Table 1 How to adjust the Doppler settings in large vessel vasculitis
From: Settings and artefacts relevant for Doppler ultrasound in large vessel vasculitis
Flow type | The flow is fast and in vasculitis direction and velocity are important for diagnosis |
|---|---|
PRF and wall filters | Different PRF for different vessels: |
Temporal and facial arteries, PRF range = 2–3.5 kHz | |
Carotis, subclavian and axillary arteries, PRF range = 3–4 kHz | |
Vertebral and occipital arteries, PRF range = 0.7–1.5 kHz | |
High PRF ensures display of correct flow direction and velocity | |
Wall filters are linked controls and with a high PRF, the wall filter will also be high to eliminate motion artefacts from moving arterial walls | |
Choice of Doppler | CD as it displays the mean blood velocity |
Spectral Doppler for indicating correct insonation angle and for calculating the correct velocity of the flow | |
Doppler frequency | Optimal frequency varies according to the location of the vessel |
Higher for temporal arteries lower for the larger arteries because of penetration | |
Gain | Gain should be adjusted according to noise level for both CD and spectral Doppler but with a minimum of blooming |
Colour priority | If adjustable, then it should be kept high to ensure Doppler filling in the vessel |
Focus | At the level of region of interest to ensure optimal Doppler sensitivity |