Eye Lens Dose Research Articles

How much do 68Ga-, 177Lu- and 131I-based radiopharmaceuticals contribute to the global radiation exposure of nuclear medicine staff?

The radiation exposure of nuclear medicine personnel, especially concerning extremity doses, has been a significant focus over the past two decades. This study addresses the evolving practice of NM, particularly with the rise of radionuclide therapy and theranostic procedures, which involve a variety of radionuclides such as 68Ga, 177Lu, and 131I. Traditional studies have concentrated on common radioisotopes like 99mTc, 18F, and 90Y, but there is limited data on these radionuclides, which are more and more frequently used. This study, part of the European SINFONIA project, aims to fill this gap by providing new dosimetry data through a multicenter approach. The research monitors extremity doses to hands, eye lens doses, and whole-body doses in nuclear medicine staff handling 68Ga, 177Lu, and 131I. It examines the type of activities performed and the protective measures used. The study extrapolates measured doses to annual doses, comparing them with annual dose limits, and assesses the contribution of these specific procedures to the overall occupational dose of nuclear medicine personnel. Measurements were conducted from November 2020 to August 2023 across nine hospitals. The highest whole-body, eye lens and extremity doses were observed for 68Ga. Average maximum extremity doses, normalized per manipulated activity, were found of 6200µSv/GBq, 30µSv/GBq and 260µSV/GBq for 68Ga, 177Lu and 131I, respectively. Average whole-body doses stayed below 60µSv/GBq for all 3 isotopes and below 200µSv/GBq for the eye lens dose. The variation in doses also depends on the task performed. For 68Ga there is a risk of reaching the annual dose limit for skin dose during synthesis and dispensing. This study's measurement campaigns across various European countries have provided new and extensive occupational dosimetry data for nuclear medicine staff handling 68Ga, 177Lu and 131I radiopharmaceuticals. The results indicate that 68Ga contributes significantly to the global occupational dose, despite its relatively low usage compared to other isotopes. Staff working in radiopharmacy hot labs, labeling and dispensing 177Lu contribute less to the finger dose compared to other isotopes.

Assessment of air dose distribution in the vertical plane for better occupational exposure management.

The International Commission on Radiological Protection recommended a significant reduction of the equivalent dose limit for the eye lens. Reportedly, medical staff in charge of diagnostic imaging procedures may exceed the new dose limits for the eye lens. The use of dosimeters dedicated to the eye lens remains low, and dosimeters for the neck region were often used to assess eye lens doses. However, measurements by neck badges may overestimate or underestimate the recommended eye lens doses because the height of the neck differs from that of the eye. This study aimed to evaluate the air dose distribution in the vertical plane to understand the difference between neck and eye doses. H*(10) in the height of the eye position was 52.8% lower than that in the height of the neck position in the under-table position. Thus, the equivalent eye lens dose evaluated using a neck badge dosimeter may be overestimated.

Automated Injectors versus Manual Administration: A Comparative Analysis of Radiation Exposure Reduction in 18F-FDG Delivery

Abstract Background Despite the presence of safety protocols, the manual manipulation of radiopharmaceuticals continues to pose a significant occupational radiation risk. Health care professionals in nuclear medicine are at risk of radiation exposure, particularly to their hands and eyes. Despite existing protective measures, manual handling of radiopharmaceuticals remains a significant source of occupational radiation. Objective This study evaluates the effectiveness of automated injectors in reducing radiation exposure among health care workers during fluorine-18 fluorodeoxyglucose (18F-FDG) administrations, compared with traditional manual injection methods. Methods We assessed radiation exposure levels associated with manual versus automated 18F-FDG injection techniques using specialized dosimeters. Measurements focused on whole-body, extremity, and eye-lens radiation doses to evaluate the potential benefits of automation in minimizing exposure. Results Findings reveal that automated injectors significantly reduce radiation exposure, with decreases of 97.97 and 98.96% in left- and right-hand extremity doses, respectively, 43.24% in eye-lens dose, and 91.66% in whole-body dose compared with manual methods. Conclusion Automated injection systems offer considerable advantages in reducing health care worker radiation exposure in nuclear medicine. The substantial reduction in staff doses underscores the necessity of transitioning to such technology to promote safer clinical environments. This study highlights the critical role of automation in enhancing occupational safety standards within diagnostic radiology settings.

Impact of Patient Head Posture on Lens Radiation Exposure During Cerebral Angiography.

