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Ando Y, Okada M, Matsumoto N, Ikuhiro K, Ishihara S, Kiriu H, Tanabe Y. Evaluation of output factors of different radiotherapy planning systems using Exradin W2 plastic scintillator detector. Phys Eng Sci Med 2024; 47:1177-1189. [PMID: 38753285 DOI: 10.1007/s13246-024-01438-5] [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: 12/23/2022] [Accepted: 05/02/2024] [Indexed: 09/18/2024]
Abstract
This study aims to evaluate the output factors (OPF) of different radiation therapy planning systems (TPSs) using a plastic scintillator detector (PSD). The validation results for determining a practical field size for clinical use were verified. The implemented validation system was an Exradin W2 PSD. The focus was to validate the OPFs of the small irradiation fields of two modeled radiation TPSs using RayStation version 10.0.1 and Monaco version 5.51.10. The linear accelerator used for irradiation was a TrueBeam with three energies: 4, 6, and 10 MV. RayStation calculations showed that when the irradiation field size was reduced from 10 × 10 to 0.5 × 0.5 cm2, the results were within 2.0% of the measured values for all energies. Similarly, the values calculated using Monaco were within approximately 2.0% of the measured values for irradiation field sizes between 10 × 10 and 1.5 × 1.5 cm2 for all beam energies of interest. Thus, PSDs are effective validation tools for OPF calculations in TPS. A TPS modeled with the same source data has different minimum irradiation field sizes that can be calculated. These findings could aid in verification of equipment accuracy for treatment planning requiring highly accurate dose calculations and for third-party evaluation of OPF calculations for TPS.
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Affiliation(s)
| | - Masahiro Okada
- Hiroshima City North Medical Center Asa Citizens Hospital, Hiroshima, Japan
| | - Natsuko Matsumoto
- Hiroshima City North Medical Center Asa Citizens Hospital, Hiroshima, Japan
| | - Kawasaki Ikuhiro
- Hiroshima City North Medical Center Asa Citizens Hospital, Hiroshima, Japan
| | | | | | - Yoshinori Tanabe
- Department of Radiological Technology, Graduate School of Health Sciences, Okayama University, 5-1 Shikata-cho, 2-chome, Kita-ku, Okayama, 700-8558, Japan.
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Das IJ, Sohn JJ, Lim SN, Sengupta B, Feijoo M, Yadav P. Characteristics of a plastic scintillation detector in photon beam dosimetry. J Appl Clin Med Phys 2024; 25:e14209. [PMID: 37983685 PMCID: PMC10795454 DOI: 10.1002/acm2.14209] [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: 07/18/2023] [Revised: 10/24/2023] [Accepted: 11/04/2023] [Indexed: 11/22/2023] Open
Abstract
BACKGROUND Plastic scintillating detectors (PSD) have gained popularity due to small size and are ideally suited in small-field dosimetry due to no correction needed and hence detector reading can be compared to dose. Likewise, these detectors are active and water equivalent. A new PSD from Blue Physics is characterized in photon beam. PURPOSE Innovation in small-field dosimetry detector has led us to examine Blue Physics PSD (BP-PSD) for use in photon beams from linear accelerator. METHODS BP-PSD was acquired and its characteristics were evaluated in photon beams from a Varian TrueBeam. Data were collected in a 3D water tank. Standard parameters; dose, dose rate, energy, angular dependence and temperature dependence were studied. Depth dose, profiles and output in a reference condition as well as small fields were measured. RESULTS BP-PSD is versatile and provides data very similar to an ion chamber when Cerenkov radiation is properly accounted. This device measures data pulse by pulse which very few detectors can perform. The differences between ion chamber data and PSD are < 2% in most cases. The angular dependence is a bit pronounces to 1.5% which is due to PSD housing. Depth dose and profiles are comparable within < 1% to an ion chamber. For small fields this detector provides suitable field output factor compared to other detectors and Monte Carlo (MC) simulated data without any added correction factor. CONCLUSIONS The characteristics of Blue Physics PSD is uniquely suitable in photon beam and more so in small fields. The data are reproducible compared to ion chamber for most parameters and ideally suitable for small-field dosimetry without any correction factor.
