Anthropometric Points Research Articles

Assessment of Computer-assisted Comparison between 3D and 2D Facial Images.

The face-to-face superimposition was experimentally performed to assess the reliability of the facial image comparison with the computer-assisted facial image identification system. For evaluating the match of the 3D and 2D facial images of the same person, the 3D facial image obtained from 25 examinees was compared to the 2D oblique facial image of the same examinees ten times, yielding 250 superimpositions. In the case of the different person, the 3D facial images of 25 examinees were each compared to the 2D facial images of other 24 examinees, yielding 600 superimpositions. The average distance obtained from the reciprocal point-to-point differences on sixteen anthropometrical points of the 3D and 2D images was used as a matching criterion. The results showed that the measuring system for the reciprocal point-to-point differences on the superimposition image was reproducible. The ranges of the average distance were 1.4-3.3 for the same person and 2.6-7.0 for a different person, respectively. The average distance and percentage error at the FP/FN crossover point were 3.1 and 4.2%. In this experiment, it was suggested that the facial image comparison using the reciprocal points matching was reliable when the threshold of the average distance was 2.5.

Development of a 3-D measurement and evaluation system for facial forms with a liquid crystal range finder

A 3-D measurement and evaluation system for facial forms was developed with a liquid crystal range finder (LCRF). Its mechanical resolution was ≈0.4 mm, and it was capable of measuring >30 000 points from the entire facial surface in one second. An original program was developed to identify facial landmarks using not only linear distances, but also 3D-curvatures and discriminant analysis of the RGB data. With this program, the 3-D identification of anthropometrical points became possible with high accuracy. Due to the rapidity of the measuring apparatus and morphological evaluation system, it became possible to analyze the facial forms of infants such as cleft lip patients three dimensionally, without any sedation. Therefore, 97 normal infants (mean: 4.3 months of age) were measured and analyzed with this system. A cleft lip infant was measured and compared with the normal infants before and after cleft lip surgery, and the improved points and remaining problems were clearly recognized.

Computer-assisted skull identification system using video superimposition

This system consists of two main units, namely a video superimposition system and a computer-assisted skull identification system. The video superimposition system is comprised of the following five parts: a skull-positioning box having a monochrome CCD camera, a photo-stand having a color CCD camera, a video image mixing device, a TV monitor and a videotape recorder. The computer-assisted skull identification system is composed of a host computer including our original application software, a film recorder and a color printer. After the determination of the orientation and size of the skull to those of the facial photograph using the video superimposition system, the skull and facial photograph images are digitized and stored within the computer, and then both digitized images are superimposed on the monitor. For the assessment of anatomical consistency between the digitized skull and face, the distance between the landmarks and the thickness of soft tissue of the anthropometrical points are semi-automatically measured on the monitor. The wipe images facilitates the comparison of positional relationships between the digitized skull and face. The software includes the polynomial functions and Fourier harmonic analysis for evaluating the match of the outline such as the forehead and mandibular line in both the digitized images.

