A portable multi-wavelength near infrared photon time-of-flight instrument for measuring light scattering

摘要

Measured light scattering properties can be used to improve quantitative spectroscopic analyses of turbid samples. Instruments currently used to measure scattering coefficients are not optimised for portability. A hand-held, dual-wavelength instrument was developed and validated for rapid measurement of reduced scattering coefficients in tandem with near infrared spectra. Tissue simulating phantoms composed of Intralipid and dye were used to model clinically relevant optical properties. Time-dependent intensity profiles of diffusely reflected near infrared pulsed laser light were collected from phantoms and processed to estimate scattering coefficients. In turbid solutions, optical scattering was measured at 850 nm and 905nm with coefficients of variation of 14.1% and 11.6% over a clinically-relevant reduced scattering coefficient range of 1 mm~(-1) to 6mm~(-1). This dual-wavelength scattering measurement provides a practical method for measuring optical scattering. A 35% precision improvement in quantification of an absorbing dye is shown by incorporating the measured reduced scattering coefficients when processing NIR spectra. We discuss the new instrument, methods for estimating the scattering coefficient from the measured temporal profiles and, finally, how the reduced scattering coefficient is used to correct NIR measurements. Correction of near infrared spectra using optical scattering measurements offers one direction for improving practical non-invasive biomedical quantification techniques.