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Oh K, Gallagher KJ, Hyun M, Schott D, Wisnoskie S, Lei Y, Hendley S, Wong J, Wang S, Graff B, Jenkins C, Rutar F, Ahmed M, McNeur J, Taylor J, Schmidt M, Senadheera L, Smith W, Umstadter D, Lele SM, Dai R, Jianghu (James) D, Yan Y, Su‐min Z. Initial experience with an electron FLASH research extension (FLEX) for the Clinac system. J Appl Clin Med Phys 2024; 25:e14159. [PMID: 37735808 PMCID: PMC10860433 DOI: 10.1002/acm2.14159] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 08/04/2023] [Accepted: 08/21/2023] [Indexed: 09/23/2023] Open
Abstract
PURPOSE Radiotherapy delivered at ultra-high-dose-rates (≥40 Gy/s), that is, FLASH, has the potential to effectively widen the therapeutic window and considerably improve the care of cancer patients. The underlying mechanism of the FLASH effect is not well understood, and commercial systems capable of delivering such dose rates are scarce. The purpose of this study was to perform the initial acceptance and commissioning tests of an electron FLASH research product for preclinical studies. METHODS A linear accelerator (Clinac 23EX) was modified to include a non-clinical FLASH research extension (the Clinac-FLEX system) by Varian, a Siemens Healthineers company (Palo Alto, CA) capable of delivering a 16 MeV electron beam with FLASH and conventional dose rates. The acceptance, commissioning, and dosimetric characterization of the FLEX system was performed using radiochromic film, optically stimulated luminescent dosimeters, and a plane-parallel ionization chamber. A radiation survey was conducted for which the shielding of the pre-existing vault was deemed sufficient. RESULTS The Clinac-FLEX system is capable of delivering a 16 MeV electron FLASH beam of approximately 1 Gy/pulse at isocenter and reached a maximum dose rate >3.8 Gy/pulse near the upper accessory mount on the linac gantry. The percent depth dose curves of the 16 MeV FLASH and conventional modes for the 10 × 10 cm2 applicator agreed within 0.5 mm at a range of 50% of the maximum dose. Their respective profiles agreed well in terms of flatness but deviated for field sizes >10 × 10 cm2 . The output stability of the FLASH system exhibited a dose deviation of <1%. Preliminary cell studies showed that the FLASH dose rate (180 Gy/s) had much less impact on the cell morphology of 76N breast normal cells compared to the non-FLASH dose rate (18 Gy/s), which induced large-size cells. CONCLUSION Our studies characterized the non-clinical Clinac-FLEX system as a viable solution to conduct FLASH research that could substantially increase access to ultra-high-dose-rate capabilities for scientists.
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Affiliation(s)
- Kyuhak Oh
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | | | - Megan Hyun
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | - Diane Schott
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | | | - Yu Lei
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | | | - Jeffrey Wong
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | - Shuo Wang
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | - Brendan Graff
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | | | - Frank Rutar
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | - Md Ahmed
- Varian Medical SystemsPalo AltoCaliforniaUSA
| | | | | | | | | | - Wendy Smith
- Varian Medical SystemsPalo AltoCaliforniaUSA
| | | | | | - Ran Dai
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | | | - Ying Yan
- University of Nebraska Medical CenterOmahaNebraskaUSA
| | - Zhou Su‐min
- University of Nebraska Medical CenterOmahaNebraskaUSA
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Baghani HR, Robatjazi M. Evaluating the induced photon contamination by different breast IOERT shields using Monte Carlo simulation. J Appl Clin Med Phys 2023; 24:e14098. [PMID: 37461859 PMCID: PMC10647956 DOI: 10.1002/acm2.14098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 06/25/2023] [Accepted: 07/05/2023] [Indexed: 11/16/2023] Open
Abstract
