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Shaw M, Lye J, Alves A, Lehmann J, Sanagou M, Geso M, Brown R. Measuring dose in lung identifies peripheral tumour dose inaccuracy in SBRT audit. Phys Med 2023; 112:102632. [PMID: 37406592 DOI: 10.1016/j.ejmp.2023.102632] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 04/25/2023] [Accepted: 06/21/2023] [Indexed: 07/07/2023] Open
Abstract
PURPOSE Stereotactic Body Radiotherapy (SBRT) for lung tumours has become a mainstay of clinical practice worldwide. Measurements in anthropomorphic phantoms enable verification of patient dose in clinically realistic scenarios. Correction factors for reporting dose to the tissue equivalent materials in a lung phantom are presented in the context of a national dosimetry audit for SBRT. Analysis of dosimetry audit results is performed showing inaccuracies of common dose calculation algorithms in soft tissue lung target, inhale lung material and at tissue interfaces. METHODS Monte Carlo based simulation of correction factors for detectors in non-water tissue was performed for the soft tissue lung target and inhale lung materials of a modified CIRS SBRT thorax phantom. The corrections were determined for Gafchromic EBT3 Film and PTW 60019 microDiamond detectors used for measurements of 168 SBRT lung plans in an end-to-end dosimetry audit. Corrections were derived for dose to medium (Dm,m) and dose to water (Dw,w) scenarios. RESULTS Correction factors were up to -3.4% and 9.2% for in field and out of field lung respectively. Overall, application of the correction factors improved the measurement-to-plan dose discrepancy. For the soft tissue lung target, agreement between planned and measured dose was within average of 3% for both film and microDiamond measurements. CONCLUSIONS The correction factors developed for this work are provided for clinical users to apply to commissioning measurements using a commercially available thorax phantom where inhomogeneity is present. The end-to-end dosimetry audit demonstrates dose calculation algorithms can underestimate dose at lung tumour/lung tissue interfaces by an average of 2-5%.
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Affiliation(s)
- Maddison Shaw
- Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Melbourne, Australia; School of Health and Biomedical Sciences, RMIT University, Melbourne, Australia.
| | - Jessica Lye
- Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Melbourne, Australia; Olivia Newton John Cancer Wellness and Research Centre, Austin Health, Australia
| | - Andrew Alves
- Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Melbourne, Australia
| | - Joerg Lehmann
- Department of Radiation Oncology, Calvary Mater Newcastle, Newcastle, Australia; School of Science, RMIT University, Melbourne, Australia; School of Mathematical and Physical Sciences, University of Newcastle, Australia; Institute of Medical Physics, University of Sydney, Australia
| | - Masoumeh Sanagou
- Australian Radiation Protection and Nuclear Safety Agency, Melbourne, Australia
| | - Moshi Geso
- School of Health and Biomedical Sciences, RMIT University, Melbourne, Australia
| | - Rhonda Brown
- Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Melbourne, Australia
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Li Y, Wu W, Yuan W, Chai L, Tang F, He R, Lu Y, Zhang Y, Lu Y, Wang L, Wang M, Zhang X, Zhang L. A method for selecting reference beam model of VMAT plans with three 6MV beam-matched linear accelerators during radiation oncology. Sci Rep 2023; 13:10131. [PMID: 37349531 PMCID: PMC10287655 DOI: 10.1038/s41598-023-36930-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Accepted: 06/13/2023] [Indexed: 06/24/2023] Open
Abstract
Our objective was to provide a method for selecting reference beam model and evaluating the dosimetric accuracy of volumetric modulated arc therapy (VMAT) plans delivered on three Elekta beam-matched linacs during radiation oncology. Beam data was measured on three beam-matched linacs including Synergy1, Synergy2 and VersaHD. For eighteen lung and esophagus cases, fifty-four plans were generated using VMAT technique with three linac beam models respectively for point dose measurement and three-dimensional dose measurement. Each VMAT plan was executed sequentially on three linacs respectively. Measurement results were compared with treatment planning system (TPS) calculation results for all VMAT plans. Among three beam-matched linacs, discrepancy in beam output factor, percentage depth dose at 5 cm, 10 cm, 20 cm depth and MLC leaf offset are all within 1% except 20 × 20 cm2 and 30 × 30 cm2 field sizes, and discrepancy in beam profile is all within 2%. With comparison between measurement result and TPS calculation result, the absolute dose deviations are within the range of ± 3%, and the gamma passing rates are all over 95% for all VMAT plans, which are within the tolerance of clinical acceptability. Compared with all plans delivered on Synegy1 and VersaHD, the point dose discrepancy between measured results and TPS calculated results for plans delivered on Synergy2 is smallest, and the gamma passing rate between measured results and TPS calculated results for plans delivered on Synergy2 is highest. The beam-matched linacs demonstrate good agreement between measurement result and TPS calculation result for VMAT plans. The method can be used for selecting reference beam model for VMAT plans.
