ESTRO 2025 - Abstract Book

S3617

Physics - Quality assurance and auditing

ESTRO 2025

Conclusion: A new phantom has been designed to allow interstitial cervical brachytherapy treatment assessment with MRI- or CT-based planning, the first to use virtual structures and two dosimetry systems. The results of three pilot audits have been presented, validating the approach. The system will now be used for dose audit at over 40 radiotherapy centres in the UK.

Keywords: brachytherapy, dosimetry, end to end

References: [1] NHS England. Service Specification: brachytherapy (all ages). 18 September 2024. https://www.england.nhs.uk/publication/service-specification-brachytherapy-all-ages/ [2] Palmer A.L. et al. A multicentre ‘end to end’ dosimetry audit for cervix HDR brachytherapy treatment. Radiother. Oncol. 2015;114:264-71 [3] Palmer A.L. et al. Design and implementation of a film dosimetry audit tool for comparison of planned and delivered dose distributions in high dose rate (HDR) brachytherapy. Phys. Med. Biol. 2013;58:6623-40 [4] 3D slicer. https://www.slicer.org/ (Accessed: 02 September 2024) [5] Fedorov A. et al. 3D Slicer as an image computing platform for the quantitative imaging network. Mag. Res. Imaging 2012;30(9):1323-41

1551

Digital Poster Analysis of Elekta MLC performance using statistics process control Andrea Rodríguez Álvarez, Pablo López Expósito, Daniel Díaz Martín, Breixo Carmelo Portas Ferradás, Abel Niebla Piñero Medical Physics and Radiation Protection Department, Complejo Hospitalario Universitario Nuestra Señora de la Candelaria (CHUSNC), Santa Cruz de Tenerife, Spain Purpose/Objective: The aim of this work is to perform a statistical analysis of three Agility MLC systems installed in Elekta Versa HD linear accelerators, used clinically at the CHUNSC. Material/Methods: Leaf position deviation data was collected weekly for three Elekta Versa HD accelerators over 13-24 months using the "MLC Leaf and Jaw Position Linac Connect" test [1]. All data was processed and analyzed using a Python script. Distribution of all leaves in each bank was studied. Mean leaf deviation was assessed using histogram and cumulative percentage deviation. Each nominal position in the picket fence was studied using moving range control charts. Moreover, these behavior charts were used to analyze globally each bank. Results: All-leaf distributions were studied and displayed, finding minor deviation for central leaves and greater for outermost. Mean differences were 0.1 mm (range 0.05-0.2). Hence, the deviations of the leaves as a whole were studied more thoroughly, as seen in the following histograms separated by banks (figure 1).