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Oliver PAK, Yip E, Tari SY, Wachowicz K, Reynolds M, Burke B, Warkentin B, Fallone BG. Skin dose investigations on a 0.5 T parallel rotating biplanar linac-MR using Monte Carlo simulations and measurements. Med Phys 2024. [PMID: 38873942 DOI: 10.1002/mp.17246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 05/06/2024] [Accepted: 05/30/2024] [Indexed: 06/15/2024] Open
Abstract
BACKGROUND The Alberta rotating biplanar linac-MR has a 0.5 T magnetic field parallel to the beamline. When developing a new linac-MR system, interactions of charged particles with the magnetic field necessitate careful consideration of skin dose and tissue interface effects. PURPOSE To investigate the effect of the magnetic field on skin dose using measurements and Monte Carlo (MC) simulations. METHODS We develop an MC model of our linac-MR, which we validate by comparison with ion chamber measurements in a water tank. Additionally, MC simulation results are compared with radiochromic film surface dose measurements on solid water. Variations in surface dose as a function of field size are measured using a parallel plate ion chamber in solid water. Using an anthropomorphic computational phantom with a 2 mm-thick skin layer, we investigate dose distributions resulting from three beam arrangements. Magnetic field on and off scenarios are considered for all measurements and simulations. RESULTS For a 20 × 20 cm2 field size,D 0.2 c c ${D_{0.2cc}}$ (the minimum dose to the hottest contiguous 0.2 cc volume) for the top 2 mm of a simple water phantom is 72% when the magnetic field is on, compared to 34% with magnetic field off (values are normalized to the central axis dose maximum). Parallel plate ion chamber measurements demonstrate that the relative increase in surface dose due to the magnetic field decreases with increasing field size. For the anthropomorphic phantom,D ∼ 0.2 c c ${D_{ \sim 0.2cc}}$ (minimum skin dose in the hottest 1 × 1 × 1 cm3 cube) shows relative increases of 20%-28% when the magnetic field is on compared to when it is off. With magnetic field off, skinD ∼ 0.2 c c ${D_{ \sim 0.2cc}}$ is 71%, 56%, and 21% for medial-lateral tangents, anterior-posterior beams, and a five-field arrangement, respectively. For magnetic field on, the corresponding skinD ∼ 0.2 c c ${D_{ \sim 0.2cc}}$ values are 91%, 67%, and 25%. CONCLUSIONS Using a validated MC model of our linac-MR, surface doses are calculated in various scenarios. MC-calculated skin dose varies depending on field sizes, obliquity, and the number of beams. In general, the parallel linac-MR arrangement results in skin dose enhancement due to charged particles spiraling along magnetic field lines, which impedes lateral motion away from the central axis. Nonetheless, considering the results presented herein, treatment plans can be designed to minimize skin dose by, for example, avoiding oblique beams and using a larger number of fields.
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Affiliation(s)
- Patricia A K Oliver
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
- Dept. of Medical Physics, Nova Scotia Health and Dept. of Radiation Oncology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Eugene Yip
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
| | - Shima Y Tari
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
| | - Keith Wachowicz
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
| | - Michael Reynolds
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
| | - Ben Burke
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
| | - Brad Warkentin
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
| | - Biagio G Fallone
- Dept. of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
- Dept. of Oncology, Medical Physics Division, University of Alberta, Edmonton, Alberta, Canada
- MagnetTx Oncology Solutions, Edmonton, Alberta, Canada
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2
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Begg J, Jelen U, Moutrie Z, Oliver C, Holloway L, Brown R. ACPSEM position paper: dosimetry for magnetic resonance imaging linear accelerators. Phys Eng Sci Med 2023; 46:1-17. [PMID: 36806156 PMCID: PMC10030536 DOI: 10.1007/s13246-023-01223-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/19/2023] [Indexed: 02/23/2023]
Abstract
Consistency and clear guidelines on dosimetry are essential for accurate and precise dosimetry, to ensure the best patient outcomes and to allow direct dose comparison across different centres. Magnetic Resonance Imaging Linac (MRI-linac) systems have recently been introduced to Australasian clinics. This report provides recommendations on reference dosimetry measurements for MRI-linacs on behalf of the Australiasian College of Physical Scientists and Engineers in Medicine (ACPSEM) MRI-linac working group. There are two configurations considered for MRI-linacs, perpendicular and parallel, referring to the relative direction of the magnetic field and radiation beam, with different impacts on dose deposition in a medium. These recommendations focus on ion chambers which are most commonly used in the clinic for reference dosimetry. Water phantoms must be MR safe or conditional and practical limitations on phantom set-up must be considered. Solid phantoms are not advised for reference dosimetry. For reference dosimetry, IAEA TRS-398 recommendations cannot be followed completely due to physical differences between conventional linac and MRI-linac systems. Manufacturers' advice on reference conditions should be followed. Beam quality specification of TPR20,10 is recommended. The configuration of the central axis of the ion chamber relative to the magnetic field and radiation beam impacts the chamber response and must be considered carefully. Recommended corrections to delivered dose are [Formula: see text], a correction for beam quality and [Formula: see text], for the impact of the magnetic field on dosimeter response in the magnetic field. Literature based values for [Formula: see text] are given. It is important to note that this is a developing field and these recommendations should be used together with a review of current literature.
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Affiliation(s)
- Jarrad Begg
- Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centre, Liverpool, NSW, 2170, Australia.
- Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia.
- South Western Sydney Clinical School, University of New South Wales, Liverpool, NSW, 2170, Australia.
| | - Urszula Jelen
- St Vincents Clinic, GenesisCare, Darlinghurst, NSW, 2010, Australia
| | - Zoe Moutrie
- Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centre, Liverpool, NSW, 2170, Australia
| | - Chris Oliver
- Primary Standards Dosimetry Laboratory, Australian Radiation Protection and Nuclear Safety Agency, Yallambie, VIC, 3085, Australia
| | - Lois Holloway
- Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centre, Liverpool, NSW, 2170, Australia
- Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
- South Western Sydney Clinical School, University of New South Wales, Liverpool, NSW, 2170, Australia
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia
- Institute of Medical Physics, University of Sydney, Camperdown, NSW, 2505, Australia
| | - Rhonda Brown
- Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Yallambie, VIC, 3085, Australia
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3
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Begg J, Jelen U, Keall P, Liney G, Holloway L. Experimental characterisation of the magnetic field correction factor,kB⃗,for Roos chambers in a parallel MRI-linac. Phys Med Biol 2022; 67. [PMID: 35413694 DOI: 10.1088/1361-6560/ac66b8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Accepted: 04/12/2022] [Indexed: 12/15/2022]
Abstract
Objective.Reference dosimetry on an MRI-linac requires a chamber specific magnetic field correction factor,kB⃗.This work aims to measure the correction factor for a parallel plate chamber on a parallel MRI-linac.Approach.kB⃗is defined as the ratio of the absorbed dose to water calibration coefficient in the presence of the magnetic field,ND,wB⃗relative to that under 0 T conditions,ND,w0T.kB⃗was measured via aND,wtransfer to a field chamber at each magnetic field strength from a chamber with knownND,wandkB⃗.This was achieved on the parallel MRI-linac by moving the measurement set-up between a high magnetic field strength region at the MRI-isocentre and a low magnetic field strength region at the end of the bore whilst maintaining consistent set-up and scatter conditions. Three PTW 34001 Roos chambers were investigated as well as a PTW 30013 Farmer used to validate methodology.Main Results.The beam quality used for the measurements ofkB⃗wasTPR20/10 = 0.632. ThekB⃗for the PTW Farmer chamber at 1 T on a parallel MRI-linac was 0.993 ± 0.013 (k = 1). The averagekB⃗factor measured for the three Roos chambers on a 1 T parallel MRI-linac was 0.999 ± 0.014 (k = 1).Significance.The results presented are the first measurements ofkB⃗for a Roos chamber on a parallel MRI-linac. The Roos chamber results demonstrate the potential for the chamber as a reference dosimeter in parallel MRI-linacs.
