Measurement of blood flow velocity using temporally-modulated contrast injection based on Digital Subtraction Angiography*

Real-time hemodynamic information is closely related to the pathophysiology of vascular diseases. By tracking contrast agent concentration, digital subtraction angiography (DSA) can provide quantitative blood flow measurements. Traditional methods typically employ fixed-rate contrast agent injection and the resulting contrast concentration oscillation is due to the inherent pulsatility of the cardiac cycle. Such method is limited in its robustness in distal vascular regions. In the current study, a temporally-modulated contrast injection is generated using a programmable syringe pump. This method is benchmarked in a straight 4 mm diameter vascular model with prescribed constant blood flow rate. The blood-mimicking fluid was prepared from glycerol, distilled water, and ethanol. Signal quality was evaluated at various injection frequencies (0.5 Hz - 4 Hz) using so-called sideband ratio, with 1 Hz identified as optimal. The velocity profile in the blood vessel, derived by applying the shifted least squares algorithm to the concentration curve between any two points at different radial positions of the vessel, matches well with the results from dye tracking and PIV, which serve as measurement benchmarks. Flow velocity measurement was also performed in a patient-specific intracranial artery model, with a total flow rate measurement error of 8.3%. This study presents valuable data for developing a commercial medical device capable of generating contrast agent pulsatility for flow quantification during standard DSA procedures.