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Kierkels RGJ, Hernandez V, Saez J, Angerud A, Hilgers GC, Surmann K, Schuring D, Minken AWH. Multileaf collimator characterization and modeling for a 1.5 T MR-linac using static synchronous and asynchronous sweeping gaps. Phys Med Biol 2024; 69:075004. [PMID: 38412538 DOI: 10.1088/1361-6560/ad2d7d] [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: 11/20/2023] [Accepted: 02/27/2024] [Indexed: 02/29/2024]
Abstract
Objective.The Elekta unity MR-linac delivers step-and-shoot intensity modulated radiotherapy plans using a multileaf collimator (MLC) based on the Agility MLC used on conventional Elekta linacs. Currently, details of the physical Unity MLC and the computational model within its treatment planning system (TPS)Monacoare lacking in published literature. Recently, a novel approach to characterize the physical properties of MLCs was introduced using dynamic synchronous and asynchronous sweeping gap (aSG) tests. Our objective was to develop a step-and-shoot version of the dynamic aSG test to characterize the Unity MLC and the computational MLC models in theMonacoandRayStationTPSs.Approach.Dynamic aSG were discretized into a step-and-shoot aSG by investigating the number of segments/sweep and the minimal number of monitor units (MU) per segment. The step-and-shoot aSG tests were compared to the dynamic aSG tests on a conventional linac at a source-to-detector distance of 143.5 cm, mimicking the Unity configuration. the step-and-shoot aSG tests were used to characterize the Unity MLC through measurements and dose calculations in both TPSs.Main results.The step-and-shoot aSGs tests with 100 segments and 5 MU/segment gave results very similar to the dynamic aSG experiments. The effective tongue-and-groove width of the Unity gradually increased up to 1.4 cm from the leaf tip end. The MLC models inRayStationandMonacoagreed with experimental data within 2.0% and 10%, respectively. The largest discrepancies inMonacowere found for aSG tests with >10 mm leaf interdigitation, which are non-typical for clinical plans.Significance.The step-and-shoot aSG tests accurately characterize the MLC in step-and-shoot delivery mode. The MLC model inRayStation2023B accurately describes the tongue-and-groove and leaf tip effects whereasMonacooverestimates the tongue-and-groove shadowing further away from the leaf tip end.
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Affiliation(s)
| | - Victor Hernandez
- Hospital Sant Joan de Reus, Department of Medical Physics, Reus, Spain
| | - Jordi Saez
- Hospital Clínic de Barcelona, Department of Radiation Oncology, Barcelona, Spain
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Gauter-Fleckenstein B, Schönig S, Mertens L, Oppitz H, Siebenlist K, Ehmann M, Fleckenstein J. Effect of simultaneous integrated boost concepts on photoneutron and distant out-of-field doses in VMAT for prostate cancer. Strahlenther Onkol 2024; 200:219-229. [PMID: 37707518 PMCID: PMC10876496 DOI: 10.1007/s00066-023-02138-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2023] [Accepted: 08/08/2023] [Indexed: 09/15/2023]
Abstract
BACKGROUND A simultaneous integrated boost (SIB) may result in increased out-of-field (DOOF) and photoneutron (HPN) doses in volumetric modulated arc therapy (VMAT) for prostate cancer (PCA). This work therefore aimed to compare DOOF and HPN in flattened (FLAT) and flattening filter-free (FFF) 6‑MV and 10-MV VMAT treatment plans with and without SIB. METHODS Eight groups of 30 VMAT plans for PCA with 6 MV or 10 MV, with or without FF and with uniform (2 Gy) or SIB target dose (2.5/3.0 Gy) prescriptions (CONV, SIB), were generated. All 240 plans were delivered on a slab-phantom and compared with respect to measured DOOF and HPN in 61.8 cm distance from the isocenter. The 6‑ and 10-MV flattened VMAT plans with conventional fractionation (6- and 10-MV FLAT CONV) served as standard reference groups. Doses were analyzed as a function of delivered monitor units (MU) and weighted equivalent square field size Aeq. Pearson's correlation coefficients between the presented quantities were determined. RESULTS The SIB plans resulted in decreased HPN over an entire prostate RT treatment course (10-MV SIB vs. CONV -38.2%). Omission of the flattening filter yielded less HPN (10-MV CONV -17.2%; 10-MV SIB -22.5%). The SIB decreased DOOF likewise by 39% for all given scenarios, while the FFF mode reduced DOOF on average by 60%. A strong Pearson correlation was found between MU and HPN (r > 0.9) as well as DOOF (0.7 < r < 0.9). CONCLUSION For a complete treatment, SIB reduces both photoneutron and OOF doses to almost the same extent as FFF deliveries. It is recommended to apply moderately hypofractionated 6‑MV SIB FFF-VMAT when considering photoneutron or OOF doses.
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Affiliation(s)
- Benjamin Gauter-Fleckenstein
- Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Theodor-Kutzer Ufer 1-3, 68167, Mannheim, Germany.
| | - Sebastian Schönig
- Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Theodor-Kutzer Ufer 1-3, 68167, Mannheim, Germany
| | - Lena Mertens
- Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Theodor-Kutzer Ufer 1-3, 68167, Mannheim, Germany
| | - Hans Oppitz
- Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Theodor-Kutzer Ufer 1-3, 68167, Mannheim, Germany
| | - Kerstin Siebenlist
- Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Theodor-Kutzer Ufer 1-3, 68167, Mannheim, Germany
| | - Michael Ehmann
- Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Theodor-Kutzer Ufer 1-3, 68167, Mannheim, Germany
| | - Jens Fleckenstein
- Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Theodor-Kutzer Ufer 1-3, 68167, Mannheim, Germany
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Guo J, Zhu M, Zeng W, Wang H, Qin S, Li Z, Tang Y, Ying B, Sang J, Ji M, Meng K, Hui Z, Wang J, Zhou J, Zhou Y, Huan J. Multileaf Collimator Modeling and Commissioning for Complex Radiation Treatment Plans Using 2-Dimensional (2D) Diode Array MapCHECK2. Technol Cancer Res Treat 2024; 23:15330338231225864. [PMID: 38311933 PMCID: PMC10846010 DOI: 10.1177/15330338231225864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 09/27/2023] [Accepted: 12/17/2023] [Indexed: 02/06/2024] Open
Abstract
Purpose: This study aims to develop a data-collecting package ExpressMLC and investigate the applicability of MapCHECK2 for multileaf collimator (MLC) modeling and commissioning for complex radiation treatment plans. Materials and methods: The MLC model incorporates realistic parameters to account for sophisticated MLC features. A set of 8 single-beam plans, denoted by ExpressMLC, is created for the determination of parameters. For the commissioning of the MLC model, 4 intensity modulated radiation therapy (IMRT) plans specified by the AAPM TG 119 report were transferred to a computed tomography study of MapCHECK2, recalculated, and compared to measurements on a Varian accelerator. Both per-beam and composite-beam dose verification were conducted. Results: Through sufficient characterization of the MLC model, under 3%/2 mm and 2%/2 mm criteria, MapCHECK2 can be used to accurately verify per beam dose with gamma passing rate better than 90.9% and 89.3%, respectively, while the Gafchromic EBT3 films can achieve gamma passing rate better than 89.3% and 85.7%, respectively. Under the same criteria, MapCHECK2 can achieve composite beam dose verification with a gamma passing rate better than 95.9% and 90.3%, while the Gafchromic EBT3 films can achieve a gamma passing rate better than 96.1% and 91.8%; the p-value from the Mann Whitney test between gamma passing rates of the per beam dose verification using full MapCHECK2 package calibrated MLC model and film calibrated MLC model is .44 and .47, respectively; the p-value between those of the true composite beam dose verification is .62 and .36, respectively. Conclusion: It is confirmed that the 2-dimensional (2D) diode array MapCHECK2 can be used for data collection for MLC modeling with the combination of the ExpressMLC package of plans, whose doses are sufficient for the determination of MLC parameters. It could be a fitting alternative to films to boost the efficiency of MLC modeling and commissioning without sacrificing accuracy.
