1
|
Mizoguchi T, Tameshige Y, Kaneda T, Ogawa Y, Muranaka Y, Tamamura H. [Estimation of Uncertainty of the VMAT Absolute Dose Measurement Due to the Phantom Setup Error Using a Treatment Planning System]. Nihon Hoshasen Gijutsu Gakkai Zasshi 2024; 80:345-353. [PMID: 38447969 DOI: 10.6009/jjrt.2024-1371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/08/2024]
Abstract
PURPOSE When performing single-point dose verification in VMAT, it is necessary to avoid the regions with steep dose gradient. We propose a method to obtain the estimated value ( Uplan) of uncertainty of the absolute dose measurement due to the phantom setup error by using dose gradient calculated from treatment planning system (TPS), for evaluating the appropriate measurement points. METHODS The dose gradient was calculated from the planned dose values in the vicinity of the isocenter point using TPS. The phantom setup error was estimated. The Uplan was calculated using the proposed formula after estimating the phantom setup error. Then, the dose gradient was calculated from the measured dose values in the vicinity of the isocenter point specified by TPS using the Tough water phantom with ionization chamber (IC), and Umeas was calculated as in Uplan. RESULTS The correlation coefficient between Uplan and Umeas was 0.984, which indicates a high correlation. The average of the difference between Umeas and Uplan was -0.24%. We considered that this result was caused by the influence of volume averaging effect of IC. CONCLUSION The Uplan obtained from this proposed method reflects the uncertainty of the absolute dose measurement due to the phantom setup error and is useful for evaluating the appropriate measurement points for absolute dose measurement.
Collapse
Affiliation(s)
| | - Yuji Tameshige
- Division of Radiation Therapy, Nuclear Medicine Department, Fukui, Prefectural Hospital
| | - Tatsuya Kaneda
- Department of Radiological Technology, Fukui Prefectural Hospital
| | - Yoshiji Ogawa
- Department of Radiological Technology, Fukui Prefectural Hospital
| | | | | |
Collapse
|
2
|
Zhang B, Zhuang Y, Li Y, Chen L, Liu X, Liu Z, Wang X, Zhu J. Generalisation of radiotherapy dose calculation for Monte Carlo algorithm combined with 3D Swin-Unet: a multi-institutional IMRT evaluation. Phys Med Biol 2023; 68:215015. [PMID: 37827160 DOI: 10.1088/1361-6560/ad02d8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2023] [Accepted: 10/12/2023] [Indexed: 10/14/2023]
Abstract
Objective.Accurate dose calculations are essential prerequisites for precise radiotherapy. The integration of deep learning into dosimetry could consider computational accuracy and efficiency and has potential applicability to clinical dose calculation. The generalisation of a deep learning dose calculation method (hereinafter referred to as TERMA-Monte Carlo network, T-MC net) was evaluated in clinical practice using intensity-modulated radiotherapy (IMRT) plans for various human body regions and multiple institutions, with the Monte Carlo (MC) algorithm serving as a benchmark.Approach. Sixty IMRT plans were selected from four institutions for testing the head and neck, chest and abdomen, and pelvis regions. Using the MC results as the benchmark, the T-MC net calculation results were used to perform three-dimensional dose distribution and dose-volume histogram (DVH) comparisons of the entire body, planning target volume (PTV) and organs at risk (OARs), respectively, and calculate the mean ±95% confidence interval of gamma pass rate (GPR), percentage of agreement (PA) and dose difference ratio (DDR) of dose indices D95, D50, and D5.Main results. For the entire body, the GPRs of 3%/3 mm, 2%/2 mm, 2%/1 mm, and the PA were 99.62 ± 0.32%, 98.50 ± 1.09%, 95.60 ± 2.90% and 97.80 ± 1.12%, respectively. For the PTV, the GPRs of 3%/3 mm, 2%/2 mm, 2%/1 mm and the PA were 98.90 ± 1.00%, 95.78 ± 2.83%, 92.23 ± 4.74% and 98.93 ± 0.62%, respectively. The absolute value of average DDR was less than 1.4%.Significance. We proposed a general dose calculation framework based on deep learning, using the MC algorithm as a benchmark, performing a generalisation test for IMRT treatment plans across multiple institutions. The framework provides high computational speed while maintaining the accuracy of MC and may become an effective dose algorithm engine in treatment planning, adaptive radiotherapy, and dose verification.
Collapse
Affiliation(s)
- Bailin Zhang
- The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou, Guangdong 510006, People's Republic of China
| | - Yongdong Zhuang
- Department of Radiation Oncology, The Key Laboratory of Advanced Interdisciplinary Studies Center, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong 510120, People's Republic of China
| | - Yinghui Li
- Department of Radiation Oncology physics, The First People's Hospital of FoShan, Foshan, 528000, Guangdong, People's Republic of China
| | - Lixin Chen
- State Key Laboratory of Oncology in South China, Guangdong Key Laboratory of Nasopharyngeal Carcinoma Diagnosis and Therapy, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou 510060, People's Republic of China
| | - Xiaowei Liu
- School of Physics, Sun Yat-sen University, Guangzhou, 510275, People's Republic of China
| | - Zhibin Liu
- Department of Radiation Oncology physics, The First People's Hospital of FoShan, Foshan, 528000, Guangdong, People's Republic of China
| | - Xuetao Wang
- The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou, Guangdong 510006, People's Republic of China
| | - Jinhan Zhu
- State Key Laboratory of Oncology in South China, Guangdong Key Laboratory of Nasopharyngeal Carcinoma Diagnosis and Therapy, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou 510060, People's Republic of China
| |
Collapse
|
3
|
Saez J, Bar-Deroma R, Bogaert E, Cayez R, Chow T, Clark CH, Esposito M, Feygelman V, Monti AF, Garcia-Miguel J, Gershkevitsh E, Goossens J, Herrero C, Hussein M, Khamphan C, Kierkels RGJ, Lechner W, Lemire M, Nevelsky A, Nguyen D, Paganini L, Pasler M, Fernando Pérez Azorín J, Ramos Garcia LI, Russo S, Shakeshaft J, Vieillevigne L, Hernandez V. Universal evaluation of MLC models in treatment planning systems based on a common set of dynamic tests. Radiother Oncol 2023; 186:109775. [PMID: 37385376 DOI: 10.1016/j.radonc.2023.109775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2023] [Revised: 06/19/2023] [Accepted: 06/23/2023] [Indexed: 07/01/2023]
Abstract
PURPOSE To demonstrate the feasibility of characterising MLCs and MLC models implemented in TPSs using a common set of dynamic beams. MATERIALS AND METHODS A set of tests containing synchronous (SG) and asynchronous sweeping gaps (aSG) was distributed among twenty-five participating centres. Doses were measured with a Farmer-type ion chamber and computed in TPSs, which provided a dosimetric characterisation of the leaf tip, tongue-and-groove, and MLC transmission of each MLC, as well as an assessment of the MLC model in each TPS. Five MLC types and four TPSs were evaluated, covering the most frequent combinations used in radiotherapy departments. RESULTS Measured differences within each MLC type were minimal, while large differences were found between MLC models implemented in clinical TPSs. This resulted in some concerning discrepancies, especially for the HD120 and Agility MLCs, for which differences between measured and calculated doses for some MLC-TPS combinations exceeded 10%. These large differences were particularly evident for small gap sizes (5 and 10 mm), as well as for larger gaps in the presence of tongue-and-groove effects. A much better agreement was found for the Millennium120 and Halcyon MLCs, differences being within ± 5% and ± 2.5%, respectively. CONCLUSIONS The feasibility of using a common set of tests to assess MLC models in TPSs was demonstrated. Measurements within MLC types were very similar, but TPS dose calculations showed large variations. Standardisation of the MLC configuration in TPSs is necessary. The proposed procedure can be readily applied in radiotherapy departments and can be a valuable tool in IMRT and credentialing audits.
Collapse
Affiliation(s)
- Jordi Saez
- Hospital Clínic de Barcelona, Department of Radiation Oncology, Barcelona, Spain.
| | - Raquel Bar-Deroma
- Rambam Health Care Campus, Department of Radiotherapy, Division of Oncology, Haifa, Israel
| | - Evelien Bogaert
- Ghent University Hospital and Ghent University, Department of Radiation Oncology, Ghent, Belgium
| | - Romain Cayez
- Oscar Lambret Center, Department of Medical Physics, Lille, France
| | - Tom Chow
- Juravinski Hospital and Cancer Centre at Hamilton Health Sciences, Department of Medical Physics, Ontario, Canada
| | - Catharine H Clark
- National Physical Laboratory, Metrology for Medical Physics Centre, London TW11 0PX, UK; Radiotherapy Physics, University College London Hospital, 250 Euston Rd, London NW1 2PG, UK; Dept Medical Physics and Bioengineering, University College London, Malet Place, London WC1 6BT, UK
| | - Marco Esposito
- AUSL Toscana Centro, Medical Physics Unit, Florence, Italy; The Abdus Salam International Center for Theoretical, Trieste, Italy
| | | | - Angelo F Monti
- ASST GOM Niguarda, Department of Medical Physics, Milano, Italy
| | - Julia Garcia-Miguel
- Consorci Sanitari de Terrassa, Department of Radiation Oncology, Terrassa, Spain
| | - Eduard Gershkevitsh
- North Estonia Medical Centre, Department of Medical Physics, Tallinn, Estonia
| | - Jo Goossens
- Iridium Netwerk, Department of Medical Physics, Antwerp, Belgium
| | - Carmen Herrero
- Centro Médico de Asturias-IMOMA, Department of Medical Physics, Oviedo, Spain
| | - Mohammad Hussein
- National Physical Laboratory, Metrology for Medical Physics Centre, London TW11 0PX, UK
| | - Catherine Khamphan
- Institut du Cancer - Avignon Provence, Department of Medical Physics, Avignon, France
| | - Roel G J Kierkels
- Radiotherapiegroep, Department of Medical Physics, Arnhem/Deventer, the Netherlands
| | - Wolfgang Lechner
- Medical University of Vienna, Department of Radiation Oncology, Vienna, Austria
| | - Matthieu Lemire
- CIUSSS de l'Est-de-l'Île-de-Montréal, Service de Radio-Physique, Montréal, Canada
| | - Alexander Nevelsky
- Rambam Health Care Campus, Department of Radiotherapy, Division of Oncology, Haifa, Israel
| | | | - Lucia Paganini
- Humanitas Clinical and Research Center, Radiotherapy and Radiosurgery Department, Rozzano, Italy
| | - Marlies Pasler
- Lake Constance Radiation Oncology Center, Department of Radiation Oncology, Singen, Friedrichshafen, Germany; Radiotherapy Hirslanden, St. Gallen, Switzerland
| | - José Fernando Pérez Azorín
- Medical Physics and Radiation Protection Department, Gurutzeta-Cruces University Hospital, Barakaldo, Spain; Biocruces Health Research Institute, Barakaldo, Spain
| | | | | | - John Shakeshaft
- Gold Coast University Hospital, ICON Cancer Centre, Gold Coast, Australia
| | - Laure Vieillevigne
- Institut Claudius Regaud-Institut Universitaire du Cancer de Toulouse, Department of Medical Physics, Toulouse, France
| | - Victor Hernandez
- Hospital Sant Joan de Reus, Department of Medical Physics, Reus, Spain; Universitat Rovira i Virgili, Tarragona, Spain
| |
Collapse
|
4
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
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
| |
Collapse
|
5
|
Adam DP, Bednarz BP, Frigo SP. Static MLC transmission simulation using two-dimensional ray tracing. J Appl Clin Med Phys 2022; 23:e13646. [PMID: 35596533 PMCID: PMC9359033 DOI: 10.1002/acm2.13646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 04/08/2022] [Accepted: 04/28/2022] [Indexed: 11/10/2022] Open
Abstract
Purpose We investigated the hypothesis that the transmission function of rounded end linearly traveling multileaf collimators (MLCs) is constant with position. This assumption is made by some MLC models used in clinical treatment planning systems (TPSs) and in the Varian MLC calibration convention. If not constant, this would have implications for treatment plan QA results. Methods A two‐dimensional ray‐tracing tool to generate transmission curves as a function of leaf position was created and validated. The curves for clinically available leaf tip positions (−20 to 20 cm) were analyzed to determine the location of the beam edge (half‐attenuation X‐ray [XR]) location, the beam edge broadening (BEB, 80%–20% width), as well as the leaf tip zone width. More generalized scenarios were then simulated to elucidate trends as a function of leaf tip radius. Results In the analysis of the Varian high‐definition MLC, two regions were identified: a quasi‐static inner region centered about central axis (CAX), and an outer one, in which large deviations were observed. A phenomenon was identified where the half‐attenuation ray position, relative to that of the tip or tangential ray, increases dramatically at definitive points from CAX. Similar behavior is seen for BEB. An analysis shows that as the leaf radius parameter value is made smaller, the size of the quasi‐static region is greater (and vice versa). Conclusion The MLC transmission curve properties determined by this study have implications both for MLC position calibrations and modeling within TPSs. Two‐dimensional ray tracing can be utilized to identify where simple behaviors hold, and where they deviate. These results can help clinical physicists engage with vendors to improve MLC models, subsequent fluence calculations, and hence dose calculation accuracy.