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Affiliation(s)
- Jarrad Begg
- Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centre, Liverpool, NSW, 2170, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia.,South Western Sydney Clinical School, University of New South Wales, Liverpool, NSW, 2170, Australia
| | - Urszula Jelen
- Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
| | - Paul Keall
- Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia.,Image X Institute, Faculty of Medicine and Health, University of Sydney, Camperdown, NSW, 2005, Australia
| | - Gary Liney
- Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centre, Liverpool, NSW, 2170, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia.,South Western Sydney Clinical School, University of New South Wales, Liverpool, NSW, 2170, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Lois Holloway
- Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centre, Liverpool, NSW, 2170, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia.,South Western Sydney Clinical School, University of New South Wales, Liverpool, NSW, 2170, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia.,Institute of Medical Physics, University of Sydney, Camperdown, NSW, 2005, Australia
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Causer TJ, Rosenfeld AB, Metcalfe PE, Oborn BM. A portable magnet for radiation biology and dosimetry studies in magnetic fields. Med Phys 2022; 49:1924-1931. [PMID: 35023145 DOI: 10.1002/mp.15447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 11/01/2021] [Accepted: 12/14/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND AND PURPOSE In the current and rapidly evolving era of real-time MRI-guided radiotherapy, our radiation biology and dosimetry knowledge is being tested in a novel way. This paper presents the successful design and implementation of a portable device used to generate strong localized magnetic fields. These are ideally suited for small scale experiments that mimic the magnetic field environment inside an MRI-linac system, or more broadly MRI-guided particle therapy as well. MATERIALS AND METHODS A portable permanent magnet based device employing an adjustable steel yoke and magnetic field focusing cones has been designed, constructed and tested. The apparatus utilises two banks of Nd2 Fe14 B permanent magnets totalling around 50 kg in mass to generate a strong magnetic field throughout a small volume between two pole tips. The yoke design allows adjustment of the pole tip gap and exchanging of the focusing cones. Further to this, beam portal holes are present in the yoke and focusing cones, allowing for radiation beams of up to 5 x 5 cm2 to pass through the region of high magnetic field between the focusing cone tips. Finite element magnetic modelling was performed to design and characterise the performance of the device. Automated physical measurements of the magnetic field components at various locations were measured to confirm the performance. The adjustable pole gap and interchangeable cones allows rapid changing of the experimental set-up to allow different styles of measurements to be performed. RESULTS A mostly uniform magnetic field of 1.2 T can be achieved over a volume of at least 3 x 3 x 3 cm3 . This can be reduced in strength to 0.3 T but increased in volume to 10 x 10 x 10 cm3 via removal of the cone tips and/or adjustment of the steel yoke. Although small, these volumes are sufficient to house radiation detectors, cell culture dishes and various phantom arrangements targeted at examining small radiation field dosimetry inside magnetic field strengths that can be changed with ease. Most important is the ability to align the magnetic field both perpendicular to, or inline with the radiation beam. To date, the system has been successfully used to conduct published research in the areas of radiation detector performance, lung phantom dosimetry, and how small clinical electron beams behave in these strong magnetic fields. CONCLUSIONS A portable, relatively inexpensive, and simple to operate device has successfully been constructed and used for performing radiation oncology studies around the theme of MRI-guided radiotherapy. This can be in either inline and perpendicular magnetic fields of up to 1.2 T with x-ray and particle beams.
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Affiliation(s)
- Trent J Causer
- Illawarra Cancer Care Centre, Wollongong, NSW, 2500, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2500, Australia
| | | | - Peter E Metcalfe
- Illawarra Cancer Care Centre, Wollongong, NSW, 2500, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
| | - Bradley M Oborn
- Illawarra Cancer Care Centre, Wollongong, NSW, 2500, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2500, Australia
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5
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Madden L, Roberts N, Jelen U, Dong B, Holloway L, Metcalfe P, Rosenfeld A, Li E. In-line MRI-LINAC depth dose measurements using an in-house plastic scintillation dosimeter. Biomed Phys Eng Express 2021; 7. [PMID: 33530066 DOI: 10.1088/2057-1976/abe295] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 02/02/2021] [Indexed: 11/12/2022]
Abstract
Plastic scintillation dosimeters (PSDs) have many properties that make them desirable for relative dosimetry with MRI-LINACs. An in-house PSD, Farmer ionisation chamber and Gafchromic EBT3 film were used to measure central axis percentage depth dose distributions (PDDs) at the Australian MRI-LINAC Mean errors were calculated between each detector's responses, where the in-house PSD was on average within 0.7% of the Farmer chamber and 1.4% of film, while the Farmer chamber and film were on average within 1.1% of each other. However, the PSD systematically over-estimated the dose as depth increased, approaching a maximum overestimation of the order of 3.5% for the smallest field size measured. This trend was statistically insignificant for all other field sizes measured; further investigation is required to determine the source of this effect. The calculated values of mean absolute error are comparable to the those of trusted dosimeters reported in the literature. These mean absolute errors, and the ubiquity of desirable dosimetric qualities inherent to PSDs suggest that PSDs in general are accurate for relative dosimetry with the MRI-LINAC. Further investigation is required into the source of the reported systematic trends dependent on field-size and depth of measurement.