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Affiliation(s)
- Yi Li
- Department of Radiation Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, China
| | - Wenjing Wu
- Department of Radiological Health, Xi'an Center for Disease Control and Prevention, Xi'an, 710054, China.
| | - Wei Yuan
- Department of Radiation Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, China
| | - Linyan Chai
- Department of Radiation Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, China
| | - Fengwen Tang
- Department of Radiation Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, China
| | - Ruixin He
- Department of Radiation Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, China
| | - Yongkai Lu
- Department of Radiation Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, China
| | - Yuemei Zhang
- Department of Radiation Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, China
| | - Yongkai Lu
- Department of Radiation Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, China
| | - Long Wang
- Department of Radiation Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, China
| | - Mengfei Wang
- Department of Radiation Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, China
| | - Xiaozhi Zhang
- Department of Radiation Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, China
| | - Long Zhang
- Department of Radiation Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, China.
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Hughes J, Lye JE, Kadeer F, Alves A, Shaw M, Supple J, Keehan S, Gibbons F, Lehmann J, Kron T. Calculation algorithms and penumbra: Underestimation of dose in organs at risk in dosimetry audits. Med Phys 2021; 48:6184-6197. [PMID: 34287963 DOI: 10.1002/mp.15123] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 06/27/2021] [Accepted: 07/07/2021] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The aim of this study is to investigate overdose to organs at risk (OARs) observed in dosimetry audits in Monte Carlo (MC) algorithms and Linear Boltzmann Transport Equation (LBTE) algorithms. The impact of penumbra modeling on OAR dose was assessed with the adjustment of MC modeling parameters and the clinical relevance of the audit cases was explored with a planning study of spine and head and neck (H&N) patient cases. METHODS Dosimetric audits performed by the Australian Clinical Dosimetry Service (ACDS) of 43 anthropomorphic spine plans and 1318 C-shaped target plans compared the planned dose to doses measured with ion chamber, microdiamond, film, and ion chamber array. An MC EGSnrc model was created to simulate the C-shape target case. The electron cut-off energy Ecut(kinetic) was set at 500, 200, and 10 keV, and differences between 1 and 3 mm voxel were calculated. A planning study with 10 patient stereotactic body radiotherapy (SBRT) spine plans and 10 patient H&N plans was calculated in both Acuros XB (AXB) v15.6.06 and Anisotropic Analytical Algorithm (AAA) v15.6.06. The patient contour was overridden to water as only the penumbral differences between the two different algorithms were under investigation. RESULTS The dosimetry audit results show that for the SBRT spine case, plans calculated in AXB are colder than what is measured in the spinal cord by 5%-10%. This was also observed for other audit cases where a C-shape target is wrapped around an OAR where the plans were colder by 3%-10%. Plans calculated with Monaco MC were colder than measurements by approximately 7% with the OAR surround by a C-shape target, but these differences were not noted in the SBRT spine case. Results from the clinical patient plans showed that the AXB was on average 7.4% colder than AAA when comparing the minimum dose in the spinal cord OAR. This average difference between AXB and AAA reduced to 4.5% when using the more clinically relevant metric of maximum dose in the spinal cord. For the H&N plans, AXB was cooler on average than AAA in the spinal cord OAR (1.1%), left parotid (1.7%), and right parotid (2.3%). The EGSnrc investigation also noted similar, but smaller differences. The beam penumbra modeled by Ecut(kinetic) = 500 keV was steeper than the beam penumbra modeled by Ecut(kinetic) = 10 keV as the full scatter is not accounted for, which resulted in less dose being calculated in a central OAR region where the penumbra contributes much of the dose. The dose difference when using 2.5 mm voxels of the center of the OAR between 500 and 10 keV was 3%, reducing to 1% between 200 and 10 keV. CONCLUSIONS Lack of full penumbral modeling due to approximations in the algorithms in MC based or LBTE algorithms are a contributing factor as to why these algorithms under-predict the dose to OAR when the treatment volume is wrapped around the OAR. The penumbra modeling approximations also contribute to AXB plans predicting colder doses than AAA in areas that are in the vicinity of beam penumbra. This effect is magnified in regions where there are many beam penumbras, for example in the spinal cord for spine SBRT cases.
