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Hybrid Monte Carlo source model: Advantages and deficiencies. POLISH JOURNAL OF MEDICAL PHYSICS AND ENGINEERING 2018. [DOI: 10.2478/pjmpe-2018-0009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Abstract
Monte Carlo (MC) simulation is the gold standard for dose calculation. An accurate mathematical source model can be used for the radiation beams. Source models can consist of sub-sources or fewer sources with data that need to be measured. This can speed up treatment plan verification without the need for a full simulation of the radiation treatment machine.
Aims: This study aimed to construct a novel hybrid source model for 6 MV photon beams for an Elekta Synergy accelerator and to commission it against measured beam data and treatments plans.
Methods and Material: The model comprised of a circular photon and planar electron contamination source. The modified Schiff formula provided off-axis variable bremsstrahlung spectra. Collimation and scatter were modelled with error functions. An exponential function modelled the transmitted fluence through the collimators. The source model was commissioned by comparing simulated and measured MC data. Dose data included profiles, depth dose and film measurements in a Rando phantom. Field sizes ranged from 1 × 1 cm2 to 40 × 40 cm2.
Results: Regular, wedged and asymmetrical fields could be modelled within 1.5% or 1.5 mm. More than 95% of all points lie within 3% or 3 mm for the multi-leaf collimators contours data. A gamma criterion of 3% or 3 mm was met for a complex treatment case.
Conclusions: The two sub-source model replicated clinical 6 MV Elekta Synergy photons beams and could calculate the dose accurately for conformal treatments in complex geometries such as a head-and-neck case.
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Rucci A, Carletti C, Cravero W, Strbac B. Use of IAEA’s phase-space files for virtual source model implementation: Extension to large fields. Phys Med 2016; 32:1030-3. [DOI: 10.1016/j.ejmp.2016.07.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 07/07/2016] [Accepted: 07/10/2016] [Indexed: 11/15/2022] Open
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Rucci A, Carletti C, Cravero W, Strbac B. Use of IAEA's phase-space files for the implementation of a clinical accelerator virtual source model. Phys Med 2013; 30:242-8. [PMID: 23932845 DOI: 10.1016/j.ejmp.2013.07.127] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Revised: 07/05/2013] [Accepted: 07/19/2013] [Indexed: 11/29/2022] Open
Abstract
In the present work, phase-space data files (phsp) provided by the International Atomic Energy Agency (IAEA) for different accelerators were used in order to develop a Virtual Source Model (VSM) for clinical photon beams. Spectral energy distributions extracted from supplied phsp files were used to define the radiation pattern of a virtual extended source in a hybrid model which is completed with a virtual diaphragm used to simulate both electron contamination and the shape of the penumbra region. This simple virtual model was used as the radiation source for dosimetry calculations in a water phantom. The proposed model proved easy to build and test, and good agreement with clinical accelerators dosimetry measurements were obtained for different field sizes. Our results suggest this simple method could be useful for treatment planning systems (TPS) verification purposes.
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Affiliation(s)
- Alexis Rucci
- Instituto de Física del Sur, Universidad Nacional del Sur, Consejo Nacional de Investigaciones Científicas y Técnicas, Av. Alem 1253, 8000 Bahía Blanca, Argentina; Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, 8000 Bahía Blanca, Argentina.
| | - Claudia Carletti
- Instituto de Física del Sur, Universidad Nacional del Sur, Consejo Nacional de Investigaciones Científicas y Técnicas, Av. Alem 1253, 8000 Bahía Blanca, Argentina; Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, 8000 Bahía Blanca, Argentina
| | - Walter Cravero
- Instituto de Física del Sur, Universidad Nacional del Sur, Consejo Nacional de Investigaciones Científicas y Técnicas, Av. Alem 1253, 8000 Bahía Blanca, Argentina; Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, 8000 Bahía Blanca, Argentina
| | - Bojan Strbac
- International Medical Centres, Centre for Radiotherapy, Dvanaest beba bb, 78000 Banja Luka, Bosnia and Herzegovina
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Ezzati AO, Sohrabpour M, Mahdavi SR, Buzurovic I, Studenski MT. A comprehensive procedure for characterizing arbitrary azimuthally symmetric photon beams. Phys Med 2013; 30:191-201. [PMID: 23768452 DOI: 10.1016/j.ejmp.2013.05.040] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2012] [Revised: 05/10/2013] [Accepted: 05/18/2013] [Indexed: 01/18/2023] Open
Abstract
PURPOSE A new Monte Carlo (MC) source model (SM) has been developed for azimuthally symmetric photon beams. METHODS The MC simulation tallied phase space file (PSF) is divided into two categories depending on the relationship of the particle track line to the beam central axis: multiple point source (MPS) and spatial mesh based surface source (SMBSS). To validate this SM, MCNPX2.6 was used to generate two PSFs for a 6 MV photon beam from a Varian 2100C/D linear accelerator. RESULTS PDDs and profiles were calculated using the SM and original PSF for different field sizes from 5 × 5 to 40 × 40 cm2. Agreement was within 2% of the maximum dose at 100 cm SSD and 2.5% of the maximum dose at 200 cm SSD for beam profiles at depths of 3.5 cm and 15 cm with respect to the original PSF. Differences between the source model and the PSF in the out-of-field regions were less than 0.5% of the profile maximum value at 100 cm SSD. Differences between measured and calculated points were less than 2% of the maximum dose or 2 mm distance to agreement (DTA) at 100 cm SSD. CONCLUSIONS This SM is unique in that it accounts for a higher level of energy dependence on the particle's direction and it is independent from accelerator components, unlike other published SMs. The model can be applied to any arbitrary azimuthally symmetric beam and has source biasing capabilities that significantly increase the simulation speed up to 3300 for certain field sizes.
