Automated coronary flow reserve assessment using planair x-ray angiography

Coronary lesions like stenosis, blocking the blood supply to the heart muscle, contribute significantly to the cause of heart failure. In this research we propose a method to quantify coronary stenosis using planar x-ray angiography image processing. The method we present here has a clinical equivalent called Thrombolysis in Myocardial Infarction frame counting (TFC), which is widely used as a qualitative measure for flow velocity. The TFC is measured by counting the number of frames between injection of the contrast agent in the artery until it reaches the most distal bifurcation. The approach used in this research is to reconstruct a 3-d model which is used to track the coronary arteries and measure the contrast density in 2-d image sequences containing hyperemic or basal acquisitions. Then we focus on the generation of a flow map, this is in fact a 2-d representation of a set of time density curves, which is used to analyze contrast agent propagation. With flow maps we are able to analyze the contrast density along the vessel centerline with a higher spatial resolution compared to using only a limited number of regions of interest. The research is concluded with a comparison of the algorithm to clinical results on a dedicated clinical dataset used for TIMI frame counting. From nine patients we had sufficient data to create a 3-d model and measure the coronary flow velocity. These measurements have a correlation r=0.98 (P<0.0001, 95% CI 0.92 to 0.99) with the clinical equivalent.