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Karger CP, Elter A, Dorsch S, Mann P, Pappas E, Oldham M. Validation of complex radiotherapy techniques using polymer gel dosimetry. Phys Med Biol 2024; 69:06TR01. [PMID: 38330494 DOI: 10.1088/1361-6560/ad278f] [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: 02/06/2023] [Accepted: 02/08/2024] [Indexed: 02/10/2024]
Abstract
Modern radiotherapy delivers highly conformal dose distributions to irregularly shaped target volumes while sparing the surrounding normal tissue. Due to the complex planning and delivery techniques, dose verification and validation of the whole treatment workflow by end-to-end tests became much more important and polymer gel dosimeters are one of the few possibilities to capture the delivered dose distribution in 3D. The basic principles and formulations of gel dosimetry and its evaluation methods are described and the available studies validating device-specific geometrical parameters as well as the dose delivery by advanced radiotherapy techniques, such as 3D-CRT/IMRT and stereotactic radiosurgery treatments, the treatment of moving targets, online-adaptive magnetic resonance-guided radiotherapy as well as proton and ion beam treatments, are reviewed. The present status and limitations as well as future challenges of polymer gel dosimetry for the validation of complex radiotherapy techniques are discussed.
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Affiliation(s)
- Christian P Karger
- Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
- National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany
| | - Alina Elter
- Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
- National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany
- Department of Radiation Oncology, University Hospital Heidelberg, Im Neuenheimer Feld 400, D-69120 Heidelberg, Germany
| | - Stefan Dorsch
- Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
- National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany
| | - Philipp Mann
- Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
- National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany
| | - Evangelos Pappas
- Radiology & Radiotherapy Sector, Department of Biomedical Sciences, University of West Attica, Athens, Greece
| | - Mark Oldham
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, United States of America
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Kim JP. MRgRT Quality Assurance for a Low-Field MR-Linac. Semin Radiat Oncol 2024; 34:129-134. [PMID: 38105087 DOI: 10.1016/j.semradonc.2023.10.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
The introduction of MR-guided treatment machines into the radiation oncology clinic has provided unique challenges for the radiotherapy QA program. These MR-linac systems require that existing QA procedures be adapted to verify linac performance within the magnetic field environment and that new procedures be added to ensure acceptable image quality for the MR system. While both high and low-field MR-linac options exist, this chapter is intended to provide a structure for implementing a QA program within the low-field MR environment. This review is divided into three sections. The first section focuses on machine QA tasks including mechanical and dosimetric verification. The second section is concentrated on the procedures implemented for imaging QA. Finally, the last section covers patient specific QA tasks including special considerations related to the performance of patient specific QA within the framework of online adaptive radiotherapy.
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Affiliation(s)
- Joshua P Kim
- Department of Radiation Oncology, Henry Ford Health System, Detroit, MI..
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De Deene Y. Radiation Dosimetry by Use of Radiosensitive Hydrogels and Polymers: Mechanisms, State-of-the-Art and Perspective from 3D to 4D. Gels 2022; 8:gels8090599. [PMID: 36135311 PMCID: PMC9498652 DOI: 10.3390/gels8090599] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 09/07/2022] [Accepted: 09/10/2022] [Indexed: 12/22/2022] Open
Abstract
Gel dosimetry was developed in the 1990s in response to a growing need for methods to validate the radiation dose distribution delivered to cancer patients receiving high-precision radiotherapy. Three different classes of gel dosimeters were developed and extensively studied. The first class of gel dosimeters is the Fricke gel dosimeters, which consist of a hydrogel with dissolved ferrous ions that oxidize upon exposure to ionizing radiation. The oxidation results in a change in the nuclear magnetic resonance (NMR) relaxation, which makes it possible to read out Fricke gel dosimeters by use of quantitative magnetic resonance imaging (MRI). The radiation-induced oxidation in Fricke gel dosimeters can also be visualized by adding an indicator such as xylenol orange. The second class of gel dosimeters is the radiochromic gel dosimeters, which also exhibit a color change upon irradiation but do not use a metal ion. These radiochromic gel dosimeters do not demonstrate a significant radiation-induced change in NMR properties. The third class is the polymer gel dosimeters, which contain vinyl monomers that polymerize upon irradiation. Polymer gel dosimeters are predominantly read out by quantitative MRI or X-ray CT. The accuracy of the dosimeters depends on both the physico-chemical properties of the gel dosimeters and on the readout technique. Many different gel formulations have been proposed and discussed in the scientific literature in the last three decades, and scanning methods have been optimized to achieve an acceptable accuracy for clinical dosimetry. More recently, with the introduction of the MR-Linac, which combines an MRI-scanner and a clinical linear accelerator in one, it was shown possible to acquire dose maps during radiation, but new challenges arise.
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Affiliation(s)
- Yves De Deene
- Liverpool & Macarthur Cancer Therapy Centres, Liverpool, NSW 1871, Australia; or
- Ingham Institute, Liverpool, NSW 2170, Australia
- School of Science, Western Sydney University, Penrith, NSW 2751, Australia
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Kim JH, Kim B, Shin W, Son J, Choi CH, Park JM, Hwang U, Kim J, Jung S. 3D star shot analysis using MAGAT gel dosimeter for integrated imaging and radiation isocenter verification of MR-Linac system. J Appl Clin Med Phys 2022; 23:e13615. [PMID: 35436031 PMCID: PMC9195025 DOI: 10.1002/acm2.13615] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 02/24/2022] [Accepted: 03/28/2022] [Indexed: 01/08/2023] Open
Abstract
Purpose This study aims to investigate a star shot analysis using a three‐dimensional (3D) gel dosimeter for the imaging and radiation isocenter verification of a magnetic resonance linear accelerator (MR‐Linac). Methods A mixture of methacrylic acid, gelatin, and tetrakis (hydroxymethyl) phosphonium chloride, called MAGAT gel, was fabricated. One MAGAT gel for each Linac and MR‐Linac was irradiated under six gantry angles. A 6 MV photon beam of Linac and a 6 MV flattening filter free beam of MR‐Linac were delivered to two MAGAT gels and EBT3 films. MR images were acquired by MR‐Linac with a clinical sequence (i.e., TrueFISP). The 3D star shot analysis for seven consecutive slices of the MR images with TrueFISP was performed. The 2D star shot analysis for the central plane of the gel was compared to the results from the EBT3 films. The radius of isocircle (ICr) and the distance between the center of the circle and the center marked on the image (ICd) were evaluated. Results For MR‐Linac with MAGAT gel measurements, ICd at the central plane was 0.46 mm for TrueFISP. Compared to EBT3 film measurements, the differences in ICd and ICr for both Linac and MR‐Linac were within 0.11 and 0.13 mm, respectively. For the 3D analysis, seven consecutive slices of TrueFISP images were analyzed and the maximum radii of isocircles (ICr_max) were 0.18 mm for Linac and 0.73 mm for MR‐Linac. The tilting angles of radiation axis were 0.31° for Linac and 0.10° for MR‐Linac. Conclusion The accuracy of 3D star shot analysis using MAGAT gel was comparable to that of EBT3 film, having a capability for integrated analysis for imaging isocenter and radiation isocenter. 3D star shot analysis using MAGAT gel can provide 3D information of radiation isocenter, suggesting a quantitative extent of gantry‐tilting.
