Electronic brachytherapy—current status and future directions

Eaton, D.

doi:10.1259/bjr.20150002

Cited by 64 publications

(73 citation statements)

References 81 publications

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“…8 Evaluation and verification of the absorbed depth-dose and the corresponding beam calibration represent an essential part of the quality control procedure for an eBT system. [9][10][11] Currently, the most common calibration protocols make use of the experimentally measured half-value layer (HVL) as the beam quality index. 12,13 Performing such measurement requires the availability of aluminum slabs of high purity (99.9%) with a thickness accuracy better than 0.05 mm.…”

Section: Introductionmentioning

confidence: 99%

On the use of the absorbed depth‐dose measurements in the beam calibration of a surface electronic high‐dose‐rate brachytherapy unit, a Monte Carlo‐based study

Valdes-Cortez¹,

Niatsetski²,

Ballester³

et al. 2019

Medical Physics

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Purpose To evaluate the use of the absorbed depth‐dose as a surrogate of the half‐value layer in the calibration of a high‐dose‐rate electronic brachytherapy (eBT) equipment. The effect of the manufacturing tolerances and the absorbed depth‐dose measurement uncertainties in the calibration process are also addressed. Methods The eBT system Esteya® (Elekta Brachytherapy, Veenendaal, The Netherlands) has been chosen as a proof‐of‐concept to illustrate the feasibility of the proposed method, using its 10 mm diameter applicator. Two calibration protocols recommended by the AAPM (TG‐61) and the IAEA (TRS‐398) for low‐energy photon beams were evaluated. The required Monte Carlo (MC) simulations were carried out using PENELOPE2014. Several MC simulations were performed modifying the flattening filter thickness and the x‐ray tube potential, generating one absorbed depth‐dose curve and a complete set of parameters required in the beam calibration (i.e., HVL, backscatter factor (Bw), and mass energy‐absorption coefficient ratios (µen/ρ)water,air), for each configuration. Fits between each parameter and some absorbed dose‐ratios calculated from the absorbed depth‐dose curves were established. The effect of the manufacturing tolerances and the absorbed dose‐ratio uncertainties over the calibration process were evaluated by propagating their values over the fitting function, comparing the overall calibration uncertainties against reference values. We proposed four scenarios of uncertainty (from 0% to 10%) in the dose‐ratio determination to evaluate its effect in the calibration process. Results The manufacturing tolerance of the flattening filter (±0.035 mm) produces a change of 1.4% in the calculated HVL and a negligible effect over the Bw, (µen/ρ)water,air, and the overall calibration uncertainty. A potential variation of 14% of the electron energies due to manufacturing tolerances in the x‐ray tube (69.5 ± ~10 keV) generates a variation of 10% in the HVL. However, this change has a negligible effect over the Bw and (µen/ρ)water,air, adding 0.1% to the overall calibration uncertainty. The fitting functions reproduce the data with an uncertainty (k = 2) below 1%, 0.5%, and 0.4% for the HVL, Bw, and (µen/ρ)water,air, respectively. The four studied absorbed dose‐ratio uncertainty scenarios add, in the worst‐case scenario, 0.2% to the overall uncertainty of the calibration process. Conclusions This work shows the feasibility of using the absorbed depth‐dose curve in the calibration of an eBT system with minimal loss of precision.

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Section: Introductionmentioning

confidence: 99%

On the use of the absorbed depth‐dose measurements in the beam calibration of a surface electronic high‐dose‐rate brachytherapy unit, a Monte Carlo‐based study

Valdes-Cortez¹,

Niatsetski²,

Ballester³

et al. 2019

Medical Physics

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“…The output characteristics, spectrum, and features of the INTRABEAM system have been described. [9][10][11][12] 2.B | Calibration and specialized Zeiss water phantom Zeiss calibrates the INTRABEAM system using the setup published by Beatty et al 11 Per this setup, a DDC is measured from the XRS for 3-to 45-mm depth in steps of 0.5 mm as shown in [ Fig. 2(A)].…”

Section: A | Device Descriptionmentioning

confidence: 99%

Evaluation of the dosimetric impact of manufacturing variations for the INTRABEAM x‐ray source