BACKGROUND AND OBJECTIVE Avoiding the underlying healthy tissue over-exposure during breast intraoperative electron radiotherapy (IOERT) is owing to the use of some dedicated radioprotection disks during patient irradiation. The originated contaminant photons from some widely used double-layered shielding disks including PMMA+Cu, PTFE+steel, and Al+Pb configurations during the breast IOERT have been evaluated through a Monte Carlo (MC) simulation approach. METHODS Produced electron beam with energies of 6, 8, 10, and 12 MeV by a validated MC model of Liac12 dedicated IOERT accelerator was used for disk irradiations. Each of above-mentioned radioprotection disks was simulated inside a water phantom, so that the upper disk surface was positioned at R90 depth of each considered electron energy. Simulations were performed by MCNPX (version 2.6.0) MC code. Then, the energy spectra of the contaminant photons at different disk surfaces (upper, middle, and lower one) and relevant contaminant dose beneath the studied disks were determined and compared. RESULTS None of studied shielding disks show significant photon contamination up to 10 MeV electron energy, so that the induced photon dose by the contaminant X-rays was lower than those observed in the disk absence under the same conditions. In return, the induced photon dose at a close distance to the lower disk surface exceeded from calculated values in the disk absence at 12 MeV electron energy. The best performance in contaminant dose reduction at the energy range of 6-10 MeV belonged to the Al+Pb disk, while the PMMA+Cu configuration showed the best performance in this regard at 12 MeV energy. CONCLUSION Finally, it can be concluded that all studied shielding disks not only don't produce considerable photon contamination but also absorb the originated X-rays from electron interactions with water at the electron energy range of 6-10 MeV. The only concern is related to 12 MeV energy where the induced photon dose exceeds the dose values in the disk absence. Nevertheless, the administered dose by contaminant photons to underlying healthy tissues remains beneath the tolerance dose level by these organs at the entire range of studied electron energies.
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Affiliation(s)
| | - Mostafa Robatjazi
- Medical Physics and Radiological Sciences DepartmentSabzevar University of Medical SciencesSabzevarIran
- Non‐communicable Disease Research CenterSabzevar University of Medical SciencesSabzevarIran
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Kim KT, Choi Y, Cho GS, Jang WI, Yang KM, Lee SS, Bahng J. Evaluation of the water-equivalent characteristics of the SP34 plastic phantom for film dosimetry in a clinical linear accelerator. PLoS One 2023; 18:e0293191. [PMID: 37871021 PMCID: PMC10593237 DOI: 10.1371/journal.pone.0293191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 10/08/2023] [Indexed: 10/25/2023] Open
Abstract
In this study, some confusing points about electron film dosimetry using white polystyrene suggested by international protocols were verified using a clinical linear accelerator (LINAC). According to international protocol recommendations, ionometric measurements and film dosimetry were performed on an SP34 slab phantom at various electron energies. Scaling factor analysis using ionometric measurements yielded a depth scaling factor of 0.923 and a fluence scaling factor of 1.019 at an electron beam energy of <10 MeV (i.e., R50 < 4.0 g/cm2). It was confirmed that the water-equivalent characteristics were similar because they have values similar to white polystyrene (i.e., depth scaling factor of 0.922 and fluence scaling factor of 1.019) presented in international protocols. Furthermore, percentage depth dose (PDD) curve analysis using film dosimetry showed that when the density thickness of the SP34 slab phantom was assumed to be water-equivalent, it was found to be most similar to the PDD curve measured using an ionization chamber in water as a reference medium. Therefore, we proved that the international protocol recommendation that no correction for measured depth dose is required means that no scaling factor correction for the plastic phantom is necessary. This study confirmed two confusing points that could occur while determining beam characteristics using electron film dosimetry, and it is expected to be used as basic data for future research on clinical LINACs.
