An ultrasound system is used to measure the percent stenosis of a vessel in terms of residual lumen area. A measurement of volume blood flow is made at an unobstructed point of the vessel near the site of the stenosis. A measurement of the time averaged mean blood flow velocity is made at the stenosis. The quotient of these two values is computed to produce an estimate of the residual lumen area and the percent stenosis at site of the obstruction.
