A system and method is provided for assessing efficacy of placement of a vascular implant medical device that has been implanted in a subject. The method includes accessing, with a computer system, image data acquired from a subject using a medical imaging system. The image data include at least one image of the vascular implant device implanted within a vascular structure of the subject after the subject has received an injection of a contrast agent at a contrast injection site. The method also includes determining, from the image data, a region of interest (ROI) that includes the vascular structure and is downstream of the contrast injection site and developing a contrast model from the image data. The method further includes, using the contrast model, determining a flow time constant and, using the flow time constant, assessing an efficacy of the vascular implant device implanted in the vascular structure.