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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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Hewson EA, Butson MJ, Hill R. Evaluating TOPAS for the calculation of backscatter factors for low energy x-ray beams. ACTA ACUST UNITED AC 2018; 63:195014. [DOI: 10.1088/1361-6560/aadf28] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Damodar J, Odgers D, Pope D, Hill R. A study on the suitability of the PTW microDiamond detector for kilovoltage x-ray beam dosimetry. Appl Radiat Isot 2018; 135:104-109. [DOI: 10.1016/j.apradiso.2018.01.025] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2017] [Revised: 12/12/2017] [Accepted: 01/16/2018] [Indexed: 11/25/2022]
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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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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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Baldwin Z, Fitchew R. The influence of focal spot size, shape, emission profile and position on field coverage in a Gulmay D3300 Kilovoltage X-ray therapy unit. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2014; 37:515-23. [PMID: 24919986 DOI: 10.1007/s13246-014-0280-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2013] [Accepted: 05/25/2014] [Indexed: 10/25/2022]
Abstract
An important characteristic of kilovoltage therapy is the narrow penumbra obtainable with a well designed collimator system. A graphical illustration of applicator geometry is used to show that undesirable penumbral broadening and consequent reduction of field coverage could result if the upper aperture in an applicator is smaller than a critical size or if the applicator is not sufficiently well aligned with the focal spot. This concept is applied in an investigation of the formation of penumbra in the Gulmay D3300, in which the influence of the focal spot size, shape and emission profile, obtained from an image of the focal spot produced using a pin-hole in a sheet of lead, is elucidated. The effective focal spot of the Varian X-ray tube was observed to be rectangular, significantly longer in the front-back direction (6 mm) than in the anode-cathode direction (3.5 mm) and quite non-uniform in emission intensity over its length, with pronounced hot-spots at each end. It is shown that this results in a penumbra which is slightly broadened in the front-back direction when the alignment is perfect, but significantly broadened asymmetrically even when the alignment just meets the manufacturer's stated tolerance. Consequently the alignment, which is performed with an alignment jig supplied by the manufacturer, needs to be very precise to obtain acceptable field coverage, which needs to be checked following an X-ray tube change.
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Affiliation(s)
- Z Baldwin
- Cancer Care Services, Royal Brisbane and Women's Hospital, Level 4, Joyce Tweddell Building, Herston, QLD, 4029, Australia,
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Hill R, Healy B, Holloway L, Kuncic Z, Thwaites D, Baldock C. Advances in kilovoltage x-ray beam dosimetry. Phys Med Biol 2014; 59:R183-231. [DOI: 10.1088/0031-9155/59/6/r183] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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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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Perichon N, Rapp B, Denoziere M, Daures J, Ostrowsky A, Bordy JM. Comparison between absorbed dose to water standards established by water calorimetry at the LNE-LNHB and by application of international air-kerma based protocols for kilovoltage medium energy x-rays. Phys Med Biol 2013; 58:2787-806. [DOI: 10.1088/0031-9155/58/9/2787] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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The dosimetry of eye shields for kilovoltage X-ray beams. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2012. [DOI: 10.1007/s13246-012-0166-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Eaton DJ. Quality assurance and independent dosimetry for an intraoperative x-ray device. Med Phys 2012; 39:6908-20. [DOI: 10.1118/1.4761865] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Backscatter factor measurements for kilovoltage X-ray beams using thermoluminescent dosimeters (TLDs). RADIAT MEAS 2011. [DOI: 10.1016/j.radmeas.2011.08.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Carpenter CM, Pratx G, Sun C, Xing L. Limited-angle x-ray luminescence tomography: methodology and feasibility study. Phys Med Biol 2011; 56:3487-502. [PMID: 21606553 DOI: 10.1088/0031-9155/56/12/003] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
X-ray luminescence tomography (XLT) has recently been proposed as a new imaging modality for biological imaging applications. This modality utilizes phosphor nanoparticles which luminesce near-infrared light when excited by x-ray photons. The advantages of this modality are that it uniquely combines the high sensitivity of radioluminescent nanoparticles and the high spatial localization of collimated x-ray beams. Currently, XLT has been demonstrated using x-ray spatial encoding to resolve the imaging volume. However, there are applications where the x-ray excitation may be limited by geometry, where increased temporal resolution is desired, or where a lower dose is mandatory. This paper extends the utility of XLT to meet these requirements by incorporating a photon propagation model into the reconstruction algorithm in an x-ray limited-angle (LA) geometry. This enables such applications as image-guided surgery, where the ability to resolve lesions at depths of several centimeters can be the key to successful resection. The hybrid x-ray/diffuse optical model is first formulated and then demonstrated in a breast-sized phantom, simulating a breast lumpectomy geometry. Both numerical and experimental phantoms are tested, with lesion-simulating objects of various sizes and depths. Results show localization accuracy with median error of 2.2 mm, or 4% of object depth, for small 2-14 mm diameter lesions positioned from 1 to 4.5 cm in depth. This compares favorably with fluorescence optical imaging, which is not able to resolve such small objects at this depth. The recovered lesion size has lower size bias in the x-ray excitation direction than the optical direction, which is expected due to the increased optical scatter. However, the technique is shown to be quite invariant in recovered size with respect to depth, as the standard deviation is less than 2.5 mm. Sensitivity is a function of dose; radiological doses are found to provide sufficient recovery for µg ml(-1) concentrations, while therapy dosages provide recovery for ng ml(-1) concentrations. Experimental phantom results agree closely with the numerical results, with positional errors recovered within 8.6% of the effective depth for a 5 mm object, and within 5.2% of the depth for a 10 mm object. Object-size median error is within 2.3% and 2% for the 5 and 10 mm objects, respectively. For shallow-to-medium depth applications where optical and radio-emission imaging modalities are not ideal, such as in intra-operative procedures, LAXLT may be a useful tool to detect molecular signatures of disease.
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Affiliation(s)
- C M Carpenter
- Department of Radiation Oncology, School of Medicine, Stanford University, Stanford, CA 94305, USA.
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Smith L, Hill R, Nakano M, Kim J, Kuncic Z. The measurement of backscatter factors of kilovoltage X-ray beams using Gafchromic™ EBT2 film. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2011; 34:261-6. [DOI: 10.1007/s13246-011-0073-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2010] [Accepted: 04/05/2011] [Indexed: 10/18/2022]
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The Bland–Altman analysis: Does it have a role in assessing radiation dosimeter performance relative to an established standard? RADIAT MEAS 2010. [DOI: 10.1016/j.radmeas.2010.02.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Kim J, Hill R, Claridge Mackonis E, Kuncic Z. An investigation of backscatter factors for kilovoltage x-rays: a comparison between Monte Carlo simulations and Gafchromic EBT film measurements. Phys Med Biol 2010; 55:783-97. [DOI: 10.1088/0031-9155/55/3/016] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Hill R, Mo Z, Haque M, Baldock C. An evaluation of ionization chambers for the relative dosimetry of kilovoltage x-ray beams. Med Phys 2009; 36:3971-81. [DOI: 10.1118/1.3183820] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
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Jhala E, Steer B, Laban J, Greig L. Issues encountered with kilovoltage x-ray reference dosimetry when changing codes of practice from TRS 277 to TRS 398. ACTA ACUST UNITED AC 2009; 32:11-5. [DOI: 10.1007/bf03178622] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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