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Affiliation(s)
- Jian Guo
- Department of Radiation Oncology, The First Affiliated Hospital of Soochow University, Suzhou, China
| | - Meng Zhu
- Qiusuo Health Technologies Inc., Suzhou, China
| | - Weijin Zeng
- Department of Radiation Oncology, Yihui Foundation Hospital, Shanwei, China
| | - He Wang
- Qiusuo Health Technologies Inc., Suzhou, China
| | - Songbing Qin
- Department of Radiation Oncology, The First Affiliated Hospital of Soochow University, Suzhou, China
| | - Zhibin Li
- Department of Radiation Oncology, The First Affiliated Hospital of Soochow University, Suzhou, China
| | - Yu Tang
- Qiusuo Health Technologies Inc., Suzhou, China
| | - Binbin Ying
- Department of Stomatology, Ningbo First Hospital, Ningbo, China
| | - Jiugao Sang
- Department of Radiation Oncology, Rudong County Hospital, Nantong, China
| | - Ming Ji
- Qiusuo Health Technologies Inc., Suzhou, China
| | - Kuo Meng
- Department of Radiation Oncology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Zhouguang Hui
- Department of Radiation Oncology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Jianyang Wang
- Department of Radiation Oncology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Juying Zhou
- Department of Radiation Oncology, The First Affiliated Hospital of Soochow University, Suzhou, China
| | - Yin Zhou
- Homology Medical Technologies Inc., Ningbo, China
| | - Jian Huan
- Department of Radiation Oncology, Suzhou Science and Technology Town Hospital, Suzhou, China
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Hussein M, Angerud A, Saez J, Bogaert E, Lemire M, Barry M, Silvestre Patallo I, Shipley D, Clark CH, Hernandez V. Improving the modelling of a multi-leaf collimator with tilted leaf sides used in radiotherapy. Phys Imaging Radiat Oncol 2024; 29:100543. [PMID: 38390588 PMCID: PMC10881418 DOI: 10.1016/j.phro.2024.100543] [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: 12/11/2023] [Revised: 01/24/2024] [Accepted: 01/25/2024] [Indexed: 02/24/2024] Open
Abstract
Background and purpose Multi-leaf collimators (MLCs) with tilted leaf sides have a complex transmission behaviour that is not easily matched by radiotherapy treatment planning systems (TPSs). We sought to develop an MLC model that can accurately match test fields and clinically relevant plans at different centres. Materials and methods Two new MLC models were developed and evaluated within a research version of a commercial TPS. Prototype I used adjusted-constant transmissions and Prototype II used variable transmissions at the tongue-and-groove and leaf-tip regions. Three different centres evaluated these prototypes for a tilted MLC and compared them with their initial MLC model using test fields and patient-specific quality-assurance measurements of clinically relevant plans. For the latter, gamma passing rates (GPR) at 2 %/2mm were recorded. Results For the prototypes the same set of MLC parameters could be used at all centres, with only a slight adjustment of the offset parameter. For centres A and C, average GPR were >95 % and within 0.5 % GPR difference between the standard, and prototype models. In center B, prototypes I and II improved the agreement in clinically relevant plans, with an increase in GPR of 2.3 % ± 0.8 % and 3.0 ± 0.8 %, respectively. Conclusions The prototype MLC models were either similar or superior to the initial MLC model, and simpler to configure because fewer trade-offs were required. Prototype I performed comparably to the more sophisticated Prototype II and its configuration can be easily standardized, which can be useful to reduce variability and improve safety in clinical practice.
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Affiliation(s)
- Mohammad Hussein
- Metrology for Medical Physics Centre, National Physical Laboratory, Teddington, UK
| | | | - Jordi Saez
- Department of Radiation Oncology, Hospital Clínic de Barcelona, Barcelona, Spain
| | - Evelien Bogaert
- Department of Radiation Oncology, Ghent University Hospital, Belgium
| | | | - Miriam Barry
- Metrology for Medical Physics Centre, National Physical Laboratory, Teddington, UK
| | | | - David Shipley
- Metrology for Medical Physics Centre, National Physical Laboratory, Teddington, UK
| | - Catharine H Clark
- Metrology for Medical Physics Centre, National Physical Laboratory, Teddington, UK
- Medical Physics, University College London Hospital, London, UK
- Medical Physics and Bioengineering, University College London, London, UK
| | - Victor Hernandez
- Department of Medical Physics, Hospital Sant Joan de Reus, IISPV, Tarragona, Spain
- Universitat Rovira i Virgili, Tarragona, Spain
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Shiha M, Cygler JE, MacRae R, Heath E. 4D Monte Carlo dose reconstructions using surface motion measurements. Phys Med 2023; 114:103135. [PMID: 37738806 DOI: 10.1016/j.ejmp.2023.103135] [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: 05/15/2023] [Revised: 08/01/2023] [Accepted: 09/13/2023] [Indexed: 09/24/2023] Open
Abstract
PURPOSE To investigate the feasibility of a 4D Monte Carlo based dose reconstruction method to study the dosimetric impact of respiratory motion using surface motion measurements for patients undergoing VMAT treatments for Non-Small Cell Lung Cancer. METHODS The 4Ddefdosxyznrc/EGSnrc algorithm was used to reconstruct VMAT doses delivered to the patients using machine log files and respiratory traces measured with the RADPOS 4D dosimetry system. The RADPOS sensor was adhered to the patient's abdomen prior to each treatment fraction and its position was used as a surrogate for tumour motion. Treatment log files were synchronized with the patient respiratory traces. Patient specific respiratory models were generated from deformable registration of the inhale and exhale 4DCT images and the respiratory traces. The reconstructed doses were compared to planned doses calculated with DOSXYZnrc/EGSnrc on the average-intensity and the exhale phase CT images. RESULTS Respiratory motion measurements and log files were acquired for 2 patients over 5 treatment fractions each. The motion was predominantly along the anterior/posterior direction (A/P). The average respiratory amplitudes were 8.7 ± 2.7 mm and 10.0 ± 1.2 mm for Patient 1 and 2, respectively. Both patients displayed inter- and intra-fractional variations in the baseline position. Small inter-fractional differences were observed in the reconstructed doses for each patient. Differences between the reconstructed and planned doses were attributed to differences in organ volumes. CONCLUSION The 4D reconstruction method was successfully implemented for the two patients studied. Small differences between the planned and reconstructed doses were observed due to the small tumour motion of these patients.