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Affiliation(s)
- Levi Madden
- Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW 2170, Australia
| | - Natalia Roberts
- Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW 2170, Australia
| | - Urszula Jelen
- GenesisCare St Vincent's Clinic, Darlinghurst, NSW 2010, Australia
| | - Bin Dong
- Ingham Institute for Applied Medical Research, Liverpool, NSW 2170, Australia
| | - Lois Holloway
- Ingham Institute for Applied Medical Research, Liverpool, NSW 2170, Australia.,Liverpool Cancer Therapy Centre, Liverpool, NSW 2170, Australia.,Macauthur Cancer Therapy Clinic, Campbelltown, NSW 2560, Australia
| | - Peter Metcalfe
- Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia.,Illawarra Medical and Health Research Institute, University of Wollongong, NSW 2522, Australia
| | - Anatoly Rosenfeld
- Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia.,Illawarra Medical and Health Research Institute, University of Wollongong, NSW 2522, Australia
| | - Enbang Li
- Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia
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6
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Whelan B, Leghissa M, Amrei P, Zaitsev M, Heinrich B, Fahrig R, Rohdjess H. Magnetic modeling of actively shielded rotating MRI magnets in the presence of environmental steel. Phys Med Biol 2021; 66:045004. [PMID: 33264755 DOI: 10.1088/1361-6560/abd010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Rotating MRI systems could enable novel integrated medical devices such as MRI-Linacs, MRI-xray-angiography systems, and MRI-proton therapy systems. This work aimed to investigate the feasibility of rotating actively shielded superconducting MRI magnets in the presence of environmental steel-in particular, construction steel in the floor of the installation site. Two magnets were investigated: a 1.0 T split bore magnet, and a 1.5 T closed bore magnet. Each magnet was scaled to emulate field strengths of 0.5, 1.0, and 1.5 T. Finite Element Modeling was used to simulate these magnets in the presence of a 3 × 4 m steel plate located 1250 mm or 1400 mm below the isocenter. There are two possible rotation directions: around the longitudinal (z) axis or around the transverse (x) axis. Each model was solved for rotation angles between 0 and 360° in 30° intervals around each of these axes. For each simulation, a 300 mm DSV was extracted and decomposed into spherical harmonics. For the closed-bore magnet, total induced perturbation for the zero degree rotation angle was 223, 432, and 562 μT peak-to-peak (pk-pk) for the 0.5, 1.0, and 1.5 T models respectively (steel at 1250 mm). For the split-bore magnet, the same numbers were 1477, 16747, and 1766 μT. The substantially higher perturbation for the split-bore magnet can be traced to its larger fringe field. For rotation around the z-axis, total perturbation does not change as a function of angle but is exchanged between different harmonics. For rotation around the x-axis, total perturbation is different at each rotation angle. For the closed bore magnet, maximum perturbations occurred for a 90° rotation around the transverse axis. For the split-bore magnet, the opposite was observed, with the same 90° rotation yielding total perturbation lower than the conventional position. In all cases, at least 95% of the total perturbation was composed of 1st and 2nd order harmonics. The presence of environmental steel poses a major challenge to the realization of an actively shielded rotating superconducting MRI system, requiring some novel form of shimming. Possible shimming strategies are discussed at length.
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Affiliation(s)
- Brendan Whelan
- Innovation, Advanced Therapies, Siemens Healthineers GmbH, Forchheim, Germany. ACRF Image X Institute, Sydney School of Health Sciences, University of Sydney, Australia
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Impact of lung density on isolated lung tumor dose in VMAT using inline MR-Linac. Phys Med 2020; 80:65-74. [DOI: 10.1016/j.ejmp.2020.10.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 09/24/2020] [Accepted: 10/12/2020] [Indexed: 11/21/2022] Open
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Sim AJ, Kaza E, Singer L, Rosenberg SA. A review of the role of MRI in diagnosis and treatment of early stage lung cancer. Clin Transl Radiat Oncol 2020; 24:16-22. [PMID: 32596518 PMCID: PMC7306507 DOI: 10.1016/j.ctro.2020.06.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 05/25/2020] [Accepted: 06/01/2020] [Indexed: 12/14/2022] Open
Abstract
Despite magnetic resonance imaging (MRI) being a mainstay in the oncologic care for many disease sites, it has not routinely been used in early lung cancer diagnosis, staging, and treatment. While MRI provides improved soft tissue contrast compared to computed tomography (CT), an advantage in multiple organs, the physical properties of the lungs and mediastinum create unique challenges for lung MRI. Although multi-detector CT remains the gold standard for lung imaging, advances in MRI technology have led to its increased clinical relevance in evaluating early stage lung cancer. Even though positron emission tomography is used more frequently in this context, functional MR imaging, including diffusion-weighted MRI and dynamic contrast-enhanced MRI, are emerging as useful modalities for both diagnosis and evaluation of treatment response for lung cancer. In parallel with these advances, the development of combined MRI and linear accelerator devices (MR-linacs), has spurred the integration of MRI into radiation treatment delivery in the form of MR-guided radiotherapy (MRgRT). Despite challenges for MRgRT in early stage lung cancer radiotherapy, early data utilizing MR-linacs shows potential for the treatment of early lung cancer. In both diagnosis and treatment, MRI is a promising modality for imaging early lung cancer.
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Affiliation(s)
- Austin J. Sim
- Department of Radiation Oncology, H. Lee Moffitt Cancer Center and Research Institute, 12902 USF Magnolia Dr., Tampa, FL, USA
| | - Evangelia Kaza
- Department of Radiation Oncology, Dana Farber Cancer Institute, Brigham & Women’s Hospital & Harvard Medical School, 75 Francis St., Boston, MA, USA
| | - Lisa Singer
- Department of Radiation Oncology, Dana Farber Cancer Institute, Brigham & Women’s Hospital & Harvard Medical School, 75 Francis St., Boston, MA, USA
| | - Stephen A. Rosenberg
- Department of Radiation Oncology, H. Lee Moffitt Cancer Center and Research Institute, 12902 USF Magnolia Dr., Tampa, FL, USA
- University of South Florida Morsani College of Medicine, 12901 Bruce B. Downs Blvd., Tampa, FL, USA
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Kubota T, Araki F, Ohno T. Impact of the cavity on sinus wall dose in magnetic resonance image-guided radiation therapy. Phys Med 2020; 74:100-109. [PMID: 32450541 DOI: 10.1016/j.ejmp.2020.05.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2020] [Revised: 05/12/2020] [Accepted: 05/14/2020] [Indexed: 10/24/2022] Open
Abstract
PURPOSE This study aims to investigate the impact of the cavity on the sinus wall dose by comparing dose distributions with and without the sinus under magnetic fields using Monte Carlo calculations. METHODS A water phantom containing a sinus cavity (Empty) was created, and dose distributions were calculated for 1, 2, and 4 irradiation fields with 6 MV photons. The sinus in the phantom was then filled with water (Full), and the dose distributions were calculated again. The sinus was set to cubes of 2 cm and 4 cm. The magnetic field was applied to the transverse and inline direction under the magnetic flux densities of 0 T, 0.35 T, 0.5 T, 1.0 T, and 1.5 T. The dose distributions were analyzed by the dose difference, dose volume histogram, and D2 with sinus wall thicknesses of 1 and 5 mm. RESULTS D2 in the "Empty" sinus wall under transverse magnetic fields for the 1-field and 4-field cases was 51.9% higher and 3.7% lower than that in the "Full" sinus wall at 1.5 T, respectively. Meanwhile, D2 in the Empty sinus wall under inline magnetic fields for 1-field and 4-fields was 2.3% and 2.6% lower than that in the "Full" sinus at B = 0 T, respectively, whereas D2 was 0.9% and 0.7% larger at 1.0 T, respectively. CONCLUSIONS The impact of the cavity on the sinus wall dose depends on the magnetic flux density, direction of the magnetic field and irradiation beam, and number of irradiation fields.
