ESTRO 2025 - Abstract Book

S3618

Physics - Quality assurance and auditing

ESTRO 2025

Figure 1: Histogram for both left and right banks in Elekta Versa HD nº2

The displayed graphs indicate that the majority of leaf deviations are below 0.15 mm, remaining well within tolerance limits and showing a higher concentration at smaller deviations. As suggested by literature of statistical process control for radiotherapy quality assurance [2], behavior charts were applied to each nominal position of the picket fence and globally for all positions. Figure 2 displays mean values for all nominal positions.

Figure 2: Behavior charts for mean values of all positions of the picket fence in Elekta Versa HD nº2

Previous graphics reflect the stability of MLC Agility, with the vast majority of points falling within control limits, and corrective actions taken when predefined values were exceeded.

Control limit

Lower left

Upper left

Lower right

Upper right

VERSA 1

-0.065

0.269

-0.136

0.233

VERSA 2

-0.196

0.287

-0.240

0.253

VERSA 3

-0.158

0.261

-0.057

0.315

Data table: Control limits for all three Elekta Versa HD

Control limits were found to be lower than the tolerance; however, in some cases, only small differences between the three machines were observed.

Conclusion: The Elekta Agility MLC model demonstrates excellent performance, as indicated by the tight control limits, which are