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Affiliation(s)
- Kyo-Tae Kim
- Neuroscience Research Institute, Seoul National University Medical Research Center, Seoul, Korea
- Research and Development team, Radexel Inc., Seoul, Korea
| | - Yona Choi
- Department of Accelerator Science, Korea University Sejong Campus, Sejong, Korea
| | - Gyu-Seok Cho
- Research Team of Radiological Physics & Engineering, Korea Institute of Radiological & Medical Sciences, Seoul, Korea
| | - Won-Il Jang
- Department of Radiation Oncology, Korea Institute of Radiological & Medical Sciences, Seoul, Korea
| | - Kwang-Mo Yang
- Department of Radiation Oncology, Korea Institute of Radiological & Medical Sciences, Seoul, Korea
| | - Soon-Sung Lee
- Research Team of Radiological Physics & Engineering, Korea Institute of Radiological & Medical Sciences, Seoul, Korea
| | - Jungbae Bahng
- Research and Development team, Radexel Inc., Seoul, Korea
- Department of Radiation Oncology, Kangwon National University hospital, Chun-cheon, Korea
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Hosseini Aghdam SR, Aghamiri SMR, Malekie S, Mosayebi A. Evaluating the linearity response for a PVA/MWCNT-OH nanocomposite dosimeter in photon beam of linear accelerator. Radiat Phys Chem Oxf Engl 1993 2023; 210:111044. [DOI: https:/doi.org/10.1016/j.radphyschem.2023.111044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/21/2023]
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Hosseini Aghdam SR, Aghamiri SMR, Malekie S, Mosayebi A. Evaluating the linearity response for a PVA/MWCNT-OH nanocomposite dosimeter in photon beam of linear accelerator. Radiat Phys Chem Oxf Engl 1993 2023; 210:111044. [DOI: 10.1016/j.radphyschem.2023.111044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/22/2023]
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Baghani HR, Shiri A, Gholamhosseinian H. Comparing the DNA-damage RBE of intraoperative and conventional electron beams using a hybrid simulation approach. Int J Radiat Biol 2023; 100:46-60. [PMID: 37523649 DOI: 10.1080/09553002.2023.2242931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 06/17/2023] [Accepted: 07/20/2023] [Indexed: 08/02/2023]
Abstract
PURPOSE Employing electron beam for radiotherapy purposes now has been established as one of the standard cancer treatment modalities. Both dedicated intraoperative and conventional electron beams can be employed in patient irradiation. Due to the differences between accelerating structure and electron beam delivery of dedicated intraoperative radiotherapy (IORT) machines and conventional ones, the initial energy spectra of the produced electron beam by these machines may be different. Accordingly, this study aims to evaluate whether these spectral differences can affect the relevant relative biological effectiveness (RBE) values of intraoperative and conventional electron beams. MATERIALS AND METHODS A hybrid Monte Carlo simulation approach was considered. At first, the head LIAC12 machine (as an IORT accelerator) and Varian 2100C/D (as a conventional accelerator) were simulated by MCNPX code and electron energy spectra at different depths and off-axis distances were scored for two nominal electron energies of 6 and 12 MeV at the field sizes of 6 and 10 cm. Then, the calculated spectra were imported to MCDS code to estimate the induced DNA-damage RBE values. Finally, the obtained RBE values for intraoperative and conventional electron beams were compared together. RESULTS The results showed that the RBE values of the intraoperative electron beam are superior to those obtained for conventional electron beam at the same energy/field size combination. Variations of the depth can regularly affect the RBE value for both conventional and intraoperative electron beams, while no ordered variation trend was observed for RBE with changing the off-axis distance. Variations of electron energy and field size can also influence the RBE value for both types of studied electron beams. CONCLUSIONS From the results, it can be concluded the structural differences between the dedicated IORT and conventional Linacs can lead to distinct initial electron energy spectra for intraoperative and conventional electron beams. These physical differences can finally lead to different RBE values for intraoperative and conventional electron beams at the same energy and field size.
