Impact of radiotherapy plan complexity on dosimetric measurement verification: A technical evaluation of two O-ring...

The measurement verification is an essential process of radiotherapy pre-treatment patient-specific quality assurance. The impact of plan complexity on measurement verification needs to be investigated.

Sixty clinical radiotherapy plans were retrospectively analyzed using two types of O-ring detector arrays, ArcCHECK and ArcMap, to implement the measurement verification. Forty-three complexity indexes were calculated to comprehensively quantify plan characteristics. Spearman's correlation analysis statistically evaluated the correlations between complexity indexes and gamma passing rates (GPRs).

ArcMap achieved higher GPRs compared with ArcCHECK. Higher correlation coefficients |r| were achieved with the criteria of gamma analysis were tightened. At the 2 %/1 mm criteria, complexity indexes characterizing leaf motion, notably A_4-5 (proportion of leaf accelerations ranged 4-5 cm/s², |r|=0.72), S_1.2-1.6 (proportion of leaf speed ranged 1.2-1.6 cm/s, |r|=0.71), maximum leaf acceleration (LA_max, |r|=0.70) and leaf sequence variability (LSV, |r|=0.68) exhibited stronger GPRs correlations for ArcMap. Conversely, indexes related to beam area, including cross axis score (CAS, |r|=0.64), aperture area variability (AAV, |r|=0.57), small aperture score 5 mm (SAS₅, |r|=0.56) and converted aperture metric (CAM, |r|=0.56) demonstrated stronger correlations for ArcCHECK.

The impact of radiotherapy plan complexity on measurement verification displayed detector dependency, with detector size, spatial resolution, and geometric configuration critically influencing GPR-complexity correlations.