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Affiliation(s)
- Jeong Ho Kim
- Department of Radiation OncologySamsung Changwon HospitalSungkyunkwan University School of MedicineChangwonRepublic of Korea
| | - Bitbyeol Kim
- Department of Radiation OncologySeoul National University HospitalSeoulRepublic of Korea
| | - Wook‐Geun Shin
- Department of Radiation OncologySeoul National University HospitalSeoulRepublic of Korea
| | - Jaeman Son
- Department of Radiation OncologySeoul National University HospitalSeoulRepublic of Korea
- Institute of Radiation MedicineSeoul National University Medical Research CenterSeoulRepublic of Korea
- Biomedical Research InstituteSeoul National University HospitalSeoulRepublic of Korea
| | - Chang Heon Choi
- Department of Radiation OncologySeoul National University HospitalSeoulRepublic of Korea
- Institute of Radiation MedicineSeoul National University Medical Research CenterSeoulRepublic of Korea
- Biomedical Research InstituteSeoul National University HospitalSeoulRepublic of Korea
| | - Jong Min Park
- Department of Radiation OncologySeoul National University HospitalSeoulRepublic of Korea
- Institute of Radiation MedicineSeoul National University Medical Research CenterSeoulRepublic of Korea
- Biomedical Research InstituteSeoul National University HospitalSeoulRepublic of Korea
- Department of Radiation OncologySeoul National University College of MedicineSeoulRepublic of Korea
- Robotics Research Laboratory for Extreme EnvironmentsAdvanced Institute of Convergence TechnologySuwonRepublic of Korea
| | - Ui‐Jung Hwang
- Department of Radiation OncologyChungnam National University Sejong HospitalSejongRepublic of Korea
| | - Jung‐in Kim
- Department of Radiation OncologySeoul National University HospitalSeoulRepublic of Korea
- Institute of Radiation MedicineSeoul National University Medical Research CenterSeoulRepublic of Korea
- Biomedical Research InstituteSeoul National University HospitalSeoulRepublic of Korea
| | - Seongmoon Jung
- Department of Radiation OncologySeoul National University HospitalSeoulRepublic of Korea
- Institute of Radiation MedicineSeoul National University Medical Research CenterSeoulRepublic of Korea
- Biomedical Research InstituteSeoul National University HospitalSeoulRepublic of Korea
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Nierer L, Kamp F, Reiner M, Corradini S, Rabe M, Dietrich O, Parodi K, Belka C, Kurz C, Landry G. Evaluation of an anthropomorphic ion chamber and 3D gel dosimetry head phantom at a 0.35 T MR-linac using separate 1.5 T MR-scanners for gel readout. Z Med Phys 2022; 32:312-325. [PMID: 35305857 PMCID: PMC9948847 DOI: 10.1016/j.zemedi.2022.01.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 01/27/2022] [Accepted: 01/31/2022] [Indexed: 12/22/2022]
Abstract
PURPOSE To date, no universally accepted technique for the evaluation of the overall dosimetric performance of hybrid integrated magnetic resonance imaging (MR) - linear accelerators (linacs) is available. We report on the suitability and reliability of a novel phantom with modular inserts for combined polymer gel (PG) and ionisation chamber (IC) measurements at a 0.35 T MR-linac. METHODS Three 3D-printed, modular head phantoms, based on real patient anatomy, were used for repeated (2 times) PG irradiations of cranial treatment plans on a 0.35 T MR-linac. The PG readout was performed on two 1.5 T diagnostic MR-scanners to reduce scanning time. The PG dose volumes were normalised to the IC dose (normalised dose N1) and to the median planning target volume dose (normalised dose N2). Linearity of the PG dose response was validated and dose profiles, centres of mass (COM) of the 95% isodoses and dose volume histograms (DVH) were compared between planned and measured dose distributions and a 3D gamma analysis was performed. RESULTS Dose linearity of the PG was good (R2> 0.99 for all linear fit functions). High agreement was found between planned and measured dose volumes in the dose profiles and DVHs. The largest dose deviation was found in the intermediate dose region (mean dose deviation 0.2Gy; 5.6%). A mean COM offset of 1.2mm indicated high spatial accuracy. Mean 3D gamma passing rates (2%, 2mm) of 83.3% for N1 and 91.6% for N2 dose distributions were determined. When comparing repeated PG measurements to each other, a mean gamma passing rate of 95.7% was found. CONCLUSION The new modular phantom was found practical for use at a 0.35 T MR-linac. In contrast to the high dose region, larger mean deviations were found in the mid dose range. The PG measurements showed high reproducibility. The MR-linac performed well in a non-adaptive setting in terms of spatial and dosimetric accuracy.
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Affiliation(s)
- Lukas Nierer
- Department of Radiation Oncology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, Germany.
| | - Florian Kamp
- Department of Radiation Oncology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, Germany; Department of Radiation Oncology, University Hospital Cologne, Kerpener Str. 62, 50937 Cologne, Germany
| | - Michael Reiner
- Department of Radiation Oncology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, Germany
| | - Stefanie Corradini
- Department of Radiation Oncology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, Germany
| | - Moritz Rabe
- Department of Radiation Oncology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, Germany
| | - Olaf Dietrich
- Department of Radiology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, Germany
| | - Katia Parodi
- Department of Medical Physics, Faculty of Physics, Ludwig-Maximilians-Universität München, 85748 Garching, Germany
| | - Claus Belka
- Department of Radiation Oncology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, Germany; German Cancer Consortium (DKTK), partner site Munich, Munich, Germany
| | - Christopher Kurz
- Department of Radiation Oncology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, Germany
| | - Guillaume Landry
- Department of Radiation Oncology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, Germany
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Marrale M, d’Errico F. Hydrogels for Three-Dimensional Ionizing-Radiation Dosimetry. Gels 2021; 7:74. [PMID: 34205640 PMCID: PMC8293215 DOI: 10.3390/gels7020074] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 06/15/2021] [Accepted: 06/16/2021] [Indexed: 11/28/2022] Open
Abstract
Radiation-sensitive gels are among the most recent and promising developments for radiation therapy (RT) dosimetry. RT dosimetry has the twofold goal of ensuring the quality of the treatment and the radiation protection of the patient. Benchmark dosimetry for acceptance testing and commissioning of RT systems is still based on ionization chambers. However, even the smallest chambers cannot resolve the steep dose gradients of up to 30-50% per mm generated with the most advanced techniques. While a multitude of systems based, e.g., on luminescence, silicon diodes and radiochromic materials have been developed, they do not allow the truly continuous 3D dose measurements offered by radiation-sensitive gels. The gels are tissue equivalent, so they also serve as phantoms, and their response is largely independent of radiation quality and dose rate. Some of them are infused with ferrous sulfate and rely on the radiation-induced oxidation of ferrous ions to ferric ions (Fricke-gels). Other formulations consist of monomers dispersed in a gelatinous medium (Polyacrylamide gels) and rely on radiation-induced polymerization, which creates a stable polymer structure. In both gel types, irradiation causes changes in proton relaxation rates that are proportional to locally absorbed dose and can be imaged using magnetic resonance imaging (MRI). Changes in color and/or opacification of the gels also occur upon irradiation, allowing the use of optical tomography techniques. In this work, we review both Fricke and polyacrylamide gels with emphasis on their chemical and physical properties and on their applications for radiation dosimetry.
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Affiliation(s)
- Maurizio Marrale
- Department of Physics and Chemistry, “Emilio Segrè” ATeN Center, University of Palermo, 90128 Palermo, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Catania, 95123 Catania, Italy
| | - Francesco d’Errico
- Scuola di Ingegneria, Università degli Studi di Pisa, 56126 Pisa, Italy;
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Pisa, 56127 Pisa, Italy
- School of Medicine, Yale University New Haven, CT 06510, USA
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Desai V, Bayouth J, Smilowitz J, Yadav P. A clinical validation of the MR-compatible Delta 4 QA system in a 0.35 tesla MR linear accelerator. J Appl Clin Med Phys 2021; 22:82-91. [PMID: 33666360 PMCID: PMC8035559 DOI: 10.1002/acm2.13216] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 01/21/2021] [Accepted: 02/15/2021] [Indexed: 12/27/2022] Open
Abstract
PURPOSE To validate an MR-compatible version of the ScandiDos Delta4 Phantom+ on a 0.35T MR guided linear accelerator (MR-Linac) system and to determine the effect of plan complexity on the measurement results. METHODS/MATERIALS 36 clinical treatment plans originally delivered on a 0.35T MR linac system were re-planned on the Delta4 Phantom+ MR geometry following our clinical quality assurance (QA) protocol. The QA plans were then measured using the Delta4 Phantom+ MR and the global gamma pass rates were compared to previous results measured using a Sun Nuclear ArcCHECK-MR. Both 3%/3mm and 2%/2mm global gamma pass rates with a 20% dose threshold were recorded and compared. Plan complexity was quantified for each clinical plan investigated using 24 different plan metrics and each metric's correlation with the overall 2%/2mm global gamma pass rate was investigated using Pearson correlation coefficients. RESULTS Both systems demonstrated comparable levels of gamma pass rates at both the 3%/3mm and 2%/2mm level for all plan complexity metrics. Nine plan metrics including area, number of active MLCs, perimeter, edge metric, leaf segment variability, complete irradiation area outline, irregularity, leaf travel index, and unique opening index were moderately (|r| > 0.5) correlated with the Delta4 2%/2mm global gamma pass rates whereas those same metrics had weak correlation with the ArcCHECK-MR pass rates. Only the perimeter to area ratio and small aperture score (20 mm) metrics showed moderate correlation with the ArcCHECK-MR gamma pass rates. CONCLUSIONS The MR-compatible version of the ScandiDos Delta4 Phantom+ MR has been validated for clinical use on a 0.35T MR-Linac with results being comparable to an ArcCHECK-MR system in use clinically for almost five years. Most plan complexity metrics did not correlate with lower 2%/2mm gamma pass rates using the ArcCHECK-MR but several metrics were found to be moderately correlated with lower 2%/2mm global gamma pass rates for the Delta4 Phantom+ MR.
