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Dogan N, Mijnheer BJ, Padgett K, Nalichowski A, Wu C, Nyflot MJ, Olch AJ, Papanikolaou N, Shi J, Holmes SM, Moran J, Greer PB. AAPM Task Group Report 307: Use of EPIDs for Patient-Specific IMRT and VMAT QA. Med Phys 2023; 50:e865-e903. [PMID: 37384416 PMCID: PMC11230298 DOI: 10.1002/mp.16536] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 04/23/2023] [Accepted: 05/15/2023] [Indexed: 07/01/2023] Open
Abstract
PURPOSE Electronic portal imaging devices (EPIDs) have been widely utilized for patient-specific quality assurance (PSQA) and their use for transit dosimetry applications is emerging. Yet there are no specific guidelines on the potential uses, limitations, and correct utilization of EPIDs for these purposes. The American Association of Physicists in Medicine (AAPM) Task Group 307 (TG-307) provides a comprehensive review of the physics, modeling, algorithms and clinical experience with EPID-based pre-treatment and transit dosimetry techniques. This review also includes the limitations and challenges in the clinical implementation of EPIDs, including recommendations for commissioning, calibration and validation, routine QA, tolerance levels for gamma analysis and risk-based analysis. METHODS Characteristics of the currently available EPID systems and EPID-based PSQA techniques are reviewed. The details of the physics, modeling, and algorithms for both pre-treatment and transit dosimetry methods are discussed, including clinical experience with different EPID dosimetry systems. Commissioning, calibration, and validation, tolerance levels and recommended tests, are reviewed, and analyzed. Risk-based analysis for EPID dosimetry is also addressed. RESULTS Clinical experience, commissioning methods and tolerances for EPID-based PSQA system are described for pre-treatment and transit dosimetry applications. The sensitivity, specificity, and clinical results for EPID dosimetry techniques are presented as well as examples of patient-related and machine-related error detection by these dosimetry solutions. Limitations and challenges in clinical implementation of EPIDs for dosimetric purposes are discussed and acceptance and rejection criteria are outlined. Potential causes of and evaluations of pre-treatment and transit dosimetry failures are discussed. Guidelines and recommendations developed in this report are based on the extensive published data on EPID QA along with the clinical experience of the TG-307 members. CONCLUSION TG-307 focused on the commercially available EPID-based dosimetric tools and provides guidance for medical physicists in the clinical implementation of EPID-based patient-specific pre-treatment and transit dosimetry QA solutions including intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) treatments.
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Affiliation(s)
- Nesrin Dogan
- Department of Radiation Oncology, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Ben J Mijnheer
- Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, Netherlands
| | - Kyle Padgett
- Department of Radiation Oncology, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Adrian Nalichowski
- Department of Radiation Oncology, Karmanos Cancer Institute, Detroit, Michigan, USA
| | - Chuan Wu
- Department of Radiation Oncology, Sutter Medical Foundation, Roseville, California, USA
| | - Matthew J Nyflot
- Department of Radiation Oncology, University of Washington, Seattle, Washington, USA
| | - Arthur J Olch
- Department of Radiation Oncology, University of Southern California, and Children's Hospital Los Angeles, Los Angeles, California, USA
| | - Niko Papanikolaou
- Division of Medical Physics, UT Health-MD Anderson, San Antonio, Texas, USA
| | - Jie Shi
- Sun Nuclear Corporation - A Mirion Medical Company, Melbourne, Florida, USA
| | | | - Jean Moran
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York, USA
| | - Peter B Greer
- Department of Radiation Oncology, Calvary Mater Newcastle Hospital, Newcastle, NSW, Australia
- School of Information and Physical Sciences, University of Newcastle, Newcastle, NSW, Australia
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Schade S, Engenhart-Cabillic R, Zink K, Czarnecki D. The fast calibration model for dosimetry with an electronic portal imaging device. J Appl Clin Med Phys 2022; 23:e13599. [PMID: 35876832 DOI: 10.1002/acm2.13599] [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: 03/01/2021] [Revised: 08/27/2021] [Accepted: 11/01/2021] [Indexed: 11/09/2022] Open
Abstract
PURPOSE The aim of this study was to develop an algorithm that corrects the image of an electronic portal imaging device (EPID) of a linear accelerator so that it can be used for dosimetric purposes, such as in vivo dosimetry or quality assurance for photon radiotherapy. For that purpose, the impact of the field size, phantom thickness, and the varying spectral photon distribution within the irradiation field on the EPID image was investigated. METHODS The EPID measurements were verified using reference measurements with ionization chambers. Therefore, absolute dose measurements with an ionization chamber and relative dose measurements with a detector array were performed. An EPID calibration and correction algorithm was developed to convert the EPID image to a dose distribution. The algorithm was validated by irradiating inhomogeneous phantoms using square fields as well as irregular IMRT fields. RESULTS It was possible to correct the influence of the field size, phantom thickness on the EPID signal as well as the homogenization of the image profile by several correction factors within 0.6%. A gamma index analysis (3%, 3 mm) of IMRT fields showed a pass rate of above 99%, when comparing to the planning system. CONCLUSION The developed algorithm enables an online dose measurement with the EPID during the radiation treatment. The algorithm is characterized by a robust, non-iterative, and thus real-time capable procedure with little measuring effort and does not depend on system-specific parameters. The EPID image is corrected by multiplying three independent correction factors. Therefore, it can easily be extent by further correction factors for other influencing variables, so it can be transferred to other linear accelerators and EPID configurations.
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Affiliation(s)
- Stephanie Schade
- Department of Radiotherapy and Radiation Oncology, University Medical Center Giessen and Marburg, Klinikstrasse, Giessen, Germany.,Institute of Medical Physics and Radiation Protection, University of Applied Sciences Giessen, Wiesenstrasse, Giessen, Germany
| | - Rita Engenhart-Cabillic
- Department of Radiotherapy and Radiation Oncology, University Medical Center Giessen and Marburg, Klinikstrasse, Giessen, Germany.,Marburg Ion Therapy Center (MIT), Albrecht-Kossel-Strasse, Marburg, Germany
| | - Klemens Zink
- Department of Radiotherapy and Radiation Oncology, University Medical Center Giessen and Marburg, Klinikstrasse, Giessen, Germany.,Institute of Medical Physics and Radiation Protection, University of Applied Sciences Giessen, Wiesenstrasse, Giessen, Germany.,Marburg Ion Therapy Center (MIT), Albrecht-Kossel-Strasse, Marburg, Germany
| | - Damian Czarnecki
- Institute of Medical Physics and Radiation Protection, University of Applied Sciences Giessen, Wiesenstrasse, Giessen, Germany
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Renaud J, Muir B. Assessing the accuracy of electronic portal imaging device (EPID)-based dosimetry: I. Quantities influencing long-term stability. Med Phys 2021; 49:1231-1237. [PMID: 34964136 DOI: 10.1002/mp.15434] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 12/08/2021] [Accepted: 12/12/2021] [Indexed: 11/07/2022] 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 identifying and accounting for operational and environmental factors influencing long-term stability of EPID response. METHODS Measurements of the EPID relative response, corrected for variations in linear accelerator (linac) output, were performed regularly over a period of 12 months. For every acquired image set, measurements of detector supply voltages, internal operating temperature, and ambient environmental conditions were obtained. Pearson r correlation coefficients were then calculated for each pair of variables, a subset of which were fitted using multiple linear regression to develop a predictive model of EPID response. Principal component analysis was performed on the dataset to reveal the internal structure of the data in a way that best accounts for the observed variations. RESULTS The +5.5 V power supply voltage, internal operating temperature, and the accumulated dose absorbed in EPID were identified as having the greatest influence on the long-term stability of EPID response. By correcting for the combined effect of these variables, the mean difference in linac output as measured by the EPID relative to a reference-class chamber improved from -0.46 % to 0.23 % over the period of the study. CONCLUSIONS This work suggests that the stability of an EPID over a period of a year can be improved by a factor of two by monitoring and accounting for the effects of variations in power supply voltage, internal temperature of the detector, and accumulated absorbed dose. 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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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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Liu W, Zhang L, Dai G, Zhang X, Li G, Yi Z. Deep Neural Network with Structural Similarity Difference and Orientation-based Loss for Position Error Classification in The Radiotherapy of Graves' Ophthalmopathy Patients. IEEE J Biomed Health Inform 2021; 26:2606-2614. [PMID: 34941537 DOI: 10.1109/jbhi.2021.3137451] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Identifying position errors for Graves' ophthalmopathy (GO) patients using electronic portal imaging device (EPID) transmission fluence maps is helpful in monitoring treatment.} However, most of the existing models only extract features from dose difference maps computed from EPID images, which do not fully characterize all information of the positional errors. In addition, the position error has a three-dimensional spatial nature, which has never been explored in previous work. To address the above problems, a deep neural network (DNN) model with structural similarity difference and orientation-based loss is proposed in this paper, which consists of a feature extraction network and a feature enhancement network. To capture more information, three types of Structural SIMilarity (SSIM) sub-index maps are computed to enhance the luminance, contrast, and structural features of EPID images, respectively. These maps and the dose difference maps are fed into different networks to extract radiomic features. To acquire spatial features of the position errors, an orientation-based loss function is proposed for optimal training. It makes the data distribution more consistent with the realistic 3D space by integrating the error deviations of the predicted values in the left-right, superior-inferior, anterior-posterior directions. Experimental results on a constructed dataset demonstrate the effectiveness of the proposed model, compared with other related models and existing state-of-the-art methods.
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Guo K, Ingleby H, Van Uytven E, Elbakri I, Van Beek T, McCurdy B. Performance optimization of a tri-hybrid method for estimation of patient scatter into the EPID. J Appl Clin Med Phys 2021; 22:99-114. [PMID: 34697889 PMCID: PMC8598147 DOI: 10.1002/acm2.13439] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2021] [Revised: 05/29/2021] [Accepted: 09/14/2021] [Indexed: 12/02/2022] Open
Abstract
On‐treatment EPID images are contaminated with patient‐generated scattered photons. If this component can be accurately estimated, its effect can be removed, and therefore a corresponding in vivo patient dose estimate will be more accurate. Our group previously developed a "tri‐hybrid" (TH) algorithm to provide fast but accurate estimates of patient‐generated photon scatter. The algorithm uses an analytical method to solve for singly‐scattered photon fluence, a modified Monte Carlo hybrid method to solve for multiply‐scattered photon fluence, and a pencil beam scatter kernel method to solve for electron interaction generated scattered photon fluence. However, for efficient clinical implementation, spatial and energy sampling must be optimized for speed while maintaining overall accuracy. In this work, the most significant sampling issues were examined, including spatial sampling settings for the patient voxel size, the number of Monte Carlo histories used in the modified hybrid MC method, scatter order sampling for the hybrid method, and also a range of energy spectrum sampling (i.e., energy bin sizes). The total predicted patient‐scattered photon fluence entering the EPID was compared with full MC simulation (EGSnrc) for validation. Three phantoms were tested with 6 and 18 MV beam energies, field sizes of 4 × 4, 10 × 10, and 20 × 20 cm2, and source‐to‐imager distance of 140 cm to develop a set of optimal sampling settings. With the recommended sampling, accuracy and precision of the total‐scattered energy fluence of the TH patient scatter prediction method are within 0.9% and 1.2%, respectively, for all test cases compared with full MC simulation results. For the mean energy spectrum across the imaging plane, comparison of TH with full MC simulation showed 95% overlap. This study has optimized sampling settings so that they have minimal impact on patient scatter prediction accuracy while maintaining maximum execution speed, a critical step for future clinical implementation.