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Affiliation(s)
- Jeremy Hughes
- Australian Clinical Dosimetry Service, ARPANSA, Yallambie, Victoria, Australia.,Physical Sciences, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Jessica Elizabeth Lye
- Australian Clinical Dosimetry Service, ARPANSA, Yallambie, Victoria, Australia.,Physical Sciences, Olivia Newton-John Cancer Wellness Centre, Heidelberg, Victoria, Australia
| | - Fayz Kadeer
- Australian Clinical Dosimetry Service, ARPANSA, Yallambie, Victoria, Australia
| | - Andrew Alves
- Australian Clinical Dosimetry Service, ARPANSA, Yallambie, Victoria, Australia
| | - Maddison Shaw
- Australian Clinical Dosimetry Service, ARPANSA, Yallambie, Victoria, Australia.,Applied Sciences Physics Department, RMIT University, Melbourne, Victoria, Australia
| | - Jeremy Supple
- Australian Clinical Dosimetry Service, ARPANSA, Yallambie, Victoria, Australia
| | - Stephanie Keehan
- Australian Clinical Dosimetry Service, ARPANSA, Yallambie, Victoria, Australia.,Alfred Health Radiation Oncology, The Alfred Hospital, Melbourne, Victoria, Australia
| | - Francis Gibbons
- Australian Clinical Dosimetry Service, ARPANSA, Yallambie, Victoria, Australia.,Physical Sciences, Sunshine Coast University Hospital, Birtinya, Queensland, Australia
| | - Joerg Lehmann
- Applied Sciences Physics Department, RMIT University, Melbourne, Victoria, Australia.,Department of Radiation Oncology, Calvary Mater Newcastle, Newcastle, New South Wales, Australia.,School of Mathematical and Physical Sciences, University of Newcastle, Callaghan, New South Wales, Australia.,Institute of Medical Physics, University of Sydney, Camperdown, New South Wales, Australia
| | - Tomas Kron
- Physical Sciences, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.,Applied Sciences Physics Department, RMIT University, Melbourne, Victoria, Australia
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Shaw M, Lye J, Alves A, Hanlon M, Lehmann J, Supple J, Porumb C, Williams I, Geso M, Brown R. Measuring the dose in bone for spine stereotactic body radiotherapy. Phys Med 2021; 84:265-273. [PMID: 33773909 DOI: 10.1016/j.ejmp.2021.03.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 02/08/2021] [Accepted: 03/05/2021] [Indexed: 11/29/2022] Open
Abstract
PURPOSE Current quality assurance of radiotherapy involving bony regions generally utilises homogeneous phantoms and dose calculations, ignoring the challenges of heterogeneities with dosimetry problems likely occurring around bone. Anthropomorphic phantoms with synthetic bony materials enable realistic end-to-end testing in clinical scenarios. This work reports on measurements and calculated corrections required to directly report dose in bony materials in the context of comprehensive end-to-end dosimetry audit measurements (63 plans, 6 planning systems). MATERIALS AND METHODS Radiochromic film and microDiamond measurements were performed in an anthropomorphic spine phantom containing bone equivalent materials. Medium dependent correction factors, kmed, were established using 6 MV and 10 MV Linear Accelerator Monte Carlo simulations to account for the detectors being calibrated in water, but measuring in regions of bony material. Both cortical and trabecular bony material were investigated for verification of dose calculations in dose-to-medium (Dm,m) and dose-to-water (Dw,w) scenarios. RESULTS For Dm,m calculations, modelled correction factors for cortical and trabecular bone in film measurements, and for trabecular bone in microDiamond measurements were 0.875(±0.1%), 0.953(±0.3%) and 0.962(±0.4%), respectively. For Dw,w calculations, the corrections were 0.920(±0.1%), 0.982(±0.3%) and 0.993(±0.4%), respectively. In the audit, application of the correction factors improves the mean agreement between treatment plans and measured microDiamond dose from -2.4%(±3.9%) to 0.4%(±3.7%). CONCLUSION Monte Carlo simulations provide a method for correcting the dose measured in bony materials allowing more accurate comparison with treatment planning system doses. In verification measurements, algorithm specific correction factors should be applied to account for variations in bony material for calculations based on Dm,m and Dw,w.
