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Schofield A, Newall M, Inwood D, Downes S, Corde S. Commissioning of Aktina SRS cones and dosimetric validation of the RayStation photon Monte Carlo dose calculation algorithm. Phys Eng Sci Med 2023; 46:1503-1518. [PMID: 37603132 DOI: 10.1007/s13246-023-01315-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Accepted: 07/27/2023] [Indexed: 08/22/2023]
Abstract
Clinical implementation of SRS cones demands particular experimental care and dosimetric considerations in order to deliver precise and safe radiotherapy to patients. The purpose of this work was to present the commissioning data of recent Aktina cones combined with a 6MV flattened beam produced by an Elekta VersaHD linear accelerator. Additionally, the modelling process, and an assessment of dosimetric accuracy of the RayStation Monte Carlo dose calculation algorithm for cone based SRS was performed. There are currently no studies presenting beam data for this equipment and none that outlines the modelling parameters and validation of dose calculation using RayStation's photon Monte Carlo dose engine with cones. Beam data was measured using an SFD and a microDiamond and benchmarked against EBT3 film for cones of diameter 5-39 mm. Modelling was completed and validated within homogeneous and heterogeneous phantoms. End-to-end image-guided validation was performed using a StereoPHAN™ housing, an SRS MapCHECK and EBT3 film, and calculation time was investigated as a function of statistical uncertainty and field diameter. The TPS calculations agreed with measured data within their estimated uncertainties and clinical treatment plans could be calculated in under a minute. The data presented serves as a reference for others commissioning Aktina stereotactic cones and the modelling parameters serve similarly, while providing a starting point for those commissioning the same TPS algorithm for use with cones. It has been shown in this work that RayStation's Monte Carlo photon dose algorithm performs satisfactorily in the presence of SRS cones.
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Affiliation(s)
- Andy Schofield
- Radiation Oncology Department, Prince of Wales Hospital, Randwick, NSW, 2031, Australia
| | - Matthew Newall
- Radiation Oncology Department, Prince of Wales Hospital, Randwick, NSW, 2031, Australia
| | - Dean Inwood
- Radiation Oncology Department, Prince of Wales Hospital, Randwick, NSW, 2031, Australia
| | - Simon Downes
- Radiation Oncology Department, Prince of Wales Hospital, Randwick, NSW, 2031, Australia
| | - Stéphanie Corde
- Radiation Oncology Department, Prince of Wales Hospital, Randwick, NSW, 2031, Australia.
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia.
- Illawara Health and Medical Research Institute, University of Wollongong, Wollongong, NSW, 2522, Australia.
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2
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Tahmasbi M, Capela M, Santos T, Mateus J, Ventura T, do Carmo Lopes M. Particular issues to be considered in small field dosimetry for TrueBeam STx commissioning. Appl Radiat Isot 2023; 202:111066. [PMID: 37865066 DOI: 10.1016/j.apradiso.2023.111066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 08/28/2023] [Accepted: 10/05/2023] [Indexed: 10/23/2023]
Abstract
This study aims to report the relevant issues concerning small fields in the commissioning of a TrueBeam STx for photon energies of 6MV, 10MV, 6FFF, and 10FFF. Percent depth doses, profiles, and field output factors were measured according to the beam model configuration of the treatment planning system. Multiple detectors were used based on the IAEA TRS-483 protocol as well as EBT3 radiochromic film. Analytical Anisotropic and Acuros XB algorithms, were configured and validated through basic dosimetry comparisons and end-to-end clinical tests.
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Affiliation(s)
- Marziyeh Tahmasbi
- Radiologic Technology Department, School of Allied Medical Sciences, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran; Medical Physics Department, Instituto Portugues de Oncologia Coimbra Francisco Gentil, E.P.E., Portugal.
| | - Miguel Capela
- Medical Physics Department, Instituto Portugues de Oncologia Coimbra Francisco Gentil, E.P.E., Portugal
| | - Tania Santos
- Medical Physics Department, Instituto Portugues de Oncologia Coimbra Francisco Gentil, E.P.E., Portugal
| | - Josefina Mateus
- Medical Physics Department, Instituto Portugues de Oncologia Coimbra Francisco Gentil, E.P.E., Portugal
| | - Tiago Ventura
- Medical Physics Department, Instituto Portugues de Oncologia Coimbra Francisco Gentil, E.P.E., Portugal
| | - Maria do Carmo Lopes
- Medical Physics Department, Instituto Portugues de Oncologia Coimbra Francisco Gentil, E.P.E., Portugal
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3
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Looe HK, Blum I, Schönfeld AB, Tekin T, Delfs B, Poppe B. Model-based machine learning for the recovery of lateral dose profiles of small photon fields in magnetic field. Phys Med Biol 2022; 67. [DOI: 10.1088/1361-6560/ac5bfa] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Accepted: 03/09/2022] [Indexed: 11/12/2022]
Abstract
Abstract
Objective. To investigate the feasibility to train artificial neural networks (NN) to recover lateral dose profiles from detector measurements in a magnetic field. Approach. A novel framework based on a mathematical convolution model has been proposed to generate measurement-less training dataset. 2D dose deposition kernels and detector lateral fluence response functions of two air-filled ionization chambers and two diode-type detectors have been simulated without magnetic field and for magnetic field B = 0.35 and 1.5 T. Using these convolution kernels, training dataset consisting pairs of dose profiles
D
x
,
y
and signal profiles
M
x
,
y
were computed for a total of 108 2D photon fluence profiles
ψ
(
x
,
y
)
(80% training/20% validation). The NN were tested using three independent datasets, where the second test dataset has been obtained from simulations using realistic phase space files of clinical linear accelerator and the third test dataset was measured at a conventional linac equipped with electromagnets. Main results. The convolution kernels show magnetic field dependence due to the influence of the Lorentz force on the electron transport in the water phantom and detectors. The NN show good performance during training and validation with mean square error reaching a value of 1e-6 or smaller. The corresponding correlation coefficients R reached the value of 1 for all models indicating an excellent agreement between expected
D
x
,
y
and predicted
D
pred
x
,
y
.
The comparisons between
D
x
,
y
and
D
pred
x
,
y
using the three test datasets resulted in gamma indices (1 mm/1% global) <1 for all evaluated data points. Significance. Two verification approaches have been proposed to warrant the mathematical consistencies of the NN outputs. Besides offering a correction strategy not existed so far for relative dosimetry in a magnetic field, this work could help to raise awareness and to improve understanding on the distortion of detector’s signal profiles by a magnetic field.
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Duchaine J, Wahl M, Markel D, Bouchard H. A probabilistic approach for determining Monte Carlo beam source parameters: II. Impact of beam modeling uncertainties on dosimetric functions and treatment plans. Phys Med Biol 2022; 67. [DOI: 10.1088/1361-6560/ac4efb] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 01/26/2022] [Indexed: 11/11/2022]
Abstract
Abstract
Objective. The Monte Carlo method is recognized as a valid approach for the evaluation of dosimetric functions for clinical use. This procedure requires the accurate modeling of the considered linear accelerator. In Part I, we propose a new method to extract the probability density function of the beam model physical parameters. The aim of this work is to evaluate the impact of beam modeling uncertainties on Monte Carlo evaluated dosimetric functions and treatment plans in the context of small fields. Approach. Simulations of output factors, output correction factors, dose profiles, percent-depth doses and treatment plans are performed using the CyberKnife M6 model developed in Part I. The optimized pair of electron beam energy and spot size, and eight additional pairs of beam parameters representing a 95% confidence region are used to propagate the uncertainties associated to the source parameters to the dosimetric functions. Main results. For output factors, the impact of beam modeling uncertainties increases with the reduction of the field size and confidence interval half widths reach 1.8% for the 5 mm collimator. The impact on output correction factors cancels in part, leading to a maximum confidence interval half width of 0.44%. The impact is less significant for percent-depth doses in comparison to dose profiles. For these types of measurement, in absolute terms and in comparison to the reference dose, confidence interval half widths less than or equal to 1.4% are observed. For simulated treatment plans, the impact is more significant for the treatment delivered with a smaller field size with confidence interval half widths reaching 2.5% and 1.4% for the 5 and 20 mm collimators, respectively. Significance. Results confirm that AAPM TG-157's tolerances cannot apply to the field sizes studied. This study provides an insight on the reachable dose calculation accuracy in a clinical setup.
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Investigation of field output factors using IAEA-AAPM TRS-483 code of practice recommendations and Monte Carlo simulation for 6 MV photon beams. JOURNAL OF RADIOTHERAPY IN PRACTICE 2021. [DOI: 10.1017/s1460396921000662] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Abstract
Introduction:
This study aims to experimentally determine field output factors using the methodologies suggested by the IAEA-AAPM TRS-483 for small field dosimetry and compare with the calculation from Monte Carlo (MC) simulation.
Methods:
The IBA-CC01, Sun Nuclear EDGE and IBA-SFD detectors were employed to determine the uncorrected and the corrected field output factors for 6 MV photon beams. Measurements were performed at 100 cm source to axis distance, 10 cm depth in water, and the field sizes ranged from 1 × 1 to 10 × 10 cm2. The use of field output correction factors proposed by the TRS-483 was utilised to determine field output factors. The measured field output factors were compared to that calculated using the egs_chamber user code.
Results:
The decrease in the percentage standard deviation of the measured three detectors was observed after applying the field output correction factors. Measured field output factors using CC01 and EDGE detectors agreed with MC values within 3% for field sizes down to 1 × 1 cm2, except the SFD detector.
Conclusions:
The corrected field output factors agree with the calculation from MC, except the SFD detector. CC01 and EDGE are suitable for determining field output factors, while the SFD may need more implementation of the intermediate field method.
