Detection of Small Vessel Occlusion Using Doppler Ultrasound; an in Vitro Study

'Small vessel knock' is a recently reported Doppler ultrasound finding detected in patients with acute ischemic stroke. Knock signals are periodic, of short-duration (<100ms), and localised within the head. Typically, signals have a unidirectional component in systole and a reflected component during diastole. Currently it is not known whether this signal arises due to occluded blood-flow, wall motion, or some other mechanism. The potential uses of Doppler ultrasound for location of small-vessel occlusion in stroke patients therefore remains controversial.