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Msimang ZLM, Van Der Merwe D, Maphumulo N. Effect of Three-Dimensional Detector Orientation on Small-Field Output Factors. J Med Phys 2021; 45:256-260. [PMID: 33953502 PMCID: PMC8074723 DOI: 10.4103/jmp.jmp_50_20] [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: 06/10/2020] [Revised: 01/04/2021] [Accepted: 01/04/2021] [Indexed: 11/04/2022] Open
Abstract
The IAEA TRS 483 has recommended that the orientation for cylindrical ionization chambers be perpendicular to the beam for small-field output factor (OF) measurements. The recommendation was based on the unavailability of field output correction factor data for measurements using parallel orientation at the time of publication. Two three-dimensional (3D) air ionization chambers were used to perform measurements in parallel and perpendicular orientations and compared to data determined using a PTW 31018. The aim of the study was to establish whether the 3D detectors behaved as spherical or cylindrical devices. From the results, it was confirmed that the PTW 31016 and PTW 31021 detectors are suitable for OF measurements in both orientations for field sizes down to an equivalent square field of 1.8 cm and 0.96 cm, respectively, using the field output correction factor data published in the IAEA TRS 483. The preferred orientation is parallel to the beam to facilitate beam profile measurements and minimize the irradiation of the chamber stem and detector cable and decrease the volume averaging factor.
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Affiliation(s)
| | - Debbie Van Der Merwe
- Department of Physics, University of the Witwatersrand, Johannesburg, South Africa
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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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Bouchard H, Billas I, Subiel A, Duane S. Eigencolor radiochromic film dosimetry. Med Phys 2021; 48:2592-2603. [PMID: 33525060 DOI: 10.1002/mp.14742] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 12/21/2020] [Accepted: 01/16/2021] [Indexed: 11/06/2022] Open
Abstract
PURPOSE The goal of this work is to propose a new multichannel method correcting for systematic thickness disturbances and to evaluate its precision in relevant radiation dosimetry applications. METHODS The eigencolor ratio technique is introduced and theoretically developed to provide a method correcting for thickness disturbances. The method is applied to EBT3 GafchromicTM film irradiated with cobalt-60 and 6 MV photon beams and digitized with an Epson 10000XL photo scanner. Dose profiles and output factors of different field sizes are measured and analyzed. Variance analysis of the previous method of Bouchard et al. ["On the characterization and uncertainty analysis of radiochromic film dosimetry" Med Phys. 2009;36:1931-1946] is adapted to the new approach. Uncertainties are predicted for relevant applications. RESULTS Results show that systematic disturbances attributed to thickness variations are efficiently corrected. The method is shown efficient to identify and correct for dark spots which cause systematic errors in single-channel distributions. Applications of the method in the context of relative dosimetry yields standard uncertainties ranging between 0.8% and 1.9%, depending on the region of interest (ROI) size and the film irradiation. Variance analysis predicts that uncertainty levels between 0.3% and 0.6% are achievable with repeated measurements. Uncertainties are found to vary with absorbed dose and ROI size. CONCLUSIONS The proposed multichannel method is efficient for accurate dosimetry, reaching uncertainty levels comparable to previous publications with EBT film. The method is also promising for applications beyond clinical QA, such as machine characterization and other advanced dosimetry applications.
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Affiliation(s)
- Hugo Bouchard
- Département de physique, Université de Montréal, Complexe des sciences, 1375 Avenue Thérèse-Lavoie-Roux, Montréal, QC, H2V 0B3, Canada.,Centre de recherche du CHUM, 900 Rue Saint-Denis, Montréal, QC, H2X 3H8, Canada.,Département de radio-oncologie, Centre hospitalier de l'Université de Montréal (CHUM), 1051 rue Sanguinet, Montréal, QC, H2X 3E4, Canada
| | - Ilias Billas
- National Physical Laboratory, Chemical, Medical and Environmental Science Department, Hampton Rd, Teddington, TW11 0LW, UK
| | - Anna Subiel
- National Physical Laboratory, Chemical, Medical and Environmental Science Department, Hampton Rd, Teddington, TW11 0LW, UK
| | - Simon Duane
- National Physical Laboratory, Chemical, Medical and Environmental Science Department, Hampton Rd, Teddington, TW11 0LW, UK
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Mancosu P, Russo S, Antonucci AR, Stasi M. Lean Thinking to manage a national working group on physics aspects of Stereotactic Body Radiation Therapy. Med Phys 2021; 48:2050-2056. [PMID: 33598932 DOI: 10.1002/mp.14783] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 01/21/2021] [Accepted: 02/09/2021] [Indexed: 12/14/2022] Open
Abstract
PURPOSE To report how the adoption of a Lean Thinking mindset in the management of a national working group (WG) on the physics of stereotactic body radiation therapy (SBRT) contributed to achieve SBRT standardization objectives. METHODS Vision for the WG has been established as fragmentation reduction and process harmonization enhancement in SBRT for Italian centers. Two main research themes of the technical aspects of SBRT emerged as areas with major standardization improvement needs, small field dosimetry and SBRT planning comparisons, to be investigated through multi-institutional studies. The management of the WG leveraged on the Lean concept of fostering self-organization in a non-hierarchical environment. Four progressive involvement levels were defined for each study. No specific "scientific" pre-experience was required to propose and coordinate a project, just requiring a voluntary commitment. People engagement was measured in terms of number of published articles. The standardization goals have been conducted through a simplified "5S" (Sort, Set in Order, Shine, Standardize, and Sustain) methodology, first considering a phase of awareness (the first three "S"), then identifying and implementing standardization actions (the last two "S"). RESULTS Since the beginning, 157 medical physicists joined the AIFM/SBRT-WG. Twenty-four papers/reviews/letters have been published in the period 2014-2019 on major radiation oncology journals, authored by >100 physicists (>50% working in small hospitals). Six over 12 first authors worked in peripheral/small hospitals, with no prior publication as first author. These studies contributed to the awareness and standardization phases for both small-field dosimetry and planning. In particular, errors in small-field measurements in 8% of centers were detected thanks to a generalized output factor curve in function of the effective field size created by averaging data available from different Linacs. Furthermore, planner's experience in SBRT was correlated with dosimetric parameters in the awareness phase; while sharing median dose volume histograms (DVHs) reduced variability among centers while keeping the same level of plan complexity. Finally, all the dosimetric parameters statistically significant to the planner experience during the awareness phase, were no longer significantly different in the standardization phase. CONCLUSIONS The experience of our SBRT-WG has shown how a Lean Thinking mindset could foster the SBRT procedure standardization and spread the physics of SBRT knowledge, enhancing personal growth. Our expectation is to inspire other scientific societies that have to deal with fragmented contexts or pursue processes harmonization through Lean principles.
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Affiliation(s)
- Pietro Mancosu
- Medical Physics Unit, Radiotherapy Department, IRCCS Humanitas Research Hospital, Milano, Italy
| | - Serenella Russo
- Medical Physics Unit, Azienda USL Toscana Centro, Firenze, Italy
| | | | - Michele Stasi
- Medical Physics Department, A.O. Ordine Mauriziano di Torino, Turin, Italy
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Akino Y, Okamura K, Das IJ, Isohashi F, Seo Y, Tamari K, Hirata T, Hayashi K, Inoue S, Ogawa K. Technical Note: Characteristics of a microSilicon X shielded diode detector for photon beam dosimetry. Med Phys 2021; 48:2004-2009. [DOI: 10.1002/mp.14639] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 11/09/2020] [Accepted: 11/24/2020] [Indexed: 11/07/2022] Open
Affiliation(s)
- Yuichi Akino
- Oncology Center Osaka University Hospital 2‐2 (D10) Yamadaoka, Suita Osaka565‐0871Japan
| | - Keita Okamura
- Department of Medical Technology Osaka University Hospital 2‐15 Yamadaoka, Suita Osaka565‐0871Japan
| | - Indra J. Das
- Department of Radiation Oncology Northwestern Memorial HospitalNorthwestern University Feinberg School of Medicine 251 East Huron Street, Galter Pavilion Chicago ILLC‐17860611USA
| | - Fumiaki Isohashi
- Department of Radiation Oncology Osaka University Graduate School of Medicine 2‐2 (D10) Yamadaoka, Suita Osaka565‐0871Japan
| | - Yuji Seo
- Department of Radiation Oncology Osaka University Graduate School of Medicine 2‐2 (D10) Yamadaoka, Suita Osaka565‐0871Japan
| | - Keisuke Tamari
- Department of Radiation Oncology Osaka University Graduate School of Medicine 2‐2 (D10) Yamadaoka, Suita Osaka565‐0871Japan
| | - Takero Hirata
- Department of Radiation Oncology Osaka University Graduate School of Medicine 2‐2 (D10) Yamadaoka, Suita Osaka565‐0871Japan
| | - Kazuhiko Hayashi
- Department of Radiation Oncology Osaka University Graduate School of Medicine 2‐2 (D10) Yamadaoka, Suita Osaka565‐0871Japan
| | - Shinichi Inoue
- Department of Medical Technology Osaka University Hospital 2‐15 Yamadaoka, Suita Osaka565‐0871Japan
| | - Kazuhiko Ogawa
- Department of Radiation Oncology Osaka University Graduate School of Medicine 2‐2 (D10) Yamadaoka, Suita Osaka565‐0871Japan
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de Pooter J, Billas I, de Prez L, Duane S, Kapsch RP, Karger CP, van Asselen B, Wolthaus J. Reference dosimetry in MRI-linacs: evaluation of available protocols and data to establish a Code of Practice. Phys Med Biol 2021; 66:05TR02. [PMID: 32570225 DOI: 10.1088/1361-6560/ab9efe] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
With the rapid increase in clinical treatments with MRI-linacs, a consistent, harmonized and sustainable ground for reference dosimetry in MRI-linacs is needed. Specific for reference dosimetry in MRI-linacs is the presence of a strong magnetic field. Therefore, existing Code of Practices (CoPs) are inadequate. In recent years, a vast amount of papers have been published in relation to this topic. The purpose of this review paper is twofold: to give an overview and evaluate the existing literature for reference dosimetry in MRI-linacs and to discuss whether the literature and datasets are adequate and complete to serve as a basis for the development of a new or to extend existing CoPs. This review is prefaced with an overview of existing MRI-linac facilities. Then an introduction on the physics of radiation transport in magnetic fields is given. The main part of the review is devoted to the evaluation of the literature with respect to the following subjects: • beam characteristics of MRI-linac facilities; • formalisms for reference dosimetry in MRI-linacs; • characteristics of ionization chambers in the presence of magnetic fields; • ionization chamber beam quality correction factors; and • ionization chamber magnetic field correction factors. The review is completed with a discussion as to whether the existing literature is adequate to serve as basis for a CoP. In addition, it highlights subjects for future research on this topic.