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Affiliation(s)
- Indra J. Das
- Department of Radiation OncologyNorthwest Memorial HospitalNorthwestern University Feinberg School of MedicineChicagoIllinoisUSA
| | - Jooyoung J. Sohn
- Department of Radiation OncologyNorthwest Memorial HospitalNorthwestern University Feinberg School of MedicineChicagoIllinoisUSA
| | - Sara N. Lim
- Department of Radiation OncologyNorthwest Memorial HospitalNorthwestern University Feinberg School of MedicineChicagoIllinoisUSA
| | - Bishwambhar Sengupta
- Department of Radiation OncologyNorthwest Memorial HospitalNorthwestern University Feinberg School of MedicineChicagoIllinoisUSA
| | | | - Poonam Yadav
- Department of Radiation OncologyNorthwest Memorial HospitalNorthwestern University Feinberg School of MedicineChicagoIllinoisUSA
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Small field output factor measurement and verification for CyberKnife robotic radiotherapy and radiosurgery system using 3D polymer gel, ionization chamber, diode, diamond and scintillator detectors, Gafchromic film and Monte Carlo simulation. Appl Radiat Isot 2023; 192:110576. [PMID: 36473319 DOI: 10.1016/j.apradiso.2022.110576] [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: 08/22/2022] [Revised: 11/19/2022] [Accepted: 11/21/2022] [Indexed: 11/24/2022]
Abstract
The dosimetry of small fields has become tremendously important with the advent of intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery, where small field segments or very small fields are used to treat tumors. With high dose gradients in the stereotactic radiosurgery or radiotherapy treatment, small field dosimetry becomes challenging due to the lack of lateral electronic equilibrium in the field, x-ray source occlusion, and detector volume averaging. Small volume and tissue-equivalent detectors are recommended to overcome the challenges. With the lack of a perfect radiation detector, studies on available detectors are ongoing with reasonable disagreement and uncertainties. The joint IAEA and AAPM international code of practice (CoP) for small field dosimetry, TRS 483 (Alfonso et al., 2017) provides guidelines and recommendations for the dosimetry of small static fields in external beam radiotherapy. The CoP provides a methodology for field output factor (FOF) measurements and use of field output correction factors for a series of small field detectors and strongly recommends additional measurements, data collection and verification for CyberKnife (CK) robotic stereotactic radiotherapy/radiosurgery system using the listed detectors and more new detectors so that the FOFs can be implemented clinically. The present investigation is focused on using 3D gel along with some other commercially available detectors for the measurement and verification of field output factors (FOFs) for the small fields available in the CK system. The FOF verification was performed through a comparison with published data and Monte Carlo simulation. The results of this study have proved the suitability of an in-house developed 3D polymer gel dosimeter, several commercially available detectors, and Gafchromic films as a part of small field dosimetric measurements for the CK system.
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Jacqmin DJ, Miller JR, Barraclough BA, Labby ZE. Commissioning an Exradin W2 plastic scintillation detector for clinical use in small radiation fields. J Appl Clin Med Phys 2022; 23:e13728. [PMID: 35861648 PMCID: PMC9359019 DOI: 10.1002/acm2.13728] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 06/29/2022] [Indexed: 12/02/2022] Open
Abstract
Purpose The purpose of this work is to evaluate the Standard Imaging Exradin W2 plastic scintillation detector (W2) for use in the types of fields used for stereotactic radiosurgery. Methods Prior to testing the W2 in small fields, the W2 was evaluated in standard large field conditions to ensure good detector performance. These tests included energy dependence, short‐term repeatability, dose‐response linearity, angular dependence, temperature dependence, and dose rate dependence. Next, scan settings and calibration of the W2 were optimized to ensure high quality data acquisition. Profiles of small fields shaped by cones and multi‐leaf collimator (MLCs) were measured using the W2 and IBA RAZOR diode in a scanning water tank. Output factors for cones (4–17.5 mm) and MLC fields (1, 2, 3 cm) were acquired with both detectors. Finally, the dose at isocenter for seven radiosurgery plans was measured with the W2 detector. Results W2 exhibited acceptable warm‐up behavior, short‐term reproducibility, axial angular dependence, dose‐rate linearity, and dose linearity. The detector exhibits a dependence upon energy, polar angle, and temperature. Scanning measurements taken with the W2 and RAZOR were in good agreement, with full‐width half‐maximum and penumbra widths agreeing to within 0.1 mm. The output factors measured by the W2 and RAZOR exhibited a maximum difference of 1.8%. For the seven point‐dose measurements of radiosurgery plans, the W2 agreed well with our treatment planning system with a maximum deviation of 2.2%. The Čerenkov light ratio calibration method did not significantly impact the measurement of relative profiles, output factors, or point dose measurements. Conclusion The W2 demonstrated dosimetric characteristics that are suitable for radiosurgery field measurements. The detector agreed well with the RAZOR diode for output factors and scanned profiles and showed good agreement with the treatment planning system in measurements of clinical treatment plans.
