Effect of TLD-700H (LiF: Mg, Cu, P) sensitivity loss at multiple read-irradiation cycles on TLD reader calibration

Voss, S.; Sucheta, Artur; Romanyukha, A.; Moscovitch, M; Kennemur, Lisa; Benevides, Luis A.

doi:10.1016/j.radmeas.2011.04.017

Cited by 10 publications

(5 citation statements)

References 4 publications

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“…These were chosen due to their high sensitivity (Nakajima et al 1978, Horowitz andMoscovitch 2013), near tissue equivalence and linearity with dose up to 20 Gy (Moscovitch 1999, Velbeck et al 2006. However, TLDs of this type are known to have decreasing sensitivity when exposed to increasing values of dose (DeWerd et al 1983, Kim et al 2010, Konnai et al 2010, Voss et al 2011, Horowitz and Moscovitch 2013) so all measurements were caa risk of errors arrefully controlled to account for this decrease. The same three TLDs were used throughout the study and an optimum glow curve was used based on the advice of the manufacturer.…”

Section: 14mentioning

confidence: 99%

A method to calibrate the RS 2000 x-ray biological irradiator for radiobiological flank irradiation of mice

Moore

Wood

Cawthorne

et al. 2016

Biomed. Phys. Eng. Express

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This work investigated a method to calibrate the irradiation by an x-ray cabinet of tumours inserted on the flanks of mice. For the x-ray energies used by such devices, the radiotherapy treatment metric of absorbed dose to water (D W ) requires knowledge of the half value layer (HVL) of the beam spectrum. This is usually measured in a scatter free environment, but such a measurement inside a cabinet with our specific exposure geometry is impractical. Therefore, a novel way of evaluating HVL was devised and used to calibrate an RS 2000 cabinet in terms of D W . This calibration used the relevant IPEMB code of practice and was traceable to the UK primary standard for air kerma. This code is used by every radiotherapy department in the UK. To facilitate convenient calibration of different types of dosimeter in the hospital radiotherapy department a cabinet was produced in-house and used with a clinical superficial x-ray device to mimic the spectral properties in the university based RS 2000. To measure the HVL inside the cabinet, the response of thermoluminescent dosimeters (TLDs) to that of a secondary-standard ionisation chamber (M TLD /M S ) was derived across an appropriate range of HVLs free-in-air. Measurements were then taken in the in-house cabinet with TLDs and ion chamber under conditions that simulated the position of the animal flank implanted tumour (i.e. with our specific experimental geometry) to derive an average M TLD /M S from which the HVL of the incident beam was calculated. Chamber readings were converted to D W (without the need to use modified backscatter factors) and used to calibrate TLDs which were subsequently employed in the RS 2000 cabinet to allow conversion of exposure time to dose. The uncertainty in calculated dose was ±3.8%.

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Section: 14mentioning

confidence: 99%

A method to calibrate the RS 2000 x-ray biological irradiator for radiobiological flank irradiation of mice

Moore

Wood

Cawthorne

et al. 2016

Biomed. Phys. Eng. Express

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“…Exceeding a maximum temperature of 260°C causes a loss of TLD sensitivity (Voss et al 2011), whereas a maximum temperature below 260°C results Cs dose equivalent, which was used as the source of irradiation. The following standard time-temperature profile (TTP) was applied to the TLDs being studied: first, a pre-read annealing to remove the low temperature peaks at a constant temperature of 165°C for 10 s; then linear heating at 15°C s −1 from 165°C to a maximum temperature of 260°C over a total time of 16.66 s for acquisition of data; and finally, a post-read annealing for 10 s at 260°C.…”

Section: Experimental Facilities and Test Plansmentioning

confidence: 99%

The High Dose Response and Functional Capability of the DT-702/Pd Lithium fluoride Thermoluminescent Dosimeter

Lawlor

Talmadge²,

Murray³

et al. 2015

Health Physics

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The United States Navy monitors the dose its radiation workers receive using the DT-702/PD thermoluminescent dosimeter, which consists of the Harshaw 8840 holder and the four-element Harshaw 8841 card. There were two main objectives of this research. In the first objective, the dosimeters were exposed to 100 Gy using electron and x-ray beams and found to respond approximately 30-40% lower than the delivered dose. No significant effect on the under-response was found when dose rate, radiation type, dosimeter position on the phantom, and dosimeter material were varied or when the card was irradiated while enclosed in its holder. Since the current naval policy is to remove from occupational use any thermoluminescent dosimeter with an accumulated deep dose equivalent of 0.05 Sv or greater, the functionality of the dosimeter was also investigated at deep dose equivalents of 0.05, 0.15, and 0.25 Sv using 60Co and 137Cs sources as the second main objective. All dosimeters were annealed following exposure and then exposed to 5.0 mSv from a 90Sr source. In all cases, the dosimeters responded within 3% of the delivered dose, indicating that the dosimeters remained functional as defined by naval dosimetry requirements. However, the anneal time required to clear the thermoluminescent dosimeter's reading was found to increase approximately as the cube root with the delivered dose.

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“…Thus, for a 20-y-old card the number of heatings will be below 100. According to Voss et al (2011), 100 heatings would cause about 1% of sensitivity loss but not the 20% difference that was seen for new and old TLD cards. Furthermore, according to NDC internal policy, every 2 y every TLD card is the subject of new calibration.…”

Section: Introductionmentioning

confidence: 98%

“…It depends on many factors, including the dosimeter's usage. In 2011, Voss et al (2011) investigated the effect of multiple read irradiation cycles on TLD card sensitivity. According to this research, 1,000 heat-irradiation cycles causes about 10% sensitivity loss for card elements 1, 2, and 4 if reader is functioning properly.…”

Section: Introductionmentioning

confidence: 99%

Effect of Teflon Transmittance on Sensitivity of Thermoluminescence Dosimeter Cards

et al. 2020

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Thermoluminescence dosimeter cards purchased by the US Navy in recent years have different radiation sensitivities, e.g., they exhibit a different amount of light per dose unit. Presented tests indicate that the optical transparency of the Teflon encapsulation is partially responsible for the significant variation of the DT-702/PD radiation sensitivity. It was confirmed also that the Teflon transparency is in fact a primary cause of the radiation sensitivity increase in the most recently produced dosimetric cards. This conclusion is based on the correlation found between the calibrated radiation sensitivity of the dosimeter card element and the optical transparency of its Teflon encapsulation. The transparency measurements were performed at the wavelength of 400 nm within a 10 nm spectral interval effectively covering the spectral range of the thermoluminescence. It is anticipated that the experimentally determined correlation will help to approve the acceptance of new thermoluminescence dosimeter cards in the Naval Dosimetry Center inventory as well as improve the production process.

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Effect of TLD-700H (LiF: Mg, Cu, P) sensitivity loss at multiple read-irradiation cycles on TLD reader calibration

Cited by 10 publications

References 4 publications

A method to calibrate the RS 2000 x-ray biological irradiator for radiobiological flank irradiation of mice

A method to calibrate the RS 2000 x-ray biological irradiator for radiobiological flank irradiation of mice

The High Dose Response and Functional Capability of the DT-702/Pd Lithium fluoride Thermoluminescent Dosimeter

Effect of Teflon Transmittance on Sensitivity of Thermoluminescence Dosimeter Cards

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