Collapse
Affiliation(s)
- David P Adam
- Department of Medical Physics, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Bryan P Bednarz
- Department of Medical Physics, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Sean P Frigo
- Department of Human Oncology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
| |
Collapse
|
6
|
Ramachandran P, Smith A, Hagekyriakou J, Hughes J, Lonski P, Howard B, Osbourne G, Orr K, Kaur R, Kron T. Contralateral breast dose with electronic compensators and conventional tangential fields - A clinical dosimetric study. Z Med Phys 2021; 31:347-354. [PMID: 34127361 DOI: 10.1016/j.zemedi.2021.04.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 03/16/2021] [Accepted: 04/26/2021] [Indexed: 12/24/2022]
Abstract
Dose to the contralateral breast (CLB) from radiotherapy treatment has the potential to induce secondary breast cancer. Electronic tissue compensation (eComp) for breast cancer patients is one of the alternative methods to conventional 3D-conformal radiotherapy that eliminates the use of wedges. Several studies have investigated dose to the CLB using tangential fields involving wedges, intensity-modulated radiation therapy and volumetric modulated arc radiation therapy and various other techniques via treatment planning system calculations, Monte Carlo methods and phantoms. However, there are limited data published in assessing the actual dose received by the CLB from treatment with eComp-based tangential fields. In this study, the CLB dose for patients undergoing tangential field radiotherapy with eComp and enhanced dynamic wedged (standard) tangential fields was measured and compared to assess the CLB dose between the two methods. Measurements were conducted on a randomised trial of 40 patients, 20 of them had undergone standard planning, and the remaining 20 were treated with eComp. The mean surface dose measured with TLDs at 3cm from the medial tangential border for eComp and standard techniques was 10.04±1.37% and 10.14±2.05%, respectively for a prescription dose of 2.65Gy/fraction. The estimated dose at 1cm depth in tissue, measured with the use of perspex domes placed over the TLD at the same location, was 5.12±0.87% and 6.29±2.01% for eComp and standard, respectively. The CLB dose is dependent on the proximity of the medial tangential field edge to the contralateral breast and is patient-specific. The results of this study show that at 1cm depth, eComp technique delivers significantly less dose (p<0.05) to the CLB as compared to standard tangential fields. Furthermore, the surface dose measured for both eComp and standard are comparable indicating that the eComp-based tangential field technique does not contribute any excess dose to CLB when compared to standard tangential fields. The excess relative risk (ERR) for radiation-induced cancers for eComp was found to be 0.08, compared to 0.11 for standard tangential fields.
Collapse
Affiliation(s)
| | - Amanda Smith
- Peter MacCallum Cancer Centre, Victoria, Australia
| | | | | | - Peta Lonski
- Peter MacCallum Cancer Centre, Victoria, Australia
| | - Beth Howard
- Peter MacCallum Cancer Centre, Victoria, Australia
| | | | - Kylie Orr
- Peter MacCallum Cancer Centre, Victoria, Australia
| | - Ravneet Kaur
- Peter MacCallum Cancer Centre, Victoria, Australia
| | - Tomas Kron
- Peter MacCallum Cancer Centre, Victoria, Australia
| |
Collapse
|
7
|
Hernandez V, Saez J, Angerud A, Cayez R, Khamphan C, Nguyen D, Vieillevigne L, Feygelman V. Dosimetric leaf gap and leaf trailing effect in a double-stacked multileaf collimator. Med Phys 2021; 48:3413-3424. [PMID: 33932237 DOI: 10.1002/mp.14914] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Revised: 04/02/2021] [Accepted: 04/23/2021] [Indexed: 01/21/2023] Open
Abstract
PURPOSE To investigate (i) the dosimetric leaf gap (DLG) and the effect of the "trailing distance" between leaves from different multileaf collimator (MLC) layers in Halcyon systems and (ii) the ability of the currently available treatment planning systems (TPSs) to approximate this effect. METHODS DICOM plans with transmission beams and sweeping gap tests were created in Python for measuring the DLG for each MLC layer independently and for both layers combined. In clinical Halcyon plans both MLC layers are interchangeably used and leaves from different layers are offset, thus forming a trailing pattern. To characterize the impact of such configuration, new tests called "trailing sweeping gaps" were designed and created where the leaves from one layer follow the leaves from the other layer at a fixed "trailing distance" t between the tips. Measurements were carried out on five Halcyons SX2 from different institutions and calculations from both the Eclipse and RayStation TPSs were compared with measurements. RESULTS The dose accumulated during a sweeping gap delivery progressively increased with the trailing distance t . We call this "the trailing effect." It is most pronounced for t between 0 and 5 mm, although some changes were obtained up to 20 mm. The dose variation was independent of the gap size. The measured DLG values also increased with t up to 20 mm, again with the steepest variation between 0 and 5 mm. Measured DLG values were negative at t = 0 (the leaves from both layers at the same position) but changed sign for t ≥ 1 mm, in line with the positive DLG sign usually observed with single-layer rounded-end MLCs. The Eclipse TPS does not explicitly model the leaf tip and, as a consequence, could not predict the dose reduction due to the trailing effect. This resulted in dose discrepancies up to +10% and -8% for the 5 mm sweeping gap and up to ±5% for the 10 mm one depending on the distance t . RayStation implements a simple model of the leaf tip that was able to approximate the trailing effect and improved the agreement with measured doses. In particular, with a prototype version of RayStation that assigned a higher transmission at the leaf tip the agreement with measured doses was within ±3% even for the 5 mm gap. The five Halcyon systems behaved very similarly but differences in the DLG around 0.2 mm were found across different treatment units and between MLC layers from the same system. The DLG for the proximal layer was consistently higher than for the distal layer, with differences ranging between 0.10 mm and 0.24 mm. CONCLUSIONS The trailing distance between the leaves from different layers substantially affected the doses delivered by sweeping gaps and the measured DLG values. Stacked MLCs introduce a new level of complexity in TPSs, which ideally need to implement an explicit model of the leaf tip in order to reproduce the trailing effect. Dynamic tests called "trailing sweeping gaps" were designed that are useful for characterizing and commissioning dual-layer MLC systems.
Collapse
Affiliation(s)
- Victor Hernandez
- Department of Medical Physics, Hospital Sant Joan de Reus, IISPV, 43204, Tarragona, Spain
| | - Jordi Saez
- Department of Radiation Oncology, Hospital Clínic de Barcelona, 08036, Barcelona, Spain
| | | | - Romain Cayez
- Department of Medical Physics, Oscar Lambret Center, 59000, Lille, France
| | - Catherine Khamphan
- Medical Physics Department, Institut Sainte-Catherine, 84000, Avignon, France
| | - Daniel Nguyen
- Centre de Radiothérapie de Mâcon, 71000, Mâcon, France
| | - Laure Vieillevigne
- Department of Medical Physics, Institut Claudius Regaud-Institut Universitaire du Cancer de Toulouse, 31059, Toulouse, France.,Centre de Recherche en Cancérologie de Toulouse UMR1037 INSERM, Université Toulouse 3-ERL5294 CNRS, Oncopole, 31037, Toulouse, France
| | - Vladimir Feygelman
- Department of Radiation Oncology, Moffitt Cancer Center, Tampa, 12902, Florida, USA
| |
Collapse
|
8
|
Thaper D, Oinam AS, Kamal R, Singh G, Handa B, Kumar V, Yadav HP. Interplay effect modeling in stereotactic body radiotherapy treatment of liver cancer using volumetric modulated arc therapy. Phys Eng Sci Med 2021; 44:123-34. [PMID: 33543451 DOI: 10.1007/s13246-020-00961-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Accepted: 12/11/2020] [Indexed: 12/15/2022]
Abstract
To model the interplay effect and minimize it by a selection of optimum parameters value using a predictive model for SBRT of liver cancers. Ten cases of liver tumors treated with the VMAT technique were selected retrospectively. The dosimetric error due to the interplay effect was measured with a micro ionization chamber (0.015cm3) in a Quasar phantom simulating the moving tumor. The interplay effect dependent parameter's viz. patient breaths per minute, the amplitude of respiration, fractional dose (FD), plan complexity due to different energies (Relative degree of modulation), degree of modulation due to a different level of dose optimization constraints, and dose rate (DR) were measured. For the predictive model, mathematical equations were modeled in python from 300 combinations of proposed parameters using multivariate regression analysis. It was observed that the dose variation reduced from -8.44% to -5.16% for change in the BPM values from 7 to 31 and similarly for amplitude, the dose variation reduced from -9.44% to -4.93% for change in amplitude value from 16 mm to 2 mm. The DR and FD have a prominent effect with R2 values of 0.990 and 0.880 respectively. The calculated mean square errors of equations excluding amplitude for the predictive model were 0.90 and 0.82 whereas those for equations excluding BPM were 1.31 and 1.41 for 6 MV and 10 MV beams respectively. The values of the parameters can be prospectively optimized by the use of the predictive model according to clinical situations, so dose variation can be minimized.
