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Peters I, Nelson V, Deshpande S, Walker A, Hiatt J, Roach D, Erven T, Rajapakse S, Gray A. The assessment of the clinical impact of using a single set of radiotherapy planning data for two kilovoltage therapy units. Phys Eng Sci Med 2024; 47:49-59. [PMID: 37843767 DOI: 10.1007/s13246-023-01339-z] [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: 12/19/2022] [Accepted: 09/14/2023] [Indexed: 10/17/2023]
Abstract
Kilovoltage therapy units are used for superficial radiotherapy treatment delivery. Peer reviewed studies for MV linear accelerators describe tolerances to dosimetrically match multiple linear accelerators enabling patient treatment on any matched machine. There is an absence of literature on using a single planning data set for multiple kilovoltage units which have limited ability for beam adjustment. This study reviewed kilovoltage dosimetry and treatment planning scenarios to evaluate the feasibility of using ACPSEM annual QA tolerances to determine whether two units (of the same make and model) were dosimetrically matched. The dosimetric characteristics, such as measured half value layer (HVL), percentage depth dose (PDD), applicator factor and output variation with stand-off distance for each kV unit were compared to assess the agreement. Independent planning data based on the measured HVL for each beam energy from each kV unit was prepared. Monitor unit (MU) calculations were performed using both sets of planning data for approximately 200 clinical scenarios and compared with an overall agreement between units of < 2%. Additionally, a dosimetry measurement comparison was completed at each site for a subset of nine scenarios. All machine characterisation measurements were within the ACPSEM Annual QA tolerances, and dosimetric testing was within 2.5%. This work demonstrates that using a single set of planning data for two kilovoltage units is feasible, resulting in a clinical impact within published uncertainty.
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Affiliation(s)
- Iliana Peters
- South Western Sydney Local Health District, Liverpool and Macarthur Cancer Therapy Centres, Sydney, NSW, Australia.
| | - Vinod Nelson
- South Western Sydney Local Health District, Liverpool and Macarthur Cancer Therapy Centres, Sydney, NSW, Australia
| | - Shrikant Deshpande
- South Western Sydney Local Health District, Liverpool and Macarthur Cancer Therapy Centres, Sydney, NSW, Australia
- Ingham Institute for Applied Medical Research, Liverpool, NSW, Australia
- South West Sydney Clinical School, School of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Amy Walker
- South Western Sydney Local Health District, Liverpool and Macarthur Cancer Therapy Centres, Sydney, NSW, Australia
- Ingham Institute for Applied Medical Research, Liverpool, NSW, Australia
- South West Sydney Clinical School, School of Medicine, University of New South Wales, Sydney, NSW, Australia
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia
| | - Joshua Hiatt
- South Western Sydney Local Health District, Liverpool and Macarthur Cancer Therapy Centres, Sydney, NSW, Australia
| | - Dale Roach
- South Western Sydney Local Health District, Liverpool and Macarthur Cancer Therapy Centres, Sydney, NSW, Australia
| | - Tania Erven
- South Western Sydney Local Health District, Liverpool and Macarthur Cancer Therapy Centres, Sydney, NSW, Australia
| | - Satya Rajapakse
- South Western Sydney Local Health District, Liverpool and Macarthur Cancer Therapy Centres, Sydney, NSW, Australia
| | - Alison Gray
- South Western Sydney Local Health District, Liverpool and Macarthur Cancer Therapy Centres, Sydney, NSW, Australia
- Ingham Institute for Applied Medical Research, Liverpool, NSW, Australia
- South West Sydney Clinical School, School of Medicine, University of New South Wales, Sydney, NSW, Australia
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Robatjazi M, Dareyni A, Baghani HR, Hosseinzade M, Akbarzadeh R, Mehrpoyan M. Investigation of radiation dose around C-arm fluoroscopy and relevant cancer risk to operating room staff. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2022; 61:301-307. [PMID: 35171318 DOI: 10.1007/s00411-022-00965-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 01/29/2022] [Indexed: 06/14/2023]
Abstract
This study aimed to evaluate the ambient dose equivalent around a C-arm device during spinal surgeries and determine the optimum locations for the surgeon and staff to keep radiation exposure as low as reasonably achievable. Furthermore, cancer risk incidence was estimated using the excess relative risk (ERR) concept of the biologic effects of ionizing radiation VII report for operating room (OR) staff. A lateral projection of the C-arm setup was considered in the current study. The ambient dose equivalent rate was measured using an electronic dosimeter in 30° steps all around for 1, and 1.6-m heights as well as 1, and 2-m distances away from a water tank (scattering medium). By assuming a typical workload, the annual ambient dose and a maximum number of permissible operations were determined. For a worst-case scenario, the dose was used to estimate the ERR for various organs including prostate, ovary, breast, lung, thyroid, and colon for attained ages of 35, 40, and 50 years. The maximum ambient dose equivalent rate was seen at 330° and 30° (about 600 µSv/h at 1 m height and a distance of 1 m from the scattering medium). The corresponding permissible workload for an OR staff was about 30,660 operations. Based on the obtained results, 60° next to the image intensifier was the optimum position for the surgeon, while 30° next to the tube was the worst position because of backscattered radiation. The ERR results showed that the lung and colon have the highest cancer risk incidence among the considered organs for both males and females, respectively.
