Again I think this is a question for experts however:
Standard ultrasound used on your chest arteries is called an echo-cardiogram. It does not detect flow or direction of blood because it is not Doppler. Doppler, if I understand it correctly, uses reflections of an ultrasound sound and the Doppler shift (the same that makes sirens sound like they are changing pitch as they get closer to you or farther away). That results from the addition or subtraction of the speed of the ambulance or police car to or from from the speed of the sound waves their sirens are making.
The exact same shift can be 'heard' by an ultrasound probe. Doppler ultrasound is easier to do, the more shallow (closer to the surface) that the veins are. For this reason, a higher-frequency probe (the sound is measured in millions of cycles per second -- ordinary sound can only be detected by human ears up to about twenty thousand cycles per second) must be used for deep cerebral veins, as the lower-frequency probe normally used for ultrasound (like for baby pictures or echo-cardiograms) will not detect the Doppler shift at those depths.
This is new science, and the tool is infrequently used, and rarer. Many labs now have one, but it has only been used for leg veins. Dr. Zamboni's use of it is a new one, and training is recommended.
"Try - Just A Little Bit Harder" - Janis Joplin
CCSVI procedure Albany Aug 2010
'MS' is over - if you want it
Patients sans/without patience
I am not a doctor. Do not take anything I say as medical advice.