Collapse
|
9
|
Bouchard H. Reference dosimetry of modulated and dynamic photon beams. Phys Med Biol 2021; 65:24TR05. [PMID: 33438582 DOI: 10.1088/1361-6560/abc3fb] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In the late 1980s, a new technique was proposed that would revolutionize radiotherapy. Now referred to as intensity-modulated radiotherapy, it is at the core of state-of-the-art photon beam delivery techniques, such as helical tomotherapy and volumetric modulated arc therapy. Despite over two decades of clinical application, there are still no established guidelines on the calibration of dynamic modulated photon beams. In 2008, the IAEA-AAPM work group on nonstandard photon beam dosimetry published a formalism to support the development of a new generation of protocols applicable to nonstandard beam reference dosimetry (Alfonso et al 2008 Med. Phys. 35 5179-86). The recent IAEA Code of Practice TRS-483 was published as a result of this initiative and addresses exclusively small static beams. But the plan-class specific reference calibration route proposed by Alfonso et al (2008 Med. Phys. 35 5179-86) is a change of paradigm that is yet to be implemented in radiotherapy clinics. The main goals of this paper are to provide a literature review on the dosimetry of nonstandard photon beams, including dynamic deliveries, and to discuss anticipated benefits and challenges in a future implementation of the IAEA-AAPM formalism on dynamic photon beams.
Collapse
Affiliation(s)
- Hugo Bouchard
- Département de physique, Université de Montréal, Complexe des sciences, 1375 Avenue Thérèse-Lavoie-Roux, Montréal, Québec H2V 0B3, Canada. Centre de recherche du Centre hospitalier de l'Université de Montréal, 900 Rue Saint-Denis, Montréal, Québec H2X 0A9, Canada. Département de radio-oncologie, Centre hospitalier de l'Université de Montréal (CHUM), 1051 Rue Sanguinet, Montréal, Québec H2X 3E4, Canada
| |
Collapse
|
10
|
Ghazal M, Södergren L, Westermark M, Söderström J, Pommer T. Dosimetric and mechanical equivalency of Varian TrueBeam linear accelerators. J Appl Clin Med Phys 2020; 21:43-53. [PMID: 33070456 PMCID: PMC7769408 DOI: 10.1002/acm2.13058] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 09/17/2020] [Accepted: 09/22/2020] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To investigate and improve the level of equivalency of Varian TrueBeam linear accelerators (linacs) in energy-, dosimetric leaf gap- (DLG) and jaw calibration. METHODS Eight linacs with four photon energies: 6 MV, 6 MV FFF, 10 MV FFF, and 15 MV, and three electron energies (on two linacs): 6, 9, and 12 MeV were commisioned and beam-matched. Initially, symmetry of lateral profiles was calibrated for maximum field size. Energy-matching was then performed for photons by adjusting diagonal profiles at maximum field size and depth of maximum dose to coincide with the reference linac, and for electrons by matching the range at percentage depth of ionization of 90%, 80%, and 50%. Calibration of DLG was performed for 6 MV and evaluated among the linacs. The relationship between DLG and the Gap value was investigated. A method using electronic portal imaging device (EPID) was developed and implemented for jaw calibration. RESULTS Symmetry calibration for photons (electrons) was within 1% (0.7%), further improving the vendor's acceptance criteria. Photon and electron energy-matching was within 0.5% and 0.1 mm, respectively. Calibration of DLG was within 0.032 mm among the linacs and utilizing the relationship between DLG and the Gap value resulted in an empirical calibration method which was implemented to simplify DLG adjustment. Using EPID-based method of calibration, evaluation of the jaw-positioning among the linacs for 30 cm × 30 cm field size was within 0.4 mm and in the junction area within 0.2 mm. Dose delivery error of VMAT-plans were at least 99.2% gamma pass rate (1%, 1 mm). CONCLUSIONS High level of equivalency, beyond clinically accepted criteria, of TrueBeam linacs could be achieved which reduced dose delivery systematic errors and increased confidence in interchanging patients among linacs.
Collapse
Affiliation(s)
- Mohammed Ghazal
- Department of Medical Radiation Physics and Nuclear MedicineKarolinska University HospitalStockholmSweden
| | - Lars Södergren
- Department of Medical Radiation Physics and Nuclear MedicineKarolinska University HospitalStockholmSweden
| | - Mathias Westermark
- Department of Medical Radiation Physics and Nuclear MedicineKarolinska University HospitalStockholmSweden
| | - Julia Söderström
- Department of Medical Radiation Physics and Nuclear MedicineKarolinska University HospitalStockholmSweden
| | - Tobias Pommer
- Department of Medical Radiation Physics and Nuclear MedicineKarolinska University HospitalStockholmSweden
- Department of Hematology, Oncology and Radiation PhysicsSkåne University HospitalLundSweden
| |
Collapse
|
11
|
Saez J, Hernandez V, Goossens J, De Kerf G, Verellen D. A novel procedure for determining the optimal MLC configuration parameters in treatment planning systems based on measurements with a Farmer chamber. Phys Med Biol 2020; 65:155006. [PMID: 32330917 DOI: 10.1088/1361-6560/ab8cd5] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Modelling of the multi-leaf collimator (MLC) in treatment planning systems (TPS) is crucial for the dose calculation accuracy of intensity-modulated radiation therapy plans. However, no standardised methodology for their configuration exists to date. In this study we present a method that separates the effect of each dosimetric characteristic of the MLC, offering comprehensive equations for the determination of the configuration parameters used in the TPS model. The main advantage of the method is that it only requires prior knowledge of the nominal leaf width and is based on doses measured with a Farmer chamber, which is a very well established and robust methodology. Another significant advantage is the required time, since measuring the tests takes only about 30 minutes per energy. Firstly, we provide a theoretical general formalism in terms of the primary fluence constructed from the transmission map obtained from an MLC model for synchronous and asynchronous sweeping beams. Secondly, we apply the formalism to the RayStation TPS as a proof of concept and we derive analytical expressions that allow the determination of the configuration parameters (leaf tip width, tongue-and-groove width, x-position offset and MLC transmission) and describe how they intertwine. Finally, we apply the method to Varian's Millennium120 and HD120 MLCs in a TrueBeam linear accelerator for different energies and determine the optimal configuration parameters. The proposed procedure is much faster and streamlined than the typical trial-and-error methods and increases the accuracy of dose calculation in clinical plans. Additionally, the procedure can be useful for standardising the MLC configuration process and it exposes the limitations of the implemented MLC model, providing guidance for further improvement of these models in TPSs.
Collapse
Affiliation(s)
- Jordi Saez
- Department of Radiation Oncology, Hospital Clínic de Barcelona, 08036 Barcelona, Spain. The first two authors contributed equally to this work
| | | | | | | | | |
Collapse
|
12
|
Rose MS, Tirpak L, Van Casteren K, Zack J, Simon T, Schoenfeld A, Simon W. Multi‐institution validation of a new high spatial resolution diode array for SRS and SBRT plan pretreatment quality assurance. Med Phys 2020; 47:3153-3164. [DOI: 10.1002/mp.14153] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 02/20/2020] [Accepted: 03/12/2020] [Indexed: 12/31/2022] Open
Affiliation(s)
- Mark S. Rose
- Sun Nuclear Corporation 3275 Suntree Blvd Melbourne Florida 32940 USA
| | - Lena Tirpak
- Sun Nuclear Corporation 3275 Suntree Blvd Melbourne Florida 32940 USA
| | | | - Jeff Zack
- Sun Nuclear Corporation 3275 Suntree Blvd Melbourne Florida 32940 USA
| | - Tom Simon
- Sun Nuclear Corporation 3275 Suntree Blvd Melbourne Florida 32940 USA
| | | | - William Simon
- Sun Nuclear Corporation 3275 Suntree Blvd Melbourne Florida 32940 USA
| |
Collapse
|
13
|
Jelen U, Dong B, Begg J, Roberts N, Whelan B, Keall P, Liney G. Dosimetric Optimization and Commissioning of a High Field Inline MRI-Linac. Front Oncol 2020; 10:136. [PMID: 32117776 PMCID: PMC7033562 DOI: 10.3389/fonc.2020.00136] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 01/27/2020] [Indexed: 11/17/2022] Open
Abstract
Purpose: Unique characteristics of MRI-linac systems and mutual interactions between their components pose specific challenges for their commissioning and quality assurance. The Australian MRI-linac is a prototype system which explores the inline orientation, with radiation beam parallel to the main magnetic field. The aim of this work was to commission the radiation-related aspects of this system for its application in clinical treatments. Methods: Physical alignment of the radiation beam to the magnetic field was fine-tuned and magnetic shielding of the radiation head was designed to achieve optimal beam characteristics. These steps were guided by investigative measurements of the beam properties. Subsequently, machine performance was benchmarked against the requirements of the IEC60976/77 standards. Finally, the geometric and dosimetric data was acquired, following the AAPM Task Group 106 recommendations, to characterize the beam for modeling in the treatment planning system and with Monte Carlo simulations. The magnetic field effects on the dose deposition and on the detector response have been taken into account and issues specific to the inline design have been highlighted. Results: Alignment of the radiation beam axis and the imaging isocentre within 2 mm tolerance was obtained. The system was commissioned at two source-to-isocentre distances (SIDs): 2.4 and 1.8 m. Reproducibility and proportionality of the dose monitoring system met IEC criteria at the larger SID but slightly exceeded it at the shorter SID. Profile symmetry remained under 103% for the fields up to ~34 × 34 and 21 × 21 cm2 at the larger and shorter SID, respectively. No penumbra asymmetry, characteristic for transverse systems, was observed. The electron focusing effect, which results in high entrance doses on central axis, was quantified and methods to minimize it have been investigated. Conclusion: Methods were developed and employed to investigate and quantify the dosimetric properties of an inline MRI-Linac system. The Australian MRI-linac system has been fine-tuned in terms of beam properties and commissioned, constituting a key step toward the application of inline MRI-linacs for patient treatments.
