1
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B Wrammerfors ET, Törnquist E, Pierantoni M, Sjögren A, Tengattini A, Kaestner A, Zandt RI', Englund M, Isaksson H. Exploratory neutron tomography of articular cartilage. Osteoarthritis Cartilage 2024; 32:702-712. [PMID: 38447631 DOI: 10.1016/j.joca.2024.02.889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 02/28/2024] [Accepted: 02/28/2024] [Indexed: 03/08/2024]
Abstract
OBJECTIVE To investigate the feasibility of using neutron tomography to gain new knowledge of human articular cartilage degeneration in osteoarthritis (OA). Different sample preparation techniques were evaluated to identify maximum intra-tissue contrast. DESIGN Human articular cartilage samples from 14 deceased donors (18-75 years, 9 males, 5 females) and 4 patients undergoing total knee replacement due to known OA (all female, 61-75 years) were prepared using different techniques: control in saline, treated with heavy water saline, fixed and treated in heavy water saline, and fixed and dehydrated with ethanol. Neutron tomographic imaging (isotropic voxel sizes from 7.5 to 13.5 µm) was performed at two large scale facilities. The 3D images were evaluated for gradients in hydrogen attenuation as well as compared to images from absorption X-ray tomography, magnetic resonance imaging, and histology. RESULTS Cartilage was distinguishable from background and other tissues in neutron tomographs. Intra-tissue contrast was highest in heavy water-treated samples, which showed a clear gradient from the cartilage surface to the bone interface. Increased neutron flux or exposure time improved image quality but did not affect the ability to detect gradients. Samples from older donors showed high variation in gradient profile, especially from donors with known OA. CONCLUSIONS Neutron tomography is a viable technique for specialized studies of cartilage, particularly for quantifying properties relating to the hydrogen density of the tissue matrix or water movement in the tissue.
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Affiliation(s)
| | - Elin Törnquist
- Department of Biomedical Engineering, Lund University (LU), Sweden
| | - Maria Pierantoni
- Department of Biomedical Engineering, Lund University (LU), Sweden
| | - Amanda Sjögren
- Clinical Epidemiology Unit, Orthopedics, Department of Clinical Sciences Lund, LU, Sweden
| | | | - Anders Kaestner
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut (PSI), Switzerland
| | | | - Martin Englund
- Clinical Epidemiology Unit, Orthopedics, Department of Clinical Sciences Lund, LU, Sweden
| | - Hanna Isaksson
- Department of Biomedical Engineering, Lund University (LU), Sweden
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2
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Davies TW, Gunz P, Spoor F, Alemseged Z, Gidna A, Hublin JJ, Kimbel WH, Kullmer O, Plummer WP, Zanolli C, Skinner MM. Dental morphology in Homo habilis and its implications for the evolution of early Homo. Nat Commun 2024; 15:286. [PMID: 38177110 PMCID: PMC10767101 DOI: 10.1038/s41467-023-44375-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Accepted: 12/11/2023] [Indexed: 01/06/2024] Open
Abstract
The phylogenetic position of Homo habilis is central to debates over the origin and early evolution of the genus Homo. A large portion of the species hypodigm consists of dental remains, but they have only been studied at the often worn enamel surface. We investigate the morphology of the H. habilis enamel-dentine junction (EDJ), which is preserved in cases of moderate tooth wear and known to carry a strong taxonomic signal. Geometric morphometrics is used to characterise dentine crown shape and size across the entire mandibular and maxillary tooth rows, compared with a broad comparative sample (n = 712). We find that EDJ morphology in H. habilis is for the most part remarkably primitive, supporting the hypothesis that the H. habilis hypodigm has more in common with Australopithecus than later Homo. Additionally, the chronologically younger specimen OH 16 displays a suite of derived features; its inclusion in H. habilis leads to excessive levels of variation.
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Affiliation(s)
- Thomas W Davies
- Department of Human Origins, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.
