Blood flow measurement by cone-beam CT bolus imaging

Abstract

Via angiographic injection, blood vessels become visible in X-ray imaging. Based on dynamic bolus tracking and static vessel volume depiction, this paper presents a three-dimensional (3D) imaging method for blood flow measurement. After angiographic injection, the bolus motion in vessels in a scan field of view can be described by wash-in, equilibrium, and wash-out phases in the order of time. The cone-beam scanning produces a sequence of projection images, of which the wash-in images are used for bolus tracking, and the equilibrium images for vessel volume reconstruction. From a vessel volume, not only can we depict the vessel diameter by digital anatomical analysis, but also extract vessel centerlines by volumetric vessel segmentation and 3D skeletonization. We assume that bolus travels along the vessel centerlines, and the 3D bolus passageways can be time ticked by consulting the bolus motion in a sequence of wash-in projection images. By splitting this sequence into two subsequences (different by a delay of a few frames) and considering them as two sequences of two-view image pairs, we can calculate a 3D bolus passageway by two-view stereo reconstruction and then correct the excursions by a nudge algorithm (3D bolus point adjustment in reference to 3D vessel skeleton). Alternatively, by cone-beam reprojecting the 3D skeleton and consulting the 2D bolus motion manifested in wash-in projection images, we can tick off the 3D skeleton by time and thereby calculating bolus pathlength and flow velocity. Numerical simulations and phantom experiments are reported.