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Yabsantia S, Suriyapee S, Phaisangittisakul N, Oonsiri S, Sanghangthum T, Mirzakhanian L, Heng VJ, Seuntjens J. Determination of field output correction factors of radiophotoluminescence glass dosimeter and CC01 ionization chamber and validation against IAEA-AAPM TRS-483 code of practice. Phys Med 2021; 88:167-174. [PMID: 34280729 DOI: 10.1016/j.ejmp.2021.07.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 06/24/2021] [Accepted: 07/05/2021] [Indexed: 10/20/2022] Open
Abstract
PURPOSE To determine the field output correction factors of the radiophotoluminescence glass dosimeter (RPLGD) in parallel and perpendicular orientations with reference to CC01, the ionization chamber. METHODS The dose to a small water volume and the sensitive volume of the RPLGD and the IBA-CC01 were determined for 6-MV, 100-cm SAD, 10-cm depth using egs_chamber user-code. The RPLGD in perpendicular and parallel orientations to the beam axis were studied. The field output correction factors of each detector for 0.5 × 0.5 to 10 × 10 cm2 field sizes were determined. These field output correction factors were validated by comparing field output factors against data determined from IAEA-AAPM TRS-483 code of practice. RESULTS The field output correction factors of all detectors were within 5% for field sizes down to 0.8 × 0.8 cm2. For 0.5 × 0.5 cm2, the field output correction factors of CC01, RPLGD in perpendicular and parallel orientations differed from unity by 14%, 19%, and 5%, respectively. The percentage difference between field output factors determined using RPLGD and CC01 data, corrected using the field output correction factors determined in this work and measurements with CC01 data corrected using TRS-483, was less than 3% for all field sizes, except for the smallest field size of RPLGD in perpendicular orientation and the CC01. CONCLUSIONS The field output correction factors of RPLGD and CC01 are reported. The validation proves that RPLGD in parallel orientation combined with the field output correction factors is the most suitable for determining the field output factors for the smallest field used in this study.
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Affiliation(s)
- Sumalee Yabsantia
- Medical Physics Program, Department of Radiology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Sivalee Suriyapee
- Medical Physics Program, Department of Radiology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
| | | | - Sornjarod Oonsiri
- Department of Radiation Oncology, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand
| | - Taweap Sanghangthum
- Medical Physics Program, Department of Radiology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Lalageh Mirzakhanian
- Health Sciences North, Sudbury, Ontario, Canada; Northern Ontario School of Medicine, Sudbury, Ontario, Canada
| | - Veng Jean Heng
- Medical Physics Unit, McGill University, Montreal, Québec H3G 1A4, Canada
| | - Jan Seuntjens
- Medical Physics Unit, McGill University, Montreal, Québec H3G 1A4, Canada
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7
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Das IJ, Francescon P, Moran JM, Ahnesjö A, Aspradakis MM, Cheng CW, Ding GX, Fenwick JD, Saiful Huq M, Oldham M, Reft CS, Sauer OA. Report of AAPM Task Group 155: Megavoltage photon beam dosimetry in small fields and non-equilibrium conditions. Med Phys 2021; 48:e886-e921. [PMID: 34101836 DOI: 10.1002/mp.15030] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 05/06/2021] [Accepted: 06/02/2021] [Indexed: 12/14/2022] Open
Abstract
Small-field dosimetry used in advance treatment technologies poses challenges due to loss of lateral charged particle equilibrium (LCPE), occlusion of the primary photon source, and the limited choice of suitable radiation detectors. These challenges greatly influence dosimetric accuracy. Many high-profile radiation incidents have demonstrated a poor understanding of appropriate methodology for small-field dosimetry. These incidents are a cause for concern because the use of small fields in various specialized radiation treatment techniques continues to grow rapidly. Reference and relative dosimetry in small and composite fields are the subject of the International Atomic Energy Agency (IAEA) dosimetry code of practice that has been published as TRS-483 and an AAPM summary publication (IAEA TRS 483; Dosimetry of small static fields used in external beam radiotherapy: An IAEA/AAPM International Code of Practice for reference and relative dose determination, Technical Report Series No. 483; Palmans et al., Med Phys 45(11):e1123, 2018). The charge of AAPM task group 155 (TG-155) is to summarize current knowledge on small-field dosimetry and to provide recommendations of best practices for relative dose determination in small megavoltage photon beams. An overview of the issue of LCPE and the changes in photon beam perturbations with decreasing field size is provided. Recommendations are included on appropriate detector systems and measurement methodologies. Existing published data on dosimetric parameters in small photon fields (e.g., percentage depth dose, tissue phantom ratio/tissue maximum ratio, off-axis ratios, and field output factors) together with the necessary perturbation corrections for various detectors are reviewed. A discussion on errors and an uncertainty analysis in measurements is provided. The design of beam models in treatment planning systems to simulate small fields necessitates special attention on the influence of the primary beam source and collimating devices in the computation of energy fluence and dose. The general requirements for fluence and dose calculation engines suitable for modeling dose in small fields are reviewed. Implementations in commercial treatment planning systems vary widely, and the aims of this report are to provide insight for the medical physicist and guidance to developers of beams models for radiotherapy treatment planning systems.
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Affiliation(s)
- Indra J Das
- Department of Radiation Oncology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Paolo Francescon
- Department of Radiation Oncology, Ospedale Di Vicenza, Vicenza, Italy
| | - Jean M Moran
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Anders Ahnesjö
- Medical Radiation Sciences, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Maria M Aspradakis
- Institute of Radiation Oncology, Cantonal Hospital of Graubünden, Chur, Switzerland
| | - Chee-Wai Cheng
- Department of Radiation Oncology, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
| | - George X Ding
- Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - John D Fenwick
- Molecular and Clinical Cancer Medicine, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, UK
| | - M Saiful Huq
- Department of Radiation Oncology, University of Pittsburgh, School of Medicine and UPMC Hillman Cancer Center, Pittsburgh, PA, USA
| | - Mark Oldham
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, USA
| | - Chester S Reft
- Department of Radiation Oncology, University of Chicago, Chicago, IL, USA
| | - Otto A Sauer
- Department of Radiation Oncology, Klinik fur Strahlentherapie, University of Würzburg, Würzburg, Germany
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Hachemi T, Chaoui ZEA, Khoudri S. PENELOPE simulations and experiment for 6 MV clinac iX accelerator for standard and small static fields. Appl Radiat Isot 2021; 174:109749. [PMID: 33940355 DOI: 10.1016/j.apradiso.2021.109749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 03/25/2021] [Accepted: 04/23/2021] [Indexed: 11/18/2022]
Abstract
The goal of this work was to produce accurate data for use as a 'gold standard' and a valid tool for measurements in reference dosimetry for standard/small static field sizes from 0.5 × 0.5 to 10 × 10 cm2. It is based on the accuracy of the phase space files (PSFs) as a key quantity. Because the IAEA general public database provides few PSFs for the Varian iX, we simulated the head through Monte Carlo (MC) simulations and calculated validated PSFs for 12 square field sizes including seven for small static fields. The resulting dosimetric calculations allowed us to reach a good level of agreement in comparison to our relative and absolute dose measurements performed on a Varian iX in water phantom. Measured and MC calculated output factors were investigated for different detectors. Based on the TRS 483 formalism and MC (PENELOPE/penEasy), we calculated output correction factors for the unshielded Diode-E (T60017) and the PinPoint-3D (T31016) micro-chamber according to manufacturers' blueprints. Our MC results were in agreement with the recommended data; they compete with recent measurements and MC simulations and in particular the TRS 483 MC data obtained from similar simulations. Moreover, our MC results provide supplemental data in comparison to TRS 483 data in particular for the PinPoint-3D (T31016). We suggest our MC output correction factors as new datasets for future TRS compilations. The work was substantial, used different robust MC strategies depending on the scoring regions, and led in most cases to uncertainties of less than 1%.
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Affiliation(s)
- Taha Hachemi
- Physics Department, Faculty of Sciences, Laboratory of Optoelectronic and Devices, University Ferhat Abbas Sétif 1, Algeria.
| | - Zine-El-Abidine Chaoui
- Physics Department, Faculty of Sciences, Laboratory of Optoelectronic and Devices, University Ferhat Abbas Sétif 1, Algeria
| | - Saad Khoudri
- Physics Department, Faculty of Sciences, Laboratory of Optoelectronic and Devices, University Ferhat Abbas Sétif 1, Algeria; Centre de Lutte Contre le Cancer de Sétif, Algeria
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Hernández-Becerril MA, Lárraga-Gutiérrez JM, Saldivar B, Hernández-Servín JA. Monte Carlo verification of output correction factors for a TrueBeam STx®. Appl Radiat Isot 2021; 173:109701. [PMID: 33813187 DOI: 10.1016/j.apradiso.2021.109701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 03/18/2021] [Accepted: 03/19/2021] [Indexed: 11/15/2022]
Abstract
The recent publication of the new code of practice IAEA/AAPM TRS-483 introduces output correction factors to correct detector response changes in relative dosimetry of small photon beams. In TRS-483, average correction factors are reported for several detectors in high-energy photon beams at 6 and 10 MV with and without flattening filter. These correction factors were determined by Monte Carlo simulation or experimental measurements using several linacs of different brands and vendors. The goal of this work was to validate the output correction factors reported in TRS-483 for 6 MV photon beams of a TrueBeam STx® linac. The validation was performed using Monte Carlo simulations of four radiation detectors employed in the dosimetry of small photon beams and whose output correction factors were determined using a different radiation source than TrueBeam STx®. The results show that Monte Carlo calculated output correction factors, and those reported in the code of practice TRS-483 fully agree within ∼1%. The use of generic correction factors for a TrueBeam STx® and the detectors studied in this work is suitable for small field dosimetry static beams within the uncertainties of Monte Carlo calculations and output correction factors reported in TRS-483.