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Affiliation(s)
- Kaiming Guo
- Division of Medical Physics, CancerCare Manitoba, Winnipeg, Manitoba, Canada.,Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Harry Ingleby
- Division of Medical Physics, CancerCare Manitoba, Winnipeg, Manitoba, Canada.,Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Eric Van Uytven
- Division of Medical Physics, CancerCare Manitoba, Winnipeg, Manitoba, Canada
| | - Idris Elbakri
- Division of Medical Physics, CancerCare Manitoba, Winnipeg, Manitoba, Canada.,Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Timothy Van Beek
- Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Boyd McCurdy
- Division of Medical Physics, CancerCare Manitoba, Winnipeg, Manitoba, Canada.,Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada.,Department of Radiology, University of Manitoba, Winnipeg, Manitoba, Canada
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Wolfs CJA, Canters RAM, Verhaegen F. Identification of treatment error types for lung cancer patients using convolutional neural networks and EPID dosimetry. Radiother Oncol 2020; 153:243-249. [PMID: 33011206 DOI: 10.1016/j.radonc.2020.09.048] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 09/16/2020] [Accepted: 09/26/2020] [Indexed: 12/29/2022]
Abstract
BACKGROUND/PURPOSE Electronic portal imaging device (EPID) dosimetry aims to detect treatment errors, potentially leading to treatment adaptation. Clinically used threshold classification methods for detecting errors lead to loss of information (from multi-dimensional EPID data to a few numbers) and cannot be used for identifying causes of errors. Advanced classification methods, such as deep learning, can use all available information. In this study, convolutional neural networks (CNNs) were trained to detect and identify error type and magnitude of simulated treatment errors in lung cancer patients. The purpose of this simulation study is to provide a proof-of-concept of CNNs for error identification using EPID dosimetry in an in vivo scenario. MATERIALS AND METHODS Clinically realistic ranges of anatomical changes, positioning errors and mechanical errors were simulated for lung cancer patients. Predicted portal dose images (PDIs) containing errors were compared to error-free PDIs using the widely used gamma analysis. CNNs were trained to classify errors using 2D gamma maps. Three classification levels were assessed: Level 1 (main error type, e.g., anatomical change), Level 2 (error subtype, e.g., tumor regression) and Level 3 (error magnitude, e.g., >50% tumor regression). RESULTS CNNs showed good performance for all classification levels (training/test accuracy 99.5%/96.1%, 92.5%/86.8%, 82.0%/72.9%). For Level 3, overfitting became more apparent. CONCLUSION This simulation study indicates that deep learning is a promising powerful tool for identifying types and magnitude of treatment errors with EPID dosimetry, providing additional information not currently available from EPID dosimetry. This is a first step towards rapid, automated models for identification of treatment errors using EPID dosimetry.
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Affiliation(s)
- Cecile J A Wolfs
- Department of Radiation Oncology (Maastro), GROW School for Oncology, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Richard A M Canters
- Department of Radiation Oncology (Maastro), GROW School for Oncology, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Frank Verhaegen
- Department of Radiation Oncology (Maastro), GROW School for Oncology, Maastricht University Medical Centre, Maastricht, The Netherlands.
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Wolfs CJA, Varfalvy N, Canters RAM, Nijsten SMJJG, Hattu D, Archambault L, Verhaegen F. External validation of a hidden Markov model for gamma-based classification of anatomical changes in lung cancer patients using EPID dosimetry. Med Phys 2020; 47:4675-4682. [PMID: 32654162 DOI: 10.1002/mp.14385] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 06/26/2020] [Accepted: 07/06/2020] [Indexed: 01/13/2023] Open
Abstract
PURPOSE To externally validate a hidden Markov model (HMM) for classifying gamma analysis results of in vivo electronic portal imaging device (EPID) measurements into different categories of anatomical change for lung cancer patients. Additionally, the relationship between HMM classification and deviations in dose-volume histogram (DVH) metrics was evaluated. METHODS The HMM was developed at CHU de Québec (CHUQ), and trained on features extracted from gamma analysis maps of in vivo EPID measurements from 483 fractions (24 patients, treated with three-dimensional 3D-CRT or intensity modulated radiotherapy), using the EPID measurement of the first treatment fraction as reference. The model inputs were the average gamma value, standard deviation, and average value of the highest 1% of gamma values, all averaged over all beams in a fraction. The HMM classified each fraction into one of three categories: no anatomical change (Category 1), some anatomical change (no clinical action needed, Category 2) and severe anatomical change (clinical action needed, Category 3). The external validation dataset consisted of EPID measurements from 263 fractions of 30 patients treated at Maastro with volumetric modulated arc therapy (VMAT) or hybrid plans (containing both static beams and VMAT arcs). Gamma analysis features were extracted in the same way as in the CHUQ dataset, by using the EPID measurement of the first fraction as reference (γQ), and additionally by using an EPID dose prediction as reference (γM). For Maastro patients, cone beam computed tomography (CBCT) scans and image-guided radiotherapy (IGRT) classification of these images were available for each fraction. Contours were propagated from the planning CT to the CBCTs, and the dose was recalculated using a Monte Carlo dose engine. Dose-volume histogram metrics for targets and organs-at-risk (OARs: lungs, heart, mediastinum, spinal cord, brachial plexus) were extracted for each fraction, and compared to the planned dose. HMM classification of the external validation set was compared to threshold classification based on the average gamma value alone (a surrogate for clinical classification at CHUQ), IGRT classification as performed at Maastro, and differences in DVH metrics extracted from 3D dose recalculations on the CBCTs. RESULTS The HMM achieved 65.4%/65.0% accuracy for γQ and γM, respectively, compared to average gamma threshold classification. When comparing HMM classification with IGRT classification, the overall accuracy was 29.7% for γQ and 23.2% for γM. Hence, HMM classification and IGRT classification of anatomical changes did not correspond. However, there is a trend towards higher deviations in DVH metrics with classification into higher categories by the HMM for large OARs (lungs, heart, mediastinum), but not for the targets and small OARs (spinal cord, brachial plexus). CONCLUSION The external validation shows that transferring the HMM for anatomical change classification to a different center is challenging, but can still be valuable. The HMM trained at CHUQ cannot be used directly to classify anatomical changes in the Maastro data. However, it may be possible to use the model in a different capacity, as an indicator for changes in the 3D dose based on two-dimensional EPID measurements.
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Affiliation(s)
- Cecile J A Wolfs
- Department of Radiation Oncology (Maastro), GROW School for Oncology, Maastricht University Medical Centre+, Maastricht, The Netherlands
| | - Nicolas Varfalvy
- Département de Radio-oncologie, CHU de Québec, Québec, QC, Canada
| | - Richard A M Canters
- Department of Radiation Oncology (Maastro), GROW School for Oncology, Maastricht University Medical Centre+, Maastricht, The Netherlands
| | - Sebastiaan M J J G Nijsten
- Department of Radiation Oncology (Maastro), GROW School for Oncology, Maastricht University Medical Centre+, Maastricht, The Netherlands
| | - Djoya Hattu
- Department of Radiation Oncology (Maastro), GROW School for Oncology, Maastricht University Medical Centre+, Maastricht, The Netherlands
| | - Louis Archambault
- Département de Radio-oncologie, CHU de Québec, Québec, QC, Canada.,Physics Department, Université Laval, Québec City, QC, Canada
| | - Frank Verhaegen
- Department of Radiation Oncology (Maastro), GROW School for Oncology, Maastricht University Medical Centre+, Maastricht, The Netherlands
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Olaciregui-Ruiz I, Beddar S, Greer P, Jornet N, McCurdy B, Paiva-Fonseca G, Mijnheer B, Verhaegen F. In vivo dosimetry in external beam photon radiotherapy: Requirements and future directions for research, development, and clinical practice. Phys Imaging Radiat Oncol 2020; 15:108-116. [PMID: 33458335 PMCID: PMC7807612 DOI: 10.1016/j.phro.2020.08.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 08/17/2020] [Accepted: 08/18/2020] [Indexed: 11/18/2022] Open
Abstract
External beam radiotherapy with photon beams is a highly accurate treatment modality, but requires extensive quality assurance programs to confirm that radiation therapy will be or was administered appropriately. In vivo dosimetry (IVD) is an essential element of modern radiation therapy because it provides the ability to catch treatment delivery errors, assist in treatment adaptation, and record the actual dose delivered to the patient. However, for various reasons, its clinical implementation has been slow and limited. The purpose of this report is to stimulate the wider use of IVD for external beam radiotherapy, and in particular of systems using electronic portal imaging devices (EPIDs). After documenting the current IVD methods, this report provides detailed software, hardware and system requirements for in vivo EPID dosimetry systems in order to help in bridging the current vendor-user gap. The report also outlines directions for further development and research. In vivo EPID dosimetry vendors, in collaboration with users across multiple institutions, are requested to improve the understanding and reduce the uncertainties of the system and to help in the determination of optimal action limits for error detection. Finally, the report recommends that automation of all aspects of IVD is needed to help facilitate clinical adoption, including automation of image acquisition, analysis, result interpretation, and reporting/documentation. With the guidance of this report, it is hoped that widespread clinical use of IVD will be significantly accelerated.
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Affiliation(s)
- Igor Olaciregui-Ruiz
- Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Sam Beddar
- Division of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Peter Greer
- Calvary Mater Newcastle Hospital and University of Newcastle, Newcastle, New South Wales, Australia
| | - Nuria Jornet
- Servei de Radiofísica i Radioprotecció, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Boyd McCurdy
- Medical Physics Department, CancerCare Manitoba, Winnipeg, Manitoba, Canada
| | - Gabriel Paiva-Fonseca
- Department of Radiation Oncology (Maastro), GROW School for Oncology, Maastricht University Medical Centre+, Maastricht, the Netherlands
| | - Ben Mijnheer
- Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Frank Verhaegen
- Department of Radiation Oncology (Maastro), GROW School for Oncology, Maastricht University Medical Centre+, Maastricht, the Netherlands
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Puyati W, Khawne A, Barnes M, Zwan B, Greer P, Fuangrod T. Predictive quality assurance of a linear accelerator based on the machine performance check application using statistical process control and ARIMA forecast modeling. J Appl Clin Med Phys 2020; 21:73-82. [PMID: 32543097 PMCID: PMC7484849 DOI: 10.1002/acm2.12917] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 12/04/2019] [Accepted: 04/21/2020] [Indexed: 12/16/2022] Open
Abstract
Purpose A predictive linac quality assurance system based on the output of the Machine Performance Check (MPC) application was developed using statistical process control and autoregressive integrated moving average forecast modeling. The aim of this study is to demonstrate the feasibility of predictive quality assurance based on MPC tests that allow proactive preventative maintenance procedures to be carried out to better ensure optimal linac performance and minimize downtime. Method and Materials Daily MPC data were acquired for a total of 490 measurements. The initial 85% of data were used in prediction model learning with the autoregressive integrated moving average technique and in calculating upper and lower control limits for statistical process control analysis. The remaining 15% of data were used in testing the accuracy of the predictions of the proposed system. Two types of prediction were studied, namely, one‐step‐ahead values for predicting the next day's quality assurance results and six‐step‐ahead values for predicting up to a week ahead. Results that fall within the upper and lower control limits indicate a normal stage of machine performance, while the tolerance, determined from AAPM TG‐142, is the clinically required performance. The gap between the control limits and the clinical tolerances (as the warning stage) provides a window of opportunity for rectifying linac performance issues before they become clinically significant. The accuracy of the predictive model was tested using the root‐mean‐square error, absolute error, and average accuracy rate for all MPC test parameters. Results The accuracy of the predictive model is considered high (average root‐mean‐square error and absolute error for all parameters of less than 0.05). The average accuracy rate for indicating the normal/warning stages was higher than 85.00%. Conclusion Predictive quality assurance with the MPC will allow preventative maintenance, which could lead to improved linac performance and a reduction in unscheduled linac downtime.
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Affiliation(s)
- Wayo Puyati
- Department of Computer Engineering, Faculty of Engineering, King Mongkut's Institute of Technology Ladkrabang, Bangkok, 10520, Thailand.,Department of Mathematics Statistics and Computer, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani, 34190, Thailand
| | - Amnach Khawne
- Department of Computer Engineering, Faculty of Engineering, King Mongkut's Institute of Technology Ladkrabang, Bangkok, 10520, Thailand
| | - Michael Barnes
- Department of Radiation Oncology, Calvary Mater Hospital Newcastle, NSW, 2298, Australia.,School of Mathematical and Physical Sciences, University of Newcastle, Newcastle, NSW, 2308, Australia
| | - Benjamin Zwan
- School of Mathematical and Physical Sciences, University of Newcastle, Newcastle, NSW, 2308, Australia.,Central Coast Cancer Centre, Gosford Hospital, Gosford, NSW, 2250, Australia
| | - Peter Greer
- Department of Radiation Oncology, Calvary Mater Hospital Newcastle, NSW, 2298, Australia.,School of Mathematical and Physical Sciences, University of Newcastle, Newcastle, NSW, 2308, Australia
| | - Todsaporn Fuangrod
- Faculty of Medicine and Public Health, HRH Princess Chulabhorn College of Medical Science, Chulabhorn Royal Academy, Bangkok, 10210, Thailand
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S M H, M H B, M M, S N, S B, H G, R S, F S, M M. An Empirical Transmitted EPID Dosimetry Method using a Back-Projection Algorithm. J Biomed Phys Eng 2019; 9:551-558. [PMID: 31750269 PMCID: PMC6820021 DOI: 10.31661/jbpe.v0i0.1082] [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: 12/12/2018] [Accepted: 01/25/2019] [Indexed: 11/16/2022]
Abstract
Background: The present study aimed to introduce a rapid transmission dosimetry through an electronic portal-imaging device (EPID) to achieve two-dimensional (2D) dose distribution for homogenous environments.
