ESTRO 2025 - Abstract Book

S4396

RTT - Treatment planning, OAR and target definitions

ESTRO 2025

Material/Methods: The scripts were developed for Eclipse (v16.1). The first generates CTV volumes for bony treatment sites based on the intersection of autosegmented bone with the VS field projection through the patient. It then adds a margin to create the PTV. For soft tissue disease the CTV and PTV are created manually. The second script generates a site specific IMRT treatment plan. The script sets the isocentre position, treatment gantry angles, optimisation objectives and then optimises, calculates and normalises the plan. Repeated execution allows gantry angles to be customised to patient specific requirements. Data from seventy-three clinical patient deliveries covering a range of sites (Figure 1) including seventy-seven treatment plans were assessed. The quality of the resulting plan was evaluated using D99%, D95% and Dmax PTV statistics. The efficiency of the solution was evaluated by the occurrences of multiple script runs to refine gantry angles per patient and in the overall planning time.

Results: The average PTV D99%, D95% and Dmax were found to be 97.3% (SD = 1.1%), 98.4% (SD = 0.6%) and 103.9% (SD = 1.6%) respectively (Figure 2). The total planning time using this method (30-40 minutes) was comparable to the time taken for conventional VS planning. Approximately half of the treated cases required multiple script runs to refine beam directions.