"F is Doppler frequency shift"
"Q is the angle between ultrasound beam and axis of flow"
"Colour flow Doppler (ultrasound)"
"Spectral Doppler (ultrasound)"
Expected headings
"Doppler equation"
"The magnitude of the Doppler shift is affected by the angle at which the reflecting source is travelling in relation to the transmitting source. This is accounted for in the Doppler equation with the "cosine(θ)" parameter; the maximum Doppler shift occurs when the relative motion occurs at a Doppler angle of 0 degrees (the cosine of 0 = 1) and no Doppler shift will be noted when the motion of the reflecting source is perpendicular (cosine of 90 = 0) 3."