Rob: In 1988 I began doing some research into the applicability of using
volume flows in the vertebral arteries.  At that time I was using two
different ultrasound systems, one which automatically calculated the volume
flow and the other that did not.  I used mean TAVs for the calculations.
The biggest surprise from this research was the difference that I was noting
between systems.  Rather than pursue my original plan, I decided to submit
an abstract in which a controlled group of normals were used and the volume
flows were calculated from the CCAs, ICAs and vertebrals.  I believe that I
included over 30 normals of each vessel group for comparison.  In the
meantime I obtained the service of another manufactureer and had three
systems to use for comparison.  The bottom line was that there was a
statistically significant difference between systems and that regardless of
the values obtained, they could not be used in a diagnostic fashion.  I had
hoped to obtain a reliable flow phantom and then compare the volume flows to
the phantom. The bottom line was that we needed to standardize the method
for obtaining the flows for the manufactureers and concentrate some
dedicated research to the accuracy of the volume values. By the way, the
abstract was rejected but I am happy to see someone attempt to pick it up
again.  Sandy Katanick 
>I need some opinions, (ya Terry, I know I'm ugly). 
>How important are flow volume measurements in the peripheral vascular world?
>Does anyone measure flow volumes in dialysis access grafts, and if so, does
>your system calculate the time averaged velocity from the peaks or from the
>mean? Do you think it's important for manufacturers to include the capability
>of flow volume assessment on their systems??  I've been asked about the
>importance of this feature by a number of manufacturers and I don't want my
>opinions alone to make or break their products!  Thanks for your views.
>Rob Daigle
>