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Bertinetti A, Garcia T, Palmer B, Rodrigues M, Bradshaw T, Vija AH, Culberson W. Active and passive dosimetry for beta-emitting radiopharmaceutical therapy agents in a custom SPECT/CT compatible phantom. Phys Med Biol 2024; 69:115031. [PMID: 38684165 DOI: 10.1088/1361-6560/ad450c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2023] [Accepted: 04/29/2024] [Indexed: 05/02/2024]
Abstract
Objective. This work introduces a novel approach to performing active and passive dosimetry for beta-emitting radionuclides in solution using common dosimeters. The measurements are compared to absorbed dose to water (Dw) estimates from Monte Carlo (MC) simulations. We present a method for obtaining absorbed dose to water, measured with dosimeters, from beta-emitting radiopharmaceutical agents using a custom SPECT/CT compatible phantom for validation of Monte Carlo based absorbed dose to water estimates.Approach. A cylindrical, acrylic SPECT/CT compatible phantom capable of housing an IBA EFD diode, Exradin A20-375 parallel plate ion chamber, unlaminated EBT3 film, and thin TLD100 microcubes was constructed for the purpose of measuring absorbed dose to water from solutions of common beta-emitting radiopharmaceutical therapy agents. The phantom is equipped with removable detector inserts that allow for multiple configurations and is designed to be used for validation of image-based absorbed dose estimates with detector measurements. Two experiments with131I and one experiment with177Lu were conducted over extended measurement intervals with starting activities of approximately 150-350 MBq. Measurement data was compared to Monte Carlo simulations using the egs_chamber user code in EGSnrc 2019.Main results. Agreement withink= 1 uncertainty between measured and MC predictedDwwas observed for all dosimeters, except the A20-375 ion chamber during the second131I experiment. Despite the agreement, the measured values were generally lower than predicted values by 5%-15%. The uncertainties atk = 1 remain large (5%-30% depending on the dosimeter) relative to other forms of radiation therapy.Significance. Despite high uncertainties, the overall agreement between measured and simulated absorbed doses is promising for the use of dosimeter-based RPT measurements in the validation of MC predictedDw.
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Affiliation(s)
| | | | - Benjamin Palmer
- University of Wisconsin-Madison, WI, United States of America
| | | | - Tyler Bradshaw
- University of Wisconsin-Madison, WI, United States of America
| | - A Hans Vija
- Siemens Healthineers, United States of America
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2
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Das IJ, Francescon P, Moran JM, Ahnesjö A, Aspradakis MM, Cheng CW, Ding GX, Fenwick JD, Saiful Huq M, Oldham M, Reft CS, Sauer OA. Report of AAPM Task Group 155: Megavoltage photon beam dosimetry in small fields and non-equilibrium conditions. Med Phys 2021; 48:e886-e921. [PMID: 34101836 DOI: 10.1002/mp.15030] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 05/06/2021] [Accepted: 06/02/2021] [Indexed: 12/14/2022] Open
Abstract
Small-field dosimetry used in advance treatment technologies poses challenges due to loss of lateral charged particle equilibrium (LCPE), occlusion of the primary photon source, and the limited choice of suitable radiation detectors. These challenges greatly influence dosimetric accuracy. Many high-profile radiation incidents have demonstrated a poor understanding of appropriate methodology for small-field dosimetry. These incidents are a cause for concern because the use of small fields in various specialized radiation treatment techniques continues to grow rapidly. Reference and relative dosimetry in small and composite fields are the subject of the International Atomic Energy Agency (IAEA) dosimetry code of practice that has been published as TRS-483 and an AAPM summary publication (IAEA TRS 483; Dosimetry of small static fields used in external beam radiotherapy: An IAEA/AAPM International Code of Practice for reference and relative dose determination, Technical Report Series No. 483; Palmans et al., Med Phys 45(11):e1123, 2018). The charge of AAPM task group 155 (TG-155) is to summarize current knowledge on small-field dosimetry and to provide recommendations of best practices for relative dose determination in small megavoltage photon beams. An overview of the issue of LCPE and the changes in photon beam perturbations with decreasing field size is provided. Recommendations are included on appropriate detector systems and measurement methodologies. Existing published data on dosimetric parameters in small photon fields (e.g., percentage depth dose, tissue phantom ratio/tissue maximum ratio, off-axis ratios, and field output factors) together with the necessary perturbation corrections for various detectors are reviewed. A discussion on errors and an uncertainty analysis in measurements is provided. The design of beam models in treatment planning systems to simulate small fields necessitates special attention on the influence of the primary beam source and collimating devices in the computation of energy fluence and dose. The general requirements for fluence and dose calculation engines suitable for modeling dose in small fields are reviewed. Implementations in commercial treatment planning systems vary widely, and the aims of this report are to provide insight for the medical physicist and guidance to developers of beams models for radiotherapy treatment planning systems.
