The appearance of the nostril in cleft lip patients is very important in the subjective assessment of naso-labial forms and patient satisfaction. To improve the outcome of plastic surgery, a computer aided diagnostic system was developed. Facial forms were measured with a three-dimensional optical scanner (Ogis Range Finder RFX-IV) XYZ coordinates (256 x 240) and RGB (red, green, blue) image (512 x 480) data sets were then obtained with the apparatus. The nostril area was determined by discriminant analysis of the RGB data, and the landmarks of the nostril were extracted under geometric conditions. To assess the reliability of this technique with head inclination, five volunteers were measured in seven postures. Landmark stability was within approximately 1 mm when the Frankfort plane was 45-60°. Subsequently, this system was applied to two cleft lip patients who had undergone a secondary nasal correction. For control data, 37 healthy adults (22 males and 15 females) were measured in the same manner. Nasal asymmetry in the unilateral case and wide and flat nostrils in the bilateral case were greatly improved after surgery. Conversely, the volume of the nasal tip decreased. This system was a great help in the diagnosis of nostril abnormalities. (C) 1999 European Association for Cranio-Maxillofacial Surgery.
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