1. A method of evaluating tissue characteristics in a patient, comprising: obtaining a first image of tissue including a region of interest during a first acquisition; obtaining a second image of the tissue including the region of interest during a second, subsequent acquisition; and determining a global characteristic of the region of interest of the first image and of the second image so as to allow a comparison of the global characteristic of the first image and the second image to determine a potential for a global injury of the tissue of the region of interest.