Theory and practice have confirmed that the propagation of converted transverse waves in azimuthally anisotropic media results in shear-wave splitting,causing differences in travel time and reflection amplitude betwee...Theory and practice have confirmed that the propagation of converted transverse waves in azimuthally anisotropic media results in shear-wave splitting,causing differences in travel time and reflection amplitude between S1/S2 waves,which reduces the imaging quality and vertical resolution of converted transverse wave.Therefore,eliminating shear-wave splitting is one of the important steps in the imaging processing of converted transverse wave.Due to the limitations of actual data acquisition and signal-tonoise ratio,it is difficult to directly determine a set of orthogonal four components for shear-wave splitting analysis,which cannot achieve good correction processing results.To this end,starting from Alford rotation,an orthogonal four component equation system is derived,and the least squares method is used to stably solve the high signal-to-noise ratio orthogonal four components.Based on this,the crack orientation and fast/slow wave delay are estimated through azimuth and time-delay scanning,and the shear-wave splitting correction and fast/slow wave separation are completed by layer striping from shallow to deep.The synthetic data and actual data calculations show that this method can achieve good azimuthal anisotropy correction,separation of S1/S2 waves,and accurate imaging.展开更多
目的观察兔左室内、外膜侧心肌电活动动态恢复曲线、局部S1S2恢复曲线,以及短期记忆特性随刺激频率的变化。方法采用8只冠状动脉灌注兔左室楔形组织块标本,同步记录跨壁心电图和内、外膜侧心肌细胞动作电位,测量每一次搏动的动作电位时...目的观察兔左室内、外膜侧心肌电活动动态恢复曲线、局部S1S2恢复曲线,以及短期记忆特性随刺激频率的变化。方法采用8只冠状动脉灌注兔左室楔形组织块标本,同步记录跨壁心电图和内、外膜侧心肌细胞动作电位,测量每一次搏动的动作电位时程。对标本经心内膜侧心尖部施加干扰向下扫描刺激方式刺激。首先给予基础刺激周长(BCL0)为2 000 ms 10次刺激后,改变BCL1刺激(自600～300 ms),观察恢复曲线整体图及其跨壁异质性。结果随刺激加快两种恢复曲线斜率均逐渐增大。但内膜侧斜率增大更为明显,随刺激加快内、外膜间差异具显著性(P<0.05)。动态恢复曲线斜率的改变较局部S1S2恢复曲线斜率更为明显。动态恢复曲线与S1S2恢复曲线斜率的夹角α值反映瞬时短期记忆现象,随BCL减小α值逐渐增大,且内膜侧增大更为明显(P<0.05)。结论兔左心室壁内膜侧的动态恢复曲线和局部S1S2恢复曲线斜率均较外膜侧大,内膜侧心肌的短期记忆现象更为明显,可能为起源于心内膜侧期前刺激所引起单向传导阻滞易损窗大于外膜侧的机制之一。展开更多
基金supported by Sinopec Science and Technology Research Project(P23098,P25152).
文摘Theory and practice have confirmed that the propagation of converted transverse waves in azimuthally anisotropic media results in shear-wave splitting,causing differences in travel time and reflection amplitude between S1/S2 waves,which reduces the imaging quality and vertical resolution of converted transverse wave.Therefore,eliminating shear-wave splitting is one of the important steps in the imaging processing of converted transverse wave.Due to the limitations of actual data acquisition and signal-tonoise ratio,it is difficult to directly determine a set of orthogonal four components for shear-wave splitting analysis,which cannot achieve good correction processing results.To this end,starting from Alford rotation,an orthogonal four component equation system is derived,and the least squares method is used to stably solve the high signal-to-noise ratio orthogonal four components.Based on this,the crack orientation and fast/slow wave delay are estimated through azimuth and time-delay scanning,and the shear-wave splitting correction and fast/slow wave separation are completed by layer striping from shallow to deep.The synthetic data and actual data calculations show that this method can achieve good azimuthal anisotropy correction,separation of S1/S2 waves,and accurate imaging.
文摘目的观察兔左室内、外膜侧心肌电活动动态恢复曲线、局部S1S2恢复曲线,以及短期记忆特性随刺激频率的变化。方法采用8只冠状动脉灌注兔左室楔形组织块标本,同步记录跨壁心电图和内、外膜侧心肌细胞动作电位,测量每一次搏动的动作电位时程。对标本经心内膜侧心尖部施加干扰向下扫描刺激方式刺激。首先给予基础刺激周长(BCL0)为2 000 ms 10次刺激后,改变BCL1刺激(自600～300 ms),观察恢复曲线整体图及其跨壁异质性。结果随刺激加快两种恢复曲线斜率均逐渐增大。但内膜侧斜率增大更为明显,随刺激加快内、外膜间差异具显著性(P<0.05)。动态恢复曲线斜率的改变较局部S1S2恢复曲线斜率更为明显。动态恢复曲线与S1S2恢复曲线斜率的夹角α值反映瞬时短期记忆现象,随BCL减小α值逐渐增大,且内膜侧增大更为明显(P<0.05)。结论兔左心室壁内膜侧的动态恢复曲线和局部S1S2恢复曲线斜率均较外膜侧大,内膜侧心肌的短期记忆现象更为明显,可能为起源于心内膜侧期前刺激所引起单向传导阻滞易损窗大于外膜侧的机制之一。