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Affiliation(s)
- Mostafa Robatjazi
- Department of Medical Physics and Radiological Sciences, Sabzevar University of Medical Sciences, Sabzevar, Iran
- Non-communicable Disease Research Center, Sabzevar University of Medical Sciences, Sabzevar, Iran
| | - Amir Dareyni
- Department of Medical Physics and Radiological Sciences, Sabzevar University of Medical Sciences, Sabzevar, Iran
| | | | - Mohammad Hosseinzade
- Department of Operating Room, Sabzevar University of Medical Sciences, Sabzevar, Iran
| | - Roya Akbarzadeh
- Department of Anesthesia, Sabzevar University of Medical Sciences, Sabzevar, Iran
| | - Mohammad Mehrpoyan
- Department of Medical Physics and Radiological Sciences, Sabzevar University of Medical Sciences, Sabzevar, Iran
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Lim TY, Mirkovic D, Wang X, Tailor R. Devices for dosimetric measurements and quality assurance of the Xstrahl 300 orthovoltage unit. J Appl Clin Med Phys 2021; 22:151-157. [PMID: 33733608 PMCID: PMC8035565 DOI: 10.1002/acm2.13220] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 02/05/2021] [Accepted: 02/15/2021] [Indexed: 02/02/2023] Open
Abstract
The Xstrahl 300 orthovoltage unit is designed to deliver kilovoltage radiation therapy using the appositional technique. However, it is not equipped with some typical linear accelerator features, such as mechanical distance indicator and crosshair projection, which are useful for facilitating equipment setup during various quality assurance (QA) and research activities. Therefore, we designed and constructed slip‐in devices to facilitate QA for dosimetric measurements of our Xstrahl 300 unit. These include: (a) an ion chamber positioning system for dosimetric measurements, (b) a mechanical pointer for setting dosimeter distance to a nominal 50 cm, and (c) a crosshair projector with built‐in light to facilitate alignment of dosimeter to the center of the radiation field. These devices provide a high degree of setup reproducibility thereby minimizing setup errors. We used these devices to perform QA of the Xstrahl 300 orthovoltage unit. One of the QA tests we perform is a constancy check of beam output and energy. Our data since start of clinical use of this unit (approximately 2.5 yr) show dose outputs to be remarkably reproducible (2σ = ±0.4%) for all three clinical beams (75, 125, and 250 kVp). These devices have provided both convenience and high‐precision during the unit’s commissioning, and continue to provide the same for various QA activities on the Xstrahl 300 orthovoltage unit.