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Affiliation(s)
- Dustin J Jacqmin
- Department of Human Oncology, University of Wisconsin-Madison, Madison, Wisconsin, USA.,Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Jessica R Miller
- Department of Human Oncology, University of Wisconsin-Madison, Madison, Wisconsin, USA.,Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Brendan A Barraclough
- Department of Human Oncology, University of Wisconsin-Madison, Madison, Wisconsin, USA.,Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina, USA
| | - Zacariah E Labby
- Department of Human Oncology, University of Wisconsin-Madison, Madison, Wisconsin, USA
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Rudek B, Bernstein K, Osterman S, Qu T. Replacing gamma knife beam-profiles on film with point-detector scans. J Appl Clin Med Phys 2022; 23:e13522. [PMID: 35001499 DOI: 10.1002/acm2.13522] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 12/02/2021] [Accepted: 12/15/2021] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Detector arrays and profile-scans have widely replaced film-measurements for quality assurance (QA) on linear accelerators. Film is still used for relative output factor (ROF) measurements, positioning, and dose-profile verification for annual Leksell Gamma Knife (LGK) QA. This study shows that small-field active detector measurements can be performed in the easily accessed clinical mode and that they are an effective replacement to time-consuming and exacting film measurements. METHODS Beam profiles and positioning scans for 4-mm, 8-mm, and 16-mm-collimated fields were collected along the x-, y-, and z-axes. The Exradin W2-scintillator and the PTW microdiamond-detector were placed in custom inserts centered in the Elekta solid-water phantom for these scans. GafChromic EBT3-film was irradiated with single uniformly collimated exposures as the clinical-standard reference, using the same solid-water phantom for profile tests and the Elekta film holder for radiation focal point (RFP)/patient-positioning system (PPS) coincidence. All experimental data were compared to the tissue-maximum-ratio-based (TMR10) dose calculation. RESULTS The detector-measured beam profiles and film-based profiles showed excellent agreement with TMR10-predicted full-width, half-maximum (FWHM) values. Absolute differences between the measured FWHM and FWHM from the treatment-planning system were on average 0.13 mm, 0.08 mm, and 0.04 mm for film, microdiamond, and scintillator, respectively. The coincidence between the RFP and the PPS was measured to be ≤0.5 mm with microdiamond, ≤0.41 mm with the W2-1 × 1 scintillator, and ≤0.22 mm using the film-technique. CONCLUSIONS Small-volume field detectors, used in conjunction with a clinically available phantom, an electrometer with data-logging, and treatment plans created in clinical mode offer an efficient and viable alternative for film-based profile tests. Position verification can be accurately performed when CBCT-imaging is available to correct for residual detector-position uncertainty. Scans are easily set up within the treatment-planning-system and, when coupled with an automated analysis, can provide accurate measurements within minutes.