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Renil Mon PS, Meena Devi VN, Bhasi S, Nair SS. Monte Carlo calculated detector-specific correction factors for Elekta radiosurgery cones. Biomed Phys Eng Express 2021; 7. [PMID: 33535198 DOI: 10.1088/2057-1976/abe2bb] [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: 09/04/2020] [Accepted: 02/03/2021] [Indexed: 11/12/2022]
Abstract
A radiation field is considered small if its dimension is lower than the range of secondary electrons and the collimating devices partially occlude the source. Different detector types, such as unshielded diodes, diamond detectors, and small-volume ion chambers, are used for small-field measurements. Although the active volumes of these detectors are small, their non-water equivalent materials cause response variations. Herein, we aim to calculate the correction factors for our clinical detectors, EDGE detector (Sun Nuclear), 60017 diode (PTW), and CC01 ion chamber (IBA), for stereotactic radiosurgery cones of diameters of 5-15 mm in an Elekta Synergy linear accelerator using a Monte Carlo simulation. An Elekta Synergy linear accelerator treatment head was simulated using BEAMnrc Monte Carlo code as per the manufacturer specification. All three detectors were simulated as per the manufacturer specification. Three EGSnrc user codes were used for the detector simulation based on the detector geometry. The Monte Carlo model of the treatment head was validated against the measured data for a standard field size of 10 × 10 cm2. The off-axis profile, percentage depth dose, and tissue phantom ratioTPR1020were verified in the validation procedure. The measured and Monte Carlo calculated relative output factors (ROFs) were not consistent. In a 5 mm field size, EDGE diode overestimated the ROF by 7.06%, and 60017 diode to 4.611%. In a 7.5 mm field size, the variations were 4.295% and 3.691% for EDGE and 60017 diodes, respectively. CC01 ion chamber under-responded up to 10% because of its low-density active volume. The maximum corrections were obtained in the smallest field size, which were 0.939(0.007), 0.962(0.006), and 1.117(0.008) for EDGE, PTW T60017, and CC01 detectors, respectively. After applying the Monte Carlo calculated correction factor to the measured ROF, it became consistent with the Monte Carlo calculated ROF.
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Affiliation(s)
- P S Renil Mon
- Department of Physics, Noorul Islam Centre for Higher Education, Kumarakoil, Kanyakumari District, Tamil Nadu, India.,Department of Medical Physics and Radiation Safety, Amrita Institute of Medical Sciences and Research Centre, Cochin, India.,National Center for Cancer Care and Research, Hamad Medical Corporation, Doha, Qatar
| | - V N Meena Devi
- Department of Physics, Noorul Islam Centre for Higher Education, Kumarakoil, Kanyakumari District, Tamil Nadu, India
| | - Saju Bhasi
- Department of Radiation Physics, Regional Cancer Centre, Thiruvananthapuram, Kerala, India
| | - Sneha S Nair
- Department of Medical Physics and Radiation Safety, Amrita Institute of Medical Sciences and Research Centre, Cochin, India
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Clemente S, Falco MD, Cagni E, Talamonti C, Boccia M, Gino E, Lorenzini E, Rosica F, Russo S, Alparone A, Zefiro D, Fiandra C. The influence of small field output factors simulated uncertainties on the calculated dose in VMAT plans for brain metastases: a multicentre study. Br J Radiol 2021; 94:20201354. [PMID: 33481637 DOI: 10.1259/bjr.20201354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVES This multicentric study was carried out to investigate the impact of small field output factors (OFs) inaccuracies on the calculated dose in volumetric arctherapy (VMAT) radiosurgery brain plans. METHODS Nine centres, realised the same five VMAT plans with common planning rules and their specific clinical equipment Linac/treatment planning system commissioned with their OFs measured values (OFbaseline). In order to simulate OFs errors, two new OFs sets were generated for each centre by changing only the OFs values of the smallest field sizes (from 3.2 × 3.2 cm2 to 1 × 1 cm2) with well-defined amounts (positive and negative). Consequently, two virtual machines for each centre were recommissioned using the new OFs and the percentage dose differences ΔD (%) between the baseline plans and the same plans recalculated using the incremented (OFup) and decremented (OFdown) values were evaluated. The ΔD (%) were analysed in terms of planning target volume (PTV) coverage and organs at risk (OARs) sparing at selected dose/volume points. RESULTS The plans recalculated with OFdown sets resulted in higher variation of doses than baseline within 1.6 and 3.4% to PTVs and OARs respectively; while the plans with OFup sets resulted in lower variation within 1.3% to both PTVs and OARs. Our analysis highlights that OFs variations affect calculated dose depending on the algorithm and on the delivery mode (field jaw/MLC-defined). The Monte Carlo (MC) algorithm resulted significantly more sensitive to OFs variations than all of the other algorithms. CONCLUSION The aim of our study was to evaluate how small fields OFs inaccuracies can affect the dose calculation in VMAT brain radiosurgery treatments plans. It was observed that simulated OFs errors, return dosimetric calculation accuracies within the 3% between concurrent plans analysed in terms of percentage dose differences at selected dose/volume points of the PTV coverage and OARs sparing. ADVANCES IN KNOWLEDGE First multicentre study involving different Planning/Linacs about undetectable errors in commissioning output factor for small fields.
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Affiliation(s)
- Stefania Clemente
- Unit of Medical Physics and Radioprotection, Federico II University Hospital, Napoli, Italy
| | - Maria Daniela Falco
- Department of Radiation Oncology, "G. D'Annunzio" University, "SS. Annunziata" Hospital, Chieti, Italy
| | - Elisabetta Cagni
- Medical Physics Unit, Azienda USL-IRCCS di Reggio Emilia, Reggio Emilia, Italy
| | - Cinzia Talamonti
- Medical Physics Unit, University Of Florence, Azienda Ospedaliero Universitaria Careggi, Florence, Italy
| | | | - Eva Gino
- Medical PhysicDepartment, A.O. Ordine Mauriziano, Turin, Italy
| | - Elena Lorenzini
- U.O.C Fisica Sanitaria Area Nord, Azienda USL Nord Ovest Toscana, Massa Carrara, Italy
| | | | | | | | - Daniele Zefiro
- MedicaPhysics Unit, ASL5 Sistema Sanitario Regione Liguria, La Spezia, Italy
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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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Msimang ZLM, van der Merwe D, Maphumulo N. Repeatability of Small Field Output Factor Measurements with Various Detectors. J Med Phys 2021; 46:47-51. [PMID: 34267489 PMCID: PMC8240910 DOI: 10.4103/jmp.jmp_93_20] [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: 10/05/2020] [Revised: 01/08/2021] [Accepted: 01/24/2021] [Indexed: 11/05/2022] Open
Abstract
There are well established dosimetry reference standards for broad beams; however, there are no reference standards that can be used for both broad and small fields. The variation of the equivalent square fields and field output factors in small static photon fields when using a synthetic diamond, an electron diode, and ionization chambers (pin point, semiflex, and liquid filled) was investigated over time. Data from this study were compared to the data from other hospitals in the country and standard data sets, i.e., the British Journal of Radiology Supplement No. 25 of 1996 (BJR25) and the Radiological Physics Centre (RPC) 2012 data. The results showed that reliance on one detector and one measurement session, could yield incorrect field output factors (FOFs) for small fields. At least one of the detectors should be a solid state type with published field output correction factors and at least three measurement sessions should be performed for each FOF data point. Comparing measured data with published datasets, like RPC, will assist in verifying data. BJR25 datasets should not be used for S clin ≤4 cm.
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Affiliation(s)
| | - Debbie van der Merwe
- Department of Physics, University of the Witwatersrand, Johannesburg, South Africa
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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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Cervantes Y, Billas I, Shipley D, Duane S, Bouchard H. Small-cavity chamber dose response in megavoltage photon beams coupled to magnetic fields. Phys Med Biol 2020; 65:245008. [PMID: 32674077 DOI: 10.1088/1361-6560/aba6d6] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In MRgRT, dosimetry measurements are performed in the presence of magnetic fields. For high-resolution measurements, small-cavity ionization chambers are required. While Monte Carlo simulations are essential to determine dosimetry correction factors, models of small-chambers require careful validation with experimental measurements. The aim of this study is to characterize small-cavity chamber response coupled to magnetic fields. Small-cavity chambers (PTW31010, PTW31016, PTW31021 and PTW3022) are irradiated by a 6 MV photon beam for 9 magnetic field strengths between -1.5 T and +1.5 T. The chamber axis is orientated either parallel or perpendicular to the irradiation beam, with the magnetic field always perpendicular to the beam. MC simulations are performed in EGSnrc. The sensitive volume of the chambers is reduced to account for the inefficiency adjacent to the guard electrode (dead volume) based on COMSOL calculations of electric potentials. The magnetic field affects the chamber response by up to 4.1% and 4.5% in the parallel and perpendicular orientations, respectively, compared to no magnetic field. The maximal difference in dose response between experiments and simulations is up to 6.1% and 4.5% for parallel and perpendicular orientation, respectively. When the dead volume is removed, which accounts for the 15%-23% of the nominal volume, the difference, in most cases, is within the stated uncertainties. Nevertheless, for a particular chamber, the reduced nominal volume barely improved the agreement between the experimental and calculated relative response (4.53% to 4.13%). This disagreement may be due to the imperfect chamber geometry model, as was found from microCT images. A detailed uncertainty analysis is presented. The characterization of small-cavity ion chamber response coupled to magnetic fields is complex. Small differences between real and model chamber geometry that normally would be insignificant become an issue in the presence of magnetic fields. Accurate characterization of the nominal volume is essential for small-cavity ion chamber modelling.