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Affiliation(s)
- Vimal Desai
- Department of Human OncologySchool of Medicine and Public HealthUniversity of Wisconsin‐MadisonMadisonWIUSA
| | - John Bayouth
- Department of Human OncologySchool of Medicine and Public HealthUniversity of Wisconsin‐MadisonMadisonWIUSA
| | - Jennifer Smilowitz
- Department of Human OncologySchool of Medicine and Public HealthUniversity of Wisconsin‐MadisonMadisonWIUSA
| | - Poonam Yadav
- Department of Human OncologySchool of Medicine and Public HealthUniversity of Wisconsin‐MadisonMadisonWIUSA
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8
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Jensen MB, Balling P, Doran SJ, Petersen JB, Wahlstedt IH, Muren LP. Dose response of three-dimensional silicone-based radiochromic dosimeters for photon irradiation in the presence of a magnetic field. PHYSICS & IMAGING IN RADIATION ONCOLOGY 2021; 16:81-84. [PMID: 33458348 PMCID: PMC7807676 DOI: 10.1016/j.phro.2020.10.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 10/02/2020] [Accepted: 10/05/2020] [Indexed: 11/18/2022]
Abstract
The magnetic field in magnetic resonance imaging guided radiotherapy (MRgRT) delivery systems influences charged-particle trajectories and hence the three-dimensional (3D) radiation dose distributions. This study investigated the dose-response as well as dose-rate and fractionation dependencies of silicone-based 3D radiochromic dosimeters for photon irradiation in a magnetic field using a 0.35 T MRgRT system. We found a linear dose response up to 22.6 Gy and no significant dose-rate dependency as a function of depth. A difference in optical response was observed for dosimeters irradiated in a single compared to multiple fractions. The dosimeter showed clinical potential for verification of MRgRT delivery.
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Affiliation(s)
- Morten B. Jensen
- Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
- Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark
- Corresponding author.
| | - Peter Balling
- Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark
- Interdisciplinary Nanoscience Center, Aarhus University, Aarhus, Denmark
| | | | | | - Isak H. Wahlstedt
- Technical University of Denmark, Lyngby, Denmark
- Department of Clinical Oncology, Rigshospitalet, Copenhagen, Denmark
- Department of Oncology, Herlev and Gentofte Hospital, Copenhagen, Denmark
| | - Ludvig P. Muren
- Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
- Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark
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Schwahofer A, Mann P, Spindeldreier CK, Karger CP. On the feasibility of absolute 3D dosimetry using LiF thermoluminescence detectors and polymer gels on a 0.35T MR-LINAC. ACTA ACUST UNITED AC 2020; 65:215002. [DOI: 10.1088/1361-6560/aba6d7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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10
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Baldock C, Karger CP, Zaidi H. Gel dosimetry provides the optimal end‐to‐end quality assurance dosimetry for MR‐linacs. Med Phys 2020; 47:3259-3262. [DOI: 10.1002/mp.14239] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2020] [Accepted: 05/09/2020] [Indexed: 01/08/2023] Open
Affiliation(s)
- Clive Baldock
- School of Engineering College of Science and Engineering University of Tasmania TAS Hobart 7005Australia
| | - Christian P. Karger
- Medical Physics in Radiation Oncology German Cancer Research Center (DKFZ), and National Center for Radiation Research in Oncology (NCRO) Heidelberg Institute for Radiation Oncology (HIRO) Im Neuenheimer Feld 280 Heidelberg Germany
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Kurz C, Buizza G, Landry G, Kamp F, Rabe M, Paganelli C, Baroni G, Reiner M, Keall PJ, van den Berg CAT, Riboldi M. Medical physics challenges in clinical MR-guided radiotherapy. Radiat Oncol 2020; 15:93. [PMID: 32370788 PMCID: PMC7201982 DOI: 10.1186/s13014-020-01524-4] [Citation(s) in RCA: 77] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 03/24/2020] [Indexed: 12/18/2022] Open
Abstract
The integration of magnetic resonance imaging (MRI) for guidance in external beam radiotherapy has faced significant research and development efforts in recent years. The current availability of linear accelerators with an embedded MRI unit, providing volumetric imaging at excellent soft tissue contrast, is expected to provide novel possibilities in the implementation of image-guided adaptive radiotherapy (IGART) protocols. This study reviews open medical physics issues in MR-guided radiotherapy (MRgRT) implementation, with a focus on current approaches and on the potential for innovation in IGART.Daily imaging in MRgRT provides the ability to visualize the static anatomy, to capture internal tumor motion and to extract quantitative image features for treatment verification and monitoring. Those capabilities enable the use of treatment adaptation, with potential benefits in terms of personalized medicine. The use of online MRI requires dedicated efforts to perform accurate dose measurements and calculations, due to the presence of magnetic fields. Likewise, MRgRT requires dedicated quality assurance (QA) protocols for safe clinical implementation.Reaction to anatomical changes in MRgRT, as visualized on daily images, demands for treatment adaptation concepts, with stringent requirements in terms of fast and accurate validation before the treatment fraction can be delivered. This entails specific challenges in terms of treatment workflow optimization, QA, and verification of the expected delivered dose while the patient is in treatment position. Those challenges require specialized medical physics developments towards the aim of fully exploiting MRI capabilities. Conversely, the use of MRgRT allows for higher confidence in tumor targeting and organs-at-risk (OAR) sparing.The systematic use of MRgRT brings the possibility of leveraging IGART methods for the optimization of tumor targeting and quantitative treatment verification. Although several challenges exist, the intrinsic benefits of MRgRT will provide a deeper understanding of dose delivery effects on an individual basis, with the potential for further treatment personalization.
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Affiliation(s)
- Christopher Kurz
- Department of Radiation Oncology, University Hospital, LMU Munich, Marchioninistraße 15, 81377, Munich, Germany
- Department of Medical Physics, Ludwig-Maximilians-Universität München, Am Coulombwall 1, 85748, Garching, Germany
| | - Giulia Buizza
- Department of Electronics, Information and Bioengineering, Politecnico di Milano, P.za Leonardo da Vinci 32, 20133, Milano, Italy
| | - Guillaume Landry
- Department of Radiation Oncology, University Hospital, LMU Munich, Marchioninistraße 15, 81377, Munich, Germany
- Department of Medical Physics, Ludwig-Maximilians-Universität München, Am Coulombwall 1, 85748, Garching, Germany
- German Cancer Consortium (DKTK), 81377, Munich, Germany
| | - Florian Kamp
- Department of Radiation Oncology, University Hospital, LMU Munich, Marchioninistraße 15, 81377, Munich, Germany
| | - Moritz Rabe
- Department of Radiation Oncology, University Hospital, LMU Munich, Marchioninistraße 15, 81377, Munich, Germany
| | - Chiara Paganelli
- Department of Electronics, Information and Bioengineering, Politecnico di Milano, P.za Leonardo da Vinci 32, 20133, Milano, Italy
| | - Guido Baroni
- Department of Electronics, Information and Bioengineering, Politecnico di Milano, P.za Leonardo da Vinci 32, 20133, Milano, Italy
- Bioengineering Unit, National Center of Oncological Hadrontherapy (CNAO), Strada Privata Campeggi 53, 27100, Pavia, Italy
| | - Michael Reiner
- Department of Radiation Oncology, University Hospital, LMU Munich, Marchioninistraße 15, 81377, Munich, Germany
| | - Paul J Keall
- ACRF Image X Institute, University of Sydney, Sydney, NSW, 2006, Australia
| | - Cornelis A T van den Berg
- Department of Radiotherapy, University Medical Centre Utrecht, PO box 85500, 3508 GA, Utrecht, The Netherlands
| | - Marco Riboldi
- Department of Medical Physics, Ludwig-Maximilians-Universität München, Am Coulombwall 1, 85748, Garching, Germany.