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Affiliation(s)
- Tze Yee Lim
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Dragan Mirkovic
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Xin Wang
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Ramesh Tailor
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
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4
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Joubert MM, van Eeden D, du Plessis FCP. The relation between XR-QA2 and RT-QA2 Gafchromic TMfilm optical density and absorbed dose in water produced by radionuclides. Biomed Phys Eng Express 2021; 7. [PMID: 33601352 DOI: 10.1088/2057-1976/abe7c3] [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: 08/20/2020] [Accepted: 02/18/2021] [Indexed: 11/12/2022]
Abstract
Purpose. In this study, Monte Carlo (MC) simulations were done to relate the dose-response of the film to that in water. The effect of backscattering materials (PMMA, lead, polystyrene, and air) was investigated on its influence on film density for radionuclides including Am-241, Tc-99m, I-131, Cs-137.Methods. A BEAMnrc MC simulation was designed to score a phase-space file (PSF) below the container of the radionuclide under consideration to use as an input file for the subsequent DOSXYZnrc MC simulation. The geometry of the container holding the radionuclide was built using the component modules available in BEAMnrc. BEAMDP was used to investigate the container effect on the radionuclide spectrum as well as the fluence. The DOSXYZnrc simulation produced the absorbed dose in XR-QA2 and RT-QA2 GafchromicTMfilms. The DOSXYZnrc simulations were repeated for the GafchromicTMfilm now replaced with water to get the absorbed dose in water. From these results, conversion factors for the dose in water to the film dose for the different radionuclides, Am-241, Tc-99m, I-131, and Cs-137 were obtained. The actual film dose was calculated using the specific gamma exposure constant (Γ) at a distance of 50 cm for a point source approximation. From the BEAMnrc simulations, the particle fluence was extracted from PSFs to correct for the fluence at 0.1 cm below the sources from the fluence 50 cm away since the inverse square law will not apply to finite-size sources. The absorbed dose profiles in the film were compared to the absorbed dose profiles from the MC simulations.Results. A fitting function based on the neutron depletion model fits the optical density versus absorbed film dose data well and can be used as a calibration tool to obtain the film dose from its optical density. Lead as a backscatter material results in a higher optical density change but a lower absorbed dose. The XR-QA2 GafchromicTMfilm is more sensitive than the RT-QA2 GafchromicTMfilm, showing a more responsive optical density (OD) change in the energy range of radionuclides used in this study. Conversion factors were determined to convert the dose in water to the dose in GafchromicTMfilm. The Am-241 and I-131 simulated absorbed dose in the film to dose in water does not fluctuate as much as the simulated absorbed dose in film and water when using Tc-99m and Cs-137. Validation was shown for the comparison of the film and MC simulation absorbed dose profiles.Conclusions. MC BEAMnrc simulations are useful to simulate radionuclides and their containers. BEAMDP extracted energy spectra showed that the radionuclide containers produced a Compton effect on the energy spectra and added filtration on the lower spectral photon components. Extracted fluence ratios from PSFs were used to calculate the absorbed dose value at 0.1 cm distance from the source. By using the fit function, the dose in the film can be determined for known optical density values. The effect of the backscatter materials showed that the XR-QA2 GafchromicTMfilm results in higher optical density values than the RT-QA2 GafchromicTMfilm. The absorbed dose in both the films is comparable but not for a radionuclide such as Am-241 with an activity of 74MBq. The lead backscatter material showed to be the most prominent in optical density enhancement, and the air equivalent material was the least prominent. The XR-QA2 GafchromicTMfilm is the most sensitive and will be the best option if working with low energies. The absorbed dose in the XR-QA2 GafchromicTMfilm also showed a good comparison to the absorbed dose in water for the Am-241 radionuclide with an activity of 74MBq. The absorbed dose in the films compares well to the MC simulated doses.
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Affiliation(s)
- Maria M Joubert
- Department of Medical Physics, University of the Free State, Bloemfontein 9301, South Africa
| | - Déte van Eeden
- Department of Medical Physics, University of the Free State, Bloemfontein 9301, South Africa
| | - Freek C P du Plessis
- Department of Medical Physics, University of the Free State, Bloemfontein 9301, South Africa
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Pearse J, Chow JCL. An Internet of Things app for monitor unit calculation in superficial and orthovoltage skin therapy. IOP SCINOTES 2020. [DOI: 10.1088/2633-1357/ab8be0] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Abstract
Purpose: We developed an app for Internet of Things (IoT) device such as smartphone or tablet to calculate the monitor unit in superficial and orthovoltage skin therapy. The app can run both on the Windows and Android operation system. Methods: The IoT app was created based on the formula to calculate the monitor unit in skin therapy using kV photon beams. The calculation was based on databases of dose variables such as relative exposure factor and backscatter factor. The calculation also considered the stand-off and stand-in correction according to the inverse-square and inverse-cube law. Verification of the app was carried out by comparing the monitor unit results with those from hand calculations. Results: The frontend window of the app provided a user-friendly interface to the user for inputting prescription dose, beam and treatment setup variables. The user could save the calculation record electronically, generate a printout or send it to other radiation staff using the IoT. Verification of the app showing that deviation between the monitor units calculated by the app and by hand is insignificant. Conclusion: The verified IoT app can effectively calculate the monitor unit in superficial and orthovoltage skin therapy. The app takes advantages of all innate features of IoT such as real time communication, Internet access, data transfer and sharing.
