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Klimanov VA, Kirpichev YS, Serikbekova ZK, Belousov AV, Krusanov GA, Walwyn‐Salas G, Morozov VN, Kolyvanova MA. Monte-Carlo calculation of output correction factors for ionization chambers, solid-state detectors, and EBT3 film in small fields of high-energy photons. J Appl Clin Med Phys 2022; 24:e13753. [PMID: 35998153 PMCID: PMC9860002 DOI: 10.1002/acm2.13753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Revised: 07/13/2022] [Accepted: 07/25/2022] [Indexed: 01/26/2023] Open
Abstract
High-energy accelerators are often used in oncological practice, but the information on the small-field dosimetry for the photon beams with nominal energy above 10 MV is limited. The goal of the present work was to determine the values of the output correction factor ( k Q clin , Q ref f clin , f ref $k_{{Q}_{{\rm{clin}}},{Q}_{{\rm{ref}}}}^{{f}_{{\rm{clin}}},{f}_{{\rm{ref}}}}$ ) for solid-state detectors (Diode E, PTW 60017; microDiamond, PTW 60019), EBT3 film, and ionization chambers (Semiflex, PTW 31010; Semiflex 3D, PTW 31021; PinPoint, PTW 31015; PinPoint 3D, PTW 31016) in the small fields formed by 10, 15, 18, and 20 MV photon beams. The output correction factors were calculated by Monte-Carlo method using EGSnrc toolkit for six field sizes (from 0.5 × 0.5 cm 2 $0.5 \times 0.5\ {\rm{cm}}^2$ to 10 × 10 cm 2 $10 \times 10\ {\rm{cm}}^2$ ) for isocentric and constant source-to-surface distance (SSD) techniques. The decrease in the field size led to an increase in k Q clin , Q ref f clin , f ref $k_{{Q}_{{\rm{clin}}},{Q}_{{\rm{ref}}}}^{{f}_{{\rm{clin}}},{f}_{{\rm{ref}}}}$ for ionization chambers, while for solid-state detectors and radiochromic film, k Q clin , Q ref f clin , f ref $k_{{Q}_{{\rm{clin}}},{Q}_{{\rm{ref}}}}^{{f}_{{\rm{clin}}},{f}_{{\rm{ref}}}}$ were less than unity at the smallest field size. A larger sensitive volume of ionization chamber corresponded to a stronger deviation of output correction factor from unity: 1.847 (125 mm3 PTW 31010) versus up to 1.183 (16 mm3 PTW 31016) at the smallest field of 10 MV beam. The calculated output correction factors were used to correct the output factors for PTW 60017, PTW 60019, and EBT3. The deviation of the corrected output factor from the results of Monte-Carlo simulation did not exceed 3% in the fields from 1.0 × 1.0 cm 2 $1.0 \times 1.0\ {\rm{cm}}^2$ to 4.0 × 4.0 cm 2 $4.0 \times 4.0\ {\rm{cm}}^2$ for 10 and 18 MV beams. Thus, Diode E, microDiamond, and EBT3 film can be recommended for small-field dosimetry of high-energy photons.
