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Investigation of Small Egyptian Mummies by 3D Computed Tomography M. Rossi, F. Casali, D. Romani Physics Department, University of Bologna and I.N.F.N. Viale Berti Pichat 6/2, 40127 Bologna, Italy D. Picchi Archaeological Museum of Bologna Via dei Musei 8, 40126 Bologna, Italy Contact

ABSTRACT

In the last years, a collaboration between the Physics Department of the University of Bologna and the Archaeological Museum of Bologna has been set up in order to examine archaeological artifacts using advanced NonDestructive Techniques (NDT). In the framework of this collaboration, bronze objects of the Etruscan section have been investigated in the past by means of Digital Radiography (DR) and 3D Computed Tomography (CT) techniques. Important results have been obtained concerning the inner structure and the assembly of the samples as well as the manufacturing techniques.
In this work, Egyptian artifacts have been considered to be investigated. The Egyptian collection of the Archaeological Museum of Bologna, with its 3500 objects, is one of the richest in Europe and in Italy.
Small mummies have been analyzed by means of an experimental 3D CT system arranged for this purpose at the Physics Department.
CT data allow a very fine discrimination among materials with different densities, providing an enormous amount of information not only about mummies, but also about coffins and ornaments eventually included. Moreover, multiple axial images and full 3D visualization of the samples allow to extract numerical measurements of size and position of all the items identified.

Small Egyptian Mummies of the Archaeological Museum of Bologna

The examination of archaeological artifacts using advanced NDT can provide important information for the artistic and historical analysis allowing to determine materials, structures and technologies. Among advanced methods, 3D CT can be successfully used for the investigation of ancient artifacts because preserves their integrity and provides images of the inner part, otherwise not visible.
In this work, Egyptian artifacts have been considered to be investigated. The Egyptian collection of the Archaeological Museum of Bologna, with its 3500 objects, is one of the richest in Europe and in Italy.
In Bologna the initial interest in ancient Egypt derives from the 16th and 17th centuries, when a hundred of items are known to have been part of the University Museum. However, it is only in the 19th century that the interest for Egypt becomes more concrete; in such a cultural milieu the local artist Pelagio Palagi (1775-1860) puts together his Egyptian collection of 3109 objects. As the Archaeological Museum of Bologna was inaugurated in 1881 on the premises of the ancient "Hospital of Death", the finds of the University Museum and, in the following years until 1994, other minor collections were added to this one.
Among the Palagi Collection's artifacts of particular interest for investigation by 3D CT, two items have been selected: a cat-shaped coffin with its mummy inside [1], made up of wood with the right eye of glass or crystal rock and the mummified cat wrapped up in linen bandage (Fig.1); an interesting mummy-shaped statue of god Osiris [2], with a mask made up of cartonnage enriched by golden leaf, the surviving part of a wooden crown at the top of the head, linen bandage around the body, sand and barely or minerals inside it according to the "Rites of Khoiak" [3 ] (Fig.2).

Fig 1: Photograph of the cat-shaped coffin (size: 37.7x10x19.5 cm).

Fig 2: Photograph of the mummy-shaped statue of god Osiris (size: 33x9.8x9.5 cm).

Both the objects are so elaborate as structure, execution and material composition that DR and CT can help to complete their knowledge.
CT data allow a very fine discrimination among materials with different densities, providing an enormous amount of information not only about the animal or clay body beneath the linen bandage, but also about coffin and ornaments eventually included. Moreover, multiple axial images and full 3D visualization of the samples allow to extract numerical measurements of size and position of all the items identified.

CT SET-UP

The Physics Department of the University of Bologna holds at present several experimental CT systems able to inspect from very small samples up to large objects. Special devices can be used for the inspection of important artifacts or a simple set-up can be arranged quickly to investigate ordinary samples [4][5][6].
In this work, an advanced X-ray detector based on a Electron Bombarded Charge Coupled Device (EBCCD) camera has been set up in order to arrange a 2D detector able to collect instantaneously digital radiographs of the object investigated. In this way, a large number of CT projections can be acquired in short time increasing the quality of the reconstructed images. Moreover, this camera can be optically coupled to different lens in order to set a proper size of the detector matching the size of the object (Fig.3).

Fig 3: Sketch of the CT set-up

A microfocus 200 kVp X-ray tube provides a cone-beam source which, irradiating the object, projects its attenuation profile to a 40x30 cm² Gd₂O₂S scintillating screen.
The light image produced by the screen is grabbed by the intensified EBCCD camera (1024x512 pixels - 12bits) and stored on a personal computer.
A programming turntable rotates the sample with a fixed angular step and a set of digital radiographs of the object is collected at fixed viewpoints.
Radiographic data are then processed using specific mathematical algorithms and cross-section images of the object are reconstructed. In this work, data-sets of 360 up to 600 radiographic views have been collected and reconstructed to more than 500 tomographic slices.

