Thermoluminescent Dosimeter Badges Research Articles

A multi-stage machine learning algorithm for estimating personal dose equivalent using thermoluminescent dosimeter

In the present age, marked by data-driven advancements in various fields, the importance of machine learning (ML) holds a prominent position. The ability of ML algorithms to resolve complex patterns and extract insights from large datasets has solidified its transformative potential in various scientific domains. This paper introduces an innovative application of ML techniques in the domain of radiation dosimetry. Specifically, it shows the applicability of ML in estimating the radiation dose received by occupational workers. This estimation is expressed in terms of personal dose equivalent, and it involves the utilization of thermoluminescence signals emitted by CaSO4:Dy-based personnel monitoring badges. To estimate personal dose equivalent, three-stage algorithm driven by ML models is proposed. This algorithm systematically identifies the photon energy ranges, calculates the average photon energy, and determines personal dose equivalent. By implementing this approach to the conventional three-element dosimeter, the study overcomes existing limitations and enhances accuracy in dose estimation. The algorithm demonstrates 97.8% classification accuracy in discerning photon energy ranges and achieves a coefficient of determination of 0.988 for estimating average photon energy. Importantly, it also reduces the coefficient of variation of relative deviations by up to 6% for estimated personal dose equivalent, compared to existing algorithms. The study improves accuracy and establishes a new methodology for evaluating radiation exposure to occupational workers using conventional thermoluminescent dosimeter badge.

Occupational exposure risk to radiation in open cast artisanal and small-scale gold mining in Western Kenya

Artisanal and small-scale gold mining (ASSGM) is practiced at open-cast gold mines in Western Kenya. Mining is still going on in deep mines, with huge tailings littering the workplace for most miners. This mining exercise brings to the surface myriad radioactive materials from the earth’s crust, which pose physical and radiation hazards to miners. The aim of this study was to determine occupational exposure to radiation at artisanal gold mining sites. Four sites were studied for a period of six months. Environmental radiation exposure levels were measured using the Geiger Mueller tube (GMT) model; PHYWE, whereas thermoluminescent dosimeter badges (TLB) 802A were used to record personal radiation exposure levels. d-Orbital Limited Company provided UD-716AGL, used to read the radiation levels from the TLB. Exposure levels were reported in terms of monthly skin, eye, and body exposures. Results revealed an increase in counts per minute with an increase in depth in a range of 19.83 ± 3.87 to 27.83 ± 2.10 and a mean of 23.62 ± 5.17 cpm. Personal effective radiation exposure doses for the skin, eye and body were 0.19 ± 0.01, 0.19 ± 0.01 and 0.18 ± 0.015 for two sites in Western Kenya, whereas those in Nyanza had 0.27 ± 0.01, 0.27 ± 0.01 and 0.25 ± 0.05 mSv on skin, eye and body. The maximum dose threshold limit was estimated at 1.67 mSv per month. There was no significant difference in the radiation exposure of the eye, skin, and body between the sites as indicated by χ2 = 2.0 and p = 0.157 (at p<0.05) with df = 1. The study revealed that workers are exposed to ionising radiation, but the measured levels were within safe limits.

A Comparison of Readings from Thermoluminescent Dosimeter Ring Badges Worn in Different Positions

Our purpose was to evaluate whether the position of a thermoluminescent dosimeter (TLD) crystal results in different exposure readings. Methods: Nine subjects wore 2 TLD badges (one facing inward, toward the palm, and one facing outward) for 2 mo. Both TLDs were worn on the middle finger of the dominant hand, with the inward-facing TLD placed at the bottom and the outward-facing TLD at the top. At the end of the first month, these TLDs were replaced with new ones for another month. Combined results from the badges for the 2 mo were recorded in millisieverts. A paired t test with 2-sample means was performed to compare the 2 positions in general nuclear medicine and PET/CT subjects, with an α of 0.05. Results: For all subjects and for the general nuclear medicine and PET/CT groups, mean exposure was greater for the inward-facing TLD. Conclusion: For a TLD worn on the dominant hand, extremity-exposure readings are maximized when the TLD faces inward.

