Biomedical Engineering Reference
In-Depth Information
Chapter 3
Reconstruction of the Human Airways
3.1
Introduction
Construction of a computational model of the human airways can be divided into three
stages: image acquisition, segmentation and surface/volume reconstruction. Image
acquisition involves medical images that can be obtained from various sources such
as computed tomography (CT) and magnetic resonance imaging (MRI), which essen-
tially provide similar information. A 3D matrix of a series of 2D cross-sections, sepa-
rated by an interval distance, contains information about tissues and structures which
are distinguished from one another by differences in brightness or greyscale. These
images provide medical practitioners with 3D realistic computational models that can
assist clinical diagnosis and medical treatment and planning. Visualisation and recon-
struction of morphological structures from the medical image series involves segmen-
tation of the desired region of interest of organs or structures. The general problem
of segmentation can be summarised as the partitioning of an image into a number of
homogeneous segments, such that any two neighbouring segments yields a hetero-
geneous segment. Some common algorithms based on thresholding, edge detection,
and region characteristics are given in this chapter. The basics of these algorithms
are given to introduce the reader to this active research field. While each segmenta-
tion technique is presented individually, in practice it is common to apply multiple
segmentation techniques to a given problem. Finally the chapter concludes with
examples to demonstrate different methods to develop respiratory airway models.
3.2
Medical Image Acquistion
3.2.1
Computed Tomography (CT)
Computed Tomography (CT) or by its older name computed axial tomography, is
a medical imaging procedure that using x-rays to create a series of planar cross-
sectional images along an axis. It is a combination of mechanical and computer
engineering which was first developed in 1972 by Sir Godfrey Hounsfield (Richmond
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