Sex and ancestry estimation using computed tomography: a comparison of the reliability of digital versus physical data collection
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Sex and ancestry are most commonly estimated by anthropologists using the skull. Typically, measurements and observations are taken on the skull itself, but for the purpose of convenience, computed tomography (CT) scans are increasingly used in place of skulls in research and forensic casework. Researchers work under the assumption that the dry skull-to-CT scan ratio is one-to-one; however, research on the accuracy of CT scans is sparse. In this study, eight skulls from the Boston University Donated Skeletal Collection were scored for sex and ancestral morphological traits following Buikstra and Ubelaker (1994) and Hefner and Ousley (2014), and measured using standard cranial measurements according to Langley et al. (2016). CT scans were then taken of the eight skulls and the same morphological observations and measurements were taken using the RadiAnt 5.5.1 CT viewer. Additionally, the measurements of each skull and scan were entered into FORDISC 3.1, a software program that provides discriminant functions for the processes of sex and ancestry estimation. The measurements for each dry skull-CT scan pairing were then analyzed for variance and mean differences. The results of the morphological and metric analyses indicate that the majority of the data gathered from dry skulls did not vary significantly from the measurements taken on the CT scans. The morphological sex estimation resulted in the same estimation for each skull-to-CT scan pairing; however, the morphological ancestry estimation results indicated that skeletal information lost in CT scans can make full visualization and therefore assessment of the facial region difficult. The FORDISC 3.1 results generally support the indication that there is not a significant difference between skull and CT scan measurements, with consistent sex estimation results for each dry skull-to-CT scan pairing and consistent ancestry estimation results for the majority of the pairings. However, the sex and ancestry estimations were not always accurate considering the true ancestral backgrounds of the individuals. Based on these outcomes, it is evident that CT scans can be used to obtain reliable morphological assessments and measurements of a skull, which can then be used to estimate sex using FORDISC 3.1. However, to ensure accuracy of the sex and ancestry estimations, other methods should be used in conjunction with FORDISC 3.1.