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.