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Affiliation(s)
- Maddison Shaw
- Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Melbourne, Australia; School of Health and Biomedical Sciences, RMIT University, Melbourne, Australia.
| | - Jessica Lye
- Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Melbourne, Australia; Olivia Newton John Cancer Wellness Centre, Melbourne, Australia
| | - Andrew Alves
- Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Melbourne, Australia
| | - Maximilian Hanlon
- Primary Standards Dosimetry Laboratory, ARPANSA, Melbourne, Australia
| | - Joerg Lehmann
- Department of Radiation Oncology, Calvary Mater Newcastle, Newcastle, Australia; School of Science, RMIT University, Melbourne, Australia; School of Mathematical and Physical Sciences, University of Newcastle, Australia; Institute of Medical Physics, University of Sydney, Australia
| | - Jeremy Supple
- Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Melbourne, Australia
| | - Claudiu Porumb
- Alfred Health Radiation Oncology, The Alfred Hospital, Melbourne, Australia
| | - Ivan Williams
- Australian Radiation Protection and Nuclear Safety Agency, Melbourne, Australia
| | - Moshi Geso
- School of Health and Biomedical Sciences, RMIT University, Melbourne, Australia
| | - Rhonda Brown
- Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Melbourne, Australia
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5
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Momin S, Gräfe J, Georgiou K, Khan R. Simultaneous optimization of mixed photon energy beams in volumetric modulated arc therapy. Med Phys 2019; 46:3844-3863. [PMID: 31276215 DOI: 10.1002/mp.13700] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 06/25/2019] [Accepted: 06/25/2019] [Indexed: 11/12/2022] Open
Abstract
PURPOSE Despite the availability of multiple energy photon beams on clinical linear accelerators, volumetric modulated arc therapy (VMAT) optimization is currently limited to a single photon beam. The purpose of this work was to present a proof-of-principle study on an algorithm for simultaneous optimization of mixed photon beams for VMAT (MP - VMAT), utilizing an additional photon energy as an additional degree of freedom. METHODS The MP - VMAT optimization algorithm is presented as a two-step heuristic approach. First, a convex linear programming problem is solved for simultaneous optimization of nonuniform dual energy intensity maps (DEIMs) for an angular resolution of 36 equi-spaced beam segments. Subsequently, for a given gantry speed schedule, the second step aims to best replicate each DEIM by dispersing MP - VMAT apertures along with their corresponding intensities over their respective beam segment. This constitutes a nonlinear problem, which is linearized using McCormick relaxation. The final large-scale mixed integer linear programming (MILP) dispersion model ensures a contiguous and smooth transition of multileaf collimators (MLCs) from one beam segment to the next. To demonstrate the proof-of-principle, we first compared the quality of dose volume histograms (DVHs) of MP - VMAT to the ones calculated from 36 DEIMs following the step 1 of MP - VMAT model. Additionally, the MLCs motion violations were evaluated for the complete 360° gantry rotation for gantry speeds ranging from 1 to 6° per second. The quality of MP - VMAT plans were also compared to conventional single energy VMAT plans via DVH, homogeneity index (HI), and conformity number (CN) for two prostate