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Affiliation(s)
- Mario A Hernández-Becerril
- Facultad de Ingeniería,Universidad Autónoma del Estado de México, Cerro de Coatepec s/n, Ciudad Universitaria, Toluca 50100, Estado de México, Mexico
| | - José M Lárraga-Gutiérrez
- Laboratorio de Física Médica, Instituto Nacional de Neurología y Neurocirugía, Insurgentes sur 3877, Tlalpan 14269, CDMX, Mexico.
| | - Belem Saldivar
- Facultad de Ingeniería,Universidad Autónoma del Estado de México, Cerro de Coatepec s/n, Ciudad Universitaria, Toluca 50100, Estado de México, Mexico; Cátedras CONACYT, Av. Insurgentes sur 1582, Col. Crédito Constructor, Alcaldía Benito Juárez, CDMX 03940, Mexico
| | - J A Hernández-Servín
- Facultad de Ingeniería,Universidad Autónoma del Estado de México, Cerro de Coatepec s/n, Ciudad Universitaria, Toluca 50100, Estado de México, Mexico
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Charles PH, Crowe SB, Kairn T. Technical Note: Small field dose correction factors for radiochromic film in lung phantoms. Med Phys 2021; 48:2667-2672. [PMID: 33619729 DOI: 10.1002/mp.14799] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 02/02/2021] [Accepted: 02/16/2021] [Indexed: 12/20/2022] Open
Abstract
PURPOSE Radiochromic film has been established as a detector that can be used without the need for perturbation correction factors for small field dosimetry in water. However, perturbation factors in low density media such as lung have yet to be published. This study calculated the factors required to account for the perturbation of radiochromic film when used for small field dosimetry in lung equivalent material. METHOD Monte Carlo simulations were used to calculate dose to Gafchromic EBT3 film when placed inside a lung phantom. The beam simulated had a nominal energy of 6 MV and the field sizes simulated ranged from 10 × 10 mm2 to 30 × 30 mm2 . The lung density simulated was varied between 0.2 and 0.3 g/cm3 . Each simulation was repeated with the film replaced by lung material (the same as the surrounding medium), and the required correction factors for film dosimetry in lung ( D M e d , Q D D e t , Q ) were calculated by dividing the dose in lung by the dose in film. RESULTS For field sizes 30 × 30 mm2 and larger, no correction factors were required. At a 20 × 20 mm2 field size, small corrections were required, but were within the approximate accuracy of film dosimetry (~2%). For a 10 × 10 mm2 field size, significant correction factors need to be applied (0.935 for lung density of 0.20 g/cm3 to 0.963 for lung density of 0.30 g/cm3 ). The values lower than one mean that the film is over-responding. At the "upstream" lung-water interface the correction factors were close to unity; while at the downstream interface the corrections required were marginally smaller to those at the center of lung. One centimeter or more away from the interfaces, the correction factor did not vary as a function distance from the interface (in the beam direction). Away from the central axis (perpendicular to the beam direction), the correction factors increased slightly (away from unity) as a function of off-axis distance, before abruptly changing direction at the penumbra, with the film actually under-responding by ~10% outside the field edges. CONCLUSION Accurate dosimetry of very small fields (15 × 15 mm2 or smaller) using radiochromic film requires correction factors for the perturbation of the film on the surrounding lung material. This correction factor was as high as 6.5% for a 10 × 10 mm2 field size and a density of 0.2 g/cm3 . This will increase if either the density or the field size decrease further. This correction factor does not vary as a function of depth in lung once charged particle equilibrium is established.
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Affiliation(s)
- Paul H Charles
- Herston Biofabrication Institute, Metro North Hospital and Health Service, Herston, Queensland, 4029, Australia.,School of Information Technology and Electrical Engineering, University of Queensland, St Lucia, Queensland, 4072, Australia.,School of Chemistry and Physics, Queensland University of Technology, Brisbane, Queensland, 4000, Australia
| | - Scott B Crowe
- Herston Biofabrication Institute, Metro North Hospital and Health Service, Herston, Queensland, 4029, Australia.,School of Information Technology and Electrical Engineering, University of Queensland, St Lucia, Queensland, 4072, Australia.,School of Chemistry and Physics, Queensland University of Technology, Brisbane, Queensland, 4000, Australia.,Cancer Care Services, Royal Brisbane & Women's Hospital, Herston, Queensland, 4029, Australia
| | - Tanya Kairn
- Herston Biofabrication Institute, Metro North Hospital and Health Service, Herston, Queensland, 4029, Australia.,School of Information Technology and Electrical Engineering, University of Queensland, St Lucia, Queensland, 4072, Australia.,School of Chemistry and Physics, Queensland University of Technology, Brisbane, Queensland, 4000, Australia.,Cancer Care Services, Royal Brisbane & Women's Hospital, Herston, Queensland, 4029, Australia
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11
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Bouchard H. Reference dosimetry of modulated and dynamic photon beams. Phys Med Biol 2021; 65:24TR05. [PMID: 33438582 DOI: 10.1088/1361-6560/abc3fb] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In the late 1980s, a new technique was proposed that would revolutionize radiotherapy. Now referred to as intensity-modulated radiotherapy, it is at the core of state-of-the-art photon beam delivery techniques, such as helical tomotherapy and volumetric modulated arc therapy. Despite over two decades of clinical application, there are still no established guidelines on the calibration of dynamic modulated photon beams. In 2008, the IAEA-AAPM work group on nonstandard photon beam dosimetry published a formalism to support the development of a new generation of protocols applicable to nonstandard beam reference dosimetry (Alfonso et al 2008 Med. Phys. 35 5179-86). The recent IAEA Code of Practice TRS-483 was published as a result of this initiative and addresses exclusively small static beams. But the plan-class specific reference calibration route proposed by Alfonso et al (2008 Med. Phys. 35 5179-86) is a change of paradigm that is yet to be implemented in radiotherapy clinics. The main goals of this paper are to provide a literature review on the dosimetry of nonstandard photon beams, including dynamic deliveries, and to discuss anticipated benefits and challenges in a future implementation of the IAEA-AAPM formalism on dynamic photon beams.
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Affiliation(s)
- Hugo Bouchard
- Département de physique, Université de Montréal, Complexe des sciences, 1375 Avenue Thérèse-Lavoie-Roux, Montréal, Québec H2V 0B3, Canada. Centre de recherche du Centre hospitalier de l'Université de Montréal, 900 Rue Saint-Denis, Montréal, Québec H2X 0A9, Canada. Département de radio-oncologie, Centre hospitalier de l'Université de Montréal (CHUM), 1051 Rue Sanguinet, Montréal, Québec H2X 3E4, Canada
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12
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Lam S, Bradley D, Khandaker M. Small-field radiotherapy photon beam output evaluation: Detectors reviewed. Radiat Phys Chem Oxf Engl 1993 2021. [DOI: 10.1016/j.radphyschem.2020.108950] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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13
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Yani S, Budiansah I, Rhani MF, Haryanto F. Monte carlo model and output factors of elekta infinity™ 6 and 10 MV photon beam. Rep Pract Oncol Radiother 2020; 25:470-478. [PMID: 32494222 DOI: 10.1016/j.rpor.2020.03.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 02/02/2020] [Accepted: 03/20/2020] [Indexed: 10/24/2022] Open
Abstract
Aim This study aimed to commission the Elekta Infinity™ working in 6 and 10 MV photon beam installed in Concord International Hospital, Singapore, and compare the OFs between MC simulation and measurement using PTW semiflex and microDiamond detector for small field sizes. Material and Methods There are two main steps in this study: modelling of Linac 6 and 10 MV photon beam and analysis of the output factors for field size 2 × 2-10 × 10 cm2. The EGSnrc/BEAMnrc-DOSXYZnrc code was used to model and characterize the Linac and to calculate the dose distributions in a water phantom. The dose distribution and OFs were compared to the measurement data in the same condition. Results The commissioning process was only conducted for a 10 × 10 cm2 field size. The PDD obtained from MC simulation showed a good agreement with the measurement. The local dose difference of PDDs was less than 2% for 6 and 10 MV. The initial electron energy was 5.2 and 9.4 MeV for 6 and 10 MV photon beam, respectively. This Linac model can be used for dose calculation in other situations and different field sizes because this Linac has been commissioned and validated using Monte Carlo simulation. The 10 MV Linac produces higher electron contamination than that of 6 MV. Conclusions The Linac model in this study was acceptable. The most important result in this work comes from OFs resulted from MC calculation. This value was more significant than the OFs from measurement using semiflex and microDiamond for all beam energy and field sizes because of the CPE phenomenon.
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Affiliation(s)
- Sitti Yani
- Department of Physics, Faculty of Mathematics and Natural Sciences, IPB University (Bogor Agricultural University), Babakan, Bogor, Indonesia.,Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jalan Ganesa 10, Bandung, Indonesia
| | - Indra Budiansah
- Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jalan Ganesa 10, Bandung, Indonesia
| | | | - Freddy Haryanto
- Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jalan Ganesa 10, Bandung, Indonesia
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M K, D SG, M B T. A Novel GPU-based Fast Monte Carlo Photon Dose Calculating Method for Accurate Radiotherapy Treatment Planning. J Biomed Phys Eng 2020; 10:329-340. [PMID: 32637377 PMCID: PMC7321392 DOI: 10.31661/jbpe.v0i0.716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2017] [Accepted: 03/14/2017] [Indexed: 06/11/2023]
Abstract
BACKGROUND An accurate and fast radiation dose calculations method is the main part of treatment planning for successful radiation therapy. OBJECTIVE This work aimed to create a novel GPU-based fast Monte Carlo Photon Dose Code (MCPDC) as a fast and accurate tool in dose calculation for radiotherapy treatment planning. MATERIALS AND METHODS In this analytical study, MCDPC was written to implement photon MC simulation for energies 0.01 to 20 MeV and run on an NVIDIA GTX970. The code was validated using DOSXYZnrc results and experimental measurements, performed by a Mapcheck dosimeter. Using the innovative definition of photon and electron interactions, mean calculation time for the MCPDC was 5.4 sec for 5e7 source particle history, significantly less than that of DOSXYZnrc which was 400 min. RESULTS Considering the simulations in the anthropomorphic phantom with bone and lung inhomogeneity, more than 96.1% of all significant voxels passed the gamma criteria of 3%-3 mm. Compared to the experimental dosimetry results, 97.6% or more of all significant voxels passed the acceptable clinical gamma index of 3%-3 mm. CONCLUSION Very fast calculation speed and high accuracy in dose calculation may allow the MCPDC to be used in radiotherapy as a central component of a treatment plan verification system and also as the dose calculation engine for MC-based planning. MCPDC is currently being developed for electron dose calculation module and graphic user interface. In addition, future work on the applicability of the improved version of the MCPDC in transit dosimetry of megavoltage CT is in process.