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Affiliation(s)
- Takahiro Kubota
- Department of Radiology, Kokura Memorial Hospital, 3 Chome-2-1 Asano, Kokurakita Ward, Kitakyushu, Fukuoka 802-8555, Japan; Graduate School of Health Sciences, Kumamoto University, 4-24-1 Kuhonji, Chuo Ward, Kumamoto 862-0976, Japan
| | - Fujio Araki
- Department of Health Sciences, Faculty of Life Sciences, Kumamoto University, 4-24-1 Kuhonji, Chuo Ward, Kumamoto 862-0976, Japan.
| | - Takeshi Ohno
- Department of Health Sciences, Faculty of Life Sciences, Kumamoto University, 4-24-1 Kuhonji, Chuo Ward, Kumamoto 862-0976, Japan
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10
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Jelen U, Dong B, Begg J, Roberts N, Whelan B, Keall P, Liney G. Dosimetric Optimization and Commissioning of a High Field Inline MRI-Linac. Front Oncol 2020; 10:136. [PMID: 32117776 PMCID: PMC7033562 DOI: 10.3389/fonc.2020.00136] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 01/27/2020] [Indexed: 11/17/2022] Open
Abstract
Purpose: Unique characteristics of MRI-linac systems and mutual interactions between their components pose specific challenges for their commissioning and quality assurance. The Australian MRI-linac is a prototype system which explores the inline orientation, with radiation beam parallel to the main magnetic field. The aim of this work was to commission the radiation-related aspects of this system for its application in clinical treatments. Methods: Physical alignment of the radiation beam to the magnetic field was fine-tuned and magnetic shielding of the radiation head was designed to achieve optimal beam characteristics. These steps were guided by investigative measurements of the beam properties. Subsequently, machine performance was benchmarked against the requirements of the IEC60976/77 standards. Finally, the geometric and dosimetric data was acquired, following the AAPM Task Group 106 recommendations, to characterize the beam for modeling in the treatment planning system and with Monte Carlo simulations. The magnetic field effects on the dose deposition and on the detector response have been taken into account and issues specific to the inline design have been highlighted. Results: Alignment of the radiation beam axis and the imaging isocentre within 2 mm tolerance was obtained. The system was commissioned at two source-to-isocentre distances (SIDs): 2.4 and 1.8 m. Reproducibility and proportionality of the dose monitoring system met IEC criteria at the larger SID but slightly exceeded it at the shorter SID. Profile symmetry remained under 103% for the fields up to ~34 × 34 and 21 × 21 cm2 at the larger and shorter SID, respectively. No penumbra asymmetry, characteristic for transverse systems, was observed. The electron focusing effect, which results in high entrance doses on central axis, was quantified and methods to minimize it have been investigated. Conclusion: Methods were developed and employed to investigate and quantify the dosimetric properties of an inline MRI-Linac system. The Australian MRI-linac system has been fine-tuned in terms of beam properties and commissioned, constituting a key step toward the application of inline MRI-linacs for patient treatments.
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Affiliation(s)
- Urszula Jelen
- Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool, NSW, Australia
| | - Bin Dong
- Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool, NSW, Australia
| | - Jarrad Begg
- Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool, NSW, Australia.,Liverpool Cancer Therapy Centre, Radiation Physics, Liverpool, NSW, Australia.,School of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Natalia Roberts
- Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool, NSW, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Brendan Whelan
- Sydney Medical School, ACRF Image X Institute, University of Sydney, Sydney, NSW, Australia
| | - Paul Keall
- Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool, NSW, Australia.,Sydney Medical School, ACRF Image X Institute, University of Sydney, Sydney, NSW, Australia
| | - Gary Liney
- Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool, NSW, Australia.,Liverpool Cancer Therapy Centre, Radiation Physics, Liverpool, NSW, Australia.,School of Medicine, University of New South Wales, Sydney, NSW, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
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11
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Roberts NF, Patterson E, Jelen U, Causer T, Holloway L, Liney G, Lerch M, Rosenfeld AB, Cutajar D, Oborn BM, Metcalfe P. Experimental characterization of magnetically focused electron contamination at the surface of a high-field inline MRI-linac. Med Phys 2019; 46:5780-5789. [PMID: 31633212 DOI: 10.1002/mp.13847] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 08/26/2019] [Accepted: 09/23/2019] [Indexed: 11/08/2022] Open
Abstract
PURPOSE The fringe field of the Australian MRI-linac causes contaminant electrons to be focused along the central axis resulting in a high surface dose. This work aims to characterize this effect using Gafchromic film and high-resolution detectors, MOSkinTM and microDiamond. The secondary aim is to investigate the influence of the inline magnetic field on the relative dose response of these detectors. METHODS The Australian MRI-linac has the unique feature that the linac is mounted on rails allowing for measurements to be performed at different magnetic field strengths while maintaining a constant source-to-surface distance (SSD). Percentage depth doses (PDD) were collected at SSD 1.82 m in a solid water phantom positioned in a low magnetic field region and then at isocenter of the MRI where the magnetic field is 1 T. Measurements for a range of field sizes were taken with the MOSkinTM , microDiamond, and Gafchromic® EBT3 film. The detectors' relative responses at 1 T were compared to the near 0 T PDD beyond the region of electron contamination, that is, 20 mm depth. The near surface measurements inside the MRI bore were compared among the different detectors. RESULTS Skin dose in the MRI, as measured with the MOSkinTM , was 104.5% for 2.1 × 1.9 cm2 , 185.6% for 6.1 × 5.8 cm2 , 369.1% for 11.8 × 11.5 cm2 , and 711.1% for 23.5 × 23 cm2 . The detector measurements beyond the electron contamination region showed agreement between the relative response at 1 T and near 0 T. Film was in agreement with both detectors in this region further demonstrating their relative response is unaffected by the magnetic field. CONCLUSIONS Experimental characterization of the high electron contamination at the surface was performed for a range of field sizes. The relative response of MOSkinTM and microDiamond detectors, beyond the electron contamination region, were confirmed to be unaffected by the 1-T inline magnetic field.
