Image-based metrics of arterial embolization endpoints using an in vitro model

In recent years transcatheter arterial embolization procedures have grown in volume and complexity but the lack of quantitative measures of embolization endpoints has limited procedure standardization. Interventional radiologists use visual cues in angiographic images for qualitative characterization of the stages of embolization. Image-based metrics for assessing embolization endpoints can be used to prevent over- or under- embolization. In this work we use a benchtop flow system and a 3D printed phantom of hepatic arterial vasculature to build an in vitro model of the dynamic conditions of the blood flow proximal to the catheter tip location during transcatheter embolization of the hepatic arteries. The gradual reduction of the downstream flow is realized using needle valves on the phantom outlets and is monitored using flow sensor measurements thus allowing reproducible levels of vessel occlusion. Optical images are acquired during repeated automated catheter injections of dye solution with controlled injection parameters (injection rate and volume). The optical imaging data is post-processed to simulate digital subtraction angiography and is analyzed to derive image-based metrics characterizing the levels of occlusion. Using data collected over repeated controlled experiments, dependent variables including time constants and area under the curve, are derived from time-varying intensity profiles and characterized as a function of the occlusion rate. The experimental results demonstrate reproducible patterns and suggest that such image-based features are correlated to the underlying dynamic phenomenon and can be used as quantitative measures of vessel occlusion.