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Angelou C, Patallo IS, Doherty D, Romano F, Schettino G. A review of diamond dosimeters in advanced radiotherapy techniques. Med Phys 2024. [PMID: 39221583 DOI: 10.1002/mp.17370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2024] [Revised: 07/08/2024] [Accepted: 08/10/2024] [Indexed: 09/04/2024] Open
Abstract
This review article synthesizes key findings from studies on the use of diamond dosimeters in advanced radiotherapy techniques, showcasing their applications, challenges, and contributions to enhancing dosimetric accuracy. The article explores various dosimeters, highlighting synthetic diamond dosimeters as potential candidates especially due to their high spatial resolution and negligible ion recombination effect. The clinically validated commercial dosimeter, PTW microDiamond (mD), faces limitations in small fields, proton and hadron therapy and ultra-high dose per pulse (UHDPP) conditions. Variability in reported values for field sizes < $<$ 2 × $\times$ 2cm 2 ${\rm cm}^2$ is noted, reflecting the competition between volume averaging and density perturbation effects. PTW's introduction of flashDiamond (fD) holds promise for dosimetric measurements in UHDPP conditions and is reliable for commissioning ultra-high dose rate (UHDR) electron beam systems, pending the clinical validation of the device. Other advancements in diamond detectors, such as in 3D configurations and real-time dose per pulse x-ray detectors, are considered valuable in overcoming challenges posed by modern radiotherapy techniques, alongside relative dosimetry and pre-treatment verifications. The studies discussed collectively provide a comprehensive overview of the evolving landscape of diamond dosimetry in the field of radiotherapy, and offer insights into future directions for research and development in the field.
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Affiliation(s)
- Christina Angelou
- Department of Physics, University of Surrey, Guildford, UK
- Radiotherapy and Radiation Dosimetry, National Physical Laboratory (NPL), Teddington, UK
| | | | - Daniel Doherty
- Department of Physics, University of Surrey, Guildford, UK
| | - Francesco Romano
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Catania, Catania, Italy
| | - Giuseppe Schettino
- Radiotherapy and Radiation Dosimetry, National Physical Laboratory (NPL), Teddington, UK
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Alashkar EM, Abdelhafez HM, Kenawy MA, Hassan GM, Ereiba KT, Megahed A. Comparison Flattening Filter and Flattening Filter-Free Techniques in Small-Fields Dosimetry with Various Types of Detectors. Asian Pac J Cancer Prev 2024; 25:2105-2112. [PMID: 38918673 PMCID: PMC11382863 DOI: 10.31557/apjcp.2024.25.6.2105] [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: 01/27/2024] [Indexed: 06/27/2024] Open
Abstract
PURPOSE The aim of this study was to investigate the detector size effect on small-field dosimetry and compare the performance of 6MV WFF/FFF techniques. METHODS We investigated the detector size effect on small-field dosimetry and compared the performance of 6MV WFF/FFF techniques. PDD, profile curves, and absorbed dose were measured in water under reference conditions with 6MV (WFF/FFF) techniques. We employed Farmer FC65-P, CC13, CC01, and IBA Razor diode, with Versa Lineac. Subsequently, we replicated this assessment for small-fields under 5cmx5cm dimensions. RESULTS For both 6MV WFF/FFF, significant dose differences (Dmax=1.47cm), were ±4.55%, ±6.7, ±12.75% and ±33.3% for 4cmx4cm, 3cmx3cm, 2cmx2cm, and 1cmx1cm, respectively. The average difference relative to D10 was observed to be ±4.66%, ±5.73%, ±6.58%, and ±8.75% for the previous field sizes. Differences between WFF/FFF are neglected values at all field sizes>2.3%, also, the output of the largest detector FC65-P is lower at 55% in the smallest field size. Variation in the profile doesn't exceed a difference of >5% in flatness between WFF/FFF at depth10cm, across all fields, while symmetry is >1%, but radiation output is considerably lower at 55% for FC65-P chamber in 2cmx2cm, 1cmx1cm compared to the CC01 chamber and Razor diode. Significant differences in 1cmx1cm, where FC65-P chamber exhibits around 49% difference compared to Razor diode with 6MV (WFF/FFF). Conclusions: Significant differences were observed in doses with various detectors. Detector-size influences the dose. WFF/FFF techniques show no major differences in small-fields dosimetry. Utilize some situations the advantage of FFF boasting a higher dose rate, consequently reducing treatment time to half.
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Affiliation(s)
- Elsayed M Alashkar
- Physics Department, Faculty of Science, Al-Azhar University, Cairo, Egypt
| | | | - Mahmoud A Kenawy
- Physics Department, Faculty of Science, Al-Azhar University, Cairo, Egypt
- Radiology Techniques Department, College of Health and Medical Techniques, Al-Mustaqbal University, Iraq
| | - Gamal M Hassan
- Ionizing Radiation Metrology Laboratory, National Institute of Standards (NIS), Giza, Egypt
| | - Khairy T Ereiba
- Physics Department, Faculty of Science, Al-Azhar University, Cairo, Egypt
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Chi DD, Toan TN, Hill R. A multi-detector comparison to determine convergence of measured relative output factors for small field dosimetry. Phys Eng Sci Med 2024; 47:371-379. [PMID: 37943444 DOI: 10.1007/s13246-023-01351-3] [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: 12/22/2021] [Accepted: 10/24/2023] [Indexed: 11/10/2023]
Abstract
The TRS-483 Code of Practice (CoP) provides generic relative output correction factors, [Formula: see text], for a range of detectors and beam energies as used in small field dosimetry. In this work, the convergence of the relative output factors (ROFs) for 6 MV X-ray beams with and without flattening filters was investigated under different combinations of beam collimation and published detector correction factors. The SFD, PFD and CC04 (IBA) were used to measure ROFs of a TrueBeam STx linear accelerator with small fields collimated by the high-definition MLC, which has 2.5 and 5.0 mm projected leaves. Two configurations were used for the collimators: (1) fixed jaws at 10 × 10 cm2 and (2) with a 2 mm offset from the MLC edge, in line with the recommended geometry from IROC-H as part of their auditing program and published dataset. The [Formula: see text] factors for the three detectors were taken from the TRS483 CoP and other published works. The average differences of ROFs measured by detectors under MLC fields with fixed jaws and with 2 mm jaws offset for the 6 MV-WFF beam are 1.4% and 1.9%, respectively. Similarly, they are 2.3% and 2.4% for the 6MV-FFF beam. The relative differences between the detector-average ROFs and the corresponding IROC-H dataset are 2.0% and 3.1% for the 6 MV-WFF beam, while they are 2.4% and 3.2% for the 6MV-FFF beam at the smallest available field size of 2 × 2 cm2. For smaller field sizes, the average ROFs of the three detectors and corresponding results from Akino and Dufreneix showed the largest difference to be 6.6% and 6.2% under the 6 MV-WFF beam, while they are 3.4% and 3.6% under the 6 MV-WFF beam at the smallest field size of 0.5 × 0.5 cm2. Some well-published specific output correction factors for different small field detector types give better convergence in the calculation of the relative output factor in comparison with the generic data provided by the TRS-483 CoP. Relative output factor measurements should be performed as close as possible to the clinical settings including a combination of collimation systems, beam types and using at least three different types of small field detector for more accurate computation of the treatment planning system. The IROC-H dataset is not available for field size smaller than 2 × 2 cm2 for double checks and so that user should carefully check with other publications with the same setting.
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Affiliation(s)
- Do Duc Chi
- 108 Military Central Hospital, Hanoi, Vietnam.
- Vietnam Atomic Energy Institute, Hanoi, Vietnam.
| | | | - Robin Hill
- Department of Radiation Oncology, Chris O'Brien Lifehouse, Missenden Rd, Camperdown, Sydney, NSW, 2050, Australia
- Arto Hardy Family Biomedical Innovation Hub, Chris O'Brien Lifehouse, Missenden Rd, Camperdown, Sydney, NSW, 2050, Australia
- Institute of Medical Physics, School of Physics, The University of Sydney, Sydney, NSW, 2006, Australia
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Casar B, Mendez I, Gershkevitsh E, Wegener S, Jaffray D, Heaton R, Pesznyak C, Stelczer G, Bulski W, Chełminski K, Smirnov G, Antipina N, Beavis AW, Harding N, Jurković S, Hwang MS, Saiful Huq M. On dosimetric characteristics of detectors for relative dosimetry in small fields: a multicenter experimental study. Phys Med Biol 2024; 69:035009. [PMID: 38091616 DOI: 10.1088/1361-6560/ad154c] [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: 07/21/2023] [Accepted: 12/13/2023] [Indexed: 01/25/2024]
Abstract
Objective. In this multicentric collaborative study, we aimed to verify whether the selected radiation detectors satisfy the requirements of TRS-483 Code of Practice for relative small field dosimetry in megavoltage photon beams used in radiotherapy, by investigating four dosimetric characteristics. Furthermore, we intended to analyze and complement the recommendations given in TRS-483.Approach. Short-term stability, dose linearity, dose-rate dependence, and leakage were determined for 17 models of detectors considered suitable for small field dosimetry. Altogether, 47 detectors were used in this study across ten institutions. Photon beams with 6 and 10 MV, with and without flattening filters, generated by Elekta Versa HDTMor Varian TrueBeamTMlinear accelerators, were used.Main results. The tolerance level of 0.1% for stability was fulfilled by 70% of the data points. For the determination of dose linearity, two methods were considered. Results from the use of a stricter method show that the guideline of 0.1% for dose linearity is not attainable for most of the detectors used in the study. Following the second approach (squared Pearson's correlation coefficientr2), it was found that 100% of the data fulfill the criteriar2> 0.999 (0.1% guideline for tolerance). Less than 50% of all data points satisfied the published tolerance of 0.1% for dose-rate dependence. Almost all data points (98.2%) satisfied the 0.1% criterion for leakage.Significance. For short-term stability (repeatability), it was found that the 0.1% guideline could not be met. Therefore, a less rigorous criterion of 0.25% is proposed. For dose linearity, our recommendation is to adopt a simple and clear methodology and to define an achievable tolerance based on the experimental data. For dose-rate dependence, a realistic criterion of 1% is proposed instead of the present 0.1%. Agreement was found with published guidelines for background signal (leakage).
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Affiliation(s)
- Božidar Casar
- Institute of Oncology Ljubljana, Ljubljana, Slovenia
- Faculty of Natural Sciences and Mathematics, University of Maribor, Slovenia
| | - Ignasi Mendez
- Institute of Oncology Ljubljana, Ljubljana, Slovenia
| | | | - Sonja Wegener
- University of Wuerzburg, Radiation Oncology, Wuerzburg, Germany
| | | | | | | | | | - Wojciech Bulski
- Maria Skłodowska-Curie National Research Institute of Oncology, Warsaw, Poland
| | | | | | | | - Andrew W Beavis
- Hull University Teaching Hospitals NHS Trust, Hull, United Kingdom
| | - Nicholas Harding
- Hull University Teaching Hospitals NHS Trust, Hull, United Kingdom
| | - Slaven Jurković
- Medical Physics Department, University Hospital Rijeka, Rijeka, Croatia
- Faculty of Medicine, University of Rijeka, Croatia
| | - Min-Sig Hwang
- University of Pittsburgh School of Medicine and UPMC Hillman Cancer Center, Pittsburgh, PA, United States of America
| | - M Saiful Huq
- Department of Radiation Oncology, Division of Medical Physics, University of Pittsburgh School of Medicine and UPMC Hillman Cancer Center, Pittsburgh, PA, United States of America
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Tahmasbi M, Capela M, Santos T, Mateus J, Ventura T, do Carmo Lopes M. Particular issues to be considered in small field dosimetry for TrueBeam STx commissioning. Appl Radiat Isot 2023; 202:111066. [PMID: 37865066 DOI: 10.1016/j.apradiso.2023.111066] [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: 11/09/2022] [Revised: 08/28/2023] [Accepted: 10/05/2023] [Indexed: 10/23/2023]
Abstract
This study aims to report the relevant issues concerning small fields in the commissioning of a TrueBeam STx for photon energies of 6MV, 10MV, 6FFF, and 10FFF. Percent depth doses, profiles, and field output factors were measured according to the beam model configuration of the treatment planning system. Multiple detectors were used based on the IAEA TRS-483 protocol as well as EBT3 radiochromic film. Analytical Anisotropic and Acuros XB algorithms, were configured and validated through basic dosimetry comparisons and end-to-end clinical tests.
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Affiliation(s)
- Marziyeh Tahmasbi
- Radiologic Technology Department, School of Allied Medical Sciences, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran; Medical Physics Department, Instituto Portugues de Oncologia Coimbra Francisco Gentil, E.P.E., Portugal.
| | - Miguel Capela
- Medical Physics Department, Instituto Portugues de Oncologia Coimbra Francisco Gentil, E.P.E., Portugal
| | - Tania Santos
- Medical Physics Department, Instituto Portugues de Oncologia Coimbra Francisco Gentil, E.P.E., Portugal
| | - Josefina Mateus
- Medical Physics Department, Instituto Portugues de Oncologia Coimbra Francisco Gentil, E.P.E., Portugal
| | - Tiago Ventura
- Medical Physics Department, Instituto Portugues de Oncologia Coimbra Francisco Gentil, E.P.E., Portugal
| | - Maria do Carmo Lopes
- Medical Physics Department, Instituto Portugues de Oncologia Coimbra Francisco Gentil, E.P.E., Portugal
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Neupane T, Shang C, Kassel M, Muhammad W, Leventouri T, Williams TR. Viability of the virtual cone technique using a fixed small multi-leaf collimator field for stereotactic radiosurgery of trigeminal neuralgia. J Appl Clin Med Phys 2023; 24:e14148. [PMID: 37722766 PMCID: PMC10691631 DOI: 10.1002/acm2.14148] [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: 11/09/2022] [Revised: 08/04/2023] [Accepted: 08/20/2023] [Indexed: 09/20/2023] Open
Abstract
Dosimetric uncertainties in very small (≤1.5 × 1.5 cm2 ) photon fields are remarkably higher, which undermines the validity of the virtual cone (VC) technique with a diminutive and variable MLC fields. We evaluate the accuracy and reproducibility of the VC method with a very small, fixed MLC field setting, called a fixed virtual cone (fVC), for small target radiosurgery such as trigeminal neuralgia (TGN). The fVC is characterized by 0.5 cm x 0.5 cm high-definition (HD) MLC field of 10MV FFF beam defined at 100 cm SAD, while backup jaws are positioned at 1.5 cm x 1.5 cm. A spherical dose distribution equivalent to 5 mm (diameter) physical cone was generated using 10-14 non-coplanar, partial arcs. Dosimetric accuracy was validated using SRS diode (PTW 60018), SRS MapCHECK (SNC) measurements. As a quality assurance measure, 10 treatment plans (SRS) for TGN, consisting of various arc ranges at different collimator angles were analyzed using 6 MV FFF and 10 MV FFF beams, including a field-by-field study (n = 130 fields). Dose outputs were compared between the Eclipse TPS and measurements (SRS MapCHECK). Moreover, dosimetric changes in the field defining fVC, prompted by a minute (± 0.5-1.0 mm) leaf shift, was examined among TPS, diode measurements, and Monte Carlo (MC) simulations. The beam model for fVC was validated (≤3% difference) using SRS MapCHECK based absolute dose measurements. The equivalent diameters of the 50% isodose distribution were found comparable to that of a 5 mm cone. Additionally, the comparison of field output factors, dose per MU between the TPS and SRS diode measurements using the fVC field, including ± 1 mm leaf shift, yielded average discrepancies within 5.5% and 3.5% for 6 MV FFF and 10 MV FFF beams, respectively. Overall, the fVC method is a credible alternative to the physical cone (5 mm) that can be applied in routine radiosurgical treatment of TGN.