cases. RESULTS The MP - VMAT model resulted in a successful convergence of DVHs relative to the ones from DEIMs with HI and CN of 0.05 and 0.9, respectively, for 1 and 2° per second gantry speed schedules. In replicating the DEIMs, the MILP dispersion model was able to achieve optimality for almost all segments at 1° per second and for majority of segments at 2° per second. Although, DVHs quality was slightly inferior for 3° per second gantry speed, the target conformity of 0.9 and heterogeneity of 0.08 were achievable even for the suboptimal solutions. No violations of the MLC constraints were observed throughout the complete 360 degree arc rotation for any gantry speed schedule, thereby confirming MILP dispersion model. For the two prostate cases, the results showed MP - VMAT's ability to achieve substantial dose reduction in rectum and bladder while yielding similar target coverage compared to single energy VMAT. Bladder volume was mostly spared in low-to-intermediate dose region. Rectal volume sparing (3 % to 12 %) was observed in the intermediate (from 25 to 50 Gy) dose region. CONCLUSION We demonstrate the first formalism of a large-scale simultaneous optimization of mixed photon energy beams for VMAT. Dosimetric comparison of MP - VMAT to single energy VMAT demonstrated potential advantages of using mixed photon energy beams for prostate plans, thus providing an impetus for further testing on a large clinical cohort.
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Affiliation(s)
- Shadab Momin
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, USA.,Department of Physics, Ryerson University, Toronto, ON, Canada
| | - James Gräfe
- Department of Physics, Ryerson University, Toronto, ON, Canada
| | | | - Rao Khan
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, USA
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Evaluation of beam matching accuracy among six linacs from the same vendor. Radiol Phys Technol 2018; 11:423-433. [PMID: 30269310 DOI: 10.1007/s12194-018-0480-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Revised: 09/21/2018] [Accepted: 09/24/2018] [Indexed: 10/28/2022]
Abstract
The purpose of this study was to evaluate the dosimetric variation among six non-beam-matched Varian linacs using different techniques for the same plans. Six non-beam-matched Varian machines, comprising two Clinac iX, two 600 C/D (Unique), and two True Beam Tx photon 6 MV X-ray devices were acquired. Sixty patients with of head and neck (H&N; 30) and pelvic (30) treatment sites were chosen. For all 60 patients, three-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT), and volumetric-modulated radiotherapy (VMAT) plans were generated for the Clinac iX-1 device; all plans were migrated to the remaining machines, using the eclipse treatment planning system without any modification. The dosimetric variation among the six machines for each target volume and organ at risk was recorded and analyzed. In H&N cases, the maximum variation among the six machines with 3DCRT, IMRT, and VMAT was 2.57%, 2.6%, and 2.6%, respectively. In pelvic cases, the maximum variation among the six machines with 3DCRT, IMRT, and VMAT was 2.2%, 1.95%, and 2.05%, respectively. Our overall results show that dosimetric variation, while interchanging the plans among the six machines at phantom and patient levels, remains within the limits of clinical acceptability. The noted variation was not correlated with any of these treatment techniques: 3DCRT, IMRT, or VMAT.