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Affiliation(s)
- Benedikt Rudek
- Department of Radiation Oncology, Laura and Isaac Perlmutter Cancer Center, NYU Langone Health, New York, New York, USA
| | - Kenneth Bernstein
- Department of Radiation Oncology, Laura and Isaac Perlmutter Cancer Center, NYU Langone Health, New York, New York, USA
| | - Sunshine Osterman
- Department of Radiation Oncology, NYU Grossman School of Medicine, New York University, New York, New York, USA
| | - Tanxia Qu
- Department of Radiation Oncology, NYU Grossman School of Medicine, New York University, New York, New York, USA
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Parwaie W, Geraily G, Shirazi A, Yarahmadi M, Shakeri A, Ardekani MA. Evaluation of lung heterogeneity effects on dosimetric parameters in small photon fields using MAGIC polymer gel, Gafchromic film, and Monte Carlo simulation. Appl Radiat Isot 2020; 166:109233. [PMID: 32836165 DOI: 10.1016/j.apradiso.2020.109233] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 04/20/2020] [Accepted: 05/17/2020] [Indexed: 10/23/2022]
Abstract
In this work, the performance of MAGIC polymer gel in measuring dosimetric parameters beyond lung heterogeneity in small fields was investigated. All data were obtained using MAGIC, EBT2, and MC in four small field sizes. The maximum local differences between MAGIC and MC were less than 5.1, 3.9, 3.1, and 2.6% for PDD values behind lung heterogeneity at 5, 10, 20, and 30 mm field sizes, respectively. The findings showed that MAGIC is a suitable tool for dosimetry behind low-density heterogeneity.
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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
| | - Ghazale Geraily
- Department of Medical Physics and Biomedical Engineering, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
| | - Alireza Shirazi
- Department of Medical Physics and Biomedical Engineering, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Mehran Yarahmadi
- Department of Medical Physics, Faculty of Medicine, Kurdistan University of Medical Sciences, Sanandaj, Iran
| | - Ahmad Shakeri
- Valiasr Radiotherapy Oncology Center, Valiasr Hospital, Qom, Iran
| | - Mahdieh Afkhami Ardekani
- Department of Radiology, Faculty of Para-Medicine, Hormozgan University of Medical Sciences, Bandar Abbas, Iran.
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Weber C, Kranzer R, Weidner J, Kröninger K, Poppe B, Looe HK, Poppinga D. Small field output correction factors of the microSilicon detector and a deeper understanding of their origin by quantifying perturbation factors. Med Phys 2020; 47:3165-3173. [PMID: 32196683 PMCID: PMC7496769 DOI: 10.1002/mp.14149] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 01/31/2020] [Accepted: 03/13/2020] [Indexed: 11/09/2022] Open
Abstract
PURPOSE The aim of this study is the experimental and Monte Carlo-based determination of small field correction factors for the unshielded silicon detector microSilicon for a standard linear accelerator as well as the Cyberknife System. In addition, a detailed Monte Carlo analysis has been performed by modifying the detector models stepwise to study the influences of the detector's components. METHODS Small field output correction factors have been determined for the new unshielded silicon diode detector, microSilicon (type 60023, PTW Freiburg, Germany) as well as for the predecessors Diode E (type 60017, PTW Freiburg, Germany) and Diode SRS (type 60018, PTW Freiburg, Germany) for a Varian TrueBeam linear accelerator at 6 MV and a Cyberknife system. For the experimental determination, an Exradin W1 scintillation detector (Standard Imaging, Middleton, USA) has been used as reference. The Monte Carlo simulations have been performed with EGSnrc and phase space files from IAEA as well as detector models according to manufacturer blueprints. To investigate the influence of the detector's components, the detector models have been modified stepwise. RESULTS The correction factors for the smallest field size investigated at the TrueBeam linear accelerator (equivalent dosimetric square field side length Sclin = 6.3 mm) are 0.983 and 0.939 for the microSilicon and Diode E, respectively. At the Cyberknife system, the correction factors of the microSilicon are 0.967 at the smallest 5-mm collimator compared to 0.928 for the Diode SRS. Monte Carlo simulations show comparable results from the measurements and literature. CONCLUSION The microSilicon (type 60023) detector requires less correction than its predecessors, Diode E (type 60017) and Diode SRS (type 60018). The detector housing has been demonstrated to cause the largest perturbation, mainly due to the enhanced density of the epoxy encapsulation surrounding the silicon chip. This density has been rendered more water equivalent in case of the microSilicon detector to minimize the associated perturbation. The sensitive volume itself has been shown not to cause observable field size-dependent perturbation except for the volume-averaging effect, where the slightly larger diameter of the sensitive volume of the microSilicon (1.5 mm) is still small at the smallest field size investigated with corrections <2%. The new microSilicon fulfils the 5% correction limit recommended by the TRS 483 for output factor measurements at all conditions investigated in this work.