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Davey K, Moore M, Cleary S, Kleefeld C, Foley MJ. Off-axis dose distribution with stand-in and stand-off configurations for superficial radiotherapy treatments. J Appl Clin Med Phys 2019; 20:142-151. [PMID: 31605464 PMCID: PMC6806473 DOI: 10.1002/acm2.12730] [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: 11/27/2018] [Revised: 08/07/2019] [Accepted: 09/03/2019] [Indexed: 11/10/2022] Open
Abstract
Current practice when delivering dose for superficial skin radiotherapy is to adjust the monitor units so that the prescribed dose is delivered to the central axis of the superficial unit applicator. Variations of source‐to‐surface distance due to patient’s anatomy protruding into the applicator or extending away from the applicator require adjustments to the monitor units using the inverse square law. Off‐axis dose distribution varies significantly from the central axis dose and is not currently being quantified. The dose falloff at the periphery of the field is not symmetrical in the anode–cathode axis due to the heel effect. This study was conducted to quantify the variation of dose across the surface being treated and model a simple geometric shape to estimate a patient’s surface with stand‐in and stand‐off. Isodose plots and color‐coded dose distribution maps were produced from scans of GAFChromic EBT‐3 film irradiated by a Gulmay D3300 orthovoltage x‐ray therapy system. It was clear that larger applicators show a greater dose falloff toward the periphery than smaller applicators. Larger applicators were found to have a lower percentage of points above 90% of central axis dose (SA90). Current clinical practice does not take this field variation into account. Stand‐in can result in significant dose falloff off‐axis depending on the depth and width of the protrusion, while stand‐off can result in a flatter field due to the high‐dose region near the central axis being further from the source than the peripheral regions. The central axis also received a 7% increased or decreased dose for stand‐in or stand‐off, respectively.
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Affiliation(s)
- Keith Davey
- School of Physics, National University of Ireland Galway, Galway, Ireland
| | - Margaret Moore
- Radiotherapy Department, University Hospital Galway, Galway, Ireland
| | - Sinéad Cleary
- Radiotherapy Department, University Hospital Galway, Galway, Ireland
| | - Christoph Kleefeld
- School of Physics, National University of Ireland Galway, Galway, Ireland.,Radiotherapy Department, University Hospital Galway, Galway, Ireland
| | - Mark J Foley
- School of Physics, National University of Ireland Galway, Galway, Ireland
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Poirier Y, Johnstone CD, Kirkby C. The potential impact of ultrathin filter design on dosimetry and relative biological effectiveness in modern image-guided small animal irradiators. Br J Radiol 2018; 92:20180537. [PMID: 30281330 DOI: 10.1259/bjr.20180537] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVE: Modern image-guided small animal irradiators like the Xstrahl Small Animal Radiation Research Platform (SARRP) are designed with ultrathin 0.15 mm Cu filters, which compared with more heavily filtrated traditional cabinet-style biological irradiators, produce X-ray spectra weighted toward lower energies, impacting the dosimetric properties and the relative biological effectiveness (RBE). This study quantifies the effect of ultrathin filter design on relative depth dose profiles, absolute dose output, and RBE using Monte Carlo techniques. METHODS: The percent depth-dose and absolute dose output are calculated using kVDoseCalc and EGSnrc, respectively, while a tally based on the induction of double-strand breaks as a function of electron spectra invoked in PENELOPE is used to estimate the RBE. RESULTS: The RBE increases by >2.4% in the ultrathin filter design compared to a traditional irradiator. Furthermore, minute variations in filter thickness have notable effects on the dosimetric properties of the X-ray beam, increasing the percent depth dose (at 2 cm in water) by + 0.4%/0.01 mm Cu and decreasing absolute dose (at 2 cm depth in water) by -1.8%/0.01 mm Cu for the SARRP. CONCLUSIONS: These results show that modern image-guided irradiators are quite sensitive to small manufacturing variations in filter thickness, and show a small change in RBE compared to traditional X-ray irradiators. ADVANCES IN KNOWLEDGE: We quantify the consequences of ultrathin filter design in modern image-guided biological irradiators on relative and absolute dose, and RBE. Our results show these to be small, but not insignificant, suggesting laboratories transitioning between irradiators should carefully design their radiobiological experiments.
