Micro-CT and histological investigation of the spatial pattern of feto-placental vascular density

Introduction: There are considerable variations in villous morphology within a normal placenta. However, whether there is a reproducible spatial pattern of variation in villous vascular density is not known. Micro-CT provides three-dimensional volume imaging with spatial resolution down to the micrometer scale. In this study, we applied Micro-CT and histological analysis to investigate the degree of heterogeneity of vascularisation within the placenta. Method: Ten term placentas were collected at elective caesarean section, perfused with contrast agent and imaged whole with Micro-CT. Eight full depth tissue blocks were then taken from each placenta and imaged. Sections were taken for histological analysis. Data was analysed to investigate vascular fill, and vascular density in relation to location from cord insertion to placental edge at each scale. Results: Whole placental imaging revealed no spatially consistent difference in villous vessel density within the main placental tissue, although there was a great degree of heterogeneity. Both block imaging and histological analysis found a large degree of heterogeneity of vascular density within placentas, but no strong correlation between villous vascular density and block location (rs = 0.066, p = 0.7 block imaging, rs = 0.06, p = 0.6 histological analysis). Discussion: This work presents a novel method for imaging the human placenta vascular tree using multiscale Micro-CT imaging. It demonstrates that there is a large degree of variation in vascular density throughout normal term human placentas. The three-dimensional data created by this technique could be used, with more advanced computer analysis, to further investigate the structure of the vascular tree

Understanding the Structure of 3D Shapes

Compact representations of three dimensional objects are very often used in computer graphics to create effective ways to analyse, manipulate and transmit 3D models. Their ability to abstract from the concrete shapes and expose their structure is important in a number of applications, spanning from computer animation, to medicine, to physical simulations. This thesis will investigate new methods for the generation of compact shape representations. In the first part, the problem of computing optimal PolyCube base complexes will be considered. PolyCubes are orthogonal polyhedra used in computer graphics to map both surfaces and volumes. Their ability to resemble the original models and at the same time expose a very simple and regular structure is important in a number of applications, such as texture mapping, spline fitting and hex-meshing. The second part will focus on medial descriptors. In particular, two new algorithms for the generation of curve-skeletons will be presented. These methods are completely based on the visual appearance of the input, therefore they are independent from the type, number and quality of the primitives used to describe a shape, determining, thus, an advancement to the state of the art in the field

Understanding the Structure of 3D Shapes

Compact representations of three dimensional objects are very often used in computer graphics to create effective ways to analyse, manipulate and transmit 3D models. Their ability to abstract from the concrete shapes and expose their structure is important in a number of applications, spanning from computer animation, to medicine, to physical simulations. This thesis will investigate new methods for the generation of compact shape representations. In the first part, the problem of computing optimal PolyCube base complexes will be considered. PolyCubes are orthogonal polyhedra used in computer graphics to map both surfaces and volumes. Their ability to resemble the original models and at the same time expose a very simple and regular structure is important in a number of applications, such as texture mapping, spline fitting and hex-meshing. The second part will focus on medial descriptors. In particular, two new algorithms for the generation of curve-skeletons will be presented. These methods are completely based on the visual appearance of the input, therefore they are independent from the type, number and quality of the primitives used to describe a shape, determining, thus, an advancement to the state of the art in the field

Mise en place d'une chaîne complète d'analyse de l'arbre trachéo-bronchique à partir d'examen(s) issus d'un scanner-CT (de la 3D vers la 4D)

Afin de répondre au problème de santé publique que représente l'asthme, l'imagerie tomodensitométrique associé aux traitements informatiques permettent la quantification et le suivi des dommages subis par les bronches. Le but de l'imagerie bronchique, lors d'un examen de type scanner-CT est de disposer de mesures fiables et reproductibles des différents paramètres bronchiques qui sont des marqueurs de l'importance de la pathologie et de son évolution sous traitements. Ces marqueurs correspondent à deux mesures LA ( Lumen Area) et WA ( Wall Area) prises sur des coupes perpendiculaires à la bronche. La mise en place d'une chaîne de traitements constitué de maillons d'extraction et de squelettisation de l'arbre trachéo-bronchique permet l'obtention de tels mesures. Durant cette thèse nous nous sommes focalisés sur la création d'une chaîne de traitements en proposant une contribution sur chacun des maillons. Notre chaîne est modulable et adaptée au travail en 4D (différentes phases respiratoires) et à fait l'objet d'une implémentation logiciel intitulée Neko4D.[Abstract not provided]BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Investigating Perfusion of the Human Placenta

