A system includes acquisition of a first image of a portion of a body, the first image representing the portion during a first phase of motion, acquisition of a second image of the portion of the body, the second image representing the portion during a second phase of motion, generation of a composite image based on the first image and the second image, the composite image indicating a position of a target during the first phase of motion and a position of the target during the second phase of motion, and identification of a target region based on the composite image.