Medical diagnostics q - Ultrasound

I had an Echo / Stress Echo and Carotid scan yesterday. Happily, the preliminary results looked good (although, it’s still unclear why my Cardiologist heard a “bruit” in my left Carotid). My question is: if an Ultrasound scan can give a decent image in regards to the artery diameter, why isn’t this used all the time to detect coronary artery blockages, instead of an Angiogram, which is a much more invasive and dangerous procedure?

The carotid is a nice big structure relatively close to the surface with out many major structures in between to block the ultrasound. The length of carotid which needs to be seen is also relatively short. By contrast, the coronaries are long arteries, deep in the chest, sheltered by bone, muscle, and the heart itself, depending which ones you are looking at and from which direction. Unlike the carotid which is essentially running in one plane, each coronary wraps around the heart in various directions, and they move as the heart does. Even a basic echocardiogram like the one you had can have difficulty determining the sizes of the (comparatively huge) ventricles and details about the heart valves due to some of the above technical factors, so you can imagine that accurately imaging the coronaries would be very difficult.

I can see where that would make imaging difficult, but it seems like all those issues could be solved my technology (time-of-flight gating, for example) and computing power. Is research being done to make coronary artery ultrasound imaging practical? It would be yuge! Yuge I say!

I’m far removed from the cutting edge of medical imaging technology, but back in the day I was taught that sound waves could only be enhanced so far before you just couldn’t squeeze any more consistently reliable information out of them. Hence the gold standards for such testing remain the optical images you get from such procedures as catheterization.