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Riis HL, Christiansen RL, Tilly N, Tilly D. Dosimetric validation of the couch and coil model for high-field MR-linac treatment planning. Z Med Phys 2023; 33:567-577. [PMID: 36990882 PMCID: PMC10751701 DOI: 10.1016/j.zemedi.2023.02.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 02/01/2023] [Accepted: 02/09/2023] [Indexed: 03/29/2023]
Abstract
PURPOSE The precision of the dose delivery in radiation therapy with high-field MR-linacs is challenging due to the substantial variation in the beam attenuation of the patient positioning system (PPS) (the couch and coils) as a function of the gantry angle. This work aimed to compare the attenuation of two PPSs located at two different MR-linac sites through measurements and calculations in the treatment planning system (TPS). METHODS Attenuation measurements were performed at every 1° gantry angle at the two sites with a cylindrical water phantom with a Farmer chamber inserted along the rotational axis of the phantom. The phantom was positioned with the chamber reference point (CRP) at the MR-linac isocentre. A compensation strategy was applied to minimise sinusoidal measurement errors due to, e.g. air cavity or setup. A series of tests were performed to assess the sensitivity to measurement uncertainties. The dose to a model of the cylindrical water phantom with the PPS added was calculated in the TPS (Monaco v5.4 as well as in a development version Dev of an upcoming release), for the same gantry angles as for the measurements. The TPS PPS model dependency of the dose calculation voxelisation resolution was also investigated. RESULTS A comparison of the measured attenuation of the two PPSs yielded differences of less than 0.5% for most gantry angles. The maximum deviation between the attenuation measurements for the two different PPSs exceeded ±1% at two specific gantry angles 115° and 245°, where the beam traverses the most complex PPS structures. The attenuation increases from 0% to 25% in 15° intervals around these angles. The measured and calculated attenuation, as calculated in v5.4, was generally within 1-2% with a systematic overestimation of the attenuation for gantry angles around 180°, as well as a maximum error of 4-5% for a few discrete angles in 10° gantry angle intervals around the complex PPS structures. The PPS modelling was improved compared to v5.4 in Dev, especially around 180°, and the results of those calculations were within ±1%, but with a similar 4% maximum deviation for the most complex PPS structures. CONCLUSIONS Generally, the two tested PPS structures exhibit very similar attenuation as a function of the gantry angle, including the angles with a steep change in attenuation. Both TPS versions, v5.4 and Dev delivered clinically acceptable accuracy of the calculated dose, as the differences in the measurements were overall better than ±2%. Additionally, Dev improved the accuracy of the dose calculation to ±1% for gantry angles around 180°.
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Affiliation(s)
- Hans Lynggaard Riis
- Odense University Hospital, Department of Oncology, Odense, Denmark; University of Southern Denmark, Department of Clinical Research, Odense, Denmark.
| | - Rasmus Lübeck Christiansen
- Odense University Hospital, Department of Oncology, Odense, Denmark; University of Southern Denmark, Department of Clinical Research, Odense, Denmark
| | - Nina Tilly
- Medical Radiation Physics, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden; Elekta Instrument AB, Stockholm, Sweden
| | - David Tilly
- Medical Radiation Physics, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden; Elekta Instrument AB, Stockholm, Sweden; Medical Physics, Akademiska Sjukhuset, Uppsala, Sweden
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Uijtewaal P, Côté B, Foppen T, de Vries W, Woodings S, Borman P, Lambert-Girard S, Therriault-Proulx F, Raaymakers B, Fast M. Performance of the HYPERSCINT scintillation dosimetry research platform for the 1.5 T MR-linac. Phys Med Biol 2023; 68. [PMID: 36638536 DOI: 10.1088/1361-6560/acb30c] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Accepted: 01/13/2023] [Indexed: 01/15/2023]
Abstract
Objective.Adaptive radiotherapy techniques available on the MR-linac, such as daily plan adaptation, gating, and dynamic tracking, require versatile dosimetric detectors to validate end-to-end workflows. Plastic scintillator detectors (PSDs) offer great potential with features including: water equivalency, MRI-compatibility, and time-resolved dose measurements. Here, we characterize the performance of the HYPERSCINT RP-200 PSD (MedScint, Quebec, CA) in a 1.5 T MR-linac, and we demonstrate its suitability for dosimetry, including in a moving target.Approach.Standard techniques of detector testing were performed using a Beamscan water tank (PTW, Freiburg, DE) and compared to microDiamond (PTW, Freiburg, DE) readings. Orientation dependency was tested using the same phantom. An RW3 solid water phantom was used to evaluate detector consistency, dose linearity, and dose rate dependence. To determine the sensitivity to motion and to MRI scanning, the Quasar MRI4Dphantom (Modus, London, ON) was used statically or with sinusoidal motion (A= 10 mm,T= 4 s) to compare PSD and Semiflex ionization chamber (PTW, Freiburg, DE) readings. Conformal beams from gantry 0° and 90° were used as well as a 15-beam 8 × 7.5 Gy lung IMRT plan.Main results.Measured profiles, PDD curves and field-size dependence were consistent with the microDiamond readings with differences well within our clinical tolerances. The angular dependence gave variations up to 0.8% when not irradiating directly from behind the scintillation point. Experiments revealed excellent detector consistency between repeated measurements (SD = 0.06%), near-perfect dose linearity (R2= 1) and a dose rate dependence <0.3%. Dosimetric effects of MRI scanning (≤0.3%) and motion (≤1.3%) were minimal. Measurements were consistent with the Semiflex (differences ≤1%), and with the treatment planning system with differences of 0.8% and 0.4%, with and without motion.Significance.This study demonstrates the suitability of the HYPERSCINT PSD for accurate time-resolved dosimetry measurements in the 1.5 T MR-linac, including during MR scanning and target motion.
