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Brekner MC, Imhoff D, Rödel C, Filmann N, Licher J, Ramm U, Köhn J. Stereotactic body radiotherapy with volumetric intensity-modulated arc therapy and flattening filter-free beams: dosimetric considerations. Strahlenther Onkol 2024; 200:346-357. [PMID: 38092967 DOI: 10.1007/s00066-023-02181-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 11/01/2023] [Indexed: 03/27/2024]
Abstract
PURPOSE The present study comparatively evaluates the impact of energy-matched flattening filter-free (FFF) photon beams with different energy levels on the physical-dosimetric quality of lung and liver stereotactic body radiotherapy (SBRT) treatment plans. METHODS For this purpose, 54 different lung and liver lesions from 44 patients who had already received SBRT combined with volumetric modulated arc therapy (VMAT) were included in this retrospective planning study. Planning computed tomography scans already available were used for the renewed planning with 6 MV, 6 MV-FFF, 10 MV, and 10 MV-FFF under constant planning objectives. The treatment delivery data, dosimetric distributions, and dose-volume histograms as well as parameters such as the conformity index and gradient indices were the basis for the evaluation and comparison of treatment plans. RESULTS A significant reduction of beam-on time (BOT) was achieved due to the high dose rates of FFF beams. In addition, we showed that for FFF beams compared to flattened beams of the same energy level, smaller planning target volumes (PTV) require fewer monitor units (MU) than larger PTVs. An equal to slightly superior target volume coverage and sparing of healthy tissue as well as organs at risk in both lung and liver lesions were found. Significant differences were seen mainly in the medium to lower dose range. CONCLUSION We found that FFF beams together with VMAT represent an excellent combination for SBRT of lung or liver lesions with shortest BOT for 10 MV-FFF but significant dose savings for 6 MV-FFF in lung lesions.
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Affiliation(s)
- Mark Christoph Brekner
- Department of Radiation Oncology, University Hospital, Johann Wolfgang Goethe University Frankfurt, Theodor Stern Kai 7, 60590, Frankfurt, Germany.
| | - Detlef Imhoff
- Department of Radiation Oncology, University Hospital, Johann Wolfgang Goethe University Frankfurt, Theodor Stern Kai 7, 60590, Frankfurt, Germany
| | - Claus Rödel
- Department of Radiation Oncology, University Hospital, Johann Wolfgang Goethe University Frankfurt, Theodor Stern Kai 7, 60590, Frankfurt, Germany
| | - Natalie Filmann
- Institute for Biostatistics and Mathematical Modeling, University Hospital, Goethe University, 60590, Frankfurt, Germany
| | - Jörg Licher
- Department of Radiation Oncology, University Hospital, Johann Wolfgang Goethe University Frankfurt, Theodor Stern Kai 7, 60590, Frankfurt, Germany
| | - Ulla Ramm
- Department of Radiation Oncology, University Hospital, Johann Wolfgang Goethe University Frankfurt, Theodor Stern Kai 7, 60590, Frankfurt, Germany
| | - Janett Köhn
- Department of Radiation Oncology, University Hospital, Johann Wolfgang Goethe University Frankfurt, Theodor Stern Kai 7, 60590, Frankfurt, Germany
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Jia SB, Shamsabadi R. Secondary cancer risk assessments following the proton therapy of lung cancer as the functions of field characteristics and patient age. Int J Radiat Biol 2024; 100:183-189. [PMID: 37747407 DOI: 10.1080/09553002.2023.2263546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 09/19/2023] [Indexed: 09/26/2023]
Abstract
INTRODUCTION Radiation-induced secondary cancers relevant to proton therapy are still a main concern among cancer survivors. This study aims to determine the effects of age at exposure and treatment field size on radiation-induced secondary tumors following the proton therapy of lung cancer within out of field organs through the Monte Carlo (MC) simulation approach. MATERIAL AND METHODS A full MC model of ICRP-110 male phantom was simulated to calculate the absorbed dose corresponding to secondary radiations within distant organs from the tumor volume. Then, the risks of secondary malignancies were estimated by employing the recommended risk model by the Committee of Biological Effects of Ionizing Radiation (BEIR) for different treatment field sizes and various patient ages at exposure. RESULTS The results revealed that by increasing the patient age from 25 to 45 years, lifetime attributable risk (LAR) values were decreased. Maximum and minimum mortality rates were obtained for the liver and thyroid at the fixed age of 25 years, respectively. Calculated risk values for most near organs to the tumor were higher than those for distant organs. Changing the aperture size from 5 × 5 cm2 to 8 × 10 cm2 resulted in LAR increments with maximum variations of 12.5% for the stomach and a rough variation of 1.12 times in LAR for all exposure ages. CONCLUSION Our work on whole-body phantom addresses the impact of age at exposure and aperture size on LAR during the proton therapy of lung cancer. To minimize secondary cancer risks relevant to proton therapy of lung cancer, extra attention should be considered.
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Affiliation(s)
| | - Reza Shamsabadi
- Physics Department, Hakim Sabzevari University, Sabzevar, Iran
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3
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Aras S, Tanzer İO, Can Ü, Demir H, Sümer E, Baydili KN, Orak R. Radioprotective effects of melatonin against varying dose rates on radiotherapy-induced salivary gland damage scintigraphy findings. Radiat Phys Chem Oxf Engl 1993 2022. [DOI: 10.1016/j.radphyschem.2021.109953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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4
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Potter NJ, Yan G, Liu H, Alahmad H, Kahler DL, Liu C, Li JG, Lu B. Beam flatness modulation for a flattening filter free photon beam utilizing a novel direct leaf trajectory optimization model. J Appl Clin Med Phys 2020; 21:142-152. [PMID: 32176453 PMCID: PMC7075388 DOI: 10.1002/acm2.12837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 12/02/2019] [Accepted: 01/26/2019] [Indexed: 11/30/2022] Open
Abstract
Flattening filter free (FFF) linear accelerators produce a fluence distribution that is forward peaked. Various dosimetric benefits, such as increased dose rate, reduced leakage and out of field dose has led to the growth of FFF technology in the clinic. The literature has suggested the idea of vendors offering dedicated FFF units where the flattening filter (FF) is removed completely and manipulating the beam to deliver conventional flat radiotherapy treatments. This work aims to develop an effective way to deliver modulated flat beam treatments, rather than utilizing a physical FF. This novel optimization model is an extension of the direct leaf trajectory optimization (DLTO) previously developed for volumetric modulated radiation therapy (VMAT) and is capable of accounting for all machine and multileaf collimator (MLC) dynamic delivery constraints, using a combination of linear constraints and a convex objective function. Furthermore, the tongue and groove (T&G) effect was also incorporated directly into our model without introducing nonlinearity to the constraints, nor nonconvexity to the objective function. The overall beam flatness, machine deliverability, and treatment time efficiency were assessed. Regular square fields, including field sizes of 10 × 10 cm2 to 40 × 40 cm2 were analyzed, as well as three clinical fields, and three arbitrary contours with "concave" features. Quantitative flatness was measured for all modulated FFF fields, and the results were comparable or better than their open FF counterparts, with the majority having a quantitative flatness of less than 3.0%. The modulated FFF beams, due to the included efficiency constraint, were able to achieve acceptable delivery time compared to their open FF counterpart. The results indicated that the dose uniformity and flatness for the modulated FFF beams optimized with the DLTO model can successfully match the uniformity and flatness of their conventional FF counterparts, and may even provide further benefit by taking advantage of the unique FFF beam characteristics.
