A brachytherapy photon radiation quality index Q BT for probe-type dosimetry

Quast, Ulrich; Kaulich, Theodor W.; Álvarez-Romero, José T.; Tedgren, Åsa Carlsson; Enger, Shirin A.; Medich, David C.; Mourtada, Firas; Pérez‐Calatayud, José; Rivard, Mark J.; Zakaria, Golam Abu

doi:10.1016/j.ejmp.2016.03.008

Cited by 4 publications

(3 citation statements)

References 27 publications

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“…It is a constant for an ideal detector. Real detectors in BT may exhibit dependence of R Q on the beam quality Q owing to differences in LET of secondary particles . In general, the

R_{Q_{0}} / R_{Q}

ratio has to be determined experimentally.…”

Section: Theorymentioning

confidence: 99%

“…Real detectors in BT may exhibit dependence of R Q on the beam quality Q owing to differences in LET of secondary particles. 30 In general, the R Q 0 =R Q ratio has to be determined experimentally. Since photon energy spectrum of 192 Ir sources depends on the point of measurement, k Q;Q 0 might be a function of source-to-detector distance (SDD) depending on the type of the detector.…”

Section: A Dosimetry Formalismmentioning

confidence: 99%

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Suitability of microDiamond detectors for the determination of absorbed dose to water around high‐dose‐rate ¹⁹²Ir brachytherapy sources

et al. 2017

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Purpose: Experimental dosimetry of high-dose-rate (HDR) 192 Ir brachytherapy (BT) sources is complicated due to high dose and dose-rate gradients, and softening of photon energy spectrum with depth. A single crystal synthetic diamond detector microDiamond (PTW 60019, Freiburg, Germany) has a small active volume, high sensitivity, direct readout, and nearly water-equivalent active volume. The purpose of this study was to evaluate the suitability of microDiamond detectors for the determination of absorbed dose to water around HDR 192 Ir BT sources. Three microDiamond detectors were used, allowing for the comparison of their properties. Methods: In-phantom measurements were performed using microSelectron and VariSource iX HDR 192 Ir BT treatment units. Their treatment planning systems (TPSs), Oncentra (v. 4.3) and BrachyVision (v. 13.6), respectively, were used to create irradiation plans for a cubic PMMA phantom with the microDiamond positioned at one of three source-to-detector distances (SDDs) (1.5, 2.5, and 5.5 cm) at a time. The source was stepped in increments of 0.5 cm over a total length of 6 cm to yield absorbed dose of 2 Gy at the nominal reference-point of the detector. Detectors were calibrated in 60 Co beam in terms of absorbed dose to water, and Monte Carlo (MC) calculated beam quality correction factors were applied to account for absorbed-dose energy dependence. Phantom correction factors were applied to account for differences in dimensions between the measurement phantom and a water phantom used for absorbed dose calculations made with a TPS. The same measurements were made with all three of the detectors. Additionally, dose-rate dependence and stability of the detectors were evaluated in 60 Co beam. Results: The percentage differences between experimentally determined and TPS-calculated absorbed doses to water were from À1.3% to +2.9%. The values agreed to within experimental uncertainties, which were from 1.9% to 4.3% (k = 2) depending on the detector, SDD and treatment delivery unit. No dose-rate or intrinsic energy dependence corrections were applied. All microDiamonds were comparable in terms of preirradiation dose, stability of the readings and energy response, and showed a good agreement. Conclusions:The results indicate that the microDiamond is potentially suitable for the determination of absorbed dose to water around HDR 192 Ir BT sources and may be used for independent verification of TPS's calculations, as well as for QA measurements of HDR 192 Ir BT treatment delivery units at clinical sites.