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Affiliation(s)
- Vladimir A. Klimanov
- State Research Center—Burnazyan Federal Medical Biophysical CenterFederal Medical Biological Agency of the Russian FederationMoscowRussia,National Research Nuclear University MEPhIMoscowRussia
| | | | | | - Alexandr V. Belousov
- State Research Center—Burnazyan Federal Medical Biophysical CenterFederal Medical Biological Agency of the Russian FederationMoscowRussia
| | - Grigorii A. Krusanov
- State Research Center—Burnazyan Federal Medical Biophysical CenterFederal Medical Biological Agency of the Russian FederationMoscowRussia
| | | | - Vladimir N. Morozov
- Emanuel Institute of Biochemical PhysicsRussian Academy of SciencesMoscowRussia
| | - Maria A. Kolyvanova
- State Research Center—Burnazyan Federal Medical Biophysical CenterFederal Medical Biological Agency of the Russian FederationMoscowRussia,Emanuel Institute of Biochemical PhysicsRussian Academy of SciencesMoscowRussia
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Buchegger N, Grogan G, Hug B, Oliver C, Ebert M. CyberKnife reference dosimetry: An assessment of the impact of evolving recommendations on correction factors and measured dose. Med Phys 2020; 47:3573-3585. [DOI: 10.1002/mp.14190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 03/29/2020] [Accepted: 03/30/2020] [Indexed: 11/06/2022] Open
Affiliation(s)
- Nicole Buchegger
- Department of Radiation Oncology Sir Charles Gairdner Hospital Nedlands WA 6009 Australia
| | - Garry Grogan
- Department of Radiation Oncology Sir Charles Gairdner Hospital Nedlands WA 6009 Australia
| | - Ben Hug
- 5D Clinics Claremont WA 6010 Australia
| | - Chris Oliver
- Australian Radiation Protection and Nuclear Safety Agency Yallambie Vic. 3085 Australia
| | - Martin Ebert
- Department of Radiation Oncology Sir Charles Gairdner Hospital Nedlands WA 6009 Australia
- 5D Clinics Claremont WA 6010 Australia
- Department of Physics University of Western Australia Crawley WA 6009 Australia
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Palmans H, Andreo P, Huq MS, Seuntjens J, Christaki KE, Meghzifene A. Dosimetry of small static fields used in external photon beam radiotherapy: Summary of TRS‐483, the IAEA–AAPM international Code of Practice for reference and relative dose determination. Med Phys 2018; 45:e1123-e1145. [DOI: 10.1002/mp.13208] [Citation(s) in RCA: 123] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 07/24/2018] [Accepted: 07/30/2018] [Indexed: 12/18/2022] Open
Affiliation(s)
- Hugo Palmans
- Medical Radiation Science National Physical Laboratory Teddington TW11 0LWUK
- Department of Medical Physics EBG MedAustron GmbH A‐2700Wiener Neustadt Austria
| | - Pedro Andreo
- Department of Medical Physics and Nuclear Medicine Karolinska University Hospital SE‐17176Stockholm Sweden
| | - M. Saiful Huq
- Department of Radiation Oncology University of Pittsburgh School of Medicine and UPMC Hillman Cancer Center Pittsburgh PA15232USA
| | - Jan Seuntjens
- Medical Physics Unit McGill University Montréal QCH3A 0G4Canada
| | - Karen E. Christaki
- Dosimetry and Medical Radiation Physics Section International Atomic Energy Agency A‐1400Vienna Austria
| | - Ahmed Meghzifene
- Dosimetry and Medical Radiation Physics Section International Atomic Energy Agency A‐1400Vienna Austria
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Huq MS, Hwang MS, Teo TP, Jang SY, Heron DE, Lalonde RJ. A dosimetric evaluation of the IAEA-AAPM TRS483 code of practice for dosimetry of small static fields used in conventional linac beams and comparison with IAEA TRS-398, AAPM TG51, and TG51 Addendum protocols. Med Phys 2018; 45:4257-4273. [PMID: 30009526 DOI: 10.1002/mp.13092] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 06/03/2018] [Accepted: 06/13/2018] [Indexed: 12/14/2022] Open
Abstract
PURPOSE The International Atomic Energy Agency (IAEA) and the American Association of Physicists in Medicine (AAPM) have jointly published a new code of practice (CoP), TRS483, for the dosimetry of small static photon fields used in external beam radiotherapy. It gave recommendations on how to perform reference dosimetry in nonstandard machine-specific reference (msr) fields and measure field output factors in small fields. The purpose of this work was to perform a dosimetric evaluation of the recommendations given in this CoP. METHODS All measurements were done in a Varian TrueBeam™ STx linear accelerator. Five ionization chambers were used for beam quality measurements, four Farmer type ionization chambers for performing