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Affiliation(s)
- Yunuen Cervantes
- 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
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Häger W, Kaveckyte V, Benmakhlouf H. Experimental investigation of TRS-483 reference dosimetry correction factors for Leksell Gamma Knife® Icon™ beams. Med Phys 2020; 48:434-444. [PMID: 33119131 PMCID: PMC7894485 DOI: 10.1002/mp.14561] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 09/22/2020] [Accepted: 09/29/2020] [Indexed: 11/28/2022] Open
Abstract
Purpose Radiosurgery using the Leksell Gamma Knife® (LGK) Icon™ is an established technique used for treating intracranial lesions. The largest beam field size the LGK Icon can produce is a 16 mm diameter sphere. Despite this, reference dosimetry on the LGK Icon is typically performed using ionization chambers calibrated in 10 × 10 cm2 fields. Furthermore, plastic phantoms are widely used instead of liquid water phantoms. In an effort to resolve these issues, the International Atomic Energy Agency (IAEA) in collaboration with American Association of Physicists in medicine (AAPM) recently published Technical Report Series No. 483 (TRS‐483) as a Code of Practice for small‐field dosimetry. TRS‐483 includes small‐field correction factors, kQmsr,Q0fmsr,fref, intended to account for the differences between setups when using small‐field modalities such as the LGK Icon, and conventional setups. Since the publication of TRS‐483, at least three new sets of values of kQmsr,Q0fmsr,fref for the LGK Icon have been published. The purpose of this study was to experimentally investigate the published values of kQmsr,Q0fmsr,fref for commonly used phantom and ionization chamber (IC) models for the LGK Icon. Methods Dose‐rates from two LGK units were determined using acrylonitrile butadiene styrene (ABS) and Certified Medical Grade Solid Water® (SW) phantoms, and PTW 31010 and PTW 31016 ICs. Correction factors were applied, and the resulting dose‐rates compared. Relative validity of the correction factors was investigated by taking the ratios of dose‐rate correction factor products. Additionally, dose‐rates from the individual sectors were determined in order to calculate the beam attenuation caused by the ABS phantom adapter. Results and Conclusions It was seen that the dose‐rate is underestimated by at least 1% when using the ABS phantom, which was attributed to fluence perturbation caused by the IC and phantom adapter. Published correction factors kQmsr,Q0fmsr,fref account for these effects to varying degree and should be used. The SW phantom is unlikely to underestimate the dose‐rate by more than 1%, and applying kQmsr,Q0fmsr,fref could not be shown to be necessary. Out of the two phantom models, the ABS phantom is not recommended for use in LGK reference dosimetry. The use of newly published values of kQmsr,Q0fmsr,fref should be considered.
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Affiliation(s)
- Wille Häger
- Department of Physics, Stockholm University, Stockholm, SE-106 91, Sweden
| | - Vaiva Kaveckyte
- Radiation Physics, Department of Medical and Health Sciences, Linköping University, Linköping, SE-581 85, Sweden.,Department of Medical Radiation Physics and Nuclear Medicine, Karolinska University Hospital, Stockholm, SE-171 76, Sweden
| | - Hamza Benmakhlouf
- Department of Medical Radiation Physics and Nuclear Medicine, Karolinska University Hospital, Stockholm, SE-171 76, Sweden
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Lam SE, Noor NM, Bradley DA, Mahmud R, Pawanchek M, Abdul Rashid HA. Small-field output ratio determination using 6 mol% Ge-doped silica fibre dosimeters. Biomed Phys Eng Express 2020; 6. [PMID: 35042836 DOI: 10.1088/2057-1976/abc2a4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Accepted: 10/19/2020] [Indexed: 11/12/2022]
Abstract
This work investigates the suitability of locally fabricated 6 mol% Ge-doped optical fibres as dosimeters for small-field output ratio measurements. Two fabrications of fibre, cylindrical (CF) and flat (FF) fibres, were used to measure doses in small photon fields, from 4 to 15 mm. The findings were compared to those of commercial Ge-doped fibre (COMM), EBT3 film and an IBA CC01 ionization chamber. Irradiations were carried out using a 6 MV SRS photon beam operating at a dose rate of 1000 cGy min-1, delivering a dose of 16 Gy. To minimise the possibility of the fibres failing to be exposed to the intended dose in small fields, the fibres were accommodated in a custom-made Perspex phantom. For the 4 mm cone the CF and FF measured output ratios were found to be smaller than obtained with EBT3 film by 32% and 13% respectively. Conversely, while for the 6 to 15 mm cone fields the FF output ratios were consistently greater than those obtained using EBT3 film, the CF output ratios differed from those of EBT3 film by at most 3.2%, at 6 mm, otherwise essentially agreeing with EBT3 values at the other field sizes. For the 4 to 7.5 mm cones, all output ratios obtained from Ge-doped optical fibre measurements were greater than those of IBA CC01 ionization chamber. The measured FF and CF output ratios for the 7.5 to 15 mm cones agreed with published MC estimates to within 15% and 13%, respectively. Down to 6 mm cone field, present measurements point to the potential of CF as a small-field dosimeter, its use recommended to be complemented by the use of EBT3 film for small-field dosimetry.
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Affiliation(s)
- S E Lam
- Centre for Biomedical Physics, School of Healthcare and Medical Sciences, Sunway University, 47500 Petaling Jaya, Selangor, Malaysia.,Department of Radiology, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
| | - N Mohd Noor
- Department of Radiology, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia.,Department of Radiology, Teaching Hospital Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
| | - D A Bradley
- Centre for Biomedical Physics, School of Healthcare and Medical Sciences, Sunway University, 47500 Petaling Jaya, Selangor, Malaysia.,Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom
| | - R Mahmud
- Department of Radiology, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia.,Centre for Diagnostic Nuclear Imaging, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
| | - M Pawanchek
- Department of Radiotherapy and Oncology, National Cancer Institute, 62250 W.P. Putrajaya, Malaysia
| | - H A Abdul Rashid
- Faculty of Engineering, Multimedia University, 63100 Cyberjaya, Selangor, Malaysia
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66
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Kinhikar R, Saini V, Upreti RR, Kale S, Sutar A, Tambe C, Kadam S. Measurement of the small field output factors for 10 MV photon beam using IAEA TRS-483 dosimetry protocol and implementation in Eclipse TPS commissioning. Biomed Phys Eng Express 2020; 6. [DOI: 10.1088/2057-1976/abb319] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 08/27/2020] [Indexed: 11/11/2022]
Abstract
Abstract
Dosimetry of small fields (SF) is vital for the success of highly conformal techniques. IAEA along with AAPM recently published a code of practice TRS-483 for SF dosimetry. The scope of this paper is to investigate the performance of three different detectors with 10 MV with-flatting-filter (WFF) beam using TRS-483 for SF dosimetry and subsequent commissioning of the Eclipse treatment planning system (TPS version-13.6) for SF data. SF dosimetry data (beam-quality TPR
20,10(10), cross-calibration, beam-profile, and field-output-factor (F.O.F)) measurements were performed for PTW31006-pinpoint, IBA-CC01 and IBA-EFD-3G diode detectors in nominal field size (F.S) range 0.5 × 0.5cm2 to 10 × 10 cm2 with water and solid water medium using Varian Truebeam linac. However, Eclipse-TPS commissioning data was acquired using IBA-EFD-3G diode, and absolute dose calibration was performed with FC-65G detector. The dosimetric performance of the Eclipse-TPS was validated using TLD-LiF chips, IBA-PFD, and IBA-EFD-3G diodes. Dosimetric performance of the PTW31006-pinpoint, IBA-CC01, and IBA-EFD-3G detectors was successfully tested for SF dosimetry. The F.O.Fs were generated and found in close agreement for all F.S except 0.5 × 0.5cm2. It is also found that TPR20,10(10) value can be derived within 0.5% accuracy from a non-reference field using Palmans equation. Cross-calibration can be performed in F.S 6 × 6 cm2 with a maximum variation of 0.5% with respect to 10 × 10cm2. During profile measurement, the full-width half-maxima (FWHM) of F.S 0.5 × 0.5cm2 was found maximum deviated from the geometric F.S. In addition, Eclipse-TPS was commissioned along with some limitations: F.O.F below F.S 1 × 1cm2 was ignored by TPS, PDD and profiles were dropped from configuration below F.S 2 × 2 cm2, and F.O.F which does not satisfy the condition 0.7 < A/B < 1.4 (A and B are FWHM in cross-line and in-line direction) have higher uncertainty than specified in TRS-483. Validation tests for Eclipse-TPS generated plans were also performed. The measured dose was in close agreement (3%) with TPS calculated dose up to F.S 1.5 × 1.5cm2.
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Gul A, Fukuda S, Mizuno H, Taku N, Kakakhel MB, Mirza SM. Feasibility study of using Stereotactic Field Diode for field output factors measurement and evaluating three new detectors for small field relative dosimetry of 6 and 10 MV photon beams. J Appl Clin Med Phys 2020; 21:23-36. [PMID: 33078544 PMCID: PMC7700919 DOI: 10.1002/acm2.13007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 06/29/2020] [Accepted: 07/10/2020] [Indexed: 11/23/2022] Open
Abstract
This study assesses the feasibility of using stereotactic field diode (SFD) as an alternate to gaf chromic films for field output factor (FF) measurement and further evaluating three new detectors for small field dosimetry. Varian 21EX linear accelerator was used to generate 6 and 10 MV beams of nominal square fields ranging from 0.5 × 0.5 cm2 to 10 × 10 cm2. One passive (EBT3 films) and five active detectors including IBA RAZOR diode(RD), SFD, RAZOR nanochamber (RNC), pinpoint chamber (PTW31023), and semiflex chamber (PTW31010) were employed. FFs were measured using films and SFD while beam profiles and percentage depth dose (PDD) distribution were acquired with active detectors. Polarity (kpol) and recombination (ks) effects of ion chambers were determined and corrected for output ratio measurement. Correction factors (CF) of RD, RNC, and PTW31023 in axial and radial orientation were also measured. Stereotactic field diode measured FFs have shown good agreement with films (with difference of <1%). RD and RNC measured beam profiles were within 3% deviation from the SFD values. Variation in kpol with field size for RNC and PTW31023 was up to 4% and 0.4% (for fields ≥ 1 × 1 cm2), respectively, while variation in ks of PTW31023 was <0.2 %. The maximum values of CF have been calculated to be 5.2%, 2.0%, 13.6%, and 25.5% for RD, RNC, PTW31023‐axial, and PTW31023‐radial respectively. This study concludes that SFD with appropriate CFs as given in TRS 483 may be used for measuring FFs as an alternate to EBT3 films. Whereas RD and RNC may be used for beam profile and PDD measurement in small fields. Considering the limit of usability of 2%, RNC may be used without CF for FF measurement in the smallfields investigated in this study.