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Affiliation(s)
- Taindra Neupane
- Department of PhysicsFlorida Atlantic UniversityBoca RatonFloridaUSA
| | - Charles Shang
- RSOSouth Florida Proton Therapy InstituteDelray BeachFloridaUSA
| | - Maxwell Kassel
- Department of PhysicsFlorida Atlantic UniversityBoca RatonFloridaUSA
| | - Wazir Muhammad
- Department of PhysicsFlorida Atlantic UniversityBoca RatonFloridaUSA
| | - Theodora Leventouri
- Center for Biological and Materials Physics (CBAMP)Department of PhysicsFlorida Atlantic UniversityBoca RatonFloridaUSA
| | - Timothy R. Williams
- Medical DirectorSouth Florida Proton Therapy InstituteDelray BeachFloridaUSA
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Ringholz J, Sauer OA, Wegener S. Small field output correction factors at 18 MV. Med Phys 2023; 50:7177-7191. [PMID: 37531177 DOI: 10.1002/mp.16635] [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: 11/15/2022] [Revised: 04/25/2023] [Accepted: 04/30/2023] [Indexed: 08/03/2023] Open
Abstract
BACKGROUND The response of various detectors in the radiotherapy energy range has been investigated, especially for 6 and 10 MV energies for small fields, and is summarized in TRS-483. However, data for accelerator energies above 10 MV are sparse or unavailable for many detectors, especially for the energy of 18 MV. Small variations in field output factors for the commissioning of a treatment planning system can have a high impact on calculation of dose distributions. PURPOSE Many studies describe an energy dependence of the response for a large number of detectors. We wanted to close the gap for the 18 MV energy regime and determined field output correction factors for different detectors at 18 MV. METHODS An ELEKTA Versa HD accelerator at 18 MV was used together with a PTW MP3 water phantom at an SSD of 90 cm. The following detectors were examined: PTW Semiflex 31021, PinPoint 3D 31022, diode 60012, diode 60008 and microDiamond 60019, Sun Nuclear EDGE detector, IBA PFD, SFD, Razor Chamber, Razor Nano Chamber and Razor Diode, Standard Imaging Scintillator Exradin W2 1x3, W2 1x1 and Gafchromic EBT3 film. The dose response was determined at a depth of 10 cm for square fields between 0.5 and 10 cm side length. As reference data a composure of radiochromic film data for small fields (s ≤ 3 $s\le 3$ cm) and data of all compatible chambers for larger fields (s ≥ 3 $s\ge 3$ cm) was used. The effective field sizes of small fields were determined from profiles obtained on radiochromic film. The obtained field output correction factors obey the rules of the TRS-483 protocol. RESULTS The W2 1x1 scintillator and the Razor Chamber showed the smallest deviations from the reference curve. The shielded diodes (diode 60008, EDGE detector) showed the highest over-response at small fields, followed by PFD, microDiamond and the unshielded diodes (diode 60012, SFD). The ionization chambers exhibited the well-known volume effect, that is, strong under-response at small fields of up to 9% for the PinPoint 3D, 7% for the Razor Chamber and up to 30% for the Semiflex detector for the smallest studied field size. The small chambers showed a polarity effect in axial orientation, especially the Razor Nano Chamber. Corrections at 18 MV are generally larger than those provided by TRS-483, continuing the trend of increasing corrections between 6 and 10 MV also at a higher accelerator energy. Only the PinPoint 3D Chamber showed a slightly smaller correction. CONCLUSIONS Field output correction factors were determined for square field sizes between 0.5 and 10 cm at 18 MV. Most detectors needed a larger correction than at 6 and 10 MV. Thus, the use of correction factors will improve beam data for 18 MV.
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Affiliation(s)
- Jonas Ringholz
- Department of Radiation Oncology, University Hospital Würzburg, Würzburg, Germany
| | - Otto A Sauer
- Department of Radiation Oncology, University Hospital Würzburg, Würzburg, Germany
| | - Sonja Wegener
- Department of Radiation Oncology, University Hospital Würzburg, Würzburg, Germany
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Knill C, Sandhu R, Loughery B, Lin L, Halford R, Drake D, Snyder M. Commissioning and validation of a Monte Carlo algorithm for spine stereotactic radiosurgery. J Appl Clin Med Phys 2023; 24:e14092. [PMID: 37431696 PMCID: PMC10647963 DOI: 10.1002/acm2.14092] [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: 11/15/2022] [Revised: 06/12/2023] [Accepted: 06/15/2023] [Indexed: 07/12/2023] Open
Abstract
PURPOSE A 6FFF Monte Carlo (MC) dose calculation algorithm was commissioned for spine stereotactic radiosurgery (SRS). Model generation, validation, and ensuing model tuning are presented. METHODS The model was generated using in-air and in-water commissioning measurements of field sizes between 10 and 400 mm2 . Commissioning measurements were compared to simulated water tank MC calculations to validate output factors, percent depth doses (PDDs), profile sizes and penumbras. Previously treated Spine SRS patients were re-optimized with the MC model to achieve clinically acceptable plans. Resulting plans were calculated on the StereoPHAN phantom and subsequently delivered to the microDiamond and SRSMapcheck to verify calculated dose accuracy. Model tuning was performed by adjusting the model's light field offset (LO) distance between physical and radiological positions of the MLCs, to improve field size and StereoPHAN calculation accuracy. Following tuning, plans were generated and delivered to an anthropomorphic 3D-printed spine phantom featuring realistic bone anatomy, to validate heterogeneity corrections. Finally, plans were validated using polymer gel (VIPAR based formulation) measurements. RESULTS Compared to open field measurements, MC calculated output factors and PDDs were within 2%, profile penumbra widths were within 1 mm, and field sizes were within 0.5 mm. Calculated point dose measurements in the StereoPHAN were within 0.26% ± 0.93% and -0.10% ± 1.37% for targets and spinal canals, respectively. Average SRSMapcheck per-plan pass rates using a 2%/2 mm/10% threshold relative gamma analysis was 99.1% ± 0.89%. Adjusting LOs improved open field and patient-specific dosimetric agreement. Anthropomorphic phantom measurements were within -1.29% ± 1.00% and 0.27% ± 1.36% of MC calculated for the vertebral body (target) and spinal canal, respectively. VIPAR gel measurements confirmed good dosimetric agreement near the target-spine junction. CONCLUSION Validation of a MC algorithm for simple fields and complex SRS spine deliveries in homogeneous and heterogeneous phantoms has been performed. The MC algorithm has been released for clinical use.
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Affiliation(s)
- Cory Knill
- Department of Radiation OncologyCorewell Health William Beaumont University HospitalRoyal OakMichiganUSA
| | - Raminder Sandhu
- Department of Radiation OncologyCorewell Health William Beaumont University HospitalRoyal OakMichiganUSA
| | - Brian Loughery
- Department of Radiation OncologyCorewell Health William Beaumont University HospitalRoyal OakMichiganUSA
| | - Lifeng Lin
- Department of Radiation OncologyCorewell Health William Beaumont University HospitalRoyal OakMichiganUSA
| | - Robert Halford
- Department of Radiation OncologyCorewell Health William Beaumont University HospitalRoyal OakMichiganUSA
| | - Doug Drake
- Department of Radiation OncologyCorewell Health William Beaumont University HospitalRoyal OakMichiganUSA
| | - Michael Snyder
- Department of Radiation OncologyCorewell Health William Beaumont University HospitalRoyal OakMichiganUSA
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Šegedin N, Hršak H, Babić SD, Jurković S. Determination of volume averaging correction factors using an elliptical absorbed dose model for Gamma Knife Perfexion. J Appl Clin Med Phys 2023; 24:e14109. [PMID: 37632162 PMCID: PMC10562043 DOI: 10.1002/acm2.14109] [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: 05/02/2023] [Revised: 06/06/2023] [Accepted: 07/17/2022] [Indexed: 08/27/2023] Open
Abstract
PURPOSE The purpose of this study is to calculate volume averaging correction factors for detectors used in the dosimetry of Gamma Knife's narrow photon beams, and to determine the impact of volume averaging on the field output correction factor. METHODS Simulations of different Gamma Knife fields were done using elliptical dose model formalism with newly introduced fit functions. To determine volume averaging correction factors a calculation of the absorbed dose over the volume of the detector was performed. The elliptical dose model was tested with respect to absorbed dose distribution for different volumes and compared with the calculations of Leksell GammaPlan v.11.3.1. RESULTS The largest differences in absorbed dose calculated by the elliptical model and Leksell GammaPlan are 2.25%, 1.5%, and 0.6% for 16, 8, and 4 mm field sizes, respectively. Volume averaging correction factors were determined for six ionization chambers, five semiconductor detectors, a diamond, and two plastic scintillator detectors. In general, for all examined detectors the impact of volume averaging is more pronounced for smaller field sizes. All studied ionization chambers had a larger volume than other detectors, therefore the volume averaging correction factors for ionization chambers are larger for all investigated field sizes. Besides the fact that plastic scintillator detectors can be considered tissue-equivalent, volume averaging correction factor should be applied. CONCLUSION Volume averaging correction factors for different detectors are determined and suitable detectors for dosimetry of Gamma Knife's narrow photon beams are recommended. It is shown that volume averaging has a dominant contribution to a field output correction factor.
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Affiliation(s)
- Nikola Šegedin
- Department for Physics and BiophysicsSchool of MedicineUniversity of ZagrebZagrebCroatia
| | - Hrvoje Hršak
- Department for Medical PhysicsUniversity Hospital Centre ZagrebZagrebCroatia
| | - Sanja Dolanski Babić
- Department for Physics and BiophysicsSchool of MedicineUniversity of ZagrebZagrebCroatia
| | - Slaven Jurković
- Department for Medical Physics and BiophysicsFaculty of MedicineUniversity of RijekaRijekaCroatia
- Department for Medical Physics and Radiation ProtectionUniversity Hospital Centre RijekaRijekaCroatia
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Younes T, Chatrie F, Zinutti M, Simon L, Fares G, Vieillevigne L. Optimization of the Eclipse TPS beam configuration parameters for small field dosimetry using Monte Carlo simulations and experimental measurements. Phys Med 2023; 114:103141. [PMID: 37820506 DOI: 10.1016/j.ejmp.2023.103141] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 08/24/2023] [Accepted: 09/19/2023] [Indexed: 10/13/2023] Open
Abstract
PURPOSE To evaluate the impact of tuning the beam configurations parameters on the Analytical Anisotropic Algorithm (AAA) and the Acuros XB (AXB) algorithm for small fields using Monte Carlo simulations and measurements. METHODS The TrueBeam STx with the high-definition 120 multi-leaf collimator (HD120-MLC) was modeled with Geant4 application for emission tomography (GATE) Monte Carlo platform and validated against measurements. The impact of varying the effective spot size (ESS) and dosimetric leaf gap (DLG) on AAA and AXB calculations was carried out for small MLC-fields ranging from 0.5×0.5 cm2 to 3 × 3 cm2. Beam penumbras, field sizes and output factors calculated by AAA and AXB were compared to GATE calculations and measurements. RESULTS The beam penumbra comparisons showed that the best ESS value for AXB was about 1.0 mm in the crossplane direction and 0.5 mm in the inplane direction. By optimizing the ESS values, AXB could provide output factor results almost within 2% of GATE calculations and measurements for fields down to 0.5×0.5 cm2. For AAA, significant output factor differences were observed for all ESS values and tuning the DLG in addition to the ESS optimization resulted in an absorbed dose difference of less than 2.5% for MLC-fields down to 1 × 1 cm2. CONCLUSION By optimizing the ESS values, AXB can achieve accurate output factors in the case of small MLC-fields without the need of DLG tuning. Nevertheless, compromises between the output factor, DLG and ESS values were found necessary for AAA calculations. A MLC model improvement would allow to avoid the complexity related to tuning the configuration parameters.