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Affiliation(s)
- Yannick Poirier
- 1 Department of Radiation Oncology, Division of Translational Radiation Sciences, University of Maryland School of Medicine , Baltimore, MD , USA.,2 Department of Radiation Oncology, Division of Medical Physics, University of Maryland School of Medicine , Baltimore, MD , USA
| | - Christopher Daniel Johnstone
- 1 Department of Radiation Oncology, Division of Translational Radiation Sciences, University of Maryland School of Medicine , Baltimore, MD , USA.,3 Department of Physics and Astronomy, University of Victoria , Victoria, BC , Canada
| | - Charles Kirkby
- 4 Department of Medical Physics, Jack Ady Cancer Center , Lethbridge, AB , Canada.,5 Department of Physics and Astronomy, University of Calgary , Calgary, AB , Canada.,6 Department of Oncology, University of Calgary , Calgary, AB , Canada
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Martell K, Poirier Y, Zhang T, Hudson A, Spencer D, Jacso F, Hayashi R, Banerjee R, Khan R, Wolfe N, Voroney JP. Radiation therapy for deep periocular cancer treatments when protons are unavailable: is combining electrons and orthovoltage therapy beneficial? JOURNAL OF RADIATION RESEARCH 2018; 59:593-603. [PMID: 30053071 PMCID: PMC6151628 DOI: 10.1093/jrr/rry045] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2017] [Revised: 01/31/2018] [Indexed: 06/08/2023]
Abstract
Deep periocular cancers can be difficult to plan and treat with radiation, given the difficulties in apposing bolus to skin, and the proximity to the retina and other optic structures. We sought to compare the combination of electrons and orthovoltage therapy (OBE) with existing modalities for these lesions. Four cases-a retro-orbital melanoma (Case 1) and basal cell carcinomas, extending across the eyelid (Case 2) or along the medial canthus (Cases 3-4)-were selected for comparison. In each case, radiotherapy plans for electron only, 70% electron and 30% orthovoltage (OBE), volumetric-modulated arc therapy (VMAT), conformal arc, and protons were compared. Dose-volume histograms for planning target volume coverage and selected organs at risk (OARs) were then calculated. The V90% coverage of the planning target volume was >98% for electrons, VMAT, conformal arc and proton plans and 90.2% and 89.5% in OBE plans for Cases 2 and 3, respectively. The retinal V80% was >98% in electron, VMAT and proton plans and 79.4%; and 87.1% in OBE and conformal arcs for Case 2 and 91.3%, 36.4%, 56.9%, 52.4% and 43.7% for Case 3 in electrons, OBE, VMAT, conformal arc and proton plans, respectively. Protons provided superior coverage, homogeneity and OAR sparing, compared with all other modalities. However, given its simplicity and widespread availability, OBE is a potential alternative treatment option for moderately deep lesions where bolus placement is difficult.