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Affiliation(s)
- Attia Gul
- QST Hospital, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan.,Department of Physics & Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan
| | - Shigekazu Fukuda
- QST Hospital, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan
| | - Hideyuki Mizuno
- QST Hospital, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan
| | - Nakaji Taku
- QST Hospital, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan
| | - M Basim Kakakhel
- Department of Physics & Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan
| | - Sikander M Mirza
- Department of Physics & Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan
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Eaton DJ, Bass G, Booker P, Byrne J, Duane S, Frame J, Grattan M, Thomas RAS, Thorp N, Nisbet A. IPEM code of practice for high-energy photon therapy dosimetry based on the NPL absorbed dose calibration service. ACTA ACUST UNITED AC 2020; 65:195006. [DOI: 10.1088/1361-6560/ab99e3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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69
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Kumar S, Nahum AE, Chetty IJ. Monte-Carlo-computed dose, kerma and fluence distributions in heterogeneous slab geometries irradiated by small megavoltage photon fields. ACTA ACUST UNITED AC 2020; 65:175012. [DOI: 10.1088/1361-6560/ab98d1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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70
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Rosenfeld AB, Biasi G, Petasecca M, Lerch MLF, Villani G, Feygelman V. Semiconductor dosimetry in modern external-beam radiation therapy. Phys Med Biol 2020; 65:16TR01. [PMID: 32604077 DOI: 10.1088/1361-6560/aba163] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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71
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Mirzakhanian L, Bassalow R, Huntzinger C, Seuntjens J. Extending the IAEA‐AAPM TRS‐483 methodology for radiation therapy machines with field sizes down to 10 × 2 cm
2. Med Phys 2020; 47:5209-5221. [DOI: 10.1002/mp.14325] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 04/17/2020] [Accepted: 05/21/2020] [Indexed: 11/10/2022] Open
Affiliation(s)
| | | | | | - Jan Seuntjens
- Medical Physics Unit McGill University Montreal QCH4A 3J1Canada
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72
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Georgiou G, Kumar S, Würfel JU, Underwood TSA, Thompson JM, Hill MA, Rowbottom CG, Fenwick JD. Density compensated diodes for small field dosimetry: comprehensive testing and implications for design. Phys Med Biol 2020; 65:155011. [PMID: 32392539 DOI: 10.1088/1361-6560/ab91d9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE In small megavoltage photon fields, the accuracies of an unmodified PTW 60017-type diode dosimeter and six diodes modified by adding airgaps of thickness 0.6-1.6 mm and diameter 3.6 mm have been comprehensively characterized experimentally and computationally. The optimally thick airgap for density compensation was determined, and detectors were micro-CT imaged to investigate differences between experimentally measured radiation responses and those predicted computationally. METHODS Detectors were tested on- and off-axis, at 5 and 15 cm depths in 6 and 15 MV fields ≥ 0.5 × 0.5 cm2. Computational studies were carried out using the EGSnrc/BEAMnrc Monte Carlo radiation transport code. Experimentally, radiation was delivered using a Varian TrueBeam linac and doses absorbed by water were measured using Gafchromic EBT3 film and ionization chambers, and compared with diode readings. Detector response was characterized via the [Formula: see text] formalism, choosing a 4 × 4 cm2 reference field. RESULTS For the unmodified 60017 diode, the maximum error in small field doses obtained from diode readings uncorrected by [Formula: see text] factors was determined as 11.9% computationally at +0.25 mm off-axis and 5 cm depth in a 15 MV 0.5 × 0.5 cm2 field, and 11.7% experimentally at -0.30 mm off-axis and 5 cm depth in the same field. A detector modified to include a 1.6 mm thick airgap performed best, with maximum computationally and experimentally determined errors of 2.2% and 4.1%. The 1.6 mm airgap deepened the modified dosimeter's effective point of measurement by 0.5 mm. For some detectors significant differences existed between responses in small fields determined computationally and experimentally, micro-CT imaging indicating that these differences were due to within-tolerance variations in the thickness of an epoxy resin layer. CONCLUSIONS The dosimetric performance of a 60017 diode detector was comprehensively improved throughout 6 and 15 MV small photon fields via density compensation. For this approach to work well with good detector-to-detector reproducibility, tolerances on dense component dimensions should be reduced to limit associated variations of response in small fields, or these components should be modified to have more water-like densities.
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Affiliation(s)
- Georgios Georgiou
- Department of Molecular and Clinical Cancer Medicine, Institute of Translational Medicine, University of Liverpool, The Sherrington Building, Ashton Street, Liverpool L69 3BX, United Kingdom. Department of Physics, Clatterbridge Cancer Centre, Clatterbridge Road, Wirral CH63 4JY, United Kingdom. Department of Physics, University of Liverpool, Oliver Lodge Laboratory, Oxford Street, Liverpool L69 7ZE, United Kingdom
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73
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Buchegger N, Grogan G, Hug B, Oliver C, Ebert M. CyberKnife reference dosimetry: An assessment of the impact of evolving recommendations on correction factors and measured dose. Med Phys 2020; 47:3573-3585. [DOI: 10.1002/mp.14190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 03/29/2020] [Accepted: 03/30/2020] [Indexed: 11/06/2022] Open
Affiliation(s)
- Nicole Buchegger
- Department of Radiation Oncology Sir Charles Gairdner Hospital Nedlands WA 6009 Australia
| | - Garry Grogan
- Department of Radiation Oncology Sir Charles Gairdner Hospital Nedlands WA 6009 Australia
| | - Ben Hug
- 5D Clinics Claremont WA 6010 Australia
| | - Chris Oliver
- Australian Radiation Protection and Nuclear Safety Agency Yallambie Vic. 3085 Australia
| | - Martin Ebert
- Department of Radiation Oncology Sir Charles Gairdner Hospital Nedlands WA 6009 Australia
- 5D Clinics Claremont WA 6010 Australia
- Department of Physics University of Western Australia Crawley WA 6009 Australia
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74
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Weber C, Kranzer R, Weidner J, Kröninger K, Poppe B, Looe HK, Poppinga D. Small field output correction factors of the microSilicon detector and a deeper understanding of their origin by quantifying perturbation factors. Med Phys 2020; 47:3165-3173. [PMID: 32196683 PMCID: PMC7496769 DOI: 10.1002/mp.14149] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 01/31/2020] [Accepted: 03/13/2020] [Indexed: 11/09/2022] Open
Abstract
PURPOSE The aim of this study is the experimental and Monte Carlo-based determination of small field correction factors for the unshielded silicon detector microSilicon for a standard linear accelerator as well as the Cyberknife System. In addition, a detailed Monte Carlo analysis has been performed by modifying the detector models stepwise to study the influences of the detector's components. METHODS Small field output correction factors have been determined for the new unshielded silicon diode detector, microSilicon (type 60023, PTW Freiburg, Germany) as well as for the predecessors Diode E (type 60017, PTW Freiburg, Germany) and Diode SRS (type 60018, PTW Freiburg, Germany) for a Varian TrueBeam linear accelerator at 6 MV and a Cyberknife system. For the experimental determination, an Exradin W1 scintillation detector (Standard Imaging, Middleton, USA) has been used as reference. The Monte Carlo simulations have been performed with EGSnrc and phase space files from IAEA as well as detector models according to manufacturer blueprints. To investigate the influence of the detector's components, the detector models have been modified stepwise. RESULTS The correction factors for the smallest field size investigated at the TrueBeam linear accelerator (equivalent dosimetric square field side length Sclin = 6.3 mm) are 0.983 and 0.939 for the microSilicon and Diode E, respectively. At the Cyberknife system, the correction factors of the microSilicon are 0.967 at the smallest 5-mm collimator compared to 0.928 for the Diode SRS. Monte Carlo simulations show comparable results from the measurements and literature. CONCLUSION The microSilicon (type 60023) detector requires less correction than its predecessors, Diode E (type 60017) and Diode SRS (type 60018). The detector housing has been demonstrated to cause the largest perturbation, mainly due to the enhanced density of the epoxy encapsulation surrounding the silicon chip. This density has been rendered more water equivalent in case of the microSilicon detector to minimize the associated perturbation. The sensitive volume itself has been shown not to cause observable field size-dependent perturbation except for the volume-averaging effect, where the slightly larger diameter of the sensitive volume of the microSilicon (1.5 mm) is still small at the smallest field size investigated with corrections <2%. The new microSilicon fulfils the 5% correction limit recommended by the TRS 483 for output factor measurements at all conditions investigated in this work.
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Affiliation(s)
- Carolin Weber
- PTW FreiburgFreiburg79115Germany
- TU Dortmund UniversityDortmund44227Germany
| | | | | | | | - Björn Poppe
- University Clinic for Medical Radiation PhysicsMedical Campus Pius HospitalCarl von Ossietzky UniversityOldenburg26121Germany
| | - Hui Khee Looe
- University Clinic for Medical Radiation PhysicsMedical Campus Pius HospitalCarl von Ossietzky UniversityOldenburg26121Germany
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75
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Multi-institutional dosimetric delivery assessment of intracranial stereotactic radiosurgery on different treatment platforms. Radiother Oncol 2020; 147:153-161. [DOI: 10.1016/j.radonc.2020.05.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 04/30/2020] [Accepted: 05/12/2020] [Indexed: 11/22/2022]
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Brace OJ, Alhujaili SF, Paino JR, Butler DJ, Wilkinson D, Oborn BM, Rosenfeld AB, Lerch MLF, Petasecca M, Davis JA. Evaluation of the PTW microDiamond in edge-on orientation for dosimetry in small fields. J Appl Clin Med Phys 2020; 21:278-288. [PMID: 32441884 PMCID: PMC7484886 DOI: 10.1002/acm2.12906] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 03/16/2020] [Accepted: 04/20/2020] [Indexed: 12/11/2022] Open
Abstract
Purpose The PTW microDiamond has an enhanced spatial resolution when operated in an edge‐on orientation but is not typically utilized in this orientation due to the specifications of the IAEA TRS‐483 code of practice for small field dosimetry. In this work the suitability of an edge‐on orientation and advantages over the recommended face‐on orientation will be presented. Methods The PTW microDiamond in both orientations was compared on a Varian TrueBeam linac for: machine output factor (OF), percentage depth dose (PDD), and beam profile measurements from 10 × 10 cm2 to a 0.5 × 0.5 cm2 field size for 6X and 6FFF beam energies in a water tank. A quantification of the stem effect was performed in edge‐on orientation along with tissue to phantom ratio (TPR) measurements. An extensive angular dependence study for the two orientations was also undertaken within two custom PMMA plastic cylindrical phantoms. Results The OF of the PTW microDiamond in both orientations agrees within 1% down to the 2 × 2 cm2 field size. The edge‐on orientation overresponds in the build‐up region but provides improved penumbra and has a maximum observed stem effect of 1%. In the edge‐on orientation there is an angular independent response with a maximum of 2% variation down to a 2 × 2 cm2 field. The PTW microDiamond in edge‐on orientation for TPR measurements agreed to the CC01 ionization chamber within 1% for all field sizes. Conclusions The microDiamond was shown to be suitable for small field dosimetry when operated in edge‐on orientation. When edge‐on, a significantly reduced angular dependence is observed with no significant stem effect, making it a more versatile QA instrument for rotational delivery techniques.
