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D P, D K, P M, Bhalla NK, R P, M C, Puri A. A Study to Analyze Impact of Treatment Couch and Immobilization Devices on Surface Dose for Megavoltage Photon Beams. Asian Pac J Cancer Prev 2023; 24:4133-4138. [PMID: 38156848 PMCID: PMC10909093 DOI: 10.31557/apjcp.2023.24.12.4133] [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: 06/23/2023] [Accepted: 12/17/2023] [Indexed: 01/03/2024] Open
Abstract
PURPOSE/OBJECTIVE The purpose of this study is to investigate the effect of treatment couch and immobilization devices on surface dose for megavoltage photon beams. MATERIAL/METHODS Percentage surface dose (PSD) measurement was carried out in Elekta Synergy™ Linear accelerator using PTW Markus® Parallel plate ionization chamber of volume 0.05cm3 with water equivalent RW3 Slab phantom (PTW, Germany). The measurement depth was considered at 0.07mm. The reference PSD was measured at 0° gantry angle with 10×10cm2, 20×20cm2 and 30×30cm2 field sizes and 100cm SSD for 4MV, 6MV and 15MV photon beams. For comparison, PSD measurement was carried out at 180° gantry angle inclusion of treatment couch (TC), All in One positioning system (AIO - PS) and Vac lok Cushions (VLC). RESULTS Beam angle at 0°, for field sizes 10×10cm2, 20×20cm2 and 30×30cm2, the PSD was observed as 30.9%, 40.5%, 48.7% for 4MV; 23.7%, 33.8%, 42.2% for 6MV; and 17.0%, 29.6%, 38.6% for 15MV respectively. Beam angle at 180° with TC, an increase in PSD by maximum of 65.0% for 4MV, 64.9% for 6MV and 55.9% for 15MV as compared to 0° angle. The PSD increased when beam angle was 180° with TC and AIO - PS were 65.0% for 4MV, 67.4% for 6MV, and 60.9% for 15MV than 0° angle. Similarly, increased PSD for beam angle at 180° with TC and VLC were 66.8% for 4MV, 66.8% for 6MV and 61.3% for 15MV as compared to 0° angle. CONCLUSION For all three-photon energies, at 180° gantry angle, the PSD increased significantly in case of TC, VLC, and AIO - PS for all the field sizes as compared to gantry angle at 0°. It is necessary to consider TC, AIO - PS and VLC during dose calculation to ensure accuracy of patient treatment delivery.
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Affiliation(s)
- Palanivelu D
- Department of Physical Sciences, School of Sciences, Arts and Media, Karunya Institute of Technology and Sciences, Coimbatore, Tamilnadu, India
- Department of Radiation Oncology, Fortis Cancer Institute, Fortis Hospital, Mohali, Punjab, India
| | - Khanna D
- Department of Physical Sciences, School of Sciences, Arts and Media, Karunya Institute of Technology and Sciences, Coimbatore, Tamilnadu, India
| | - Mohandass P
- Department of Radiation Oncology, Fortis Cancer Institute, Fortis Hospital, Mohali, Punjab, India
| | - Narandra Kumar Bhalla
- Department of Radiation Oncology, Fortis Cancer Institute, Fortis Hospital, Mohali, Punjab, India
| | - Prabhu R
- Department of Radiation Oncology, Fortis Cancer Institute, Fortis Hospital, Mohali, Punjab, India
| | - Chandru M
- Department of Radiation Oncology, Fortis Cancer Institute, Fortis Hospital, Mohali, Punjab, India
| | - Abhishek Puri
- Department of Radiation Oncology, Fortis Cancer Institute, Fortis Hospital, Mohali, Punjab, India
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Mahur M, Singh M, Gurjar OP, Semwal MK. Assessment of Surface and Build-up Doses for a 6 MV Photon Beam using Parallel Plate Chamber, EBT3 Gafchromic Films, and PRIMO Monte Carlo Simulation Code. J Biomed Phys Eng 2022; 12:455-464. [PMID: 36313413 PMCID: PMC9589075 DOI: 10.31661/jbpe.v0i0.2101-1274] [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: 01/30/2021] [Accepted: 05/25/2021] [Indexed: 11/06/2022]
Abstract
Background: Accurate assessment of surface and build-up doses has a key role in radiotherapy, especially for the superficial lesions with uncertainties involved while performing measurements in the build-up region. Objective: This study aimed to assess surface and build-up doses for 6 MV photon beam from linear accelerator using parallel plate ionization chamber, EBT3 Gafchromic films, and PRIMO Monte Carlo (MC) simulation code. Material and Methods: In this experimental study, parallel plate chamber (PPC05) and EBT3 Gafchromic films were used to measure doses in a build-up region for 6 MV beam from the linear accelerator for different field sizes at various depths ranging from 0 to 2 cm from