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Kawata K, Hirashima H, Tsuruta Y, Sasaki M, Matsushita N, Fujimoto T, Nakamura M, Nakata M. Applicability evaluation of the TRS-483 protocol for the determination of small-field output factors using different multi-leaf collimator and field-shaping types. Phys Med 2023; 113:102664. [PMID: 37573811 DOI: 10.1016/j.ejmp.2023.102664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 08/06/2023] [Accepted: 08/07/2023] [Indexed: 08/15/2023] Open
Abstract
PURPOSE To evaluate the applicability of TRS-483 output correction factors (CFs) for small-field output factors (OFs) using different multi-leaf collimators (MLC) and field-shaping types. METHODS All measurements were performed on TrueBeam, TrueBeam STx, and Halcyon using 6 MV flattening filter-free energy. Four detectors, including CC01, CC04, microDiamond, and EDGE, were used. Nominal field sizes ranging from 1 × 1 to 4 × 4, and 10 × 10 cm2 were used to measure small-field OFs at source-to-axis distance of 100 cm with a 0° gantry angle in a 3D water phantom. Further, the field-shaping types were defined using jaw collimator or MLC (five different configurations). A field size of 10 × 10 cm2 was used as the reference for calculation of OFs obtained as ratio of detector readings (OFdet). The percentage difference and coefficient of variation of OFdet and OFdet corrected by applying CF were compared for each field size and configuration. RESULTS For OFdet corrected by applying CF, the ranges of percentage difference and coefficient of variation in all configurations for ≥ 2 × 2 cm2 fields were reduced from 1.2-2.2 to 0.8-1.3 percentage points (%pt) and from 0.5-1.0 to 0.4-0.7%, respectively. For 1 × 1 cm2 field, the ranges of percentage difference and coefficient of variation were reduced from 3.3-5.7 to 1.2-2.2 %pt and from 2.2-3.7 to 0.8-1.1%, respectively. CONCLUSIONS The CFs described in TRS-483 dosimetry protocol have broad applicability in reducing OF variations between detectors under different MLC and field-shaping types.
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Affiliation(s)
- Kohei Kawata
- Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan
| | - Hideaki Hirashima
- Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan.
| | - Yusuke Tsuruta
- Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan; Department of Advanced Medical Physics, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Makoto Sasaki
- Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan
| | - Norimasa Matsushita
- Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan
| | - Takahiro Fujimoto
- Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan
| | - Mitsuhiro Nakamura
- Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan; Department of Advanced Medical Physics, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Manabu Nakata
- Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan
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Momeni Harzanji Z, Larizadeh MH, Namiranian N, Nickfarjam A. Evaluation and Comparison of Dosimetric Characteristics of Semiflex ®3D and Microdiamond in Relative Dosimetry under 6 and 15 MV Photon Beams in Small Fields. J Biomed Phys Eng 2022; 12:477-488. [PMID: 36313410 PMCID: PMC9589081 DOI: 10.31661/jbpe.v0i0.2008-1160] [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: 08/16/2020] [Accepted: 01/14/2021] [Indexed: 06/16/2023]
Abstract
BACKGROUND In modern radiotherapy techniques, the frequently small and non-uniformed fields can increase treatment efficiency due to their highly conformal dose distribution. Particular features including lack of Lateral Charge Particle Equilibrium (LCPE) lead to detectors with high resolution since any error in obtained dosimetric data could cause patient mistreatments. OBJECTIVE This study aims to evaluate and compare two small detectors (Semiflex®3D and microdiamond) dosimetric characteristics in small field relative dosimetry. MATERIAL AND METHODS In this experimental study, the dosimetric properties of Semiflex®3D and microdiamond were assessed under 6 and 15 MV photon beams. The linearity and stability of the detector's response and dose rate were measured. Square-field sizes ranging from 0.6×0.6 - 5×5 cm2 were used for obtaining percentage depth dose curves (PDDs) and in-plane profiles. The angular and temperature dependence of both detectors' responses were also studied. RESULTS The detector response shows good stability, no deviation from linearity, and low dose rate dependence (≤1.6%). PDDs and in-plan profiles of both detectors are in good agreement and no significant difference was observed except for the high dose gradient regions (P-value≤0.017). Both detectors demonstrated low angular dependence (<0.3%) with temperature dependence lower than 1% for both detectors. CONCLUSION The results indicate both investigated detectors were well performed in small field relative dosimetry and for measuring penumbra, it is better to use microdiamond detector.