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“…It is a constant for an ideal detector. Real detectors in BT may exhibit dependence of R Q on the beam quality Q owing to differences in LET of secondary particles . In general, the

R_{Q_{0}} / R_{Q}

ratio has to be determined experimentally.…”

Section: Theorymentioning

confidence: 99%

Section: A Dosimetry Formalismmentioning

confidence: 99%

Suitability of microDiamond detectors for the determination of absorbed dose to water around high‐dose‐rate ¹⁹²Ir brachytherapy sources

et al. 2017

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“…In BT, a strict beam quality specification does not exist. It has been proposed to use a ratio of absorbed dose to water values at 2 and 1 cm distances for a specific source type as the beam quality specification and to treat k Q,Q0 as a function of source-todetector distance (Quast et al 2016). The suggested notation has not caught on in the BT field.…”

Section: Determination Of Absorbed Dose To Watermentioning

confidence: 99%

Development of Experimental Brachytherapy Dosimetry Using Monte Carlo Simulations for Detector Characterization

Kaveckyte

2021

Linköping University Medical Dissertations

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Brachytherapy (BT) is advantageous due to high absorbed dose conformity and possibility to deliver high dose in few fractions. It is often used for prostate and gynecological tumors as monotherapy or as a boost alongside external beam radiotherapy (EBRT). However, a number of things can compromise treatment delivery, starting from incorrect source data in a treatment planning system to malfunctioning of a treatment delivery unit. The established quality assurance (QA) covers individual aspects, such as software checks of absorbed dose calculations, mechanical checks, source dosimetry. None of them emulate treatment delivery where the planned dose could be compared with the experimentally determined values. While such practices are employed in EBRT, BT suffers from the lack of detectors that would be water-equivalent and convenient to use for regular measurements. First-choice thermoluminescence dosimeters are water-equivalent but have passive readout. Sporadic attempts to use other detectors have not led to any established practices at clinical sites. Stepping ahead, the safety of treatment delivery could be further evaluated using real-time in vivo dosimetry. If detectors were characterized with high accuracy, a reliable error detection level could be set to terminate treatments if needed. Contrary to the inphantom QA, there are detectors suitable for such applications, but their characterization is incomplete. In this thesis we address both problems.Focusing on high-dose-rate 192 Ir remote afterloading treatments, which are among the most common in BT, we investigate and propose a direct readout synthetic diamond detector for the in-phantom QA of treatment units. The detector was designed for small-field highenergy EBRT dosimetry, but our findings demonstrate its suitability for BT dosimetry. Additionally, due to the detector calibration with traceability to primary standards of absorbed dose to water of high-energy EBRT and a combination of experimental and Monte Carlo (MC) characterization, the uncertainties in the determined absorbed dose to water values were comparable to or lower than for other detectors used in BT. We complemented the investigation with a theoretical study on diamond material properties and which values (mass density, mean excitation energy, number of conduction electrons per atom) shall be used for the most faithful description of ionizing radiation interactions in diamond for MC simulations and calculations of mass electronic stopping power. The findings improve diamond dosimetry accuracy not only in BT but also in EBRT where the detectors are used.

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Feasibility of a Tungsten-181 HDR brachytherapy source: Analysis of isotope production and source dosimetry

Jalbert,

Munro,

Medich

2024

Applied Radiation and Isotopes

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A brachytherapy photon radiation quality index Q BT for probe-type dosimetry

Cited by 4 publications

References 27 publications

Suitability of microDiamond detectors for the determination of absorbed dose to water around high‐dose‐rate ¹⁹²Ir brachytherapy sources

Suitability of microDiamond detectors for the determination of absorbed dose to water around high‐dose‐rate ¹⁹²Ir brachytherapy sources

Development of Experimental Brachytherapy Dosimetry Using Monte Carlo Simulations for Detector Characterization

Feasibility of a Tungsten-181 HDR brachytherapy source: Analysis of isotope production and source dosimetry

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A brachytherapy photon radiation quality index Q BT for probe-type dosimetry

Cited by 4 publications

References 27 publications

Suitability of microDiamond detectors for the determination of absorbed dose to water around high‐dose‐rate 192Ir brachytherapy sources

Suitability of microDiamond detectors for the determination of absorbed dose to water around high‐dose‐rate 192Ir brachytherapy sources

Development of Experimental Brachytherapy Dosimetry Using Monte Carlo Simulations for Detector Characterization

Feasibility of a Tungsten-181 HDR brachytherapy source: Analysis of isotope production and source dosimetry

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Suitability of microDiamond detectors for the determination of absorbed dose to water around high‐dose‐rate ¹⁹²Ir brachytherapy sources

Suitability of microDiamond detectors for the determination of absorbed dose to water around high‐dose‐rate ¹⁹²Ir brachytherapy sources