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Affiliation(s)
- Carolin Weber
- PTW FreiburgFreiburg79115Germany
- TU Dortmund UniversityDortmund44227Germany
| | | | | | | | - Björn Poppe
- University Clinic for Medical Radiation PhysicsMedical Campus Pius HospitalCarl von Ossietzky UniversityOldenburg26121Germany
| | - Hui Khee Looe
- University Clinic for Medical Radiation PhysicsMedical Campus Pius HospitalCarl von Ossietzky UniversityOldenburg26121Germany
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Snyder JD, Sullivan RJ, Wu X, Covington EL, Popple RA. Use of a plastic scintillator detector for patient-specific quality assurance of VMAT SRS. J Appl Clin Med Phys 2020; 20:143-148. [PMID: 31538717 PMCID: PMC6753731 DOI: 10.1002/acm2.12705] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 07/13/2019] [Accepted: 07/25/2019] [Indexed: 11/30/2022] Open
Abstract
Purpose To evaluate a scintillator detector for patient‐specific quality assurance of VMAT radiosurgery plans. Methods The detector was comprised of a 1 mm diameter, 1 mm high scintillator coupled to an acrylic optical fiber. Sixty VMAT SRS plans for treatment of single targets having sizes ranging from 3 mm to 30.2 mm equivalent diameter (median 16.3 mm) were selected. The plans were delivered to a 20 cm × 20 cm x 15 cm water equivalent plastic phantom having either the scintillator detector or radiochromic film at the center. Calibration films were obtained for each measurement session. The films were scanned and converted to dose using a 3‐channel technique. Results The mean difference between scintillator and film was ‒0.45% (95% confidence interval ‒0.1% to 0.8%). For target equivalent diameter smaller than the median, the mean difference was 1.1% (95% confidence interval 0.5% to 1.7%). For targets larger than the median, the mean difference was ‒0.2% (95% confidence interval ‒0.7% to 0.1%). Conclusions The scintillator detector response is independent of target size for targets as small as 3 mm and is well‐suited for patient‐specific quality assurance of VMAT SRS plans. Further work is needed to evaluate the accuracy for VMAT plans that treat multiple targets using a single isocenter.
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Affiliation(s)
- Jesse D Snyder
- Department of Radiation Oncology, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Rodney J Sullivan
- Department of Radiation Oncology, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Xingen Wu
- Department of Radiation Oncology, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Elizabeth L Covington
- Department of Radiation Oncology, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Richard A Popple
- Department of Radiation Oncology, The University of Alabama at Birmingham, Birmingham, AL, USA
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Schönfeld AB, Poppinga D, Kranzer R, De Wilde RL, Willborn K, Poppe B, Looe HK. Technical Note: Characterization of the new microSilicon diode detector. Med Phys 2019; 46:4257-4262. [PMID: 31309594 PMCID: PMC6852691 DOI: 10.1002/mp.13710] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 06/24/2019] [Accepted: 06/24/2019] [Indexed: 12/31/2022] Open
Abstract
Purpose Dosimetric properties of the new microSilicon diode detector (60023) have been studied with focus on application in small‐field dosimetry. The influences of the dimensions of the sensitive volume and the density of the epoxy layer surrounding the silicon chip of microSilicon have been quantified and compared to its predecessor (Diode E 60017) and the microDiamond (60019, all PTW‐Freiburg, Germany). Methods Dose linearity has been studied in the range from 0.01 to 8.55 Gy and dose‐per‐pulse dependence from 0.13 to 0.86 mGy/pulse. The effective point of measurement (EPOM) was determined by comparing measured percentage depth dose curves with a reference curve (Roos chamber). Output ratios were measured for nominal field sizes from 0.5 × 0.5 cm2 to 4 × 4 cm2. The corresponding small‐field output correction factors, k, were derived with a plastic scintillation detector as reference. The lateral dose–response function, K(x), was determined using a slit beam geometry. Results MicroSilicon shows linear dose response (R2 = 1.000) in both low and high dose range up to 8.55 Gy with deviations of only up to 1% within the dose‐per‐pulse values investigated. The EPOM was found to lie (0.7 ± 0.2) mm below the front detector’s surface. The derived k for microSilicon (0.960 at seff = 0.55 cm) is similar to that of microDiamond (0.956), while Diode E requires larger corrections (0.929). This improved behavior of microSilicon in small‐fields is reflected in the slightly wider K(x) compared to Diode E. Furthermore, the amplitude of the negative values in K(x) at the borders of the sensitive volume has been reduced. Conclusions Compared to its predecessor, microSilicon shows improved dosimetric behavior with higher sensitivity and smaller dose‐per‐pulse dependence. Profile measurements demonstrated that microSilicon causes less perturbation in off‐axis measurements. It is especially suitable for the applications in small‐field output factors and profile measurements.