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Affiliation(s)
| | - Ali Shiri
- Medical Physics Department, Mashhad University of Medical Sciences, Mashhad, Iran
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Hosseini Bojdani SM, Baghani HR, Robatjazi M, Andreoli S, Azadegan B. Comparison of derived correction factors for effects of ion recombination and photon beam quality index following TG-51 and TRS-398 dosimetry protocols. Appl Radiat Isot 2023; 197:110796. [PMID: 37037135 DOI: 10.1016/j.apradiso.2023.110796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 03/07/2023] [Accepted: 03/28/2023] [Indexed: 04/12/2023]
Abstract
In this study, ion recombination correction factor (kS) and beam quality conversion factor ( [Formula: see text] ) values were extracted following the recommendations of the TRS-398 and TG-51 dosimetry protocols for widely used cylindrical ionization chambers for high energy photon beam dosimetry to quantify the agreement between the instructions for these two protocols for absolute dosimetry inside water. Four different types of cylindrical ionization chambers comprising Farmer (TM30013), Semiflex 0.125 cm3 (TM31010), Semiflex 0.3 cm3 (TM31013), and PinPoint (TM31016) were considered, and kS and [Formula: see text] values were determined at photon energies of 6 MV and 15 MV. The maximum difference between the measured kS values according to the instructions in the TRS-398 and TG-51 protocols was 0.03%. The kS data measured with both protocols agreed well with those measured by using the Jaffe-plot approach, where the maximum difference was about 0.33%. The observed differences between the [Formula: see text] factors measured by using the TRS-398 and TG-51 dosimetry protocols at photon energies of 6 MV and 15 MV were 0.37% and 0.55%, respectively. The [Formula: see text] values measured using the TG-51 dosimetry protocols were slightly closer to those measured by a reference ionization chamber dosimeter. We conclude that the maximum differences were about 0.4% and 0.6% in the absorbed dose measurements according to the TRS-398 and TG-51 instructions at photon energies of 6 MV and 15 MV, respectively. The type of ionization chamber employed also affected the differences, where the maximum and minimum dose differences were found using the Farmer and PinPoint chambers, respectively.
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Affiliation(s)
| | | | - Mostafa Robatjazi
- Medical Physics and Radiological Sciences Department, Sabzevar University of Medical Sciences, Sabzevar, Iran
| | | | - Behnam Azadegan
- Physics Department, Hakim Sabzevari University, Sabzevar, Iran
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Azhar D, Gul A, Javid MA, Hussain MM, Shehzadi NN. Evaluation of scanning resolution, detector choice and detector orientation to be used for accurate and time-efficient commissioning of a 6MV clinical linear accelerator. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2023; 62:83-96. [PMID: 36520198 DOI: 10.1007/s00411-022-01008-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Accepted: 12/03/2022] [Indexed: 06/17/2023]
Abstract
The present study is aimed at exploring different scanning parameters, detectors and their orientations for time-efficient and accurate commissioning of a 6 MV clinical linear accelerator (LINAC). Beam profiles and percentage depth dose (PDD) curves were measured with a PTW dosimetry diode, a PTW Semiflex and a PinPoint ion chamber in different orientations. To acquire beam data, equidistant (step size of 0.5 mm, 1 mm, 2 mm and 3 mm) and fanline (step size of 2-0.5 mm, 2-1 mm, 3-0.5 mm and 3-1 mm) scanning modes were employed and data measurement time was recorded. Scan time per measurement point was also varied (0.2 s, 0.5 s and 1.0 s) to investigate its effect on the accuracy and acquisition time of beam data. Accuracy of the measured data was analyzed on the basis of the variation between measured data and data modeled by a treatment planning system. Beam profiles (particularly in penumbra region) were found to be sensitive to variation in scanning resolution and showed an improved accuracy with decrease in step size, while PDD curves were affected negligibly. The accuracy of beam data obtained with the PTW dosimetry diode and the PinPoint ion chamber was higher than those obtained with the PTW Semiflex ion chamber for small fields (2 × 2 cm2 and 3 × 3 cm2). However, the response of the PTW diode and the PinPoint ion chamber was significantly indifferent in these fields. Furthermore, axial orientation of the PTW Semiflex ion chamber improved accuracy of profiles and PDDs as compared to radial orientation, while such a difference was not significant for the PinPoint ion chamber. It is concluded that a scan time of 0.2 s/point with a fanline scanning resolution of 2-1 mm for beam profiles and 3 mm for PDDs are most favorable in terms of accuracy and time efficiency. For small fields (2 × 2 cm2 and 3 × 3 cm2), a PinPoint ion chamber in radial orientation or a dosimetry diode in axial orientation are recommended for both beam profiles and PDDs. If a PinPoint ion chamber and a PTW dosimetry diode are not available, a Semiflex ion chamber in axial orientation may be used for small fields.