Cranio-Facial Identification

This article constitutes a review of the literature and an evaluation of the anatomical relationships between skull and face including the soft tissue thickness at various anthropometrical points of the skull, along with a comparison of the methodologies involved in the three techniques, that is, photographic, video and computer-assisted superimposition techniques used in forensic science. In addition, an evaluation of cosistency between skull and face is discussed from the aspect of personal identification. Forensic examiner must be well versed in the anatomy of skull and face for effective utilization of the superimposition technique. When evaluating anatomical consistency between these parts, special attention should be paid their outline, the facial tissue thickness at the anthropometrical points, and positional relationships between skull and face. Data on the thickness of facial soft tissue has been accumulated for each race, Caucasoid, Negroid and Mongoloid. The positional relation of the eyebrow and eye to the orbit, the ala to the nasal aperture, and the lips to the teeth has been investigated by many researchers. Over the last two decades, video superimposition technique has widely been used for identifying unknown skull. The video superimposition presents enormous advantage over the conventional photographic superimposition. This technique allows the fade-out of either the skull or facial image on the monitor for overall assessment of how well the two images match. This also allows the various sectioning images of the skull and facial images for evaluating the positional relationships between the skull and face. In this technique, however, the anthropometrical examination including soft tissue thickness could not directly be performed on the TV monitor. On the other hand, in the last ten years, the computer-assisted cranio-facial superimposition has been developed. The use of a video-computer with appropriate software allows to take the images of the skull and facial photograph with only one camera and to directly compare the digitized both images on the monitor. The computer technology has also been used to determine the size of natural head and optimum objective length. The software such as the polynomial functions and Fourier harmonic analysis has been applied to evaluate the fit between the outline of skull and facial photograph. It is suggested that the outline from the forehead to the gnathion in the lateral or oblique view is the preferable portion for personal identification, and the cranio-facial superimposition method is reliable for personal identification when two or more facial photographs taken from different angles are used in the examination. The computer-assisted skull identification system using video superimposition is useful to demonstrate the cosistency between skull and facial photograph because the quantitative data including anthropometrical measurements obtained from this system provide objective and reliable results in skull identification.

Three-Dimensional Facial Anthropometry Using a Laser Surface Scanner: Validation of the Technique

Three-dimensional measurement and characterization of facial surface anatomy are fundamental to the objective analysis of facial deformity. However, existing clinical tools are inadequate. Recent innovations in laser scanning technology provide a potentially useful technique for accurate three-dimensional documentation of the face. The purpose of this study is to evaluate the reliability of interactive anthropometric landmark localization based on digitized three-dimensional facial images and to identify sources of error associated with the technique. Three-dimensional surface data were acquired using a commercially available laser scanning device (Cyberware 3030RGB digitizer), and all subsequent anthropometric analyses were performed interactively on the computer monitor. Four experimental conditions were studied, with 10 observations for each condition. A stable anthropomorphic model with prelabeled anatomic landmarks was scanned repeatedly under varying conditions of head inclination and position within the scanning gantry to determine the effect of these variables on the reliability of the technique. The scanning protocol was then repeated with the labels removed to evaluate the reliability of interactive localization of anthropometric landmarks on a digitized three-dimensional image. Optimal results were obtained with the head positioned in the center of the scanning gantry and with the Frankfort plane elevated 10 degrees from the horizontal. Under these circumstances, all 22 labeled landmarks were visualized and the variance in landmark localization was less than 0.6 mm in the x (horizontal), y (vertical), and z (depth) dimensions. Varying head position or inclination caused significant degradation of the digitized image. The variance of interactive landmark localization was analyzed in three dimensions. The reliability and the spatial orientation of variability were determined for each anthropometric point. These findings have direct implications for the clinical adaptation of this diagnostic tool for quantitative evaluation of facial surface anatomy.

The Lateral Craniographic Method of Facial Reconstruction

Abstract Fifty-four lateral cephalographs with clear soft tissue profiles of American Caucasians (17 males, ages 14 to 36; 37 females, ages 14 to 34) were traced and measured to establish the ranges and means of midline soft tissue depths and facial angles. With these data it is possible to reconstruct “approximate” profiles over X-ray tracings of unidentified skulls. The lateral craniographic method of facial reconstruction requires four steps: (1) a cephalometric analysis is first made to determine the facial proportions and individual skull type; (2) the mean soft tissue thicknesses and angles are then plotted against the basic midline anthropometric points to establish the average dimensions of the nose, lips, and chin; (3) the points are connected and “harmonized” in accordance with the known anthropological data (sex, age, race); and (4) the profile is finally “humanized” by adding tone, a stylized eye, hair patterns, age lines, and any other features that can be determined from an anatomic examination of the skull. The validity of the method is illustrated with three study cases of living orthodontic patients.

Extension of cephalo-photometric analysis

Once specific anthropometric points have been determined more accurately, photometric analysis may now also be made from a cephalogram. The maxillo-zygomatic region, and especially its hypoplastic appearance, may be determined from additional geometrics based on the length of the facial thirds.