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Liu C, Wang B, Bai X, Cheng X, Wang X, Yang X, Shan G. A novel EPID-based MLC QA method with log files achieving submillimeter accuracy. J Appl Clin Med Phys 2024; 25:e14450. [PMID: 39031891 DOI: 10.1002/acm2.14450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2024] [Revised: 04/26/2024] [Accepted: 06/07/2024] [Indexed: 07/22/2024] Open
Abstract
The purpose of this study is to develop an electronic portal imaging device-based multi-leaf collimator calibration procedure using log files. Picket fence fields with 2-14 mm nominal strip widths were performed and normalized by open field. Normalized pixel intensity profiles along the direction of leaf motion for each leaf pair were taken. Three independent algorithms and an integration method derived from them were developed according to the valley value, valley area, full-width half-maximum (FWHM) of the profile, and the abutment width of the leaf pairs obtained from the log files. Three data processing schemes (Scheme A, Scheme B, and Scheme C) were performed based on different data processing methods. To test the usefulness and robustness of the algorithm, the known leaf position errors along the direction of perpendicular leaf motion via the treatment planning system were introduced in the picket fence field with nominal 5, 8, and 11 mm. Algorithm tests were performed every 2 weeks over 4 months. According to the log files, about 17.628% and 1.060% of the leaves had position errors beyond ± 0.1 and ± 0.2 mm, respectively. The absolute position errors of the algorithm tests for different data schemes were 0.062 ± 0.067 (Scheme A), 0.041 ± 0.045 (Scheme B), and 0.037 ± 0.043 (Scheme C). The absolute position errors of the algorithms developed by Scheme C were 0.054 ± 0.063 (valley depth method), 0.040 ± 0.038 (valley area method), 0.031 ± 0.031 (FWHM method), and 0.021 ± 0.024 (integrated method). For the efficiency and robustness test of the algorithm, the absolute position errors of the integration method of Scheme C were 0.020 ± 0.024 (5 mm), 0.024 ± 0.026 (8 mm), and 0.018 ± 0.024 (11 mm). Different data processing schemes could affect the accuracy of the developed algorithms. The integration method could integrate the benefits of each algorithm, which improved the level of robustness and accuracy of the algorithm. The integration method can perform multi-leaf collimator (MLC) quality assurance with an accuracy of 0.1 mm. This method is simple, effective, robust, quantitative, and can detect a wide range of MLC leaf position errors.
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Affiliation(s)
- Chenlu Liu
- School of Nuclear Science and Technology, University of South China, Hengyang, Hunan, PR China
- Department of Radiation Physics, Zhejiang Cancer Hospital, Hangzhou Institute of Medicine (HIM), Chinese Academy of Sciences, Hangzhou, Zhejiang, PR China
| | - Binbing Wang
- Department of Radiation Physics, Zhejiang Cancer Hospital, Hangzhou Institute of Medicine (HIM), Chinese Academy of Sciences, Hangzhou, Zhejiang, PR China
| | - Xue Bai
- Department of Radiation Physics, Zhejiang Cancer Hospital, Hangzhou Institute of Medicine (HIM), Chinese Academy of Sciences, Hangzhou, Zhejiang, PR China
| | - Xiaolong Cheng
- Department of Radiation Physics, Zhejiang Cancer Hospital, Hangzhou Institute of Medicine (HIM), Chinese Academy of Sciences, Hangzhou, Zhejiang, PR China
| | - Xiaotong Wang
- Department of Radiation Physics, Zhejiang Cancer Hospital, Hangzhou Institute of Medicine (HIM), Chinese Academy of Sciences, Hangzhou, Zhejiang, PR China
| | - Xiaohua Yang
- School of Nuclear Science and Technology, University of South China, Hengyang, Hunan, PR China
| | - Guoping Shan
- Department of Radiation Physics, Zhejiang Cancer Hospital, Hangzhou Institute of Medicine (HIM), Chinese Academy of Sciences, Hangzhou, Zhejiang, PR China
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Norvill CAJ. Impact of electronic portal image quality on Elekta AQUA ® collimator isocenter. J Appl Clin Med Phys 2023; 24:e13934. [PMID: 36855933 PMCID: PMC10113691 DOI: 10.1002/acm2.13934] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 12/20/2022] [Accepted: 02/03/2023] [Indexed: 03/02/2023] Open
Abstract
PURPOSE The collimator radiation isocenter position determined in AQUA® v3.0 [Elekta AB, Stockholm, Sweden] software test "MLC Leaf and Jaw Position" was independently validated using an in-house MATLAB [Natick, MA: The MathWorks Inc.] script. METHODS The AQUA test determines radiation isocenter using the mean field center of nine 4 cm × 4 cm electronic portal imager (EPID) exposures at equidistant collimator angles. Impact of EPID image quality on AQUA reported isocenter for thirteen Elekta linear accelerators with Agility MLC heads were evaluated. RESULTS Of the thirteen, three had visually and quantitatively identifiable artifacts. For the ten good EPID's there was a systematic 0.25 mm offset of the MATLAB calculated mean field center relative to AQUA in the X-axis and Y-axis. This corresponds to one image pixel and was found to be due to differences in software co-ordinate convention. After subtracting this offset there was no significant difference in AQUA and MATLAB calculated isocenter. CONCLUSIONS For the three machines with poor image quality there was a demonstrated variation in AQUA calculated field center and therefore radiation isocenter relative to MATLAB. Restricting the region of interest (ROI) in AQUA software to only the irradiated section of the EPID brought AQUA and MATLAB result for these three machines into agreement.
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Ma Y, Mou X, Beeraka NM, Guo Y, Liu J, Dai J, Fan R. Machine Log File and Calibration Errors-based Patient-specific Quality Assurance (QA) for Volumetric Modulated Arc Therapy (VMAT). Curr Pharm Des 2023; 29:2738-2751. [PMID: 37916622 DOI: 10.2174/0113816128226519231017050459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 05/19/2023] [Accepted: 06/05/2023] [Indexed: 11/03/2023]
Abstract
INTRODUCTION Dose reconstructed based on linear accelerator (linac) log-files is one of the widely used solutions to perform patient-specific quality assurance (QA). However, it has a drawback that the accuracy of log-file is highly dependent on the linac calibration. The objective of the current study is to represent a new practical approach for a patient-specific QA during Volumetric modulated arc therapy (VMAT) using both log-file and calibration errors of linac. METHODS A total of six cases, including two head and neck neoplasms, two lung cancers, and two rectal carcinomas, were selected. The VMAT-based delivery was optimized by the TPS of Pinnacle^3 subsequently, using Elekta Synergy VMAT linac (Elekta Oncology Systems, Crawley, UK), which was equipped with 80 Multi-leaf collimators (MLCs) and the energy of the ray selected at 6 MV. Clinical mode log-file of this linac was used in this study. A series of test fields validate the accuracy of log-file. Then, six plans of test cases were delivered and log-file of each was obtained. The log-file errors were added to the corresponding plans through the house script and the first reconstructed plan was obtained. Later, a series of tests were performed to evaluate the major calibration errors of the linac (dose-rate, gantry angle, MLC leaf position) and the errors were added to the first reconstruction plan to generate the second reconstruction plan. At last, all plans were imported to Pinnacle and recalculated dose distribution on patient CT and ArcCheck phantom (SUN Nuclear). For the former, both target and OAR dose differences between them were compared. For the latter, γ was evaluated by ArcCheck, and subsequently, the surface dose differences between them were performed. RESULTS Accuracy of log-file was validated. If error recordings in the log file were only considered, there were four arcs whose proportion of control points with gantry angle errors more than ± 1°larger than 35%. Errors of leaves within ± 0.5 mm were 95% for all arcs. The distinctness of a single control point MU was bigger, but the distinctness of cumulative MU was smaller. The maximum, minimum, and mean doses for all targets were distributed between -6.79E-02-0.42%, -0.38-0.4%, 2.69E-02-8.54E-02% respectively, whereas for all OAR, the maximum and mean dose were distributed between -1.16-2.51%, -1.21-3.12% respectively. For the second reconstructed dose: the maximum, minimum, and mean dose for all targets was distributed between 0.0995~5.7145%, 0.6892~4.4727%, 0.5829~1.8931% separately. Due to OAR, maximum and mean dose distribution was observed between -3.1462~6.8920%, -6.9899~1.9316%, respectively. CONCLUSION Patient-specific QA based on the log-file could reflect the accuracy of the linac execution plan, which usually has a small influence on dose delivery. When the linac calibration errors were considered, the reconstructed dose was closer to the actual delivery and the developed method was accurate and practical.