reference dosimetry and two diodes for performing field output factor measurements. Field output factor measurements were done for fourteen field sizes (ranging from 0.5 cm × 0.5 cm to 10 cm × 10 cm). Beam energies used were: 6 MV WFF, 6 MV FFF, 10 MV WFF, and 10 MV FFF. Where appropriate, results from this study were compared with those obtained from the recommendations given in the IAEA TRS398 CoP, AAPM TG51 and TG51 Addendum protocols. RESULTS Beam quality measurements show that for all beam energies and for equivalent square msr field sizes ranging from 4 cm × 4 cm to 10 cm × 10 cm, agreement between calculated and measured values of TPR20,10 (10) was within 0.6%. When %dd(10,10)X was used as beam quality specifier, the agreement was found to be within 0.8%. Absorbed dose to water per unit monitor unit at the depth of maximum dose zmax in a beam of quality Q, Dw,Qzmax/MU, was determined using both %dd(10,10)X and TPR20,10 (10) as beam quality specifiers. Measured ratios of Dw,Q (zmax )/MU, determined using the two approaches, ranged between 0.999 and 1.000 for all the beam energies investigated. Comparison with TRS398, TG51 and TG51 addendum protocols show that depending on beam energy, the mean values of the ratios TRS398/TRS483, TG51/TRS483, and TG51 Addendum/TRS483 of Dw,Q (zmax )/MU determined using both approaches show excellent agreement with TRS398 CoP (to within 0.05%); agreement with TG51 and TG51 addendum was to within 0.3% for all four beam energies investigated. Field output factors, determined using the two methods recommended in the TRS483 CoP, showed excellent agreement between the two methods. For the 1 cm collimator field size, the mean value of the field output factor obtained from an average of the two detectors investigated was found to be 2% lower than the mean value of the uncorrected ratio of readings. CONCLUSION For beams with and without flattening filters, the values of Dw,Q (zmax )/MU obtained following the new CoP are found to be consistent with those obtained using TRS398, TG51 and TG51 addendum protocols to within 0.3%. Field output factors for small beams can be improved when the correction factors for different detectors included in TRS483 are appropriately incorporated into their dosimetry.
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Affiliation(s)
- M Saiful Huq
- Division of Medical Physics, Department of Radiation Oncology, University of Pittsburgh School of Medicine and UPMC Hillman Cancer Center, Pittsburgh, PA 15232, USA
| | - Min-Sig Hwang
- Division of Medical Physics, Department of Radiation Oncology, University of Pittsburgh School of Medicine and UPMC Hillman Cancer Center, Pittsburgh, PA 15232, USA
| | - Troy P Teo
- Division of Medical Physics, Department of Radiation Oncology, University of Pittsburgh School of Medicine and UPMC Hillman Cancer Center, Pittsburgh, PA 15232, USA
| | - Si Young Jang
- Division of Medical Physics, Department of Radiation Oncology, University of Pittsburgh School of Medicine and UPMC Hillman Cancer Center, Pittsburgh, PA 15232, USA
| | - Dwight E Heron
- Division of Medical Physics, Department of Radiation Oncology, University of Pittsburgh School of Medicine and UPMC Hillman Cancer Center, Pittsburgh, PA 15232, USA
| | - Ronald J Lalonde
- Division of Medical Physics, Department of Radiation Oncology, University of Pittsburgh School of Medicine and UPMC Hillman Cancer Center, Pittsburgh, PA 15232, USA
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Howitz S, Schwedas M, Wiezorek T, Zink K. Experimental and Monte Carlo-based determination of the beam quality specifier for TomoTherapyHD treatment units. Z Med Phys 2017; 28:142-149. [PMID: 29031915 DOI: 10.1016/j.zemedi.2017.09.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 08/08/2017] [Accepted: 09/18/2017] [Indexed: 10/18/2022]
Abstract
Reference dosimetry by means of clinical linear accelerators in high-energy photon fields requires the determination of the beam quality specifier TPR20,10, which characterizes the relative particle flux density of the photon beam. The measurement of TPR20,10 has to be performed in homogenous photon beams of size 10×10cm2 with a focus-detector distance of 100cm. These requirements cannot be fulfilled by TomoTherapy treatment units from Accuray. The TomoTherapy unit provides a flattening-filter-free photon fan beam with a maximum field width of 40cm and field lengths of 1.0cm, 2.5cm and 5.0cm at a focus-isocenter distance of 85cm. For the determination of the beam quality specifier from measurements under nonstandard