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Affiliation(s)
- Prescilla Uijtewaal
- Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
| | - Benjamin Côté
- MedScint, 1405 Bd du Parc Technologique, Québec, QC G1P 4P5, Canada
| | - Thomas Foppen
- Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
| | - Wilfred de Vries
- Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
| | - Simon Woodings
- Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
| | - Pim Borman
- Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
| | | | | | - Bas Raaymakers
- Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
| | - Martin Fast
- Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
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Roberts DA, Sandin C, Vesanen PT, Lee H, Hanson IM, Nill S, Perik T, Lim SB, Vedam S, Yang J, Woodings SW, Wolthaus JWH, Keller B, Budgell G, Chen X, Li XA. Machine QA for the Elekta Unity system: A Report from the Elekta MR-linac consortium. Med Phys 2021; 48:e67-e85. [PMID: 33577091 PMCID: PMC8251771 DOI: 10.1002/mp.14764] [Citation(s) in RCA: 54] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 01/21/2021] [Accepted: 02/03/2021] [Indexed: 12/31/2022] Open
Abstract
Over the last few years, magnetic resonance image‐guided radiotherapy systems have been introduced into the clinic, allowing for daily online plan adaption. While quality assurance (QA) is similar to conventional radiotherapy systems, there is a need to introduce or modify measurement techniques. As yet, there is no consensus guidance on the QA equipment and test requirements for such systems. Therefore, this report provides an overview of QA equipment and techniques for mechanical, dosimetric, and imaging performance of such systems and recommendation of the QA procedures, particularly for a 1.5T MR‐linac device. An overview of the system design and considerations for QA measurements, particularly the effect of the machine geometry and magnetic field on the radiation beam measurements is given. The effect of the magnetic field on measurement equipment and methods is reviewed to provide a foundation for interpreting measurement results and devising appropriate methods. And lastly, a consensus overview of recommended QA, appropriate methods, and tolerances is provided based on conventional QA protocols. The aim of this consensus work was to provide a foundation for QA protocols, comparative studies of system performance, and for future development of QA protocols and measurement methods.
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Affiliation(s)
- David A Roberts
- Elekta Limited, Cornerstone, London Road, Crawley, RH10 9BL, United Kingdom
| | - Carlos Sandin
- Elekta Limited, Cornerstone, London Road, Crawley, RH10 9BL, United Kingdom
| | | | - Hannah Lee
- Allegheny Health Network Cancer Institute, Pennsylvania, USA
| | - Ian M Hanson
- The Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, UK
| | - Simeon Nill
- The Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, UK
| | - Thijs Perik
- Department of Radiation Oncology, The Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Amsterdam, the Netherlands
| | - Seng Boh Lim
- Memorial Sloan Kettering Cancer Center, New York, USA
| | - Sastry Vedam
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Texas, USA
| | - Jinzhong Yang
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Texas, USA
| | - Simon W Woodings
- Department of Radiotherapy, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Jochem W H Wolthaus
- Department of Radiotherapy, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Brian Keller
- Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada
| | - Geoff Budgell
- Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Wilmslow Road, Manchester, United Kingdom
| | - Xinfeng Chen
- Department of Radiation Oncology, Froedtert Hospital and Medical College of Wisconsin, Milwaukee, USA
| | - X Allen Li
- Department of Radiation Oncology, Froedtert Hospital and Medical College of Wisconsin, Milwaukee, USA
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de Pooter J, Billas I, de Prez L, Duane S, Kapsch RP, Karger CP, van Asselen B, Wolthaus J. Reference dosimetry in MRI-linacs: evaluation of available protocols and data to establish a Code of Practice. Phys Med Biol 2021; 66:05TR02. [PMID: 32570225 DOI: 10.1088/1361-6560/ab9efe] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
With the rapid increase in clinical treatments with MRI-linacs, a consistent, harmonized and sustainable ground for reference dosimetry in MRI-linacs is needed. Specific for reference dosimetry in MRI-linacs is the presence of a strong magnetic field. Therefore, existing Code of Practices (CoPs) are inadequate. In recent years, a vast amount of papers have been published in relation to this topic. The purpose of this review paper is twofold: to give an overview and evaluate the existing literature for reference dosimetry in MRI-linacs and to discuss whether the literature and datasets are adequate and complete to serve as a basis for the development of a new or to extend existing CoPs. This review is prefaced with an overview of existing MRI-linac facilities. Then an introduction on the physics of radiation transport in magnetic fields is given. The main part of the review is devoted to the evaluation of the literature with respect to the following subjects: • beam characteristics of MRI-linac facilities; • formalisms for reference dosimetry in MRI-linacs; • characteristics of ionization chambers in the presence of magnetic fields; • ionization chamber beam quality correction factors; and • ionization chamber magnetic field correction factors. The review is completed with a discussion as to whether the existing literature is adequate to serve as basis for a CoP. In addition, it highlights subjects for future research on this topic.
