Accuracy of standard craniometric measurements using multiple data formats

With continuing advancements in biomedical imaging technologies, anthropologists are increasingly making use of data derived from indirect measurement and analysis of skeletal material. To that end, the purpose of this study was to test the reliability of 26 standard craniometric measurements routinely utilized in forensic casework across several different imaging technologies. Measurements from five crania of known individuals were collected in duplicate by two anthropologists via computed tomography (CT) scans and three-dimensional (3D) laser scans of the known skulls. The laser scans were also used to create prototype models of the known skulls. These prototypes were, themselves, laser-scanned, and measurements were also collected from the prototypes and the laser scans of the prototypes. Measurement sets from each technology were then compared with one another using the previously collected osteometric measurements taken on the crania themselves as the ground truth.

Result: indicate that, while the majority of measurements showed no significant differences across data formats, a handful were found to be problematic for particular technologies. For instance, measurements taken in a supero-inferior direction (e.g., BBH, OBH) from CT scans were prone to greater deviation from direct measurements of the cranium than other technologies, especially for CT scans taken at 5 mm thickness and increment. Also, several measurements defined by Type 1 landmarks, particularly those occurring at complicated or indistinct suture junctures (e.g., ASB, ZMB), were found to have high variance across all technologies while measurements based on Type 3 landmarks proved to be highly reproducible. This is contrary to measurements taken directly on crania, in which measures defined by Type 1 landmarks are typically the most reliable, likely attributable to diminished or totally obscured suture definition in the scan data. If medical imaging data are to be increasingly utilized in anthropological studies, it may be prudent to bear in mind that the reliability of measurements taken on an actual skull may not be the same as for measurements taken from medical scans.