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Affiliation(s)
- Ann-Britt Schönfeld
- University Clinic for Medical Radiation Physics, Medical Campus Pius Hospital, Carl von Ossietzky University, Oldenburg, Germany
| | | | | | | | - Kay Willborn
- Clinic for Radiation Therapy, Pius Hospital, Oldenburg, Germany
| | - Björn Poppe
- University Clinic for Medical Radiation Physics, Medical Campus Pius Hospital, Carl von Ossietzky University, Oldenburg, Germany
| | - Hui Khee Looe
- University Clinic for Medical Radiation Physics, Medical Campus Pius Hospital, Carl von Ossietzky University, Oldenburg, Germany
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Galavis PE, Hu L, Holmes S, Das IJ. Characterization of the plastic scintillation detector Exradin W2 for small field dosimetry. Med Phys 2019; 46:2468-2476. [DOI: 10.1002/mp.13501] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 03/11/2019] [Accepted: 03/11/2019] [Indexed: 11/10/2022] Open
Affiliation(s)
- Paulina E. Galavis
- Department of Radiation Oncology New York University, Langone Medical Center & Laura and Issac Perlmutter Cancer Center New York NY 10016USA
| | - Lei Hu
- Department of Radiation Oncology New York University, Langone Medical Center & Laura and Issac Perlmutter Cancer Center New York NY 10016USA
| | | | - Indra J. Das
- Department of Radiation Oncology New York University, Langone Medical Center & Laura and Issac Perlmutter Cancer Center New York NY 10016USA
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Casar B, Gershkevitsh E, Mendez I, Jurković S, Huq MS. A novel method for the determination of field output factors and output correction factors for small static fields for six diodes and a microdiamond detector in megavoltage photon beams. Med Phys 2018; 46:944-963. [PMID: 30521073 PMCID: PMC7379629 DOI: 10.1002/mp.13318] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 11/21/2018] [Accepted: 11/21/2018] [Indexed: 12/04/2022] Open
Abstract
Purpose The goal of this work is to provide a large and consistent set of data for detector‐specific output correction factors, kQclin,Qreffclin,fref, for small static fields for seven solid‐state detectors and to determine field output factors, ΩQclin,Qreffclin,fref, using EBT3 radiochromic films and W1 plastic scintillator as reference detectors on two different linear accelerators and four megavoltage photon beams. Consistent measurement conditions and recommendations given in the International Code of Practice TRS‐483 for small‐field dosimetry were followed throughout the study. Methods ΩQclin,Qreffclin,fref were determined on two linacs, Elekta Versa HD and Varian TrueBeam, for 6 and 10 MV beams with and without flattening filter and for nine fields ranging from 0.5 × 0.5 cm2 to 10 × 10 cm2. Signal readings obtained with EBT3 radiochromic films and W1 plastic scintillator were fitted by an analytical function. Volume averaging correction factors, determined from two‐dimensional (2D) dose matrices obtained with EBT3 films and fitted to bivariate Gaussian function, were used to correct measured signals. kQclin,Qreffclin,fref were determined empirically for six diodes, IBA SFD, IBA Razor, PTW 60008 P, PTW 60012 E, PTW 60018 SRS, and SN EDGE, and a PTW 60019 microDiamond detector. Results Field output factors and detector‐specific kQclin,Qreffclin,fref are presented in the form of analytical functions as well as in the form of discrete values. It is found that in general, for a given linac, small‐field output factors need to be determined for every combination of beam energy and filtration (WFF or FFF) and field size as the differences between them can be statistically significant (P < 0.05). For different beam energies, the present data for kQclin,Qreffclin,fref are