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Costa F, Doran SJ, Hanson IM, Adamovics J, Nill S, Oelfke U. Edge effects in 3D dosimetry: characterisation and correction of the non-uniform dose response of PRESAGE ®. Phys Med Biol 2020; 65:095003. [PMID: 32143198 DOI: 10.1088/1361-6560/ab7d52] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Previous work has shown that PRESAGE® can be used successfully to perform 3D dosimetric measurements of complex radiotherapy treatments. However, measurements near the sample edges are known to be difficult to achieve. This is an issue when the doses at air-material interfaces are of interest, for example when investigating the electron return effect (ERE) present in treatments delivered by magnetic resonance (MR)-linac systems. To study this effect, a set of 3.5 cm-diameter cylindrical PRESAGE® samples was uniformly irradiated with multiple dose fractions, using either a conventional linac or an MR-linac. The samples were imaged between fractions using an optical-CT, to read out the corresponding accumulated doses. A calibration between TPS-predicted dose and optical-CT pixel value was determined for individual dosimeters as a function of radial distance from the axis of rotation. This data was used to develop a correction that was applied to four additional samples of PRESAGE® of the same formulation, irradiated with 3D-CRT and IMRT treatment plans, to recover significantly improved 3D measurements of dose. An alternative strategy was also tested, in which the outer surface of the sample was physically removed prior to irradiation. Results show that for the formulation studied here, PRESAGE® samples have a central region that responds uniformly and an edge region of 6-7 mm where there is gradual increase in dosimeter response, rising to an over-response of 24%-36% at the outer boundary. This non-uniform dose response increases in both extent and magnitude over time. Both mitigation strategies investigated were successful. In our four exemplar studies, we show how discrepancies at edges are reduced from 13%-37% of the maximum dose to between 2 and 8%. Quantitative analysis shows that the 3D gamma passing rates rise from 90.4, 69.3, 63.7 and 43.6% to 97.3, 99.9, 96.7 and 98.9% respectively.
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Affiliation(s)
- F Costa
- Joint Department of Physics, The Institute of Cancer Research and Royal Marsden Hospital and, London SM2 5NG, United Kingdom. Author to whom any correspondence should be addressed
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Maraghechi B, Gach HM, Setianegara J, Yang D, Li HH. Dose uncertainty and resolution of polymer gel dosimetry using an MRI guided radiation therapy system's onboard 0.35 T scanner. Phys Med 2020; 73:8-12. [PMID: 32279048 DOI: 10.1016/j.ejmp.2020.04.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 03/19/2020] [Accepted: 04/02/2020] [Indexed: 10/24/2022] Open
Abstract
Magnetic Resonance Imaging (MRI) scanners are widely used for 3D gel dosimeters readout. However, limited access to MRI scanners is a challenge in MRI-based gel dosimetry. Recent clinical implementation of MRI-guided radiation therapy machines provides potential opportunities for onboard gel dosimetry using its MRI subsystem. The objective of this study was to investigate the feasibility of gel dosimetry using ViewRay's onboard 0.35 T MRI scanner. A BANG® polymer gel dosimeter was irradiated by three beams of 3 × 3 cm2 field size. The T2 relaxation rate (R2) of the irradiated gel was measured using a Philips 1.5 T Ingenia MRI and a ViewRay 0.35 T onboard MRI and spin-echo pulse sequences. The number of signal averages (NSA) was set to 16 for the ViewRay acquisitions and one for the Philips 1.5 T MRI to achieve similar signal-to-noise ratios. The in-plane spatial resolution was 1.5 × 1.5 mm2 and the slice thickness was 5 mm. The relative dose uncertainty was obtained using R2 versus dose curves to compare the performance of dosimetry using the two different MRIs and field strengths. The dose uncertainty decreased from 12% at 2 Gy to 3.5% at 7.5 Gy at 1.5 T. The dose uncertainty decreased from 13% at 2 Gy to 4% at 7.5 Gy with NSA = 16 and 3 × 3 mm2 pixel size, and from 10.5% at 2 Gy to 3.2% at 7.5 Gy with NSA = 16 and denoised R2 maps (1.5 × 1.5 mm2 pixel size) at 0.35 T. The mean of dose resolution was 0.4 Gy at 1.5 T while the mean of dose resolution was 0.8 Gy and 0.64 Gy at 0.35 T by downsampling and denoising the R2 map, respectively. Therefore, comparable dose uncertainty was achievable using the ViewRay's onboard 0.35 T and Philips 1.5 T MRI scanners. 3D gel dosimetry using onboard low-field MRI scanner provides ViewRay users a 3D high resolution dosimetry option besides film and ionization chamber.
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Affiliation(s)
- Borna Maraghechi
- Departments of Radiation Oncology, Washington University in St. Louis, MO 63110, USA
| | - H Michael Gach
- Departments of Radiation Oncology, Washington University in St. Louis, MO 63110, USA; Departments of Biomedical Engineering, Washington University in St. Louis, MO 63110, USA; Departments of Radiology, Washington University in St. Louis, MO 63110, USA
| | - Jufri Setianegara
- Departments of Radiation Oncology, Washington University in St. Louis, MO 63110, USA; Departments of Physics, Washington University in St. Louis, MO 63110, USA
| | - Deshan Yang
- Departments of Radiation Oncology, Washington University in St. Louis, MO 63110, USA
| | - H Harold Li
- Departments of Radiation Oncology, Washington University in St. Louis, MO 63110, USA; Departments of Biomedical Engineering, Washington University in St. Louis, MO 63110, USA.
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Ito S, Araki F, Ohno T. Impact of transverse magnetic fields on dose response of a radiophotoluminescent glass dosimeter in megavoltage photon beams. Med Phys 2020; 47:1995-2004. [DOI: 10.1002/mp.14054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 01/13/2020] [Accepted: 01/20/2020] [Indexed: 11/10/2022] Open
Affiliation(s)
- Shotaro Ito
- Graduate school of Health Sciences Kumamoto University 4‐24‐1 Kuhonji, Chuo‐ku Kumamoto 862‐0976Japan
| | - Fujio Araki
- Department of Health Sciences Faculty of Life Sciences Kumamoto University 4‐24‐1 Kuhonji, Chuo‐ku Kumamoto 862‐0976Japan
| | - Takeshi Ohno
- Department of Health Sciences Faculty of Life Sciences Kumamoto University 4‐24‐1 Kuhonji, Chuo‐ku Kumamoto 862‐0976Japan
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Torres-Xirau I, Olaciregui-Ruiz I, Kaas J, Nowee ME, van der Heide UA, Mans A. 3D dosimetric verification of unity MR-linac treatments by portal dosimetry. Radiother Oncol 2020; 146:161-166. [PMID: 32182503 DOI: 10.1016/j.radonc.2020.02.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 02/11/2020] [Accepted: 02/12/2020] [Indexed: 11/16/2022]
Abstract
PURPOSE AND BACKGROUND 3D dosimetric verification of online adaptive workflows is essential as their complexity is unprecedented in radiation oncology. The aim of this work is to demonstrate the feasibility of back-projection portal dosimetry for 3D dosimetric verification of Unity MR-linac treatments. MATERIAL AND METHODS An earlier presented 2D back-projection algorithm for the Unity MR-linac geometry was extended for 3D dose reconstruction and comparison against planned dose distributions. 'In-air' as well as in-vivo portal EPID images can be used as input. The method was validated using data from treatments of 5 patients (2 rectal, 2 prostate cancer and one oligo metastasis). 3D pre-treatment verification of the reference plan using 'in-air' EPID images was performed and compared against measured (with the Octavius 4D system) and planned (in the planning CT) dose distributions. In-vivo EPID dose distributions were compared to the TPS for the first three adaptations of all treatments. For all comparisons, dose difference values at the reference point and γ-parameters were reported. RESULTS The comparison against the OCTAVIUS 4D system (3%, 2 mm, local) showed y-mean = 0.52 ± 0.10 and y-passrate = 91.9%, 95% CI [85.4, 98.4], and ΔDRP = -0.1 ± 1.1%. Pre-treatment verification against TPS data (3%, 2 mm, global) showed y-mean = 0.52 ± 0.04, y-passrate = 93.5%, 95% CI [92.4, 94.6] and ΔDRP = -0.9 ± 1.5%. The averaged y-results for the in-vivo 3D verification were y-mean = 0.52 ± 0.05, y-passrate = 92.5%, 95% CI [90.2, 94.8] and ΔDRP = 0.8 ± 2.1%. CONCLUSION 3D dosimetric verification of Unity MR-linac treatments using portal dosimetry is feasible, pre-treatment as well as in-vivo.