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Affiliation(s)
- Meaghen Shiha
- Department of Physics, Carleton University, Ottawa, ON K1S 5B6, Canada.
| | - Joanna E Cygler
- Department of Physics, Carleton University, Ottawa, ON K1S 5B6, Canada; Department of Medical Physics, The Ottawa Hospital Cancer Centre, Ottawa, ON K1H 8L6, Canada; Department of Radiology, University of Ottawa, Ottawa, ON K1H 8L6, Canada
| | - Robert MacRae
- Department of Radiology, Division of Radiation Oncology, University of Ottawa, 501 Smyth Road, Ottawa, ON K1H8L6, Canada
| | - Emily Heath
- Department of Physics, Carleton University, Ottawa, ON K1S 5B6, Canada
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Thewes L, Eckl M, Schneider F. Transmission probability filter optimization for Agility MLC in Monaco treatment planning system. J Appl Clin Med Phys 2023; 24:e14105. [PMID: 37494135 PMCID: PMC10476981 DOI: 10.1002/acm2.14105] [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: 10/11/2022] [Revised: 05/30/2023] [Accepted: 07/12/2023] [Indexed: 07/28/2023] Open
Abstract
In the Monte Carlo-based treatment planning system (TPS) Monaco, transmission probability filters (TPF) are utilized to describe the transmission through the multi leaf collimator (MLC). By having knowledge of the TPF parameters for various photon beam energies, adjusting the MLC transmission parameters becomes easier, enhancing the accuracy of the Monte Carlo algorithm in achieving a dose distribution that closely aligns with the irradiated dose at the Versa HD linear accelerator (linac). The objective of this study was to determine the TPF parameters for 6MV, 10MV, 6MV flattening filter free (FFF) and 10MV FFF for a Versa HD linac equipped with Agility MLC. The TPF parameters were adjusted using point dose measurements and vendor-provided fields specifically designed to fine-tune the MLC. After adjusting the TPF parameters, a gamma passing rate (GPR) analysis was conducted on 25 treatment plans to ensure that the Monte Carlo model, with the updated TPF parameters, accurately matched the actual linac delivery. The TPF values ranged from 0.0018 to 0.0032 for leaf transmission and 1.15 to 1.25 for Leaf Tip leakage across the different energies. The average GPR ranged from 97.8% for 10MV FFF to 98.5% for 6MV photon energies. Additionally, the TPF parameters for 6MV obtained in this study were consistent with previously published TPF values for 6MV photon energy. Hence, it was concluded that optimizing the TPF does not need to be performed for every individual Versa HD linac with Agility MLC. Instead, the published parameters can be applied to other Versa HD linacs to enhance clinical accuracy. In conclusion, this study determined the TPF parameters for 6MV and previously unpublished photon energies 10MV, 6MV FFF and 10MV FFF. These parameters can be easily transferred to other facilities, resulting in improved agreement between the dose distribution from the TPS and the linac.
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Affiliation(s)
- Lena Thewes
- Department of Radiation OncologyUniversity Medical Centre MannheimUniversity of HeidelbergMannheimGermany
| | - Miriam Eckl
- Department of Radiation OncologyUniversity Medical Centre MannheimUniversity of HeidelbergMannheimGermany
| | - Frank Schneider
- Department of Radiation OncologyUniversity Medical Centre MannheimUniversity of HeidelbergMannheimGermany
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Cheng B, Xu Y, Li S, Ren Q, Pei X, Men K, Dai J, Xu XG. Development and clinical application of a GPU-based Monte Carlo dose verification module and software for 1.5 T MR-LINAC. Med Phys 2023; 50:3172-3183. [PMID: 36862110 DOI: 10.1002/mp.16337] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 02/14/2023] [Accepted: 02/20/2023] [Indexed: 03/03/2023] Open
Abstract
BACKGROUND Adaptive radiotherapy (ART) has made significant advances owing to magnetic resonance linear accelerator (MR-LINAC), which provides superior soft-tissue contrast, fast speed and rich functional magnetic resonance imaging (MRI) to guide radiotherapy. Independent dose verification plays a critical role in discovering errors, while several challenges remain in MR-LINAC. PURPOSE A Monte Carlo-based GPU-accelerated dose verification module for Unity is proposed and integrated into the commercial software ArcherQA to achieve fast and accurate quality assurance (QA) for online ART. METHODS Electron or positron motion in a magnetic field was implemented, and a material-dependent step-length limit method was used to trade off speed and accuracy. Transport was verified by dose comparison with EGSnrc in three A-B-A phantoms. Then, an accurate Monte Carlo-based Unity machine model was built in ArcherQA, including an MR-LINAC head, cryostat, coils, and treatment couch. In particular, a mixed model combining measured attenuation and homogeneous geometry was adopted for the cryostat. Several parameters in the LINAC model were tuned to commission it in the water tank. An alternating open-closed MLC plan on solid water measured with EBT-XD film was used to verify the LINAC model. Finally, the ArcherQA dose was compared with ArcCHECK measurements and GPUMCD in 30 clinical cases through the gamma test. RESULTS ArcherQA and EGSnrc were well matched in three A-B-A phantom tests, and the relative dose difference (RDD) was less than 1.6% in the homogenous region. A Unity model was commissioned in the water tank, and the RDD in the homogenous region was less than 2%. In the alternating open-closed MLC plan, the gamma result (3%/3 mm) between ArcherQA and Film was 96.55%, better than the gamma result between GPUMCD and Film (92.13%). In 30 clinical cases, the mean three-dimensional (3D) gamma result (3%/2 mm) was 99.36% ± 1.28% between ArcherQA and ArcCHECK for the QA plans and 99.27% ± 1.04% between ArcherQA and GPUMCD for the clinical patient plans. The average dose calculation time was 106 s in all clinical patient plans. CONCLUSIONS A GPU-accelerated Monte Carlo-based dose verification module was developed and built for the Unity MR-LINAC. The fast speed and high accuracy were proven by comparison with EGSnrc, commission data, the ArcCHECK measurement dose, and the GPUMCD dose. This module can achieve fast and accurate independent dose verification for Unity.
