In addition to the 4 grades of aortic injury, the risk of rupture can also be categorized. If both the inner layer and the muscle layer of the aortic wall are both involved in the injury then the injury is categorized as significant aortic injury.[8] If just the inner layer and a portion of the muscle layer are involved in the injury then the injury is characterized as minimal aortic injury.[8] Radiographically this would be seen as an intimal flap less than 1 cm in size.[8]