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Affiliation(s)
- Iban Torres-Xirau
- Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
| | - Igor Olaciregui-Ruiz
- Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
| | - Jochem Kaas
- Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Marlies E Nowee
- Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Uulke A van der Heide
- Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Anton Mans
- Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
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Andreozzi JM, Brůža P, Cammin J, Pogue BW, Gladstone DJ, Green O. Optical imaging method to quantify spatial dose variation due to the electron return effect in an MR-linac. Med Phys 2020; 47:1258-1267. [PMID: 31821573 PMCID: PMC7112467 DOI: 10.1002/mp.13954] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 11/21/2019] [Accepted: 11/26/2019] [Indexed: 11/12/2022] Open
Abstract
PURPOSE Treatment planning systems (TPSs) for MR-linacs must employ Monte Carlo-based simulations of dose deposition to model the effects of the primary magnetic field on dose. However, the accuracy of these simulations, especially for areas of tissue-air interfaces where the electron return effect (ERE) is expected, is difficult to validate due to physical constraints and magnetic field compatibility of available detectors. This study employs a novel dosimetric method based on remotely captured, real-time optical Cherenkov and scintillation imaging to visualize and quantify the ERE. METHODS An intensified CMOS camera was used to image two phantoms with designed ERE cavities. Phantom A was a 40 cm × 10 cm × 10 cm clear acrylic block drilled with five holes of increasing diameters (0.5, 1, 2, 3, 4 cm). Phantom B was a clear acrylic block (25 cm × 20 cm × 5 cm) with three cavities of increasing diameter (3, 2, 1 cm) split into two halves in the transverse plane to accommodate radiochromic film. Both phantoms were imaged while being irradiated by 6 MV flattening filter free (FFF) beams within a MRIdian Viewray (Viewray, Cleveland, OH) MR-linac (0.34 T primary field). Phantom A was imaged while being irradiated by 6 MV FFF beams on a conventional linac (TrueBeam, Varian Medical Systems, San Jose, CA) to serve as a control. Images were post processed in Matlab (Mathworks Inc., Natick, MA) and compared to TPS dose volumes. RESULTS Control imaging of Phantom A without the presence of a magnetic field supports the validity of the optical image data to a depth of 6 cm. In the presence of the magnetic field, the optical data shows deviations from the commissioned TPS dose in both intensity and localization. The largest air cavity examined (3 cm) indicated the largest dose differences, which were above 20% at some locations. Experiments with Phantom B illustrated similar agreement between optical and film dosimetry comparisons with TPS data in areas not affected by ERE. CONCLUSION There are some appreciable differences in dose intensity and spatial dose distribution observed between the novel experimental data set and the dose models produced by the current clinically implemented MR-IGRT TPS.
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Affiliation(s)
- Jacqueline M. Andreozzi
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, USA
- Current: Department of Radiation Oncology, University of Florida, Gainesville, Florida 32608
| | - Petr Brůža
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, USA
| | - Jochen Cammin
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Brian W. Pogue
- Thayer School of Engineering and Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755, USA
| | - David J. Gladstone
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03756, Geisel School of Medicine and Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, USA
| | - Olga Green
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Du Y, Wang R, Yue H, Zhang Y, Wu H, Wang W. Dose response and stability of silicone-based deformable radiochromic dosimeters (FlexyDos3D) using spectrophotometer and flatbed scanner. Radiat Phys Chem Oxf Engl 1993 2020. [DOI: 10.1016/j.radphyschem.2019.108574] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Olaciregui-Ruiz I, Torres-Xirau I, Teuwen J, van der Heide UA, Mans A. A Deep Learning-based correction to EPID dosimetry for attenuation and scatter in the Unity MR-Linac system. Phys Med 2020; 71:124-131. [DOI: 10.1016/j.ejmp.2020.02.020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 01/08/2020] [Accepted: 02/23/2020] [Indexed: 10/24/2022] Open
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Ito S, Araki F, Hoshida K, Ohno T. Impact of transverse magnetic fields on dose response of a nanoDot OSLD in megavoltage photon beams. Phys Med 2020; 70:153-160. [PMID: 32028172 DOI: 10.1016/j.ejmp.2020.01.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 01/24/2020] [Accepted: 01/26/2020] [Indexed: 10/25/2022] Open
Abstract
PURPOSE We investigated the impact of transverse magnetic fields on the dose response of a nanoDot optically stimulated luminescence dosimetry (OSLD) in megavoltage photon beams. METHODS The nanoDot OSLD response was calculated via Monte Carlo (MC) simulations. The responses RQ and RQ,B without and with the transverse magnetic fields of 0.35-3 T were analyzed as a function of depth at a 10 cm × 10 cm field for 4-18 MV photons in a solid water phantom. All responses were determined based on comparisons with the response under the reference conditions (depth of 10 cm and a 10 cm × 10 cm field) for 6 MV without the magnetic field. In addition, the influence of air-gaps on the nanoDot response in the magnetic field was estimated according to Burlin's general cavity theory. RESULTS The RQ as a function of depth for 4-18 MV ranged from 1.013 to 0.993, excepting the buildup region. The RQ,B increased from 2.8% to 1.5% at 1.5 T and decreased from 3.0% to 1.1% at 3 T in comparison with RQ as the photon energy increased. The depth dependence of RQ,B was less than 1%, excepting the buildup region. The top air-gap and the bottom air- gap were responsible for the response reduction and the response increase, respectively. CONCLUSIONS The response RQ,B varied depending on the magnetic field intensity, and the variation of RQ,B reduced as the photon beam energy increased. The air-gaps affected the dose deposition in the magnetic fields.
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Affiliation(s)
- Shotaro Ito
- Graduate School of Health Sciences, Kumamoto University, 4-24-1 Kuhonji, Kumamoto, Japan
| | - Fujio Araki
- Department of Health Sciences, Faculty of Life Sciences, Kumamoto University, 4-24-1 Kuhonji, Kumamoto, Japan.
| | - Kento Hoshida
- Graduate School of Health Sciences, Kumamoto University, 4-24-1 Kuhonji, Kumamoto, Japan
| | - Takeshi Ohno
- Department of Health Sciences, Faculty of Life Sciences, Kumamoto University, 4-24-1 Kuhonji, Kumamoto, Japan
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Pappas E, Kalaitzakis G, Boursianis T, Zoros E, Zourari K, Pappas EP, Makris D, Seimenis I, Efstathopoulos E, Maris TG. Dosimetric performance of the Elekta Unity MR-linac system: 2D and 3D dosimetry in anthropomorphic inhomogeneous geometry. ACTA ACUST UNITED AC 2019; 64:225009. [DOI: 10.1088/1361-6560/ab52ce] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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Elter A, Dorsch S, Mann P, Runz A, Johnen W, Spindeldreier CK, Klüter S, Karger CP. End-to-end test of an online adaptive treatment procedure in MR-guided radiotherapy using a phantom with anthropomorphic structures. ACTA ACUST UNITED AC 2019; 64:225003. [DOI: 10.1088/1361-6560/ab4d8e] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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22
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Dorsch S, Mann P, Elter A, Runz A, Spindeldreier CK, Klüter S, Karger CP. Measurement of isocenter alignment accuracy and image distortion of an 0.35 T MR-Linac system. ACTA ACUST UNITED AC 2019; 64:205011. [DOI: 10.1088/1361-6560/ab4540] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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23
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Copty A, Rabineg G, Berg A. The Influence of Magnetic Fields (0.05 T ≤ B ≤ 7 T) on the Response of Personal Thermoluminescent Dosimeters to Ionizing Radiation. HEALTH PHYSICS 2019; 117:345-352. [PMID: 31136314 DOI: 10.1097/hp.0000000000001101] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We investigated the main question of whether thermoluminescent dosimeters indicate the correct dose when exposed to magnetic fields from low stray fields up to high magnetic resonance imaging fields inside human magnetic resonance imaging scanners (0.05 T ≤ B ≤ 7 T) during and after irradiation. Medical personnel working in radiology, oncology, or nuclear medicine are regularly monitored with thermoluminescent dosimeters. They might also enter the magnetic field of a magnetic resonance imaging scanner while supervising patients as well as during positron emission tomography-magnetic resonance imaging and magnetic resonance imaging-linac integrated imaging systems and will therefore be exposed to the magnetic fields of magnetic resonance imaging scanners and low stray fields of several millitesla outside of the magnetic resonance imaging scanner, not only before and after, but also during irradiation. Panasonic thermoluminescent dosimetry badges and ring dosimeters for personal monitoring were exposed to magnetic fields originating from a 7 T and a 3 T magnetic resonance imaging scanner as well as neodymium permanent magnets. Four different sealed Cs sources were used in two sets of experiments: (1) magnetically induced fading: irradiated thermoluminescent dosimeters (D ≈ 100 mSv) were exposed to a strong magnetic field (B = 7 T) of a human high-field magnetic resonance imaging scanner after irradiation; no magnetically induced fading (magnetoluminescence) for LiBO:Cu or CaSO:Tm was observed; (2) magnetically induced attenuation: thermoluminescent dosimeters were placed during irradiation in a magnetic field for about 60 h; a significantly reduced dose response was observed for LiBO:Cu-interestingly not at maximum B ≈ 7 T but at B ≈ 0.2 T. This experimental observation is possibly relevant especially for medical and technical personnel in nuclear medicine before and during a magnetic resonance imaging scanning procedure. Follow-up studies need to be made to clarify the kinetics of this effect.
