Deoxyhemoglobin, applications

Although algorithms are often merely referred to peripherally, in an article by Piantadosi et al., the algorithms are the main topic of discussion [163]. Using a half dozen research papers (by other workers) as examples, the authors discuss the approaches used in NIR, citing both the hardware and the software. Most of the practical applications were on blood and the analytes were hemoglobin, deoxyhemoglobin, etc. 

In vivo MR has been extensively used in the study of the human brain, its fiinctions and metabolism. MRI has a significant role to play in our understanding of how the brain works. In the last few years the most interesting application of MRI is the construction of functional maps of the brain (functional MRI, fMRI). In response to brain activation, an increase in the proportion of oxyhemoglobin with respect to the deoxyhemoglobin takes place. 

One early report of NIR for diagnostic applications came from Jobsis in 1977 [22]. He monitored the degree of oxygenation of certain metabolites. Later, Ozaki et al. [23] examined venal blood to determine the level of deoxyhemoglobin. Using a miniature integrated-sphere, the back of the hand was illuminated. The 760-nm band in the spectrum correlated well with deoxyhemoglobin. 

Earlier reports focused on the use of optical absorption properties of tissues for clinical applications (Wilson and Jacques, 1990). An example is blood oximetry, which is widely used clinically to monitor continuously blood oxygenation with the help of an optical fiber probe as described in the previous section. In this method the diffuse reflectance also collected by the fiber is analyzed based on the differences in the absorption bands of oxy and deoxyhemoglobins. Diffuse reflectance from the skin can be used to monitor changes induced, for example, by the UV radiation. Endoscopic reflectance spectroscopy from mucosa of the gastrointestinal tract has been used to determine blood content and oxygenation (Leung et al, 1989). 

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