Based on the skewness of sea waves, a modified two-scale model is developed for the non-Gaussian sea surface scattering. In this new model, a complementary term is added to the first-order scattering coefficient of th...Based on the skewness of sea waves, a modified two-scale model is developed for the non-Gaussian sea surface scattering. In this new model, a complementary term is added to the first-order scattering coefficient of the classical small perturbation method （SPM）, the additional part is proportional to the surface bispectrum and it is the critical part in explaining the scattering difference between upwind and downwind observations. Meanwhile, the effects of the shadowing function of the anisotropic surface, the curvature of the surface are also taken into account. The numerical results show the theoretical estimates obtained are consistent with the experimental result, and the influence of the wind speed, the trend and the incident frequency on the backscattering coefficients from the non-Gaussian oceanic surface is discussed in detail.展开更多
AIM: To determine which modification to a vascular puncture needle results in increased visualization during ultrasound (US)-guided vascular puncture. METHODS: We evaluated US images of a phantom made of degassed gela...AIM: To determine which modification to a vascular puncture needle results in increased visualization during ultrasound (US)-guided vascular puncture. METHODS: We evaluated US images of a phantom made of degassed gelatin and each of the following four modified versions of a commercially available vascular puncture needle (18 G): re-cut needle, dimple needle, rough-surface needle (rough over the sections of needle located 3-6 mm from the tip), and a needle with four side holes (side holes covered by the sheath). An unmodified commercially available puncture needle was used as a control. Five interventional radiologists evaluated image quality according to the following classification grade:?I, invisible; II, poor; III, moderate; IV, good; V, excellent. RESULTS: The highest score for needle visualization was obtained for the needle with four side holes. The re-cut needle scored the same as the control. Multiple comparisons were conducted using overall evaluation scores among the commercially available needle, dimple needle, rough-surface needle (3-6 mm), and the needle with four side holes. A significantly higher score was obtained for the needle with four side holes (P < 0.05/6). CONCLUSION: The needle with four side holes was prominently visualized and gained a significantly higher score (compared with the other needles) in a phantom evaluation.展开更多
文摘Based on the skewness of sea waves, a modified two-scale model is developed for the non-Gaussian sea surface scattering. In this new model, a complementary term is added to the first-order scattering coefficient of the classical small perturbation method （SPM）, the additional part is proportional to the surface bispectrum and it is the critical part in explaining the scattering difference between upwind and downwind observations. Meanwhile, the effects of the shadowing function of the anisotropic surface, the curvature of the surface are also taken into account. The numerical results show the theoretical estimates obtained are consistent with the experimental result, and the influence of the wind speed, the trend and the incident frequency on the backscattering coefficients from the non-Gaussian oceanic surface is discussed in detail.
文摘AIM: To determine which modification to a vascular puncture needle results in increased visualization during ultrasound (US)-guided vascular puncture. METHODS: We evaluated US images of a phantom made of degassed gelatin and each of the following four modified versions of a commercially available vascular puncture needle (18 G): re-cut needle, dimple needle, rough-surface needle (rough over the sections of needle located 3-6 mm from the tip), and a needle with four side holes (side holes covered by the sheath). An unmodified commercially available puncture needle was used as a control. Five interventional radiologists evaluated image quality according to the following classification grade:?I, invisible; II, poor; III, moderate; IV, good; V, excellent. RESULTS: The highest score for needle visualization was obtained for the needle with four side holes. The re-cut needle scored the same as the control. Multiple comparisons were conducted using overall evaluation scores among the commercially available needle, dimple needle, rough-surface needle (3-6 mm), and the needle with four side holes. A significantly higher score was obtained for the needle with four side holes (P < 0.05/6). CONCLUSION: The needle with four side holes was prominently visualized and gained a significantly higher score (compared with the other needles) in a phantom evaluation.