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Affiliation(s)
- Tony Younes
- Department of Medical Physics, Institut Claudius Regaud - Institut Universitaire du Cancer de Toulouse Oncopole, 1 avenue Irène Joliot Curie, 31059 Toulouse Cedex 9, France; Centre de Recherche et de Cancérologie de Toulouse, UMR1037 INSERM - Université Toulouse 3 - ERL5294 CNRS, 2 avenue Hubert Curien, 31037 Toulouse Cedex 1, France; Laboratoire de "Mathématiques et Applications", Unité de recherche "Mathématiques et Modélisation", Centre d'analyses et de recherche, Faculté des sciences, Université Saint-Joseph, Beyrouth 1104 2020, Lebanon.
| | - Frédéric Chatrie
- Centre de Recherche et de Cancérologie de Toulouse, UMR1037 INSERM - Université Toulouse 3 - ERL5294 CNRS, 2 avenue Hubert Curien, 31037 Toulouse Cedex 1, France
| | - Marianne Zinutti
- Department of Medical Physics, Institut Claudius Regaud - Institut Universitaire du Cancer de Toulouse Oncopole, 1 avenue Irène Joliot Curie, 31059 Toulouse Cedex 9, France
| | - Luc Simon
- Department of Medical Physics, Institut Claudius Regaud - Institut Universitaire du Cancer de Toulouse Oncopole, 1 avenue Irène Joliot Curie, 31059 Toulouse Cedex 9, France; Centre de Recherche et de Cancérologie de Toulouse, UMR1037 INSERM - Université Toulouse 3 - ERL5294 CNRS, 2 avenue Hubert Curien, 31037 Toulouse Cedex 1, France
| | - Georges Fares
- Laboratoire de "Mathématiques et Applications", Unité de recherche "Mathématiques et Modélisation", Centre d'analyses et de recherche, Faculté des sciences, Université Saint-Joseph, Beyrouth 1104 2020, Lebanon
| | - Laure Vieillevigne
- Department of Medical Physics, Institut Claudius Regaud - Institut Universitaire du Cancer de Toulouse Oncopole, 1 avenue Irène Joliot Curie, 31059 Toulouse Cedex 9, France; Centre de Recherche et de Cancérologie de Toulouse, UMR1037 INSERM - Université Toulouse 3 - ERL5294 CNRS, 2 avenue Hubert Curien, 31037 Toulouse Cedex 1, France
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Kawata K, Hirashima H, Tsuruta Y, Sasaki M, Matsushita N, Fujimoto T, Nakamura M, Nakata M. Applicability evaluation of the TRS-483 protocol for the determination of small-field output factors using different multi-leaf collimator and field-shaping types. Phys Med 2023; 113:102664. [PMID: 37573811 DOI: 10.1016/j.ejmp.2023.102664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 08/06/2023] [Accepted: 08/07/2023] [Indexed: 08/15/2023] Open
Abstract
PURPOSE To evaluate the applicability of TRS-483 output correction factors (CFs) for small-field output factors (OFs) using different multi-leaf collimators (MLC) and field-shaping types. METHODS All measurements were performed on TrueBeam, TrueBeam STx, and Halcyon using 6 MV flattening filter-free energy. Four detectors, including CC01, CC04, microDiamond, and EDGE, were used. Nominal field sizes ranging from 1 × 1 to 4 × 4, and 10 × 10 cm2 were used to measure small-field OFs at source-to-axis distance of 100 cm with a 0° gantry angle in a 3D water phantom. Further, the field-shaping types were defined using jaw collimator or MLC (five different configurations). A field size of 10 × 10 cm2 was used as the reference for calculation of OFs obtained as ratio of detector readings (OFdet). The percentage difference and coefficient of variation of OFdet and OFdet corrected by applying CF were compared for each field size and configuration. RESULTS For OFdet corrected by applying CF, the ranges of percentage difference and coefficient of variation in all configurations for ≥ 2 × 2 cm2 fields were reduced from 1.2-2.2 to 0.8-1.3 percentage points (%pt) and from 0.5-1.0 to 0.4-0.7%, respectively. For 1 × 1 cm2 field, the ranges of percentage difference and coefficient of variation were reduced from 3.3-5.7 to 1.2-2.2 %pt and from 2.2-3.7 to 0.8-1.1%, respectively. CONCLUSIONS The CFs described in TRS-483 dosimetry protocol have broad applicability in reducing OF variations between detectors under different MLC and field-shaping types.
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Affiliation(s)
- Kohei Kawata
- Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan
| | - Hideaki Hirashima
- Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan.
| | - Yusuke Tsuruta
- Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan; Department of Advanced Medical Physics, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Makoto Sasaki
- Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan
| | - Norimasa Matsushita
- Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan
| | - Takahiro Fujimoto
- Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan
| | - Mitsuhiro Nakamura
- Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan; Department of Advanced Medical Physics, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Manabu Nakata
- Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan
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12
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Kannan M, Saminathan S, Chandraraj V, Raj DG, Ganesh KM. Evaluation of International Atomic Energy Agency Technical Report Series-483 Detector-specific Output Correction Factor for Various Collimator Systems. J Med Phys 2023; 48:281-288. [PMID: 37969152 PMCID: PMC10642599 DOI: 10.4103/jmp.jmp_59_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: 04/28/2023] [Revised: 06/25/2023] [Accepted: 07/01/2023] [Indexed: 11/17/2023] Open
Abstract
Aim In this study, a 6MV flattening filter (FF) and 6MV FF Free (FFF) photon beam small-field output factors (OF) were measured with various collimators using different detectors. The corrected OFs were compared with the treatment planning system (TPS) calculated OFs. Materials and Methods OF measurements were performed with four different types of collimators: Varian Millennium multi-leaf collimator (MLC), Elekta Agility MLC, Apex micro-MLC (mMLC) and a stereotactic cone. Ten detectors (four ionization chambers and six diodes) were used to perform the OF measurements at a depth of 10 cm with a source-to-surface distance of 90 cm. The corrected OF was calculated from the measurements. The corrected OFs were compared with existing TPS-generated OFs. Results The use of detector-specific output correction factor (OCF) in the PTW diode P detector reduced the OF uncertainty by <4.1% for 1 cm × 1 cm Sclin. The corrected OF was compared with TPS calculated OF; the maximum variation with the IBA CC01 chamber was 3.75%, 3.72%, 1.16%, and 0.90% for 5 mm stereotactic cone, 0.49 cm × 0.49 cm Apex mMLC, 1 cm × 1 cm Agility MLC, and 1 cm × 1 cm Millennium MLC, respectively. Conclusion The technical report series-483 protocol recommends that detector-specific OCF should be used to calculate the corrected OF from the measured OF. The implementation of OCF in the TPS commissioning will reduce the small-field OF variation by <3% for any type of detector.
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Affiliation(s)
- Mageshraja Kannan
- Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bengaluru, Karnataka, India
| | - Sathiyan Saminathan
- Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bengaluru, Karnataka, India
| | - Varatharaj Chandraraj
- Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bengaluru, Karnataka, India
| | - D. Gowtham Raj
- 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
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13
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Kannan M, Saminathan S, Chandraraj V, Gowtham Raj D, Ganesh KM. Determination of small-field output factors for beam-matched linear accelerators using various detectors and comparison of detector-specific output correction factors using IAEA Technical Report Series 483 protocol. Rep Pract Oncol Radiother 2023; 28:241-254. [PMID: 37456703 PMCID: PMC10348327 DOI: 10.5603/rpor.a2023.0024] [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: 11/19/2022] [Accepted: 04/06/2023] [Indexed: 07/18/2023] Open
Abstract
Background Beam matching is widely used to ensure that linear accelerators used in radiotherapy have equal dosimetry characteristics. Small-field output factors (OF) were measured using different detectors infour beam-matched linear accelerators and the measured OFs were compared with existing treatment planning system (TPS) Monte Carlo algorithm calculated OFs. Materials and methods Three Elekta Versa HDTM and one Elekta InfinityTMlinear accelerators with photon energies of 6 MV flattening filter (FF), 10 MVFF, 6 MV flattening filter free (FFF) and 10 MVFFF were used in this study. All the Linac'swere beam-matched, Dosimetry beam data were ± 1% compare with Reference Linac. Ten different type of detectors (four ionizationchambers and six diode detectors) were used for small-field OF measurements. The OFs were measured for field sizes of 1 × 1 to 10 × 10 cm2, and normalized to 10 × 10 cm2 field size. The uncorrected and corrected OFs were calculated from these measurements. The corrected OF was compare with existing treatment planning system (TPS) Monte Carlo algorithm calculated OFs. Results The small-field corrected and Uncorrected OF variations among the linear accelerators was within 1% for all energies and detectors. An increase in field size led to a reduction in the difference between OFs among the detectors, which was the case for all energies. The RSD values decreased with increasing field size. The TRS 483 provided Detector-specificoutput-correction factor (OCF) reduced uncertainty in small-field measurements. Conclusion It is necessary to implement the OF-correction of small fields in a TPS. Special care must be taken to incorporate the corrected small-field OF in a TPS.
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Affiliation(s)
- Mageshraja Kannan
- Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bengaluru, Karnataka, India
| | - Sathiyan Saminathan
- Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bengaluru, Karnataka, India
| | - Varatharaj Chandraraj
- Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bengaluru, Karnataka, India
| | - D Gowtham Raj
- 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
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Esteves J, Pivot O, Ribouton J, Jalade P, Zouaoui A, Desbat L, Rit S, Blanc F, Haefeli G, Hopchev P, Galvan JM, Lu GN, Pittet P. A novel QA phantom based on scintillating fiber ribbons with implementation of 2D dose tomography for small-field radiotherapy. Med Phys 2023; 50:619-632. [PMID: 35933612 PMCID: PMC10087208 DOI: 10.1002/mp.15902] [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: 03/08/2022] [Revised: 07/10/2022] [Accepted: 07/20/2022] [Indexed: 01/25/2023] Open
Abstract
PURPOSE To develop a novel instrument for real-time quality assurance (QA) procedures in radiotherapy. The system implements a scintillation-based phantom and associated signal acquisition and processing modules and aims to monitor two-dimensional (2D) dose distributions of small fields. MATERIALS AND METHODS For the proposed phantom, we have designed and realized a prototype implementing six high-resolution tissue-equivalent scintillating fiber ribbons stacked with in-plane 30° rotated orientations from each other. Each ribbon output is coupled to a silicon photodiode linear array (with an element pitch of 400 μm) to detect scintillating signal, which represents the projected irradiation profile perpendicular to the ribbon's orientation. For the system providing six acquired projected dose profiles at different orientations, we have developed a two-step signal processing method to perform 2D dose reconstruction. The first step is to determine irradiation field geometry parameters using a tomographic geometry approach, and the second one is to perform specific penumbra estimation. The QA system prototype has been tested on a Novalis TrueBeam STX with a 6-MV photon beam for small elliptic fields defined by 5- and 10-mm cone collimators and for 10 × 10- and 20 × 10-mm2 rectangular fields defined by the micro-multileaf collimator. Gamma index analysis using EBT3 films as reference has been carried out with tight 2%-dose-difference (DD)/700-μm-distance-to-agreement (DTA) as well as 1%-DD/1-mm-DTA criteria for evaluating the system performances. The testing also includes an evaluation of the proposed two-step field reconstruction method in comparison with two conventional methods: filtered back projection (FBP) and simultaneous iterative reconstruction technique (SIRT). RESULTS The reconstructed 2D dose distributions have gamma index pass rates higher than 95% for all the tested configurations as compared with EBT3 film measurements with both 2%-DD/700-μm-DTA and 1%-DD/1-mm criteria. 2D global gamma analysis shows that the two-step and FBP radiation field reconstruction methods systematically outperform the SIRT approach. Moreover, higher gamma index success rates are obtained with the two-step method than with FBP in the case of the fields defined with the stereotactic cones. CONCLUSIONS The proposed small-field QA system makes a use of six water-equivalent scintillating detectors (fiber ribbons) to acquire dose distribution. The developed two-step signal processing method performs tomographic 2D dose reconstruction. A system prototype has been built and tested using hospital facilities with small rectangular and elliptic fields. Testing results show 2D reconstructed dose distributions with high accuracy and resolution. Such a system could potentially be an alternative approach to film dosimetry for small-field QA, which is still widely used as reference in clinical practice.
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Affiliation(s)
- Josué Esteves
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, INSA Lyon, Ecole Centrale de Lyon, CPE Lyon, INL, UMR5270, Villeurbanne, France
| | - Odran Pivot
- Univ. Grenoble Alpes, CNRS, Grenoble INP, TIMC, Grenoble, France
| | - Julien Ribouton
- Service de Radiophysique et Radiovigilance, Centre Hospitalier Lyon Sud, Hospices Civils de Lyon, Pierre-Bénite, France
| | - Patrice Jalade
- Service de Radiophysique et Radiovigilance, Centre Hospitalier Lyon Sud, Hospices Civils de Lyon, Pierre-Bénite, France
| | - Abdelaali Zouaoui
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, INSA Lyon, Ecole Centrale de Lyon, CPE Lyon, INL, UMR5270, Villeurbanne, France
| | - Laurent Desbat
- Univ. Grenoble Alpes, CNRS, Grenoble INP, TIMC, Grenoble, France
| | - Simon Rit
- Univ Lyon, INSA-Lyon, Université Claude Bernard Lyon 1, UJM-Saint Etienne, CNRS, Inserm, CREATIS UMR 5220, U1294, CREATIS, Lyon, France
| | | | | | | | - Jean-Marc Galvan
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, INSA Lyon, Ecole Centrale de Lyon, CPE Lyon, INL, UMR5270, Villeurbanne, France
| | - Guo-Neng Lu
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, INSA Lyon, Ecole Centrale de Lyon, CPE Lyon, INL, UMR5270, Villeurbanne, France
| | - Patrick Pittet
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, INSA Lyon, Ecole Centrale de Lyon, CPE Lyon, INL, UMR5270, Villeurbanne, France
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Klimanov VA, Kirpichev YS, Serikbekova ZK, Belousov AV, Krusanov GA, Walwyn‐Salas G, Morozov VN, Kolyvanova MA. Monte-Carlo calculation of output correction factors for ionization chambers, solid-state detectors, and EBT3 film in small fields of high-energy photons. J Appl Clin Med Phys 2022; 24:e13753. [PMID: 35998153 PMCID: PMC9860002 DOI: 10.1002/acm2.13753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Revised: 07/13/2022] [Accepted: 07/25/2022] [Indexed: 01/26/2023] Open
Abstract
High-energy accelerators are often used in oncological practice, but the information on the small-field dosimetry for the photon beams with nominal energy above 10 MV is limited. The goal of the present work was to determine the values of the output correction factor ( k Q clin , Q ref f clin , f ref $k_{{Q}_{{\rm{clin}}},{Q}_{{\rm{ref}}}}^{{f}_{{\rm{clin}}},{f}_{{\rm{ref}}}}$ ) for solid-state detectors (Diode E, PTW 60017; microDiamond, PTW 60019), EBT3 film, and ionization chambers (Semiflex, PTW 31010; Semiflex 3D, PTW 31021; PinPoint, PTW 31015; PinPoint 3D, PTW 31016) in the small fields formed by 10, 15, 18, and 20 MV photon beams. The output correction factors were calculated by Monte-Carlo method using EGSnrc toolkit for six field sizes (from 0.5 × 0.5 cm 2 $0.5 \times 0.5\ {\rm{cm}}^2$ to 10 × 10 cm 2 $10 \times 10\ {\rm{cm}}^2$ ) for isocentric and constant source-to-surface distance (SSD) techniques. The decrease in the field size led to an increase in k Q clin , Q ref f clin , f ref $k_{{Q}_{{\rm{clin}}},{Q}_{{\rm{ref}}}}^{{f}_{{\rm{clin}}},{f}_{{\rm{ref}}}}$ for ionization chambers, while for solid-state detectors and radiochromic film, k Q clin , Q ref f clin , f ref $k_{{Q}_{{\rm{clin}}},{Q}_{{\rm{ref}}}}^{{f}_{{\rm{clin}}},{f}_{{\rm{ref}}}}$ were less than unity at the smallest field size. A larger sensitive volume of ionization chamber corresponded to a stronger deviation of output correction factor from unity: 1.847 (125 mm3 PTW 31010) versus up to 1.183 (16 mm3 PTW 31016) at the smallest field of 10 MV beam. The calculated output correction factors were used to correct the output factors for PTW 60017, PTW 60019, and EBT3. The deviation of the corrected output factor from the results of Monte-Carlo simulation did not exceed 3% in the fields from 1.0 × 1.0 cm 2 $1.0 \times 1.0\ {\rm{cm}}^2$ to 4.0 × 4.0 cm 2 $4.0 \times 4.0\ {\rm{cm}}^2$ for 10 and 18 MV beams. Thus, Diode E, microDiamond, and EBT3 film can be recommended for small-field dosimetry of high-energy photons.