Cerebral angiography remains crucial for detailed characterization and preoperative assessments for intracranial aneurysm. Despite its diagnostic importance, cerebral angiography poses challenges due to its invasiveness, the risk of neurological complications, and radiation exposure. To investigate the impact of head posture on lens radiation exposure during cerebral angiography, this study focused on the correlation between radiation doses to the eye lens, head flexion angles, and head size. A retrospective analysis was performed on 20 patients who underwent cerebral angiography for unruptured intracranial aneurysms between October and November 2022. Radiation doses to the lens, which were measured in a prior prospective study using photoluminescent glass dosimeters, were analyzed alongside head flexion angles, anteroposterior (AP) head diameters, and kerma-area product (KAP) to evaluate their correlation with lens radiation exposure. The lateral radiation source is located on the left side of the patients. The cohort consisted of 20 patients (60% female, mean age: 62.3 ± 9.9 years). The radiation dose to the left eye (the eye closer to the x-ray source) was 2.8 times higher than that to the right eye (9.18 ± 3.31 mGy vs. 3.3 ± 0.60 mGy, P < 0.001). A strong positive correlation was observed between the left eye lens dose and head flexion angle (R = 0.815, P < 0.001). While the AP head diameter significantly correlated with the flexion angle, it showed no significant correlation with lens dose. The KAP was inversely correlated with both the left lens dose (R = -0.597, P = 0.005) and the flexion angle (R = -0.689, P < 0.001). Our findings underscore the significant impact of head posture on lens radiation exposure during cerebral angiography. Adjusting head positioning may provide a practical approach to reduce radiation exposure to the lens. Furthermore, it is worth noting that the left lens received more radiation than the right, likely due to the X-ray source being on the left side of the patient. AP = anteroposterior; KAP = kerma-area product, PLD = photoluminescent glass dosimeter.

Modification of algorithm for accurate estimation of Hp(3) based on response of head TLD badge calibrated using ISO cylindrical phantom.

In India, the prevailing approach to eye lens dosimetry is the placement of an existing dosemeter on the forehead region after slight modification serves as a dedicated Eye Lens Dosemeter. A methodology for estimating the eye lens dose in terms of the Hp(3) has been previously explored employing an algorithm based on the response characteristics of this dosemeter using ISO slab phantom. It was observed that the performance of the dosemeter in terms of Hp(3) using previous algorithm showed under response at higher angles of incidence and photon beams of energy < 200keV. Further, study was conducted to modify the algorithm following the latest ISO recommendations. This involved generation of data from the response of existing dosemeter on a cylindrical phantom. The results of this study revealed better performance of the newly established algorithm in estimating eye lens dose in terms of Hp(3) when compared to the earlier algorithm.

Occupational eye lens dose among nuclear medicine workers in a tertiary hospital in Saudi Arabia

Background: Exposure to ionizing radiation remains a major concern in nuclear medicine, especially given the possible health risks posed to medical personnel. Additionally, since the occupational eye dose limit was lowered in 2011 to an equivalent dose of 20 mSv/yr, new implications have extended to roles within nuclear medicine units. The goal of this investigation was to determine the current occupational radiation eye doses for nuclear medicine employees. Methods: A 5 yr retrospective assessment was performed on staff members involved in all nuclear medicine imaging from different categories. Optically Stimulated Luminescence (OSL) badges were used to measure occupational dose. The H-lens values were calculated for each staff member during this period. Results: Significant differences were observed between individual staff members in terms of H-lens values. They were significantly higher among hot lab technicians than among NIC (p &lt; 0.001) and NM (p &lt; 0.0001) technicians. Conclusions: Although none of the participants exceeded the eye dose limit for ionizing radiation exposure, there was significant variation in exposure across various roles and expertise. The annual average eye dose ranged from 0.2 mSv to 2.9 mSv, which is within the advised dose limit.

Effect of backscatter radiation on the occupational eye-lens dose.

