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McDermott PN. Monte Carlo evaluation of uncertainties in photon and electron TG-51 absorbed dose calibration. J Appl Clin Med Phys 2024; 25:e14339. [PMID: 38608655 PMCID: PMC11244687 DOI: 10.1002/acm2.14339] [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: 06/21/2023] [Revised: 02/09/2024] [Accepted: 03/03/2024] [Indexed: 04/14/2024] Open
Abstract
PURPOSE The accuracy of dose delivery to all patients treated with medical linacs depends on the accuracy of beam calibration. Dose delivery cannot be any more accurate than this. Given the importance of this, it seems worthwhile taking another look at the expected uncertainty in TG-51 photon dose calibration and a first look at electron calibration. This work builds on the 2014 addendum to TG-51 for photons and adds to it by also considering electrons. In that publication, estimates were made of the uncertainty in the dose calibration. In this paper, we take a deeper look at this important issue. METHODS The methodology used here is more rigorous than previous determinations as it is based on Monte Carlo simulation of uncertainties. It is assumed that mechanical QA has been performed following TG-142 prior to beam calibration and that there are no uncertainties that exceed the tolerances specified by TG-142. RESULTS/CONCLUSIONS Despite the different methodology and assumptions, the estimated uncertainty in photon beam calibration is close to that in the addendum. The careful user should be able to easily reach a 95% confidence interval (CI) of ± 2.3% for photon beam calibration with standard instrumentation. For electron beams calibrated with a Farmer chamber, the estimated uncertainties are slightly larger, and the 95% CI is ±2.6% for 6 MeV and slightly smaller than this for 18 MeV. There is no clear energy dependence in these results. It is unlikely that the user will be able to improve on these uncertainties as the dominant factor in the uncertainty resides in the ion chamber dose calibration factorN D , w 60 Co $N_{D,w}^{{}^{60}{\mathrm{Co}}}$ . For both photons and electrons, reduction in the ion chamber depth uncertainty below about 0.5 mm and SSD uncertainty below 1 mm have almost no effect on the total dose uncertainty, as uncertainties beyond the user's control totally dominate under these circumstances.
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Affiliation(s)
- Patrick N McDermott
- Department of Radiation Oncology, William Beaumont University Hospital, Corewell Health, Royal Oak, Michigan, USA
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Elbashir FEM, Ksouri W, Eisa MH, Alanazi S, Habbani F, Sulieman A, Bradley DA, Suliman II. Comparison of Dosimetry Protocols for Electron Beam Radiotherapy Calibrations and Measurement Uncertainties. Life (Basel) 2021; 12:life12010031. [PMID: 35054424 PMCID: PMC8781094 DOI: 10.3390/life12010031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 12/21/2021] [Accepted: 12/22/2021] [Indexed: 11/16/2022] Open
Abstract
This paper presents guidelines for the calibration of radiation beams that were issued by the International Atomic Energy Agency (IAEA TRS 398), the American Association of Physicists in Medicine (AAPM TG 51) and the German task group (DIN 6800-2). These protocols are based on the use of an ionization chamber calibrated in terms of absorbed dose to water in a standard laboratory’s reference quality beam, where the previous protocols were based on air kerma standards. This study aims to determine uncertainties in dosimetry for electron beam radiotherapy using internationally established high-energy radiotherapy beam calibration standards. Methods: Dw was determined in 6-, 12- and 18 MeV electron energies under reference conditions using three cylindrical and two plane-parallel ion chambers in concert with the IAEA TRS 398, AAPM TG 51 and DIN 6800-2 absorbed dose protocols. From mean measured Dw values, the ratio TRS 398/TG 51 was found to vary between 0.988 and 1.004, while for the counterpart TRS 398/DIN 6800-2 and TG 51/DIN 6800-2, the variation ranges were 0.991–1.003 and 0.997–1.005, respectively. For the cylindrical chambers, the relative combined uncertainty (k = 1) in absorbed dose measurements was 1.44%, while for the plane-parallel chambers, it ranged from 1.53 to 1.88%. Conclusions: A high degree of consistency was demonstrated among the three protocols. It is suggested that in the use of the presently determined dose conversion factors across the three protocols, dose intercomparisons can be facilitated between radiotherapy centres.
