Occupational exposure and radiobiological risk from thyroid radioiodine therapy in Saudi Arabia

Institutional Experience of Routine Radiation Surveillance of Delay and Decay Tanks Facility in a Department Having High-dose Iodine Therapy Unit

Background

Radioactive solid and liquid waste generated by patients after high-dose iodine therapy may lead to significant radiation exposure if not properly handled.

Aims and Objectives

This study was conducted to monitor the radiation exposure along the sewerage drainage system of the high-dose iodine therapy ward and to rule out leakage if any, that might pose a potential radiation hazard to the general public (sewerage workers) and radiation health professional.

Materials and Methods

The sewerage drainage system from isolation wards has multiple gate valves to regulate sewerage flow from the high-dose iodine therapy ward into delay and decay tanks (DDT) built, especially for the purpose. Radiation surveillance was done using a Geiger-Muller counter-based survey meter at 11 different locations on a weekly basis for 12 weeks.

Results

A total of 26 patients underwent high-dose iodine ablation therapy during the study period in our department, with the highest recorded radiation exposure rate in the sewerage draining system in the 9th week of patient admission. This was at the common gate valve junction (location B) that directed sewerage waste from all four isolation rooms into the common pipeline leading to DDT. Minimal radiation exposure was recorded within Atomic Energy Regulatory Board -prescribed limits with no evidence of leakage.

Conclusion

A routine radiation survey is an important component of overall radiation safety in the nuclear medicine department, including sewerage delay tank facilities, which helps keep the radiation exposure to acceptable levels by identifying timely leakage.

Evaluation of personal dose equivalents during positron emission tomography and computed tomography imaging

This study aimed to evaluate the annual occupational radiation exposure of technologists during PET/CT imaging in 2020 and 2021. Eleven nuclear medicine technologists were monitored at the PET/CT department. The personal dose equivalents (PDEs) for staff members, measured in terms of Hp (10) and Hp (0.07), were assessed annually, considering both deep and surface doses. PDEs were quantified using a thermoluminescent detector (LiF:Mg:Ti)). The average and range of PDEs and extremity doses (mSv) for the technologists were as follows: 4.5 (0.1-13.4) for Hp (10), 4.63 (0.1-13.9) for Hp (0.07), and 2.5 (0.2-17.5) for extremity, respectively. The results indicated that staff members are exposed to high-energy gamma rays while preparing radiopharmaceuticals, injections, and image acquisition. Therefore, proper handling of radiopharmaceuticals and patient management during the acquisition of parameters are crucial for maintaining the occupational dose within the defined limit.

Porous organic materials for iodine adsorption

The nuclear industry will continue to develop rapidly and produce energy in the foreseeable future; however, it presents unique challenges regarding the disposal of released waste radionuclides because of their volatility and long half-life. The release of radioactive isotopes of iodine from uranium fission reactions is a challenge. Although various adsorbents have been explored for the uptake of iodine, there is still interest in novel adsorbents. The novel adsorbents should be synthesized using reliable and economically feasible synthetic procedures. Herein, we discussed the state-of-the-art performance of various categories of porous organic materials including covalent organic frameworks, covalent triazine frameworks, porous aromatic frameworks, porous organic cages, among other porous organic polymers for the uptake of iodine. This review discussed the synthesis of porous organic materials and their iodine adsorption capacity and reusability. Finally, the challenges and prospects for iodine capture using porous organic materials are highlighted.

Reduction of thyroid radioactive iodine exposure by oral administration of cyclic oligosaccharides

Alpha-cyclodextrin, a six D-glucose cyclic oligosaccharide, has several applications in food and pharmaceuticals, but has also been reported to retain iodine in a stable manner for 16 months. Radioactive iodine, which may cause thyroid cancer and hypofunction, must be properly managed. If the absorption of radioactive iodine is suppressed, it can be expected to lead to a reduction in thyroid exposure. This study clarified the inhibition of radioactive iodine absorption by the oral administration of α-cyclodextrin in a murine model using direct measurement of single photon emission computed tomography. The uptake of radioactive iodine into the thyroid gland in mice administered with radioactive iodine and an α-cyclodextrin solution was approximately 40% lower after 24 h. The finding that oral uptake of α-cyclodextrin has an inhibitory effect on the transfer of radioactive iodine to the thyroid gland has potential for application in many fields such as food, pharmaceuticals, nuclear emergency preparedness, and medicine.

Assessment of thyroid gland hormones and ultrasonographic abnormalities in medical staff occupationally exposed to ionizing radiation

BACKGROUND

Ionizing radiation (IR) is high-energy radiation that has the potential to displace electrons from atoms and break chemical bonds. It has the ability to introduce mutations, DNA strand breakage, and cell death. Being a radiosensitive organ, exposure of the thyroid gland to IR can lead to significant changes in its function.