We quantified the level of backscatter radiation generated from physicians' heads using a phantom. We also evaluated the shielding rate of the protective eyewear and optimal placement of the eye-dedicated dosimeter (skin surface or behind the Pb-eyewear). We performed diagnostic X-rays of two head phantoms: Styrofoam (negligible backscatter radiation) and anthropomorphic (included backscatter radiation). Radiophotoluminescence glass dosimeters were used to measure the eye-lens dose, with or without 0.07-mm Pb-equivalent protective eyewear. We used tube voltages of 50, 65 and 80kV because the scattered radiation has a lower mean energy than the primary X-ray beam. The backscatter radiation accounted for 17.3-22.3% of the eye-lens dose, with the percentage increasing with increasing tube voltage. Furthermore, the shielding rate of the protective eyewear was overestimated, and the eye-lens dose was underestimated when the eye-dedicated dosimeter was placed behind the protective eyewear. We quantified the backscatter radiation generated from physicians' heads. To account for the effect of backscatter radiation, an anthropomorphic, rather than Styrofoam, phantom should be used. Close contact of the dosimeter with the skin surface is essential for accurate evaluation of backscatter radiation from physician's own heads. To assess the eye-lens dose accurately, the dosimeter should be placed near the eye. If the dosimeter is placed behind the lens of the protective eyewear, we recommend using a backscatter radiation calibration factor of 1.2-1.3.

Comparison of shielding effects of over-glasses-type and regular eyewear in terms of occupational eye dose reduction

Given the new recommendations for occupational eye lens doses, various lead glasses have been used to reduce irradiation of interventional radiologists. However, the protection afforded by lead glasses over prescription glasses (thus over-glasses-type eyewear) has not been considered in detail. We used a phantom to compare the protective effects of such eyewear and regular eyewear of 0.07 mm lead-equivalent thickness. The shielding rates behind the eyewear and on the surface of the left eye of an anthropomorphic phantom were calculated. The left eye of the phantom was irradiated at various angles and the shielding effects were evaluated. We measured the radiation dose to the left side of the phantom using RPLDs attached to the left eye and to the surface/back of the left eyewear. Over-glasses-type eyewear afforded good protection against x-rays from the left and below; the average shielding rates on the surface of the left eye ranged from 0.70–0.72. In clinical settings, scattered radiation is incident on physicians’ eyes from the left and below, and through any gap in lead glasses. Over-glasses-type eyewear afforded better protection than regular eyewear of the same lead-equivalent thickness at the irradiation angles of concern in clinical settings. Although clinical evaluation is needed, we suggest over-glasses-type Pb eyewear even for physicians who do not wear prescription glasses.

Estimating brain and eye lens dose for the cardiologist in interventional cardiology-are the dose levels of concern?

To establish conversion coefficients (CCs), between mean absorbed dose to the brain and eye lens of the cardiologist and the air kerma-area product, PKA, for a set of projections in cardiac interventional procedures. Furthermore, by taking clinical data into account, a method to estimate the doses per procedure, or annual dose, is presented. Thermoluminescence dosimeters were used together with anthropomorphic phantoms, simulating a cardiologist performing an interventional cardiac procedure, to estimate the CCs for the brain and eye lens dose for nine standard projections, and change in patient size and x-ray spectrum. Additionally, a single CC has been estimated, accounting for each projections fraction of use in the clinic and associated PKA using clinical data from the dose monitoring system in our hospital. The maximum CCs for the eye lens and segment of the brain, is 5.47 μGy/Gycm2 (left eye lens) and 1.71 μGy/Gycm2 (left brain segment). The corresponding weighted CCs: are 3.39 μGy/Gycm2 and 0.89 μGy/Gycm2, respectively. Conversion coefficients have been established under actual scatter conditions, showing higher doses on the left side of the operator. Using modern interventional x-ray equipment, interventional cardiac procedures will not cause high radiation dose levels to the operator when a ceiling mounted shield is used, otherwise there is a risk that the threshold dose values for cataract will be reached. In addition to the CCs for the different projections, methods for deriving a single CC per cardiac interventional procedure and dose per year were introduced.

Developing methodology to evaluate eye lens dose for medical staff

Due to epidemiological evidence on the increasing incidence of cataracts in interventional doctors, The International Commission on Radiological Protection (ICRP) recommended decreasing the eye lens dose limit from 150 mSv/year to 20 mSv/year. Thus, The current status of dose assessment for healthcare workers shows that it requires more precise measurements of eye lens dose. we have researched Investigating dosimetric characteristics of OSLD nanoDot and Inlight type, using a multi–filter technique to determine the average air kerma of the incident beam and other essential dosimetric factors such as the relative energy responses and conversion coefficients from the air kerma to personal dose equivalent operational quantities Hp(d). Based on it developed the methodologies to evaluate eye lens dose for medical staff, especially high-risk subjects such as interventional doctors. Results show that 3 methods to evaluate eye lens dose have been deployed in the cardiovascular intervention department: directly by nanoDot dosimeter, indirectly by personal dosimeter (Inlight), and quick method based on the relationship with exposure duration. In one case, the doctor exceeded the threshold dose of 20 mSv/year without protective measures. Besides that, the risk of cataracts is possible when considering the cumulative dose for 30 years of work.