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Affiliation(s)
- Karbalaee M
- PhD, Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Shahbazi-Gahrouei D
- PhD, Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Tavakoli M B
- PhD, Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
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15
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Lechner W, Georg D, Palmans H. An analytical formalism for the assessment of dose uncertainties due to positioning uncertainties. Med Phys 2020; 47:1357-1363. [PMID: 31880323 PMCID: PMC7078844 DOI: 10.1002/mp.13991] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 12/18/2019] [Accepted: 12/18/2019] [Indexed: 11/12/2022] Open
Abstract
PURPOSE To present an analytical formalism for the in depth assessment of uncertainties of field output factors in small fields related to detector positioning based on dose profile measurements. Additionally, a procedure for the propagation of these uncertainties was developed. METHODS Based on the assumption that one dimensional and two dimensional second-order polynomial functions can be fitted to dose profiles of small photon beams, equations for the calculation of the expectation value, the variance, and the standard deviation were developed. The following fitting procedures of the dose profiles were considered: A one-dimensional case (1D), a quasi two-dimensional case (2Dq) based on independently measured line profiles and a full 2D case (2Df) which also considers cross-correlations in a two-dimensional dose distribution. A rectangular and a Gaussian probability density function (PDF) characterizing the probability of possible positions of the detector relative to the maximum dose were used. Uncertainty components such as the finite resolution of the scanning water phantom, the reproducibility of the determination of the position of the maximum dose, and the reproducibility of the collimator system were investigated. This formalism was tested in a 0.5 x 0.5 cm2 photon field where dose profiles were measured using a radiochromic film, a synthetic diamond detector, and an unshielded diode detector. Additionally, the dose distribution measured with the radiochromic film was convoluted with a convolution kernel mimicking the active volume of the unshielded diode. RESULTS Analytic expressions for the calculation of uncertainties on field output factors were found for the 1D, the 2Dq, and the 2Df case. The uncertainty of the field output factor related to the relative position of the detector to the maximum dose increased quadratically with increasing limits of possible detector positions. Analysis of the radiochromic film showed that the 2Dq case gave a more conservative assessment of the uncertainty compared to the 2Df case with a difference of < 0.1%. The 2Dq case applied to the film measurements agreed well with the same approach as was applied to the unshielded diode. The investigated uncertainty components propagated to an uncertainty of the field output factors of 0.5% and 0.4% for the synthetic diamond and the unshielded diode, respectively. Additionally, the expectation value was lower than the maximum dose. The difference was 0.4% and 0.3% for the synthetic diamond and the unshielded diode, respectively. CONCLUSIONS The assessment of uncertainties of field output factors related to detector positioning is feasible using the proposed formalism. The 2Dq case is applicable when using online detectors. Accurate positioning in small fields is essential for accurate dosimetry as its related uncertainty increases quadratically. The observed drop of the expectation value needs to be considered in small field dosimetry.
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Affiliation(s)
- Wolfgang Lechner
- Division of Medical Physics, Department of Radiation Oncology, Medical University Vienna, 1090, Vienna, Austria
| | - Dietmar Georg
- Division of Medical Physics, Department of Radiation Oncology, Medical University Vienna, 1090, Vienna, Austria
| | - Hugo Palmans
- EBG MedAustron GmbH, Marie-Curie Straße 5, 2700, Wiener Neustadt, Austria.,National Physical Laboratory, Teddington, TW, 11 0LW, UK
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16
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Smith CL, Montesari A, Oliver CP, Butler DJ. Evaluation of the IAEA-TRS 483 protocol for the dosimetry of small fields (square and stereotactic cones) using multiple detectors. J Appl Clin Med Phys 2019; 21:98-110. [PMID: 31886615 PMCID: PMC7021012 DOI: 10.1002/acm2.12792] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 10/06/2019] [Accepted: 11/15/2019] [Indexed: 11/30/2022] Open
Abstract
The IAEA TRS 483 protocol1 for the dosimetry of small static fields in radiotherapy was used to calculate output factors for the Elekta Synergy linac at the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). Small field output factors for both square and circular fields were measured using nine different detectors. The “corrected” output factors (ratio of detector readings multiplied by the appropriate correction factor from the protocol) showed better consistency compared to the “uncorrected” output factors (ratio of detector readings only), with the relative standard deviation decreasing by approximately 1% after the application of the relevant correction factors. Comparisons relative to an arbitrarily chosen PTW 60019 microDiamond detector showed a reduction of maximal variation for the corrected values of approximately 3%. A full uncertainty budget was prepared to analyze the consistency of the output factors. Agreement within uncertainties between all detectors and field sizes was found, except for the 15 mm circular field. The results of this study show that the application of IAEA TRS 4831 when measuring small fields will improve the consistency of small field measurements when using multiple detectors contained within the protocol.
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Affiliation(s)
- Clare L Smith
- School of Health and Biomedical Sciences, RMIT University, Bundoora, VIC, Australia
| | | | - Christopher P Oliver
- Australian Radiation Protection and Nuclear Safety Agency, Yallambie, VIC, Australia
| | - Duncan J Butler
- Australian Radiation Protection and Nuclear Safety Agency, Yallambie, VIC, Australia
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17
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Borzov E, Nevelsky A, Bar-Deroma R, Orion I. Reconstruction of the electron source intensity distribution of a clinical linear accelerator using in-air measurements and a genetic algorithm. Phys Imaging Radiat Oncol 2019; 12:67-73. [PMID: 33458298 PMCID: PMC7807614 DOI: 10.1016/j.phro.2019.11.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 11/24/2019] [Accepted: 11/25/2019] [Indexed: 12/04/2022] Open
Abstract
Background and purpose The electron source intensity distribution of a clinical linear accelerator has a great influence on the calculation of output factors for small radiation fields where source occlusion by the collimating devices takes place. The purpose of this study was to present a new method for the electron source reconstruction problem. Materials and methods The measurements were performed in-air using diode and 6 MV 1 × 1 cm2 photon field in flattening filter-free mode. In Monte Carlo simulation, an electron target area was divided into a number of square subsources. Then, the in-air doses in 2D silicon chip array were calculated individually from each subsource. A genetic algorithm search was applied in order to determine the optimal weight factors for all subsources that provide the best agreement between simulated and measured doses. Results It was found that the reconstructed electron source intensity from a clinical linear accelerator has the two-dimensional elliptical double Gaussian distribution. The source intensity distribution consisted of two intensity components along the in-plane (x) and cross-plane (y) directions characterized by full width half-maximum (FWHM): FWHMx1 = 0.27 cm, FWHMx2 = 0.08 cm, FWHMy1 = 0.24 cm, FWHMy2 = 0.06 cm, where broader components are 81% and 53% of the total intensity along × and y axis respectively. Conclusions The obtained results demonstrated an elliptical double Gaussian intensity distribution of the incident electron source. We anticipate that the proposed method has universal applications independent of the type of linear accelerator, modality or energy.
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Affiliation(s)
- Egor Borzov
- Department of Radiotherapy, Division of Oncology, Rambam Health Care Campus, Haifa 32000, Israel
- Corresponding author at: HaAliya HaShniya St 8, Haifa, 3109601, Israel.
| | - Alexander Nevelsky
- Department of Radiotherapy, Division of Oncology, Rambam Health Care Campus, Haifa 32000, Israel
| | - Raquel Bar-Deroma
- Department of Radiotherapy, Division of Oncology, Rambam Health Care Campus, Haifa 32000, Israel
| | - Itzhak Orion
- Department of Nuclear Engineering, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
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Kim TH, Schaarschmidt T, Yang HJ, Kim YK, Chun KJ, Choi Y, Chung HT. Development of an IAEA phase-space dataset for the Leksell Gamma Knife® Perfexion™ using multi-threaded Geant4 simulations. Phys Med 2019; 64:222-229. [DOI: 10.1016/j.ejmp.2019.07.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Revised: 06/07/2019] [Accepted: 07/01/2019] [Indexed: 10/26/2022] Open
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Papaconstadopoulos P, Levesque IR, Aldelaijan S, O’Grady K, Devic S, Seuntjens J. Modeling the primary source intensity distribution: reconstruction and inter-comparison of six Varian TrueBeam sources. ACTA ACUST UNITED AC 2019; 64:135005. [DOI: 10.1088/1361-6560/ab1ccc] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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20
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Galavis PE, Hu L, Holmes S, Das IJ. Characterization of the plastic scintillation detector Exradin W2 for small field dosimetry. Med Phys 2019; 46:2468-2476. [DOI: 10.1002/mp.13501] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 03/11/2019] [Accepted: 03/11/2019] [Indexed: 11/10/2022] Open
Affiliation(s)
- Paulina E. Galavis
- Department of Radiation Oncology New York University, Langone Medical Center & Laura and Issac Perlmutter Cancer Center New York NY 10016USA
| | - Lei Hu
- Department of Radiation Oncology New York University, Langone Medical Center & Laura and Issac Perlmutter Cancer Center New York NY 10016USA
| | | | - Indra J. Das
- Department of Radiation Oncology New York University, Langone Medical Center & Laura and Issac Perlmutter Cancer Center New York NY 10016USA
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Monasor Denia P, Castellet García MDC, Manjón García C, Quirós Higueras JD, de Marco Blancas N, Bonaque Alandí J, Juan Senabre XJ, Santos Serra A, López-Tarjuelo J. Comparison of detector performance in small 6 MV and 6 MV FFF beams using a Versa HD accelerator. PLoS One 2019; 14:e0213253. [PMID: 30856183 PMCID: PMC6411166 DOI: 10.1371/journal.pone.0213253] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 02/18/2019] [Indexed: 11/18/2022] Open
Abstract
1. BACKGROUND & PURPOSE Investigate the applicability of a series of detectors in small field dosimetry and the possible differences between their responses to FF and FFF beams. This work extends upon the series of detectors used by other authors to also include metal-oxide-semiconductor field-effect transistors (MOSFETs) detectors and radiochromic film. We also included a later correction of output factors (OFs) recommended by the recently published IAEA´s code of practice TRS 483 on dosimetry of small static fields used in external beam radiotherapy. 2. MATERIALS & METHODS The OFs, profiles, and PDDs of 6 MV and 6 MV FFF beams were measured with 11 different detectors using field sizes between 0.6 × 0.6 cm2 and 10 × 10 cm2. 3. RESULTS The OFs of the FFF beams were lower than those of the FF beams for field sizes larger than 3 × 3 cm2 but higher for field sizes smaller than 3 × 3 cm2. After applying the IAEA´s TRS 483 corrections, the final OFs were compatible with our initial results when considering uncertainties involved. Small-volume detectors are preferable for measuring the penumbra of these small fields where this attribute is higher in the crossline direction than in the inline direction. The R100 of equivalent-quality FFF beams was higher compared to the corresponding flattened beams. 4. CONCLUSIONS We observed no difference for the dose responses between 6 MV and 6 MV FFF beams for any of the detectors. OF results, profiles and PDDs were clearly consistent with the previously published literature regarding the Versa HD linac. Correcting our first OFs, taken as ratio of detector charges, with the IAEA´s TRS 483 corrections to obtain the final OFs, did not make the former significantly different.