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Affiliation(s)
- Ahad Ollah Ezzati
- Department of Energy Engineering, Sharif University of Technology, Tehran, Iran.
| | - Mostafa Sohrabpour
- Department of Energy Engineering, Sharif University of Technology, Tehran, Iran
| | - Seied Rabi Mahdavi
- Department of Medical Physics, Tehran University of Medical Science, Tehran, Iran
| | - Ivan Buzurovic
- Department of Radiation Oncology, Dana-Farber/Brigham and Women's Cancer Center, Harvard Medical School, Boston, MA, USA
| | - Matthew T Studenski
- Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, PA, USA
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Braunstein S, Nakamura JL. Radiotherapy-induced malignancies: review of clinical features, pathobiology, and evolving approaches for mitigating risk. Front Oncol 2013; 3:73. [PMID: 23565507 PMCID: PMC3615242 DOI: 10.3389/fonc.2013.00073] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Accepted: 03/21/2013] [Indexed: 12/24/2022] Open
Abstract
One of the most significant effects of radiation therapy on normal tissues is mutagenesis, which is the basis for radiation-induced malignancies. Radiation-induced malignancies are late complications arising after radiotherapy, increasing in frequency among survivors of both pediatric and adult cancers. Genetic backgrounds harboring germline mutations in tumor suppressor genes are recognized risk factors. Some success has been found with using genome wide association studies to identify germline polymorphisms associated with susceptibility. The insights generated by genetics, epidemiology, and the development of experimental models are defining potential strategies to offer to individuals at risk for radiation-induced malignancies. Concurrent technological efforts are developing novel radiotherapy delivery to reduce irradiation of normal tissues, and thereby, to mitigate the risk of radiation-induced malignancies. The goal of this review is to discuss epidemiologic, modeling, and radiotherapy delivery data, where these lines of research intersect and their potential impact on patient care.
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Affiliation(s)
- Steve Braunstein
- Department of Radiation Oncology, University of California San FranciscoSan Francisco, CA, USA
| | - Jean L. Nakamura
- Department of Radiation Oncology, University of California San FranciscoSan Francisco, CA, USA
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Spezi E, Volken W, Frei D, Fix MK. A virtual source model for Kilo-voltage cone beam CT: Source characteristics and model validation. Med Phys 2011; 38:5254-63. [DOI: 10.1118/1.3626574] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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García-Pareja S, Galán P, Manzano F, Brualla L, Lallena AM. Ant colony algorithm implementation in electron and photon Monte Carlo transport: application to the commissioning of radiosurgery photon beams. Med Phys 2010; 37:3782-90. [PMID: 20831086 DOI: 10.1118/1.3456108] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE In this work, the authors describe an approach which has been developed to drive the application of different variance-reduction techniques to the Monte Carlo simulation of photon and electron transport in clinical accelerators. METHODS The new approach considers the following techniques: Russian roulette, splitting, a modified version of the directional bremsstrahlung splitting, and the azimuthal particle redistribution. Their application is controlled by an ant colony algorithm based on an importance map. RESULTS The procedure has been applied to radiosurgery beams. Specifically, the authors have calculated depth-dose profiles, off-axis ratios, and output factors, quantities usually considered in the commissioning of these beams. The agreement between Monte Carlo results and the corresponding measurements is within approximately 3%/0.3 mm for the central axis percentage depth dose and the dose profiles. The importance map generated in the calculation can be used to discuss simulation details in the different parts of the geometry in a simple way. The simulation CPU times are comparable to those needed within other approaches common in this field. CONCLUSIONS The new approach is competitive with those previously used in this kind of problems (PSF generation or source models) and has some practical advantages that make it to be a good tool to simulate the radiation transport in problems where the quantities of interest are difficult to obtain because of low statistics.