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Affiliation(s)
- Zahra Momeni Harzanji
- MSc, Department of Medical Physics, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Mohammad Hassan Larizadeh
- MD, Department of Radiation Oncology, School of Medicine, Kerman University of Medical Sciences, Kerman, Iran
| | - Nasim Namiranian
- MD, Yazd Diabetes Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Abolfazl Nickfarjam
- PhD, Department of Medical Physics, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
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Lechner W, Alfonso R, Arib M, Huq MS, Ismail A, Kinhikar R, Lárraga-Gutiérrez JM, Mani KR, Maphumulo N, Sauer OA, Shoeir S, Suriyapee S, Christaki K. A multi-institutional evaluation of small field output factor determination following the recommendations of IAEA/AAPM TRS-483. Med Phys 2022; 49:5537-5550. [PMID: 35717637 PMCID: PMC9541513 DOI: 10.1002/mp.15797] [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: 05/12/2021] [Revised: 03/31/2022] [Accepted: 05/25/2022] [Indexed: 11/15/2022] Open
Abstract
Purpose The aim of this work was to test the implementation of small field dosimetry following TRS‐483 and to develop quality assurance procedures for the experimental determination of small field output factors (SFOFs). Materials and methods Twelve different centers provided SFOFs determined with various detectors. Various linac models using the beam qualities 6 MV and 10 MV with flattening filter and without flattening filter were utilized to generate square fields down to a nominal field size of 0.5 cm × 0.5 cm. The detectors were positioned at 10 cm depth in water. Depending on the local situation, the source‐to‐surface distance was either set to 90 cm or 100 cm. The SFOFs were normalized to the output of the 10 cm × 10 cm field. The spread of SFOFs measured with different detectors was investigated for each individual linac beam quality and field size. Additionally, linac‐type specific SFOF curves were determined for each beam quality and the SFOFs determined using individual detectors were compared to these curves. Example uncertainty budgets were established for a solid state detector and a micro ionization chamber. Results The spread of SFOFs for each linac and field was below 5% for all field sizes. With the exception of one linac‐type, the SFOFs of all investigated detectors agreed within 10% with the respective linac‐type SFOF curve, indicating a potential inter‐detector and inter‐linac variability. Conclusion Quality assurance on the SFOF measurements can be done by investigation of the spread of SFOFs measured with multiple detectors and by comparison to linac‐type specific SFOFs. A follow‐up of a measurement session should be conducted if the spread of SFOFs is larger than 5%, 3%, and 2% for field sizes of 0.5 cm × 0.5 cm, 1 cm × 1 cm, and field sizes larger than 2 cm × 2 cm, respectively. Additionally, deviations of measured SFOFs to the linac‐type‐curves of more than 7%, 3%, and 2% for field sizes 0.5 cm × 0.5 cm, 1 cm × 1 cm, and field sizes larger than 1 cm × 1 cm, respectively, should be followed up.