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Affiliation(s)
- Bo Cheng
- School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, China
| | - Yuan Xu
- Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Shijun Li
- School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, China
| | - Qiang Ren
- Technology Development Department, Anhui Wisdom Technology Company Limited, Hefei, China
| | - Xi Pei
- School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, China.,Technology Development Department, Anhui Wisdom Technology Company Limited, Hefei, China
| | - Kuo Men
- Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Jianrong Dai
- Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Xie George Xu
- School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, China.,Department of Radiation Oncology, The First Affiliated Hospital of University of Science and Technology of China, Hefei, China
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Hernandez V, Angerud A, Bogaert E, Hussein M, Lemire M, García-Miguel J, Saez J. Challenges in modeling the Agility multileaf collimator in treatment planning systems and current needs for improvement. Med Phys 2022; 49:7404-7416. [PMID: 36217283 PMCID: PMC10092639 DOI: 10.1002/mp.16016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 08/22/2022] [Accepted: 09/12/2022] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND The Agility multileaf collimator (MLC) mounted in Elekta linear accelerators features some unique design characteristics, such as large leaf thickness, eccentric curvature at the leaf tip, and defocused leaf sides ('tilting'). These characteristics offer several advantages but modeling them in treatment planning systems (TPSs) is challenging. PURPOSE The goals of this study were to investigate the challenges faced when modeling the Agility in two commercial TPSs (Monaco and RayStation) and to explore how the implemented MLC models could be improved in the future. METHODS Four linear accelerators equipped with the Agility, located at different centers, were used for the study. Three centers use the RayStation TPS and the other one uses Monaco. For comparison purposes, data from four Varian linear accelerators with the Millennium 120 MLC were also included. Average doses measured with asynchronous sweeping gap tests were used to characterize and compare the characteristics of the Millennium and the Agility MLCs and to assess the MLC model in the TPSs. The FOURL test included in the ExpressQA package, provided by Elekta, was also used to evaluate the tongue-and-groove with radiochromic films. Finally, raytracing was used to investigate the impact of the MLC geometry and to understand the results obtained for each MLC. RESULTS The geometry of the Agility produces dosimetric effects associated with the rounded leaf end up to a distance 20 mm away from the leaf tip end measured at the isocenter plane. This affects the tongue-and-groove shadowing, which progressively increases along the distance to the tip end. The RayStation and Monaco TPSs did not account for this effect, which made trade-offs in the MLC parameters necessary and greatly varied the final MLC parameters used by different centers. Raytracing showed that these challenging leaf tip effects were directly related to the MLC geometry and that the characteristics mainly responsible for the large leaf tip effects of the Agility were its tilting design and its small source-to-collimator distance. CONCLUSIONS The MLC models implemented in RayStation and Monaco could not accurately reproduce the leaf tip effects for the Agility. Therefore, trade-offs are needed and the optimal MLC parameters are dependent on the specific characteristics of treatment plans. Refining the MLC models for the Agility to better approximate the measured leaf tip and tongue-and-groove effects would extend the validity of the MLC model, reduce the variability in the MLC parameters used by the community, and facilitate the standardization of the MLC configuration process.
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Affiliation(s)
- V Hernandez
- Department of Medical Physics, Hospital Sant Joan de Reus, IISPV, Tarragona, Spain.,Universitat Rovira i Virgili (URV), Tarragona, Spain
| | - A Angerud
- RaySearch Laboratories AB, Stockholm, Sweden
| | - E Bogaert
- Department of Radiation Oncology, Ghent University Hospital and Ghent University, Ghent, Belgium
| | - M Hussein
- Metrology for Medical Physics Centre, National Physical Laboratory, Teddington, UK
| | - M Lemire
- Department of Medical Physics, CIUSSS de l'Est-de-l'Île-de-Montréal, Montreal, QC, Canada
| | - J García-Miguel
- Department of Radiation Oncology, Consorci Sanitari de Terrassa, Barcelona, Spain
| | - J Saez
- Department of Radiation Oncology, Hospital Clínic de Barcelona, Barcelona, Spain
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Christiansen EJ, Xu T, Heath E. ALERT-RA: an aperture library-enabled real-time respiratory motion adaptive framework for 4D-VMAT. Med Phys 2022; 49:6774-6793. [PMID: 36166687 DOI: 10.1002/mp.15984] [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: 03/14/2022] [Revised: 08/16/2022] [Accepted: 08/23/2022] [Indexed: 12/13/2022] Open
Abstract
PURPOSE To develop a framework for robust optimization of real-time respiratory motion adaptive VMAT treatment plans, and to evaluate the robustness of resulting plans to variations in tumor trajectory during delivery. METHODS The proposed framework is called aperture library-enabled real-time robust adaptation (ALERT-RA). A patient-specific library of optimized MLC apertures is defined for each combination of gantry angle and respiratory phase. The method assumes that the tumor is tracked in real-time throughout delivery, and the aperture corresponding to the current phase and gantry angle will be delivered. The aperture library is optimized by considering all possible tumor trajectories determined by a probabilistic respiratory motion model. Plan robustness to trajectory variations was evaluated by sampling a trajectory, and determining the corresponding dose, from the respiratory model for each fraction. The cumulative dose of the full treatment course was simulated 50 times. Percentile dose-volume histograms (PDVHs) were computed from these simulated treatments. The resulting plan quality and robustness of this method were compared to other previously published motion 4D-VMAT methods, including: an optimized tracking approach that assumes reproducible tumor motion, conformal tracking with aperture deformation, and a motion-encompassing method. Two fractionation schemes were tested to determine the possible effect on robustness: a conventional fractionation of 66 Gy in 33 fractions, and an SBRT course with 60 Gy in 5 fractions. RESULTS When considering target coverage, the ALERT-RA method was found to produce a plan which was more robust than those produced using the optimized or conformal tracking methods. Using the PDVH analysis, the 5th and 95th percentiles of the prescription dose volume for the conventionally fractioned plan were found to be (respectively) 79% and 82% for the optimized tracking approach, 81% and 83% for the conformal tracking approach, and 92% and 97% using the new ALERT-RA method. The motion-encompassing plan was slightly more robust than the ALERT-RA plan, with 5th and 95th percentiles at 94% and 95%, respectively. This came at a cost of higher dose to OARs, with the volume of lung receiving 5 Gy or more equal to 48% for the motion-encompassing plan versus 44% for the ALERT-RA plan. For the SBRT plan, the conformal tracking plan was similarly not robust, with 5th and 95th percentiles of the prescription dose volume equal to 88% and 89%. The optimized tracking SBRT plan gave values of 93% and 95%, and the motion-encompassing plan 94% and 95%, while the ALERT-RA gave values of 93% and 96%. The volume of lung receiving 20 Gy or more was slightly higher for the optimized tracking and motion-encompassing plans compared to the ALERT-RA plan, at 15%, 15%, and 14%, respectively. CONCLUSIONS Compared to other motion-adaptive VMAT approaches, the ALERT-RA algorithm is capable of delivering high-quality plans which are robust to variations in tumor motion trajectories.
