Advanced Spectroscopy Technique for Biomedicine - Biomedical Optical Imaging Technologies: Design and Applications - page 2

Spectroscopy has been widely used in biomedicine, from photobiology to disease
diagnosis [ 1 - 10 ]. The underlying mechanism for biomedical spectroscopy is the
wavelength-dependent optical properties of many biomolecules in cells and tissues,
which can be assessed by different modes of the light-matter interactions. When
light is incident on a biological sample, photons are either absorbed or scattered
(elastically or inelastically). The absorbed light may be reemitted at a longer wave-
length, called fluorescence emission. Accordingly, spectroscopy methods to study
the absorption, elastic scattering, fluorescence, and inelastic scattering properties
of the sample are called absorption spectroscopy, diffuse reflectance spectroscopy,
fluorescence spectroscopy, and Raman spectroscopy, respectively. Different spec-
troscopic techniques are not competing but complimentary with each other as
each technology provides different aspects of the sample's optical properties. The
absorption, elastic scattering, and fluorescence signals are relatively strong, and
the spectroscopy systems for such applications are relatively easy to build. Raman
spectroscopy is considered to be particularly advantageous over other techniques
for in vivo biomedical applications because it can provide more specific and rich
information about the structure and conformation of biomolecular constituents in
tissues. However, Raman signal is extremely weak, and the instrumentation is
more complicated and challenging. With recent technology advancement, real-time
Raman spectroscopy system for in vivo biomedical applications is now a reality
[ 11 , 12 ].
In this chapter, we will focus on the designing aspects of advanced spectroscopy
system, Raman spectroscopy system in particular. We will first review the main
components of a standard spectroscopy system and their technical advancement.
Then we will present the details of designing two real-time Raman spectroscopy
systems, one for in vivo skin cancer detection and the other for lung cancer
diagnosis, and an in vivo confocal Raman spectroscopy system for skin assessment,
followed by the design review of other Raman spectroscopy systems. At the end,
we will summarize the applications of Raman spectroscopy in different fields of
medicine.

1.2 Components for Spectroscopy System

As mentioned in the introduction, a standard spectroscopy system is generally com-
posed of five components [ 13 ]. Standard spectroscopic systems are commercially
available from various manufacturers and are recommended for routine spectral
measurement and analysis. For special applications, particularly in biomedicine,
it may need to be custom designed by refining every aspect of the system. In
this section, we will briefly discuss the basic spectroscopic components and their
advancement for biomedical applications.