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Simiele E, Kapsch RP, Ankerhold U, Culberson W, DeWerd L. Technical note: characterization of spectral changes with measurement geometry and magnetic field strength in light guides used for scintillation dosimetry. ACTA ACUST UNITED AC 2020; 65:11NT01. [DOI: 10.1088/1361-6560/ab8afa] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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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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Iakovenko V, Keller B, Sahgal A, Sarfehnia A. Experimental measurement of ionization chamber angular response and associated magnetic field correction factors in MR‐linac. Med Phys 2020; 47:1940-1948. [DOI: 10.1002/mp.14025] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 01/06/2020] [Accepted: 01/07/2020] [Indexed: 11/11/2022] Open
Affiliation(s)
- Viktor Iakovenko
- Odette Cancer Centre Sunnybrook Health Sciences Centre Toronto ON M4N 3M5Canada
- Department of Radiation Oncology University of Toronto Toronto ON M4N 3M5Canada
| | - Brian Keller
- Odette Cancer Centre Sunnybrook Health Sciences Centre Toronto ON M4N 3M5Canada
- Department of Radiation Oncology University of Toronto Toronto ON M4N 3M5Canada
| | - Arjun Sahgal
- Odette Cancer Centre Sunnybrook Health Sciences Centre Toronto ON M4N 3M5Canada
- Department of Radiation Oncology University of Toronto Toronto ON M4N 3M5Canada
| | - Arman Sarfehnia
- Odette Cancer Centre Sunnybrook Health Sciences Centre Toronto ON M4N 3M5Canada
- Department of Radiation Oncology University of Toronto Toronto ON M4N 3M5Canada
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Chen X, Paulson ES, Ahunbay E, Sanli A, Klawikowski S, Li XA. Measurement validation of treatment planning for a MR-Linac. J Appl Clin Med Phys 2019; 20:28-38. [PMID: 31254376 PMCID: PMC6612768 DOI: 10.1002/acm2.12651] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 03/11/2019] [Accepted: 05/02/2019] [Indexed: 11/20/2022] Open
Abstract
Purpose The magnetic field can cause a nonnegligible dosimetric effect in an MR‐Linac system. This effect should be accurately accounted for by the beam models in treatment planning systems (TPS). The purpose of the study was to verify the beam model and the entire treatment planning and delivery process for a 1.5 T MR‐Linac based on comprehensive dosimetric measurements and end‐to‐end tests. Material and methods Dosimetry measurements and end‐to‐end tests were performed on a preclinical MR‐Linac (Elekta AB) using a multitude of detectors and were compared to the corresponding beam model calculations from the TPS for the MR‐Linac. Measurement devices included ion chambers (IC), diamond detector, radiochromic film, and MR‐compatible ion chamber array and diode array. The dose in inhomogeneous phantom was also verified. The end‐to‐end tests include the generation, delivery, and comparison of 3D and IMRT plan with measurement. Results For the depth dose measurements with Farmer IC, micro IC and diamond detector, the absolute difference between most measurement points and beam model calculation beyond the buildup region were <1%, at most 2% for a few measurement points. For the beam profile measurements, the absolute differences were no more than 1% outside the penumbra region and no more than 2.5% inside the penumbra region. Results of end‐to‐end tests demonstrated that three 3D static plans with single 5 × 10 cm2 fields (at gantry angle 0°, 90° and 270°) and two IMRT plans successfully passed gamma analysis with clinical criteria. The dose difference in the inhomogeneous phantom between the calculation and measurement was within 1.0%. Conclusions Both relative and absolute dosimetry measurements agreed well with the TPS calculation, indicating that the beam model for MR‐Linac properly accounts for the magnetic field effect. The end‐to‐end tests verified the entire treatment planning process.
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Affiliation(s)
- Xinfeng Chen
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Eric S Paulson
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Ergun Ahunbay
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Aydin Sanli
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Slade Klawikowski
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - X Allen Li
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, USA
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Simiele E, Kapsch RP, Ankerhold U, Culberson W, DeWerd L. Spectral characterization of plastic scintillation detector response as a function of magnetic field strength. ACTA ACUST UNITED AC 2018. [DOI: 10.1088/1361-6560/aab56c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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