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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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Anim-Sampong S, Arthur L, Boahen E, Botwe BO. STATUS OF RADIATION DOSE LEVELS IN PAEDIATRIC CHEST RADIOGRAPHY IN A TERTIARY HOSPITAL IN GHANA. RADIATION PROTECTION DOSIMETRY 2021; 195:75-82. [PMID: 34341827 DOI: 10.1093/rpd/ncab114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2020] [Revised: 06/15/2021] [Accepted: 07/08/2021] [Indexed: 06/13/2023]
Abstract
Determination of appropriate radiation doses to paediatric patients in accordance with the as low as reasonably achievable (ALARA) principle is important, as it allows for effective optimization of imaging techniques. This study assessed the status of radiation dose levels in paediatric patients undergoing chest X-ray examinations at a tertiary hospital in Ghana. A population encompassing 86 paediatric patients categorised as infants (<1 y), young children (1-5 y) and older children (6-12 y) was selected using a quasi-experimental study design. The patients' anatomical data and X-ray beam exposure parameters were used to indirectly calculate the entrance surface doses (ESDs) received during the examinations. The infants received the highest mean ESD of 196 μGy (uncertainty = 0.37) compared to 158 μGy (uncertainty = 0.46) among the older children. The risk of developing radiation-induced biological effects was therefore higher for infant patients. The ESDs were generally higher than the internationally recommended reference doses. Careful adoption of internationally accepted exposure factors (high tube voltage and low tube load) is most recommended to optimise the dose.
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Affiliation(s)
- Samuel Anim-Sampong
- Department of Radiography, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, PO Box KB 143 Korle Bu, Accra, Ghana
| | - Lawrence Arthur
- Department of Radiography, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, PO Box KB 143 Korle Bu, Accra, Ghana
| | - Enock Boahen
- Department of Radiography, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, PO Box KB 143 Korle Bu, Accra, Ghana
| | - Benard Ohene Botwe
- Department of Radiography, School of Biomedical and Allied Health Sciences, College of Health Sciences, University of Ghana, PO Box KB 143 Korle Bu, Accra, Ghana
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Arimoto A, Asada Y. Investigation of backscatter factor in medical radiography using anthropomorphic phantom by optically stimulated luminescence dosimeter. Biomed Phys Eng Express 2021; 7. [PMID: 34438389 DOI: 10.1088/2057-1976/ac21ac] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 08/26/2021] [Indexed: 11/11/2022]
Abstract
At the diagnostic reference level (DRL) related to medical radiation, DRL quantity for general radiography is the entrance surface dose (ESD). Calculation of the ESD in medical radiography requires the backscatter factor (BSF), but derivation of the BSF requires assessment of an irradiated simulation of a human body. The present study used optically stimulated luminescence (OSL) dosimeters and an anthropomorphic phantom as the irradiated body, and the BSF was calculated for different half value layer (HVL)s and field sizes. The need for different BSFs for different regions was also investigated by derivationing of the BSFs for different regions. The pelvis of a RANDO phantom was irradiated under the conditions of the HVL of 2.0, 3.1, and 4.6 mmAl; tube current of 200 mA; irradiation time of 0.1 s; source surface distance of 100 cm; and field sizes of 10 × 10 cm2, 20 cm2, 30 cm2, and 40 cm2. Measurement in air was performed under the same conditions. Several threads were stretched through the air with tissue paper placed on them and the nanoDot dosimeters placed on the paper. Four dosimeters were placed, and measurement was performed 5 times under each set of conditions. The compared radiographed regions were the skull, chest, and pelvis. The BSF increased with increasing HVL size and with increasing field size. The larger the HVL, the larger the difference between field sizes of 10 × 10 cm2and 40 × 40 cm2and the larger the increase in BSF relative to the increase in field size. The BSF differed by region, from large to small in the order chest, pelvis, and skull. The results thus showed that the BSF differs by the radiographed region. Thus, it is desirable to determine the BSF in each radiographed region by investigation with an anthropomorphic phantom.
