1. An apparatus for visualizing medical image data, comprising: processing circuitry configured to obtain first image data representing a first medical image and second, different image data representing a second medical image; register the first medical image data and the second, different medical image data; obtain subtraction image data representing a subtraction image by, following the registering, subtracting one of the first medical image data and the second, different medical image data from the other of the first medical image data and the second, different medical image data; process the first image data representing the first medical image to identify an anatomical feature or stent; display, on at least one display screen, a combined image comprising an overlay of the identified anatomical feature or stent from the first medical image data and one of the subtraction image and the second, different medical image such that the identified anatomical feature or stent and at least one corresponding anatomical feature or stent from the subtraction image or the second medical image at least partially overlap, wherein the corresponding anatomical feature or stent is associated with an image artifact.