Concordance of traditional osteometric and volume-rendered MSCT interlandmark cranial measurements

The statistical quantification of error and uncertainty is inherently intertwined with ascertaining the admissibility of forensic evidence in a court of law. In the forensic anthropological discipline, the robustness of any given standard should not only be evaluated according to its stated error but by the accuracy and precision of the raw data (measurements) from which they are derived. In the absence of Australian contemporary documented skeletal collections, medical scans (e.g. multislice computed tomography-MSCT) offer a source of contemporary population-specific data for the formulation of skeletal standards. As the acquisition of morphometric data from clinical MSCT scans is still relatively novel, the purpose of this study is to assess validity of the raw data that is being used to formulate Australian forensic standards. Six human crania were subjected to clinical MSCT at a slice thickness of 0.9 mm. Each cranium and its corresponding volume-rendered three-dimensional MSCT image were measured multiple times. Whether differences between MSCT and dry bone interlandmark measurements are negligible is statistically quantified; intra- and inter-observer measurement error is also assessed. We found that traditional bone measurements are more precise than their MSCT counterparts, although overall differences between the two data acquisition methods are negligible compared to sample variance. Cranial variation accounted on average for more than 20x the variance explained by MSCT vs. bone measurements. Similarly, although differences between operators were sometimes significant compared to intra-operator variance, they were negligible when compared to sample variance, which was on average 12x larger than that due to inter-operator differences.