the surface with 100 cm source to surface distance (SSD) in a solid water phantom. Measured results were compared with Monte Carlo simulated results using PENELOPE-based PRIMO simulation code for the same setup conditions. Effect of gantry angle incidence and SSD were also analyzed for depth doses at the surface and build-up regions using PPC05 ion chamber and EBT3 Gafchromic films. Results: Doses measured at the surface were 14.78%, 19.87%, 25.83%, and 31.54% for field sizes of 5×5, 10×10, 15×15, and 20×20 cm2, respectively for a 6 MV photon beam with a parallel plate chamber and 14.20%, 19.14%, 25.149%, and 30.90%, respectively for EBT3 Gafchromic films. Both measurement sets were in good agreement with corresponding simulated results from the PRIMO MC simulation code; doses increase with the increase in field sizes. Conclusion: Good agreement was observed between the measured depth doses using parallel plate ionization chamber, EBT3 Gafchromic films, and the simulated depth doses using PRIMO Monte Carlo simulation code.
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Affiliation(s)
- Mamta Mahur
- MSc, Department of Radiation Oncology, Delhi State Cancer Institute, Dilshad Garden, Delhi, India
- MSc, Department of Physics, School of Basic Sciences and Research, Sharda University, Greater Noida, Uttar Pradesh, India
| | - Munendra Singh
- PhD, Department of Physics, School of Basic Sciences and Research, Sharda University, Greater Noida, Uttar Pradesh, India
| | - Om Prakash Gurjar
- PhD, Government Cancer Hospital, Mahatma Gandhi Memorial Medical College, Indore-452001, India
| | - Manoj Kumar Semwal
- PhD, Department of Radiation Oncology, Army Hospital (Research & Referral), Delhi Cantonment New Delhi-110010, India
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Zhang Y, Yan S, Cui Z, Wang Y, Li Z, Yin Y, Li B, Quan H, Zhu J. Out-of-field dose assessment for a 1.5 T MR-Linac with optically stimulated luminescence dosimeters. Med Phys 2021; 48:4027-4037. [PMID: 33714229 PMCID: PMC8360091 DOI: 10.1002/mp.14839] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 02/04/2021] [Accepted: 03/04/2021] [Indexed: 11/06/2022] Open
Abstract
PURPOSE To assess the out-of-field surface and internal dose of the 1.5 T MR-Linac compared to the conventional external beam linac using optically stimulated luminescence dosimeters (OSLDs), and evaluate the out-of-field dose calculation accuracy of the Monaco treatment planning system (TPS) of the 1.5T MR-Linac. METHODS A cubic solid water phantom, with OSLDs on the surface, was vertically irradiated by MR-Linac square fields with different sizes. In addition, OSLDs were arranged out of the beam edges in four directions. An anthropomorphic adult phantom, with 125 cm3 simulated volume, was irradiated in four orthogonal directions by both MR-Linac and conventional linac at the head, thoracic, and pelvic sites. Out-of-field doses were measured by OSLDs on both the surface and internal emulational organs at risk (OARs). The results were compared to the simulated dose from Monaco TPS. RESULTS At different field sizes (5 × 5 to 20 × 20 cm2 ) and distances (1 to 10 cm) to beam edge, the out-of-field surface dose measured on MR-Linac varied from 0.16 % (10 cm to 5 × 5 cm2 edge) to 7.02 % (1 cm to 20 × 20 cm2 edge) of the maximum dose laterally and from 0.14 % (10 cm to 5 × 5 cm2 edge) to 8.56 % (1 cm to 20 × 20 cm2 edge) of the maximum dose longitudinally. Compared to the OSLDs measured data, the Monaco TPS presented an overestimate of the out-of-field dose of OARs at 0-2 % isodose area on both surface and internal check points, and the overestimation gets greater as the distance increases. The underestimation was found to be 0-35% at 2-5% isodose area on both surface and internal check points. Compared to the conventional linac, MR-Linac delivered higher average values of out-of-field dose on surface check points (20%, 19%, 21%) and internal simulated OARs (42%, 37%, 9%) of the anthropomorphic phantom at head, thoracic, and pelvic irradiations, respectively. CONCLUSIONS Compared to the conventional linac, MR-Linac has the same out-of-field dose distribution. However, considering the absolute dose values, MR-Linac delivered relatively higher out-of-field doses on both surface and internal OARs. Additional radiation shielding to patients undergoing MR-Linac may provide protection from out-of-field exposure.