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Affiliation(s)
- Akihiro Arimoto
- Hamamatsu Medical Center Department of Radiological Technology, Japan
| | - Yasuki Asada
- Fujita Health University School of Medical Sciences Faculty of Radiological Technology, Japan
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Chen Q, Molloy J, Izumi T, Sterpin E. Impact of backscatter material thickness on the depth dose of orthovoltage irradiators for radiobiology research. Phys Med Biol 2019; 64:055001. [PMID: 30673636 DOI: 10.1088/1361-6560/ab0120] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The orthovoltage x-ray energy frequently used in radiation research is prone to dosimetry errors due to insufficient backscatter conditions. In many radiobiology studies, especially for cell irradiations, precise dose calculation algorithms such as Convolution-Superposition or Monte Carlo are impractical and as such, less accurate hand calculation methods are used for dose estimation. These dose estimation methods typically assume full backscatter conditions. The purpose of this study is to demonstrate the magnitude of the dose error that results from insufficient backscatter, and to provide lookup tables to account this issue. The beam spectra of several widely used commercial systems (XRAD-225, XRAD-320, SARRP) were used in Monte Carlo (MC) simulations on a series of phantom setups to investigate the impact of varying backscatter conditions on dosimetry. The depth dose curves for different field sizes, water phantom thicknesses and beam qualities were generated. In addition, depth dependent backscatter factors for different field sizes and different beam qualities were calculated. It is demonstrated that as much as a 50% dose difference exists for different backscatter conditions at the beam qualities studied. The choice of cell dish size as well as other changes in the experiment setup can have more than 10% impact on the dose. The impact of backscatter is reduced with a decrease in field size. Further, the thickness needed to provide full backscatter can be approximated as being equal to the field size. It is imperative to ensure full backscatter conditions during system and dosimeter calibration, or to use the look-up table provided in this study.
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Affiliation(s)
- Quan Chen
- Department of Radiation Medicine, The University of Kentucky, Lexington, KY 40536, United States of America. Author to whom any correspondence should be addressed. Radiation Medicine, University of Kentucky, Markey Cancer Center, Rm CC063, 800 Rose St., Lexington, KY 40536-0293, United States of America
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Hill R, Healy B, Butler D, Odgers D, Gill S, Lye J, Gorjiara T, Pope D, Hill B. Australasian recommendations for quality assurance in kilovoltage radiation therapy from the Kilovoltage Dosimetry Working Group of the Australasian College of Physical Scientists and Engineers in Medicine. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2018; 41:781-808. [DOI: 10.1007/s13246-018-0692-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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A comparison of surface doses for very small field size x-ray beams: Monte Carlo calculations and radiochromic film measurements. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2014; 37:303-9. [DOI: 10.1007/s13246-014-0260-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 03/04/2014] [Indexed: 12/15/2022]
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A study on the use of Gafchromic™ EBT3 film for output factor measurements in kilovoltage X-ray beams. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2013; 36:465-71. [DOI: 10.1007/s13246-013-0226-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2013] [Accepted: 10/21/2013] [Indexed: 10/26/2022]
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Eaton DJ, Doolan PJ. Review of backscatter measurement in kilovoltage radiotherapy using novel detectors and reduction from lack of underlying scattering material. J Appl Clin Med Phys 2013; 14:4358. [PMID: 24257277 PMCID: PMC5714622 DOI: 10.1120/jacmp.v14i6.4358] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 06/18/2013] [Accepted: 06/11/2013] [Indexed: 11/23/2022] Open
Abstract
Lack of underlying material can lead to dose reduction in kilovoltage radiotherapy treatments because of backscatter reduction. Conversely, the use of lead shielding can lead to large dose enhancement close to the lead interface. GAFCHROMIC film has been shown to be of use in verification of local backscatter factors compared to reference data in codes of practice, but careful handling and multiple readings are required to reduce systematic uncertainties to between 3% and 4%. Monte Carlo modeling of the specific treatment unit should be performed in cases which are found to differ from reference values before alternative values are adopted clinically, but these cases are expected to be few. GAFCHROMIC film may also be used to estimate backscatter reduction more readily than customized ionization chambers, for a range of beam qualities, applicator sizes and depth, with and without lead shielding. Differences were found between different studies, and it is not clear to what extent these are due to variation in equipment and/or technique. However, a layer of wax around lead shielding of 1 mm thickness should be sufficient to eliminate lead enhancement effects for all kilovoltage energies from 40 kV to 300 kV.
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