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Affiliation(s)
- Deeba Azhar
- Department of Basic Sciences, University of Engineering and Technology, Taxila, 47080, Pakistan
| | - Attia Gul
- Institute of Nuclear Medicine, Oncology and Radiotherapy (INOR), Abbottabad, 22010, Pakistan.
| | - Muhamad Arshad Javid
- Institute of Physics, Islamia University of Bahawalpur, Bahawalpur, 63100, Pakistan
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Hosseini Aghdam SR, Aghamiri SMR, Malekie S, Mosayebi A. Performance characteristics of a parallel plate dosimeter based on PVA/MWCNT-OH nanocomposite for photon beam radiation. MEASUREMENT 2023; 207:112419. [DOI: https:/doi.org/10.1016/j.measurement.2022.112419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/21/2023]
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Hosseini Aghdam SR, Aghamiri SMR, Malekie S, Mosayebi A. Performance characteristics of a parallel plate dosimeter based on PVA/MWCNT-OH nanocomposite for photon beam radiation. MEASUREMENT 2023; 207:112419. [DOI: 10.1016/j.measurement.2022.112419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/22/2023]
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Mastella E, Szilagyi KE, De Guglielmo E, Fabbri S, Calderoni F, Stefanelli A, Di Domenico G, Turra A. Dosimetric characterization of a mobile accelerator dedicated for intraoperative radiation therapy: Monte Carlo simulations and experimental validation. Phys Med 2022; 104:167-173. [PMID: 36463581 DOI: 10.1016/j.ejmp.2022.11.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/12/2022] [Accepted: 11/25/2022] [Indexed: 12/03/2022] Open
Abstract
PURPOSE This Technical Note validates previously published data about the dosimetry of the electron beams produced by a mobile accelerator dedicated for intraoperative radiation therapy (IORT). The evaluation of the directional response of a PTW microDiamond detector is presented together with a detailed analysis of the output factors (OFs) for bevelled applicators. METHODS The OFs of the 6, 8, 10 and 12 MeV electron beams produced by a light intraoperative accelerator (LIAC, SIT, Italy) were measured in a commercial water phantom using the microDiamond. A set of flat and bevelled applicators with sizes ranging from 4 to 10 cm was characterized. For bevelled applicators, a correction for the angular dependence of the microDiamond was calculated using a home-made spherical phantom. Correction factors were obtained through measurements performed rotating the accelerator treatment head at 0°, 15°, 30° and 45°. RESULTS For flat applicators, the average deviation between measured and simulated OFs was (-1.1 ± 0.7)%. The microDiamond showed a higher angular dependence for the 6 MeV beam (∼8% for angles up to 45°, range 92 % ÷ 100 %), while the variations for 8, 10 and 12 MeV beams were ∼ 4 % (range 97 % ÷ 101 %). Correcting for this dependence, the average deviation of the OFs for bevelled applicators was (-0.9 ± 1.6)%. CONCLUSIONS The presented results were in very good agreement with those reported in literature. Very similar deviations were found between flat and bevelled applicators confirming the suitability of our method to determine the angular dependence correction factors of the microDiamond detector.
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Affiliation(s)
- Edoardo Mastella
- Struttura Complessa di Fisica Medica, Azienda Ospedaliero-Universitaria di Ferrara, via A. Moro 8, I-44124 Cona (Ferrara), Italy.