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Affiliation(s)
- Owen J Brace
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Sultan F Alhujaili
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Jason R Paino
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Duncan J Butler
- Australian Radiation Protection and Nuclear Safety Agency (ARPANSA), Yallambie, VIC, UK
| | - Dean Wilkinson
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia.,Illawarra Cancer Care Centre Wollongong Hospital Wollongong, Wollongong, NSW, Australia
| | - Brad M Oborn
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia.,Illawarra Cancer Care Centre Wollongong Hospital Wollongong, Wollongong, NSW, Australia
| | - Anatoly B Rosenfeld
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Michael L F Lerch
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Marco Petasecca
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Jeremy A Davis
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
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Akino Y, Fujiwara M, Okamura K, Shiomi H, Mizuno H, Isohashi F, Suzuki O, Seo Y, Tamari K, Ogawa K. Characterization of a microSilicon diode detector for small-field photon beam dosimetry. JOURNAL OF RADIATION RESEARCH 2020; 61:410-418. [PMID: 32211851 PMCID: PMC7299273 DOI: 10.1093/jrr/rraa010] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 01/15/2020] [Indexed: 06/10/2023]
Abstract
This study characterized a new unshielded diode detector, the microSilicon (model 60023), for small-field photon beam dosimetry by evaluating the photon beams generated by a TrueBeam STx and a CyberKnife. Temperature dependence was evaluated by irradiating photons and increasing the water temperature from 11.5 to 31.3°C. For Diode E, microSilicon, microDiamond and EDGE detectors, dose linearity, dose rate dependence, energy dependence, percent-depth-dose (PDD), beam profiles and detector output factor (OFdet) were evaluated. The OFdet of the microSilicon detector was compared to the field output factors of the other detectors. The microSilicon exhibited small temperature dependence within 0.4%, although the Diode E showed a linear variation with a ratio of 0.26%/°C. The Diode E and EDGE detectors showed positive correlations between the detector reading and dose rate, whereas the microSilicon showed a stable response within 0.11%. The Diode E and microSilicon demonstrated negative correlations with the beam energy. The OFdet of microSilicon was the smallest among all the detectors. The maximum differences between the OFdet of microSilicon and the field output factors of microDiamond were 2.3 and 1.6% for 5 × 5 mm2 TrueBeam and 5 mm φ CyberKnife beams, respectively. The PDD data exhibited small variations in the dose fall-off region. The microSilicon and microDiamond detectors yielded similar penumbra widths, whereas the other detectors showed steeper penumbra profiles. The microSilicon demonstrated favorable characteristics including small temperature and dose rate dependence as well as the small spatial resolution and output factors suitable for small field dosimetry.
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Affiliation(s)
- Yuichi Akino
- Oncology Center, Osaka University Hospital, 2-2 (D10), Yamadaoka, Suita, Osaka 565-0871, Japan
- Department of Radiation Oncology, Suita Tokushukai Hospital, Suita, Osaka 565-0814, Japan
| | - Masateru Fujiwara
- Department of Radiation Oncology, Suita Tokushukai Hospital, Suita, Osaka 565-0814, Japan
| | - Keita Okamura
- Department of Radiology, Osaka University Hospital, Suita, Osaka 565-0871, Japan
| | - Hiroya Shiomi
- Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Hirokazu Mizuno
- Division of Health Sciences, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Fumiaki Isohashi
- Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Osamu Suzuki
- Department of Carbon Ion Radiotherapy, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Yuji Seo
- Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Keisuke Tamari
- Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Kazuhiko Ogawa
- Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
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Desai VK, Labby ZE, DeWerd LA, Culberson WS. On the implementation of the plan‐class specific reference field using multidimensional clustering of plan features and alternative strategies for improved dosimetry in modulated clinical linear accelerator treatments. Med Phys 2020; 47:3621-3635. [DOI: 10.1002/mp.14207] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 04/14/2020] [Accepted: 04/20/2020] [Indexed: 11/08/2022] Open
Affiliation(s)
- Vimal K. Desai
- Department of Human Oncology School of Medicine and Public Health University of Wisconsin‐Madison Madison WI 53792 USA
| | - Zacariah E. Labby
- Department of Human Oncology School of Medicine and Public Health University of Wisconsin‐Madison Madison WI 53792 USA
| | - Larry A. DeWerd
- Department of Medical Physics School of Medicine and Public Health University of Wisconsin‐Madison Madison WI 53705 USA
| | - Wesley S. Culberson
- Department of Medical Physics School of Medicine and Public Health University of Wisconsin‐Madison Madison WI 53705 USA
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Mamesa S, Oonsiri S, Sanghangthum T, Yabsantia S, Suriyapee S. The impact of corrected field output factors based on IAEA/AAPM code of practice on small-field dosimetry to the calculated monitor unit in eclipse™ treatment planning system. J Appl Clin Med Phys 2020; 21:65-75. [PMID: 32237215 PMCID: PMC7286014 DOI: 10.1002/acm2.12855] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 12/13/2020] [Accepted: 02/08/2020] [Indexed: 12/14/2022] Open
Abstract
The objective of this study was to investigate the effect of field output factors (FOFs) according to the current protocol for small-field dosimetry in conjunction to treatment planning system (TPS) commissioning. The calculated monitor unit (MU) for intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans in Eclipse™ TPS were observed. Micro ion chamber (0.01 CC) (CC01), photon field diode (shielded diode) (PFD), and electron field diode (unshielded diode) (EFD) were used to measure percentage depth doses, beam profiles, and FOFs from 1 × 1 cm2 to 10 × 10 cm2 field sizes of 6 MV photon beams. CC01 illustrated the highest percentage depth doses at 10 cm depth while EFD exhibited the lowest with the difference of 1.6% at 1 × 1 cm2 . CC01 also produced slightly broader penumbra, the difference with other detectors was within 1 mm. For uncorrected FOF of three detectors, the maximum percent standard deviation (%SD) was 5.4% at 1 × 1 cm2 field size. When the correction factors were applied, this value dropped to 2.7%. For the calculated MU in symmetric field sizes, beam commissioning group from uncorrected FOF demonstrated maximum %SD of 6.0% at 1 × 1 cm2 field size. This value decreased to 2.2% when the corrected FOF was integrated. For the calculated MU in IMRT-SRS plans, the impact of corrected FOF reduced the maximum %SD from 6.0% to 2.5% in planning target volume (PTV) less than 0.5 cm3 . Beam commissioning using corrected FOF also decreased %SD for VMAT-SRS plans, although it was less pronounced in comparison to other treatment planning techniques, since the %SD remained less than 2%. The use of FOFs based on IAEA/AAPM TRS 483 has been proven in this research to reduce the discrepancy of calculated MU among three beam commissioning datasets in Eclipse™ TPS. The dose measurement of both symmetric field and clinical cases comparing to the calculation illustrated the dependence of the types of detector commissioning and the algorithm of the treatment planning for small field size.
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Affiliation(s)
- Sammuel Mamesa
- Medical Physics Program, Department of Radiology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Sornjarod Oonsiri
- Division of Radiation Oncology, Department of Radiology, King Chulalongkorn Memorial Hospital, Bangkok, Thailand
| | - Taweap Sanghangthum
- Medical Physics Program, Department of Radiology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
- Division of Radiation Oncology, Department of Radiology, King Chulalongkorn Memorial Hospital, Bangkok, Thailand
| | - 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
- Division of Radiation Oncology, Department of Radiology, King Chulalongkorn Memorial Hospital, Bangkok, Thailand
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80
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Lechner W, Primeßnig A, Nenoff L, Wesolowska P, Izewska J, Georg D. The influence of errors in small field dosimetry on the dosimetric accuracy of treatment plans. Acta Oncol 2020; 59:511-517. [PMID: 31694438 DOI: 10.1080/0284186x.2019.1685127] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Background: Dosimetric effects of inaccuracies of output factors (OFs) implemented in treatment planning systems (TPSs) were investigated.Materials and methods: Modified beam models (MBM) for which the OFs of small fields (down to 1 × 1 cm2) were increased by up to 12% compared to the original beam models (OBM) were created for two TPSs. These beam models were used to recalculate treatment plans of different complexity. Treatment plans using stereotactic 3D-conformal (s3D-CRT) for brain metastasis as well as VMAT plans for head and neck and prostate cancer patients were generated. Dose distributions calculated with the MBM and the OBM were compared to measured dose distributions acquired using film dosimetry and a 2D-detector-array. For the s3D-CRT plans the calculated and measured dose at the isocenter was evaluated. For VMAT, gamma pass rates (GPRs) were calculated using global gamma index with 3%/3 mm, 2%/3 mm, 1%/3 mm and 2%/2 mm with a 20% threshold. Contribution of small fields to the total fluence was expressed as the ratio (F) of fluence trough leaf openings smaller than 2 cm to the total fluence.Results: Using film dosimetry for the s3D-CRT plans, the average of the ratio of calculated dose to measured dose at the isocenter was 1.01 and 1.06 for the OBM and MBM model, respectively. A significantly lower GPR of the MBM compared to the OBM was only found for the localized prostate cases (F = 12.4%) measured with the 2D-detector-array and an acceptance criterion of 1%/3 mm.Conclusion: The effects of uncertainties in small field OFs implemented in TPSs are most pronounced for s3D-CRT cases and can be clearly identified using patient specific quality assurance. For VMAT these effects mainly remain undetected using standard patient specific quality assurance. Using tighter acceptance criteria combined with an analysis of the fluence generated by small fields can help identifying inaccuracies of OFs implemented in TPSs.