reference conditions Sauer and Palmans proposed experiment-based fit functions. Moreover, Sauer recommends considering the impact of the flattening-filter-free beam on the measured data. To verify these fit functions, in the present study a Monte Carlo based model of the treatment head of a TomoTherapyHD unit was designed and commissioned with existing beam data of our clinical TomoTherapy machine. Depth dose curves and dose profiles were in agreement within 1.5% between experimental and Monte Carlo-based data. Based on the fit functions from Sauer and Palmans the beam quality specifier TPR20,10 was determined from field sizes 5×5cm2, 10×5cm2, 20×5cm2 and 40×5cm2 based on dosimetric measurements and Monte Carlo simulations. The mean value from all experimental values of TPR20,10 resulted in TPR20,10¯=0.635±0.4%. The impact of the non-homogenous field due to the flattening-filter-free beam was negligible for field sizes below 20×5cm2. The beam quality specifier calculated by Monte Carlo simulations was TPR20,10=0.628 and TPR20,10=0.631 for two different calculation methods. The stopping power ratio water-to-air sw,aΔ directly depends on the beam quality specifier. The value determined from all experimental TPR20,10 data was sw,aΔ=1.126±0.1%, which is in excellent agreement with the value directly calculated by Monte Carlo simulations. The agreement is a good indication that the equations proposed by Sauer and Palmans are able to calculate the beam quality specifier under reference conditions from measurements in arbitrary photon field sizes with high accuracy and are applicable for the TomoTherapyHD treatment unit.
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Affiliation(s)
- Simon Howitz
- University Hospital Jena, Department of Radiation Oncology, Germany; Institute for Medical Physics and Radiation Protection IMPS, University of Applied Science - THM, Giessen, Germany; Philipps-University, Marburg, Germany.
| | - Michael Schwedas
- University Hospital Jena, Department of Radiation Oncology, Germany
| | - Tilo Wiezorek
- University Hospital Jena, Department of Radiation Oncology, Germany
| | - Klemens Zink
- Institute for Medical Physics and Radiation Protection IMPS, University of Applied Science - THM, Giessen, Germany; University Medical Center Giessen-Marburg, Department of Radiation Oncology, Germany; Frankfurt Institute for Advanced Studies (FIAS), Frankfurt, Germany
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Lechner W, Kuess P, Georg D, Palmans H. Equivalent (uniform) square field sizes of flattening filter free photon beams. ACTA ACUST UNITED AC 2017; 62:7694-7713. [DOI: 10.1088/1361-6560/aa83f5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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7
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Pantelis E, Moutsatsos A, Zourari K, Kilby W, Antypas C, Papagiannis P, Karaiskos P, Georgiou E, Sakelliou L. On the implementation of a recently proposed dosimetric formalism to a robotic radiosurgery system. Med Phys 2016; 37:2369-79. [DOI: 10.1118/1.3404289] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
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Kuess P, Georg D, Palmans H, Lechner W. Technical Note: On the impact of the incident electron beam energy on the primary dose component of flattening filter free photon beams. Med Phys 2016; 43:4507. [PMID: 27487867 DOI: 10.1118/1.4954849] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE For commercially available linear accelerators (Linacs), the electron energies of flattening filter free (FFF) and flattened (FF) beams are either identical or the electron energy of the FFF beam is increased to match the percentage depth dose curve (PDD) of the FF beam (in reference geometry). This study focuses on the primary dose components of FFF beams for both kinds of settings, studied on the same Linac. METHODS The measurements were conducted on a VersaHD Linac (Elekta, Crawley, UK) for both FF and FFF beams with nominal energies of 6 and 10 MV. In the clinical setting of the VersaHD, the energy of FFFM (Matched) beams is set to match the PDDs of the FF beams. In contrast the incident electron beam of the FFFU beam was set to the same energy as for the FF beam. Half value layers (HVLs) and a dual parameter beam quality specifier (DPBQS) were determined. RESULTS For the 6 MV FFFM beam, HVL and DPBQS values were very similar compared to those of the 6 MV FF beam, while for the 10 MV FFFM and FF beams, only %dd(10)x and HVL values were comparable (differences below 1.5%). This