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Affiliation(s)
- Paula Monasor Denia
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | | | - Carla Manjón García
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | - Juan David Quirós Higueras
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | - Noelia de Marco Blancas
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | - Jorge Bonaque Alandí
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | - Xavier Jordi Juan Senabre
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | - Agustín Santos Serra
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
| | - Juan López-Tarjuelo
- Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, España
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22
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Rahimi SA, Hashemi B, Mahdavi SR. Estimation of Dosimetric Parameters based on K NR and K NCSF Correction Factors for Small Field Radiation Therapy at 6 and 18 MV Linac Energies using Monte Carlo Simulation Methods. J Biomed Phys Eng 2019; 9:37-50. [PMID: 30881933 PMCID: PMC6409371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 12/24/2016] [Indexed: 06/09/2023]
Abstract
BACKGROUND Estimating dosimetric parameters for small fields under non-reference conditions leads to significant errors if done based on conventional protocols used for large fields in reference conditions. Hence, further correction factors have been introduced to take into account the influence of spectral quality changes when various detectors are used in non-reference conditions at different depths and field sizes. OBJECTIVE Determining correction factors (KNR and KNCSF) recommended recently for small field dosimetry formalism by American Association of Physicists in Medicine (AAPM) for different detectors at 6 and 18 MV photon beams. METHODS EGSnrc Monte Carlo code was used to calculate the doses measured with different detectors located in a slab phantom and the recommended KNR and KNCSF correction factors for various circular small field sizes ranging from 5-30 mm diameters. KNR and KNCSF correction factors were determined for different active detectors (a pinpoint chamber, EDP-20 and EDP-10 diodes) in a homogeneous phantom irradiated to 6 and 18 MV photon beams of a Varian linac (2100C/D). RESULTS KNR correction factor estimated for the highest small circular field size of 30 mm diameter for the pinpoint chamber, EDP-20 and EDP-10 diodes were 0.993, 1.020 and 1.054; and 0.992, 1.054 and 1.005 for the 6 and 18 MV beams, respectively. The KNCSF correction factor estimated for the lowest circular field size of 5 mm for the pinpoint chamber, EDP-20 and EDP-10 diodes were 0.994, 1.023, and 1.040; and 1.000, 1.014, and 1.022 for the 6 and 18 MV photon beams, respectively. CONCLUSION Comparing the results obtained for the detectors used in this study reveals that the unshielded diodes (EDP-20 and EDP-10) can confidently be recommended for small field dosimetry as their correction factors (KNR and KNCSF) was close to 1.0 for all small field sizes investigated and are mainly independent from the electron beam spot size.
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Affiliation(s)
- S A Rahimi
- PhD Candidate, Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
- Assistant Professor, Department of Basic Sciences, Faculty of Health Sciences, Mazandaran University of Medical Sciences, Sari, Iran
| | - B Hashemi
- Associate Professor, Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - S R Mahdavi
- Associate Professor, Department of Medical Physics, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran
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de Chavez R, Jones CE, Charles PH. Integral small field output factor measurements using a transmission ionisation chamber. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2018; 42:235-244. [DOI: 10.1007/s13246-018-0716-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Accepted: 11/22/2018] [Indexed: 10/27/2022]
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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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25
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Total scatter factor for small fields in radiotherapy: a dosimetric comparison. JOURNAL OF RADIOTHERAPY IN PRACTICE 2018. [DOI: 10.1017/s1460396917000681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractPurposeSmall field dosimetry is complicated and accuracy in the measurement of total scatter factor (TSF) is crucial for dosimetric calculations, in making optimum intensity-modulated radiotherapy plans for treating small target volumes. In this study, we intended to determine the TSF measuring properties of CC01 and CC04 detectors for field sizes ranging from sub-centimetre to the centimetre fields.Material and methodsCC01 and CC04 chamber detectors were used to measure TSF for 6 and 18 MV photon beam delivered from the linear accelerator, through small fields in a water phantom. Small fields were created by collimator jaws and multi-leaf collimators separately, with field sizes ranging from 0·6 to 10 cm2and 0·5 to 20 cm2, respectively.ResultsCC01 measured TSF at all the given field sizes created by jaws and multi-leaf collimators for both 6 and 18 MV beams whereas CC04 could not measure TSF for field sizes <1 cm2due to volume averaging and perturbation effects.ConclusionCC01 was shown to be effective for measurement of TSF in sub-centimetre field sizes. CC01 can be employed to measure other dosimetric quantities in small fields using different energy beams.
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26
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Shukaili KA, Corde S, Petasecca M, Pereveratylo V, Lerch M, Jackson M, Rosenfeld A. "Characterization of ELEKTA SRS cone collimator using high spatial resolution monolithic silicon detector array". J Appl Clin Med Phys 2018; 19:114-124. [PMID: 29790261 PMCID: PMC6036391 DOI: 10.1002/acm2.12345] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Revised: 04/03/2018] [Accepted: 04/07/2018] [Indexed: 11/05/2022] Open
Abstract
PURPOSE To investigate the accuracy of the dosimetry of radiation fields produced by small ELEKTA cone collimators used for stereotactic radiosurgery treatments (SRS) using commercially available detectors EBT3 GafchromicTM film, IBA Stereotactic diode (SFD), and the recently developed detector DUO, which is a monolithic silicon orthogonal linear diode array detector. METHODS These three detectors were used for the measurement of beam profiles, output factors, and percentage depth dose for SRS cone collimators with cone sizes ranging from 5 to 50 mm diameter. The measurements were performed at 10 cm depth and 90 cm SSD. RESULTS The SRS cone beam profiles measured with DUO, EBT3 film, and IBA SFD agreed well, results being in agreement within ±0.5 mm in the FWHM, and ±0.7 mm in the penumbra region. The output factor measured by DUO with 0.5 mm air gap above agrees within ±1% with EBT3. The OF measured by IBA SFD (corrected for the over-response) agreed with both EBT3 and DUO within ±2%. All three detectors agree within ±2% for PDD measurements for all SRS cones. CONCLUSIONS The characteristics of the ELEKTA SRS cone collimator have been evaluated by using a monolithic silicon high spatial resolution detector DUO, EBT3, and IBA SFD diode. The DUO detector is suitable for fast real-time quality assurance dosimetry in small radiation fields typical for SRS/SRT. This has been demonstrated by its good agreement of measured doses with EBT 3 films.
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Affiliation(s)
- Khalsa Al Shukaili
- Centre for Medical Radiation PhysicsUniversity of WollongongWollongongNSWAustralia
- National Oncology CentreRoyal HospitalMuscatOman
| | - Stéphanie Corde
- Centre for Medical Radiation PhysicsUniversity of WollongongWollongongNSWAustralia
- Illawarra Health and Medical Research InstituteWollongongNSWAustralia
- Nelune Comprehensive Cancer CentrePrince of Wales HospitalRandwickNSWAustralia
| | - Marco Petasecca
- Centre for Medical Radiation PhysicsUniversity of WollongongWollongongNSWAustralia
- Illawarra Health and Medical Research InstituteWollongongNSWAustralia
| | | | - Michael Lerch
- Centre for Medical Radiation PhysicsUniversity of WollongongWollongongNSWAustralia
- Illawarra Health and Medical Research InstituteWollongongNSWAustralia
| | - Michael Jackson
- Centre for Medical Radiation PhysicsUniversity of WollongongWollongongNSWAustralia
- Nelune Comprehensive Cancer CentrePrince of Wales HospitalRandwickNSWAustralia
| | - Anatoly Rosenfeld
- Centre for Medical Radiation PhysicsUniversity of WollongongWollongongNSWAustralia
- Illawarra Health and Medical Research InstituteWollongongNSWAustralia
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Fukata K, Sugimoto S, Kurokawa C, Saito A, Inoue T, Sasai K. Output factor determination based on Monte Carlo simulation for small cone field in 10-MV photon beam. Radiol Phys Technol 2018; 11:192-201. [PMID: 29619670 DOI: 10.1007/s12194-018-0455-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Revised: 03/27/2018] [Accepted: 03/31/2018] [Indexed: 12/31/2022]
Abstract
The difficulty of measuring output factor (OPF) in a small field has been frequently discussed in recent publications. This study is aimed to determine the OPF in a small field using 10-MV photon beam and stereotactic conical collimator (cone). The OPF was measured by two diode detectors (SFD, EDGE detector) and one micro-ion chamber (PinPoint 3D chamber) in a water phantom. A Monte Carlo simulation using simplified detector model was performed to obtain the correction factor for the detector measurements. About 12% OPF difference was observed in the measurement at the smallest field (7.5 mm diameter) for EDGE detector and PinPoint 3D chamber. By applying the Monte Carlo-based correction factor to the measurement, the maximum discrepancy among the three detectors was reduced to within 3%. The results indicate that determination of OPF in a small field should be carefully performed. Especially, detector choice and appropriate correction factor application are very important in this regard.
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Affiliation(s)
- Kyohei Fukata
- Cancer Center, Keio University School of Medicine, 35 Shinano-machi, Shinjuku, Tokyo, Japan.