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Affiliation(s)
- Natalia F Roberts
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia.,Centre for Oncology Education and Research Translation, Wollongong, NSW, 2522, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
| | - Elizabeth Patterson
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Urszula Jelen
- Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
| | - Trent Causer
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia.,Illawarra Cancer Care Centre, Wollongong Hospital, Wollongong, NSW, 2500, Australia
| | - Lois Holloway
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia.,Centre for Oncology Education and Research Translation, Wollongong, NSW, 2522, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia.,Department of Medical Physics, Liverpool and Macarthur Cancer Care Centres, Liverpool, NSW, 2170, Australia.,South Western Sydney Clinical School, University of New South Wales, Liverpool, NSW, Australia.,Institute of Medical Physics, University of Sydney, Camperdown, NSW, 2505, Australia
| | - Gary Liney
- Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
| | - Michael Lerch
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Anatoly B Rosenfeld
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Dean Cutajar
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Bradley M Oborn
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia.,Illawarra Cancer Care Centre, Wollongong Hospital, Wollongong, NSW, 2500, Australia
| | - Peter Metcalfe
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
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12
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Begg J, Alnaghy SJ, Causer T, Alharthi T, George A, Glaubes L, Dong B, Goozee G, Keall P, Jelen U, Liney G, Holloway L. Technical Note: Experimental characterization of the dose deposition in parallel MRI‐linacs at various magnetic field strengths. Med Phys 2019; 46:5152-5158. [DOI: 10.1002/mp.13767] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 08/05/2019] [Accepted: 08/06/2019] [Indexed: 11/05/2022] Open
Affiliation(s)
- Jarrad Begg
- Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centre Liverpool NSW 2170 Australia
- Ingham Institute for Applied Medical Research Liverpool NSW 2170 Australia
- South Western Sydney Clinical School University of New South Wales Liverpool NSW 2170 Australia
| | - Sarah J. Alnaghy
- Ingham Institute for Applied Medical Research Liverpool NSW 2170 Australia
- Centre for Medical Radiation Physics University of Wollongong Wollongong NSW 2522 Australia
| | - Trent Causer
- Ingham Institute for Applied Medical Research Liverpool NSW 2170 Australia
- Centre for Medical Radiation Physics University of Wollongong Wollongong NSW 2522 Australia
| | - Thahabah Alharthi
- Ingham Institute for Applied Medical Research Liverpool NSW 2170 Australia
- Sydney Medical School University of Sydney Camperdown NSW 2505 Australia
| | - Armia George
- Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centre Liverpool NSW 2170 Australia
- Ingham Institute for Applied Medical Research Liverpool NSW 2170 Australia
| | - Laura Glaubes
- Sydney Medical School University of Sydney Camperdown NSW 2505 Australia
| | - Bin Dong
- Ingham Institute for Applied Medical Research Liverpool NSW 2170 Australia
- Centre for Medical Radiation Physics University of Wollongong Wollongong NSW 2522 Australia
| | - Gary Goozee
- Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centre Liverpool NSW 2170 Australia
- Ingham Institute for Applied Medical Research Liverpool NSW 2170 Australia
| | - Paul Keall
- Ingham Institute for Applied Medical Research Liverpool NSW 2170 Australia
- ACRF Image X Institute , Sydney Medical School, University of Sydney Liverpool NSW2170 Australia
| | - Urszula Jelen
- Ingham Institute for Applied Medical Research Liverpool NSW 2170 Australia
| | - Gary Liney
- Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centre Liverpool NSW 2170 Australia
- Ingham Institute for Applied Medical Research Liverpool NSW 2170 Australia
- Centre for Medical Radiation Physics University of Wollongong Wollongong NSW 2522 Australia
- Sydney Medical School University of Sydney Camperdown NSW 2505 Australia
| | - Lois Holloway
- Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centre Liverpool NSW 2170 Australia
- Ingham Institute for Applied Medical Research Liverpool NSW 2170 Australia
- South Western Sydney Clinical School University of New South Wales Liverpool NSW 2170 Australia
- Centre for Medical Radiation Physics University of Wollongong Wollongong NSW 2522 Australia
- Institute of Medical Physics University of Sydney Camperdown NSW 2505 Australia
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13
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14
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den Hartogh MD, de Boer HC, de Groot-van Breugel EN, van der Voort van Zyp JR, Hes J, van der Heide UA, Pos F, Haustermans K, Depuydt T, Jan Smeenk R, Kunze-Busch M, Raaymakers BW, Kerkmeijer LG. Planning feasibility of extremely hypofractionated prostate radiotherapy on a 1.5 T magnetic resonance imaging guided linear accelerator. Phys Imaging Radiat Oncol 2019; 11:16-20. [PMID: 33458271 PMCID: PMC7807729 DOI: 10.1016/j.phro.2019.07.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 07/03/2019] [Accepted: 07/03/2019] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND AND PURPOSE Recently, intermediate and high-risk prostate cancer patients have been treated in a multicenter phase II trial with extremely hypofractionated prostate radiotherapy (hypo-FLAME trial). The purpose of the current study was to investigate whether a 1.5 T magnetic resonance imaging guided linear accelerator (MRI-linac) could achieve complex dose distributions of a quality similar to conventional linac state-of-the-art prostate treatments. MATERIALS AND METHODS The clinically delivered treatment plans of 20 hypo-FLAME patients (volumetric modulated arc therapy, 10 MV, 5 mm leaf width) were included. Prescribed dose to the prostate was 5 × 7 Gy, with a focal tumor boost up to 5 × 10 Gy. MRI-linac treatment plans (intensity modulated radiotherapy, 7 MV, 7 mm leaf width, fixed collimator angle and 1.5 T magnetic field) were calculated. Dose distributions were compared. RESULTS In both conventional and MRI-linac treatment plans, the V35Gy to the whole prostate was >99% in all patients. Mean dose to the gross tumor volume was 45 Gy for conventional and 44 Gy for MRI-linac plans, respectively. Organ at risk doses were met in the majority of plans, except for a rectal V35Gy constraint, which was exceeded in one patient, by 1 cc, for both modalities. The bladder V32Gy and V28Gy constraints were exceeded in two and one patient respectively, for both modalities. CONCLUSION Planning of stereotactic radiotherapy with focal ablative boosting in prostate cancer on a high field MRI-linac is feasible with the current MRI-linac properties, without deterioration of plan quality compared to conventional treatments.
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Affiliation(s)
- Mariska D. den Hartogh
- Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Hans C.J. de Boer
- Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands
| | | | | | - Jochem Hes
- Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Uulke A. van der Heide
- Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Floris Pos
- Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Karin Haustermans
- Department of Radiation Oncology, University Hospitals Leuven, Leuven, Belgium
| | - Tom Depuydt
- Department of Radiation Oncology, University Hospitals Leuven, Leuven, Belgium
| | - Robert Jan Smeenk
- Department of Radiation Oncology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Martina Kunze-Busch
- Department of Radiation Oncology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Bas W. Raaymakers
- Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Linda G.W. Kerkmeijer
- Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands
- Department of Radiation Oncology, Radboud University Medical Center, Nijmegen, The Netherlands
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15
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Liney GP, Jelen U, Byrne H, Dong B, Roberts TL, Kuncic Z, Keall P. Technical Note: The first live treatment on a 1.0 Tesla inline
MRI
‐linac. Med Phys 2019; 46:3254-3258. [DOI: 10.1002/mp.13556] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 03/29/2019] [Accepted: 04/16/2019] [Indexed: 11/06/2022] Open
Affiliation(s)
- Gary P. Liney
- Department of Medical Physics Ingham Institute for Applied Medical Research Liverpool NSW Australia
- Liverpool Cancer Therapy Centre, Radiation Physics Liverpool NSW Australia
- School of Medicine University of New South Wales Sydney NSW Australia
- Centre for Medical Radiation Physics University of Wollongong Wollongong NSW Australia
| | - Urszula Jelen
- Department of Medical Physics Ingham Institute for Applied Medical Research Liverpool NSW Australia
| | - Hilary Byrne
- School of Physics Faculty of Science University of Sydney Sydney NSW Australia
- ACRF ImageX Institute Sydney Medical School University of Sydney Sydney NSW Australia
| | - Bin Dong
- Department of Medical Physics Ingham Institute for Applied Medical Research Liverpool NSW Australia
| | - Tara L. Roberts
- Department of Medical Physics Ingham Institute for Applied Medical Research Liverpool NSW Australia
- School of Medicine Western Sydney University Macarthur NSW Australia
| | - Zdenka Kuncic
- School of Physics Faculty of Science University of Sydney Sydney NSW Australia
- ACRF ImageX Institute Sydney Medical School University of Sydney Sydney NSW Australia
| | - Paul Keall
- ACRF ImageX Institute Sydney Medical School University of Sydney Sydney NSW Australia
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16
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Impact of inline magnetic fields on dose distributions for VMAT in lung tumor. Phys Med 2019; 59:100-106. [DOI: 10.1016/j.ejmp.2019.03.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Revised: 03/01/2019] [Accepted: 03/05/2019] [Indexed: 12/25/2022] Open
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17
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Paganelli C, Whelan B, Peroni M, Summers P, Fast M, van de Lindt T, McClelland J, Eiben B, Keall P, Lomax T, Riboldi M, Baroni G. MRI-guidance for motion management in external beam radiotherapy: current status and future challenges. Phys Med Biol 2018; 63:22TR03. [PMID: 30457121 DOI: 10.1088/1361-6560/aaebcf] [Citation(s) in RCA: 83] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
High precision conformal radiotherapy requires sophisticated imaging techniques to aid in target localisation for planning and treatment, particularly when organ motion due to respiration is involved. X-ray based imaging is a well-established standard for radiotherapy treatments. Over the last few years, the ability of magnetic resonance imaging (MRI) to provide radiation-free images with high-resolution and superb soft tissue contrast has highlighted the potential of this imaging modality for radiotherapy treatment planning and motion management. In addition, these advantageous properties motivated several recent developments towards combined MRI radiation therapy treatment units, enabling in-room MRI-guidance and treatment adaptation. The aim of this review is to provide an overview of the state-of-the-art in MRI-based image guidance for organ motion management in external beam radiotherapy. Methodological aspects of MRI for organ motion management are reviewed and their application in treatment planning, in-room guidance and adaptive radiotherapy described. Finally, a roadmap for an optimal use of MRI-guidance is highlighted and future challenges are discussed.