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Affiliation(s)
- Yangguang Ma
- Department of Radiation Oncology, First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
- School of Information and Communications Engineering, Xi'AN Jiaotong University, Xi'an 710049, China
| | - Xuanqin Mou
- School of Information and Communications Engineering, Xi'AN Jiaotong University, Xi'an 710049, China
| | - Narasimha M Beeraka
- Raghavendra Institute of Pharmaceutical Education and Research (RIPER), Anantapuramu, Chiyyedu, Andhra Pradesh 515721, India
- Department of Human Anatomy, I.M. Sechenov First Moscow State Medical University of the Ministry of Health of the Russian Federation (Sechenov University), 8/2 Trubetskaya Str., Moscow 119991, Russia
| | - Yuexin Guo
- Department of Radiation Oncology, First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
| | - Junqi Liu
- Department of Radiation Oncology, First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
| | - Jianrong Dai
- Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer, Cancer Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100021, China
| | - Ruitai Fan
- Department of Radiation Oncology, First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
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Liang J, Yu F, Zhu J, Song T. [Impact of multi-leaf collimator positioning accuracy on quality control of volumetric modulation arc therapy plan for cervical cancer treated with Elekta linear accelerator]. NAN FANG YI KE DA XUE XUE BAO = JOURNAL OF SOUTHERN MEDICAL UNIVERSITY 2022; 42:1089-1094. [PMID: 35869775 DOI: 10.12122/j.issn.1673-4254.2022.07.19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
OBJECTIVE To investigate the influence of positioning accuracy of the multi-leaf collimators (MLC) on the passing rate of the plan dose verification for volumetric modulation arc therapy (VMAT) of cervical cancer using an Elekta linear accelerator. METHODS The dose distributions were measured using Sun Nuclear's Mapcheck and Arccheck semiconductors matrix before and after MLC calibration in30 cervical cancer patients undergoing VMAT. Dosimetric comparisons were performed with 2D and 3D gamma passing rates of 3%, 3 mm and 2%, and 2 mm. The 3D gamma distribution was reconstructed with respect to the patient's anatomy using 3DVH software to evaluate the possible influence of MLC positioning accuracy. RESULTS Before and after MLC calibration, the gamma passing rates of Mapcheck were (88.80±1.81)% and (99.25 ± 0.53)% under 3% and 3 mm standard, respectively, with an average increase of 10.45%. The corresponding gamma passing rates of Arccheck were (87.61±1.98)% and (98.13±0.99)%, respectively, with an average increase of 10.52%. The gamma passing rates of 3DVH were (89.87±2.28)% and (98.3±1.15)%, respectively, with an average increase of 8.43%. CONCLUSION The MLC positioning accuracy is one of the main factors influencing dosimetric accuracy of VMAT for cervical cancer. The application of Autocal software facilitates MLC calibration and improves the accuracy and safety of VMAT delivery for cervical cancer.
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Affiliation(s)
- J Liang
- School of Biomedical Engineering, Southern Medical University, Guangzhou 510515, China.,State Key Laboratory of Oncology in South China//Department of Radiotherapy, Sun Yat-sen University Cancer Center, Guangzhou 510060, China
| | - F Yu
- State Key Laboratory of Oncology in South China//Department of Radiotherapy, Sun Yat-sen University Cancer Center, Guangzhou 510060, China
| | - J Zhu
- State Key Laboratory of Oncology in South China//Department of Radiotherapy, Sun Yat-sen University Cancer Center, Guangzhou 510060, China
| | - T Song
- School of Biomedical Engineering, Southern Medical University, Guangzhou 510515, China
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Goodall SK, Norvill C. Variation in Elekta iView electronic portal imager pixel scale factor with gantry angle, and impact on multi-leaf collimator quality assurance. J Appl Clin Med Phys 2022; 23:e13661. [PMID: 35666629 PMCID: PMC9278680 DOI: 10.1002/acm2.13661] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 05/01/2022] [Accepted: 05/10/2022] [Indexed: 12/31/2022] Open
Abstract
For Elekta Agility linear accelerators, the iViewGT electronic portal imaging device (EPID) is positioned at a nominal X‐Ray source‐to‐panel distance of 1600 mm. For display, image registration, and data processing purposes, the image pixels are scaled to spatial units at the treatment isocenter plane. This is achieved by applying a pixel scaling factor (PSF). During this investigation, the dependence of the PSF at cardinal gantry angles was determined along with the resulting effects on the multi‐leaf collimator (MLC) quality assurance (QA) results for three linear accelerators (linacs). The PSF was found to vary by 0.0018–0.0022 mm/pixel during gantry rotation, which resulted in variations in the mean MLC reported error of up to 0.8 mm at 100 mm off‐axis with the gantry rotated to 180°. Measurement and application of a gantry angle–specific PSF is a simple process that can be implemented to improve the accuracy of EPID‐based MLC QA at cardinal gantry angles.
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Affiliation(s)
- Simon K Goodall
- GenesisCare, Wembley, Western Australia, Australia.,School of Physics, Mathematics, and Computing, Faculty of Engineering and Mathematical Sciences, University of Western Australia, Crawley, Western Australia, Australia
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Boudet J, Aubignac L, Beneux A, Mazoyer F, Bessieres I. Evaluation of QA software system analysis for the static picket fence test. J Appl Clin Med Phys 2022; 23:e13618. [PMID: 35570379 PMCID: PMC9278673 DOI: 10.1002/acm2.13618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 02/01/2022] [Accepted: 04/01/2022] [Indexed: 11/16/2022] Open
Abstract
Intensity modulation treatments are widely used in radiotherapy because of many known advantages. In this context, the picket fence test (PF) is a relevant test to check the Multileaf Collimator (MLC) performances. So this work compares and evaluates three analysis platforms for the PF used routinely by three different institutions. This study covers two linear accelerators (Linac) with two MLC types, a Millenium 120 MLC and Millenium 120 High Definition MLC respectively on a Varian Truebeam and Truebeam STx. Both linacs include an As 1200 portal imager (EPID). From a reference PF plan, MLC errors have been introduced to modify the slits in position or width (shifts from 0.1 to 0.5 mm on one or both banks). Then errors have been defined on the EPID to investigate detection system deviations (signal sensitivity and position variations). Finally, 110 DICOM‐RT images have been generated and analyzed by each software system. All software systems have shown good performances to quantify the position errors, even though the leaf pair identifications can be wrong in some cases regarding the analysis method considered. The slit width measurement (not calculated by all software systems) has shown good sensitivity, but some quantification difficulties have been highlighted regardless of the analysis method used. Linked to the expected accuracy of the PF test, the imager variations have demonstrated considerable influence in the results. Differences in the results and the analysis methods have been pointed out for each software system. The results can be helpful to optimize the settings of each analysis software system depending on expectations and treatment modalities of each institution.