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de Prez L, de Pooter J, Jansen B, Perik T, Wittkämper F. Comparison of k Q factors measured with a water calorimeter in flattening filter free (FFF) and conventional flattening filter (cFF) photon beams. Phys Med Biol 2018; 63:045023. [PMID: 29461974 DOI: 10.1088/1361-6560/aaaa93] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Recently flattening filter free (FFF) beams became available for application in modern radiotherapy. There are several advantages of FFF beams over conventional flattening filtered (cFF) beams, however differences in beam spectra at the point of interest in a phantom potentially affect the ion chamber response. Beams are also non-uniform over the length of a typical reference ion chamber and recombination is usually larger. Despite several studies describing FFF beam characteristics, only a limited number of studies investigated their effect on k Q factors. Some of those studies predicted significant discrepancies in k Q factors (0.4% up to 1.0%) if TPR20,10 based codes of practice (CoPs) were to be used. This study addresses the question to which extent k Q factors, based on a TPR20,10 CoP, can be applied in clinical reference dosimetry. It is the first study that compares k Q factors measured directly with an absorbed dose to water primary standard in FFF-cFF pairs of clinical photon beams. This was done with a transportable water calorimeter described elsewhere. The measurements corrected for recombination and beam radial non-uniformity were performed in FFF-cFF beam pairs at 6 MV and 10 MV of an Elekta Versa HD for a selection of three different Farmer-type ion chambers (eight serial numbers). The ratio of measured k Q factors of the FFF-cFF beam pairs were compared with the TPR20,10 CoPs of the NCS and IAEA and the %dd(10) x CoP of the AAPM. For the TPR20,10 based CoPs differences less than 0.23% were found in k Q factors between the corresponding FFF-cFF beams with standard uncertainties smaller than 0.35%, while for the %dd(10) x these differences were smaller than 0.46% and within the expanded uncertainty of the measurements. Based on the measurements made with the equipment described in this study the authors conclude that the k Q factors provided by the NCS-18 and IAEA TRS-398 codes of practice can be applied for flattening filter free beams without additional correction. However, existing codes of practice cannot be applied ignoring the significant volume averaging effect of the FFF beams over the ion chamber cavity. For this a corresponding volume averaging correction must be applied.
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Affiliation(s)
- Leon de Prez
- VSL-Dutch Metrology Institute, Delft, Netherlands
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First proof of bismuth oxide nanoparticles as efficient radiosensitisers on highly radioresistant cancer cells. Phys Med 2016; 32:1444-1452. [PMID: 28327297 DOI: 10.1016/j.ejmp.2016.10.015] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2016] [Revised: 09/14/2016] [Accepted: 10/18/2016] [Indexed: 02/05/2023] Open
Abstract
This study provides the first proof of the novel application of bismuth oxide as a radiosensitiser. It was shown that on the highly radioresistant 9L gliosarcoma cell line, bismuth oxide nanoparticles sensitise to both kilovoltage (kVp) or megavoltage (MV) X-rays radiation. 9L cells were exposed to a concentration of 50μg.mL-1 of nanoparticle before irradiation at 125kVp and 10MV. Sensitisation enhancement ratios of 1.48 and 1.25 for 125kVp and 10MV were obtained in vitro, respectively. The radiation enhancement of the nanoparticles is postulated to be a combination of the high Z nature of the bismuth (Z=83), and the surface chemistry. Monte Carlo simulations were performed to elucidate the physical interactions between the incident radiation and the nanoparticle. The results of this work show that Bi2O3 nanoparticles increase the radiosensitivity of 9L gliosarcoma tumour cells for both kVp and MV energies. Monte Carlo simulations demonstrate the advantage of a platelet morphology.
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Lye JE, Butler DJ, Oliver CP, Alves A, Lehmann J, Gibbons FP, Williams IM. Comparison between the TRS-398 code of practice and the TG-51 dosimetry protocol for flattening filter free beams. Phys Med Biol 2016; 61:N362-72. [DOI: 10.1088/0031-9155/61/14/n362] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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10
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Didi S, Moussa A, Yahya T, Mustafa Z. Simulation of the 6 MV Elekta Synergy Platform linac photon beam using Geant4 Application for Tomographic Emission. J Med Phys 2015; 40:136-43. [PMID: 26500399 PMCID: PMC4594382 DOI: 10.4103/0971-6203.165077] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
The present work validates the Geant4 Application for Tomographic Emission Monte Carlo software for the simulation of a 6 MV photon beam given by Elekta Synergy Platform medical linear accelerator treatment head. The simulation includes the major components of the linear accelerator (LINAC) with multi-leaf collimator and a homogeneous water phantom. Calculations were performed for the photon beam with several treatment field sizes ranging from 5 cm × 5 cm to 30 cm × 30 cm at 100 cm distance from the source. The simulation was successfully validated by comparison with experimental distributions. Good agreement between simulations and measurements was observed, with dose differences of about 0.02% and 2.5% for depth doses and lateral dose profiles, respectively. This agreement was also emphasized by the Kolmogorov-Smirnov goodness-of-fit test and by the gamma-index comparisons where more than 99% of the points for all simulations fulfill the quality assurance criteria of 2 mm/2%.