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Affiliation(s)
- Nicholas J Potter
- Department of Radiation Oncology, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Guanghua Yan
- Department of Radiation Oncology, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Hongcheng Liu
- Department of Industrial & Systems Engineering, College of Engineering, University of Florida, Gainesville, FL, USA
| | - Haitham Alahmad
- Department of Radiation Oncology, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Darren L Kahler
- Department of Radiation Oncology, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Chihray Liu
- Department of Radiation Oncology, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Jonathan G Li
- Department of Radiation Oncology, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Bo Lu
- Department of Radiation Oncology, College of Medicine, University of Florida, Gainesville, FL, USA
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A study of dose verification and comparison for complex irradiation field with high dose rate radiation by using a 3D N-isopropylacrylamide gel dosimeter. J Radioanal Nucl Chem 2019. [DOI: 10.1007/s10967-019-06828-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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6
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Ma C, Chen M, Long T, Parsons D, Gu X, Jiang S, Hou Q, Lu W. Flattening filter free in intensity-modulated radiotherapy (IMRT) - Theoretical modeling with delivery efficiency analysis. Med Phys 2018; 46:34-44. [DOI: 10.1002/mp.13267] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2018] [Revised: 10/09/2018] [Accepted: 10/17/2018] [Indexed: 12/15/2022] Open
Affiliation(s)
- Chaoqiong Ma
- Key Lab for Radiation Physics and Technology of Education Ministry of China; Institute of Nuclear Science and Technology; Sichuan University; Chengdu SC 610064 China
- Department of Radiation Oncology; University of Texas Southwestern Medical Center; Dallas TX 75390 USA
| | - Mingli Chen
- Department of Radiation Oncology; University of Texas Southwestern Medical Center; Dallas TX 75390 USA
| | - Troy Long
- Department of Radiation Oncology; University of Texas Southwestern Medical Center; Dallas TX 75390 USA
| | - David Parsons
- Department of Radiation Oncology; University of Texas Southwestern Medical Center; Dallas TX 75390 USA
| | - Xuejun Gu
- Department of Radiation Oncology; University of Texas Southwestern Medical Center; Dallas TX 75390 USA
| | - Steve Jiang
- Department of Radiation Oncology; University of Texas Southwestern Medical Center; Dallas TX 75390 USA
| | - Qing Hou
- Key Lab for Radiation Physics and Technology of Education Ministry of China; Institute of Nuclear Science and Technology; Sichuan University; Chengdu SC 610064 China
| | - Weiguo Lu
- Department of Radiation Oncology; University of Texas Southwestern Medical Center; Dallas TX 75390 USA
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Al Mashud MA, Tariquzzaman M, Jahangir Alam M, Zakaria GA. Photon beam commissioning of an Elekta Synergy linear accelerator. POLISH JOURNAL OF MEDICAL PHYSICS AND ENGINEERING 2017. [DOI: 10.1515/pjmpe-2017-0019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Abstract
The aim of this study is to present the results of commissioning of Elekta Synergy linear accelerator (linac). The acceptance test and commissioning were performed for three photon beams energies 4 MV, 6 MV and 15 MV and for the multileaf collimator (MLC). The percent depth doses (PDDs), in-plane and cross-plane beam profiles, head scatter factors (Sc), relative photon output factors (Scp), universal wedge transmission factor and MLC transmission factors were measured. The size of gantry, collimator, and couch isocenter were also measured.
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Affiliation(s)
- Md Abdullah Al Mashud
- Dept. of Applied Physics, Electronics & Communication Engineering , Islamic University , Kushtia- 7003 , Bangladesh
| | - M Tariquzzaman
- Dept. of Information and Communication Engineering , Islamic University , Kushtia- 7003 , Bangladesh
| | - M Jahangir Alam
- Medical Physics Division, Dept. of Radiation Oncology , Ahsania Mission Cancer & General Hospital , Uttara, Dhaka
| | - GA Zakaria
- Dept. of Medical Radiation Physics , Gummersbach Hospital , Academic Teaching Hospital University of Cologne , Gummersbach , Germany
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In vitro investigation of the dose-rate effect on the biological effectiveness of megavoltage X-ray radiation doses. Appl Radiat Isot 2017; 128:114-119. [DOI: 10.1016/j.apradiso.2017.07.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 05/24/2017] [Accepted: 07/05/2017] [Indexed: 12/18/2022]
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A Monte Carlo Study of the Photon Spectrum due to the Different Materials Used in the Construction of Flattening Filters of LINAC. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2017; 2017:3621631. [PMID: 28769998 PMCID: PMC5523462 DOI: 10.1155/2017/3621631] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 05/14/2017] [Indexed: 11/18/2022]
Abstract
Different types the spectrum of photons were studied; they were emitted from the flattening filter of a LINAC Varian 2100 C/D that operates at 15 MV. The simplified geometry of the LINAC head was calculated using the MCNPX code based on the studies of the materials of the flattening filter, namely, SST, W, Pb, Fe, Ta, Al, and Cu. These materials were replaced in the flattening filter to calculate the photon spectra at the output of this device to obtain the spectrum that makes an impact with the patient. The different spectra obtained were analyzed and compared to the emission from the original spectra configuration of the LINAC, which uses material W. In the study, different combinations of materials were considered in order to establish differences between the use of different materials and the original material, with the objective of establishing advantages and disadvantages from a clinical standpoint.
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Mishra B, Selvam TP, Sharma PKD. Structural Shielding Design of a 6 MV Flattening Filter Free Linear Accelerator: Indian Scenario. J Med Phys 2017; 42:18-24. [PMID: 28405104 PMCID: PMC5370334 DOI: 10.4103/jmp.jmp_99_16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Detailed structural shielding of primary and secondary barriers for a 6 MV medical linear accelerator (LINAC) operated with flattening filter (FF) and flattening filter free (FFF) modes are calculated. The calculations have been carried out by two methods, one using the approach given in National Council on Radiation Protection (NCRP) Report No. 151 and the other based on the monitor units (MUs) delivered in clinical practice. Radiation survey of the installations was also carried out. NCRP approach suggests that the primary and secondary barrier thicknesses are higher by 24% and 26%. respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes with an assumption that only 20% of the workload is shared in FFF mode. Primary and secondary barrier thicknesses calculated from MUs delivered on clinical practice method also show the same trend and are higher by 20% and 19%, respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes. Overall, the barrier thickness for a LINAC operated in FF mode is higher about 20% to that of a LINAC operated in both FF and FFF modes.
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Affiliation(s)
- Bibekananda Mishra
- Radiological Safety Division, Atomic Energy Regulatory Board, Niyamak Bhavan, Mumbai, Maharashtra, India
| | - T Palani Selvam
- Radiological Physics and Advisory Division, Health Safety and Environmental Group, Bhabha Atomic Research Centre, Mumbai, Maharashtra, India
| | - P K Dash Sharma
- Radiological Safety Division, Atomic Energy Regulatory Board, Niyamak Bhavan, Mumbai, Maharashtra, India
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11
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Budgell G, Brown K, Cashmore J, Duane S, Frame J, Hardy M, Paynter D, Thomas R. IPEM topical report 1: guidance on implementing flattening filter free (FFF) radiotherapy. Phys Med Biol 2016; 61:8360-8394. [DOI: 10.1088/0031-9155/61/23/8360] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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12
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Kumar L, Yadav G, Samuvel KR, Bhushan M, Kumar P, Suhail M, Pal M. Dosimetric influence of filtered and flattening filter free photon beam on rapid arc (RA) radiotherapy planning in case of cervix carcinoma. Rep Pract Oncol Radiother 2016; 22:10-18. [PMID: 27790073 DOI: 10.1016/j.rpor.2016.09.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2015] [Revised: 04/09/2016] [Accepted: 09/15/2016] [Indexed: 11/17/2022] Open
Abstract
AIM To investigate the dosimetric influence of filtered and flattening filter free (FFF) photon beam of 6 and 10 MV energies on cervix RA radiotherapy planning and to find possibilities to develop the clinically acceptable RA plans with FFFB photon beam and explore their potential benefits to cervix cancer patients. BACKGROUND FFF photon beams enhances the treatment delivery by increased dose rate which results in shorter treatment time, this shorter treatment time reduces intrafraction motion and enhance comfort to the patients. MATERIALS AND METHODS RA plans were generated for filtered and flattening filter free photon beams of 6 and 10 MV energies using same dose-volumes constraints. RA plans were generated to deliver a dose of 50.4 Gy in 28 fractions, for a cohort of eleven patients reported with cervix carcinoma. RA plans were evaluated in terms of PTV coverage, dose to OAR's, CI, HI, total no. of monitor units (MUs) and NTID and low dose volume of normal tissues. RESULTS Clinically acceptable and similar plans were generated for filtered and flattening filter free photon beams. FFFB delivered slightly higher mean target dose (52.28 Gy vs. 52.0 Gy, p = 0.000 for 6 MV and 52.42 Gy vs. 52.0 Gy, p = 0.000 for 10 MV) less homogeneous (1.062 vs. 1.052, p = 0.000 for 6 MV and 1.066 vs. 1.051, p = 0.000 for 10 MV) and less conformal (1.007 vs. 1.004, p = 0.104 for 6 MV and 1.012 vs. 1.003, p = 0.010 for 10 MV) RA plans compared to FB. FFFB delivered more doses to the bladder and rectum, also required more numbers of MUs in comparison to FB. CONCLUSIONS This study concludes that FB is more beneficial for cervix RA planning in comparison to FFFB, as FB generates more conformal and homogenous rapid arc plans and offers better OAR's sparing.
