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Episkopakis A, Margaroni V, Kanellopoulou S, Marinos N, Koutsouveli E, Karaiskos P, Pappas EP. Dose-response dependencies of OSL dosimeters in conventional linacs and 1.5T MR-linacs: an experimental and Monte Carlo study. Phys Med Biol 2023; 68:225002. [PMID: 37857285 DOI: 10.1088/1361-6560/ad051e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2023] [Accepted: 10/19/2023] [Indexed: 10/21/2023]
Abstract
Objective. This work focuses on the optically stimulated luminescence dosimetry (OSLD) dose-response characterization, with emphasis on 1.5T MR-Linacs.Approach. Throughout this study, the nanoDots OSLDs (Landauer, USA) were considered. In groups of three, the mean OSLD response was measured in a conventional linac and an MR-Linac under various irradiation conditions to investigate (i) dose-response linearity with and without the 1.5T magnetic field, (ii) signal fading rate and its dependencies, (iii) beam quality, detector orientation and dose rate dependencies in a conventional linac, (iii) potential MR imaging related effects on OSLD response and (iv) detector orientation dependence in an MR-Linac. Monte Carlo calculations were performed to further quantify angular dependence after rotating the detector around its central axis parallel to the magnetic field, and determine the magnetic field correction factors,kB,Q,for all cardinal detector orientations.Main results. OSLD dose-response supralinearity in an MR-Linac setting was found to agree within uncertainties with the corresponding one in a conventional linac, for the axial detector orientation investigated. Signal fading rate does not depend on irradiation conditions for the range of 3-30 d considered. OSLD angular (orientation) dependence is more pronounced under the presence of a magnetic field. OSLDs irradiated with and without real-time T2w MR imaging enabled during irradiation yielded the same response within uncertainties.kB,Qvalues were determined for all three cardinal orientations. Corrections needed reached up to 6.4%. However, if OSLDs are calibrated in the axial orientation and then irradiated in an MR-Linac placed again in the axial orientation (perpendicular to the magnetic field), then simulations suggest thatkB,Qcan be considered unity within uncertainties, irrespective of the incident beam angle.Significance. This work contributes towards OSLD dose-response characterization and relevant correction factors availability. OSLDs are suitable for QA checks in MR-based beam gating applications andin vivodosimetry in MR-Linacs.
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Affiliation(s)
- Anastasios Episkopakis
- Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, 75 Mikras Asias, 115 27 Athens, Greece
- Global Clinical Operations, Elekta Ltd., Fleming way, RH10 99RR Crawley, West Sussex, United Kingdom
| | - Vasiliki Margaroni
- Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, 75 Mikras Asias, 115 27 Athens, Greece
| | | | - Nikolas Marinos
- Global Clinical Operations, Elekta Ltd., Fleming way, RH10 99RR Crawley, West Sussex, United Kingdom
| | - Efi Koutsouveli
- Medical Physics Department, Hygeia Hospital, Kifissias Avenue & 4 Erythrou Stavrou, Marousi, 151 23 Athens, Greece
| | - Pantelis Karaiskos
- Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, 75 Mikras Asias, 115 27 Athens, Greece
| | - Eleftherios P Pappas
- Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, 75 Mikras Asias, 115 27 Athens, Greece
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2
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Song H, Hu J, He J, Ma G, Cheng L, Li X. Dosimetric impact of hollow intraoral stents for head and neck cancer radiotherapy: A phantom study. J Appl Clin Med Phys 2023; 24:e14101. [PMID: 37477628 PMCID: PMC10647986 DOI: 10.1002/acm2.14101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2023] [Revised: 06/27/2023] [Accepted: 07/06/2023] [Indexed: 07/22/2023] Open
Abstract