Collapse
Affiliation(s)
- Urszula Jelen
- Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool, NSW, Australia
| | - Bin Dong
- Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool, NSW, Australia
| | - Jarrad Begg
- Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool, NSW, Australia.,Liverpool Cancer Therapy Centre, Radiation Physics, Liverpool, NSW, Australia.,School of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Natalia Roberts
- Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool, NSW, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Brendan Whelan
- Sydney Medical School, ACRF Image X Institute, University of Sydney, Sydney, NSW, Australia
| | - Paul Keall
- Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool, NSW, Australia.,Sydney Medical School, ACRF Image X Institute, University of Sydney, Sydney, NSW, Australia
| | - Gary Liney
- Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool, NSW, Australia.,Liverpool Cancer Therapy Centre, Radiation Physics, Liverpool, NSW, Australia.,School of Medicine, University of New South Wales, Sydney, NSW, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| |
Collapse
|
14
|
Rajamanickam T, Muthu S, Murugan P, Dinesan C, Mekala C, Senthilnathan K, Arunai Nambi Raj N, Ramesh Babu P. An Assessment of Dosimetric Characteristics of Inline 2.5 Mega Voltage Unflattened Imaging X-Ray Beam. Asian Pac J Cancer Prev 2019; 20:2531-2539. [PMID: 31450929 PMCID: PMC6852810 DOI: 10.31557/apjcp.2019.20.8.2531] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Indexed: 11/25/2022] Open
Abstract
Purpose: The aim of this work is to study the dosimetric parameters of newly introduced 2.5 MV imaging x-ray beam used as inline imaging to do setup verification of the patient undergoing radiation therapy. As this x-ray beam is in megavoltage range but comprises of a lower energy spectrum. It is essential to study the pros and cons of 2.5 MV imaging x-ray beam for clinical use. Methods: The mean energy was calculated using the NIST XCOM table through MAC. Profile analysis was done using RFA to understand the percentage depth dose, degree of unflatteness, symmetry, penumbra and out of field dose. Dose to skin for the 2.5 MV x-ray beam was analysed for field sizes 10x10 cm2, 20x20 cm2, 30x30 cm2. Leakage measurements for treatment head and at the patient plane were done using IEC 819/98 protocol. Finally, the spatial resolution and contrast were analyzed with and without patient scatter medium. Results: The MAC at 15 cm off-axis was found to be lower than that at the CAX. Similarly, there was a decrease in mean energy from 0.47 MV to 0.37 MV at 15 cm off-axis. The reduction of mean energy towards off-axis is lower than the other high energy MV x-ray beams. The tuned absolute dose of 1 cGy/MU is consistent and within < ±1 %. The relative output factors were found to be in correlation with Co-60. The beam quality of 2.5 MV x-ray beam was found to be 0.4771. The profile parameters like the degree of unflatness of the 2.5 x-ray beam were studied at 85 %, 90 %, 95 % lateral distances, and the penumbra at different depth and field sizes are higher than the 6 MV treatment beam. In addition, out of field dose also drastically increases to a maximum of up to 30 % laterally at 5cm at deeper depths. The skin dose increases from 48.51 % to 88.15 % from 6 MV to 2.5 MV x-ray beam for the field size 10x10 cm2. Also, the skin dose increases from 88.15 % to 91.78 % from the field size 10x10 cm2 to 30x30 cm2. Although the measured leakage radiation for 2.5 MV x-ray beam at the patient plane and other than patient planes are with the tolerance limit, an increase in exposure towards gantry side compared to other areas around treatment head and the patient plane may lead to more skin dose to head and chest while imaging pelvis region. The MLC transmission of 2.5 MV x-ray beam such as inter, intra and edge effect are 0.40 %, 0.37 % and 11% respectively. The spatial resolution of 2.0, 1.25 and 0.9 LP/mm was observed for KV, 2.5MV, and 6 MV x-ray beams. The spatial resolution and contrast of 2.5 MV x-ray beam are superior to 6 MV x-ray beam and inferior to KV x-rays. Conclusions: The 2.5 MV x-ray imaging beam is analysed in view of beam characteristics and radiation safety to understand the above-studied concepts while using this imaging beam in a clinical situation. In future, if 2.5MV x-ray beam is used for treatment purpose with increased dose rate, the above-studied notions can be incorporated prior to implementation.
Collapse
Affiliation(s)
- Tamilarasan Rajamanickam
- Department of Radiation Oncology, Sri Shankara Cancer Hospital & Research Centre, Bengaluru, Karnataka, India.,Department of Physics, SAS, Vellore Institute of Technology, Vellore, Tamil Nadu, India.
| | - Sivakumar Muthu
- Department of Radiation Oncology, Sri Shankara Cancer Hospital & Research Centre, Bengaluru, Karnataka, India
| | - Perumal Murugan
- Department of Radiation Oncology, Sri Shankara Cancer Hospital & Research Centre, Bengaluru, Karnataka, India
| | - Chinnaiah Dinesan
- Department of Radiation Oncology, Sri Shankara Cancer Hospital & Research Centre, Bengaluru, Karnataka, India
| | - Chandrasekaran Mekala
- Principal Clinical Scientist and Stereotactic Lead, University Hospital Southampton NHS FT, Tremona Rd, Southampton SO16 6YD, UK
| | | | - Narayanasamy Arunai Nambi Raj
- Centre for Biomaterials, Cellular and Molecular Theranostics, Vellore Institute of Technology, Vellore, Tamil Nadu, India
| | | |
Collapse
|
15
|
Kandlakunta P, Momin S, Sloop A, Zhang T, Khan R. Characterizing a Geant4 Monte Carlo model of a multileaf collimator for a TrueBeam™ linear accelerator. Phys Med 2019; 59:1-12. [PMID: 30928056 DOI: 10.1016/j.ejmp.2019.02.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 02/11/2019] [Accepted: 02/12/2019] [Indexed: 11/26/2022] Open
Abstract
PURPOSE The purpose of this work was to develop and validate a multileaf collimator (MLC) model for a TrueBeam™ linac using Geant4 Monte Carlo (MC) simulation kit. METHODS A Geant4 application was developed to accurately represent TrueBeam™ linac. Pre-computed phase-space file in a plane just above the jaws was used for radiation transport. A Varian 120 leaf Millennium™ MLC was modeled using geometry and material specifications provided by the manufacturer using Geant4 constructs. Leaf characteristics e.g. tongue-groove design, variable thickness, interleaf gap were simulated. The linac model was validated by comparing simulated dose profiles and depth-doses with experimental data using an ionization chamber in water. Dosimetric characteristics of the MLC such as inter- and intra-leaf leakage, penumbra effect, MLC leaf positioning, and dynamic characteristics were also investigated. RESULTS For the depth dose curves, 99% of the calculated data points agree within 1% of the experimental values for the 4 × 4 cm2 and 10 × 10 cm2 and within 2% of the experimental values for 20 × 20, 30 × 30 and 40 × 40 cm2 jaw defined fields. The cross-plane dose profiles show agreement <2% for depths up to 10 cm and to within 4% beyond 10 cm. MLC dosimetric characterization with MC agree well with film measurements. The rounded leaf penumbra remained constant throughout the range of leaf motion. CONCLUSIONS The TrueBeam™ linac equipped with 120-leaf MLC was successfully modeled using Geant4. The accuracy of the model was verified by comparing the simulations with experiments. The model may be utilized for independent dose verification and QA of IMRT.
Collapse
Affiliation(s)
- Praneeth Kandlakunta
- Department of Radiation Oncology, Washington University in St. Louis School of Medicine, St Louis, MO, USA
| | - Shadab Momin
- Department of Radiation Oncology, Washington University in St. Louis School of Medicine, St Louis, MO, USA
| | - Austin Sloop
- Department of Radiation Oncology, Washington University in St. Louis School of Medicine, St Louis, MO, USA
| | - Tiezhi Zhang
- Department of Radiation Oncology, Washington University in St. Louis School of Medicine, St Louis, MO, USA
| | - Rao Khan
- Department of Radiation Oncology, Washington University in St. Louis School of Medicine, St Louis, MO, USA.
| |
Collapse
|
16
|
Lim TY, Dragojević I, Hoffman D, Flores-Martinez E, Kim GY. Characterization of the Halcyon TM multileaf collimator system. J Appl Clin Med Phys 2019; 20:106-114. [PMID: 30889312 PMCID: PMC6448159 DOI: 10.1002/acm2.12568] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 12/20/2018] [Accepted: 02/25/2019] [Indexed: 11/06/2022] Open
Abstract
PURPOSE To characterize the stacked and staggered dual-layer multileaf collimator (MLC) on the HalcyonTM system. METHODS The novel MLC assembly was reviewed and compared to the widely used MillenniumTM 120-leaf MLC system. We investigated the MLC positioning stability over 70 days using Machine Performance Check (MPC) data. We evaluated the leaf transmission, penumbra, leaf end effect, and leaf edge effect. Leaf transmission through distal, proximal, and both MLC layers was measured with a Farmer chamber, by comparing an open and a closed field. Leaf penumbra was measured using film for three different MLC-defined field sizes. The leaf end effect was measured with sweeping gap fields of varying gap sizes defined by the distal MLC. The leaf edge effect was evaluated using the Electronic Portal Imaging Device (EPID) for the different banks, gantry positions, and collimator angles. Point dose measurements for 10 test plans were compared to dose predictions of two dose calculation model versions. RESULTS From MPC data, the largest measured MLC positioning accuracy deviation was within 0.1 mm. The proximal MLC exhibited greater deviations compared to the distal MLC. The distal-and-proximal-combination had reduced inter-leaf and intra-leaf transmission compared to delivery with distal-only. The measured leaf transmission was 0.41% for distal-only, 0.40% for proximal-only, and negligible for distal-and-proximal-combination. The leaf end penumbra was wider compared to the leaf edge penumbra. The leaf end effect was measured to be -0.2 mm. The leaf edge effect showed minimal bank, gantry position, and collimator angle dependence. However, a systematic deviation between measurements and treatment planning system handling of the leaf edge effect was observed. The discrepancy between the measured and predicted dose in the 10 test plans improved with the latest version of the dose calculation algorithm. CONCLUSION The characteristics of the stacked and staggered dual-layer MLC on the HalcyonTM system were presented.
Collapse
Affiliation(s)
- Tze Yee Lim
- Department of Radiation Medicine and Applied Sciences, University of California San Diego, San Diego, CA, USA
| | - Irena Dragojević
- Department of Radiation Medicine and Applied Sciences, University of California San Diego, San Diego, CA, USA
| | - David Hoffman
- Department of Radiation Medicine and Applied Sciences, University of California San Diego, San Diego, CA, USA
| | - Everardo Flores-Martinez
- Department of Radiation Medicine and Applied Sciences, University of California San Diego, San Diego, CA, USA
| | - Gwe-Ya Kim
- Department of Radiation Medicine and Applied Sciences, University of California San Diego, San Diego, CA, USA
| |
Collapse
|
17
|
Shamsi Q, Ahmad Buzdar S, Altaf S, Atiq A, Atiq M, Iqbal K. Total scatter factor for small fields in radiotherapy: a dosimetric comparison. J Radiother Pract 2018; 17:292-296. [DOI: 10.1017/s1460396917000681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractPurposeSmall field dosimetry is complicated and accuracy in the measurement of total scatter factor (TSF) is crucial for dosimetric calculations, in making optimum intensity-modulated radiotherapy plans for treating small target volumes. In this study, we intended to determine the TSF measuring properties of CC01 and CC04 detectors for field sizes ranging from sub-centimetre to the centimetre fields.Material and methodsCC01 and CC04 chamber detectors were used to measure TSF for 6 and 18 MV photon beam delivered from the linear accelerator, through small fields in a water phantom. Small fields were created by collimator jaws and multi-leaf collimators separately, with field sizes ranging from 0·6 to 10 cm2and 0·5 to 20 cm2, respectively.ResultsCC01 measured TSF at all the given field sizes created by jaws and multi-leaf collimators for both 6 and 18 MV beams whereas CC04 could not measure TSF for field sizes <1 cm2due to volume averaging and perturbation effects.ConclusionCC01 was shown to be effective for measurement of TSF in sub-centimetre field sizes. CC01 can be employed to measure other dosimetric quantities in small fields using different energy beams.
