Validity of Landmark Selection Given Different 3D Scan Processing Parameters: Landmark Location on 3D Models of Yacchi Crania (original) (raw)
Related papers
International Journal of Osteoarchaeology, 2011
A total of 11 340 Cartesian coordinates of 42 homologous landmarks on five excavated human crania were recorded by three observers using a three-dimensional (3D) digitiser and computer models created with a 3D laser scanner. The aim was to compare the errors of the coordinate data of landmarks of different types recorded with these two techniques. The results showed that digitiser-based and 3D model-based coordinate measurements had overall standard deviations of, respectively, ±0.79 and ±1.05 mm. However, the 3D digitiser yielded the most precise coordinate data for landmarks defined primarily by biological criteria (Type I landmarks), while the 3D laser scanner models yielded the most precise coordinate data for landmarks defined primarily by geometric criteria (Type III landmarks). These findings are likely to influence the research design of future craniometric studies, as they indicate that the suitability of certain landmark types as reference points for geometric operations, such as partial Procrustes analysis, depends on the method by which they are measured. This information is particularly important for retrospective research or for combined databases such as FORDISC or CRANID, which may integrate different types of landmarks recorded by different researchers and/or instruments. Crania displaying poor preservation and surface discoloration yielded larger measurement errors, especially for the 3D model measurements. This is not surprising given that landmarks on 3D models cannot be located using tactile means, but have to be located solely on a visual basis. Nonetheless, even though the digitiser measurements exhibit an overall precision slightly greater than the 3D model measurements, both techniques yield coordinate data with a precision sufficient for most craniometric research.
Variation within physical and digital craniometrics
Forensic Science International, 2020
Metric assessment of human crania can provide forensic practitioners and anthropological researchers with information on an individual’s sex and biogeographical ancestry. However, metric methods rely on the ability of users to remain consistent with themselves and others, with any error in the data rendering conclusions invalid. Digital anthropology is a growing sub-field where human remains are digitised using a growing range of methods and technologies. These models have the potential to boost research collaboration and public engagement. However, not all of these digitisation methods have been examined critically to explore the veracity of their use within a research environment. There has also been limited research into the application of digital anthropology to craniometric analysis. This study examined the intra- and inter- observer variation of seven participants taking physical measurements from a human cranial cast with an associated set of reference values. The same measurements were also taken from three digital models of the cranial cast which were created using digital photogrammetry and laser scanning. This data was then compared to the reference values and the physical measurements taken by the lead author. This study found that there was excellent statistical agreement between the reference values and the measurements taken from the cranial cast, both physical and digital. However, the participants still exhibited variation within a range of −18 mm and +30 mm from the reference values. MANOVA tests showed between-subject effects on nine measurements across the participant data, and 12 measurements between the digital models. However, there is little consistency between this study and the anthropological literature as to which measurements are most prone to between-subject effects. Despite the excellent agreement shown between the reference values and the digital models this study raises a number of methodological questions regarding inter-observer error and the varying levels of data processing present in different digitisation methods.
Consistency of selected craniometric landmark locations and the resulting variation in measurements
Forensic Science International, 2017
Recently, forensic anthropology has undergone a major shift to quantitative methodologies, including the standardization of osteometric measurements. This study is an analysis of inter-observer error rates for eight “standardized” cranial measurements. Thirty participants, of varied experience, were asked to note the location of landmarks used in each measurement, and to record the resulting measurement. None of the tested measurements met the previously established 80% consensus rate necessary to be considered “standardized-in-practice” [1]. The highest consensus rate was that of nasal breadth (67.9%), followed by that of the mastoid height (57.1%). This low precision yielded percent mean differences of 2-48% of the total measurement, with range differences of up to 42 mm. These results indicate that the field should take steps to improve osteometric standardization, including re-examining all measurements currently listed in osteometric canon and re-issuing a comprehensive guide.
