Form and Function of Mammalian Lung: Analysis by Scientific Computing

ISBN-13: 9783540644941 / Angielski / Miękka / 1998 / 108 str.

Andres Kriete; A. Kriete; Y. Sano

Opis

1.1 Overview The precise knowledge of the three-dimensional (3-D) assembly of biological structures is still in its origin. As an example, a widely accepted concept and common belief of the structure of the airway network oflung is that of a regular, dichotomous branching pattern, also known as the trumpet model. This model, first introduced by Weibel in 1963, is often used in clinical and physiological applications. However, if this concept of dichotomy is used to model lung, a shape is obtained that is quite different from a real lung. As a matter of fact, many previous quantitative morphological and stereological investigations of lung did not concentrate on the spatial aspect of lung morphology but delivered data in a more statistical fashion. Accordingly, the functional behavior predicted by such a model becomes questionable and indeed, the morphometrically predicted lung capacity exceeds the physiological required capacity by a factor of 1.3 up to a factor of2. This problem has also been termed a paradox, as discussed by Weibel in 1983. In the rare cases where descriptive models of the mammalian bronchial tree exist, monopodial in small mammals, dichotomous in larger ones, the understanding of the historical and/or functional reasons for size-related changes in the general design is not explainable. This investigation is trying to overcome this gap by computer modeling and functional simulation.

Spis treści

1 Introduction.- 1.1 Overview.- 1.2 Goals.- 1.3 Scientific Image Computing.- 2 Confocal Imaging of an Acinus.- 2.1 The Imaging Problem in Lung Research.- 2.2 Material and Instrumentation.- 2.3 Prescanning and Definition of a Region of Interest.- 2.4 Confocal Laser Scanning Microscopy.- 2.4.1 Basic Principles in Confocal Microscopy.- 2.4.2 Types of Systems.- 2.4.3 Imaging Properties.- 2.4.4 Confocal Instrumentation.- 2.4.5 Contrast Generation.- 2.4.6 Application of Confocal Imaging to Thick Sections.- 2.5 A Framework for Scanning Large Volumes in Confocal 3-D Imaging.- 2.6 A 3-D Data Volume Representing a Complete Acinus.- 3 3-D Analysis of a Complete, Highly Resolved Respiratory Unit.- 3.1 Basics of 3-D Analysis.- 3.2 Image Preprocessing.- 3.3 Segmentation and Labeling.- 3.4 An Automated Segmentation Procedure.- 3.5 Quantification of Structural Components.- 3.5.1 Determination of Volumes.- 3.5.2 Fractal Analysis of Lung Parenchyma.- 3.6 3-D Topology as an Analytical Tool.- 3.6.1 Introduction.- 3.6.2 Basics of 3-D TOP.- 3.6.3 Modules and Functionality of the 3-D TOP Software.- 3.6.4 Application to a Lung Data Set.- 3.6.5 Analysis of Septae.- 4 3-D Visualization of Microscopic Volumes of Lung.- 4.1 Basics of 3-D Visualization.- 4.2 Types of Volume Rendering.- 4.2.1 Image and Object Order Rendering.- 4.2.2 Implementations.- 4.2.3 Voxel Intensities and Image Order Rendering.- 4.3 Voxel Attributes and Object Order Rendering.- 4.3.1 Alpha-Blending.- 4.3.2 Brightness.- 4.4 3-D Imaging Meets 3-D Graphics.- 4.5 Stereoscopic Displays and Virtual Reality.- 5 Discussion of 3-D Analysis at Respiratory Units.- 6 Analysis of the Conductive Part of Lung.- 6.1 Introduction.- 6.2 Stereoscopic Tracings of Casts.- 6.3 Analysis of Traced Data.- 7 A Computer Lung Modeler.- 7.1 Introduction.- 7.2 A Self-Similar, Asymmetric Model of a Lung Lobe.- 7.3 Scaling and Strahler-Ordering Scheme.- 7.4 Transition in the Bifurcation Pattern.- 7.5 Completing a Graphical Lung Model with Limited Stochastics.- 8 Computational Physics Applied to a Bronchial Tree Model.- 8.1 Introduction.- 8.2 Scaling of the Computer Lung Model.- 8.3 Dynamics with Breathing.- 8.3.1 Model Pressure and Volumes.- 8.3.2 Modeling of Respiratory Units and Volume-to-Surface Relationships.- 8.3.3 Flow Rates and Initial Partial Pressure.- 8.4 Convection.- 8.5 Resistance and Reynolds Number.- 8.6 Diffusion.- 8.6.1 Equations Describing Diffusion in Lung.- 8.7 Mass Transport Equations.- 8.8 Implementation and Run-Times.- 9 Model Predictions.- 9.1 Convection and Reynolds Numbers.- 9.2 Oxygen and Ozone Mass Transport.- 10 Discussion of Structural Modeling and Functional Simulation.- 10.1 Summary of Morphological Modeling.- 10.2 How Could the Structure of the Bronchial Tree Be Explained?.- 10.3 Functional Predictions.- 10.4 Outlook.- 11 Summary.- References.

Blurb

The study approaches the investigations of airway morphology of the lung with a new set of imaging and cmputer graphical methods, including confocal imaging, computer-guided image acquisition,visualization and fractal graphics. The key result is that, in contrast to the belief that the design of the conductive part of the lung of smaller mammals can be decribed with a trumpet model, the findings reported here document a strongly monopodial branching pattern with the functional consequence of a variation of dead space between the trachea and the acini. This non-dichotomic structural design finds its continuation within the respiratory units as the necessary requirement for an optimal space filling and dense packing which cannot be achieved by a dichotomic branching only. Based on a computer model, computational physics tightly coupled with computer visualistics enables functional simulation of the lung model regarding gas transport. The predicted variance in the ventilation of acini gives rise to an explanation of the well-known difference between the morphologically predicted and physiologically required diffusion capacity.