References 245
light will create greater interference than areas that don’t. Any light that is outside
the short coherence length will not interfere. This reflectivity profile, called an A-
scan, contains information about the spatial dimensions and location of structures
within the sample. A cross-sectional tomograph (B-scan) may be achieved by
laterally combining a series of these axial depth scans (A-scan). An axial resolution
of 1–10 μm has been achieved using advanced low-coherence light sources. And
imaging depths of 1–2 mm can be achieved in most highly scattering tissues
using a near infrared light source in the 800–1300 nm wavelength range. Optical
coherence tomography is a very rapid evolving field, for details on verious types
of imaging formation methods and practical instrumentations, refer to.
74
In biomedical researches, OCT is widely used to obtain cross-sectional images
of internal microstructures of various biological tissues in vivo and in real time.
OCT is becoming a clinically viable imaging modality for early detection of
diseases, precision guidance of surgical interventions, and repeated monitoring
of treatment. OCT has also been used to non-invasively evaluate wound heal-
ing processes.
75
As an inexpensive and non-invasive quantitative 3-D imaging
technology, OCT has great potential for biomaterials research.
76
It has already
been demonstrated for online quality monitoring of engineered tissue for surgical
implantation.
77,78
Dunkers et al
79
have also demonstrated a functional OCT system
for imaging cellular activity within tissue scaffolds, as well as imaging the scaffold
itself. In their system, functional information regarding cell activity and structural
data is obtained using a combination of confocal fluorescence microscopy and high
numerical aperture OCT.
10.4 CONCLUDING REMARKS
We have introduced a handful of methods and techniques for characterization of
bulk and surface properties of biomaterials. However, space limitations prevent
us from discussing every single analysis method used in biomaterials characteriza-
tion. One has to remember that each individual analysis method only look at a spe-
cific aspect of a biomaterial. A combination of characterization methods (whether
listed here or not) is usually required to provide the comprehensive information
necessary for correlation with biomaterials performances in the real biological
environment. The instrumentation of material analysis steadily advances and new
methods and techniques will provide additional and invaluable information about
biomaterials and lead to better performance of MEMS based medical devices.
References
1
D. Lyman., Characterization of biomaterials, in Integrated Biomaterials Science, R. Barbucci
Ed. New York: Kluwer Academic/Plenum Publishers, 325–337, (2002).
2
A. F. von Recum Ed., Handbook of Biomaterials Evaluation, New York: Macmillan Publish-
ing Company, (1986).
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