Dose rate conversion coefficients for ocular contamination in nuclear medicine: A Monte Carlo simulation with experimental validation.

Since 2011, the International Commission on Radiological Protection (ICRP) has recommended an annual eye lens dose limit of 20 mSv for radiation workers, averaged over 5 years, with no year exceeding 50 mSv. However, limited research has been conducted on dose rate conversion coefficients (DCCs) for direct contamination of the eye. This study aimed to accurately determine DCCs for the eye lens and cornea for ocular contamination with radionuclides used in nuclear medicine. DCCs for 37 radionuclides used in nuclear medicine were determined using two different methods. Method 1 involved conducting Monte Carlo (MC) simulations of an ICRU cylinder to determine the absorbed dose at a depth of 3mm resulting from a point source. The accuracy of this simulation approach was validated by experimental thermoluminescent dosimeter (TLD) measurements for 18F, 68Ga, 99mTc, and 177Lu. In method 2, average DCCs were calculated for the eye lens (complete and radiosensitive parts) and the cornea for both a point source and thin surface contamination centered on the cornea using MC simulations on the adult mesh-type reference computational phantom of the eye from the ICRP (MRCP). DCCs determined from TLD measurements showed excellent agreement (deviations: +1.4%, +4.7%, -3.1%, and -2.5% for 18F, 68Ga, 99mTc, and 177Lu, respectively) compared to MC simulations of the experimental set-up. For the 37 radionuclides, DCCs of the complete eye-lens for a point source ranged from 2.53×10-7 to 4.15×10-2 mGy MBq-1 s-1 for the adult MRCPs, being substantially smaller compared to DCCs determined via MC simulations of a ICRU cylinder. In general, point source and surface contamination showed comparable DCCs for the eye lens. Radionuclides emitting low-energy beta radiation or conversion electrons (e.g., 177Lu, 99mTc) showed low DCCs as the radiation does not penetrate to the depth of the eye lens, while radionuclides emitting high-energy beta radiation (e.g., 90Y) showed high DCCs. Overall, DCCs for the radiosensitive part of the eye lens were larger (up to a factor of 3) compared to the complete eye lens. DCCs for the cornea were larger than for the eye lens with a factor that strongly depended on the emitted radiation type. Especially alpha emitters (e.g., 211At, 223Ra) showed high DCCs for the cornea because of the short range of alpha radiation, leading to local maxima in the cornea and not reaching the eye lens. DCCs at a depth of 3mm in an ICRU cylinder and adult MRCP DCCs for both the complete and sensitive parts of the eye lens and cornea were determined for 37 radionuclides having applications in nuclear medicine. These DCCs are highly useful in radiation safety assessments and radiation dose calculations in ocular contamination incidents.

Effect of radioprotective curtain length on the scattered dose rate distribution and endoscopist eye lens dose with an over-couch fluoroscopy system

Sufficient dose reduction may not be achieved if radioprotective curtains are folded. This study aimed to evaluate the scattered dose rate distribution and physician eye lens dose at different curtain lengths. Using an over-couch fluoroscopy system, dH*(10)/dt was measured using a survey meter 150 cm from the floor at 29 positions in the examination room when the curtain lengths were 0% (no curtain), 50%, 75%, and 100%. The absorbed dose rates in the air at the positions of endoscopist and assistant were calculated using a Monte Carlo simulation by varying the curtain length from 0 to 100%. The air kerma was measured by 10 min fluoroscopy using optically stimulated luminescence dosimeters at the eye surfaces of the endoscopist phantom and the outside and inside of the radioprotective goggles. At curtain lengths of 50%, 75%, and 100%, the ratios of dH*(10)/dt relative to 0% ranged from 80.8 to 104.1%, 10.5 to 61.0%, and 11.8 to 24.8%, respectively. In the simulation, the absorbed dose rates at the endoscopist’s and assistant’s positions changed rapidly between 55 and 75% and 65% and 80% of the curtain length, respectively. At the 0%, 50%, 75%, and 100% curtain lengths, the air kerma at the left eye surface of the endoscopist phantom was 237 ± 29, 271 ± 30, 37.7 ± 7.5, and 33.5 ± 6.1 μGy, respectively. Therefore, a curtain length of 75% or greater is required to achieve a sufficient eye lens dose reduction effect at the position of the endoscopist.