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Affiliation(s)
- Wolfgang Lechner
- Department of Radiation Oncology, Division of Medical Physics, Medical University Vienna, Vienna, 1090, Austria
| | - Rodolfo Alfonso
- Department of Nuclear Engineering, Higher Institute of Technology and Applied Sciences, University of Havana, Havana, 10400, Cuba
| | - Mehenna Arib
- King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - M Saiful Huq
- Department of Radiation Oncology, University of Pittsburgh School of Medicine and UPMC Hillman Cancer Center, Pittsburgh, Pennsylvania, USA
| | - Anas Ismail
- Protection and Safety Department, Atomic Energy Commission of Syria, Damascus, PO Box 6091, Syria
| | - Rajesh Kinhikar
- Department of Medical Physics, Tata Memorial Centre, Mumbai, India 400012 & Homi Bhabha National Institute, Mumbai, 400094, India
| | - José M Lárraga-Gutiérrez
- Laboratorio de Física-Médica, Instituto Nacional de Neurología y Neurocirugía, Insurgentes sur 3877, La Fama, Tlalpan 14269, CDMX, México
| | - Karthick Raj Mani
- Department of Radiation Oncology, United Hospital Ltd., Dhaka, 1212, Bangladesh
| | - Nkosingiphile Maphumulo
- Radiation Dosimetry Section, National Metrology Institute of South Africa, Pretoria, South Africa
| | - Otto A Sauer
- Department of Radiation Oncology, University of Würzburg, 97080, Würzburg, Germany
| | | | - Sivalee Suriyapee
- Division of Radiation Oncology, Department of Radiology, Chulalongkorn University, Bangkok, Thailand
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Dose area product primary standards established by graphite calorimetry at the LNE-LNHB for small radiation fields in radiotherapy. Phys Med 2022; 98:18-27. [PMID: 35489128 DOI: 10.1016/j.ejmp.2022.03.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 03/10/2022] [Accepted: 03/19/2022] [Indexed: 11/22/2022] Open
Abstract
PURPOSE To present primary standards establishment in terms of Dose Area Product (DAP) for small field sizes. METHODS A large section graphite calorimeter and two plane-parallel ionization chambers were designed and built in-house. These chambers were calibrated in a 6MV FFF beam at the maximum dose rate of 1400 UM/min for fields defined by specifically designed circular collimators of 5, 7.5, 10, 13 and 15 mm diameter and jaws of 5, 7, 10, 13 and 15 mm side length on a Varian TrueBeam linac. RESULTS The two chambers show the same behaviour regardless of field shape and size. From 5 to 15 mm, calibration coefficients slightly increase with the field size with a magnitude of 1.8% and 1.1% respectively for the two chambers, and are independent of the field shape. This tendency was confirmed by Monte Carlo calculations. The average associated uncertainty of the calibration coefficients is around 0.6% at k=1. CONCLUSIONS For the first time, primary standards in terms of DAP were established by graphite calorimetry for an extended range of small field sizes. These promising results open the door for an alternative approach in small fields dosimetry.
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Das IJ, Dogan SK, Gopalakrishnan M, Ding GX, Longo M, Franscescon P. Validity of equivalent square field concept in small field dosimetry. Med Phys 2022; 49:4043-4055. [PMID: 35344220 DOI: 10.1002/mp.15624] [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: 06/01/2021] [Revised: 03/16/2022] [Accepted: 03/16/2022] [Indexed: 11/11/2022] Open
Abstract
PURPOSE The equivalent Square (ES) concept has been used for traditional radiation fields defined by the machine collimating system. For small fields, the concept Sclin was introduced based on measuring dosimetric field width (full-width half maximum, FWHM) of the cardinal axis of the beam profiles. The pros and cons of this concept are evaluated in small fields and compared with the traditional ES using area and perimeter (4A/P) method based on geometric field size settings e.g. light field settings. METHODS One hundred thirty-seven square and rectangular fields from 5-50 mm with every possible permutation (keeping one jaw fixed and varying other jaw from 5 mm to 50 mm) were utilized to measure FWHM for the validation of Sclin . Using a microSilicon detector and a scanning water tank, measurements were performed on an Elekta (Versa) machine with Agility head and a Varian TrueBeam with different MLC/Jaw design to evaluate the Sclin concept and to understand the effect of exchange factor in small fields. Field output factors were also measured for all 137 fields. RESULTS The data fitting for fields ranging from 5-50 mm between the traditional 4A/P method and Sclin shows differences and indicates a linear relationship with distinct separation of slope for Elekta and Varian machines. As