AIM OF THE WORK

Was to measure the levels of thyroid hormones panel and ultrasonography abnormalities in medical staff occupationally exposed to IR.

SUBJECTS AND METHODS

A total of 120 subjects were divided into three main groups: Group I: radiation-exposed workers occupationally exposed to radioiodine (131I) (n = 40), Group II: radiation-exposed workers occupationally exposed to X-ray (n = 40), and Group III: non-exposed healthy professionals matched in age and sex with the previous groups (n = 40). Thyroid hormones panel including free triiodothyronine (fT3), free thyroxine (fT4), thyroid-stimulating hormone (TSH), anti-thyroperoxidase antibodies (anti-TPO), and thyroglobulin (Tg) were measured. Thyroid ultrasonography was performed. Oxidative stress markers such as malondialdehyde (MDA), hydrogen peroxide (H2O2), and total antioxidant capacity (TAC) were measured.

RESULTS

Group I had significantly higher fT3 levels than the control group. fT3 levels were considerably higher, while TSH was substantially lower in group II participants than in the control group. Tg was markedly lower in radiation-exposed workers. However, anti-TPO levels in radiation-exposed workers were significantly higher than in the control group. MDA and H₂O₂ were substantially higher; TAC was significantly lower in radiation-exposed workers compared to the control group. According to ultrasonographic examination, thyroid volume and the percentage of thyroid nodules in all radiation workers were significantly higher than in the control group.

CONCLUSION

Despite low exposure doses, occupational exposure to IR affects the thyroid hormones and links with a higher likelihood of developing thyroid immune diseases.

Genotoxicity Associated with 131I and 99mTc Exposure in Nuclear Medicine Staff: A Physical and Biological Monitoring Study

Nuclear medicine staff are constantly exposed to low doses of ionizing radiation. This study investigated the level of genotoxic effects in hospital employees exposed to routinely used ¹³¹I and ^99mTc in comparison with a control group. The study compared the results of physical and biological monitoring in peripheral blood lymphocytes. The effects of confounding factors, such as smoking status and physical activity, were also considered. Physical dosimetry monitoring revealed differences in the individual annual effective dose as measured by finger ring dosimeter and whole-body dosimeter between the ¹³¹I- and ^99mTc-exposed groups. The DNA damage studies revealed differences between the groups in terms of excess premature chromosome condensation (PCC) fragments and tail DNA. Physical activity and smoking status differentiated the investigated groups. When assessed by the level of physical activity, the highest mean values of tail DNA were observed for the ^99mTc group. When assessed by work-related physical effort, excess PCC fragments were significantly higher in the ¹³¹I group than in the control group. In the investigated groups, the tail DNA values were significantly different between non-smokers and past or current smokers, but excess PCC fragments did not significantly differ by smoking status. It is important to measure exposure to low doses of ionizing radiation and assess the potential risk from this exposure. Such investigations support the need to continue epidemiological and experimental studies to improve our understanding of the mechanisms of the health effects of radionuclides and to develop predictive models of the behavior of these complex systems in response to low-dose radiation.

Application of a tungsten apron for occupational radiation exposure in nursing care of children with neuroblastoma during 131I-meta-iodo-benzyl-guanidine therapy

The use of effective shielding materials against radiation is important among medical staff in nuclear medicine. Hence, the current study investigated the shielding effects of a commercially available tungsten apron using gamma ray measuring instruments. Further, the occupational radiation exposure of nurses during 131I-meta-iodo-benzyl-guanidine (131I-MIBG) therapy for children with high-risk neuroblastoma was evaluated. Attachable tungsten shields in commercial tungsten aprons were set on a surface-ray source with 131I, which emit gamma rays. The mean shielding rate value was 0.1 ± 0.006 for 131I. The shielding effects of tungsten and lead aprons were evaluated using a scintillation detector. The shielding effect rates of lead and tungsten aprons against 131I was 6.3% ± 0.3% and 42.1% ± 0.2% at 50 cm; 6.1% ± 0.5% and 43.3% ± 0.3% at 1 m; and 6.4% ± 0.9% and 42.6% ± 0.6% at 2 m, respectively. Next, we assessed the occupational radiation exposure during 131I-MIBG therapy (administration dose: 666 MBq/kg, median age: 4 years). The total occupational radiation exposure dose per patient care per 131I-MIBG therapy session among nurses was 0.12 ± 0.07 mSv. The average daily radiation exposure dose per patient care among nurses was 0.03 ± 0.03 mSv. Tungsten aprons had efficient shielding effects against gamma rays and would be beneficial to reduce radiation exposures per patient care per 131I-MIBG therapy session.