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Affiliation(s)
- Vladimir A. Klimanov
- State Research Center—Burnazyan Federal Medical Biophysical CenterFederal Medical Biological Agency of the Russian FederationMoscowRussia,National Research Nuclear University MEPhIMoscowRussia
| | | | | | - Alexandr V. Belousov
- State Research Center—Burnazyan Federal Medical Biophysical CenterFederal Medical Biological Agency of the Russian FederationMoscowRussia
| | - Grigorii A. Krusanov
- State Research Center—Burnazyan Federal Medical Biophysical CenterFederal Medical Biological Agency of the Russian FederationMoscowRussia
| | | | - Vladimir N. Morozov
- Emanuel Institute of Biochemical PhysicsRussian Academy of SciencesMoscowRussia
| | - Maria A. Kolyvanova
- State Research Center—Burnazyan Federal Medical Biophysical CenterFederal Medical Biological Agency of the Russian FederationMoscowRussia,Emanuel Institute of Biochemical PhysicsRussian Academy of SciencesMoscowRussia
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Varian eclipse stereotactic 5 mm cone data commissioning. Phys Eng Sci Med 2022; 45:1013-1020. [PMID: 35997923 DOI: 10.1007/s13246-022-01168-6] [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: 04/12/2022] [Accepted: 07/26/2022] [Indexed: 10/15/2022]
Abstract
Conical collimators are effective and readily available accessories for the field shaping of small stereotactic fields, however the measurements required to accurately characterise the smallest radiation fields are difficult, prone to large errors, and there is little published commissioning data to compare measurements against. The aim of this investigation was to commission the cone dose calculation algorithm of a Varian Eclipse treatment planning system for a Varian 5 mm cone attached to a Varian TrueBeam linear accelerator beam-matched to the Varian Golden Beam Data (GBD). Tissue maximum ratios (TMRs) and off-axis ratios (OARs) were measured using PTW 60019 microDiamond and PTW 60018 SRS Diode detectors for a flattening filter free 6MV beam. The output factor (OF) was measured with the microDiamond and EBT-XD film. Results were compared to the GBD for this cone and an OF measured by the Australian Clinical Dosimetry Service during an independent audit. Film dosimetry was used to evaluate Eclipse dose calculations in a solid water phantom and end-to-end accuracy with an anthropomorphic head phantom. Output correction factors were derived from IAEA TRS-483. Gamma analysis was used to compare measured TMRs and OARs, and to compare Eclipse dose planes with film dosimetry results. Comparisons between measured and GBD TMRs passed gamma analysis within the specified criteria, while differences between distances to agreement for OARs measured with different detectors was attributed to different volume averaging characteristics. The OFs measured with the microDiamond and film agreed within measurement uncertainty. It was decided to configure Eclipse with the microDiamond measured OF and the SRS Diode measured TMR and OAR data. This was validated with various comparisons carried out to confirm both measurement accuracy and Eclipse configuration.
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Lechner W, Alfonso R, Arib M, Huq MS, Ismail A, Kinhikar R, Lárraga-Gutiérrez JM, Mani KR, Maphumulo N, Sauer OA, Shoeir S, Suriyapee S, Christaki K. A multi-institutional evaluation of small field output factor determination following the recommendations of IAEA/AAPM TRS-483. Med Phys 2022; 49:5537-5550. [PMID: 35717637 PMCID: PMC9541513 DOI: 10.1002/mp.15797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 03/31/2022] [Accepted: 05/25/2022] [Indexed: 11/15/2022] Open
Abstract
Purpose The aim of this work was to test the implementation of small field dosimetry following TRS‐483 and to develop quality assurance procedures for the experimental determination of small field output factors (SFOFs). Materials and methods Twelve different centers provided SFOFs determined with various detectors. Various linac models using the beam qualities 6 MV and 10 MV with flattening filter and without flattening filter were utilized to generate square fields down to a nominal field size of 0.5 cm × 0.5 cm. The detectors were positioned at 10 cm depth in water. Depending on the local situation, the source‐to‐surface distance was either set to 90 cm or 100 cm. The SFOFs were normalized to the output of the 10 cm × 10 cm field. The spread of SFOFs measured with different detectors was investigated for each individual linac beam quality and field size. Additionally, linac‐type specific SFOF curves were determined for each beam quality and the SFOFs determined using individual detectors were compared to these curves. Example uncertainty budgets were established for a solid state detector and a micro ionization chamber. Results The spread of SFOFs for each linac and field was below 5% for all field sizes. With the exception of one linac‐type, the SFOFs of all investigated detectors agreed within 10% with the respective linac‐type SFOF curve, indicating a potential inter‐detector and inter‐linac variability. Conclusion Quality assurance on the SFOF measurements can be done by investigation of the spread of SFOFs measured with multiple detectors and by comparison to linac‐type specific SFOFs. A follow‐up of a measurement session should be conducted if the spread of SFOFs is larger than 5%, 3%, and 2% for field sizes of 0.5 cm × 0.5 cm, 1 cm × 1 cm, and field sizes larger than 2 cm × 2 cm, respectively. Additionally, deviations of measured SFOFs to the linac‐type‐curves of more than 7%, 3%, and 2% for field sizes 0.5 cm × 0.5 cm, 1 cm × 1 cm, and field sizes larger than 1 cm × 1 cm, respectively, should be followed up.
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Affiliation(s)
- Wolfgang Lechner
- Department of Radiation Oncology, Division of Medical Physics, Medical University Vienna, Vienna, 1090, Austria
| | - Rodolfo Alfonso
- Department of Nuclear Engineering, Higher Institute of Technology and Applied Sciences, University of Havana, Havana, 10400, Cuba
| | - Mehenna Arib
- King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - M Saiful Huq
- Department of Radiation Oncology, University of Pittsburgh School of Medicine and UPMC Hillman Cancer Center, Pittsburgh, Pennsylvania, USA
| | - Anas Ismail
- Protection and Safety Department, Atomic Energy Commission of Syria, Damascus, PO Box 6091, Syria
| | - Rajesh Kinhikar
- Department of Medical Physics, Tata Memorial Centre, Mumbai, India 400012 & Homi Bhabha National Institute, Mumbai, 400094, India
| | - José M Lárraga-Gutiérrez
- Laboratorio de Física-Médica, Instituto Nacional de Neurología y Neurocirugía, Insurgentes sur 3877, La Fama, Tlalpan 14269, CDMX, México
| | - Karthick Raj Mani
- Department of Radiation Oncology, United Hospital Ltd., Dhaka, 1212, Bangladesh
| | - Nkosingiphile Maphumulo
- Radiation Dosimetry Section, National Metrology Institute of South Africa, Pretoria, South Africa
| | - Otto A Sauer
- Department of Radiation Oncology, University of Würzburg, 97080, Würzburg, Germany
| | | | - Sivalee Suriyapee
- Division of Radiation Oncology, Department of Radiology, Chulalongkorn University, Bangkok, Thailand
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McGrath AN, Golmakani S, Williams TJ. Determination of correction factors in small MLC-defined fields for the Razor and microSilicon diode detectors and evaluation of the suitability of the IAEA TRS-483 protocol for multiple detectors. J Appl Clin Med Phys 2022; 23:e13657. [PMID: 35652320 PMCID: PMC9278669 DOI: 10.1002/acm2.13657] [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: 12/15/2021] [Revised: 03/31/2022] [Accepted: 05/03/2022] [Indexed: 11/11/2022] Open
Abstract
Small field output factors for Multileaf collimator (MLC)‐defined field sizes between 0.5 × 0.5 cm2 and 3 × 3 cm2 were measured with six different detectors for a Varian TrueBeam in 6‐MV, 6‐FFF, 10‐MV, and 10‐FFF photon beams. Correction factors kQclin,Qreffclin,fref from the IAEA publication TRS‐483 were used to correct the measured output factors. The corrected output factors from the six detectors were used to calculate correction factors for the PTW microSilicon T60023 (PTW, Freiburg, Germany) and IBA Razor (IBA Dosimetry, Schwarzenbruck, Germany) detectors. The uncertainty of the output and correction factors in this study was calculated and the calculations presented in detail. The application of the TRS‐483 correction factors significantly reduced the variation in output factors between the various detectors, with the exception of the PTW 60016 diode in 6‐MV and 6‐FFF beams, and the IBA PFD in 10‐MV and 10‐FFF beams. Correction factors calculated for the Razor agreed within 2.9% of existing literature for all energies, while the microSilicon correction factors agreed within 1.6% to the literature for 6‐MV beams. The uncertainty in the microSilicon and Razor correction factors was calculated to be less than 0.9% (k = 1). This study shows that TRS‐483 correction factors reduce the variation in output factors between the detectors used in this study and presents a suitable method for determining correction factors for detectors with unpublished values.
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Affiliation(s)
- Andrew N McGrath
- W.P. Holman Clinic, Royal Hobart Hospital, Hobart, Tasmania, Australia
| | - Samane Golmakani
- W.P. Holman Clinic, Royal Hobart Hospital, Hobart, Tasmania, Australia
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Khan AU, Lotey R, DeWerd LA, Yadav P. A multi-institutional comparison of dosimetric data for a 0.35 T MR-linac. Phys Med Biol 2022; 67. [DOI: 10.1088/1361-6560/ac53df] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 02/10/2022] [Indexed: 11/11/2022]
Abstract
Abstract
Objective. A comparison of percent depth dose (PDD) curves, lateral beam profiles, output factors (OFs), multileaf collimator (MLC) leakage, and couch transmission factors was performed between ten institutes for a commercial 0.35 T MR-linac. Approach. The measured data was collected during acceptance testing of the MR-linac. The PDD curves were measured for the 3.32 × 3.32 cm2, 9.96 × 9.96 cm2, and 27.20 × 24.07 cm2 field sizes. The lateral beam profiles were acquired for a 27.20 × 24.07 cm2 field size using an ion chamber array and penumbra was defined as the distance between 80% of the maximum dose and 20% of the maximum dose after normalizing the profiles to the dose at the inflection points. The OFs were measured using solid-state dosimeters, whereas radiochromic films were utilized to measure radiation leakage through the MLC stacks. The relative couch transmission factors were measured for various gantry angles. The variation in the multi-institutional data was quantified using the percent standard deviation metric. Main results. Minimal variations (<1%) were found between the PDD data, except for the build-up region and the deeper regions of the PDD curve. The in-field region of the lateral beam profiles varied <1.5% between different institutions and a small variation (<0.7 mm) in penumbra was observed. A variation of <1% was observed in the OF data for field sizes above 1.66 × 1.66 cm2, whereas large variations were shown for small-field sizes. The average and maximum MLC leakage was calculated to be <0.3% and <0.6%, which was well below the international electrotechnical commission (IEC) leakage thresholds. The couch transmission was smallest for oblique beams and ranged from 0.83 to 0.87. Significance. The variation in the data was found to be relatively small and the different 0.35 T MR-linacs were concluded to have similar dosimetric characteristics.
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Li Y, Liu H, Huang N, Wang Z, Zhang C. The Measurement of the Surface Dose in Regular and Small Radiation Therapy Fields Using Cherenkov Imaging. Technol Cancer Res Treat 2022; 21:15330338211073432. [PMID: 35119327 PMCID: PMC8819764 DOI: 10.1177/15330338211073432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Purpose: The aim of this study is to measure the output factor (OF)
and profile of surface dose in regular and small radiation therapy fields using
Cherenkov imaging (CI). Methods: A medical linear accelerator
(linac) was employed to generate radiation fields, including regular open photon
field (ROPF), regular wedge photon field (RWPF), regular electron field (REF)
and small photon field (SPF). The photon beams consisted of two filter modes
including flattening filter (FF) and flattening filter free (FFF). All fields
were delivered to a solid water phantom. Cherenkov light was captured using a
charge-coupled device system during phantom irradiation. The OF and profile of
surface dose measured by CI were compared with those determined by film
measurement, ionization chamber measurement and treatment planning system
calculation in order to examine the feasibility of measuring surface dose OF and
profile using CI. Results: The discrepancy between surface dose OF
measured by CI and that determined by other methods is less than 6% in ROPFs
with size less than 10 × 10 cm2, REFs with size less than 10 × 10
cm2, and SPFs except for 1 × 1 cm2 field. In the flat
profile region, the discrepancy between surface dose profile measured by CI and
that determined by other methods is less than 4% in REFs and less than 3% in
ROPFs, RWPFs, and SPFs except for 1 × 1 cm2 field. The discrepancy of the
surface dose profile is in compliance with the recommendation by IAEA TRS 430
reports. The discrepancy between field width measured by CI and that determined
by film measurement is equal to or less than 2 mm, which is within the tolerance
recommend by the guidelines of linac quality assurance in regular open FF photon
fields, SPFs, and REFs with cone size of 10 × 10 cm2 in area.
Conclusion: CI can be used to quantitatively measure the OF and
profile of surface dose. It is feasible to use CI to measure the surface dose
profile and field width in regular open FF photon fields and SPFs except for
1 × 1 cm2 field.