| | - Satoru Sugimoto
- Graduate School of Medicine, Juntendo University, 2-1-1, Hongo, Bunkyo-ku, Tokyo, Japan
| | - Chie Kurokawa
- Graduate School of Medicine, Juntendo University, 2-1-1, Hongo, Bunkyo-ku, Tokyo, Japan
| | - Akito Saito
- Department of Radiation Oncology, Hiroshima University Hospital, 1-2-3, Kasumi, Minami-ku, Hiroshima, Hiroshima, 734-8551, Japan
| | - Tatsuya Inoue
- Department of Radiology, Juntendo University Urayasu Hospital, Tomioka 2-1-1, Urayasu-shi, Chiba, Japan
| | - Keisuke Sasai
- Graduate School of Medicine, Juntendo University, 2-1-1, Hongo, Bunkyo-ku, Tokyo, Japan
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Zhang Y, Brandner E, Ozhasoglu C, Lalonde R, Heron DE, Huq MS. A 3D correction method for predicting the readings of a PinPoint chamber on the CyberKnife ® M6 ™ machine. Phys Med Biol 2018; 63:045010. [PMID: 29350197 DOI: 10.1088/1361-6560/aaa90d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The use of small fields in radiation therapy techniques has increased substantially in particular in stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT). However, as field size reduces further still, the response of the detector changes more rapidly with field size, and the effects of measurement uncertainties become increasingly significant due to the lack of lateral charged particle equilibrium, spectral changes as a function of field size, detector choice, and subsequent perturbations of the charged particle fluence. This work presents a novel 3D dose volume-to-point correction method to predict the readings of a 0.015 cc PinPoint chamber (PTW 31014) for both small static-fields and composite-field dosimetry formed by fixed cones on the CyberKnife® M6™ machine. A 3D correction matrix is introduced to link the 3D dose distribution to the response of the PinPoint chamber in water. The parameters of the correction matrix are determined by modeling its 3D dose response in circular fields created using the 12 fixed cones (5 mm-60 mm) on a CyberKnife® M6™ machine. A penalized least-square optimization problem is defined by fitting the calculated detector reading to the experimental measurement data to generate the optimal correction matrix; the simulated annealing algorithm is used to solve the inverse optimization problem. All the experimental measurements are acquired for every 2 mm chamber shift in the horizontal planes for each field size. The 3D dose distributions for the measurements are calculated using the Monte Carlo calculation with the MultiPlan® treatment planning system (Accuray Inc., Sunnyvale, CA, USA). The performance evaluation of the 3D conversion matrix is carried out by comparing the predictions of the output factors (OFs), off-axis ratios (OARs) and percentage depth dose (PDD) data to the experimental measurement data. The discrepancy of the measurement and the prediction data for composite fields is also performed for clinical SRS plans. The optimization algorithm used for generating the optimal correction factors is stable, and the resulting correction factors were smooth in the spatial domain. The measurement and prediction of OFs agree closely with percentage differences of less than 1.9% for all the 12 cones. The discrepancies between the prediction and the measurement PDD readings at 50 mm and 80 mm depth are 1.7% and 1.9%, respectively. The percentage differences of OARs between measurement and prediction data are less than 2% in the low dose gradient region, and 2%/1 mm discrepancies are observed within the high dose gradient regions. The differences between the measurement and prediction data for all the CyberKnife based SRS plans are less than 1%. These results demonstrate the existence and efficiency of the novel 3D correction method for small field dosimetry. The 3D correction matrix links the 3D dose distribution and the reading of the PinPoint chamber. The comparison between the predicted reading and the measurement data for static small fields (OFs, OARs and PDDs) yield discrepancies within 2% for low dose gradient regions and 2%/1 mm for high dose gradient regions; the discrepancies between the predicted and the measurement data are less than 1% for all the SRS plans. The 3D correction method provides an access to evaluate the clinical measurement data and can be applied to non-standard composite fields intensity modulated radiation therapy point dose verification.
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Andreo P. The physics of small megavoltage photon beam dosimetry. Radiother Oncol 2018; 126:205-213. [DOI: 10.1016/j.radonc.2017.11.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 10/16/2017] [Accepted: 11/01/2017] [Indexed: 10/18/2022]
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Oliver CP, Butler DJ, Takau V, Williams I. Survey of 5 mm small-field output factor measurements in Australia. J Appl Clin Med Phys 2018; 19:329-337. [PMID: 29368796 PMCID: PMC5849830 DOI: 10.1002/acm2.12259] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Revised: 12/07/2017] [Accepted: 12/08/2017] [Indexed: 11/25/2022] Open
Abstract
The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) held a comparison exercise in April 2016 where participants came to ARPANSA and measured the output factor of a nominal 5 mm cone attached to the ARPANSA Elekta Synergy (Elekta, Crawley, UK) linear accelerator. The goal of the exercise was to compare the consistency and methods used by independent medical physicists in measuring small‐field output factors. ARPANSA provided a three‐dimensional scanning tank for detector setup and positioning, but the participants were required to measure the output factor with their own detectors. No information regarding output factors previously measured was supplied to participants to make each result as independent as possible. Fifteen groups travelled to ARPANSA bringing a wide range of detectors and methods. A total of 30 measurements of the output factor were made. The standard deviation of the measurements (excluding one expected outlier from an uncorrected ionization chamber measurement) was 3.6%. The results provide an insight into the consistency of small‐field dosimetry being performed in Australia and New Zealand at the present time.
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Affiliation(s)
- Christopher P Oliver
- Australian Radiation Protection and Nuclear Safety Agency, Yallambie, Vic, Australia
| | - Duncan J Butler
- Australian Radiation Protection and Nuclear Safety Agency, Yallambie, Vic, Australia
| | - Viliami Takau
- Australian Radiation Protection and Nuclear Safety Agency, Yallambie, Vic, Australia
| | - Ivan Williams
- Australian Radiation Protection and Nuclear Safety Agency, Yallambie, Vic, Australia
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Butler DJ, Beveridge T, Lehmann J, Oliver CP, Stevenson AW, Livingstone J. Spatial response of synthetic microDiamond and diode detectors measured with kilovoltage synchrotron radiation. Med Phys 2018; 45:943-952. [PMID: 29244899 DOI: 10.1002/mp.12733] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Revised: 11/16/2017] [Accepted: 11/30/2017] [Indexed: 11/11/2022] Open
Abstract
PURPOSE To map the spatial response of four solid-state radiation detectors of types commonly used for radiotherapy dosimetry. METHODS PTW model 60016 Diode P, 60017 Diode E, 60018 Diode SRS, and 60019 microDiamond detectors were radiographed using a high resolution conventional X-ray system. Their spatial response was then investigated using a 0.1 mm diameter beam of 95 keV average energy photons generated by a synchrotron. The detectors were scanned through the beam while their signal was recorded as a function of position, to map the response. These 2D response maps were created in both the end-on and side-on orientations. RESULTS The results show the location and size of the active region. End-on, the active area was determined to be centrally located and within 0.2 mm of the manufacturer's specified diameter. The active areas of the 60016 Diode P, 60017 Diode E, 60018 Diode SRS detectors are uniform to within approximately 5%. The 60019 microDiamond showed local variations up to 30%. The extra-cameral signal in the microDiamond was calculated from the side-on scan to be approximately 8% of the signal from the active element. CONCLUSIONS The spatial response of four solid-state detectors has been measured. The technique yielded information about the location and uniformity of the active area, and the extra-cameral signal, for the beam quality used.
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Affiliation(s)
- Duncan J Butler
- Australian Radiation Protection and Nuclear Safety Agency (ARPANSA), Yallambie, Vict., 3085, Australia
| | - Toby Beveridge
- Australian Radiation Protection and Nuclear Safety Agency (ARPANSA), Yallambie, Vict., 3085, Australia
| | - Joerg Lehmann
- Institute of Medical Physics, University of Sydney, Physics Road A28, Sydney, NSW, 2006, Australia
| | - Christopher P Oliver
- Australian Radiation Protection and Nuclear Safety Agency (ARPANSA), Yallambie, Vict., 3085, Australia
| | - Andrew W Stevenson
- Australian Synchrotron, 800 Blackburn Road, Clayton, Vict., 3168, Australia.,CSIRO, Manufacturing, Clayton, Vict., 3168, Australia
| | - Jayde Livingstone
- Australian Synchrotron, 800 Blackburn Road, Clayton, Vict., 3168, Australia
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Lechner W, Wesolowska P, Azangwe G, Arib M, Alves VGL, Suming L, Ekendahl D, Bulski W, Samper JLA, Vinatha SP, Siri S, Tomsej M, Tenhunen M, Povall J, Kry SF, Followill DS, Thwaites DI, Georg D, Izewska J. A multinational audit of small field output factors calculated by treatment planning systems used in radiotherapy. Phys Imaging Radiat Oncol 2018; 5:58-63. [PMID: 33458370 PMCID: PMC7807586 DOI: 10.1016/j.phro.2018.02.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Revised: 02/14/2018] [Accepted: 02/15/2018] [Indexed: 11/03/2022] Open
Abstract
BACKGROUND AND PURPOSE An audit methodology for verifying the implementation of output factors (OFs) of small fields in treatment planning systems (TPSs) used in radiotherapy was developed and tested through a multinational research group and performed on a national level in five different countries. MATERIALS AND METHODS Centres participating in this study were asked to provide OFs calculated by their TPSs for 10 × 10 cm2, 6 × 6 cm2, 4 × 4 cm2, 3 × 3 cm2 and 2 × 2 cm2 field sizes using an SSD of 100 cm. The ratio of these calculated OFs to reference OFs was analysed. The action limit was ±3% for the 2 × 2 cm2 field and ±2% for all other fields. RESULTS OFs for more than 200 different beams were collected in total. On average, the OFs for small fields calculated by TPSs were generally larger than measured reference data. These deviations increased with decreasing field size. On a national level, 30% and 31% of the calculated OFs of the 2 × 2 cm2 field exceeded the action limit of 3% for nominal beam energies of 6 MV and for nominal beam energies higher than 6 MV, respectively. CONCLUSION Modern TPS beam models generally overestimate the OFs for small fields. The verification of calculated small field OFs is a vital step and should be included when commissioning a TPS. The methodology outlined in this study can be used to identify potential discrepancies in clinical beam models.
