Noninvasive, in vivo, tissue modulated near infrared vibrational spectroscopic study of mobile and static tissues: Blood chemistry

We report the first noninvasive Raman spectra of in vivo human blood. `Tissue modulation' involves the use of thermal and/or mechanical stimulus to produce particular spatiotemporal distributions of mobile tissues, i.e. capillary blood, among nonmobile tissues, i.e. epidermis. Using this approach we have obtained three mutually independent lines of evidence, which unequivocally associate Raman spectra we have obtained with human blood. These spectra compare well with published spectra from other researchers of in vitro human blood. The results of a recent clinical study comparing our noninvasive in vivo spectroscopic measurements with simultaneous conventional in vitro measurements clearly demonstrate the efficacy of the tissue modulation approach. These results will be discussed in the context of noninvasive monitoring of a variety of analytes, i.e. glucose.