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Affiliation(s)
- Yi Li
- State Key Laboratory of Transient Optics and Photonics, Xi’an
Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an
710119, China
- School of Physics, Xi’an Jiaotong University, Xi’an 710049, China
- University of Chinese Academy of Sciences, Beijing 100049,
China
| | - HongJun Liu
- State Key Laboratory of Transient Optics and Photonics, Xi’an
Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an
710119, China
- Collaborative Innovation Center of Extreme Optics, Shanxi
University, Taiyuan 030006, China
- Hongjun Liu, PhD, State Key Laboratory of
Transient Optics and Photonics, Xi’an Institute of Optics and Precision
Mechanics, Chinese Academy of Sciences, Xi’an 710119, China.
Chunmin Zhang, PhD, School of Physics,
Xi’an Jiaotong University, Xi’an 710049, China.
| | - Nan Huang
- State Key Laboratory of Transient Optics and Photonics, Xi’an
Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an
710119, China
| | - Zhaolu Wang
- State Key Laboratory of Transient Optics and Photonics, Xi’an
Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an
710119, China
| | - Chunmin Zhang
- School of Physics, Xi’an Jiaotong University, Xi’an 710049, China
- Hongjun Liu, PhD, State Key Laboratory of
Transient Optics and Photonics, Xi’an Institute of Optics and Precision
Mechanics, Chinese Academy of Sciences, Xi’an 710119, China.
Chunmin Zhang, PhD, School of Physics,
Xi’an Jiaotong University, Xi’an 710049, China.
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21
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Dobberthien B, Cao F, Zhao Y, Harvey E, Badragan G. Effect of inaccurate small field output factors on brain SRS plans. Biomed Phys Eng Express 2022; 8. [PMID: 35021167 DOI: 10.1088/2057-1976/ac4a85] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Accepted: 01/12/2022] [Indexed: 11/11/2022]
Abstract
External beam radiotherapy often includes the use of field sizes 3 × 3 cm2or less, which can be defined as small fields. Dosimetry is a difficult, yet important part of the radiotherapy process. The dosimetry of small fields has additional challenges, which can lead to treatment inconsistencies if not done properly. Most important is the use of an appropriate detector, as well as the application of the necessary corrections. The International Atomic Energy Agency and the American Association of Physicists in Medicine provide the International Code of Practice (CoP) TRS-483 for the dosimetry of small static fields used in external MV photon beams. It gives guidelines on how to apply small-field correction factors for small field dosimetry. The purpose of this study was to evaluate the impact of inaccurate small-field output factors on clinical brain stereotactic radiosurgery plans with and without applying the small-field correction factors as suggested in the CoP. Small-field correction factors for a Varian TrueBeam linear accelerator were applied to uncorrected relative dose factors. Uncorrected and corrected clinical plans were created with two different beam configurations, 6 MV with a flattening filter (6 WFF) and 6 MV without a flattening filter (6 FFF). For the corrected plans, the planning target volume mean dose was 1.6 ± 0.9% lower with p < 0.001 for 6 WFF and 1.8 ± 1.5% lower with p < 0.001 for 6 FFF. For brainstem, a major organ at risk, the corrected plans had a dose that was 1.6 ± 0.9% lower with p = 0.03 for 6 WFF and 1.8 ± 1.5% lower with p = 0.10 for 6 FFF. This represents a systematic error that should and can be corrected.
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Affiliation(s)
- Brennen Dobberthien
- Radiation Medical Physics, BC Cancer Agency Fraser Valley Centre, 13750 96th Ave., Surrey, British Columbia, V3V 1Z2, CANADA
| | - Fred Cao
- Radiation Physics, BC Cancer Agency Fraser Valley Centre, 13750 96th Ave, Surrey, British Columbia, V3V 1Z2, CANADA
| | - Yingli Zhao
- Radiation Medical Physics, BC Cancer Agency Fraser Valley Centre, 13750 96th Ave., Surrey, British Columbia, V3V 1Z2, CANADA
| | - Eric Harvey
- Radiation Medical Physics, BC Cancer Agency Fraser Valley Centre, 13750 96th Ave., Surrey, British Columbia, V3V 1Z2, CANADA
| | - Genoveva Badragan
- Radiation Medical Physics, BC Cancer Agency Fraser Valley Centre, 13750 96th Ave., Surrey, British Columbia, V3V 1Z2, CANADA
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22
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George S, Ponmalar YR, Godson HF, Kumar AS, Ravindran BP. Influence of Jaw Setting in the Determination of Stereotactic Small-Field Output Factors with Different Detectors. J Med Phys 2022; 47:65-72. [PMID: 35548030 PMCID: PMC9084590 DOI: 10.4103/jmp.jmp_111_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 11/14/2021] [Accepted: 11/15/2021] [Indexed: 11/08/2022] Open
Abstract
Background The experimental determination of relative output factors presents the greatest challenge, especially for small fields with different detectors. The aim of this study is to evaluate the influence of jaw positions on small-field output factors for the fields defined by micro-multileaf collimator and circular cones with different detectors. Materials and Methods The stereotactic output factors were measured on Primus linear accelerator with BrainLab micro-multileaf collimator (mMLC) and circular cones as add-on tertiary collimators. Square field sizes ranging from 0.6 cm × 0.6 cm to 9.8 cm × 9.8 cm and circular fields of diameter ranging from 1.0 cm to 4.0 cm were defined by mMLC and circular cones, respectively. The influence of jaw position on output factor was assessed for different geometric configurations with three different detectors. Results The values obtained with PinPoint ion chamber were consistent with microDiamond detector for fields greater than 24 mm × 24 mm, but an underestimation of 23.9% was noticed in 6 mm x 6 mm field size. For the mMLC defined field size of 6 mm × 6 mm, when the X-Y jaw was moved from 8 mm × 8 mm to 80 mm × 80 mm, an increase in the output by a factor of 1.7 was observed with both microDiamond and stereotactic radiosurgery diode, whereas an increase in output by a factor of 1.9 was noticed with PinPoint ion chamber. Conclusion Output factors obtained with different detectors show high differences in the smallest field size for all collimating systems. This study confirms that the position of X and Y jaw above the tertiary collimator significantly influences the small-field output factor.
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Affiliation(s)
- Seby George
- Department of Radiation Oncology, Christian Medical College, Vellore, Tamil Nadu, India
| | - Y. Retna Ponmalar
- Department of Radiation Oncology, Christian Medical College, Vellore, Tamil Nadu, India
| | - Henry Finlay Godson
- Department of Radiation Oncology, Christian Medical College, Vellore, Tamil Nadu, India
| | - A. Sathish Kumar
- Department of Radiation Oncology, Christian Medical College, Vellore, Tamil Nadu, India,Address for correspondence: Dr. Henry Finlay Godson, Department of Radiation Oncology, Christian Medical College, Vellore - 632 004, Tamil Nadu, India. E-mail:
| | - B. Paul Ravindran
- Department of Radiation Oncology, Christian Medical College, Vellore, Tamil Nadu, India
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23
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Méndez I, Casar B. A novel approach for the definition of small-field sizes using the concept of superellipse. Radiat Phys Chem Oxf Engl 1993 2021. [DOI: 10.1016/j.radphyschem.2021.109775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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24
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Côté B, Keszti F, Bancheri J, Sarfehnia A, Seuntjens J, Renaud J. Feasibility of operating a millimeter-scale graphite calorimeter for absolute dosimetry of small-field photon beams in the clinic. Med Phys 2021; 48:7476-7492. [PMID: 34549805 DOI: 10.1002/mp.15244] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2020] [Revised: 07/06/2021] [Accepted: 08/28/2001] [Indexed: 11/11/2022] Open
Abstract
PURPOSE To characterize and build a cylindrically layered graphite calorimeter the size of a thimble ionization chamber for absolute dosimetry of small fields. This detector has been designed in a familiar probe format to facilitate integration into the clinical workflow. The feasibility of operating this absorbed dose calorimeter in quasi-adiabatic mode is assessed for high-energy accelerator-based photon beams. METHODS This detector, herein referred to as Aerrow MK7, is a miniaturized version of a previously validated aerogel-insulated graphite calorimeter known as Aerrow. The new model was designed and developed using numerical methods. Medium conversion factors from graphite to water, small-field output correction factors, and layer perturbation factors for this dosimeter were calculated using the EGSnrc Monte Carlo code system. A range of commercially available aerogel densities were studied for the insulating layers, and an optimal density was selected by minimizing the small-field output correction factors. Heat exchange within the detector was simulated using a five-body compartmental heat transfer model. In quasi-adiabatic mode, the sensitive volume (a 3 mm diameter cylindrical graphite core) experiences a temperature rise during irradiation on the order of 1.3 mK·Gy-1 . The absorbed dose is obtained by calculating the product of this temperature rise with the specific heat capacity of the graphite. The detector was irradiated with 6 MV ( % dd ( 10 ) x = 63.5%) and 10 MV ( % dd ( 10 ) x = 71.1%) flattening filter-free (FFF) photon beams for two field sizes, characterized by S clin dimensions of 2.16 and 11.0 cm. The dose readings were compared against a calibrated Exradin A1SL ionization chamber. All dose values are reported at d max in water. RESULTS The field output correction factors for this dosimeter design were computed for field sizes ranging from S clin = 0.54 to 11.0 cm. For all aerogel densities studied, these correction factors did not exceed 1.5%. The relative dose difference between the two dosimeters ranged between 0.3% and 0.7% for all beams and field sizes. The smallest field size experimentally investigated, S clin = 2.16 cm, which was irradiated with the 10 MV FFF beam, produced readings of 84.4 cGy (±1.3%) in the calorimeter and 84.5 cGy (±1.3%) in the ionization chamber. CONCLUSION The median relative difference in absorbed dose values between a calibrated A1SL ionization chamber and the proposed novel graphite calorimeter was 0.6%. This preliminary experimental validation demonstrates that Aerrow MK7 is capable of accurate and reproducible absorbed dose measurements in quasi-adiabatic mode.
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Affiliation(s)
- Benjamin Côté
- Medical Physics Unit, Gerald Bronfman Department of Oncology, McGill University, Montreal, Quebec, Canada
| | - Federico Keszti
- Medical Physics Unit, Gerald Bronfman Department of Oncology, McGill University, Montreal, Quebec, Canada
| | - Julien Bancheri
- Medical Physics Unit, Gerald Bronfman Department of Oncology, McGill University, Montreal, Quebec, Canada
| | - Arman Sarfehnia
- Medical Physics Unit, Gerald Bronfman Department of Oncology, McGill University, Montreal, Quebec, Canada.,Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
| | - Jan Seuntjens
- Medical Physics Unit, Gerald Bronfman Department of Oncology, McGill University, Montreal, Quebec, Canada
| | - James Renaud
- Medical Physics Unit, Gerald Bronfman Department of Oncology, McGill University, Montreal, Quebec, Canada.,Metrology Research Centre, National Research Council Canada, Ottawa, Ontario, Canada
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25
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Méndez I, Rovira-Escutia JJ, Casar B. A protocol for accurate radiochromic film dosimetry using Radiochromic.com. Radiol Oncol 2021; 55:369-378. [PMID: 34384012 PMCID: PMC8366735 DOI: 10.2478/raon-2021-0034] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 07/01/2021] [Indexed: 11/21/2022] Open
Abstract
BACKGROUND Radiochromic films have many applications in radiology and radiation therapy. Generally, the dosimetry system for radiochromic film dosimetry is composed of radiochromic films, flatbed scanner, and film analysis software. The purpose of this work is to present the effectiveness of a protocol for accurate radiochromic film dosimetry using Radiochromic.com as software for film analysis. MATERIALS AND METHODS Procedures for image acquisition, lot calibration, and dose calculation are explained and analyzed. Radiochromic.com enables state-of-the-art models and corrections for radiochromic film dosimetry, such as the Multigaussian model for multichannel film dosimetry, and lateral, inter-scan, and re-calibration corrections of the response. RESULTS The protocol presented here provides accurate dose results by mitigating the sources of uncertainty that affect radiochromic film dosimetry. CONCLUSIONS Appropriate procedures for film and scanner handling in combination with Radiochromic.com as software for film analysis make easy and accurate radiochromic film dosimetry feasible.
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Affiliation(s)
- Ignasi Méndez
- Department for dosimetry and quality of radiological procedures, Institute of Oncology Ljubljana, Ljubljana, Slovenia
| | | | - Bozidar Casar
- Department for dosimetry and quality of radiological procedures, Institute of Oncology Ljubljana, Ljubljana, Slovenia
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26
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Pinnaduwage DS, Srivastava SP, Yan X, Jani SS, Jenkins C, Barani IJ, Sorensen S. Small-field beam data acquisition, detector dependency, and film-based validation for a novel self-shielded stereotactic radiosurgery system. Med Phys 2021; 48:6121-6136. [PMID: 34260069 DOI: 10.1002/mp.15091] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 06/02/2021] [Accepted: 06/28/2021] [Indexed: 12/25/2022] Open
Abstract
PURPOSE This study reports a single-institution experience with beam data acquisition and film-based validation for a novel self-shielded sterotactic radiosurgery unit and investigates detector dependency on field output factors (OFs), off-axis ratios (OARs), and percent depth dose (PDD) measurements within the context of small-field dosimetry. METHODS The delivery platform for this unit consists of a 2.7-MV S-band linear accelerator mounted on coupled gimbals that rotate around a common isocenter (source-to-axis distance [SAD] = 450 mm), allowing for more than 260 noncoplanar beam angles. Beam collimation is achieved via a tungsten collimator wheel with eight circular apertures ranging from 4 mm to 25 mm in diameter. Three diodes (PTW 60012 Diode E, PTW 60018 SRS Diode, and Sun Nuclear EDGE) and a synthetic diamond detector (PTW 60019 micro Diamond [µD] detector) were used for OAR, PDD, and OF measurements. OFs were also acquired with a PTW 31022 PinPoint ionization chamber. Beam scanning was performed using a 3D water tank at depths of 7, 50, 100, 200, and 250 mm with a source-to-surface distance of 450 mm. OFs were measured at the depth of maximum dose (dmax = 7 mm) with the SAD at 450 mm. Gafchromic EBT3 film was used to validate OF and profile measurements and as a reference detector for estimating correction factors for active detector OFs. Deviations in field size, penumbra, and PDDs across the different detectors were quantified. RESULTS Relative OFs (ROFs) for the diodes were within 1.4% for all collimators except for 5 and 7.5 mm, for which SRS Diode measurements were higher by 1.6% and 2.6% versus Diode E. The µD ROFs were within 1.4% of the diode measurements. PinPoint ROFs were lower by >10% for the 4-mm and 5-mm collimators versus the Diode E and µD. Corrections to OFs using EBT3 film as a reference were within 1.2% for all diodes and the µD detector for collimators 10 mm and greater and within 2.0%, 2.8%, and 1.1% for the 7.5-, 5-, and 4-mm collimators, respectively. The maximum difference in full width at half maximum (FWHM) between the Diode E and the other active detectors was for the 25-mm collimator and was 0.09 mm (µD), 0.16 mm (SRS Diode), and 0.65 mm (EDGE). Differences seen in PDDs beyond the depth of dmax were <1% across the three diodes and the µD. FWHM and penumbra measurements made using EBT3 film were within 1.34% and 3.26%, respectively, of the processed profile data entered into the treatment planning system. CONCLUSIONS Minimal differences were seen in OAR and PDD measurements acquired with the diodes and the µD. ROFs measured with the three diodes were within 2.6% and within 1.4% versus the µD. Gafchromic Film measurements provided independent verification of the OAR and OF measurements. Estimated corrections to OFs using film as a reference were <1.6% for the Diode E, EDGE, and µD detector.
