Optimal Doppler angle should be
Ideal Doppler Angle for color doppler is 0 degrees ,Most blood vessels course parallel to the skin and zero Doppler angle is seldom obtainable. In addition, no Doppler shift is obtained at 90 degrees since the cosine of 90 degrees is 0. Thus, the optimal Doppler angle lies between 45 and 60 degrees.
90 degrees
45-60 degrees
60-80 degrees
80-110 degrees
ULTRASOUND