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Affiliation(s)
- Fawzia E. M. Elbashir
- Department of Medical Physics, National Cancer Institute, University of Gezira, Wad Madani P.O. Box 1111, Sudan;
| | - Wassim Ksouri
- Department of Medical Physics, Centre de Radiothérapie Hartmann 4, Rue Kleber, CS90004, CEDEX, 92309 Levallois-Perret, France;
| | - Mohamed Hassan Eisa
- Department of Physics, College of Science, Imam Mohammad Ibn Saud Islamic University (IMSIU), Riyadh 11642, Saudi Arabia; (M.H.E.); (S.A.)
| | - Sitah Alanazi
- Department of Physics, College of Science, Imam Mohammad Ibn Saud Islamic University (IMSIU), Riyadh 11642, Saudi Arabia; (M.H.E.); (S.A.)
| | - Farouk Habbani
- Department of Physics, Faculty of Science, University of Khartoum, Khartoum P.O. Box 321, Sudan;
| | - Abdelmoneim Sulieman
- Radiology and Medical Imaging Department, College of Applied Medical Sciences, Prince Sattam bin Abdulaziz University, Alkharj 11942, Saudi Arabia;
| | - David A. Bradley
- Centre for Applied Physics and Radiation Technologies, School of Engineering and Technology, Sunway University, Bandar Sunway 47500, Selangor, Malaysia;
- Department of Physics, University of Surrey, Guildford GU2 7XH, UK
| | - Ibrahim I. Suliman
- Department of Physics, College of Science, Imam Mohammad Ibn Saud Islamic University (IMSIU), Riyadh 11642, Saudi Arabia; (M.H.E.); (S.A.)
- Radiation and Nuclear Safety Institute, Sudan Atomic Energy Commission, Khartoum P.O. Box 3001, Sudan
- Correspondence: ; Tel.: +966-5-3891-8127
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Semwal MK, Gupta H, Singhal S, Kumar A, Kaushik A. Variation in Dosimeter Calibration Factor (N DW) Over a Period of 20 Years. J Med Phys 2021; 46:125-127. [PMID: 34566293 PMCID: PMC8415254 DOI: 10.4103/jmp.jmp_42_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 04/17/2021] [Accepted: 04/23/2021] [Indexed: 11/04/2022] Open
Abstract
Long delays in renewal of calibration of secondary standards radiation dosimeters in radiation oncology centers due to the COVID19 pandemic have aroused concerns regarding accuracy in dose delivery to patients. The concerns are mainly due to the uncertainty in the absorbed dose to water calibration factor (NDW) over a period of time. In this study, the NDWfactor for two ion chambers, thimble type (Farmer) and parallel plate type (Markus), used in most of the radiotherapy centers, were retrospectively reviewed for 20 years. The calibration on all occasions except once was carried out at the Secondary Standards Dosimetry Laboratory, Bhabha Atomic Research Centre, Mumbai. The change in the NDWfactor over this period was < ±3%. We, therefore, believe that a dosimeter with no history of repairs showed reasonable stability in the NDWfactor over a long period.
