ESTRO 2025 - Abstract Book

S3673

Physics - Quality assurance and auditing

ESTRO 2025

still require human involvement and pose a bottleneck challenge to automated workflows. To overcome this, we aimed to develop a dose-volume histogram(DVH)-based plan quality index that enables automation.

Material/Methods: We developed the advanced dose distribution index (ADDI) to evaluate plan quality. It incorporates DVHs, OAR dose constraints, Lyman's volume dependency of dose factor (L n ) [2] for each OAR, target dose homogeneity, conformity, maximum dose, and coverage (Figure 1). Finally, it expresses plan quality as a polar vector, ADDI(r, θ), where r reflects overall quality and θ indicates the balance between target and OAR scores. During validation, First, ADDI values were calculated for four cancer patient groups: Left breast (BL, n=32), right breast (BR, n=32), BL + lymph nodes (BL+LN, n=27), BR + lymph nodes (BR+LN, n=20). These values were compared with clinical observations to assess its general performance. Second, alternative plans were generated from treated plans for the BL group by adjusting cost function values in Monaco treatment planning system (Elekta, Sweden). Specifically, the parallel and serial cost function values were relaxed by 20% for the ipsilateral lung and heart, respectively. Five physicists and the ADDI selected the best plan for each patient. The arithmetic mode of the physicists’ choices for each patient was analysed alongside each physicist’s selection and ADDI to demonstrate the agreement and reliability.

Results: The OAR score trend was BR>BL>BR+LN>BL+LN (Figure 2). OAR score BR vs BL was statistically insignificant, while BR+LN vs BL+LN, BR vs BR+LN, and BL vs BL+LN were significant (α=0.05, p (Mann–Whitney U)<0.05). The target score showed slight variation, and none of the comparisons were significant. ADDI achieved a Cohen’s kappa (κ) of 0.727, while the mean κ of the physicists’ responses against the mode was 0.813±0.213. The agreement of ADDI with the mode was 88.89%, while the mean agreement of the physicists' responses was 91.11±10.83%