Collapse
|
18
|
Thanh Tai D, Oanh LT, Son ND, Loan TTH. Evaluation of jaws-only intensity modulated radiation therapy treatment plans using Octavius 4D system. Polish Journal of Medical Physics and Engineering 2018; 24:75-8. [DOI: 10.2478/pjmpe-2018-0010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Abstract
Introduction: Jaws-Only Intensity modulated radiation therapy (JO-IMRT) is a technique uses the collimator jaws of the linear accelerator (LINAC) to delivery of complex intensity patterns. In previous studies, pretreatment patient specific quality assurance for those JO-IMRT were also performed using ionization chamber, MapCHECK2, and Octavius 4D and good agreements were shown. The aim of this study is to further verify JO-IMRT plans in 2 different cases: one with the gantry angle set equal to beam angle as in the plans and the other with gantry angle set to zero degree.
Materials and Methods: Twenty-five JO-IMRT, previously verified, were executed twice for each plan. The first one used a real gantry angle, and the second one used a 0° gantry angle. Measurements were performed using Octavius 4D 1500.
Results: The results were analyzed using Verisoft software. The results show that the Gamma average was 97.32 ± 2.21% for IMRT with a 0° gantry angle and 94.72 ± 2.67% for IMRT with a true gantry angle.
Conclusion: In both cases, gamma index of more than 90% were found for all of our 25 JO-IMRT treatment plans.
Collapse
|
19
|
Abstract
The aim of this study was to investigate the potential of jaw tracking with the volumetric-modulated arc therapy (VMAT) to reduce the normal tissue dose. Plans of nasopharynx, lung, and prostate cancers (10 plans for each) were used to perform VMAT with and without jaw tracking. The dose reduction was evaluated in terms of organ doses and integral doses. Organ-dose reduction with jaw tracking was statistically significant in the volume receiving a dose of 5 Gy (V5) of bladder, rectum, and lung, the volume receiving a dose of 10 Gy (V10) of bladder, rectum, and lung, and the mean dose of lung (P < 0.05). Integral-dose reduction with jaw tracking was statistically significant in almost all the treatment plans (P < 0.05). For organ-dose reduction, jaw tracking in VMAT plan was effective in reducing V5 and V10. For integral-dose reduction, jaw tracking in VMAT plan is an efficient method for decreasing V5.
Collapse
|
20
|
Ritter TA, Schultz B, Barnes M, Popple R, Perez M, Farrey K, Kim G, Moran JM. Automated EPID-based measurement of MLC leaf offset as a quality control tool. Biomed Phys Eng Express 2018. [DOI: 10.1088/2057-1976/aa9f76] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
21
|
Shende R, Patel G. Validation of Dosimetric Leaf Gap (DLG) prior to its implementation in Treatment Planning System (TPS): TrueBeam™ millennium 120 leaf MLC. Rep Pract Oncol Radiother 2017; 22:485-494. [PMID: 29070960 DOI: 10.1016/j.rpor.2017.09.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 07/14/2017] [Accepted: 09/27/2017] [Indexed: 11/28/2022] Open
Abstract
AIM Objective of present study is to determine optimum value of DLG and its validation prior to being incorporated in TPS for Varian TrueBeam™ millennium 120 leaves MLC. BACKGROUND Partial transmission through the rounded leaf ends of the Multi Leaf Collimator (MLC) causes a conflict between the edges of the light field and radiation field. Parameter account for this partial transmission is called Dosimetric Leaf Gap (DLG). The complex high precession technique, such as Intensity Modulated Radiation Therapy (IMRT), entails the modeling of optimum value of DLG inside Eclipse Treatment Planning System (TPS) for precise dose calculation. MATERIALS AND METHODS Distinct synchronized uniformed extension of sweeping dynamic MLC leaf gap fields created by Varian MLC shaper software were use to determine DLG. DLG measurements performed with both 0.13 cc semi-flex ionization chamber and 2D-Array I-Matrix were used to validate the DLG; similarly, values of DLG from TPS were estimated from predicted dose. Similar mathematical approaches were employed to determine DLG from delivered and TPS predicted dose. DLG determined from delivered dose measured with both ionization chamber (DLGIon) and I-Matrix (DLGI-Matrix) compared with DLG estimate from TPS predicted dose (DLGTPS). Measurements were carried out for all available 6MV, 10MV, 15MV, 6MVFFF and 10MVFFF beam energies. RESULTS Maximum and minimum DLG deviation between measured and TPS calculated DLG was found to be 0.2 mm and 0.1 mm, respectively. Both of the measured DLGs (DLGIon and DLGI-Matrix) were found to be in a very good agreement with estimated DLG from TPS (DLGTPS). CONCLUSIONS Proposed method proved to be helpful in verifying and validating the DLG value prior to its clinical implementation in TPS.
Collapse
Affiliation(s)
- Ravindra Shende
- Department of Radiation Oncology, Capitol Hospital, Jalandhar, India
| | - Ganesh Patel
- Department of Radiation Oncology, AIIMS, Rishikesh, India
| |
Collapse
|
22
|
Molazadeh M, Zeinali A, Robatjazi M, Shirazi A, Geraily G. Dosimetric characteristics of LinaTech DMLC H multi leaf collimator: Monte Carlo simulation and experimental study. J Appl Clin Med Phys 2017; 18:113-124. [PMID: 28300380 PMCID: PMC5689964 DOI: 10.1002/acm2.12055] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 01/08/2017] [Accepted: 01/10/2017] [Indexed: 11/09/2022] Open
Abstract
This study evaluated the basic dosimetric characteristics of a Dynamic Multi Leaf Collimator (DMLC) using a diode detector and film measurements for Intensity Modulated Radiation Therapy Quality Assurance (IMRT QA). The EGSnrc Monte Carlo (MC) simulation system was used for the determination of MLC characteristics. Radiation transmission and abutting leaf leakage relevant to the LinaTech DMLC H were measured using an EDGE detector and EBT3 film. In this study, the BEAMnrc simulation code was used for modeling. The head of Siemens PRIMUS linac (6 MV) with external DMLC H was entered into a BEAMnrc Monte Carlo model using practical dosimetry data. Leaf material density, as well as interleaf and abutting air gaps were determined according to the computed and measured dose profiles. The IMRT QA field was used to evaluate the dose distribution of the simulated DMLC H. According to measurements taken with the EDGE detector and film, the total average measured leakage was 1.60 ± 0.03% and 1.57 ± 0.05%, respectively. For these measurements, abutting leaf transmission was 54.35 ± 1.85% and 53.08 ± 2.05%, respectively. To adapt the simulated leaf dose profiles with measurements, leaf material density, interleaf and abutting air gaps were adjusted to 18 g/cm3, 0.008 cm and 0.108 cm, respectively. Thus, the total average leakage was estimated to be about 1.59 ± 0.02%. The step‐and‐shoot IMRT was implemented and 94% agreement was achieved between the film and MC, using 3%‐3 mm gamma criteria. The results of this study showed that the dosimetric characteristics of DMLC H satisfied international standards.
Collapse
Affiliation(s)
- Mikaeil Molazadeh
- Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Ahad Zeinali
- Department of Medical Physics, Faculty of Medicine, Urmia University of Medical Science, Nazloo Campus, Urmia, Iran
| | - Mostafa Robatjazi
- Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Alireza Shirazi
- Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Ghazale Geraily
- Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| |
Collapse
|
23
|
Jabbari K, Akbari M, Tavakoli MB, Amouheidari A. Dosimetry and evaluating the effect of treatment parameters on the leakage of multi leaf collimators in ONCOR linear accelerators. Adv Biomed Res 2017; 5:193. [PMID: 28217631 PMCID: PMC5221412 DOI: 10.4103/2277-9175.190986] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 09/16/2015] [Indexed: 11/04/2022] Open
Abstract
BACKGROUND One of the standard equipment in medical linear accelerators is multi-leaf collimators (MLCs); which is used as a replacement for lead shielding. MLC's advantages are a reduction of the treatment time, the simplicity of treatment, and better dose distribution. The main disadvantage of MLC is the radiation leakages from the edges and between the leaves. The purpose of this study was to determine the effect of various treatment parameters in the magnitude of MLC leakage in linear accelerators. MATERIALS AND METHODS This project was performed with ONCOR Siemens linear accelerators. The amount of radiation leakage was determined by film dosimetry method. The films were Kodak-extended dose range-2, and the beams were 6 MV and 18 MV photons. In another part of the experiment, the fluctuation of the leakage was measured at various depths and fields. RESULTS The amount of leakage was generally up to 1.5 ± 0.2% for both energies. The results showed that the level of the leakage and the amount of dose fluctuation depends on the field size and depth of measurement. The amount of the leakage fluctuations in all energies was decreased with increasing of field size. The variation of the leakage versus field size was similar to the inverse of scattering collimator factor. CONCLUSIONS The amount of leakage was more for 18 MV compare to 6 MV The percentage of the leakage for both energies is less than the 5% value which is recommended by protocols. The fluctuation of the MLC leakage reduced by increasing the field size and depth.
Collapse
Affiliation(s)
- Keyvan Jabbari
- Department of Medical Physics and Medical Engineering, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Muhaddeseh Akbari
- Department of Medical Physics and Medical Engineering, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Mohamad Bagher Tavakoli
- Department of Medical Physics and Medical Engineering, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
| | | |
Collapse
|
24
|
Grigorov GN, Chow JCL. Leakage-Penumbra effect in intensity modulated radiation therapy step-and-shoot dose delivery. World J Radiol 2016; 8:73-81. [PMID: 26834945 PMCID: PMC4731350 DOI: 10.4329/wjr.v8.i1.73] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 11/05/2015] [Accepted: 12/03/2015] [Indexed: 02/06/2023] Open
Abstract
AIM To study the leakage-penumbra (LP) effect with a proposed correction method for the step-and-shoot intensity modulated radiation therapy (IMRT). METHODS Leakage-penumbra dose profiles from 10 randomly selected prostate IMRT plans were studied. The IMRT plans were delivered by a Varian 21 EX linear accelerator equipped with a 120-leaf multileaf collimator (MLC). For each treatment plan created by the Pinnacle(3) treatment planning system, a 3-dimensional LP dose distribution generated by 5 coplanar photon beams, starting from 0(o) with equal separation of 72(o), was investigated. For each photon beam used in the step-and-shoot IMRT plans, the first beam segment was set to have the largest area in the MLC leaf-sequencing, and was equal to the planning target volume (PTV). The overshoot effect (OSE) and the segment positional errors were measured using a solid water phantom with Kodak (TL and X-OMAT V) radiographic films. Film dosimetric analysis and calibration were carried out using a film scanner (Vidar VXR-16). The LP dose profiles were determined by eliminating the OSE and segment positional errors with specific individual irradiations. RESULTS A non-uniformly distributed leaf LP dose ranging from 3% to 5% of the beam dose was measured in clinical IMRT beams. An overdose at the gap between neighboring segments, represented as dose peaks of up to 10% of the total BP, was measured. The LP effect increased the dose to the PTV and surrounding critical tissues. In addition, the effect depends on the number of beams and segments for each beam. Segment positional error was less than the maximum tolerance of 1 mm under a dose rate of 600 monitor units per minute in the treatment plans. The OSE varying with the dose rate was observed in all photon beams, and the effect increased from 1 to 1.3 Gy per treatment of the rectal intersection. As the dosimetric impacts from the LP effect and OSE may increase the rectal post-radiation effects, a correction of LP was proposed and demonstrated for the central beam profile for one of the planned beams. CONCLUSION We concluded that the measured dosimetric impact of the LP dose inaccuracy from photon beam segment in step-and-shoot IMRT can be corrected.
