ESTRO 2025 - Abstract Book

S3629

Physics - Quality assurance and auditing

ESTRO 2025

had unacceptable deviations due to the optic nerves contouring and so the dosimetry review was not done, while the third, with a D98% of 9.02Gy and D0.03cc of 19.53Gy, was justified unacceptable variation since no further changes were possible. The median peri-hippocampal D0.03cc were: 22.68Gy (95% CI 20.82-23.10), 23.8Gy (95% CI 22.34-24.08), 24.76Gy (95% CI 23.92-24.98), 25.52Gy (95% CI 25.23-25.86), 25.9Gy (95% CI 25.66-26.40), and 26.21Gy (95% CI 26.10-26.83) from PRV05 to PRV10 [Figure 2]. The minimum distance from the hippocampi to the 25Gy isodose line was a median 6.7mm (95% CI 6.39-7.28).

Figure 2 Box and whisker plot of 1mm increments expansions of peri-hippocampal D0.03cc from Hippocampi_PRV05 until Hippocampi_PRV10

Conclusion: HA-PCI with a target prescription of 25Gy in 10 fractions is deliverable at a median 6.7mm distance from the hippocampi . The mean target coverage of plans was 93.5% (23.39±0.63). The prescription dose was achieved in all instances at Hippocampi_PRV08 25.52Gy, which may be used as a quality measure of optimal planning. Three plans exceeded the mandatory constraints to the hippocampi in favour of target dose.

Keywords: Dosimetry , PRIMALung ,PCI, Hippocampal Avoidance

References: 1. Levy, A., Berghmans, T., Koller, M., Fournier, B., Mauer, M., Andratschke, N., & Faivre-Finn, C. (2024). PRIMALung (EORTC-1901): PRophylactic cerebral irradiation (PCI) or active brain MAgnetic resonance imaging (MRI) surveillance in small-cell lung cancer (SCLC) patients. Lung Cancer , Volume 0 , Issue 0. 2. Rao, G. K., Hsu, A., Kim, M. M., & Mendez, R. (2010). Hippocampal-sparing whole-brain radiotherapy: A “how-to” technique using helical tomotherapy and linear accelerator–based intensity-modulated radiotherapy. Practical Radiation Oncology , 1 (2), 84-91.

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Digital Poster Large-scale adoption of statistical process control for routine quality assurance on two Elekta medical linear accelerators Carmela Romano 1 , Pietro Viola 1 , Maurizio Craus 1 , Erica Costantino 1 , Anna Ianiro 2 , Gabriella Macchia 3 , Francesco Deodato 3 , Alessio G Morganti 4 , Savino Cilla 1 1 Medical Physics Unit, Responsible Research Hospital, Campobasso, Italy. 2 Medical Physics Unit, IRCCS Regina Elena National Cancer Institute, Roma, Italy. 3 Radiation Oncology Unit, Responsible Research Hospital, Campobasso, Italy. 4 Department of Experimental, Diagnostic and Specialty Medicine - DIMES, S. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy