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Bharathan RK, Thasni I, Musthafa M, Cheruliyil Ayyappan S, Ajaykumar S, Jose L. Feasibility study of shielded diode detector for small field dosimetry. RADIATION PROTECTION DOSIMETRY 2024; 200:1197-1201. [PMID: 39016512 DOI: 10.1093/rpd/ncae051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 02/11/2024] [Accepted: 02/14/2024] [Indexed: 07/18/2024]
Abstract
Improved imaging techniques and modern radiotherapy treatment delivery in the treatment field are reduced to the precise size of the tumor, which necessitates the need for small-field dosimetry. Dosimetry in small-field dosimetry is challenging because most of the available code of practice for dosimetry is based on the cavity theory concept. Some small-sized detectors show good spatial resolution and sensitivity. Of the available small detectors, the diamond detector's performance is remarkably good. Most of the centers for radiotherapy lack diamond detectors. In this situation, if a diode detector is available, we can use it for small-field dosimetry by applying the Daisy Chaining method correction methods. In this study, the diode detector's response is not over-responding because of the defective diode. So this diode cannot be used for further measurements, and we have to regularly check the performance of the diode before using it for measurements.
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Affiliation(s)
- Resmi K Bharathan
- Department of Radiation Oncology, Malabar Cancer Centre, Thalassery, Kannur, Kerala, India
| | - Irfana Thasni
- Department of Physics, Calicut University, Thenjipalam, Malappuram, Kerala, India
| | - Musthafa Musthafa
- Department of Physics, Calicut University, Thenjipalam, Malappuram, Kerala, India
| | | | - Silpa Ajaykumar
- Department of Radiation Oncology, Malabar Cancer Centre, Thalassery, Kannur, Kerala, India
| | - Lisha Jose
- Department of Radiation Oncology, Malabar Cancer Centre, Thalassery, Kannur, Kerala, India
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Muir B, Davis S, Dhanesar S, Hillman Y, Iakovenko V, Kim GGY, Alves VGL, Lei Y, Lowenstein J, Renaud J, Sarfehnia A, Siebers J, Tantôt L. AAPM WGTG51 Report 385: Addendum to the AAPM's TG-51 protocol for clinical reference dosimetry of high-energy electron beams. Med Phys 2024. [PMID: 38980220 DOI: 10.1002/mp.17277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 03/29/2024] [Accepted: 06/14/2024] [Indexed: 07/10/2024] Open
Abstract
An Addendum to the AAPM's TG-51 protocol for the determination of absorbed dose to water is presented for electron beams with energies between 4 MeV and 22 MeV (1.70 cm ≤ R 50 ≤ 8.70 cm $1.70\nobreakspace {\rm cm} \le R_{\text{50}} \le 8.70\nobreakspace {\rm cm}$ ). This updated formalism allows simplified calibration procedures, including the use of calibrated cylindrical ionization chambers in all electron beams without the use of a gradient correction. Newk Q $k_{Q}$ data are provided for electron beams based on Monte Carlo simulations. Implementation guidance is provided. Components of the uncertainty budget in determining absorbed dose to water at the reference depth are discussed. Specifications for a reference-class chamber in electron beams include chamber stability, settling, ion recombination behavior, and polarity dependence. Progress in electron beam reference dosimetry is reviewed. Although this report introduces some major changes (e.g., gradient corrections are implicitly included in the electron beam quality conversion factors), they serve to simplify the calibration procedure. Results for absorbed dose per linac monitor unit are expected to be up to approximately 2 % higher using this Addendum compared to using the original TG-51 protocol.
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Affiliation(s)
- Bryan Muir
- Metrology Research Centre, National Research Council of Canada, Ottawa, Ontario, Canada
| | - Stephen Davis
- Department of Radiation Oncology, Miami Cancer Institute, Miami, Florida, USA
| | - Sandeep Dhanesar
- Department of Radiation Oncology, Houston Methodist Hospital, Houston, Texa, USA
| | - Yair Hillman
- Department of Radiation Oncology, Sharett Institute of Oncology, Hadassah Medical Center, Hebrew University of Jerusalem, Jerusalem, Israel
| | | | - Grace Gwe-Ya Kim
- Department of Radiation Medicine and Applied Sciences, UC San Diego School of Medicine, San Diego, California, USA
| | | | - Yu Lei
- Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, Nebraska, USA
| | - Jessica Lowenstein
- Department of Radiation Physics, UT M.D. Anderson Cancer Center, Houston, Texa, USA
| | - James Renaud
- Metrology Research Centre, National Research Council of Canada, Ottawa, Ontario, Canada
| | - Arman Sarfehnia
- Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada
- Department of Medical Physics, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada
| | - Jeffrey Siebers
- Department of Radiation Oncology, University of Virginia, Charlottesville, Virginia, USA
| | - Laurent Tantôt
- Département de radio-oncologie, CIUSSS de l'Est-de-l'Île-de-Montréal - Hôpital Maisonneuve-Rosemont, Montreal, Quebec, Canada
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Kandasamy K, Samuel EJJ. Dosimetric Evaluation of Semiflex Three-dimensional Chamber under Unflatten Beam in Comparison among Different Detectors. J Med Phys 2024; 49:84-94. [PMID: 38828067 PMCID: PMC11141746 DOI: 10.4103/jmp.jmp_115_23] [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: 09/02/2023] [Revised: 02/22/2024] [Accepted: 02/22/2024] [Indexed: 06/05/2024] Open
Abstract
Purpose The goal of this study is to investigate the dosimetric properties of a Semiflex three-dimensional (3D) chamber in an unflatten beam and compare its data from a small to a large field flattening filter-free (FFF) beam with different radiation detectors. Methods The sensitivity, linearity, reproducibility, dose rate dependency, and energy dependence of a Semiflex 3D detector in flattening filter and filter-free beam were fully investigated. The minimum radiation observed field widths for all detectors were calculated using lateral electronic charged particle equilibrium to investigate dosimetric characteristics such as percentage depth doses (PDDs), profiles, and output factors (OPFs) for Semiflex 3D detector under 6FFF Beam. The Semiflex 3D measured data were compared to that of other detectors employed in this study. Results The ion chamber has a dosage linearity deviation of +1.2% for <10 MU, a dose-rate dependency deviation of +0.5%, and significantly poorer sensitivity due to its small volume. There is a difference in field sizes between manufacturer specs and derived field sizes. The measured PDD, profiles, and OPFs of the Semiflex 3D chamber were within 1% of each other for all square field sizes set under linac for the 6FFF beam. Conclusion It was discovered to be an appropriate detector for relative dose measurements for 6 FFF beams with higher dose rates for field sizes more than or equal to 3 cm × 3 cm.
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Affiliation(s)
- Kanakavel Kandasamy
- Department of Physics, School of Advanced Sciences, VIT University, Vellore, Tamil Nadu, India
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Mateus D, Greco C, Peralta L. Field output correction factors of small static field for IBA razor nanochamber. Biomed Phys Eng Express 2023; 10:015004. [PMID: 37939486 DOI: 10.1088/2057-1976/ad0ae0] [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: 07/26/2023] [Accepted: 11/08/2023] [Indexed: 11/10/2023]
Abstract
Purpose.The goal of this work is present results of field output factors (OF) using an IBA CC003 (Razor NanoChamber) and compare these results with PTW 60019 (MicroDiamond) and IBA Razor Diode. The experimental results for IBA CC003 were also compared with Monte Carlo (MC) Simulation, using Penelope and Ulysses programs. In addition, field output correction factors (kQclin,Qmsrfclin,fmsr) for IBA CC003 were derived with three different methods: (1) using PTW 60019 and IBA Razor as reference detectors; (2) comparison between MC and experimental measurements; and (3) using only MC.Material and Methods. The beam collimation included in this study were (1) square field size between 10 × 10 and 0.5 × 0.5 cm2defined by the MLC and jaws and (2) cones of different diameters. For IBA CC003 it was determined the polarity and ion collection efficiency correction factors in parallel and perpendicular orientation.Results.The results indicate (1) the variation of polarity effect with the field size is relevant for the determination of OF using IBA CC003, especially for parallel orientation; (2) there is no significant variation of the ion collection efficiency with the field size using IBA CC003 in parallel orientation; (3) OF differences between IBA CC003 and PTW 60019/IBA Razor, and experimental and MC results, increase with decreasing field size;ThekQclin,Qmsrfclin,fmsrresults indicate (1) using the first and second method,kQclin,Qmsrfclin,fmsrincrease with decreasing field size, which can be related with the influence of the volume effect and (2) using the third method,kQclin,Qmsrfclin,fmsrdecrease with decreasing field size, which can be explained by the perturbation effect.Conclusions. Our results demonstrate the need of applyingkQclin,Qmsrfclin,fmsrfor IBA CC003 forSclin≤1 cm, to compensate for volume averaging and perturbations effects.
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Affiliation(s)
- D Mateus
- Faculdade de Ciências da Universidade de Lisboa, Lisboa, Portugal
- Mercurius Health S.A, Lisboa, Portugal
- Fundação Champalimaud, Lisboa, Portugal
| | - C Greco
- Fundação Champalimaud, Lisboa, Portugal
| | - L Peralta
- Faculdade de Ciências da Universidade de Lisboa, Lisboa, Portugal
- Laboratório de Instrumentação e Física Experimental de Partículas, Lisboa, Portugal
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Rahman M, Kozelka J, Hildreth J, Schönfeld A, Sloop AM, Ashraf MR, Bruza P, Gladstone DJ, Pogue BW, Simon WE, Zhang R. Characterization of a diode dosimeter for UHDR FLASH radiotherapy. Med Phys 2023; 50:5875-5883. [PMID: 37249058 DOI: 10.1002/mp.16474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 04/17/2023] [Accepted: 04/18/2023] [Indexed: 05/31/2023] Open
Abstract
BACKGROUND Ultra-high dose rate (UHDR) FLASH beams typically deliver dose at rates of >40 Gy/sec. Characterization of these beams with respect to dose, mean dose rate, and dose per pulse requires dosimeters which exhibit high temporal resolution and fast readout capabilities. PURPOSE A diode EDGE Detector with a newly designed electrometer has been characterized for use in an UHDR electron beam and demonstrated appropriateness for UHDR FLASH radiotherapy dosimetry. METHODS Dose linearity, mean dose rate, and dose per pulse dependencies of the EDGE Detector were quantified and compared with dosimeters including a W1 scintillator detector, radiochromic film, and ionization chamber that were irradiated with a 10 MeV UHDR beam. The dose, dose rate, and dose per pulse were controlled via an in-house developed scintillation-based feedback mechanism, repetition rate of the linear accelerator, and source-to-surface distance, respectively. Depth-dose profiles and temporal profiles at individual pulse resolution were compared to the film and scintillation measurements, respectively. The radiation-induced change in response sensitivity was quantified via irradiation of ∼5kGy. RESULTS The EDGE Detector agreed with film measurements in the measured range with varying dose (up to 70 Gy), dose rate (nearly 200 Gy/s), and dose per pulse (up to 0.63 Gy/pulse) on average to within 2%, 5%, and 1%, respectively. The detector also agreed with W1 scintillation detector on average to within 2% for dose per pulse (up to 0.78 Gy/pulse). The EDGE Detector signal was proportional to ion chamber (IC) measured dose, and mean dose rate in the bremsstrahlung tail to within 0.4% and 0.2% respectively. The EDGE Detector measured percent depth dose (PDD) agreed with film to within 3% and per pulse output agreed with W1 scintillator to within -6% to +5%. The radiation-induced response decrease was 0.4% per kGy. CONCLUSIONS The EDGE Detector demonstrated dose linearity, mean dose rate independence, and dose per pulse independence for UHDR electron beams. It can quantify the beam spatially, and temporally at sub millisecond resolution. It's robustness and individual pulse detectability of treatment deliveries can potentially lead to its implementation for in vivo FLASH dosimetry, and dose monitoring.
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Affiliation(s)
- Mahbubur Rahman
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
- UT Southwestern Medical Center, Dallas, Texas, USA
| | | | | | | | - Austin M Sloop
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - M Ramish Ashraf
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
- Stanford University, Stanford, California, USA
| | - Petr Bruza
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - David J Gladstone
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
- Department of Medicine, Radiation Oncology, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire, USA
- Dartmouth Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire, USA
| | - Brian W Pogue
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
- Dartmouth Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire, USA
- Department of Surgery, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire, USA
- Department of Medical Physics, Wisconsin Institutes for Medical Research, University of Wisconsin, Madison, Wisconsin, USA
| | | | - Rongxiao Zhang
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
- Department of Medicine, Radiation Oncology, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire, USA
- Department of Radiation Medicine, Westchester Medical Center, New York Medical College,Valhalla, New York, USA
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Shields L, Nikandrovs M, Vintró LL, Clean BM. Energy-dependence investigation for a range of clinically used detectors from 70 kV to 6 MV. Med Phys 2023; 50:582-589. [PMID: 36004606 DOI: 10.1002/mp.15857] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 05/26/2022] [Accepted: 05/29/2022] [Indexed: 01/25/2023] Open
Abstract
PURPOSE Accurate measurement of out-of-field dose in radiotherapy directly impacts beam data modeling in treatment planning systems, verification of implanted electronic devices/lens/fetus dose, secondary cancer risk estimation, and organ-at-risk dose reporting. When performing out-of-field dosimetry, it is therefore imperative that the response of the detector has been well characterized. Due to the softening of the radiation beam out-of-field, many detectors will exhibit energy dependence. This study investigated the energy dependence of a range of clinical available detectors over typical energies experienced out-of-field. METHODS The response of detectors to photon beams from 70 kV to 6 MV was measured. The relative change in response from 6 MV down to 70 kV highlighted the expected deviation in the response of detectors that would typically be calibrated in-field for use out-of-field. RESULTS The Pinpoint detector displayed the most energy-independent response over the energy range investigated. The Micro-Lion detector was the only detector to show an under-response to all low-energy beams relative to 6 MV. The diode-type detectors showed the largest energy dependence. CONCLUSIONS When considering detectors for use in out-of-field dose measurements, it is important that the energy dependence is investigated over a low-energy range as out-of-field the energy spectra comprise a larger component of photons in the 50-100-keV range. This study highlights the variation in response of a range of clinically available detectors to low-energy radiation beams relative to 6 MV for out-of-field dosimetry. The Pinpoint detector was the most energy-independent detector with a response close to unity over the entire energy range investigated.
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Affiliation(s)
- Laura Shields
- Medical Physics Department, St. Luke's Radiation Oncology Network, Dublin, Ireland.,School of Physics, University College Dublin, Dublin, Ireland
| | - Mihails Nikandrovs
- Medical Physics Department, St. Luke's Radiation Oncology Network, Dublin, Ireland.,School of Physics, University College Dublin, Dublin, Ireland
| | | | - Brendan Mc Clean
- Medical Physics Department, St. Luke's Radiation Oncology Network, Dublin, Ireland.,School of Physics, University College Dublin, Dublin, Ireland
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Evaluation of calibration methods of Exradin W2 plastic scintillation detector for CyberKnife small-field dosimetry. RADIAT MEAS 2022. [DOI: 10.1016/j.radmeas.2022.106821] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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Pittomvils G, Bogaert E, Traneus E, Thysebaert P, De Wagter C. Measurement-based validation of a commercial Monte Carlo dose calculation algorithm for electron beams. Med Phys 2022; 49:4755-4767. [PMID: 35543491 DOI: 10.1002/mp.15685] [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: 07/09/2022] [Revised: 03/04/2022] [Accepted: 04/06/2022] [Indexed: 11/11/2022] Open
Abstract
PURPOSE This work presents the clinical validation of RayStation's electron Monte Carlo Code by use of diodes and plane parallel radiation detectors in homogenous and heterogeneous tissues. Results are evaluated against international accepted criteria. METHODS The Monte Carlo based electron beam dose calculation code was validated using diodes, air filled and liquid filled parallel radiation detectors on a Elekta Linac with beam energies of 4,6,8,10 and 12 MeV. Treatment setups with varying SSD's, different applicators, various cut-outs and oblique beam incidences were addressed, together with dose prediction behind lung, air and bone equivalent inserts. According to NCS (Netherlands Commission of Radiation Dosimetry) report 15 for non-standard treatment setups a dose agreement of 3 % in the δ1 region (high dose region around Zref ), a distance to agreement of 3 mm or a dose agreement of 10 % in the δ2 region (regions with high dose gradients) and 4 % in the δ4 region (photon tail/low dose region) were applied. During validation, clinical routine settings of 2×2×2 mm3 dose voxels and a statistically dose uncertainty of 0.6% (250 000 histories/cm2 ) were used. RESULTS RayStation's electron Monte Carlo code dose prediction was able to achieve the tolerances of NCS report 15. Output predictions as function of the SDD improve with energy and applicator size. Cut-out data revealed no field size neither energy dependence on the accuracy of the dose prediction. Excellent agreement for the oblique incidence data was achieved and maximum one voxel difference was obtained for the distance to agreement behind heterogeneous inserts. CONCLUSIONS The accuracy of RayStation's Monte Carlo based electron beam dose prediction for Elekta accelerators is confirmed for clinical treatment planning that is not only performed within an acceptable timeframe in terms of number of histories but also addresses for homogenous and heterogeneous media. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Geert Pittomvils
- Department of Radiotherapy, Ghent University Hospital, Corneel Heymanslaan 10, Gent, 9000, Belgium
| | - Evelien Bogaert
- Department of Radiotherapy, Ghent University Hospital, Corneel Heymanslaan 10, Gent, 9000, Belgium
| | - Erik Traneus
- RaySearch Laboratories AB, Eugeniavägen 8, Stockholm, 113 68, Sweden
| | - Pieternel Thysebaert
- Odisee Hogeschool-Universiteit Brussel, Bleekerijstraat 23-29, Brussel, 1000, Belgium
| | - Carlos De Wagter
- Department of Human Structure and Repair, Ghent University, Corneel Heymanslaan 10, Gent, 9000
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Duchaine J, Markel D, Bouchard H. Efficient dose-rate correction of silicon diode relative dose measurements. Med Phys 2022; 49:4056-4070. [PMID: 35315526 DOI: 10.1002/mp.15628] [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: 03/16/2021] [Revised: 12/21/2021] [Accepted: 03/17/2022] [Indexed: 11/12/2022] Open
Abstract
PURPOSE Silicon diodes are often the detector of choice for relative dose measurements, particularly in the context of radiotherapy involving small photon beams. However, a major drawback lies in their dose-rate dependency. Although ionization chambers are often too large for small field output factor measurements, they are valuable instruments to provide reliable percent-depth dose curves in reference beams. The aim of this work is to propose a practical and accurate method for the characterization of silicon diode dose-rate dependence correction factors using ionization chamber measurements as a reference. METHODS The robustness of ionization chambers for percent-depth dose measurements is used to quantify the dose-rate dependency of a diode detector. A mathematical formalism, which exploits the error induced in percent-depth ionization curves for diodes by their dose-rate dependency, is developed to derive a dose-rate correction factor applicable to diode relative measurements. The method is based on the definition of the recombination correction factor given in the addendum to TG 51 and is applied to experimental measurements performed on a CyberKnife M6 radiotherapy unit using a PTW 60012 diode detector. A measurement-based validation is provided by comparing corrected percent-depth ionization curves to measurements performed with a PTW 60019 diamond detector which does not exhibit dose-rate dependence. RESULTS Results of dose-rate correction factors for percent-depth ionization curves, off-axis ratios, tissue-phantom ratios and small field output factors are coherent with the expected behavior of silicon diode detectors. For all considered setups and field sizes, the maximum correction and the maximum impact of the uncertainties induced by the correction are obtained for off-axis ratios for the 60 mm collimator, with a correction of 2.5% and an uncertainty of 0.34%. For output factors, corrections range from 0.33% to 0.82% for all field sizes considered, and increase with the reduction of the field size. Comparison of percent-depth ionization curves corrected for dose-rate and for in-depth beam quality variations illustrate excellent agreement with measurements performed using the diamond detector. CONCLUSIONS The proposed method allows the efficient and precise correction of the dose-rate dependence of silicon diode detectors in the context of clinical relative dosimetry. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Jasmine Duchaine
- Département de physique, Université de Montréal, Campus MIL, 1375 Av. Thérèse Lavoie-Roux, Montréal, QC, H2V 0B3, Canada.,Centre de recherche du Centre hospitalier de l'Université de Montréal, 900 rue Saint-Denis, Montréal, QC, H2X 0A9, Canada
| | - Daniel Markel
- Département de radio-oncologie, Centre hospitalier de l'Université de Montréal, 1051 Rue Sanguinet, Montréal, QC, H2X 3E4, Canada
| | - Hugo Bouchard
- Département de physique, Université de Montréal, Campus MIL, 1375 Av. Thérèse Lavoie-Roux, Montréal, QC, H2V 0B3, Canada.,Centre de recherche du Centre hospitalier de l'Université de Montréal, 900 rue Saint-Denis, Montréal, QC, H2X 0A9, Canada.,Département de radio-oncologie, Centre hospitalier de l'Université de Montréal, 1051 Rue Sanguinet, Montréal, QC, H2X 3E4, Canada
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Daniel J, Yousif Y, Zifodya J, Hill R. An evaluation of solid state detectors for the relative dosimetry of Kilovoltage x-ray beams. Med Phys 2022; 49:4082-4091. [PMID: 35179232 DOI: 10.1002/mp.15543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 02/04/2022] [Accepted: 02/07/2022] [Indexed: 11/09/2022] Open
Abstract
INTRODUCTION Kilovoltage (kV) x-ray beams are an essential modality in radiotherapy. Solid state detectors are widely available in radiotherapy departments but their use for kV dosimetry has been limited to date. This study aimed to evaluate the dosimetric performance of a range of solid state detectors for kV dosimetry. METHOD Percentage depth doses (PDDs) and Relative Output Factors (ROFs) were measured on an XStrahl 300 unit (XStrahl-Ltd., UK) using 60, 100, 150 and 300 kVp x-ray beams. The fields were defined by circular applicators with field sizes of 2, 5, 8 and 10 cm diameter and square applicators of field sizes 10×10 and 20×20 cm2 . The following PTW dosimeters were used for measurements: Advanced Markus, PinPoint 3D and Semiflex ionization chambers; Photon, Electron and SRS diodes plus the microDiamond detector. All PDDs were normalized at 5 mm depth and ROFs were measured at 3 mm depth to avoid collisions with the end of the applicators. ROFs measured using chambers were corrected for polarity and ion-recombination effects. RESULTS AND DISCUSSION PDD measurements for 60,100 and 150 kVp beam exhibited good agreement between all diodes and the ionization chambers over the entire range of depths except in the first few millimeters near the surface. However, for the 300 kVp, all diode detectors exhibited an over-responding behaviour compared to reference depth dose data measured with the Advanced Markus chamber. Relative output factors with the diodes were higher than the Advanced Markus chamber at low energy, and the magnitude of these differences is inversely proportional to the field sizes. The PTW P diode showed the highest variation of up to 15% in the output factor compared to the Advanced Markus chamber. CONCLUSION This study evaluated the dosimetric performance of a range of solid state detectors in kV relative dosimetry. This study showed that diode detectors are a suitable replacement for ionization chambers for the PDD measurement of low energy kV beams (60-150 kVp) except for the PDD of 60 kVp with the smaller field sizes. However, an over-responding behaviour of diode detectors at 300 kVp beams shows that diode detectors are not suitable for the PDD measurement of high energy kV beams. Generally, all solid state detectors over responded to ROF measurements, indicating that it is not suitable for ROF measurements. In general, both shielded and unshielded diodes produced a similar dosimetric response, which demonstrates that the energy dependence of solid state detectors should be considered before they are used for any kV relative dosimetric measurements. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- John Daniel
- North West Cancer Centre, Tamworth, NSW, Australia
| | | | | | - Robin Hill
- Department of Radiation Oncology, Chris O'Brien Lifehouse, Sydney, Australia.,Institute of Medical Physics, School of Physics, University of Sydney, Australia.,Biomedical Innovation, Chris O'Brien Lifehouse, Missenden Rd, Camperdown, Sydney, Australia
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Dosimetric Characterization of Small Radiotherapy Electron Beams Collimated by Circular Applicators with the New Microsilicon Detector. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12020600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
High-energy small electron beams, generated by linear accelerators, are used for radiotherapy of localized superficial tumours. The aim of the present study is to assess the dosimetric performance under small radiation therapy electron beams of the novel PTW microSilicon detector compared to other available dosimeters. Relative dose measurements of circular fields with 20, 30, 40, and 50 mm aperture diameters were performed for electron beams generated by an Elekta Synergy linac, with energy between 4 and 12 MeV. Percentage depth dose, transverse profiles, and output factors, normalized to the 10 × 10 cm2 reference field, were measured. All dosimetric data were collected in a PTW MP3 motorized water phantom, at SSD of 100 cm, by using the novel PTW microSilicon detector. The PTW diode E and the PTW microDiamond were also used in all beam apertures for benchmarking. Data for the biggest field size were also measured by the PTW Advanced Markus ionization chamber. Measurements performed by the microSilicon are in good agreement with the reference values for all the tubular applicators and beam energies within the stated uncertainties. This confirms the reliability of the microSilicon detector for relative dosimetry of small radiation therapy electron beams collimated by circular applicators.
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12
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Hupman MA, Hill IG, Syme A. Measuring small field profiles and output factors with a stemless plastic scintillator array. Med Phys 2021; 49:624-631. [PMID: 34792193 DOI: 10.1002/mp.15357] [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: 04/21/2021] [Revised: 09/09/2021] [Accepted: 10/30/2021] [Indexed: 11/11/2022] Open
Abstract
PURPOSE To fabricate a 1D stemless plastic scintillation detector (SPSD) array using organic photodiodes and to use the detector to measure small field profiles and output factors. METHODS An organic photodiode array was fabricated by spin coating a mixture of P3HT and PCBM organic semiconductors onto an ITO-coated glass substrate and depositing aluminum top contacts. Four bulk scintillators of various dimensions were placed on top of the photodiode array. A fifth scintillator was used that had been segmented by laser etching and the septa filled with black paint. Each detector array was first calibrated using a reference field of 95 cm SSD, 5 cm depth, and 10 × 10 cm2 field size for a 6 MV photon beam. After calibration, profiles were measured for three small field sizes: 0.5 × 0.5 cm2 , 1 × 1 cm2 , and 2 × 2 cm2 . Using the central pixel of the array, output factors were measured for field sizes of 0.5 × 0.5 cm2 to 25 × 25 cm2 . Small field profiles were compared to film measurements and output factors compared to ion chamber measurements. RESULTS The segmented scintillator measured profiles that were in good agreement with film for all three field sizes. Output factors agreed to within 1.2% of ion chamber over the field size range of 1 × 1 cm2 to 25 × 25 cm2 . At 0.5 × 0.5 cm2 the segmented scintillator underestimated the output factor compared to film and a microDiamond detector. Bulk scintillators failed to produce a good agreement with film for measured profiles and deviations from ion chamber for output factors were apparent at field sizes below 5 × 5 cm2 . In comparison to a bulk scintillator of dimensions 5 × 5 × 0.5 cm3 the etched scintillator saw a reduction of 5.1, 7.1, and 10.5 times the signal for field sizes of 0.5 × 0.5 cm2 , 1 × 1 cm2 , and 2 × 2 cm2 , respectively. The reduction of signal comes from reduced cross-talk that was present in all of the bulk scintillator geometries to various degrees. CONCLUSION A 1D SPSD array was demonstrated with various scintillator designs. The etched scintillator array demonstrated excellent small field profile measurements when compared to film and output factors (down to 1 × 1 cm2 field size) when compared to micro ion chamber and diamond detector measurements.
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Affiliation(s)
- Michael A Hupman
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Ian G Hill
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Alasdair Syme
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada.,Department of Radiation Oncology, Dalhousie University, Halifax, Nova Scotia, Canada.,Department of Medical Physics, Nova Scotia Health Authority, QEII Health Science Centre, Halifax, Nova Scotia, Canada
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Akino Y, Das IJ, Fujiwara M, Kaneko A, Masutani T, Mizuno H, Isohashi F, Suzuki O, Seo Y, Tamari K, Ogawa K. Characteristics of microSilicon diode detector for electron beam dosimetry. JOURNAL OF RADIATION RESEARCH 2021:rrab085. [PMID: 34559877 DOI: 10.1093/jrr/rrab085] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 05/31/2021] [Indexed: 06/13/2023]
Abstract
A microSilicon™ (PTW type 60023), a new unshielded diode detector succeeding Diode E (model 60017, PTW), was characterized for electron beam dosimetry and compared with other detectors. Electron beams generated from a TrueBeam linear accelerator were measured using the microSilicon, Diode E, and microDiamond synthetic single-crystal diamond detector. Positional accuracy of microSilicon was measured by data collected in air and water. The percent depth dose (PDD), off-center ratio (OCR), dose-response linearity, dose rate dependence, and cone factors were evaluated. The PDDs were compared with data measured using a PPC40 plane-parallel ionization chamber. The maximum variations of depth of 50% and 90% of the maximum dose, and practical depth among all detectors and energies were 0.9 mm. The maximum variations of the bremsstrahlung dose among all detectors and energies were within 0.3%. OCR showed good agreement within 1% for the flat and tail regions. The microSilicon detector showed a penumbra width similar to microDiamond, whereas Diode E showed the steepest penumbra shape. All detectors showed good dose-response linearity and stability against the dose rate; only Diode E demonstrated logarithmic dose rate dependency. The cone factor measured with microSilicon was within ±1% for all energies and cone sizes. We demonstrated that the characteristics of microSilicon is suitable for electron beam dosimetry. The microSilicon detector can be a good alternative for electron beam dosimetry in terms of providing an appropriate PDD curve without corrections, high spatial resolution for OCR measurements and cone factors.
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Affiliation(s)
- Yuichi Akino
- Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, 565-0871, Japan
- Department of Radiation Oncology, Suita Tokushukai Hospital, Suita, Osaka, 565-0814, Japan
| | - Indra J Das
- Department of Radiation Oncology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, Chicago, IL, 60611, USA
| | - Masateru Fujiwara
- Department of Radiation Oncology, Suita Tokushukai Hospital, Suita, Osaka, 565-0814, Japan
| | - Akari Kaneko
- Department of Radiation Oncology, Suita Tokushukai Hospital, Suita, Osaka, 565-0814, Japan
| | - Takashi Masutani
- Department of Radiation Oncology, Suita Tokushukai Hospital, Suita, Osaka, 565-0814, Japan
| | - Hirokazu Mizuno
- Department of Central Radiology, Osaka Rosai Hospital, Sakai, Osaka, 591-8025, Japan
| | - Fumiaki Isohashi
- Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, 565-0871, Japan
| | - Osamu Suzuki
- Osaka Heavy Ion Therapy Center, Osaka, 540-0008, 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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Marrale M, d’Errico F. Hydrogels for Three-Dimensional Ionizing-Radiation Dosimetry. Gels 2021; 7:74. [PMID: 34205640 PMCID: PMC8293215 DOI: 10.3390/gels7020074] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 06/15/2021] [Accepted: 06/16/2021] [Indexed: 11/28/2022] Open
Abstract
Radiation-sensitive gels are among the most recent and promising developments for radiation therapy (RT) dosimetry. RT dosimetry has the twofold goal of ensuring the quality of the treatment and the radiation protection of the patient. Benchmark dosimetry for acceptance testing and commissioning of RT systems is still based on ionization chambers. However, even the smallest chambers cannot resolve the steep dose gradients of up to 30-50% per mm generated with the most advanced techniques. While a multitude of systems based, e.g., on luminescence, silicon diodes and radiochromic materials have been developed, they do not allow the truly continuous 3D dose measurements offered by radiation-sensitive gels. The gels are tissue equivalent, so they also serve as phantoms, and their response is largely independent of radiation quality and dose rate. Some of them are infused with ferrous sulfate and rely on the radiation-induced oxidation of ferrous ions to ferric ions (Fricke-gels). Other formulations consist of monomers dispersed in a gelatinous medium (Polyacrylamide gels) and rely on radiation-induced polymerization, which creates a stable polymer structure. In both gel types, irradiation causes changes in proton relaxation rates that are proportional to locally absorbed dose and can be imaged using magnetic resonance imaging (MRI). Changes in color and/or opacification of the gels also occur upon irradiation, allowing the use of optical tomography techniques. In this work, we review both Fricke and polyacrylamide gels with emphasis on their chemical and physical properties and on their applications for radiation dosimetry.
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Affiliation(s)
- Maurizio Marrale
- Department of Physics and Chemistry, “Emilio Segrè” ATeN Center, University of Palermo, 90128 Palermo, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Catania, 95123 Catania, Italy
| | - Francesco d’Errico
- Scuola di Ingegneria, Università degli Studi di Pisa, 56126 Pisa, Italy;
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Pisa, 56127 Pisa, Italy
- School of Medicine, Yale University New Haven, CT 06510, USA
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15
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Debnath SBC, Tonneau D, Fauquet C, Tallet A, Goncalves A, Darreon J. Dosimetric characterization of a small-scale (Zn,Cd)S:Ag inorganic scintillating detector to be used in radiotherapy. Phys Med 2021; 84:15-23. [PMID: 33813200 DOI: 10.1016/j.ejmp.2021.03.022] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 03/14/2021] [Accepted: 03/20/2021] [Indexed: 12/01/2022] Open
Abstract
PURPOSE In modern radiotherapy techniques, to ensure an accurate beam modeling process, dosimeters with high accuracy and spatial resolution are required. Therefore, this work aims to propose a simple, robust, and a small-scale fiber-integrated X-ray inorganic detector and investigate the dosimetric characteristics used in radiotherapy. METHODS The detector is based on red-emitting silver-activated zinc-cadmium sulfide (Zn,Cd)S:Ag nanoclusters and the proposed system has been tested under 6 MV photons with standard dose rate used in the patient treatment protocol. The article presents the performances of the detector in terms of dose linearity, repeatability, reproducibility, percentage depth dose distribution, and field output factor. A comparative study is shown using a microdiamond dosimeter and considering data from recent literature. RESULTS We accurately measured a small field beam profile of 0.5 × 0.5 cm2 at a spatial resolution of 100 µm using a LINAC system. The dose linearity at 400 MU/min has shown less than 0.53% and 1.10% deviations from perfect linearity for the regular and smallest field. Percentage depth dose measurement agrees with microdiamond measurements within 1.30% and 2.94%, respectively for regular to small field beams. Besides, the stem effect analysis shows a negligible contribution in the measurements for fields smaller than 3x3 cm2. This study highlights the drastic decrease of the convolution effect using a point-like detector, especially in small dimension beam characterization. Field output factor has shown a good agreement while comparing it with the microdiamond dosimeter. CONCLUSION All the results presented here anticipated that the developed detector can accurately measure delivered dose to the region of interest, claim accurate depth dose distribution hence it can be a suitable candidate for beam characterization and quality assurance of LINAC system.
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Affiliation(s)
| | - Didier Tonneau
- Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
| | - Carole Fauquet
- Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
| | - Agnes Tallet
- Institut Paoli-Calmettes, 13009 Marseille, France
| | - Anthony Goncalves
- Institut Paoli-Calmettes, 13009 Marseille, France; Aix Marseille Université, CNRS UMR 7258, INSERM UMR 1068, CRCM, 13009 Marseille, France
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16
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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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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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18
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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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19
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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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Rose MS, Tirpak L, Van Casteren K, Zack J, Simon T, Schoenfeld A, Simon W. Multi‐institution validation of a new high spatial resolution diode array for SRS and SBRT plan pretreatment quality assurance. Med Phys 2020; 47:3153-3164. [DOI: 10.1002/mp.14153] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 02/20/2020] [Accepted: 03/12/2020] [Indexed: 12/31/2022] Open
Affiliation(s)
- Mark S. Rose
- Sun Nuclear Corporation 3275 Suntree Blvd Melbourne Florida 32940 USA
| | - Lena Tirpak
- Sun Nuclear Corporation 3275 Suntree Blvd Melbourne Florida 32940 USA
| | | | - Jeff Zack
- Sun Nuclear Corporation 3275 Suntree Blvd Melbourne Florida 32940 USA
| | - Tom Simon
- Sun Nuclear Corporation 3275 Suntree Blvd Melbourne Florida 32940 USA
| | | | - William Simon
- Sun Nuclear Corporation 3275 Suntree Blvd Melbourne Florida 32940 USA
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21
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Wegener S, Herzog B, Sauer OA. Detector response in the buildup region of small MV fields. Med Phys 2020; 47:1327-1339. [PMID: 31860128 DOI: 10.1002/mp.13973] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 12/11/2019] [Accepted: 12/11/2019] [Indexed: 11/11/2022] Open
Abstract
PURPOSE The model used to calculate dose distributions in a radiotherapy treatment plan relies on the data entered during beam commissioning. The quality of these data heavily depends on the detector choice made, especially in small fields and in the buildup region. Therefore, it is necessary to identify suitable detectors for measurements in the buildup region of small fields. To aid the understanding of a detector's limitations, several factors that influence the detector signal are to be analyzed, for example, the volume effect due to the detector size, the response to electron contamination, the signal dependence on the polarity used, and the effective point of measurement chosen. METHODS We tested the suitability of different small field detectors for measurements of depth dose curves with a special focus on the surface-near area of dose buildup for fields sized between 10 × 10 and 0.6 × 0.6 cm2 . Depth dose curves were measured with 14 different detectors including plane-parallel chambers, thimble chambers of different types and sizes, shielded and unshielded diodes as well as a diamond detector. Those curves were compared with depth dose curves acquired on Gafchromic film. Additionally, the magnitude of geometric volume corrections was estimated from film profiles in different depths. Furthermore, a lead foil was inserted into the beam to reduce contaminating electrons and to study the resulting changes of the detector response. The role of the effective point of measurement was investigated by quantifying the changes occurring when shifting depth dose curves. Last, measurements for the small ionization chambers taken at opposing biasing voltages were compared to study polarity effects. RESULTS Depth-dependent correction factors for relative depth dose curves with different detectors were derived. Film, the Farmer chamber FC23, a 0.13 cm3 scanning chamber CC13 and a plane-parallel chamber PPC05 agree very well in fields sized 4 × 4 and 10 × 10 cm2 . For most detectors and in smaller fields, depth dose curves differ from the film. In general, shielded diodes require larger corrections than unshielded diodes. Neither the geometric volume effect nor the electron contamination can account for the detector differences. The biggest uncertainty arises from the positioning of a detector with respect to the water surface and from the choice of the detector's effective point of measurement. Depth dose curves acquired with small ionization chambers differ by over 15% in the buildup region depending on sign of the biasing voltage used. CONCLUSIONS A scanning chamber or a PPC40 chamber is suitable for fields larger than 4 × 4 cm2 . Below that field size, the microDiamond or small ionization chambers perform best requiring the smallest corrections at depth as well as in the buildup region. Diode response changes considerably between the different types of detectors. The position of the effective point of measurement has a huge effect on the resulting curves, therefore detector specific rather than general shifts of half the inner radius of cylindrical ionization chambers for the effective point of measurement should be used. For small ionization chambers, averaging between both polarities is necessary for data obtained near the surface.
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Affiliation(s)
- Sonja Wegener
- Department of Radiation Oncology, University of Wuerzburg, Josef-Schneider-Str. 11, 97080, Wuerzburg, Germany
| | - Barbara Herzog
- Department of Radiation Oncology, University of Wuerzburg, Josef-Schneider-Str. 11, 97080, Wuerzburg, Germany.,Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120, Halle (Saale), Germany
| | - Otto A Sauer
- Department of Radiation Oncology, University of Wuerzburg, Josef-Schneider-Str. 11, 97080, Wuerzburg, Germany
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Current response stability of a commercial PIN photodiode for low dose radiation processing applications. Radiat Phys Chem Oxf Engl 1993 2020. [DOI: 10.1016/j.radphyschem.2019.04.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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23
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Irmen P, Reft C, Fitzherbert C, Solin L, Hand C. Verification of representative data for output factors of SRS cones utilizing IAEA TRS 483 recommendations. ACTA ACUST UNITED AC 2019; 64:215011. [DOI: 10.1088/1361-6560/ab47dd] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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24
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Roberts NF, Patterson E, Jelen U, Causer T, Holloway L, Liney G, Lerch M, Rosenfeld AB, Cutajar D, Oborn BM, Metcalfe P. Experimental characterization of magnetically focused electron contamination at the surface of a high-field inline MRI-linac. Med Phys 2019; 46:5780-5789. [PMID: 31633212 DOI: 10.1002/mp.13847] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 08/26/2019] [Accepted: 09/23/2019] [Indexed: 11/08/2022] Open
Abstract
PURPOSE The fringe field of the Australian MRI-linac causes contaminant electrons to be focused along the central axis resulting in a high surface dose. This work aims to characterize this effect using Gafchromic film and high-resolution detectors, MOSkinTM and microDiamond. The secondary aim is to investigate the influence of the inline magnetic field on the relative dose response of these detectors. METHODS The Australian MRI-linac has the unique feature that the linac is mounted on rails allowing for measurements to be performed at different magnetic field strengths while maintaining a constant source-to-surface distance (SSD). Percentage depth doses (PDD) were collected at SSD 1.82 m in a solid water phantom positioned in a low magnetic field region and then at isocenter of the MRI where the magnetic field is 1 T. Measurements for a range of field sizes were taken with the MOSkinTM , microDiamond, and Gafchromic® EBT3 film. The detectors' relative responses at 1 T were compared to the near 0 T PDD beyond the region of electron contamination, that is, 20 mm depth. The near surface measurements inside the MRI bore were compared among the different detectors. RESULTS Skin dose in the MRI, as measured with the MOSkinTM , was 104.5% for 2.1 × 1.9 cm2 , 185.6% for 6.1 × 5.8 cm2 , 369.1% for 11.8 × 11.5 cm2 , and 711.1% for 23.5 × 23 cm2 . The detector measurements beyond the electron contamination region showed agreement between the relative response at 1 T and near 0 T. Film was in agreement with both detectors in this region further demonstrating their relative response is unaffected by the magnetic field. CONCLUSIONS Experimental characterization of the high electron contamination at the surface was performed for a range of field sizes. The relative response of MOSkinTM and microDiamond detectors, beyond the electron contamination region, were confirmed to be unaffected by the 1-T inline magnetic field.
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Affiliation(s)
- Natalia F Roberts
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia.,Centre for Oncology Education and Research Translation, Wollongong, NSW, 2522, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
| | - Elizabeth Patterson
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Urszula Jelen
- Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
| | - Trent Causer
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia.,Illawarra Cancer Care Centre, Wollongong Hospital, Wollongong, NSW, 2500, Australia
| | - Lois Holloway
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia.,Centre for Oncology Education and Research Translation, Wollongong, NSW, 2522, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia.,Department of Medical Physics, Liverpool and Macarthur Cancer Care Centres, Liverpool, NSW, 2170, Australia.,South Western Sydney Clinical School, University of New South Wales, Liverpool, NSW, Australia.,Institute of Medical Physics, University of Sydney, Camperdown, NSW, 2505, Australia
| | - Gary Liney
- Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
| | - Michael Lerch
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Anatoly B Rosenfeld
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Dean Cutajar
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Bradley M Oborn
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia.,Illawarra Cancer Care Centre, Wollongong Hospital, Wollongong, NSW, 2500, Australia
| | - Peter Metcalfe
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
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Neira S, Brualla-Gónzalez L, Prieto-Pena J, Gómez F, Pardo-Montero J. A kinetic model of diode detector response to pulsed radiation beams. Phys Med Biol 2019; 64:205007. [PMID: 31519004 DOI: 10.1088/1361-6560/ab4460] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Diodes dosimeters present a complex response to pulsed beams, with diode sensitivity varying with dose-per-pulse, monitor unit rate (time between pulses) or number of integrated pulses. Such a response is caused by the complex kinetics of the interplay among charge carriers, recombination-generation centers, which capture excess minority charge carriers and facilitate recombination with a majority charge carrier, and traps with energy levels close to the conduction/valence band, which can trap and release charge carriers. This behavior has been well characterized experimentally, and modeled with phenomenological models. In this work we present a kinetic multi-compartment model of the response of diode detectors, which includes the interplay among charge carriers, recombination-generation centers, and traps. The model can qualitatively fit experimental data extracted from the literature on diode response versus dose-per-pulse, monitor unit rate (time between pulses), or number of integrated pulses. In this regard, our work provides further insight on the response of diode detectors, and a theoretical framework for the development of simple phenomenological models.
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Affiliation(s)
- Sara Neira
- Group of Medical Physics and Biomathematics, Instituto de Investigación Sanitaria (IDIS), Santiago de Compostela, Spain. Equal contribution
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26
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Wegener S, Sauer OA. The effective point of measurement for depth-dose measurements in small MV photon beams with different detectors. Med Phys 2019; 46:5209-5215. [PMID: 31461533 DOI: 10.1002/mp.13788] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Revised: 07/11/2019] [Accepted: 08/06/2019] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The effective point of measurement (EPOM) of cylindrical ionization chambers differs from their geometric center. The exact shift depends on chamber construction details, above all the chamber size, and to some degree on the field-size and beam quality. It generally decreases as the chamber dimensions get smaller. In this work, effective points of measurement in small photon fields of a range of cylindrical chambers of different sizes are investigated, including small chambers that have not been studied previously. METHODS In this investigation, effective points of measurement for different ionization chambers (Farmer type, scanning chambers, micro-ionization chambers) and solid state detectors were determined by measuring depth-ionization curves in a 6 MV beam in field sizes between 2 × 2 cm2 and 10 × 10 cm2 and comparing those curves with curves measured with plane-parallel chambers. RESULTS It was possible to average the results to one shift per detector, as the results were sufficiently independent of the studied field sizes. For cylindrical ion chambers, shifts of the EPOM were determined to be between 0.49 and 0.30 times the inner chamber radius from the reference point. CONCLUSIONS We experimentally confirmed the previously reported decrease of the EPOM shift with decreasing detector size. Highly accurate data for a large range of detectors, including new very small ones, were determined. Thus, small chambers noticeably differ from the 0.5-times to 0.6-times the inner chamber radius recommendations in current dosimetry protocols. The detector-individual EPOMs need to be considered for measurements of depth-dose curves.
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Affiliation(s)
- Sonja Wegener
- Radiation Oncology, University of Wuerzburg, Josef-Schneider-Str. 11, 97080, Wuerzburg, Germany
| | - Otto A Sauer
- Radiation Oncology, University of Wuerzburg, Josef-Schneider-Str. 11, 97080, Wuerzburg, Germany
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27
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Delfs B, Kapsch RP, Chofor N, Looe HK, Harder D, Poppe B. A new reference-type ionization chamber with direction-independent response for use in small-field photon-beam dosimetry – An experimental and Monte Carlo study. Z Med Phys 2019; 29:39-48. [DOI: 10.1016/j.zemedi.2018.05.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 04/18/2018] [Accepted: 05/04/2018] [Indexed: 10/14/2022]
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28
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Wegener S, Weick S, Sauer OA. Influence of a transverse magnetic field on the response of different detectors in a high energy photon beam near the surface. Z Med Phys 2019; 29:22-30. [DOI: 10.1016/j.zemedi.2018.07.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 05/29/2018] [Accepted: 07/02/2018] [Indexed: 10/28/2022]
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29
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Can Gafchromic EBT3 films effectively characterize small fields of 6 MV unflattened photon beams of Cyberknife system? POLISH JOURNAL OF MEDICAL PHYSICS AND ENGINEERING 2018. [DOI: 10.2478/pjmpe-2018-0025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Abstract
Shielded silicon diodes are commonly employed in commissioning of Cyberknife 6 MV photon beams. This study aims to measure output factors, off centered ratio (OCR), percentage depth dose (PDD) of 6 MV photons using shielded and unshielded diodes and to compare with Gafchromic EBT3 film measurements to investigate whether EBT3 could effectively characterize small 6 MV photon beams. Output factors, OCR and PDD were measured with shielded and unshielded silicon detectors in a radiation field analyzer system at reference condition. Water equivalent solid phantom were used while irradiating EBT3 films. From multiuser data, diodes underestimated output factor by 3% for collimator fields ≤ 10 mm, while EBT3 underestimated the output factor by 3.9% for 5 mm collimator. 1D Gamma analysis of OCR between diode and film, results in gamma ≤ 1 for all measured points with 1 mm distance to agreement (DTA) and 1% relative dose difference (DD). Dose at surface is overestimated with diodes compared to EBT3. PDD results were within 2% relative dose values between diode and EBT3 except for 5 mm collimator. Except for small collimator fields of up to 10 mm, results of output factor, OCR, PDD of all detectors used in this study exhibited similar results. Relative dose measurements with Gafchromic EBT3 in this work show that EBT3 films can be used effectively as an independent tool to verify commissioning beam data of small fields only after careful verification of methodology for any systematic errors with appropriate readout procedure.
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Talamonti C, Russo S, Pimpinella M, Falco MD, Cagni E, Pallotta S, Stasi M, Mancosu P. Community approach for reducing small field measurement errors: Experience over 24 centres. Radiother Oncol 2018; 132:218-222. [PMID: 30385173 DOI: 10.1016/j.radonc.2018.10.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Revised: 08/20/2018] [Accepted: 10/10/2018] [Indexed: 11/18/2022]
Abstract
PURPOSE The complexity of the modern Stereotactic Body Radiation Therapy (SBRT) techniques requires comprehensive quality assurance programs, to ensure the right treatment to the patient. Dosimetry of small radiation fields is a challenge especially for radiotherapy centres starting to work on this issue. The matter to be discussed here concerns the need of detailed measurement procedures and cross checks to be paired to the usual recommendations on detectors and correction factors. MATERIALS AND METHODS The presented work involved 24 Italian radiotherapy centres, with the specific purpose to minimize systematic errors in output factor measurements over different radiotherapy centres. Using the unshielded silicon diode IBA Razor, reference curves for the relative signal ratio (RSR) as a function of beam size were created for each Linac family. RESULTS With this study we have demonstrated consistency of small field dosimetry on all the centres involved, moreover all radiotherapy centres using Razor are allowed to compare measurements amongst each other and centres with values deviating more than 5% from the reference curve are advised to repeat their measurements. With this procedure, some critical issues were detected from two centres in RSR measurements, that, if implemented into the own treatment planning system, would induce an unwanted overdosage larger than 5%. CONCLUSIONS The proposed approach could allow one to envision high-skilled therapy centres providing support to those featuring minor experience and could represent an important strategy for the clinical implementation of emerging technologies at high quality levels. The methodology adopted exploits crowd knowledge methods which could be applied in others areas of radiation dosimetry.
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Affiliation(s)
- Cinzia Talamonti
- University of Florence, Dept Biomedical Experimental and Clinical Science, "Mario Serio", Medical Physics Unit, AOU Careggi, Florence, Italy.
| | - Serenella Russo
- Medical Physics Unit, Azienda USL Toscana Centro, Florence, Italy
| | - Maria Pimpinella
- Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti, ENEA-INMRI C R Casaccia, I-00123 Roma, Italy
| | - Maria Daniela Falco
- Department of Radiation Oncology "G. D'Annunzio", University of Chieti, SS. Annunziata Hospital, Chieti, Italy
| | - Elisabetta Cagni
- Medical Physics Unit, Azienda USL-IRCCS di Reggio Emilia, Reggio Emilia, Italy
| | - Stefania Pallotta
- University of Florence, Dept Biomedical Experimental and Clinical Science, "Mario Serio", Medical Physics Unit, AOU Careggi, Florence, Italy
| | - Michele Stasi
- Medical Physics Department, A.O. Ordine Mauriziano, Turin, Italy
| | - Pietro Mancosu
- Medical Physics Unit of Radiation Oncology Dept., Humanitas Clinical and Research Hospital, Milano, Italy
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31
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Nascimento CR, Asfora VK, Gonçalves JAC, Khoury HJ, Barros VSM, Kalil LF, Bueno CC. The performance of a multi guard ring (MGR) diode for clinical electron beams dosimetry. Appl Radiat Isot 2018; 141:112-117. [PMID: 30212784 DOI: 10.1016/j.apradiso.2018.07.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 03/26/2018] [Accepted: 07/02/2018] [Indexed: 11/17/2022]
Abstract
The dosimetric response of a multi guard ring structure (MGR) diode has been studied with clinical electron beam energies from 5 MeV to 15 MeV. The results showed that the MGR dose response is linear in the range of 5-320 cGy and presents reproducibility with variation coefficients less than 0.4%. The field output factors measured with the MGR agreed within 2% with those measured with an ionization chamber. This study evidences that this diode can be used for clinical electron beam dosimetry.
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Affiliation(s)
- C R Nascimento
- Departamento de Energia Nuclear- UFPE, Av. Prof. Luiz Freire, 1000, 50740-545, Cidade Universitária, Recife, PE, Brazil; Instituto Federal de Educação, Ciência e Tecnologia de Pernambuco - IFPE, Recife, PE, Brazil
| | - V K Asfora
- Departamento de Energia Nuclear- UFPE, Av. Prof. Luiz Freire, 1000, 50740-545, Cidade Universitária, Recife, PE, Brazil
| | - J A C Gonçalves
- Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP, São Paulo, SP, Brazil
| | - H J Khoury
- Departamento de Energia Nuclear- UFPE, Av. Prof. Luiz Freire, 1000, 50740-545, Cidade Universitária, Recife, PE, Brazil.
| | - V S M Barros
- Departamento de Energia Nuclear- UFPE, Av. Prof. Luiz Freire, 1000, 50740-545, Cidade Universitária, Recife, PE, Brazil
| | - L F Kalil
- Liga Norte-Rio-Grandense Contra o Câncer - CECAN, Natal, RN, Brazil
| | - C C Bueno
- Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP, São Paulo, SP, Brazil
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Parwaie W, Refahi S, Ardekani MA, Farhood B. Different Dosimeters/Detectors Used in Small-Field Dosimetry: Pros and Cons. JOURNAL OF MEDICAL SIGNALS & SENSORS 2018; 8:195-203. [PMID: 30181968 PMCID: PMC6116321 DOI: 10.4103/jmss.jmss_3_18] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
With the advent of complex and precise radiation therapy techniques, the use of relatively small fields is needed. Using such field sizes can cause uncertainty in dosimetry; therefore, special attention is required both in dose calculations and measurements. There are several challenges in small-field dosimetry such as the steep gradient of the radiation field, volume averaging effect, lack of charged particle equilibrium, partial occlusion of radiation source, beam alignment, and unable to use a reference dosimeter. Due to these challenges, special dosimeters are needed for small-field dosimetry, and this review article discusses this topic.
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Affiliation(s)
- Wrya Parwaie
- Department of Medical Physics and Biomedical Engineering, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Soheila Refahi
- Department of Medical Physics, Faculty of Medicine, Ardabil University of Medical Sciences, Ardabil, Iran
| | - Mahdieh Afkhami Ardekani
- Department of Radiology, Faculty of Para-Medicine, Hormozgan University of Medical Sciences, Bandar Abbas, Iran
| | - Bagher Farhood
- Department of Radiology and Medical Physics, Faculty of Paramedical Sciences, Kashan University of Medical Sciences, Kashan, Iran
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Shukaili KA, Corde S, Petasecca M, Pereveratylo V, Lerch M, Jackson M, Rosenfeld A. "Characterization of ELEKTA SRS cone collimator using high spatial resolution monolithic silicon detector array". J Appl Clin Med Phys 2018; 19:114-124. [PMID: 29790261 PMCID: PMC6036391 DOI: 10.1002/acm2.12345] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Revised: 04/03/2018] [Accepted: 04/07/2018] [Indexed: 11/05/2022] Open
Abstract
PURPOSE To investigate the accuracy of the dosimetry of radiation fields produced by small ELEKTA cone collimators used for stereotactic radiosurgery treatments (SRS) using commercially available detectors EBT3 GafchromicTM film, IBA Stereotactic diode (SFD), and the recently developed detector DUO, which is a monolithic silicon orthogonal linear diode array detector. METHODS These three detectors were used for the measurement of beam profiles, output factors, and percentage depth dose for SRS cone collimators with cone sizes ranging from 5 to 50 mm diameter. The measurements were performed at 10 cm depth and 90 cm SSD. RESULTS The SRS cone beam profiles measured with DUO, EBT3 film, and IBA SFD agreed well, results being in agreement within ±0.5 mm in the FWHM, and ±0.7 mm in the penumbra region. The output factor measured by DUO with 0.5 mm air gap above agrees within ±1% with EBT3. The OF measured by IBA SFD (corrected for the over-response) agreed with both EBT3 and DUO within ±2%. All three detectors agree within ±2% for PDD measurements for all SRS cones. CONCLUSIONS The characteristics of the ELEKTA SRS cone collimator have been evaluated by using a monolithic silicon high spatial resolution detector DUO, EBT3, and IBA SFD diode. The DUO detector is suitable for fast real-time quality assurance dosimetry in small radiation fields typical for SRS/SRT. This has been demonstrated by its good agreement of measured doses with EBT 3 films.
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Affiliation(s)
- Khalsa Al Shukaili
- Centre for Medical Radiation PhysicsUniversity of WollongongWollongongNSWAustralia
- National Oncology CentreRoyal HospitalMuscatOman
| | - Stéphanie Corde
- Centre for Medical Radiation PhysicsUniversity of WollongongWollongongNSWAustralia
- Illawarra Health and Medical Research InstituteWollongongNSWAustralia
- Nelune Comprehensive Cancer CentrePrince of Wales HospitalRandwickNSWAustralia
| | - Marco Petasecca
- Centre for Medical Radiation PhysicsUniversity of WollongongWollongongNSWAustralia
- Illawarra Health and Medical Research InstituteWollongongNSWAustralia
| | | | - Michael Lerch
- Centre for Medical Radiation PhysicsUniversity of WollongongWollongongNSWAustralia
- Illawarra Health and Medical Research InstituteWollongongNSWAustralia
| | - Michael Jackson
- Centre for Medical Radiation PhysicsUniversity of WollongongWollongongNSWAustralia
- Nelune Comprehensive Cancer CentrePrince of Wales HospitalRandwickNSWAustralia
| | - Anatoly Rosenfeld
- Centre for Medical Radiation PhysicsUniversity of WollongongWollongongNSWAustralia
- Illawarra Health and Medical Research InstituteWollongongNSWAustralia
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Stanhope CW, Drake DG, Liang J, Alber M, Söhn M, Habib C, Willcut V, Yan D. Evaluation of machine log files/MC-based treatment planning and delivery QA as compared to ArcCHECK QA. Med Phys 2018; 45:2864-2874. [PMID: 29676463 DOI: 10.1002/mp.12926] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 02/26/2018] [Accepted: 03/31/2018] [Indexed: 11/05/2022] Open
Abstract
PURPOSE A treatment planning/delivery QA tool using linac log files (LF) and Monte Carlo (MC) dose calculation is investigated as a standalone alternative to phantom-based patient-specific QA (ArcCHECK (AC)). METHODS Delivering a variety of fields onto MapCHECK2 and ArcCHECK, diode sensitivity dependence on dose rate (in-field) and energy (primarily out-of-field) was quantified. AC and LF QAs were analyzed with respect to delivery complexity by delivering 12 × 12 cm static fields/arcs comprised of varying numbers of abutting sub-fields onto ArcCHECK. About 11 clinical dual-arc VMAT patients planned using Pinnacle's convolution-superposition (CS) were delivered on ArcCHECK and log file dose (LF-CS and LF-MC) calculated. To minimize calculation time, reduced LF-CS sampling (1/2/3/4° control point spacing) was investigated. Planned ("Plan") and LF-reconstructed CS and MC doses were compared with each other and AC measurement via statistical [mean ± StdDev(σ)] and gamma analyses to isolate dosimetric uncertainties and quantify the relative accuracies of AC QA and MC-based LF QA. RESULTS Calculation and ArcCHECK measurement differed by up to 1.5% in-field due to variation in dose rate and up to 5% out-of-field. For the experimental segment-varying plans, despite CS calculation deviating by as much as 13% from measurement, Plan-MC and LF-MC doses generally matched AC measurement within 3%. Utilizing 1° control point spacing, 2%/2 mm LF-CS vs AC pass rates (97%) were slightly lower than Plan-CS vs AC pass rates (97.5%). Utilizing all log file samples, 2%/2 mm LF-MC vs AC pass rates (97.3%) were higher than Plan-MC vs AC (96.5%). Phantom-dependent, calculation algorithm-dependent (MC vs CS), and delivery error-dependent dose uncertainties were 0.8 ± 1.2%, 0.2 ± 1.1%, and 0.1 ± 0.9% respectively. CONCLUSION Reconstructing every log file sample with no increase in computational cost, MC-based LF QA is faster and more accurate than CS-based LF QA. Offering similar dosimetric accuracy compared to AC measurement, MC-based log files can be used for treatment planning QA.
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Affiliation(s)
- Carl W Stanhope
- Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, MI, 48073, USA.,Department of Medical Physics, Wayne State University, Detroit, MI, 48202, USA
| | - Douglas G Drake
- Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, MI, 48073, USA
| | - Jian Liang
- Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, MI, 48073, USA
| | - Markus Alber
- ScientificRT GmbH, Munich, 81373, Germany.,Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, 61920, Germany
| | | | - Charbel Habib
- Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, MI, 48073, USA
| | | | - Di Yan
- Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, MI, 48073, USA
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Shimono T. [3. Selection of Measurement Instruments]. Nihon Hoshasen Gijutsu Gakkai Zasshi 2018; 74:1212-1220. [PMID: 30344219 DOI: 10.6009/jjrt.2018_jsrt_74.10.1212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
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36
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Biasi G, Petasecca M, Guatelli S, Hardcastle N, Carolan M, Perevertaylo V, Kron T, Rosenfeld AB. A novel high-resolution 2D silicon array detector for small field dosimetry with FFF photon beams. Phys Med 2017; 45:117-126. [PMID: 29472075 DOI: 10.1016/j.ejmp.2017.12.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 12/13/2017] [Accepted: 12/15/2017] [Indexed: 11/19/2022] Open
Abstract
PURPOSE Flattening filter free (FFF) beams are increasingly being considered for stereotactic radiotherapy (SRT). For the first time, the performance of a monolithic silicon array detector under 6 and 10 MV FFF beams was evaluated. The dosimeter, named "Octa" and designed by the Centre for Medical Radiation Physics (CMRP), was tested also under flattened beams for comparison. METHODS Output factors (OFs), percentage depth-dose (PDD), dose profiles (DPs) and dose per pulse (DPP) dependence were investigated. Results were benchmarked against commercially available detectors for small field dosimetry. RESULTS The dosimeter was shown to be a 'correction-free' silicon array detector for OFs and PDD measurements for all the beam qualities investigated. Measured OFs were accurate within 3% and PDD values within 2% compared against the benchmarks. Cross-plane, in-plane and diagonal DPs were measured simultaneously with high spatial resolution (0.3 mm) and real time read-out. A DPP dependence (24% at 0.021 mGy/pulse relative to 0.278 mGy/pulse) was found and could be easily corrected for in the case of machine specific quality assurance applications. CONCLUSIONS Results were consistent with those for monolithic silicon array detectors designed by the CMRP and previously characterized under flattened beams only, supporting the robustness of this technology for relative dosimetry for a wide range of beam qualities and dose per pulses. In contrast to its predecessors, the design of the Octa offers an exhaustive high-resolution 2D dose map characterization, making it a unique real-time radiation detector for small field dosimetry for field sizes up to 3 cm side.
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Affiliation(s)
- G Biasi
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - M Petasecca
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - S Guatelli
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - N Hardcastle
- Peter MacCallum Cancer Centre, Melbourne, Australia
| | - M Carolan
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia; Illawarra Cancer Care Centre, Wollongong Hospital, Wollongong, NSW, Australia
| | | | - T Kron
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia; Peter MacCallum Cancer Centre, Melbourne, Australia; Sir Peter MacCallum Cancer Institute, University of Melbourne, Australia
| | - A B Rosenfeld
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia.
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Jafari S, Distefano G, Lee J, Gouldstone C, Mayles H, Jupp T, Nisbet A, Clark C. Feasibility study of silica bead thermoluminescence detectors (TLDs) in an external radiotherapy dosimetry audit programme. Radiat Phys Chem Oxf Engl 1993 2017. [DOI: 10.1016/j.radphyschem.2017.07.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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38
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Poppinga D, Halbur J, Lemmer S, Delfs B, Harder D, Looe HK, Poppe B. Test study of boron nitride as a new detector material for dosimetry in high-energy photon beams. Phys Med Biol 2017; 62:N436-N444. [DOI: 10.1088/1361-6560/aa81f7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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39
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Chaudhari SH, Dobhal R, Kinhikar RA, Kadam SS, Deshpande DD. Measurement of Total Scatter Factor for Stereotactic Cones with Plastic Scintillation Detector. J Med Phys 2017; 42:9-13. [PMID: 28405102 PMCID: PMC5370342 DOI: 10.4103/jmp.jmp_114_16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Advanced radiotherapy modalities such as stereotactic radiosurgery (SRS) and image-guided radiotherapy may employ very small beam apertures for accurate localized high dose to target. Accurate measurement of small radiation fields is a well-known challenge for many dosimeters. The purpose of this study was to measure total scatter factors for stereotactic cones with plastic scintillation detector and its comparison against diode detector and theoretical estimates. Measurements were performed on Novalis Tx™ linear accelerator for 6MV SRS beam with stereotactic cones of diameter 6 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm. The advantage of plastic scintillator detector is in its energy dependence. The total scatter factor was measured in water at the depth of dose maximum. Total scatter factor with plastic scintillation detector was determined by normalizing the readings to field size of 10 cm × 10 cm. To overcome energy dependence of diode detector for the determination of scatter factor with diode detector, daisy chaining method was used. The plastic scintillator detector was calibrated against the ionization chamber, and the reproducibility in the measured doses was found to be within ± 1%. Total scatter factor measured with plastic scintillation detector was 0.728 ± 0.3, 0.783 ± 0.05, 0.866 ± 0.55, 0.885 ± 0.5, and 0.910 ± 0.06 for cone sizes of 6 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm, respectively. Total scatter factor measured with diode detector was 0.733 ± 0.03, 0.782 ± 0.02, 0.834 ± 0.07, 0.854 ± 0.02, and 0.872 ± 0.02 for cone sizes of 6 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm, respectively. The variation in the measurement of total scatter factor with published Monte Carlo data was found to be −1.3%, 1.9%, −0.4%, and 0.4% for cone sizes of 7.5 mm, 10 mm, 12.5 mm, and 15 mm, respectively. We conclude that total scatter factor measurements for stereotactic cones can be adequately carried out with a plastic scintillation detector. Our results show a high level of consistency within our data and compared well with published data.
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Affiliation(s)
- Suresh H Chaudhari
- Department of Radiation Oncology, Apollo Hospitals, Navi Mumbai, Maharashtra, India
| | - Rishabh Dobhal
- Department of Radiation Oncology, Batra Hospital and Medical Research Centre, New Delhi, India
| | - Rajesh A Kinhikar
- Department of Medical Physics, Tata Memorial Hospital, Mumbai, Maharashtra, India
| | - Sudarshan S Kadam
- Department of Medical Physics, Tata Memorial Hospital, Mumbai, Maharashtra, India
| | - Deepak D Deshpande
- Department of Medical Physics, Tata Memorial Hospital, Mumbai, Maharashtra, India
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40
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Yarahmadi M, Wegener S, Sauer OA. Energy and field size dependence of a silicon diode designed for small-field dosimetry. Med Phys 2017; 44:1958-1964. [DOI: 10.1002/mp.12195] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 02/17/2017] [Accepted: 02/28/2017] [Indexed: 11/10/2022] Open
Affiliation(s)
- Mehran Yarahmadi
- Department of Medical Physics; Faculty of Medicine; Kurdistan University of Medical Sciences; Sanandaj Iran
| | - Sonja Wegener
- Department of Radiation Oncology; University of Würzburg; Josef-Schneider-Strasse 11 97080 Würzburg Germany
| | - Otto A. Sauer
- Department of Radiation Oncology; University of Würzburg; Josef-Schneider-Strasse 11 97080 Würzburg Germany
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41
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Valdenaire S, Mailleux H, Fau P. Modeling of flattening filter free photon beams with analytical and Monte Carlo TPS. Biomed Phys Eng Express 2016. [DOI: 10.1088/2057-1976/2/3/035010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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42
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Cheng JY, Ning H, Arora BC, Zhuge Y, Miller RW. Output factor comparison of Monte Carlo and measurement for Varian TrueBeam 6 MV and 10 MV flattening filter-free stereotactic radiosurgery system. J Appl Clin Med Phys 2016; 17:100-110. [PMID: 27167266 PMCID: PMC5690931 DOI: 10.1120/jacmp.v17i3.5956] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Revised: 12/30/2015] [Accepted: 12/22/2015] [Indexed: 11/25/2022] Open
Abstract
The dose measurements of the small field sizes, such as conical collimators used in stereotactic radiosurgery (SRS), are a significant challenge due to many factors including source occlusion, detector size limitation, and lack of lateral electronic equilibrium. One useful tool in dealing with the small field effect is Monte Carlo (MC) simulation. In this study, we report a comparison of Monte Carlo simulations and measurements of output factors for the Varian SRS system with conical collimators for energies of 6 MV flattening filter‐free (6 MV) and 10 MV flattening filter‐free (10 MV) on the TrueBeam accelerator. Monte Carlo simulations of Varian's SRS system for 6 MV and 10 MV photon energies with cones sizes of 17.5 mm, 15.0 mm, 12.5 mm, 10.0 mm, 7.5 mm, 5.0 mm, and 4.0 mm were performed using EGSnrc (release V4 2.4.0) codes. Varian's version‐2 phase‐space files for 6 MV and 10 MV of TrueBeam accelerator were utilized in the Monte Carlo simulations. Two small diode detectors Edge (Sun Nuclear) and Small Field Detector (SFD) (IBA Dosimetry) were applied to measure the output factors. Significant errors may result if detector correction factors are not applied to small field dosimetric measurements. Although it lacked the machine‐specific kQclin,Qmsrfclin,fmsr correction factors for diode detectors in this study, correction factors were applied utilizing published studies conducted under similar conditions. For cone diameters greater than or equal to 12.5 mm, the differences between output factors for the Edge detector, SFD detector, and MC simulations are within 3.0% for both energies. For cone diameters below 12.5 mm, output factors differences exhibit greater variations. PACS number(s): 87.55.k, 87.55.Qr
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Affiliation(s)
- Jason Y Cheng
- National Cancer Institute; National Institutes of Health.
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43
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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: 1.8] [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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44
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Barrett JC, Knill C. Monte Carlo calculated correction factors for the PTW microDiamond detector in the Gamma Knife‐Model C. Med Phys 2016; 43:1035-44. [DOI: 10.1118/1.4940790] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- J. C. Barrett
- Department of Oncology, Wayne State University, Detroit, Michigan 48201 and Department of Radiation Oncology, Karmanos Cancer Institute McLaren ‐ Macomb, Mt. Clemens, Michigan 48043
| | - Cory Knill
- Department of Oncology, Wayne State University, Detroit, Michigan 48201 and Department of Radiation Oncology, Beaumont Health, Royal Oak, Michigan 48073
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Brualla-González L, Gómez F, Pombar M, Pardo-Montero J. Dose rate dependence of the PTW 60019 microDiamond detector in high dose-per-pulse pulsed beams. Phys Med Biol 2015; 61:N11-9. [PMID: 26625177 DOI: 10.1088/0031-9155/61/1/n11] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Recombination effects can affect the detectors used for the dosimetry of radiotherapy fields. They are important when using ionization chambers, especially in liquid-filled ionization chambers, and should be corrected for. The introduction of flattening-filter-free accelerators increases the typical dose-per-pulse used in radiotherapy beams, which leads to more important recombination effects. Diamond detectors provide a good solution for the dosimetry and quality assurance of small radiotherapy fields, due to their low energy dependence and small volume. The group of Università di Roma Tor Vergata has developed a synthetic diamond detector, which is commercialized by PTW as microDiamond detector type 60019. In this work we present an experimental characterization of the collection efficiency of the microDiamond detector, focusing on high dose-per-pulse FFF beams. The collection efficiency decreases with dose-per-pulse, down to 0.978 at 2.2 mGy/pulse, following a Fowler-Attix-like curve. On the other hand, we have found no significant dependence of the collection efficiency on the pulse repetition frequency (or pulse period).
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Affiliation(s)
- Luis Brualla-González
- Servicio de Radiofísica, ERESA, Hospital General Universitario de Valencia, 46014 València, Spain
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46
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Kairn T, Asena A, Charles PH, Hill B, Langton CM, Middlebrook ND, Moylan R, Trapp JV. Field size consistency of nominally matched linacs. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2015; 38:289-97. [DOI: 10.1007/s13246-015-0349-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2014] [Accepted: 05/15/2015] [Indexed: 11/29/2022]
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47
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Sarkar V, Wang B, Zhao H, Lynch B, James JA, McCullough KT, Salter BJ. Percent depth-dose distribution discrepancies from very small volume ion chambers. J Appl Clin Med Phys 2015; 16:5230. [PMID: 26103196 PMCID: PMC5690102 DOI: 10.1120/jacmp.v16i2.5230] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2014] [Revised: 12/06/2014] [Accepted: 12/04/2014] [Indexed: 11/23/2022] Open
Abstract
As very small ion chambers become commercially available, medical physicists may be inclined to use them during the linear accelerator commissioning process to better characterize the beam in steep dose gradient areas. For this work, a total of eight different ion chambers (volumes from 0.007 cc to 0.6 cc) and four different scanning systems were used to scan PDDs at both +300V and −300V biases. We observed a reproducible, significant difference (overresponse with depth) in PDDs acquired when using very small ion chambers, with specific bias/water tank combinations — up to 5% at a depth of 25 cm in water. This difference was not observed when the PDDs were sampled using the ion chamber in static positions in conjunction with an external electrometer. This suggests noise/signal interference produced by the controller box and cable system assemblies, which can become relatively significant for the very small current signals collected by very small ion chambers, especially at depth as the signal level is even further reduced. Based on the results observed here, the use of very small active volume chambers under specific scanning conditions may lead to collection of erroneous data, introducing systematic errors into the treatment planning system. In case the use of such a chamber is required, we recommend determining whether such erroneous effect exists by comparing the scans with those obtained with a larger chamber. PACS numbers: 87.56.bd, 87.56.Fc, 87.56.Da
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48
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Clinical use of diodes and micro-chambers to obtain accurate small field output factor measurements. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2015; 38:357-67. [DOI: 10.1007/s13246-015-0334-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2014] [Accepted: 02/19/2015] [Indexed: 12/22/2022]
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49
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Correction of measured Gamma-Knife output factors for angular dependence of diode detectors and PinPoint ionization chamber. Phys Med 2014; 30:914-9. [DOI: 10.1016/j.ejmp.2014.09.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2014] [Revised: 08/28/2014] [Accepted: 09/04/2014] [Indexed: 11/18/2022] Open
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50
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Gonçalves J, Pereira L, Potiens M, Vivolo V, Bueno C. Evaluation of epitaxial silicon diodes as dosimeters in X-ray mammography. RADIAT MEAS 2014. [DOI: 10.1016/j.radmeas.2014.07.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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