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Affiliation(s)
- Indra J Das
- Department of Radiation Oncology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Paolo Francescon
- Department of Radiation Oncology, Ospedale Di Vicenza, Vicenza, Italy
| | - Jean M Moran
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Anders Ahnesjö
- Medical Radiation Sciences, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Maria M Aspradakis
- Institute of Radiation Oncology, Cantonal Hospital of Graubünden, Chur, Switzerland
| | - Chee-Wai Cheng
- Department of Radiation Oncology, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
| | - George X Ding
- Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - John D Fenwick
- Molecular and Clinical Cancer Medicine, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, UK
| | - M Saiful Huq
- Department of Radiation Oncology, University of Pittsburgh, School of Medicine and UPMC Hillman Cancer Center, Pittsburgh, PA, USA
| | - Mark Oldham
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, USA
| | - Chester S Reft
- Department of Radiation Oncology, University of Chicago, Chicago, IL, USA
| | - Otto A Sauer
- Department of Radiation Oncology, Klinik fur Strahlentherapie, University of Würzburg, Würzburg, Germany
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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: 0.6] [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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Smith CL, Montesari A, Oliver CP, Butler DJ. Evaluation of the IAEA-TRS 483 protocol for the dosimetry of small fields (square and stereotactic cones) using multiple detectors. J Appl Clin Med Phys 2019; 21:98-110. [PMID: 31886615 PMCID: PMC7021012 DOI: 10.1002/acm2.12792] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 10/06/2019] [Accepted: 11/15/2019] [Indexed: 11/30/2022] Open
Abstract
The IAEA TRS 483 protocol1 for the dosimetry of small static fields in radiotherapy was used to calculate output factors for the Elekta Synergy linac at the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). Small field output factors for both square and circular fields were measured using nine different detectors. The “corrected” output factors (ratio of detector readings multiplied by the appropriate correction factor from the protocol) showed better consistency compared to the “uncorrected” output factors (ratio of detector readings only), with the relative standard deviation decreasing by approximately 1% after the application of the relevant correction factors. Comparisons relative to an arbitrarily chosen PTW 60019 microDiamond detector showed a reduction of maximal variation for the corrected values of approximately 3%. A full uncertainty budget was prepared to analyze the consistency of the output factors. Agreement within uncertainties between all detectors and field sizes was found, except for the 15 mm circular field. The results of this study show that the application of IAEA TRS 4831 when measuring small fields will improve the consistency of small field measurements when using multiple detectors contained within the protocol.