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Affiliation(s)
- Manoj Kumar Semwal
- Department of Radiation Oncology, Army Hospital Research and Referral, Delhi, India
| | - Harishchandra Gupta
- Division of Clinical PET, Institute of Nuclear Medicine and Allied Sciences, Delhi, India
| | - Sakshi Singhal
- Division of Clinical PET, Institute of Nuclear Medicine and Allied Sciences, Delhi, India
| | - Ashok Kumar
- Department of Radiation Oncology, Army Hospital Research and Referral, Delhi, India
| | - Aruna Kaushik
- Division of Clinical PET, Institute of Nuclear Medicine and Allied Sciences, Delhi, India
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Rosado PH, Salata C, David MG, Mantuano A, Pickler A, Mota CL, de Almeida CE. Determination of the absorbed dose to water for medium-energy x-ray beams using Fricke dosimetry. Med Phys 2020; 47:5802-5809. [PMID: 32964481 DOI: 10.1002/mp.14473] [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: 07/10/2020] [Revised: 08/22/2020] [Accepted: 08/30/2020] [Indexed: 12/25/2022] Open
Abstract
PURPOSE For x-ray beams in the low and medium energy range, reference dosimetry is established in terms of air kerma. Fricke dosimetry has shown great potential in the absolute measurements of the absorbed dose to water for high-energy ranges. Therefore, the main purpose of this work was to compare the absorbed dose to water for medium-energy x-ray beams obtained through Fricke dosimetry with that obtained from the air kerma rate. METHODS To determine the absorbed dose to water using Fricke dosimetry, the polyethylene bags methodology was chosen. Fricke solution was irradiated at four different beam qualities. The absorbed dose to water values obtained using Fricke dosimetry were compared to those obtained using the standard protocol, using the Z-score. RESULTS Values of the Z-score were <2 for all measurements of absorbed dose to water, which means that the values obtained using Fricke dosimetry are equivalent to those obtained using the reference protocol. The combined standard uncertainty for the absorbed dose to water obtained by Fricke dosimetry was lower than that obtained with the ionization chamber. CONCLUSIONS Chemical dosimetry using a standard FeSO4 solution has been demonstrated to be a potential option as a standard for the quantity absorbed dose to water for medium kV x-ray qualities.
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Affiliation(s)
- Paulo Henrique Rosado
- Brazilian National Ionizing Radiation Metrology Laboratory, Radioprotection and Dosimetry Institute (IRD), Rio de Janeiro, Brazil.,Department of Medical and Research Facilities, National Nuclear Energy Authority (CNEN), Rio de Janeiro, Brazil
| | - Camila Salata
- Department of Medical and Research Facilities, National Nuclear Energy Authority (CNEN), Rio de Janeiro, Brazil.,Radiological Sciences Department, Rio de Janeiro State University (UERJ), Rio de Janeiro, Brazil
| | - Mariano Gazineu David
- Polytechnic Institute of the Rio de Janeiro State University (IPRJ/UERJ), Rio de Janeiro, Brazil
| | - Andrea Mantuano
- Radiological Sciences Department, Rio de Janeiro State University (UERJ), Rio de Janeiro, Brazil
| | - Arissa Pickler
- Radiological Sciences Department, Rio de Janeiro State University (UERJ), Rio de Janeiro, Brazil
| | - Carla Lemos Mota
- Radiological Sciences Department, Rio de Janeiro State University (UERJ), Rio de Janeiro, Brazil.,Physics Department, Rio de Janeiro State University (UERJ), Rio de Janeiro, Brazil
| | - Carlos E de Almeida
- Radiological Sciences Department, Rio de Janeiro State University (UERJ), Rio de Janeiro, Brazil
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Enhancing benefits of bolus use through minimising the effect of air-gaps on dose distribution in photon beam radiotherapy. JOURNAL OF RADIOTHERAPY IN PRACTICE 2020. [DOI: 10.1017/s1460396920000047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AbstractIntroduction:Bolus material is frequently used on patient’s skin during radiation therapy to reduce or remove build-up effect for high-energy beams. However, the air-gaps formed between the bolus and the skin’s irregular surface reduce the accuracy of treatment planning. To achieve a good treatment outcome using bolus, experimental investigations are required to choose its thickness and to quantify the air-gap effect.Material and methods:Measurements for a 6 MV photon beam with a fixed source surface distance were carried out using the 31021 Semiflex 3D chamber into the water phantom. Firstly, the depth of maximum dose (R100) and the dose value at surface (Ds) were evaluated as a function of bolus thickness for some square fields. Secondly, to test the effect of the air-gaps ranged from 5 to 30 mm with a step of 5 mm between the bolus and the phantom surface, a water-equivalent RW3 (Goettingen White Water) slab form of 10 mm thickness was considered as a bolus.Results:We observed that the linear behaviour of R100 in terms of the bolus thickness makes the choice of this parameter more convenient depending on field size. In addition, increasing the air-gaps widens the penumbra and created electrons that have a greater probability to quit the radiation field borders before reaching the surface. The dose spread of the off-field area could have a significant influence on the patient treatment.Conclusion:Based on dose distribution comparisons between the measurements with and without air-gaps for the field size of 100 mm × 100 mm, it has been demonstrated that a maximum air-gap value lower than 5 mm would be desirable for an efficient use of the bolus technique.
