Medical imaging systems and methods for determining contours of anatomical structures of vessels and vessel sections for representation in X-ray-based fluoroscopic images. Methods can include capturing a mask image, recording at least one filling image including a vascular tree filled with contrast agent, subtracting the mask image from the at least one filling image to produce at least one vessel image, generating a segmented vessel image by segmenting the vascular tree filled with contrast agent in the at least one vessel image and removing from the at least one segmented vessel image such vessels and vessel sections that do not meet a threshold value, wherein the threshold value represents a function of at least one predetermined structural feature, and superimposing the at least one segmented vessel image with a live X-ray image and reproduction on a display device.