The Ring Vortex: Concepts for a Novel Complex Flow Phantom for Medical Imaging

Calibration of medical imaging systems that provide quantitative measures relating to complex physiological flows is challenging. Physical test objects available for the purpose either offer a known simple flow far removed from the complexity of pathology (e.g. parabolic flow in a straight pipe) or complex relevant flows in which the details of the flow behaviour are unknown. This paper presents the ring vortex as a candidate for a complex flow phantom, since it is marked by inherently complex flow features that are controllable, predictable, reproducible and stable. These characteristics are demonstrated by a combination of analytical, numerical (CFD) and experimental methods. Together they provide a consistent perspective on ring vortex behaviour and highlight qualities relevant to phantom design. Discussion of the results indicates that a liquid phantom based on the ring vortex may have merit as a complex flow phantom for multimodal imaging. Furthermore, availability of such a flow reference may also serve as a benchmark for quality assurance of simulation methodologies.