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Abdemanafi M, Tavakoli MB, Akhavan A, Abedi I. Evaluation of the Lung Dose in Three-dimensional Conformal Radiation Therapy of Left-Sided Breast Cancer: A Phantom Study. JOURNAL OF MEDICAL SIGNALS & SENSORS 2020; 10:48-52. [PMID: 32166077 PMCID: PMC7038741 DOI: 10.4103/jmss.jmss_1_19] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2019] [Revised: 05/07/2019] [Accepted: 05/30/2019] [Indexed: 11/13/2022]
Abstract
Background: Three-dimensional 3D-CRT: conformal radiation therapy is a selective modality in many radiotherapy centers for the treatment of breast cancer. One of the most common side effects of this method is radiation lung injury. Considering such an injury, lung dose deserves to be studied in depth. Methods: Computed tomography scan of a node-positive left-sided breast cancer woman was used for generating a thorax phantom. Ten thermoluminescent dosimeters (TLDs) were distributed evenly in the left lung of the phantom, and the phantom was scanned. The optimal plan, including supraclavicular and tangential fields, was created by the treatment planning system (TPS). The results of TLD dose measurements at the selected points in the phantom were compared to TPS dose calculations. Results: Lung doses calculated by TPS are significantly different from those measured by the TLDs (P = 0.007). The minimum and maximum differences were −0.91% and 4.46%, respectively. TLDs that were on the inner margin of the lung and breast tissue showed higher dose differences than the TLDs in the lung. Conclusion: The results of this study showed that TPS generally overestimated doses compared to TLD measurements due to incorrect beam modeling caused by contaminated electrons in the lung.
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Affiliation(s)
- Mahsa Abdemanafi
- Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Mohammad Bagher Tavakoli
- Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Ali Akhavan
- Department of Radiotherapy Oncology, Seyed Alshohada Hospital, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Iraj Abedi
- Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
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Glamour, expression, and consequences of tattoos in radiation treatment. PLoS One 2019; 14:e0220030. [PMID: 31390347 PMCID: PMC6685677 DOI: 10.1371/journal.pone.0220030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 07/08/2019] [Indexed: 12/03/2022] Open
Abstract
It is estimated that approximately 24% of the US population has at least one tattoo. However, tattoo ink ingredients include heavy metals (high atomic number Z) that are not regulated, which can cause skin reactions. This study investigates the dosimetric effects in surface dose due to high-Z elements in tattoo ink under electron beam irradiation. Four commercially available tattoo ink colors, black, red, yellow, and blue were chosen. The elemental composition of the tattoo ink samples was analyzed using X-ray Fluorescence (XRF). An ultrathin-window parallel plate ion chamber was used to measure the surface dose perturbation (ratio of ionizations with and without tattoo ink) for 6 − 20 MeV electron beams. The elemental concentration in the tattoo ink samples showed high-Z elements, with Z ranging from 11 to 92. The dose perturbation ranged from 1.4% up to 6% for the yellow ink for the 6 MeV electron beam, with similar values across the rest of the electron energies, whereas the black, red, and blue inks presented up to 3% dose perturbation for the same range of energies. Based on this initial study, we conclude that commercially available tattoo inks contain large amounts of high-Z metals that may contribute to dose perturbation. Therefore treatment of superficial lesions with electron beams in a tattooed area should be monitored for signs of early skin reaction during radiation therapy treatments.
