Optimizing CT Scan Parameters for Dry Archaeological Bones: A Qualitative Study as a First Step Towards Standardizing CT Acquisition Protocols

Abstract

Even though the use of CT scan examinations is often required in paleopathology, the method for performing a CT scan on archaeological dry bones has received little attention. Eight different CT acquisition parameters and positions on the CT table were evaluated using five healthy tibiae (including three immature bones), four healthy vertebrae (including three immature bones), and four pathological mature bones, all in a good state of preservation. The images obtained were blindly evaluated in a psychophysical and subjective manner by four evaluators with varying levels of experience in radiology. The evaluators preferred a tube voltage of 100 kV or less, or expressed no preference, in 90.4% of cases (p < 0.001). For tube current, no preference was noted in 57.7% of cases (p < 0.001), but when a preference was given, a value between 100 and 200 mAs was chosen in 95.5% of cases. The thinnest slices and centered positioning within the gantry, both vertically and laterally, were favored in 100% of cases (p < 0.001). There was no preference for the size of the field of view in 42.3% of cases. The positioning of the bone in the headrest was preferred in 71.2% of cases (p < 0.001), particularly for immature bones. Preferences regarding the elevation of the bone using a cardboard box were not significant (p = 0.07). We therefore recommend using a tube voltage of 80 kV, a tube current between 100 and 200 mAs, the thinnest possible slice thickness, and a field of view minimized according to the CT scanner's capabilities. Bones should be positioned in the headrest, perfectly centered both vertically and laterally within the gantry. However, these conclusions are based on a limited number of bones and types of bones, all in a good state of preservation, highlighting the need for further research.