Material and Methods: In this Phantom study, first, the EPID calibration curve and correction coefficients for field size were obtained from EPID and ionization chamber. Second, the EPID off-axis pixel response was measured, and the grey-scale image of the EPID was converted into portal dose image using the calibration curve. Next, the scattering contribution was calculated to obtain the primary dose. Then, by means of a verified back-projection algorithm and the Scatter-to-Primary dose ratio, a 2D dose distribution at the mid-plane was obtained.
Results: The results obtained from comparing the transmitted EPID dosimetry to the calculated dose, using commercial treatment planning system with gamma function while there is 3% dose difference and 3mm distance to agreement criteria, were in a good agreement. In addition, the pass rates of γ < 1 was 94.89% for the homogeneous volumes.
Conclusion: Based on the results, the method proposed can be used in EPID dosimetry.
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Affiliation(s)
- Hashemi S M
- PhD, Medical Physics Research Center, Mashhad University of medical Science, Mashhad, Iran
| | - Bahreyni M H
- PhD, Medical Physics Research Center, Mashhad University of medical Science, Mashhad, Iran
| | - Mohammadi M
- PhD, Department of Medical Physics, Royal Adelaide Hospital, Adelaide, SA 5000, Australia
- PhD, School of Physical Sciences, University of Adelaide, Adelaide, SA 5005, Australia
| | - Nasseri S
- PhD, Medical Physics Research Center, Mashhad University of medical Science, Mashhad, Iran
| | - Bayani S
- MSC, Medical Physics Research Center, Mashhad University of medical Science, Mashhad, Iran
| | - Gholamhosseinian H
- PhD, Medical Physics Research Center, Mashhad University of medical Science, Mashhad, Iran
| | - Salek R
- MD, Cancer Research Center, Mashhad University of medical Science, Mashhad, Iran
| | - Shahedi F
- MSC, Department of Radiology, School of Paramedical Sciences, Torbat Heydariyeh University of Medical Sciences, Torbat Heydariyeh, Iran
| | - Momennezhad M
- PhD, Medical Physics Research Center, Mashhad University of medical Science, Mashhad, Iran
- PhD, Nuclear Medicine Research Center, Mashhad University of medical Science, Mashhad, Iran
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Ray X, Bojechko C, Moore KL. Evaluating the sensitivity of Halcyon's automatic transit image acquisition for treatment error detection: A phantom study using static IMRT. J Appl Clin Med Phys 2019; 20:131-143. [PMID: 31587477 PMCID: PMC6839375 DOI: 10.1002/acm2.12749] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 07/12/2019] [Accepted: 09/11/2019] [Indexed: 11/06/2022] Open
Abstract
PURPOSE The Varian Halcyon™ electronic portal imaging detector is always in-line with the beam and automatically acquires transit images for every patient with full-field coverage. These images could be used for "every patient, every monitor unit" quality assurance (QA) and eventually adaptive radiotherapy. This study evaluated the imager's sensitivity to potential clinical errors and day-to-day variations from clinical exit images. METHODS Open and modulated fields were delivered for each potential error. To evaluate output changes, monitor units were scaled by 2%-10% and delivered to solid water slabs and a homogeneous CIRS phantom. To mimic weight changes, 0.5-5.0 cm of buildup was added to the solid water. To evaluate positioning changes, a homogeneous and heterogeneous CIRS phantom were shifted 2-10 cm and 0.2-1.5 cm, respectively. For each test, mean relative differences (MRDs) and standard deviations in the pixel-difference histograms (σRD ) between test and baseline images were calculated. Lateral shift magnitudes were calculated using cross-correlation and edge-detection filtration. To assess patient variations, MRD and σRD were calculated from six prostate patients' daily exit images and compared between fractions with and without gas present. RESULTS MRDs responded linearly to output and buildup changes with a standard deviation of 0.3%, implying a 1% output change and 0.2 cm changes in buildup could be detected with 2.5σ confidence. Shifting the homogenous phantom laterally resulted in detectable MRD and σRD changes, and the cross-correlation function calculated the shift to within 0.5 mm for the heterogeneous phantom. MRD and σRD values were significantly associated with the presence of gas for five of the six patients. CONCLUSIONS Rapid analyses of automatically acquired Halcyon™ exit images could detect mid-treatment changes with high sensitivity, though appropriate thresholds will need to be set. This study presents the first steps toward developing effortless image evaluation for all aspects of every patient's treatment.
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Affiliation(s)
- Xenia Ray
- Department of Radiation Medicine and Applied SciencesUCSD Moores Cancer CenterLa JollaCAUSA
| | - Casey Bojechko
- Department of Radiation Medicine and Applied SciencesUCSD Moores Cancer CenterLa JollaCAUSA
| | - Kevin L. Moore
- Department of Radiation Medicine and Applied SciencesUCSD Moores Cancer CenterLa JollaCAUSA
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Hartgerink D, Swinnen A, Roberge D, Nichol A, Zygmanski P, Yin FF, Deblois F, Hurkmans C, Ong CL, Bruynzeel A, Aizer A, Fiveash J, Kirckpatrick J, Guckenberger M, Andratschke N, de Ruysscher D, Popple R, Zindler J. LINAC based stereotactic radiosurgery for multiple brain metastases: guidance for clinical implementation. Acta Oncol 2019; 58:1275-1282. [PMID: 31257960 DOI: 10.1080/0284186x.2019.1633016] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Introduction: Stereotactic radiosurgery (SRS) is a promising treatment option for patients with multiple brain metastases (BM). Recent technical advances have made LINAC based SRS a patient friendly technique, allowing for accurate patient positioning and a short treatment time. Since SRS is increasingly being used for patients with multiple BM, it remains essential that SRS be performed with the highest achievable quality in order to prevent unnecessary complications such as radionecrosis. The purpose of this article is to provide guidance for high-quality LINAC based SRS for patients with BM, with a focus on single isocenter non-coplanar volumetric modulated arc therapy (VMAT). Methods: The article is based on a consensus statement by the study coordinators and medical physicists of four trials which investigated whether patients with multiple BM are better palliated with SRS instead of whole brain radiotherapy (WBRT): A European trial (NCT02353000), two American trials and a Canadian CCTG lead intergroup trial (CE.7). This manuscript summarizes the quality assurance measures concerning imaging, planning and delivery. Results: To optimize the treatment, the interval between the planning-MRI (gadolinium contrast-enhanced, maximum slice thickness of 1.5 mm) and treatment should be kept as short as possible (< two weeks). The BM are contoured based on the planning-MRI, fused with the planning-CT. GTV-PTV margins are minimized or even avoided when possible. To maximize efficiency, the preferable technique is single isocenter (non-)coplanar VMAT, which delivers high doses to the target with maximal sparing of the organs at risk. The use of flattening filter free photon beams ensures a lower peripheral dose and shortens the treatment time. To bench mark SRS treatment plan quality, it is advisable to compare treatment plans between hospitals. Conclusion: This paper provides guidance for quality assurance and optimization of treatment delivery for LINAC-based radiosurgery for patients with multiple BM.
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Affiliation(s)
- Dianne Hartgerink
- Department of Radiation Oncology (MAASTRO), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Ans Swinnen
- Department of Radiation Oncology (MAASTRO), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - David Roberge
- Department of Radiation Oncology, CHUM, Montreal, QC, Canada
| | - Alan Nichol
- Department of Radiation Oncology, CHUM, Montreal, QC, Canada
| | - Piotr Zygmanski
- Brigham and Women’s Hospital, Dana Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts, USA
| | - Fang-Fang Yin
- Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina, USA
| | | | - Coen Hurkmans
- Department of Radiation Oncology, Catharina Hospital, Eindhoven, The Netherlands
| | - Chin Loon Ong
- Department of Radiation Oncology, HagaZiekenhuis, Den Haag, The Netherlands
| | - Anna Bruynzeel
- Department of Radiotherapy, Cancer Center Amsterdam, VU University medical center, Amsterdam, The Netherlands
| | - Ayal Aizer
- Brigham and Women’s Hospital, Dana Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts, USA
| | - John Fiveash
- Department of Radiation Oncology, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - John Kirckpatrick
- Brigham and Women’s Hospital, Dana Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts, USA
| | | | - Nicolaus Andratschke
- Department of Radiation Oncology, University Hospital Zürich, Zürich, Switzerland
| | - Dirk de Ruysscher
- Department of Radiation Oncology (MAASTRO), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Richard Popple
- Department of Radiation Oncology, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Jaap Zindler
- Department of Radiation Oncology (MAASTRO), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands
- Department of Radiation Oncology, Erasmus MC, Rotterdam, The Netherlands
- Holland Proton Therapy Center, Delft, The Netherlands
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Piron O, Varfalvy N, Archambault L. Establishing action threshold for change in patient anatomy using EPID gamma analysis and PTV coverage for head and neck radiotherapy treatment. Med Phys 2018; 45:3534-3545. [PMID: 29896916 DOI: 10.1002/mp.13045] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2017] [Revised: 05/24/2018] [Accepted: 05/31/2018] [Indexed: 02/28/2024] Open
Abstract
PURPOSE To present a new adaptive radiotherapy (ART) method based on relative gamma analysis and patient classification for the identification of anatomical changes that induce a sufficient dosimetric impact to affect the treatment delivery and require complete replanning. METHODS This retrospective study includes 55 patients treated for a head and neck cancer with IMRT, VMAT, or 3D conformal RT. Electronic Portal Imaging Device images for all treatment fields were acquired daily at every fraction. CBCTs were collected at least once a week. Gamma analysis was performed using the first fraction of the treatment as a reference once validated that it was delivered without error. Gamma analysis parameters (<γ>, standard deviation and the Top 1% γ) were used to define categories using statistic from a k-means clustering analysis. From these categories an action threshold was defined and correlated with dosimetric changes. For 23 of 55 patients, the V100% for PTV was computed for both, the planning CT and original contours deformed onto CBCT acquired at the last fraction. These values were then compared with 2D image relative γ-analysis of EPID images. Sensitivity and specificity of the method for the detection of dosimetric changes were computed. RESULTS Three categories indicating an increasing level of change with the planned treatment were identified. A threshold was established for which patients were at risk of deviation at <γ> = 0.42. From 23 recomputing plans, it has been confirmed that patients with a strong dosimetric impact were above this threshold, with a specificity of 0.80 and a sensitivity of 0.84. CONCLUSIONS The specificity and the sensitivity value confirmed the performance of the method to detect anatomical changes. The γ-analysis threshold correlated well with morphological changes that have a relevant dosimetric impact. Analysis of daily EPID images provides a method to identify patients at risk of deviation from their planned treatment and can support an early replanning decision.
