month.