X-ray based imaging techniques (digital radiography and computed tomography) are widely used in the field of Cultural Heritage and beyond, above all thanks to their non-invasiveness. The high penetrating power of X-rays allows us to investigate the internal structure of the analysed objects, thus obtaining valuable information related to the history of artistic and archaeological finds. In particular, CT provides data that are more significant when objects with a not negligible volume are studied. Even the use of advanced instruments can help having better final data from which getting more information. In this paper, we will show the case study of an Ancient Egyptian wooden statuette representing a “bearer”, for which an upgraded version of the X-ray imagingapparatus located in the Centro Conservazione e Restauro “La Venaria Reale” (CCR) was used for the first time. Thanks to this, much information on the technique of execution was obtained, especially from the tomographic analysis

Borla, M.

Buscaglia, P.

Cavaleri, T.

Del Vesco, P.

Grassini, S.

Lo Giudice, A.

Nervo, M.

Re, A.

Vigorelli, L.

L. Vigorelli

A. Lo Giudice

T. Cavaleri

P. Buscaglia

M. Nervo

P. Del Vesco

M. Borla

S. Grassini

A. Re

PORTO@iris (Publications Open Repository TOrino - Politecnico di Torino)

16 July 2022POLITECNICO DI TORINORepository ISTITUZIONALEUpgrade of the x-ray imaging set-up at CCR “La Venaria Reale”: the case study of an Egyptian wooden statuette /Vigorelli, L.; Lo Giudice, A.; Cavaleri, T.; Buscaglia, P.; Nervo, M.; Del Vesco, P.; Borla, M.; Grassini, S.; Re, A.. -ELETTRONICO. - (2020). ((Intervento presentato al convegno 2020 IMEKO TC-4 International Conference on Metrologyfor Archaeology and Cultural Heritage Trento, Italy, October 22-24, 2020 tenutosi a Online edition nel 22-24 October2020.OriginalUpgrade of the x-ray imaging set-up at CCR “La Venaria Reale”: the case study of an Egyptian woodenstatuettePublisher:PublishedDOI:Terms of use:openAccessPublisher copyright(Article begins on next page)This article is made available under terms and conditions as specified in the  corresponding bibliographic description inthe repositoryAvailability:This version is available at: 11583/2849902 since: 2020-10-25T21:48:45Z2020 IMEKO TC-4 International Conference on Metrology for Archaeology and Cultural Heritage Trento,2020 IMEKO TC-4 International Conference on Metrology for Archaeology and Cultural Heritage Trento, Italy, October 22-24, 2020   Upgrade of the x-ray imaging set-up at CCR “La Venaria Reale”: the case study of an Egyptian wooden statuette L. Vigorelli1,2,3, A. Lo Giudice2,3, T. Cavaleri4, P. Buscaglia4, M. Nervo3,4, P. Del Vesco5, M. Borla6, S. Grassini1, A. Re2,3 1 Dipartimento di Scienza dei Materiali e Ingegneria Chimica, Politecnico di Torino, C.so Duca degli Abruzzi, 24 I-10129 Torino, Italy, luisa.vigorelli@polito.it, sabrina.grassini@polito.it  2 Dipartimento di Fisica, Università degli Studi di Torino, Via Pietro Giuria 1, 10125 Torino, Italy, alessandro.logiudice@unito.it, alessandro.re@unito.it  3INFN, Sezione di Torino, Via Pietro Giuria 1, 10125 Torino, Italy  4 Centro Conservazione e Restauro “La Venaria Reale”, Piazza della Repubblica, 10078 Venaria Reale, Torino, Italy, tiziana.cavaleri@centrorestaurovenaria.it, paola.buscaglia@centrorestaurovenaria.it, marco.nervo@centrorestaurovenaria.it  5 Fondazione Museo delle Antichità Egizie di Torino, Via Accademia delle Scienze 6, 10123 Torino, Italy, paolo.delvesco@museoegizio.it  6 Soprintendenza ABAP-TO, Torino, Piazza San Giovanni 2, 10122 Torino, Italy, matilde.borla@beniculturali.it  Abstract – X-ray based imaging techniques (digital radiography and computed tomography) are widely used in the field of Cultural Heritage and beyond, above all thanks to their non-invasiveness. The high penetrating power of X-rays allows us to investigate the internal structure of the analysed objects, thus obtaining valuable information related to the history of artistic and archaeological finds. In particular, CT provides data that are more significant when objects with a not negligible volume are studied. Even the use of advanced instruments can help having better final data from which getting more information. In this paper, we will show the case study of an Ancient Egyptian wooden statuette representing a “bearer”, for which an upgraded version of the X-ray imaging apparatus located in the Centro Conservazione e Restauro “La Venaria Reale” (CCR) was used for the first time. Thanks to this, much information on the technique of execution was obtained, especially from the tomographic analysis.  