shows that matching the PDD at one depth does not guarantee other beam quality dependent parameters to be matched. For FFFU beams, all investigated beam quality specifiers were significantly different compared to those for FF beams of the same nominal accelerator potential. The DPBQS of the 6 MV FF and FFFM beams was equal within the measurement uncertainty and was comparable to published data of a machine with similar TPR20,10 and %dd(10)x. In contrast to that, the DPBQS's two parameters of the 10 MV FFFM beam were substantially higher compared to those for the 10 MV FF beam. CONCLUSIONS PDD-matched FF and FFF beams of both nominal accelerator potentials were observed to have similar HVL values, indicating similarity of their primary dose components. Using the DPBQS revealed that the mean attenuation coefficient was found to be the same within the uncertainty of 0.8% for 6 MV FF and 6 MV FFFM beams, while for 10 MV beams, they differed by 6.4%. This shows that the DPBQS can provide a differentiation of photon beam characteristics that would remain hidden by the use of a single beam quality specifier, such as %dd(10)x or HVL.
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Affiliation(s)
- Peter Kuess
- Department of Radiation Oncology, Division Medical Physics, Medical University Vienna, Vienna 1090, Austria and Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna 1090, Austria
| | - Dietmar Georg
- Department of Radiation Oncology, Division Medical Physics, Medical University Vienna, Vienna 1090, Austria and Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna 1090, Austria
| | - Hugo Palmans
- EBG MedAustron GmbH, Wiener Neustadt 2700, Austria and National Physical Laboratory, Teddington TW 11 0LW, United Kingdom
| | - Wolfgang Lechner
- Department of Radiation Oncology, Division Medical Physics, Medical University Vienna, Vienna 1090, Austria and Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna 1090, Austria
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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: 108] [Impact Index Per Article: 12.0] [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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Muralidhar KR. Derivation of equations to define inflection point and its analysis in flattening filter free photon beams based on the principle of polynomial function. INTERNATIONAL JOURNAL OF CANCER THERAPY AND ONCOLOGY 2014. [DOI: 10.14319/ijcto.0301.5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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A comparison of phantom scatter from flattened and flattening filter free high-energy photon beams. Med Dosim 2014; 40:58-63. [PMID: 25454113 DOI: 10.1016/j.meddos.2014.10.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Revised: 08/13/2014] [Accepted: 10/03/2014] [Indexed: 11/21/2022]
Abstract
Flattening filter free (FFF) photon beams have different dosimetric properties from those of flattened beams. The aim of this work was to characterize the collimator scatter (Sc) and total scatter (Scp) from 3 FFF beams of differing quality indices and use the resulting mathematical fits to generate phantom scatter (Sp) data. The similarities and differences between Sp of flattened and FFF beams are described. Sc and Scp data were measured for 3 flattened and 3 FFF high-energy photon beams (Varian 6 and 10MV and Elekta 6MV). These data were fitted to logarithmic power law functions with 4 numerical coefficients. The agreement between our experimentally determined flattened beam Sp and published data was within ± 1.2% for all 3 beams investigated and all field sizes from 4 × 4 to 40 × 40cm(2). For the FFF beams, Sp was only within 1% of the same flattened beam published data for field sizes between 6 × 6 and 14 × 14cm(2). Outside this range, the differences were much greater, reaching - 3.2%, - 4.5%, and - 4.3% for the fields of 40 × 40cm(2) for the Varian 6-MV, Varian 10-MV, and Elekta 6-MV FFF beams, respectively. The FFF beam Sp increased more slowly with increasing field size than that of the published and measured flattened beam of a similar reference field size quality index, i.e., there is less Phantom Scatter than that found with flattened beams for a given field size. This difference can be explained when the fluence profiles of the flattened and FFF beams are considered. The FFF beam has greatly reduced fluence off axis, especially as field size increases, compared with the flattened beam profile; hence, less scatter is generated in the phantom reaching the central axis.
