Dual-Energy X-ray Absorptiometry (DEXA) as an Instrument for Assessing Bone Mineral Density in Historic Human Remains

Dual-energy X-ray absorptiometry (DEXA) is the gold standard, non-invasive method for the measurement of bone mineral density (BMD). DEXA measures BMD using two X-ray beams of different energies. These beams are attenuated differently by bone and soft tissue, allowing for the determination of BMD. DEXA requires the presence of soft tissue and bone to measure BMD, but if a soft tissue proxy (STP), such as rice or gelatin, is used - DEXA can be used to scan human remains,specifically bones. The purpose of this study was twofold: develop a criterion method to measure BMD, using DEXA on historical human remains, then use the criterion method to investigate bilateral asymmetry and agreement (test re-test reliability) in a sample of historic human remains, specifically paired radii from the Mary Rose Trust’s collection of fairly complete skeletons (FCS). The study developed a criterion method initially, by testing the efficacy, in terms of reliability, of using a suspension bracket to position the radius in a consistent position. Machine capability was tested by DEXA scanning one radius 16 times without moving it and using these values to calculate precision error. Method capability was tested by scanning one radius 16 times, removing it and replacing between scans, and using these values to calculate precision error. Once the optimum method of positioning samples was established, the optimum STP was determined. To determine optimum STP, the machine capability of dry rice was compared to that of differing concentrations of gelatin. Upondetermination of the criterion method for measuring BMD using DEXA on historic human remains, agreement and bilateral asymmetry of BMD was measured in a population of 20 pairs of radii. This was done for samples in pronated and supinated orientation. Significant differences were tested for between dominant and nondominant arm BMD (dominant arm being assumed as the arm with higher BMD). The criterion method for measurement of BMD using DEXA within historic human remains was found to be the use of a suspension bracket to position the sample with 11.7% gelatin blocks as an STP. This method resulted in a mean ± standard error of the mean (SEM) of 0.751±0.00028 mass/cm2 (±0.037%), compared to the rice bed method (no suspension bracket and dry rice as an STP) which resulted in a mean ± SEM of 0.795±0.0015 mass/cm2 (±0.19%). Once established, the criterion method was applied to the full sample of 20 pairs of radii to establish reliability and bilateralasymmetry. Reliability was assessed using Bland and Altman limits of agreement iii (LOA) analysis which produced a sample mean = 0.762 mass/cm2, a systematic bias = 0.002 mass/cm2 (0.03%), upper LOA = 0.003 mass/cm2 (0.39%) and lower LOA = -0.0026 mass/cm2 (-0.34%). Significant differences were observed in pronated BMD, supinated BMD, and combined BMD values between dominant/non-dominant arm radii (p 10% with the largest difference being 46.2%. To conclude, the criterion method for measuring BMD using DEXA on historic human remains is to position samples using a suspension bracket and use 11.7% gelatin blocks as an STP. Additionally, significant bilateral asymmetry was observed between dominant and non-dominant arm BMD in a population of 20 pairs of radii

Développement d'un processus coopératif de traitement d'images ultrasonores pour le référencement géométrique de structures osseuses en chirurgie orthopédique

La radiologie est actuellement la modalité d'imagerie la plus utilisée en chirurgie orthopédique, que ce soit en planification opératoire, en contrôle per-opératoire ou pour le suivi du patient. Un de ses inconvénients est de ne pas permettre un référencement géométrique des objets représentés. Il est donc impossible tout au long du processus chirurgical orthopédique, de mesurer précisément les modifications de géométrie des structures osseuses. En salle d'opération les instruments chirurgicaux sont référencés spatialement et permettent par palpations de points de référence une identification géométrique des structures osseuses. Ceci est limité au contexte chirurgical car ces palpations requièrent des incisions. Dans cette thèse, nous proposons d'introduire en chirurgie orthopédique une nouvelle approche fondée sur l'utilisation d'un capteur d'images ultrasonores dont le positionnement spatial est connu. Nous présentons une méthode d'analyse d'images ultrasonores qui aboutit à la détection des points de référence dans un contexte non chirurgical. Cet apport est fondamental car il introduit une continuité dans le contrôle précis de la géométrie des structures osseuses tout au long du processus chirurgical orthopédique de la planification opératoire jusqu'au suivi du patient. Pour déterminer la position des points de référence sur les images ultrasonores osseuses nous sommes passés par une étape intermédiaire consistant en la détection de l'interface osseuse par des approches fondées sur des modèles de contours. Devant la difficulté du problème lié à la très faible qualité des images ultrasonores osseuses, nous nous sommes orientés vers une approche coopérative innovante. Dès que la sonde est positionnée sur le patient, le système affiche en temps réel le contour détecté et le clinicien peut, par un mouvement continu de la sonde, faire converger le système vers une solution optimale au regard de son expertise et des propriétés images. La validation de nos algorithmes s'est tout d'abord effectuée en mode non coopératif sur une base de données contenant 651 images ultrasonores. Le meilleur algorithme fondé sur la recherche d'un chemin optimal parmi un ensemble de points de contours candidats a été validé en mode coopératif sur un prototype appelé PhysioPilot dédié à la mesure de paramètres physiologiques dans un contexte non chirurgicalX-rays remain the preferred imaging modality for orthopedic surgery for surgical planning, intra-operative control or patient follow-up. Nevertheless, it does not allow anatomical bone structures referencing. It is then impossible to control geometrical modifications of bone structures during the surgical process. However, surgical tools are referenced in the operating-room space and allow the surgeon to define anatomical structures geometrically by defining landmark positions. This process is only allowed during surgical procedures because it requires to do cuts on the patient. In this work, we propose a new approach using an ultrasound probe that is referenced in the operating-room space. We present an image processing algorithm to extract anatomical landmark position in a surgical context. It is a crucial improvement because it allows a complete patient follow-up from pre-operative planning to post-operative consults. To determine anatomical landmark positions on ultrasound images we added an intermediate step to extract the bone/soft tissues interface via several segmentation methods as active contours. Due to the low quality of ultrasound images we decided to design a innovative cooperative process. As the surgeon positions the ultrasound probe on the patient, the bone interface appears on the system screen in real time. Then the clinician can help the segmentation result to converge to the final solution by a soft movement of the probe. The validation of our work was performed on a database of 651 ultrasound images, in a non-cooperative way. The best algorithm that extracts the bone interface by defining the optimal path in a graph of potential candidates was validated with a cooperative protocol on a prototype called PhysioPilot, in order to perform physiological measurements in a non-surgical contextPARIS-EST-Université (770839901) / SudocSudocFranceF