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Affiliation(s)
- Clare L Smith
- School of Health and Biomedical Sciences, RMIT University, Bundoora, VIC, Australia
| | | | - Christopher P Oliver
- Australian Radiation Protection and Nuclear Safety Agency, Yallambie, VIC, Australia
| | - Duncan J Butler
- Australian Radiation Protection and Nuclear Safety Agency, Yallambie, VIC, Australia
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5
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Akino Y, Mizuno H, Tanaka Y, Isono M, Masai N, Yamamoto T. Inter-institutional variability of small-field-dosimetry beams among HD120™ multileaf collimators: a multi-institutional analysis. ACTA ACUST UNITED AC 2018; 63:205018. [DOI: 10.1088/1361-6560/aae450] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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6
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Prado A, Lozano FR, Cabello E, Díaz R, Rot MJ. Dosimetric characterization of a 5 mm diameter BrainLab cone for radiosurgery. Biomed Phys Eng Express 2018. [DOI: 10.1088/2057-1976/aace50] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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7
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Wegener S, Sauer OA. Energy response corrections for profile measurements using a combination of different detector types. Med Phys 2017; 45:898-907. [DOI: 10.1002/mp.12706] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 11/21/2017] [Accepted: 11/25/2017] [Indexed: 12/25/2022] Open
Affiliation(s)
- Sonja Wegener
- Department of Radiation Oncology; University of Würzburg; Würzburg Germany
| | - Otto A. Sauer
- Department of Radiation Oncology; University of Würzburg; Würzburg Germany
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8
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Zoros E, Moutsatsos A, Pappas EP, Georgiou E, Kollias G, Karaiskos P, Pantelis E. Monte Carlo and experimental determination of correction factors for gamma knife perfexion small field dosimetry measurements. Phys Med Biol 2017; 62:7532-7555. [PMID: 28796643 DOI: 10.1088/1361-6560/aa8590] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Detector-, field size- and machine-specific correction factors are required for precise dosimetry measurements in small and non-standard photon fields. In this work, Monte Carlo (MC) simulation techniques were used to calculate the [Formula: see text] and [Formula: see text] correction factors for a series of ionization chambers, a synthetic microDiamond and diode dosimeters, used for reference and/or output factor (OF) measurements in the Gamma Knife Perfexion photon fields. Calculations were performed for the solid water (SW) and ABS plastic phantoms, as well as for a water phantom of the same geometry. MC calculations for the [Formula: see text] correction factors in SW were compared against corresponding experimental results for a subset of ionization chambers and diode detectors. Reference experimental OF data were obtained through the weighted average of corresponding measurements using TLDs, EBT-2 films and alanine pellets. [Formula: see text] values close to unity (within 1%) were calculated for most of ionization chambers in water. Greater corrections of up to 6.0% were observed for chambers with relatively large air-cavity dimensions and steel central electrode. A phantom correction of 1.006 and 1.024 (breaking down to 1.014 from the ABS sphere and 1.010 from the accompanying ABS phantom adapter) were calculated for the SW and ABS phantoms, respectively, adding up to [Formula: see text] corrections in water. Both measurements and MC calculations for the diode and microDiamond detectors resulted in lower than unit [Formula: see text] correction factors, due to their denser sensitive volume and encapsulation materials. In comparison, higher than unit [Formula: see text] results for the ionization chambers suggested field size depended dose underestimations (being significant for the 4 mm field), with magnitude depending on the combination of contradicting phenomena associated with volume averaging and electron fluence perturbations. Finally, the presence of 0.5 mm air-gap between the diodes' frontal surface and their phantom-inserts may considerably influence OF measurements, reaching 4.6% for the Razor diode.
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Affiliation(s)
- E Zoros
- Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, 75 Mikras Asias, 115 27 Athens, Greece
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Reggiori G, Stravato A, Pimpinella M, Lobefalo F, De Coste V, Fogliata A, Mancosu P, De Rose F, Palumbo V, Scorsetti M, Tomatis S. Use of PTW-microDiamond for relative dosimetry of unflattened photon beams. Phys Med 2017; 38:45-53. [PMID: 28610696 DOI: 10.1016/j.ejmp.2017.05.046] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 01/31/2017] [Accepted: 05/03/2017] [Indexed: 10/19/2022] Open
Abstract
PURPOSE The increasing interest in SBRT treatments encourages the use of flattening filter free (FFF) beams. Aim of this work was to evaluate the performance of the PTW60019 microDiamond detector under 6MV and 10MVFFF beams delivered with the EDGE accelerator (Varian Medical System, Palo Alto, USA). A flattened 6MV beam was also considered for comparison. METHODS Short term stability, dose linearity and dose rate dependence were evaluated. Dose per pulse dependence was investigated in the range 0.2-2.2mGy/pulse. MicroDiamond profiles and output factors (OFs) were compared to those obtained with other detectors for field sizes ranging from 40×40cm2 to 0.6×0.6cm2. In small fields, volume averaging effects were evaluated and the relevant correction factors were applied for each detector. RESULTS MicroDiamond short term stability, dose linearity and dependence on monitor unit rate were less than 0.8% for all energies. Response variations with dose per pulse were found within 1.8%. MicroDiamond output factors (OF) values differed from those measured with the reference ion-chamber for less than 1% up to 40×40cm2 fields where silicon diodes overestimate the dose of ≈3%. For small fields (<3×3cm2) microDiamond and the unshielded silicon diode were in good agreement. CONCLUSIONS MicroDiamond showed optimal characteristics for relative dosimetry even under high dose rate beams. The effects due to dose per pulse dependence up to 2.2mGy/pulse are negligible. Compared to other detectors, microDiamond provides accurate OF measurements in the whole range of field sizes. For fields <1cm correction factors accounting for fluence perturbation and volume averaging could be required.
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Affiliation(s)
- Giacomo Reggiori
- Physics Service of Radiation Oncology Dept., Humanitas Clinical and Research Hospital, Milan-Rozzano, Italy.
| | - Antonella Stravato
- Physics Service of Radiation Oncology Dept., Humanitas Clinical and Research Hospital, Milan-Rozzano, Italy
| | - Maria Pimpinella
- Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti, ENEA-INMRI C R Casaccia, Roma, Italy
| | - Francesca Lobefalo
- Physics Service of Radiation Oncology Dept., Humanitas Clinical and Research Hospital, Milan-Rozzano, Italy
| | - Vanessa De Coste
- Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti, ENEA-INMRI C R Casaccia, Roma, Italy
| | - Antonella Fogliata
- Physics Service of Radiation Oncology Dept., Humanitas Clinical and Research Hospital, Milan-Rozzano, Italy
| | - Pietro Mancosu
- Physics Service of Radiation Oncology Dept., Humanitas Clinical and Research Hospital, Milan-Rozzano, Italy
| | - Fiorenza De Rose
- Radiotherapy and Radiosurgery Department, Humanitas Clinical and Research Hospital, Milan-Rozzano, Italy
| | - Valentina Palumbo
- Physics Service of Radiation Oncology Dept., Humanitas Clinical and Research Hospital, Milan-Rozzano, Italy
| | - Marta Scorsetti
- Radiotherapy and Radiosurgery Department, Humanitas Clinical and Research Hospital, Milan-Rozzano, Italy; Department of Biomedical Sciences, Humanitas University, Rozzano, Milano, Italy
| | - Stefano Tomatis
- Physics Service of Radiation Oncology Dept., Humanitas Clinical and Research Hospital, Milan-Rozzano, Italy
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Puxeu-Vaqué J, Duch MA, Nailon WH, Cruz Lizuain M, Ginjaume M. Field correction factors for a PTW-31016 Pinpoint ionization chamber for both flattened and unflattened beams. Study of the main sources of uncertainties. Med Phys 2017; 44:1930-1938. [DOI: 10.1002/mp.12189] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2016] [Revised: 02/20/2017] [Accepted: 02/23/2017] [Indexed: 11/07/2022] Open
Affiliation(s)
- Josep Puxeu-Vaqué
- Servei de Física Mèdica i Protecció radiològica; Institut Català d'Oncologia (ICO); L'Hospitalet de Llobregat; Barcelona Spain
- Department of Oncology Physics; Edinburgh Cancer Centre; Western General Hospital; Edinburgh Scotland
| | - Maria A. Duch
- Institut de Tècniques Energètiques (INTE); Universitat Politècnica de Catalunya; Barcelona Spain
| | - William H. Nailon
- Department of Oncology Physics; Edinburgh Cancer Centre; Western General Hospital; Edinburgh Scotland
| | - M. Cruz Lizuain
- Servei de Física Mèdica i Protecció radiològica; Institut Català d'Oncologia (ICO); L'Hospitalet de Llobregat; Barcelona Spain
| | - Mercè Ginjaume
- Institut de Tècniques Energètiques (INTE); Universitat Politècnica de Catalunya; Barcelona Spain
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Yarahmadi M, Wegener S, Sauer OA. Energy and field size dependence of a silicon diode designed for small-field dosimetry. Med Phys 2017; 44:1958-1964. [DOI: 10.1002/mp.12195] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 02/17/2017] [Accepted: 02/28/2017] [Indexed: 11/10/2022] Open
Affiliation(s)
- Mehran Yarahmadi
- Department of Medical Physics; Faculty of Medicine; Kurdistan University of Medical Sciences; Sanandaj Iran
| | - Sonja Wegener
- Department of Radiation Oncology; University of Würzburg; Josef-Schneider-Strasse 11 97080 Würzburg Germany
| | - Otto A. Sauer
- Department of Radiation Oncology; University of Würzburg; Josef-Schneider-Strasse 11 97080 Würzburg Germany
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12
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Wegener S, Sauer OA. Separation of scatter from small MV beams and its effect on detector response. Med Phys 2017; 44:1139-1148. [PMID: 28063164 DOI: 10.1002/mp.12091] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 12/20/2016] [Accepted: 01/01/2017] [Indexed: 11/09/2022] Open
Abstract