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Affiliation(s)
- Julien Boudet
- Department of Physics Centre Georges François Leclerc Dijon France
| | - Léone Aubignac
- Department of Physics Centre Georges François Leclerc Dijon France
| | - Amandine Beneux
- Department of Physics Hospices Civils de Lyon Pierre Bénite France
| | - Frédéric Mazoyer
- Department of Radiotherapy Centre Hospitalier Annecy Genevois Epagny Metz‐Tessy France
| | - Igor Bessieres
- Department of Physics Centre Georges François Leclerc Dijon France
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Hanley J, Dresser S, Simon W, Flynn R, Klein EE, Letourneau D, Liu C, Yin FF, Arjomandy B, Ma L, Aguirre F, Jones J, Bayouth J, Holmes T. AAPM Task Group 198 Report: An implementation guide for TG 142 quality assurance of medical accelerators. Med Phys 2021; 48:e830-e885. [PMID: 34036590 DOI: 10.1002/mp.14992] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 03/16/2021] [Accepted: 04/28/2021] [Indexed: 11/11/2022] Open
Abstract
The charges on this task group (TG) were as follows: (a) provide specific procedural guidelines for performing the tests recommended in TG 142; (b) provide estimate of the range of time, appropriate personnel, and qualifications necessary to complete the tests in TG 142; and (c) provide sample daily, weekly, monthly, or annual quality assurance (QA) forms. Many of the guidelines in this report are drawn from the literature and are included in the references. When literature was not available, specific test methods reflect the experiences of the TG members (e.g., a test method for door interlock is self-evident with no literature necessary). In other cases, the technology is so new that no literature for test methods was available. Given broad clinical adaptation of volumetric modulated arc therapy (VMAT), which is not a specific topic of TG 142, several tests and criteria specific to VMAT were added.
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Affiliation(s)
- Joseph Hanley
- Princeton Radiation Oncology, Monroe, New Jersey, 08831, USA
| | - Sean Dresser
- Winship Cancer Institute, Radiation Oncology, Emory University, Atlanta, Georgia, 30322, USA
| | | | - Ryan Flynn
- Department of Radiation Oncology, University of Iowa, Iowa City, Iowa, 52242, USA
| | - Eric E Klein
- Brown university, Rhode Island Hospital, Providence, Rhode Island, 02905, USA
| | | | - Chihray Liu
- University of Florida, Gainesville, Florida, 32610-0385, USA
| | - Fang-Fang Yin
- Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina, 27710, USA
| | - Bijan Arjomandy
- Karmanos Cancer Institute at McLaren-Flint, Flint, Michigan, 48532, USA
| | - Lijun Ma
- Department of Radiation Oncology, University of California San Francisco, San Francisco, 94143-0226, USA
| | | | - Jimmy Jones
- Department of Radiation Oncology, The University of Colorado Health-Poudre Valley, Fort Collins, Colorado, 80525, USA
| | - John Bayouth
- Department of Human Oncology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, 53792-0600, USA
| | - Todd Holmes
- Varian Medical Systems, Palo Alto, California, 94304, USA
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Mittauer KE, Yadav P, Paliwal B, Bayouth JE. Characterization of positional accuracy of a double‐focused and double‐stack multileaf collimator on an MR‐guided radiotherapy (MRgRT) Linac using an IC‐profiler array. Med Phys 2019; 47:317-330. [DOI: 10.1002/mp.13902] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 10/23/2019] [Accepted: 10/24/2019] [Indexed: 11/07/2022] Open
Affiliation(s)
- Kathryn E. Mittauer
- Department of Radiation Oncology Miami Cancer Institute Baptist Health South Florida Miami FL USA
- Department of Human Oncology School of Medicine and Public Health University of Wisconsin‐Madison Madison WI USA
| | - Poonam Yadav
- Department of Human Oncology School of Medicine and Public Health University of Wisconsin‐Madison Madison WI USA
| | - Bhudatt Paliwal
- Department of Human Oncology School of Medicine and Public Health University of Wisconsin‐Madison Madison WI USA
| | - John E. Bayouth
- Department of Human Oncology School of Medicine and Public Health University of Wisconsin‐Madison Madison WI USA
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Kang H, Patel R, Roeske JC. Efficient quality assurance method with automated data acquisition of a single phantom setup to determine radiation and imaging isocenter congruence. J Appl Clin Med Phys 2019; 20:127-133. [PMID: 31535781 PMCID: PMC6806465 DOI: 10.1002/acm2.12723] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Revised: 07/22/2019] [Accepted: 08/27/2019] [Indexed: 12/31/2022] Open
Abstract
We developed a quality assurance (QA) method to determine the isocenter congruence of Optical Surface Monitoring System (OSMS, Varian, CA, USA), kilovoltage (kV), and megavoltage (MV) imaging, and the radiation isocenter using a single setup of the OSMS phantom for frameless Stereotactic Radiosurgery (SRS) treatment. After aligning the phantom to the OSMS isocenter, a cone‐beam computed tomography (CBCT) of the phantom was acquired and registered to a computed tomography (CT) scan of the phantom to determine the CBCT isocenter. Without moving the phantom, MV and kV images were simultaneously acquired at four gantry angles to localize MV and kV isocenters. Then, Winston‐Lutz (W‐L) test images of the central BB in the phantom were acquired to analyze the radiation isocenter. The gantry and couch were automatically controlled using the TrueBeam Developer Mode during MV, kV, and W‐L image acquisition. All the images were acquired weekly for 17 weeks to track the congruence of all the imaging modalities' isocenter in six‐dimensional (6D) translations and rotations, and the radiation isocenter in three‐dimensional (3D) translations. The shifts of isocenters of all imaging modalities and the radiation isocenter from the OSMS isocenter were within 0.2 mm and 0.2° on average over 17 weeks. The maximum discrepancy between OSMS and other imaging modalities or radiation isocenters was 0.8 mm and 0.3°. However, systematic shifts of radiation isocenter anteriorly and laterally relative to the OSMS isocenter were observed. The measured discrepancies were consistent from week‐to‐week except for two weeks when the isocenter discrepancies of 0.8 mm were noted due to drifts of the OSMS isocenter. Once recalibration was performed on OSMS, the discrepancy was reduced to 0.3 mm and 0.2°.By performing the proposed QA on a weekly basis, the isocenter congruencies of multiple imaging systems and radiation isocenter were validated for a linear accelerator.
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Affiliation(s)
- Hyejoo Kang
- Department of Radiation Oncology, Loyola Medicine, Maywood, IL, USA
| | - Rakesh Patel
- Department of Radiation Oncology, Loyola Medicine, Maywood, IL, USA
| | - John C Roeske
- Department of Radiation Oncology, Loyola Medicine, Maywood, IL, USA
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Quality assurance of linear accelerator: a comprehensive system using electronic portal imaging device. JOURNAL OF RADIOTHERAPY IN PRACTICE 2019. [DOI: 10.1017/s146039691800050x] [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
AbstractAimThe Electronic Portal Imaging Device (EPID), primarily used for patient setup during radiotherapy sessions is also used for dosimetric measurements. In the present study, the feasibility of EPID in both machine and patient-specific quality assurance (QA) are investigated. We have developed a comprehensive software tool for effective utilisation of EPID in our institutional QA protocol.Materials and methodsPortal Vision aS1000, amorphous silicon portal detector attached to Clinac iX—Linear Accelerator (LINAC) was used to measure daily profile and output constancy, various Multi-Leaf Collimator (MLC) checks and patient plan verification. Different QA plans were generated with the help of Eclipse Treatment Planning System (TPS) and MLC shaper software. The indigenously developed MATLAB programs were used for image analysis. Flatness, symmetry, output constancy, Field Width at Half Maximum (FWHM) and fluence comparison were studied from images obtained from TPS and EPID dosimetry.ResultsThe 3 years institutional data of profile constancy and patient-specific QA measured using EPID were found within the acceptable limits. The daily output of photon beam correlated with the output obtained through solid phantom measurements. The Pearson correlation coefficients are 0.941 (p = 0.0001), 0.888 (p = 0.0188) and 0.917 (p = 0.0007) for the years of 2014, 2015 and 2016, respectively. The accuracy of MLC for shaping complex treatment fields was studied in terms of FWHM at different portions of various fields, showed good agreement between TPS-generated and EPID-measured MLC positions. The comparison of selected patient plans in EPID with an independent 2D array detector system showed statistically significant correlation between these two systems. Percentage difference between TPS computed and EPID measured fluence maps calculated for number of patients using MATLAB code also exhibited the validity of those plans for treatment.