RESULTS

Fig 4: Digital radiographs of the cat-shaped coffin with its mummy inside grabbed respectively at 0° (left) and 90° (right) viewpoints. Marks A, B, and C fix locations of interest for CT analysis.

THE CAT-SHAPED COFFIN AND ITS MUMMY
The first NDT analysis has been carried out on the cat-shaped coffin in order to determine the position and the characteristics of the mummy included inside. The radiographic inspection has been accomplished in real time during the X-ray irradiation of the object allowing to perform quickly a preliminary examination of the sample (Fig.4).
The digital radiographs clearly show the cat mummy put inside the carved body of the cat-shaped coffin. The structure of the skeleton is accurately identifiable and reveal the typical position of the limbs of a mummified cat. The images confirm that the coffin consists of two adjoining halves.
Fig.5 reports cross-section CT images extracted at different locations marked in Fig.4. The tomographic slices of the head, neck and body of the wooden cat underline the different thickness of each half and allow to explain the structure of the coffin (Fig.5A, B and C), whereas the image of the body (Fig.5C) shows the position of the mummy inside the carved body and that one of the linen bandage with regard to the coffin and the skeleton.
It must be pointed out that cross-section CT images can be extracted for every part of the object permitting to accomplish a detailed analysis of the mummy.

Fig 5: Tomographic slices of the cat-shaped coffin extracted at locations marked in Fig.4. (A) cross-section of the head, (B) of the neck, and (C) of the body.

Fig 6: Digital radiographs of the mummy-shaped statue of god Osiris grabbed respectively at 0° (left) and 90° (right) viewpoints. Marks A, B, C, and D fix locations of interest for CT analysis.

THE MUMMY-SHAPED STATUE OF GOD OSIRIS
The digital radiographs of the Osiris statuette reveal a very significant discrimination among the several elements which compose the mummy-shaped god.
In the lateral view (Fig.6 left) it is possible to distinguish: the clear profile of the mask made up of cartonnage; the transparency of the linen bandage, in particular from the neck to the top of the head, where wooden parts of a lost crown survive; the compactness of the body. In the frontal view (Fig.6 right) the body appears to consist of two adjoining halves with a regular lack from the neck to the feet. Moreover, radiographs show the presence of a nail inserted in the lower part of the artifact, added later to fix the statuette and the modern base.

Fig 7: Tomographic slices of the Osiris statuette extracted at locations marked in Fig.6. (A) cross-section of the cap, (B) of the face, (C) of the neck, and (D) of the fallus region.

The tomographic slices (Fig.7) allow to identify and measure the shape of the different components such as the wooden structure of the cap (Fig.7A), the face with the mask (Fig.7B and C), and the granular structure of the halves made up of sand and barely or minerals (Fig.7D). Moreover, Fig.7D permits to state that the god fallus is connected only to the left part of the body, probably through a wire. Fig.7B, C and Fig.8 clearly reveal the thickness and shape of the mask.

Fig 8: 3D tomographic reconstruction of the surface of the Osiris statuette displayed at different viewpoints.

CONCLUSIONS

3D CT technique has been applied successfully for the inspection of Egyptian artifacts of the Archaeological Museum of Bologna. Cross-section and 3D reconstruction images of the objects investigated have allowed to carry out a detailed archaeological analysis and to extract quantitative information of the internal structure of the samples. A study of special data-processing techniques is in progress to allow an easy and quick analysis of specific items inside the volume investigated.

ACKNOWLEDGMENTS

The authors would like to thank Dr. Cristiana Morigi Govi, director of the Archaeological Museum of Bologna and the staff of the Museum. Thanks also to Dr. Serguei Golovkin and Dr. Vladimir Govorun for supporting the EBCCD set-up.

REFERENCES

1. G.Kminek-Szedlo, Catalogo di antichità egizie. Torino, 1895, n. 2040.
2. G.Kminek-Szedlo, Catalogo di antichità egizie. Torino, 1895, n. 242.
3. Dend. X/1, 3-176; X/2, pl. 3-86; S.Cauville, Dendera. Les chapelles osiriennes, III (IFAO), Le Caire, 1997: I, pp. 14-28; II, pp. 1-81.
4. F.Casali, M.Rossi, E.Querzola, M.Giacometti, P.Chirco, M.Zanarini, "Three Dimensional X-Ray Computed Tomography Applied to Cultural Heritages", "5th International Conference on Non-Destructive Testing, Microanalytical Methods and Environmental Evaluation for Study and Conservation of Works and Art", 24-28/9/1996, Budapest (Hungary).
5. M.Rossi et al., "High resolution 3D Computed Tomography of small archaeological sculptures", 7th European Conference on Non-Destructive Testing, 26-29/5/1998, Copenhagen (Denmark).
6. M.Rossi et.al. , "X-ray 3D Computed Tomography of Bronze Archaeological Samples", IEEE Transaction on Nuclear Science, Vol.46, No.4 August 1999, pp.897-903, The Institute of Electrical Engineers Inc., Piscataway, NJ (USA).

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