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Affiliation(s)
- Samir Didi
- Department of Physics, Laboratory of Physics of Radiation and Matter, Faculty of Sciences, University Mohammed First, Oujda 60000, Morocco ; Department of Physics, Regional Hassan II Oncology Center, Oujda 60000, Morocco
| | - Abdelilah Moussa
- Department of Physics, Laboratory of Physics of Radiation and Matter, Faculty of Sciences, University Mohammed First, Oujda 60000, Morocco ; Department of Physics, National School of Applied sciences of Al-Hoceima, Morocco
| | - Tayalati Yahya
- Department of Physics, Laboratory of Physics of Radiation and Matter, Faculty of Sciences, University Mohammed First, Oujda 60000, Morocco
| | - Zerfaoui Mustafa
- Department of Physics, Laboratory of Physics of Radiation and Matter, Faculty of Sciences, University Mohammed First, Oujda 60000, Morocco ; Department of Physics, Regional Hassan II Oncology Center, Oujda 60000, Morocco
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Simpson E, Gajewski R, Flower E, Stensmyr R. Experimental validation of the dual parameter beam quality specifier for reference dosimetry in flattening-filter-free (FFF) photon beams. Phys Med Biol 2015; 60:N271-81. [DOI: 10.1088/0031-9155/60/14/n271] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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12
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Wright T, Lye JE, Ramanathan G, Harty PD, Oliver C, Webb DV, Butler DJ. Direct calibration in megavoltage photon beams using Monte Carlo conversion factor: validation and clinical implications. Phys Med Biol 2015; 60:883-904. [PMID: 25565406 DOI: 10.1088/0031-9155/60/2/883] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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13
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Butler DJ, Ramanathan G, Oliver C, Cole A, Lye J, Harty PD, Wright T, Webb DV, Followill DS. Direct megavoltage photon calibration service in Australia. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2014; 37:753-61. [PMID: 25146559 PMCID: PMC4297255 DOI: 10.1007/s13246-014-0293-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 08/12/2014] [Indexed: 10/24/2022]
Abstract
The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) maintains the Australian primary standard of absorbed dose. Until recently, the standard was used to calibrate ionisation chambers only in (60)Co gamma rays. These chambers are then used by radiotherapy clinics to determine linac output, using a correction factor (k Q) to take into account the different spectra of (60)Co and the linac. Over the period 2010-2013, ARPANSA adapted the primary standard to work in megavoltage linac beams, and has developed a calibration service at three photon beams (6, 10 and 18 MV) from an Elekta Synergy linac. We describe the details of the new calibration service, the method validation and the use of the new calibration factors with the International Atomic Energy Agency's TRS-398 dosimetry Code of Practice. The expected changes in absorbed dose measurements in the clinic when shifting from (60)Co to the direct calibration are determined. For a Farmer chamber (model 2571), the measured chamber calibration coefficient is expected to be reduced by 0.4, 1.0 and 1.1 % respectively for these three beams when compared to the factor derived from (60)Co. These results are in overall agreement with international absorbed dose standards and calculations by Muir and Rogers in 2010 of k Q factors using Monte Carlo techniques. The reasons for and against moving to the new service are discussed in the light of the requirements of clinical dosimetry.
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Affiliation(s)
- D J Butler
- Australian Radiation Protection and Nuclear Safety Agency, 619 Lower Plenty Road, Yallambie, VIC, 3085, Australia,
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Lehmann J, Dunn L, Lye JE, Kenny JW, Alves ADC, Cole A, Asena A, Kron T, Williams IM. Angular dependence of the response of the nanoDot OSLD system for measurements at depth in clinical megavoltage beams. Med Phys 2014; 41:061712. [DOI: 10.1118/1.4875698] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Lye J, Dunn L, Kenny J, Lehmann J, Kron T, Oliver C, Butler D, Alves A, Johnston P, Franich R, Williams I. Remote auditing of radiotherapy facilities using optically stimulated luminescence dosimeters. Med Phys 2014; 41:032102. [DOI: 10.1118/1.4865786] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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