I. INTRODUCTION Radiographic (DR) and tomographic (CT) techniques gained increasing importance since the discovery of X-rays by Röntgen in 1895, thanks to their non-invasiveness, in various fields of application. X-ray imaging techniques are widely used in the Cultural Heritage field thanks to the possibility of investigating the inner part of the objects, not otherwise visible, without any type of damage. In fact, digital radiographic and CT analysis have been performed over the years on different types of archaeological and anthropological finds [1,2] in order to evaluate thstate of preservation and to get a more detailed knowledge of ancient objects. In this paper the results of the X-ray DR and CT analysis performed at CCR on an Ancient Egyptian wooden statuette are presented. The figurine belongs to the collection of Museo Egizio in Turin, and the measurements have been conducted before its conservation treatment. The fixed X-ray imaging set-up at CCR was developed in the context of the neu_ART project [3-5] and optimized for CT of large artefacts as, for example, furniture [6], wooden coffins [7] and objects difficult to analyze in normal medical systems, e.g. soil blocks [8]. For this study, a X-ray flat panel detector with a higher spatial resoluti n than the previous one has been used for the first time. It issuitable for small objects, but the better resolutin s a   more advantageous tool in the Cultural Heritage field, because of high quality images and consequently better interpretation of data.  II. MATERIALS AND METHODS The statuette, representing an offering bearer (S.8795, Fig.1), was found during the 1908 excavation season of the Italian Archaeological Mission, directed by Ernesto Schiaparelli, in the necropolis of Asyut (Egypt), a site situated some 375 km south of Cairo. The statuette was part of the conspicuous funerary assemblage of the so-called “tomb of Minhotep”, which included more statuettes of offering bearers, larger wooden statues, a model bakery, boat models, as well as coffins, wooden sticks, a bow with arrows and numerous terracotta jars and bowls [9]. Most of the equipment derived from specialized workshops operating in Asyut during the early Middle Kingdom (ca. 1980-1900 BCE).                           Fig.1. The analysed “Bearer” statuette (S. 08795), frontal and lateral views after the conservation treatment.   The analysis was conducted at the CCR, in a shielded room created to house the necessary equipment for X-ray imaging investigations. The instrumentation mainly consists of a General Electric Eresco 42MF4 X-ray source, a rotating platform on which the object is placed, allowing the acquisition of multi-angle images, and a Hamamatsu C9750-20TCN linear X-ray detector of 200×200 μm2 pixel dimension that scans at about 0.2÷6 m/min over an area of about 2×2 m2. Details on the experimental set up and on performance in term of spatial resolution, scan speed and image quality are given in [5]. For this work, a flt panel (FP) Shad-o-Box 6K HS by Teledyne Dalsa that upgrade the previous apparatus was employed for the first time and placed, at requirement, in correspondence with the linear one generally used in CCR’s equipment. Having an area of only about 160 cm2 FP is more suitable for small object or for part of large objects where a higher resolution s needed. To cover large areas it is possible to exploit the precision scanning system already present to acquire images in different positions (tile scanning). The main characteristics of the two detectors are summarized n Table 1.   Table 1.  Comparison of some specifications between th  flat panel (FP) and the detector for large objects already present at CCR (Linear)                  FP                Linear Pixel number 2304 × 2940 2560 × 1 Active area (cm × cm) 11.4 × 14.6  51.2 × 0.02  Pixel dimension (µm) 49.5  200 Energy range (source kV) 15-225 25-200 Scintillator CsI CsI Image dimension (Mb/m2) ~800       ~50        Radiographic analysis were performed on the whole statuette in order to evaluate the optimal parameters and the most interesting areas for tomographic measurements. In both DR and CT phases, the object has been positioned as close as possible to the detector in order to minimize the penumbra effect. The radiographs were acquired both frontally and laterally to have a more accurate view of all the components of the figurine. Due to the larger size of the entire object compared to the active volume of the FP detector, several images were collected (8 in frontal view and 10 in lateral view), then assembled during the processing phase by means of the ImageAssembler software by PanaVue. On the basis of radiography results, it was decided to perform CT analysis only for the upper part of the figurine.  