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Affiliation(s)
| | - Tong Xu
- Carleton Laboratory for Radiotherapy Physics, Carleton University, Ottawa, ON, K1S 5B6, Canada
| | - Emily Heath
- Carleton Laboratory for Radiotherapy Physics, Carleton University, Ottawa, ON, K1S 5B6, Canada
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10
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Paschal HMP, Kabat CN, Papaconstadopoulos P, Kirby NA, Myers PA, Wagner TD, Stathakis S. Monte Carlo modeling of the Elekta Versa HD and patient dose calculation with EGSnrc/BEAMnrc. J Appl Clin Med Phys 2022; 23:e13715. [PMID: 35985698 PMCID: PMC9512349 DOI: 10.1002/acm2.13715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 04/18/2022] [Accepted: 06/12/2022] [Indexed: 11/10/2022] Open
Abstract
Introduction Numerous studies have proven the Monte Carlo method to be an accurate means of dose calculation. Although there are several commercial Monte Carlo treatment planning systems (TPSs), some clinics may not have access to these resources. We present a method for routine, independent patient dose calculations from treatment plans generated in a commercial TPS with our own Monte Carlo model using free, open‐source software. Materials and methods A model of the Elekta Versa HD linear accelerator was developed using the EGSnrc codes. A MATLAB script was created to take clinical patient plans and convert the DICOM RTP files into a format usable by EGSnrc. Ten patients’ treatment plans were exported from the Monaco TPS to be recalculated using EGSnrc. Treatment simulations were done in BEAMnrc, and doses were calculated using Source 21 in DOSXYZnrc. Results were compared to patient plans calculated in the Monaco TPS and evaluated in Verisoft with a gamma criterion of 3%/2 mm. Results Our Monte Carlo model was validated within 1%/1‐mm accuracy of measured percent depth doses and profiles. Gamma passing rates ranged from 82.1% to 99.8%, with 7 out of 10 plans having a gamma pass rate over 95%. Lung and prostate patients showed the best agreement with doses calculated in Monaco. All statistical uncertainties in DOSXYZnrc were less than 3.0%. Conclusion A Monte Carlo model for routine patient dose calculation was successfully developed and tested. This model allows users to directly recalculate DICOM RP files containing patients’ plans that have been exported from a commercial TPS.
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Affiliation(s)
- Holly M Parenica Paschal
- Department of Radiation Oncology, School of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA
| | - Christopher N Kabat
- Department of Radiation Oncology, School of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA
| | | | - Neil A Kirby
- Department of Radiation Oncology, School of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA
| | - Pamela A Myers
- Department of Radiation Oncology, School of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA
| | - Timothy D Wagner
- Department of Radiation Oncology, School of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA
| | - Sotirios Stathakis
- Department of Radiation Oncology, School of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA
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11
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Chand B, Singh R, Kumar M. Determination and validation of the initial beam parameters of Elekta Agility collimator head by Monte Carlo simulations. Phys Eng Sci Med 2022; 45:889-899. [PMID: 35849322 DOI: 10.1007/s13246-022-01159-7] [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: 01/16/2022] [Accepted: 07/01/2022] [Indexed: 11/24/2022]
Abstract
The availability of geometrical, physical, and initial beam parameters for Monte Carlo (MC) simulations of the Elekta Agility collimator head has become very difficult due to the proprietary nature of this data. This study presents strategies to independently determine the geometrical and physical properties of the components and initial beam parameters of the Agility collimator head for full beam simulations and postulates a benchmarking process using the EGSnrc MC toolkit. Target material of W (90%) and Re (10%) of 0.09 cm thickness, flattening filter of 1.77 cm thick stainless steel placed on 0.5 cm Al disc, and primary and secondary collimators of Tungsten alloy have been found to best fit the Agility head. The initial beam energy of 6.0 MeV with a radial distribution given as full-width half maxima (FWHM) of 0.301 cm (crossline) × 0.201 cm (inline) for 6 MV beam with a mean angular spread of 1.34° has been found best fitting the model. Variations of 0.29% and 0.59% have been noted in the measured and calculated values of TPR20,10 and D10 respectively. More than 90% dose points for all simulations passed the 2D gamma criteria of 3% DD, 3 mm DTA. This MC model of the Agility head can be used for dose calculation and validation of advanced treatment techniques.
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Affiliation(s)
- Bhagat Chand
- Department of Physics, Lovely Professional University, Phagwara, 1444141, Punjab, India.,Department of Radiotherapy, Dr. Rajendra Prasad Government Medical College, Tanda, Kangra, 176001, Himachal Pradesh, India
| | - Ranjit Singh
- Department of Radiotherapy, Postgraduate Institute of Medical Education and Research, Chandigarh, 160012, India
| | - Mukesh Kumar
- Department of Physics, Lovely Professional University, Phagwara, 1444141, Punjab, India.