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Affiliation(s)
- Lalit Kumar
- Medical Physics Division & Radiotherapy Department, Rajiv Gandhi Cancer Institute & Research Centre, Rohini, New Delhi 110085, India
| | - Girigesh Yadav
- Medical Physics Division & Radiotherapy Department, Rajiv Gandhi Cancer Institute & Research Centre, Rohini, New Delhi 110085, India
| | - Kothanda Raman Samuvel
- Medical Physics Division & Radiotherapy Department, Rajiv Gandhi Cancer Institute & Research Centre, Rohini, New Delhi 110085, India
| | - Manindra Bhushan
- Medical Physics Division & Radiotherapy Department, Rajiv Gandhi Cancer Institute & Research Centre, Rohini, New Delhi 110085, India
| | - Pawan Kumar
- Medical Physics Division & Radiotherapy Department, Rajiv Gandhi Cancer Institute & Research Centre, Rohini, New Delhi 110085, India
| | - Mahammood Suhail
- Medical Physics Division & Radiotherapy Department, Rajiv Gandhi Cancer Institute & Research Centre, Rohini, New Delhi 110085, India
| | - Manoj Pal
- Medical Physics Division & Radiotherapy Department, Rajiv Gandhi Cancer Institute & Research Centre, Rohini, New Delhi 110085, India
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Valdenaire S, Mailleux H, Fau P. Modeling of flattening filter free photon beams with analytical and Monte Carlo TPS. Biomed Phys Eng Express 2016. [DOI: 10.1088/2057-1976/2/3/035010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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14
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Saenz DL, Narayanasamy G, Cruz W, Papanikolaou N, Stathakis S. Pinnacle3 modeling and end-to-end dosimetric testing of a Versa HD linear accelerator with the Agility head and flattening filter-free modes. J Appl Clin Med Phys 2016; 17:192-206. [PMID: 26894352 PMCID: PMC5690210 DOI: 10.1120/jacmp.v17i1.5808] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Revised: 08/27/2015] [Accepted: 08/26/2015] [Indexed: 11/23/2022] Open
Abstract
The Elekta Versa HD incorporates a variety of upgrades to the line of Elekta linear accelerators, primarily including the Agility head and flattening filter‐free (FFF) photon beam delivery. The completely distinct dosimetric output of the head from its predecessors, combined with the FFF beams, requires a new investigation of modeling in treatment planning systems. A model was created in Pinnacle3 v9.8 with the commissioned beam data. A phantom consisting of several plastic water and Styrofoam slabs was scanned and imported into Pinnacle3, where beams of different field sizes, source‐to‐surface distances (SSDs), wedges, and gantry angles were devised. Beams included all of the available photon energies (6, 10, 18, 6 FFF, and 10 FFF MV), as well as the four electron energies commissioned for clinical use (6, 9, 12, and 15 MeV). The plans were verified at calculation points by measurement with a calibrated ionization chamber. Homogeneous and heterogeneous point‐dose measurements agreed within 2% relative to maximum dose for all photon and electron beams. AP photon open field measurements along the central axis at 100 cm SSD passed within 1%. In addition, IMRT testing was also performed with three standard plans (step and shoot IMRT, as well as a small‐ and large‐field VMAT plan). The IMRT plans were delivered on the Delta4 IMRT QA phantom, for which a gamma passing rate was >99.5% for all plans with a 3% dose deviation, 3 mm distance‐to‐agreement, and 10% dose threshold. The IMRT QA results for the first 23 patients yielded gamma passing rates of 97.4%±2.3%. Such testing ensures confidence in the ability of Pinnacle3 to model photon and electron beams with the Agility head. PACS numbers: 87.55.D, 87.56.bd
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Affiliation(s)
- Daniel L Saenz
- University of Texas Health Science Center - San Antonio.
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15
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Narayanasamy G, Saenz D, Cruz W, Ha CS, Papanikolaou N, Stathakis S. Commissioning an Elekta Versa HD linear accelerator. J Appl Clin Med Phys 2016; 17:179-191. [PMID: 26894351 PMCID: PMC5690217 DOI: 10.1120/jacmp.v17i1.5799] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 10/12/2015] [Accepted: 09/28/2015] [Indexed: 12/31/2022] Open
Abstract
The purpose of this study is to report the dosimetric aspects of commissioning performed on an Elekta Versa HD linear accelerator (linac) with high-dose-rate flattening filter-free (FFF) photon modes and electron modes. Acceptance and commissioning was performed on the Elekta Versa HD linac with five photon energies (6 MV, 10 MV, 18 MV, 6 MV FFF, 10 MV FFF), four electron energies (6 MeV, 9MeV, 12 MeV, 15 MeV) and 160-leaf (5 mm wide) multileaf collimators (MLCs). Mechanical and dosimetric data were measured and evaluated. The measurements include percent depth doses (PDDs), in-plane and cross-plane profiles, head scatter factor (Sc), relative photon output factors (Scp), universal wedge transmission factor, MLC transmission factors, and electron cone factors. Gantry, collimator, and couch isocentricity measurements were within 1 mm, 0.7 mm, and 0.7 mm diameter, respectively. The PDDs of 6 MV FFF and 10 MV FFF beams show deeper dmax and steeper falloff with depth than the corresponding flattened beams. While flatness values of 6 MV FFF and 10 MV FFF normalized profiles were expectedly higher than the corresponding flattened beams, the symmetry values were almost identical. The cross-plane penumbra values were higher than the in-plane penumbra values for all the energies. The MLC transmission values were 0.5%, 0.6%, and 0.6% for 6 MV, 10 MV, and 18 MV photon beams, respectively. The electron PDDs, profiles, and cone factors agree well with the literature. The outcome of radiation treatment is directly related to the accuracy in the dose modeled in the treatment planning system, which is based on the commissioned data. Commissioning data provided us a valuable insight into the dosimetric characteristics of the beam. This set of commissioning data can provide comparison data to others performing Versa HD commissioning, thereby improving patient safety.
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Affiliation(s)
- Ganesh Narayanasamy
- University of Texas Health Science Center at San Antonio; University of Arkansas for Medical Sciences.
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16
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Barbiero S, Rink A, Matteucci F, Fedele D, Paiar F, Pasqualetti F, Avanzo M. Single-fraction flattening filter–free volumetric modulated arc therapy for lung cancer: Dosimetric results and comparison with flattened beams technique. Med Dosim 2016; 41:334-338. [DOI: 10.1016/j.meddos.2016.09.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 08/19/2016] [Accepted: 09/09/2016] [Indexed: 12/31/2022]
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17
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Chow JCL, Owrangi AM. A surface energy spectral study on the bone heterogeneity and beam obliquity using the flattened and unflattened photon beams. Rep Pract Oncol Radiother 2015; 21:63-70. [PMID: 26900360 DOI: 10.1016/j.rpor.2015.11.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 09/30/2015] [Accepted: 11/05/2015] [Indexed: 11/28/2022] Open
Abstract
AIM Using flattened and unflattened photon beams, this study investigated the spectral variations of surface photon energy and energy fluence in the bone heterogeneity and beam obliquity. BACKGROUND Surface dose enhancement is a dosimetric concern when using unflattened photon beam in radiotherapy. It is because the unflattened photon beam contains more low-energy photons which are removed by the flattening filter of the flattened photon beam. MATERIALS AND METHODS We used a water and bone heterogeneity phantom to study the distributions of energy, energy fluence and mean energy of the 6 MV flattened and unflattened photon beams (field size = 10 cm × 10 cm) produced by a Varian TrueBEAM linear accelerator. These elements were calculated at the phantom surfaces using Monte Carlo simulations. The photon energy and energy fluence calculations were repeated with the beam angle turned from 0° to 15°, 30° and 45° in the water and bone phantom. RESULTS Spectral results at the phantom surfaces showed that the unflattened photon beams contained more photons concentrated mainly in the low-energy range (0-2 MeV) than the flattened beams associated with a flattening filter. With a bone layer of 1 cm under the phantom surface and within the build-up region of the 6 MV photon beam, it is found that both the flattened and unflattened beams had slightly less photons in the energy range <0.4 MeV compared to the water phantom. This shows that the presence of the bone decreased the low-energy photon backscatters to the phantom surface. When both the flattened and unflattened photon beams were rotated from 0° to 45°, the number of photon and mean photon energy increased. This indicates that both photon beams became more hardened or penetrate when the beam angle increased. In the presence of bone, the mean energies of both photon beams increased. This is due to the absorption of low-energy photons by the bone, resulting in more beam hardening. CONCLUSIONS This study explores the spectral relationships of surface photon energy and energy fluence with bone heterogeneity and beam obliquity for the flattened and unflattened photon beams. The photon spectral information is important in studies on the patient's surface dose enhancement using unflattened photon beams in radiotherapy.
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Affiliation(s)
- James C L Chow
- Department of Radiation Oncology, University of Toronto, Toronto, ON M5G 2M9, Canada; Radiation Medicine Program, Princess Margaret Caner Center, University Health Network, Toronto, ON M5G 2M9, Canada
| | - Amir M Owrangi
- Department of Radiation Oncology, University of Toronto, Toronto, ON M5G 2M9, Canada; Department of Medical Physics, Sunnybrook Health Sciences Center, Toronto ON M4N 3M5, Canada
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Geng J, Shi A, Yu R, Wu H, Zhu G. [Stereotactic Radiotherapy for Non-small Cell Lung Cancer with Small Lesions
Applying A Flattening Filter Free Clinac]. ZHONGGUO FEI AI ZA ZHI = CHINESE JOURNAL OF LUNG CANCER 2015; 18:301-7. [PMID: 25975301 PMCID: PMC6015217 DOI: 10.3779/j.issn.1009-3419.2015.05.08] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND AND OBJECTIVE With the rapid development of technology, stereotactic radiotherapy has been widely used. In a cohort of medically operable non-small cell lung cancer patients receiving stereotactic body radiation therapy (SBRT) survival rates "potentially equivalent to those of surgery" have been reported. Removing the field flattening filter, Clinac is capable of delivering dose rates much higher than conventional linac as well as reducing the treatment time. The goals of this work were to report safety and efficacy of SBRT treatment using a flattening filter-free model for non-small cell lung cancer (NSCLC) with small lesions. METHODS From December 2011 to December 2013, 31 NSCLC patients who were T1-2N0M0, solitary pulmonary recurrence after surgery, and stage IV with oligo metastasis were enrolled, receiving SBRT treatment (60 Gy/8 f or 48 Gy/4 f) applying a flattening filter-free model. RESULTS Compared with conventional technique, flattening filter-free model shortened the treating time with equivalent target dose and normal tissue dose. The median follow-up time is 19.4 mo. The 1-yr local control, regional control, distant control, progression free survival and overall survival rates were 96.8%, 96.8%, 83.9%, 77.4% and 96.8%. The most common side effects were radiation pneumonitis (29% grade 1, 3.2% grade 2) and chest pain (12.9% grade 1, 6.5% grade 2). CONCLUSIONS The use of flattening filter-free model in SBRT for small lesions of NSCLC patients is safe and effective. Long time follow-up and additional studies are still needed to validate our conclusions.