Collapse
|
25
|
Kumaraswamy LK, Xu Z, Bailey DW, Schmitt JD, Podgorsak MB. Evaluation of fluence-based dose delivery incorporating the spatial variation of dosimetric leaf gap (DLG). J Appl Clin Med Phys 2016; 17:12-21. [PMID: 26894361 PMCID: PMC5690211 DOI: 10.1120/jacmp.v17i1.5883] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Revised: 09/16/2015] [Accepted: 09/11/2015] [Indexed: 11/23/2022] Open
Abstract
The Eclipse treatment planning system uses a single dosimetric leaf gap (DLG) value to retract all multileaf collimator leaf positions during dose calculation to model the rounded leaf ends. This study evaluates the dosimetric impact of the 2D variation of DLG on clinical treatment plans based on their degree of fluence modulation. In-house software was developed to retrospectively apply the 2D variation of DLG to 61 clinically treated VMAT plans, as well as to several test plans. The level of modulation of the VMAT cases were determined by calculating their modulation complexity score (MCS). Dose measurements were done using the MapCHECK device at a depth of 5.0 cm for plans with and without the 2D DLG correction. Measurements were compared against predicted dose planes from the TPS using absolute 3%/3 mm and 2%/2 mm gamma criteria for test plans and for VMAT cases, respectively. The gamma pass rate for the 2 mm, 4 mm, and 6 mm sweep test plans increased by 23.2%, 28.7%, and 26.0%, respectively, when the measurements were corrected with 2D variation of DLG. The clinical anal VMAT cases, which had very high MLC modulation, showed the most improvement. The majority of the improvement occurred for doses created by the 1.0 cm width leaves for both the test plans and the VMAT cases. The gamma pass rates for the highly modulated head and neck (H&N) cases, moderately modulated prostate and esophageal cases, and minimally modulated brain cases improved only slightly when corrected with 2D variation of DLG. This is because these cases did not employ the 1.0 cm width leaves for dose calculation and delivery. These data suggest that, at the very least, the TPS plans with highly modulated fluences created by the 1.0 cm fields require 2D DLG correction. Incorporating the 2D variation of DLG for the highly modulated clinical treatment plans improves their planar dose gamma pass rates, especially for fields employing the outer 1.0 cm width MLC leaves. This is because there are differences in DLG between the true DLG exhibited by the 1.0 cm width outer leaves and the constant DLG value modeled by the TPS for dose calculation.
Collapse
|
26
|
Balasingh STP, Singh IRR, Rafic KM, Babu SES, Ravindran BP. Determination of dosimetric leaf gap using amorphous silicon electronic portal imaging device and its influence on intensity modulated radiotherapy dose delivery. J Med Phys 2015; 40:129-35. [PMID: 26500398 PMCID: PMC4594381 DOI: 10.4103/0971-6203.165072] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
As complex treatment techniques such as intensity modulated radiotherapy (IMRT) entail the modeling of rounded leaf-end transmission in the treatment planning system, it is important to accurately determine the dosimetric leaf gap (DLG) value for a precise calculation of dose. The advancements in the application of the electronic portal imaging device (EPID) in quality assurance (QA) and dosimetry have facilitated the determination of DLG in this study. The DLG measurements were performed using both the ionization chamber (DLGion) and EPID (DLGEPID) for sweeping gap fields of different widths. The DLGion values were found to be 1.133 mm and 1.120 mm for perpendicular and parallel orientations of the 0.125 cm3 ionization chamber, while the corresponding DLGEPID values were 0.843 mm and 0.819 mm, respectively. It was found that the DLG was independent of volume and orientation of the ionization chamber, depth, source to surface distance (SSD), and the rate of dose delivery. Since the patient-specific QA tests showed comparable results between the IMRT plans based on the DLGEPID and DLGion, it is concluded that the EPID can be a suitable alternative in the determination of DLG.
Collapse
Affiliation(s)
| | - I Rabi Raja Singh
- Department of Radiotherapy, Christian Medical College, Vellore, Tamil Nadu, India
| | - K Mohamathu Rafic
- Department of Radiotherapy, Christian Medical College, Vellore, Tamil Nadu, India
| | | | - B Paul Ravindran
- Department of Radiotherapy, Christian Medical College, Vellore, Tamil Nadu, India
| |
Collapse
|
27
|
Kumaraswamy LK, Schmitt JD, Bailey DW, Xu ZZ, Podgorsak MB. Spatial variation of dosimetric leaf gap and its impact on dose delivery. Med Phys 2015; 41:111711. [PMID: 25370625 DOI: 10.1118/1.4897572] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE During dose calculation, the Eclipse treatment planning system (TPS) retracts the multileaf collimator (MLC) leaf positions by half of the dosimetric leaf gap (DLG) value (measured at central axis) for all leaf positions in a dynamic MLC plan to accurately model the rounded leaf ends. The aim of this study is to map the variation of DLG along the travel path of each MLC leaf pair and quantify how this variation impacts delivered dose. METHODS 6 MV DLG values were measured for all MLC leaf pairs in increments of 1.0 cm (from the line intersecting the CAX and perpendicular to MLC motion) to 13.0 cm off axis distance at dmax. The measurements were performed on two Varian linear accelerators, both employing the Millennium 120-leaf MLCs. The measurements were performed at several locations in the beam with both a Sun Nuclear MapCHECK device and a PTW pinpoint ion chamber. RESULTS The measured DLGs for the middle 40 MLC leaf pairs (each 0.5 cm width) at positions along a line through the CAX and perpendicular to MLC leaf travel direction were very similar, varying maximally by only 0.2 mm. The outer 20 MLC leaf pairs (each 1.0 cm width) have much lower DLG values, about 0.3-0.5 mm lower than the central MLC leaf pair, at their respective central line position. Overall, the mean and the maximum variation between the 0.5 cm width leaves and the 1.0 cm width leaf pairs are 0.32 and 0.65 mm, respectively. CONCLUSIONS The spatial variation in DLG is caused by the variation of intraleaf transmission through MLC leaves. Fluences centered on the CAX would not be affected since DLG does not vary; but any fluences residing significantly off axis with narrow sweeping leaves may exhibit significant dose differences. This is due to the fact that there are differences in DLG between the true DLG exhibited by the 1.0 cm width outer leaves and the constant DLG value utilized by the TPS for dose calculation. Since there are large differences in DLG between the 0.5 cm width leaf pairs and 1.0 cm width leaf pairs, there is a need to correct the TPS plans, especially those with high modulation (narrow dynamic MLC gap), with 2D variation of DLG.
Collapse
Affiliation(s)
- Lalith K Kumaraswamy
- Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, New York 14263 and Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, New York 14263
| | - Jonathan D Schmitt
- Department of Radiation Medicine, RadAmerica, LLC-MedStar Health, Baltimore, Maryland 21237
| | - Daniel W Bailey
- Department of Radiation Oncology, Northside Hospital, Atlanta, Georgia 30342
| | - Zheng Zheng Xu
- Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, New York 14263 and Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14260
| | - Matthew B Podgorsak
- Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, New York 14263; Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, New York 14263; and Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14260
| |
Collapse
|
28
|
Abstract
Individual QA for IMRT/VMAT plans is required by protocols. Sometimes plans cannot pass the institute's QA criteria. For the Eclipse treatment planning system (TPS) with rounded leaf‐end multileaf collimator (MLC), one practical way to improve the agreement of planned and delivered doses is to tune the value of dosimetric leaf gap (DLG) in the TPS from the measured DLG. We propose that this step may be necessary due to the complexity of the MLC system, including dosimetry of small fields and the tongue‐and‐groove (T&G) effects, and report our use of test fields to obtain linac‐specific optimal DLGs in TPSs. More than 20 original patient plans were reoptimized with the linac‐specific optimal DLG value. We examined the distribution of gaps and T&G extensions in typical patient plans and the effect of using the optimal DLG on the distribution. The QA pass rate of patient plans using the optimal DLG was investigated. The dose‐volume histograms (DVHs) of targets and organs at risk were checked. We tested three MLC systems (Varian millennium 120 MLC, high‐definition 120 MLC, and Siemens 160 MLC) installed in four Varian linear accelerators (linacs) (TrueBEAM STx, Trilogy, Clinac 2300 iX, and Clinac 21 EX) and 1 Siemens linac (Artiste). With an optimal DLG, the individual QA for all those patient plans passed the institute's criteria (95% in DTA test or gamma test with 3%/3 mm/10%), even though most of these plans had failed to pass QA when using original DLGs optimized from typical patient plans or from the optimization process (automodeler) of Pinnacle TPS. Using either our optimal DLG or one optimized from typical patient plans or from the Pinnacle optimization process yielded similar DVHs. PACS number: 87.55Qr
Collapse
|
29
|
Koca T, Basaran H, Sezen D, Karaca S, Ors Y, Arslan D, Aydin A. Comparison of linear accelerator and helical tomotherapy plans for glioblastoma multiforme patients. Asian Pac J Cancer Prev 2015; 15:7811-6. [PMID: 25292068 DOI: 10.7314/apjcp.2014.15.18.7811] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Despite advances in radiotherapy, overall survival of glioblastoma multiforme (GBM) patients is still poor. Moreover dosimetrical analyses with these newer treatment methods are insufficient. The current study is aimed to compare intensity modulated radiation therapy (IMRT) linear accelerator (linac) and helical tomotherapy (HT) treatment plans for patients with prognostic aggressive brain tumors. MATERIAL AND METHODS A total of 20 GBM patient plans were prospectively evaluated in both linac and HT planning systems. Plans are compared with respect to homogenity index, conformity index and organs at risk (OAR) sparing effects of the treatments. RESULTS Both treatment plans provided good results that can be applied to GBM patients but it was concluded that if the critical organs with relatively lower dose constraints are closer to the target region, HT for radiotherapeutical application could be preferred. CONCLUSION Tomotherapy plans were superior to linear accelerator plans from the aspect of OAR sparing with slightly broader low dose ranges over the healthy tissues. In case a clinic has both of these IMRT systems, employment of HT is recommended based on the observed results and future re-irradiation strategies must be considered.
