488
S. Biswas et al.
predictions of acquired data can be made. While the propagation of light through
optical components can be modeled using methods available from other spectral regions, the interaction of light with the sample is an area of continuing development.
While specific geometries such as spheres, cylinders or slabs can be modeled, the
general case remains to be shown in an efficient manner. Nevertheless, the framework presented forms the basis for physics-based modeling of any sample. though
Em theory is rigorous and can provide the most detailed picture of light-matter
interactions, its implementation and interpretation of results are both significantly
complex. Recently, a conceptually simpler approach has been proposed to understand the optics of microscopy using scalar wave theory [24]. In this approach, the
major difference is that the wave propagation is simplified and computations can
potentially be faster. We invoked the same structural model of the sample as in
the complete Em treatment, in terms of decomposition into Fourier frequencies.
together, the two approaches should be useful in describing light matter interactions in a number of sample geometries and configurations [45, 46].
16.3.4 Applications of IR Imaging in Solid Tumor Histopathology
and Corresponding Normal Tissues
In this chapter, we do not aim to thoroughly cover every example of application of
IR imaging for histopathology. We also do not cover the older work using single
elements detectors. many excellent reviews exist to provide the reader a guidance
of the development of the field and a comprehensive view of the variety of possible
applications. Instead, we focus here on providing an overview and a flavor of the
possibilities using IR imaging. We also point to salient aspects of the process and
key features of any diagnostic protocol using illustrative examples.
16.3.4.1 Basic Concept of Using Absorption Spectra for Medical Diagnostics
Biological samples are composed of several complex small molecule and macromolecular assemblies, including proteins, nucleic acids, lipids and carbohydrates, as
well as constituent small molecules [47]. very rarely (with notable exceptions such
as collagen) do spectra reflect compositions of any of these constitutents directly.
hence, IR absorption spectra contain this entire diversity, simultaneously making
them both very sensitive to all constituents and exceptionally non-specific to any
particular molecule. Spectra comprise of some significant, spectral characteristic
features, however, and significant “mesoscale” chemistry can be examined as, in
general, classes of compounds can be distinguished. For example, Fig. 16.7 demonstrates the spectra from different classes of compounds that make up the bulk
of human cells and tissues. Spectra from these four classes are markedly different
from each other. At a finer level, spectra from specific molecules of each type may
also demonstrate differences, but those will be much finer than the differences be-
S. Biswas et al.
predictions of acquired data can be made. While the propagation of light through
optical components can be modeled using methods available from other spectral regions, the interaction of light with the sample is an area of continuing development.
While specific geometries such as spheres, cylinders or slabs can be modeled, the
general case remains to be shown in an efficient manner. Nevertheless, the framework presented forms the basis for physics-based modeling of any sample. though
Em theory is rigorous and can provide the most detailed picture of light-matter
interactions, its implementation and interpretation of results are both significantly
complex. Recently, a conceptually simpler approach has been proposed to understand the optics of microscopy using scalar wave theory [24]. In this approach, the
major difference is that the wave propagation is simplified and computations can
potentially be faster. We invoked the same structural model of the sample as in
the complete Em treatment, in terms of decomposition into Fourier frequencies.
together, the two approaches should be useful in describing light matter interactions in a number of sample geometries and configurations [45, 46].
16.3.4 Applications of IR Imaging in Solid Tumor Histopathology
and Corresponding Normal Tissues
In this chapter, we do not aim to thoroughly cover every example of application of
IR imaging for histopathology. We also do not cover the older work using single
elements detectors. many excellent reviews exist to provide the reader a guidance
of the development of the field and a comprehensive view of the variety of possible
applications. Instead, we focus here on providing an overview and a flavor of the
possibilities using IR imaging. We also point to salient aspects of the process and
key features of any diagnostic protocol using illustrative examples.
16.3.4.1 Basic Concept of Using Absorption Spectra for Medical Diagnostics
Biological samples are composed of several complex small molecule and macromolecular assemblies, including proteins, nucleic acids, lipids and carbohydrates, as
well as constituent small molecules [47]. very rarely (with notable exceptions such
as collagen) do spectra reflect compositions of any of these constitutents directly.
hence, IR absorption spectra contain this entire diversity, simultaneously making
them both very sensitive to all constituents and exceptionally non-specific to any
particular molecule. Spectra comprise of some significant, spectral characteristic
features, however, and significant “mesoscale” chemistry can be examined as, in
general, classes of compounds can be distinguished. For example, Fig. 16.7 demonstrates the spectra from different classes of compounds that make up the bulk
of human cells and tissues. Spectra from these four classes are markedly different
from each other. At a finer level, spectra from specific molecules of each type may
also demonstrate differences, but those will be much finer than the differences be-