A method is disclosed of providing time dependent three dimensional imaging of a region of a patient comprising blood vessels in a perfusion bed. Such a method may involve determining dimensions of a container, portal, or dimensionally constrained path in which an instance of a given item is handled and determining estimated dimensions of the item dependent on dimensions of the container, portal, or path. The AFS system also includes a side-slip rate sub-system that generates a desired side-slip rate feedback signal.