Elekta does not have y jaws, the ES based on 4A/P < Sclin but for the Varian linac 4A/P > Sclin for square fields. Our measured data shows that both methods are equally valid but does vary by the machine design. The field output factor is dependent on the elongation factor as well as machine design. For fields with sides ≥10 mm, the exchange factor is nearly identical in both machines with magnitude up to 4% which is close to measurement uncertainty (±3%) but for small fields (<10 mm) the Elekta machine has higher exchange factors compared to the Varian machine. CONCLUSION The results demonstrate that the two concepts for defining equivalent field (Sclin and 4A/P) are equivalent and can be directly related through an empirical equation. This study confirms that 4A/P is still valid for small fields except for very small fields (≤10 mm) where source occlusion is a dominating factor. The Sclin method is potentially sensitive to measurement uncertainty due to measurement of FWHM which is machine, detector and user dependent, while the 4A/P method relies mainly on geometry of the machine and has less dependency on type of machine, detector and user. The exchange factors are comparable for both types of machines. The conclusion is based on data from an Elekta with Agility head and a Varian TrueBeam machine that may have potential for bias due to light field/collimator set up and alignment. Care should be taken in extrapolating these data to any other machine. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Indra J Das
- Department of Radiation Oncology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, Chicago, IL, 60611, USA
| | - Serpil K Dogan
- Department of Radiation Oncology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, Chicago, IL, 60611, USA
| | - Mahesh Gopalakrishnan
- Department of Radiation Oncology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, Chicago, IL, 60611, USA
| | - George X Ding
- Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA
| | - Mariaconcetta Longo
- Department of Radiation Oncology Ospedale Di Vicenza, Viale Rodolfi, Vicenza, 36100, Italy
| | - Paolo Franscescon
- Department of Radiation Oncology Ospedale Di Vicenza, Viale Rodolfi, Vicenza, 36100, Italy
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Muñoz L, Kron T, Petasecca M, Bucci J, Jackson M, Metcalfe P, Rosenfeld AB, Biasi G. Consistency of small-field dosimetry, on and off axis, in beam-matched linacs used for stereotactic radiosurgery. J Appl Clin Med Phys 2021; 22:185-193. [PMID: 33440049 PMCID: PMC7882112 DOI: 10.1002/acm2.13160] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 12/08/2020] [Accepted: 12/17/2020] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Stereotactic radiosurgery (SRS) can be delivered with a standard linear accelerator (linac). At institutions having more than one linac, beam matching is common practice. In the literature, there are indications that machine central axis (CAX) matching for broad fields does not guarantee matching of small fields with side ≤2 cm. There is no indication on how matching for broad fields on axis translates to matching small fields off axis. These are of interest to multitarget single-isocenter (MTSI) SRS planning and the present work addresses that gap in the literature. METHODS We used 6 MV flattening filter free (FFF) beams from four Elekta VersaHD® linacs equipped with an Agility™ multileaf collimator (MLC). The linacs were strictly matched for broad fields on CAX. We compared output factors (OPFs) and effective field size, measured concurrently using a novel 2D solid-state dosimeter "Duo" with a spatial resolution of 0.2 mm, in square and rectangular static fields with sides from 0.5 to 2 cm, either on axis or away from it by 5 to 15 cm. RESULTS Among the four linacs, OPF for fields ≥1 × 1 cm2 ranged 1.3% on CAX, whereas off axis a maximum range of 1.9% was observed at 15 cm. A larger variability in OPF was noted for the 0.5 × 0.5 cm2 field, with a range of 5.9% on CAX, which improved to a maximum of 2.3% moving off axis. Two linacs showed greater consistency with a range of 1.4% on CAX and 2.2% at 15 cm off axis. Between linacs, the effective field size varied by <0.04 cm in most cases, both on and off axis. Tighter matching was observed for linacs with a similar focal spot position. CONCLUSIONS Verification of small-field consistency for matched linacs used for SRS is an important task for dosimetric validation. A significant benefit of concurrent measurement of field size and OPF allowed for a comprehensive assessment using a novel diode array. Our study showed the four linacs, strictly matched for broad fields on CAX, were still matched down to a field size of 1 x 1 cm2 on and off axis.
