S1851
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
interactive modifications during optimization to minimize planner-dependent bias. All plans were normalized to 100 % at PTV mean dose. We recorded D98%, D2% (PTV), Dmean (bladder, rectum), the 50%- isodose volume and total MU. Exact Wilcoxon signed- rank test was used to compare the two approaches, with a significance level adjusted by Bonferroni to p = 0.05/5 = 0.01. Results: Figure 1 illustrates that both plans achieved clinically acceptable coverage, with D98% > 95.6 % and D2% < 103.6 %. The difference is not statistically significant, suggesting that RAD partially restores coverage to levels comparable with STD. No statistically significant differences were found in Dmean for rectum (p = 0.77) nor bladder (p = 0.89), indicating similar sparing across techniques.
Conclusion: RapidArc Dynamic enables efficient single-arc prostate treatments with plan quality comparable to two-arc VMAT, halving beam-on time and improving workflow efficiency and patient comfort. Keywords: RapidArc Dynamic, VMAT, Prostate radiotherapy
Digital Poster 1660
An investigation into minimum bladder filling volumes for prostate radiotherapy treatments. Miriam Kennedy 1,2 , Triona Brosnahan 1 , Margaret Moore 1 1 Medical Physics & Clinical Engineering, University Hospital Galway, Galway, Ireland. 2 Physics Department, University of Galway, Galway, Ireland Purpose/Objective: Bladder filling protocols are used within prostate radiotherapy to reduce dose to OARs, particularly the small bowel, by displacing them away from the high dose region of the treatment field. When bladders examined on CBCTs prior to treatment are smaller than the planned volume, treatment can be delayed due to dosimetric concern for OARs. This study aimed to determine a threshold minimum treatable bladder volume (VBmin) that would allow treatment to proceed at volumes smaller than the planned volume,
The STD plan provides better dose conformity than RAD (p < 0.01), but Figure 2 suggests that this difference is clinically not relevant ( Δ <V> = 25.6 cm3).Mean MUs were 820 ± 90 [range: 626-1028] for STD and 1010 ± 130 [range: 743-1359] for RAD. With gantry rotation speed as the limiting factor, the resulting beam-on time is 2 min for STD and 1 min for RAD.
Made with FlippingBook - Share PDF online