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Kinoshita N, Oguchi H, Adachi T, Shioura H, Kimura H. Uncertainty in positioning ion chamber at reference depth for various water phantoms. Rep Pract Oncol Radiother 2018; 23:199-206. [PMID: 29760594 PMCID: PMC5948320 DOI: 10.1016/j.rpor.2018.03.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 12/28/2017] [Accepted: 03/09/2018] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Uncertainty in the calibration of high-energy radiation sources is dependent on user and equipment type. AIM We evaluated the uncertainty in the positioning of a cylindrical chamber at a reference depth for reference dosimetry of high-energy photon beams and the resulting uncertainty in the chamber readings for 6- and 10-MV photon beams. The aim was to investigate major contributions to the positioning uncertainty to reduce the uncertainty in calibration for external photon beam radiotherapy. MATERIALS AND METHODS The following phantoms were used: DoseView 1D, WP1D, 1D SCANNER, and QWP-07 as one-dimensional (1D) phantoms for a vertical-beam geometry; GRI-7632 as a phantom for a fixed waterproofing sleeve; and PTW type 41023 and QWP-04 as 1D phantoms for a horizontal-beam geometry. The uncertainties were analyzed as per the Guide to the Expression of Uncertainty in Measurement. RESULTS The positioning and resultant uncertainties in chamber readings ranged from 0.22 to 0.35 mm and 0.12-0.25%, respectively, among the phantoms (using a coverage factor k = 1 in both cases). The major contributions to positioning uncertainty are: definition of the origin for phantoms among users for the 1D phantoms for a vertical-beam geometry, water level adjustment among users for the phantom for a fixed waterproofing sleeve, phantom window deformation, and non-water material of the window for the 1D phantoms for a horizontal-beam geometry. CONCLUSION The positioning and resultant uncertainties in chamber readings exhibited minor differences among the seven phantoms. The major components of these uncertainties differed among the phantom types investigated.
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Affiliation(s)
- Naoki Kinoshita
- Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya-shi, Aichi-ken 461-8673, Japan
- Radiological Center, University of Fukui Hospital, Yoshida-gun, Fukui-ken 910-1193, Japan
| | - Hiroshi Oguchi
- Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya-shi, Aichi-ken 461-8673, Japan
| | - Toshiki Adachi
- Radiological Center, University of Fukui Hospital, Yoshida-gun, Fukui-ken 910-1193, Japan
| | - Hiroki Shioura
- Department of Radiology, University of Fukui Hospital, Yoshida-gun, Fukui-ken 910-1193, Japan
| | - Hirohiko Kimura
- Department of Radiology, University of Fukui Hospital, Yoshida-gun, Fukui-ken 910-1193, Japan
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Vera-Sánchez JA, Ruiz-Morales C, González-López A. Monte Carlo uncertainty analysis of dose estimates in radiochromic film dosimetry with single-channel and multichannel algorithms. Phys Med 2018; 47:23-33. [PMID: 29609815 DOI: 10.1016/j.ejmp.2018.02.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 02/07/2018] [Accepted: 02/09/2018] [Indexed: 10/18/2022] Open
Abstract
PURPOSE To provide a multi-stage model to calculate uncertainty in radiochromic film dosimetry with Monte-Carlo techniques. This new approach is applied to single-channel and multichannel algorithms. MATERIAL AND METHODS Two lots of Gafchromic EBT3 are exposed in two different Varian linacs. They are read with an EPSON V800 flatbed scanner. The Monte-Carlo techniques in uncertainty analysis provide a numerical representation of the probability density functions of the output magnitudes. From this numerical representation, traditional parameters of uncertainty analysis as the standard deviations and bias are calculated. Moreover, these numerical representations are used to investigate the shape of the probability density functions of the output magnitudes. Also, another calibration film is read in four EPSON scanners (two V800 and two 10000XL) and the uncertainty analysis is carried out with the four images. RESULTS The dose estimates of single-channel and multichannel algorithms show a Gaussian behavior and low bias. The multichannel algorithms lead to less uncertainty in the final dose estimates when the EPSON V800 is employed as reading device. In the case of the EPSON 10000XL, the single-channel algorithms provide less uncertainty in the dose estimates for doses higher than four Gy. CONCLUSION A multi-stage model has been presented. With the aid of this model and the use of the Monte-Carlo techniques, the uncertainty of dose estimates for single-channel and multichannel algorithms are estimated. The application of the model together with Monte-Carlo techniques leads to a complete characterization of the uncertainties in radiochromic film dosimetry.
