X-Ray Computed Tomography In Situ: An Opportunity for Museums and Restoration Laboratories

X-ray Computed Tomography (X-ray CT) is a sophisticated non-destructive imaging technique to investigate structures and materials of complex objects, and its application can answer many conservation and restoration questions. However, for Cultural Heritage investigations, medical CT scanners are not optimized for many case-studies: These instruments are designed for the human body, are not flexible and are difficult to use in situ. To overcome these limitations and to safely investigate works of art on site\u2014in a restoration laboratory or in a museum\u2014the X-ray Tomography Laboratory of the University of Bologna designed several CT systems. Here we present two of these facilities and the results of important measurement campaigns performed in situ. The first instrument, light and flexible, is designed to investigate medium-size objects with a resolution of a few tens of microns and was used for the CT analysis of several Japanese theater masks belonging to the collection of the \u201cL. Pigorini\u201d Museum (Rome). The second is designed to analyze larger objects, up to 200 cm and was used to investigate the collection of the so-called \u201cStatue Vestite\u201d (devotional dressed statues) of the Diocesan Museum of Massa

SYSTEM FOR AUTOMATIC DETECTION OF CLUSTERED MICROCALCIFICATIONS IN DIGITAL MAMMOGRAMS

In this paper, we investigate the performance of a Computer Aided Diagnosis (CAD) system for the detection of clustered microcalcifications in mammograms. Our detection algorithm consists of the combination of two different methods. The first, based on difference-image techniques and gaussianity statistical tests, finds out the most obvious signals. The second, is able to discover more subtle microcalcifications by exploiting a multiresolution analysis by means of the wavelet transform. We can separately tune the two methods, so that each one of them is able to detect signals with similar features. By combining signals coming out from the two parts through a logical OR operation, we can discover microcalcifications with different characteristics. Our algorithm yields a sensitivity of 91.4% with 0.4 false positive cluster per image on the 40 images of the Nijmegen database

Identification and modelling of a GT-A fold in the α-dystroglycan glycosylating enzyme LARGE1

LARGE xylosyl- and glucuronyltransferase 1 (LARGE1)is an enzyme responsible for the final steps of the post-translational modifications of dystroglycan (DG), a membrane receptor that links the cytoskeleton with the extracellular matrix in skeletal muscle and in a variety of other tissues. LARGE1 acts by adding the repeating disaccharide unit [-3Xyl-\u3b11,3GlcA\u3b21-] to the extracellular portion of the DG complex (\u3b1-DG); defects in the LARGE1 gene result in an aberrant glycosylation of \u3b1-DG and consequent impairment of its binding to laminin, eventually affecting the connection between the cell and the extracellular environment. In skeletal muscle, this leads to degeneration of the muscular tissue and muscular dystrophy. So far, a few missense mutations have been identified within the LARGE1 protein and linked to congenital muscular dystrophy and, since no structural information is available on this enzyme, our understanding of the molecular mechanisms underlying these pathologies is still very limited. Here, we generated a 3D model structure of the two catalytic domains of LARGE1, combining different molecular modelling approaches. Furthermore, by using molecular dynamics simulations we analyzed the effect on the structure and stability of the first catalytic domain of the pathological missense mutation S331F that gives rise to a severe form of muscle-eye-brain disease

X-ray tomography of large wooden artworks: The case study of "Doppio corpo" by Pietro Piffetti

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Micromechanical Properties of Injection-Molded Starch–Wood Particle Composites

The micromechanical properties of injection molded starch–wood particle composites were investigated as a function of particle content and humidity conditions. The composite materials were characterized by scanning electron microscopy and X-ray diffraction methods. The microhardness of the composites was shown to increase notably with the concentration of the wood particles. In addition,creep behavior under the indenter and temperature dependence were evaluated in terms of the independent contribution of the starch matrix and the wood microparticles to the hardness value. The influence of drying time on the density and weight uptake of the injection-molded composites was highlighted. The results revealed the role of the mechanism of water evaporation, showing that the dependence of water uptake and temperature was greater for the starch–wood composites than for the pure starch sample. Experiments performed during the drying process at 70°C indicated that the wood in the starch composites did not prevent water loss from the samples.Peer reviewe

Calibration-free 3D ray-tracing beam hardening correction in computed tomography

In this paper we introduce a calibration -free beam -hardening correction technique in computed tomography, which improves the results achieved by a state-of-the-art correction method. Two main practical points are here underlined: (1) the need to perform a beam hardening correction without previous calibration; (2) the need to consider the shape of the object in all its whole three-dimensional extent. The proposed method requires: (a) a first complete reconstruction of the object by means of a cone -beam filtered back projection algorithm; (b) a segmentation of the reconstructed volume; (c) the construction of the attenuation when varying path -length graph; (d) the interpolation of the experimental data on the graph with a convenient mathematical function; (e) the correction of the measured attenuation values; (f) to perform again the complete cone -beam reconstruction. The result is an effective beam -hardening calibration -free correction over a large variety of objects, easy to use and quite fast. The proposed method results particularly useful when both the measurement time and the control of the geometry of the system are limited, like the ones generally faced in Cultural Heritage diagnostics. Computed Tomography reconstructions for test samples and for real cases are provided to highlight the effectiveness and the advantages of the new suggested approach

Geotechnical aspects in the restoration of Insula dei Casti Amanti in Pompeii

This paper deals with the geotechnical aspects of the restoration of the Insula dei Casti Amanti (IX-12), in the ancient town of Pompeii. Such works will include the restoration of some archaeological ruins, the stabilization of artificial slopes realized during archaeological excavations and the replacement of the actual roofing system with a single-span covering. Remedial measures for excavation fronts will be adopted by re-profiling them with variable slope angles, taking advantage from the conditions of partial saturation in the pyroclastic surge. The system of roofing will be replaced by a unique, single-span covering equipped with seismic isolators and supported by steel columns founded on circular embedded foundations. Seismic site response analyses, carried out to predict the seismic behaviour of the new covering, revealed that depending on the frequency content of the seismic excitation, a ‘double resonance’ between the seismic input, the subsoil and the ancient architectures may occur

A mobile computed tomography system for on-site cultural heritage analysis

In consequence of the increasing request of on-site analysis the availability of portable systems for imaging paintings and other works of art has become really an issue for cultural heritage investigation. In many cases, authorities do not allow to transport paintings and works of art outside museums because of their value. We thus developed and used successfully a transportable X-ray Computed Tomography (CT) system that the operators can transport in a regular van and then mount inside museums or conservation centers. The system is composed of spare components that have to be properly mounted and carefully aligned in order to perform the radiographic or tomographic analysis. The basic elements are a 200 kV X-ray tube and a 12x12 cm2 flat-panel detector. With this system, it is possible to scan painting and works of art up to 1.5x1.5 m2 of size thanks to three mechanical translation axes. In the tomographic mode, a rotating platform provides high-resolution rotation of the object carrying up to 50 kg in weight. The operators control all the components of the system with a remote connection computer at a safe distance. In the present work, we report details about the development of this transportable X-ray CT system, we describe how it operates and the technical solutions we used and we show examples of application to real case studies with their specificity