Rader R D
Med Instrum. 1976 Jul-Aug;10(4):185-8.
A phase difference technique for measuring true volume flow rate has been developed. The concept utilizes the phase difference from unequal transit times between bursts of ultrasonic energy transmitted simultaneously against and with the blood flow. A theoretical analysis reveals that the volume flow rate sensitivity (V/ml/sec) for a point crystal illumination pattern directed diagonally through the center of the vessel is a function of the inverse of the diameter. But an illumination pattern orientated perpendicularly to the vessel axis, which spans the entire diameter of the vessel, yields a volume flow rate sensitivity independent of the diameter. Line illumination, in contrast to point illumination, does not require the vessel diameter to be measured in order to establish the sensitivity factor, and a change in diameter does not alter the sensitivity factor. Line illumination has a considerable advantage when used on small vessels in which the ratio of wall thickness to the lumen diameter is large and is often variable.
一种用于测量真实体积流量的相位差技术已被开发出来。该概念利用了同时逆着和顺着血流传输的超声能量脉冲之间不等传播时间产生的相位差。理论分析表明，对于对角穿过血管中心的点晶体照明模式，体积流量灵敏度（V/ml/秒）是直径倒数的函数。但是，垂直于血管轴且跨越血管整个直径的照明模式产生的体积流量灵敏度与直径无关。与点照明相比，线照明在确定灵敏度因子时不需要测量血管直径，并且直径变化不会改变灵敏度因子。当用于壁厚与管腔直径之比大且经常变化的小血管时，线照明具有相当大的优势。
