Estimates of flow velocity with controlled spatio-temporal variations in contrast media properties

A method for estimating a flow velocity of a fluid flow in a vessel, comprising:

• providing a fluid flow having contrast media therein, the contrast media having a contrast media property variation;
• emitting a first signal with a first energy source at a known periodicity, the first signal interacting with the contrast media to produce a first altered signal relating to the contrast media property variation, the first altered signal having a defined pattern;
• receiving the first altered signal at an upstream receiver positioned to be sensitive to signals from the first energy source that have interacted with the contrast agents;
• emitting a second signal with a second energy source at the known periodicity, the second energy source being located downstream of the first signal at a known length (L), the second signal interacting with the contrast agents to produce a second altered signal related to the contrast media property variation, the second altered signal having the defined pattern;
• receiving the second altered signal at a downstream receiver located downstream of the upstream receiver and positioned to be sensitive to signals from the second energy source that have interacted with the contrast agents;
• filtering the first altered signal and the second altered signal through a contrast media variant filter to produce a first filtered signal and a second filtered signal;
• cross-correlating the first filtered signal with the second filtered signal to determine a time shift (Δt) between the first filtered signal and the second filtered signal that corresponds to a maximum correlation between the first filtered signal and the second filtered signal;
• and
• estimating the velocity of the fluid flow using a relationship vflow=L/Δt.