VELOCITY-MEASUREMENT BASED ON BOLUS TRACKING WITH THE AID OF 3-DIMENSIONAL RECONSTRUCTION FROM DIGITAL SUBTRACTION ANGIOGRAPHY

The problem of blood flow measurement in x-ray angiography using measu rements of the leading edge of the contrast bolus as it traverses the vascular bed is considered. A new technique for velocity measurement i s presented based upon the ratio of the temporal derivative to the spa tial derivative of the contrast bolus in the direction of flow. With t he addition of a small correction factor, the value obtained is shown to reflect the transport velocity, or the velocity at which the contra st is transported down the vessel of interest. Most blood flow measure ments based on bolus tracking techniques are actually using the contra st transport velocity to represent the blood flow velocity. Because of the streaming that occurs due to laminary flow conditions, the measur ed transport velocity is found to be somewhere between the average and the peak (central) fluid velocities for measurements taken during the traversal of the bolus leading edge. The spatial and temporal variati on of the transport velocity are found to be consistent with the bolus motion expected in the presence of laminar flow. From x-ray images of contrast passage through simple tubes, we find that the derivative me thod measures the transport velocity during passage of the bolus leadi ng edge. In most cases of laminar blood flow, the leading edge transpo rt velocity can be 20%-40% higher than the average blood velocity. (C) 1997 American Association of Physicists in Medicine.