Utilizing x-ray computed tomography for heritage conservation : the case of megalosaurus bucklandii

Of key importance to any cultural institution is the practice of conservation, the method by which specimens at risk of severe degradation or destruction are treated to ensure that they survive into the future. However, surface inspection is often insufficient to properly inform conservators of the best treatment approach, and where there is little to no record of the conservational history of an object it can be difficult to identify exactly what form of conservation has been undertaken. X-Ray Computed Tomography (XCT) grants a way to overcome these issues by allowing conservators to non-destructively investigate the subsurface details of an artefact to provide essential information on condition of a specimen. Here, the potential of this approach is demonstrated using the first XCT scans of the iconic dentary of Megalosaurus bucklandii Mantell, 1827 (1); the first dinosaur ever named and described scientifically. XCT analysis reveals that the degree of repair is less extensive than previously thought and also elucidates two different material types, M1 and M2, thought to be representative of at least two phases of repair. Finally the potential of this approach is further explored, highlighting its importance for conservation practice, identifying forgeries and hoaxes in addition to potential applications in public engagement

Internal 3D Printing of Intricate Structures

International audienceAdditive technologies are increasingly used in Cultural Heritage process , for example in order to reproduce, complete, study or exhibit artefacts. 3D copies are based on digitization techniques such as laser scan or photogramme-try. In this case, the 3d copy remains limited to the external surface of objects. Medical images based digitization such as MRI or CT scan are also increasingly used in CH as they provide information on the internal structure of archaeological material. Different previous works illustrated the interest of combining 3D printing and CT scan in order to extract concealed artefacts from larger archaeological material. The method was based on 3D segmentation techniques within volume data obtained by CT scan to isolate nested objects. This approach was useful to perform a digital extraction, but in some case it is also interesting to observe the internal spatial organization of an intricate object in order to understand its production process. We propose a method for the representation of a complex internal structure based on a combination of CT scan and emerging 3D printing techniques mixing colored and transparent parts. This method was successfully applied to visualize the interior of a funeral urn and is currently applied on a set of tools agglomerated in a gangue of corrosion

X-ray computed tomography for additive manufacturing: a review

In this review, the use of x-ray computed tomography (XCT) is examined, identifying the requirement for volumetric dimensional measurements in industrial verification of additively manufactured (AM) parts. The XCT technology and AM processes are summarised, and their historical use is documented. The use of XCT and AM as tools for medical reverse engineering is discussed, and the transition of XCT from a tool used solely for imaging to a vital metrological instrument is documented. The current states of the combined technologies are then examined in detail, separated into porosity measurements and general dimensional measurements. In the conclusions of this review, the limitation of resolution on improvement of porosity measurements and the lack of research regarding the measurement of surface texture are identified as the primary barriers to ongoing adoption of XCT in AM. The limitations of both AM and XCT regarding slow speeds and high costs, when compared to other manufacturing and measurement techniques, are also noted as general barriers to continued adoption of XCT and AM

A RE Methodology to achieve Accurate Polygon Models and NURBS Surfaces by Applying Different Data Processing Techniques

The scope of this work is to present a reverse engineering (RE) methodology to achieve accurate polygon models for 3D printing or additive manufacturing (AM) applications, as well as NURBS (Non-Uniform Rational B-Splines) surfaces for advanced machining processes. The accuracy of the 3D models generated by this RE process depends on the data acquisition system, the scanning conditions and the data processing techniques. To carry out this study, workpieces of different material and geometry were selected, using X-ray computed tomography (XRCT) and a Laser Scanner (LS) as data acquisition systems for scanning purposes. Once this is done, this work focuses on the data processing step in order to assess the accuracy of applying different processing techniques. Special attention is given to the XRCT data processing step. For that reason, the models generated from the LS point clouds processing step were utilized as a reference to perform the deviation analysis. Nonetheless, the proposed methodology could be applied for both data inputs: 2D cross-sectional images and point clouds. Finally, the target outputs of this data processing chain were evaluated due to their own reverse engineering applications, highlighting the promising future of the proposed methodology.This research was funded by the he Department of Economic Development, Sustainability and Environment of the Basque Government for funding the KK-2020/00094 (INSPECTA) research project and the Spanish Ministry of Science and Innovation for funding the ALASURF project (PID2019-109220RB-I00)

A Survey of Geometric Analysis in Cultural Heritage

We present a review of recent techniques for performing geometric analysis in cultural heritage (CH) applications. The survey is aimed at researchers in the areas of computer graphics, computer vision and CH computing, as well as to scholars and practitioners in the CH field. The problems considered include shape perception enhancement, restoration and preservation support, monitoring over time, object interpretation and collection analysis. All of these problems typically rely on an understanding of the structure of the shapes in question at both a local and global level. In this survey, we discuss the different problem forms and review the main solution methods, aided by classification criteria based on the geometric scale at which the analysis is performed and the cardinality of the relationships among object parts exploited during the analysis. We finalize the report by discussing open problems and future perspectives

Confección de Prótesis Maxilofacial Ósea, In Silico, a Partir de la Impresión 3D a Través de la Tomografía Cone Beam, Arequipa 2019

