Winkler P, Helmke K, Mahl M
Department of Pediatric Radiology, University Hospital Eppendorf, Hamburg, FRG.
Pediatr Radiol. 1990;20(5):304-10. doi: 10.1007/BF02013161.
Many pitfalls result from the limited ability of Doppler instruments to record low flow velocities. These include a misleading resistance or pulsatility index due to diastolic cut-off and taking no signal to equal no flow assuming that no signal means no flow. Comparison of actual flow velocities as measured in an in-vitro system (range: 0.8 to 3.4 cm/s) with the lowest recordable spectral or colour signals in 3 Duplexscanners showed that reduced sensitivity to low flow velocities is not only dependent on the high pass ("wall") filter setting, Doppler frequency or angle of incidence, but also on factors such as vessel diameter, impairing the signal to noise ratio. Characteristic errors of colour flow mapping (misleading vascular anatomy, imitation of pathological findings, erroneous exclusion of flow) are due to partial volume effect, limited temporal and velocity resolution, changing angle of incidence, aliasing and failure to detect low flow velocities.
由于多普勒仪器记录低流速的能力有限，会导致许多陷阱。这些包括由于舒张期截止而产生的误导性阻力或搏动指数，以及在假定无信号就意味着无血流的情况下，将无信号等同于无血流。将体外系统中测量的实际流速（范围：0.8至3.4厘米/秒）与3台双功能扫描仪中可记录的最低频谱或彩色信号进行比较，结果表明，对低流速的敏感性降低不仅取决于高通（“壁”）滤波器设置、多普勒频率或入射角，还取决于诸如血管直径等因素，这些因素会损害信噪比。彩色血流图的特征性误差（误导性血管解剖结构、模拟病理结果、错误排除血流）是由于部分容积效应、有限的时间和速度分辨率、入射角变化、混叠以及未能检测到低流速所致。
