S1934
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
Material/Methods: Treatment planning fan-beam CT’s were obtained for 20 anonymized patients previously treated for prostate cancer. The prescription was 60 Gy/20 fx to the prostate only and plans involved 9 or 12 fixed-field IMRT beams. A common generalized planning template was created using a weighted averaged order of both target and OAR dose goals across all original personalized plans. This class solution template was used as a physician’s intent in Ethos Treatment Management to generate a new plan for each patient. These generalized plans were then compared to the clinically approved personalized plans for non-inferiority in target coverage and OAR
Conclusion: Although the ELM provides a more realistic geometric representation of the leaf tip and an automated configuration workflow, the TG model remains unchanged, leading to systematic dose underestimation unless the DLGELM is manually tuned. Therefore, optimization of DLG remains necessary for clinical implementation of the Enhanced Leaf Model in Eclipse v18. References: 1Hernandez, et al., "Commissioning Of The Tongue- And-Groove Modelling In Treatment Planning Systems: From Static Fields To Vmat Treatments". Phys Med Biol, 2017.2Saez, et al. "Universal Evaluation Of Mlc Models In Treatment Planning Systems Based On A Common Set Of Dynamic Tests". Radiother Oncol, 2023. Keywords: TPS, MLC, comissioning Reference-free direct-to-unit prostate radiation therapy using generalized optimization and on- couch adaptation K. Maiti McGrath 1,2 , Amanda Cherpak 1,2 1 Physics and Atmospheric Sciences, Dalhousie University, Halifax, Canada. 2 Radiation Oncology, Dalhousie University, Halifax, Canada Purpose/Objective: Treatment planning is a fundamental part of the radiation therapy workflow. It involves personalization of optimization parameters to tailor the dose distribution to individual cases followed by detailed review and approval. For online adaptive radiation therapy, oART, the reference plan created at this step may never be delivered and is used as a starting point for re-optimization. Personalization of a reference plan also creates a barrier for direct-to-unit workflows as it Digital Poster 3384 requires consideration of patient imaging prior to arrival at the unit. This work explores the utilization of a class solution for reference-free direct-to-unit treatment for prostate cancer. This would enable personalization of a plan to begin with a CBCT and implementation of oART at the time of first treatment.
sparing. Results:
The dose goals used for comparison across the two plans (personalized and generalized) for each patient were CTV V99% > 99% > 98%, PTV V95% > 99% > 95%, Bladder D0.03 cm3 < 6000 cGy < 6200 cGy, Bowel bag V4350 cGy < 195 cm3 < 350 cm3, Large Bowel D0.03 cm3 < 6000 cGy < 6100 cGy, Rectum V6000 cGy < 3% < 4%, and Small bowel D0.03 cm3 < 5200 cGy < 5200 cGy. These dose metrics were compared using a signed Wilcoxon rank test. All generalized template dose metrics, except for bowel bag, were found to not be significantly different from the clinical dose metrics.
Figure 1 DVH of patient 001 comparing the personalized (Clinic) and generalized (Ethos) plans and includes the dose goals shown as black triangles.
Figure 1 Wilcoxon signed rank test results for the CTV dose goal V99% > 99% > 98%. Conclusion: The generalized template and clinical plans did not differ significantly from one another despite careful optimization and personalization of each plan by an experienced clinician. This could be incorporated into the clinical workflow, reducing plan preparation time. Further personalization may be achieved with other oART planning techniques.
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