CAPTURING DATA FROM 3-DIMENSIONAL SURFACES USING FUZZY LANDMARKS

Anatomical landmarks are defined as biologically meaningful loci that can be unambiguously defined and repeatedly located with a high degree of accuracy and precision. The neurocranial surface is characteristic ally void of such loci. We define a new class of landmarks, termed fuz zy landmarks, that will allow us to represent the form of the neurocra nium. A fuzzy landmark represents the position of a biological structu re that is precisely delineated, but occupies an area that is larger t han a single point in the observer's reference system. In this study, we present a test case in which the cranial bosses are evaluated as fu zzy landmarks. Five fuzzy landmarks (the cranial bosses) and three tra ditional landmarks were placed repeatedly by a single observer on thre e-dimensional (3D) computed tomography (CT) surface reconstructions of pediatric dry skulls and skulls of pediatric patients, and directly o n four of the same dry skulls using a 3Space digitizer. Thirty landmar k digitizing trials from CT scans show an average error of 1.15 mm loc al to each fuzzy landmark, while the average error for the last ten tr ials was 0.75 mm, suggesting a learning curve. Data collected with the 3Space digitizer was comparable. Measurement error of fuzzy landmarks is larger than that of traditional landmarks, but is acceptable, espe cially since fuzzy landmarks allow inclusion of areas that would other wise go unsampled. The information obtained is valuable in growth stud ies, clinical evaluation, and volume measurements. Our method of fuzzy landmarking is not limited to cranial bosses, and can be applied to a ny other anatomical features with fuzzy boundaries. (C) 1998 Wiley-Lis s Inc.