Personal Dosimeters Research Articles

Estimation of inhomogeneous occupational exposure to the lens of the eyes and the extremities of radiation workers in a research accelerator facility.

We performed an experimental investigation on occupational exposure of the eye lens and the extremity of radiation workers engaged in handling of highly activated materials in a small research accelerator facility. Using a simplified physical phantom to simulate the relevant inhomogeneous radiation exposure situations, the personal dose equivalents obtained at the eye lens and the extremities of radiation workers handling heavily radioactive converters were measured together with the dose measured by personal dosemeters worn on their trunk. Results of mockup experiments and the Monte Carlo calculations suggest that the quantitative estimation of the eye lens doses can be estimated from the trunk dose, while the extremity doses vary considerably from the dose readings from the trunk, depending on the use of simple point-source or volume source geometry.

Use of secondary air kerma from dose area product and fluoroscopy time for preventive effective dose estimation in interventional radiology procedures for staff

Introduction: interventional radiology workers are potentially exposed to high levels of ionizing radiation, therefore preventive dose estimation is mandatory for the correct risk classification of staff. Effective dose (ED) is a radiation protection quantity strictly related to the secondary air kerma (K S), using appropriate multiplicative conversion factors (ICRP 106). The aim of this work is to evaluate the accuracy of K S estimated from physically measurable quantities such as dose-area product (DAP) or fluoroscopy time (FT). Methods: radiological units (n = 4) were characterized in terms of primary beam air kerma and DAP-meter response, consequently defining a DAP-meter correction factor (CF) for each unit. K S, scattered from an anthropomorphic phantom and measured by a digital multimeter, was then compared with the value estimated from DAP and FT. Different combinations of tube voltages, field sizes, current and scattering angles were used to simulate the variation of working conditions. Further measurements were performed to estimate the couch transmission factor for different phantom placements on the operational couch, defining a CF as the mean transmission factor. Results: when no CFs were applied, the measured K S showed a median percentage difference of between 33.8% and 115.7% with respect to K S evaluated from DAP, and between −46.3% and 101.8% for K S evaluated from FT. By contrast, when previously defined CFs were applied to the evaluated K S, the median percentage difference between the measured K S and the value evaluated from DAP ranged from between −7.94% and 15.0%, and between −66.2% and 17.2% for that evaluated from FT. Conclusion: when appropriate CF are applied, the preventive ED estimation from the median DAP value seems to be more conservative and easier to obtain with respect to the one obtained from the FT value. Further measurements should be performed with a personal dosimeter during routine activities to assess the proper K S to ED conversion factor.

Investigation of Personal Dosimeter Loss Case and Measures to Prevent Loss

Purpose: It is intended to improve the management efficiency of personal dosimeters by analyzing and sharing personal dosimeter loss cases and loss prevention measures. Materials and Methods: From 2017 to 2021, data on the number of lost personal dosimeters were collected at large hospitals, and the number of personal dosimeters issued and lost were investigated. Results: In order to prevent loss by institution, methods such as the use of auxiliary rings, contact stickers and dosimeter necklaces were implemented. Conclusion: Hospitals are a business that frequently changes clothes, such as surgical gowns and work clothes, so there is a lot of loss. In addition, it was confirmed that the loss rate increases as the number of personal dosimeters issued increases.

What happened when medical staff in Beijing, China wore over-apron dosemeters?

The wearing method of personal dosemeters for medical staff changed from under to outside the operator's protective apron in April 2020. We measured the radiation dose Hp(10) for medical staff in Beijing from September 2020 to October 2021. The study population consisted of 3291 medical staff. All participants were divided into three groups. After excluding unusually low doses, the collected data higher than the detection limit involved 811 (7.8%) of 10395 readings from 479 (14.6%) of 3291 staff. The mean equivalent dose was 1.4mSv/3months, with an SD of 2.3mSv. The calculated average annual effective doses of radiation workers in the three groups after the interventional procedures from September 2020 to October 2021 ranged from 0.47 to 0.63mSv/year, with median values of 0.32, 0.23 and 0.26mSv/year, respectively.