- School of Anthropology and Conservation, University of Kent, Canterbury, UK.
| | - Philipp Gunz
- Department of Human Origins, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Fred Spoor
- Department of Human Origins, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Centre for Human Evolution Research, Natural History Museum, London, UK
| | - Zeresenay Alemseged
- Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL, USA
| | - Agness Gidna
- Department of Cultural Heritage, Ngorongoro Conservation Area Authority, P. O. Box 1, Ngorongoro Crater, Arusha, Tanzania
| | - Jean-Jacques Hublin
- Collège de France, Paris, France
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - William H Kimbel
- Institute of Human Origins, and School of Human Evolution and Social Change, Arizona State University, Tempe, AZ, USA
| | - Ottmar Kullmer
- Palaeobiology and Environment workgroup, Institute of Ecology, Evolution, and Diversity, Goethe University, Frankfurt, Germany
- Division of Palaeoanthropology, Senckenberg Research Institute and Natural History Museum Frankfurt, Frankfurt am Main, Germany
| | - William P Plummer
- School of Anthropology and Conservation, University of Kent, Canterbury, UK
| | - Clément Zanolli
- Univ. Bordeaux, CNRS, MCC, PACEA, UMR 5199, 33600, Pessac, France
| | - Matthew M Skinner
- School of Anthropology and Conservation, University of Kent, Canterbury, UK
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa
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3
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Østergaard M, Naver EB, Schüpbach D, Kaestner A, Strobl M, Brüel A, Thomsen JS, Schmidt S, Poulsen HF, Kuhn LT, Birkedal H. Correlative study of liquid in human bone by 3D neutron microscopy and lab-based X-ray μCT. Bone 2023; 175:116837. [PMID: 37419297 DOI: 10.1016/j.bone.2023.116837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 06/30/2023] [Accepted: 07/04/2023] [Indexed: 07/09/2023]
Abstract
Liquid plays an important role in bone that has a complex 3D hierarchical pore structure. However, liquid (water) is difficult to discern from e.g. an organic matrix by X-ray imaging. Therefore, we use a correlative approach using both high resolution X-ray and neutron imaging. Human femoral bone with liquid adsorbed into some of the pores was imaged with both the Neutron Microscope at the ICON beamline, SINQ at PSI, and by lab-based μCT using 2.7 μm voxel size. Segmentation of the two datasets showed that, even though the liquid was clearly distinguishable in the neutron data and not in the X-ray data, it remained challenging to segment it from bone due to overlaps of peaks in the gray level histograms. In consequence, segmentations from X-ray and neutron data varied significantly. To address this issue, the segmented X-ray porosities was overlaid on the neutron data, making it possible to localize the liquid in the vascular porosities of the bone sample and use the neutron attenuation to identify it as H2O. The contrast in the neutron images was lowered slightly between the bone and the liquid compared to the bone and the air. This correlative study shows that the complementary use of X-rays and neutrons is very favorable, since H2O is very distinct in the neutron data, while D2O, H2O, and organic matter can barely be distinguished from air in the X-ray data.
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Affiliation(s)
- Maja Østergaard
- Department of Chemistry and iNANO, Aarhus University, Aarhus, Denmark.
| | - Estrid Buhl Naver
- Department of Energy Conversion and Storage, Technical University of Denmark, Kongens Lyngby, Denmark.
| | - Delia Schüpbach
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, Villigen, Switzerland.
| | - Anders Kaestner
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, Villigen, Switzerland.
| | - Markus Strobl
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, Villigen, Switzerland; Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark.
| | - Annemarie Brüel
- Department of Biomedicine, Aarhus University, Aarhus, Denmark.
| | | | - Søren Schmidt
- Data Management and Software Centre, European Spallation Source, Lund, Sweden.
| | | | - Luise Theil Kuhn
- Department of Energy Conversion and Storage, Technical University of Denmark, Kongens Lyngby, Denmark.
| | - Henrik Birkedal
- Department of Chemistry and iNANO, Aarhus University, Aarhus, Denmark.
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4
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Gaboutchian AV, Knyaz VA, Maschenko EN, Dac LX, Maksimov AA, Emelyanov AV, Korost DV, Stepanov NV. Measuring Dental Enamel Thickness: Morphological and Functional Relevance of Topographic Mapping. J Imaging 2023; 9:127. [PMID: 37504804 PMCID: PMC10381522 DOI: 10.3390/jimaging9070127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2023] [Revised: 05/10/2023] [Accepted: 06/01/2023] [Indexed: 07/29/2023] Open
Abstract
The interest in the development of dental enamel thickness measurement techniques is connected to the importance of metric data in taxonomic assessments and evolutionary research as well as in other directions of dental studies. At the same time, advances in non-destructive imaging techniques and the application of scanning methods, such as micro-focus-computed X-ray tomography, has enabled researchers to study the internal morpho-histological layers of teeth with a greater degree of accuracy and detail. These tendencies have contributed to changes in established views in different areas of dental research, ranging from the interpretation of morphology to metric assessments. In fact, a significant amount of data have been obtained using traditional metric techniques, which now should be critically reassessed using current technologies and methodologies. Hence, we propose new approaches for measuring dental enamel thickness using palaeontological material from the territories of northern Vietnam by means of automated and manually operated techniques. We also discuss method improvements, taking into account their relevance for dental morphology and occlusion. As we have shown, our approaches demonstrate the potential to form closer links between the metric data and dental morphology and provide the possibility for objective and replicable studies on dental enamel thickness through the application of automated techniques. These features are likely to be effective in more profound taxonomic research and for the development of metric and analytical systems. Our technique provides scope for its targeted application in clinical methods, which could help to reveal functional changes in the masticatory system. However, this will likely require improvements in clinically applicable imaging techniques.