PURPOSE To investigate the dosimetric impact of the calculation boundaries and dose calculation algorithms of radiotherapy in head and neck cancer patients with an opened oral cavity connected to the exterior by a hollow intraoral positioning stent. METHODS AND MATERIALS A homemade silicone phantom with an opened oral cavity was placed in a CIRS head phantom to model head and neck cancer patients with a hollow intraoral positioning stent. 3D-CRT plans were designed on CT images of the phantom in Monaco and Pinnacle3 treatment planning systems (TPSs) with the same beam parameters. The default boundary and manually extrapolated boundary were both adopted in these two TPSs to explore the dosimetric impact on treatment plans. The nanoDot™ optically stimulated luminescence dosimeters (OSLDs) were chosen to measure the planned dose surrounding the oral cavity of the head phantom after calibration. RESULT The doses in the air cavity and two measuring points at the joint area were dramatically changed from 0.0, 92.4 and 148.8 cGy to 177.8, 244.2 and 244.1 cGy in Monaco after adopting the extrapolated boundary. While the calculated doses at the same place were changed from 61.2, 143.7 and 198.3 cGy to 175.4, 234.7 and 233.2 cGy in Pinnacle3 with a similar calculation boundary. For the Monaco TPS, the relative errors compared to the OSLD measured doses were 2.94 ± 1.93%, 0.53 ± 8.64%, 2.65 ± 1.87% and 3.93 ± 1.69% at 4 measuring positions. In contrast, the relative errors 4.03 ± 1.93%, 4.85 ± 8.64%, 7.61 ± 1.87% and 5.61 ± 1.69% were observed in Pinnacle3 . CONCLUSION The boundary setting of an opened oral cavity in TPSs has a significant dosimetric impact on head and neck cancer radiotherapy. An extrapolated boundary should be manually set up to include the whole oral cavity in the dose calculation domain to avoid major dose deviations.
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Affiliation(s)
- Hongbing Song
- Department of RadiotherapyRenmin Hospital of Wuhan UniversityWuhanHubeiChina
| | - Jian Hu
- Department of RadiotherapyRenmin Hospital of Wuhan UniversityWuhanHubeiChina
| | - Junxiang He
- Department of RadiotherapyRenmin Hospital of Wuhan UniversityWuhanHubeiChina
| | - Guangdong Ma
- Department of RadiotherapyRenmin Hospital of Wuhan UniversityWuhanHubeiChina
| | - Lan Cheng
- Department of RadiologyUnion HospitalTongJi Medical CollegeHuazhong University of Science and TechnologyWuhanHubeiChina
| | - Xiangpan Li
- Department of RadiotherapyRenmin Hospital of Wuhan UniversityWuhanHubeiChina
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3
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Patterson E, Stokes P, Cutajar D, Rosenfeld A, Baines J, Metcalfe P, Powers M. High-resolution entry and exit surface dosimetry in a 1.5 T MR-linac. Phys Eng Sci Med 2023; 46:787-800. [PMID: 36988905 DOI: 10.1007/s13246-023-01251-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Accepted: 03/21/2023] [Indexed: 03/30/2023]
Abstract
The magnetic field of a transverse MR-linac alters electron trajectories as the photon beam transits through materials, causing lower doses at flat entry surfaces and increased doses at flat beam-exiting surfaces. This study investigated the response of a MOSFET detector, known as the MOSkin™, for high-resolution surface and near-surface percentage depth dose measurements on an Elekta Unity. Simulations with Geant4 and the Monaco treatment planning system (TPS), and EBT-3 film measurements, were also performed for comparison. Measured MOSkin™ entry surface doses, relative to Dmax, were (9.9 ± 0.2)%, (10.1 ± 0.3)%, (11.3 ± 0.6)%, (12.9 ± 1.0)%, and (13.4 ± 1.0)% for 1 × 1 cm2, 3 × 3 cm2, 5 × 5 cm2, 10 × 10 cm2, and 22 × 22 cm2 fields, respectively. For the investigated fields, the maximum percent differences of Geant4, TPS, and film doses extrapolated and interpolated to a depth suitable for skin dose assessment at the beam entry, relative to MOSkin™ measurements at an equivalent depth were 1.0%, 2.8%, and 14.3%, respectively, and at a WED of 199.67 mm at the beam exit, 3.2%, 3.7% and 5.7%, respectively. The largest measured increase in exit dose, due to the electron return effect, was 15.4% for the 10 × 10 cm2 field size using the MOSkin™ and 17.9% for the 22 × 22 cm2 field size, using Geant4 calculations. The results presented in the study validate the suitability of the MOSkin™ detector for transverse MR-linac surface dosimetry.
