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Tzomakas MK, Peppa V, Alexiou A, Karakatsanis G, Episkopakis A, Michail C, Valais I, Fountos G, Kalyvas N, Kandarakis IS. A phantom based evaluation of the clinical imaging performance of electronic portal imaging devices. Heliyon 2023; 9:e21116. [PMID: 37916082 PMCID: PMC10616349 DOI: 10.1016/j.heliyon.2023.e21116] [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: 03/08/2023] [Revised: 10/14/2023] [Accepted: 10/16/2023] [Indexed: 11/03/2023] Open
Abstract
Purpose In this study an evaluation of the imaging performance of an electronic portal imaging device (EPID) is presented. The evaluation performed employing the QC-3V image quality phantom. Methods An EPID system of a 6 MV LINAC, was used to obtain images of a QC-3V EPID phantom. The X-ray source to phantom distance was 100 cm and the field size was 15x15 cm2. The irradiation conditions comprised Dose Rates (DR) of 200, 400 and 600 for a 2 MU-100 MU range. The Contrast Transfer Function (CTF), the Noise Power Spectrum (NPS), the Normalized Noise Power Spectrum (NNPS) and the Contrast-to-Noise Ratio (CNR) were studied. In addition, an alternative factor showing a frequency related output signal-to-noise ratio (SNR), the Signal-to-Noise-Frequency Response (SNFR), has been introduced. SNFR is a comprehensive quality index, easily determined in clinical environment. Results The CTF curves were found comparable to each other. The lowest values were measured at 2 MU and 200 MU/min. Concerning the NPS and NNPS graphs it was found that the values decrease up to approximately 0.3 lp/mm and demonstrate a white noise shape afterwards. SNFR values were found reducing with spatial frequency. Highest CNR were found between the region 7 and 11 of the phantom. Conclusions The influence of MU and DR on EPID performance were investigated. Image quality was assessed using the QC-3V phantom. The presented results can lead to image quality amelioration and act supportively to current image quality control routine protocols.
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Affiliation(s)
- Marios K. Tzomakas
- Radiation Physics, Materials Technology and Biomedical Imaging Laboratory, Department of Biomedical Engineering, University of West Attica, Egaleo, 12210 Athens, Greece
| | - Vasiliki Peppa
- General Hospital of Athens Alexandra, Department of Radiotherapy, 11528 Athens, Greece
| | - Antigoni Alexiou
- General Hospital of Athens Alexandra, Department of Radiotherapy, 11528 Athens, Greece
| | - Georgios Karakatsanis
- General Hospital of Athens Alexandra, Department of Radiotherapy, 11528 Athens, Greece
| | - Anastasios Episkopakis
- Elekta, 15124 Athens, Greece
- Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, 115 27 Athens, Greece
| | - Christos Michail
- Radiation Physics, Materials Technology and Biomedical Imaging Laboratory, Department of Biomedical Engineering, University of West Attica, Egaleo, 12210 Athens, Greece
| | - Ioannis Valais
- Radiation Physics, Materials Technology and Biomedical Imaging Laboratory, Department of Biomedical Engineering, University of West Attica, Egaleo, 12210 Athens, Greece
| | - George Fountos
- Radiation Physics, Materials Technology and Biomedical Imaging Laboratory, Department of Biomedical Engineering, University of West Attica, Egaleo, 12210 Athens, Greece
| | - Nektarios Kalyvas
- Radiation Physics, Materials Technology and Biomedical Imaging Laboratory, Department of Biomedical Engineering, University of West Attica, Egaleo, 12210 Athens, Greece
| | - Ioannis S. Kandarakis
- Radiation Physics, Materials Technology and Biomedical Imaging Laboratory, Department of Biomedical Engineering, University of West Attica, Egaleo, 12210 Athens, Greece
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Renaud J, Muir B. Assessing the accuracy of electronic portal imaging device (EPID)-based dosimetry: II. Evaluation of a dosimetric uncertainty budget and development of a new film-in-EPID absorbed dose calibration methodology. Med Phys 2021; 49:1238-1247. [PMID: 34954834 DOI: 10.1002/mp.15425] [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: 11/22/2021] [Accepted: 12/12/2021] [Indexed: 11/08/2022] Open
Abstract