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12
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Chuah K, Abdul Aziz M, Jayamani J. Determination of the Small-Field Output Factor for 6 MV Photon Beam Using EGSnrc Monte Carlo. J Med Phys 2022; 47:301-308. [PMID: 36684700 PMCID: PMC9846995 DOI: 10.4103/jmp.jmp_40_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 07/04/2022] [Accepted: 07/20/2022] [Indexed: 11/10/2022] Open
Abstract
Accuracy of ionization chamber (IC) to measure the scatter output factor (Scp) of a linear accelerator (linac) is crucial, especially in small field (<4 cm × 4 cm). The common IC volume of 0.6 cc is not adequate for small-field measurement and not all radiotherapy centers can afford to purchase additional IC due to the additional cost. This study aimed to determine the efficiency of the EGSnrc Monte Carlo (MC) to calculate the Scp for various field sizes including small field in Elekta Synergy (Agility multileaf collimator) linac. The BEAMnrc and DOSXYZnrc user codes were used to simulate a 6 MV linac model for various field sizes and calculate the radiation dose output in water phantom. The modeled linac treatment head was validated by comparing the percentage depth dose (PDD), beam profile, and beam quality (Tissue Phantom Ratio (TPR)20,10) with the IC measurement. The validated linac model was simulated to calculate the Scp consisting of collimator scatter factor (Sc) and phantom scatter factor (Sp). The PDD and beam profile of the simulated field sizes were within a good agreement of ±2% compared with the measured data. The TPR20,10 value was 0.675 for field size 10 cm × 10 cm. The Scp, Sc, and Sp simulated values were close to the IC measurement within ±2% difference. The simulation for Sc and Sp in 3 cm × 3 cm field size was calculated to be 0.955 and 0.884, respectively. In conclusion, this study validated the efficiency of the MC simulation as a promising tool for the Scp calculation including small-field size for linac.
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Affiliation(s)
- K.W. Chuah
- Medical Radiation Programme, School of Health Sciences, Health Campus, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
| | - M.Z. Abdul Aziz
- Department of Biomedical Imaging, Advanced Medical and Dental Institute, Universiti Sains Malaysia, 13200 Kepala Batas, Pulau Pinang, Malaysia
| | - J Jayamani
- Medical Radiation Programme, School of Health Sciences, Health Campus, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
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13
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Almatani T, Hugtenburg RP, Smakovs A. A Monte Carlo model of an agility head for a 10-MV photon beam. JOURNAL OF TAIBAH UNIVERSITY FOR SCIENCE 2022. [DOI: 10.1080/16583655.2022.2050097] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
| | - Richard P. Hugtenburg
- College of Medicine, Swansea University, Swansea, UK
- Department of Medical Physics and Clinical Engineering, Swansea Bay University Health Board, Swansea, UK
| | - Artjoms Smakovs
- Department of Medical Physics and Clinical Engineering, Swansea Bay University Health Board, Swansea, UK
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14
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Castle JR, Duan J, Feng X, Chen Q. Development of a virtual source model for Monte Carlo-based independent dose calculation for varian linac. J Appl Clin Med Phys 2022; 23:e13556. [PMID: 35138686 PMCID: PMC9121055 DOI: 10.1002/acm2.13556] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 01/05/2022] [Accepted: 01/26/2022] [Indexed: 11/10/2022] Open
Abstract
Monte Carlo (MC) independent dose calculations are often based on phase-space files (PSF), as they can accurately represent particle characteristics. PSF generally are large and create a bottleneck in computation time. In addition, the number of independent particles is limited by the PSF, preventing further reduction of statistical uncertainty. The purpose of this study is to develop and validate a virtual source model (VSM) to address these limitations. Particles from existing PSF for the Varian TrueBeam medical linear accelerator 6X, 6XFFF, 10X, and 10XFFF beam configurations were tallied, analyzed, and used to generate a dual-source photon VSM that includes electron contamination. The particle density distribution, kinetic energy spectrum, particle direction, and the correlations between characteristics were computed. The VSM models for each beam configuration were validated with water phantom measurements as well as clinical test cases against the original PSF. The new VSM requires 67 MB of disk space for each beam configuration, compared to 50 GB for the PSF from which they are based and effectively remove the bottleneck set by the PSF. At 3% MC uncertainty, the VSM approach reduces the calculation time by a factor of 14 on our server. MC doses obtained using the VSM approach were compared against PSF-generated doses in clinical test cases and measurements in a water phantom using a gamma index analysis. For all tests, the VSMs were in excellent agreement with PSF doses and measurements (>90% passing voxels between doses and measurements). Results of this study indicate the successful derivation and implementation of a VSM model for Varian Linac that significantly saves computation time without sacrificing accuracy for independent dose calculation.
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Affiliation(s)
| | - Jingwei Duan
- Department of Radiation Medicine, University of Kentucky School of Medicine, Lexington, Kentucky, USA
| | - Xue Feng
- Carina Medical LLC, Lexington, Kentucky, USA
| | - Quan Chen
- Department of Radiation Medicine, University of Kentucky School of Medicine, Lexington, Kentucky, USA
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15
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Neutron and photon out-of-field doses at cardiac implantable electronic device (CIED) depths. Appl Radiat Isot 2021; 176:109895. [PMID: 34419874 DOI: 10.1016/j.apradiso.2021.109895] [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: 12/23/2020] [Revised: 08/08/2021] [Accepted: 08/08/2021] [Indexed: 11/20/2022]
Abstract
The accuracy of an out-of-field dose from an Elekta Synergy accelerator calculated using the X-ray Voxel Monte Carlo (XVMC) dose algorithm in the Monaco treatment planning system (TPS) for both low-energy (6 MV) and high-energy (15 MV) photons at cardiac implantable electronic device (CIED) depths was investigated through a comparison between MCNPX simulated out-of-field doses and measured out-of-field doses using three high spatial and sensitive active detectors. In addition, total neutron equivalent dose and fluence at CIED depths of a 15-MV dose from an Elekta Synergy accelerator were calculated, and the corresponding CIED relative neutron damage was quantified. The results showed that for 6-MV photons, the XVMC dose algorithm in Monaco underestimated out-of-field doses in all off-axis distances (average errors: -17% at distances X < 10 cm from the field edge and -31% at distances between 10 < X ≤ 16 cm from the field edge), with an increasing magnitude of underestimation for high-energy (15 MV) photons (up to 11%). According to the results, an out-of-field photon dose at a shallower CIED depth of 1 cm was associated with greater statistical uncertainty in the dose estimate compared to a CIED depth of 2 cm and clinical depth of 10 cm. Our results showed that the relative neutron damage at a CIED depth range for 15 MV photon is 36% less than that reported for 18 MV photon in the literature.
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16
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Norvill C, Goodall S. Investigation of pixel scale calibration on the Elekta iView electronic portal imager. J Appl Clin Med Phys 2021; 22:148-155. [PMID: 34250752 PMCID: PMC8364275 DOI: 10.1002/acm2.13339] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 05/10/2021] [Accepted: 06/16/2021] [Indexed: 01/09/2023] Open
Abstract
This study investigated the variation in electronic portal imager pixel scale at the isocenter plane for Elekta Agility linear accelerators. An in‐house MATLAB script was written to process and calculate the pixel scale based on a metal calibration plate supplied by Elekta. Eight pixel plates were compared and found to have manufacturing tolerances within 0.1 mm of nominal dimensions. The impact of these variations on pixel scale factor was negligible, and plates could be used interchangeably. Uncertainties from other parameters such as source‐to‐surface distance and user variability summed to a combined uncertainty of 0.0003 mm/pixel, compared to a pixel scale range of 0.003 mm/pixel measured across 10 machines. Most of the inter‐machine variation was shown to be attributable to differences in source‐to‐panel distance. Other factors such as focal spot size and shape, electronic portal imager manufacturing consistency, panel sag, and setup errors may account for the residual variation. Individual characterization of machine and imaging panel pixel scale factors is important to ensure accurate geometric information is derived from electronic portal images, which is critical where the portal imager is used for multi‐leaf collimator calibration or other clinical tasks.
