Measuring blood velocity using 4D-DSA: A feasibility study

Four-dimensional (4D) DSA reconstruction provides three-dimensional (3D) time-resolved visualization of contrast bolus passage through arterial vasculature in the interventional setting. The purpose of this study was to evaluate the feasibility of using these data in measuring blood velocity and flow.

The pulsatile signals in the time concentration curves (TCCs) measured at different points along a vessel are markers of the movement of a contrast bolus and thus of blood flow. When combined with the spatial content, that is, geometry of the vasculature, this information then provides the data required to determine blood velocity. A Fourier-based algorithm was used to identify and follow the pulsatility signal. A Side Band Ratio (SBR) metric was used to reduce uncertainty in identifying the pulsatility in regions where the signal was weak. We tested this method using 4D-DSA reconstructions from vascular phantoms as well as from human studies.

In five studies using 3D printed patient-specific cerebrovascular phantoms, velocities calculated from the 4D-DSAs were found to be within 10% of velocities measured with a flow meter. Calculated velocity and flow values from three human studies were within the range of those reported in the literature.

4D-DSA provides temporal and spatial information about blood flow and vascular geometry. This information is obtained using conventional rotational angiographic systems. In this small feasibility study, these data allowed calculations of velocity values that correlated well with measured values. The availability of velocity and blood flow information in the interventional setting would support a more quantitative approach to diagnosis, treatment planning and post-treatment evaluations of a variety of cerebrovascular diseases.