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Affiliation(s)
- Armen V Gaboutchian
- Medical Institute, Peoples' Friendship University (RUDN), 117198 Moscow, Russia
| | - Vladimir A Knyaz
- Phystech School of Applied Mathematics and Informatics, Moscow Institute of Physics and Technology (MIPT), 141701 Dolgoprudny, Russia
- State Research Institute of Aviation Systems (GosNIIAS), 125319 Moscow, Russia
| | - Evgeniy N Maschenko
- Borissiak Paleontological Institute, Russian Academy of Sciences, 117647 Moscow, Russia
| | - Le Xuan Dac
- Joint Russian-Vietnamese Tropical Scientific and Technological Center, Hanoi 650000, Vietnam
- Institute of Tropical Ecology of the Joint Russian-Vietnamese Tropical Scientific and Technological Center, Hanoi 650000, Vietnam
| | - Anatoly A Maksimov
- State Research Institute of Aviation Systems (GosNIIAS), 125319 Moscow, Russia
| | - Anton V Emelyanov
- State Research Institute of Aviation Systems (GosNIIAS), 125319 Moscow, Russia
| | - Dmitry V Korost
- Faculty of Geology, Moscow State University, 119991 Moscow, Russia
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5
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Cazenave M, Kivell TL. Challenges and perspectives on functional interpretations of australopith postcrania and the reconstruction of hominin locomotion. J Hum Evol 2023; 175:103304. [PMID: 36563461 DOI: 10.1016/j.jhevol.2022.103304] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 11/15/2022] [Accepted: 11/16/2022] [Indexed: 12/24/2022]
Abstract
In 1994, Hunt published the 'postural feeding hypothesis'-a seminal paper on the origins of hominin bipedalism-founded on the detailed study of chimpanzee positional behavior and the functional inferences derived from the upper and lower limb morphology of the Australopithecus afarensis A.L. 288-1 partial skeleton. Hunt proposed a model for understanding the potential selective pressures on hominins, made robust, testable predictions based on Au. afarensis functional morphology, and presented a hypothesis that aimed to explain the dual functional signals of the Au. afarensis and, more generally, early hominin postcranium. Here we synthesize what we have learned about Au. afarensis functional morphology and the dual functional signals of two new australopith discoveries with relatively complete skeletons (Australopithecus sediba and StW 573 'Australopithecus prometheus'). We follow this with a discussion of three research approaches that have been developed for the purpose of drawing behavioral inferences in early hominins: (1) developments in the study of extant apes as models for understanding hominin origins; (2) novel and continued developments to quantify bipedal gait and locomotor economy in extant primates to infer the locomotor costs from the anatomy of fossil taxa; and (3) novel developments in the study of internal bone structure to extract functional signals from fossil remains. In conclusion of this review, we discuss some of the inherent challenges of the approaches and methodologies adopted to reconstruct the locomotor modes and behavioral repertoires in extinct primate taxa, and notably the assessment of habitual terrestrial bipedalism in early hominins.
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Affiliation(s)
- Marine Cazenave
- Division of Anthropology, American Museum of Natural History, New York, USA; Skeletal Biology Research Centre, School of Anthropology and Conservation, University of Kent, Canterbury, UK; Department of Anatomy, Faculty of Health Sciences, University of Pretoria, South Africa.
