Multispectral Imaging of Metabolic Fluorophores: Comparing In Vivo and Fresh Ex Vivo Tissue.

The enhanced uptake of glucose by cancer cells via aerobic glycolysis occurs when the lactic acid pathway is favored over the citric acid cycle. The lactic acid cycle in cancer cells influences the cytosolic concentration of metabolic fluorophores including NADH (the reduced form of nicotinamide adenine dinucleotide) and flavin adenine dinucleotide (FAD). In particular, the literature has shown that breast cancer influences the relative magnitude of fluorescence from NADH and FAD. A multispectral imaging system has been developed for rapid non-destructive imaging of intrinsic fluorescence in tissue. This paper compares in vivo data to fresh ex vivo data gathered as a function of time in mouse models. The data indicate that, if measured within 30 min of excision, a cancer diagnosis in fresh ex vivo tissue correlates with a cancer diagnosis in in vivo tissue. These results justify a plan to evaluate fresh ex vivo human tissue to quantify the sensitivity and specificity of the multispectral system.

Optical and physical properties of annealed amorphous niobium oxide thin films.

The physical and optical properties of coatings deposited using physical vapor deposition techniques exhibit changes during post deposition annealing. Optical properties including the index of refraction and spectral transmission vary when coatings are annealed. Physical and mechanical properties such as thickness, density, and stress are also impacted by annealing. In this paper, we study the source of these changes by examining the impact of 150-500°C annealing on N b 2 O 5 films deposited using thermal evaporation and reactive magnetron sputtering. Models based on the Lorentz-Lorenz equation and potential energy considerations explain the data, and rationalize conflicts between previously reported results.

Real-time detection of breast cancer at the cellular level.

Novel optoelectronic instrumentation has been developed for the multispectral imaging of autofluorescence emitted by metabolic fluorophores. The images resolve individual cells while spectra are collected for each pixel in the images. These datacubes are generated at a rate of 10 per second-fast enough for surgical guidance. The data is processed in real time to provide a single color-coded image to the surgeon. To date, the system has been applied to fresh, ex vivo, human surgical specimens and has distinguished breast cancer from benign tissue. The approach is applicable to in vivo measurements of surgical margins and needle-based optical biopsies. Ongoing work demonstrates that the system has great potential for translation to a hand-held probe with high sensitivity and specificity.

High-speed multispectral confocal biomedical imaging.

A new approach for generating high-speed multispectral confocal images has been developed. The central concept is that spectra can be acquired for each pixel in a confocal spatial scan by using a fast spectrometer based on optical fiber delay lines. This approach merges fast spectroscopy with standard spatial scanning to create datacubes in real time. The spectrometer is based on a serial array of reflecting spectral elements, delay lines between these elements, and a single element detector. The spatial, spectral, and temporal resolution of the instrument is described and illustrated by multispectral images of laser-induced autofluorescence in biological tissues.

Scattering from nonuniform tilted fiber gratings.

Using volume current analysis, we describe the scattering from intracore fiber gratings with various nonuniformities and find that effects of cross-sectional and longitudinal variations can be roughly decoupled. We show that cross-sectional asymmetry affects the azimuthal pattern of scattering around the fiber and find good agreement with real gratings exhibiting UV-induced grating asymmetry across the core. We also show that longitudinal variations affect the spread of scatter angles with respect to the fiber axis, and this angular spread depends on the Fourier transform of the profiles of the grating period, the average index, and the index modulation of the grating.

Influence of the longitudinal mode field in grating scattering from weakly guided optical fiber waveguides.

We measured the polarization dependence of light scattered from a tilted fiber grating and found disagreement with previous volume-current perturbation analysis. However, by including the longitudinal E field of the guided wave we were able to obtain good agreement, demonstrating that, although it is small, this component cannot be neglected when scattering of weakly guided waves is considered. A first-order approximation formula for the polarization dependence was also obtained and is shown to be accurate within most of the resonance band of scattering.