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Rohani SA, Mahdavi SR, Mostaar A, Ueltzhöffer S, Mohammadi R, Geraily G. Physical and Dosimetric Aspect of Euromechanics Add-on Multileaf Collimator on Varian Clinac 2100 C/D. J Biomed Phys Eng 2019; 9:29-36. [PMID: 30881932 PMCID: PMC6409378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2018] [Accepted: 11/20/2018] [Indexed: 06/09/2023]
Abstract
BACKGROUND Before treatment planning and dose delivery, quality assurance of multi-leaf collimator (MLC) has an important role in intensity-modulated radiation therapy (IMRT) due to the creation of multiple segments from optimization process. OBJECTIVE The purpose of this study is to assess the quality control of MLC leaves using EBT3 Gafchromic films. MATERIAL AND METHODS Leaf Position accuracy and leaf gap reproducibility were checked with Garden fence test. The garden fence test consists of 5 thin bands A) 0.2 Cm width spaced at 2 Cm intervals and B) 1 Cm width spaced at 1 Cm intervals. Each leaf accuracy was analyzed with measuring the full-width half-maximum (FWHM). Maximum and average leaf transmission were measured with gafchromic EBT3 films from Ashland for both 6 MV and 18 MV beams. RESULTS Leaf positions were found to be in a range between 1.78 - 2.53 mm, instead of nominal 2 mm for the test A and between 9.09 - 10.36 mm, instead of nominal 10 mm for the test B. The Average radiation transmission of the MLC was noted 1.79% and 1.98% of the open 10x10 Cm2 field at isocenter for 6 MV and 18 MV beams, respectively. Maximum radiation transmission was noted 4.1% and 4.4% for 6 MV and 18 MV beams, respectively. CONCLUSION In this study, application of gafchromic EBT3 films for the quality assurance of Euromechanics multileaf collimator was studied. Our results showed that the average leaf leakage and positional accuracy of this type of MLC were in the acceptance level based on the Protocols.
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Affiliation(s)
- S A Rohani
- Department of Medical Physics, Tehran University of Medical Sciences, Tehran, Iran
| | - S R Mahdavi
- Radiation biology research center & medical Physics department, faculty of medicine, Iran University of Medical Sciences, Tehran, Iran
| | - A Mostaar
- Department of Medical Physics, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - S Ueltzhöffer
- Department of Clinic for Radiotherapy and RadioOncology, Medical Faculty Mannheim of the University of Heidelberg, Heidelberg, Germany
| | - R Mohammadi
- Department of Medical Physics, Iran University of Medical Sciences, Tehran, Iran
| | - Gh Geraily
- Department of Medical Physics, Tehran University of Medical Sciences, Tehran, Iran
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Hiatt J, Mukwada G, Barnes M, Riis HL, Huynh D, Rowshanfarzad P. MLC positioning verification for small fields: a new investigation into automatic EPID-based verification methods. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2018; 41:945-955. [PMID: 30259333 DOI: 10.1007/s13246-018-0690-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 09/24/2018] [Indexed: 12/31/2022]
Abstract
Multileaf-collimator (MLC) defined small fields in radiotherapy are used in high dose, ultra-conformal techniques such as stereotactic radiotherapy and stereotactic radiosurgery. Proximity to critical structures and irreversible damage arising from inaccurate delivery mean that correct positioning of the MLC system is of the utmost importance. Some of the existing techniques for MLC positioning quality assurance make use of electronic portal imaging device (EPID) images. However, conventional collimation verification algorithms based on the full width at half maximum (FWHM) fail when applied to small field images acquired by an EPID due to overlapping aperture penumbrae, lateral electron disequilibrium and radiation source occlusion. The objective of this study was to investigate sub-pixel edge detection and other techniques with the aim of developing an automatic and autonomous EPID-based method suitable for MLC positional verification of small static fields with arbitrary shapes. Methods investigated included derivative interpolation, Laplacian of Gaussian (LoG) and an algorithm based on the partial area effect hypothesis. None of these methods were found to be suitable for MLC positioning verification in small field conditions. A method is proposed which uses a manufacturer-specific empirically modified FWHM algorithm which shows improvement over the conventional techniques in the small field size range. With a measured mean absolute difference from planned position for Varian linacs of 0.01 ± 0.26 mm, compared with the erroneous FWHM value of 0.70 ± 0.51 mm. For Elekta linacs the proposed algorithm returned 0.26 ± 0.25 mm, in contrast to the FWHM result of 1.79 ± 1.07 mm.
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Affiliation(s)
- Joshua Hiatt
- Department of Radiation Oncology, Liverpool & Macarthur Cancer Therapy Centres, Liverpool, NSW, 2170, Australia. .,School of Physics, Mathematics and Computing, Faculty of Engineering and Mathematical Sciences, The University of Western Australia, Crawley, WA, 6009, Australia.
| | - Godfrey Mukwada
- Department of Radiation Oncology, Sir Charles Gairdner Hospital, Nedlands, WA, 6009, Australia
| | - Michael Barnes
- Department of Radiation Oncology, Calvary Mater Newcastle Hospital, Newcastle, NSW, 2310, Australia.,University of Newcastle, Newcastle, NSW, 2308, Australia
| | | | - Du Huynh
- School of Physics, Mathematics and Computing, Faculty of Engineering and Mathematical Sciences, The University of Western Australia, Crawley, WA, 6009, Australia
| | - Pejman Rowshanfarzad
- School of Physics, Mathematics and Computing, Faculty of Engineering and Mathematical Sciences, The University of Western Australia, Crawley, WA, 6009, Australia
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Cai B, Goddu SM, Yaddanapudi S, Caruthers D, Wen J, Noel C, Mutic S, Sun B. Normalize the response of EPID in pursuit of linear accelerator dosimetry standardization. J Appl Clin Med Phys 2017; 19:73-85. [PMID: 29125224 PMCID: PMC5768011 DOI: 10.1002/acm2.12222] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2017] [Revised: 08/06/2017] [Accepted: 09/28/2017] [Indexed: 12/18/2022] Open
Abstract
Normalize the response of electronic portal imaging device (EPID) is the first step toward an EPID‐based standardization of Linear Accelerator (linac) dosimetry quality assurance. In this study, we described an approach to generate two‐dimensional (2D) pixel sensitivity maps (PSM) for EPIDs response normalization utilizing an alternative beam and dark‐field (ABDF) image acquisition technique and large overlapping field irradiations. The automated image acquisition was performed by XML‐controlled machine operation and the PSM was generated based on a recursive calculation algorithm for Varian linacs equipped with aS1000 and aS1200 imager panels. Cross‐comparisons of normalized beam profiles and 1.5%/1.5 mm 1D Gamma analysis was adopted to quantify the improvement of beam profile matching before and after PSM corrections. PSMs were derived for both photon (6, 10, 15 MV) and electron (6, 20 MeV) beams via proposed method. The PSM‐corrected images reproduced a horn‐shaped profile for photon beams and a relative uniform profiles for electrons. For dosimetrically matched linacs equipped with aS1000 panels, PSM‐corrected images showed increased 1D‐Gamma passing rates for all energies, with an average 10.5% improvement for crossline and 37% for inline beam profiles. Similar improvements in the phantom study were observed with a maximum improvement of 32% for 15 MV and 22% for 20 MeV. The PSM value showed no significant change for all energies over a 3‐month period. In conclusion, the proposed approach correct EPID response for both aS1000 and aS1200 panels. This strategy enables the possibility to standardize linac dosimetry QA and to benchmark linac performance utilizing EPID as the common detector.