Collapse
Affiliation(s)
- Timur Koca
- Regional Training and Research Hospital, Department of Radiation Oncology, Erzurum, TurkeyE-mail :
| | | | | | | | | | | | | |
Collapse
|
30
|
Ashokkumar S, Nambi Raj NA, Sinha SN, Yadav G, Thiyagarajan R, Raman K, Mishra MB. Comparison of Head Scatter Factor for 6MV and 10MV flattened (FB) and Unflattened (FFF) Photon Beam using indigenously Designed Columnar Mini Phantom. J Med Phys 2014; 39:184-91. [PMID: 25190997 PMCID: PMC4154186 DOI: 10.4103/0971-6203.139010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 04/23/2014] [Accepted: 04/23/2014] [Indexed: 11/12/2022] Open
Abstract
To measure and compare the head scatter factor for flattened (FB) and unflattened (FFF) of 6MV and 10MV photon beam using indigenously designed mini phantom. A columnar mini phantom was designed as recommended by AAPM Task Group 74 with low and high atomic number materials at 10 cm (mini phantom) and at approximately twice the depth of maximum dose water equivalent thickness (brass build-up cap). Scatter in the accelerator (Sc) values of 6MV-FFF photon beams are lesser than that of the 6MV-FB photon beams (0.66-2.8%; Clinac iX, 2300CD) and (0.47-1.74%; True beam) for field sizes ranging from 10 × 10 cm2 to 40 × 40 cm2. Sc values of 10MV-FFF photon beams are lesser (0.61-2.19%; True beam) than that of the 10MV-FB photons beams for field sizes ranging from 10 × 10 cm2 to 40 × 40 cm2. The SSD had no influence on head scatter for both flattened and unflattened beams and irrespective of head design of the different linear accelerators. The presence of field shaping device influences the Sc values. The collimator exchange effect reveals that the opening of the upper jaw increases Sc irrespective of FB or FFF photon beams and different linear accelerators, and it is less significant in FFF beams. Sc values of 6MV-FB square field were in good agreement with that of AAPM, TG-74 published data for Varian (Clinac iX, 2300CD) accelerator. Our results confirm that the removal of flattening filter decreases in the head scatter factor compared to flattened beam. This could reduce the out-of-field dose in advanced treatment delivery techniques.
Collapse
Affiliation(s)
- Sigamani Ashokkumar
- Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India ; School of Advanced Sciences, Vellore Institute of Technology University, Vellore, Tamil Nadu, India
| | - N Arunai Nambi Raj
- School of Advanced Sciences, Vellore Institute of Technology University, Vellore, Tamil Nadu, India
| | - Sujit Nath Sinha
- Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India
| | - Girigesh Yadav
- Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India
| | - Rajesh Thiyagarajan
- Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India
| | - Kothanda Raman
- Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India
| | - Manindra Bhushan Mishra
- Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India
| |
Collapse
|
31
|
Crowe SB, Kairn T, Kenny J, Knight RT, Hill B, Langton CM, Trapp JV. Treatment plan complexity metrics for predicting IMRT pre-treatment quality assurance results. Australas Phys Eng Sci Med 2014; 37:475-82. [DOI: 10.1007/s13246-014-0274-9] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2014] [Accepted: 04/22/2014] [Indexed: 10/25/2022]
|
32
|
Lárraga-Gutiérrez J, Galván de la Cruz O, García-Garduño O, Ballesteros-Zebadúa P. Comparative analysis of several detectors for the measurement of radiation transmission and leakage from a multileaf collimator. Phys Med 2014; 30:391-5. [DOI: 10.1016/j.ejmp.2013.10.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 10/17/2013] [Accepted: 10/21/2013] [Indexed: 10/26/2022] Open
|
33
|
Arumugam S, Xing A, Jameson M, Holloway L. An algorithm to calculate a collapsed arc dose matrix in volumetric modulated arc therapy. Med Phys 2013; 40:071724. [DOI: 10.1118/1.4810964] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
|
34
|
Matsumoto K, Okumura M, Asai Y, Shimomura K, Tamura M, Nishimura Y. Dosimetric properties and clinical application of an a-Si EPID for dynamic IMRT quality assurance. Radiol Phys Technol 2012. [DOI: 10.1007/s12194-012-0190-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
35
|
Fujimoto S, Ono K, Furukawa K, Kudo T, Akagi Y, Koyama T, Hirokawa Y, Kawai S, Nakashima T. [Influence of high-definition multileaf collimator for three-dimensional conformal radiotherapy and intensity-modulated radiotherapy of prostate cancer]. Nihon Hoshasen Gijutsu Gakkai Zasshi 2012; 68:825-834. [PMID: 22821155 DOI: 10.6009/jjrt.2012_jsrt_68.7.825] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The focus of this work is to evaluate the dosimetric impact of treatment planning for three-dimensional conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT) of prostate cancer using Varian/BrainLAB 120-leaf high-definition multileaf collimator (HD120 MLC) with 2.5 mm leaf width and Varian 120-leaf millennium multileaf collimator (M120 MLC) with 5 mm leaf width. We measured the leaf transmission and dosimetric leaf gap (DLG) of two multileaf collimator (MLC) systems using Farmer ionization chamber. The dosimetric impact of treatment planning for 3DCRT and IMRT of prostate cancer for ten clinical cases using two MLC systems was evaluated quantitatively. 3DCRT was divided to 3DCRT(middle) as fitting at middle of leaf tip and 3DCRT(outside) as fitting at outside of leaf tip. The leaf transmission factor and DLG of HD120 MLC for 6 and 10 MV X-ray decreased by 0.2% and 1 mm, respectively, compared to M120 MLC. The mean conformity index of PTV of treatment planning for prostate 3DCRT(middle), 3DCRT(outside) , and IMRT decreased by 0.9%, 6.6%, and 0.9% and the mean homogeneity index increased 2.3%, 13.0%, and 4.2%, respectively. The mean V20, V40, and V65 decreased by 2.4%, 6.6%, and 4.5% for bladder and 3.3%, 6.1%, and 5.9% for rectum, respectively. The results of this work demonstrated that the dose conformity of PTV improved and the dose of bladder and rectum decreased for 3DCRT and IMRT of prostate cancer using HD120 MLC compared to M120 MLC, because of reduction of leaf width, leaf transmission, and rounded leaf end transmission.
Collapse
|
36
|
Fix MK, Volken W, Frei D, Frauchiger D, Born EJ, Manser P. Monte Carlo implementation, validation, and characterization of a 120 leaf MLC. Med Phys 2011; 38:5311-20. [PMID: 21992349 DOI: 10.1118/1.3626485] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Recently, the new high definition multileaf collimator (HD120 MLC) was commercialized by Varian Medical Systems providing high resolution in the center section of the treatment field. The aim of this work is to investigate the characteristics of the HD120 MLC using Monte Carlo (MC) methods. METHODS Based on the information of the manufacturer, the HD120 MLC was implemented into the already existing Swiss MC Plan (SMCP). The implementation has been configured by adjusting the physical density and the air gap between adjacent leaves in order to match transmission profile measurements for 6 and 15 MV beams of a Novalis TX. These measurements have been performed in water using gafchromic films and an ionization chamber at an SSD of 95 cm and a depth of 5 cm. The implementation was validated by comparing diamond measured and calculated penumbra values (80%-20%) for different field sizes and water depths. Additionally, measured and calculated dose distributions for a head and neck IMRT case using the DELTA(4) phantom have been compared. The validated HD120 MLC implementation has been used for its physical characterization. For this purpose, phase space (PS) files have been generated below the fully closed multileaf collimator (MLC) of a 40 × 22 cm(2) field size for 6 and 15 MV. The PS files have been analyzed in terms of energy spectra, mean energy, fluence, and energy fluence in the direction perpendicular to the MLC leaves and have been compared with the corresponding data using the well established Varian 80 leaf (MLC80) and Millennium M120 (M120 MLC) MLCs. Additionally, the impact of the tongue and groove design of the MLCs on dose has been characterized. RESULTS Calculated transmission values for the HD120 MLC are 1.25% and 1.34% in the central part of the field for the 6 and 15 MV beam, respectively. The corresponding ionization chamber measurements result in a transmission of 1.20% and 1.35%. Good agreement has been found for the comparison between transmission profiles resulting from MC simulations and film measurements. The simulated and measured values for the penumbra agreed within <0.5 mm for all field sizes, depths, and beam energies, and a good agreement has been found between the measured and the calculated dose distributions for the IMRT case. The total energy spectra are almost identical for the three MLCs. However, the mean energy, fluence and energy fluence are significantly different. Due to the different leaf widths of the MLCs, the shape of these distributions is different, each representing its leave structure. Due to the increase in width from the inner to the outer HD120 MLC leaves, the fluence and energy fluence clearly decrease below the outer leaves. The MLC80 and the M120 MLC resulted in an increase of the fluence and energy fluence compared with those resulted for the HD120 MLC. The dose reduction can exceed 20% compared with the dose of the open field due to the tongue and groove design of the HD120 MLC. CONCLUSIONS The HD120 MLC has been successfully implemented into the SMCP. Comparisons between MC calculations and measurements show very good agreement. The SMCP is now able to calculate accurate dose distributions for treatment plans using the HD120 MLC.
Collapse
Affiliation(s)
- Michael K Fix
- Division of Medical Radiation Physics, Inselspital and University of Bern, CH-3010 Bern, Switzerland.
| | | | | | | | | | | |
Collapse
|
37
|
Wu S, Chao T, Tung C, Lin M, Lee C. MLC mediated beam hardening effects in IMRT. RADIAT MEAS 2011; 46:1989-92. [DOI: 10.1016/j.radmeas.2011.05.034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
38
|
Tsiamas P, Seco J, Han Z, Bhagwat M, Maddox J, Kappas C, Theodorou K, Makrigiorgos M, Marcus K, Zygmanski P. A modification of flattening filter free linac for IMRT. Med Phys 2011; 38:2342-52. [PMID: 21776768 DOI: 10.1118/1.3571419] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE This study investigates the benefits of a modified flattening filter free (FFF) linac over the standard (STD) linac equipped with the flattening filter. Energy and angular spread of the electron beam of the FFF linac were modified. Modification of FFF beam parameters is explored to maximize the monitor unit efficiency and to minimize the head scatter in IMRT delivery for large target volumes or targets lying away from the central axis. METHODS The EGSnrc code is used to model FFF and STD linacs and study basic beam properties for both linac types in various beam configurations. Increasing energy of FFF linac results in similar beam attenuation properties and maximized dose rate compared to STD linac. Matching beam attenuation properties allows a more direct exploration of beam flatness of FFF linac in regard to IMRT delivery, especially away from the central axis where the effective dose rate is considerably smaller than the one at the central axis. Flatness of open beam dose profile of FFF linac is improved by increasing the angular spread of the electron beam. The resulting dose rate within the treatment field and outside of the field (peripheral dose) are characterized and compared to the unmodified FFF and STD linacs, RESULTS In order to match beam penetration properties, the energy of FFF is adjusted from 6.5 to 8.0 MeV for small to medium field sizes and from 6.5 to 8.5 MeV for larger ones. Dose rate of FFF vs STD linac increased by a factor of 1.9 (6.5 MeV) and 3.4-4.1 (8.0-8.5 MeV). Adjusting the mean angular spread of the electron beam from 0 degrees to 5 degrees-10 degrees resulted in complete flattening of photon beam for field sizes between 10 x 10 cm2 and 15 x 15 cm2 and partial flattening for field sizes from 15 x 15 cm2 to 30 x 30 cm2. Values of angular spread > or =14 degrees are not recommended as they exceed the opening of the primary collimator, affecting the area at the edges of the field. FFF fields of sizes smaller than 6 x 6 cm2 are already flat and beam flattening is not necessary. Overall, the angular spread of 5 degrees-10 degrees is sufficient and can satisfactorily flatten open beam dose profiles even for larger field sizes. Increasing the electron beam angular spread amounts to a slight decrease of dose rate of FFF linac. However, for angular spread, 5 degrees-10 degrees dose rate factor of FFF vs STD is still about 1.6-2.6, depending on the field size (and the adjusted energy). Similarly, in case of peripheral dose, a moderate increase in dose can be observed for angular spread of 5 degrees-10 degrees and for field sizes 10 x 10 cm2 to 30 x 30 cm2. Lastly, beam flatness of not modified FFF linac can be conveniently described by an analytical function representing a ratio of STD vs FFF doses: 1 + b|r|(n). CONCLUSIONS A modified FFF beamline with increased energy and electron beam angular spread results in satisfactory flattened beam and high dose rate within the field. Peripheral dose remaining at similar (or smaller) level than that of STD linac for the same delivered dose within the treatment field.