The tomographic analysis was performed by setting the integration time and the angular step on all the 360° in order to optimize the quality of the final reconstruction. The acquisitions were divided into 3 scan phases, one f r each portion: the basket, the head and the body. The main experimental details of this measurement are summarized in Table 2. The reconstruction of the CT sections wa made using a filtered back-projection algorithm by means of a non-commercial software-utility developed by Dan Schneberk of the Lawrence Livermore National    Laboratory (USA), while the 3D rendering and segmentation are still under processing using VGStudio   MAX 2.2 from Volume Graphics.  Table 2. CT experimental details  Statuette dimension 60     ×12.5     ×25.5 cm3 Source-Detector distance (SDD) 3.75 m Source-Object distance (SOD) 3.51 m Magnification 1.07 Tube voltage 80 kV Tube current 10 mA Integration time 1.75 s Scan phases (portions) 3 Projection/portion 1440 Angular step 0.25°   III.  RESULTS AND DISCUSSION The high resolution analysis carried out by means of the FP, especially the tomographic ones, allow to obtain important information on the technique of execution and previous interventions carried out on this statuette, probably not obtainable with the previous setup. As mentioned before, the data of the CT scans were acquired starting from the basket up to the hips. At first glance, it is possible to notice areas of the radiographic images with different radiopacity over the entire volume of the body (Fig.2). This reflects (i) the distribution of the preparatory layer, which is more radiopaque than the wooden support underneath, and (ii) the presence of some deep gaps in this layer. Thanks to the CT slices it is possible to observe the presence of a double layer of preparation (confirmed by the conservation interventions) in some points with different thicknesses.  In general, it is possible to affirm that the preparation material has contributed to partially correct the modelling technique (e.g. breasts and hips), and the volumes due to defects of the building blocks, while where the carving was enough refined to obtain the correct shape, a single preparation layer has been laid (Fig. 3d).  As regards the assembly between the basket and the head, the junction has been realized by means of wooden dowels insertions as the radiographic, but even better the tomographic images, have shown. From the tomographic sections of the head (Fig.3a), multiple portions assembled by wooden dowels is observed, in order to achieve the final volume. Furthermore, the same double preparation layer as in the breast is evident from the head slice (probably to correct wood defects and damage during the carving, see Fig.3a). Also in correspondence with the body, at the                                Fig.2. The DR of the statuette, frontal and lateral views (blue arrows: wooden joints; green arrows: wooden portion joined to the body; pink arrow: thicker preparation layer; red arrows: height of the CT slices reported in Fig.3 with the correspondence letters)  height of the right breast, the same type of assembly technique can be seen: the observation of the internal growth rings trend allows recognizing this insertion as a remediation for a material detachment probably in the notching phase (Fig.3c). The same anchoring system is evident in correspondence of the missing arms, as shown in Fig.3b. For the lower part of the statuette, the radiographic analysis is useful to study some peculiarities of the object. In particular, there is evidence of a fracture of the wooden matter in the right leg of the bearer and, at the calf level, a tongue and rebate joint for the completion of the leg anatomy is visible (Fig.2), superficially retouched in occasion of a previous intervention. In occasion of the cleaning treatment, that pursued the