Bismuth Shielding in Head Computed Tomography-Still Necessary?

Introduction: Cranial CT scans are associated with radiation exposure to the eye lens, which is a particularly radiosensitive organ. Children are more vulnerable to radiation than adults. Therefore, it is essential to use the available dose reduction techniques to minimize radiation exposure. According to the European Consensus on patient contact shielding by the IRCP from 2021, shielding is not recommended in most body areas anymore. This study aims to evaluate whether bismuth shielding as well as its combination with other dose-saving technologies could still be useful. Methods: Cranial CT scans of a pediatric anthropomorphic phantom were performed on two up-to-date MDCT scanners. Eye lens dose measurements were performed using thermoluminescent dosimeters. Furthermore, the impact of BS and of the additional placement of standoff foam between the patient and BS on image quality was also assessed. Results: Bismuth shielding showed a significant lens dose reduction in both CT scanners (GE: 41.50 ± 4.04%, p < 0.001; Siemens: 29.75 ± 6.55%, p = 0.00). When combined with AEC, the dose was lowered even more (GE: 60.75 ± 3.30%, p < 0.001; Siemens: 41.25 ± 8.02%, p = 0.00). The highest eye dose reduction was achieved using BS + AEC + OBTCM (GE: 71.25 ± 2.98%, p < 0.001; Siemens: 58.75 ± 5.85%, p < 0.001). BS caused increased image noise in the orbital region, which could be mitigated by foam placement. Eye shielding had no effect on the image noise in the cranium. Conclusions: The use of BS in cranial CT can lead to a significant dose reduction, which can be further enhanced by its combination with other modern dose reduction methods. BS causes increase in image noise in the orbital region but not in the cranium. The additional use of standoff foam reduces image noise in the orbital region.

Evaluasi Tata Laksana Pemeriksaan CT Scan Kepala: Efek Miscentering Pada Dosis Lensa Mata dan Kualitas Citra

Improper patient position in the isocenter position can interfere with optimization efforts. This study aimed to evaluate the management of head CT scans by knowing the effect of miscentering on the eye lens dose and noise. We used a water phantom and patient image and conducted a retrospective study of 1025 patients. Doses were calculated using IndoseCT software, while noise and miscentering were calculated using IndoQCT software. The difference in the right and left eye lens doses was tested using the student's t-test. The water phantom's position is above and below the isocenter of ±10, ±20, and ±30 mm. While the patient is correct at the center of the gantry (isocenter), the laser marker is between the patient's eyes and the symphysis pubic, and the height of the table is adjusted to the patient's center of mass. The vertical miscentering rate (posterior-anterior) is around 67.8%, with a miscentering range from -30 to -21 mm. There was no significant difference between the right and left eye lens doses (P-value &gt; 0.05). The eye lens dose increases as the phantom or patient position decreases from the isocenter and decreases as the phantom or patient position increases from the isocenter. Likewise, with noise, it increases as the phantom or patient position increases from the isocenter and decreases as the phantom or patient position decreases from the isocenter. Miscentering above the isocenter position can potentially reduce the eye lens dose. Keywords: Miscentering, Eye lens dose, noise

Eye lens dose in spine surgeons during myelography procedures: a dosimetry study

To determine the eye lens dose (3 mm dose equivalent [Hp(3)]) received by spine surgeons during myelography and evaluate the effectiveness of radiation-protective glasses and x-ray tube system positioning in reducing radiation exposure. This study included spine surgeons who performed myelography using over- or under-table x-ray tube systems. Hp(3) was measured for each examination using a radio-photoluminescence glass dosimeter (GD-352M) mounted on radiation-protective glass. This study identified significantly high Hp(3) levels, especially in the right eye lens in spinal surgeons. The median Hp(3) values in the right eye were 524 (391–719) and 58 (42–83) μSv/examination for over- and under-table x-ray tube systems, respectively. Further, Hp(3)AK, which was obtained by dividing the cumulative air kerma from Hp(3), was 8.09 (6.69–10.21) and 5.11 (4.06–6.31) μSv mGy−1 for the over- and under-table x-ray tube systems, respectively. Implementing radiation-protective glasses resulted in dose reduction rates of 54% (50%–57%) and 54% (51%–60%) for the over- and under-table x-ray tube systems, respectively. The use of radiation protection glasses significantly reduced the radiation dose in the eye lens during myelography, with the most effective measures being the combination of using radiation protection glasses and an under-table x-ray tube system.