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Affiliation(s)
- Wolfgang Lechner
- Department of Radiation Oncology, Division Medical Physics, Medical University Vienna, Vienna, Austria
- Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Alexander Primeßnig
- Department of Radiation Oncology, Division Medical Physics, Medical University Vienna, Vienna, Austria
- Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Lena Nenoff
- Department of Radiation Oncology, Division Medical Physics, Medical University Vienna, Vienna, Austria
- Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Paulina Wesolowska
- International Atomic Energy Agency, Vienna International Centre, Vienna, Austria
| | - Joanna Izewska
- International Atomic Energy Agency, Vienna International Centre, Vienna, Austria
| | - Dietmar Georg
- Department of Radiation Oncology, Division Medical Physics, Medical University Vienna, Vienna, Austria
- Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria
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Monte Carlo calculated output correction factors for Gafchromic EBT3 film for relative dosimetry in small stereotactic radiosurgery fields. Phys Eng Sci Med 2020; 43:609-616. [DOI: 10.1007/s13246-020-00860-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Accepted: 03/17/2020] [Indexed: 10/24/2022]
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82
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A novel extrapolation method using OSL detectors for very small field output factor measurement for stereotactic radiosurgery. Phys Eng Sci Med 2020; 43:593-599. [DOI: 10.1007/s13246-020-00859-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 03/10/2020] [Indexed: 11/26/2022]
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83
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Mirzakhanian L, Sarfehnia A, Seuntjens J. Experimental validation of recommended msr-correction factors for the calibration of Leksell Gamma Knife® Icontm unit following IAEA TRS-483. ACTA ACUST UNITED AC 2020; 65:065003. [DOI: 10.1088/1361-6560/ab6953] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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84
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Evaluation of dosimetric parameters of small fields of 6 MV flattening filter free photon beam measured using various detectors against Monte Carlo simulation. JOURNAL OF RADIOTHERAPY IN PRACTICE 2020. [DOI: 10.1017/s1460396920000114] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractPurpose:This study aims to evaluate dosimetric parameters like percentage depth dose, dosimetric field size, depth of maximum dose surface dose, penumbra and output factors measured using IBA CC01 pinpoint chamber, IBA stereotactic field diode (SFD), PTW microDiamond against Monte Carlo (MC) simulation for 6 MV flattening filter-free small fields.Materials and Methods:The linear accelerator used in the study was a Varian TrueBeam® STx. All field sizes were defined by jaws. The required shift to effective point of measurement was given for CC01, SFD and microdiamond for depth dose measurements. The output factor of a given field size was taken as the ratio of meter readings normalised to 10 × 10 cm2 reference field size without applying any correction to account for changes in detector response. MC simulation was performed using PRIMO (PENELOPE-based program). The phase space files for MC simulation were adopted from the MyVarian Website.Results and Discussion:Variations were seen between the detectors and MC, especially for fields smaller than 2 × 2 cm2 where the lateral charge particle equilibrium was not satisfied. Diamond detector was seen as most suitable for all measurements above 1 × 1 cm2. SFD was seen very close to MC results except for under-response in output factor measurements. CC01 was observed to be suitable for field sizes above 2 × 2 cm2. Volume averaging effect for penumbra measurements in CC01 was observed. No detector was found suitable for surface dose measurement as surface ionisation was different from surface dose due to the effect of perturbation of fluence. Some discrepancies in measurements and MC values were observed which may suggest effects of source occlusion, shift in focal point or mismatch between real accelerator geometry and simulation geometry.Conclusion:For output factor measurement, TRS483 suggested correction factor needs to be applied to account for the difference in detector response. CC01 can be used for field sizes above 2 × 2 cm2 and microdiamond detector is suitable for above 1 × 1 cm2. Below these field sizes, perturbation corrections and volume averaging corrections need to be applied.
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85
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Renaud J, Palmans H, Sarfehnia A, Seuntjens J. Absorbed dose calorimetry. ACTA ACUST UNITED AC 2020; 65:05TR02. [DOI: 10.1088/1361-6560/ab4f29] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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86
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Kawata K, Kamomae T, Oguchi H, Kawabata F, Okudaira K, Kawamura M, Ohtakara K, Itoh Y, Naganawa S. Evaluation of newly implemented dose calculation algorithms for multileaf collimator-based CyberKnife tumor-tracking radiotherapy. Med Phys 2020; 47:1391-1403. [PMID: 31913508 DOI: 10.1002/mp.14013] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Revised: 12/30/2019] [Accepted: 12/30/2019] [Indexed: 11/09/2022] Open
Abstract
PURPOSE In the previous treatment planning system (TPS) for CyberKnife (CK), multileaf collimator (MLC)-based treatment plans could be created only by using the finite-size pencil beam (FSPB) algorithm. Recently, a new TPS, including the FSPB with lateral scaling option (FSPB+) and Monte Carlo (MC) algorithms, was developed. In this study, we performed basic and clinical end-to-end evaluations for MLC-based CK tumor-tracking radiotherapy using the MC, FSPB+, and FSPB. METHODS Water- and lung-equivalent slab phantoms were combined to obtain the percentage depth dose (PDD) and off-center ratio (OCR). The CK M6 system and Precision TPS were employed, and PDDs and OCRs calculated by the MC, FSPB+, and FSPB were compared with the measured doses obtained for 30.8 × 30.8 mm2 and 60.0 × 61.6 mm2 fields. A lung motion phantom was used for clinical evaluation and MLC-based treatment plans were created using the MC. The doses were subsequently recalculated using the FSPB+ and FSPB, while maintaining the irradiation parameters. The calculated doses were compared with the doses measured using a microchamber (for target doses) or a radiochromic film (for dose profiles). The dose volume histogram (DVH) indices were compared for all plans. RESULTS In homogeneous and inhomogeneous phantom geometries, the PDDs calculated by the MC and FSPB+ agreed with the measurements within ±2.0% for the region between the surface and a depth of 250 mm, whereas the doses calculated by the FSPB in the lung-equivalent phantom region were noticeably higher than the measurements, and the maximum dose differences were 6.1% and 4.4% for the 30.8 × 30.8 mm2 and 60.0 × 61.6 mm2 fields, respectively. The maximum distance to agreement values of the MC, FSPB+, and FSPB at the penumbra regions of OCRs were 1.0, 0.6, and 1.1 mm, respectively, but the best agreement was obtained between the MC-calculated curve and measurements at the boundary of the water- and lung-equivalent slabs, compared with those of the FSPB+ and FSPB. For clinical evaluations using the lung motion phantom, under the static motion condition, the dose errors measured by the microchamber were -1.0%, -1.9%, and 8.8% for MC, FSPB+, and FSPB, respectively; their gamma pass rates for the 3%/2 mm criterion comparing to film measurement were 98.4%, 87.6%, and 31.4% respectively. Under respiratory motion conditions, there was no noticeable decline in the gamma pass rates. In the DVH indices, for most of the gross tumor volume and planning target volume, significant differences were observed between the MC and FSPB, and between the FSPB+ and FSPB. Furthermore, significant differences were observed for lung Dmean , V15 Gy , and V20 Gy between the MC, FSPB+, and FSPB. CONCLUSIONS The results indicate that the doses calculated using the MC and FSPB+ differed remarkably in inhomogeneous regions, compared with the FSPB. Because the MC was the most consistent with the measurements, it is recommended for final dose calculations in inhomogeneous regions such as the lung. Furthermore, the sufficient accuracy of dose delivery using MLC-based tumor-tracking radiotherapy by CK was demonstrated for clinical implementation.
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Affiliation(s)
- Kohei Kawata
- Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya, Aichi, 461-8673, Japan
| | - Takeshi Kamomae
- Department of Radiology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, 466-8550, Japan
| | - Hiroshi Oguchi
- Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya, Aichi, 461-8673, Japan
| | - Fumitaka Kawabata
- Department of Radiological Technology, Nagoya University Hospital, Nagoya, Aichi, 466-8560, Japan
| | - Kuniyasu Okudaira
- Department of Radiological Technology, Nagoya University Hospital, Nagoya, Aichi, 466-8560, Japan
| | - Mariko Kawamura
- Department of Radiology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, 466-8550, Japan
| | - Kazuhiro Ohtakara
- Department of Radiology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, 466-8550, Japan
| | - Yoshiyuki Itoh
- Department of Radiology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, 466-8550, Japan
| | - Shinji Naganawa
- Department of Radiology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, 466-8550, Japan
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Patera V, Sarti A. Recent Advances in Detector Technologies for Particle Therapy Beam Monitoring and Dosimetry. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2020. [DOI: 10.1109/trpms.2019.2951848] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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88
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Costa NA, Patallo IS, Dimitriadis A, Saraiva CW, Potiens MDPA. Phantom development and implementation for Gamma Knife® dosimetry. Radiat Phys Chem Oxf Engl 1993 2020. [DOI: 10.1016/j.radphyschem.2019.108355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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89
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Francescon P, Kilby W, Noll JM, Satariano N, Orlandi C. Small field dosimetry correction factors for circular and MLC shaped fields with the CyberKnife M6 System: evaluation of the PTW 60023 microSilicon detector. Phys Med Biol 2020; 65:01NT01. [PMID: 31829983 DOI: 10.1088/1361-6560/ab6154] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The PTW 60023 microSilicon is a new unshielded diode detector for small-field photon dosimetry. It provides improved water equivalence and a slightly larger sensitive region diameter in comparison to previous diode detectors in this range. In this study we evaluated the correction factors relevant to commissioning a CyberKnife System with this detector by Monte Carlo simulation and verified this data by multi-detector measurement comparison. The correction factors required for output factor determination were substantially closer to unity at small field sizes than for previous diode versions (e.g. [Formula: see text] = 0.981 at 5 mm field size which compares with corrections of 5%-6% with other stereotactic diodes). Because of these differences we recommend that corrections to small field output factor measurements generated specifically for the microSilicon detector rather than generic data taken from other diode types should be used with this new detector. For depth-dose measurements the microSilicon is consistent with a microDiamond detector to <1% (global), except at depths <10 mm where the diode gives a significantly lower measurement, by 6%-8% at the surface. For profile measurements, the microSilicon requires negligible corrections except in the low dose region outside the beam, where it underestimates off-axis-ratio (OAR) for small fields and overestimates for large fields. Where this effect is most noticeable at the largest field size and depth (115 mm × 100 mm and 300 mm depth) the microSilicon overestimates OAR by 2.3% (global) in the profile tail. This is consistent with other unshielded diodes.