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Affiliation(s)
- Ophélie Piron
- Department de Radio-oncologie, CHU de Quebec, 11 Côte du Palais, Quebec, QC, Canada
- Université Laval, 2325 Rue de l'Université, Ville de Québec, QC, G1V 0A6, Canada
| | - Nicolas Varfalvy
- Department de Radio-oncologie, CHU de Quebec, 11 Côte du Palais, Quebec, QC, Canada
- Université Laval, 2325 Rue de l'Université, Ville de Québec, QC, G1V 0A6, Canada
| | - Louis Archambault
- Department de Radio-oncologie, CHU de Quebec, 11 Côte du Palais, Quebec, QC, Canada
- Université Laval, 2325 Rue de l'Université, Ville de Québec, QC, G1V 0A6, Canada
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Held M, Cheung J, Perez Andujar A, Husson F, Morin O. Commissioning and Evaluation of an Electronic Portal Imaging Device-Based In-Vivo Dosimetry Software. Cureus 2018; 10:e2139. [PMID: 29632749 PMCID: PMC5880591 DOI: 10.7759/cureus.2139] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
This study reports on our experience with the in-vivo dose verification software, EPIgray® (DOSIsoft, Cachan, France). After the initial commissioning process, clinical experiments on phantom treatments were evaluated to assess the level of accuracy of the electronic portal imaging device (EPID) based in-vivo dose verification. EPIgray was commissioned based on the company’s instructions. This involved ion chamber measurements and portal imaging of solid water blocks of various thicknesses between 5 and 35 cm. Field sizes varied between 2 x 2 cm2 and 20 x 20 cm2. The determined conversion factors were adjusted through an additional iterative process using treatment planning system calculations. Subsequently, evaluation was performed using treatment plans of single and opposed beams, as well as intensity modulated radiotherapy (IMRT) plans, based on recommendations from the task group report TG-119 to test for dose reconstruction accuracy. All tests were performed using blocks of solid water slabs as a phantom. For single square fields, the dose at isocenter was reconstructed within 3% accuracy in EPIgray compared to the treatment planning system dose. Similarly, the relative deviation of the total dose was accurately reconstructed within 3% for all IMRT plans with points placed inside a high-dose region near the isocenter. Predictions became less accurate than < 5% when the evaluation point was outside the treatment target. Dose at points 5 cm or more away from the isocenter or within an avoidance structure was reconstructed less reliably. EPIgray formalism accuracy is adequate for an efficient error detection system with verifications performed in high-dose volumes. It provides immediate intra-fractional feedback on the delivery of treatment plans without affecting the treatment beam. Besides the EPID, no additional hardware is required. The software evaluates local point dose measurements to verify treatment plan delivery and patient positioning within 5% accuracy, depending on the placement of evaluation points.
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Affiliation(s)
- Mareike Held
- Radiation Oncology, University of California San Francisco
| | - Joey Cheung
- Radiation Oncology, University of California San Francisco
| | | | | | - Olivier Morin
- Radiation Oncology, University of California San Francisco
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Falco MD, Giancaterino S, De Nicola A, Adorante N, De Lorenzo RG, Di Tommaso M, Vinciguerra A, Trignani M, Perrotti F, Allajbej A, Fidanzio A, Greco F, Grusio M, Genovesi D, Piermattei A. A Feasibility Study for in vivo Dosimetry Procedure in Routine Clinical Practice. Technol Cancer Res Treat 2018; 17:1533033818779201. [PMID: 29871570 PMCID: PMC5992805 DOI: 10.1177/1533033818779201] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Purpose: The aim of the in vivo dosimetry, during the fractionated radiation therapy, is the verification of the correct dose delivery to patient. Nowadays, in vivo dosimetry procedures for photon beams are based on the use of the electronic portal imaging device and dedicated software to elaborate electronic portal imaging device images. Methods: In total, 8474 in vivo dosimetry tests were carried out for 386 patients treated with 3-dimensional conformal radiotherapy, intensity-modulated radiotherapy, and volumetric modulated arc therapy techniques, using the SOFTDISO. SOFTDISO is a dedicated software that uses electronic portal imaging device images in order to (1) calculate the R index, that is, the ratio between daily reconstructed dose and the planned one at isocenter and (2) perform a γ-like analysis between the signals, S, of a reference electronic portal imaging device image and that obtained in a daily fraction. It supplies 2 indexes, the percentage γ% of points with γ < 1 and the mean γ value, γmean. In γ-like analysis, the pass criteria for the signals agreement ΔS% and distance to agreement Δd have been selected based on the clinical experience and technology used. The adopted tolerance levels for the 3 indexes were fixed in 0.95 ≤ R ≤ 1.05, γ% ≥ 90%, and γmean ≤ 0.5. Results: The results of R ratio, γ-like, and a visual inspection of these data reported on a monitor screen permitted to individuate 2 classes of errors (1) class 1 that included errors due to inadequate standard quality controls and (2) class 2, due to patient morphological changes. Depending on the technique and anatomical site, a maximum of 18% of tests had at least 1 index out of tolerance; once removed the causes of class-1 errors, almost all patients (except patients with 4 lung and 2 breast cancer treated with 3-dimensional conformal radiotherapy) presented mean indexes values (R¯, γ¯%, and γ¯mean
) within tolerance at the end of treatment course. Class-2 errors were found in some patients. Conclusions: The in vivo dosimetry procedure with SOFTDISO resulted easily implementable, able to individuate errors with a limited workload.
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Affiliation(s)
- Maria D Falco
- 1 Department of Radiation Oncology "G. D'Annunzio", University of Chieti, SS. Annunziata Hospital, Chieti, Italy
| | - Stefano Giancaterino
- 1 Department of Radiation Oncology "G. D'Annunzio", University of Chieti, SS. Annunziata Hospital, Chieti, Italy
| | - Andrea De Nicola
- 1 Department of Radiation Oncology "G. D'Annunzio", University of Chieti, SS. Annunziata Hospital, Chieti, Italy
| | - Nico Adorante
- 1 Department of Radiation Oncology "G. D'Annunzio", University of Chieti, SS. Annunziata Hospital, Chieti, Italy
| | - Ramon Gimenez De Lorenzo
- 1 Department of Radiation Oncology "G. D'Annunzio", University of Chieti, SS. Annunziata Hospital, Chieti, Italy
| | - Monica Di Tommaso
- 1 Department of Radiation Oncology "G. D'Annunzio", University of Chieti, SS. Annunziata Hospital, Chieti, Italy
| | - Annamaria Vinciguerra
- 1 Department of Radiation Oncology "G. D'Annunzio", University of Chieti, SS. Annunziata Hospital, Chieti, Italy
| | - Marianna Trignani
- 1 Department of Radiation Oncology "G. D'Annunzio", University of Chieti, SS. Annunziata Hospital, Chieti, Italy
| | - Francesca Perrotti
- 1 Department of Radiation Oncology "G. D'Annunzio", University of Chieti, SS. Annunziata Hospital, Chieti, Italy
| | - Albina Allajbej
- 1 Department of Radiation Oncology "G. D'Annunzio", University of Chieti, SS. Annunziata Hospital, Chieti, Italy
| | - Andrea Fidanzio
- 2 Unità Operativa di Fisica Sanitaria; Fondazione Policlinico Universitario A. Gemelli, Università Cattolica del Sacro Cuore, Roma, Italy
| | - Francesca Greco
- 2 Unità Operativa di Fisica Sanitaria; Fondazione Policlinico Universitario A. Gemelli, Università Cattolica del Sacro Cuore, Roma, Italy
| | - Mattia Grusio
- 2 Unità Operativa di Fisica Sanitaria; Fondazione Policlinico Universitario A. Gemelli, Università Cattolica del Sacro Cuore, Roma, Italy
| | - Domenico Genovesi
- 1 Department of Radiation Oncology "G. D'Annunzio", University of Chieti, SS. Annunziata Hospital, Chieti, Italy
| | - Angelo Piermattei
- 2 Unità Operativa di Fisica Sanitaria; Fondazione Policlinico Universitario A. Gemelli, Università Cattolica del Sacro Cuore, Roma, Italy
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17
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Abstract ID: 130 Energy response correction for EPID dosimetry in photon radiation therapy. Phys Med 2017. [DOI: 10.1016/j.ejmp.2017.09.069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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18
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Peca S, Sinha RS, Brown DW, Smith WL. In vivo Portal Imaging Dosimetry Identifies Delivery Errors in Rectal Cancer Radiotherapy on the Belly Board Device. Technol Cancer Res Treat 2017; 16:956-963. [PMID: 28585490 PMCID: PMC5762054 DOI: 10.1177/1533034617711519] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Purpose: We recently developed a novel, open-source in vivo dosimetry that uses the electronic portal imaging device to detect dose delivery discrepancies. We applied our method on patients with rectal cancer treated on a belly board device. Methods: In vivo dosimetry was performed on 10 patients with rectal cancer treated prone on the belly board with a 4-field box arrangement. Portal images were acquired approximately once per week from each treatment beam. Our dosimetry method used these images along with the planning CT to reconstruct patient planar dose at isocenter depth. Results: Our algorithm proved sensitive to dose discrepancies and detected discordances in 7 patients. The majority of these were due to soft tissue differences between planning and treatment, present despite matching to bony anatomy. As a result of this work, quality assurance procedures have been implemented for our immobilization devices. Conclusion: In vivo dosimetry is a powerful quality assurance tool that can detect delivery discrepancies, including changes in patient setup and position. The added information on actual dose delivery may be used to evaluate equipment and process quality and to guide for adaptive radiotherapy.
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Affiliation(s)
- Stefano Peca
- Department of Physics and Astronomy, University of Calgary, Calgary, AB, Canada.,Department of Medical Physics, Tom Baker Cancer Centre, Calgary, AB, Canada
| | | | - Derek Wilson Brown
- Department of Physics and Astronomy, University of Calgary, Calgary, AB, Canada.,Department of Radiation Medicine and Applied Sciences, Moores Cancer Center, UC San Diego, La Jolla, CA, USA
| | - Wendy Lani Smith
- Department of Physics and Astronomy, University of Calgary, Calgary, AB, Canada.,Department of Medical Physics, Tom Baker Cancer Centre, Calgary, AB, Canada.,Department of Radiation Oncology, University of Calgary, Calgary, AB, Canada
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Köhn J, Licher J, Mielke M, Loutfi-Krauss B, Blümer N, Heine B, Rödel C, Scherf C, Ramm U. Image movement of the Elekta EPID during gantry rotation: Effects on the verification of dose distributions. Phys Med 2017; 34:72-79. [DOI: 10.1016/j.ejmp.2017.01.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 12/31/2016] [Accepted: 01/26/2017] [Indexed: 11/29/2022] Open
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20
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In silico investigation of factors affecting the MV imaging performance of a novel water-equivalent EPID. Phys Med 2016; 32:1819-1826. [DOI: 10.1016/j.ejmp.2016.09.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 09/21/2016] [Accepted: 09/22/2016] [Indexed: 11/21/2022] Open
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21
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Garcia-Romero A, Hernandez-Vitoria A, Millan-Cebrian E, Alba-Escorihuela V, Serrano-Zabaleta S, Ortega-Pardina P. On the new metrics for IMRT QA verification. Med Phys 2016; 43:6058. [PMID: 27806610 DOI: 10.1118/1.4964796] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The aim of this work is to search for new metrics that could give more reliable acceptance/rejection criteria on the IMRT verification process and to offer solutions to the discrepancies found among different conventional metrics. Therefore, besides conventional metrics, new ones are proposed and evaluated with new tools to find correlations among them. These new metrics are based on the processing of the dose-volume histogram information, evaluating the absorbed dose differences, the dose constraint fulfillment, or modified biomathematical treatment outcome models such as tumor control probability (TCP) and normal tissue complication probability (NTCP). An additional purpose is to establish whether the new metrics yield the same acceptance/rejection plan distribution as the conventional ones. METHODS Fifty eight treatment plans concerning several patient locations are analyzed. All of them were verified prior to the treatment, using conventional metrics, and retrospectively after the treatment with the new metrics. These new metrics include the definition of three continuous functions, based on dose-volume histograms resulting from measurements evaluated with a reconstructed dose system and also with a Monte Carlo redundant calculation. The 3D gamma function for every volume of interest is also calculated. The information is also processed to obtain ΔTCP or ΔNTCP for the considered volumes of interest. These biomathematical treatment outcome models have been modified to increase their sensitivity to dose changes. A robustness index from a radiobiological point of view is defined to classify plans in robustness against dose changes. RESULTS Dose difference metrics can be condensed in a single parameter: the dose difference global function, with an optimal cutoff that can be determined from a receiver operating characteristics (ROC) analysis of the metric. It is not always possible to correlate differences in biomathematical treatment outcome models with dose difference metrics. This is due to the fact that the dose constraint is often far from the dose that has an actual impact on the radiobiological model, and therefore, biomathematical treatment outcome models are insensitive to big dose differences between the verification system and the treatment planning system. As an alternative, the use of modified radiobiological models which provides a better correlation is proposed. In any case, it is better to choose robust plans from a radiobiological point of view. The robustness index defined in this work is a good predictor of the plan rejection probability according to metrics derived from modified radiobiological models. The global 3D gamma-based metric calculated for each plan volume shows a good correlation with the dose difference metrics and presents a good performance in the acceptance/rejection process. Some discrepancies have been found in dose reconstruction depending on the algorithm employed. Significant and unavoidable discrepancies were found between the conventional metrics and the new ones. CONCLUSIONS The dose difference global function and the 3D gamma for each plan volume are good classifiers regarding dose difference metrics. ROC analysis is useful to evaluate the predictive power of the new metrics. The correlation between biomathematical treatment outcome models and the dose difference-based metrics is enhanced by using modified TCP and NTCP functions that take into account the dose constraints for each plan. The robustness index is useful to evaluate if a plan is likely to be rejected. Conventional verification should be replaced by the new metrics, which are clinically more relevant.