Radiation exposure assessment of nuclear medicine staff administering [177Lu]Lu-DOTA-TATE with active and passive dosimetry

BackgroundThe use of lutetium-177 (177Lu)-based radiopharmaceuticals in peptide receptor nuclear therapy is increasing, but so is the number of nuclear medicine workers exposed to higher levels of radiation. In recent years, [177Lu]Lu-DOTA-TATE has begun to be widely used for the treatment of neuroendocrine tumours. However, there are few studies evaluating the occupational radiation exposure during its administration, and there are still some challenges that can result in higher doses to the staff, such as a lack of trained personnel or fully standardised procedures. In response, this study aims to provide a comprehensive analysis of occupational doses to the staff involved in the administration of [177Lu]Lu-DOTA-TATE.ResultsA total of 32 administrations of [177Lu]Lu-DOTA-TATE (7.4 GBq/session) carried out by a physician and a nurse, were studied. In total, two physicians and four nurses were independently monitored with cumulative (passive) and/or real-time (active) dosemeters. Extremity, eye lens and whole-body doses were evaluated in terms of the dosimetric quantities Hp(0.07), Hp(3) and Hp(10), respectively. It was obtained that lead aprons reduced dose rates and whole-body doses by 71% and 69% for the physicians, respectively, and by 56% and 68% for the nurses. On average, normalised Hp(10) values of 0.65 ± 0.18 µSv/GBq were obtained with active dosimetry, which is generally consistent with passive dosemeters. For physicians, the median of the maximum normalised Hp(0.07) values was 41.5 µSv/GBq on the non-dominant hand and 45.2 µSv/GBq on the dominant hand. For nurses 15.4 µSv/GBq on the non-dominant and 13.9 µSv/GBq on the dominant hand. The ratio or correction factor between the maximum dose measured on the hand and the dose measured on the base of the middle/ring finger of the non-dominant hand resulted in a factor of 5/6 for the physicians and 3/4 for the nurses. Finally, maximum normalised Hp(3) doses resulted in 2.02 µSv/GBq for physicians and 1.76 µSv/GBq for nurses.ConclusionsIf appropriate safety measures are taken, the administration of [177Lu]Lu-DOTA-TATE is a safe procedure for workers. However, regular monitoring is recommended to ensure that the annual dose limits are not exceeded.

A practical method for routine eye lens dosimetry of staff in interventional radiology.

Hospital staff doing fluoroscopy-guided interventions receive the highest doses and are at risk of exceeding the new occupational eye lens dose limit of 20mSv. Since the introduction of the new limit in the International Commission on Radiological Protection recommendations different eye lens dose monitoring techniques have been tested on phantoms. This study uses real-life dose data to assess the need for routine eye lens dose monitoring. The correlation of eye lens dose and Hp (10) measured with a whole-body dosemeter above the lead apron was investigated as an alternative to dedicated eye lens dosimetry. A survey taken among the medical personnel allowed to determine the preferred method for measuring eye lens doses in daily practice.

Type-testing of the TLD system used for the assessing the eye lens doses due to ionising radiation

Individual monitoring service at the Department for Radiation and Environmental Protection of Vinca Institute of Nuclear Sciences performs individual whole-body and extremities monitoring of exposed workers, using thermoluminescent dosimetry (TLD) method. The dosemeters for eye-lens personal dose equivalent measurements, Hp(3), are not regularly used at the workplaces in Serbia, even though the individual monitoring method is accredited and available at the dosimetry service. Type testing of Hp(3) dosemeters based on LiF: Mg,Ti, placed in modified ring holders was done following the changes in ISO 4037:2019 and IEC 62387:2020. The type testing was done by varying radiation-based influence quantities: photon energies ranging from 33.3 keV up to 1.25 MeV, angle of incidence values of 0°, 45°, 60°, 75°, dose range from 0.05 mSv to 10 Sv. The results show that the passive dosimetry monitoring system satisfies IEC 62387:2020 requirements in the mandatory range of influence quantities, except for the lowest tested energy of 33 keV, when incident radiation angle is ±60° and higher.

