Fig. 3From: Settings and artefacts relevant for Doppler ultrasound in large vessel vasculitisA lower Doppler frequency allows more penetration but also a lower resolution. A higher Doppler frequency gives a more detailed image of the vessels at the expense of penetration. Left: carotid artery with a Doppler frequency of 7.7 MHz. Right: carotid artery with a Doppler frequency of 14.3 MHz; this cannot penetrate well enough to give optimal flow informationBack to article page