1000 fps High-Speed Angiography (HSA) Evaluation of Vortex Flow Characteristics in 3D-printed Cerebral Vascular Aneurysm Phantoms

Quantification of flow features within aneurysms from angiographic x-ray acquisitions provides essential information regarding aneurysm diagnosis, rupture risk, and treatment. Conventional endovascular procedures use angiography acquired at 3-15 fps which is mainly used for morphologic visualization, but its hemodynamic temporal resolution is inadequate for fine flow pattern analysis. For this, high frame rate is essential. In this study, 1000 fps High-Speed Angiography (HSA) is used to visualize detailed hemodynamic patterns, including vortex-flow features. These acquisitions were made with a high-speed CdTe photon-counting detector (Aries, Varex) (7.5 cm x 5 cm FOV) which was mounted to an automatic-changer mechanism, allowing for the utilization of the x-ray source of a Canon Biplane Unit. The flow studies used a fluid mixture of 40%/60% glycerol/water to mimic hemodynamics with anatomically specific pulsatile flow from a computer-controlled pump (CardioFlow, MR5000), with injection of omnipaque iodinated solution at 2 ml/s for 1 s to visualize contrast flow within 3D-printed patient-specific cerebral aneurysm phantoms. Pre-processing and noise reduction was performed on the 1-ms frame images. Velocities of the injected contrast were calculated with an Optical Flow (OF) method and were mapped over the vessel. The OF velocities were then used to calculate vortex characteristics. At 1000 fps, fine fluctuations in vortex formation and core location are observed from the vorticity analysis. The detailed analysis of vortex-flow phenomena made possible by 1000 fps HSA could provide significant information for future analysis of patient aneurysms and improve patient care.