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Affiliation(s)
- Juan Antonio Vera-Sánchez
- Hospital Universitari Sant Joan de Reus, Servicio de Física Médica, Reus (Tarragona), Spain; PhD Programme in Physics and Space Science of the University of Granada, Granada, Spain.
| | - Carmen Ruiz-Morales
- PhD Programme in Physics and Space Science of the University of Granada, Granada, Spain
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Pantelis E, Moutsatsos A, Zourari K, Kilby W, Antypas C, Papagiannis P, Karaiskos P, Georgiou E, Sakelliou L. On the implementation of a recently proposed dosimetric formalism to a robotic radiosurgery system. Med Phys 2016; 37:2369-79. [DOI: 10.1118/1.3404289] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
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Candela-Juan C, Vijande J, García-Martínez T, Niatsetski Y, Nauta G, Schuurman J, Ouhib Z, Ballester F, Perez-Calatayud J. Comparison and uncertainty evaluation of different calibration protocols and ionization chambers for low-energy surface brachytherapy dosimetry. Med Phys 2015; 42:4954-64. [PMID: 26233221 DOI: 10.1118/1.4927059] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
PURPOSE A surface electronic brachytherapy (EBT) device is in fact an x-ray source collimated with specific applicators. Low-energy (<100 kVp) x-ray beam dosimetry faces several challenges that need to be addressed. A number of calibration protocols have been published for x-ray beam dosimetry. The media in which measurements are performed are the fundamental difference between them. The aim of this study was to evaluate the surface dose rate of a low-energy x-ray source with small field applicators using different calibration standards and different small-volume ionization chambers, comparing the values and uncertainties of each methodology. METHODS The surface dose rate of the EBT unit Esteya (Elekta Brachytherapy, The Netherlands), a 69.5 kVp x-ray source with applicators of 10, 15, 20, 25, and 30 mm diameter, was evaluated using the AAPM TG-61 (based on air kerma) and International Atomic Energy Agency (IAEA) TRS-398 (based on absorbed dose to water) dosimetry protocols for low-energy photon beams. A plane parallel T34013 ionization chamber (PTW Freiburg, Germany) calibrated in terms of both absorbed dose to water and air kerma was used to compare the two dosimetry protocols. Another PTW chamber of the same model was used to evaluate the reproducibility between these chambers. Measurements were also performed with two different Exradin A20 (Standard Imaging, Inc., Middleton, WI) chambers calibrated in terms of air kerma. RESULTS Differences between surface dose rates measured in air and in water using the T34013 chamber range from 1.6% to 3.3%. No field size dependence has been observed. Differences are below 3.7% when measurements with the A20 and the T34013 chambers calibrated in air are compared. Estimated uncertainty (with coverage factor k = 1) for the T34013 chamber calibrated in water is 2.2%-2.4%, whereas it increases to 2.5% and 2.7% for the A20 and T34013 chambers calibrated in air, respectively. The output factors, measured with the PTW chambers, differ by less than 1.1% for any applicator size when compared to the output factors that were measured with the A20 chamber. CONCLUSIONS Measurements using both dosimetric protocols are consistent, once the overall uncertainties are considered. There is also consistency between measurements performed with both chambers calibrated in air. Both the T34013 and A20 chambers have negligible stem effect. Any x-ray surface brachytherapy system, including Esteya, can be characterized using either one of these calibration protocols and ionization chambers. Having less correction factors, lower uncertainty, and based on measurements, performed in closer to clinical conditions, the TRS-398 protocol seems to be the preferred option.