Shaikh¹,

Joiner

Nalichowski

et al. 2020

J Applied Clin Med Phys

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Introduction INTRABEAM x‐ray sources (XRSs) have distinct output characteristics due to subtle variations between the ideal and manufactured products. The objective of this study is to intercompare 15 XRSs and to dosimetrically quantify the impact of manufacturing variations on the delivered dose. Methods and Materials The normality of the XRS datasets was evaluated with the Shapiro–Wilk test, the accuracy of the calibrated depth–dose curves (DDCs) was validated with ionization chamber measurements, and the shape of each DDC was evaluated using depth–dose ratios (DDRs). For 20 Gy prescribed to the spherical applicator surface, the dose was computed at 5‐mm and 10‐mm depths from the spherical applicator surface for all XRSs. Results At 5‐, 10‐, 20‐, and 30‐mm depths from the source, the coefficient of variation (CV) of the XRS output for 40 kVp was 4.4%, 2.8%, 2.0%, and 3.1% and for 50 kVp was 4.2%, 3.8%, 3.8%, and 3.4%, respectively. At a 20‐mm depth from the source, the 40‐kVp energy had a mean output in Gy/Minute = 0.36, standard deviation (SD) = 0.0072, minimum output = 0.34, and maximum output = 0.37 and a 50‐kVp energy had a mean output = 0.56, SD = 0.021, minimum output = 0.52, and maximum output = 0.60. We noted the maximum DRR values of 2.8% and 2.5% for 40 kVp and 50 kVp, respectively. For all XRSs, the maximum dosimetric effect of these variations within a 10‐mm depth of the applicator surface is ≤ 2.5%. The CV increased as depth increased and as applicator size decreased. Conclusion The American Association of Physicist in Medicine Task Group‐167 requires that the impurities in radionuclides used for brachytherapy produce ≤ 5.0% dosimetric variations. Because of differences in an XRS output and DDC, we have demonstrated the dosimetric variations within a 10‐mm depth of the applicator surface to be ≤ 2.5%.

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“…However, clinical opinion remains divided on their utility for some indications. 3 The 18 centres with no kV units were asked the reason for having no unit, with some centres giving more than 1 answer. Only four centres did not have enough patients, and two centres send patients elsewhere.…”

Section: Kilovoltage Equipment Profile In the Ukmentioning

confidence: 99%

“…2 More recently, electronic brachytherapy devices have been developed, which are miniature kV X-ray sources that mimic traditional radioactive sources. 3 The 2014 survey of clinical practice for skin cancer in the British Journal of Radiology (BJR) showed wide variation in workload, energies and non-standard fractionation regimes. 4 Publication of more data on local outcomes was suggested to improve consistency of prescribing.…”

Section: Introductionmentioning

confidence: 99%

Current status of kilovoltage (kV) radiotherapy in the UK: installed equipment, clinical workload, physics quality control and radiation dosimetry

Palmer

Pearson

Whittard

et al. 2016

The British Journal of Radiology

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Objective: To assess the status and practice of kilovoltage (kV) radiotherapy in the UK. Methods: 96% of the radiotherapy centres in the UK responded to a comprehensive survey. An analysis of the installed equipment base, patient numbers, clinical treatment sites, quality control (QC) testing and radiation dosimetry processes were undertaken. Results: 73% of UK centres have at least one kV treatment unit, with 58 units installed across the UK. Although 35% of units are over 10 years old, 39% units have been installed in the last 5 years. Approximately 6000 patients are treated with kV units in the UK each year, the most common site (44%) being basal cell carcinoma. A benchmark of QC practice in the UK is presented, against which individual centres can compare their procedures, frequency of testing and acceptable tolerance values. We propose the use of internal "notification" and "suspension" levels for analysis. All surveyed centres were using recommended Codes of Practice for kV dosimetry in the UK; approximately the same number using in-air and in-water methodologies for medium energy, with two-thirds of all centres citing "clinical relevance" as the reason for choice of code. 64% of centres had hosted an external dosimetry audit within the last 3 years, with only one centre never being independently audited. The majority of centres use locally measured applicator factors and published backscatter factors for treatments. Monitor unit calculations are performed using software in only 36% of centres. Conclusion: A comprehensive review of current kV practice in the UK is presented. Advances in knowledge: Data and discussion on contemporary kV radiotherapy in the UK, with a particular focus on physics aspects.

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Electronic brachytherapy—current status and future directions

Cited by 64 publications

References 81 publications

On the use of the absorbed depth‐dose measurements in the beam calibration of a surface electronic high‐dose‐rate brachytherapy unit, a Monte Carlo‐based study

On the use of the absorbed depth‐dose measurements in the beam calibration of a surface electronic high‐dose‐rate brachytherapy unit, a Monte Carlo‐based study

Evaluation of the dosimetric impact of manufacturing variations for the INTRABEAM x‐ray source

Current status of kilovoltage (kV) radiotherapy in the UK: installed equipment, clinical workload, physics quality control and radiation dosimetry

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