Investigation of the specificity of Raman spectroscopy in non-invasive blood glucose measurements |
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Authors: | Narahara Chari Dingari Ishan Barman Gajendra P Singh Jeon Woong Kang Ramachandra R Dasari Michael S Feld |
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Institution: | (1) George R. Harrison Spectroscopy Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; |
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Abstract: | Although several in vivo blood glucose measurement studies have been performed by different research groups using near-infrared
(NIR) absorption and Raman spectroscopic techniques, prospective prediction has proven to be a challenging problem. An important
issue in this case is the demonstration of causality of glucose concentration to the spectral information, especially as the
intrinsic glucose signal is smaller compared with that of the other analytes in the blood–tissue matrix. Furthermore, time-dependent
physiological processes make the relation between glucose concentration and spectral data more complex. In this article, chance
correlations in Raman spectroscopy-based calibration model for glucose measurements are investigated for both in vitro (physical
tissue models) and in vivo (animal model and human subject) cases. Different spurious glucose concentration profiles are assigned
to the Raman spectra acquired from physical tissue models, where the glucose concentration is intentionally held constant.
Analogous concentration profiles, in addition to the true concentration profile, are also assigned to the datasets acquired
from an animal model during a glucose clamping study as well as a human subject during an oral glucose tolerance test. We
demonstrate that the spurious concentration profile-based calibration models are unable to provide prospective predictions,
in contrast to those based on actual concentration profiles, especially for the physical tissue models. We also show that
chance correlations incorporated by the calibration models are significantly less in Raman as compared to NIR absorption spectroscopy,
even for the in vivo studies. Finally, our results suggest that the incorporation of chance correlations for in vivo cases
can be largely attributed to the uncontrolled physiological sources of variations. Such uncontrolled physiological variations
could either be intrinsic to the subject or stem from changes in the measurement conditions. |
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