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Affiliation(s)
- Alejandro Garcia-Romero
- Servicio de Fisica y Proteccion Radiologica, Hospital Clinico Universitario "Lozano Blesa" de Zaragoza, Avenida San Juan Bosco 15, Zaragoza E-50009, Spain
| | - Araceli Hernandez-Vitoria
- Servicio de Fisica y Proteccion Radiologica, Hospital Clinico Universitario "Lozano Blesa" de Zaragoza, Avenida San Juan Bosco 15, Zaragoza E-50009, Spain
| | - Esther Millan-Cebrian
- Servicio de Fisica y Proteccion Radiologica, Hospital Clinico Universitario "Lozano Blesa" de Zaragoza, Avenida San Juan Bosco 15, Zaragoza E-50009, Spain
| | - Veronica Alba-Escorihuela
- Servicio de Fisica y Proteccion Radiologica, Hospital Clinico Universitario "Lozano Blesa" de Zaragoza, Avenida San Juan Bosco 15, Zaragoza E-50009, Spain
| | - Sonia Serrano-Zabaleta
- Servicio de Fisica y Proteccion Radiologica, Hospital Clinico Universitario "Lozano Blesa" de Zaragoza, Avenida San Juan Bosco 15, Zaragoza E-50009, Spain
| | - Pablo Ortega-Pardina
- Servicio de Fisica y Proteccion Radiologica, Hospital Clinico Universitario "Lozano Blesa" de Zaragoza, Avenida San Juan Bosco 15, Zaragoza E-50009, Spain
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22
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Kron T, Lehmann J, Greer PB. Dosimetry of ionising radiation in modern radiation oncology. Phys Med Biol 2016; 61:R167-205. [DOI: 10.1088/0031-9155/61/14/r167] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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23
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Schyns LEJR, Persoon LCGG, Podesta M, van Elmpt WJC, Verhaegen F. Time-resolved versus time-integrated portal dosimetry: the role of an object’s position with respect to the isocenter in volumetric modulated arc therapy. Phys Med Biol 2016; 61:3969-84. [PMID: 27156786 DOI: 10.1088/0031-9155/61/10/3969] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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2D EPID dose calibration for pretreatment quality control of conformal and IMRT fields: A simple and fast convolution approach. Phys Med 2016; 32:133-40. [DOI: 10.1016/j.ejmp.2015.10.094] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 09/28/2015] [Accepted: 10/26/2015] [Indexed: 11/16/2022] Open
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Alshanqity M, Nisbet A. Dosimetric Performance of A-Si Electronic Portal Imaging Devices. ACTA ACUST UNITED AC 2016. [DOI: 10.4236/ijmpcero.2016.52018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Persoon LCGG, Podesta M, Hoffmann L, Sanizadeh A, Schyns LEJR, de Ruiter BM, Nijsten SMJJG, Muren LP, Troost EGC, Verhaegen F. Is integrated transit planar portal dosimetry able to detect geometric changes in lung cancer patients treated with volumetric modulated arc therapy? Acta Oncol 2015; 54:1501-7. [PMID: 26179632 DOI: 10.3109/0284186x.2015.1061213] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
BACKGROUND Geometric changes are frequent during the course of treatment of lung cancer patients. This may potentially result in deviations between the planned and actual delivered dose. Electronic portal imaging device (EPID)-based integrated transit planar portal dosimetry (ITPD) is a fast method for absolute in-treatment dose verification. The aim of this study was to investigate if ITPD could detect geometric changes in lung cancer patients. MATERIALS AND METHODS A total of 460 patients treated with volumetric modulated arc therapy (VMAT) following daily cone beam computed tomography (CT)-based setup were visually inspected for geometrical changes on a daily basis. Forty-six patients were subject to changes and had a re-CT and an adaptive treatment plan. The reasons for adaptation were: change in atelectasis (n = 18), tumor regression (n = 9), change in pleural effusion (n = 8) or other causes (n = 11). The ITPDs were calculated on both the initial planning CT and the re-CT and compared with a global gamma (γ) evaluation (criteria: 3%\3mm). A treatment fraction failed when the percentage of pixels failing in the radiation fields exceeded 10%. Dose-volume histograms (DVHs) were compared between the initial plan versus the plan re-calculated on the re-CT. RESULTS The ITPD threshold method detected 76% of the changes in atelectasis, while only 50% of the tumor regression cases and 42% of the pleural effusion cases were detected. Only 10% of the cases adapted for other reasons were detected with ITPD. The method has a 17% false-positive rate. No significant correlations were found between changes in DVH metrics and γ fail-rates. CONCLUSIONS This study showed that most cases with geometric changes caused by atelectasis could be captured by ITPD, however for other causes ITPD is not sensitive enough to detect the clinically relevant changes and no predictive power of ITPD was found.
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Affiliation(s)
- Lucas C G G Persoon
- a Department of Radiation Oncology (MAASTRO) , GROW - School for Oncology and Developmental Biology, Maastricht University Medical Centre , Maastricht , the Netherlands
| | - Mark Podesta
- a Department of Radiation Oncology (MAASTRO) , GROW - School for Oncology and Developmental Biology, Maastricht University Medical Centre , Maastricht , the Netherlands
| | - Lone Hoffmann
- b Department of Medical Physics , Aarhus University Hospital , Aarhus , Denmark
| | - Abir Sanizadeh
- a Department of Radiation Oncology (MAASTRO) , GROW - School for Oncology and Developmental Biology, Maastricht University Medical Centre , Maastricht , the Netherlands
| | - Lotte E J R Schyns
- a Department of Radiation Oncology (MAASTRO) , GROW - School for Oncology and Developmental Biology, Maastricht University Medical Centre , Maastricht , the Netherlands
| | - Ben-Max de Ruiter
- a Department of Radiation Oncology (MAASTRO) , GROW - School for Oncology and Developmental Biology, Maastricht University Medical Centre , Maastricht , the Netherlands
| | - Sebastiaan M J J G Nijsten
- a Department of Radiation Oncology (MAASTRO) , GROW - School for Oncology and Developmental Biology, Maastricht University Medical Centre , Maastricht , the Netherlands
| | - Ludvig P Muren
- b Department of Medical Physics , Aarhus University Hospital , Aarhus , Denmark
| | - Esther G C Troost
- a Department of Radiation Oncology (MAASTRO) , GROW - School for Oncology and Developmental Biology, Maastricht University Medical Centre , Maastricht , the Netherlands
- c Helmholtz Zentrum Dresden-Rossendorf , Dresden , Germany
- d OncoRay, National Center for Radiation Research in Oncology , Dresden , Germany
- e Department of Radiation Oncology , Medical Faculty and University Hospital Carl Gustav Carus, Technische Universität Dresden , Dresden , Germany
| | - Frank Verhaegen
- a Department of Radiation Oncology (MAASTRO) , GROW - School for Oncology and Developmental Biology, Maastricht University Medical Centre , Maastricht , the Netherlands
- f Medical Physics Unit, Department of Oncology , McGill University , Montréal, Québec , Canada
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Russo M, Piermattei A, Greco F, Azario L, Orlandini L, Zucca S, Cilla S, Menna S, Grusio M, Chiatti L, Fidanzio A. Step-and-Shoot IMRT by Siemens Beams: An EPID Dosimetry Verification During Treatment. Technol Cancer Res Treat 2015; 15:535-45. [PMID: 26134437 DOI: 10.1177/1533034615590962] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 05/15/2015] [Indexed: 11/15/2022] Open
Abstract
PURPOSE This work reports the extension of a semiempirical method based on the correlation ratios to convert electronic portal imaging devices transit signals into in vivo doses for the step-and-shoot intensity-modulated radiotherapy Siemens beams. The dose reconstructed at the isocenter point Diso, compared to the planned dose, Diso,TPS, and a γ-analysis between 2-dimensional electronic portal imaging device images obtained day to day, seems to supply a practical method to verify the beam delivery reproducibility. METHOD The electronic portal imaging device images were obtained by the superposition of many segment fields, and the algorithm for the Diso reconstruction for intensity-modulated radiotherapy step and shoot was formulated using a set of simulated intensity-modulated radiotherapy beams. Moreover, the in vivo dose-dedicated software was integrated with the record and verify system of the centers. RESULTS Three radiotherapy centers applied the in vivo dose procedure at 30 clinical intensity-modulated radiotherapy treatments, each one obtained with 5 or 7 beams, and planned for patients undergoing radiotherapy for prostatic tumors. Each treatment beam was checked 5 times, obtaining 900 tests of the ratios R = Diso/Diso,TPS. The average R value was equal to 1.002 ± 0.056 (2 standard deviation), while the mean R value for each patient was well within 5%, once the causes of errors were removed. The γ-analysis of the electronic portal imaging device images, with 3% 3 mm acceptance criteria, showed 90% of the tests with Pγ < 1 ≥ 95% and γmean ≤ 0.5. The off-tolerance tests were found due to incorrect setup or presence of morphological changes. This preliminary experience shows the great utility of obtaining the in vivo dose results in quasi real time and close to the linac, where the radiotherapy staff may immediately spot possible causes of errors. The in vivo dose procedure presented here is one of the objectives of a project, for the development of practical in vivo dose procedures, financially supported by the Istituto Nazionale di Fisica Nucleare.