DOIN: a novel electronic personal dosemeter for neutrons

Electronic personal dosemeters (EPD) are powerful tools for achieving ALARA (As Low As Reasonably Achievable) objectives in operational radiation protection. EPD for photons are well developed and their performances usually comply with relevant Standards. By contrast, a very few commercial models exist for neutrons and their energy dependence is too large for using them without pre-information on the workplace neutron spectrum. Within the INFN-based DOIN (DOsimetro Indossabile per Neutroni) project, a new EPD for neutrons was prototyped. Owing to a new patented design, a good dose response was achieved in the energy interval from thermal neutrons up to the quality of ^{241}Am-Be. The response is nearly isotropic and, if compared to commercial models, exhibits higher sensitivity.

The ESA Active Dosimeter (EAD) system onboard the International Space Station (ISS)

Ionizing radiation in general and mixed fields of space radiation in particular pose a risk of serious harm to human health. The risk of such adverse effects increases with the duration of the mission, and for all missions outside the protective properties of the Earth’s magnetic field and atmosphere. Accordingly, radiation protection is of central importance for all human spaceflight, which is recognized by all international space agencies. To date various systems, analyze and determine the exposure to ionizing radiation within the environment and to the crew onboard the International Space Station (ISS). In addition to this operational monitoring, experiments and technology demonstrations are carried out. This to further enhance systems capabilities, to prepare for exploratory missions, to the Deep Space Gateway and/or to enable for human presence at other celestial bodies. Subsequently the European Space Agency (ESA) decided early to support the development of an active personal dosimeter. Under the auspices of the European Space Research and Technology Center (ESTEC) together with the European Astronaut Center's (EAC) Medical Operations and Space Medicine (HRE-OM) team, a European industrial consortium was formed to develop, build, and test this system. To complete the ESA Active Dosimeter (EAD) Technology Demonstration in space, EAD components were delivered to ISS with the ESA’s space missions ‘iriss’ and ‘proxima’ in 2015 and 2016. This marked Phase 1 (2015) and 2 (2016–2017) of the EAD Technology Demonstration to which focus is given in this publication. All EAD systems and their functionalities, the different radiation detector, their properties, and calibrations procedures are described. Emphasis is first on the “iriss” mission of September 2015, that provided a complete set of data for an entire space mission from launch to landing, for the first time. Data obtained during Phase 2 in 2016–2017 are discussed thereafter. Measurements with the active radiation detectors of the EAD system provided data of the absorbed dose, dose equivalent, quality factor as well as the various dose contributions during the crossings of the South Atlantic Anomaly (SAA) and/or resulting from galactic cosmic radiation (GCR). Results of the in-flight cross-calibrations among the internal sensors of the EAD systems are discussed and alternative usage of the EAD Mobile Units as area monitors at various different locations inside the ISS is described.

Personal noise exposure during daily commutes and subjectively reported stress: A trip stage level analysis of MobiliSense data

BackgroundThe auditory and non-auditory health effects of noise have long been established in the literature but previous studies have mainly been in the context of occupational risk. Recent research suggests that daily noise exposures occurring during social activities and commute may be associated with higher psychological stress. Our aim was to explore the association between modes of transportation and noise on the one hand and noise exposures and reported stress on the other hand. Although existing literature shows that noise exposure is especially high during commutes, studies on the topic have been sparse due to cost and logistic constraints; furthermore, sample sizes have been small. MethodsThe present study uses data collected on the daily commutes of 253 participants of the Mobilisense cohort study between 2018 and 2020. Personal dosimeters were used to measure noise exposure by frequency bands over a period of 4 days, resulting in a sample of 7800 trip stage windows. Participants reported trip stress levels during an a posteriori phone mobility survey on a scale from 1 (no stress) to 7 (significantly stressful conditions). Modes of transportation (metro, car, walking, etc.) were collected from the same mobility survey based on Global Positioning System (GPS) receivers. ResultsWhile all transport modes resulted in higher exposure to low frequency noise compared to walking, all modes but tramway and driving or being the passenger of a car were associated with an increased exposure to high frequency noise. The LAeq noise indicator (overall noise) was associated with reported stress: for every 10 dB(A) increase in LAeq, individuals reported experiencing 1.118 times (95% confidence interval: 1.067, 1.172) higher levels of stress. Multiple noise indicator models did not show evidence that specific frequency components were associated with stress beyond overall noise. ConclusionOur findings suggest that noise exposure during commutes vary according to modes of transportation. Given that noise exposure resulted in higher reported levels of stress, future research should examine transportation noise effects on physiological variables.

