Applications of Raman Spectroscopy in Medicine

The sensitivity of the method is illustrated by Fig. 15.26, which depicts the time variation of the CO2, O2, and N2 concentration in the exhaled air of a human patient. Note the variation of the concentrations with changing breathing periods. The technique can be used routinely in clinical practice for anesthetic control during operations and obviously also for alcohol tests of car drivers. 

Instead of Raman spectroscopy, infrared absorption spectroscopy can be used in cases of infrared-active transition, for example, for CO, CO2, NO, and CH4. With cavity ring-down spectroscopy a high sensitivity can be reached and spurious molecular concentrations resulting from fermentation processes in the stomach can still be detected [15.152]. 

During the operation of a patient, the optimum concentration and composition of narcotic gases can be indicated by the composition of the respiratory gases, i.e. with the concentration ratio of N2 02 C02. This ratio can be measured in vivo with Raman spectroscopy [15.119]. The gas flows through a cell which is placed inside a multipass arrangement for an argon-laser beam (Fig. 15.21). In a plane perpendicular to the beam axis several detectors with special spectral filters are arranged. Each detector monitors a selected Raman line which allows the simultaneous detection of all molecular components of the gas. 

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An interesting application of Raman spectroscopy in medicine is the in vivo detection of breast cancer [382]. This technique is very promising because the spatial and spectral resolution allows the localization of spots with a different molecular composition and is able to distinguish between benign and malign cancer cells. 

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