Evaluating the morphological and metric sex of human crania using 3-dimensional (3D) technology
International Journal of Legal Medicine, 2020
Identifying the skeletal remains of an unidentified individual is a priority for the medico-legal system because identification increases the chances of finding the person responsible and provides closure to the family. The purpose of this research was to develop a combined morphological and metric cranial sex assessment method using 3D technology that accommodates the medico-legal system, and their use of 3D models facilitates the technological transition to digitally archived skeletal collections. A total of 91 individuals of European biogeographical ancestry from the William M. Bass Donated Skeletal Collection (University of Tennessee Knoxville) were imaged using photogrammetry, turned into 3D models using Agisoft PhotoScan, and digitally evaluated using 3D Studio Max. This novel method digitally evaluated five cranial traits, including the nasal aperture height, nasal aperture width, mastoid length, the general size and architecture, and the supraorbital ridges, combining techniques that can only be done digitally with those that can be completed on the actual bone. Preliminary statistical tests demonstrate an overall accuracy rate of 90% when tested against the training sample (20 males, 20 females) and 75% when tested against the test sample (51 individuals). Although no intra-or inter-observer error rate tests were done, and further testing on other skeletal collections is necessary, this method allows forensic anthropologists to perform relatively easy point-to-point measurements, the quantification of traditionally non-quantified traits, the possibility of reproducible results, and the ability for future analyses or research.
In Biological Anthropology, as with many sciences, the potential for corruption of data due to interobserver differences is ever present. This article presents results of an experiment in which 11 observers analysed a single cranium using CranID. These user data were then compared using Degrees of Variation to proportionally represent the degree of disparity in results on the assumption that no single set could purport to be more accurate than any other without further study. MANOVA analysis was also applied to see if any of the cranial measurements were more consistent than others. Finally the data were subjected to CranID analysis and the results for each of the 11 observers compared to see what effect interobserver variation would have on identifying ancestry.
Morphometric analysis of Cartesian coordinates of the human skull
American Journal of Physical Anthropology, 1975
A method for locating the three dimensional coordinates of cranial landmarks with respect to the Frankfort, midsagittal, and coronal planes is presented. Sliding calipers were used to obtain the distances from left and right porion and apex to each landmark, except for a few points where spreading calipers are required. In the present example, 35 landmarks (for a total of 105 measurements) were located for each of 35 Peruvian precolumbian skulls. These distances were entered into a program (SKULL) which calculates the Cartesian coordinates of each landmark. The XYZ coordinates of each landmark contain all the information necessary for calculation of the distances between any two landmarks, and these distances may also be obtained as output from program SKULL, if desired (595 distances if all 35 landmarks are used). Reliability of the location of coordinates was determined by comparing computed distances among selected landmarks from program SKULL with traditional anthropometric measurements. Satisfactory agreements were found. Direct multivariate analysis of the coordinates of the landmarks produced insights not available in traditional multivariate analysis of conventional anthropometric measuremen ts.
Three-dimensional measurement accuracy of skull surface landmarks
American Journal of Physical Anthropology, 1988
Craniometric measuremnts from a three-dimensional (3-D) digitizing system were compared with those from sliding and spreading calipers. The 3-D system consisted of a 3-Space Digitizer, Macintosh Plus computer, and Unigraphics CAD/CAhl system. Twenty-nine standard measurements were made and repeated on two normal and three deformed skulls. The percentage of difference was calculated for original versus repeat measures and caliper versus 3-D measures.
Objective three-dimensional analysis of cranial morphology
Eplasty, 2008
The lack of adequate means to objectively characterize cranial shape contributes to ongoing controversies in the surgical management of craniosynostosis. Cranial shape analysis must address relevant clinical questions objectively and thoroughly and must be broadly applicable across the spectrum of normal and abnormal. Herein, we demonstrate and statistically validate an automated computed tomography (CT)-based application for 3-dimensional characterization of skull morphology. The technology is intended for application to diagnostic imaging, surgical planning, and outcomes assessment. Three-dimensional vector analysis (3DVA) was applied to craniofacial CT data, generating three-dimensional cranial surface point clouds. To assess accuracy, measurements derived from the 3DVA analysis of a CT scan of a skull phantom were compared to those made directly from the Digital Imaging and Communications in Medicine data on a Vitrea workstation. To assess reproducibility, 3 readers independentl...