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Affiliation(s)
- C Paganelli
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano, Italy. Author to whom any correspondence should be addressed. www.cartcas.polimi.it
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18
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Liney G, Whelan B, Oborn B, Barton M, Keall P. MRI-Linear Accelerator Radiotherapy Systems. Clin Oncol (R Coll Radiol) 2018; 30:686-691. [DOI: 10.1016/j.clon.2018.08.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Revised: 07/25/2018] [Accepted: 08/20/2018] [Indexed: 12/25/2022]
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19
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Mohajer JK, Nisbet A, Velliou E, Ajaz M, Schettino G. Biological effects of static magnetic field exposure in the context of MR-guided radiotherapy. Br J Radiol 2018; 92:20180484. [PMID: 30359096 DOI: 10.1259/bjr.20180484] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The clinical introduction of MRI-guided radiotherapy has prompted consideration of the potential impact of the static magnetic field on biological responses to radiation. This review provides an introduction to the mechanisms of biological interaction of radiation and magnetic fields individually, in addition to a description of the magnetic field effects on megavoltage photon beams at the macroscale, microscale and nanoscale arising from the Lorentz force on secondary charged particles. A relatively small number of scientific studies have measured the impact of combined static magnetic fields and ionising radiation on biological endpoints of relevance to radiotherapy. Approximately, half of these investigations found that static magnetic fields in combination with ionising radiation produced a significantly different outcome compared with ionising radiation alone. strength static magnetic fields appear to modestly influence the radiation response via a mechanism distinct from modification to the dose distribution. This review intends to serve as a reference for future biological studies, such that understanding of static magnetic field plus ionising radiation synergism may be improved, and if necessary, accounted for in MRI-guided radiotherapy treatment planning.
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Affiliation(s)
- Jonathan Kim Mohajer
- 1 Department of Physics, University of Surrey , Guildford , UK.,2 Medical Radiation Science group, National Physical Laboratory , Teddington , UK
| | - Andrew Nisbet
- 1 Department of Physics, University of Surrey , Guildford , UK.,3 The Royal Surrey County Hospital NHS Foundation Trust , Guildford , UK
| | - Eirini Velliou
- 4 Department of Chemical and Process Engineering, Bioprocess and Biochemical Engineering group (BioProChem), University of Surrey , Guildford , UK
| | - Mazhar Ajaz
- 3 The Royal Surrey County Hospital NHS Foundation Trust , Guildford , UK.,5 Department of Microbial and Cellular Sciences, University of Surrey , Guildford , UK
| | - Giuseppe Schettino
- 1 Department of Physics, University of Surrey , Guildford , UK.,2 Medical Radiation Science group, National Physical Laboratory , Teddington , UK
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20
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Gargett M, Oborn B, Alnaghy SJ, Causer T, Petasecca M, Rosenfeld AB, Metcalfe P. A high resolution 2D array detector system for small-field MRI-linac applications. Biomed Phys Eng Express 2018. [DOI: 10.1088/2057-1976/aabd08] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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21
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Bainbridge H, Salem A, Tijssen RHN, Dubec M, Wetscherek A, Van Es C, Belderbos J, Faivre-Finn C, McDonald F. Magnetic resonance imaging in precision radiation therapy for lung cancer. Transl Lung Cancer Res 2017; 6:689-707. [PMID: 29218271 PMCID: PMC5709138 DOI: 10.21037/tlcr.2017.09.02] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 09/08/2017] [Indexed: 12/25/2022]
Abstract
Radiotherapy remains the cornerstone of curative treatment for inoperable locally advanced lung cancer, given concomitantly with platinum-based chemotherapy. With poor overall survival, research efforts continue to explore whether integration of advanced radiation techniques will assist safe treatment intensification with the potential for improving outcomes. One advance is the integration of magnetic resonance imaging (MRI) in the treatment pathway, providing anatomical and functional information with excellent soft tissue contrast without exposure of the patient to radiation. MRI may complement or improve the diagnostic staging accuracy of F-18 fluorodeoxyglucose position emission tomography and computerized tomography imaging, particularly in assessing local tumour invasion and is also effective for identification of nodal and distant metastatic disease. Incorporating anatomical MRI sequences into lung radiotherapy treatment planning is a novel application and may improve target volume and organs at risk delineation reproducibility. Furthermore, functional MRI may facilitate dose painting for heterogeneous target volumes and prediction of normal tissue toxicity to guide adaptive strategies. MRI sequences are rapidly developing and although the issue of intra-thoracic motion has historically hindered the quality of MRI due to the effect of motion, progress is being made in this field. Four-dimensional MRI has the potential to complement or supersede 4D CT and 4D F-18-FDG PET, by providing superior spatial resolution. A number of MR-guided radiotherapy delivery units are now available, combining a radiotherapy delivery machine (linear accelerator or cobalt-60 unit) with MRI at varying magnetic field strengths. This novel hybrid technology is evolving with many technical challenges to overcome. It is anticipated that the clinical benefits of MR-guided radiotherapy will be derived from the ability to adapt treatment on the fly for each fraction and in real-time, using 'beam-on' imaging. The lung tumour site group of the Atlantic MR-Linac consortium is working to generate a challenging MR-guided adaptive workflow for multi-institution treatment intensification trials in this patient group.