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Affiliation(s)
- Kevin Martell
- Department of Oncology, University of Calgary, Tom Baker Cancer Centre 1331 29 Street Northwest, Calgary, Alberta, Canada
- Calgary Zone, Alberta Health Services, Foothills Medical Centre, 1331-29 ST NW, Calgary, Alberta, Canada
| | - Yannick Poirier
- Department of Radiation Oncology, University of Maryland, 22 S Greene St, Baltimore, MD, USA
| | - Tiezhi Zhang
- Department of Radiation Oncology, Washington University in St. Louis, 660 S. Euclid Ave., CB, St. Louis, MO, USA
| | - Alana Hudson
- Department of Oncology, University of Calgary, Tom Baker Cancer Centre 1331 29 Street Northwest, Calgary, Alberta, Canada
- Calgary Zone, Alberta Health Services, Foothills Medical Centre, 1331-29 ST NW, Calgary, Alberta, Canada
| | - David Spencer
- Department of Oncology, University of Calgary, Tom Baker Cancer Centre 1331 29 Street Northwest, Calgary, Alberta, Canada
- Calgary Zone, Alberta Health Services, Foothills Medical Centre, 1331-29 ST NW, Calgary, Alberta, Canada
| | - Ferenc Jacso
- Department of Oncology, University of Calgary, Tom Baker Cancer Centre 1331 29 Street Northwest, Calgary, Alberta, Canada
- Calgary Zone, Alberta Health Services, Foothills Medical Centre, 1331-29 ST NW, Calgary, Alberta, Canada
| | - Richard Hayashi
- Calgary Zone, Alberta Health Services, Foothills Medical Centre, 1331-29 ST NW, Calgary, Alberta, Canada
| | - Robyn Banerjee
- Department of Oncology, University of Calgary, Tom Baker Cancer Centre 1331 29 Street Northwest, Calgary, Alberta, Canada
- Calgary Zone, Alberta Health Services, Foothills Medical Centre, 1331-29 ST NW, Calgary, Alberta, Canada
| | - Rao Khan
- Department of Radiation Oncology, Washington University in St. Louis, 660 S. Euclid Ave., CB, St. Louis, MO, USA
| | - Nathan Wolfe
- Calgary Zone, Alberta Health Services, Foothills Medical Centre, 1331-29 ST NW, Calgary, Alberta, Canada
| | - Jon-Paul Voroney
- Department of Oncology, University of Calgary, Tom Baker Cancer Centre 1331 29 Street Northwest, Calgary, Alberta, Canada
- Calgary Zone, Alberta Health Services, Foothills Medical Centre, 1331-29 ST NW, Calgary, Alberta, Canada
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Liang LH, Tomic N, Vuong T, Aldelaijan S, Bekerat H, DeBlois F, Seuntjens J, Devic S. Physics aspects of the Papillon technique-Five decades later. Brachytherapy 2017; 17:234-243. [PMID: 29102741 DOI: 10.1016/j.brachy.2017.09.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 09/26/2017] [Accepted: 09/26/2017] [Indexed: 12/15/2022]
Abstract
PURPOSE The Papillon technique using 50-kVp soft X-rays to treat rectal adenocarcinomas was developed and clinically implemented in the 1960s. We describe differences between accurate dosimetry and clinical implementation of this technique that is extending from its very inception to date. METHODS AND MATERIALS A renaissance of the Papillon technique occurred with two recently introduced 50-kVp systems: Papillon+ by Ariane and a custom-made rectal applicator (consisting of a surface applicator inserted into a proctoscope) by iCAD's Xoft Axxent Electronic Brachytherapy (eBT) System (iCad, Inc., Sunnyvale, CA). In contrast to the initial design, we investigated the impact of introducing a plastic lid, which would provide more reproducible and more accurate dose delivery across the rectal adenocarcinoma patient population. We use both parallel-plate chamber and radiochromic film dosimeters to determine differences in basic dosimetry characteristics (beam half-value layers, outputs, percent depth doses, and profiles) between the Xoft Electronic Brachytherapy rectal applicator system with and without the plastic lid in place. RESULTS Compared to the open-cone applicator, the proposed applicator with the plastic lid produces a slightly harder (more penetrating) beam quality (half-value layer of 1.4 vs. 1.3-mm Al), but with reduced output (by 33%), and a slightly broader beam with flatness not worse than 3% and symmetry not worse than 2%. CONCLUSIONS In addition to characterizing beam properties modified by the possible introduction of the plastic cap, we also pointed out and addressed misconceptions in the use of radiochromic films for dose measurements at low-energy photon beams.