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Affiliation(s)
- Dilini S Pinnaduwage
- Department of Radiation Oncology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Shiv P Srivastava
- Department of Radiation Oncology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Xiangsheng Yan
- Department of Radiation Oncology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Shyam S Jani
- Department of Radiation Oncology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | | | - Igor J Barani
- Department of Radiation Oncology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Stephen Sorensen
- Department of Radiation Oncology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
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27
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Das IJ, Francescon P, Moran JM, Ahnesjö A, Aspradakis MM, Cheng CW, Ding GX, Fenwick JD, Saiful Huq M, Oldham M, Reft CS, Sauer OA. Report of AAPM Task Group 155: Megavoltage photon beam dosimetry in small fields and non-equilibrium conditions. Med Phys 2021; 48:e886-e921. [PMID: 34101836 DOI: 10.1002/mp.15030] [Citation(s) in RCA: 56] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 05/06/2021] [Accepted: 06/02/2021] [Indexed: 12/14/2022] Open
Abstract
Small-field dosimetry used in advance treatment technologies poses challenges due to loss of lateral charged particle equilibrium (LCPE), occlusion of the primary photon source, and the limited choice of suitable radiation detectors. These challenges greatly influence dosimetric accuracy. Many high-profile radiation incidents have demonstrated a poor understanding of appropriate methodology for small-field dosimetry. These incidents are a cause for concern because the use of small fields in various specialized radiation treatment techniques continues to grow rapidly. Reference and relative dosimetry in small and composite fields are the subject of the International Atomic Energy Agency (IAEA) dosimetry code of practice that has been published as TRS-483 and an AAPM summary publication (IAEA TRS 483; Dosimetry of small static fields used in external beam radiotherapy: An IAEA/AAPM International Code of Practice for reference and relative dose determination, Technical Report Series No. 483; Palmans et al., Med Phys 45(11):e1123, 2018). The charge of AAPM task group 155 (TG-155) is to summarize current knowledge on small-field dosimetry and to provide recommendations of best practices for relative dose determination in small megavoltage photon beams. An overview of the issue of LCPE and the changes in photon beam perturbations with decreasing field size is provided. Recommendations are included on appropriate detector systems and measurement methodologies. Existing published data on dosimetric parameters in small photon fields (e.g., percentage depth dose, tissue phantom ratio/tissue maximum ratio, off-axis ratios, and field output factors) together with the necessary perturbation corrections for various detectors are reviewed. A discussion on errors and an uncertainty analysis in measurements is provided. The design of beam models in treatment planning systems to simulate small fields necessitates special attention on the influence of the primary beam source and collimating devices in the computation of energy fluence and dose. The general requirements for fluence and dose calculation engines suitable for modeling dose in small fields are reviewed. Implementations in commercial treatment planning systems vary widely, and the aims of this report are to provide insight for the medical physicist and guidance to developers of beams models for radiotherapy treatment planning systems.
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Affiliation(s)
- Indra J Das
- Department of Radiation Oncology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Paolo Francescon
- Department of Radiation Oncology, Ospedale Di Vicenza, Vicenza, Italy
| | - Jean M Moran
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Anders Ahnesjö
- Medical Radiation Sciences, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Maria M Aspradakis
- Institute of Radiation Oncology, Cantonal Hospital of Graubünden, Chur, Switzerland
| | - Chee-Wai Cheng
- Department of Radiation Oncology, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
| | - George X Ding
- Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - John D Fenwick
- Molecular and Clinical Cancer Medicine, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, UK
| | - M Saiful Huq
- Department of Radiation Oncology, University of Pittsburgh, School of Medicine and UPMC Hillman Cancer Center, Pittsburgh, PA, USA
| | - Mark Oldham
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, USA
| | - Chester S Reft
- Department of Radiation Oncology, University of Chicago, Chicago, IL, USA
| | - Otto A Sauer
- Department of Radiation Oncology, Klinik fur Strahlentherapie, University of Würzburg, Würzburg, Germany
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28
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Passal V, Barreau M, Tiplica T, Dufreneix S. Optimizing the effective spot size and the dosimetric leaf gap of the AcurosXB algorithm for VMAT treatment planning. J Appl Clin Med Phys 2021; 22:154-161. [PMID: 34042259 PMCID: PMC8200512 DOI: 10.1002/acm2.13256] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 03/10/2021] [Accepted: 03/31/2021] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The aim of this study is to provide and test a new methodology to adjust the AcurosXB beam model for VMAT treatment plans. METHOD The effective target spot size of the AcurosXB v15 algorithm was adjusted in order to minimize the difference between calculated and measured penumbras. The dosimetric leaf gap (DLG) was adjusted using the asynchronous oscillating sweeping gap tests defined in the literature and the MLC transmission was measured. The impact of the four parameters on the small field output factors was assessed using a design of experiment methodology. Patient quality controls were performed for the three beam models investigated including two energies and two MLC models. RESULTS Effective target spot sizes differed from the manufacturer recommendations and strongly depended on the MLC model considered. DLG values ranged from 0.7 to 2.3 mm and were found to be larger than the ones based on the sweeping gap tests. All parameters were found to significantly influence the calculated output factors, especially for the 0.5 cm × 0.5 cm field size. Interactions were also identified for fields smaller than 2 cm × 2 cm, suggesting that adjusting the parameters on the small field output factors should be done with caution. All patient quality controls passed the universal action limit of 90%. CONCLUSION The methodology provided is simple to implement in clinical practice. It was validated for three beam models covering a large variety of treatment types and localizations.
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Affiliation(s)
- V. Passal
- Institut de Cancérologie de l’OuestAngersFrance
| | - M. Barreau
- LARIS Systems Engineering Research LaboratoryUniversity of AngersAngersFrance
| | - T. Tiplica
- LARIS Systems Engineering Research LaboratoryUniversity of AngersAngersFrance
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29
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Dwivedi S, Kansal S, Dangwal VK, Bharati A, Shukla J. Dosimetry of a 6 MV flattening filter-free small photon beam using various detectors. Biomed Phys Eng Express 2021; 7. [PMID: 33930875 DOI: 10.1088/2057-1976/abfd80] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 04/30/2021] [Indexed: 11/12/2022]
Abstract
The present study aimed to dosimetrically evaluate the small-fields of a 6 MV flattening filter-free (FFF) photon beam using different detectors.The 6 MV FFF photon beam was used for measurement of output factor, depth dose, and beam profile of small-fields of sizes 0.6 cm × 0.6 cm to 6.0 cm × 6.0 cm. The five detectors used were SNC125c, PinPoint, EDGE, EBT3, and TLD-100. All measurements were performed as per the International Atomic Energy Agency TRS 483 protocol. Output factors measured using different detectors as direct reading ratios showed significant variation for the smallest fields, whereas after correcting them according to TRS 483, all sets of output factors were nearly compatible with each other when measurement uncertainty was also considered. The beam profile measured using SNC125c showed the largest penumbra for all field sizes, whereas the smallest was recorded with EDGE. Compared with that of EBT3, the surface dose was found to be much higher for all the other detectors. PinPoint, EBT3, TLD-100, and EDGE were found to be the detector of choice for small-field output factor measurements; however, PinPoint needs special attention when used for the smallest field size (0.6 cm × 0.6 cm). EDGE and EBT3 are optimal for measuring beam profiles. EBT3, PinPoint, and EDGE can be selected for depth dose measurements, and EBT3 is suitable for surface dose estimation.
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Affiliation(s)
- Shekhar Dwivedi
- Department of Medical Physics, Tata Memorial Centre, Homi Bhabha Cancer Hospital and Research Centre, Mullanpur, Mohali, Punjab, 140901, India.,Department of Physics, Maharaja Ranjit Singh Punjab Technical University, Bathinda, Punjab, 151001, India
| | - Sandeep Kansal
- Department of Physics, Maharaja Ranjit Singh Punjab Technical University, Bathinda, Punjab, 151001, India
| | - Vinod Kumar Dangwal
- Department of Radiotherapy, Government Medical College, Patiala, Punjab, 147001, India
| | - Avinav Bharati
- Department of Radiation Oncology, Dr Ram Manohar Lohia Institute of Medical Sciences, Lucknow, Uttar Pradesh, 226010, India
| | - Jooli Shukla
- Department of Physics, Dr Bhimrao Ambedkar University, Agra, Uttar Pradesh, 282004, India
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Hermida-López M, Sánchez-Artuñedo D, Rodríguez M, Brualla L. Monte Carlo simulation of conical collimators for stereotactic radiosurgery with a 6 MV flattening-filter-free photon beam. Med Phys 2021; 48:3160-3171. [PMID: 33715167 DOI: 10.1002/mp.14837] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Revised: 02/19/2021] [Accepted: 03/08/2021] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Conical collimators, or cones, are tertiary collimators that attach to a radiotherapy linac and are suited for the stereotactic radiosurgery treatment of small brain lesions. The small diameter of the most used cones makes difficult the acquisition of the dosimetry data needed for the commissioning of treatment planning systems. Although many publications report dosimetric data of conical collimators for stereotactic radiosurgery, most of the works use different setups, which complicates comparisons. In other cases, the cone output factors reported do not take into account the effect of the small cone diameter on the detector response. Finally, few data exist on the dosimetry of cones with flattening-filter-free (FFF) beams from modern linac models. This work aims at obtaining a dosimetric characterization of the conical collimators manufactured by Brainlab AG (Munich, Germany) in a 6 MV FFF beam from a TrueBeam STx linac (Varian Medical Systems). METHODS Percentage depth dose curves, lateral dose profiles and cone output factors were obtained using Monte Carlo simulations for the cones with diameters of 4, 5, 6, 7.5, 8, 10, 12.5, 15, 17.5, 20, 25, and 30 mm. The simulation of the linac head was carried out with the PRIMO Monte Carlo software, and the simulations of the cones and the water phantom were run with the general-purpose Monte Carlo code PENELOPE. The Monte Carlo model was validated by comparing the simulation results with measurements performed for the cones of 4, 5, and 7.5 mm of diameter using a stereotactic field diode, a microDiamond detector and EBT3 radiochromic film. In addition, for those cones, simulations and measurements were done for comparison purposes, by reproducing the experimental setups from the available publications. RESULTS The experimental data acquired for the cones of 4, 5, and 7.5 mm validated the developed Monte Carlo model. The simulations accurately reproduced the experimental depths of maximum dose and the dose ratio at 20- and 10-cm depth (PDD20/10 ). A good agreement was obtained between simulated and experimental lateral dose profiles: The differences in the full-width at half-maximum were smaller than 0.2 mm, and the differences in the penumbra 80%-20% were smaller than 0.25 mm. The difference between the simulated and the average of the experimental output factors for the cones of 4, 5, and 7.5 mm of diameter was 0.0%, 0.0%, and 3.0%, respectively, well within the statistical uncertainty of the simulations (4.4% with coverage factor k = 2). It was also found that the simulated cone output factors agreed within 2% with the average of output factors reported in the literature for a variety of setup conditions, detectors, beam qualities, and cone manufacturers. CONCLUSION A Monte Carlo model of cones for stereotactic radiosurgery has been developed and validated. The cone dosimetry dataset obtained in this work, consisting of percentage depth doses, lateral dose profiles and output factors, is useful to benchmark data acquired for the commissioning of cone-based radiosurgery treatment planning systems.
