Towards an improved assignment of spectral features in tissue modulated non-invasive Raman spectroscopy of human fingertips

We have constructed a new LighTouch TM device having improved measurement and control of applied force and tissue position in noninvasive probing of human volar side fingertip capillary beds in vivo using near infrared Raman spectroscopy. These improvements have translated into improved capacity to observe and classify the behavior of specific spectral features under tissue and pulse modulation. Using this and other measurements on various other samples in vitro have demonstrated the validity of associating specific functions of the observed spectra with medically relevant quantities like hematocrit and bicarbonate ion. In addition we can say more about how much of the observed tissue modulated spectra must be associated with a "modulation defect" resulting from various errors affecting the accuracy and precision in subtraction of static tissue contributions.