Part of the problem, unfortunately, is that the "gold standard" method for

measuring % diam. stenosis is flawed.  Angiography cannot tell where the true

vessle diameter is, so they must measure downstream in a PRESUMED normal

segment.  Of course the vessel lumen becomes increasing smaller with distance

and the distal segment may or may not have atherosclerotic narrowing.

The angio findings inherently under exaggerate the degree of stenosis.

For dimensional or area measurement of stenosis ultrasound is not truly

accurate unless the region is perpendicular to the transducer and superficial

allowing adequate visualization of the lateral and medial segments.  Then of

course you may be deemed inaccurate by the "gold standard" for reasons

mentioned above.

We rely on doppler criteria : 0-15%, 16-49%, 50-79%, 80-99%, 100% because it

most closely follows angio grading categories.  This a common criteria and is

available in most references.

Doppler still tends to over estimate stenosis relative to angiography.

Personally I think one reason may the accepted procedure of correcting all

angles to 60 degrees.  We set our H-P to correct to 50 degrees - less

mathmatical "correction", less exaggeration.

Good Luck,

T Cunningham, RVT, RDCS