| | - Tracy L Kivell
- Skeletal Biology Research Centre, School of Anthropology and Conservation, University of Kent, Canterbury, UK; Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa
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6
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Törnquist E, Le Cann S, Tengattini A, Helfen L, Kok J, Hall SA, Isaksson H. The Hydration State of Bone Tissue Affects Contrast in Neutron Tomographic Images. Front Bioeng Biotechnol 2022; 10:911866. [PMID: 35782510 PMCID: PMC9247154 DOI: 10.3389/fbioe.2022.911866] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Accepted: 05/24/2022] [Indexed: 12/25/2022] Open
Abstract
Neutron tomography has emerged as a promising imaging technique for specific applications in bone research. Neutrons have a strong interaction with hydrogen, which is abundant in biological tissues, and they can penetrate through dense materials such as metallic implants. However, in addition to long imaging times, two factors have led to challenges in running in situ mechanical characterization experiments on bone tissue using neutron tomography: 1) the high water content in specimens reduces the visibility of internal trabecular structures; 2) the mechanical properties of bone are dependent on the hydration state of the tissue, with drying being reported to cause increased stiffness and brittleness. This study investigates the possibility of improving image quality in terms of neutron transmission and contrast between material phases by drying and rehydrating in heavy water. Rat tibiae and trabecular bovine bone plugs were imaged with neutron tomography at different hydration states and mechanical testing of the bone plugs was carried out to assess effects of drying and rehydration on the mechanical properties of bone. From analysis of image histograms, it was found that drying reduced the contrast between bone and soft tissue, but the contrast was restored with rehydration. Contrast-to-noise ratios and line profiles revealed that the contrast between bone tissue and background was reduced with increasing rehydration duration but remained sufficient for identifying internal structures as long as no free liquid was present inside the specimen. The mechanical analysis indicated that the proposed fluid exchange protocol had no adverse effects on the mechanical properties.
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Affiliation(s)
- Elin Törnquist
- Department of Biomedical Engineering, Lund University, Lund, Sweden
| | - Sophie Le Cann
- CNRS, Université Paris Est Créteil, Université Gustave Eiffel, UMR 8208, MSME, F-94010, Créteil, France
| | - Alessandro Tengattini
- Institut Laue-Langevin, Grenoble, France
- Université Grenoble Alpes, CNRS, Grenoble INP 3SR, Grenoble, France
| | | | - Joeri Kok
- Department of Biomedical Engineering, Lund University, Lund, Sweden
| | | | - Hanna Isaksson
- Department of Biomedical Engineering, Lund University, Lund, Sweden
- *Correspondence: Hanna Isaksson,
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7
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Bayle P, Armand D, Bessou M, Cochard D, Couture C, Deguilloux M, Ferrier C, Haget C, Jaubert J, Knüsel C, Martins S, Pubert É, Rottier S, Souron A, Beauval C, Caillo A, Dutailly B, Girault T, Hesry M, Lacrampe‐Cuyaubère F, Ledevin R, Masset C, Mesa‐Saborido M, Mora P, Muth X, Pinson R, Thibeault A, Thomas M, Vanderesse N, Bordes J. Enhancing the learning of evolutionary anthropology skills by combining student‐active teaching with actual and virtual immersion of Master's students in fieldwork, laboratory practice, and dissemination. Ecol Evol 2022; 12:e8825. [PMID: 35441006 PMCID: PMC9012909 DOI: 10.1002/ece3.8825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 02/26/2022] [Accepted: 03/29/2022] [Indexed: 11/19/2022] Open
Abstract
Higher education in evolutionary anthropology involves providing students with in‐depth knowledge of biological and cultural heritage sites and collections that are frequently inaccessible. Indeed, most sites, fossils, and archaeological remains can be visited or manipulated only rarely and solely by specialists with extensive experience. Owing to the development of 3D and medical imaging techniques, this fragile heritage is now more widely accessible, and in a dynamic way. However, exclusive adoption of virtual teaching and learning has a negative impact on student engagement and, naturally, on exchanges with instructors, and thus cannot be used without some reservations. In the ITAP (Immersion dans les Terrains de l’Anthropologie biologique et de la Préhistoire) project of the higher education STEP (Soutien à la Transformation et à l’Expérimentation Pédagogiques) transformation program at the University of Bordeaux, we combine student‐active teaching with Master's students fully immersed in ongoing fieldwork, laboratory study, and dissemination of research results in order to develop more individually shaped learning curricula and to foster both professional and new interdisciplinary skills. Here, we present examples of experiments conducted in the ITAP project using both authentic and virtual collections of archaeological, experimental, and reference materials that help to break down the barriers between research activities and higher education, as well as providing a more general appraisal of the appropriate use of virtual tools in higher education by combining them with real‐life situations.