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Affiliation(s)
- Marcelino Hermida-López
- Servei de Física i Protecció Radiològica, Hospital Universitari Vall d'Hebron, Vall d'Hebron Barcelona Hospital Campus, Passeig Vall d'Hebron 119-129, Barcelona, 08035, Spain
| | - David Sánchez-Artuñedo
- Servei de Física i Protecció Radiològica, Hospital Universitari Vall d'Hebron, Vall d'Hebron Barcelona Hospital Campus, Passeig Vall d'Hebron 119-129, Barcelona, 08035, Spain
| | - Miguel Rodríguez
- Centro Médico Paitilla, Calle 53 y ave. Balboa, Panama City, Panama.,Instituto de Investigaciones Científicas y de Alta Tecnología, INDICASAT-AIP, City of Knowledge, Building 219, Panama City, Panama
| | - Lorenzo Brualla
- West German Proton Therapy Centre Essen (WPE), Hufelandstr. 55, Essen, 45147, Germany.,West German Cancer Centre (WTZ), Hufelandstr. 55, Essen, 45147, Germany.,Faculty of Medicine, University of Duisburg-Essen, Hufelandstr. 55, Essen, 45147, Germany
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Knill C, Sandhu R, Halford R, Snyder M, Seymour Z. Commissioning cranial single-isocenter multi-target radiosurgery for the Versa HD. J Appl Clin Med Phys 2021; 22:108-114. [PMID: 33756044 PMCID: PMC8035552 DOI: 10.1002/acm2.13223] [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: 11/12/2020] [Revised: 01/29/2021] [Accepted: 02/16/2021] [Indexed: 11/12/2022] Open
Abstract
PURPOSE Brainlab's Elements Multiple Brain Mets SRS (MBMS) is a dedicated treatment planning system for single-isocenter multi-target (SIMT) cranial stereotactic radiosurgery (SRS) treatments. The purpose of this study is to present the commissioning experience of MBMS on an Elekta Versa HD. METHODS MBMS was commissioned for 6 X, 6 FFF, and 10 FFF. Beam data collected included: output factors, percent depth doses (PDDs), diagonal profiles, collimator transmission, and penumbra. Beam data were processed by Brainlab and resulting parameters were entered into the planning system to generate the beam model. Beam model accuracy was verified for simple fields. MBMS plans were created on previously treated cranial SRS patient data sets. Plans were evaluated using Paddick inverse conformity (ICI), gradient indices (GI), and cumulative volume of brain receiving 12 Gy. Dosimetric accuracy of the MBMS plans was verified using microDiamond, Gafchromic film, and SRS Mapcheck measurements of absolute dose and dose profiles for individual targets. Finally, an end-to-end (E2E) test was performed with a MR-CT compatible phantom to validate the accuracy of the simulation-to-delivery process. RESULTS For square fields, calculated scatter factors were within 1.0% of measured, PDDs were within 0.5% past dmax, and diagonal profiles were within 0.5% for clinically relevant off-axis distances (<10 cm). MBMS produced plans with ICIs < 1.5 and GIs < 5.0 for targets > 10 mm. Average point doses of the MBMS plans, measured by microDiamond, were within 0.31% of calculated (max 2.84%). Average per-field planar pass rates were 98.0% (95.5% minimum) using a 2%/1 mm/10% threshold relative gamma analysis. E2E point dose measurements were within 1.5% of calculated and Gafchromic film pass rates were 99.6% using a 5%/1 mm/10% threshold gamma analysis. CONCLUSION The experience presented can be used to aid the commissioning of the Versa HD in the Brainlab MBMS treatment planning system, to produce safe and accurate SIMT cranial SRS treatments.
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Affiliation(s)
- Cory Knill
- Department of Radiation Oncology, Beaumont Health, Royal Oak, MI, 48073, USA
| | - Raminder Sandhu
- Department of Radiation Oncology, Beaumont Health, Royal Oak, MI, 48073, USA
| | - Robert Halford
- Department of Radiation Oncology, Beaumont Health, Royal Oak, MI, 48073, USA
| | - Michael Snyder
- Department of Radiation Oncology, Beaumont Health, Royal Oak, MI, 48073, USA
| | - Zachary Seymour
- Department of Radiation Oncology, Beaumont Health, Royal Oak, MI, 48073, USA
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Clemente S, Falco MD, Cagni E, Talamonti C, Boccia M, Gino E, Lorenzini E, Rosica F, Russo S, Alparone A, Zefiro D, Fiandra C. The influence of small field output factors simulated uncertainties on the calculated dose in VMAT plans for brain metastases: a multicentre study. Br J Radiol 2021; 94:20201354. [PMID: 33481637 DOI: 10.1259/bjr.20201354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVES This multicentric study was carried out to investigate the impact of small field output factors (OFs) inaccuracies on the calculated dose in volumetric arctherapy (VMAT) radiosurgery brain plans. METHODS Nine centres, realised the same five VMAT plans with common planning rules and their specific clinical equipment Linac/treatment planning system commissioned with their OFs measured values (OFbaseline). In order to simulate OFs errors, two new OFs sets were generated for each centre by changing only the OFs values of the smallest field sizes (from 3.2 × 3.2 cm2 to 1 × 1 cm2) with well-defined amounts (positive and negative). Consequently, two virtual machines for each centre were recommissioned using the new OFs and the percentage dose differences ΔD (%) between the baseline plans and the same plans recalculated using the incremented (OFup) and decremented (OFdown) values were evaluated. The ΔD (%) were analysed in terms of planning target volume (PTV) coverage and organs at risk (OARs) sparing at selected dose/volume points. RESULTS The plans recalculated with OFdown sets resulted in higher variation of doses than baseline within 1.6 and 3.4% to PTVs and OARs respectively; while the plans with OFup sets resulted in lower variation within 1.3% to both PTVs and OARs. Our analysis highlights that OFs variations affect calculated dose depending on the algorithm and on the delivery mode (field jaw/MLC-defined). The Monte Carlo (MC) algorithm resulted significantly more sensitive to OFs variations than all of the other algorithms. CONCLUSION The aim of our study was to evaluate how small fields OFs inaccuracies can affect the dose calculation in VMAT brain radiosurgery treatments plans. It was observed that simulated OFs errors, return dosimetric calculation accuracies within the 3% between concurrent plans analysed in terms of percentage dose differences at selected dose/volume points of the PTV coverage and OARs sparing. ADVANCES IN KNOWLEDGE First multicentre study involving different Planning/Linacs about undetectable errors in commissioning output factor for small fields.
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Affiliation(s)
- Stefania Clemente
- Unit of Medical Physics and Radioprotection, Federico II University Hospital, Napoli, Italy
| | - Maria Daniela Falco
- Department of Radiation Oncology, "G. D'Annunzio" University, "SS. Annunziata" Hospital, Chieti, Italy
| | - Elisabetta Cagni
- Medical Physics Unit, Azienda USL-IRCCS di Reggio Emilia, Reggio Emilia, Italy
| | - Cinzia Talamonti
- Medical Physics Unit, University Of Florence, Azienda Ospedaliero Universitaria Careggi, Florence, Italy
| | | | - Eva Gino
- Medical PhysicDepartment, A.O. Ordine Mauriziano, Turin, Italy
| | - Elena Lorenzini
- U.O.C Fisica Sanitaria Area Nord, Azienda USL Nord Ovest Toscana, Massa Carrara, Italy
| | | | | | | | - Daniele Zefiro
- MedicaPhysics Unit, ASL5 Sistema Sanitario Regione Liguria, La Spezia, Italy
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Dufreneix S, Bellec J, Josset S, Vieillevigne L. Field output factors for small fields: A large multicentre study. Phys Med 2021; 81:191-196. [PMID: 33465756 DOI: 10.1016/j.ejmp.2021.01.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 12/30/2020] [Accepted: 01/02/2021] [Indexed: 02/06/2023] Open
Abstract
PURPOSE The determination of output factors in small field dosimetry is a crucial point, especially when implementing stereotactic radiotherapy (SRT). Herein, a working group of the French medical physicist society (SFPM) was created to collect small field output factors. The objective was to gather and disseminate information on small field output factors based on different detectors for various clinical SRT equipment and measurement configurations. METHOD Participants were surveyed for information about their SRT equipment, including the type of linear particle accelerator (linac), collimator settings, measurement conditions for the output factors and the detectors used. Participants had to report both the ratio of detector readings and the correction factors applied as described in the IAEA TRS-483 code of practice for nominal field sizes smaller or equal to 3 cm. Mean field output factors and their associated standard deviations were calculated when data from at least 3 linacs were available. RESULTS 23 centres were enrolled in the project. Standard deviations of the mean field output factors were systematically smaller than 1.5% for field sizes larger or equal to 1 cm and reached 5% for the smallest field size (0.5 cm). Deviations with published data were smaller than 2% except for the 0.5 cm circular fixed aperture collimator of the CyberKnife where it reached 3.5%. CONCLUSION These field output factor values obtained via a large multicentre study can be considered as an external cross verification for any radiotherapy centre starting a SRT program and should help minimize systematic errors when determining small field output factors.
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Affiliation(s)
- S Dufreneix
- Institut de Cancérologie de l'Ouest, Angers, Saint-Herblain, France.
| | - J Bellec
- Centre Eugène Marquis, Rennes, France
| | - S Josset
- Institut de Cancérologie de l'Ouest, Angers, Saint-Herblain, France
| | - L Vieillevigne
- Institut Claudius Régaud, Institut Universitaire du Cancer de Toulouse, France; Centre de Recherche et de Cancérologie de Toulouse, UMR1037 INSERM - Université Toulouse 3 - ERL5294 CNRS, Oncopole, Toulouse, France
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Msimang ZLM, van der Merwe D, Maphumulo N. Repeatability of Small Field Output Factor Measurements with Various Detectors. J Med Phys 2021; 46:47-51. [PMID: 34267489 PMCID: PMC8240910 DOI: 10.4103/jmp.jmp_93_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Revised: 01/08/2021] [Accepted: 01/24/2021] [Indexed: 11/05/2022] Open
Abstract
There are well established dosimetry reference standards for broad beams; however, there are no reference standards that can be used for both broad and small fields. The variation of the equivalent square fields and field output factors in small static photon fields when using a synthetic diamond, an electron diode, and ionization chambers (pin point, semiflex, and liquid filled) was investigated over time. Data from this study were compared to the data from other hospitals in the country and standard data sets, i.e., the British Journal of Radiology Supplement No. 25 of 1996 (BJR25) and the Radiological Physics Centre (RPC) 2012 data. The results showed that reliance on one detector and one measurement session, could yield incorrect field output factors (FOFs) for small fields. At least one of the detectors should be a solid state type with published field output correction factors and at least three measurement sessions should be performed for each FOF data point. Comparing measured data with published datasets, like RPC, will assist in verifying data. BJR25 datasets should not be used for S clin ≤4 cm.
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Affiliation(s)
| | - Debbie van der Merwe
- Department of Physics, University of the Witwatersrand, Johannesburg, South Africa
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Kinhikar R, Saini V, Upreti RR, Kale S, Sutar A, Tambe C, Kadam S. Measurement of the small field output factors for 10 MV photon beam using IAEA TRS-483 dosimetry protocol and implementation in Eclipse TPS commissioning. Biomed Phys Eng Express 2020; 6. [DOI: 10.1088/2057-1976/abb319] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 08/27/2020] [Indexed: 11/11/2022]
Abstract
Abstract
Dosimetry of small fields (SF) is vital for the success of highly conformal techniques. IAEA along with AAPM recently published a code of practice TRS-483 for SF dosimetry. The scope of this paper is to investigate the performance of three different detectors with 10 MV with-flatting-filter (WFF) beam using TRS-483 for SF dosimetry and subsequent commissioning of the Eclipse treatment planning system (TPS version-13.6) for SF data. SF dosimetry data (beam-quality TPR
20,10(10), cross-calibration, beam-profile, and field-output-factor (F.O.F)) measurements were performed for PTW31006-pinpoint, IBA-CC01 and IBA-EFD-3G diode detectors in nominal field size (F.S) range 0.5 × 0.5cm2 to 10 × 10 cm2 with water and solid water medium using Varian Truebeam linac. However, Eclipse-TPS commissioning data was acquired using IBA-EFD-3G diode, and absolute dose calibration was performed with FC-65G detector. The dosimetric performance of the Eclipse-TPS was validated using TLD-LiF chips, IBA-PFD, and IBA-EFD-3G diodes. Dosimetric performance of the PTW31006-pinpoint, IBA-CC01, and IBA-EFD-3G detectors was successfully tested for SF dosimetry. The F.O.Fs were generated and found in close agreement for all F.S except 0.5 × 0.5cm2. It is also found that TPR20,10(10) value can be derived within 0.5% accuracy from a non-reference field using Palmans equation. Cross-calibration can be performed in F.S 6 × 6 cm2 with a maximum variation of 0.5% with respect to 10 × 10cm2. During profile measurement, the full-width half-maxima (FWHM) of F.S 0.5 × 0.5cm2 was found maximum deviated from the geometric F.S. In addition, Eclipse-TPS was commissioned along with some limitations: F.O.F below F.S 1 × 1cm2 was ignored by TPS, PDD and profiles were dropped from configuration below F.S 2 × 2 cm2, and F.O.F which does not satisfy the condition 0.7 < A/B < 1.4 (A and B are FWHM in cross-line and in-line direction) have higher uncertainty than specified in TRS-483. Validation tests for Eclipse-TPS generated plans were also performed. The measured dose was in close agreement (3%) with TPS calculated dose up to F.S 1.5 × 1.5cm2.
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Gul A, Fukuda S, Mizuno H, Taku N, Kakakhel MB, Mirza SM. Feasibility study of using Stereotactic Field Diode for field output factors measurement and evaluating three new detectors for small field relative dosimetry of 6 and 10 MV photon beams. J Appl Clin Med Phys 2020; 21:23-36. [PMID: 33078544 PMCID: PMC7700919 DOI: 10.1002/acm2.13007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 06/29/2020] [Accepted: 07/10/2020] [Indexed: 11/23/2022] Open
Abstract
This study assesses the feasibility of using stereotactic field diode (SFD) as an alternate to gaf chromic films for field output factor (FF) measurement and further evaluating three new detectors for small field dosimetry. Varian 21EX linear accelerator was used to generate 6 and 10 MV beams of nominal square fields ranging from 0.5 × 0.5 cm2 to 10 × 10 cm2. One passive (EBT3 films) and five active detectors including IBA RAZOR diode(RD), SFD, RAZOR nanochamber (RNC), pinpoint chamber (PTW31023), and semiflex chamber (PTW31010) were employed. FFs were measured using films and SFD while beam profiles and percentage depth dose (PDD) distribution were acquired with active detectors. Polarity (kpol) and recombination (ks) effects of ion chambers were determined and corrected for output ratio measurement. Correction factors (CF) of RD, RNC, and PTW31023 in axial and radial orientation were also measured. Stereotactic field diode measured FFs have shown good agreement with films (with difference of <1%). RD and RNC measured beam profiles were within 3% deviation from the SFD values. Variation in kpol with field size for RNC and PTW31023 was up to 4% and 0.4% (for fields ≥ 1 × 1 cm2), respectively, while variation in ks of PTW31023 was <0.2 %. The maximum values of CF have been calculated to be 5.2%, 2.0%, 13.6%, and 25.5% for RD, RNC, PTW31023‐axial, and PTW31023‐radial respectively. This study concludes that SFD with appropriate CFs as given in TRS 483 may be used for measuring FFs as an alternate to EBT3 films. Whereas RD and RNC may be used for beam profile and PDD measurement in small fields. Considering the limit of usability of 2%, RNC may be used without CF for FF measurement in the smallfields investigated in this study.