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Affiliation(s)
- Wolfgang Lechner
- International Atomic Energy Agency, Vienna, Austria
- Medical University of Vienna, Department of Radiation Oncology, Vienna, Austria
- Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Vienna, Austria
| | | | - Godfrey Azangwe
- International Atomic Energy Agency, Vienna, Austria
- National University of Science and Technology, Bulawayo, Zimbabwe
| | - Mehenna Arib
- Centre De Recherche Nucleaire D’alger, Alger Gare, Algeria
| | | | - Luo Suming
- Chinese Centre for Disease Control and Prevention, Beijing, China
| | | | - Wojciech Bulski
- Maria Sklodowska-Curie Memorial Cancer Centre and Institute of Oncology, Warsaw, Poland
| | | | - Sumanth Panyam Vinatha
- Radiation Standards Section, Radiation Safety Systems Division, Bhabha Atomic Research Centre Trombay, Mumbai, India
| | - Srimanoroth Siri
- SSDL, Bureau of Radiation and Medical Devices, Department of Medical Science, Nonthaburi, Thailand
| | - Milan Tomsej
- CHU Charleroi, Hopital Andre Vesale, Montigny-le-Tilleul, Belgium
| | - Mikko Tenhunen
- Helsinki University Hospital, Cancer Centre, Helsinki, Finland
| | - Julie Povall
- Department of Medical Physics & Engineering, St James’s University Hospital, Leeds, United Kingdom
| | - Stephen F. Kry
- Imaging and Radiation Oncology Core Houston QA Centre, MD Anderson Cancer Centre, Houston, TX, United States
| | - David S. Followill
- Imaging and Radiation Oncology Core Houston QA Centre, MD Anderson Cancer Centre, Houston, TX, United States
| | - David I. Thwaites
- University of Leeds, St James’s University Hospital, Leeds, United Kingdom
- Institute of Medical Physics, School of Physics, University of Sydney, Sydney, Australia
| | - Dietmar Georg
- Medical University of Vienna, Department of Radiation Oncology, Vienna, Austria
- Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Vienna, Austria
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Borzov E, Nevelsky A, Bar-Deroma R, Orion I. Dosimetric characterization of Elekta stereotactic cones. J Appl Clin Med Phys 2017; 19:194-203. [PMID: 29266744 PMCID: PMC5768017 DOI: 10.1002/acm2.12242] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 11/18/2017] [Accepted: 11/20/2017] [Indexed: 11/14/2022] Open
Abstract
Purpose Dosimetry of small fields defined by stereotactic cones remains a challenging task. In this work, we report the results of commissioning measurements for the new Elekta stereotactic conical collimator system attached to the Elekta VersaHD linac and present the comparison between the measured and Monte Carlo (MC) calculated data for the 6 MV FFF beam. In addition, relative output factor (ROF) dependence on the stereotactic cone aperture variation was studied and penumbra comparison for small MLC‐based and cone‐based fields was performed. Methods Cones with nominal diameters of 15 mm, 12.5 mm, 10 mm, 7.5 mm, and 5 mm were employed in our study. Percentage depth dose (PDD), off‐axis ratios (OAR), and ROF were measured using a stereotactic field diode (SFD). BEAMnrc code was used for MC simulations. Results MC calculated and measured PDDs for all cones agreed within 1%/0.5 mm, and OAR profiles agreed within 1%/0.5 mm. ROF obtained from the measurements and MC calculations agreed within 2% for all cone sizes. Small‐field correction factors for the SFD detector Kfield,3 × 3(SFD) were derived using MC calculations as a baseline and were found to be 0.982, 0.992, 0.997, 1.015, and 1.017 for the 5, 7.5, 10, 12.5, and 15‐mm cones respectively. The difference in ROF was about 10%, 6%, 3.5%, 3%, 2.5%, and 2% for ±0.3 mm variations in 5, 7.5, 10, 12.5, and 15‐mm cone aperture respectively. In case of single static field, cone‐based collimation produced a sharper penumbra compared to the MLC‐based. Conclusions Accurate MC simulation can be an effective tool for verification of dosimetric measurements of small fields. Due to the very high sensitivity of output factors on the cone diameter, manufacture‐related variations in cone size may lead to considerable variations in dosimetric characteristics of stereotactic cones.
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Affiliation(s)
- Egor Borzov
- Department of Radiotherapy, Division of Oncology, Rambam Health Care Campus, Haifa, Israel
| | - Alexander Nevelsky
- Department of Radiotherapy, Division of Oncology, Rambam Health Care Campus, Haifa, Israel
| | - Raquel Bar-Deroma
- Department of Radiotherapy, Division of Oncology, Rambam Health Care Campus, Haifa, Israel
| | - Itzhak Orion
- Department of Nuclear Engineering, Ben-Gurion University of the Negev, Beer Sheva, Israel
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Veselsky T, Novotny J, Pastykova V, Koniarova I. Determination of small field synthetic single-crystal diamond detector correction factors for CyberKnife, Leksell Gamma Knife Perfexion and linear accelerator. Phys Med 2017; 44:66-71. [DOI: 10.1016/j.ejmp.2017.11.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Revised: 10/09/2017] [Accepted: 11/09/2017] [Indexed: 10/18/2022] Open
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Aland T, Jhala E, Kairn T, Trapp J. Film dosimetry using a smart device camera: a feasibility study for point dose measurements. ACTA ACUST UNITED AC 2017; 62:N506-N515. [DOI: 10.1088/1361-6560/aa8b36] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Zoros E, Moutsatsos A, Pappas EP, Georgiou E, Kollias G, Karaiskos P, Pantelis E. Monte Carlo and experimental determination of correction factors for gamma knife perfexion small field dosimetry measurements. Phys Med Biol 2017; 62:7532-7555. [PMID: 28796643 DOI: 10.1088/1361-6560/aa8590] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Detector-, field size- and machine-specific correction factors are required for precise dosimetry measurements in small and non-standard photon fields. In this work, Monte Carlo (MC) simulation techniques were used to calculate the [Formula: see text] and [Formula: see text] correction factors for a series of ionization chambers, a synthetic microDiamond and diode dosimeters, used for reference and/or output factor (OF) measurements in the Gamma Knife Perfexion photon fields. Calculations were performed for the solid water (SW) and ABS plastic phantoms, as well as for a water phantom of the same geometry. MC calculations for the [Formula: see text] correction factors in SW were compared against corresponding experimental results for a subset of ionization chambers and diode detectors. Reference experimental OF data were obtained through the weighted average of corresponding measurements using TLDs, EBT-2 films and alanine pellets. [Formula: see text] values close to unity (within 1%) were calculated for most of ionization chambers in water. Greater corrections of up to 6.0% were observed for chambers with relatively large air-cavity dimensions and steel central electrode. A phantom correction of 1.006 and 1.024 (breaking down to 1.014 from the ABS sphere and 1.010 from the accompanying ABS phantom adapter) were calculated for the SW and ABS phantoms, respectively, adding up to [Formula: see text] corrections in water. Both measurements and MC calculations for the diode and microDiamond detectors resulted in lower than unit [Formula: see text] correction factors, due to their denser sensitive volume and encapsulation materials. In comparison, higher than unit [Formula: see text] results for the ionization chambers suggested field size depended dose underestimations (being significant for the 4 mm field), with magnitude depending on the combination of contradicting phenomena associated with volume averaging and electron fluence perturbations. Finally, the presence of 0.5 mm air-gap between the diodes' frontal surface and their phantom-inserts may considerably influence OF measurements, reaching 4.6% for the Razor diode.
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Affiliation(s)
- E Zoros
- Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, 75 Mikras Asias, 115 27 Athens, Greece
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Poppinga D, Delfs B, Meyners J, Harder D, Poppe B, Looe HK. The output factor correction as function of the photon beam field size - direct measurement and calculation from the lateral dose response functions of gas-filled and solid detectors. Z Med Phys 2017; 28:224-235. [PMID: 28869164 DOI: 10.1016/j.zemedi.2017.07.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 07/07/2017] [Accepted: 07/17/2017] [Indexed: 10/19/2022]
Abstract
The first aim of this study has been to extend the systematic experimental study of the field size dependence of the output factor correction for three micro-ionization chambers (PTW 31014, PTW 31022 and IBA Razor chamber), two silicon diodes (PTW 60017 and IBA Razor Diode) and the synthetic diamond detector microDiamond (PTW 60019) in a 6 MV photon beam down to an effective field side length of 2.6mm, and to summarize the present knowledge of this factor by treating it as a function of the dosimetric field size. In order to vary the dosimetric field size over this large range, output factors measurements were performed at source-to-surface distances of 60cm and 90cm. Since the output factors obtained with the organic scintillation detector Exradin W1 (Standard Imaging, Middleton, USA) at all field sizes closely agreed with those measured by EBT3 radiochromic films (ISP Corp, Wayne, USA), the scintillation detector served as the reference detector. The measured output correction factors reflect the influences of the volume averaging and density effects upon the uncorrected output factor values. In case of the microDiamond detector these opposing influences result in output factor correction values less than 1 for moderately small field sizes and larger than 1 for very small field sizes. Our results agree with most of the published experimental as well as Monte-Carlo simulated data within detector-specific limits of uncertainty. The dosimetric field side length has been identified as a reliable determinant of the output factor correction, and typical functional curve shapes of the field-size dependent output factor correction vs. dosimetric field side length have been associated with gas-filled, silicon diode and synthetic diamond detectors. The second aim of this study has been a novel, semi-empirical approach to calculate the field-size dependent output correction factors of small photon detectors by convolving film measured true dose profile data with measured lateral response functions of the detectors. To achieve this, the set of previously published 2D lateral dose response functions was complemented by those of the novel detectors PTW PinPoint chamber 31022 (PTW Freiburg, Freiburg, Germany), Razor chamber and Razor Diode (IBA Dosimetry, Schwarzenbruck, Germany). The output correction factors calculated from the lateral dose response functions closely fit with the directly measured output correction factors, thus supporting the latter by an independent method.
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Affiliation(s)
- Daniela Poppinga
- University Clinic for Medical Radiation Physics, Medical Campus Pius-Hospital, Carl von Ossietzky University, Georgstraße 12, 26121 Oldenburg, Germany.
