Mid-infrared photoacoustic spectroscopy using a quantum cascade laser for non-invasive blood component analysis

Abstract

Abstract We developed a photoacoustic spectroscopic method using mid-IR light for non-invasive analysis of blood components in living bodies. The ultra-low-volume photoacoustic cell enabled highly sensitive measurement, and, using a glucose-containing gel, the photoacoustic spectrum showed an almost linear relationship with the absorption spectrum. The optimum modulation frequency was determined both theoretically and experimentally using the photoacoustic spectra of glucose gels obtained at different modulation frequencies. The photoacoustic spectrum of the human wrist was measured at the same time as blood glucose levels were measured by blood sampling. Discriminant analysis of whether the blood glucose level was higher or lower than 130 mg dl−1 was relatively accurate (70.8%). The wavelengths used for discrimination were those absorbed by insulin and lipids, the levels of which change according to the blood glucose levels, and that absorbed by glucose.