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Affiliation(s)
- E Patterson
- Centre of Medical and Radiation Physics, University of Wollongong, Wollongong, NSW, Australia.
| | - P Stokes
- Townsville Cancer Centre, Townsville Hospital and Health Service, Townsville, QLD, Australia
| | - D Cutajar
- Centre of Medical and Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - A Rosenfeld
- Centre of Medical and Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
- Illawarra Health Medical Research Institute, University of Wollongong, Wollongong, NSW, Australia
| | - J Baines
- Townsville Cancer Centre, Townsville Hospital and Health Service, Townsville, QLD, Australia
- College of Science and Engineering, James Cook University, Townsville, QLD, Australia
| | - P Metcalfe
- Centre of Medical and Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
- Illawarra Health Medical Research Institute, University of Wollongong, Wollongong, NSW, Australia
- Ingham Institute for Applied Medical Research, Liverpool, NSW, Australia
| | - M Powers
- Townsville Cancer Centre, Townsville Hospital and Health Service, Townsville, QLD, Australia
- College of Science and Engineering, James Cook University, Townsville, QLD, Australia
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Wang MH, Kim A, Ruschin M, Tan H, Soliman H, Myrehaug S, Detsky J, Husain Z, Atenafu EG, Keller B, Sahgal A, Tseng CL. Comparison of Prospectively Generated Glioma Treatment Plans Clinically Delivered on Magnetic Resonance Imaging (MRI)-Linear Accelerator (MR-Linac) Versus Conventional Linac: Predicted and Measured Skin Dose. Technol Cancer Res Treat 2022; 21:15330338221124695. [PMID: 36071647 PMCID: PMC9459463 DOI: 10.1177/15330338221124695] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Introduction: Magnetic resonance imaging-linear accelerator
radiotherapy is an innovative technology that requires special consideration for
secondary electron interactions within the magnetic field, which can alter dose
deposition at air–tissue interfaces. As part of ongoing quality assurance and
quality improvement of new radiotherapy technologies, the purpose of this study
was to evaluate skin dose modelled from the treatment planning systems of a
magnetic resonance imaging-linear accelerator and a conventional linear
accelerator, and then correlate with in vivo measurements of delivered skin dose
from each linear accelerator. Methods: In this prospective cohort
study, 37 consecutive glioma patients had treatment planning completed and
approved prior to radiotherapy initiation using commercial treatment planning
systems: a Monte Carlo-based algorithm for magnetic resonance imaging-linear
accelerator or a convolution-based algorithm for conventional linear
accelerator. In vivo skin dose was measured using an optically stimulated
luminescent dosimeter. Results: Monte Carlo-based magnetic
resonance imaging-linear accelerator plans and convolution-based conventional
linear accelerator plans had similar dosimetric parameters for target volumes
and organs-at-risk. However, magnetic resonance imaging-linear accelerator plans
had 1.52 Gy higher mean dose to air cavities (P < .0001) and
1.10 Gy higher mean dose to skin (P < .0001). In vivo skin
dose was 14.5% greater for magnetic resonance imaging-linear accelerator
treatments (P = .0027), and was more accurately predicted by
Monte Carlo-based calculation (ρ = 0.95,
P < .0001) versus convolution-based
(ρ = 0.80, P = .0096).
