ABSTRACT

Hint: It can sometimes be difficult to identify the ECA versus the ICA. Remember that the ECA: ●● has extracranial branches – use colour Doppler to help identify them ●● demonstrates the ‘temporal tapping’ phenomena – tap the temporal artery in front of the ear and look for alteration in the spectral waveform of the ECA (there is no effect on the ICA waveform)

SCM

SCM

Colour Doppler box

ECA

Branches of ECA

SCM

Colour Doppler

box Spectral

Doppler gate

Caliper measuring peak velocity50

40 30 20 10 0

Peak velocity = 50.4 cm/s

cm /s

CCA in LS

Colour Doppler box

Spectral Doppler gate

Characteristic notch

Pulsatile

PulsatileLow diastolic ow

80 60 40 20

cm /s

‘Saw-tooth’ appearance

after temporal tap

●● Repeat Step 4 for the ICA. ●● Measure peak velocity. ●● The normal ICA waveform is:

− less pulsatile than the ECA − low resistance flow − higher diastolic flow

●● Acquire one or two spectral waveforms.