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Affiliation(s)
- Li Heng Liang
- Radiation Oncology Department, Jewish General Hospital, Montreal, Quebec, Canada; Medical Physics Unit, McGill University, Montreal, Quebec, Canada
| | - Nada Tomic
- Radiation Oncology Department, Jewish General Hospital, Montreal, Quebec, Canada; Medical Physics Unit, McGill University, Montreal, Quebec, Canada
| | - Te Vuong
- Radiation Oncology Department, Jewish General Hospital, Montreal, Quebec, Canada; Oncology Department, McGill University, Montreal, Quebec, Canada
| | - Saad Aldelaijan
- Medical Physics Unit, McGill University, Montreal, Quebec, Canada; Biological & Biomedical Engineering Department, Montreal Neurological Institute, Montréal, Québec, Canada; Biomedical Physics Department, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Hamed Bekerat
- Radiation Oncology Department, Jewish General Hospital, Montreal, Quebec, Canada; Medical Physics Unit, McGill University, Montreal, Quebec, Canada
| | - Francois DeBlois
- Radiation Oncology Department, Jewish General Hospital, Montreal, Quebec, Canada; Medical Physics Unit, McGill University, Montreal, Quebec, Canada
| | - Jan Seuntjens
- Medical Physics Unit, McGill University, Montreal, Quebec, Canada; Oncology Department, McGill University, Montreal, Quebec, Canada
| | - Slobodan Devic
- Radiation Oncology Department, Jewish General Hospital, Montreal, Quebec, Canada; Medical Physics Unit, McGill University, Montreal, Quebec, Canada; Segal Cancer Centre, Jewish General Hospital, McGill University, Montréal, Québec, Canada.
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10
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Palmer AL, Jafari SM, Mone I, Muscat S. Evaluation and clinical implementation of in vivo dosimetry for kV radiotherapy using radiochromic film and micro-silica bead thermoluminescent detectors. Phys Med 2017; 42:47-54. [PMID: 29173920 DOI: 10.1016/j.ejmp.2017.08.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 07/09/2017] [Accepted: 08/23/2017] [Indexed: 11/19/2022] Open
Affiliation(s)
- Antony L Palmer
- Portsmouth Hospitals NHS Trust, Portsmouth, UK; University of Surrey, Guildford, UK.
| | - Shakardokht M Jafari
- Portsmouth Hospitals NHS Trust, Portsmouth, UK; University of Surrey, Guildford, UK
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11
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Dowdell S, Tyler M, McNamara J, Sloan K, Ceylan A, Rinks A. Potential errors in relative dose measurements in kilovoltage photon beams due to polarity effects in plane-parallel ionisation chambers. Phys Med Biol 2016; 61:8395-8407. [DOI: 10.1088/0031-9155/61/23/8395] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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12
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Poirier Y, Tambasco M. Experimental validation of a kV source model and dose computation method for CBCT imaging in an anthropomorphic phantom. J Appl Clin Med Phys 2016; 17:155-171. [PMID: 27455477 PMCID: PMC5690031 DOI: 10.1120/jacmp.v17i4.6021] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Revised: 03/15/2016] [Accepted: 02/29/2016] [Indexed: 11/25/2022] Open
Abstract
We present an experimental validation of a kilovoltage (kV) X‐ray source characterization model in an anthropomorphic phantom to estimate patient‐specific absorbed dose from kV cone‐beam computed tomography (CBCT) imaging procedures and compare these doses to nominal weighted CT‐dose index (CTDIw) dose estimates. We simulated the default Varian on‐board imager 1.4 (OBI) default CBCT imaging protocols (i.e., standard‐dose head, low‐dose thorax, pelvis, and pelvis spotlight) using our previously developed and easy to implement X‐ray point‐source model and source characterization approach. We used this characterized source model to compute absorbed dose in homogeneous and anthropomorphic phantoms using our previously validated in‐house kV dose computation software (kVDoseCalc). We compared these computed absorbed doses to doses derived from ionization chamber measurements acquired at several points in a homogeneous cylindrical phantom and from thermoluminescent detectors (TLDs) placed in the anthropomorphic phantom. In the homogeneous cylindrical phantom, computed values of absorbed dose relative to the center of the phantom agreed with measured values within ≤2% of local dose, except in regions of high‐dose gradient where the distance to agreement (DTA) was 2 mm. The computed absorbed dose in the anthropomorphic phantom generally agreed with TLD measurements, with an average percent dose difference ranging from 2.4%±6.0% to 5.7%±10.3%, depending on the characterized CBCT imaging protocol. The low‐dose thorax and the standard dose scans showed the best and worst agreement, respectively. Our results also broadly agree with published values, which are approximately twice as high as the nominal CTDIw would suggest. The results demonstrate that our previously developed method for modeling and characterizing a kV X‐ray source could be used to accurately assess patient‐specific absorbed dose from kV CBCT procedures within reasonable accuracy, and serve as further evidence that existing CTDIw assessments underestimate absorbed dose delivered to patients. PACS number(s): 87.57.Q‐, 87.57.uq, 87.10.Rt
