PRECISION, REPEATABILITY, AND VALIDATION OF THE LOCALIZATION OF CRANIAL LANDMARKS USING COMPUTED-TOMOGRAPHY SCANS

Computed tomography (CT) has brought to the craniofacial surgeon a thr ee-dimensional representation of internal structures, CT scans provide visualization of anatomy for preoperative planning and postoperative evaluation, Beyond visualization, however, a CT scan enables assessmen t of measurements useful to clinicians and basic scientists, All measu rement systems used with CT require the ability to accurately locate r egions of interest on the image (i.e., areas, volumes, outlines, curve s, surfaces, points), This study evaluates the precision and repeatabi lity of locating anatomic landmarks in three dimensions on CT slice im ages, and validates these locations using an established measurement s ystem. The average error of landmark position is always less than 0.5 mm and for some landmarks error is negligible, Repeatability studies s how that less than 2% of the total variance in our data is due to meas urement inaccuracy. Although data collected from CT scans are internal ly consistent, validation results caution the use of CT data in combin ation with data collected using calipers or other direct means of meas urement.