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Affiliation(s)
- P Francescon
- Department of Radiation Oncology, Ospedale Di Vicenza, I-36100 Vicenza, Italy
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90
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Casar B, Gershkevitsh E, Mendez I, Jurković S, Saiful Huq M. Output correction factors for small static fields in megavoltage photon beams for seven ionization chambers in two orientations - perpendicular and parallel. Med Phys 2020; 47:242-259. [PMID: 31677278 PMCID: PMC7003763 DOI: 10.1002/mp.13894] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 10/22/2019] [Accepted: 10/28/2019] [Indexed: 12/03/2022] Open
Abstract
PURPOSE The goal of the present work was to provide a large set of detector-specific output correction factors for seven small volume ionization chambers on two linear accelerators in four megavoltage photon beams utilizing perpendicular and parallel orientation of ionization chambers in the beam for nominal field sizes ranging from 0.5 cm2 × 0.5 cm2 to 10 cm2 × 10 cm2 . The present study is the second part of an extensive research conducted by our group. METHODS Output correction factors k Q clin , Q ref f clin , f ref were experimentally determined on two linacs, Elekta Versa HD and Varian TrueBeam for 6 and 10 MV beams with and without flattening filter for nine square fields ranging from 0.5 cm2 × 0.5 cm2 to 10 cm2 × 10 cm2 , for seven mini and micro ionization chambers, IBA CC04, IBA Razor, PTW 31016 3D PinPoint, PTW 31021 3D Semiflex, PTW 31022 3D PinPoint, PTW 31023 PinPoint, and SI Exradin A16. An Exradin W1 plastic scintillator and EBT3 radiochromic films were used as the reference detectors. RESULTS For all ionization chambers, values of output correction factors k Q clin , Q ref f clin , f ref were lower for parallel orientation compared to those obtained in the perpendicular orientation. Five ionization chambers from our study set, IBA Razor, PTW 31016 3D PinPoint, PTW 31022 3D PinPoint, PTW 31023 PinPoint, and SI Exradin A16, fulfill the requirement recommended in the TRS-483 Code of Practice, that is, 0.95 < k Q clin , Q ref f clin , f ref < 1.05 , down to the field size 0.8 cm2 × 0.8 cm2 , when they are positioned in parallel orientation; two of the ionization chambers, IBA Razor and PTW 31023 PinPoint, satisfy this condition down to the field size of 0.5 cm2 × 0.5 cm2 . CONCLUSIONS The present paper provides experimental results of detector-specific output correction factors for seven small volume ionization chambers. Output correction factors were determined in 6 and 10 MV photon beams with and without flattening filter down to the square field size of 0.5 cm2 × 0.5 cm2 for two orientations of ionization chambers - perpendicular and parallel. Our main finding is that output correction factors are smaller if they are determined in a parallel orientation compared to those obtained in a perpendicular orientation for all ionization chambers regardless of the photon beam energy, filtration, or linear accelerator being used. Based on our findings, we recommend using ionization chambers in parallel orientation, to minimize corrections in the experimental determination of field output factors. Latter holds even for field sizes below 1.0 cm2 × 1.0 cm2 , whenever necessary corrections remain within 5%, which was the case for several ionization chambers from our set. TRS-483 recommended perpendicular orientation of ionization chambers for the determination of field output factors. The present study presents results for both perpendicular and parallel orientation of ionization chambers. When validated by other researchers, the present results for parallel orientation can be considered as a complementary dataset to those given in TRS-483.
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Affiliation(s)
- Božidar Casar
- Department for Dosimetry and Quality of Radiological ProceduresInstitute of Oncology LjubljanaLjubljanaSlovenia
| | | | - Ignasi Mendez
- Department for Dosimetry and Quality of Radiological ProceduresInstitute of Oncology LjubljanaLjubljanaSlovenia
| | - Slaven Jurković
- Medical Physics DepartmentUniversity Hospital RijekaRijekaCroatia
- Department of Physics and BiophysicsFaculty of MedicineUniversity of RijekaRijekaCroatia
| | - M. Saiful Huq
- Department of Radiation OncologyUniversity of Pittsburgh School of Medicine and UPMC Hillman Cancer CenterPittsburghPAUSA
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Akino Y, Mizuno H, Isono M, Tanaka Y, Masai N, Yamamoto T. Small-field dosimetry of TrueBeam TM flattened and flattening filter-free beams: A multi-institutional analysis. J Appl Clin Med Phys 2020; 21:78-87. [PMID: 31816176 PMCID: PMC6964782 DOI: 10.1002/acm2.12791] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 09/23/2019] [Accepted: 11/18/2019] [Indexed: 11/21/2022] Open
Abstract
PURPOSE Detector-dependent interinstitutional variations of the beam data may lead to uncertainties of the delivered dose to patients. Here we evaluated the inter-unit variability of the flattened and flattening filter-free (FFF) beam data of multiple TrueBeam (Varian Medical Systems) linear accelerators focusing on the small-field dosimetry. METHODS The beam data of 6- and 10-MV photon beams with and without flattening filter measured for modeling of an iPLAN treatment planning system (BrainLAB) were collected from 12 institutions - ten HD120 Multileaf Collimator (MLC) and two Millennium120 MLC. Percent-depth dose (PDD), off-center ratio (OCR), and detector output factors (OFdet ) measured with different detectors were evaluated. To investigate the detector-associated effects, we evaluated the inter-unit variations of the OFdet before and after having applied the output correction factors provided by the International Atomic Energy Agency (IAEA) Technical Reports Series no. 483. RESULTS PDD measured with a field size of 5 × 5 mm2 showed that the data measured using an ionization chamber had variations exceeding 1% from the median values. The maximum difference from median value was 2.87% for 10 MV photon beam. The maximum variations of the penumbra width for OCR with 10 × 10 mm2 field size were 0.97 mm. The OFdet showed large variations exceeding 15% for a field size of 5 × 5 mm2 . When the output correction factors were applied to the OFdet , the variations were greatly reduced. The relative difference of almost all field output factors were within ± 5% from the median field output factors. CONCLUSION In this study, the inter-unit variability of small-field dosimetry was evaluated for TrueBeam linear accelerators. The variations were large at a field size of 5 × 5 mm2 , and most occurred in a detector-dependent manner.
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Affiliation(s)
- Yuichi Akino
- Oncology CenterOsaka University HospitalSuitaOsakaJapan
| | - Hirokazu Mizuno
- Department of Medical Physics and EngineeringOsaka University Graduate School of MedicineSuitaOsakaJapan
| | - Masaru Isono
- Department of Radiation OncologyOsaka International Cancer InstituteOsakaJapan
| | - Yoshihiro Tanaka
- Department of Radiation TherapyJapanese Red Cross Society Kyoto Daiichi HospitalKyoto PrefectureJapan
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Renaud J, Sarfehnia A, Bancheri J, Seuntjens J. Absolute dosimetry of a 1.5 T MR-guided accelerator-based high-energy photon beam in water and solid phantoms using Aerrow. Med Phys 2019; 47:1291-1304. [PMID: 31834640 DOI: 10.1002/mp.13968] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 12/03/2019] [Accepted: 12/05/2019] [Indexed: 11/09/2022] Open
Abstract
PURPOSE In this work, the fabrication, operation, and evaluation of a probe-format graphite calorimeter - herein referred to as Aerrow - as an absolute clinical dosimeter of high-energy photon beams while in the presence of a B = 1.5 T magnetic field is described. Comparable to a cylindrical ionization chamber (IC) in terms of utility and usability, Aerrow has been developed for the purpose of accurately measuring absorbed dose to water in the clinic with a minimum disruption to the existing clinical workflow. To our knowledge, this is the first reported application of graphite calorimetry to magnetic resonance imaging (MRI)-guided radiotherapy. METHODS Based on a previously numerically optimized and experimentally validated design, an Aerrow prototype capable of isothermal operation was constructed in-house. Graphite-to-water dose conversions as well as magnetic field perturbation factors were calculated using Monte Carlo, while heat transfer and mass impurity corrections and uncertainties were assessed analytically. Reference dose measurements were performed in the absence and presence of a B = 1.5 T magnetic field using Aerrow in the 7 MV FFF photon beam of an Elekta MRI-linac and were directly compared to the results obtained using two calibrated reference-class IC types. The feasibility of performing solid phantom-based dosimetry with Aerrow and the possible influence of clearance gaps is also investigated by performing reference-type dosimetry measurements for multiple rotational positions of the detector and comparing the results to those obtained in water. RESULTS In the absence of the B-field, as well as in the parallel orientation while in the presence of the B-field, the absorbed dose to water measured using Aerrow was found to agree within combined uncertainties with those derived from TG-51 using calibrated reference-class ICs. Statistically significant differences on the order of (2-4)%, however, were observed when measuring absorbed dose to water using the ICs in the perpendicular orientation in the presence of the B-field. Aerrow had a peak-to-peak response of about 0.5% when rotated within the solid phantom regardless of whether the B-field was present or not. CONCLUSIONS This work describes the successful use of Aerrow as a straightforward means of measuring absolute dose to water for large high-energy photon fields in the presence of a 1.5 T B-field to a greater accuracy than currently achievable with ICs. The detector-phantom air gap does not appear to significantly influence the response of Aerrow in absolute terms, nor does it contribute to its rotational dependence. This work suggests that the accurate use of solid phantoms for absolute point dose measurement is possible with Aerrow.