| | - Klarisa E Szilagyi
- Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, via Saragat 1, I-44122 Ferrara, Italy
| | - Eleonora De Guglielmo
- Struttura Complessa di Fisica Medica, Azienda Ospedaliero-Universitaria di Ferrara, via A. Moro 8, I-44124 Cona (Ferrara), Italy
| | - Sara Fabbri
- Struttura Complessa di Fisica Medica, Azienda Ospedaliero-Universitaria di Ferrara, via A. Moro 8, I-44124 Cona (Ferrara), Italy
| | - Francesca Calderoni
- Struttura Complessa di Fisica Medica, Azienda Ospedaliero-Universitaria di Ferrara, via A. Moro 8, I-44124 Cona (Ferrara), Italy
| | - Antonio Stefanelli
- Struttura Complessa di Radioterapia Oncologica, Azienda Ospedaliero-Universitaria di Ferrara, via A. Moro 8, I-44124 Cona (Ferrara), Italy
| | - Giovanni Di Domenico
- Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, via Saragat 1, I-44122 Ferrara, Italy
| | - Alessandro Turra
- Struttura Complessa di Fisica Medica, Azienda Ospedaliero-Universitaria di Ferrara, via A. Moro 8, I-44124 Cona (Ferrara), Italy
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Baghani HR, Robatjazi M, Andreoli S. Comparing the dosimeter-specific corrections for influence quantities of some parallel-plate ionization chambers in conventional electron beam dosimetry. Appl Radiat Isot 2021; 179:110031. [PMID: 34801928 DOI: 10.1016/j.apradiso.2021.110031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2021] [Revised: 11/06/2021] [Accepted: 11/14/2021] [Indexed: 11/28/2022]
Abstract
The performance characteristics of some widely employed parallel-plate ionization chambers in dosimetry of conventional high energy electron beams were evaluated and compared in the present study following the recommendations of the IAEA TRS-398 reference dosimetry protocol. Three different types of PTW-made parallel-plate ionization chambers including Roos (TM34001), Markus (TM23343), and Advanced Markus (TM34045) were employed, and correction factors for polarity (kpol), recombination (ks), and quality conversion factor ( [Formula: see text] ) were determined at different nominal electron energies of 4, 6, 9, 12, 16, and 20 MeV produced by a Varian Trilogy clinical Linac. All measurements were performed inside a MP3-M automatic water phantom in the reference condition of 100 cm SSD (source to surface distance), reference measurement depth (zref), and 10 × 10 cm2 field size at the phantom surface. The maximum and minimum range of kpol deviations from unity were respectively found for Markus and Roos ionization chambers. The maximum ks values also belonged to the Markus ionization chamber, while the minimum ks values were observed for the Advanced Markus chamber. The measured ks values through recommendations of the TRS-398 dosimetry protocol were in good accordance with those obtained by Jaffe-plot analysis for all considered ionization chambers. The type of employed ionization chamber can minimally affect the measured electron beam quality index (R50), while it can have a more considerable impact on [Formula: see text] value, especially in the case of the Markus chamber. From the results, it can be concluded that the Roos and Advanced Markus ionization chambers have a superior performance in the case of electron beam dosimetry, although all considered ionization chambers fulfilled the criteria requested by relevant reference dosimetry protocols.
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Affiliation(s)
| | - Mostafa Robatjazi
- Medical Physics and Radiological Sciences Department, Sabzevar University of Medical Sciences, Sabzevar, Iran; Non-Communicable Diseases Research Center, Sabzevar University of Medical Sciences, Sabzevar, Iran
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Lashkari S, Baghani HR, Tavakoli MB, Mahdavi SR. An inter-comparison between accuracy of EGSnrc and MCNPX Monte Carlo codes in dosimetric characterization of intraoperative electron beam. Comput Biol Med 2020; 128:104113. [PMID: 33197735 DOI: 10.1016/j.compbiomed.2020.104113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 10/20/2020] [Accepted: 11/05/2020] [Indexed: 10/23/2022]
Abstract
BACKGROUND Ionometric dosimetry in IOERT is a complicated process, due to the sophisticated beam setup and the necessity for dedicated protocols for ion chamber response correction. On the other hand, the Monte Carlo (MC) technique can easily overcome such limitations and be considered as an alternative dosimetry approach. This paper presents a comparative analysis of two widely used MC codes, EGSnrc and MCNPX, for intraoperative electron beam dosimetry. METHOD The head of LIAC12, a dedicated IOERT accelerator, was modeled by both mentioned MC codes. Then, the percentage depth dose (PDD) curves, transverse dose profiles (TDPs), and output factor (OF) values were accordingly calculated within the water phantom. To realize the accuracy of MC codes in dosimetric characterization of intraoperative electron beam, their results were finally compared with those measured by corresponding ionometric dosimetry for all forms of electron energy/applicator size. RESULTS A good agreement was observed between the simulated and measured PDDs/TDPs for both considered MC codes, such that the calculated gamma index values were always lower than unity for both considered MC codes. Nevertheless, the lower gamma index values were found in the case of the EGSnrc code. The maximum difference between the measured and calculated OF was obtained as 2.3% and 3.1% for EGSnrc and MCNPX code, respectively. CONCLUSIONS Although both studied MC codes showed compatible results with the measured ones, EGSnrc code has superior accuracy in this regard and can be considered as a more reliable toolkit in Monte Carlo-based commissioning of dedicated IOERT accelerators.
