Pain in feet or toe when not walking is a symptom of progressive peripheral arterial disease (narrow or blocked arteries, mainly in legs).
Absent or weak pulses at the groin, behind the knee, on the inner ankle, and on the top of the foot, indicates obstruction of blood flow through the certain arteries.
Another signs of this condition are blue or purple marks on the legs, feet, or toes; feet that turn red when dangled, and feet and toes that become pale from exercise or when elevated.
His legs may feel cold, with dry skin, and loss of hair.
Arterial and vascular Doppler ultrasound means the same, since vascular in translation is "related to blood vessels".
Probably, your question was if to chose arterial or venous (related to veins) Doppler.
My personal opinion is to chose arterial Doppler ultrasound.
Best wishes for you and your brother!
Marija