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Affiliation(s)
- M Russo
- Istituto Nazionale di Fisica Nucleare, Sezione di Roma Tre, Roma, Italy Unità Operativa di Fisica Sanitaria, Ospedale Belcolle, Viterbo, Italy
| | - A Piermattei
- Istituto Nazionale di Fisica Nucleare, Sezione di Roma Tre, Roma, Italy Istituto di Fisica e Unità Operativa di Fisica Sanitaria, Università Cattolica del S. Cuore, Roma, Italy
| | - F Greco
- Istituto Nazionale di Fisica Nucleare, Sezione di Roma Tre, Roma, Italy Istituto di Fisica e Unità Operativa di Fisica Sanitaria, Università Cattolica del S. Cuore, Roma, Italy
| | - L Azario
- Istituto Nazionale di Fisica Nucleare, Sezione di Roma Tre, Roma, Italy Istituto di Fisica e Unità Operativa di Fisica Sanitaria, Università Cattolica del S. Cuore, Roma, Italy
| | - L Orlandini
- Unità Operativa di Fisica Medica, Centro Oncologico Fiorentino, Firenze, Italy
| | - S Zucca
- Istituto Nazionale di Fisica Nucleare, Sezione di Roma Tre, Roma, Italy Unità Operativa di Fisica Sanitaria, Presidio Oncologico Businco, Cagliari, Italy
| | - S Cilla
- Istituto Nazionale di Fisica Nucleare, Sezione di Roma Tre, Roma, Italy Unità Operativa di Fisica Sanitaria, Fondazione per la Ricerca e Cura "Giovanni Paolo II," Campobasso, Italy
| | - S Menna
- Istituto di Fisica e Unità Operativa di Fisica Sanitaria, Università Cattolica del S. Cuore, Roma, Italy
| | - M Grusio
- Istituto di Fisica e Unità Operativa di Fisica Sanitaria, Università Cattolica del S. Cuore, Roma, Italy
| | - L Chiatti
- Unità Operativa di Fisica Sanitaria, Ospedale Belcolle, Viterbo, Italy
| | - A Fidanzio
- Istituto Nazionale di Fisica Nucleare, Sezione di Roma Tre, Roma, Italy Istituto di Fisica e Unità Operativa di Fisica Sanitaria, Università Cattolica del S. Cuore, Roma, Italy
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Spreeuw H, Rozendaal R, Camargo P, Mans A, Wendling M, Olaciregui-Ruiz I, Sonke JJ, Van Herk M, Mijnheer B. Portal dosimetry in wedged beams. J Appl Clin Med Phys 2015; 16:5375. [PMID: 26103497 PMCID: PMC5690135 DOI: 10.1120/jacmp.v16i3.5375] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Revised: 01/03/2015] [Accepted: 01/28/2015] [Indexed: 11/23/2022] Open
Abstract
Portal dosimetry using electronic portal imaging devices (EPIDs) is often applied to verify high‐energy photon beam treatments. Due to the change in photon energy spectrum, the resulting dose values are, however, not very accurate in the case of wedged beams if the pixel‐to‐dose conversion for the situation without wedge is used. A possible solution would be to consider a wedged beam as another photon beam quality requiring separate beam modeling of the dose calculation algorithm. The aim of this study was to investigate a more practical solution: to make aSi EPID‐based dosimetry models also applicable for wedged beams without an extra commissioning effort of the parameters of the model. For this purpose two energy‐dependent wedge multiplication factors have been introduced to be applied for portal images taken with and without a patient/phantom in the beam. These wedge multiplication factors were derived from EPID and ionization chamber measurements at the EPID level for wedged and nonwedged beams, both with and without a polystyrene slab phantom in the beam. This method was verified for an EPID dosimetry model used for wedged beams at three photon beam energies (6, 10, and 18 MV) by comparing dose values reconstructed in a phantom with data provided by a treatment planning system (TPS), as a function of field size, depth, and off‐axis distance. Generally good agreement, within 2%, was observed for depths between dose maximum and 15 cm. Applying the new model to EPID dose measurements performed during ten breast cancer patient treatments with wedged 6 MV photon beams showed that the average isocenter underdosage of 5.3% was reduced to 0.4%. Gamma‐evaluation (global 3%/3 mm) of these in vivo data showed an increase in percentage of points with γ≤1 from 60.2% to 87.4%, while γmean reduced from 1.01 to 0.55. It can be concluded that, for wedged beams, the multiplication of EPID pixel values with an energy‐dependent correction factor provides good agreement between dose values determined by an EPID and a TPS, indicating the usefulness of such a practical solution. PACS numbers: 87.55.km, 87.55.kd, 87.55.Qr, 87.56a.ng
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Laliena V, García-Romero A. Monte Carlo modeling of the Siemens Optifocus multileaf collimator. Phys Med 2015; 31:301-6. [DOI: 10.1016/j.ejmp.2015.01.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 01/21/2015] [Accepted: 01/25/2015] [Indexed: 10/24/2022] Open
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Set-up verification and 2-dimensional electronic portal imaging device dosimetry during breath hold compared with free breathing in breast cancer radiation therapy. Pract Radiat Oncol 2015; 5:e135-e141. [DOI: 10.1016/j.prro.2014.10.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 09/29/2014] [Accepted: 10/20/2014] [Indexed: 11/18/2022]
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Deshpande S, McNamara AL, Holloway L, Metcalfe P, Vial P. Feasibility study of a dual detector configuration concept for simultaneous megavoltage imaging and dose verification in radiotherapy. Med Phys 2015; 42:1753-64. [DOI: 10.1118/1.4907966] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
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Dosimetric properties of fluoroscopic EPID for transit dosimetry. JOURNAL OF RADIOTHERAPY IN PRACTICE 2015. [DOI: 10.1017/s1460396914000405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractThe aim of this work was to evaluate dose response of fluoroscopic EPID for transit dosimetry applications. Properties studied included warm up time, build-up thickness evaluation, dose history, linearity, stability, and short and long-term reproducibility of EPID response, as well as field size dependence.Pixel value matrices of electronic portal images in DICOM format were analysed in central and 8 off axis points using customised written codes in Matlab. In order to do this, nine 26×26 pixel matrices were selected as regions of interest, the regions represented by these arrays were 1×1 and 0·65×0·65 cm2 at the EPID and isocentre level, respectively.Necessary warm up time for stable operation of EPID is 30 minutes, and there is no need for extra build-up layer to increase the dose response. Linearity tests indicate charged coupled device camera of EPID saturates at 50 cGy level, and does not have linear relationship with dose. Reproducibility and stability of the measurements were excellent and the detector showed same signal with a maximum deviation of <0·3% both in short and long terms. Results of dosimetric evaluation have shown the TheraView fluoroscopic EPID can be used for transit dosimetry purposes.
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Fidanzio A, Porcelli A, Azario L, Greco F, Cilla S, Grusio M, Balducci M, Valentini V, Piermattei A. Quasi real time in vivo dosimetry for VMAT. Med Phys 2015; 41:062103. [PMID: 24877830 DOI: 10.1118/1.4875685] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Results about the feasibility of a method for quasi real time in vivo dosimetry (IVD) at the isocenter point for volumetric modulated arc therapy (VMAT) are here reported. The method is based on correlations between the EPID signal and the dose on the beam central axis. Moreover, the γ-analysis of EPID images was adopted to verify off-axis reproducibility of fractionated plan delivery. METHODS An algorithm to reconstruct in vivo the isocenter dose, D(iso), for RapidArc treatments has been developed. 20 VMAT plans, optimized with two opposite arcs, for prostate, pancreas, and head treatments have been delivered by a Varian linac both to a conic PMMA phantom with elliptical section and to patients. The ratios R between reconstructed D(iso) and the planned doses were determined for phantom and patient irradiations adopting an acceptance criterion of ±5%. In total, 40 phantom checks and 400 patient checks were analyzed. Moreover, 3% and 3 mm criteria were adopted for portal image γ-analysis to assess patient irradiation reproducibility. RESULTS The average ratio R, between reconstructed and planned doses for the PMMA phantom irradiations was equal to 1.007 ± 0.024. When the IVD method was applied to the 20 patients, the average R ratio was equal to 1.003 ± 0.017 and 96% of the tests were within the acceptance criteria. The portal image γ-analysis supplied 88% of the tests within the pass rates γ(mean) ≤ 0.4 and P(γ<1) ≥ 98%. All the warnings were understood comparing the CT and the cone beam CT images and in one case a patient's setup error was detected and corrected for the successive fractions. CONCLUSIONS This preliminary experience suggests that the method is able to detect dosimetric errors in quasi real time at the end of the therapy session. The authors intend to extend this procedure to other pathologies with the integration of in-room imaging verification by cone beam CT.
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Affiliation(s)
- A Fidanzio
- Istituto di Fisica, Università Cattolica del Sacro Cuore, Rome 00168, Italy; U.O.C di Fisica Sanitaria, Università Cattolica del Sacro Cuore, Rome 00168, Italy; and Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Roma Tre, Rome 00146, Italy
| | - A Porcelli
- U.O.C di Fisica Sanitaria, Università Cattolica del Sacro Cuore, Rome 00168, Italy
| | - L Azario
- Istituto di Fisica, Università Cattolica del Sacro Cuore, Rome 00168, Italy; U.O.C di Fisica Sanitaria, Università Cattolica del Sacro Cuore, Rome 00168, Italy; and Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Roma Tre, Rome 00146, Italy
| | - F Greco
- U.O.C di Fisica Sanitaria, Università Cattolica del Sacro Cuore, Rome 00168, Italy and Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Roma Tre, Rome 00146, Italy
| | - S Cilla
- U.O di Fisica Sanitaria, Fondazione di Ricerca e Cura Giovanni Paolo II, Campobasso 86100, Italy and Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Roma Tre, Rome 00146, Italy
| | - M Grusio
- Istituto di Fisica, Università Cattolica del Sacro Cuore, Rome 00168, Italy
| | - M Balducci
- U.O.C di Radioterapia, Università Cattolica del Sacro Cuore, Rome 00168, Italy
| | - V Valentini
- U.O.C di Radioterapia, Università Cattolica del Sacro Cuore, Rome 00168, Italy
| | - A Piermattei
- Istituto di Fisica, Università Cattolica del Sacro Cuore, Rome 00168, Italy; U.O.C di Fisica Sanitaria, Università Cattolica del Sacro Cuore, Rome 00168, Italy; and Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Roma Tre, Rome 00168, Italy
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Baek TS, Chung EJ, Son J, Yoon M. Feasibility study on the verification of actual beam delivery in a treatment room using EPID transit dosimetry. Radiat Oncol 2014; 9:273. [PMID: 25472838 PMCID: PMC4262986 DOI: 10.1186/s13014-014-0273-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Accepted: 09/24/2014] [Indexed: 11/20/2022] Open
Abstract
Purpose The aim of this study is to evaluate the ability of transit dosimetry using commercial treatment planning system (TPS) and an electronic portal imaging device (EPID) with simple calibration method to verify the beam delivery based on detection of large errors in treatment room. Methods and materials Twenty four fields of intensity modulated radiotherapy (IMRT) plans were selected from four lung cancer patients and used in the irradiation of an anthropomorphic phantom. The proposed method was evaluated by comparing the calculated dose map from TPS and EPID measurement on the same plane using a gamma index method with a 3% dose and 3 mm distance-to-dose agreement tolerance limit. Results In a simulation using a homogeneous plastic water phantom, performed to verify the effectiveness of the proposed method, the average passing rate of the transit dose based on gamma index was high enough, averaging 94.2% when there was no error during beam delivery. The passing rate of the transit dose for 24 IMRT fields was lower with the anthropomorphic phantom, averaging 86.8% ± 3.8%, a reduction partially due to the inaccuracy of TPS calculations for inhomogeneity. Compared with the TPS, the absolute value of the transit dose at the beam center differed by −0.38% ± 2.1%. The simulation study indicated that the passing rate of the gamma index was significantly reduced, to less than 40%, when a wrong field was erroneously irradiated to patient in the treatment room. Conclusions This feasibility study suggested that transit dosimetry based on the calculation with commercial TPS and EPID measurement with simple calibration can provide information about large errors for treatment beam delivery.
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Affiliation(s)
- Tae Seong Baek
- Department of Bio-convergence Engineering, Korea University, Jeongneungro 161, Seongbuk-gu, Seoul, 136-703, Korea. .,Department of Radiation Oncology, National Health Insurance Co. Ilsan Hospital, Ilsan, Korea.
| | - Eun Ji Chung
- Department of Radiation Oncology, National Health Insurance Co. Ilsan Hospital, Ilsan, Korea.
| | - Jaeman Son
- Department of Bio-convergence Engineering, Korea University, Jeongneungro 161, Seongbuk-gu, Seoul, 136-703, Korea.
| | - Myonggeun Yoon
- Department of Bio-convergence Engineering, Korea University, Jeongneungro 161, Seongbuk-gu, Seoul, 136-703, Korea.
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Souris JS, Cheng SH, Pelizzari C, Chen NT, La Riviere P, Chen CT, Lo LW. Radioluminescence characterization of in situ x-ray nanodosimeters: Potential real-time monitors and modulators of external beam radiation therapy. APPLIED PHYSICS LETTERS 2014; 105:203110. [PMID: 25425747 PMCID: PMC4240777 DOI: 10.1063/1.4900962] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Accepted: 10/22/2014] [Indexed: 05/25/2023]
Abstract
Europium-doped yttrium oxide (Y2O3:Eu) has garnered considerable interest recently for its use as a highly efficient, red phosphor in a variety of lighting applications that include fluorescent lamps, plasma, and field emission display panels, light emitting diodes (LEDs), and lasers. In the present work, we describe the development of Y2O3:Eu nanoparticles for a very different application: in situ, in vivo x-ray dosimetry. Spectroscopic analyses of these nanoparticles during x-ray irradiation reveal surprisingly bright and stable radioluminescence at near-infrared wavelengths, with markedly linear response to changes in x-ray flux and energy. Monte Carlo modeling of incident flux and broadband, wide-field imaging of mouse phantoms bearing both Y2O3:Eu nanoparticles and calibrated LEDs of similar spectral emission demonstrated significant transmission of radioluminescence, in agreement with spectroscopic studies; with approximately 15 visible photons being generated for every x-ray photon incident. Unlike the dosimeters currently employed in clinical practice, these nanodosimeters can sample both dose and dose rate rapidly enough as to provide real-time feedback for x-ray based external beam radiotherapy (EBRT). The technique's use of remote sensing and absence of supporting structures enable perturbation-free dosing of the targeted region and complete sampling from any direction. With the conjugation of pathology-targeting ligands onto their surfaces, these nanodosimeters offer a potential paradigm shift in the real-time monitoring and modulation of delivered dose in the EBRT of cancer in situ.