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Affiliation(s)
- C Candela-Juan
- Radiation Oncology Department, La Fe University and Polytechnic Hospital, Valencia 46026, Spain
| | - J Vijande
- Department of Atomic, Molecular, and Nuclear Physics, University of Valencia, Burjassot 46100, Spain and Instituto de Física Corpuscular (UV-CSIC), Paterna 46980, Spain
| | - T García-Martínez
- Radiation Oncology Department, Hospital La Ribera, Alzira 46600, Spain
| | - Y Niatsetski
- Elekta Brachytherapy, Veenendaal 3905 TH, The Netherlands
| | - G Nauta
- Elekta Brachytherapy, Veenendaal 3905 TH, The Netherlands
| | - J Schuurman
- Elekta Brachytherapy, Veenendaal 3905 TH, The Netherlands
| | - Z Ouhib
- Radiation Oncology Department, Lynn Regional Cancer Center, Boca Raton Community Hospital, Boca Raton, Florida 33486
| | - F Ballester
- Department of Atomic, Molecular, and Nuclear Physics, University of Valencia, Burjassot 46100, Spain
| | - J Perez-Calatayud
- Radiation Oncology Department, La Fe University and Polytechnic Hospital, Valencia 46026, Spain and Department of Radiotherapy, Clínica Benidorm, Benidorm 03501, Spain
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Butler DJ, Ramanathan G, Oliver C, Cole A, Lye J, Harty PD, Wright T, Webb DV, Followill DS. Direct megavoltage photon calibration service in Australia. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2014; 37:753-61. [PMID: 25146559 PMCID: PMC4297255 DOI: 10.1007/s13246-014-0293-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 08/12/2014] [Indexed: 10/24/2022]
Abstract
The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) maintains the Australian primary standard of absorbed dose. Until recently, the standard was used to calibrate ionisation chambers only in (60)Co gamma rays. These chambers are then used by radiotherapy clinics to determine linac output, using a correction factor (k Q) to take into account the different spectra of (60)Co and the linac. Over the period 2010-2013, ARPANSA adapted the primary standard to work in megavoltage linac beams, and has developed a calibration service at three photon beams (6, 10 and 18 MV) from an Elekta Synergy linac. We describe the details of the new calibration service, the method validation and the use of the new calibration factors with the International Atomic Energy Agency's TRS-398 dosimetry Code of Practice. The expected changes in absorbed dose measurements in the clinic when shifting from (60)Co to the direct calibration are determined. For a Farmer chamber (model 2571), the measured chamber calibration coefficient is expected to be reduced by 0.4, 1.0 and 1.1 % respectively for these three beams when compared to the factor derived from (60)Co. These results are in overall agreement with international absorbed dose standards and calculations by Muir and Rogers in 2010 of k Q factors using Monte Carlo techniques. The reasons for and against moving to the new service are discussed in the light of the requirements of clinical dosimetry.
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Affiliation(s)
- D J Butler
- Australian Radiation Protection and Nuclear Safety Agency, 619 Lower Plenty Road, Yallambie, VIC, 3085, Australia,
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El Shahat K, El Saeid A, Attalla E, Yassin A. Comparative Study between Measurement Data and Treatment Planning System (TPS) in Small Fields for High Energy Photon Beams. ISRN ONCOLOGY 2014; 2014:901436. [PMID: 24944831 PMCID: PMC4040206 DOI: 10.1155/2014/901436] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/11/2014] [Accepted: 02/18/2014] [Indexed: 12/04/2022]
Abstract
To achieve tumor control for radiotherapy, a dose distribution is planned which has a good chance of sterilizing all cancer cells without causing unacceptable normal tissue complications. The aim of the present study was to achieve an accurate calculation of dose for small field dimensions and perform this by evaluating the accuracy of planning system calculation. This will be compared with real measurement of dose for the same small field dimensions using different detectors. Practical work was performed in two steps: (i) determination of the physical factors required for dose estimation measured by three ionization chambers and calculated by treatment planning system (TPS) based on the latest technical report series (IAEATRS-398) and (ii) comparison of the calculated and measured data. Our data analysis for small field is irradiated by photon energy matched with the data obtained from the ionization chambers and the treatment planning system. Radiographic films were used as an additional detector for the obtained data and showed matching with TPS calculation. It can be concluded that studied small field dimensions were averaged 6% and 4% for 6 MV and 15 MV, respectively. Radiographic film measurements showed a variation in results within ±2% than TPS calculation.
