Micro-CT calibraƟon using dental Ɵssue for bone mineral research

Ian Towle* (Corresponding Author), Carolina Loch, Marc Oxenham, Kristin L. Krueger, Amira Samir Salem, Marina Martinez de Pinillos, Mario Modesto-Mata, Leslea J. Hlusko

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Objectives: Computed Tomography (CT) and Micro-Computed Tomography (μCT) require calibration against density phantoms scanned with specimens or during routine internal calibration for assessment of mineral concentration and density. In clinical bone studies, alternative calibration methods using bodily tissues and fluids (termed ‘phantomless’ calibration) have been suggested. However, such materials are seldom available in archaeological and osteological research.
Materials and Methods: This study investigates the potential of dental tissue as internal reference for calibrating μCT scans, facilitating the analysis of bone mineral concentration (MC). We analyzed 70 molars from 24 extant primate species, including eight human teeth, each scanned with density phantoms for calibration.
Results: Our findings indicate that sampling specific regions of molars (lateral aspects of the mesial cusps) yields low variation in enamel and dentine values, averaging 1.27 g/cm³ (± 0.03) for dentine and 2.25 g/cm³ (± 0.03) for enamel. No significant variances were observed across molar types or commonly used scanning procedures, including scanner model, resolution, and filters. An ad hoc test on 12 mandibles revealed low variance in MC; all 36 measurements (low, medium, and high MC for each mandible) were within 0.05 g/cm³ of those obtained via the conventional phantoms—81% were within 0.03 g/cm³, and 94% within 0.04 g/cm³.
Discussion: Based on these results, we propose a new ‘phantomless’ calibration technique using these mean enamel and dentine MC values. The presented phantomless calibration method could aid in the assessment of bone pathologies and enhance the scope of studies investigating bone structure and physical property variations in archaeological, osteological, and laboratory-based research.
Original languageEnglish
JournalAmerican Journal of Biological Anthropology
Publication statusAccepted/In press - 29 Apr 2024

Bibliographical note

Acknowledgements
Collection of the µCT scans was supported by a Sir Thomas Kay Sidey Postdoctoral fellowship from the Faculty of Dentistry, University of Otago, to Ian Towle. This research was additionally facilitated by the European Research Council within the European Union's Horizon Europe (ERC-2021-ADG, Tied2Teeth, project number 101054659). The authors thank the Study Material Committee from the Primate Research Institute (PRI), Kyoto University, for access to their collections, and T. Ito for assistance during data collection. The research was performed under the Cooperative Research Program of the PRI (2019-C-20). We also thank the museums in New Zealand that provided samples for this study and the curators for their assistance and support, including Otago Museum (E. Burns), Museum of Natural Mystery (B. Mahalski), and Auckland Museum (M. Rayner and R. Moore). Lastly, we thank A. Hara for helpful discussions during the inception of this study. The authors have no conflict of interests to declare.

Keywords

  • Micro-CT Calibration
  • μCT
  • Phantomless Calibration
  • Bone mineral Concentration

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