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Affiliation(s)
- S García-Pareja
- Servicio de Radiofísica Hospitalaria, Hospital Regional Universitario Carlos Haya, Avda. Carlos Haya s/n, E-29010 Málaga, Spain
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Hsiao Y, Stewart RD, Li XA. A Monte-Carlo derived dual-source model for helical tomotherapy treatment planning. Technol Cancer Res Treat 2008; 7:141-7. [PMID: 18345703 DOI: 10.1177/153303460800700207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Full Monte Carlo radiation transport simulations of accelerator heads are impractical for routine treatment planning because of the excessive computational burden and memory requirements. To improve the accuracy and efficiency of treatment plans for helical tomotherapy, we have developed a dual-source model to characterize the radiation emitted from the head of a commercial helical tomotherapy accelerator. Percentage depth dose (PDD) and beam profiles computed using the dual-source model with the EGS/BEAMnrc Monte Carlo package agree within 2% of measurements for a wide range of field sizes, which suggests that the proposed dual-source model provides an adequate representation of the tomotherapy head for dose calculations in routine treatment planning.
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Affiliation(s)
- Yayun Hsiao
- Department of Physics, Purdue University, West Lafayette, IN 47907-2036, USA
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Chetty IJ, Curran B, Cygler JE, DeMarco JJ, Ezzell G, Faddegon BA, Kawrakow I, Keall PJ, Liu H, Ma CMC, Rogers DWO, Seuntjens J, Sheikh-Bagheri D, Siebers JV. Report of the AAPM Task Group No. 105: Issues associated with clinical implementation of Monte Carlo-based photon and electron external beam treatment planning. Med Phys 2007; 34:4818-53. [PMID: 18196810 DOI: 10.1118/1.2795842] [Citation(s) in RCA: 438] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
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Ding GX, Duggan DM, Coffey CW. Commissioning stereotactic radiosurgery beams using both experimental and theoretical methods. Phys Med Biol 2006; 51:2549-66. [PMID: 16675869 DOI: 10.1088/0031-9155/51/10/013] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The purpose of this investigation is to study the feasibility of using an alternative method to commission stereotactic radiosurgery beams shaped by micro multi-leaf collimators by using Monte Carlo simulations to obtain beam characteristics of small photon beams, such as incident beam particle fluence and energy distributions, scatter ratios, depth-dose curves and dose profiles where measurements are impossible or difficult. Ionization chambers and diode detectors with different sensitive volumes were used in the measurements in a water phantom and the Monte Carlo codes BEAMnrc/DOSXYZnrc were used in the simulation. The Monte Carlo calculated data were benchmarked against measured data for photon beams with energies of 6 MV and 10 MV produced from a Varian Trilogy accelerator. The measured scatter ratios and cross-beam dose profiles for very small fields are shown to be not only dependent on the size of the sensitive volume of the detector used but also on the type of detectors. It is known that the response of some detectors changes at small field sizes. Excellent agreement was seen between scatter ratios measured with a small ion chamber and those calculated from Monte Carlo simulations. The values of scatter ratios, for field sizes from 6 x 6 mm2 to 98 x 98 mm2, range from 0.67 to 1.0 and from 0.59 to 1.0 for 6 and 10 MV, respectively. The Monte Carlo calculations predicted that the incident beam particle fluence is strongly affected by the X-Y-jaw openings, especially for small fields due to the finite size of the radiation source. Our measurement confirmed this prediction. This study demonstrates that Monte Carlo calculations not only provide accurate dose distributions for small fields where measurements are difficult but also provide additional beam characteristics that cannot be obtained from experimental methods. Detailed beam characteristics such as incident photon fluence distribution, energy spectra, including composition of primary and scattered photons, can be independently used in dose calculation models and to improve the accuracy of measurements with detectors with an energy-dependent response. Furthermore, when there are discrepancies between results measured with different detectors, the Monte Carlo calculated values can indicate the most correct result. The data set presented in this study can be used as a reference in commissioning stereotactic radiosurgery beams shaped by a BrainLAB m3 on a Varian 2100EX or 600C accelerator.
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Affiliation(s)
- George X Ding
- Department of Radiation Oncology, B-902, TVC, Vanderbilt University Medical Center, Nashville, TN 37232-5671, USA.
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