Energy Calibration of MVT Digitizers in All-Digital Gamma Cameras

The multiple voltage threshold (MVT) digitizer implements data acquisition for the gamma camera by sampling pulses with all-digital electronics and recovering them with the prior pulse model. It has been employed in several nuclear science applications, such as positron emission tomography detectors, personal dosimeters, survey meters, and wastewater activity probes. In these applications, a wide dynamic range of energy is usually required to measure multiple energies accurately. However, the energy nonlinearity of the MVT digitizer constrains the dynamic range of energy. To calibrate the nonlinearity of digitizers in gamma cameras, we propose a novel method to acquire the mapping from digitizer energy to pulse energy by obtaining their scatter plot with a high-speed oscilloscope. To demonstrate our method, we use a gamma camera based on the silicon photomultiplier and an inorganic scintillator to detect gamma photons from a Na-22 radioactive source. We show that the mapping can be empirically modeled as the quadratic function for the MVT digitizer. We further perform the calibration on the MVT digitizer, showing that the average deviation between digitizer energy and pulse energy is reduced from 245 keV to 28 keV at 1274 keV. Moreover, we show the energy spectra obtained with different sequences of digitizer calibration and photoelectric converter calibration. The energy spectrum obtained with digitizer calibration and then photoelectric converter calibration shows the most minor distortion. This suggests that digitizer calibration should be performed before photoelectric converter calibration. It is reasonable to extend our method to other gamma cameras by simulating sampling patterns of corresponding digitizers. This provides a way to realize gamma spectrometry with higher accuracy and a wider dynamic range.

Radiation exposure in emergency ureteric stenting: A subgroup analysis by operator.

To review radiation exposure during emergency ureteric stent insertion to identify differences based on operator experience, specialty operator and stone characteristics. A retrospective audit over 10 years was performed for patients who underwent emergency stent insertion for urolithiasis with intraoperative fluoroscopy. Outcomes measured included operator experience, radiation exposure (mGy), dose area product (Gy/cm2), fluoroscopy time, stone characteristics and patient BMI. Analysis was performed in IBM SPSS Version 28. p < 0.05 was considered statistically significant. Four hundred ten patients were identified, with a median age of 57 years, 64.6% male and a median BMI of 30. Urolithiasis was left-sided in 50.8%, with a median size of 7 mm and predominantly proximal (49%) followed by mid (34.5%) and distal (12.1%) location. Median radiation exposure was 12.6 mGy, 2.94 Gy/cm2 and fluoroscopy time 44.5 s, with no significant difference between consultants and registrars. No significant association between radiation exposure for subgroups of stone location, gender, size, laterality or specialty registrar (general surgery vs. urology). No significant difference in radiation exposure was identified between registrars and consultants or between subspecialty registrars. We suggest formal radiation safety education for all health professionals involved with intra-operative fluoroscopy and personal dosimeters.

Comparison and estimation of photoneutron dose produce between 10 MV flattened and unflattened beam in Elekta Versa HD™ medical linac.

In a high-energy medical linear accelerator (linac), if the interaction of photon energy is higher than the neutron binding energy of high atomic material, it emits a neutron field through photonuclear (γ, n) reaction. The current study, evaluates the photoneutron dose equivalent (PNDE) produced between the 10 MV flattened and unflattened beams as a function of field sizes in the Elekta Versa HD™ linac. The PNDE produced from Versa linac was recorded along the patient plane using the bubble detector personal neutron dosimeter and from the measured PNDE values, the theoretical PNDE values were simulated for various field sizes using nonlinear least-squares curve-fitting as a function of a polynomial. The percentage of deviation (PoD) and Chi-square (χ2) tests were performed between the measured and simulated PNDE values to study the reliability and validity. The results show that the mean PoD between the measured and simulated PNDE values for respective positions of a field size of FF beam was found to be -1.99% for 0.3×0.3, -4.39% for 5×5, -3.868% for 10×10, 0.590% for 15×15, 9.18% for 20×20, -4.133% for 25×25, and 0.467% for 30×30 cm2. Similarly, the mean PoD between the measured and simulated PNDE values for flattening filter-free (FFF) beam was found to be 1.36% for 0.3×0.3, -1.39% for 5×5, -5.38% for 10×10, 4.41% for 15×15, 3.84% for 20×20, 5.69% for 25×25, and -1.75% for 30×30 cm2. The maximum deviation between the measured and simulated PNDE values lies within the range ± 5%. From the study, it is observed that the FFF beam produces lesser neutron contamination than the FF beam.

