Biomedical Engineering Reference
In-Depth Information
Fig. 8.9.
Screenshots from the renal nephron modelling portal available at
www.abi.auckland.ac.nz/nephron. The two images illustrate the current extremes of the spa-
tial scales encompassed by the portal, with the individual transporter on the left and simulation
results from the whole nephron on the right
8.14 The cardiac physiome project
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The following example is intended to illustrate the use of these VPH-Physiome stan-
dards and tools in a clinically focused multi-scale heart modelling project, since car-
diac modelling provides a good example of the use of multi-physics and multi-scale
physiome modelling standards and tools. At the organ level the models include the
coupled electro-mechanics of the myocardium, with detailed models of tissue struc-
ture, coupled to blood flow in the ventricles and coronaries. At the cell level the
models include membrane ion channel electrophysiology, calcium transport, my-
ofilament mechanics, signalling pathways and metabolic pathways. We first briefly
review the technologies used for imaging cardiac structure at multiple length scales
and how these images are segmented and used to construct anatomically based mod-
els on which the equations representing physical laws can be solved.
Cardiac Imaging technologies
The structure of biological tissues can be imaged at spatial scales from protein and
subcellular levels to tissue, organ and organ system levels. Some of these imag-
ing techniques are illustrated for the heart in Fig. 8.10. Starting at the smallest
scale, X-ray diffraction techniques yield protein structure at about 0.5nm resolution
(Fig. 8.10a). Electron tomography has the capacity to image 3D sub-cellular struc-
ture at the 5nm level (Fig. 8.10b). With image registration across multiple scanned
tissue samples, confocal imaging can provide 3D reconstruction of complete trans-
mural cross-sections of, for example, the ventricular wall (see Fig. 8.10c). Multi-
photon and confocal imaging routinely gives 500nm resolution on soft tissues, al-
though with the use of single molecule fluorescent markers such as GFPs coupled to
quenching techniques that eliminate background illumination (Soeller et al., 2009),
optical imaging techniques are now pushing down to 50nm resolution. Micro-CT, in
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This section is based on Hunter & Viceconti, 2009.