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Affiliation(s)
| | - Simon Goodall
- Genesis Care, Perth, Australia.,School of Physics, Mathematics, and Computing, Faculty of Engineering and Mathematical Sciences, University of Western Australia, Crawley, Western Australia, Australia
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17
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Yani S, Budiansah I, Rhani MF, Haryanto F. Monte carlo model and output factors of elekta infinity™ 6 and 10 MV photon beam. Rep Pract Oncol Radiother 2020; 25:470-478. [PMID: 32494222 DOI: 10.1016/j.rpor.2020.03.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 02/02/2020] [Accepted: 03/20/2020] [Indexed: 10/24/2022] Open
Abstract
Aim This study aimed to commission the Elekta Infinity™ working in 6 and 10 MV photon beam installed in Concord International Hospital, Singapore, and compare the OFs between MC simulation and measurement using PTW semiflex and microDiamond detector for small field sizes. Material and Methods There are two main steps in this study: modelling of Linac 6 and 10 MV photon beam and analysis of the output factors for field size 2 × 2-10 × 10 cm2. The EGSnrc/BEAMnrc-DOSXYZnrc code was used to model and characterize the Linac and to calculate the dose distributions in a water phantom. The dose distribution and OFs were compared to the measurement data in the same condition. Results The commissioning process was only conducted for a 10 × 10 cm2 field size. The PDD obtained from MC simulation showed a good agreement with the measurement. The local dose difference of PDDs was less than 2% for 6 and 10 MV. The initial electron energy was 5.2 and 9.4 MeV for 6 and 10 MV photon beam, respectively. This Linac model can be used for dose calculation in other situations and different field sizes because this Linac has been commissioned and validated using Monte Carlo simulation. The 10 MV Linac produces higher electron contamination than that of 6 MV. Conclusions The Linac model in this study was acceptable. The most important result in this work comes from OFs resulted from MC calculation. This value was more significant than the OFs from measurement using semiflex and microDiamond for all beam energy and field sizes because of the CPE phenomenon.
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Affiliation(s)
- Sitti Yani
- Department of Physics, Faculty of Mathematics and Natural Sciences, IPB University (Bogor Agricultural University), Babakan, Bogor, Indonesia.,Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jalan Ganesa 10, Bandung, Indonesia
| | - Indra Budiansah
- Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jalan Ganesa 10, Bandung, Indonesia
| | | | - Freddy Haryanto
- Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jalan Ganesa 10, Bandung, Indonesia
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18
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Aldosary G, Tse T, Arnaout A, Caudrelier JM, Czyrnyj C, Romain R, McLean L, Foottit C, Belec J, Vandervoort E. Radiological, dosimetric and mechanical properties of a deformable breast phantom for radiation therapy and surgical applications. Biomed Phys Eng Express 2020; 6:035028. [PMID: 33438673 DOI: 10.1088/2057-1976/ab834a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The displacement of tumor bed walls during oncoplastic breast surgery (OBS) decreases the accuracy of using surgical clips as the sole surrogate for tumor bed location. This highlights the need for better communication of OBS techniques to radiation oncologists. To facilitate OBS practice and investigate clip placement reliability, a realistic silicone-based breast phantom was constructed with components emulating a breast parenchyma, epidermis, areola, nipple, chest wall, and a tumor. OBS was performed on the phantom and surgical clips were placed to mark the tumor bed. The phantom was imaged with CT, MRI, and ultrasound (US). The parenchyma's signal-to-noise ratio (SNR) and clips to parenchyma's contrast-to-noise ratio (CNR) were measured. The phantom's CT Hounsfield Unit (HU), relative electron density (RED), and mass density were determined. 6 and 10 MV photon beam attenuation measurements were performed in phantom material. The Young's Modulus and ultimate tensile strength (UTS) of the phantom parenchyma and epidermis were measured. Results showed that the breast phantom components were visible on all imaging modalities with adequate SNR and CNR. The phantom's HU is 130 ± 10. The RED is 0.983. Its mass density is 1.01 ± 0.01 g cm-3. Photon attenuation measurements in phantom material were within 1% of those in water. The Young's Moduli were 13.4 ± 4.2 kPa (mechanical) and 30.2 ± 4.1 kPa (US elastography) for the phantom parenchyma. The UTS' were 0.05 ± 0.01 MPa (parenchyma) and 0.23 ± 0.12 MPa (epidermis). We conclude that the phantom's imaging characteristics resemble a fibroglandular breast's and allow clear visualization of high-density markers used in radiation therapy. The phantom material is suitable for dose measurements in MV photon beams. Mechanical results confirmed the phantom's similarity to breast tissue. The phantom enables investigation of surgical clip displacements pre- and post-OBS, and is useful for radiation therapy quality assurance applications.
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Affiliation(s)
- Ghada Aldosary
- Department of Physics, Carleton University, Ottawa, Ontario, Canada. Radiation Oncology Section, Department of Oncology, King Abdulaziz Medical City, National Guard Health Affairs, Riyadh, Saudi Arabia
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19
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Gray T, Bassiri N, Kirby N, Stathakis S, Mayer KM. Implementation of a simple clinical linear accelerator beam model in MCNP6 and comparison with measured beam characteristics. Appl Radiat Isot 2019; 155:108925. [PMID: 31757713 DOI: 10.1016/j.apradiso.2019.108925] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2019] [Revised: 09/12/2019] [Accepted: 10/03/2019] [Indexed: 10/25/2022]
Abstract
Monte Carlo N-Particle 6 (MCNP6) is the latest version of Los Alamos National Laboratory's powerful Monte Carlo software designed to compute general photon, neutron, and electron transport using stochastic algorithms. Here we provide a case study of modeling the photon beam of a Varian 600C Clinical Linear Accelerator (linac), which is used to deliver radiation therapy, along with a comparison to experimentally measured beam characteristics. The source definition parameters in MCNP6, including the energy spectrum and angular spectrum of the photons, secondary and tertiary collimators, and a water phantom that tallied dose delivered at different points along the phantom are included. The experimental data for comparison was in the form of a percent depth dose curve as well as crossline and inline beam profiles. Experimental depth dose curve and beam profiles were acquired using a standard 0.125 cc ion chamber within a water phantom. In the computational model, the simulated depth dose curve was computed by tallying the total energy deposited in a stack of vertical slices down the depth of the phantom for percent depth dose curves. The simulated beam profiles were computed in a similar fashion, by tallying the energy deposited in a horizontal row, both in the x- and y-directions of cubic cells located at various depths. For the percent depth dose curve, a mean absolute percentage difference of 1.02%, 1.07%, and 1.94% were calculated for field sizes of 5 × 5 cm2, 10 × 10 cm2 and 20 × 20 cm2, respectively, between the model and experimental measurements were calculated. We present our model as an example to guide other MCNP6 users in the medical physics community to create similar beam models for biomedical dose estimation and research calculations for predicting dose to newly developed phantoms.