Placental insufficiency is a significant cause of morbidity and mortality, accounting for one third of antenatal stillbirths. It occurs when the maternal spiral arteries fail to remodel normally in early pregnancy, leading to inadequate maternal perfusion of the placenta. The fetus becomes hypoxic and if not delivered prematurely may ultimately die. Assessing the placenta is therefore clinically important, to diagnose placental insufficiency in vivo, and investigate poor pregnancy outcome ex vivo. Ex vivo placental assessment relies on subjective histological analysis of a small proportion of the placenta, looking for features such as oedema, inflammation and the presence of avascular villi. Regional variation and heterogeneity are not defined. In utero clinical assessment is via ultrasound Doppler measurements, looking for increased resistance in the uterine arteries, suggesting poor spiral artery remodeling, and increased resistance within the umbilical artery, suggesting inadequate development of the feto-placental microcirculation. There is therefore an urgent need to develop new ways to evaluate the perfusion of the placenta both in and ex vivo. In this thesis I investigate two imaging modalities with the potential to improve our understanding of placental perfusion. Ex vivo I develop a placental perfusion and micro-CT imaging technique, to directly visualise the feto-placental microcirculation, before applying the technique to investigate heterogeneity within a cohort of normal term placentae. I investigate differences in vascular density through the placenta at multiple scales. In vivo I investigate a novel Magnetic Resonance Imaging model of placental perfusion, that combines diffusion weighted imaging with T2 relaxometry, to estimate maternal and fetal placental perfusion. I develop this technique, exploring MRI parameters relating to perfusion in normally grown and growth restricted pregnancies. This work is important as the techniques developed improve our ability to investigate and understand placental perfusion, and provide potential new parameters of placental function in vivo

La micro-architecture de l'os trabéculaire en croissance : variabilité tridimensionnelle normale et pathologique analysée par microtomodensitométrie

Medical imaging and 3D reconstructions are used increasingly by anthropologists; they allow both investigating and preserving internal structures. Study of trabecular bone microarchitecture allows understanding variability of human skeleton at a smaller scale. This variability is observed and characterized in terms of normal growth and maturation according to age and sex, and for several pathological conditions. μCT scans of proximal metaphysis of humerus from 43 immature individuals (coming from 3 identified skeletons collections and representing all periods of age development) and 8 paleopathological cases (corresponding to 5 different etiologies) have been analyzed to quantify bone microarchitecture. Our results show that this microarchitecture varies during and between different phases of growth. Correlations with age are highlighted, even if they do not sufficiently explain the observed variability in order to represent specific age estimators; it nevertheless appears that the variations observed between the different volumes of interest could characterize different periods of growth. The measured variables showed significant sex differences only during the adolescence period, but they cannot be used, in the present state, for sex determination. The study of the trabecular bone microarchitecture of pathological individuals attests of the abnormal development of bone and therefore of their pathological status.L’imagerie médicale et la 3D, en pleine expansion dans le champ de l'anthropologie biologique, permettent d’explorer les structures internes tout en les préservant. L’étude de la micro-architecture osseuse trabéculaire permet d’appréhender la variabilité de l'os humain à une échelle jusqu'à présent peu explorée. Dans le cadre de cette recherche, cette variabilité est analysée et caractérisée en termes de croissance et de maturation, en fonction des critères individuels d’âge et de sexe, ainsi que dans des contextes pathologiques variés. Les images microtomodensitométriques des métaphyses humérales proximales de 43 sujets immatures (provenant de 3 collections ostéologiques de référence et couvrant l’ensemble des âges du développement) et celles de 8 cas paléopathologiques (représentant 5 étiologies différentes) ont été analysées pour quantifier la micro-architecture osseuse trabéculaire. Nos résultats montrent que cette micro-architecture varie pendant et entre les différentes phases de la croissance. Des corrélations avec l’âge sont mises en évidence, si elles n’expliquent pas suffisamment la variabilité observée pour en faire des estimateurs d'âge précis, il apparaît néanmoins que les variations relevées entre les différents volumes d’intérêt pourraient caractériser différentes périodes de la croissance. Les variables mesurées présentent des différences sexuelles significatives pendant l’adolescence, mais ne peuvent pas en l'état être utilisées pour la diagnose sexuelle. L'étude de la microarchitecture trabéculaire osseuse des sujets pathologiques atteste d’un développement anormal de l’os et donc du statut pathologique de l’individu observé