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Affiliation(s)
- Hannah Bainbridge
- The Institute of Cancer Research and The Royal Marsden Hospital NHS Foundation Trust, London, UK
| | - Ahmed Salem
- The University of Manchester and The Christie NHS Foundation Trust, Manchester, UK
| | | | - Michael Dubec
- The University of Manchester and The Christie NHS Foundation Trust, Manchester, UK
| | - Andreas Wetscherek
- The Institute of Cancer Research and The Royal Marsden Hospital NHS Foundation Trust, London, UK
| | - Corinne Van Es
- The University Medical Center Utrecht, Utrecht, the Netherlands
| | - Jose Belderbos
- The Netherlands Cancer Institute and The Antoni van Leeuwenhoek Hospital, Amsterdam, the Netherlands
| | - Corinne Faivre-Finn
- The University of Manchester and The Christie NHS Foundation Trust, Manchester, UK
| | - Fiona McDonald
- The Institute of Cancer Research and The Royal Marsden Hospital NHS Foundation Trust, London, UK
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22
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Menten MJ, Wetscherek A, Fast MF. MRI-guided lung SBRT: Present and future developments. Phys Med 2017; 44:139-149. [PMID: 28242140 DOI: 10.1016/j.ejmp.2017.02.003] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 01/25/2017] [Accepted: 02/07/2017] [Indexed: 12/25/2022] Open
Abstract
Stereotactic body radiotherapy (SBRT) is rapidly becoming an alternative to surgery for the treatment of early-stage non-small cell lung cancer patients. Lung SBRT is administered in a hypo-fractionated, conformal manner, delivering high doses to the target. To avoid normal-tissue toxicity, it is crucial to limit the exposure of nearby healthy organs-at-risk (OAR). Current image-guided radiotherapy strategies for lung SBRT are mostly based on X-ray imaging modalities. Although still in its infancy, magnetic resonance imaging (MRI) guidance for lung SBRT is not exposure-limited and MRI promises to improve crucial soft-tissue contrast. Looking beyond anatomical imaging, functional MRI is expected to inform treatment decisions and adaptations in the future. This review summarises and discusses how MRI could be advantageous to the different links of the radiotherapy treatment chain for lung SBRT: diagnosis and staging, tumour and OAR delineation, treatment planning, and inter- or intrafractional motion management. Special emphasis is placed on a new generation of hybrid MRI treatment devices and their potential for real-time adaptive radiotherapy.
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Affiliation(s)
- Martin J Menten
- Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, UK.
| | - Andreas Wetscherek
- Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, UK
| | - Martin F Fast
- Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, UK.
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23
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Experimental verification of dose enhancement effects in a lung phantom from inline magnetic fields. Radiother Oncol 2017; 125:433-438. [DOI: 10.1016/j.radonc.2017.09.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 09/14/2017] [Accepted: 09/15/2017] [Indexed: 11/18/2022]
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24
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Bainbridge HE, Menten MJ, Fast MF, Nill S, Oelfke U, McDonald F. Treating locally advanced lung cancer with a 1.5T MR-Linac - Effects of the magnetic field and irradiation geometry on conventionally fractionated and isotoxic dose-escalated radiotherapy. Radiother Oncol 2017; 125:280-285. [PMID: 28987747 PMCID: PMC5710994 DOI: 10.1016/j.radonc.2017.09.009] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 08/21/2017] [Accepted: 09/09/2017] [Indexed: 12/25/2022]
Abstract
PURPOSE This study investigates the feasibility and potential benefits of radiotherapy with a 1.5T MR-Linac for locally advanced non-small cell lung cancer (LA NSCLC) patients. MATERIAL AND METHODS Ten patients with LA NSCLC were retrospectively re-planned six times: three treatment plans were created according to a protocol for conventionally fractionated radiotherapy and three treatment plans following guidelines for isotoxic target dose escalation. In each case, two plans were designed for the MR-Linac, either with standard (∼7mm) or reduced (∼3mm) planning target volume (PTV) margins, while one conventional linac plan was created with standard margins. Treatment plan quality was evaluated using dose-volume metrics or by quantifying dose escalation potential. RESULTS All generated treatment plans fulfilled their respective planning constraints. For conventionally fractionated treatments, MR-Linac plans with standard margins had slightly increased skin dose when compared to conventional linac plans. Using reduced margins alleviated this issue and decreased exposure of several other organs-at-risk (OAR). Reduced margins also enabled increased isotoxic target dose escalation. CONCLUSION It is feasible to generate treatment plans for LA NSCLC patients on a 1.5T MR-Linac. Margin reduction, facilitated by an envisioned MRI-guided workflow, enables increased OAR sparing and isotoxic target dose escalation for the respective treatment approaches.
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Affiliation(s)
- Hannah E Bainbridge
- Department of Radiotherapy at The Royal Marsden NHS Foundation Trust, United Kingdom; The Institute of Cancer Research, United Kingdom.
| | - Martin J Menten
- Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, United Kingdom.
| | - Martin F Fast
- Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, United Kingdom
| | - Simeon Nill
- Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, United Kingdom
| | - Uwe Oelfke
- Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, United Kingdom
| | - Fiona McDonald
- Department of Radiotherapy at The Royal Marsden NHS Foundation Trust, United Kingdom; The Institute of Cancer Research, United Kingdom
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25
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Schrenk O, Spindeldreier CK, Burigo LN, Hoerner-Rieber J, Pfaffenberger A. Effects of magnetic field orientation and strength on the treatment planning of nonsmall cell lung cancer. Med Phys 2017; 44:6621-6631. [PMID: 29064573 DOI: 10.1002/mp.12631] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 09/14/2017] [Accepted: 10/11/2017] [Indexed: 11/08/2022] Open
Abstract
PURPOSE Magnetic resonance image-guided radiotherapy (MRgRT) has the potential to increase the accuracy of radiation treatment delivery. Several research groups have developed hybrid MRgRT devices differing by radiation source used and magnetic field orientation and strength. In this work, we investigate the impact of different magnetic field orientations and strengths on the treatment planning of nonsmall cell lung cancer patients (NSCLC). METHODS A framework using the in-house developed treatment planning system matRad and the EGSnrc Monte Carlo code system was introduced to perform Monte Carlo-based treatment planning in the presence of a magnetic field. A specialized spectrum-based source model for the beam qualities of 6 MV and cobalt-60 was applied. Optimized plans for stereotactic body radiation therapy (SBRT) and intensity-modulated radiation therapy (IMRT) were generated for four NSCLC patients in the presence of different magnetic field orientations and strengths which are applied in hybrid MRgRT devices currently under development or in clinical use. RESULTS SBRT and IMRT treatment planning could be performed with consistent plan quality for all magnetic field setups. Only minor effects on the treatment planning outcome were found in the case of magnetic fields orientated perpendicular to the beam direction. Compared to the perpendicular magnetic field orientation, the inline orientation showed the capability to reduce the dose to lung while maintaining equal target coverage. Particularly for tumors with a central position in lung, a distinct dose reduction was obtained which led to a maximum reduction of mean lung dose by 18.5% (0.5 Gy), when applying a 1 T inline magnetic field. CONCLUSION All plans generated in this work obtained dose metrics within clinical constraints according to RTOG guidelines. When considering conventional dose metrics, no detrimental effects due to the magnetic fields were observed on the dose to the tumor or to organs at risk. An evaluation of the effects on skin dose was not ascertainable due to the simplified specification of the source model used. By accounting for the magnetic field during treatment planning, a dose reduction in lung could be achieved for inline-oriented magnetic fields. An inline orientation of the magnetic field therefore showed a potential benefit when treating NSCLC with MRgRT.