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Affiliation(s)
- Sara Lashkari
- Department of Medical Physics and Medical Engineering, Isfahan University of Medical Sciences, Isfahan, Iran
| | | | - Mohammad Bagher Tavakoli
- Department of Medical Physics and Medical Engineering, Isfahan University of Medical Sciences, Isfahan, Iran.
| | - Seyed Rabi Mahdavi
- Medical Physics Department, Iran University of Medical Sciences, Tehran, Iran
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Zoljalali Moghaddam SH, Baghani HR, Mahdavi SR. Construction and performance evaluation of a buildup bolus for breast intraoperative electron radiotherapy. Radiat Phys Chem Oxf Engl 1993 2020. [DOI: 10.1016/j.radphyschem.2020.108952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Evaluating the radiation contamination dose around a high dose per pulse intraoperative radiotherapy accelerator: a Monte Carlo study. JOURNAL OF RADIOTHERAPY IN PRACTICE 2020. [DOI: 10.1017/s1460396920000084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractAim:In this study, the radiation contamination dose (RCD) for different combinations of electron energy/distance, applicator and radius around the light intraoperative accelerator (LIAC), a high dose per pulse dedicated intraoperative electron radiotherapy machine, has been estimated. Being aware about the amount of RCDs is highly recommended for linear medical electron accelerators.Methods and methods:Monte Carlo Nuclear Particles (MCNP) code was used to simulate the LIAC® head and calculate RCDs. Experimental RCDs measurements were also done by Advanced Markus chamber inside a MP3-XS water phantom. Relative differences of simulations and measurements were calculated.Result:RCD reduction by distance from the machine follows the inverse-square law, as expected. The RCD was decreased by increasing angle from applicator walls opposed to the electron beam direction. The maximum differences between the simulation and measurement results were lower than 3%.Conclusions:The RCD is strongly dependent on electron beam energy, applicator size and distance from the accelerator head. Agreement between the MCNP results and ionometric dosimetry confirms the applicability of this simulation code in modelling the intraoperative electron beam and obtaining the dosimetric parameters. The RCD is a parameter that would restrict working with LIAC in an unshielded operative room.
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Baghani HR, Robatjazi M. Charge collection efficiency determination for a Farmer-type ion chamber through different recommended methods. Radiat Phys Chem Oxf Engl 1993 2020. [DOI: 10.1016/j.radphyschem.2020.108865] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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17
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Organ at risk dose calculation for left sided breast cancer treatments using intraoperative electron radiotherapy: A Monte Carlo-based feasibility study. Appl Radiat Isot 2020; 156:108977. [DOI: 10.1016/j.apradiso.2019.108977] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2019] [Revised: 10/14/2019] [Accepted: 11/07/2019] [Indexed: 12/24/2022]
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18
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In-field radiation contamination during intraoperative electron radiation therapy with a dedicated accelerator. Appl Radiat Isot 2020; 155:108918. [DOI: 10.1016/j.apradiso.2019.108918] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 09/05/2019] [Accepted: 10/02/2019] [Indexed: 01/30/2023]
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