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Affiliation(s)
- Jianhao Geng
- Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing 100142, China
| | - Anhui Shi
- Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing 100142, China
| | - Rong Yu
- Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing 100142, China
| | - Hao Wu
- Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing 100142, China
| | - Guangying Zhu
- Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing 100142, China
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Xiao Y, Kry SF, Popple R, Yorke E, Papanikolaou N, Stathakis S, Xia P, Huq S, Bayouth J, Galvin J, Yin FF. Flattening filter-free accelerators: a report from the AAPM Therapy Emerging Technology Assessment Work Group. J Appl Clin Med Phys 2015; 16:5219. [PMID: 26103482 PMCID: PMC5690108 DOI: 10.1120/jacmp.v16i3.5219] [Citation(s) in RCA: 116] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2014] [Revised: 02/06/2015] [Accepted: 01/23/2015] [Indexed: 11/23/2022] Open
Abstract
This report describes the current state of flattening filter‐free (FFF) radiotherapy beams implemented on conventional linear accelerators, and is aimed primarily at practicing medical physicists. The Therapy Emerging Technology Assessment Work Group of the American Association of Physicists in Medicine (AAPM) formed a writing group to assess FFF technology. The published literature on FFF technology was reviewed, along with technical specifications provided by vendors. Based on this information, supplemented by the clinical experience of the group members, consensus guidelines and recommendations for implementation of FFF technology were developed. Areas in need of further investigation were identified. Removing the flattening filter increases beam intensity, especially near the central axis. Increased intensity reduces treatment time, especially for high‐dose stereotactic radiotherapy/radiosurgery (SRT/SRS). Furthermore, removing the flattening filter reduces out‐of‐field dose and improves beam modeling accuracy. FFF beams are advantageous for small field (e.g., SRS) treatments and are appropriate for intensity‐modulated radiotherapy (IMRT). For conventional 3D radiotherapy of large targets, FFF beams may be disadvantageous compared to flattened beams because of the heterogeneity of FFF beam across the target (unless modulation is employed). For any application, the nonflat beam characteristics and substantially higher dose rates require consideration during the commissioning and quality assurance processes relative to flattened beams, and the appropriate clinical use of the technology needs to be identified. Consideration also needs to be given to these unique characteristics when undertaking facility planning. Several areas still warrant further research and development. Recommendations pertinent to FFF technology, including acceptance testing, commissioning, quality assurance, radiation safety, and facility planning, are presented. Examples of clinical applications are provided. Several of the areas in which future research and development are needed are also indicated. PACS number: 87.53.‐j, 87.53.Bn, 87.53.Ly, 87.55.‐x, 87.55.N‐, 87.56.bc
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Affiliation(s)
- Ying Xiao
- Thomas Jefferson University Hospital.
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Wakai N, Sumida I, Otani Y, Suzuki O, Seo Y, Isohashi F, Yoshioka Y, Hasegawa M, Ogawa K. Optimization of leaf margins for lung stereotactic body radiotherapy using a flattening filter-free beam. Med Phys 2015; 42:2125-31. [DOI: 10.1118/1.4916683] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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21
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Wen N, Zhao B, Kim J, Chin-Snyder K, Bellon M, Glide-Hurst C, Barton K, Chen D, Chetty IJ. IMRT and RapidArc commissioning of a TrueBeam linear accelerator using TG-119 protocol cases. J Appl Clin Med Phys 2014; 15:4843. [PMID: 25207569 PMCID: PMC5711094 DOI: 10.1120/jacmp.v15i5.4843] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 06/11/2014] [Accepted: 06/04/2014] [Indexed: 12/03/2022] Open
Abstract
The purpose of this study is to evaluate the overall accuracy of intensity‐modulated radiation therapy (IMRT) and RapidArc delivery using both flattening filter (FF) and flattening filter‐free (FFF) modalities based on test cases developed by AAPM Task Group 119. Institutional confidence limits (CLs) were established as the baseline for patient specific treatment plan quality assurance (QA). The effects of gantry range, gantry speed, leaf speed, dose rate, as well as the capability to capture intentional errors, were evaluated by measuring a series of Picket Fence (PF) tests using the electronic portal imaging device (EPID) and EBT3 films. Both IMRT and RapidArc plans were created in a Solid Water phantom (30 × 30 × 15 cm3) for the TG‐119 test cases representative of normal clinical treatment sites for all five photon energies (6X, 10X, 15X, 6X‐FFF, 10X‐FFF) and the Exact IGRT couch was included in the dose calculation. One high‐dose point in the PTV and one low‐dose point in the avoidance structure were measured with an ion chamber in each case for each energy. Similarly, two GAFCHROMIC EBT3 films were placed in the coronal planes to measure planar dose distributions in both high‐ and low‐dose regions. The confidence limit was set to have 95% of the measured data fall within the tolerance. The mean of the absolute dose deviation for variable dose rate and gantry speed during RapidArc delivery was within 0.5% for all energies. The corresponding results for leaf speed tests were all within 0.4%. The combinations of dynamic leaf gap (DLG) and MLC transmission factor were optimized based on the ion chamber measurement results of RapidArc delivery for each energy. The average 95% CLs for the high‐dose point in the PTV were 0.030 ± 0.007 (range, 0.022–0.038) for the IMRT plans and 0.029 ± 0.011 (range, 0.016–0.043) for the RapidArc plans. For low‐point dose in the avoidance structures, the CLs were 0.029 ± 0.006 (range, 0.024–0.039) for the IMRT plans and 0.027 ± 0.013 (range, 0.017–0.047) for the RapidArc plans. The average 95% CLs using 3%/3 mm gamma criteria in the high‐dose region were 5.9 ± 2.7 (range, 1.4–8.6) and 3.9 ± 2.9 (range, 1.5–8.8) for IMRT and RapidArc plans, respectively. The average 95% CLs in the low‐dose region were 5.3 ± 2.6 (range, 1.2–7.4) and 3.7 ± 2.8 (range, 1.8–8.3) for IMRT and RapidArc plans, respectively. Based on ion chamber, as well as film measurements, we have established CLs values to ensure the high precision of IMRT and RapidArc delivery for both FF and FFF modalities. PACS number: 87
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22
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Rout B, Muralidhar K, Ali M, Shekar M, Kumar A. Dosimetric study of RapidArc plans with flattened beam (FB) and flattening filter-free (FFF) beam for localized prostate cancer based on physical indices. INTERNATIONAL JOURNAL OF CANCER THERAPY AND ONCOLOGY 2014. [DOI: 10.14319/ijcto.0204.6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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23
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Paynter D, Weston SJ, Cosgrove VP, Evans JA, Thwaites DI. Beam characteristics of energy-matched flattening filter free beams. Med Phys 2014; 41:052103. [DOI: 10.1118/1.4871615] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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24
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Dzierma Y, Nuesken FG, Fleckenstein J, Melchior P, Licht NP, Rübe C. Comparative planning of flattening-filter-free and flat beam IMRT for hypopharynx cancer as a function of beam and segment number. PLoS One 2014; 9:e94371. [PMID: 24722621 PMCID: PMC3983129 DOI: 10.1371/journal.pone.0094371] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 03/14/2014] [Indexed: 11/18/2022] Open
Abstract
Although highly conformal dose distributions can be achieved by IMRT planning, this often requires a large number of segments or beams, resulting in increased treatment times. While flattening-filter-free beams offer a higher dose rate, even more segments may be required to create homogeneous target coverage. Therefore, it is worthwhile to systematically investigate the dependence of plan quality on gantry angles and number of segments for flat vs. FFF beams in IMRT planning. For the practical example of hypopharynx cancer, we present a planning study of flat vs. FFF beams using three different configurations of gantry angles and different segment numbers. The two beams are very similar in physical properties, and are hence well-suited for comparative planning. Starting with a set of plans of equal quality for flat and FFF beams, we assess how far the number of segments can be reduced before the plan quality is markedly compromised, and compare monitor units and treatment times for the resulting plans. As long as a sufficiently large number of segments is permitted, all planning scenarios give good results, independently of gantry angles and flat or FFF beams. For smaller numbers of segments, plan quality decreases both for flat and FFF energies; this effect is stronger for fewer gantry angles and for FFF beams. For low segment numbers, FFF plans are generally worse than the corresponding flat beam plans, but they are less sensitive to a decrease in segment number if many gantry angles are used (18 beams); in this case the quality of flat and FFF plans remains comparable even for few segments.
