S2003
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
series of plans with more combinations of the optimization parameters has been performed considering one lesion at the center of the brain. The Conformity index, Paddick index, Gradient index and V12Gy were used to evaluate the dosimetries. The t- test for paired samples was used to compare the indices. Results: The mean, standard deviation, and range of the indices studied are shown at Table 1. Significant differences were observed in all the parameters analyzed (p < 0.001 ), achieving better indices in metastases.
heart dose, particularly in right-sided treatments. The presence of a simultaneous integrated boost did not significantly increase MHD. Ipsilateral lung exposure was low in both patients with and without boost. Ultra- hypofractionation reduces the number of treatment sessions, offering logistical advantages. Long-term follow-up is required to assess late clinical toxicity. References: 1. Murray Brunt A, Haviland JS, Wheatley DA. et al. FAST-Forward Trial Management Group. Hypofractionated breast radiotherapy for 1 week versus 3 weeks (FAST-Forward): 5-year efficacy and late normal tissue effects results from a multicentre, non-inferiority, randomised, phase 3 trial. Lancet. 2020 May 23;395(10237):1613-1626. doi: 10.1016/S0140- 6736(20)30932-6. Epub 2020 Apr 28. PMID: 32580883; PMCID: PMC7262592.2. Ratosa I, Montero A, Ciervide R, et al. Ultra-hypofractionated one-week locoregional radiotherapy for patients with early breast cancer: Acute toxicity results. Clin Transl Radiat Oncol. 2024 Mar 13;46:100764. doi: 10.1016/j.ctro.2024.100764. PMID: 38516338; PMCID: PMC10955656. Keywords: breast cancer, ultra-hypofractionation, MHD Digital Poster 4555 Comparison of dosimetry in brain metastasis planned for LINAC and Gamma Knife Diana Andrés 1 , Raúl Pascual 1 , Iago Mosquera 1 , Mari Carmen Baños-Capìlla 2 , Juan Carlos Sánchez 1 , Ana Castelló 1 1 Radiophysics and Radiation Protection, Hospital Clínico Universitario de Valencia, Valencia, Spain. 2 Radiotherapy, Hospital Vithas Valencia Consuelo, Valencia, Spain
When comparing V12Gy, it is seen among the 6 studied patients that this index is a 50-75% smaller in the Gamma Knife-planned patients (p < 0.01), with small differences when varying the optimization parameters or the prescription dose.At Figure 1, it is shown how using different combinations of the optimization parameters, time and gradient index varies in an inverse way. Differences between these plans are small when both BoT and LD are in the range 0.4-0.7, allowing for better customization of the prescription dose and treatment time for each patient.
Purpose/Objective: The Gammaknife (Elekta) is a specific unit for
radiosurgery. Its high precision in patient positioning and its 192 Co-60 sources allow direct treatment of the GTV, reducing the dose to healthy tissue compared to LINAC.The aim of this study is to evaluate the differences between brain metastasis planned with the software Monaco for LINAC and with Gammaplan for Gamma Knife. Material/Methods: Dosimetry was compared in 6 patients with one or more lesions, planned in Monaco using cones, with a dose of 18 Gy to PTV (GTV + 2 mm). Images and structures were imported to Gammaplan, where inverse optimization takes two parameters: Low Dose (reduces dose to healthy tissue) and Beam on Time (reduces treatment time). Three plans were performed for each lesion, varying these parameters, and one extra plan increasing the dose to 21 Gy. An extra
Conclusion: The dosimetric comparison between LINAC and Gamma Knife in brain metastases shows that Gamma Knife plans significantly reduce V12Gy in patients and offer better conformality indices. This is due to the large number of sources, the small size of their fields and the precise positioning of the patient, which allow for large dose gradients that protect healthy tissue and can be tuned by varying the Gamma Knife characteristic optimization parameters. Keywords: Gamma Knife, radiosurgery, brain metastasis
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