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Affiliation(s)
- Bin Cai
- Department of Radiation Oncology, Washington University, St. Louis, MO, USA
| | - S Murty Goddu
- Department of Radiation Oncology, Washington University, St. Louis, MO, USA
| | - Sridhar Yaddanapudi
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
| | - Douglas Caruthers
- Department of Radiation Oncology, Washington University, St. Louis, MO, USA
| | - Jie Wen
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO, USA
| | | | - Sasa Mutic
- Department of Radiation Oncology, Washington University, St. Louis, MO, USA
| | - Baozhou Sun
- Department of Radiation Oncology, Washington University, St. Louis, MO, USA
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Yaddanapudi S, Cai B, Harry T, Dolly S, Sun B, Li H, Stinson K, Noel C, Santanam L, Pawlicki T, Mutic S, Goddu SM. Rapid acceptance testing of modern linac using on-board MV and kV imaging systems. Med Phys 2017; 44:3393-3406. [PMID: 28432806 DOI: 10.1002/mp.12294] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 04/11/2017] [Accepted: 04/11/2017] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The purpose of this study was to develop a novel process for using on-board MV and kV Electronic Portal Imaging Devices (EPIDs) to perform linac acceptance testing (AT) for two reasons: (a) to standardize the assessment of new equipment performance, and (b) to reduce the time to clinical use while reducing physicist workload. METHODS AND MATERIALS In this study, Varian TrueBeam linacs equipped with amorphous silicon-based EPID (aS1000) were used. The conventional set of AT tests and tolerances were used as a baseline guide. A novel methodology was developed or adopted from published literature to perform as many tests as possible using the MV and kV EPIDs. The developer mode on Varian TrueBeam linacs was used to automate the process. In the EPID-based approach, most of mechanical tests were conducted by acquiring images through a custom phantom and software tools were developed for quantitative analysis to extract different performance parameters. The embedded steel-spheres in a custom phantom provided both visual and radiographic guidance for beam geometry testing. For photon beams, open field EPID images were used to extract inline/crossline profiles to verify the beam energy, flatness and symmetry. EPID images through a double wedge phantom were used for evaluating electron beam properties via diagonal profile. Testing was augmented with a commercial automated application (Machine Performance Check) which was used to perform several geometric accuracy tests such as gantry, collimator rotations, and couch rotations/translations. RESULTS The developed process demonstrated that the tests, which required customer demonstration, were efficiently performed using EPIDs. The AT tests that were performed using EPIDs were fully automated using the developer mode on the Varian TrueBeam system, while some tests, such as the light field versus radiation field congruence, and collision interlock checks required user interaction. CONCLUSIONS On-board imagers are quite suitable for both geometric and dosimetric testing of linac system involved in AT. Electronic format of the acquired data lends itself to benchmarking, transparency, as well as longitudinal use of AT data. While the tests were performed on a specific model of a linear accelerator, the proposed approach can be extended to other linacs.
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Affiliation(s)
- Sridhar Yaddanapudi
- Department of Radiation Oncology, Washington University School of Medicine, 4921 Parkview Place, St. Louis, MO, 63110, USA
| | - Bin Cai
- Department of Radiation Oncology, Washington University School of Medicine, 4921 Parkview Place, St. Louis, MO, 63110, USA
| | - Taylor Harry
- Department of Radiation Medicine and Applied Sciences, University of California San Diego, Moores Cancer Center, 3855 Health Sciences Dr., La Jolla, CA, 92093, USA
| | - Steven Dolly
- Department of Radiation Oncology, Washington University School of Medicine, 4921 Parkview Place, St. Louis, MO, 63110, USA
| | - Baozhou Sun
- Department of Radiation Oncology, Washington University School of Medicine, 4921 Parkview Place, St. Louis, MO, 63110, USA
| | - Hua Li
- Department of Radiation Oncology, Washington University School of Medicine, 4921 Parkview Place, St. Louis, MO, 63110, USA
| | - Keith Stinson
- Varian Medical Systems, 3100 Hansen Way, Palo Alto, CA, 94304, USA
| | - Camille Noel
- Varian Medical Systems, 3100 Hansen Way, Palo Alto, CA, 94304, USA
| | - Lakshmi Santanam
- Department of Radiation Oncology, Washington University School of Medicine, 4921 Parkview Place, St. Louis, MO, 63110, USA
| | - Todd Pawlicki
- Department of Radiation Medicine and Applied Sciences, University of California San Diego, Moores Cancer Center, 3855 Health Sciences Dr., La Jolla, CA, 92093, USA
| | - Sasa Mutic
- Department of Radiation Oncology, Washington University School of Medicine, 4921 Parkview Place, St. Louis, MO, 63110, USA
| | - S Murty Goddu
- Department of Radiation Oncology, Washington University School of Medicine, 4921 Parkview Place, St. Louis, MO, 63110, USA
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Li Y, Chen L, Zhu J, Wang B, Liu X. A quantitative method to the analysis of MLC leaf position and speed based on EPID and EBT3 film for dynamic IMRT treatment with different types of MLC. J Appl Clin Med Phys 2017; 18:106-115. [PMID: 28517613 PMCID: PMC7663986 DOI: 10.1002/acm2.12102] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 04/03/2017] [Accepted: 03/04/2017] [Indexed: 12/03/2022] Open
Abstract
A quantitative method based on the electronic portal imaging system (EPID) and film was developed for MLC position and speed testing; this method was used for three MLC types (Millennium, MLCi, and Agility MLC). To determine the leaf position, a picket fence designed by the dynamic (DMLC) model was used. The full‐width half‐maximum (FWHM) values of each gap measured by EPID and EBT3 were converted to the gap width using the FWHM versus nominal gap width relationship. The algorithm developed for the picket fence analysis was able to quantify the gap width, the distance between gaps, and each individual leaf position. To determine the leaf speed, a 0.5 × 20 cm2MLC‐defined sliding gap was applied across a 14 × 20 cm2 symmetry field. The linacs ran at a fixed‐dose rate. The use of different monitor units (MUs) for this test led to different leaf speeds. The effect of leaf transmission was considered in a speed accuracy analysis. The difference between the EPID and film results for the MLC position is less than 0.1 mm. For the three MLC types, twice the standard deviation (2 SD) is provided; 0.2, 0.4, and 0.4 mm for gap widths of three MLC types, and 0.1, 0.2, and 0.2 mm for distances between gaps. The individual leaf positions deviate from the preset positions within 0.1 mm. The variations in the speed profiles for the EPID and EBT3 results are consistent, but the EPID results are slightly better than the film results. Different speeds were measured for each MLC type. For all three MLC types, speed errors increase with increasing speed. The analysis speeds deviate from the preset speeds within approximately 0.01 cm s−1. This quantitative analysis of MLC position and speed provides an intuitive evaluation for MLC quality assurance (QA).