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Affiliation(s)
- Yan Zhang
- School of Physics and Technology, Wuhan University, Wuhan, P.R. China.,Department of Radiation Oncology Physics and Technology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, P.R. China
| | - Shaojie Yan
- Department of Radiation Oncology Physics and Technology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, P.R. China.,School of Nuclear Science and Technology, University of South China, Hengyang, P.R. China
| | - Zhen Cui
- Department of Radiation Oncology Physics and Technology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, P.R. China
| | - Yungang Wang
- Department of Radiation Oncology Physics and Technology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, P.R. China
| | - Zhenjiang Li
- Department of Radiation Oncology Physics and Technology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, P.R. China
| | - Yong Yin
- Department of Radiation Oncology Physics and Technology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, P.R. China
| | - Baosheng Li
- Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, P.R. China
| | - Hong Quan
- School of Physics and Technology, Wuhan University, Wuhan, P.R. China
| | - Jian Zhu
- Department of Radiation Oncology Physics and Technology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, P.R. China.,Shandong Medical Imaging and Radiotherapy Engineering Center, Jinan, P.R. China.,Shandong Key Laboratory of Digital Medicine and Computer Assisted Surgery, The Affiliated Hospital of Qingdao University, Qingdao, P.R. China
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Rani AR, Ayyangar K, Reddy AR, Kumar AA, Reddy PRY. Estimation of Skin doses for Retrofit Prototype Multileaf Collimators Designed for Telecobalt Therapy Machine. J Med Phys 2021; 45:215-220. [PMID: 33953496 PMCID: PMC8074722 DOI: 10.4103/jmp.jmp_25_20] [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: 04/09/2020] [Revised: 10/12/2020] [Accepted: 10/13/2020] [Indexed: 11/04/2022] Open
Abstract
Aim The objective of this study was to evaluate skin dose based on retrofit prototype multileaf collimators (MLCs), designed for cobalt-60 teletherapy machine. Since patient's skin is sensitive to radiation, evaluation of skin dose is of utmost importance for investigating the risk of late effects. Materials and Methods Measurements were performed with a Phoenix cobalt-60 teletherapy machine and the detector used was EBT3 radiochromic film. The experiments were performed in a solid water phantom with two prototype MLCs mounted to the machine. Dose readings were taken by placing the films at source-to-surface distance (SSD) of 60 cm, 65 cm, 70 cm, 75 cm, 80 cm, 85 cm, and 90 cm for various MLC-generated field sizes starting from 2 cm × 2 cm to 14 cm × 14 cm. The films were analyzed using custom made programs. The measured doses were normalized to the dose at dmax for that particular measurement of SSD. Results The skin dose is expressed as a percentage of dose at dose maximum. In general, the skin dose increases with field size and decreases with SSD. The measurements indicate surface doses within 20%-60% for the investigated SSD range. Furthermore, there is no significant difference between the surface doses of two prototype MLCs studied. Conclusions From the measurements, it can be concluded that there is good skin sparing even at close distance to the MLCs. The skin dose is <50% for SSDs >65 cm. A minimum gap of 5 cm is required to produce acceptable skin dose.
