20 Medical Applications of NIR Spectroscopy
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cytochromes to mention a few compounds of great interest especially for medical
practice. Some applications have been established in form of valuable sensors for
patient monitoring with the pulse oximeter, representing the most prominent device
for measuring arterial oxygen saturation through oxy and deoxyhemoglobin quantification. Further in vivo medical spectroscopy was initiated by Frans Jöbsis in
the 1970ies, who reported on the high transparency of brain tissue in the optical
window to be used for non-invasive measurements on vital physiological parameters
[1]. The groups around David Delpy and Brittan Chance had brought much progress
into the field of analyte quantification in near-infrared tissue spectroscopy, exploiting
different spectral signatures of redox-active substances for brain and muscle oximetry
[2, 3]. Finally, different techniques were developed for functional imaging used in
monitoring brain activities.
All aforementioned near-infrared spectroscopic applications are based on absorption measurements. Quite different are applications with fluorescence spectroscopy,
which is finding more interest in biomedical applications such as for sensitive analyte
detection using immunoassays with according fluorescent labels and for bio-imaging
by achieving better contrast.
The importance of this chapter is to provide an overview of the different areas
with applications of NIR spectroscopy in the medical sciences, including clinical
chemistry with its aim for diagnostics using mainly bodyfluids, non-invasive sensing
for monitoring dynamic physiological states, and processes and imaging of organs
such as skin, brain, heart and others.
20.2 Applications in Clinical Chemistry
Early clinical chemistry applications using near-infrared spectroscopy have followed
research work from several groups worldwide, who had started with mid-infrared
(MIR) spectroscopy. Due to the high information content especially of the fingerprint
region, biofluid analysis could be achieved for analytes of “high” concentrations as
mentioned above. The fascination about the spectroscopic methods came from the
fact that these worked fast and without reagents and could be exploited for multianalyte applications. Therefore, it had attracted also companies involved in medical
diagnostics and sensing, mainly for the development of analyzer instrumentation.
The rationale behind medical diagnosis by spectroscopy is based on the fact that
diseases are accompanied by changes in the biochemistry of the cells and tissues
within the organs in our body. Deviations from homeostasis can thus be monitored
by analytical spectroscopy of body fluids with physiological parameters usually fluctuating for the healthy state around a normal range. Since spectroscopic methods,
in particular vibrational spectroscopy with infrared, near-infrared and Raman, can
provide information on biological molecules like proteins and peptides, nucleic acids,
carbohydrates, lipids and others, it is a useful tool for medical diagnostics. There are
some restrictions for the near-infrared, as mid-infrared and Raman spectroscopy
make use of fingerprint region information, which cover many low-wavenumber
439
cytochromes to mention a few compounds of great interest especially for medical
practice. Some applications have been established in form of valuable sensors for
patient monitoring with the pulse oximeter, representing the most prominent device
for measuring arterial oxygen saturation through oxy and deoxyhemoglobin quantification. Further in vivo medical spectroscopy was initiated by Frans Jöbsis in
the 1970ies, who reported on the high transparency of brain tissue in the optical
window to be used for non-invasive measurements on vital physiological parameters
[1]. The groups around David Delpy and Brittan Chance had brought much progress
into the field of analyte quantification in near-infrared tissue spectroscopy, exploiting
different spectral signatures of redox-active substances for brain and muscle oximetry
[2, 3]. Finally, different techniques were developed for functional imaging used in
monitoring brain activities.
All aforementioned near-infrared spectroscopic applications are based on absorption measurements. Quite different are applications with fluorescence spectroscopy,
which is finding more interest in biomedical applications such as for sensitive analyte
detection using immunoassays with according fluorescent labels and for bio-imaging
by achieving better contrast.
The importance of this chapter is to provide an overview of the different areas
with applications of NIR spectroscopy in the medical sciences, including clinical
chemistry with its aim for diagnostics using mainly bodyfluids, non-invasive sensing
for monitoring dynamic physiological states, and processes and imaging of organs
such as skin, brain, heart and others.
20.2 Applications in Clinical Chemistry
Early clinical chemistry applications using near-infrared spectroscopy have followed
research work from several groups worldwide, who had started with mid-infrared
(MIR) spectroscopy. Due to the high information content especially of the fingerprint
region, biofluid analysis could be achieved for analytes of “high” concentrations as
mentioned above. The fascination about the spectroscopic methods came from the
fact that these worked fast and without reagents and could be exploited for multianalyte applications. Therefore, it had attracted also companies involved in medical
diagnostics and sensing, mainly for the development of analyzer instrumentation.
The rationale behind medical diagnosis by spectroscopy is based on the fact that
diseases are accompanied by changes in the biochemistry of the cells and tissues
within the organs in our body. Deviations from homeostasis can thus be monitored
by analytical spectroscopy of body fluids with physiological parameters usually fluctuating for the healthy state around a normal range. Since spectroscopic methods,
in particular vibrational spectroscopy with infrared, near-infrared and Raman, can
provide information on biological molecules like proteins and peptides, nucleic acids,
carbohydrates, lipids and others, it is a useful tool for medical diagnostics. There are
some restrictions for the near-infrared, as mid-infrared and Raman spectroscopy
make use of fingerprint region information, which cover many low-wavenumber