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Affiliation(s)
- Yvonne Dzierma
- Department of Radiation Oncology, Saarland University Medical Center, Homburg/Saar, Germany
| | - Frank G. Nuesken
- Department of Radiation Oncology, Saarland University Medical Center, Homburg/Saar, Germany
| | - Jochen Fleckenstein
- Department of Radiation Oncology, Saarland University Medical Center, Homburg/Saar, Germany
| | - Patrick Melchior
- Department of Radiation Oncology, Saarland University Medical Center, Homburg/Saar, Germany
| | - Norbert P. Licht
- Department of Radiation Oncology, Saarland University Medical Center, Homburg/Saar, Germany
| | - Christian Rübe
- Department of Radiation Oncology, Saarland University Medical Center, Homburg/Saar, Germany
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25
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Foster RD, Speiser MP, Solberg TD. Commissioning and verification of the collapsed cone convolution superposition algorithm for SBRT delivery using flattening filter-free beams. J Appl Clin Med Phys 2014; 15:4631. [PMID: 24710452 PMCID: PMC5875462 DOI: 10.1120/jacmp.v15i2.4631] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Revised: 10/22/2013] [Accepted: 10/22/2013] [Indexed: 11/25/2022] Open
Abstract
Linacs equipped with flattening filter‐free (FFF) megavoltage photon beams are now commercially available. However, the commissioning of FFF beams poses challenges that are not shared with traditional flattened megavoltage X‐ray beams. The planning system must model a beam that is peaked in the center and has an energy spectrum that is softer than the flattened beam. Removing the flattening filter also increases the maximum possible dose rates from 600 MU/min up to 2400 MU/min in some cases; this increase in dose rate affects the recombination correction factor, Pion, used during absolute dose calibration with ionization chambers. We present the first‐reported experience of commissioning, verification, and clinical use of the collapsed cone convolution superposition (CCCS) dose calculation algorithm for commercially available flattening filter‐free beams. Our commissioning data are compared to previously reported measurements and Monte Carlo studies of FFF beams. Commissioning was verified by making point‐dose measurement of test plans, irradiating the RPC lung phantom, and performing patient‐specific QA. The average point‐dose difference between calculations and measurements of all test plans and all patient specific QA measurements is 0.80%, and the RPC phantom absolute dose differences for the two thermoluminescent dosimeters (TLDs) in the phantom planning target volume (PTV) were 1% and 2%, respectively. One hundred percent (100%) of points in the RPC phantom films passed the RPC gamma criteria of 5% and 5 mm. Our results show that the CCCS algorithm can accurately model FFF beams and calculate SBRT dose distributions using those beams. PACS number: 87.55.kh
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Hrbacek J, Lang S, Graydon SN, Klöck S, Riesterer O. Dosimetric comparison of flattened and unflattened beams for stereotactic ablative radiotherapy of stage I non-small cell lung cancer. Med Phys 2014; 41:031709. [DOI: 10.1118/1.4866231] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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27
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Chung H, Prado KL, Yi BY. An analytical formalism to calculate phantom scatter factors for flattening filter free (FFF) mode photon beams. Phys Med Biol 2014; 59:951-60. [PMID: 24503449 DOI: 10.1088/0031-9155/59/4/951] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Phantom Scatter Factors, Sp in the Khan formalism (Khan et al 1980 J. Radiat. Oncol. Biol. Phys. 6 745-51) describe medium-induced changes in photon-beam intensity as a function of size of the beam. According to the British Journal of Radiology, Supplement 25, megavoltage phantom scatter factors are invariant as a function of photon-beam energy. However, during the commissioning of an accelerator with flattening filter free (FFF) photon beams (Varian TrueBeam(TM) 6-MV FFF and 10-MV FFF), differences were noted in phantom scatter between the filtered beams and FFF-mode beams. The purpose of this work was to evaluate this difference and provide an analytical formalism to explain the phantom scatter differences between FFF-mode and the filtered mode. An analytical formalism was devised to demonstrate the source of phantom scatter differences between the filtered and the FFF-mode beams. The reason for the differences in the phantom scatter factors between the filtered and the FFF-mode beams is hypothesized to be the non-uniform beam profiles of the FFF-mode beams. The analytical formalism proposed here is based on this idea, taking the product of the filtered phantom scatter factors and the ratio of the off-axis ratio between the FFF-mode and the filtered beams. All measurements were performed using a Varian TrueBeam(TM) linear accelerator with photon energies of 6-MV and 10-MV in both filtered and FFF-modes. For all measurements, a PTW Farmer type chamber and a Scanditronix CC04 cylindrical ionization were used. The in-water measurements were made at depth dose maximum and 100 cm source-to-axis distance. The in-air measurements were done at 100 cm source-to-axis distance with appropriate build-up cap. From these measurements, the phantom scatter factors were derived for the filtered beams and the FFF-mode beams for both energies to be evaluated against the phantoms scatter factors calculated using the proposed algorithm. For 6-MV, the difference between the measured and the calculated FFF-mode phantom scatter factors ranged from -0.34% to 0.73%. The average per cent difference was -0.17% (1σ = 0.25%). For 10-MV, the difference ranged from -0.19% to 0.24%. The average per cent difference was -0.17% (1σ = 0.13%). An analytical formalism was presented to calculate the phantom scatter factors for FFF-mode beams using filtered phantom scatter factors as a basis. The overall differences between measurements and calculations were within ± 0.5% for 6-MV and ± 0.25% for 10-MV.
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Affiliation(s)
- Heeteak Chung
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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28
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Liu C, Snyder MG, Orton CG. Point/counterpoint. The future of IMRT∕SBRT lies in the use of unflattened x-ray beams. Med Phys 2014; 40:060601. [PMID: 23718578 DOI: 10.1118/1.4793410] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- Chihray Liu
- Department of Radiation Oncology, University of Florida, Gainesville, Florida 32610-0385, USA.
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Wang Y, Vassil A, Tendulkar R, Bayouth J, Xia P. Feasibility of using nonflat photon beams for whole-breast irradiation with breath hold. J Appl Clin Med Phys 2014; 15:4397. [PMID: 24423835 PMCID: PMC5711254 DOI: 10.1120/jacmp.v15i1.4397] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 05/01/2013] [Accepted: 08/03/2013] [Indexed: 11/23/2022] Open
Abstract
Removing a flattening filter or replacing it with a thinner filter alters the characteristics of a photon beam, creating a forward peaked intensity profile to make the photon beam nonflat. This study is to investigate the feasibility of applying nonflat photon beams to the whole-breast irradiation with breath holds for a potential of delivery time reduction during the gated treatment. Photon beams of 6 MV with flat and nonflat intensity profiles were commissioned. Fifteen patients with early-stage breast cancer, who received whole-breast radiation without breathing control, were retrospectively selected for this study. For each patient, three plans were created using a commercial treatment planning system: (a) the clinically approved plan using forward planning method (FP); (b) a hybrid intensity-modulated radiation therapy (IMRT) plan where the flat beam open fields were combined with the nonflat beam IMRT fields using direct aperture optimization method (mixed DAO); (c) a hybrid IMRT plan where both open and IMRT fields were from nonflat beams using direct aperture optimization (nonflat DAO). All plans were prescribed for ≥ 95% of the breast volume receiving the prescription dose of 50 Gy (2.0 Gy per fraction). In comparison, all plans achieved a similar dosimetric coverage to the targeted volume. The average homogeneity index of the FP, mixed DAO, and nonflat DAO plans were 0.882 ± 0.024, 0.879 ± 0.023, and 0.867 ± 0.027, respectively. The average percentage volume of V105 was 57.66% ± 5.21%, 34.67% ± 4.91%, 41.64% ± 5.32% for the FP, mixed, and nonflat DAO plans, respectively. There was no significant difference (p > 0.05) observed for the defined endpoint doses in organs at risk (OARs). In conclusion, both mixed DAO and nonflat DAO plans can achieve similar plan quality as the clinically approved FP plan, measured by plan homogeneity and endpoint doses to the ORAs. Nonflat beam plans may reduce treatment time in breath-hold treatment, especially for hypofractionated treatment.
