ABSTRACT
Due to the present industrial world, the risk of radioactivity is notably increasing. Thus, an appropriate shielding material needs to be designed to protect humans and the environment against radiation. In view of this, the present study aims to design new composites of the main matrix of bentonite-gypsum with a low-cost, abundant, and natural matrix. This main matrix was intercalated in various amounts with micro- and nanosized particles of bismuth oxide (Bi2O3) as the filler. Energy dispersive X-ray analysis (EDX) recognized the chemical composition of the prepared specimen. The morphology of the bentonite-gypsum specimen was tested using scanning electron microscopy (SEM). The SEM images showed the uniformity and porosity of a cross-section of samples. The NaI (Tl) scintillation detector was used with four radioactive sources (241Am, 137Cs, 133Ba, and 60Co) of various photon energies. Genie 2000 software was used to determine the area under the peak of the energy spectrum observed in the presence and absence of each specimen. Then, the linear and mass attenuation coefficients were obtained. After comparing the experimental results of the mass attenuation coefficient with the theoretical values from XCOM software, it was found that the experimental results were valid. The radiation shielding parameters were computed, including the mass attenuation coefficients (MAC), half-value layer (HVL), tenth-value layer (TVL), and mean free path (MFP), which are dependent on the linear attenuation coefficient. In addition, the effective atomic number and buildup factors were calculated. The results of all of these parameters provided the same conclusion, which confirms the improvement of the properties of γ-ray shielding materials using a mixture of bentonite and gypsum as the main matrix, which is much better than using bentonite alone. Moreover, bentonite mixed with gypsum is a more economical means of production. Therefore, the investigated bentonite-gypsum materials have potential uses in applications such as gamma-ray shielding materials.
ABSTRACT
OBJECTIVES: Thyroid malignancy constitutes the sixth common cancer type in the United Arab Emirates (UAE). There are no epidemiological data outlining the prevalence of cancer in thyroid nodules, nor previous analysis of ultra-sonographic features correlating with thyroid malignancy in the UAE. This study aimed to estimate the prevalence of thyroid malignancy in patients with thyroid nodules and to describe the ultra-sonographic characteristics of thyroid nodules harbouring malignancy. METHODS: A retrospective electronic medical records review of all thyroid nodules in patients (aged 18 to 80 years) with normal thyroid-stimulating hormone (TSH) levels, who underwent ultrasound guided fine needle aspiration cytology (UG-FNA) at Sheikh Khalifa Medical City (SKMC) during 2011-2015. RESULTS: 436 patients with normal TSH underwent UG-FNA cytological examination of thyroid nodules (n = 555 nodules). The overall crude prevalence of thyroid cancer among patients was 10.1% (95% CI 7.5-13.3). The age-adjusted prevalence of thyroid cancer among UAE nationals, Arabs, Far East Asians, and Caucasians were 9.6% (3.6-15.6), 10.0% (6.2-13.8), 16.8% (4.5-29.0) and 16.3% (1.7-30.9), respectively. The crude prevalence was 14.5%(95% CI 6.2-22.8) in men, and 9.3%(95% CI 6.3-12.2) in women. The echogenicity features were significantly different between the cancerous and noncancerous nodules (p = 0.025). Cancerous nodules were relatively more hyper- and hypo-echoic, while noncancerous nodules were mostly complex. CONCLUSION: We report a higher prevalence of thyroid malignancy among patients with thyroid nodules relative to that reported in other parts of the world. The rate of thyroid malignancy was higher in patients of Far-East Asian and Caucasian ethnic background.
