A strategy for quantitative spectral imaging of tissue absorption and scattering using light emitting diodes and photodiodes

Abstract

A diffuse reflectance spectroscopy system was modified as a step towards miniaturization and spectral imaging of tissue absorption and scattering. The modified system uses a tunable source and an optical fiber for illumination and a photodiode in contact with tissue for detection. Compared to the previous system, it is smaller, less costly, and has comparable performance in extracting optical properties in tissue phantoms. Wavelength reduction simulations show the feasibility of replacing the source with LEDs to further decrease system size and cost. Simulated crosstalk analysis indicates that this evolving system can be multiplexed for spectral imaging in the future.

A low-cost, portable, and quantitative spectral imaging system for application to biological tissues

“…The SNR was calculated by taking the mean and dividing by the standard deviation of these measurements. This SNR measurement from the compact spectral imaging system was compared to the previously measured SNR by Lo et al [31]. The SNR reported in that study was measured on a benchtop diffuse reflectance spectroscopy system with instrumentation identical to the clinical spectral imaging system.…”

“…1(B)] involved replacing the spectrograph in the clinical system with a simple 8- slot filter wheel on the illumination end. Instead of a 2D CCD, silicon photodiodes were used for detection by multiplexing the previous single-pixel design reported in the publication by Lo et al into a 9-pixel 3x3 matrix [31]. The light source for the compact optical spectral imaging system is a broadband 350-Watt Xenon arc lamp (MAX-302, Asahi Spectra).…”

“…In the end, the collected data comprised of an 8 wavelength spectral measurement from each of the nine pixels. The impact of measuring with a reduced number of wavelengths on the extraction of optical properties was previously addressed and investigated by Lo et al [31]. It was demonstrated, through phantom experiments and simulations, that using as few as 5 to 8 discrete wavelengths with a FWHM bandwidth of 20 nm was adequate for extracting absorption and scattering properties of phantoms containing polystyrene spheres and hemoglobin.…”

“…Each photodiode serves as a single pixel of the spectral imaging system and can be scaled for different sizes and pixel densities by simply scaling the size and number of photodiodes, respectively. Previously, we demonstrated that a silicon photodiode with a centrally placed optical fiber coupled to a broadband source provides excellent signal-to-noise ratio (SNR) for quantitative measurements of tissue absorption and scattering from diffuse reflectance measurements of tissue mimicking liquid phantoms [31,32]. The goal of this paper is to extend this proof-ofconcept device to a multi-pixel quantitative optical spectral imaging system with at minimum, similar performance characteristics to the current clinical spectral imaging system used in the 100-patient clinical study.…”

Diffuse reflectance spectroscopy of human liver tumor specimens - towards a tissue differentiating optical biopsy needle using light emitting diodes

“…Several groups have recently concentrated on the progress of tissue differentiating methods using only a few, but representative, spectral bands in DRS [22][23][24][25]. The results suggest that this simplification is not necessarily associated with a loss in classification accuracy.…”