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Aspradakis MM, Zucchetti P. Acceptance, commissioning and clinical use of the WOmed T-200 kilovoltage X-ray therapy unit. Br J Radiol 2015. [PMID: 26224430 DOI: 10.1259/bjr.20150001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVE The objective of this work was to characterize the performance of the WOmed T-200-kilovoltage (kV) therapy machine. METHODS Mechanical functionality, radiation leakage, alignment and interlocks were investigated. Half-value layers (HVLs) (first and second HVLs) from X-ray beams generated from tube potentials between 30 and 200 kV were measured. Reference dose was determined in water. Beam start-up characteristics, dose linearity and reproducibility, beam flatness, and uniformity as well as deviations from inverse square law were assessed. Relative depth doses (RDDs) were determined in water and water-equivalent plastic. The quality assurance program included a dosimetry audit with thermoluminescent dosemeters. RESULTS All checks on machine performance were satisfactory. HVLs ranged between 0.45-4.52 mmAl and 0.69-1.78 mmCu. Dose rates varied between 0.2 and 3 Gy min(-1) with negligible time-end errors. There were differences in measured RDDs from published data. Beam outputs were confirmed with the dosimetry audit. The use of published backscatter factors was implemented to account for changes in phantom scatter for treatments with irregularly shaped fields. CONCLUSION Guidance on the determination of HVL and RDD in kV beams can be contradictory. RDDs were determined through measurement and curve fitting. These differed from published RDD data, and the differences observed were larger in the low-kV energy range. ADVANCES IN KNOWLEDGE This article reports on the comprehensive and novel approach to the acceptance, commissioning and clinical use of a modern kV therapy machine. The challenges in the dosimetry of kV beams faced by the medical physicist in the clinic are highlighted.
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Affiliation(s)
- Maria M Aspradakis
- Institute of Radiation Oncology, Cantonal hospital of Lucerne, Lucerne, Switzerland
| | - Paolo Zucchetti
- Institute of Radiation Oncology, Cantonal hospital of Lucerne, Lucerne, Switzerland
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Role of in vivo dosimetry with radiochromic films for dose verification during cutaneous radiation therapy. Radiat Oncol 2015; 10:12. [PMID: 25582565 PMCID: PMC4300174 DOI: 10.1186/s13014-014-0325-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 12/29/2014] [Indexed: 11/10/2022] Open
Abstract
PURPOSE To evaluate the role of in vivo dosimetry with radiochromic films for dose verification in cutaneous radiation therapy (RT). METHODS Five patients with 8 cutaneous or sub-cutaneous malignancies of the face, neck, trunk and extremity receiving RT were included. Orthovoltage, megavoltage photon therapies were applied based on anatomic location. The delivered dose for each target was measured with GAFCHROMIC EBT3TM film. The differences between the prescribed and measured doses in each target were analyzed based on the RT characteristics, target location and custom patient set up. The accuracy of EBT3TM film measurement was verified by measurements in a solid water phantom. RESULTS The mean measured dose was -3.2% (-9.6% to +2.3%, P=0.86) lower than prescribed over 23 measurements. A wide range of under dose was detected in orthovoltage therapy when a gap existed between skin and a closed-ended applicator surface. The magnitude of the under dosage was correlated with the degree of the gap (P=0.01). The phantom study confirmed the accuracy of GAFCHROMIC EBT3TM film measurement and found that the low measured dose in orthovoltage therapy was caused by the deviation from the inverse square law (ISL) of the beam output at extended source surface distance (SSD) for closed-ended applicators. CONCLUSIONS A significantly low delivered dose for extended SSD orthovoltage therapy was demonstrated during cutaneous RT. The dose fall-off with distance is not completely compensated by the ISL standoff correction for orthovoltage therapy. GAFCHROMIC EBT3™ film is a useful and accurate tool for quality assurance of patients receiving a curative intended cutaneous RT.
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