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引言动脉受连续波超声的作用而产生的回波多普勒频谱在一个心动周期内是变化的。一种简单的描述变动的方法是确定频谱的最高频率和平均频率。在没有由于声束几何形状产生的谱增宽时,频谱的最高频率分量正比于声速所遇到的红细胞的最高速度。并且,在没有谱增宽和假定血管受单一声束作用时,频谱的平均频率正比于平均血流速度。因为这两种分量均受到中度和重度狭窄的影响,所以它们在定量诊断血管疾病中有非常重要的应用。例如最高频率分量可用来确定脉动指数(Gosling and king,1974;Johnston…1987),因为该指数是归一化形式,所以它或多或少独立于声束作用的角度。
INTRODUCTION The echo Doppler spectrum generated by the effects of continuous wave ultrasound on a coronary artery varies during one cardiac cycle. A simple way to describe the changes is to determine the maximum frequency and the average frequency of the spectrum. Without spectral broadening due to the beam geometry, the highest frequency component of the spectrum is proportional to the maximum velocity of red blood cells encountered by the sound velocity. And, in the absence of spectral broadening and assuming that the vessel is subjected to a single beam, the average frequency of the spectrum is proportional to the mean blood flow velocity. Because both components are affected by moderate and severe stenosis, they have very important applications in the quantitative diagnosis of vascular diseases. For example, the highest frequency component can be used to determine the pulsatility index (Gosling and King, 1974; Johnston ... 1987). Because the index is normalized, it is more or less independent of the angle at which the sound beam acts.