Radiation protection knowledge and practices in interventional cardiologists practicing in Africa: a cross sectional survey

We conducted a survey of doctors working in the cardiac catheterisation laboratories in Africa on their knowledge, attitude and practice with respect to radiation protection. Of seventy-two respondents contacted, 61 (84.7%) completed the questionnaire. Twenty-eight, (45.9%) were younger than 45 years. Thirty-seven, (60.6%) had less than 10 years of experience in the laboratory. Only 28 (45.9%) had undertaken radiation protection training. Fifty-eight, (95.1%) consistently used lead aprons. Forty-seven, (77%) reported consistently using thyroid shields. Ten (16.4%) consistently used radiation protection eyeglasses, whilst 36 (59%) never used them. Thermoluminescent Dosimeter badges were consistently used in 23 (37.7%). Forty-two, (68.9%) reported having ceiling mounted lead/acrylic shields. Level of radiation exposure in the most recent one year was ≤2 mSv in 14, between 2 and 20 mSv in 8 and between 20 and 30 mSv in 2, whilst 33 did not know their dose readings. The use of basic radiation protection tools as well as the knowledge and measurement of radiation exposure among interventional cardiologists working in Africa is low. The unavailability of some of the protective tools and a knowledge gap in terms of radiation protection and monitoring of self-exposure were some of the reasons for suboptimal self-protection against ionising radiation among our respondents. We suggest that initiatives be taken by all stakeholders to train this group of medical professionals in basic radiation protection to avoid unnecessary exposure to themselves, co-workers and patients.

A case of azoospermia in a non-destructive testing\xa0worker exposed to radiation

BackgroundInterest in radiation-related health problems has been growing with the increase in the number of workers in radiation-related jobs. Although an occupational level of radiation exposure would not likely cause azoospermia, several studies have reported the relation between radiation exposure and azoospermia after accidental or therapeutic radiation exposure. We describe a case of azoospermia in a non-destructive testing (NDT) worker exposed to radiation and discuss the problems of the related monitoring system.Case presentationA 39-year-old man who was childless after 8 years of marriage was diagnosed with azoospermia through medical evaluations, including testicular biopsy. He did not have any abnormal findings on biochemical evaluations, other risk factors, or evidence of congenital azoospermia. He had been working in an NDT facility from 2005 to 2013, attaching and arranging gamma-ray films on the structures and inner spaces of ships. The patient’s thermoluminescent dosimeter (TLD) badge recorded an exposure level of 0.01781 Gy for 80 months, whereas results of his florescence in situ hybridization (FISH) translocation assay showed an exposure level of up to 1.926 Gy of cumulative radiation, which was sufficient to cause azoospermia. Thus, we concluded that his azoospermia was caused by occupational radiation exposure.ConclusionThe difference between the exposure dose records measured through TLD badge and the actual exposure dose implies that the monitor used by the NDT worker did not work properly, and such a difference could threaten the health and safety of workers. Thus, to protect the safety and health of NDT workers, education of workers and strengthening of law enforcement are required to ensure that regulations are strictly followed, and if necessary, random sampling of NDT workers using a cytogenetic dosimeter, such as FISH, should be considered.

Radiation Exposure to Staff in Intensive Care Unit with Portable CT Scanner.

Background. Bedside radiological procedures pose a risk of radiation exposure to ICU staff. The perception of risk may increase the degree of caution among the health care staff and raise new barriers preventing patients from obtaining prompt care. Objective. The aim of this study was to estimate the annual cumulative radiation dose to individual ICU staff. Methods. In this prospective study, forty subjects were required to wear thermoluminescent dosimeter badges during their working hours. The badges were analyzed to determine the exposure after 3 months. Results. A total of 802 radiological procedures were completed at bedside during the study period. The estimated annual dosage to doctors and nurses on average was 0.99 mSv and 0.88 mSv (p < 0.001), respectively. Residents were subjected to the highest radiation exposure (1.04 mSv per year, p = 0.002). The radiation dose was correlated with day shift working hours (r = 0.426; p = 0.006) and length of service (r = −0.403; p < 0.01). Conclusions. With standard precautions, bedside radiological procedures—including portable CT scans—do not expose ICU staff to high dose of ionizing radiation. The level of radiation exposure is related to the daytime working hours and length of service.