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Improvement of the penumbra for small radiosurgical fields using flattening filter free low megavoltage beams. Z Med Phys 2013; 23:291-9. [DOI: 10.1016/j.zemedi.2013.03.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Revised: 03/12/2013] [Accepted: 03/18/2013] [Indexed: 11/21/2022]
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Prendergast BM, Dobelbower MC, Bonner JA, Popple RA, Baden CJ, Minnich DJ, Cerfolio RJ, Spencer SA, Fiveash JB. Stereotactic body radiation therapy (SBRT) for lung malignancies: preliminary toxicity results using a flattening filter-free linear accelerator operating at 2400 monitor units per minute. Radiat Oncol 2013; 8:273. [PMID: 24256563 PMCID: PMC3842766 DOI: 10.1186/1748-717x-8-273] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Accepted: 11/13/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Flattening filter-free (FFF) linear accelerators (linacs) are capable of delivering dose rates more than 4-times higher than conventional linacs during SBRT treatments, causing some to speculate whether the higher dose rate leads to increased toxicity owing to radiobiological dose rate effects. Despite wide clinical use of this emerging technology, clinical toxicity data for FFF SBRT are lacking. In this retrospective study, we report the acute and late toxicities observed in our lung radiosurgery experience using a FFF linac operating at 2400 MU/min. METHODS We reviewed all flattening filter-free (FFF) lung SBRT cases treated at our institution from August 2010 through July 2012. Patients were eligible for inclusion if they had at least one clinical assessment at least 30 days following SBRT. Pulmonary, cardiac, dermatologic, neurologic, and gastrointestinal treatment related toxicities were scored according to CTCAE version 4.0. Toxicity observed within 90 days of SBRT was categorized as acute, whereas toxicity observed more than 90 days from SBRT was categorized as late. Factors thought to influence risk of toxicity were examined to assess relationship to grade > =2 toxicity. RESULTS Sixty-four patients with >30 day follow up were eligible for inclusion. All patients were treated using 10 MV unflattened photons beams with intensity modulated radiation therapy (IMRT) inverse planning. Median SBRT dose was 48 Gy in 4 fractions (range: 30-60 Gy in 3-5 fractions). Six patients (9%) experienced > = grade 2 acute pulmonary toxicity; no non-pulmonary acute toxicities were observed. In a subset of 49 patients with greater than 90 day follow up (median 11.5 months), 11 pulmonary and three nerve related grade > =2 late toxicities were recorded. Pulmonary toxicities comprised six grade 2, three grade 3, and one each grade 4 and 5 events. Nerve related events were rare and included two cases of grade 2 chest wall pain and one grade 3 brachial plexopathy which spontaneously resolved. No grade > =2 late gastrointestinal, skin, or cardiac toxicities were observed. Tumor size, biologically effective dose (BED10, assuming α/β of 10), and tumor location (central vs peripheral) were not significantly associated with grade > =2 toxicity. CONCLUSIONS In this early clinical experience, lung SBRT using a FFF linac operating at 2400 MU/min yields minimal acute toxicity. Preliminary results of late treatment related toxicity suggest reasonable rates of grade > =2 toxicities. Further assessment of late effects and confirmation of the clinical efficacy of FFF SBRT is warranted.
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Lechner W, Kragl G, Georg D. Evaluation of treatment plan quality of IMRT and VMAT with and without flattening filter using Pareto optimal fronts. Radiother Oncol 2013; 109:437-41. [PMID: 24183067 DOI: 10.1016/j.radonc.2013.09.020] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Revised: 09/19/2013] [Accepted: 09/22/2013] [Indexed: 11/18/2022]
Abstract
PURPOSE To investigate the differences in treatment plan quality of IMRT and VMAT with and without flattening filter using Pareto optimal fronts, for two treatment sites of different anatomic complexity. MATERIALS AND METHODS Pareto optimal fronts (POFs) were generated for six prostate and head-and-neck cancer patients by stepwise reduction of the constraint (during the optimization process) of the primary organ-at-risk (OAR). 9-static field IMRT and 360°-single-arc VMAT plans with flattening filter (FF) and without flattening filter (FFF) were compared. The volume receiving 5 Gy or more (V5 Gy) was used to estimate the low dose exposure. Furthermore, the number of monitor units (MUs) and measurements of the delivery time (T) were used to assess the efficiency of the treatment plans. RESULTS A significant increase in MUs was found when using FFF-beams while the treatment plan quality was at least equivalent to the FF-beams. T was decreased by 18% for prostate for IMRT with FFF-beams and by 4% for head-and-neck cases, but increased by 22% and 16% for VMAT. A reduction of up to 5% of V5 Gy was found for IMRT prostate cases with FFF-beams. CONCLUSIONS The evaluation of the POFs showed an at least comparable treatment plan quality of FFF-beams compared to FF-beams for both treatment sites and modalities. For smaller targets the advantageous characteristics of FFF-beams could be better exploited.
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Affiliation(s)
- Wolfgang Lechner
- Department of Radiation Oncology, Medical University of Vienna / AKH Wien, Vienna, Austria; Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria.
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Huang Y, Flynn RT, Siochi RAC, Bayouth JE. Equivalent-quality unflattened photon beam modeling, planning, and delivery. J Appl Clin Med Phys 2013; 14:4211. [PMID: 23835385 PMCID: PMC5714540 DOI: 10.1120/jacmp.v14i4.4211] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Revised: 02/11/2013] [Accepted: 02/07/2013] [Indexed: 11/23/2022] Open
Abstract
The clinical application of the flattening filter‐free photon beam (FFF) has enjoyed greater use due to its advantage of reduced treatment time because of the increased dose rate. Its unique beam characteristics, along with the very high‐dose rate, require a thorough knowledge of the capability and accuracy in FFF beam modeling, planning, and delivery. This work verifies the feasibility of modeling an equivalent quality unflattened photon beam (eqUF), and the dosimetric accuracy in eqUF beam planning and delivery. An eqUF beam with a beam quality equivalent to a conventional 6 MV photon beam with the filter in place (WF) was modeled for the Pinnacle3 TPS and the beam model quality was evaluated by gamma index test. Results showed that the eqUF beam modeling was similar to that of the WF beam, as the overall passing rate of the 2%/2mm gamma index test was 99.5% in the eqUF beam model and 96% in the WF beam model. Hypofractionated IMRT plans were then generated with the same constraints using both WF and eqUF beams, and the similarity was evaluated by DVH comparison and generalized 3D gamma index test. The WF and eqUF plans showed no clinically significant differences in DVH comparison and, on average >98% voxels passed the 3%/3mm 3D gamma index test. Dosimetric accuracy in gated phantom delivery was verified by ion chamber and film measurements. All ion chamber measurements at the isocenter were within 1% of calculated values and film measurements passed the 3mm/3% gamma index test with an overall passing rate >95% in the high‐dose and low‐gradient region in both WF and eqUF cases. Treatment plan quality assurance (QA), using either measurement‐based or independent calculation‐based methods of ten clinically treated eqUF IMRT plans were analyzed. In both methods, the point dose differences were all within 2% difference. In the relative 2D dose distribution comparison, >95% points were within 3% dose difference or 3 mm DTA. PACS number: 87.55.kh
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Affiliation(s)
- Yunfei Huang
- Department of Radiation Oncology, Division of Medical Physics, University of Iowa Hospitals and Clinics, Iowa City, IA 52242, USA.
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Prendergast BM, Fiveash JB, Popple RA, Clark GM, Thomas EM, Minnich DJ, Jacob R, Spencer SA, Bonner JA, Dobelbower MC. Flattening filter-free linac improves treatment delivery efficiency in stereotactic body radiation therapy. J Appl Clin Med Phys 2013; 14:4126. [PMID: 23652246 PMCID: PMC5714408 DOI: 10.1120/jacmp.v14i3.4126] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Revised: 01/11/2013] [Accepted: 12/19/2012] [Indexed: 12/14/2022] Open
Abstract
Stereotactic body radiation therapy (SBRT) employs precision target tracking and image‐guidance techniques to deliver ablative doses of radiation to localized malignancies; however, treatment with conventional photon beams requires lengthy treatment and immobilization times. The use of flattening filter‐free (FFF) beams operating at higher dose rates can shorten beam‐on time, and we hypothesize that it will shorten overall treatment delivery time. A total of 111 lung and liver SBRT cases treated at our institution from July 2008 to July 2011 were reviewed and 99 cases with complete data were identified. Treatment delivery times for cases treated with a FFF linac versus a conventional dose rate linac were compared. The frequency and type of intrafraction image guidance was also collected and compared between groups. Three hundred and ninety‐one individual SBRT fractions from 99 treatment plans were examined; 36 plans were treated with a FFF linac. In the FFF cohort, the mean (± standard deviation) treatment time (time elapsed from beam‐on until treatment end) and patient's immobilization time (time from first alignment image until treatment end) was 11.44 (± 6.3) and 21.08 (± 6.8) minutes compared to 32.94 (± 14.8) and 47.05 (± 17.6) minutes for the conventional cohort (p<0.01 for all values). Intrafraction‐computed tomography (CT) was used more often in the conventional cohort (84% vs. 25%; p<0.05), but use of orthogonal X‐ray imaging remained the same (16% vs. 19%). For lung and liver SBRT, a FFF linac reduces treatment and immobilization time by more than 50% compared to a conventional linac. In addition, treatment with a FFF linac is associated with less physician‐ordered image guidance, which contributes to further improvement in treatment delivery efficiency. PACS number: 87.55.‐x
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Affiliation(s)
- Brendan M Prendergast
- Department of Radiation Oncology, University of Alabama at Birmingham, Birmingham, AL 35249, USA.