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Affiliation(s)
- Luis Muñoz
- Genesiscare Flinders Private HospitalBedford ParkSAAustralia
- Centre for Medical Radiation PhysicsUniversity of WollongongNSWAustralia
| | - Tomas Kron
- Centre for Medical Radiation PhysicsUniversity of WollongongNSWAustralia
- Peter MacCallum Cancer CentreMelbourneVICAustralia
| | - Marco Petasecca
- Centre for Medical Radiation PhysicsUniversity of WollongongNSWAustralia
| | - Joseph Bucci
- St. George Cancer Care CentreSt George HospitalKogarahNSWAustralia
- Genesiscare Waratah Private HospitalHurstvilleNSWAustralia
| | - Michael Jackson
- Centre for Medical Radiation PhysicsUniversity of WollongongNSWAustralia
- University of New South WalesKensingtonNSWAustralia
| | - Peter Metcalfe
- Centre for Medical Radiation PhysicsUniversity of WollongongNSWAustralia
| | | | - Giordano Biasi
- Centre for Medical Radiation PhysicsUniversity of WollongongNSWAustralia
- Peter MacCallum Cancer CentreMelbourneVICAustralia
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Dufreneix S, Bellec J, Josset S, Vieillevigne L. Field output factors for small fields: A large multicentre study. Phys Med 2021; 81:191-196. [PMID: 33465756 DOI: 10.1016/j.ejmp.2021.01.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 12/30/2020] [Accepted: 01/02/2021] [Indexed: 02/06/2023] Open
Abstract
PURPOSE The determination of output factors in small field dosimetry is a crucial point, especially when implementing stereotactic radiotherapy (SRT). Herein, a working group of the French medical physicist society (SFPM) was created to collect small field output factors. The objective was to gather and disseminate information on small field output factors based on different detectors for various clinical SRT equipment and measurement configurations. METHOD Participants were surveyed for information about their SRT equipment, including the type of linear particle accelerator (linac), collimator settings, measurement conditions for the output factors and the detectors used. Participants had to report both the ratio of detector readings and the correction factors applied as described in the IAEA TRS-483 code of practice for nominal field sizes smaller or equal to 3 cm. Mean field output factors and their associated standard deviations were calculated when data from at least 3 linacs were available. RESULTS 23 centres were enrolled in the project. Standard deviations of the mean field output factors were systematically smaller than 1.5% for field sizes larger or equal to 1 cm and reached 5% for the smallest field size (0.5 cm). Deviations with published data were smaller than 2% except for the 0.5 cm circular fixed aperture collimator of the CyberKnife where it reached 3.5%. CONCLUSION These field output factor values obtained via a large multicentre study can be considered as an external cross verification for any radiotherapy centre starting a SRT program and should help minimize systematic errors when determining small field output factors.
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Affiliation(s)
- S Dufreneix
- Institut de Cancérologie de l'Ouest, Angers, Saint-Herblain, France.
| | - J Bellec
- Centre Eugène Marquis, Rennes, France
| | - S Josset
- Institut de Cancérologie de l'Ouest, Angers, Saint-Herblain, France
| | - L Vieillevigne
- Institut Claudius Régaud, Institut Universitaire du Cancer de Toulouse, France; Centre de Recherche et de Cancérologie de Toulouse, UMR1037 INSERM - Université Toulouse 3 - ERL5294 CNRS, Oncopole, Toulouse, France
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