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Affiliation(s)
- Priscilla Bayle
- UMR5199 CNRS, MC, PACEA University of Bordeaux Pessac France
| | | | - Maryelle Bessou
- UMR5199 CNRS, MC, PACEA University of Bordeaux Pessac France
| | - David Cochard
- UMR5199 CNRS, MC, PACEA University of Bordeaux Pessac France
| | | | | | | | - Cathy Haget
- UMR5199 CNRS, MC, PACEA University of Bordeaux Pessac France
| | - Jacques Jaubert
- UMR5199 CNRS, MC, PACEA University of Bordeaux Pessac France
| | | | - Stéphanie Martins
- Mission d'Appui à la Pédagogie et à l'Innovation University of Bordeaux Bordeaux France
| | - Éric Pubert
- UMR5199 CNRS, MC, PACEA University of Bordeaux Pessac France
| | | | - Antoine Souron
- UMR5199 CNRS, MC, PACEA University of Bordeaux Pessac France
| | | | - Arnaud Caillo
- UMR5199 CNRS, MC, PACEA University of Bordeaux Pessac France
| | - Bruno Dutailly
- UMR5199 CNRS, MC, PACEA University of Bordeaux Pessac France
- UMS 3657 CNRS, Archéovision Bordeaux Montaigne University Pessac France
| | - Thomas Girault
- UMR5199 CNRS, MC, PACEA University of Bordeaux Pessac France
| | - Malo Hesry
- UMR5199 CNRS, MC, PACEA University of Bordeaux Pessac France
| | | | - Ronan Ledevin
- UMR5199 CNRS, MC, PACEA University of Bordeaux Pessac France
| | | | | | - Pascal Mora
- UMS 3657 CNRS, Archéovision Bordeaux Montaigne University Pessac France
| | | | - Raphaël Pinson
- UMR5199 CNRS, MC, PACEA University of Bordeaux Pessac France
| | | | - Marc Thomas
- UMR 5608 CNRS, TRACES University of Toulouse Jean Jaurès Toulouse France
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8
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Törnquist E, Le Cann S, Tudisco E, Tengattini A, Andò E, Lenoir N, Hektor J, Raina DB, Tägil M, Hall SA, Isaksson H. Dual modality neutron and x-ray tomography for enhanced image analysis of the bone-metal interface. Phys Med Biol 2021; 66. [PMID: 34010812 DOI: 10.1088/1361-6560/ac02d4] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 05/19/2021] [Indexed: 11/11/2022]
Abstract
The bone tissue formed at the contact interface with metallic implants, particularly its 3D microstructure, plays a pivotal role for the structural integrity of implant fixation. X-ray tomography is the classical imaging technique used for accessing microstructural information from bone tissue. However, neutron tomography has shown promise for visualising the immediate bone-metal implant interface, something which is highly challenging with x-rays due to large differences in attenuation between metal and biological tissue causing image artefacts. To highlight and explore the complementary nature of neutron and x-ray tomography, proximal rat tibiae with titanium-based implants were imaged with both modalities. The two techniques were compared in terms of visualisation of different material phases and by comparing the properties of the individual images, such as the contrast-to-noise ratio. After superimposing the images using a dedicated image registration algorithm, the complementarity was further investigated via analysis of the dual modality histogram, joining the neutron and x-ray data. From these joint histograms, peaks with well-defined grey value intervals corresponding to the different material phases observed in the specimens were identified and compared. The results highlight differences in how neutrons and x-rays interact with biological tissues and metallic implants, as well as the benefits of combining both modalities. Future refinement of the joint histogram analysis could improve the segmentation of structures and tissues, and yield novel information about specimen-specific properties such as moisture content.