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Affiliation(s)
- Oliver Schrenk
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), 69120, Heidelberg, Germany.,Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), 69120, Heidelberg, Germany
| | - Claudia Katharina Spindeldreier
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), 69120, Heidelberg, Germany.,Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), 69120, Heidelberg, Germany
| | - Lucas Norberto Burigo
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), 69120, Heidelberg, Germany.,Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), 69120, Heidelberg, Germany
| | - Juliane Hoerner-Rieber
- Department of Radiation Oncology, University Hospital Heidelberg, 69120, Heidelberg, Germany.,Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), 69120, Heidelberg, Germany
| | - Asja Pfaffenberger
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), 69120, Heidelberg, Germany.,Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), 69120, Heidelberg, Germany
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26
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Liney GP, Dong B, Begg J, Vial P, Zhang K, Lee F, Walker A, Rai R, Causer T, Alnaghy SJ, Oborn BM, Holloway L, Metcalfe P, Barton M, Crozier S, Keall P. Technical Note: Experimental results from a prototype high-field inline MRI-linac. Med Phys 2017; 43:5188. [PMID: 27587049 DOI: 10.1118/1.4961395] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The pursuit of real-time image guided radiotherapy using optimal tissue contrast has seen the development of several hybrid magnetic resonance imaging (MRI)-treatment systems, high field and low field, and inline and perpendicular configurations. As part of a new MRI-linac program, an MRI scanner was integrated with a linear accelerator to enable investigations of a coupled inline MRI-linac system. This work describes results from a prototype experimental system to demonstrate the feasibility of a high field inline MR-linac. METHODS The magnet is a 1.5 T MRI system (Sonata, Siemens Healthcare) was located in a purpose built radiofrequency (RF) cage enabling shielding from and close proximity to a linear accelerator with inline (and future perpendicular) orientation. A portable linear accelerator (Linatron, Varian) was installed together with a multileaf collimator (Millennium, Varian) to provide dynamic field collimation and the whole assembly built onto a stainless-steel rail system. A series of MRI-linac experiments was performed to investigate (1) image quality with beam on measured using a macropodine (kangaroo) ex vivo phantom; (2) the noise as a function of beam state measured using a 6-channel surface coil array; and (3) electron contamination effects measured using Gafchromic film and an electronic portal imaging device (EPID). RESULTS (1) Image quality was unaffected by the radiation beam with the macropodine phantom image with the beam on being almost identical to the image with the beam off. (2) Noise measured with a surface RF coil produced a 25% elevation of background intensity when the radiation beam was on. (3) Film and EPID measurements demonstrated electron focusing occurring along the centerline of the magnet axis. CONCLUSIONS A proof-of-concept high-field MRI-linac has been built and experimentally characterized. This system has allowed us to establish the efficacy of a high field inline MRI-linac and study a number of the technical challenges and solutions.
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Affiliation(s)
- G P Liney
- Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool NSW 2170, Australia; Radiation Physics, Liverpool Cancer Therapy Centre, Liverpool NSW 2170, Australia; School of Medicine, University of New South Wales, Sydney NSW 2170, Australia; and Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia
| | - B Dong
- Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool NSW 2170, Australia
| | - J Begg
- Radiation Physics, Liverpool Cancer Therapy Centre, Liverpool NSW 2170, Australia
| | - P Vial
- Radiation Physics & Liverpool Cancer Therapy Centre, Liverpool, NSW 2170, Australia and Radiation Physics Laboratory, Sydney Medical School, University of Sydney, NSW 2006, Australia
| | - K Zhang
- Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool NSW 2170, Australia
| | - F Lee
- Radiation Physics Laboratory, Sydney Medical School, University of Sydney, NSW 2006, Australia
| | - A Walker
- Medical Physics, Ingham Institute for Applied Medical Research, Liverpool, NSW 2170, Australia and Radiation Physics, Liverpool Cancer Therapy Centre, Liverpool NSW 2170, Australia
| | - R Rai
- Medical Physics, Ingham Institute for Applied Medical Research, Liverpool, NSW 2170, Australia and Radiation Physics, Liverpool Cancer Therapy Centre, Liverpool NSW 2170, Australia
| | - T Causer
- Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia
| | - S J Alnaghy
- Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia
| | - B M Oborn
- Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia and Illawarra Cancer Care Centre, Wollongong Hospital, NSW 2500, Australia
| | - L Holloway
- Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool NSW 2170, Australia; Radiation Physics, Liverpool Cancer Therapy Centre, Liverpool NSW 2170, Australia; School of Medicine, University of New South Wales, Sydney NSW 2170, Australia; Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia; and Radiation Physics Laboratory, Sydney Medical School, University of Sydney, NSW 2006, Australia
| | - P Metcalfe
- Centre for Medical Radiation Physics, University of Wollongong, NSW 2522, Australia
| | - M Barton
- Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool NSW 2170, Australia and School of Medicine, University of New South Wales, Sydney NSW 2170, Australia
| | - S Crozier
- School of Information Technology & Electrical Engineering, University of Queensland, Brisbane, QLD 4072, Australia
| | - P Keall
- Radiation Physics Laboratory, Sydney Medical School, University of Sydney, Sydney NSW 2170, Australia
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27
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Wang L, Hoogcarspel SJ, Wen Z, van Vulpen M, Molkentine DP, Kok J, Lin SH, Broekhuizen R, Ang KK, Bovenschen N, Raaymakers BW, Frank SJ. Biological responses of human solid tumor cells to X-ray irradiation within a 1.5-Tesla magnetic field generated by a magnetic resonance imaging-linear accelerator. Bioelectromagnetics 2016; 37:471-80. [PMID: 27434783 DOI: 10.1002/bem.21991] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 06/30/2016] [Indexed: 01/20/2023]
Abstract
Devices that combine magnetic resonance imaging with linear accelerators (MRL) represent a novel tool for MR-guided radiotherapy. However, whether magnetic fields (MFs) generated by these devices affect the radiosensitivity of tumors is unknown. We investigated the influence of a 1.5-T MF on cell viability and radioresponse of human solid tumors. Human head/neck cancer and lung cancer cells were exposed to single or fractionated 6-MV X-ray radiation; effects of the MF on cell viability were determined by cell plating efficiency and on radioresponsiveness by clonogenic cell survival. Doses needed to reduce the fraction of surviving cells to 37% of the initial value (D0s) were calculated for multiple exposures to MF and radiation. Results were analyzed using Student's t-tests. Cell viability was no different after single or multiple exposures to MRL than after exposure to a conventional linear accelerator (Linac, without MR-generated MF) in 12 of 15 experiments (all P > 0.05). Single or multiple exposures to MF had no influence on cell radioresponse (all P > 0.05). Cells treated up to four times with an MRL or a Linac further showed no changes in D0s with MF versus without MF (all P > 0.05). In conclusion, MF within the MRL does not seem to affect in vitro tumor radioresponsiveness as compared with a conventional Linac. Bioelectromagnetics. 37:471-480, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Li Wang
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Stan Jelle Hoogcarspel
- Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Zhifei Wen
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Marco van Vulpen
- Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - David P Molkentine
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Jan Kok
- Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Steven H Lin
- Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Roel Broekhuizen
- Department of Pathology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Kie-Kian Ang
- Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Niels Bovenschen
- Department of Pathology, University Medical Center Utrecht, Utrecht, The Netherlands.,Laboratory of Translational Immunology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Bas W Raaymakers
- Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Steven J Frank
- Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
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