1. A method for use with a portion of a body of a subject that contains a lumen, the method comprising: acquiring at least one extraluminal image of the portion of the subject's body, the extraluminal image including a longitudinal portion of the lumen; displaying, on a display, the acquired, extraluminal image; and using at least one processor: in response to receiving a single input from a user designating a single point within the extraluminal image of the portion of the subject's body, identifying a region within the lumen that corresponds to a lesion, by identifying edge lines of the lumen and longitudinal extremities of the lesion, within the extraluminal image, in a vicinity of the single point; in response thereto, automatically, performing an identification selected from the group consisting of: identification of at least one tool that is suitable for being placed at the region, and identification of a dimension of at least one tool that is suitable for being placed at the region; and generating an output in response to the identification.