Response evaluation of two commercial thermoluminescence dosimeters (TLDs) against different parameters.

It is essential to study the dosimetric performance and reliability of personal dosimeters. This study examines and compares the responses of two commercial thermoluminescence dosimeters (TLDs), the TLD-100 and the MTS-N. We compared the two TLDs to various parameters such as energy dependence, linearity, homogeneity, reproducibility, light sensitivity (zero point), angular dependence, and temperature effects using the IEC 61066 standard. The results acquired showed that both TLD materials show linear behavior as indicated by the quality of the fit. In addition, the angular dependence results for both detectors show that all dose responses are within the range of acceptable values. However, the TLD-100 outperformed the MTS-N in terms of light sensitivity reproducibility for all detectors together, while the MTS-N outperforms the TLD-100 for each detector independently and that showed TLD-100 has more stability than MTS-N. The MTS-N shows better batch homogeneity (10.84%) than TLD-100 (13.65%). The effect of temperature in signal loss was clearer at higher temperature 65°C and it was however below ±30%. The overall results for dosimetric properties determined in terms of dose equivalents for all combinations of detectors are satisfactory. The MTS-N cards have better results in the energy dependence, angular dependency, batch homogeneity and less signal fading, whereas the TLD-100 cards are less sensitive to light and more reproducible. Although previous studies showed several types of comparisons between TLDs, they have used limited parameters and different data analysis. This study has dealt with more comprehensive characterization methods and examinations combining TLD-100 and MTS-N cards.

Digitally measuring solar ultraviolet radiation in outdoor workers: A study protocol for establishing the use of electronic personal dosimeters in Portugal.

The rising incidence of skin cancer over the years has made it a significant public and occupational health issue. However, skin cancer is highly preventable, mainly through reduced exposure to solar ultraviolet radiation (UVR), which can be achieved by a variety of individual and collective protective measures and interventions. The relative risk associated with different patterns of exposure to solar UVR differs for the subtypes of keratinocyte cancers (KC). Specifically, whether the exposure is intermittent or continuous, and occurs in an occupational or leisure/recreational setting. The main aim of the study using this protocol is to contribute to raising public and policy awareness on solar UVR-inflicted occupational skin cancers in Lisbon. This will be achieved by performing direct measurements of the solar UVR dose received by outdoor workers using a digital platform. Results will likely contribute to further understanding the risk estimates for keratinocyte cancer estimations in this population. A prospective observational study will be conducted in Lisbon, Portugal. Personal electronic dosimeters (GENESIS-UV system) integrated with a digital platform will be used to assess occupational solar UVR doses of gardeners, masons, and gravediggers of the municipality of Lisbon. Two hundred and ten outdoor workers will be selected to wear the dosimeter for 1 month each, between April and October during their daily working hours. A digital web-based platform that offers private access to information through dashboard visualization will provide information for the outdoor workers and facilitate communication with the participants. The expected results of the overall proposal comprise the occupational solar UVR doses, expressed in standard erythemal dose (SEDs) per day of outdoor work for 7 months. Study data will provide outdoor workers with information on their personal solar UVR exposure during their working hours and an estimate of their risk of developing skin cancer. It is expected that the occupational solar UVR doses of the outdoor workers in Portugal will be above the threshold of 1 to 1.33 SED/day, due to the latitude of Lisbon and the nature of the occupations. The results prospectively should flow into the design of adequate prevention campaigns for skin cancer in outdoor workers.