Esta investigación tuvo como objetivo de demostrar que se puede obtener prótesis maxilofaciales para reemplazar tejido óseo perdido por medio de tomografías e impresoras 3D. Se trata de un estudio experimental en el cual se utilizó un cráneo donde se le hicieron 3 osteotomías, en la calota en el parietal izquierdo, apófisis temporal del maxilar y la apófisis zigomática, simulando traumatismos en el cráneo facial. Siendo así, fue adquirida las imágenes 3D por Tomografía Cone Beam para luego analizar las estructuras dañadas. Seguidamente, el formato DICOM (Digital Imaging and Communications in Medicine / Imagen Digital y Comunicación en Medicina) del estudio fue transformado en sólido utilizando el programa InVesalius para luego trabajarlo en el programa Blender donde se duplicó el cráneo, se espejó y se rellenaron las partes óseas faltantes donde se trataron para su posterior impresión. Utilizando el programa PreForm, fueron colocadas las estructuras y fueron impresas en la impresora 3D FormLabs Form 2 donde se obtuvieron las estructuras en sólido. Se esperó a que se polimerizaran para luego colocarlas en las zonas óseas faltantes del cráneo. Se puedo concluir que es factible de realizar prótesis maxilofaciales óseas por impresión 3D utilizando imágenes tomográficas, programas de uso libre e impresoras 3D de escritorio, con un alto grado de precisión. Palabras clave Prótesis maxilofacial, impresión 3DTesi

Use of 3D virtual models and physical replicas to enhance user experience within heritage applications

Museums are dedicated to preserving the legacy of the past and educating their visitors, both practices at odds with each other. The rise of multisensory experiences in museology has emphasized the use of touch as a pedagogical tool, but this risks destruction of precious museum objects. The art of3D printing has the potential to overcome this conservational barrier, but such applications are typically ad-hoc, with little design consideration. Furthermore, there is a lack of research into developing best practices for the creation of tangible 3D printed replicas. This thesis employed user experience (UX) methods from consumer industries with pragmatic mixed-methods in order to explore this issue. The research questions addressed a number of issues: 1) The perceptions of museum visitors in regard to 3D printed replicas; 2) The design considerations for replicas in order to provide positive UX for audiences; 3) How they can benefit museum audiences; 4) How they can benefit blind and partially-sighted (BPS) individuals; 5) How replication impacts wider museum practice; 6) How effective UX methods are in understanding museum audiences. Over the course of four studies, a number of key findings were elucidated: •Museum visitors expressed positivity towards the concept of tangible 3D printed replicas but had a limited understanding of it. •Preference was strongly dependant on verisimilitude, a one-dimensional requirement, while print quality was a must-be requirement. •BPS perception was reliant on multisensory interpretation. Object and material judgements were interrelated, highlighting the complex design problems in 3D printing for BPS audiences. •Replicating an object can result in unexpected insights, resulting in novel research opportunities. A set of best design practices were created and a number of emergent research topics highlighted that were unable to be fully explored. These included the preferences of younger visitors, empirical assessment of the impact of3D printed replicas and how print properties truly influence BPS perception

Surface texture measurement of metal additively manufactured parts by X-ray computed tomography

Additive manufacturing (AM) is beginning to come of age. With the freedom of design that is offered by AM, new functionality is now available that has not previously been possible because of tool access limits in machining processes. However, as with any emerging technology, a long list of unsolved problems exist. Particularly, in order for AM to become an established method of high value part manufacture, rigorous verification protocols must be followed, and the processes that produce these parts must be well understood in order for them to be well controlled. In verification, surface characterisation is a well-accepted tool in ensuring that a surface has a set of desired functional properties. Surface characterisation is also commonly used in process development, where it is used to improve process understanding. However, verification of AM parts represents a great challenge, as the tools and processes that exist in current standards fall down when the demands of ultra-complex AM components are considered, and the processes themselves are also not yet well understood. In this Thesis, I present the use of X-ray computed tomography (XCT) for surface measurement, for the purpose of verification and process improvement in an AM context. In particular, I focus on the surfaces of metal powder bed fusion parts. In the first portion of this Thesis, I examine metal AM surfaces in detail, using established methods of surface measurement and visualisation to build up a deep understanding of the features present on these surfaces. Particularly, I find that when compared, discrepancies between measurements of surface features made on data acquired using different measurement instruments can be of similar magnitudes to the sizes of the features in question. Following this work, I detail new methods for the measurement of surfaces using XCT, describing a pipeline for extracting and characterising surface information from raw XCT data. Later, I examine some of the factors that affect XCT surface measurements, particularly investigating how varying scan magnification and volumetric reconstruction grid resolution affects measurements. In this work, I find that increasing magnification improves precision, while accuracy and bias do not always improve. Altering resolution, I find that decreasing sampling resolution worsens metrological performance, while increasing it may lead to slight improvements. Finally, I bring together the various aspect of the Thesis by applying the techniques developed throughout to an industrial case involving the measurement of internal channel surfaces. In this study, I discuss the outcomes of the Thesis as a whole, showing that XCT is capable of surface measurement in cases where the surfaces of interest are relatively rough (i.e. with an arithmetic mean height of the scale limited surface, Sa > 1 μm) and are located on or inside parts that are generally penetrable by X-rays produced using state-of-the-art systems (e.g. a cube of Ti6Al4V < 20 mm × 20 mm × 20 mm in size). In the future work, further characterisation of the factors influencing the measurement, overcoming issues relating to ‘black-box’ commercial systems and the development of existing methods of data comparison are identified as core research avenues, and a need for developing metrological traceability in XCT measurement is noted