| | - Björn Delfs
- University Clinic for Medical Radiation Physics, Medical Campus Pius-Hospital, Carl von Ossietzky University, Georgstraße 12, 26121 Oldenburg, Germany
| | - Jutta Meyners
- Radiotherapy Department, Imland Hospital, Lilienstraße 20-28, 24768 Rendsburg, Germany
| | - Dietrich Harder
- Prof. em., Medical Physics and Biophysics, Georg August University, Wilhelmsplatz 1, 37073 Göttingen, Germany
| | - Björn Poppe
- University Clinic for Medical Radiation Physics, Medical Campus Pius-Hospital, Carl von Ossietzky University, Georgstraße 12, 26121 Oldenburg, Germany
| | - Hui Khee Looe
- University Clinic for Medical Radiation Physics, Medical Campus Pius-Hospital, Carl von Ossietzky University, Georgstraße 12, 26121 Oldenburg, Germany
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De Coste V, Francescon P, Marinelli M, Masi L, Paganini L, Pimpinella M, Prestopino G, Russo S, Stravato A, Verona C, Verona-Rinati G. Is the PTW 60019 microDiamond a suitable candidate for small field reference dosimetry? ACTA ACUST UNITED AC 2017; 62:7036-7055. [DOI: 10.1088/1361-6560/aa7e59] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Yarahmadi M, Wegener S, Sauer OA. Energy and field size dependence of a silicon diode designed for small-field dosimetry. Med Phys 2017; 44:1958-1964. [DOI: 10.1002/mp.12195] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 02/17/2017] [Accepted: 02/28/2017] [Indexed: 11/10/2022] Open
Affiliation(s)
- Mehran Yarahmadi
- Department of Medical Physics; Faculty of Medicine; Kurdistan University of Medical Sciences; Sanandaj Iran
| | - Sonja Wegener
- Department of Radiation Oncology; University of Würzburg; Josef-Schneider-Strasse 11 97080 Würzburg Germany
| | - Otto A. Sauer
- Department of Radiation Oncology; University of Würzburg; Josef-Schneider-Strasse 11 97080 Würzburg Germany
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Davis W, Crewson C, Alexander A, Kundapur V, Cranmer-Sargison G. Dosimetric characterization of an accessory mounted mini-beam collimator across clinically beam matched medical linear accelerators. Biomed Phys Eng Express 2017. [DOI: 10.1088/2057-1976/aa586d] [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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Benmakhlouf H, Andreo P. Spectral distribution of particle fluence in small field detectors and its implication on small field dosimetry. Med Phys 2017; 44:713-724. [DOI: 10.1002/mp.12042] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2016] [Revised: 11/14/2016] [Accepted: 11/27/2016] [Indexed: 11/07/2022] Open
Affiliation(s)
- Hamza Benmakhlouf
- Department of Medical Radiation Physics and Nuclear Medicine; Karolinska University Hospital; SE-17176 Stockholm Sweden
| | - Pedro Andreo
- Department of Medical Radiation Physics and Nuclear Medicine; Karolinska University Hospital; SE-17176 Stockholm Sweden
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Small field output factors evaluation with a microDiamond detector over 30 Italian centers. Phys Med 2016; 32:1644-1650. [DOI: 10.1016/j.ejmp.2016.10.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2016] [Revised: 10/25/2016] [Accepted: 10/26/2016] [Indexed: 11/18/2022] Open
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Qin Y, Zhong H, Wen N, Snyder K, Huang Y, Chetty IJ. Deriving detector-specific correction factors for rectangular small fields using a scintillator detector. J Appl Clin Med Phys 2016; 17:379-391. [PMID: 27929510 PMCID: PMC5690516 DOI: 10.1120/jacmp.v17i6.6433] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 08/30/2016] [Accepted: 08/29/2016] [Indexed: 11/23/2022] Open
Abstract
The goal of this study was to investigate small field output factors (OFs) for flattening filter‐free (FFF) beams on a dedicated stereotactic linear accelerator‐based system. From this data, the collimator exchange effect was quantified, and detector‐specific correction factors were generated. Output factors for 16 jaw‐collimated small fields (from 0.5 to 2 cm) were measured using five different detectors including an ion chamber (CC01), a stereotactic field diode (SFD), a diode detector (Edge), Gafchromic film (EBT3), and a plastic scintillator detector (PSD, W1). Chamber, diodes, and PSD measurements were performed in a Wellhofer water tank, while films were irradiated in solid water at 100 cm source‐to‐surface distance and 10 cm depth. The collimator exchange effect was quantified for rectangular fields. Monte Carlo (MC) simulations of the measured configurations were also performed using the EGSnrc/DOSXYZnrc code. Output factors measured by the PSD and verified against film and MC calculations were chosen as the benchmark measurements. Compared with plastic scintillator detector (PSD), the small volume ion chamber (CC01) underestimated output factors by an average of ‐1.0%±4.9%(max.=‐11.7% for 0.5×0.5cm2 square field). The stereotactic diode (SFD) overestimated output factors by 2.5%±0.4%(max.=3.3% for 0.5×1cm2 rectangular field). The other diode detector (Edge) also overestimated the OFs by an average of 4.2%±0.9%(max.=6.0% for 1×1cm2 square field). Gafchromic film (EBT3) measurements and MC calculations agreed with the scintillator detector measurements within 0.6%±1.8% and 1.2%±1.5%, respectively. Across all the X and Y jaw combinations, the average collimator exchange effect was computed: 1.4%±1.1% (CC01), 5.8%±5.4% (SFD), 5.1%±4.8% (Edge diode), 3.5%±5.0% (Monte Carlo), 3.8%±4.7% (film), and 5.5%±5.1% (PSD). Small field detectors should be used with caution with a clear understanding of their behaviors, especially for FFF beams and small, elongated fields. The scintillator detector exhibited good agreement against Gafchromic film measurements and MC simulations over the range of field sizes studied. The collimator exchange effect was found to be important at these small field sizes. Detector‐specific correction factors were computed using the scintillator measurements as the benchmark. PACS number(s): 87.56.Fc
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Park K, Bak J, Park S, Choi W, Park SW. Determination of small-field correction factors for cylindrical ionization chambers using a semiempirical method. Phys Med Biol 2016; 61:1293-308. [PMID: 26796623 DOI: 10.1088/0031-9155/61/3/1293] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A semiempirical method based on the averaging effect of the sensitive volumes of different air-filled ionization chambers (ICs) was employed to approximate the correction factors for beam quality produced from the difference in the sizes of the reference field and small fields.We measured the output factors using several cylindrical ICs and calculated the correction factors using a mathematical method similar to deconvolution; in the method, we modeled the variable and inhomogeneous energy fluence function within the chamber cavity. The parameters of the modeled function and the correction factors were determined by solving a developed system of equations as well as on the basis of the measurement data and the geometry of the chambers. Further, Monte Carlo (MC) computations were performed using the Monaco® treatment planning system to validate the proposed method.The determined correction factors () were comparable to the values derived from the MC computations performed using Monaco®. For example, for a 6 MV photon beam and a field size of 1 × 1 cm2, was calculated to be for a PTW 31010 chamber and for a PTW 31016 chamber. On the other hand, the values determined from the MC computations were 1.121 and 1.031, respectively; the difference between the proposed method and the MC computation is less than 2%. In addition, we determined the values for PTW 30013, PTW 31010, PTW 31016, IBA FC23-C, and IBA CC13 chambers as well.We devised a method for determining from both the measurement of the output factors and model-based mathematical computation. The proposed method can be useful in case the MC simulation would not be applicable for the clinical settings.
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Fogliata A, Lobefalo F, Reggiori G, Stravato A, Tomatis S, Scorsetti M, Cozzi L. Evaluation of the dose calculation accuracy for small fields defined by jaw or MLC for AAA and Acuros XB algorithms. Med Phys 2016; 43:5685. [DOI: 10.1118/1.4963219] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Morales JE, Butson M, Crowe SB, Hill R, Trapp JV. An experimental extrapolation technique using the Gafchromic EBT3 film for relative output factor measurements in small x-ray fields. Med Phys 2016; 43:4687. [DOI: 10.1118/1.4958679] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Effects of inaccurate small field dose measurements on calculated treatment doses. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2016; 39:747-53. [DOI: 10.1007/s13246-016-0461-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2016] [Accepted: 06/23/2016] [Indexed: 12/31/2022]
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Study of commercial detector responses in non-equilibrium small photon fields of a 1000 MU/min CyberKnife system. Phys Med 2016; 32:818-25. [DOI: 10.1016/j.ejmp.2016.05.052] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 05/09/2016] [Accepted: 05/10/2016] [Indexed: 11/30/2022] Open
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Cheng JY, Ning H, Arora BC, Zhuge Y, Miller RW. Output factor comparison of Monte Carlo and measurement for Varian TrueBeam 6 MV and 10 MV flattening filter-free stereotactic radiosurgery system. J Appl Clin Med Phys 2016; 17:100-110. [PMID: 27167266 PMCID: PMC5690931 DOI: 10.1120/jacmp.v17i3.5956] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Revised: 12/30/2015] [Accepted: 12/22/2015] [Indexed: 11/25/2022] Open
Abstract
The dose measurements of the small field sizes, such as conical collimators used in stereotactic radiosurgery (SRS), are a significant challenge due to many factors including source occlusion, detector size limitation, and lack of lateral electronic equilibrium. One useful tool in dealing with the small field effect is Monte Carlo (MC) simulation. In this study, we report a comparison of Monte Carlo simulations and measurements of output factors for the Varian SRS system with conical collimators for energies of 6 MV flattening filter‐free (6 MV) and 10 MV flattening filter‐free (10 MV) on the TrueBeam accelerator. Monte Carlo simulations of Varian's SRS system for 6 MV and 10 MV photon energies with cones sizes of 17.5 mm, 15.0 mm, 12.5 mm, 10.0 mm, 7.5 mm, 5.0 mm, and 4.0 mm were performed using EGSnrc (release V4 2.4.0) codes. Varian's version‐2 phase‐space files for 6 MV and 10 MV of TrueBeam accelerator were utilized in the Monte Carlo simulations. Two small diode detectors Edge (Sun Nuclear) and Small Field Detector (SFD) (IBA Dosimetry) were applied to measure the output factors. Significant errors may result if detector correction factors are not applied to small field dosimetric measurements. Although it lacked the machine‐specific kQclin,Qmsrfclin,fmsr correction factors for diode detectors in this study, correction factors were applied utilizing published studies conducted under similar conditions. For cone diameters greater than or equal to 12.5 mm, the differences between output factors for the Edge detector, SFD detector, and MC simulations are within 3.0% for both energies. For cone diameters below 12.5 mm, output factors differences exhibit greater variations. PACS number(s): 87.55.k, 87.55.Qr
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Affiliation(s)
- Jason Y Cheng
- National Cancer Institute; National Institutes of Health.
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Papaconstadopoulos P, Levesque IR, Maglieri R, Seuntjens J. Direct reconstruction of the source intensity distribution of a clinical linear accelerator using a maximum likelihood expectation maximization algorithm. Phys Med Biol 2016; 61:1078-94. [PMID: 26758232 DOI: 10.1088/0031-9155/61/3/1078] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Direct determination of the source intensity distribution of clinical linear accelerators is still a challenging problem for small field beam modeling. Current techniques most often involve special equipment and are difficult to implement in the clinic. In this work we present a maximum-likelihood expectation-maximization (MLEM) approach to the source reconstruction problem utilizing small fields and a simple experimental set-up. The MLEM algorithm iteratively ray-traces photons from the source plane to the exit plane and extracts corrections based on photon fluence profile measurements. The photon fluence profiles were determined by dose profile film measurements in air using a high density thin foil as build-up material and an appropriate point spread function (PSF). The effect of other beam parameters and scatter sources was minimized by using the smallest field size ([Formula: see text] cm(2)). The source occlusion effect was reproduced by estimating the position of the collimating jaws during this process. The method was first benchmarked against simulations for a range of typical accelerator source sizes. The sources were reconstructed with an accuracy better than 0.12 mm in the full width at half maximum (FWHM) to the respective electron sources incident on the target. The estimated jaw positions agreed within 0.2 mm with the expected values. The reconstruction technique was also tested against measurements on a Varian Novalis Tx linear accelerator and compared to a previously commissioned Monte Carlo model. The reconstructed FWHM of the source agreed within 0.03 mm and 0.11 mm to the commissioned electron source in the crossplane and inplane orientations respectively. The impact of the jaw positioning, experimental and PSF uncertainties on the reconstructed source distribution was evaluated with the former presenting the dominant effect.
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Affiliation(s)
- P Papaconstadopoulos
- McGill University, Medical Physics Unit and the Research Institute of the McGill University Health Centre, Montreal, QC H3A 0G4, Canada
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