PURPOSE Separating the scatter from the primary component of a MV beam to study detector response separately in each case for a better understanding of the role of different effects influencing the response in nonstandard fields. METHODS Detector response in three different experimental setups was investigated for a variety of different types (diamond, shielded and unshielded diodes, ionization chamber and film): (a). Detectors positioned in water under a thin steel pole blocking the central part of the beam, yielding only the response to the scatter part of the beam. (b). Detectors positioned in air under a PMMA cap to approximate the contribution of the primary beam without scatter. (c). Detectors positioned in water in the standard open field configuration to obtain a superposition of both. RESULTS Detector differences became more clearly observable when the primary beam was blocked and detector behavior heavily depended on the construction type. It was possible to calculate the response in the open fields from the values measured in the blocked configuration with 1% accuracy for all studied field sizes between 0.8 and 10 cm and for all detectors. CONCLUSIONS The limitations of clinically used detectors in nonstandard situations were illustrated in the extreme situation of just scattered radiation reaching the detector. By experimentally separating scatter from the primary beam, the roles of different effects on the detector response were observed.
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Affiliation(s)
- Sonja Wegener
- Department of Radiation Oncology, University of Würzburg, 97080, Würzburg, Germany
| | - Otto A Sauer
- Department of Radiation Oncology, University of Würzburg, 97080, Würzburg, Germany
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13
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Benmakhlouf H, Andreo P. Spectral distribution of particle fluence in small field detectors and its implication on small field dosimetry. Med Phys 2017; 44:713-724. [DOI: 10.1002/mp.12042] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2016] [Revised: 11/14/2016] [Accepted: 11/27/2016] [Indexed: 11/07/2022] Open
Affiliation(s)
- Hamza Benmakhlouf
- Department of Medical Radiation Physics and Nuclear Medicine; Karolinska University Hospital; SE-17176 Stockholm Sweden
| | - Pedro Andreo
- Department of Medical Radiation Physics and Nuclear Medicine; Karolinska University Hospital; SE-17176 Stockholm Sweden
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14
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Godson HF, Ravikumar M, Sathiyan S, Ganesh KM, Ponmalar YR, Varatharaj C. Analysis of small field percent depth dose and profiles: Comparison of measurements with various detectors and effects of detector orientation with different jaw settings. J Med Phys 2016; 41:12-20. [PMID: 27051165 PMCID: PMC4795411 DOI: 10.4103/0971-6203.177284] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
The advent of modern technologies in radiotherapy poses an increased challenge in the determination of dosimetric parameters of small fields that exhibit a high degree of uncertainty. Percent depth dose and beam profiles were acquired using different detectors in two different orientations. The parameters such as relative surface dose (DS), depth of dose maximum (Dmax), percentage dose at 10 cm (D10), penumbral width, flatness, and symmetry were evaluated with different detectors. The dosimetric data were acquired for fields defined by jaws alone, multileaf collimator (MLC) alone, and by MLC while the jaws were positioned at 0, 0.25, 0.5, and 1.0 cm away from MLC leaf-end using a Varian linear accelerator with 6 MV photon beam. The accuracy in the measurement of dosimetric parameters with various detectors for three different field definitions was evaluated. The relative DS(38.1%) with photon field diode in parallel orientation was higher than electron field diode (EFD) (27.9%) values for 1 cm ×1 cm field. An overestimation of 5.7% and 8.6% in D10 depth were observed for 1 cm ×1 cm field with RK ion chamber in parallel and perpendicular orientation, respectively, for the fields defined by MLC while jaw positioned at the edge of the field when compared to EFD values in parallel orientation. For this field definition, the in-plane penumbral widths obtained with ion chamber in parallel and perpendicular orientation were 3.9 mm, 5.6 mm for 1 cm ×1 cm field, respectively. Among all detectors used in the study, the unshielded diodes were found to be an appropriate choice of detector for the measurement of beam parameters in small fields.
