Implementation and validation of the method for the energy spectra reconstruction of electron beams generated by the AQURE mobile accelerator
Abstract
Background: The energy spectrum is the main component of the Monte Carlo model of the electron beam. One possible method to obtain it is a backward reconstruction from the measured depth dose distribution, owing to solving the inverse first-degree Fredholm integral equation with appropriate regularisation. This study aimed to reconstruct and validate energy spectra for mobile intraoperative accelerators.
Materials and methods: The Geant4 package was used to simulate percentage depth dose (PDD) distributions. The microDiamond detector and the BeamScan water phantom were used to measure PDD. 160 PDDs were simulated for quasi-monoenergetic beams with energies from 0 to 20 MeV for a 10 cm diameter applicator. Using the simulated and measured PDDs, energy spectra were reconstructed for all available nominal energies by solving the inverse Fredholm equation. A single Gaussian peak was used as a reference solution, and the regularisation parameter λ was set to 0.05. Obtained spectra were used to simulate PDD for 5 and 6 cm applicators and compared with the measurements.
Results: Simulated and measured PDDs were compared using the gamma analysis method with 2% DD and 2 mm distance to agreement (DTA) criteria. Measured and simulated PDDs agree perfectly for the 4 MeV beam. For higher energies, the PDDs agree at all depths except for depths less than 2 mm.
Conclusion: The numerical solution of the inverse Fredholm equation with Tikhonov regularisation using simulated annealing optimisation is a reliable method to reconstruct the energy spectrum for electron beams produced by mobile intraoperative accelerators.
Keywords: IOERTMonte Carlodual annealing
References
- Calvo FA, Meirino RM, Orecchia R. Intraoperative radiation therapy first part: rationale and techniques. Crit Rev Oncol Hematol. 2006; 59(2): 106–115.
- Willett CG, Czito BG, Tyler DS. Intraoperative radiation therapy. J Clin Oncol. 2007; 25(8): 971–977.
- Oses G, Biete A, Muñoz-Guglielmetti D, et al. Intraoperative electron radiation therapy after salvage surgery in gynecological cancers and retroperitoneal sarcomas: outcomes and adverse effects. Rep Pract Oncol Radiother. 2022; 27(5): 905–913.
- Adrich P, Baczewski A, Baran M, et al. A new mobile electron accelerator for intra-operative electron radiation therapy. Int J Mod Phys Conf Ser. 2014; 1(27): 1460125.
- Adrich P, Hanke R, Kulczycka E, et al. The IOERT IntraLine accelerator — the development, current state, and future plans. Nukleonika. 2016; 61(1): 3–9.
- Rezzoug M, Zerfaoui M, Oulhouq Y, et al. Using PRIMO to determine the initial beam parameters of Elekta Synergy linac for electron beam energies of 6, 9, 12, and 15 MeV. Rep Pract Oncol Radiother. 2023; 28(5): 592–600.
- Tabor Z, Kabat D, Waligórski MPR. DeepBeam: a machine learning framework for tuning the primary electron beam of the PRIMO Monte Carlo software. Radiat Oncol. 2021; 16(1): 124.
- Robatjazi M, Tanha K, Mahdavi SR, et al. Monte Carlo Simulation of Electron Beams produced by LIAC Intraoperative Radiation Therapy Accelerator. J Biomed Phys Eng. 2018; 8(1): 43–52.
- Ryczkowski A, Piotrowski T, Staszczak M, et al. Optimization of the regularization parameter in the Dual Annealing method used for the reconstruction of energy spectrum of electron beam generated by the AQURE mobile accelerator. Z Med Phys. 2024; 34(4): 510–520.
- Geant4 — A simulation toolkit. https://geant4.web.cern.ch/ (02.01.2024).
- Zhengming L, Jette D. On the possibility of determining an effective energy spectrum of clinical electron beams from percentage depth dose (PDD) data of broad beams. Phys Med Biol. 1999; 44(8): N177–N182.
- Chvetsov AV, Sandison GA. Angular correction in reconstruction of electron spectra from depth dose distributions. Med Phys. 2003; 30(8): 2155–2158.
- Das IJ, Cheng CW, Watts RJ, et al. TG-106 of the Therapy Physics Committee of the AAPM. Accelerator beam data commissioning equipment and procedures: report of the TG-106 of the Therapy Physics Committee of the AAPM. Med Phys. 2008; 35(9): 4186–4215.
- Pimpinella M, Stravato A, Guerra AS, et al. Energy dependence of PTW microdiamond detector in radiotherapy photon and electron beams. Phys Med. 2014; 30: e64.
- Di Venanzio C, Marinelli M, Tonnetti A, et al. Characterization of a microDiamond detector in high-dose-per-pulse electron beams for intra operative radiation therapy. Phys Med. 2015; 31(8): 897–902.
- International Atomic Energy Agency (IAEA). Absorbed Dose Determination in External Beam Radiotherapy; Technical Reports Series No. 398; IAEA: Vienna, Austria, 2000.
- Wazwaz AM. The regularization method for Fredholm integral equations of the first kind. Comput Math with Appl. 2011; 61(10): 2981–2986.
- Low DA, Harms WB, Mutic S, et al. A technique for the quantitative evaluation of dose distributions. Med Phys. 1998; 25(5): 656–661.
- Wegener S, Herzog B, Sauer OA. Detector response in the buildup region of small MV fields. Med Phys. 2020; 47(3): 1327–1339.
- Mani K, Bhuiyan M, Rahman M, et al. Open beam dosimetric characteristics of True Beam medical linear accelerator with flattening filter (WFF) and flattening filter free (FFF) beam. Pol J Med Phys Eng. 2018; 24(2): 79–89.
- Chung H, Jin H, Dempsey JF, et al. Evaluation of surface and build-up region dose for intensity-modulated radiation therapy in head and neck cancer. Med Phys. 2005; 32(8): 2682–2689.
- Abdel-Rahman W, Seuntjens JP, Verhaegen F, et al. Validation of Monte Carlo calculated surface doses for megavoltage photon beams. Med Phys. 2005; 32(1): 286–298.
- Brace OJ, Alhujaili SF, Paino JR, et al. Evaluation of the PTW microDiamond in edge-on orientation for dosimetry in small fields. J Appl Clin Med Phys. 2020; 21(8): 278–288.
- Reynolds TA, Higgins P. Surface dose measurements with commonly used detectors: a consistent thickness correction method. J Appl Clin Med Phys. 2015; 16(5): 358–366.
- Björk P, Nilsson P, Knöös 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): 239–256.
- Jabbari N, Hashemi-Malayeri B. Monte Carlo modeling of electron beams from a NEPTUN 10PC medical linear accelerator. Nukleonika. 2009; 54(4): 233–238.
- van der Geer B, De Loos M. The general particle tracer code: design, implementation and application. J Bus Commun — J Bus Comm. 2001; Apr 2.