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Affiliation(s)
- Tara Gray
- Department of Physics and Astronomy, The University of Texas at San Antonio, USA
| | - Nema Bassiri
- Department of Radiation Oncology, The University of Texas Health Science Center at San Antonio, USA
| | - Neil Kirby
- Department of Radiation Oncology, The University of Texas Health Science Center at San Antonio, USA
| | - Sotirios Stathakis
- Department of Radiation Oncology, The University of Texas Health Science Center at San Antonio, USA
| | - Kathryn M Mayer
- Department of Physics and Astronomy, The University of Texas at San Antonio, USA.
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20
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Gul A, Farrukh S, Kakakhel MB, Ilyas N, Naveed M, Haseeb A, Mirza SM. Measurement of 6 MV small field beam profiles - comparison of micro ionization chamber and linear diode array with monte carlo code. JOURNAL OF X-RAY SCIENCE AND TECHNOLOGY 2019; 27:655-664. [PMID: 31205012 DOI: 10.3233/xst-190493] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The objective of this study is to analyze small field photon beams acquired with commonly available detectors. Beam profiles of 6 MV photons from the Siemens Primus Linear Accelerator were measured with a micro ion chamber (IC CC01, IBA) and linear diode array (LDA-99SC, IBA). Data was acquired using a water phantom for small fields (0.5×0.5 cm2 to 4×4 cm2) at depth of maximum dose, 5 cm and 10 cm. Profiles were also generated with EGSnrc Monte Carlo code. Measured and simulated profiles were compared in terms of percentage difference of the area under the simulated and measured profiles (PD), ratio of the measured to simulated dose at the point of maximum deviation within the central region of profile (R), full width half maximum (FWHM) and penumbra. For field sizes ≥1×1 cm2, the maximum PD is 3.17 % and 2.87 % for IC and LDA respectively, whereas R is in the range of 0.95-1.05 for IC and 0.99-1.05 for LDA. LDA measured FWHM and penumbra are also in better agreement with the simulated results. This study demonstrated that LDA can be used for acquisition of beam profiles for field size as low as 1×1 cm2.
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Affiliation(s)
- Attia Gul
- Department of Physics & Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan
| | - Salman Farrukh
- Atomic Energy Medical Centre (AEMC), Jinnah Postgraduate Medical Centre (JPMC), Karachi, Pakistan
| | - M Basim Kakakhel
- Department of Physics & Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan
| | - Nasir Ilyas
- Institution of Space and Planetary Astrophysics (ISPA), University of Karachi, Karachi, Pakistan
| | - Muhammad Naveed
- Atomic Energy Medical Centre (AEMC), Jinnah Postgraduate Medical Centre (JPMC), Karachi, Pakistan
| | - Abdul Haseeb
- Atomic Energy Medical Centre (AEMC), Jinnah Postgraduate Medical Centre (JPMC), Karachi, Pakistan
| | - Sikander M Mirza
- Department of Physics & Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan
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21
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Najafzadeh M, Hoseini-Ghafarokhi M, Bolagh RSM, Haghparast M, Zarifi S, Nickfarjam A, Farhood B, Chow JCL. Benchmarking of Monte Carlo model of Siemens Oncor® linear accelerator for 18MV photon beam: Determination of initial electron beam parameters. JOURNAL OF X-RAY SCIENCE AND TECHNOLOGY 2019; 27:1047-1070. [PMID: 31498147 DOI: 10.3233/xst-190568] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
OBJECTIVE This study aims to benchmark a Monte Carlo (MC) model of the 18 MV photon beam produced by the Siemens Oncor® linac using the BEAMnrc and DOSXYZnrc codes. METHODS By matching the percentage depth doses and beam profiles calculated by MC simulations with measurements, the initial electron beam parameters including electron energy, full width at half maximum (spatial FWHM), and mean angular spread were derived for the 10×10 cm2 and 20×20 cm2 field sizes. The MC model of the 18 MV photon beam was then validated against the measurements for different field sizes (5×5, 30×30 and 40×40 cm2) by gamma index analysis. RESULTS The optimum values for electron energy, spatial FWHM and mean angular spread were 14.2 MeV, 0.08 cm and 0.8 degree, respectively. The MC simulations yielded the comparable measurement results of these optimum parameters. The gamma passing rates (with acceptance criteria of 1% /1 mm) for percentage depth doses were found to be 100% for all field sizes. For cross-line profiles, the gamma passing rates were 100%, 97%, 95%, 96% and 95% for 5×5, 10×10, 20×20, 30×30 and 40×40 cm2 field sizes, respectively. CONCLUSIONS By validation of the MC model of Siemens Oncor® linac using various field sizes, it was found that both dose profiles of small and large field sizes were very sensitive to the changes in spatial FWHM and mean angular spread of the primary electron beam from the bending magnet. Hence, it is recommended that both small and large field sizes of the 18 MV photon beams should be considered in the Monte Carlo linac modeling.
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Affiliation(s)
- Milad Najafzadeh
- Department of Radiology, Faculty of Para-Medicine, Hormozgan University of Medical Sciences, Bandare-Abbas, Iran
| | - Mojtaba Hoseini-Ghafarokhi
- Department of Radiology and Nuclear Medicine, School of Para Medical Science, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | | | - Mohammad Haghparast
- Department of Radiology, Faculty of Para-Medicine, Hormozgan University of Medical Sciences, Bandare-Abbas, Iran
| | - Shiva Zarifi
- Department of Medical Physics, Faculty of Medicine, Semnan University of Medical Sciences, Semnan, Iran
| | - Abolfazl Nickfarjam
- Department of Medical Physics, Faculty of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Bagher Farhood
- Department of Medical Physics and Radiology, Faculty of Paramedical Sciences, Kashan University of Medical Sciences, Kashan, Iran
| | - James C L Chow
- Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada
- Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada
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