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.

Regional distribution of gas and tissue in acute respiratory distress syndrome. I. Consequences for lung morphology. CT Scan ARDS Study Group.

OBJECTIVE: To compare the computed tomographic (CT) analysis of the distribution of gas and tissue in the lungs of patients with ARDS with that in healthy volunteers. DESIGN: Prospective study over a 53-month period. SETTING: Fourteen-bed surgical intensive care unit of a university hospital. PATIENTS AND PARTICIPANTS: Seventy-one consecutive patients with early ARDS and 11 healthy volunteers. MEASUREMENTS AND RESULTS: A lung CT was performed at end-expiration in patients with ARDS (at zero PEEP) and healthy volunteers. In patients with ARDS, end-expiratory lung volume (gas + tissue) and functional residual capacity (FRC) were reduced by 17% and 58% respectively, and an excess lung tissue of 701+/-321 ml was observed. The loss of gas was more pronounced in the lower than in the upper lobes. The lower lobes of 27% of the patients were characterized by "compression atelectasis," defined as a massive loss of aeration with no concomitant excess in lung tissue, and "inflammatory atelectasis," defined as a massive loss of aeration associated with an excess lung tissue, was observed in 73% of the patients. Three groups of patients were differentiated according to the appearance of their CT: 23% had diffuse attenuations evenly distributed in the two lungs, 36% had lobar attenuations predominating in the lower lobes, and 41% had patchy attenuations unevenly distributed in the two lungs. The three groups were similar regarding excess lung tissue in the upper and lower lobes and reduction in FRC in the lower lobes. In contrast, the FRC of the upper lobes was markedly lower in patients with diffuse or patchy attenuations than in healthy volunteers or patients with lobar attenuations. CONCLUSIONS: These results demonstrate that striking differences in lung morphology, corresponding to different distributions of gas within the lungs, are observed in patients whose respiratory condition fulfills the definition criteria of ARDS.

Validation of a software designed for computed tomographic (CT) measurement of lung water.

OBJECTIVE: The in-vitro validation of a computed tomographic (CT) software specifically designed for quantifying the volume of water contained in the lung. DESIGN: An in-vitro, ex-vivo study. In 1993, a postmortem left pneumonectomy was performed in a patient who died from acute respiratory distress syndrome. The lung was fixed, inflated and dried according to a technique proposed by Markarian and Dailey in 1975 aimed at producing a lung specimen spongy in texture and suitable for radiography. MEASUREMENTS AND RESULTS: In 1999, 13 CT scans of this lung specimen were performed corresponding to different bronchial instillations of known volumes of water and albumin 4%. The different lung weights resulting from the successive bronchial instillations were calculated using a specially designed software, Lungview, adapted for CT measurements and compared with the actual lung weight measured by an electronic scale. The increase in lung weight measured by Lungview was closely correlated with the actual increase in lung weight resulting from bronchial instillation of water and albumin (y = 0.99x - 23, r = 1 for water and y = x - 17, r = 1 for albumin 4%) and the precision of the bias was 7 g for water and 3 g for albumin 4%. CONCLUSIONS: This study shows that the CT software Lungview accurately measured the volume of lung water present within an air-dried exsanguine human lung.

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.

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.

Estimating Gaussian Markov random field parameters in a nonstationary framework: application to remote sensing imaging.

In this paper, we tackle the problem of estimating textural parameters. We do not consider the problem of texture synthesis, but the problem of extracting textural features for tasks such as image segmentation. We take into account nonstationarities occurring in the local mean. We focus on Gaussian Markov random fields for which two estimation methods are proposed, and applied in a nonstationary framework. The first one consists of extracting conditional probabilities and performing a least square approximation. This method is applied to a nonstationary framework, dealing with the piecewise constant local mean. This framework is adapted to practical tasks when discriminating several textures on a single image. The blurring effect affecting edges between two different textures is thus reduced. The second proposed method is based on renormalization theory. Statistics involved only concern variances of Gaussian laws, leading to Cramer-Rao estimators. This method is thus especially robust with respect to the size of sampling. Moreover, nonstationarities of the local mean do not affect results. We then demonstrate that the estimated parameters allow texture discrimination for remote sensing data. The first proposed estimation method is applied to extract urban areas from SPOT images. Since discontinuities of the local mean are taken into account, we obtain an accurate urban areas delineation. Finally, we apply the renormalization based on method to segment ice in polar regions from AVHRR data.

Quantification of bronchial dimensions at MDCT using dedicated software.

This study aimed to assess the feasibility of quantification of bronchial dimensions at MDCT using dedicated software (BronCare). We evaluated the reliability of the software to segment the airways and defined criteria ensuring accurate measurements. BronCare was applied on two successive examinations in 10 mild asthmatic patients. Acquisitions were performed at pneumotachographically controlled lung volume (65% TLC), with reconstructions focused on the right lung base. Five validation criteria were imposed: (1) bronchus type: segmental and subsegmental; (2) lumen area (LA)>4 mm2; (3) bronchus length (Lg) > 7 mm; (4) confidence index - giving the percentage of the bronchus not abutted by a vessel - (CI) >55% for validation of wall area (WA) and (5) a minimum of 10 contiguous cross-sectional images fulfilling the criteria. A complete segmentation procedure on both acquisitions made possible an evaluation of LA and WA in 174/223 (78%) and 171/174 (98%) of bronchi, respectively. The validation criteria were met for 56/69 (81%) and for 16/69 (23%) of segmental bronchi and for 73/102 (72%) and 58/102 (57%) of subsegmental bronchi, for LA and WA, respectively. In conclusion, BronCare is reliable to segment the airways in clinical practice. The proposed criteria seem appropriate to select bronchi candidates for measurement.

Hepatic disposition of tilorone hydrochloride in the rat.

1. The hepatic disposition of tilorone HCl, an antiviral and antitumour agent, was studied in male Wistar rats after intraduodenal administration. 2. A concentrative transfer into the liver occurred, the liver/portal blood concentration ratio being 120 or higher. The relationship between dose and hepatic concentration was linear. 3. Biliary excretion of tilorone was low and dose-related; whole blood concentration was also dose-related. 4. Neither hepatic concentration nor biliary excretion exhibited saturation over the dosage studied (6--174 mg/kg). The hepatic 'depot' of tilorone lacked the characteristics of a true 'first-pass' effect.

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.

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.

Mathematical morphology for automatic detection of brain lesions at magnetic resonance imaging.

An original method of image analysis has been developed, using 'mathematical morphology', in order to detect brain tumors at magnetic resonance imaging of the head following injection of gadolinium-DPTA. The main steps of the analysis are as follows: 1) Spatial reduction by automatic determination of a region of interest, 2) elimination of noise by morphologic filtering (increasing alternate closing-opening sequence), 3) localization of tumor by searching for r-h maxima, and 4) extraction of tumor contours using three-dimensional structuring elements. The preliminary results of this automatic and robust method encourage further studies of the potential of tissue analysis as an aid to tumor diagnosis.