Determination of absorbed dose to water around a clinical HDR<sup>192</sup>Ir source using LiF:Mg,Ti TLDs demonstrates an LET dependence of detector response

Tedgren, Åsa Carlsson; Elia, Rouba; Hedtjärn, Håkan; Olsson, Sara; Carlsson, Gudrun Alm

doi:10.1118/1.3675401

Cited by 20 publications

(21 citation statements)

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“…Such an agreement was better than or comparable to that reported in similar studies with lithium formate and alanine EPR dosimeters, TLDs, MOSFETs, and plastic scintillators . The total uncertainties in ( D w, Q ) w ranged from 1.9% to 4.3% ( k = 2), and were also comparable to those estimated for TLDs, EPR detectors and MOSFETs in similar studies. Since the experimental determination of absorbed doses to water was independent of TPS's calculations, these results show that the microDiamond is potentially useful for end‐to‐end checks of HDR 192 Ir treatment delivery units.…”

Section: Resultssupporting

confidence: 82%

“…For details, see Refs. and . Note that the data from these studies are presented without the correction for the relative intrinsic energy dependence

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

of the detectors.…”

Section: Resultsmentioning

confidence: 99%

“…However, their labor‐intensive signal readout process and individual calibration make their routine use impractical at clinical sites. The use of TLDs calibrated in high energy photon beams is further complicated due to their intrinsic energy dependence which is related to the linear energy transfer (LET) of secondary electrons and affected by annealing and readout conditions . EPR dosimeters made of lithium formate (LiFo) and alanine were shown to have dosimetric properties suitable for dosimetry of HDR 192 Ir BT sources but do not provide high spatial resolution due to their size (typically, diameter 5 mm, thickness 2.5 mm), exhibit intrinsic energy dependence, are time‐consuming to use and require dedicated readout equipment.…”

Section: Introductionmentioning

confidence: 99%

“…The use of TLDs calibrated in high energy photon beams is further complicated due to their intrinsic energy dependence which is related to the linear energy transfer (LET) of secondary electrons and affected by annealing and readout conditions. [2][3][4][5][6] EPR dosimeters made of lithium formate (LiFo) and alanine were shown to have dosimetric properties suitable for dosimetry of HDR 192 Ir BT sources 7-10 but do not provide high spatial resolution due to their size (typically, diameter 5 mm, thickness 2.5 mm), exhibit intrinsic energy dependence, are time-consuming to use and require dedicated readout equipment. MOSFET detectors made of silicon are favorable due to small size and direct readout, but suffer from absorbed-dose energy dependence, as well as accumulateddose and angular dependences, all of which may be sensor dependent and require extensive characterization to reduce uncertainties associated with the performance of the detector.…”

Section: Introductionmentioning

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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Section: Resultssupporting

confidence: 82%

“…For details, see Refs. and . Note that the data from these studies are presented without the correction for the relative intrinsic energy dependence

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

of the detectors.…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

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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“…where D TLD ðQÞ is the average absorbed dose in TLD for a given radiation quality Q, k bq (Q) is the intrinsic energy dependence, which is associated with the signal formation process of the dosimeter and its dependence on the linear energy transfer of the radiation, 36,41,[46][47][48][49] and it can only be determined experimentally if one uses MC or other techniques to calculate f(Q) and thereby extract k bq ðQÞ from the measured value of S AD;med ðQÞ, and f(Q) is the absorbed dose energy dependence, which depends on medium and TLD cross-sections, TLD self-attenuation and volume averaging, and can be estimated using MC simulation techniques.…”

Section: D Tld Dosimetry Correctionsmentioning

confidence: 99%

Supplement 2 for the 2004 update of theAAPMTask Group No. 43 Report: Joint recommendations by theAAPMandGEC‐ESTRO

et al. 2017

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Cs (IsoRay Medical model CS-1 Rev2). Observations are included on the behavior of these dosimetry parameters as a function of radionuclide. Recommendations are presented on the selection of dosimetry parameters, such as from societal reports issuing consensus datasets (e.g., TG-43U1, AAPM Report #229), the joint AAPM/IROC Houston Registry, the GEC-ESTRO website, the Carleton University website, and those included in software releases from vendors of treatment planning systems. Aspects such as timeliness, maintenance, and rigor of these resources are discussed.Links to reference data are provided for radionuclides (radiation spectra and half-lives) and dose scoring materials (compositions and mass densities). The recent literature is examined on photon energy response corrections for thermoluminescent dosimetry of low-energy photon-emitting brachytherapy sources. Depending upon the dosimetry parameters currently used by individual physicists, use of these recommended consensus datasets may result in changes to patient dose calculations. These changes must be carefully evaluated and reviewed with the radiation oncologist prior to their implementation.

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Energy dependence of a radiophotoluminescent glass dosimeter for HDR¹⁹²Ir brachytherapy source

et al. 2018

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Purpose We determined correction factors for absorbed dose energy dependence and intrinsic energy dependence for measurements of absorbed dose to water around an 192Ir source using a radiophotoluminescent glass dosimeter (RPLD) calibrated with a 4‐MV photon beam. Methods The ratio of the absorbed dose to the water and the average absorbed dose to RPLD for the 192Ir beam relative to the same ratio in a 4 MV photon beam defines the absorbed dose energy dependence and was determined at distances of 2–10 cm (at intervals of 1 cm) from the 192Ir source in a water phantom using the egs_chamber user code. The RPLD was calibrated to measure absorbed dose to water, Dw, in a 4 MV photon beam using an ionization chamber, which was also used to measure absorbed dose to water, Dw, in a water phantom using the 192Ir source. The detector response radiophotoluminescence (RPL signal per average absorbed dose in the detector) in the 192Ir beam relative to that in the 4 MV photon beam (the relative intrinsic efficiency) was determined experimentally. Finally, the beam quality correction factor was obtained as the quotient between the absorbed dose energy dependence and the relative intrinsic efficiency and corrects for the difference between the beam quality Q0 used at calibration and the beam quality Q used in the measurements. Results The relative dose ratio of the average absorbed dose to water relative to RPLD ranged from 0.930 to 0.746, and the beam quality correction factor ranged from 0.999 to 0.794 for distances of 2–10 cm from the 192Ir source. The relative detector response to an 192Ir source and a 4‐MV photon beam was 0.930, and it did not vary significantly with distance. Conclusions These results demonstrate that corrections for absorbed dose energy dependence and intrinsic energy dependence are required when using an RPLD to measure with sources different from the reference source providing the primary calibration.

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Determination of absorbed dose to water around a clinical HDR¹⁹²Ir source using LiF:Mg,Ti TLDs demonstrates an LET dependence of detector response

Cited by 20 publications

References 20 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

Supplement 2 for the 2004 update of theAAPMTask Group No. 43 Report: Joint recommendations by theAAPMandGEC‐ESTRO

Energy dependence of a radiophotoluminescent glass dosimeter for HDR¹⁹²Ir brachytherapy source

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Determination of absorbed dose to water around a clinical HDR192Ir source using LiF:Mg,Ti TLDs demonstrates an LET dependence of detector response

Cited by 20 publications

References 20 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

Supplement 2 for the 2004 update of theAAPMTask Group No. 43 Report: Joint recommendations by theAAPMandGEC‐ESTRO

Energy dependence of a radiophotoluminescent glass dosimeter for HDR192Ir brachytherapy source

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Determination of absorbed dose to water around a clinical HDR¹⁹²Ir source using LiF:Mg,Ti TLDs demonstrates an LET dependence of detector response

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

Energy dependence of a radiophotoluminescent glass dosimeter for HDR¹⁹²Ir brachytherapy source