Document Type : Original Article
Authors
- Sahar Hashemian 1
- Razieh Rashidfar 2
- Hossein Parsaei 1
- Ahmadreza Azarm 3
- Mohammad Amin Mosleh-Shirazi 2, 4
1 Department of Medical Physics and Engineering, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
2 Ionizing and Non-Ionizing Radiation Protection Research Center, School of Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran
3 Breast Diseases Research Center, Department of Surgery, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
4 Radiotherapy Physics Unit, Department of Radiooncology, Namazi Hospital, Shiraz University of Medical Sciences, Shiraz, Iran
Abstract
Introduction: The commissioning and treatment planning of the LIAC 12 MeV intraoperative electron radiotherapy (IOERT) unit rely heavily on the performance of the SWL-LIAC software. This software simulates the relative dosimetric data of the unit based on four percentage depth dose (PDD) curves. This study aimed to evaluate the software’s performance by comparing the simulated and experimentally measured PDD curves.
Methods: Percentage depth dose measurements were conducted for various beveled applicators across all available energies (6, 8, 10, 12 MeV), encompassing 24 fields. Measurements were performed using an E-type electron diode in a water phantom, assisted by custom-made positioning tools, and verified via radiochromic film dosimetry. The measured and calculated PDDs were subsequently compared using one-dimensional gamma analysis.
Results: In the comparisons between the measured PDD curves and the software output for the 24 applicators, the mean gamma passing rate was 100% using a 3 mm/3% (global dose difference) acceptance criterion. When applying a stricter 2 mm/2% criterion, the gamma passing rate for the 3 cm diameter, 15° applicator at 12 MeV was 98.7%, resulting in an overall mean gamma passing rate of 99.9% across all fields at this criterion. The maximum absolute dose difference was 2.9%, which was observed in the 3 cm diameter, 15° applicator at 12 MeV and the 30° applicator at 6 MeV.
Conclusion: The SWL-LIAC software demonstrated sufficient accuracy in its percentage depth dose calculations for beveled applicators.
Keywords
- Beddar AS, Biggs PJ, Chang S, Ezzell GA, Faddegon BA, Hensley FW, et al. Intraoperative radiation therapy using mobile electron linear accelerators: report of AAPM Radiation Therapy Committee Task Group No. 72. Med Phys. 2006;33(5):1476-89.
- Iaccarino G, Strigari L, D’Andrea M, Bellesi L, Felici G, Ciccotelli A, et al. Monte Carlo simulation of electron beams generated by a 12 MeV dedicated mobile IORT accelerator. Phys Med Biol. 2011;56(14):4579-96.
- Gunderson LL, Willett CG, Calvo FA, Harrison LB. Intraoperative irradiation: techniques and results. New York: Springer Science & Business Media; 2011.
- SWL–LIAC Monte Carlo simulation, users manual. Rome: Sordina IORT SpA; 2013.
- Mosleh-Shirazi MA, Rashidfar R, Karbasi S, Pashnehsaz M, Mahdavi M. Independent validation of a dedicated commissioning software and investigation of the direction dependence of the field symmetry for the LIAC intraoperative electron radiotherapy accelerator. Radiat Phys Chem. 2021;186:109529.
- Mosleh-Shirazi MA, Rashidfar R, Karbasi S, Pashnehsaz M, Mahdavi M. The LIAC 12 MeV intraoperative electron radiotherapy unit: bi-directional assessment of field symmetry and independent evaluation of the SWL-LIAC simulation software. Med Phys. 2021;48(Suppl 1):E1-E2.
- Bjork P, Nilsson P, Knoos T. Dosimetry characteristics of degraded electron beams investigated by Monte Carlo calculations in a setup for intraoperative radiation therapy. Phys Med Biol. 2002;47(2):239-56.
- Pimpinella M, Mihailescu D, Guerra AS, Laitano RF. Dosimetric characteristics of electron beams produced by a mobile accelerator for IORT. Phys Med Biol. 2007;52(20):6197-214.
- Di Venanzio C, Marinelli M, Tonnetti A, Verona-Rinati G, Falco MD, Pimpinella M, et al. Characterization of a microDiamond detector in high-dose-per-pulse electron beams for intraoperative radiation therapy. Phys Med. 2015;31(8):897-902.
- Gungor G, Aydin G, Mustafayev TZ, Ozyar E. Output factors of ionization chambers and solid state detectors for mobile intraoperative radiotherapy (IORT) accelerator electron beams. J Appl Clin Med Phys. 2019;20(2):13-23.
- Andreoli S, Pimpinella M, De Angelis C, Menegotti L, Silvi L, Della Monaca S. Detectors comparison for absorbed dose and output factors determination in high dose per pulse electron beams produced by a mobile linac for intraoperative radiation therapy (IORT). Phys Med. 2018;56:102.
- Mosleh-Shirazi MA, Ketabi A, Karbasi S, Faghihi R. Assessment of an unshielded electron field diode dosimeter for beam scanning in small-to medium-sized 6 MV photon fields. Iran J Med Phys. 2013;10(1-2):51.
- Bjork P, Knoos T, Nilsson P. Comparative dosimetry of diode and diamond detectors in electron beams for intraoperative radiation therapy. Med Phys. 2000;27(11):2580-8.
- Palta JR, Biggs PJ, Hazle JD, Huq MS, Dahl RA, Ochran TG, et al. Intraoperative electron beam radiation therapy: technique, dosimetry, and dose specification: report of task force 48 of the Radiation Therapy Committee, American Association of Physicists in Medicine. Int J Radiat Oncol Biol Phys. 1995;33(3):725-46.
- Di Martino F, Giannelli M, Traino A, Lazzeri M. Ion recombination correction for very high dose-per-pulse high-energy electron beams. Med Phys. 2005;32(7 Pt 1):2204-10.
- Smilowitz JB, Das IJ, Feygelman V, Fraass BA, Kry SF, Marshall IR, et al. AAPM Medical Physics Practice Guideline 5.a.: commissioning and QA of treatment planning dose calculations—megavoltage photon and electron beams. J Appl Clin Med Phys. 2015;16(5):14-34.
- Fatis LM, Felici G, Ciccotelli A, Grusio M. Intercomparison between Monte Carlo calculations and measurements for electron beams produced by a dedicated mobile IORT accelerator. Med Phys Conf Italy. 2013;71:1-5.
- Van Dyk J, Barnett RB, Cygler JE, Shragge PC. Commissioning and quality assurance of treatment planning computers. Int J Radiat Oncol Biol Phys. 1993;26(2):261-73.
)