Flow Velocity Determination from 1000 FPS High Speed Angiography Images Using Temporal-Shift Matching and Threshold-Bolus Tracking Methods

1000 fps High-Speed Angiography (HSAngio) provides physicians with an unprecedented ability to visualize and accurately quantify vascular flow as influenced by the individual phases of the cardiac cycle. Here, we present two new alternative methods to estimate flow velocity from HSAngio images: Temporal-Shift Matching (TSM) and Threshold-Bolus Tracking (TBT). An in-vitro model representing the internal-carotid-artery was connected to a pump circulating blood analogue at a constant rate. Micro-boluses of iodinated contrast were injected using an injector and rotating-valve via a 5-French catheter. Sequences of 300 continuous 1-ms images of contrast agent flow through the model were acquired for two different circulating flow rates of 300 ml/min and 375 ml/min, using a Varex Imaging Aries Photon-Counting Detector. From these images, Time-Density Curves (TDCs) for regions-of-interest (ROI) within the vasculature were created. The TSM method calculated velocity as the ratio of the distance between two ROIs to the temporal shift between the TDCs of the two ROIs. For the TBT method, the images were first thresholded, then from these images, TDCs for the same two ROIs were derived, and the velocity was calculated from the distance and the temporal shift between equal-density points on the thresholded TDCs. An In-Silico Simulation was also used for validation. At the slower flow rate, velocities were 36.1±5.1 (TSM) and 34.3 ± 5.5 (TBT); at the faster rate, 50.8 ± 6.3 (TSM) and 45.8±6.3 (TBT). Both methods gave reliable blood velocity estimates that agreed within uncertainties and provides means for hemodynamic evaluation of blood flow with HSAngio.