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Affiliation(s)
- Yinghui Li
- School of Physics, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Lixin Chen
- State Key Laboratory of Oncology in South China, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong, China
| | - Jinhan Zhu
- State Key Laboratory of Oncology in South China, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong, China
| | - Bin Wang
- State Key Laboratory of Oncology in South China, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong, China
| | - Xiaowei Liu
- School of Physics, Sun Yat-sen University, Guangzhou, Guangdong, China
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Brezovich IA, Popple RA, Duan J, Shen S, Wu X, Benhabib S, Huang M, Cardan RA. A novel phantom and procedure providing submillimeter accuracy in daily QA tests of accelerators used for stereotactic radiosurgery*. J Appl Clin Med Phys 2016; 17:246-253. [PMID: 27455506 PMCID: PMC5690062 DOI: 10.1120/jacmp.v17i4.6295] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2016] [Revised: 03/17/2016] [Accepted: 03/15/2016] [Indexed: 12/01/2022] Open
Abstract
Stereotactic radiosurgery (SRS) places great demands on spatial accuracy. Steel BBs used as markers in quality assurance (QA) phantoms are clearly visible in MV and planar kV images, but artifacts compromise cone‐beam CT (CBCT) isocenter localization. The purpose of this work was to develop a QA phantom for measuring with sub‐mm accuracy isocenter congruence of planar kV, MV, and CBCT imaging systems and to design a practical QA procedure that includes daily Winston‐Lutz (WL) tests and does not require computer aid. The salient feature of the phantom (Universal Alignment Ball (UAB)) is a novel marker for precisely localizing isocenters of CBCT, planar kV, and MV beams. It consists of a 25.4 mm diameter sphere of polymethylmetacrylate (PMMA) containing a concentric 6.35 mm diameter tungsten carbide ball. The large density difference between PMMA and the polystyrene foam in which the PMMA sphere is embedded yields a sharp image of the sphere for accurate CBCT registration. The tungsten carbide ball serves in finding isocenter in planar kV and MV images and in doing WL tests. With the aid of the UAB, CBCT isocenter was located within 0.10±0.05 mm of its true positon, and MV isocenter was pinpointed in planar images to within 0.06±0.04 mm. In clinical morning QA tests extending over an 18 months period the UAB consistently yielded measurements with sub‐mm accuracy. The average distance between isocenter defined by orthogonal kV images and CBCT measured 0.16±0.12 mm. In WL tests the central ray of anterior beams defined by a 1.5×1.5 cm2 MLC field agreed with CBCT isocenter within 0.03±0.14 mm in the lateral direction and within 0.10±0.19 mm in the longitudinal direction. Lateral MV beams approached CBCT isocenter within 0.00±0.11 mm in the vertical direction and within ‐0.14±0.15 mm longitudinally. It took therapists about 10 min to do the tests. The novel QA phantom allows pinpointing CBCT and MV isocenter positions to better than 0.2 mm, using visual image registration. Under CBCT guidance, MLC‐defined beams are deliverable with sub‐mm spatial accuracy. The QA procedure is practical for daily tests by therapists. PACS number(s): 87.53.Ly, 87.56.Fc
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Shameem TJ. Evaluation of AutoCAL for electronic portal imaging device-based multi-leaf collimator quality assurance. Radiol Phys Technol 2016; 9:95-8. [DOI: 10.1007/s12194-015-0338-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2015] [Revised: 10/10/2015] [Accepted: 10/16/2015] [Indexed: 11/24/2022]
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Eckhause T, Al-Hallaq H, Ritter T, DeMarco J, Farrey K, Pawlicki T, Kim GY, Popple R, Sharma V, Perez M, Park S, Booth JT, Thorwarth R, Moran JM. Automating linear accelerator quality assurance. Med Phys 2015; 42:6074-83. [DOI: 10.1118/1.4931415] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
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Létourneau D, Wang A, Amin MN, Pearce J, McNiven A, Keller H, Norrlinger B, Jaffray DA. Multileaf collimator performance monitoring and improvement using semiautomated quality control testing and statistical process control. Med Phys 2014; 41:121713. [DOI: 10.1118/1.4901520] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Rice JR. Optimization of the rounded leaf offset table in modeling the multileaf collimator leaf edge in a commercial treatment planning system. J Appl Clin Med Phys 2014; 15:4899. [PMID: 25493515 PMCID: PMC5711105 DOI: 10.1120/jacmp.v15i6.4899] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Revised: 08/29/2014] [Accepted: 07/07/2014] [Indexed: 11/23/2022] Open
Abstract
An editable rounded leaf offset (RLO) table is provided in the Pinnacle3 treatment planning software. Default tables are provided for major linear accelerator manufacturers, but it is not clear how the default table values should be adjusted by the user to optimize agreement between the calculated leaf tip value and the actual measured value. Since we wish for the calculated MLC‐defined field edge to closely match the actual delivered field edge, optimal RLO table values are crucial. This is especially true for IMRT fields containing a large number of segments, since any errors would add together. A method based on the calculated MLC‐defined field edge was developed for optimizing and modifying the default RLO table values. Modified RLO tables were developed and evaluated for both dosimetric and light field‐based MLC leaf calibrations. It was shown, using a Picket Fence type test, that the optimized RLO table better modeled the calculated leaf tip than the Pinnacle3 default table. This was demonstrated for both an Elekta Synergy 80‐leaf and a Varian 120‐leaf MLC. PACS numbers: 87.55.D‐, 87.55.de, 87.55.Qr
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Affiliation(s)
- John R Rice
- Brody School of Medicine, East Carolina University.
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Manikandan A, Sarkar B, Nandy M, Sureka CS, Gossman MS, Sujatha N, Rajendran VT. Detector system dose verification comparisons for arc therapy: couch vs. gantry mount. J Appl Clin Med Phys 2014; 15:4495. [PMID: 24892330 PMCID: PMC5711059 DOI: 10.1120/jacmp.v15i3.4495] [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: 04/12/2013] [Revised: 12/11/2013] [Accepted: 01/04/2014] [Indexed: 11/29/2022] Open
Abstract
The aim of this study was to assess the performance of a gantry‐mounted detector system and a couch set detector system using a systematic multileaf collimator positional error manually introduced for volumetric‐modulated arc therapy. Four head and neck and esophagus VMAT plans were evaluated by measurement using an electronic portal imaging device and an ion chamber array. Each plan was copied and duplicated with a 1 mm systematic MLC positional error in the left leaf bank. Direct comparison of measurements for plans with and without the error permitted observational characteristics for quality assurance performance between detectors. A total of 48 different plans were evaluated for this testing. The mean percentage planar dose differences required to satisfy a 95% match between plans with and without the MLCPE were 5.2% ± 0.5% for the chamber array with gantry motion, 8.12% ± 1.04% for the chamber array with a static gantry at 0°, and 10.9% ± 1.4% for the EPID with gantry motion. It was observed that the EPID was less accurate due to overresponse of the MLCPE in the left leaf bank. The EPID always images bank‐A on the ipsilateral side of the detector, whereas for a chamber array or for a patient, that bank changes as it crosses the ‐90° or +90° position. A couch set detector system can reproduce the TPS calculated values most consistently. We recommend it as the most reliable patient specific QA system for MLC position error testing. This research is highlighted by the finding of up to 12.7% dose variation for H/N and esophagus cases for VMAT delivery, where the mere source of error was the stated clinically acceptability of 1 mm MLC position deviation of TG‐142. PACS numbers: 87.56.‐v, 87.55.‐x, 07.57.KP, 29.40.‐n, 85.25.Pb
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Fuangrod T, Woodruff HC, Rowshanfarzad P, O'Connor DJ, Middleton RH, Greer PB. An independent system for real-time dynamic multileaf collimation trajectory verification using EPID. Phys Med Biol 2013; 59:61-81. [PMID: 24334552 DOI: 10.1088/0031-9155/59/1/61] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A new tool has been developed to verify the trajectory of dynamic multileaf collimators (MLCs) used in advanced radiotherapy techniques using only the information provided by the electronic portal imaging devices (EPID) measured image frames. The prescribed leaf positions are resampled to a higher resolution in a pre-processing stage to improve the verification precision. Measured MLC positions are extracted from the EPID frames using a template matching method. A cosine similarity metric is then applied to synchronise measured and planned leaf positions for comparison. Three additional comparison functions were incorporated to ensure robust synchronisation. The MLC leaf trajectory error detection was simulated for both intensity modulated radiation therapy (IMRT) (prostate) and volumetric modulated arc therapy (VMAT) (head-and-neck) deliveries with anthropomorphic phantoms in the beam. The overall accuracy for MLC positions automatically extracted from EPID image frames was approximately 0.5 mm. The MLC leaf trajectory verification system can detect leaf position errors during IMRT and VMAT with a tolerance of 3.5 mm within 1 s.