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Affiliation(s)
- Henry Finlay Godson
- Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bengaluru, Karnataka, India; Department of Radiotherapy, Christian Medical College, Vellore, Tamil Nadu, India
| | - M Ravikumar
- Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bengaluru, Karnataka, India
| | - S Sathiyan
- Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bengaluru, Karnataka, India
| | - K M Ganesh
- Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bengaluru, Karnataka, India
| | - Y Retna Ponmalar
- Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bengaluru, Karnataka, India; Department of Radiotherapy, Christian Medical College, Vellore, Tamil Nadu, India
| | - C Varatharaj
- Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bengaluru, Karnataka, India
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15
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Reynolds M, Fallone BG, Rathee S. Dose response of selected solid state detectors in applied homogeneous transverse and longitudinal magnetic fields. Med Phys 2015; 41:092103. [PMID: 25186403 DOI: 10.1118/1.4893276] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE MR-Linac devices under development worldwide will require standard calibration, commissioning, and quality assurance. Solid state radiation detectors are often used for dose profiles and percent depth dose measurements. The dose response of selected solid state detectors is therefore evaluated in varying transverse and longitudinal magnetic fields for this purpose. METHODS The Monte Carlo code PENELOPE was used to model irradiation of a PTW 60003 diamond detector and IBA PFD diode detector in the presence of a magnetic field. The field itself was varied in strength, and oriented both transversely and longitudinally with respect to the incident photon beam. The long axis of the detectors was oriented either parallel or perpendicular to the photon beam. The dose to the active volume of each detector in air was scored, and its ratio to dose with zero magnetic field strength was determined as the "dose response" in magnetic field. Measurements at low fields for both detectors in transverse magnetic fields were taken to evaluate the accuracy of the simulations. Additional simulations were performed in a water phantom to obtain few representative points for beam profile and percent depth dose measurements. RESULTS Simulations show significant dose response as a function of magnetic field in transverse field geometries. This response can be near 20% at 1.5 T, and it is highly dependent on the detectors' relative orientation to the magnetic field, the energy of the photon beam, and detector composition. Measurements at low transverse magnetic fields verify the simulations for both detectors in their relative orientations to radiation beam. Longitudinal magnetic fields, in contrast, show little dose response, rising slowly with magnetic field, and reaching 0.5%-1% at 1.5 T regardless of detector orientation. Water tank and in air simulation results were the same within simulation uncertainty where lateral electronic equilibrium is present and expectedly differed at the beam edge in transverse field orientations only. Due to the difference in design, the two detectors behaved differently. CONCLUSIONS When transverse magnetic fields are present, great care must be taken when using diamond or diode detectors. Dose response varies with relative detector orientation, magnetic field strength, and between detectors. This response can be considerable (∼20% for both detectors). Both detectors in longitudinal fields exhibit little to no dose response as a function of magnetic field. Water tank simulations seem to suggest that the diode detector is better suited to general beam commissioning, and each detector must be investigated separately.
