Regarding the site for obtaining CCA velocity, we (at Grossmont Hospital,
and also my teaching at Grossmont College) make it "mid-to-proximal" as
opposed to mid-to-distal. That seems to keep us getting reasonable,
representative velocity estimates. We usually also take a straight segment
over a curved one, even if that's in the mid portion.
Some scenarios based on a PSV difference of, say, 20 cm/sec proximal vs.
60/100 = .60
60/80 = .75
125/100 = 1.25
125/80 = 1.56
250/100 = 2.50
250/80 = 3.13
400/100 = 4.00
400/80 = 5.00
What does this mean? I'm not sure. It kind of looks as though it's a bigger
deal with the abnormally elevated ICA velocities than in normals.