Validation of the RayOcular Treatment Planning System for Proton Therapy of the Eye
B Koska1,2,3*, J Wulff1,2,3, C M Baecker1,2,3,5, C Baeumer1,2,3,4,5, C Behrends1,2,3,5, B Timmermann1,2,3,4,6, (1) Westgerman Proton Therapy Center Essen, Essen, DE, (2) University Hospital Essen, Essen, DE, (3) West German Cancer Centre (WTZ), Essen, DE, (4) German Cancer Consortium (DKTK), Heidelberg, DE, (5) TU Dortmund University, Department of Physics, Dortmund, DE, (6) Department of Particle Therapy, Essen , DE
Presentations
SU-J-206-8 (Sunday, 7/10/2022) 4:00 PM - 5:00 PM [Eastern Time (GMT-4)]
Room 206
Purpose: To validate the RayOcular (RaySearch, Sweden) TPS developed for proton therapy (PT) of ocular disease and commission it for clinical application.
Methods: Dedicated eye ball phantoms were constructed including landmarks, radiopaque markers and tantalum clips as used for delineation and position verification in ocular PT. Eye models were created within the TPS based on CT and MRI scans. X-ray-imaging was carried out at the ocular treatment facility to verify appropriate representation of the PPVS geometry. Fundus images of the phantoms were acquired with a Clarus 700 camera (Zeiss, Germany) and distances of known landmarks compared to the predictions of the TPS in Fundus view. The accuracy of the model’s Fundus projection was assessed.Treatment plans with several ranges, modulations and field sizes (N>152) were calculated using the pencil beam algorithm (PBA) employed in the TPS. Wedges were included in some cases. Lateral profiles as well as PDDs were compared to measurements in air and water, including 1D gamma-analyses with different thresholds.
Results: Eye model and representation agree within 0.2mm. Overlay of the TPS model with Fundus images shows agreement <0.2mm in the central region. Peripherally, discrepancies of 0.5mm – 1mm are present.TPS-calculations of profiles and PDDs compared to measurements yield gamma pass rates >95% for 2% / 0.3mm and agreement of lateral penumbra <0.3mm respectively 90-100% at 3% / 0.3mm and lateral agreement <0.4mm including wedges.
Conclusion: Geometric modelling and transformations in the TPS yield accurate eye models for treatment planning and patient positioning. Remaining deviations in Fundus projection are attributed to distortions and imperfections of the phantom. Dose calculation with the PBA proves to be accurate. Due to the superiority of the dose calculation algorithm compared to other TPS, wedge scatter effects are properly modelled. The validation shows the TPS to be safe for patient treatment.
Keywords
Treatment Planning, Protons, Validation
Taxonomy
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