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Affiliation(s)
- Khaled El Shahat
- Radiation Oncology Department, Faculty of Medicine, Al Azhar University, Egypt
| | - Aziza El Saeid
- Biophysics Branch, Physics Department, Faculty of Sciences (Girls), Al Azhar University, Egypt
| | - Ehab Attalla
- National Cancer Institute (NCI), Cairo University, Egypt
| | - Adel Yassin
- Radiation Oncology Department, Faculty of Medicine, Al Azhar University, Egypt
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McEwen M, DeWerd L, Ibbott G, Followill D, Rogers DWO, Seltzer S, Seuntjens J. Addendum to the AAPM's TG-51 protocol for clinical reference dosimetry of high-energy photon beams. Med Phys 2014; 41:041501. [PMID: 24694120 PMCID: PMC5148035 DOI: 10.1118/1.4866223] [Citation(s) in RCA: 201] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 02/03/2014] [Accepted: 02/06/2014] [Indexed: 11/07/2022] Open
Abstract
An addendum to the AAPM's TG-51 protocol for the determination of absorbed dose to water in megavoltage photon beams is presented. This addendum continues the procedure laid out in TG-51 but new kQ data for photon beams, based on Monte Carlo simulations, are presented and recommendations are given to improve the accuracy and consistency of the protocol's implementation. The components of the uncertainty budget in determining absorbed dose to water at the reference point are introduced and the magnitude of each component discussed. Finally, the consistency of experimental determination of ND,w coefficients is discussed. It is expected that the implementation of this addendum will be straightforward, assuming that the user is already familiar with TG-51. The changes introduced by this report are generally minor, although new recommendations could result in procedural changes for individual users. It is expected that the effort on the medical physicist's part to implement this addendum will not be significant and could be done as part of the annual linac calibration.
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Affiliation(s)
- Malcolm McEwen
- National Research Council, 1200 Montreal Road, Ottawa, Ontario, Canada
| | - Larry DeWerd
- University of Wisconsin, 1111 Highland Avenue, Madison, Wisconsin 53705
| | - Geoffrey Ibbott
- Department of Radiation Physics, M D Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030
| | - David Followill
- IROC Houston QA Center, Radiological Physics Center, 8060 El Rio Street, Houston, Texas 77054
| | - David W O Rogers
- Carleton Laboratory for Radiotherapy Physics, Physics Department, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada
| | - Stephen Seltzer
- National Institute of Standards and Technology, Gaithersburg, Maryland 20899
| | - Jan Seuntjens
- Medical Physics Unit, McGill University, 1650 Cedar Avenue, Montreal, Québec, Canada
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Pantelis E, Moutsatsos A, Zourari K, Petrokokkinos L, Sakelliou L, Kilby W, Antypas C, Papagiannis P, Karaiskos P, Georgiou E, Seimenis I. On the output factor measurements of the CyberKnife iris collimator small fields: Experimental determination of the kQclin,Qmsrfclin,fmsr correction factors for microchamber and diode detectors. Med Phys 2012; 39:4875-85. [DOI: 10.1118/1.4736810] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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16
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Bouchard H, Seuntjens J, Kawrakow I. A Monte Carlo method to evaluate the impact of positioning errors on detector response and quality correction factors in nonstandard beams. Phys Med Biol 2011; 56:2617-34. [DOI: 10.1088/0031-9155/56/8/018] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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17
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Linear-accelerator X-ray output: a multicentre chamber-based intercomparison study in Australia and New Zealand. ACTA ACUST UNITED AC 2008; 31:268-79. [DOI: 10.1007/bf03178596] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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