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Affiliation(s)
- Akula Roopa Rani
- Department of Physics, Osmania University, Hyderabad, Telangana, India.,Department of Radiation Oncology, MNJ Institute of Oncology and Regional Cancer Center, Hyderabad, Telangana, India.,Department of Radiation Oncology, International Cancer Centre, MGMMT, Bhimavaram, Andhra Pradesh, India
| | - Komanduri Ayyangar
- Department of Radiation Oncology, International Cancer Centre, MGMMT, Bhimavaram, Andhra Pradesh, India
| | - A R Reddy
- Department of Radiation Oncology, International Cancer Centre, MGMMT, Bhimavaram, Andhra Pradesh, India
| | - Ayyalasomayajula Anil Kumar
- Department of Radiation Oncology, Mahatma Gandhi Cancer Hospital and Research Institute, Visakhapatnam, Andhra Pradesh, India
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Wong G, Lam E, Bosnic S, Karam I, Drost L, Yee C, Ariello K, Chow E, Wronski M. Quantitative Effect of Bolus on Skin Dose in Postmastectomy Radiation Therapy. J Med Imaging Radiat Sci 2020; 51:462-469. [PMID: 32646668 DOI: 10.1016/j.jmir.2020.06.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 06/05/2020] [Accepted: 06/08/2020] [Indexed: 11/27/2022]
Abstract
BACKGROUND In postmastectomy radiation therapy (PMRT), some centres prescribe the use of a tissue-equivalent bolus to the skin to reduce the risk of chest wall recurrence. The addition of bolus causes an increase in the skin dose, which may lead to increased risk of radiodermatitis. Radiodermatitis can decrease patients' overall quality of life, bringing into question the benefit of using the bolus. The purpose of this retrospective chart review was to quantify the increase in skin dose associated with the use of bolus in the PMRT setting. MATERIALS AND METHODS We evaluated 70 patients who underwent PMRT at our institution during 2012-2018. Two similar treatment plans were generated for each patient: one with bolus and one without. Skin dose-volume histogram values were evaluated, and statistical analysis was performed using MATLAB R2015b. RESULTS There was no significant difference in the maximum skin dose within a depth of 5 mm for bolus versus nonbolus plans (P = 0.4). However, within a depth of 3 mm, bolus plans had a maximum skin dose 7% ± 2.5% higher than the nonbolus plans (P < .00001). Mean skin dose within depths of 3 and 5 mm were both significantly higher (P < .00001) for bolus plans. The photon beam energy and chest wall separation showed minimal or no effect on skin dose. CONCLUSION Given the differing opinions in the literature regarding the role for bolus in PMRT, there is still uncertainty of the optimal treatment method. This retrospective study demonstrates a 20%-30% reduction in mean skin dose when bolus is not used.
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Affiliation(s)
- Gina Wong
- Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Emily Lam
- Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Sandi Bosnic
- Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Irene Karam
- Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Leah Drost
- Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Caitlin Yee
- Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Krista Ariello
- Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Edward Chow
- Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
| | - Matt Wronski
- Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
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Tuğrul T. Absorption ratio of treatment couch and effect on surface and build-up region doses. Rep Pract Oncol Radiother 2017; 23:1-5. [PMID: 29187806 DOI: 10.1016/j.rpor.2017.10.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 10/29/2017] [Indexed: 10/18/2022] Open
Abstract
Aim In this study, at different fields, energies and gantry angles, treatment couch and rails dose absorption ratio and treatment couch effect on surface and build-up region doses were examined. Background It is assumed that radiation attenuation is minimal because the carbon fiber couches have low density and it is not generally accounted for during treatment planning. Consequently, it leads to a major dosimetric mistake. Materials and methods Solid water phantom was used for relative dose measurement. The measurements were done using a Farmer ion chamber with 0.6 cc volume and a parallel plane ion chamber starting from surface with 1 mm depth intervals at 10 × 10 cm2 field, SSD 100 cm. Measurements were taken for situations where the beams intersect the couch and couch rails. Results Dose absorption ratio of carbon fiber couch obtained at gantry angle of 180° was 1.52%, 0.69%, 0.33% and 0.25% at different field sizes for 6 MV. For 15 MV, this ratio was 0.95%, 0.27%, 0.20% and 0.05%. The absorption ratio is between 3.4% and 1.22% when the beams intersect with couch rails. The couch effect increased surface dose from 14% to 70% for 6 MV and from 11.34% to 53.03% for 15 MV. Conclusions The results showed that the carbon fiber couch increased surface dose during posterior irradiation. Therefore, the skin-sparing effect of the high energy beams was decreased. If the effect of couch is not considered, it may cause significant differences at dose which reaches the patient and may cause tissue problems such as erythema.