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Affiliation(s)
- M Reynolds
- Department of Oncology, Medical Physics Division, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2, Canada
| | - B G Fallone
- Department of Medical Physics, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2, Canada and Departments of Oncology and Physics, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2, Canada
| | - S Rathee
- Department of Medical Physics, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2, Canada and Department of Oncology, Medical Physics Division, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2, Canada
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Chalkley A, Heyes G. Evaluation of a synthetic single-crystal diamond detector for relative dosimetry measurements on a CyberKnife. Br J Radiol 2014; 87:20130768. [PMID: 24588671 PMCID: PMC4064610 DOI: 10.1259/bjr.20130768] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Revised: 01/07/2014] [Accepted: 01/08/2014] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVE To evaluate a new commercial PTW-60019 microDiamond (PTW, Freiburg, Germany) synthetic single-crystal diamond detector for relative dosimetry measurements on a clinical CyberKnife™ VSI (Accuray Inc., Sunnyvale, CA) system. METHODS Relative output factors (ROFs) were measured for collimator diameters from 5 to 60 mm, and compared with diode [PTW-60017, PTW-60018 and IBA Dosimetry (Schwarzenbruck, Germany) SFD] and ionization chamber (PTW-31014 PinPoint and PTW-31010 Semiflex) measurements. Beam profiles were measured at a range of depths, and collimator sizes, with the detector stem oriented both parallel and perpendicular to the central axis (CAX). Percentage depth-dose (PDD) curves were obtained for the 60-mm collimator and compared with natural Diamond Detector (PTW-60003) and ionization chamber curves to evaluate energy dependence. RESULTS Penumbral broadening was noted on profile measurements made with the microDiamond oriented with the stem parallel to the CAX, in comparison with diodes. Oriented perpendicular to the CAX, the profile penumbra was sharper, but stem effects could not be ruled out. The PDD measurements were within 0.5% of ionization chamber measurements, indicating insignificant dose-rate dependence. The ROF for the microDiamond fell between diode and ionization chamber results. Published Monte Carlo-derived CyberKnife-specific factors were applied to the PTW-60017, PTW-60018 and PTW-31014 ROFs, and the microDiamond factors agreed within 2.0% of the mean of these. CONCLUSION Over a range of small field relative dosimetry measurements, the microDiamond detector shows excellent spatial resolution, dose-rate independence and water equivalence. ADVANCES IN KNOWLEDGE The microDiamond is a suitable tool for commissioning stereotactic systems.
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Affiliation(s)
- A Chalkley
- Radiotherapy Physics and Cancer Centre, Hall-Edwards Radiotherapy Research Group, Queen Elizabeth Hospital Birmingham, Edgbaston, Birmingham, UK
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Marsolat F, Tromson D, Tranchant N, Pomorski M, Le Roy M, Donois M, Moignau F, Ostrowsky A, De Carlan L, Bassinet C, Huet C, Derreumaux S, Chea M, Cristina K, Boisserie G, Bergonzo P. A new single crystal diamond dosimeter for small beam: comparison with different commercial active detectors. Phys Med Biol 2013; 58:7647-60. [DOI: 10.1088/0031-9155/58/21/7647] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Tyler M, Liu PZY, Chan KW, Ralston A, McKenzie DR, Downes S, Suchowerska N. Characterization of small-field stereotactic radiosurgery beams with modern detectors. Phys Med Biol 2013; 58:7595-608. [DOI: 10.1088/0031-9155/58/21/7595] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Cranmer-Sargison G, Weston S, Evans JA, Sidhu NP, Thwaites DI. Monte Carlo modelling of diode detectors for small field MV photon dosimetry: detector model simplification and the sensitivity of correction factors to source parameterization. Phys Med Biol 2012; 57:5141-53. [DOI: 10.1088/0031-9155/57/16/5141] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Scott AJD, Kumar S, Nahum AE, Fenwick JD. Characterizing the influence of detector density on dosimeter response in non-equilibrium small photon fields. Phys Med Biol 2012; 57:4461-76. [DOI: 10.1088/0031-9155/57/14/4461] [Citation(s) in RCA: 134] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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