Beta response of CaSO4:Dy based thermoluminescent dosimeter badge and its angular dependence studies for personnel monitoring applications

Studies on the response of 0.4 mm and 0.8 mm thick Teflon embedded CaSO4:Dy discs are carried out using different beta sources having energy ranging from 0.224 to 3.54 MeV. Angular dependence of the response for 0.4 and 0.8 mm thick thermoluminescence (TL) discs was also studied for 85 Kr and 90 Sr/90 Y beta sources. The ratio of the response of the open disc to that under 1.5 mm thick Perspex filter (DOpen/DPerspex) was estimated for 0.4 and 0.8 mm thick TL discs in the energy range from 0.689 to 3.54 MeV. The evaluation of (DOpen/DPerspex) ratio is necessary as same is used to estimate the energy of beta particles and to apply appropriate correction factor while evaluating beta dose. In addition to above, the optical density and transmission characteristics for 0.4 and 0.8 mm thick Teflon and CaSO4:Dy Teflon embedded discs are also reported.

Radiation hazards in operation theatre: Anaesthesiologist's concerns and preventive strategies.

Sir, The use of X-ray fluoroscopy has led to remarkable advancements in management of various disorders. However, operation theatre staff are repeatedly exposed to radiation, which can cause bone marrow suppression, genetic mutations and carcinogenesis, etc. The aim of this letter is to draw the attention of senior authorities to the fact that guidelines should be prepared and followed strictly to monitor radiation exposure to anaesthesiologists. Knowledge of various physical and biochemical aspects of radiation is important to prevent potential hazardous consequences of its exposure.[1] In a study comparing the effect of the use of single or two C-arms, duplicate thermoluminescent dosimeter (TLD) badges were placed on surgeons’ and scrub technicians’ eyewear, thyroid shields, and waist. It was concluded that the use of lead aprons and thyroid shields reduced radiation exposure by 50%.[2] The National Council on Radiation Protection was established in United States (US) to help set US policy on radiation protection.[3] Various prophylactic measures include increased filtration and use of higher tube voltage or lower tube current. Pulsed fluoroscopic operation should be set at rate of 4 pulses/s and C-arm should be positioned underneath the table. Recommended distance to avoid exposure is approximately 3 feet from the source.[4] The use of biplanar fluoroscopy reduces both radiation exposure and surgical time. Lead aprons should be regularly checked for any breakage by an assigned technician. Mobile full body lead shield can be used, as it can both effectively shield off scattered radiation and do not add extra weight. During repeated and long procedures, patients should also be protected with lead shield. Educational programs should be conducted for awareness of radiation hazards and safety measures among operation theatre personnel. Staff should be taught to avoid close contact with tilted side of fluoroscope as scattered radiation increases when emission tube gets tilted.[5] Certain adjustments in fluoroscopy machine such as avoiding any metal parts within fluoroscopy field, by closing iris and adjusting size of collimator, the amount of radiation generated can be reduced.[5] Lead acrylic glasses can be used to avoid damage to lens. Lead impregnated gloves can be used in high-risk procedures. Both ionising and non-ionising radiations pose potential hazards to anaesthesiologists. If recommended dose limit exceeds 15 mSv/year, cumulative effects of radiation can affect whole body or can result in localised effects such as cataract. Anaesthesiologists posted in OTs where fluoroscopy is used routinely should have two badges including one for cumulative and another for individual exposure. These badges should be made available from the reputed suppliers. Their use establishes the dose received and verifies the adequacies of facilities for radiation protection. As part of safety, according to Atomic Energy (Radiation Protection) Rules 2004 section (3), a licence/registration is necessary for establishing the radiation installation. This procedure involves three steps: The director, directorate of radiation safety (DRS) first approves the site where equipment has to be installed Then quality assurance test is done by the manufacturer or supplier under intimation to DRS After that licence/registration is issued by Atomic Energy Regulatory Board (AERB) through DRS. Recommendations from AERB to improve quality of care include: It is the responsibility of the employer to provide radiation-monitoring devices (TLD badges) to radiation workers X-ray installations should be located as far as possible from areas of high occupancy such as maternity, paediatric and ultrasonography rooms Quality assurance should be conducted once in 2 years on every X-ray equipment and records to be maintained by registrant/licensee. Thus by taking various prophylactic measures, safety of the anaesthesiologists can be enhanced.