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King RB, Hyland WB, Cole AJ, Butterworth KT, McMahon SJ, Redmond KM, Trainer C, Prise KM, McGarry CK, Hounsell AR. Anin vitrostudy of the radiobiological effects of flattening filter free radiotherapy treatments. Phys Med Biol 2013; 58:N83-94. [DOI: 10.1088/0031-9155/58/5/n83] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Lang S, Shrestha B, Graydon S, Cavelaars F, Linsenmeier C, Hrbacek J, Klöck S, Studer G, Riesterer O. Clinical application of flattening filter free beams for extracranial stereotactic radiotherapy. Radiother Oncol 2013; 106:255-9. [DOI: 10.1016/j.radonc.2012.12.012] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Revised: 11/15/2012] [Accepted: 12/19/2012] [Indexed: 11/16/2022]
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Kalantzis G, Qian J, Han B, Luxton G. Fidelity of dose delivery at high dose rate of volumetric modulated arc therapy in a truebeam linac with flattening filter free beams. J Med Phys 2013; 37:193-9. [PMID: 23293450 PMCID: PMC3532747 DOI: 10.4103/0971-6203.103604] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Revised: 07/20/2012] [Accepted: 09/12/2012] [Indexed: 11/04/2022] Open
Abstract
The purpose of this study is to assess fidelity of radiation delivery between high and low dose rates of the flattening filter free (FFF) modes of a new all-digital design medical linear accelerator (Varian TrueBeam™), particularly for plans optimized for volumetric modulated arc therapy (VMAT). Measurements were made for the two energies of flattening filter free photon beams with a Varian TrueBeam™ linac: 6 MV (6 XFFF) at 400 and 1400 MU/min, and 10 MV (10 XFFF) at 400 and 2400 MU/min. Data acquisition and analysis was performed with both ionization chambers and diode detector system Delta(4), for square radiation fields and for 8 VMAT treatment plans optimized for SBRT treatment of lung tumors. For the square fields, a percent dose difference between high and low dose rate of the order of 0.3-0.4% for both photon energies was seen with the ionization chambers, while the contribution to the difference from ion recombination was found to be negligible. For both the VMAT and square-field deliveries, the Delta(4) showed the same average percent dose difference between the two dose rates of ~0.8% and ~0.6% for 10 MV and 6 MV, respectively, with the lower dose rate values giving the greater measured dose compared to the high dose rate. Thus, the VMAT deliveries introduced negligible dose differences between high and low dose rate. Finally, reproducibility of dose measurements was good for both energies.
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Affiliation(s)
- Georgios Kalantzis
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California, USA
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Dzierma Y, Licht N, Nuesken F, Ruebe C. Beam properties and stability of a flattening-filter free 7 MV beam-an overview. Med Phys 2012; 39:2595-602. [PMID: 22559630 DOI: 10.1118/1.3703835] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Several works have recently focused on flattening-filter-free (FFF) beams of linear accelerators of various companies (in particular, Varian and Elekta), but no overview as yet exists for the flattening-filter free 7XU beam (Siemens Artiste). METHODS Dosimetric properties of the 7XU beam were measured in May and September 2011. We present depth dose curves and beam profiles, output factors, and MLC transmission and assess the stability of the measurements. The 7XU beam was commissioned in the Pinnacle[superscript three] treatment planning system (TPS), and modeling results including the spectrum are presented. RESULTS The percent depth dose curve of the 7XU beam is similar to the flat 6X beam line, with a slightly smaller surface dose. The beam profiles show the characteristic shape of flattening-filter free beams, with deviations between measurements of generally less than 1%. The output factors of the 7XU beam decrease more slowly than for the 6X beam. The MLC transmission is comparable but slightly less for the 7XU beam. The 7XU beam can be adequately modeled by the Pinnacle[superscript three] TPS, with successful dosimetric verification. The spectrum of the 7XU beam has lower photon fluence up to approximately 2.5 MeV and higher fluence beyond, with a slightly higher mean energy. CONCLUSIONS The 7XU beam has been commissioned for clinical use after successful modeling, stability checks, and dosimetric verification.
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Affiliation(s)
- Yvonne Dzierma
- Department of Radiation Oncology, Saarland University Medical Center, Saarland, Germany.
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Zwahlen DR, Lang S, Hrbacek J, Glanzmann C, Kloeck S, Najafi Y, Streller T, Studer G, Zaugg K, Luetolf UM. The use of photon beams of a flattening filter-free linear accelerator for hypofractionated volumetric modulated arc therapy in localized prostate cancer. Int J Radiat Oncol Biol Phys 2012; 83:1655-60. [PMID: 22572080 DOI: 10.1016/j.ijrobp.2011.10.019] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Revised: 09/23/2011] [Accepted: 10/04/2011] [Indexed: 10/28/2022]
Abstract
PURPOSE To evaluate the potential usage of flattening filter-free (FFF) photon beams in the treatment of prostate cancer. METHODS AND MATERIALS Volumetric-modulated arc therapy (VMAT) treatment planning was performed for 7 patients using TrueBeam(®) linear accelerator and photon beams with (X6, X10) and without (X6FFF, X10FFF) flattening filter. Prescribed dose was 19 × 3 Gy = 57 Gy. One or two 360° arcs with dose rate of 600 MU/min for flattened beams, and 1,200 MU/min for FFF beams were used. RESULTS No difference was detected between the four beams in PTV coverage, conformity, and homogeneity. Mean body dose and body volume receiving 50% of the prescribed dose decreased with increasing mean energy (r(2) = 0.8275, p < 0.01). X6FFF delivered 3.6% more dose compared with the X6 (p < 0.01). X10FFF delivered 3.0% (p < 0.01), and the X10 5.8% (p < 0.01) less mean body dose compared with X6. There was a significant increase in the mean dose to the rectum for the X10 compared with X6 (2.6%, p < 0.01). Mean dose to the bladder increased by 1.3% for X6FFF and decreased by 2.3% for X10FFF. Using a single arc and FFF, treatment time was reduced by 35% (2 SD = 10%). CONCLUSION FFF beams resulted in dose distributions similar to flattened beams. X10FFF beam provided the best solution, sparing rectum and bladder and minimizing whole-body dose. FFF beams lead to a time efficient treatment delivery, particularly when combined with hypofractionated VMAT.
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Affiliation(s)
- Daniel R Zwahlen
- Department of Radiation Oncology, University Hospital Zurich, Zurich, Switzerland.
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40
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Ong CL, Verbakel WF, Dahele M, Cuijpers JP, Slotman BJ, Senan S. Fast Arc Delivery for Stereotactic Body Radiotherapy of Vertebral and Lung Tumors. Int J Radiat Oncol Biol Phys 2012; 83:e137-43. [DOI: 10.1016/j.ijrobp.2011.12.014] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Revised: 11/21/2011] [Accepted: 12/01/2011] [Indexed: 11/29/2022]
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Lang S, Reggiori G, Puxeu Vaqué J, Calle C, Hrbacek J, Klöck S, Scorsetti M, Cozzi L, Mancosu P. Pretreatment quality assurance of flattening filter free beams on 224 patients for intensity modulated plans: A multicentric study. Med Phys 2012; 39:1351-6. [DOI: 10.1118/1.3685461] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Comparison of anisotropic aperture based intensity modulated radiotherapy with 3D-conformal radiotherapy for the treatment of large lung tumors. Radiother Oncol 2012; 102:268-73. [DOI: 10.1016/j.radonc.2011.10.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Revised: 09/19/2011] [Accepted: 10/07/2011] [Indexed: 12/25/2022]
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Radiation therapy with unflattened photon beams: Dosimetric accuracy of advanced dose calculation algorithms. Radiother Oncol 2011; 100:417-23. [DOI: 10.1016/j.radonc.2011.09.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2011] [Revised: 08/30/2011] [Accepted: 09/02/2011] [Indexed: 11/15/2022]
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Qian J, Xing L, Liu W, Luxton G. Dose verification for respiratory-gated volumetric modulated arc therapy. Phys Med Biol 2011; 56:4827-38. [PMID: 21753232 DOI: 10.1088/0031-9155/56/15/013] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A novel commercial medical linac system (TrueBeam™, Varian Medical Systems, Palo Alto, CA) allows respiratory-gated volumetric modulated arc therapy (VMAT), a new modality for treating moving tumors with high precision and improved accuracy by allowing for regular motion associated with a patient's breathing during VMAT delivery. The purpose of this work is to adapt a previously-developed dose reconstruction technique to evaluate the fidelity of VMAT treatment during gated delivery under clinic-relevant periodic motion related to patient breathing. A Varian TrueBeam system was used in this study. VMAT plans were created for three patients with lung or pancreas tumors. Conventional 6 and 15 MV beams with flattening filter and high-dose-rate 10 MV beams with no flattening filter were used in these plans. Each patient plan was delivered to a phantom first without gating and then with gating for three simulated respiratory periods (3, 4.5 and 6 s). Using the adapted log-file-based dose reconstruction procedure supplemented with ion chamber array (Seven29™, PTW, Freiburg, Germany) measurements, the delivered dose was used to evaluate the fidelity of gated VMAT delivery. Comparison of Seven29 measurements with and without gating showed good agreement with gamma-index passing rates above 99% for 1%/1 mm dose accuracy/distance-to-agreement criteria. With original plans as reference, gamma-index passing rates were 100% for the reconstituted plans (1%/1 mm criteria) and 93.5-100% for gated Seven29 measurements (3%/3 mm criteria). In the presence of leaf error deliberately introduced into the gated delivery of a pancreas patient plan, both dose reconstruction and Seven29 measurement consistently indicated substantial dosimetric differences from the original plan. In summary, a dose reconstruction procedure was demonstrated for evaluating the accuracy of respiratory-gated VMAT delivery. This technique showed that under clinical operation, the TrueBeam system faithfully realized treatment plans with gated delivery. This methodology affords a useful tool for machine- and patient-specific quality assurance of the newly available respiratory-gated VMAT.