THE DEVELOPMENT OF GAMMA RADIATION DOSIMETERS REAL-TIME NETWORK-BASED SENSOR WIRELESS IEEE 802.15.4 PROTOCOL

Several studies have been carried out on the development of real-time gamma radiation dosimeter based on the wireless sensor network (WSN) protocol IEEE 802.15.4. WSN technology can be adopted to develop a gamma radiation dose monitoring system on a large scale due to its real-time, centralized, efficient, and relatively low-cost attributes. This study aims to develop a personal radiation dosimeter that can collect data from the measurement results of several sensor nodes or multi-sensors. The measurement results of radiation dose values from many radiation workers are sent to a coordinator node consisting of the Xbee module and Arduino as a microcontroller. The system test is compared with a calibrated dosimeter reading and is expected to be one of the instruments for determining radiation dose in real-time. It can also reduce the risk of receiving a radiation dose that exceeds the threshold allowed by the ionizing control agency and a program in radiation protection. Changes in the intensity of radiation emitted by Cs-137 (gamma radiation) are carried out by varying each detector's distance to the source, which indirectly varies the value of the dose rate received by the detector. This relationship is shown from the value of R2 = 0.99, which indicates a strong correlation between changes in the dose given to the detector's response being developed. The system built is efficient, inexpensive, and collecting radiation exposure data can monitor radiation exposure received by workers in real-time. This technique can help speed up reporting of radiation exposure received by radiation workers.

Frequency compensation for in-ear noise dosimetry

Personal noise dosimeters (PNDs) are used in the prevention of noise induced hearing loss (NIHL) by monitoring noise exposure. Exposure of a worker is typically estimated by measuring the noise level at the shoulder location and subtracting the estimated protection provided by any worn hearing protection devices. Current noise dosimeters in the marketplace are deficient because the noise level at the shoulder does not necessarily represent the noise exposure in the ear canal due to shadowing, canal resonances and other acoustical phenomena. Moreover, workers often deliberately insert earplugs to shallow canal depths to better hear their environments, and earmuff attenuation is inconsistent due to variations in head geometry. Thus, the estimated hearing protection is often in error. In-ear personal noise dosimeters (iPNDs) can solve these problems because they incorporate a microphone within a hearing protection earplug that measures the actual noise level in an ear canal. However, the acoustics of the in-ear measurement are quite different compared to the shoulder measurement, and in-ear measurements must be frequency compensated to achieve valid results. This paper discusses in-ear noise dosimetry, why frequency compensation is needed and how to compensate the microphone signal. [This work was funded by a CDC SBIR grant.]

Flexible fully organic indirect detector for megaelectronvolts proton beams

A flexible, fully organic detector for proton beams is presented here. The detector operates in the indirect mode and is composed of a polysiloxane-based scintillating layer coupled to an organic phototransistor, that is assessed for flexibility and low-voltage operation (V = −1 V), with a limit of detection of 0.026 Gy min−1. We present a kinetic model able to precisely reproduce the dynamic response of the device under irradiation and to provide further insight into the physical processes controlling it. This detector is designed to target real-time and in-situ dose monitoring during proton therapy and demonstrates mechanical flexibility and low power operation, assessing its potential employment as a personal dosimeter with high comfort and low risk for the patient. The results show how such a proton detector represents a promising tool for real-time particle detection over a large area and irregular surfaces, suitable for many applications, from experimental scientific research to innovative theranostics.

Effect of radiation exposure on function human body by CBC parameter for workers in nuclear medicine field

In this study, eight cases of workers in gamma camera scans and Positron Emission Tomography (PET/CT scan) fields (employed for various medical diagnoses) had their complete blood counts (CBCs) assessed. From the first hour of work until the last, the investigation of radiation’s impact on hematology was ongoing. By using a personal dose meter (Geiger Badge), the radiation exposure reading for a whole workday is directly recorded in (μSv). The study concluded that while the number of WBC count increased for all workers after radiation exposure, the number of RBC count decreased after exposure, suggesting that RBC amount may be a reliable indicator of exposure degree.

Occupational and patient doses for interventional radiology integrated into a dose management system.