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Affiliation(s)
- Jeffrey S Souris
- Department of Radiology, The University of Chicago , Chicago, Illinois 60637, USA
| | | | - Charles Pelizzari
- Deaprtment of Radiation and Cellular Oncology, The University of Chicago , Chicago, Illinois 60637, USA
| | | | - Patrick La Riviere
- Department of Radiology, The University of Chicago , Chicago, Illinois 60637, USA
| | - Chin-Tu Chen
- Department of Radiology, The University of Chicago , Chicago, Illinois 60637, USA
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Deshpande S, Xing A, Holloway L, Metcalfe P, Vial P. Dose calibration of EPIDs for segmented IMRT dosimetry. J Appl Clin Med Phys 2014; 15:4895. [PMID: 25493513 PMCID: PMC5711103 DOI: 10.1120/jacmp.v15i6.4895] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Revised: 06/18/2014] [Accepted: 07/18/2014] [Indexed: 11/25/2022] Open
Abstract
The purpose of this study was to investigate the dose response of amorphous silicon (a‐Si) electronic portal imaging devices (EPIDs) under different acquisition settings for both open jaw defined fields and segmented intensity‐modulated radiation therapy (IMRT) fields. Four different EPIDs were used. Two Siemens and one Elekta plus a standalone Perkin Elmer research EPID. Each was operated with different acquisition systems and settings. Dose response linearity was measured for open static jaw defined fields and ‘simple’ segmented IMRT fields for a range of equipment and system settings. Six ‘simple’ segmented IMRT fields were used. The segments of each IMRT field were fixed at 10×10cm2 field size with equal MU per segment, each field having a total of 20 MU. Simultaneous measurements with an ionization chamber array (ICA) and EPID were performed to separate beam and detector response characteristics. Three different pixel calibration methods were demonstrated and compared for an example ‘clinical IMRT field’. The dose response with the Elekta EPID for ‘simple’ segmented IMRT fields versus static fields agreed to within 2.5% for monitor unit (MU)≥2. The dose response for the Siemens systems was difficult to interpret due to the poor reproducibility for segmented delivery, at MU≤5, which was not observed with the standalone research EPID nor ICA on the same machine. The dose response measured under different acquisition settings and different linac/EPID combinations matched closely (≤1%), except for the Siemens EPID. Clinical IMRT EPID dosimetry implemented with the different pixel‐to‐dose calibration methods indicated that calibration at 20 MU provides equivalent results to implementing a ghosting correction model. The nonlinear dose response was consistent across both clinical EPIDs and the standalone research EPID, with the exception of the poor reproducibility seen with Siemens EPID images of IMRT fields. The nonlinear dose response was relatively insensitive to acquisition settings and appears to be primarily due to gain ghosting effects. No additional ghosting correction factor is necessary when the pixel‐to‐dose calibration factor at small MU calibration method is used. PACS numbers: 87.53.Bn, 87.55.Qr, 87.56.Fc, 87.57.uq
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Affiliation(s)
- Shrikant Deshpande
- Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centre, Sydney Centre for Medical Radiation Physics, University of Wollongong, Wollongong, Australia Ingham Institute for Applied Medical Research, Sydney, NSW, Australia.
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Baek TS, Chung EJ, Koh EK, Seo J, Yoon M. Evaluation of the accuracy of dose delivery for IMRT based on transit dosimetry. HEALTH PHYSICS 2014; 107:200-205. [PMID: 25068957 DOI: 10.1097/hp.0000000000000098] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The authors have developed and evaluated a new method that uses transit dose in the treatment room in verification of dose delivery to patients. Five intensity modulated radiotherapy (IMRT) plans were selected from actual cancer patients, and transit dose was measured using MapCHECK 2 and an anthropomorphic phantom. The criteria used as a verification tool for the dose delivery to the patient were gamma-index-based dose comparison between the computed dose and measured dose. When the doses were delivered to an anthropomorphic phantom normally, the average passing rate was 95.2% based on a gamma index analysis. This feasibility study suggested that transit dose-based quality assurance can provide information about the accuracy of an inhomogeneity correction algorithm and patient positioning during treatment, allowing its use as a verification tool for actual dose delivery to patients in the treatment room.
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Affiliation(s)
- Tae Seong Baek
- *Department of Radiation Oncology, National Health Insurance Co., Ilsan Hospital, Ilsan, Korea; †Seoul Center, Korea Basic Science Institute, Seoul, Korea; ‡Department of Radiological Science, Korea University, Seoul, Korea
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Podesta M, Nijsten SMJJG, Persoon LCGG, Scheib SG, Baltes C, Verhaegen F. Time dependent pre-treatment EPID dosimetry for standard and FFF VMAT. Phys Med Biol 2014; 59:4749-68. [PMID: 25088064 DOI: 10.1088/0031-9155/59/16/4749] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Methods to calibrate Megavoltage electronic portal imaging devices (EPIDs) for dosimetry have been previously documented for dynamic treatments such as intensity modulated radiotherapy (IMRT) using flattened beams and typically using integrated fields. While these methods verify the accumulated field shape and dose, the dose rate and differential fields remain unverified. The aim of this work is to provide an accurate calibration model for time dependent pre-treatment dose verification using amorphous silicon (a-Si) EPIDs in volumetric modulated arc therapy (VMAT) for both flattened and flattening filter free (FFF) beams. A general calibration model was created using a Varian TrueBeam accelerator, equipped with an aS1000 EPID, for each photon spectrum 6 MV, 10 MV, 6 MV-FFF, 10 MV-FFF. As planned VMAT treatments use control points (CPs) for optimization, measured images are separated into corresponding time intervals for direct comparison with predictions. The accuracy of the calibration model was determined for a range of treatment conditions. Measured and predicted CP dose images were compared using a time dependent gamma evaluation using criteria (3%, 3 mm, 0.5 sec). Time dependent pre-treatment dose verification is possible without an additional measurement device or phantom, using the on-board EPID. Sufficient data is present in trajectory log files and EPID frame headers to reliably synchronize and resample portal images. For the VMAT plans tested, significantly more deviation is observed when analysed in a time dependent manner for FFF and non-FFF plans than when analysed using only the integrated field. We show EPID-based pre-treatment dose verification can be performed on a CP basis for VMAT plans. This model can measure pre-treatment doses for both flattened and unflattened beams in a time dependent manner which highlights deviations that are missed in integrated field verifications.
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Affiliation(s)
- Mark Podesta
- Department of Radiation Oncology (MAASTRO), Maastricht University Medical Center (MUMC), Maastricht, the Netherlands
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Peca S, Brown DW. Two-dimensional in vivo dose verification using portal imaging and correlation ratios. J Appl Clin Med Phys 2014; 15:4752. [PMID: 25207402 PMCID: PMC5875516 DOI: 10.1120/jacmp.v15i4.4752] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Revised: 03/06/2014] [Accepted: 03/05/2014] [Indexed: 12/03/2022] Open
Abstract
The electronic portal imaging device (EPID) has the potential to be used for in vivo dosimetry during radiation therapy as an additional dose delivery check. In this study we have extended a method developed by A. Piermattei and colleagues in 2006 that made use of EPID transit images (acquired during treatment) to calculate dose in the isocenter point. The extension allows calculation of two-dimensional dose maps of the entire radiation field at the depth of isocenter. We quantified the variability of the ratio of EPID signal to dose in the isocenter plane in Solid Water phantoms of various thicknesses and with various field sizes, and designed a field edge dose calculation correction. To validate the method, we designed three realistic conventional radiation therapy treatment plans on a thorax and head anthropomorphic phantom (whole brain, brain primary, lung tumor). Using CT data, EPID transit images, EPID signal-to-dose correlation, and our edge correction, we calculated dose in the isocenter plane and compared it with the treatment planning system's prediction. Gamma evaluation (3%, 3 mm) showed good agreement (Pγ<1 ≥ 96.5%) for all fields of the whole brain and brain primary plans. In the presence of lung, however, our algorithm overestimated dose by 7%-9%. This 2D EPID-based in vivo dosimetry method can be used for posttreatment dose verification, thereby improving the safety and quality of patient treatments. With future work, it may be extended to measure dose in real time and to prevent harmful delivery errors.
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Cilla S, Azario L, Greco F, Fidanzio A, Porcelli A, Grusio M, Macchia G, Morganti A, Meluccio D, Piermattei A. An in-vivo dosimetry procedure for Elekta step and shoot IMRT. Phys Med 2014; 30:419-26. [DOI: 10.1016/j.ejmp.2013.11.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 11/22/2013] [Accepted: 11/23/2013] [Indexed: 10/25/2022] Open
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Transit dosimetry in dynamic IMRT with an a-Si EPID. Med Biol Eng Comput 2014; 52:579-88. [PMID: 24878699 DOI: 10.1007/s11517-014-1161-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2013] [Accepted: 05/19/2014] [Indexed: 10/25/2022]
Abstract
Using an amorphous silicon (a-Si) EPID for transit dosimetry requires detailed characterization of its dosimetric response in a variety of conditions. In this study, a measurement-based model was developed to calibrate an a-Si EPID response to dose for transit dosimetry by comparison with a reference ionization chamber. The ionization chamber reference depth and the required additional buildup thickness for electronic portal imaging devices (EPID) transit dosimetry were determined. The combined effects of changes in radiation field size, phantom thickness, and the off-axis distance on EPID transit dosimetry were characterized. The effect of scattered radiation on out-of-field response was investigated for different field sizes and phantom thicknesses by evaluation of the differences in image profiles and in-water measured profiles. An algorithm was developed to automatically apply these corrections to EPID images based on the user-specified field size and phantom thickness. The average phantom thickness and an effective field size were used for IMRT fields, and images were acquired in cine mode in the presence of an anthropomorphic phantom. The effective field size was defined as the percentage of the jaw-defined field that was involved during the delivery. Nine head and neck dynamic IMRT fields were tested by comparison with a MatriXX two-dimensional array dosimeter using the Gamma (3%, 3 mm) evaluation. A depth of 1.5 cm was selected as the ionization chamber reference depth. An additional 2.2 mm of copper buildup was added to the EPID. Comparison of EPID and MatriXX dose images for the tested fields showed that using a 10% threshold, the average number of points with Gamma index <1 was 96.5%. The agreement in the out-of field area was shown by selection of a 2% threshold which on average resulted in 94.8% of points with a Gamma index <1. The suggested method is less complicated than previously reported techniques and can be used for all a-Si EPIDs regardless of the manufacturer.
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Nicolini G, Clivio A, Vanetti E, Krauss H, Fenoglietto P, Cozzi L, Fogliata A. Evaluation of an aSi-EPID with flattening filter free beams: Applicability to the GLAaS algorithm for portal dosimetry and first experience for pretreatment QA of RapidArc. Med Phys 2013; 40:111719. [PMID: 24320427 DOI: 10.1118/1.4824923] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- G Nicolini
- IOSI, Oncology Institute of Southern Switzerland, Radiation Oncology Department, Medical Physics Unit, Bellinzona CH-6500, Switzerland
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Persoon LCGG, Egelmeer AGTM, Ollers MC, Nijsten SMJJG, Troost EGC, Verhaegen F. First clinical results of adaptive radiotherapy based on 3D portal dosimetry for lung cancer patients with atelectasis treated with volumetric-modulated arc therapy (VMAT). Acta Oncol 2013; 52:1484-9. [PMID: 24000957 DOI: 10.3109/0284186x.2013.813642] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
UNLABELLED Atelectasis in lung cancer patients can change rapidly during a treatment course, which may displace the tumor/healthy tissues, or change tissue densities locally. This may result in differences between the planned and the actually delivered dose. With complex delivery techniques treatment verification is essential and inter-fractional adaptation may be necessary. We present the first clinical results of treatment adaptation based on an in-house developed three-dimensional (3D) portal dose measurement (PDM) system. MATERIAL AND METHODS A method was developed for 3D PDM combined with cone beam computed tomography (kV-CBCT) imaging. Lung cancer patients are monitored routinely with this imaging technique. During treatment, the first three fractions are analyzed with 3D PDM and weekly thereafter. The reconstructed measured dose is compared to the planned dose using dose-volume histograms and a γ evaluation. Patients having |γ|> 1 in more than 5% of the (primary tumor or organ at risk) volume were subjected to further analysis. In this study we show the PDM dose changes for five patients. RESULTS We detected relevant dose changes induced by changes in atelectasis in the presented cases. Two patients received two treatment adaptations after being detected with PDM confirmed by visual inspection of the kV-CBCTs, and in two other patients the radiation treatment plan was adapted once. In one case no dose delivery change was detected with PDM. CONCLUSION The first clinical patients show that 3D PDM combined with kV-CBCT is a valuable quality assurance tool for detecting anatomical alterations and their dosimetric consequences during the course of radiotherapy. In our clinic, 3D PDM is fully automated for ease and speed of the procedure, and for minimization of human error. The technique is able to flag patients with suspected dose discrepancies for potential adaptation of the treatment plan.
