S2393
Physics - Quality assurance and auditing
ESTRO 2026
manufacturers (figure 1) and the UK (IPEM) protocol for measurements in medium-energy X- rays.
Med. Phys. 39 2839–472. Zhen H, Nelms B E and Tomé WA 2011. Moving from gamma passing rates to patient DVH-based QA metrics in pretreatment dose QA, Med. Phys. 38 5477–89. 3. Lehmann J, Hussain M, Barry MA, et al. 2022 SEAFARER – A new concept for validation radiotherapy patient specific QA for clinical trials and clinical practice, Radiato Oncol 171 121-28. Keywords: EPID dosimetry, DVH-based verification, VMAT QA Mini-Oral 4145 Reference Dosimetry Audit of Preclinical Radiotherapy Platforms Across CRUK RadNet London Centres. Ileana Silvestre Patallo 1 , Jayanta Kumar Bordoloi 2 , Rebecca Carter 3 , Julie Cleaver 4 , Jana Kim 4 , Jenasee Mynerich 5 , Thomas Snoeks 2 , Samantha Terry 5 , Giuseppe Schettino 1 1 Radiation Dosimetry Group, National Physical Laboratory (NPL), London, United Kingdom. 2 Biological Research Facility, The Francis Crick Institute, London, United Kingdom. 3 Department of Medical Physics & Biomedical Engineer, University College London (UCL), London, United Kingdom. 4 Preclinical Imaging Core Facility, Queen Mary University of London, London, United Kingdom. 5 Department of Imaging Chemistry and Biology, King’s College London, London, United Kingdom Purpose/Objective: Preclinical radiotherapy research is often hindered by variability in dose delivery and lack of harmonized dosimetric protocols, limiting reproducibility and translational potential. Standardizing dosimetry in preclinical platforms is critical for reliable interinstitutional comparisons and improved translatability of radiation-related outcomes [1,2]. Accurate dose delivery and traceability to National Measurement Institutes are prerequisites for clinical trial participation, and recent recommendations advocate similar standards in preclinical research [3]. This study establishes, for the first time, a baseline for dose accuracy across four image-guided small animal radiotherapy platforms (three SARRP/Xstrahl and one SmART+/Precision-X-Ray) at CRUK City of London Centre, using a consistent methodology. Material/Methods: A standardized measurement set—comprising a calibrated barometer, thermometer, reference-class electrometer, and secondary standard Farmer-type ionization chamber—was used to assess beam quality and reference output. All instruments were traceable to the UK primary standard of air kerma (NPL Free Air Chamber). Reference absorbed dose was determined following the setup recommended by the
An end-to-end dosimetry audit was conducted using two different phantoms and alanine and Gafchromic films as detectors. Alanine response in medium- energy X-rays has been previously characterized at NPL [4]. Treatment plans with 7 × 7 mm ² and 10 × 10 mm ² field sizes and varying complexity were generated using Muriplan (SARRP) and SmART-Plan (SmART+). Difference between measured and TPS- calculated doses to alanine, contoured as a region of interest (ROI), were assessed. Positional and film analyses were conducted using μ RayStation and an in- house MATLAB program, Vigo (Versatile Independent Gamma sOftware). The workflow illustrating positional differences is presented in Figure 2.
All measurements were performed on-site, in collaboration with local facility managers. Results: Measured X-ray beam quality (Half-Value-Layer, HVL) ranged from 0.82 to 0.87 mm Cu, with a maximum
Made with FlippingBook - Share PDF online