Concentration changes of haemoglobin and cytochromes indicative of tissue perfusion and oxygenation can be quantitatively evaluated from near-infrared (NIR) measurements of absorption and optical pathlength through tissue. The accuracy of such measurements is limited as current bedside instrumentation cannot measure optical pathlength. Using a recently developed phase-resolved spectroscopic tec...

www.lcgceurope.com Introduction The quality of photometric detection in capillary electrophoresis (CE) can be characterized by detector sensitivity and linearity. From the Beer-Lambert law it follows that the detector sensitivity is directly proportional to the detection pathlength. However, this might not be easy to estimate with cells with geometries that result in a range of possible pathlen...

Photon pathlength distributions as a function of the number of scattering events in cylindrical turbid samples are studied using a polarization-sensitive Monte Carlo model with linearly polarized light input. Sample scattering causes extensive depolarization, yielding a photon field comprised of polarized and depolarized sub-populations. It is found that the pathlength of polarization-preservin...

Quantitation of near infrared spectroscopic data in a scattering medium such as tissue requires knowledge of the optical pathlength in the medium. This can now be estimated directly from the time of flight of picosecond length light pulses. Monte Carlo modelling of light pulses in tissue has shown that the mean value of the time dispersed light pulse correlates with the pathlength used in quant...

Near-infrared spectroscopy (NIRS) is a noninvasive optical technique to monitor cerebral oxygen saturation at the bedside. Despite its applicability, NIRS has had limited clinical use because of concerns about accuracy, noted by intersubject variability in slope and intercept of the line between NIRS- and weighted-average arterial-cerebrovenous saturation (SMO2). This study evaluated transcrani...

Resolving for changes in concentration of tissue chromophores in the human adult brain with near-infrared spectroscopy has generally been based on the assumption that optical scattering and pathlength remain constant. We have used a novel hybrid optical spectrometer that combines multi-distance frequency and broadband systems to investigate the changes in scattering and pathlength during a Vals...

Gas in scattering media absorption spectroscopy (GASMAS) has been extensively studied and applied during recent years in, e.g., food packaging, human sinus monitoring, gas diffusion studies, and pharmaceutical tablet characterization. The focus has been on the evaluation of the gas absorption pathlength in porous media, which a priori is unknown due to heavy light scattering. In this paper, thr...

The geometry of the cortex and nucleus of excised human lenses was determined by photography and dissection. Samples of the cortex and nucleus were measured spectrophotometrically to allow determination of light loss through the whole lens and the light loss per unit pathlength. It was concluded that the reduction of short wavelength light transmission with increasing age is due to two processe...

Using optical methods through a closed cranial window over the rat primary sensory cortex in chloralose/urethane-anesthetized rats we evaluated the time course of oxygen delivery and consumption in response to a physiological stimulus (whisker deflection). Independent methodological approaches (optical imaging spectroscopy, single fiber spectroscopy, oxygen-dependent phosphorescence quenching) ...

6 We use matrix analysis to study a cycle plus random, uniform shortcuts—the classic small world model. 7 For such graphs, in addition to the usual edge and vertex information there is an underlying metric that 8 determines distance between vertices. The metric induces a natural greedy algorithm for navigating between 9 vertices and we use this to define a pathlength. This pathlength definition...