Biomedical subjects

F Prêteux

Publications and source records attributed to F Prêteux.

5 recordsLinked to original sources

PubMed2005

An image-based computational model of oscillatory flow in the proximal part of tracheobronchial trees.

A computational model of an oscillatory laminar flow of an incompressible Newtonian fluid has been carried out in the proximal part of human tracheobronchial trees, either normal or with a strongly stenosed right main bronchus. After acquisition with a multislice spiral CT, the thoracic images are processed to reconstruct the geometry of the trachea and the first six bronchus generations and to virtually travel inside this duct network. The facetisation associated with the 3D reconstruction of the tracheobronchial tree is improved to get a computation-adapted surface triangulation, which leads to a volumic mesh composed of tetrahedra. The Navier-Stokes equations associated with the classical boundary conditions and different values of the flow dimensionless parameters are solved using the finite element method. The airways are supposed to be rigid during rest breathing. The flow distribution among the set of bronchi is determined during the respiratory cycle. Cycle reproducibility and mesh size effects on the numerical results are examined. Helpful qualitative data are provided rather than accurate quantitative results in the context of multimodelling, from image processing to numerical simulations.

Bronchi↗

PubMed1988

Measurement of anisotropic vertebral trabecular bone loss during aging by quantitative image analysis.

Age-dependent variations in the architecture of vertebral trabeculae in both the vertical and horizontal planes were characterized by quantitative image analysis. Images were obtained from autopsy specimens of the third lumbar vertebrae in 61 subjects (30 men and 31 women) whose ages ranged between 33 and 89 years). All subjects had died acutely either after trauma or illnesses unrelated to the skeleton. Using mathematical morphology techniques, we measured total bone area and perimeter, and the width of trabecular particles and medullary spaces in each slice. Between the age intervals 33-49 and 80-89 years: total bone loss in the vertical and horizontal planes was 51 and 64% for women, and 38 and 29% for men, respectively. Mean trabecular width (MTW) in the vertical plane decreased from 172 to 128 micron in women and from 181 to 144 micron in men; MTW in the horizontal plane fell from 144 to 112 micron in women and remained at 114 micron in men. Maximum trabecular width decreased with age in both planes in both sexes. The mode for trabecular width was 111 micron in both sexes for all ages and in both planes. The total number of trabeculae decreased only for women in the vertical plane. Intertrabecular spaces enlarged reciprocally as the trabeculae became thinner, but the widening of spaces was much greater than that expected with trabecular thinning alone. We conclude that age-related bone loss is comprised of two processes: reduction of MTW and fragmentation and complete loss of some trabeculae. We found no evidence of vertical trabeculae thickening during normal aging.

Adult↗

PubMed1985

Automatic quantification of vertebral cancellous bone remodeling during aging.

Anatomical transformation changes in vertebral spongy bone were quantified by automatic image analysis of microradiographs of 1 mm-thick sagittal slices from autopsied normal lumbar vertebrae (24 men and 28 women, age 35 to 96). Over a period of four decades, aging bone loss is 60% in women and 45% in men in the center of the vertebral body. With age, there is a new distribution of trabeculae: weight-bearing ones are twice (in young people) to six times (in old people) more numerous than transverse ones (measured on a sagittal slice). In the elderly, intertrabecular spaces enlarge while the proportion of the thinnest trabeculae increases.

Adult↗

PubMed1985

New prospects in CT image processing via mathematical morphology.

New prospects are foreseen in CT image processing via mathematical morphology (M.M.). M.M. is a set theory based upon the concept of "structuring elements" and allows texture analysis and pattern recognition by performing sequences of neighborhood transformations. This results in a wide range of quantifications. Mathematical morphology applied to CT densitometry allows obtaining the mean density of an organ after its automatic extraction from the background. This operation eliminates the approximations due to the manual selection of the Region of Interest (ROI). Precision, reliability and reproducibility are therefore improved. In this study, we performed the automatic isolation of a sole vertebral body in thoracic or abdominal CT slices to quantify numerous parameters, among them, density of the vertebral trabecular and cortical bones. On scans of the second and third metacarpals, morphomathematical analysis allowed quantification of the parameters of bone evolution: mean cortical density, directional cortico-diaphyseal index, and medullar area. In a different connection, M.M. has allowed automatic segmentation of lung parenchyma, the measurement of its mean density and the determination of the relative importance of the vascular network.

Absorptiometry, Photon↗

PubMed1985

Observer variation in bone lesion detection in thoraco-abdominal visceral CT images.

This study measured missed bone diagnosis on CT performed for lymph nodes or visceral spread of cancers and lymphomas. A bone-expert reading was compared to that of visceral-cancer oriented observers. From 100 examinations, 65% of bone abnormalities were not described by current reporting of cancer cases. Changes in windowing and contrast of the image produced large variations in CT readings. A slow search with different windowing decreases the false-negative ratio. A fast reading with invariable viewing parameters increases false interpretations, even for experienced radiologists.

Bone Neoplasms↗