Ocular Radiation Exposure in Modern Urological Practice

The human eye is a highly radiosensitive portion of the body and repeat radiation exposure can lead to cataract. The minimum fractionated long-term dose to initiate cataract formation is about 2,500 mSv. We determined whether further radiation related precautions are necessary to protect the eyes of the surgeon. Radiation doses received near the right eye of the operating surgeon were measured with a thermoluminescent dosimeter badge worn near the eye of 6 urologists for a single endourological procedure at an academic center. Procedures included stent insertion, ureteroscopic lithotripsy and percutaneous nephrolithotomy. The mean radiation dose was calculated. Extrapolated doses required to potentiate cataract formation were also calculated. We assessed 28 urological procedures for radiation exposure, of which 13 were ureteroscopy done for calculus disease (range 0.05 to 0.66 mSv) and 7 were ureteral stent insertion (range 0.13 to 0.32 mSv). The mean radiation dose received during these cases was 0.208 mSv. Based on the mean dose and an average of 20 such cases per month, it would take about 50 years to reach the minimum threshold for progressive cataract formation. Eight percutaneous renal operations were performed and the mean dose received was 0.125 mSv (range 0.04 to 0.22). Based on 10 cases per month, this would require more than 160 years of exposure to reach the minimal threshold. Long-term radiation can lead to cataract formation. However, the accumulated lifetime exposure of the typical urologist may not necessitate further safety precautions, such as lead-lined glasses.

Outpatient 131I-Rituximab Radioimmunotherapy for Non-Hodgkin Lymphoma

This study aimed to establish the safety of outpatient 131I-rituximab radioimmunotherapy by measuring the radiation exposure of hospital staff, carers, and members of the public and by estimating the environmental impact of radioactive urinary excretion. Two hundred consecutive outpatients treated with 131I-rituximab radioimmunotherapy of non-Hodgkin lymphoma (NHL) with therapeutic activities between 1 and 4.5 GBq (mean, 2.3 GBq; or between 27 and 121 mCi; mean, 62 mCi) predicated on a prescribed whole-body radiation-absorbed dose of 0.75 Gy were studied. Their 279 family members/carers and 432 visitors wore thermoluminescent dosimeter badges for the week during which the patients were confined to their home after treatment. All 200 patients received 131I-rituximab activities according to the prescribed dose of 0.75 Gy to the whole body. From 200 consecutive patients, over the 7 days after therapy, mean radiation exposure of adult carers was 0.49 mSv (range, <0.01 to 3.67 mSv). To other coresiding family members, mean exposure was 0.23 mSv (range, <0.01 to 1.20 mSv), and for visitors sharing badges, the mean exposure was 0.17 mSv (range, <0.01 to 0.73 mSv). Urinary activity excreted over the week after 131I-rituximab therapy was typically less than 25% of the administered activity. 131I-rituximab radioimmunotherapy for non-Hodgkin lymphoma may be safely administered on an outpatient basis. The median radiation exposure of carers, cohabitants of the patient, and visitors is well within the limits recommended by international guidelines. Local regulatory agency-designated patient release rate limit of less than 25 μSv/h at 1 m was attained within 1 week of therapeutic 131I-rituximab administration.

