1. A method for imaging a portion of a body of a subject that undergoes a motion cycle, the method comprising: acquiring a plurality of image frames of the portion of the subject's body; identifying a given feature in at least some of the image frames; image tracking the at least some image frames with respect to the feature, by aligning the at least some image frames with respect to the feature; displaying, as a stream of image frames, the image frames that have been image tracked with respect to the first given feature; and at least partially reducing visibility of a periphery of the displayed stream of image frames, wherein reducing the visibility of the periphery of the displayed stream of image frames comprises applying a mask to the displayed stream of image frames.