Noninvasive Alcohol Testing Using Diffuse Reflectance Near-Infrared Spectroscopy

Abstract

A diffuse reflectance near-infrared (NIR) spectrometer was evaluated as a noninvasive alternative to breath and blood measurements for in vivo alcohol testing. A hybrid partial least squares (PLS) calibration was constructed using a combination of in vivo and in vitro spectral data. This model was subsequently evaluated for its performance in quantifying alcohol concentrations in vivo using a prospective validation study involving subjects who did not participate in the calibration. The validation study entailed induction of alcohol excursions in ten human subjects and comparison of the noninvasive NIR alcohol measurements to blood and breath alcohol measurements. Blood and breath alcohol measurements were performed at the time of each noninvasive NIR measurement (N = 372), establishing the noninvasive NIR measurement standard error relative to blood alcohol at 4.9 mg/dL (0.0049%). Assessment of the hybrid calibration model's sensitivity and selectivity provided strong evidence that the hybrid calibration yielded measurements that were both sensitive to alcohol and independent of other absorbing analytes in human tissue.

Comparison of spectroscopically measured tissue alcohol concentration to blood and breath alcohol measurements

“…where a is the absorption coefficient at wave number , l i is the path length through tissue of photon i as determined by Monte Carlo simulation, 14 and N is the total number of collected photons. The effective path length, l ef f , depends on the scattering properties of skin, the geometry of the tissue optical probe ͑both of which are incorporated into the determination of l in the Monte Carlo simulation͒, and the absorptivities of major absorbers, a , which are dominated by water in tissue measurements.…”

“…Additional discussion and investigations of the NIR instrumentation, calibration method, and initial characterization of the method's sensitivity and selectivity for alcohol can be found elsewhere. [13][14][15] At this point, it is worth briefly discussing the properties of the noninvasive tissue alcohol measurement in this work relative to another recently developed technology. On first glance, one might assume that "tissue" and "dermal" alcohol equate to "transdermal" alcohol.…”

Review of Technology to Prevent Alcohol-Impaired Crashes (TOPIC)

“…Initial published data [53] comparing estimates of BAC made with tissue spectroscopy against true BAC show excellent correlation, as shown in Figure 5-1. This data was based on measurements at 28 different wavelengths over a period of 30 seconds.…”

“…A regression analysis of the reflectance spectrum from the subject's skin is performed against a matrix of a few hundred spectra from samples with known BACs. The invention of this technology is described in two articles in the Journal of Applied Spectroscopy published in 2005 by Trent Ridder et al of InLight Solutions, Inc. [52,53] The physics and engineering of tissue spectroscopes are complex; a convenient summary is provided in a paper by Simon Ghionea. [54] InLight Solutions has licensed its patents and technology to its subsidiaries, Lumidigm, Inc., and TruTouch Technologies, Inc. Lumidigm is developing low-cost biometric sensors for personal identification and may be able to derive useful measures of alcohol concentration from them, although that is not the primary objective of its current development efforts.…”

Comparison of spectroscopically measured finger and forearm tissue ethanol concentration to blood and breath ethanol measurements

“…(1)] through tissue of a given optical probe design. 1,23,24 Similarly, Monte Carlo simulations were used in this work to provide insights into the differences in effective path-length between the two optical probe designs under investigation. The effective path-length is defined as:…”