Radiation exposure in emergency physicians working in an urban ED: a prospective cohort study

Objective The National Council on Radiation Protection (NCRP) limits health care–associated occupational exposures to radiation to 5000 mrem/y. Previous studies suggested that emergency physicians were not exposed over this limit. Their relevance to contemporary practice is unknown. We hypothesized that emergency physicians are currently exposed to radiation levels above the NCRP limits. Methods This prospective cohort study was conducted at an urban, academic, level I trauma center emergency department (ED). Thermoluminescent dosimeter radiation badges were placed on the torso and ring finger of all physicians staffing the ED during May 2008. Thermoluminescent dosimeter badges were affixed to 8 portable phones that are carried by physicians in the ED 24 hours a day. At the end of the study period, exposure dose for each subject was estimated. Results Seventy-five physicians enrolled in the study; 41 residents worked a median of 94 hours and 34 attendings worked a median of 54 hours. Compliance for physician badge wearing was 99%, ring wearing was 98%, and phone wearing was 100%. Two subjects had detectable levels of radiation on their torso thermoluminescent dosimeters of 4 and 1 mrem, respectively. One phone badge had a detectable level of 1 mrem. The annual extrapolated exposure for the subject with the highest radiation level would have been 50 mrem, below the 5000 mrem exposure limit for health care workers. Conclusion Emergency physicians working in an urban, academic, level I trauma center ED do not appear to be at risk of exceeding the NCRP dose limits for ionizing radiation exposure to their torso or extremities.

Note: Studies on target placement in TE111 cylindrical cavity of electron cyclotron resonance x-ray source for the enhancement of x-ray dose

X-ray source based on electron cyclotron resonance principle has been constructed using TE(111) cylindrical cavity. At present the device is used to provide low energy x-ray field for thermoluminescent dosimeter badge calibration. Theoretical and experimental studies on the effect of target placement inside the TE(111) cylindrical cavity for enhancing the x-ray output are carried out and the results are presented in this note. Optimum target location is identified by theoretical analysis on the electric field distribution inside the cavity using MICROWAVE STUDIO program. By modifying the magnetic field configuration, the resonance region is shifted to the optimum target location. The microwave transmission line is upgraded with a three stub tuner which improves the microwave coupling from the source to the target loaded cavity. Molybdenum target is located at a radial distance of 2.5 cm from the cavity center and the x-ray dose rate is measured at 20 cm from the exit port for different microwave power. With the introduction of the target, the x-ray output has improved nearly from 70% to 160% in the microwave power of 150-500 W.

Radiation exposure to anaesthetists during interventional radiology*

This prospective study determined the level of radiation exposure of anaesthetists during interventional radiological procedures performed in the endoscopic retrograde cholangiopancreatography suite and cardiac catheterisation laboratory and compared it with the current safety guidelines. Anaesthetists wore area-specific lithium fluoride thermo-luminescent dosimeter badges at standardised positions. A total of 1344 procedures were performed over a 6-month period. Anaesthetists were involved in 39/645 (6.0%) procedures associated with ionisation radiation in the endoscopic retrograde cholangiopancreatography suite and 86/699 (12.3%) in the cardiac catheterisation laboratory. The mean (SD) duration of endoscopic retrograde cholangiopancreatography was 54.8 (29.1) min compared with 67.9 (42.8) min for cardiac catheterisation suite procedures (p = 0.058). The mean (SD) fluoroscopy time per procedure for endoscopic retrograde cholangiopancreatography was 5.5 (4.1) min compared with 12 (10.9) min in the cardiac catheterisation suite (p < 0.001). The combined net radiation exposure over 6 months was 0.28 mSv for endoscopic retrograde cholangiopancreatography procedures and 2.32 mSv in the cardiac catheterisation suite. The combined exposure was less than the maximum recommended exposure of 20 mSv per year.

