Trade-off between breast dose and image quality using composite bismuth shields in computed tomography: A phantom study.

INTRODUCTION: Many researchers have suggested that bismuth composite shields (BCS) reduce breast dose remarkably; however, the level of this reduction and its impact on image quality has not been assessed. This study aimed to evaluate the efficiency of nano- and micro- BCS in reducing the dose and image quality during chest computed tomography (CT) scans. MATERIALS AND METHODS: Bismuth shields composed of 15 weighting percentage (wt%) and 20 wt% bismuth oxide (Bi2O3) nano- and micro-particles mixed in silicon rubber polymer were constructed in 1 and 1.5 mm thicknesses. The physical properties of nanoparticles were assessed using a scanning electron microscope (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray (EDX). Breast radiation doses were measured experimentally during chest CT using PMMA standard dosimetry phantom (body phantom, 76-419-4150, Fluke Biomedical) in the presence of the shields. The image quality was assessed by calculating signal and noise values in different regions. RESULTS: The SEM images showed that the average size of Bi2O3 nano- and micro-particles was about 70 nm and 150 µm, respectively. The breast doses were reduced by increasing the shield thickness/bismuth weight percentage. The maximum dose reduction was related to the 20% weight of Bi2O3 nano-particles and a thickness of 1.5 mm. The minimum dose reduction was related to the 15% weight of Bi2O3 micro-particles with a thickness of 1 mm. The mean noise was higher in nano-particle bismuth shields than in micro-particles. CONCLUSION: Composite shields containing bismuth nano- and micro-particles can reduce the breast dose during chest CT examinations while negatively impacting diagnostic image quality. Several critical factors, such as bismuth concentration, particle size, and shield thickness, directly affect the efficiency.

Liver Function in Novel Coronavirus Disease (COVID-19): A Systematic Review and Meta-Analysis

IntroductionThe outbreak of new coronavirus has become a global public health challenge. Given a consequential liver function, and the high risk of death coming from liver disorders, the assessment of Novel Coronavirus Disease on liver function is importance. Hence, we carried out this meta-analysis to heightening insight into the occult features of COVID 19, which is likely to affect liver function. MethodThis study was performed using databases of Web of Science, Scopus, and PubMed. We considered English cross-sectional and case-series papers, which reported available findings on the association between liver injury and COVID-19 infection. We used the STATA v.11 and random effect model for data analysis. ResultIn this present meta-analysis, 52 papers, including 8,463 COVID-19 patients, were studied. The prevalence of increased liver enzymes among the patients, including Alanine aminotransferase, Aspartate aminotransferase, were 30% and 21% in non-severe patients, respectively, which were 38% and 48% in severe patients. The prevalence of increasing C-reactive protein, Lactate dehydrogenase, D-dimer, and Bilirubin were 55%, 39%, 28%, and 10% in non-severe patients respectively, which were 78%, 75%, 79% and 17% in sever patients.The prevalence of liver toxicity as a complication of COVID-19 was 20%.Also patients who have severe condition are 5.54, 4.22, 4.96, 4.13 and 4.34 times more likely to have elevated CRP, ALT, AST, LDH, D-dimer enzymes retrospectively. ConclusionElevation of some liver markers were higher in patients with severe COVID-19 infection. All to gather, we assumed that abnormal liver markers could act as a prognostic factor for a better survey of COVID-19.

Influence of the size of nano- and microparticles and photon energy on mass attenuation coefficients of bismuth-silicon shields in diagnostic radiology.

Recent studies have shown that the particle size of the shielding material and photon energy has significant effects on the efficiency of radiation-shielding materials. The purpose of the current study was to investigate the shielding properties of the bismuth-silicon (Bi-Si) composite containing varying percentages of micro- and nano-sized Bi particles for low-energy X-rays. Radiation composite shields composed of nano- and micro-sized Bi particles in Si-based matrix were constructed. The mass attenuation coefficients of the designed shields were experimentally assessed for diagnostic radiology energy range. In addition, the mass attenuation coefficients of the composite were comprehensively investigated using the MCNPX Monte Carlo (MC) code and XCOM. The X-ray attenuation for two different micro-sized Bi composites of radii of 50 µm and 0.50 µm showed enhancement in the range of 37-79% and 5-24%, respectively, for mono-energy photons (60-150 keV). Furthermore, the experimental and MC results indicated that nano-structured composites had higher photon attenuation properties (approximately 11-18%) than those of micro-sized samples for poly-energy X-ray photons. The amount of radiation attenuation for lower energies was more than that of higher energies. Thus, it was found that the shielding properties of composites were considerably strengthened by adding Bi nano-particles for lower energy photons.

Use of bismuth shield for protection of superficial radiosensitive organs in patients undergoing computed tomography: a literature review and meta-analysis.

The study aimed to assess the effect of bismuth (Bi) shielding on dose reduction and image quality in computed tomography (CT) through a literature review. A search was conducted in the following databases: Web of Science, PubMed, Google Scholar, and Scopus. Studies that reported estimated dose reduction with bismuth shielding during imaging of the eye, thyroid, and breast were included, and a meta-regression analysis was used to examine the influence of the CT scanner type on the dose reduction. The studies included a total of 237 patients and 34 pediatric and adult anthropomorphic phantoms for whom the radiation dose was reported. Bismuth shielding was recommended in 88.89% of the studies based on the maintenance of appropriate image quality under shielding. Noise associated with Bi shielding was 7.5%, 263%, and 23.5% for the eye, thyroid, and breast, respectively. The fixed-effects pooled estimate of dose reduction was 34% (95% CI: 13-55; p < 0.001) for the eye, 37% (95% CI 14-61; p < 0.001) for the thyroid, and 36% (95% CI 36-55; p < 0.001) for the breast. The image quality, usage of foams, CT scanner type, beam energies, and backscatter radiation were important factors that directly affected the efficacy of Bi shielding to reduce the radiation dose at the superficial radiosensitive organs.