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Affiliation(s)
- Elin Törnquist
- Department of Biomedical Engineering, Lund University, Lund, Sweden
| | - Sophie Le Cann
- Department of Biomedical Engineering, Lund University, Lund, Sweden.,MSME, CNRS UMR 8208, Univ Paris Est Creteil, Univ Gustave Eiffel, Creteil, France
| | - Erika Tudisco
- Division of Geotechnical Engineering, Lund University, Lund, Sweden
| | - Alessandro Tengattini
- Institut Laue-Langevin (ILL), Grenoble, France.,Univ. Grenoble Alpes, CNRS, Grenoble INP, 3SR, Grenoble, France
| | - Edward Andò
- Univ. Grenoble Alpes, CNRS, Grenoble INP, 3SR, Grenoble, France
| | - Nicolas Lenoir
- Institut Laue-Langevin (ILL), Grenoble, France.,Univ. Grenoble Alpes, CNRS, Grenoble INP, 3SR, Grenoble, France
| | - Johan Hektor
- LUNARC-Centre for Scientific and Technical Computing at Lund University, Lund University, Lund, Sweden
| | - Deepak Bushan Raina
- Orthopaedics, Department of Clinical Sciences, Lund, Lund University, Lund, Sweden
| | - Magnus Tägil
- Orthopaedics, Department of Clinical Sciences, Lund, Lund University, Lund, Sweden
| | - Stephen A Hall
- Division of Solid Mechanics, Lund University, Lund, Sweden.,Lund Institute of Advanced Neutron and X-ray Science (LINXS), Lund, Sweden
| | - Hanna Isaksson
- Department of Biomedical Engineering, Lund University, Lund, Sweden.,Orthopaedics, Department of Clinical Sciences, Lund, Lund University, Lund, Sweden
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9
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Davies TW, Alemseged Z, Gidna A, Hublin JJ, Kimbel WH, Kullmer O, Spoor F, Zanolli C, Skinner MM. Accessory cusp expression at the enamel-dentine junction of hominin mandibular molars. PeerJ 2021; 9:e11415. [PMID: 34055484 PMCID: PMC8141287 DOI: 10.7717/peerj.11415] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 04/16/2021] [Indexed: 11/20/2022] Open
Abstract
Studies of hominin dental morphology frequently consider accessory cusps on the lower molars, in particular those on the distal margin of the tooth (C6 or distal accessory cusp) and the lingual margin of the tooth (C7 or lingual accessory cusp). They are often utilized in studies of hominin systematics, where their presence or absence is assessed at the outer enamel surface (OES). However, studies of the enamel-dentine junction (EDJ) suggest these traits may be more variable in development, morphology and position than previously thought. Building on these studies, we outline a scoring procedure for the EDJ expression of these accessory cusps that considers the relationship between these accessory cusps and the surrounding primary cusps. We apply this scoring system to a sample of Plio-Pleistocene hominin mandibular molars of Paranthropus robustus, Paranthropus boisei, Australopithecus afarensis, Australopithecus africanus, Homo sp., Homo habilis and Homo erectus from Africa and Asia (n = 132). We find that there are taxon-specific patterns in accessory cusp expression at the EDJ that are consistent with previous findings at the OES. For example, P. robustus M1s and M2s very often have a distal accessory cusp but no lingual accessory cusp, while H. habilis M1s and M2s show the opposite pattern. The EDJ also reveals a number of complicating factors; some apparent accessory cusps at the enamel surface are represented at the EDJ only by shouldering on the ridges associated with the main cusps, while other accessory cusps appear to have little or no EDJ expression at all. We also discuss the presence of double and triple accessory cusps, including the presence of a double lingual accessory cusp on the distal ridge of the metaconid in the type specimen of H. habilis (OH 7–M1) that is not clear at the OES due to occlusal wear. Overall, our observations, as well as our understanding of the developmental underpinnings of cusp patterning, suggest that we should be cautious in our comparisons of accessory cusps for taxonomic interpretations.
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Affiliation(s)
- Thomas W Davies
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Zeresenay Alemseged
- Department of Organismal Biology and Anatomy, University of Chicago, Chicago, Illinois, United States
| | - Agness Gidna
- Paleontology Unit, National Museum of Tanzania, Dar es Salaam, Tanzania
| | - Jean-Jacques Hublin
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.,Collège de France, Paris, France
| | - William H Kimbel
- Institute of Human Origins, and School of Human Evolution and Social Change, Arizona State University, Tempe, Arizona, United States
| | - Ottmar Kullmer
- Department of Paleobiology and Environment, Institute of Ecology, Evolution, and Diversity, Goethe University, Frankfurt, Germany.,Department of Palaeoanthropology, Senckenberg Research Institute and Natural History Museum Frankfurt, Frankfurt am Main, Germany
| | - Fred Spoor
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.,Centre for Human Evolution Research, Department of Earth Sciences, Natural History Museum, London, United Kingdom.,Department of Anthropology, University College London, London, United Kingdom
| | - Clément Zanolli
- Univ. Bordeaux, CNRS, MCC, PACEA, UMR 5199, F-33600 Pessac, France
| | - Matthew M Skinner
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.,School of Anthropology and Conservation, University of Kent, Canterbury, United Kingdom.,Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa
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