PURPOSE The aim of this study is to reduce the uncertainty associated with determining dose-to-water using an amorphous silicon electronic portal imaging detector (EPID) under reference conditions by developing a direct calibration formalism based on radiochromic film measurements made within the EPID panel and detailed Monte Carlo simulations. To our knowledge, this is the first EPID-based dosimetry study reporting an uncertainty budget . METHODS Pixel sensitivity and relative off-axis response was mapped by simultaneously irradiating film contained within the imager panel and acquiring an EPID image set. The detector panel was disassembled for the purpose of modeling the EPID in detail using the EGSnrc DOSXYZnrc usercode, which was in turn used to calculate dose-to-film in EPID to dose-to-water in water conversion factors . RESULTS A direct comparison of the two correction methodologies investigated in this work, the previously established empirical method and the proposed simultaneous measurement approach involving in-EPID film dosimetry, produced an agreement with an RMS deviation of 1.4 % overall. A combined standard relative uncertainty of 3.3 % (k = 1) was estimated for the determination of absorbed dose to water at the position of the EPID using the proposed calibration methodology . CONCLUSIONS This work describes a direct method of calibrating EPID response in terms of absorbed dose to water requiring fewer measurements than other empirical approaches, and without 2D spatial interpolation of correction factors. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- James Renaud
- Metrology Research Centre, National Research Council Canada, Ottawa, Ontario, Canada
| | - Bryan Muir
- Metrology Research Centre, National Research Council Canada, Ottawa, Ontario, Canada
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Hanley J, Dresser S, Simon W, Flynn R, Klein EE, Letourneau D, Liu C, Yin FF, Arjomandy B, Ma L, Aguirre F, Jones J, Bayouth J, Holmes T. AAPM Task Group 198 Report: An implementation guide for TG 142 quality assurance of medical accelerators. Med Phys 2021; 48:e830-e885. [PMID: 34036590 DOI: 10.1002/mp.14992] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 03/16/2021] [Accepted: 04/28/2021] [Indexed: 11/11/2022] Open
Abstract
The charges on this task group (TG) were as follows: (a) provide specific procedural guidelines for performing the tests recommended in TG 142; (b) provide estimate of the range of time, appropriate personnel, and qualifications necessary to complete the tests in TG 142; and (c) provide sample daily, weekly, monthly, or annual quality assurance (QA) forms. Many of the guidelines in this report are drawn from the literature and are included in the references. When literature was not available, specific test methods reflect the experiences of the TG members (e.g., a test method for door interlock is self-evident with no literature necessary). In other cases, the technology is so new that no literature for test methods was available. Given broad clinical adaptation of volumetric modulated arc therapy (VMAT), which is not a specific topic of TG 142, several tests and criteria specific to VMAT were added.
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Affiliation(s)
- Joseph Hanley
- Princeton Radiation Oncology, Monroe, New Jersey, 08831, USA
| | - Sean Dresser
- Winship Cancer Institute, Radiation Oncology, Emory University, Atlanta, Georgia, 30322, USA
| | | | - Ryan Flynn
- Department of Radiation Oncology, University of Iowa, Iowa City, Iowa, 52242, USA
| | - Eric E Klein
- Brown university, Rhode Island Hospital, Providence, Rhode Island, 02905, USA
| | | | - Chihray Liu
- University of Florida, Gainesville, Florida, 32610-0385, USA
| | - Fang-Fang Yin
- Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina, 27710, USA
| | - Bijan Arjomandy
- Karmanos Cancer Institute at McLaren-Flint, Flint, Michigan, 48532, USA
| | - Lijun Ma
- Department of Radiation Oncology, University of California San Francisco, San Francisco, 94143-0226, USA
| | | | - Jimmy Jones
- Department of Radiation Oncology, The University of Colorado Health-Poudre Valley, Fort Collins, Colorado, 80525, USA
| | - John Bayouth
- Department of Human Oncology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, 53792-0600, USA
| | - Todd Holmes
- Varian Medical Systems, Palo Alto, California, 94304, USA
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