Collapse
Affiliation(s)
- P Tsiamas
- Brigham and Women Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
39
|
Abstract
Multileaf collimators (MLCs) have been in clinical use for many years and meanwhile are commonly used to deliver intensity-modulated radiotherapy (IMRT) beams. For this purpose it is important to know their dosimetric properties precisely, one of them being inter- and intraleaf leakage. The Siemens 160 MLC features a single focus design with flat-sided and tilted leaves instead of tongue-and-groove. The leakage performance of the 160 MLC was investigated on a dual energy linear accelerator Siemens ARTISTE with 6 MV and 18 MV photon energies. While the intraleaf leakage amounted to nearly the same dose for 6 and for 18 MV, a much higher interleaf leakage for 6 MV was measured. It could be reduced by simply rotating the collimator, and also by changing the voltage applied to the beam steering coils. The leakage of the 160 MLC is shown to be sensitive to beam alignment. This is of special interest for dual energy accelerators, as the two focal spots of both energies, neither in position nor in shape, do not necessarily always coincide. As a consequence of that, a higher leakage can be expected for one out of two energies for the 160 MLC.
Collapse
Affiliation(s)
- Sebastian Klüter
- Department of Radiation Oncology, University Hospital Heidelberg, Heidelberg, Germany.
| | | | | | | |
Collapse
|
40
|
Nakamura M, Sawada A, Ishihara Y, Takayama K, Mizowaki T, Kaneko S, Yamashita M, Tanabe H, Kokubo M, Hiraoka M. Dosimetric characterization of a multileaf collimator for a new four-dimensional image-guided radiotherapy system with a gimbaled x-ray head, MHI-TM2000a). Med Phys 2010; 37:4684-91. [DOI: 10.1118/1.3480510] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
|
41
|
Smith D, MacDougall N, Monk J, Sibtain A, Powell ME, Plowman PN. First quinquennial review of intensity-modulated radiotherapy at St Bartholomew's Hospital, London. Clin Oncol (R Coll Radiol) 2010; 22:666-74. [PMID: 20674299 DOI: 10.1016/j.clon.2010.06.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Revised: 06/17/2010] [Accepted: 06/28/2010] [Indexed: 10/19/2022]
Abstract
Intensity-modulated radiotherapy (IMRT) is a relatively new technique of delivering external beam radiotherapy that is becoming increasingly available in the UK. This paper summarises the introduction and initial clinical work in IMRT over the period 2004-2009. Physics aspects of commissioning are described, including the development of a robust method of quality control using a sweeping gap test. Details of the organisational changes necessary to introduce IMRT are given. The clinical selection and practice in head and neck sites are described, together with promising early results on the maintenance of salivary flow after IMRT. A summary of research into optimal planning for pelvic cancer follows. The controversial areas of breast and paediatric IMRT are discussed with recommendations on practice. The potential for concomitant boost therapy is exemplified in the treatment of brain metastatic disease.
Collapse
Affiliation(s)
- D Smith
- Department of Radiotherapy, St Bartholomew's Hospital, London, UK
| | | | | | | | | | | |
Collapse
|
42
|
Zhu TC, Ahnesjö A, Lam KL, Li XA, Ma CMC, Palta JR, Sharpe MB, Thomadsen B, Tailor RC. Report of AAPM Therapy Physics Committee Task Group 74: In-air output ratio, Sc, for megavoltage photon beams. Med Phys 2009; 36:5261-91. [PMID: 19994536 DOI: 10.1118/1.3227367] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- Timothy C Zhu
- University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
43
|
Wang S, Gardner JK, Gordon JJ, Li W, Clews L, Greer PB, Siebers JV. Monte Carlo-based adaptive EPID dose kernel accounting for different field size responses of imagers. Med Phys 2009; 36:3582-95. [PMID: 19746793 DOI: 10.1118/1.3158732] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The aim of this study is to present an efficient method to generate imager-specific Monte Carlo (MC)-based dose kernels for amorphous silicon-based electronic portal image device dose prediction and determine the effective backscattering thicknesses for such imagers. EPID field size-dependent responses were measured for five matched Varian accelerators from three institutions with 6 MV beams at the source to detector distance (SDD) of 105 cm. For two imagers, measurements were made with and without the imager mounted on the robotic supporting arm. Monoenergetic energy deposition kernels with 0-2.5 cm of water backscattering thicknesses were simultaneously computed by MC to a high precision. For each imager, the backscattering thickness required to match measured field size responses was determined. The monoenergetic kernel method was validated by comparing measured and predicted field size responses at 150 cm SDD, 10 x 10 cm2 multileaf collimator (MLC) sliding window fields created with 5, 10, 20, and 50 mm gaps, and a head-and-neck (H&N) intensity modulated radiation therapy (IMRT) patient field. Field size responses for the five different imagers deviated by up to 1.3%. When imagers were removed from the robotic arms, response deviations were reduced to 0.2%. All imager field size responses were captured by using between 1.0 and 1.6 cm backscatter. The predicted field size responses by the imager-specific kernels matched measurements for all involved imagers with the maximal deviation of 0.34%. The maximal deviation between the predicted and measured field size responses at 150 cm SDD is 0.39%. The maximal deviation between the predicted and measured MLC sliding window fields is 0.39%. For the patient field, gamma analysis yielded that 99.0% of the pixels have gamma < 1 by the 2%, 2 mm criteria with a 3% dose threshold. Tunable imager-specific kernels can be generated rapidly and accurately in a single MC simulation. The resultant kernels are imager position independent and are able to predict fields with varied incident energy spectra and a H&N IMRT patient field. The proposed adaptive EPID dose kernel method provides the necessary infrastructure to build reliable and accurate portal dosimetry systems.
Collapse
Affiliation(s)
- Song Wang
- Department of Radiation Oncology, Medical College of Virginia Hospitals, Virginia Commonwealth University, Richmond, Virginia 23298, USA.
| | | | | | | | | | | | | |
Collapse
|
44
|
|
45
|
Abstract
New technical developments constantly aim at improving the outcome of radiation therapy. With the use of a computer-controlled multileaf collimator (MLC), the quality of the treatment and the efficiency in patient throughput is significantly increased. New MLC designs aim to further enhance the advantages. In this article, we present the first detailed experimental investigation of the new 160 MLC, Siemens Medical Solutions. The assessment included the experimental investigation of typical MLC characteristics such as leakage, tongue-and-groove effect, penumbra, leaf speed, and leaf positioning accuracy with a 6 MV treatment beam. The leakage is remarkably low with an average of 0.37% due to a new design principle of slightly tilted leaves instead of the common tongue-and-groove design. But due to the tilt, the triangular tongue-and-groove effect occurs. Its magnitude of approximately 19% is similar to the dose defect measured for MLCs with the common tongue-and-groove design. The average longitudinal penumbra measured at depth d(max) = 15 mm with standard 100 x 100 mm2 fields is 4.1 +/- 0.5 mm for the central range and increases to 4.9 +/- 1.3 mm for the entire field range of 400 x 400 mm2. The increase is partly due to the single-focusing design and the large distance between the MLC and the isocenter enabling a large patient clearance. Regarding the leaf speed, different velocity tests were performed. The positions of the moving leaves were continuously recorded with the kilovoltage-imaging panel. The maximum leaf velocities measured were 42.9 +/- 0.6 mm/s. In addition, several typical intensity-modulated radiation therapy treatments were performed and the delivery times compared to the Siemens OPTIFOCUS MLC. An average decrease of 11% in delivery time was observed. The experimental results presented in this article indicate that the dosimetric characteristics of the 160 MLC are capable of improving the quality of dose delivery with respect to precision and dose conformity.
Collapse
Affiliation(s)
- Martin B Tacke
- Department of Medical Physics in Radiation Oncology, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
| | | | | | | |
Collapse
|
46
|
Sawant A, Venkat R, Srivastava V, Carlson D, Povzner S, Cattell H, Keall P. Management of three-dimensional intrafraction motion through real-time DMLC tracking. Med Phys 2008; 35:2050-61. [PMID: 18561681 PMCID: PMC2809733 DOI: 10.1118/1.2905355] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2007] [Revised: 02/18/2008] [Accepted: 03/15/2008] [Indexed: 12/25/2022] Open
Abstract
Tumor tracking using a dynamic multileaf collimator (DMLC) represents a promising approach for intrafraction motion management in thoracic and abdominal cancer radiotherapy. In this work, we develop, empirically demonstrate, and characterize a novel 3D tracking algorithm for real-time, conformal, intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT)-based radiation delivery to targets moving in three dimensions. The algorithm obtains real-time information of target location from an independent position monitoring system and dynamically calculates MLC leaf positions to account for changes in target position. Initial studies were performed to evaluate the geometric accuracy of DMLC tracking of 3D target motion. In addition, dosimetric studies were performed on a clinical linac to evaluate the impact of real-time DMLC tracking for conformal, step-and-shoot (S-IMRT), dynamic (D-IMRT), and VMAT deliveries to a moving target. The efficiency of conformal and IMRT delivery in the presence of tracking was determined. Results show that submillimeter geometric accuracy in all three dimensions is achievable with DMLC tracking. Significant dosimetric improvements were observed in the presence of tracking for conformal and IMRT deliveries to moving targets. A gamma index evaluation with a 3%-3 mm criterion showed that deliveries without DMLC tracking exhibit between 1.7 (S-IMRT) and 4.8 (D-IMRT) times more dose points that fail the evaluation compared to corresponding deliveries with tracking. The efficiency of IMRT delivery, as measured in the lab, was observed to be significantly lower in case of tracking target motion perpendicular to MLC leaf travel compared to motion parallel to leaf travel. Nevertheless, these early results indicate that accurate, real-time DMLC tracking of 3D tumor motion is feasible and can potentially result in significant geometric and dosimetric advantages leading to more effective management of intrafraction motion.
Collapse
Affiliation(s)
- Amit Sawant
- Department of Radiation Oncology, Stanford University, Stanford, California 94305, USA.
| | | | | | | | | | | | | |
Collapse
|
47
|
Losasso T. IMRT Delivery Performance With a Varian Multileaf Collimator. Int J Radiat Oncol Biol Phys 2008; 71:S85-8. [DOI: 10.1016/j.ijrobp.2007.06.082] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2007] [Revised: 06/29/2007] [Accepted: 06/30/2007] [Indexed: 11/23/2022]
|
48
|
Sterpin E, Salvat F, Cravens R, Ruchala K, Olivera GH, Vynckier S. Monte Carlo simulation of helical tomotherapy with PENELOPE. Phys Med Biol 2008; 53:2161-80. [DOI: 10.1088/0031-9155/53/8/011] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
|
49
|
|
50
|
|