recovery of the original materials without any mimetic pictorial integration, it has been possible to observe a slight difference in colour and porosity of the wood in this portion compared to that of the original parts. This could suggest its belonging to a previous intervention, even if more insights should be provided to ascertain this.      a b c d                       Fig.3. CT slice of the statuette: (a) head; (b), (c),(d) body. (orange arrows: wooden  dowels for assemblage; blue arrows: wooden joints; pink arrows: thicker preparation layer)  In the base of the statuette, the DR images allow to distinguish a portion of material that reaches about half the total thickness of the base that correspond to a different wooden insertion in the housing area of the sculpture due to previous interventions. Furthermore, the X-ray analyses are also able to define how the wooden inserts were applied and fix: in fact, two holes made to accommodate the end portions of the two legs can be identified. The legs were inserted and then fixed by means of application of filler material, that have more pronounced radiopacity respect to the wooden material (Fig.4).            Fig.4. Particular of radiographic image of the statuette base  IV.CONCLUSION The smaller pixel dimension and the higher integration time of the flat panel, compared to the setup developed in neu_ART projects, permitted to obtain new information on small wooden artefacts. The studies performed on the Egyptian “Bearer” statuette provided valuable information about the techniques of assembly, technique of execution and previous interventions. Most of the evidences came out from CT measurement, that allow to obtain more useful information about the inner structures of wooden finds.      ACKNOWLEDGMENTS The NEXTO project (progetto di Ateneo 2017) funded by Compagnia di San Paolo, and the neu_ART project funded by Regione Piemonte are warmly acknowledged.      REFERENCES [1] M.P. Morigi et al.  “Application of X-ray Computed Tomography to Cultural Heritage diagnostics”, Applied Physics A, 100, 2010, pp. 653-661. [2] A. Otte et al., “Computed tomography alone reveals the secrets of ancient mummies in medical archaeology”, Hellenic Journal of Nuclear Medicine, 16(2), 2013, pp. 148-149. [3] A. Re et al., “Results of the Italian neu_ART project”, IOP Conference Series: Materials Science and Engineering 37, 2012, 012007. [4] M. Nervo, “Il Progetto neu_ART. Studi e applicazioni/Neutron and X-ray Tomography and Imaging for Cultural Heritage”, Cronache, 4, Editris, Torino, 2013 [5] A. Lo Giudice et al., "A new digital radiography system for paintings on canvas and on wooden panels of large dimensions" 2017, IEEE International Instrumentation and Measurement Technology Conference (I2MTC 2017), Proceedings, IEEE (NJ, USA) [6] A. Re et al., “X-ray tomography of large wooden artworks: the case study of “Doppio corpo” by Pietro Piffetti”, Heritage Science, 2(19), 2014, pp. 1-9. [7] A.Re et al., “The importance of tomography studying wooden artefacts: a comparison with radiography in the case of a coffin lid from ancient Egypt”, Internation Journal of Conservation Science, Volume 7, Special Issue 2, 2016: 935-944 [8] A. Re et al., “X-ray tomography of a soil block: a useful tool for the restoration of archaeological finds”, Heritage Science, 3(4), 2015, pp. 1-7. [9] J. Kahl et al., “Asyut. The excavations of the Italian Archaeological Mission (1906-1913)”, Modena, 2019  a c b d 

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Upgrade of the x-ray imaging set-up at CCR “La Venaria Reale”: the case study of an Egyptian wooden statuette

Institutional Research Information System University of Turin

Upgrade of the x-ray imaging set-up at CCR "La Venaria Reale": The case study of an Egyptian wooden statuette

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Upgrade of the x-ray imaging set-up at CCR &quot;La Venaria Reale&quot;: The case study of an Egyptian wooden statuette

Upgrade of the x-ray imaging set-up at CCR "La Venaria Reale": The case study of an Egyptian wooden statuette

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Upgrade of the x-ray imaging set-up at CCR &quot;La Venaria Reale&quot;: The case study of an Egyptian wooden statuette

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Upgrade of the x-ray imaging set-up at CCR "La Venaria Reale": The case study of an Egyptian wooden statuette