Characteristic of venous blood flow of lower limb in duplex Doppler is?

* Doppler is based on frequency shift and color coding depends on the direction of blood flow* Direction of blood flow:- Flow towards the probe- Red- Flow away from probe- Blue Intensity of color depends on velocity of flow Doppler effect: change in frequency because of relative motion between moving source of sound and observer. Direction of flow Color doppler showing CCA bifurcation Spectral doppler: Cursor is placed into the area of blood vessel we want to trace and its velocity is measured.An angle has to be maintained to obtain a proper image- Ideal angle = 0o (practically not possible)- Optimal angle = 45o-60o (never 90o) Spectral doppler of aeries Low resistance High resistance Example:* Brain aeries* ICA* CCA* VA- Renal aeries| Monophasic with pattern pulsatility Example: - Extremity aeries* ECA | Triphasic pattern Normal Peripheral Aerial Waveform Triphasic waveform Initial high velocity forward flow component Early diastolic reverse flow component Late diastolic forward flow component Narrow systolic window * Venous doppler:- It is Monophasic- during free breathing variations in amplitude due to cardiac and respiratory phasicity- In breath hold- pressure changes of . Atrium are reflected back in the major veins