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Affiliation(s)
- Jianguo Qian
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305, USA
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Chofor N, Harder D, Willborn K, Rühmann A, Poppe B. A direction-selective flattening filter for clinical photon beams. Monte Carlo evaluation of a new concept. Phys Med Biol 2011; 56:4355-76. [DOI: 10.1088/0031-9155/56/14/009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Georg D, Knöös T, McClean B. Current status and future perspective of flattening filter free photon beams. Med Phys 2011; 38:1280-93. [PMID: 21520840 DOI: 10.1118/1.3554643] [Citation(s) in RCA: 208] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Flattening filters (FFs) have been considered as an integral part of the treatment head of a medical accelerator for more than 50 years. The reasons for the longstanding use are, however, historical ones. Advanced treatment techniques, such as stereotactic radiotherapy or intensity modulated radiotherapy have stimulated the interest in operating linear accelerators in a flattening filter free (FFF) mode. The current manuscript reviews treatment head physics of FFF beams, describes their characteristics and the resulting potential advantages in their medical use, and closes with an outlook. METHODS A number of dosimetric benefits have been determined for FFF beams, which range from increased dose rate and dose per pulse to favorable output ratio in-air variation with field size, reduced energy variation across the beam, and reduced leakage and out-of-field dose, respectively. Finally, the softer photon spectrum of unflattened beams has implications on imaging strategies and radiation protection. RESULTS The dosimetric characteristics of FFF beams have an effect on treatment delivery, patient comfort, dose calculation accuracy, beam matching, absorbed dose determination, treatment planning, machine specific quality assurance, imaging, and radiation protection. When considering conventional C-arm linacs in a FFF mode, more studies are needed to specify and quantify the clinical advantages, especially with respect to treatment plan quality and quality assurance. CONCLUSIONS New treatment units are already on the market that operate without a FF or can be operated in a dedicated clinical FFF mode. Due to the convincing arguments of removing the FF, it is expected that more vendors will offer dedicated treatment units for advanced photon beam therapy in the near future. Several aspects related to standardization, dosimetry, treatment planning, and optimization need to be addressed in more detail in order to facilitate the clinical implementation of unflattened beams.
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Affiliation(s)
- Dietmar Georg
- Department of Radiotherapy, Division of Medical Radiation Physics, Medical University of Vienna/AKH Vienna, A-1090 Vienna, Austria.
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Flattening filter free beams in SBRT and IMRT: Dosimetric assessment of peripheral doses. Z Med Phys 2011; 21:91-101. [DOI: 10.1016/j.zemedi.2010.07.003] [Citation(s) in RCA: 109] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2010] [Revised: 06/30/2010] [Accepted: 07/17/2010] [Indexed: 11/20/2022]
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Kim T, Zhu L, Suh TS, Geneser S, Meng B, Xing L. Inverse planning for IMRT with nonuniform beam profiles using total-variation regularization (TVR). Med Phys 2011; 38:57-66. [PMID: 21361175 DOI: 10.1118/1.3521465] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Radiation therapy with high dose rate and flattening filter-free (FFF) beams has the potential advantage of greatly reduced treatment time and out-of-field dose. Current inverse planning algorithms are, however, not customized for beams with nonuniform incident profiles and the resultant IMRT plans are often inefficient in delivery. The authors propose a total-variation regularization (TVR)-based formalism by taking the inherent shapes of incident beam profiles into account. METHODS A novel TVR-based inverse planning formalism is established for IMRT with nonuniform beam profiles. The authors introduce a TVR term into the objective function, which encourages piecewise constant fluence in the nonuniform FFF fluence domain. The proposed algorithm is applied to lung and prostate and head and neck cases and its performance is evaluated by comparing the resulting plans to those obtained using a conventional beamlet-based optimization (BBO). RESULTS For the prostate case, the authors' algorithm produces acceptable dose distributions with only 21 segments, while the conventional BBO requires 114 segments. For the lung case and the head and neck case, the proposed method generates similar coverage of target volume and sparing of the organs-at-risk as compared to BBO, but with a markedly reduced segment number. CONCLUSIONS TVR-based optimization in nonflat beam domain provides an effective way to maximally leverage the technical capacity of radiation therapy with FFF fields. The technique can generate effective IMRT plans with improved dose delivery efficiency without significant deterioration of the dose distribution.
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Affiliation(s)
- Taeho Kim
- Department of Radiation Oncology, Stanford University, Stanford, California 94305, USA
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Salter BJ, Sarkar V, Wang B, Shukla H, Szegedi M, Rassiah-Szegedi P. Rotational IMRT delivery using a digital linear accelerator in very high dose rate 'burst mode'. Phys Med Biol 2011; 56:1931-46. [PMID: 21364260 DOI: 10.1088/0031-9155/56/7/002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Recently, there has been a resurgence of interest in arc-based IMRT, through the use of 'conventional' multileaf collimator (MLC) systems that can treat large tumor volumes in a single, or very few pass(es) of the gantry. Here we present a novel 'burst mode' modulated arc delivery approach, wherein 2000 monitor units per minute (MU min(-1)) high dose rate bursts of dose are facilitated by a flattening-filter-free treatment beam on a Siemens Artiste (Oncology Care Systems, Siemens Medical Solutions, Concord, CA, USA) digital linear accelerator in a non-clinical configuration. Burst mode delivery differs from continuous mode delivery, used by Elekta's VMAT (Elekta Ltd, Crawley, UK) and Varian's RapidArc (Varian Medical Systems, Palo Alto, CA, USA) implementations, in that dose is not delivered while MLC leaves are moving. Instead, dose is delivered in bursts over very short arc angles and only after an MLC segment shape has been completely formed and verified by the controller. The new system was confirmed to be capable of delivering a wide array of clinically relevant treatment plans, without machine fault or other delivery anomalies. Dosimetric accuracy of the modulated arc platform, as well as the Prowess (Prowess Inc., Concord, CA, USA) prototype treatment planning version utilized here, was quantified and confirmed, and delivery times were measured as significantly brief, even with large hypofractionated doses. The burst mode modulated arc approach evaluated here appears to represent a capable, accurate and efficient delivery approach.
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Affiliation(s)
- Bill J Salter
- Department of Radiation Oncology, University of Utah, Salt Lake City, UT, USA.
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Cashmore J, Ramtohul M, Ford D. Lowering whole-body radiation doses in pediatric intensity-modulated radiotherapy through the use of unflattened photon beams. Int J Radiat Oncol Biol Phys 2010; 80:1220-7. [PMID: 21167659 DOI: 10.1016/j.ijrobp.2010.10.002] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Revised: 09/23/2010] [Accepted: 10/07/2010] [Indexed: 11/29/2022]
Abstract
PURPOSE Intensity modulated radiotherapy (IMRT) has been linked with an increased risk of secondary cancer induction due to the extra leakage radiation associated with delivery of these techniques. Removal of the flattening filter offers a simple way of reducing head leakage, and it may be possible to generate equivalent IMRT plans and to deliver these on a standard linear accelerator operating in unflattened mode. METHODS AND MATERIALS An Elekta Precise linear accelerator has been commissioned to operate in both conventional and unflattened modes (energy matched at 6 MV) and a direct comparison made between the treatment planning and delivery of pediatric intracranial treatments using both approaches. These plans have been evaluated and delivered to an anthropomorphic phantom. RESULTS Plans generated in unflattened mode are clinically identical to those for conventional IMRT but can be delivered with greatly reduced leakage radiation. Measurements in an anthropomorphic phantom at clinically relevant positions including the thyroid, lung, ovaries, and testes show an average reduction in peripheral doses of 23.7%, 29.9%, 64.9%, and 70.0%, respectively, for identical plan delivery compared to conventional IMRT. CONCLUSIONS IMRT delivery in unflattened mode removes an unwanted and unnecessary source of scatter from the treatment head and lowers leakage doses by up to 70%, thereby reducing the risk of radiation-induced second cancers. Removal of the flattening filter is recommended for IMRT treatments.
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Affiliation(s)
- Jason Cashmore
- University Hospital Birmingham, Edgbaston, Birmingham, UK.
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