New operational quantities (RBE × D p lens/Φ) for eye lens neutron dosimetry as a function of energy and angle of incidence in the ICRU 95 formalism

This paper is a continuation of a study published recently by the authors. It presents and discusses computed personal absorbed dose in the lens of the eye (D p lens/Φ), and a relative biological effectiveness (RBE)-weighted absorbed dose (in terms of an newly proposed operational quantity RBE × D p lens/Φ), conversion coefficients for the lens of the eye for neutron exposure at incident energies from thermal to ∼20 MeV and at angles of incidence from 0° to 90° in 15° increments, at 180° and for rotational incidence irradiation geometry (from 0° to 360° in 5° increments). These conversion coefficients were obtained from a simulation model developed for this study that contains the stylised eye model, embedded in the adult UF-ORNL mathematical phantom, whereby the previously stated RBE-weighted absorbed dose was obtained using the proposed RBE versus neutron energy distribution compiled in a previous paper by the authors. The simulations carried out for this study using the Monte Carlo N-Particle transport code version 6.2, were conducted in a realistic human eye model, for the left and right sensitive and whole volume of the lens of the eye, considering the recent proposed redefinition of the operational quantities for external radiation exposure in International Commission on Radiation Units and Measurements (ICRU) report 95. A comprehensive set of tabulated data for neutron fluence-to-dose conversion coefficients (D p lens/Φ in pGy cm2) and RBE-weighted absorbed dose (RBE × D p lens/Φ in pGy cm2) conversion coefficients is included in this paper as a function of incident neutron energy and angle of incidence. Data for D p lens/Φ (pGy cm2) are compared to similar data from the literature for validation of our model. Data for RBE × D p lens/Φ (in pGy cm2), were also compared to the equivalent operational quantity H p(3,α)/Φ (in pSv cm2) conversion coefficients calculated at 3 mm depth in a cylindrical phantom for different incident neutron energies and angles of incidence from 0° to 75° in 15° increments to demonstrate the relevance of this newly proposed operational quantity for doses resulting in tissue reactions (deterministic effects) which should be quoted in Gray (RBE-weighted absorbed dose, RBE × D (Gy)), rather than Sievert (Sv) which is reserved for stochastic effects. The current neutron weighted absorbed dose (RBE × D p lens) is proposed for the tissue reactions in the eye-lens for neutron radiation as per National Council on Radiation Protection and Measurements report 180 and in line with the recent proposal for the review and revision of the System of Radiological Protection to Keeping the International Commission on Radiological Protection (ICRP) recommendations fit for purpose. This method would bring better alignment between the dose limits in ICRP 118 and the new operational quantity consistent with the units of the new eye-lens dose limits without being overly conservative. The utilization of the proposed new operational quantities, as outlined in ICRU 95, has the potential to address the ongoing challenge in enforcing regulatory limits for neutron eye dose, specifically the use of Gy instead of Sv. It should be noted that the applicability of this will vary from country to country as in many countries the legislation is likely to mandate the use of H p(3) until the regulation is amended. This approach can serve as an interim solution while awaiting the issuance of the new ICRP general recommendations, which is expected to take several years. Implementing the new operational quantities can contribute to enhancing the accuracy and effectiveness of neutron eye dose limit enforcement.

A New Software for the Calculation of Eye-lens Dosimetry Quantities Based on Dose-rate Coefficients.

In the last decade, the International Commission on Radiological Protection recommended a reduction in the annual limits to the dose to the lens of the eye from 150 mSv to 20 mSv y-1, averaged over defined periods of 5 y, with no single year exceeding 50 mSv. To assist the health physics community in this task, many groups have calculated protection and operational fluence dose coefficients. This led to the publication of multiple coefficient tables that were calculated for arrays of different parameters, including particle type, angle of incidence, target phantom models, presence or absence of secondary charged particle equilibrium, etc. The coefficients available in the literature include protection dose values calculated in a realistic eye model and operational values calculated in a simplified cylindrical head phantom at a point 3 mm below the surface. This paper reports on a simple Windows™ application that was written to aid health physics professionals in accessing and using the large body of available protection and operational eye-lens data. The application is called the Eye-Lens Dose Calculator, as it also performs calculations of the eye-lens dose for radionuclides, where the complete emissions of the selected radionuclides are considered. Test cases show that there is good agreement between the calculated protection and operational dose quantities when radionuclide emission characteristics are considered.