The Possible Effect on Personnel Dose by Two Copper Filters Covering Element 1 of the Harshaw 8814 TLD Badge

Ongoing uncertainties have existed regarding possible effects at low photon energies of two copper filters covering Element 1 of the Harshaw Type-8814 thermoluminescent dosimeter badge casing. To address these, Brookhaven National Laboratory's (BNL) Personnel Monitoring Group conducted a test in which Type-8814 badges with one copper filter covering Element 1 were irradiated at several low-energy levels side-by-side with the same number of badges with two copper filters covering Element 1. A review of exposures to personnel at Brookhaven Laboratory to possible low-energy photon flux was also conducted. From both the test and the review of exposures, it can be concluded that, for radiological work under the conditions at BNL, there is no apparent dosimetric difference if one or two copper filters cover Element 1 of the Type-8814 badge.

Response of CaSO 4:Dy phosphor based TLD badge system to high energy electron beams from medical linear accelerator and estimation of whole body dose and skin dose

Response of thermoluminescent dosimeter (TLD) badge based on CaSO 4:Dy phosphor to high energy electron beams from medical linear accelerators was simulated using FLUKA Monte Carlo code and experimentally verified. This study was carried out in order to determine the response of TL discs under different filter regions of the TLD badge and their ratios under different irradiation conditions in the energy range 6–20 MeV of high energy electron beams. It was found that the response of TL disc under metal filters of the TLD badge (D1) is always higher than the response of the TL discs under Polystyrene filter (D2) and open window (D3) and its response was found to decrease with increase in the energy of the electron beam. Estimation of whole body dose and skin dose including its error was carried out as an extension of the present study in case of accidental exposure of radiation worker to high energy electron beam.

Application of radiation physics in the design of the Harshaw 8828 beta–gamma TLD badge

A thermoluminescent dosimeter (TLD) badge has been developed to measure beta and gamma doses for routine personal dosimetry. The badge uses a card with four elements of LiF:Mg,Ti enriched in 7Li and sandwiched between layers of Teflon™. The Element 1 filter is 1000 mg cm - 2 of low-Z material, the Element 2 filter is 464 mg cm - 2 of tin plus 536 mg cm - 2 of low-Z material, the Element 3 filter is a 5 – 7 mg cm - 2 Mylar window, and the Element 4 filter is 64 mg cm - 2 of low-Z material. The filters for Elements 2 and 4 were optimized by testing and by application of radiation physics principles and calculation. Elements 1 and 2 are used to measure the response to photons, and from these results, H p (10), H p (0.07) for photons, and the photon contribution to the signals for Elements 3 and 4 are obtained. The photon contribution to the signals from Elements 3 and 4 is subtracted from their total signals to obtain two signals due to betas. These are used to derive a corrected value for H p (0.07) for betas. The badge has been in use since early 1999, and provides accurate results in a nuclear power station environment.

Studies on the effective energy of x-rays generated by ECR and their use for the calibration of thermoluminescent dosimeter badges in low energy region

The effective energy of electron cyclotron resonance (ECR) x-ray source has been altered by keeping a target disk at the cavity wall in the exit port. The source has been tuned for the effective energy of 40 and 70 keV. The use of the source for the calibration of thermoluminescent dosimeter badges in the low energy region (&amp;lt;150keV) has been explored.

A personal dosimeter TLD badge based on CaSO4:Dy teflon TLD discs.

A thermoluminescent dosimeter badge has been designed for use in a countrywide personnel monitoring program. The badge is based on CaSO4: Dy phosphorembedded Teflon TLD discs. A set of metal filters has been incorporated in the badge to compensate for the energy-dependent response of the CaSO4: Dy phosphor at low photon energies. An open-window region has been provided for estimating beta dose. The response of the badge to beta and gamma radiation, its energy and angular dependence, and its reusability in a number of repeated cycles of measurements are discussed.