Proceedings Article | 16 March 2020
KEYWORDS: Modulation, Blood circulation, Angiography, Actuators, Control systems, Fluid dynamics, Prototyping, Computing systems, Human-machine interfaces, Calibration
Catheter-based vascular interventions performed in the interventional radiology suite rely heavily on digital subtraction angiography (DSA) for intraprocedural evaluation of vessel morphology. Recently, DSA methods have been reported which quantify blood flow based on the tracking of temporal oscillations in contrast agent density through vessels. This signal, termed contrast pulsatility, arises naturally from the mixing of a fixed rate contrast injection with periodic arterial blood flow. Although these tools promise quantitative intraprocedural evaluation of flow, quantification is limited by a decline in contrast pulsatility strength in distal arterial vasculature, and, in venous structures, minimally observable or no pulsatility. To improve pulsatility strength in DSA images, a custom dual-barrel power injector was constructed that dynamically modulates the injected contrast flow (or concentration). Each barrel can follow sinusoidal and square wave injection profiles of specified frequency, amplitude, phase, and duty cycle. Improvement in contrast pulsatility was evaluated in a vessel phantom with simulated 60 bpm arterial flow and low-frequency sinusoidal contrast injections of 0.25, 0.50, and 1.0Hz. The ability to establish contrast pulsatility in a venous structure was evaluated in a porcine study. In the arterial phantom, sinusoidal contrast injections at 0.25Hz, 0.5Hz, and 1.0Hz displayed increased distal contrast pulsatility relative to a DC contrast injection at the same mean rate, with energy spectral density (ESD) ratios of 215, 59.9, and 5.3 respectively. In the animal study, a custom 0.67Hz square wave injection into the inferior vena cava showed a large improvement in pulsatility relative to DC injection (ESD ratio of 7208).