The International Commission on Radiological Protection recommends managing patient and occupational doses as an integrated approach, for the optimisation of interventional procedures. The conventional passive personal dosimeters only allow one to know the accumulated occupational doses during a certain period of time. This information is not enough to identify if there is a lack of occupational radiation protection during some procedures. This paper describes the use of a dose management system (DMS) allowing patient and occupational doses for individual procedures to be audited. The DMS manages patient and occupational doses measured by electronic personal dosimeters. One dosemeter located at the C-arm is used as a reference for scatter radiation. Data have been collected from five interventional rooms. Dosimetry data can be managed for the whole procedure and the different radiation events. Optimisation is done through auditing different sets of parameters for individual procedures: patient dose indicators, occupational dose values, the ratio between occupational doses, and the doses measured by the reference dosemeter at the C-arm, and the ratio between occupational and patient dose values. The managed data correspond to the year 2021, with around 4500 procedures, and 8000 records on occupational exposures. Patient and staff dose data (for 11 cardiologists, 7 radiologists and 8 nurses) were available for 3043 procedures. The DMS allows alerts for patient dose indicators and occupational exposures to be set. The main advantage of this integrated approach is the capacity to improve radiation safety for patients and workers together, auditing alerts for individual procedures. The management of patient and occupational doses together (measured with electronic personal dosimeters) for individual interventional procedures, using dose management systems, allows alerting optimisation on high-dose values for patients and staff.

Establishment and quality assessment of X-ray narrow spectrum series according to ISO 4037:2019 at SSDL of center for nuclear technologies

Narrow spectrum series from N-40 to N-120 were established according to ISO 4037:2019. This study was made through experimental measurements and the software modeling toolkit SpekPy v2.0. Experiments were performed to determine Inherent filtration (0.332 &amp; 0.492 mm Al at 100 cm &amp; 250 cm, respectively). The maximum deviation compared to ISO 4037:2019 of the measured HVLs values are not more then 0.10 mm Al and for modeling not exceed 0.09 mm Al; h range 0.91 to 0.97 for experimently and 0.89 to 0.96 for modeling (0.88 - 1, ISO 4037-1:2019). The maximum contribution of scattering is value 4.0% (&lt; 5%, ISO 4037-1:2019). Radiation field uniformity of N-40 to N-120 should list all categories in detail 12.5, 11.0, 10.0, 9.0, 8.5 cm at 100 cm distance; and 35.5, 31.5, 29.0, 26.5, 24.5 cm at 250 cm beam center axis distance. On the basis of ISO 4037:2019, air kerma values at 100 cm and 250 cm have also been determined with uncertainties 3.85% to 5.18% for experimently and 3.41% to 4.19% for modeling (not exceed 10%, ISO 4037:2019). Therefore, the X-ray radiation field has been well established in compliance with the ISO 4037:2019, it can be used for calibrating survey meters and personal dosimeters.

Personal neutron dosimetry: State-of-the-art and new technologies

Neutron personal dosimetry is necessary for the monitoring of exposed workers, not only in nuclear industry and related activities but also in the growing number of neutron producing facilities, so new techniques and devices are continuously developed and improved. This article provides a review of the present state-of-the-art as well as the main new results and innovative developments in neutron personal dosimetry using electronic personal dosimeters (EPDs), track dosimeters (etched track dosimeters, FNTD), luminescent dosimeters (TL, OSL, RPL), superheated drop dosimeters and direct ion storage (DIS) dosimeters.

Thermoluminescence and Optically Stimulated Luminescence properties of in-vitro aged dental porcelain

Among the materials applied in dentistry, porcelain is the most predominant one, as it has been used for dental restorations for decades. Towards the Thermoluminescence (TL) investigation of dental porcelain, and its capability to act as a personal accident dosimeter, the present work further examines -through a series of measurement protocols-the physical mechanisms responsible for the isothermal TL signal of its main dosimetric TL peak. Moreover, the influence of light on the TL of the same main peak is studied by means of Optically Stimulated Luminescence (OSL) measurements, while the origin of the OSL signal is further investigated. Finally, the existence of very deep traps of the material is examined and discussed via specific protocols.