Simulation evaluation of NIST air‐kerma rate calibration standard for electronic brachytherapy

Hiatt, Jessica R.; Rivard, Mark J.; Hughes, H.G.

doi:10.1118/1.4940791

Cited by 9 publications

(6 citation statements)

References 31 publications

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“…The accurate description of eBT sources may be one of the most challenging Monte Carlo calculations in radiation dosimetry . The analysis of the differences between the four source models used in this work shows that the main source of discrepancies comes from differences in the electron energy distribution.…”

Section: Discussionmentioning

confidence: 53%

A Monte Carlo‐based dosimetric characterization of Esteya^®, an electronic surface brachytherapy unit

Valdes-Cortez

Niatsetski²,

Pérez‐Calatayud

et al. 2018

Medical Physics

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Purpose: The purpose of this work is threefold: First, to obtain the phase space of an electronic brachytherapy (eBT) system designed for surface skin treatments. Second, to explore the use of some efficiency enhancing (EFEN) strategies in the determination of the phase space. Third, to use the phase space previously obtained to perform a dosimetric characterization of the Esteya eBT system. Methods: The Monte Carlo study of the 69.5 kVp x-ray beam of the Esteya â unit (Elekta Brachytherapy, Veenendaal, The Netherlands) was performed with PENELOPE2014. The EFEN strategies included the use of variance reduction techniques and mixed Class II simulations, where transport parameters were fine-tuned. Four source models were studied varying the most relevant parameters characterizing the electron beam impinging the target: the energy spectrum (mono-energetic or Gaussian shaped), and the electron distribution over the focal spot (uniform or Gaussian shaped). Phase spaces obtained were analyzed to detect differences in the calculated data due to the EFEN strategy or the source configuration. Depth dose curves and absorbed dose profiles were obtained for each source model and compared to experimental data previously published. Results: In our EFEN strategy, the interaction forcing variance reduction (VRIF) technique increases efficiency by a factor~20. Tailoring the transport parameters values (C1 and C2) does not increase the efficiency in a significant way. Applying a universal cutoff energy EABS of 10 keV saves 84% of CPU time while showing negligible impact on the calculated results. Disabling the electron transport by imposing an electron energy cutoff of 70 keV (except for the target) saves an extra 8% (losing in the process 1.2% of the photons). The Gaussian energy source (FWHM = 10%, centered at the nominal kVp, homogeneous electron distribution) shows characteristic K-lines in its energy spectrum, not observed experimentally. The average photon energy using an ideal source (mono-energetic, homogeneous electron distribution) was 36.19 AE 0.09 keV, in agreement with the published measured data of 36.2 AE 0.2 keV. The use of a Gaussian-distributed electron source (mono-energetic) increases the penumbra by 50%, which is closer to the measurement results. The maximum discrepancy of the calculated percent depth dose with the corresponding measured values is 4.5% (at the phantom surface, less than 2% beyond 1 mm depth) and 5% (for the 80% of the field) in the dose profile. Our results agree with the findings published by other authors and are consistent within the expected Type A and B uncertainties. Conclusions: Our results agree with the published measurement results within the reported uncertainties. The observed differences in PDD, dose profiles, and photon spectrum come from three main sources of uncertainty: intermachine variations, measurements, and Monte Carlo calculations. It has been observed that a mono-energetic source with a Gaussian electron distribution over the focal spot is a suitable choice to reproduc...

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Section: Discussionmentioning

confidence: 53%

A Monte Carlo‐based dosimetric characterization of Esteya^®, an electronic surface brachytherapy unit

Valdes-Cortez

Niatsetski²,

Pérez‐Calatayud

et al. 2018

Medical Physics

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“…As for the calculation method used, it is recommended to consider tissue composition and to perform the calculations based on Monte Carlo models . Our calculations were based on TG‐43, which was modified for eBT, with no correction for heterogeneity, since this was the algorithm used in our TPS and in many other hospitals, for which our results will prove useful.…”

Section: Discussionmentioning

confidence: 99%

Treatment of cervical cancer with electronic brachytherapy

Lozares

Gandía-Martínez

Miranda-Burgos

et al. 2019

J Applied Clin Med Phys

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Purpose We report the first cervical cancer cases treated with interstitial electronic brachytherapy (eBT) at our hospital and compare them with plans made with high‐dose‐rate interstitial brachytherapy based on Ir192 (HDR‐BT). Materials and methods Eight patients with cervical cancer were treated with the Axxent eBT device (Xoft, Inc.). Planning was with magnetic resonance imaging and computed tomography following the recommendations of the EMBRACE protocol. The dosimetry parameters of organs at risk (OAR) were evaluated for the bladder, rectum, and sigmoid colon (D2cc, D1cc, and D0.1cc). In addition, the V150 and V200 of irradiated tissue were compared for both eBT and HDR‐BT. All patients received intensity‐modulated external beam radiation therapy with a regimen of 23 sessions of 2 Gy followed by four sessions of 7 Gy of eBT performed over 2 weeks (two sessions followed by another two sessions a week later) following the EMBRACE recommendations. Each of the eight patients was followed to assess acute toxicity associated with treatment. Results The doses reaching OAR for eBT plans were lower than for HDR‐BT plans. As for acute toxicity associated with eBT, very few cases of mucositis were detected. No cases of rectal toxicity and one case with grade 1 urinary toxicity were detected. The results at 1 month are equally good, and no relapses have occurred to date. Conclusions The first results of treatment with the Axxent eBT device are promising, as no recurrences have been observed and toxicity is very low. eBT is a good alternative for treating cervical cancer in centers without access to conventional HDR.

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“…It has been reported that spectral discrepancies have been observed in the modeling of an electronic brachytherapy source depending on the MC code (and code version) used, due in part to the number of explicit subshells considered. 13,14 In addition to low-energy and Mand N-shell averaging would also affect the modeling of dose enhancement with gold nanoparticles, as the emission of Auger electrons and characteristic x-rays is one of the primary mechanisms for enhancing dose to surrounding tissue. 15…”

Section: Discussionmentioning

confidence: 99%

Technical Note: Effect of explicit M and N‐shell atomic transitions on a low‐energy x‐ray source

Watson

Seuntjens

2016

Medical Physics

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Simulation evaluation of NIST air‐kerma rate calibration standard for electronic brachytherapy

Cited by 9 publications

References 31 publications

A Monte Carlo‐based dosimetric characterization of Esteya^®, an electronic surface brachytherapy unit

A Monte Carlo‐based dosimetric characterization of Esteya^®, an electronic surface brachytherapy unit

Treatment of cervical cancer with electronic brachytherapy

Technical Note: Effect of explicit M and N‐shell atomic transitions on a low‐energy x‐ray source

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Simulation evaluation of NIST air‐kerma rate calibration standard for electronic brachytherapy

Cited by 9 publications

References 31 publications

A Monte Carlo‐based dosimetric characterization of Esteya®, an electronic surface brachytherapy unit

A Monte Carlo‐based dosimetric characterization of Esteya®, an electronic surface brachytherapy unit

Treatment of cervical cancer with electronic brachytherapy

Technical Note: Effect of explicit M and N‐shell atomic transitions on a low‐energy x‐ray source

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A Monte Carlo‐based dosimetric characterization of Esteya^®, an electronic surface brachytherapy unit

A Monte Carlo‐based dosimetric characterization of Esteya^®, an electronic surface brachytherapy unit