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Affiliation(s)
- Lucas C G G Persoon
- Department of Radiation Oncology (MAASTRO), GROW-School for Oncology and Developmental Biology, Maastricht University Medical Centre , Maastricht , The Netherlands
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Huber S, Mooslechner M, Mitterlechner B, Weichenberger H, Serpa M, Sedlmayer F, Deutschmann H. Image quality improvements of electronic portal imaging devices by multi-level gain calibration and temperature correction. Phys Med Biol 2013; 58:6429-46. [PMID: 23999060 DOI: 10.1088/0031-9155/58/18/6429] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Amorphous silicon (aSi:H) flat panel detectors are prevalent in radiotherapy for megavoltage imaging tasks. Any clinical and dosimetrical application requires a well-defined dose response of the system to achieve meaningful results. Due to radiation damages, panels deteriorate and the linearity of pixel response to dose as well as the stability with regard to changing operating temperatures get worse with time. Using a single level gain correction can lead to an error of about 23% when irradiating a flood field image with 100 MU min(-1) on an old detector. A multi-level gain (MLG) correction is introduced, emending the nonlinearities and subpanel-related artifacts caused by insufficient radiation hardness of amplifiers in the read-out electronics. With rising temperature, offset values typically increase (up to 300 gray values) while the response at higher dose values per frame remain constant for a majority of pixels. To account for temperature-related image artifacts, two additional temperature correction methods have been developed. MLG in combination with temperature corrections can re-establish the aSi:H image quality to the performance required by reliable medical verification tools. Furthermore, the life span and recalibration intervals of these costly devices can be prolonged decisively.
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Affiliation(s)
- S Huber
- Institute for Research and Development on Advanced Radiation Technologies (radART), Paracelsus Medical University, Muellner Hauptstrasse 48, A-5020 Salzburg, Austria.
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Blake SJ, McNamara AL, Deshpande S, Holloway L, Greer PB, Kuncic Z, Vial P. Characterization of a novel EPID designed for simultaneous imaging and dose verification in radiotherapy. Med Phys 2013; 40:091902. [DOI: 10.1118/1.4816657] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
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46
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Greco F, Piermattei A, Azario L, Placidi L, Cilla S, Caivano R, Fusco V, Fidanzio A. aSi-EPID transit signal calibration for dynamic beams: a needful step for the IMRT in vivo dosimetry. Med Biol Eng Comput 2013; 51:1137-45. [PMID: 23835663 PMCID: PMC3751319 DOI: 10.1007/s11517-013-1094-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Accepted: 06/23/2013] [Indexed: 11/24/2022]
Abstract
This work reports a method based on correlation functions to convert EPID transit signals into in vivo dose values at the isocenter point, Diso, of dynamic IMRT beams supplied by Varian linac. Dose reconstruction for intensity-modulated beams required significant corrections of EPID response, due to the X-ray component transmitted through multileaf collimator. The algorithm was formulated using a set of simulated IMRT beams. The beams were parameterized by means of a fluence inhomogeneity index, FI, introduced to describe the degree of beam modulation with respect to open beams. This way, all dosimetric parameters involved in Diso reconstruction algorithm, such as the correlation functions, the correction factor for EPID to phantom distance and the modulated tissue maximum ratios, were determined as a function of the FI index. Clinical IMRT beams were used to irradiate a homogeneous phantom, and for each beam, the agreement between the reconstructed dose, Diso, and the dose computed by TPS, Diso,TPS, was well within 5 %. Moreover, the average ratios, R, between the Diso, and Diso,TPS, resulted equal to 1.002 ± 0.030. Thirty-five IMRT fields of 5 different patients undergoing radiotherapy for head–neck tumors were tested and the results were displayed on a computer screen after 2 min from the end of the treatment. However, 350 in vivo tests supplied an average ratio R equal to 1.004 ± 0.040. The in vivo dosimetry procedure here presented is among the objectives of a National Project financially supported by the Istituto Nazionale di Fisica Nucleare for the development of in vivo dosimetry procedures (Piermattei et al. in Nucl Instrum Methods Phys Res B 274:42–50, 2012) connected to the Record–Verify system of the radiotherapy center.
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Affiliation(s)
- Francesca Greco
- U.O.C di Fisica Sanitaria, Università Cattolica del Sacro Cuore, Rome, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Roma Tre, Rome, Italy
| | - Angelo Piermattei
- Istituto di Fisica, Università Cattolica del Sacro Cuore, Largo F. Vito 1, 00168 Rome, Italy
- U.O.C di Fisica Sanitaria, Università Cattolica del Sacro Cuore, Rome, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Roma Tre, Rome, Italy
| | - Luigi Azario
- Istituto di Fisica, Università Cattolica del Sacro Cuore, Largo F. Vito 1, 00168 Rome, Italy
- U.O.C di Fisica Sanitaria, Università Cattolica del Sacro Cuore, Rome, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Roma Tre, Rome, Italy
| | - Lorenzo Placidi
- Istituto di Fisica, Università Cattolica del Sacro Cuore, Largo F. Vito 1, 00168 Rome, Italy
| | - Savino Cilla
- U.O di Fisica Sanitaria, Fondazione di Ricerca e Cura Giovanni Paolo II, Campobasso, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Roma Tre, Rome, Italy
| | - Rocchina Caivano
- Unità Operativa di Radioterapia e Fisica Sanitaria, Centro di Riferimento Oncologico della Basilicata, IRCCS, Rionero, PZ Italy
| | - Vincenzo Fusco
- Unità Operativa di Radioterapia e Fisica Sanitaria, Centro di Riferimento Oncologico della Basilicata, IRCCS, Rionero, PZ Italy
| | - Andrea Fidanzio
- Istituto di Fisica, Università Cattolica del Sacro Cuore, Largo F. Vito 1, 00168 Rome, Italy
- U.O.C di Fisica Sanitaria, Università Cattolica del Sacro Cuore, Rome, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Roma Tre, Rome, Italy
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Mijnheer B, Beddar S, Izewska J, Reft C. In vivo
dosimetry in external beam radiotherapy. Med Phys 2013; 40:070903. [DOI: 10.1118/1.4811216] [Citation(s) in RCA: 211] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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Podesta M, Nijsten SMJJG, Snaith J, Orlandini M, Lustberg T, Emans D, Aland T, Verhaegen F. Measured vs simulated portal images for low MU fields on three accelerator types: Possible consequences for 2D portal dosimetry. Med Phys 2012; 39:7470-9. [DOI: 10.1118/1.4761950] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Rowshanfarzad P, Sabet M, O'Connor DJ, Greer PB. Impact of backscattered radiation from the bunker structure on EPID dosimetry. J Appl Clin Med Phys 2012; 13:4024. [PMID: 23149798 PMCID: PMC5718534 DOI: 10.1120/jacmp.v13i6.4024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Revised: 07/18/2012] [Accepted: 07/20/2012] [Indexed: 11/23/2022] Open
Abstract
Amorphous silicon electronic portal imaging devices (EPIDs) have been investigated and used for dosimetry in radiotherapy for several years. The presence of a phosphor scintillator layer in the structure of these EPIDs has made them sensitive to low-energy scattered and backscattered radiation. In this study, the backscattered radiation from the walls, ceiling, and floor of a linac bunker has been investigated as a possible source of inaccuracy in EPID dosimetry. EPID images acquired in integrated mode at discrete gantry angles and cine images taken during arcs were used with different field setups (18 × 18 and 10 × 10 cm2 open square fields at 150 and 105 cm source-to-detector distances) to compare the EPID response at different gantry angles. A sliding gap and a dynamic head-and-neck IMRT field and a square field with a 15 cm thick cylindrical phantom in the beam were also investigated using integrated EPID images at several gantry angles. The contribution of linac output variations at different angles was evaluated using a 2D array of ion chambers. In addition, a portable brick wall was moved to different distances from the EPID to check the effect at a single angle. The results showed an agreement of within 0.1% between the arc mode and gantry-static mode measurements, and the variation of EPID response during gantry rotation was about 1% in all measurement conditions.
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Affiliation(s)
- Pejman Rowshanfarzad
- School of Mathematical and Physical Sciences, University of Newcastle, Newcastle, NSW 2308, Australia.
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Warkentin B, Rathee S, Steciw S. 2D lag and signal nonlinearity correction in an amorphous silicon EPID and their impact on pretreatment dosimetric verification. Med Phys 2012; 39:6597-608. [PMID: 23127054 DOI: 10.1118/1.4757582] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
PURPOSE This investigation provides measurements of signal lag and nonlinearity separately for the Varian aS500 electronic portal imaging device (EPID), and an algorithm to correct for these effects in 2D; their potential impact on intensity modulated radiation therapy (IMRT) verification is also investigated. The authors quantify lag, as a function of both delivered monitor units (MU) and time, by using a range of MUs delivered at a clinically used rate of 400 MU∕min. Explicit cumulative lag curves are thus determined for a range of MUs and times between the end of irradiation and the end of image acquisition. Signal nonlinearity is also investigated as a function of total MUs delivered. The family of cumulative lag curves and signal nonlinearity are then used to determine their effects on dynamic multileaf collimator (MLC) (IMRT) deliveries, and to correct for theses effects in 2D. METHODS Images acquired with an aS500 EPID and Varis Portal-Vision software were used to quantify detector lag and signal-nonlinearity. For the signal lag investigation, Portal-Vision's service monitor was used to acquire EPID images at a rate of 8 frames/s. The images were acquired during irradiation and 66 s thereafter, by inhibiting the M-holdoff-In signal of the Linac for a range of 4.5-198.5 MUs. Relative cumulative lag was calculated by integrating the EPID signal for a time after beam-off, and normalizing this to the integrated EPID signal accumulated during radiation. Signal nonlinearity was studied by acquiring 10 × 10 cm(2) open-field EPID images in "integrated image" mode for a range of 2-500 MUs, and normalized to the 100 MU case. All data were incorporated into in-house written software to create a 2D correction map for these effects, using the field's MLC file and a field-specific calculated 2D "time-map," which keeps track of the time elapsed from the last fluence delivered at each given point in the image to the end of the beam delivery. RESULTS Relative cumulative lag curves reveal that the lag alone can deviate the EPID's perceived dose by as large as 6% (1 MU delivery, 60 s postirradiation). For signal nonlinearity relative to 100 MU, EPID signals per MU of 0.84 and 1.01 were observed for 2 and 500 MUs, respectively. Correction maps were applied to a 1 cm sweeping-window 14 × 14 cm(2) field and clinical head-and-neck IMRT field. A mean correction of 1.028 was implemented in the head-and-neck field, which significantly reduced lag-related asymmetries in the EPID images, and restored linearity to the EPID imager's dose response. Corrections made to the sweeping-field showed good agreement with the treatment planning system-predicted field, yielding an average percent difference of 0.05% ± 0.91%, compared to the -1.32% ± 1.02% before corrections, or 1.75% ± 1.04% when only a signal nonlinearity correction is made. CONCLUSIONS Lag and signal-nonlinearity have been quantified for an aS500 EPID imager, and an effective 2D correction method has been developed which effectively removes nonlinearity and lag effects. Both of these effects were shown to negatively impact IMRT verifications. Especially fields that involve prolonged irradiation and small overall MUs should be corrected for in 2D.
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Affiliation(s)
- B Warkentin
- Department of Medical Physics, Cross Cancer Institute, Alberta T6G 1Z2, Canada
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