Enhancing Dosimetry Accuracy: Characterization and Verification of an Experimental Cylindrical Graphite Ionization Chamber for Dosimetry of Therapeutic Photon Beams in Reference Conditions

• Autorzy: Wołowiec Paweł , Niedziałek Weronika , Szymko Magdalena , Tulik Piotr , Zaczek Krzysztof , Stemplowska Joanna , Buliński Krzysztof , Braziewicz Janusz

Identyfikatory

DOI

10.2478/pjmpe-2025-0018

• Języki publikacji: EN

Abstrakty

EN

Introduction: Three cylindrical graphite ionization chambers have been constructed, one of which, DW3, participated in the BIPM.RI(I)-K4 key comparisons for absorbed dose to water in a gamma radiation field of the ⁶⁰Co radionuclide, achieving a positive result. This prompted us to attempt to use the experimental DW2 chamber (twin to DW3 chamber) for dosimetry of high-energy photon beams used clinically with the aim of reducing the value of the total standard uncertainty of the measured radiation dose. Material and methods: The performance of the DW2 chamber was first tested in gamma ray fields of ¹³⁷Cs and ⁶⁰Co. Subsequently, the chamber was calibrated in a ⁶⁰Co beam relative to the GUM primary standard (DW3). Then, the kQ factors for 6, 10, and 15 MV photon beams produced by Versa HD, Elekta accelerators were determined using Monte Carlo methods. Next, for the same beams, the correction factors for saturation (ks) and the polarity (kpol) were experimentally determined. Finally, the DW2 chamber was used to measure the absorbed dose to water under reference conditions. The obtained results were compared to those of a commercial Farmer-type ionization chamber, model 30013 by PTW. A metrological conformity test was used for evaluation. Results: The relative differences between the two chambers (DW2 vs Farmer chamber) in measured absorbed dose to water for 6, 10, and 15 MV photon beams were −0.1 %, 0.2 %, and 0.7 %, respectively. The relative standard uncertainties of the dose measurement under reference conditions using the DW2 chamber were approximately 0.6 % which are lower than those for the commercial chamber (Farmer) of 0.89 %. Conclusions: The obtained results confirm that the DW2 ionization chamber is an accurate tool for measuring absorbed dose to water under reference conditions for therapeutic photon beams. Lower measurement uncertainty will translate into higher precision in monitoring and calibration of the accelerator’s output.

Słowa kluczowe

EN

dosimetry; cylindrical graphite ionization chambers; DW2 ionization chamber

• Wydawca: Polskie Towarzystwo Fizyki Medycznej
• Czasopismo: Polish Journal of Medical Physics and Engineering
• Rocznik: 2025
• Tom: Vol. 31, Iss. 2
• Strony: 158--163
• Opis fizyczny: Bibliogr. 14 poz., rys., tab.

Twórcy

autor

Wołowiec Paweł

• Holy Cross Cancer Centre, Medical Physics Department, Kielce, Poland

• https://orcid.org/0000-0001-6698-9331

autor

Niedziałek Weronika

• Central Office of Measures, Electricity and Radiation Department, Ionizing Radiation Laboratory, Warsaw, Poland

• https://orcid.org/0009-0008-0402-935X

autor

Szymko Magdalena

• Central Office of Measures, Electricity and Radiation Department, Ionizing Radiation Laboratory, Warsaw, Poland

• https://orcid.org/0000-0002-3219-9259

autor

Tulik Piotr

• Faculty of Mechatronics, Institute of Metrology and Biomedical Engineering, Warsaw University of Technology, Warsaw, Poland

• https://orcid.org/piotr.tulik%40pw.edu.pl

autor

Zaczek Krzysztof

• Central Office of Measures, Electricity and Radiation Department, Ionizing Radiation Laboratory, Warsaw, Poland

autor

Stemplowska Joanna

• Holy Cross Cancer Centre, Medical Physics Department, Kielce, Poland

autor

Buliński Krzysztof

• Holy Cross Cancer Centre, Medical Physics Department, Kielce, Poland
• Central Office of Measures, Electricity and Radiation Department, Ionizing Radiation Laboratory, Warsaw, Poland

autor

Braziewicz Janusz

• Jan Kochanowski University, Institute of Physics, Kielce, Poland
• Holy Cross Cancer Centre, Nuclear Medicine Department with PET Division, Kielce, Poland

• https://orcid.org/0000-0002-6972-7027

Bibliografia

• 1. Kessler C, Burns D, Knyziak A, Szymko M, Derlaciński M. Key comparison BIPM.RI(I)-K4 of the absorbed dose to water standards of the GUM, Poland and the BIPM in 60Co gamma radiation. Metrologia. 2021;58(1A):06014. doi:10.1088/0026-1394/58/1a/06014
• 2. International Commission on Radiation Units & Measurements. ICRU REPORT 90: Key Data for Ionizing-Radiation Dosimetry: Measurement Standards and Applications. ICRU; 2016.
• 3. International Atomic Energy Agency. Absorbed Dose Determination in External Beam Radiotherapy, Technical Reports Series No. 398 (Rev. 1). IAEA, Vienna; 2024.
• 4. Szymko MM, Knyziak AB, Derlaciński M. Graphite ionization chamber as an ionometric standard of absorbed dose to water for Co-60 gamma radiation. Measurement. 2022;194:110928. doi:10.1016/j.measurement.2022.110928
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• 12. Evaluation of Measurement Data - Guide to the Expression of Uncertainty in Measurement, Technical report, Joint Committee for Guides in Metrology, JCGM 100:2008.
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