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Affiliation(s)
- Atallah Copty
- Radiation Protection Laboratory, Vienna City Administration, Vienna, Austria
| | - Günter Rabineg
- Radiation Protection Laboratory, Vienna City Administration, Vienna, Austria
| | - Andreas Berg
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
- High-field MR Centre, Medical University of Vienna/AKH, Vienna, Austria
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Höfel S, Fix MK, Zwicker F, Sterpin E, Drescher M. EPR imaging of magnetic field effects on radiation dose distributions around millimeter-size air cavities. Phys Med Biol 2019; 64:175013. [PMID: 31307018 DOI: 10.1088/1361-6560/ab325b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
New hybrid radiotherapy treatment systems combining an MRI scanner with a source of ionizing radiation are being introduced in the clinic. The strong magnetic fields of MRI considerably affect radiation dose distributions, especially at tissue-air interfaces due to the electron return effect (ERE). Experimental investigation of the ERE within a sub-millimeter thick surface layer is still highly challenging. In the present work, we examine and quantify the magnetic field induced perturbations of dose distributions within a 0.5 mm layer surrounding millimeter-size air cavities by applying electron paramagnetic resonance imaging (EPRI). Air-filled fused quartz tubes (inner diameter 3 or 4 mm) mimic small air cavities and serve as model systems. The tubes were irradiated inside a PMMA phantom by a 6 MV photon beam. The irradiations were performed in the presence or absence of a transverse, magnetic field providing a magnetic field strength of 1.0 Tesla. The spatial distributions of radiation induced paramagnetic defects in the quartz tubes were subsequently determined by applying field-swept echo-detected EPRI and were then converted to relative dose distributions. The transverse magnetic field leads to considerable local dose enhancements and reductions (up to 35%) with respect to the mean dose within the quartz tubes. The experimentally determined dose distributions are in good quantitative agreement with Monte Carlo radiation transport simulations. The results of this work demonstrate the feasibility of field-swept echo-detected EPRI to measure magnetic field induced perturbations of dose distributions within a sub-millimeter thick surface layer at the dosimeter-air interface.
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Affiliation(s)
- Sebastian Höfel
- Department of Chemistry and Konstanz Research School Chemical Biology, University of Konstanz, Konstanz, Germany. Klinik und Praxis für Strahlentherapie am Klinikum Konstanz, Konstanz, Germany
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Torres-Xirau I, Olaciregui-Ruiz I, van der Heide UA, Mans A. Two-dimensional EPID dosimetry for an MR-linac: Proof of concept. Med Phys 2019; 46:4193-4203. [PMID: 31199521 DOI: 10.1002/mp.13664] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 05/29/2019] [Accepted: 05/29/2019] [Indexed: 12/14/2022] Open
Abstract
PURPOSE At our institute, in vivo patient dose distributions are reconstructed for all treatments delivered using conventional linacs from electronic portal imaging device (EPID) transit images acquired during treatment using a simple back-projection model. Currently, the clinical implementation of MRI-guided radiotherapy systems, which aims for online and real-time adaptation of the treatment plan, is progressing. In our department, the MR-linac (Unity, Elekta AB, Stockholm, Sweden) is now in clinical use. The aim of this work is to demonstrate the feasibility of two-dimensional (2D) EPID dosimetric verification for the magnetic resonance (MR)-linac by comparing back-projected EPID doses to ionization chamber (IC) array dose distributions. MATERIALS AND METHODS Our conventional back-projection algorithm was adapted for the MR-linac. The most important changes involve modeling of the attenuation by and scatter from the cryostat. The commissioning process involved the acquisition of square field EPID measurements using various phantom setups (varying SSD, phantom thickness, and field size). Commissioning models were created for gantry 0°, 90°, and 180° and verified by comparing EPID-reconstructed 2D dose distributions to measurements made with the OCTAVIUS 1500 IC array (PTW, Freiburg, Germany) for two prostate and one rectum IMRT plans (25 beams total). The average of the γ parameters (y-mean and y-pass rate) and the dose difference at a reference point were reported. Due to their construction, the attenuation of couch, bridge, and cryostat shows a much stronger dependence on gantry angle in the MR-linac compared to conventional linacs. We present a method to correct for these effects. This method is validated by dose reconstruction of the 25 intensity-modulated radiation therapy beams recorded at a certain gantry angle using the model of another gantry angle, combined with the correction method. RESULTS For dose verification performed at a gantry angle identical to the commissioned model, the average y-mean and y-pass rate values (3% global dose, 2 mm, 10% isodose) were 0.37 ± 0.07 and 98.1, 95% CI [98.1 ± 2.4], respectively. The average dose difference at the reference point was -0.5% ± 1.8%. Verification at gantry angles different from the commissioned model (i.e., using the gantry angle dependent correction) reported 0.39 ± 0.08 and 97.6, 95% CI [96.9, 98.3] average y-mean and y-pass rate values. The average dose difference at the reference point was -0.1% ± 1.8%. CONCLUSION The EPID dosimetry back-projection model was successfully adapted for the MR-linac at gantry 0°, 90°, and 180°, accounting for the presence of the MRI housing between phantom (or patient) and the EPID. A method to account for the gantry angle dependence was also tested reporting similar results.
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Affiliation(s)
- Iban Torres-Xirau
- Department of Radiation Oncology, The Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands
| | - Igor Olaciregui-Ruiz
- Department of Radiation Oncology, The Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands
| | - Uulke A van der Heide
- Department of Radiation Oncology, The Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands
| | - Anton Mans
- Department of Radiation Oncology, The Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands
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Du Y, Wang R, Wang M, Yue H, Zhang Y, Wu H, Wang W. Radiological tissue equivalence of deformable silicone-based chemical radiation dosimeters (FlexyDos3D). J Appl Clin Med Phys 2019; 20:87-99. [PMID: 31183949 PMCID: PMC6612691 DOI: 10.1002/acm2.12658] [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: 03/26/2019] [Revised: 05/12/2019] [Accepted: 05/21/2019] [Indexed: 11/10/2022] Open
Abstract
FlexyDos3D, a silicone‐based chemical radiation dosimeter, has great potential to serve as a three‐dimensional (3D) deformable dosimetric tool to verify complex dose distributions delivered by modern radiotherapy techniques. To facilitate its clinical application, its radiological tissue needs to be clarified. In this study we investigated its tissue‐equivalence in comparison with water and Solid Water (RMI457). We found that its effective and mean atomic numbers were 40% and 20% higher and the total interaction probabilities for kV x‐ray photons were larger than those of water respectively. To assess the influence of its over‐response to kV photons, its HU value was measured by kV computed tomography (CT) and was found higher than all the soft‐tissue substitutes. When applied for dose calculation without correction, this effect led to an 8% overestimation in electron density via HU‐value mapping and 0.65% underestimation in target dose. Furthermore, depth dose curves (PDDs) and off‐axis ratios (profiles) at various beam conditions as well as the dose distribution of a full‐arc VMAT plan in FlexyDos3D and reference materials were simulated by Monte Carlo, where the results showed great agreement. As indicated, FlexyDos3D exhibits excellent radiological water‐equivalence for clinical MV x‐ray dosimetry, while its nonwater‐equivalent effect for low energy x‐ray dosimetry requires necessary correction. The key findings of this study provide pertinent reference for further FlexyDos3D characterization research.