Conclusion: This is the first prospective dosimetric comparison
of glioma patients clinically treated on both magnetic resonance imaging-linear
accelerator and conventional linear accelerator. Our findings suggest that skin
doses were significantly greater with magnetic resonance imaging-linear
accelerator plans but correlated better with in vivo measurements of actual skin
dose from delivered treatments. Future magnetic resonance imaging-linear
accelerator planning processes are being designed to account for skin dosimetry
and treatment delivery.
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Affiliation(s)
- Michael H Wang
- Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, 7938University of Toronto, Toronto, Ontario, Canada
| | - Anthony Kim
- Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, 7938University of Toronto, Toronto, Ontario, Canada.,Department of Medical Physics, Sunnybrook Odette Cancer Centre, 7938University of Toronto, Toronto, Ontario, Canada
| | - Mark Ruschin
- Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, 7938University of Toronto, Toronto, Ontario, Canada.,Department of Medical Physics, Sunnybrook Odette Cancer Centre, 7938University of Toronto, Toronto, Ontario, Canada
| | - Hendrick Tan
- Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, 7938University of Toronto, Toronto, Ontario, Canada
| | - Hany Soliman
- Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, 7938University of Toronto, Toronto, Ontario, Canada
| | - Sten Myrehaug
- Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, 7938University of Toronto, Toronto, Ontario, Canada
| | - Jay Detsky
- Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, 7938University of Toronto, Toronto, Ontario, Canada
| | - Zain Husain
- Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, 7938University of Toronto, Toronto, Ontario, Canada
| | - Eshetu G Atenafu
- Department of Biostatistics, 7989University Health Network, 7938University of Toronto, Toronto, Ontario, Canada
| | - Brian Keller
- Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, 7938University of Toronto, Toronto, Ontario, Canada.,Department of Medical Physics, Sunnybrook Odette Cancer Centre, 7938University of Toronto, Toronto, Ontario, Canada
| | - Arjun Sahgal
- Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, 7938University of Toronto, Toronto, Ontario, Canada
| | - Chia-Lin Tseng
- Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, 7938University of Toronto, Toronto, Ontario, Canada
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Tyagi N, Subashi E, Michael Lovelock D, Kry S, Alvarez PE, Hunt MA, Lim SB. Dosimetric evaluation of irradiation geometry and potential air gaps in an acrylic miniphantom used for external audit of absolute dose calibration for a hybrid 1.5 T MR-linac system. J Appl Clin Med Phys 2021; 23:e13503. [PMID: 34914175 PMCID: PMC8833292 DOI: 10.1002/acm2.13503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 10/21/2021] [Accepted: 11/30/2021] [Indexed: 11/20/2022] Open
Abstract
Introduction To investigate the impact of partial lateral scatter (LS), backscatter (BS) and presence of air gaps on optically stimulated luminescence dosimeter (OSLD) measurements in an acrylic miniphantom used for dosimetry audit on the 1.5 T magnetic resonance‐linear accelerator (MR‐linac) system. Methods The following irradiation geometries were investigated using OSLDs, A26 MR/A12 MR ion chamber (IC), and Monaco Monte Carlo system: (a) IC/OSLD in an acrylic miniphantom (partial LS, partial BS), (b) IC/OSLD in a miniphantom placed on a solid water (SW) stack at a depth of 1.5 cm (partial LS, full BS), (c) IC/OSLD placed at a depth of 1.5 cm inside a 3 cm slab of SW/buildup (full LS, partial BS), and (d) IC/OSLD centered inside a 3 cm slab of SW/buildup at a depth of 1.5 cm placed on top of a SW stack (full LS, full BS). Average of two irradiated OSLDs with and without water was used at each setup. An air gap of 1 and 2 mm, mimicking presence of potential air gap around the OSLDs in the miniphantom geometry was also simulated. The calibration condition of the machine was 1 cGy/MU at SAD = 143.5 cm, d = 5 cm, G90, and 10 × 10 cm2. Results The Monaco calculation (0.5% uncertainty and 1.0 mm voxel size) for the four setups at the measurement point were 108.2, 108.1, 109.4, and 110.0 cGy. The corresponding IC measurements were 109.0 ± 0.03, 109.5 ± 0.06, 110.2 ± 0.02, and 109.8 ± 0.03 cGy. Without water, OSLDs measurements were ∼10% higher than the expected. With added water to minimize air gaps, the measurements were significantly improved to within 2.2%. The dosimetric impacts of 1 and 2 mm air gaps were also verified with Monaco to be 13.3% and 27.9% higher, respectively, due to the electron return effect. Conclusions A minimal amount of air around or within the OSLDs can cause measurement discrepancies of 10% or higher when placed in a high b‐field MR‐linac system. Care must be taken to eliminate the air from within and around the OSLD.
