ABSTRACT
Objective: Impaired elasticity of aorta has been observed in fetuses with congenital cardiac disease, while the orientation of left ventricle outflow tract has been found to influence the blood flow in the ascending aorta. Therefore, the objective of this study is to examine the left ventricle inflow and outflow tract angle (LIOA) in healthy fetuses. Method: A total of 668 fetuses were enrolled in this prospective study. The LIOA were measured with two-line method at left ventricle inflow and outflow tract view. Pearson's correlation coefficient was utilized to assess the associations between LIOA and estimated fetal weight (EFW) and cardiac dimensions, including cardiac axis and diameters of aortic valve (AV), pulmonary artery valve (PAV), mitral valve (MV) and tricuspid valve (TV). Results: The LIOA was determined to be 44 ± 7.5° (mean ± SD). No significant difference was observed in the LIOA across different gestational ages (GAs). A mild positive correlation was observed between LIOA and cardiac axis. However, no significant associations were found between LIOA and parameters such as EFW, as well as diameters of AV, PAV, MV and TV. Conclusion: The LIOA remained constant during the mid-third trimester and was mildly positively correlated with cardiac axis in normal fetuses.
ABSTRACT
Radioactive material inspection in public is important to nuclear safety, and it is also the key security for holding large-scale events, while fast and efficient means of detecting radioactive materials are an important technical guarantee for nuclear safety. In this paper, energy and time distribution characteristics information of the natural background and target nuclide gamma particles are used to improve the sequential background comparison method. By using those energy and time distribution characteristics information, with the half-life and characteristic gamma-ray energy and branching ratio information of the nuclide, the response time and the identification accuracy of extremely low radioactive nuclides detected under natural-radiation background can be improved. Based on the theoretical research, the particle event acquisition device with the LaBr3(Ce) detector was used to carry out the experimental verification, and the results show that, this method can identify 137Cs (characteristic energy of 0.662 MeVï¼8700 Bqï¼the position relative to the detector is 30 cm) in 6.2 s, and identify 60Co (characteristic energy of 1.173 MeV and 1.332 MeV, 4500 Bq, the position relative to the detector is 15 cm) in 5.9 s. Experiments prove that the improved background comparison-based sequential Bayesian method can identify low radioactivity radionuclides under natural-radiation background rapidly.