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Affiliation(s)
- Todsaporn Fuangrod
- Faculty of Engineering and Built Environment, School of Electrical Engineering and Computer Science, the University of Newcastle, NSW 2308, Australia
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Mohammadi M, Bezak E. Evaluation of relative transmitted dose for a step and shoot head and neck intensity modulated radiation therapy using a scanning liquid ionization chamber electronic portal imaging device. J Med Phys 2012; 37:14-26. [PMID: 22363108 PMCID: PMC3283912 DOI: 10.4103/0971-6203.92716] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Revised: 09/29/2011] [Accepted: 10/06/2011] [Indexed: 11/13/2022] Open
Abstract
The dose delivery verification for a head and neck static intensity modulated radiation therapy (IMRT) case using a scanning liquid ionization chamber electronic portal imaging device (SLIC-EPID) was investigated. Acquired electronic portal images were firstly converted into transmitted dose maps using an in-house developed method. The dose distributions were then compared with those calculated in a virtual EPID using the Pinnacle3 treatment planning system (TPS). Using gamma evaluation with the ΔDmax and DTA criteria of 3%/2.54 mm, an excellent agreement was observed between transmitted dose measured using SLIC-EPID and that calculated by TPS (gamma score approximately 95%) for large MLC fields. In contrast, for several small subfields, due to SLIC-EPID image blurring, significant disagreement was found in the gamma results. Differences between EPID and TPS dose maps were also observed for several parts of the radiation subfields, when the radiation beam passed through air on the outside of tissue. The transmitted dose distributions measured using portal imagers such as SLIC-EPID can be used to verify the dose delivery to a patient. However, several aspects such as accurate calibration procedure and imager response under different conditions should be taken into the consideration. In addition, SLIC-EPID image blurring is another important issue, which should be considered if the SLIC-EPID is used for clinical dosimetry verification.
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Manikandan A, Sarkar B, Holla R, Vivek TR, Sujatha N. Quality assurance of dynamic parameters in volumetric modulated arc therapy. Br J Radiol 2012; 85:1002-10. [PMID: 22745206 DOI: 10.1259/bjr/19152959] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVES The purpose of this study was to demonstrate quality assurance checks for accuracy of gantry speed and position, dose rate and multileaf collimator (MLC) speed and position for a volumetric modulated arc treatment (VMAT) modality (Synergy S; Elekta, Stockholm, Sweden), and to check that all the necessary variables and parameters were synchronous. METHODS Three tests (for gantry position-dose delivery synchronisation, gantry speed-dose delivery synchronisation and MLC leaf speed and positions) were performed. RESULTS The average error in gantry position was 0.5° and the average difference was 3 MU for a linear and a parabolic relationship between gantry position and delivered dose. In the third part of this test (sawtooth variation), the maximum difference was 9.3 MU, with a gantry position difference of 1.2°. In the sweeping field method test, a linear relationship was observed between recorded doses and distance from the central axis, as expected. In the open field method, errors were encountered at the beginning and at the end of the delivery arc, termed the "beginning" and "end" errors. For MLC position verification, the maximum error was -2.46 mm and the mean error was 0.0153 ±0.4668 mm, and 3.4% of leaves analysed showed errors of >±1 mm. CONCLUSION This experiment demonstrates that the variables and parameters of the Synergy S are synchronous and that the system is suitable for delivering VMAT using a dynamic MLC.
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Affiliation(s)
- A Manikandan
- Department of Radiation Oncology, Narayana Hrudayalaya, Bangalore, India.
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Sumida I, Yamaguchi H, Kizaki H, Koizumi M, Ogata T, Takahashi Y, Yoshioka Y. Quality assurance of MLC leaf position accuracy and relative dose effect at the MLC abutment region using an electronic portal imaging device. JOURNAL OF RADIATION RESEARCH 2012; 53:798-806. [PMID: 22843372 PMCID: PMC3430416 DOI: 10.1093/jrr/rrs038] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Revised: 05/15/2012] [Accepted: 05/28/2012] [Indexed: 06/01/2023]
Abstract
We investigated an electronic portal image device (EPID)-based method to see whether it provides effective and accurate relative dose measurement at abutment leaves in terms of positional errors of the multi-leaf collimator (MLC) leaf position. A Siemens ONCOR machine was used. For the garden fence test, a rectangular field (0.2 20 cm) was sequentially irradiated 11 times at 2-cm intervals. Deviations from planned leaf positions were calculated. For the nongap test, relative doses at the MLC abutment region were evaluated by sequential irradiation of a rectangular field (2 20 cm) 10 times with a MLC separation of 2 cm without a leaf gap. The integral signal in a region of interest was set to position A (between leaves) and B (neighbor of A). A pixel value at position B was used as background and the pixel ratio (A/B 100) was calculated. Both tests were performed at four gantry angles (0, 90, 180 and 270°) four times over 1 month. For the nongap test the difference in pixel ratio between the first and last period was calculated. Regarding results, average deviations from planned positions with the garden fence test were within 0.5 mm at all gantry angles, and at gantry angles of 90 and 270° tended to decrease gradually over the month. For the nongap test, pixel ratio tended to increase gradually in all leaves, leading to a decrease in relative doses at abutment regions. This phenomenon was affected by both gravity arising from the gantry angle, and the hardware-associated contraction of field size with this type of machine.
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Affiliation(s)
- Iori Sumida
- Department of Oral and Maxillofacial Radiology, Osaka University Graduate School of Dentistry, 1-8 Yamada-oka, Suita, Osaka, 565-0871 Japan.
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Richart J, Pujades MC, Perez-Calatayud J, Granero D, Ballester F, Rodriguez S, Santos M. QA of dynamic MLC based on EPID portal dosimetry. Phys Med 2011; 28:262-8. [PMID: 21784685 DOI: 10.1016/j.ejmp.2011.06.046] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Revised: 06/24/2011] [Accepted: 06/28/2011] [Indexed: 10/18/2022] Open
Abstract
PURPOSE Dynamic delivery of intensity modulated beams (dIMRT) requires not only accurate verification of leaf positioning but also a control on the speed of motion. The latter is a parameter that has a major impact on the dose delivered to the patient. Time consumed in quality assurance (QA) procedures is an issue of relevance in any radiotherapy department. Electronic portal imaging dosimetry (EPID) can be very efficient for routine tests. The purpose of this work is to investigate the ability of our EPID for detecting small errors in leaf positioning, and to present our daily QA procedures for dIMRT based on EPID. METHODS AND MATERIALS A Varian 2100 CD Clinac equipped with an 80 leaf Millennium MLC and with amorphous silicon based EPID (aS500, Varian) is used. The daily QA program consists in performing: Stability check of the EPID signal, Garden fence test, Sweeping slit test, and Leaf speed test. RESULTS AND DISCUSSION The EPID system exhibits good long term reproducibility. The mean portal dose at the centre of a 10 × 10 cm(2) static field was 1.002 ± 0.004 (range 1.013-0.995) for the period evaluated of 47 weeks. Garden fence test shows that leaf position errors of up to 0.2 mm can be detected. With the Sweeping slit test we are able to detect small deviations on the gap width and errors of individual leaves of 0.5 and 0.2 mm. With the Leaf speed test problems due to motor fatigue or friction between leaves can be detected. CONCLUSIONS This set of tests takes no longer than 5 min in the linac treatment room. With EPID dosimetry, a consistent daily QA program can be applied, giving complete information about positioning/speed MLC.
