Scoring system.A, Grade 1. Scoring system.A, Grade 1. Small dot of calcification 1 mm thick is present in the left CCA wall. Grades for this plaque are 1 for extent and 1 for thickness.B, Grade 2. CT scan of the right CCA shows an atherosclerotic, calcified plaque that is crescentic but <90° of the vascular circumference. Grades are 2 for extent and 1 (1 mm) for thickness.C, Grade 3. Circumferential involvement of the right CCA calcification is 90° but <270°; therefore, the grade is 3 for extent.D, Grade 4. Both carotid arteries show complete circumferential involvement with atherosclerotic plaque, hence grade 4. Lukasz S. Babiarz et al. AJNR Am J Neuroradiol 2005;26:1505-1511 ©2005 by American Society of Neuroradiology