Application of a robotic THz imaging system for sub-surface analysis of ancient human remains

Abstract

We used a robotic-based THz imaging system to investigate the sub-surface structure of an artificially mummified ancient Egyptian human left hand. The results obtained are compared to the results of a conventional CT and a micro-CT scan. Using such a robotic THz system promises new insights into the sub-surface structure of human remains. The depth resolution of the THz images exceeds the resolution of a conventional CT scan and is comparable with a micro-CT scan. The advantage of THz measurements over micro-CT scans is the fact that even comparatively large samples, like complete bodies, can be scanned. These would not fit into a conventional micro-CT scanner.

Figure 1

Investigated ancient Egyptian artificially mummified hand (Photographs with kind permission of the Institute of Evolutionary Medicine, University of Zurich, photographer Corina Steiner (CC BY open access license)).

Figure 2

3D-Scan of the investigated mummy hand. The measurement area is highlighted in red.

Figure 3

(a) Line scan at x = 6 mm. (b) Exemplary THz time trace at x = 6 mm and y = 10 mm, indicated by the blue line in (a). (c) Impulse response function of the deconvolved THz pulse shown in (b).

Figure 4

Dielectric properties of typical tissue structures in the investigated artificially mummified ancient tissue as well as in tissue from a modern mummification experiment. We have measured 5 (skin with muscle) respectively 10 (muscle) different positions on each sample and averaged them. The error arising in the spectroscopic measurements is mainly due to inhomogeneities in the samples.

Figure 5

Comparison between reconstructed layers based on the THz measurement and a conventional CT scan. (a) The white dotted line in the 3D scan indicates the cross section at x = 5 mm, (b) THz measurement area in the CT scan. (c) Enlargement of the THz measurement area indicated by the white dotted rectangle in (b).

Figure 6

Comparison between reconstructed layers based on the THz measurement and a Micro- CT scan. (a) The white dotted lines in the 3D scan indicates the cross sections at y = 13 mm and y = −30 mm, (b) and (c) THz measurement region indicated in the CT scan. (d) Enlargement of the cross section at y = −30 mm indicated by the white dotted rectangle in (b), (e) Enlargement of the cross section at y = −13 mm indicated by the white dotted rectangle in (c).

Figure 7

(a) Overview of the robotic based THz system, (b) Photo of the THz sensor head including a sketch of the THz beam path.