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Affiliation(s)
- Taylan Tuğrul
- Radiation Oncology Department, Yüzüncü Yıl University, Van, Turkey
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Characterization of a new transmission detector for patient individualized online plan verification and its influence on 6MV X-ray beam characteristics. Z Med Phys 2015; 26:200-8. [PMID: 26303190 DOI: 10.1016/j.zemedi.2015.08.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 08/03/2015] [Accepted: 08/03/2015] [Indexed: 11/21/2022]
Abstract
PURPOSE Online verification and 3D dose reconstruction on daily patient anatomy have the potential to improve treatment delivery, accuracy and safety. One possible implementation is to recalculate dose based on online fluence measurements with a transmission detector (TD) attached to the linac. This study provides a detailed analysis of the influence of a new TD on treatment beam characteristics. METHODS The influence of the new TD on surface dose was evaluated by measurements with an Advanced Markus Chamber (Adv-MC) in the build-up region. Based on Monte Carlo simulations, correction factors were determined to scale down the over-response of the Adv-MC close to the surface. To analyze the effects beyond dmax percentage depth dose (PDD), lateral profiles and transmission measurements were performed. All measurements were carried out for various field sizes and different SSDs. Additionally, 5 IMRT-plans (head & neck, prostate, thorax) and 2 manually created test cases (3×3cm(2) fields with different dose levels, sweeping gap) were measured to investigate the influence of the TD on clinical treatment plans. To investigate the performance of the TD, dose linearity as well as dose rate dependency measurements were performed. RESULTS With the TD inside the beam an increase in surface dose was observed depending on SSD and field size (maximum of +11%, SSD = 80cm, field size = 30×30cm(2)). Beyond dmax the influence of the TD on PDDs was below 1%. The measurements showed that the transmission factor depends slightly on the field size (0.893-0.921 for 5×5cm(2) to 30×30cm(2)). However, the evaluation of clinical IMRT-plans measured with and without the TD showed good agreement after using a single transmission factor (γ(2%/2mm) > 97%, δ±3% >95%). Furthermore, the response of TD was found to be linear and dose rate independent (maximum difference <0.5% compared to reference measurements). CONCLUSIONS When placed in the path of the beam, the TD introduced a slight, clinically acceptable increase of the skin dose even for larger field sizes and smaller SSDs and the influence of the detector on the dose beyond dmax as well as on clinical IMRT-plans was negligible. Since there was no dose rate dependency and the response was linear, the device is therefore suitable for clinical use. Only its absorption has to be compensated during treatment planning, either by the use of a single transmission factor or by including the TD in the incident beam model.
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Jong WL, Wong JHD, Ung NM, Ng KH, Ho GF, Cutajar DL, Rosenfeld AB. Characterization of MOSkin detector for in vivo skin dose measurement during megavoltage radiotherapy. J Appl Clin Med Phys 2014; 15:4869. [PMID: 25207573 PMCID: PMC5711095 DOI: 10.1120/jacmp.v15i5.4869] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2013] [Revised: 05/19/2014] [Accepted: 05/14/2014] [Indexed: 11/25/2022] Open
Abstract
In vivo dosimetry is important during radiotherapy to ensure the accuracy of the dose delivered to the treatment volume. A dosimeter should be characterized based on its application before it is used for in vivo dosimetry. In this study, we characterize a new MOSFET‐based detector, the MOSkin detector, on surface for in vivo skin dosimetry. The advantages of the MOSkin detector are its water equivalent depth of measurement of 0.07 mm, small physical size with submicron dosimetric volume, and the ability to provide real‐time readout. A MOSkin detector was calibrated and the reproducibility, linearity, and response over a large dose range to different threshold voltages were determined. Surface dose on solid water phantom was measured using MOSkin detector and compared with Markus ionization chamber and GAFCHROMIC EBT2 film measurements. Dependence in the response of the MOSkin detector on the surface of solid water phantom was also tested for different (i) source to surface distances (SSDs); (ii) field sizes; (iii) surface dose; (iv) radiation incident angles; and (v) wedges. The MOSkin detector showed excellent reproducibility and linearity for dose range of 50 cGy to 300 cGy. The MOSkin detector showed reliable response to different SSDs, field sizes, surface, radiation incident angles, and wedges. The MOSkin detector is suitable for in vivo skin dosimetry. PACS number: 87.55.Qr
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Affiliation(s)
- Wei Loong Jong
- Clinical Oncology Unit, Faculty of Medicine, University of Malaya.