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Affiliation(s)
- Yi Du
- Key laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing, China
| | - Ruoxi Wang
- Key laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing, China
| | - Meijiao Wang
- Key laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing, China
| | - Haizhen Yue
- Key laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing, China
| | - Yibao Zhang
- Key laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing, China
| | - Hao Wu
- Key laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing, China
| | - Weihu Wang
- Key laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing, China
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Choi CH, Park JM, An HJ, Kim JI. Effect of low magnetic field on single-diode dosimetry for clinical use. Phys Med 2019; 60:132-138. [PMID: 31000073 DOI: 10.1016/j.ejmp.2019.04.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 03/18/2019] [Accepted: 04/01/2019] [Indexed: 01/22/2023] Open
Abstract
PURPOSE To evaluate the effect of a low magnetic field (B-field, 0.35 T) on QED™ for clinical use. METHODS Black and Blue QED were irradiated using tri-Co-60 magnetic resonance image-guided radiation therapy systems with and without the B-field. For both detectors, angular dependence of the beam orientation was evaluated by rotating the gantry and detector in parallel and perpendicular directions to the B-field. Angular dependence betweenthe directions of both QED and B-field was also measured. Response on the depth and output factor of both detectors was investigated for parallel and perpendicular setups, respectively. RESULTS When Black QED was placed on a surface, detector response decreased by 1.8% and 4.5% for parallel and perpendicular setups, respectively, owing to the B-field. The angular dependence of the beam orientation was not affected by B-field for both detectors. There was a significant angular dependence between Black QED and B-field direction and for the Black QED when the gantry was rotated. Owing to the B-field, the detector response at 90° decreased by 2.4%, response of Black QED on the depth was changed only on the surface, and output factor of Black QED was changed only on the surface. The response of Blue QED was not affected by the B-field for all examined situations. CONCLUSIONS Using Black QED on a surface in the same position as that in the calibration requires some correction to the B-field. Blue QED does not require correction as it is not affected by the B-field.
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Affiliation(s)
- Chang Heon Choi
- Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea; Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea; Biomedical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea
| | - Jong Min Park
- Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea; Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea; Biomedical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea; Center for Convergence Research on Robotics, Advanced Institutes of Convergence Technology, Suwon, Republic of Korea
| | - Hyun Joon An
- Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea; Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea; Biomedical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea
| | - Jung-In Kim
- Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea; Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea; Biomedical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea.
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Mann P, Schwahofer A, Karger CP. Absolute dosimetry with polymer gels-a TLD reference system. Phys Med Biol 2019; 64:045010. [PMID: 30630134 DOI: 10.1088/1361-6560/aafd41] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND AND PURPOSE Absolute dosimetry in 3D with polymer gels (PG) is generally complicated and usually requires a second independent measurement with conventional detectors. This is why, PG are often used only for relative dosimetry. To overcome this drawback, we combine PG with a 1D thermoluminescence (TL) detector within the same measurement. The TL detector information is then used as additional information for calibration of the gel. MATERIALS AND METHODS The PAGAT dosimetry gel was used in combination with TLD600 (LiF:Mg,Ti). TL detectors were attached on the surface of the PG container placed inside a cylindrical phantom. To test the usability of this setup, two irradiation geometries were carried out: (a) homogeneous target coverage and (b) small-field irradiation. PG was evaluated with magnetic resonance imaging (MRI) and the TL detectors with a Harshaw 5500 hot gas reader. RESULTS PG dosimetry alone showed deviations of up to 4% as compared to calculations. Including additionally the dose information of the TL detectors for PG calibration, this deviation was decreased to less than 1% for both irradiation geometries. This is also reflected by the very high [Formula: see text]-passing rates of > 96% (3%/3 mm) and >93% (2%/2 mm), respectively. CONCLUSION This study presents a novel method combining 3D PG and TL dose measurements for the purpose of absolute 3D dose measurements that can also be applied in complex anthropomorphic phantoms using only a single measurement. The method was validated for two different irradiation geometries including a homogeneous large field as well as a small field irradiation with sharp dose gradients.
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Affiliation(s)
- P Mann
- Department of Medical Physics in Radiation Therapy (E040), German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany. National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Im Neuenheimer Feld 280, Heidelberg, Germany. Author to whom any correspondence should be addressed. These authors contributed equally to this study
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Wegener S, Weick S, Sauer OA. Influence of a transverse magnetic field on the response of different detectors in a high energy photon beam near the surface. Z Med Phys 2019; 29:22-30. [DOI: 10.1016/j.zemedi.2018.07.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 05/29/2018] [Accepted: 07/02/2018] [Indexed: 10/28/2022]
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Dorsch S, Mann P, Lang C, Haering P, Runz A, Karger CP. Feasibility of polymer gel-based measurements of radiation isocenter accuracy in magnetic fields. Phys Med Biol 2018; 63:11NT02. [PMID: 29722290 DOI: 10.1088/1361-6560/aac228] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
For conventional irradiation devices, the radiation isocenter accuracy is determined by star shot measurements on films. In magnetic resonance (MR)-guided radiotherapy devices, the results of this test may be altered by the magnetic field and the need to align the radiation and imaging isocenter may require a modification of measurement procedures. Polymer dosimetry gels (PG) may offer a way to perform both, the radiation and imaging isocenter test, however, first it has to be shown that PG reveal results comparable to the conventionally applied films. Therefore, star shot measurements were performed at a linear accelerator using PG as well as radiochromic films. PG were evaluated using MR imaging and the isocircle radius and the distance between the isocircle center and the room isocenter were determined. Two different types of experiments were performed: i) a standard star-shot isocenter test and (ii) a star shot, where the detectors were placed between the pole shoes of an experimental electro magnet operated either at 0 T or 1 T. For the standard star shot, PG evaluation was independent of the time delay after irradiation (1 h, 24 h, 48 h and 216 h) and the results were comparable to those of film measurements. Within the electro magnet, the isocircle radius increased from 0.39 ± 0.01 mm to 1.37 ± 0.01 mm for the film and from 0.44 ± 0.02 mm to 0.97 ± 0.02 mm for the PG-measurements, respectively. The isocenter distance was essentially dependent on the alignment of the magnet to the isocenter and was between 0.12 ± 0.02 mm and 0.82 ± 0.02 mm. The study demonstrates that evaluation of the PG directly after irradiation is feasible, if only geometrical parameters are of interest. This allows using PG for star shot measurements to evaluate the radiation isocenter accuracy with comparable accuracy as with radiochromic films.
