实时三维经胸超声心动图测量缩流面积评价主动脉瓣反流

目的应用实时三维经胸超声心动图（3D-TTE）测量缩流面积（VCA）评价主动脉瓣反流。方法将56例主动脉瓣反流患者的三维测量的VCA以及二维经胸超声心动图（2D-TTE）测量的缩流宽度与主动脉根部造影和外科手术的主动脉瓣反流程度相比较。结果3D—TTE测得的VCA与主动脉根部造影和外科手术的主动脉瓣反流程度密切相关（r=0．95），无明显重叠。2D—TTE测得的缩流宽度亦与主动脉根部造影和手术的主动脉瓣反流程度有很好的相关性（r=0．92），但有较多的重叠。以主动脉根部造影和外科手术为主动脉瓣反流程度的标准，三维测得的1～4度主动脉瓣反流的相应VCA分别为≤0．19cm^2，0．2～0．39cm^2，0．4～0．59cm^2，≥0．6cm^2。结论实时3D—TTE彩色多普勒能准确评价主动脉瓣反流，且和主动脉根部造影有很好的相关性。

Supersonic-Subsonic Transition in Relatively Narrow Channels

The flow structure in relatively narrow channels has a strong three-dimensional character with complex flow phenomena, including regions of localized separation, various vortical smictures, etc., all of which have to be considered when dealing with the problem of supersonic-subsonic transition. In this paper only the following three problems are considered: 1. the effect of channel width on transition from supersonic to subsonic velocities, 2. transition from supersonic to subsonic velocities in a system of shock waves - pseudoshock wave, 3. transition from subsonic to supersonic velocities in a critical cross section at the end of a duct with fully developed turbulent channel flow. Problems connected with vortical structures and flow separation were discussed by the same author elsewhere (see References).