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Affiliation(s)
- Neelam Tyagi
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York, USA
| | - Ergys Subashi
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York, USA
| | - Dale Michael Lovelock
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York, USA
| | - Stephen Kry
- Department of Radiation Physics, IROC, MD Anderson Cancer Center, Houston, Texas, USA
| | - Paola Elisa Alvarez
- Department of Radiation Physics, IROC, MD Anderson Cancer Center, Houston, Texas, USA
| | - Margie A Hunt
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York, USA
| | - Seng Boh Lim
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York, USA
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6
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Huang CY, Yang B, Lam WW, Tang KK, Li TC, Law WK, Cheung KY, Yu SK. Effects on skin dose from unwanted air gaps under bolus in an MR-guided linear accelerator (MR-linac) system. Phys Med Biol 2021; 66:065021. [PMID: 33607641 DOI: 10.1088/1361-6560/abe837] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Bolus is commonly used in MV photon radiotherapy to increase superficial dose and improve dose uniformity for treating shallow lesions. However, irregular patient body contours can cause unwanted air gaps between a bolus and patient skin. The resulting dosimetric errors could be exacerbated in MR-Linac treatments, as secondary electrons generated by photons are affected by the magnetic field. This study aimed to quantify the dosimetric effect of unwanted gaps between bolus and skin surface in an MR-Linac. A parallel-plate ionization chamber and EBT3 films were utilized to evaluate the surface dose under bolus with various gantry angles, field sizes, and different air gaps. The results of surface dose measurements were then compared to Monaco 5.40 Treatment Planning System (TPS) calculations. The suitability of using a parallel-plate chamber in MR-Linac measurement was validated by benchmarking the percentage depth dose and output factors with the microDiamond detector and air-filled ionization chamber measurements in water. A non-symmetric response of the parallel-plate chamber to oblique beams in the magnetic field was characterized. Unwanted air gaps significantly reduced the skin dose. For a frontal beam, skin dose was halved when there was a 5 mm gap, a much larger difference than in a conventional linac. Skin dose manifested a non-symmetric pattern in terms of gantry angle and gap size. The TPS overestimated skin dose in general, but shared the same trend with measurement when there was no air gap, or the gap size was larger than 5 mm. However, the calculated and measured results had a large discrepancy when the bolus-skin gap was below 5 mm. When treating superficial lesions, unwanted air gaps under the bolus will compromise the dosimetric goals. Our results highlight the importance of avoiding air gaps between bolus and skin when treating superficial lesions using an MR-Linac system.