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Affiliation(s)
- J Richart
- Radiotherapy Department, Hospital Clínica Benidorm, E-03501 Benidorm, Alicante, Spain.
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Ung NM, Harper CS, Wee L. Dosimetric impact of systematic MLC positional errors on step and shoot IMRT for prostate cancer: a planning study. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2011; 34:291-8. [PMID: 21409437 DOI: 10.1007/s13246-011-0062-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2010] [Accepted: 02/28/2011] [Indexed: 02/07/2023]
Abstract
The positional accuracy of multileaf collimators (MLC) is crucial in ensuring precise delivery of intensity-modulated radiotherapy (IMRT). The aim of this planning study was to investigate the dosimetric impact of systematic MLC positional errors on step and shoot IMRT of prostate cancer. A total of 12 perturbations of MLC leaf banks were introduced to six prostate IMRT treatment plans to simulate MLC systematic positional errors. Dose volume histograms (DVHs) were generated for the extraction of dose endpoint parameters. Plans were evaluated in terms of changes to the defined endpoint dose parameters, conformity index (CI) and healthy tissue avoidance (HTA) to planning target volume (PTV), rectum and bladder. Negative perturbations of MLC had been found to produce greater changes to endpoint dose parameters than positive perturbations of MLC (p < 0.01). Negative and positive asynchronised MLC perturbations of -1 mm resulted in median changes in D(95) of -1.2 and 0.9% respectively. Negative and positive synchronised MLC perturbations of 1 mm in one direction resulted in median changes in D(95) of -2.3 and 1.8% respectively. Doses to rectum were generally more sensitive to systematic MLC errors compared to bladder (p < 0.01). Negative and positive synchronised MLC perturbations of 1 mm in one direction resulted in median changes in endpoint dose parameters of rectum and bladder from 1.0 to 2.5%. Maximum reduction of -4.4 and -7.3% were recorded for conformity index (CI) and healthy tissue avoidance (HTA) respectively due to synchronised MLC perturbation of 1 mm. MLC errors resulted in dosimetric changes in IMRT plans for prostate.
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Affiliation(s)
- N M Ung
- The University of Western Australia, Crawley, WA 6009, Australia.
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Simon TA, Kahler D, Simon WE, Fox C, Li J, Palta J, Liu C. An MLC calibration method using a detector array. Med Phys 2010; 36:4495-503. [PMID: 19928080 DOI: 10.1118/1.3218767] [Citation(s) in RCA: 9] [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 authors have developed a quantitative calibration method for a multileaf collimator (MLC) which measures individual leaf positions relative to the MLC backup jaw on an Elekta Synergy linear accelerator. METHODS The method utilizes a commercially available two-axis detector array (Profiler 2; Sun Nuclear Corporation, Melbourne, FL). To calibrate the MLC bank, its backup jaw is positioned at the central axis and the opposing jaw is retracted to create a half-beam configuration. The position of the backup jaws field edge is then measured with the array to obtain what is termed the radiation defined reference line. The positions of the individual leaf ends relative to this reference line are then inferred by the detector response in the leaf end penumbra. Iteratively adjusting and remeasuring the leaf end positions to within specifications completes the calibration. Using the backup jaw as a reference for the leaf end positions is based on three assumptions: (1) The leading edge of an MLC leaf bank is parallel to its backup jaw's leading edge, (2) the backup jaw position is reproducible, and (3) the measured radiation field edge created by each leaf end is representative of that leaf's position. Data from an electronic portal imaging device (EPID) were used in a similar analysis to check the results obtained with the array. RESULTS The relative leaf end positions measured with the array differed from those measured with the EPID by an average of 0.11+/-0.09 mm per leaf. The maximum leaf positional change measured with the Profiler 2 over a 3 month period was 0.51 mm. A leaf positional accuracy of +/-0.4 mm is easily attainable through the iterative calibration process. The method requires an average of 40 min to measure both leaf banks. CONCLUSIONS This work demonstrates that the Profiler 2 is an effective tool for efficient and quantitative MLC quality assurance and calibration.
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Affiliation(s)
- Thomas A Simon
- Department of Nuclear and Radiological Engineering, University of Florida, 202 Nuclear Science Building, Gainesville, Florida 32611-8300, USA.
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Klein EE, Hanley J, Bayouth J, Yin FF, Simon W, Dresser S, Serago C, Aguirre F, Ma L, Arjomandy B, Liu C, Sandin C, Holmes T. Task Group 142 report: quality assurance of medical accelerators. Med Phys 2009; 36:4197-212. [PMID: 19810494 DOI: 10.1118/1.3190392] [Citation(s) in RCA: 991] [Impact Index Per Article: 66.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The task group (TG) for quality assurance of medical accelerators was constituted by the American Association of Physicists in Medicine's Science Council under the direction of the Radiation Therapy Committee and the Quality Assurance and Outcome Improvement Subcommittee. The task group (TG-142) had two main charges. First to update, as needed, recommendations of Table II of the AAPM TG-40 report on quality assurance and second, to add recommendations for asymmetric jaws, multileaf collimation (MLC), and dynamic/virtual wedges. The TG accomplished the update to TG-40, specifying new test and tolerances, and has added recommendations for not only the new ancillary delivery technologies but also for imaging devices that are part of the linear accelerator. The imaging devices include x-ray imaging, photon portal imaging, and cone-beam CT. The TG report was designed to account for the types of treatments delivered with the particular machine. For example, machines that are used for radiosurgery treatments or intensity-modulated radiotherapy (IMRT) require different tests and/or tolerances. There are specific recommendations for MLC quality assurance for machines performing IMRT. The report also gives recommendations as to action levels for the physicists to implement particular actions, whether they are inspection, scheduled action, or immediate and corrective action. The report is geared to be flexible for the physicist to customize the QA program depending on clinical utility. There are specific tables according to daily, monthly, and annual reviews, along with unique tables for wedge systems, MLC, and imaging checks. The report also gives specific recommendations regarding setup of a QA program by the physicist in regards to building a QA team, establishing procedures, training of personnel, documentation, and end-to-end system checks. The tabulated items of this report have been considerably expanded as compared with the original TG-40 report and the recommended tolerances accommodate differences in the intended use of the machine functionality (non-IMRT, IMRT, and stereotactic delivery).
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Affiliation(s)
- Eric E Klein
- Washington University, St. Louis, Missouri, USA.
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Schreibmann E, Dhabaan A, Elder E, Fox T. Patient-specific quality assurance method for VMAT treatment delivery. Med Phys 2009; 36:4530-5. [DOI: 10.1118/1.3213085] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Rangel A, Dunscombe P. Tolerances on MLC leaf position accuracy for IMRT delivery with a dynamic MLC. Med Phys 2009; 36:3304-9. [DOI: 10.1118/1.3134244] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
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