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Affiliation(s)
- James Renaud
- Metrology Research Centre, National Research Council Canada, Ottawa, ON, K1T 0R6, Canada.,Medical Physics Unit, McGill University, Montréal, QC, H4A 3J1, Canada
| | - Arman Sarfehnia
- Medical Physics Unit, McGill University, Montréal, QC, H4A 3J1, Canada.,Department of Radiation Oncology, University of Toronto, Toronto, ON, M5S 3E2, Canada
| | - Julien Bancheri
- Medical Physics Unit, McGill University, Montréal, QC, H4A 3J1, Canada
| | - Jan Seuntjens
- Medical Physics Unit, McGill University, Montréal, QC, H4A 3J1, Canada
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93
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Cardon T, Amblard R, Garnier N, Villeneuve R, Gerard A, Benabdesselam M, Serrano B. 81 Application of the TRS-483 correction factors on output ratios measurements for 8 detectors in stereotactic radiosurgery with cones. Phys Med 2019. [DOI: 10.1016/j.ejmp.2019.09.162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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94
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Tanaka Y, Akino Y, Mizuno H, Isono M, Masai N, Yamamoto T. Impact of detector selections on inter-institutional variability of flattening filter-free beam data for TrueBeam™ linear accelerators. J Appl Clin Med Phys 2019; 21:36-42. [PMID: 31738002 PMCID: PMC6964765 DOI: 10.1002/acm2.12766] [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: 07/16/2019] [Revised: 10/11/2019] [Accepted: 10/14/2019] [Indexed: 11/08/2022] Open
Abstract
This study evaluates the type of detector influencing the inter-institutional variability in flattening filter-free (FFF) beam-specific parameters for TrueBeam™ linear accelerators (Varian Medical Systems,Palo Alto, CA, USA). Twenty-four beam data sets, including the percent depth dose (PDD), off-center ratio (OCR), and output factor (OPF) for modeling within the Eclipse (Varian Medical Systems) treatment planning system, were collected from 19 institutions. Although many institutions collected the data using CC13 (IBA Dosimetry, Schwarzenbruck, Germany) or PTW31010 semiflex (PTW Freiburg, Freiburg, Germany) ionization chambers, some institutions used diode detectors, diamond detectors, and ionization chambers with smaller cavities. The OCR data included penumbra width, full width at half maximum (FWHM), and FFF beam-specific parameters, including unflatness and slope. The data measured by CC13/PTW31010 ionization chambers were compared with those measured by all other detectors. PDD data demonstrated the variations within ±1% at the dose fall-off region deeper than peak depth. The penumbra widths of the OCR measured with the CC13/PTW31010 detectors were significantly larger than those measured with all other detectors (P < 0.05). Especially the EDGE detector (Sun Nuclear Corp., Melbourne, FL, USA) and the microDiamond detectors (model 60019; PTW Freiburg) demonstrated much smaller penumbra values compared to those of the CC13/PTW31010 detectors for the 30 × 30 mm2 field. There was no difference in the FWHM, unflatness, and slope parameters between the values for the CC13/PTW31010 detectors and all other detectors. OPF curves demonstrated small variations, and the relative difference from the mean value of each data point was almost within 1% for all field sizes. Although the penumbra region exhibited detector-dependent variations, all other parameters showed tiny interunit variations regardless of the detector type.
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Affiliation(s)
- Yoshihiro Tanaka
- Department of Radiation Therapy, Japanese Red Cross Society Kyoto Daiichi Hospital, Kyoto, Japan
| | - Yuichi Akino
- Oncology Center, Osaka University Hospital, Suita, Osaka, Japan
| | - Hirokazu Mizuno
- Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Masaru Isono
- Department of Radiation Oncology, Osaka International Cancer Institute, Osaka, Japan
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95
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Therriault-Proulx F, Pino R, Yang JN, Beddar AS. Quality assurance for Gamma Knife Perfexion using the Exradin W1 plastic scintillation detector and Lucy phantom. Phys Med Biol 2019; 64:225007. [PMID: 31581139 DOI: 10.1088/1361-6560/ab4ac3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The goal of this work is to validate the use of the Exradin W1 plastic scintillation detector (PSD) to measure profiles and output factors from Gamma Knife Perfexion collimators in a Lucy phantom. The Exradin W1 PSD has a small-volume, near-water-equivalent, energy-independent sensitive element. Output measurements were performed for all 3 collimators (4 mm, 8 mm, and 16 mm) of the Gamma Knife Perfexion system, and these measurements were compared to measurements made with an A16 ion chamber and an EBT3 film and to the nominal values. We showed that a configuration in which the focus or 'shot' moves while the detector remains fixed is essentially equivalent to a configuration in which the focus is fixed while the detector moves. A Lucy phantom containing a PSD was moved in small steps to acquire profiles in all three dimensions. EBT3 film was inserted in the Lucy phantom and exposed to a single shot for each collimator. The relative values for output factors measured with the PSD were 1.000, 0.892, and 0.795, for the 16 mm, 8 mm, and 4 mm collimators, respectively. The values measured with EBT3 film were 1.000, 0.881, and 0.793, and the values measured with the A16 ion chamber were 1.000, 0.883, and 0.727. The nominal output factors for the Gamma Knife Perfexion are 1.000, 0.900, and 0.814, respectively. There was excellent agreement between all profiles measured with the PSD and EBT3 as well as with the treatment planning system data provided by the vendor. In light of our results, the Exradin W1 PSD is well suited for beam quality assurance of a Gamma Knife Perfexion irradiator.
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Affiliation(s)
- Francois Therriault-Proulx
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, United States of America
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96
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Galván De la Cruz O, Rodríguez-Ávila M, Rivera-Montalvo T, García Garduño O. Measurement of percentage dose at the surface for a 6 MV photon beam. Rep Pract Oncol Radiother 2019; 24:585-592. [PMID: 31660051 PMCID: PMC6807031 DOI: 10.1016/j.rpor.2019.09.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Revised: 05/09/2019] [Accepted: 09/21/2019] [Indexed: 11/19/2022] Open
Abstract
AIM To evaluate if a radiochromic film (RF) Gafchromic EBT3 is suitable for surface dose measurements of radiotherapy treatments performed with a 6 MV linear accelerator. Two aspects of RF were analyzed, beam energy dependence and surface dose determination. BACKGROUND The measurements done at the surface or near the radiation source are done without charged electronic equilibrium and also have contribution of electron contamination. The detectors used for these measurements should not alter the dose to the target. To counteract these dosimetric problems it is proposed to do the measurements with radiochromic films which are thin detectors and have tissue equivalent properties. MATERIALS AND METHODS The measurements were done using a Novalis linear accelerator (LINAC) with nominal energy of 6 MV. To determine the surface dose, the total scatter factors (TSF) of three different field sizes were measured in a water phantom at 5 cm depth. Energy dependence of EBT3 was studied at three different depths, using a solid water phantom. The surface measurements were done with the RF for the same field sizes of the TSF measurements. The value of the percentage depth dose was calculated normalizing the doses measured in the RF with the LINAC output, at 5 cm depth, and the TSF. RESULTS The radiochromic films showed almost energy independence, the differences between the curves are 1.7% and 1.8% for the 1.5 cm and 10 cm depth, respectively. The percentage depth doses values at the surface measured for the 10 cm × 10 cm, 5 cm × 5 cm and 1 cm × 1 cm were 26.1 ± 1.3%, 21.3 ± 2.4% and 20.2 ± 2.6%, respectively. CONCLUSIONS The RF-EBT3 seems to be a detector suitable for measurements of the dose at the surface. This suggests that RF-EBT3 films might be good candidates as detectors for in vivo dosimetry.
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Affiliation(s)
- O.O. Galván De la Cruz
- Unidad de Radioneurocirugía, Instituto Nacional de Neurología y Neurocirugía, Insurgentes Sur 3877, México City, Mexico
- Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Unidad Legaria, Instituto Politécnico Nacional, Legaria 694, México city, México
| | - M.A. Rodríguez-Ávila
- Posgrado en Ciencias Físicas, Universidad Nacional Autónoma de México, Instituto de Física, Circuito de la Investigación Científica s/n. Ciudad Universitaria, 04510, Mexico City, México
| | - T. Rivera-Montalvo
- Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Unidad Legaria, Instituto Politécnico Nacional, Legaria 694, México city, México
| | - O.A. García Garduño
- Laboratorio de Física Médica, Instituto Nacional de Neurología y Neurocirugía, Insurgentes Sur 3877, México City, México
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97
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Lopes MDC, Santos T, Ventura T, Capela M. Application of the TRS 483 code of practice for reference and relative dosimetry in tomotherapy. Med Phys 2019; 46:5799-5806. [DOI: 10.1002/mp.13855] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 09/10/2019] [Accepted: 10/01/2019] [Indexed: 01/09/2023] Open
Affiliation(s)
| | - Tania Santos
- Medical Physics Department IPOCFG, E.P.E Coimbra Portugal
- Physics Department FCTUC University of Coimbra Coimbra Portugal
| | - Tiago Ventura
- Medical Physics Department IPOCFG, E.P.E Coimbra Portugal
| | - Miguel Capela
- Medical Physics Department IPOCFG, E.P.E Coimbra Portugal
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98
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Ghazal M, Westermark M, Kaveckyte V, Carlsson‐Tedgren Å, Benmakhlouf H. 6‐MV small field output factors: intra‐/intermachine comparison and implementation of TRS‐483 using various detectors and several linear accelerators. Med Phys 2019; 46:5350-5359. [DOI: 10.1002/mp.13830] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 09/05/2019] [Accepted: 09/05/2019] [Indexed: 11/10/2022] Open
Affiliation(s)
- Mohammed Ghazal
- Department of Medical Radiation Physics and Nuclear Medicine Karolinska University Hospital SE‐171 76Stockholm Sweden
| | - Mathias Westermark
- Department of Medical Radiation Physics and Nuclear Medicine Karolinska University Hospital SE‐171 76Stockholm Sweden
| | - Vaiva Kaveckyte
- Department of Medical Radiation Physics and Nuclear Medicine Karolinska University Hospital SE‐171 76Stockholm Sweden
- Radiation Physics Department of Medical and Health Sciences Linköping University SE‐581 85Linköping Sweden
| | - Åsa Carlsson‐Tedgren
- Department of Medical Radiation Physics and Nuclear Medicine Karolinska University Hospital SE‐171 76Stockholm Sweden
- Radiation Physics Department of Medical and Health Sciences Linköping University SE‐581 85Linköping Sweden
| | - Hamza Benmakhlouf
- Department of Medical Radiation Physics and Nuclear Medicine Karolinska University Hospital SE‐171 76Stockholm Sweden
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99
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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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100
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Sendani NG, Karimian A, Mahdavi SR, Jabbari I, Alaei P. Effect of beam configuration with inaccurate or incomplete small field output factors on the accuracy of treatment planning dose calculation. Med Phys 2019; 46:5273-5283. [DOI: 10.1002/mp.13796] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 08/16/2019] [Accepted: 08/16/2019] [Indexed: 11/11/2022] Open
Affiliation(s)
- Neda Gholizadeh Sendani
- Faculty of Advanced Sciences and Technologies University of Isfahan Isfahan 81746‐73441Iran
- Department of Radiation Oncology University of Minnesota Minneapolis MN 55455USA
| | - Alireza Karimian
- Department of Biomedical Engineering Faculty of Engineering University of Isfahan Isfahan 81746‐73441Iran
| | - S. Rabie Mahdavi
- Radiation Biology Research Center and Department of Medical Physics Iran University of Medical Sciences Tehran 14496Iran
| | - Iraj Jabbari
- Faculty of Advanced Sciences and Technologies University of Isfahan Isfahan 81746‐73441Iran
| | - Parham Alaei
- Department of Radiation Oncology University of Minnesota Minneapolis MN 55455USA
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