S1959
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
30mm, 30-40mm, 40-50mm, and 50-60mm from the high dose area (Figure 1A). Results: The dose distribution without magnetic field (Figure 1B) and with magnetic field (Figure 1C) show the electron streaming effect in the trachea, pharynx and skin for all patients. In the mucosa of the trachea and pharynx, the dose is generally higher in the plans with magnetic field than in plans without magnetic field. However, the dose increase in the mucosa at a distance of 10-60 mm of the high dose area remained below 2 Gy for all patients. The dose difference at a distance of 0-10 mm ranged from -0.7 to 4.0 Gy caudal, and -1.0 to 4.2 Gy cranial. However, plan differences could have influenced the measurements in this specific area (0-10mm). In the skin, the maximum dose increase (D0.03cc) caudal to the high dose area due to electron streaming was 5.4 Gy. In cranial direction, the maximum dose increase (D0.03cc) was 1.5 Gy. The dose increase due to electron streaming remained below 1.2 Gy for D5cc.
Conclusion: Plans with magnetic field showed a higher dose in the mucosa of the trachea and pharynx, and in the skin due to electron streaming. However, the absolute differences are small and clinically irrelevant. Keywords: MR-linac, SABR, electron streaming effect Digital Poster Highlight 3898 Treatment planning using a high-performance on- board imaging system for offline adaptive radiotherapy Tim Melhus 1 , Mohammed Ghazal 1,2 , Mattias Hedman 3,2 , Hamza Benmakhlouf 3,2 1 Department of Medical Radiation Physics and Nuclear Medicine, Karolinska University Hospital, Stockholm, Sweden. 2 Department of Oncology-Pathology, Karolinska Institute, Stockholm, Sweden. 3 Department of Radiation Oncology, Karolinska University Hospital, Stockholm, Sweden Purpose/Objective: Offline dose-adaptation in head and neck cancer
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