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Zhang R, Glaser AK, Gladstone DJ, Fox CJ, Pogue BW. Superficial dosimetry imaging based on Čerenkov emission for external beam radiotherapy with megavoltage x-ray beam. Med Phys 2014; 40:101914. [PMID: 24089916 DOI: 10.1118/1.4821543] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
PURPOSE Čerenkov radiation emission occurs in all tissue, when charged particles (either primary or secondary) travel at velocity above the threshold for the Čerenkov effect (about 220 KeV in tissue for electrons). This study presents the first examination of optical Čerenkov emission as a surrogate for the absorbed superficial dose for MV x-ray beams. METHODS In this study, Monte Carlo simulations of flat and curved surfaces were studied to analyze the energy spectra of charged particles produced in different regions near the surfaces when irradiated by MV x-ray beams. Čerenkov emission intensity and radiation dose were directly simulated in voxelized flat and cylindrical phantoms. The sampling region of superficial dosimetry based on Čerenkov radiation was simulated in layered skin models. Angular distributions of optical emission from the surfaces were investigated. Tissue mimicking phantoms with flat and curved surfaces were imaged with a time domain gating system. The beam field sizes (50 × 50-200 × 200 mm(2)), incident angles (0°-70°) and imaging regions were all varied. RESULTS The entrance or exit region of the tissue has nearly homogeneous energy spectra across the beam, such that their Čerenkov emission is proportional to dose. Directly simulated local intensity of Čerenkov and radiation dose in voxelized flat and cylindrical phantoms further validate that this signal is proportional to radiation dose with absolute average discrepancy within 2%, and the largest within 5% typically at the beam edges. The effective sampling depth could be tuned from near 0 up to 6 mm by spectral filtering. The angular profiles near the theoretical Lambertian emission distribution for a perfect diffusive medium, suggesting that angular correction of Čerenkov images may not be required even for curved surface. The acquisition speed and signal to noise ratio of the time domain gating system were investigated for different acquisition procedures, and the results show there is good potential for real-time superficial dose monitoring. Dose imaging under normal ambient room lighting was validated, using gated detection and a breast phantom. CONCLUSIONS This study indicates that Čerenkov emission imaging might provide a valuable way to superficial dosimetry imaging in real time for external beam radiotherapy with megavoltage x-ray beams.
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Affiliation(s)
- Rongxiao Zhang
- Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755 and Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755
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Zhang R, Fox CJ, Glaser AK, Gladstone DJ, Pogue BW. Superficial dosimetry imaging of Čerenkov emission in electron beam radiotherapy of phantoms. Phys Med Biol 2013; 58:5477-93. [PMID: 23880473 DOI: 10.1088/0031-9155/58/16/5477] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Čerenkov emission is generated from ionizing radiation in tissue above 264 keV energy. This study presents the first examination of this optical emission as a surrogate for the absorbed superficial dose. Čerenkov emission was imaged from the surface of flat tissue phantoms irradiated with electrons, using a range of field sizes from 6 cm × 6 cm to 20 cm × 20 cm, incident angles from 0° to 50°, and energies from 6 to 18 MeV. The Čerenkov images were compared with the estimated superficial dose in phantoms from direct diode measurements, as well as calculations by Monte Carlo and the treatment planning system. Intensity images showed outstanding linear agreement (R(2) = 0.97) with reference data of the known dose for energies from 6 to 18 MeV. When orthogonal delivery was carried out, the in-plane and cross-plane dose distribution comparisons indicated very little difference (± 2-4% differences) between the different methods of estimation as compared to Čerenkov light imaging. For an incident angle 50°, the Čerenkov images and Monte Carlo simulation show excellent agreement with the diode data, but the treatment planning system had a larger error (OPT = ± 1~2%, diode = ± 2~3%, TPS = ± 6-8% differences) as would be expected. The sampling depth of superficial dosimetry based on Čerenkov radiation has been simulated in a layered skin model, showing the potential of sampling depth tuning by spectral filtering. Taken together, these measurements and simulations indicate that Čerenkov emission imaging might provide a valuable method of superficial dosimetry imaging from incident radiotherapy beams of electrons.
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Affiliation(s)
- Rongxiao Zhang
- Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755, USA. Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA.
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Practical considerations for reporting surface dose in external beam radiotherapy: a 6 MV X-ray beam study. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2012; 35:271-82. [DOI: 10.1007/s13246-012-0145-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Accepted: 05/28/2012] [Indexed: 11/25/2022]
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