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Affiliation(s)
- S Dorsch
- Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), INF 280, 69120 Heidelberg, Germany. Faculty of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany. National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany
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Andreozzi JM, Mooney KE, Brůža P, Curcuru A, Gladstone DJ, Pogue BW, Green O. Remote Cherenkov imaging-based quality assurance of a magnetic resonance image-guided radiotherapy system. Med Phys 2018; 45:2647-2659. [PMID: 29663429 DOI: 10.1002/mp.12919] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Revised: 02/09/2018] [Accepted: 04/04/2018] [Indexed: 12/27/2022] Open
Abstract
PURPOSE Tools to perform regular quality assurance of magnetic resonance image-guided radiotherapy (MRIgRT) systems should ideally be independent of interference from the magnetic fields. Remotely acquired optical Cherenkov imaging-based dosimetry measurements in water were investigated for this purpose, comparing measures of dose accuracy, temporal dynamics, and overall integrated IMRT delivery. METHODS A 40 × 30.5 × 37.5 cm3 water tank doped with 1 g/L of quinine sulfate was imaged using an intensified charge-coupled device (ICCD) to capture the Cherenkov emission while being irradiated by a commercial MRIgRT system (ViewRay™). The ICCD was placed down-bore at the end of the couch, 4 m from treatment isocenter and behind the 5-Gauss line of the 0.35-T MRI. After establishing optimal camera acquisition settings, square beams of increasing size (4.2 × 4.2 cm2 , 10.5 × 10.5 cm2 , and 14.7 × 14.7 cm2 ) were imaged at 0.93 frames per second, from an individual cobalt-60 treatment head, to develop projection measures related to percent depth dose (PDD) curves and cross beam profiles (CPB). These Cherenkov-derived measurements were compared to ionization chamber (IC) and radiographic film dosimetry data, as well as simulation data from the treatment planning system (TPS). An intensity-modulated radiotherapy (IMRT) commissioning plan from AAPM TG-119 (C4:C-Shape) was also imaged at 2.1 frames per second, and the single linear sum image from 509 s of plan delivery was compared to the dose volume prediction generated by the TPS using gamma index analysis. RESULTS Analysis of standardized test target images (1024 × 1024 pixels) yielded a pixel resolution of 0.37 mm/pixel. The beam width measured from the Cherenkov image-generated projection CBPs was within 1 mm accuracy when compared to film measurements for all beams. The 502 point measurements (i.e., pixels) of the Cherenkov image-based projection percent depth dose curves (pPDDs) were compared to pPDDs simulated by the treatment planning system (TPS), with an overall average error of 0.60%, 0.56%, and 0.65% for the 4.2, 10.5, and 14.7 cm square beams, respectively. The relationships between pPDDs and central axis PDDs derived from the TPS were used to apply a weighting factor to the Cherenkov pPDD, so that the Cherenkov data could be directly compared to IC PDDs (average error of -0.07%, 0.10%, and -0.01% for the same sized beams, respectively). Finally, the composite image of the TG-119 C4 treatment plan achieved a 95.1% passing rate using 4%/4 mm gamma index agreement criteria between Cherenkov intensity and TPS dose volume data. CONCLUSIONS This is the first examination of Cherenkov-generated pPDDs and pCBPs in an MR-IGRT system. Cherenkov imaging measurements were fast to acquire, and minimal error was observed overall. Cherenkov imaging also provided novel real-time data for IMRT QA. The strengths of this imaging are the rapid data capture ability providing real-time, high spatial resolution data, combined with the remote, noncontact nature of imaging. The biggest limitation of this method is the two-dimensional (2D) projection-based imaging of three-dimensional (3D) dose distributions through the transparent water tank.
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Affiliation(s)
| | - Karen E Mooney
- Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - Petr Brůža
- Thayer School of Engineering, Dartmouth College, Hanover, NH, 03755, USA
| | - Austen Curcuru
- Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - David J Gladstone
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH, 03766, USA.,Geisel School of Medicine and Thayer School of Engineering, Dartmouth College, Hanover, NH, 03755, USA
| | - Brian W Pogue
- Thayer School of Engineering and Department of Physics and Astronomy, Dartmouth College, Hanover, NH, 03755, USA
| | - Olga Green
- Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, PA, 19107, USA
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Costa F, Doran SJ, Hanson IM, Nill S, Billas I, Shipley D, Duane S, Adamovics J, Oelfke U. Investigating the effect of a magnetic field on dose distributions at phantom-air interfaces using PRESAGE ® 3D dosimeter and Monte Carlo simulations. Phys Med Biol 2018; 63:05NT01. [PMID: 29393066 PMCID: PMC5964337 DOI: 10.1088/1361-6560/aaaca2] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 01/22/2018] [Accepted: 02/02/2018] [Indexed: 11/23/2022]
Abstract
Dosimetric quality assurance (QA) of the new Elekta Unity (MR-linac) will differ from the QA performed of a conventional linac due to the constant magnetic field, which creates an electron return effect (ERE). In this work we aim to validate PRESAGE® dosimetry in a transverse magnetic field, and assess its use to validate the research version of the Monaco TPS of the MR-linac. Cylindrical samples of PRESAGE® 3D dosimeter separated by an air gap were irradiated with a cobalt-60 unit, while placed between the poles of an electromagnet at 0.5 T and 1.5 T. This set-up was simulated in EGSnrc/Cavity Monte Carlo (MC) code and relative dose distributions were compared with measurements using 1D and 2D gamma criteria of 3% and 1.5 mm. The irradiation conditions were adapted for the MR-linac and compared with Monaco TPS simulations. Measured and EGSnrc/Cavity simulated profiles showed good agreement with a gamma passing rate of 99.9% for 0.5 T and 99.8% for 1.5 T. Measurements on the MR-linac also compared well with Monaco TPS simulations, with a gamma passing rate of 98.4% at 1.5 T. Results demonstrated that PRESAGE® can accurately measure dose and detect the ERE, encouraging its use as a QA tool to validate the Monaco TPS of the MR-linac for clinically relevant dose distributions at tissue-air boundaries.
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Affiliation(s)
- Filipa Costa
- Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS
Foundation Trust, London SM2 5NG, United
Kingdom
| | - Simon J Doran
- CRUK Cancer Imaging Centre, The Institute of Cancer Research, London SM2
5NG, United Kingdom
| | - Ian M Hanson
- Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS
Foundation Trust, London SM2 5NG, United
Kingdom
| | - Simeon Nill
- Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS
Foundation Trust, London SM2 5NG, United
Kingdom
| | - Ilias Billas
- Metrology for Medical Physics, National Physical Laboratory, Hampton Road,
Teddington TW11 0LW, United Kingdom
| | - David Shipley
- Metrology for Medical Physics, National Physical Laboratory, Hampton Road,
Teddington TW11 0LW, United Kingdom
| | - Simon Duane
- Metrology for Medical Physics, National Physical Laboratory, Hampton Road,
Teddington TW11 0LW, United Kingdom
| | - John Adamovics
- Department of Chemistry and Biology, Rider University, Lawrenceville, NJ 08648,
United States of America
| | - Uwe Oelfke
- Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS
Foundation Trust, London SM2 5NG, United
Kingdom
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Pasler M, Hernandez V, Jornet N, Clark CH. Novel methodologies for dosimetry audits: Adapting to advanced radiotherapy techniques. Phys Imaging Radiat Oncol 2018; 5:76-84. [PMID: 33458373 PMCID: PMC7807589 DOI: 10.1016/j.phro.2018.03.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 03/08/2018] [Accepted: 03/08/2018] [Indexed: 11/25/2022] Open
Abstract
With new radiotherapy techniques, treatment delivery is becoming more complex and accordingly, these treatment techniques require dosimetry audits to test advanced aspects of the delivery to ensure best practice and safe patient treatment. This review of novel methodologies for dosimetry audits for advanced radiotherapy techniques includes recent developments and future techniques to be applied in dosimetry audits. Phantom-based methods (i.e. phantom-detector combinations) including independent audit equipment and local measurement equipment as well as phantom-less methods (i.e. portal dosimetry, transmission detectors and log files) are presented and discussed. Methodologies for both conventional linear accelerator (linacs) and new types of delivery units, i.e. Tomotherapy, stereotactic devices and MR-linacs, are reviewed. Novel dosimetry audit techniques such as portal dosimetry or log file evaluation have the potential to allow parallel auditing (i.e. performing an audit at multiple institutions at the same time), automation of data analysis and evaluation of multiple steps of the radiotherapy treatment chain. These methods could also significantly reduce the time needed for audit and increase the information gained. However, to maximise the potential, further development and harmonisation of dosimetry audit techniques are required before these novel methodologies can be applied.
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Affiliation(s)
- Marlies Pasler
- Lake Constance Radiation Oncology Center Singen-Friedrichshafen, Germany
| | - Victor Hernandez
- Department of Medical Physics, Hospital Sant Joan de Reus, IISPV, Tarragona, Spain
| | - Núria Jornet
- Servei de RadiofísicaiRadioprotecció, Hospital de la Santa CreuiSant Pau, Spain
| | - Catharine H. Clark
- Department of Medical Physics, Royal Surrey County Hospital, Guildford, Surrey, UK
- Metrology for Medical Physics (MEMPHYS), National Physical Laboratory, Teddington, Middlesex, UK
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Medical physics in radiation Oncology: New challenges, needs and roles. Radiother Oncol 2017; 125:375-378. [PMID: 29150160 DOI: 10.1016/j.radonc.2017.10.035] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 10/30/2017] [Indexed: 12/21/2022]
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