A rapid script-based framework for rotational robustness evaluation in lateral-opposed IMPT under customized setup...

To develop and validate a rapid, script-based framework for assessing rotational robustness of lateral-opposed intensity-modulated proton therapy (LO-IMPT) plans under customized setup scenarios.

For LO-IMPT plans, roll or yaw errors were simulated by adjusting gantry/couch angles, while pitch was modeled by rigidly rotating the spot map of each energy layer of each beam around the isocenter. The framework was implemented through a custom RayStation 10B API script, enabling the definition of user-specific rotational setup scenarios according to clinical or institutional requirements. Clinical feasibility was evaluated in nine cases (five prostate, three pituitary adenomas, and one foot sarcoma).

For each reference plan, 78 perturbed scenarios were successfully generated by applying 26 rotational modes (pitch/roll/yaw, individually or in combination) at three magnitudes of ±1°, ±3°, and ±5°. Patient-specific robustness assessments revealed that the prostate LO-IMPT plans were relatively robust across rotational modes and magnitudes (up to ±5°), with the maximum reduction in CTV D_98% being less than 2%. In contrast, pituitary adenomas plans and the foot sarcoma plan exhibited pronounced, patient-specific sensitivity varying substantially across scenarios, underscoring the importance of individualized rotational robustness assessment.

The proposed framework provides an efficient, reproducible, and customizable tool for rotational robustness evaluation in LO-IMPT, supporting institution-specific robustness strategies and rotation-informed clinical decision-making.