Biomedical Engineering Reference
In-Depth Information
where customised or commercial (Bioquant, Bioquant Image Analysis Corpora-
tion, Nashville, TN; Osteomeasure, Osteometrics Inc., Decatur, GA) software
enables features of interest to be delineated in spatial registration with the
microscope image. Static and dynamic indices characterising the trabecular
structure are calculated based on the same stereological principles employed for
point counting techniques [
18
]. Automated quantitation of trabecular bone from
histological sections has mainly been confined to a small range of static parameters
derived from bone area, bone perimeter and tissue area measurements [
86
].
Essentially, only bone matrix can be reliably segmented by automated techniques
in histological sections, hence only global static indices of bone structure are
obtained; however, when performed in conjunction with manual or semi-quanti-
tative techniques all descriptive bone parameters can be obtained.
The importance of these techniques developed over the past 50 years is
underlined by their continued use today. While currently available imaging
technology and techniques have extended the ability to visualize and quantify
trabecular bone structure they have not replaced manual and interactive techniques
but have become complementary to them.
4 Non-Destructive Imaging and Morphometry
of Trabecular Bone
Notwithstanding the conceptual models developed to extrapolate measurements
from histological sections to represent the three-dimensional micro-architecture of
trabecular bone, the field has always strived to develop and adapt technology to
enable true 3D analysis of this complex entity. The availability of benchtop high-
resolution micro-computed tomography (micro-CT) in the mid 1990s was enthu-
siastically welcomed by the bone community [
37
,
46
]. For ex vivo studies micro-
CT scanners provide isotropic spatial resolution on the order of 10 microns albeit
for samples less than 10 mm in diameter [
76
,
77
]. However, for bone samples up
to 50 mm in diameter 15 micron spatial resolution is achievable, which enables
the thinnest trabecular elements (70 microns in diameter) to be resolved (Fig.
5
)
[
77
]. The non-destructive nature of micro-CT imaging means that complementary
methodologies can be applied to the samples, subsequent to imaging. For example,
conventional histology can be performed if cellular dynamics are of interest [
78
],
or genetic analysis can be performed to identify genes associated with bone dis-
eases [
31
,
58
] or mechanical testing can be performed to enable predictive models
of bone strength to be formulated [
7
,
38
,
44
,
62
,
88
,
102
].
While laboratory-based micro-CT has become ubiquitous for quantitative bone
studies there are other non-destructive imaging modalities available to researchers.
Synchrotron facilities provide X-ray tomography but with a monochromatic X-ray
source, which provides much better delineation between the mineral and non-
mineral phases in bone than the polychromatic X-ray source used in laboratory-
based micro-CT imaging [
11
,
17
]. However, access to synchrotron facilities, while
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