found to differ significantly (P < 0.05) from the corresponding data published in TRS‐483 mostly for the smallest fields (<1.5 cm). For the PTW microDiamond detector, statistically significant differences (P < 0.05) between kQclin,Qreffclin,fref values were found for all investigated beams on an Elekta Versa HD linac for field sizes 0.5 × 0.5 cm2 and 0.8 × 0.8 cm2. Significant differences in kQclin,Qreffclin,fref between beams of a given energy but with and without flattening filters are found for measurements made in small fields (<1.5 cm) at a given linac. Differences in kQclin,Qreffclin,fref are also found when measurements are made at different linacs using the same beam energy filtration combination; for the PTW microDiamond detector, these differences were found to be around 6% and were considered as significant. Conclusions Selection of two reference detectors, EBT3 films and W1 plastic scintillator, and use of an analytical function, is a novel approach for the determination of ΩQclin,Qreffclin,fref for small static fields in megavoltage photon beams. Large set of kQclin,Qreffclin,fref data for seven solid‐state detectors and four beam energies determined on two linacs by a single group of researchers can be considered a valuable supplement to the literature and the TRS‐483 dataset.
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Affiliation(s)
- Božidar Casar
- Department for Dosimetry and Quality of Radiological Procedures, Institute of Oncology Ljubljana, Zaloška 2, 1000, Ljubljana, Slovenia
| | - Eduard Gershkevitsh
- Medical Physics Service, North Estonia Medical Centre, J. Sütiste tee 19, 13419, Tallinn, Estonia
| | - Ignasi Mendez
- Department for Dosimetry and Quality of Radiological Procedures, Institute of Oncology Ljubljana, Zaloška 2, 1000, Ljubljana, Slovenia
| | - Slaven Jurković
- Medical Physics Department, University Hospital Rijeka, Krešimirova 42, 51000, Rijeka, Croatia
| | - M Saiful Huq
- Department of Radiation Oncology, University of Pittsburgh School of Medicine and UPMC Hillman Cancer Center, Pittsburgh, PA, USA
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Looe HK, Büsing I, Tekin T, Brant A, Delfs B, Poppinga D, Poppe B. The polarity effect of compact ionization chambers used for small field dosimetry. Med Phys 2018; 45:5608-5621. [DOI: 10.1002/mp.13227] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 09/24/2018] [Accepted: 09/28/2018] [Indexed: 11/07/2022] Open
Affiliation(s)
- Hui Khee Looe
- University Clinic for Medical Radiation Physics Medical Campus Pius Hospital Carl von Ossietzky University Oldenburg Germany
| | - Isabel Büsing
- University Clinic for Medical Radiation Physics Medical Campus Pius Hospital Carl von Ossietzky University Oldenburg Germany
| | - Tuba Tekin
- University Clinic for Medical Radiation Physics Medical Campus Pius Hospital Carl von Ossietzky University Oldenburg Germany
| | - Andre Brant
- University Clinic for Medical Radiation Physics Medical Campus Pius Hospital Carl von Ossietzky University Oldenburg Germany
| | - Björn Delfs
- University Clinic for Medical Radiation Physics Medical Campus Pius Hospital Carl von Ossietzky University Oldenburg Germany
| | | | - Björn Poppe
- University Clinic for Medical Radiation Physics Medical Campus Pius Hospital Carl von Ossietzky University Oldenburg Germany
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Delfs B, Poppinga D, Ulrichs AB, Kapsch RP, Harder D, Poppe B, Looe HK. The 1D lateral dose response functions of photon-dosimetry detectors in magnetic fields—measurement and Monte-Carlo simulation. ACTA ACUST UNITED AC 2018; 63:195002. [DOI: 10.1088/1361-6560/aadd3d] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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