Investigation of choice for screening of proximal internal carotid aery stenosis is :
Answer is A (Doppler flow USG): 'Stenosis at the origin of the internal carotid Aery can be identified and quantified reliably by ultrasonography that combines B mode ultrasound image with a Doppler ultrasound assessment of flow velocity.'
Doppler flow USG
CT substraction angiography
MRI
Angiography (DSA)