Side-viewing rotational IVUS imaging of slow flow with adaptive SVD filtering

Abstract

Coronary artery disease is a leading cause of mortality, however, it is challenging to determine the functional significance of a given plaque, i.e. the likelihood of plaque rupture and major adverse cardiac events. One indicator of plaque vulnerability is intra-plaque neovascularization. If neovascularization within the plaque could be visualized with intravascular ultrasound (IVUS) imaging, it might be possible to stratify risk of rupture and determine appropriate treatment for patients with stable coronary artery disease (CAD) while the patient is undergoing diagnostic catheterization. While side-viewing IVUS is commonly used in the cardiac catheterization lab, current methods for imaging blood flow are limited to large vessels and are not sensitive slow flow in smaller vessels (< 1 mm). We propose a power Doppler approach for imaging blood flow in smaller vessels using side-viewing, mechanically-steered IVUS and singular value decomposition (SVD) filtering. This imaging approach was tested using a laboratory setup in which porcine blood was introduced at a rate of 5.6 mm/s within a 200 µm-diameter microtube positioned adjacent to the inner wall of an ex vivo porcine artery while acquiring pulse-echo data. SVD filtering allowed sufficient tissue suppression to visualize flow in the microtube, resulting in a Doppler CNR of 13.1 ± 1 dB. In the future, such an approach may allow identification of microvasculature within plaques during IVUS exams in patients undergoing cardiac catheterization.