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Dalaryd M, Knöös T, Ceberg C. Combining tissue-phantom ratios to provide a beam-quality specifier for flattening filter free photon beams. Med Phys 2014; 41:111716. [DOI: 10.1118/1.4898325] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Krauss A, Kapsch RP. Experimental determination ofkQfactors for cylindrical ionization chambers in 10 cm × 10 cm and 3 cm × 3 cm photon beams from 4 MV to 25 MV. Phys Med Biol 2014; 59:4227-46. [DOI: 10.1088/0031-9155/59/15/4227] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Benmakhlouf H, Sempau J, Andreo P. Output correction factors for nine small field detectors in 6 MV radiation therapy photon beams: A PENELOPE Monte Carlo study. Med Phys 2014; 41:041711. [DOI: 10.1118/1.4868695] [Citation(s) in RCA: 108] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Gago-Arias A, Antolín E, Fayos-Ferrer F, Simón R, González-Castaño DM, Palmans H, Sharpe P, Gómez F, Pardo-Montero J. Correction factors for ionization chamber dosimetry in CyberKnife: Machine-specific, plan-class, and clinical fields. Med Phys 2013; 40:011721. [DOI: 10.1118/1.4773047] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Fogliata A, Garcia R, Knoos T, Nicolini G, Clivio A, Vanetti E, Khamphan C, Cozzi L. Definition of parameters for quality assurance of flattening filter free (FFF) photon beams in radiation therapy. Med Phys 2012; 39:6455-64. [PMID: 23039680 DOI: 10.1118/1.4754799] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Flattening filter free (FFF) beams generated by medical linear accelerators have recently started to be used in radiotherapy clinical practice. Such beams present fundamental differences with respect to the standard filter flattened (FF) beams, making the generally used dosimetric parameters and definitions not always viable. The present study will propose possible definitions and suggestions for some dosimetric parameters for use in quality assurance of FFF beams generated by medical linacs in radiotherapy. METHODS The main characteristics of the photon beams have been analyzed using specific data generated by a Varian TrueBeam linac having both FFF and FF beams of 6 and 10 MV energy, respectively. RESULTS Definitions for dose profile parameters are suggested starting from the renormalization of the FFF with respect to the corresponding FF beam. From this point the flatness concept has been translated into one of "unflatness" and other definitions have been proposed, maintaining a strict parallelism between FFF and FF parameter concepts. CONCLUSIONS Ideas for quality controls used in establishing a quality assurance program when introducing FFF beams into the clinical environment are given here, keeping them similar to those used for standard FF beams. By following the suggestions in this report, the authors foresee that the introduction of FFF beams into a clinical radiotherapy environment will be as safe and well controlled as standard beam modalities using the existing guidelines.
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Affiliation(s)
- A Fogliata
- Oncology Institute of Southern Switzerland, Medical Physics Unit, Bellinzona CH-6500, Switzerland.
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Palmans H. Determination of the beam quality index of high-energy photon beams under nonstandard reference conditions. Med Phys 2012; 39:5513-9. [DOI: 10.1118/1.4745565] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Gago-Arias A, Rodríguez-Romero R, Sánchez-Rubio P, Miguel González-Castaño D, Gómez F, Núñez L, Palmans H, Sharpe P, Pardo-Montero J. Correction factors for A1SL ionization chamber dosimetry in TomoTherapy: Machine-specific, plan-class, and clinical fields. Med Phys 2012; 39:1964-70. [DOI: 10.1118/1.3692181] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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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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Sauer OA, Wilbert J. Functional representation of tissue phantom ratios for photon fields. Med Phys 2009; 36:5444-50. [DOI: 10.1118/1.3250867] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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