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7
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Lim-Reinders S, Keller BM, Sahgal A, Chugh B, Kim A. Measurement of surface dose in an MR-Linac with optically stimulated luminescence dosimeters for IMRT beam geometries. Med Phys 2020; 47:3133-3142. [PMID: 32302010 DOI: 10.1002/mp.14185] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 03/24/2020] [Accepted: 04/01/2020] [Indexed: 12/31/2022] Open
Abstract
PURPOSE This study aims to measure the surface dose on an anthropomorphic phantom for intensity-modulated radiation therapy (IMRT) plans treated in a 1.5 T magnetic resonance (MR)-Linac. Previous studies have used Monte Carlo programs to simulate surface dose and have recognized high surface dose as a potential limiting factor for the MR-Linac; however, to our knowledge surface dose measurement for clinical plans has not yet been published. Given the novelty of the MR-Linac, it is important to perform in vivo measurements of a potentially dose-limiting factor such as surface dose when moving forward for clinical use. METHODS Optically stimulated luminescence dosimeters (OSLDs) were used on an anthropomorphic phantom. Intensity-modulated radiation therapy plans were generated to treat a near-surface breast tumor in the phantom. The tumor was treated with 2, 3, 5, 7, and 9 beam IMRT plans with a 1.5 T MR-Linac using a 7-MV photon beam. The plans were generated in a Monte Carlo treatment planning system (TPS) capable of modeling magnetic field effects. The surface dose was sampled in seven locations on the surface surrounding the planning target volume (PTV), and in two different OSLD configurations with the dosimeters measuring water equivalent depths of 0.16 and 0.64 mm. The TPS was used to estimate the doses at the OSLD locations. In addition, MR images were taken of a pork belly with and without an OSLD placed anteriorly placed to determine the effect of an OSLD on image fidelity. RESULTS For the 3, 5, 7, and 9-beam configurations, surface doses were approximately half that of the prescription dose to the simulated tumor, although the magnitude of the skin dose relative to the prescription is certainly also dependent on individual patient anatomy. The general trend for both TPS and measurements was that the greater the number of beams, the lower the skin doses and dose readings; also, with increasing numbers of beams, doses at shallow depths become lower relative to deeper depths. The MR images showed that the presence of the OSLD did not induce clinically relevant geometric distortions or intensity differences. CONCLUSIONS To our knowledge, this study is the first of its kind to experimentally measure the surface dose in an MR-Linac for IMRT plans. This study has explored the use of OSLDs to measure in vivo surface dose in a clinical setting. OSLDs may be used to measure skin dose clinically when there are concerns of skin radiation burns and near-surface toxicity. Optically stimulated luminescence dosimeters are promising devices for in vivo surface dosimetry in an MR-Linac.
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Affiliation(s)
- Stephanie Lim-Reinders
- Sunnybrook Health Sciences Centre/Odette Cancer Centre, 2075 Bayview Ave, Toronto, ON, M4N 3M5, Canada.,Faculty of Medicine, Medical Sciences Building, University of Toronto, 1 King's College Circle, Toronto, ON, M5S 1A8, Canada
| | - Brian M Keller
- Faculty of Medicine, Medical Sciences Building, University of Toronto, 1 King's College Circle, Toronto, ON, M5S 1A8, Canada.,Department of Radiation Oncology, Faculty of Medicine, University of Toronto, 149 College Street, Suite 504, Toronto, ON, M5T 1P5, Canada
| | - Arjun Sahgal
- Faculty of Medicine, Medical Sciences Building, University of Toronto, 1 King's College Circle, Toronto, ON, M5S 1A8, Canada.,Department of Radiation Oncology, Faculty of Medicine, University of Toronto, 149 College Street, Suite 504, Toronto, ON, M5T 1P5, Canada
| | - Brige Chugh
- Faculty of Medicine, Medical Sciences Building, University of Toronto, 1 King's College Circle, Toronto, ON, M5S 1A8, Canada.,Department of Radiation Oncology, Faculty of Medicine, University of Toronto, 149 College Street, Suite 504, Toronto, ON, M5T 1P5, Canada
| | - Anthony Kim
- Faculty of Medicine, Medical Sciences Building, University of Toronto, 1 King's College Circle, Toronto, ON, M5S 1A8, Canada.,Department of Radiation Oncology, Faculty of Medicine, University of Toronto, 149 College Street, Suite 504, Toronto, ON, M5T 1P5, Canada
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