Raman spectroscopy, blood, fluorescence, tissues, biological
Tissue modulation refers to using external stimuli such as mechanical pressure and temperature to produce various spatiotemporal distributions of blood and conceivably other fluids in tissues. Having the capacity to execute tissue modulation1 allows forms of difference spectroscopy to be used to isolate spectroscopic signals from specific components of the tissues noninvasively and in vivo. In the case of human fingertips we can think of the tissues present in the probed volume as being static tissue, plasma and red blood cells (RBCs). Static tissues deform under mechanical pressure based tissue modulation and the only possible fluid motions2 involve plasma and RBCs. Figure 1 shows the difference spectrum produced, negative modulated fluorescence and positive modulated Raman, when simultaneously a small amount of RBCs move into and some plasma is move out of the probed volume. We present spectra for all limiting forms of tissue modulation and show prototypical spectra that include fluorescence Rayleigh/Mie and Raman scattering.
Deng, Bin; Goodisman, Jerry; Shaheen, George; Bussjager, Rebecca J.; and Chaiken, Joseph, "Noninvasive, In-Vivo, Tissue Modulated Near Infrared Spectroscopy of Fingertips: Resonance Raman Spectrum of Human Hemoglobin" (2010). Chemistry - All Scholarship. 74.
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