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Affiliation(s)
- Attia Gul
- QST Hospital, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan.,Department of Physics & Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan
| | - Shigekazu Fukuda
- QST Hospital, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan
| | - Hideyuki Mizuno
- QST Hospital, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan
| | - Nakaji Taku
- QST Hospital, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan
| | - M Basim Kakakhel
- Department of Physics & Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan
| | - Sikander M Mirza
- Department of Physics & Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan
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Radojcic DS, Casar B, Rajlic D, Kolacio MS, Mendez I, Obajdin N, Debeljuh DD, Jurkovic S. Experimental validation of Monte Carlo based treatment planning system in bone density equivalent media. Radiol Oncol 2020; 54:495-504. [PMID: 32936784 PMCID: PMC7585341 DOI: 10.2478/raon-2020-0051] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 07/09/2020] [Indexed: 11/20/2022] Open
Abstract
Introduction Advanced, Monte Carlo (MC) based dose calculation algorithms, determine absorbed dose as dose to medium-in-medium (Dm,m) or dose to water-in-medium (Dw,m). Some earlier studies identified the differences in the absorbed doses related to the calculation mode, especially in the bone density equivalent (BDE) media. Since the calculation algorithms built in the treatment planning systems (TPS) should be dosimetrically verified before their use, we analyzed dose differences between two calculation modes for the Elekta Monaco TPS. We compared them with experimentally determined values, aiming to define a supplement to the existing TPS verification methodology. Materials and methods In our study, we used a 6 MV photon beam from a linear accelerator. To evaluate the accuracy of the TPS calculation approaches, measurements with a Farmer type chamber in a semi-anthropomorphic phantom were compared to those obtained by two calculation options. The comparison was made for three parts of the phantom having different densities, with a focus on the BDE part. Results Measured and calculated doses were in agreement for water and lung equivalent density materials, regardless of the calculation mode. However, in the BDE part of the phantom, mean dose differences between the calculation options ranged from 5.7 to 8.3%, depending on the method used. In the BDE part of the phantom, neither of the two calculation options were consistent with experimentally determined absorbed doses. Conclusions Based on our findings, we proposed a supplement to the current methodology for the verification of commercial MC based TPS by performing additional measurements in BDE material.
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Affiliation(s)
- Djeni Smilovic Radojcic
- Medical Physics Department, University Hospital Rijeka, Rijeka, Croatia
- Department of Medical Physics and Biophysics, Faculty of Medicine, University of Rijeka, Rijeka, Croatia
| | - Bozidar Casar
- Department for Dosimetry and Quality of Radiological procedures, Institute of Oncology Ljubljana, Ljubljana, Slovenia
- Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia
| | - David Rajlic
- Medical Physics Department, University Hospital Rijeka, Rijeka, Croatia
| | | | - Ignasi Mendez
- Department for Dosimetry and Quality of Radiological procedures, Institute of Oncology Ljubljana, Ljubljana, Slovenia
| | - Nevena Obajdin
- Medical Physics Department, University Hospital Rijeka, Rijeka, Croatia
| | - Dea Dundara Debeljuh
- Medical Physics Department, University Hospital Rijeka, Rijeka, Croatia
- General Hospital Pula, Radiology Department, Pula, Croatia
| | - Slaven Jurkovic
- Medical Physics Department, University Hospital Rijeka, Rijeka, Croatia
- Department of Medical Physics and Biophysics, Faculty of Medicine, University of Rijeka, Rijeka, Croatia
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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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Brace OJ, Alhujaili SF, Paino JR, Butler DJ, Wilkinson D, Oborn BM, Rosenfeld AB, Lerch MLF, Petasecca M, Davis JA. Evaluation of the PTW microDiamond in edge-on orientation for dosimetry in small fields. J Appl Clin Med Phys 2020; 21:278-288. [PMID: 32441884 PMCID: PMC7484886 DOI: 10.1002/acm2.12906] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 03/16/2020] [Accepted: 04/20/2020] [Indexed: 12/11/2022] Open
Abstract
Purpose The PTW microDiamond has an enhanced spatial resolution when operated in an edge‐on orientation but is not typically utilized in this orientation due to the specifications of the IAEA TRS‐483 code of practice for small field dosimetry. In this work the suitability of an edge‐on orientation and advantages over the recommended face‐on orientation will be presented. Methods The PTW microDiamond in both orientations was compared on a Varian TrueBeam linac for: machine output factor (OF), percentage depth dose (PDD), and beam profile measurements from 10 × 10 cm2 to a 0.5 × 0.5 cm2 field size for 6X and 6FFF beam energies in a water tank. A quantification of the stem effect was performed in edge‐on orientation along with tissue to phantom ratio (TPR) measurements. An extensive angular dependence study for the two orientations was also undertaken within two custom PMMA plastic cylindrical phantoms. Results The OF of the PTW microDiamond in both orientations agrees within 1% down to the 2 × 2 cm2 field size. The edge‐on orientation overresponds in the build‐up region but provides improved penumbra and has a maximum observed stem effect of 1%. In the edge‐on orientation there is an angular independent response with a maximum of 2% variation down to a 2 × 2 cm2 field. The PTW microDiamond in edge‐on orientation for TPR measurements agreed to the CC01 ionization chamber within 1% for all field sizes. Conclusions The microDiamond was shown to be suitable for small field dosimetry when operated in edge‐on orientation. When edge‐on, a significantly reduced angular dependence is observed with no significant stem effect, making it a more versatile QA instrument for rotational delivery techniques.
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Affiliation(s)
- Owen J Brace
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Sultan F Alhujaili
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Jason R Paino
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Duncan J Butler
- Australian Radiation Protection and Nuclear Safety Agency (ARPANSA), Yallambie, VIC, UK
| | - Dean Wilkinson
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia.,Illawarra Cancer Care Centre Wollongong Hospital Wollongong, Wollongong, NSW, Australia
| | - Brad M Oborn
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia.,Illawarra Cancer Care Centre Wollongong Hospital Wollongong, Wollongong, NSW, Australia
| | - Anatoly B Rosenfeld
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Michael L F Lerch
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Marco Petasecca
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Jeremy A Davis
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
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Pittet P, Esteves J, Galvan J, Lu G, Blanc F, Haefeli G, Hopchev P, Rit S, Desbat L, Ribouton J, Jalade P. SciFi detector and associated method for real-time determination of profile and output factor for small fields in stereotactic radiotherapy. Med Phys 2020; 47:1930-1939. [PMID: 31943221 PMCID: PMC7216919 DOI: 10.1002/mp.14019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 01/08/2020] [Accepted: 01/09/2020] [Indexed: 11/06/2022] Open
Abstract
PURPOSE For determining small-field profile and output factor during stereotactic radiotherapy quality assurance (QA) procedures, we propose a novel system based on the scintillating fiber (SciFi) detector with output image acquisition and processing to allow real-time monitoring of profile and output factor. MATERIALS AND METHODS The employed detector is a SciFi detector made of tissue-equivalent scintillating plastic fibers arranged in 6-layer fiber ribbons with a fiber pitch of 275 μm in each layer. The scintillating signal at the detector output is acquired by a sCMOS (scientific complementary metal-oxide-semiconductor) camera and represents the projected field profile along the fibers axis. An iterative reconstruction method of the field from its projected profile based on a priori knowledge of some features of the radiation field defined by the stereotactic cones is suggested. The detector with implemented data processing has been tested in clinical conditions, for determining beam profiles and output factors, using cone collimators of different sizes from 4 to 15 mm diameter. The detector under test was placed at 1.4 cm depth and 98.6 cm source to surface distance (SSD) in a water-equivalent phantom and irradiated by a 6 MV photon beam. RESULTS The reconstructed field profiles obtained from the detector are coherent with data from EBT3 radiochromic films, with differences within ±0.32 mm for both the FWHM and the penumbra region. For real-time determination of the field output factor, the measured data are also in good agreement with data independently determined by the French Institute for Radiological Protection and Nuclear Safety (IRSN) based on radiochromic films and thermoluminescent 1 × 1 mm2 micro-cubes dosimeters (TLD). The differences are within ±1.6% for all the tested cone sizes. CONCLUSIONS We propose and have tested a SciFi plastic scintillating detector with an optimized signal processing method to characterize small fields defined by cone collimators. It allows the determination of key field parameters such as full width at half maximum (FWHM) and field output factors. The results are consistent with those independently measured using TLD and radiochromic films. As the SciFi detector does not require a correction factor, it is in line with the International Atomic Energy Agency (IAEA) and the American Association of Physicists in Medicine (AAPM) TRS-483 recommendations, and can be suitable for online QA of small radiation fields used in photon beam radiotherapy, and is compatible with MRI-LINAC.
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Affiliation(s)
- P. Pittet
- Institut des Nanotechnologies de Lyon INLCNRS UMR5270Université de LyonUniversité Claude Bernard Lyon 1F‐69100VilleurbanneFrance
| | - J. Esteves
- Institut des Nanotechnologies de Lyon INLCNRS UMR5270Université de LyonUniversité Claude Bernard Lyon 1F‐69100VilleurbanneFrance
| | - J.‐M. Galvan
- Institut des Nanotechnologies de Lyon INLCNRS UMR5270Université de LyonUniversité Claude Bernard Lyon 1F‐69100VilleurbanneFrance
| | - G.‐N. Lu
- Institut des Nanotechnologies de Lyon INLCNRS UMR5270Université de LyonUniversité Claude Bernard Lyon 1F‐69100VilleurbanneFrance
| | - F. Blanc
- Laboratoire de Physique des Hautes Energies LPHEEPFLCH‐1015LausanneSwitzerland
| | - G. Haefeli
- Laboratoire de Physique des Hautes Energies LPHEEPFLCH‐1015LausanneSwitzerland
| | - P. Hopchev
- Laboratoire de Physique des Hautes Energies LPHEEPFLCH‐1015LausanneSwitzerland
| | - S. Rit
- University LyonINSA‐LyonUniversité Claude Bernard Lyon 1CNRS UMR 5220Inserm U1206CREATISLyonFrance
| | - L. Desbat
- University Grenoble AlpesCNRSGrenoble INPTIMC‐IMAGF‐38000GrenobleFrance
| | - J. Ribouton
- Service de Radiophysique et RadiovigilanceHospices Civils de LyonCentre Hospitalier Lyon SudF‐69495Pierre‐BéniteFrance
| | - P. Jalade
- Service de Radiophysique et RadiovigilanceHospices Civils de LyonCentre Hospitalier Lyon SudF‐69495Pierre‐BéniteFrance
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Casar B, Gershkevitsh E, Mendez I, Jurković S, Saiful Huq M. Output correction factors for small static fields in megavoltage photon beams for seven ionization chambers in two orientations - perpendicular and parallel. Med Phys 2020; 47:242-259. [PMID: 31677278 PMCID: PMC7003763 DOI: 10.1002/mp.13894] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 10/22/2019] [Accepted: 10/28/2019] [Indexed: 12/03/2022] Open
Abstract
PURPOSE The goal of the present work was to provide a large set of detector-specific output correction factors for seven small volume ionization chambers on two linear accelerators in four megavoltage photon beams utilizing perpendicular and parallel orientation of ionization chambers in the beam for nominal field sizes ranging from 0.5 cm2 × 0.5 cm2 to 10 cm2 × 10 cm2 . The present study is the second part of an extensive research conducted by our group. METHODS Output correction factors k Q clin , Q ref f clin , f ref were experimentally determined on two linacs, Elekta Versa HD and Varian TrueBeam for 6 and 10 MV beams with and without flattening filter for nine square fields ranging from 0.5 cm2 × 0.5 cm2 to 10 cm2 × 10 cm2 , for seven mini and micro ionization chambers, IBA CC04, IBA Razor, PTW 31016 3D PinPoint, PTW 31021 3D Semiflex, PTW 31022 3D PinPoint, PTW 31023 PinPoint, and SI Exradin A16. An Exradin W1 plastic scintillator and EBT3 radiochromic films were used as the reference detectors. RESULTS For all ionization chambers, values of output correction factors k Q clin , Q ref f clin , f ref were lower for parallel orientation compared to those obtained in the perpendicular orientation. Five ionization chambers from our study set, IBA Razor, PTW 31016 3D PinPoint, PTW 31022 3D PinPoint, PTW 31023 PinPoint, and SI Exradin A16, fulfill the requirement recommended in the TRS-483 Code of Practice, that is, 0.95 < k Q clin , Q ref f clin , f ref < 1.05 , down to the field size 0.8 cm2 × 0.8 cm2 , when they are positioned in parallel orientation; two of the ionization chambers, IBA Razor and PTW 31023 PinPoint, satisfy this condition down to the field size of 0.5 cm2 × 0.5 cm2 . CONCLUSIONS The present paper provides experimental results of detector-specific output correction factors for seven small volume ionization chambers. Output correction factors were determined in 6 and 10 MV photon beams with and without flattening filter down to the square field size of 0.5 cm2 × 0.5 cm2 for two orientations of ionization chambers - perpendicular and parallel. Our main finding is that output correction factors are smaller if they are determined in a parallel orientation compared to those obtained in a perpendicular orientation for all ionization chambers regardless of the photon beam energy, filtration, or linear accelerator being used. Based on our findings, we recommend using ionization chambers in parallel orientation, to minimize corrections in the experimental determination of field output factors. Latter holds even for field sizes below 1.0 cm2 × 1.0 cm2 , whenever necessary corrections remain within 5%, which was the case for several ionization chambers from our set. TRS-483 recommended perpendicular orientation of ionization chambers for the determination of field output factors. The present study presents results for both perpendicular and parallel orientation of ionization chambers. When validated by other researchers, the present results for parallel orientation can be considered as a complementary dataset to those given in TRS-483.
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Affiliation(s)
- Božidar Casar
- Department for Dosimetry and Quality of Radiological ProceduresInstitute of Oncology LjubljanaLjubljanaSlovenia
| | | | - Ignasi Mendez
- Department for Dosimetry and Quality of Radiological ProceduresInstitute of Oncology LjubljanaLjubljanaSlovenia
| | - Slaven Jurković
- Medical Physics DepartmentUniversity Hospital RijekaRijekaCroatia
- Department of Physics and BiophysicsFaculty of MedicineUniversity of RijekaRijekaCroatia
| | - M. Saiful Huq
- Department of Radiation OncologyUniversity of Pittsburgh School of Medicine and UPMC Hillman Cancer CenterPittsburghPAUSA
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Madden L, Archer J, Li E, Jelen U, Dong B, Roberts N, Holloway L, Rosenfeld A. First measurements with a plastic scintillation dosimeter at the Australian MRI-LINAC. ACTA ACUST UNITED AC 2019; 64:175015. [DOI: 10.1088/1361-6560/ab324b] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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