The absolute quantified measurement of haemoglobin skin blood saturation from collected reflectance spectra of the skin is complicated by the fact that the blood content of tissues can vary both in the spatial distribution and in the amount. These measurements require an understanding of which vascular bed is primarily responsible for the detected signal. Knowing the spatial detector depth sensitivity makes it possible to find the best range of different probe geometries for the measurements of signal from the required zones and group of vessels inside the skin. To facilitate this, a Monte Carlo simulation has been developed to estimate the sampling volume offered by fibre-optic probes with a small source-detector spacing (in the current report 250 microm, 400 microm and 800 microm). The optical properties of the modelled medium are taken to be the optical properties of the Caucasian type of skin tissue in the visible range of the spectrum. It is shown that, for a small source-detector separation (800 microm and smaller), rough boundaries between layers of different refractive index can play a significant role in skin optics. Wavy layer interfaces produce a deeper and more homogeneous distribution of photons within the skin and tend to suppress the direct channelling of photons from source to detector. The model predicts that a probe spacing of 250 microm samples primarily epidermal layers and papillary dermis, whereas spacings of 400-800 microm sample upper blood net dermis and dermis.

Variations in the amplitude and phase of diffuse photon density waves is known to yield important information about the structural properties of turbid media, such as the scattering and absorption coefficients. Information on the dynamical properties of turbid media may be obtained from the temporal fluctuations of light fields emanating from the media. In this contribution, we demonstrate that variations in temporal correlation functions of the temporal intensity fluctuations of different speckles of light can be used to derive information about the spatially varying dynamical properties of turbid media. We first present a diffusion for the temporal correlation function for systems where the dynamics are governed by Brownian motion and shear and random flow. We demonstrate the validity of the correlation diffusion for heterogeneous systems by comparing the theoretical results with experimental results for systems governed by different dynamical processes, e.g. flow. As an illustration of the usefulness of this correlation technique to biomedical optics, we discuss the application of this technique to diagnosing the thickness of burned tissue. The correlation diffusion is an important, unique tool for analyzing the complex dynamical signals that arise from heterogeneous biological systems.

The extension of the photon correlation spectroscopy (PCS) in multiple scattering regime, so-called diffusing wave spectroscopy (DWS) was employed to the study of blood samples. Multiple scattered light from a helium-neon (He-Ne) laser beam incident on the blood samples was detected by a photomultiplier, and both the temporal autocorrelation intensity functions g 2(tau) and power spectra S(omega) were measured by a spectrum analyzer. The potentials of using DWS for the qualitative and quantitative determination of the structural characteristics of the blood elements were studied experimentally. The experimental studies made, permits the use of DWS for blood cells monitoring in a multiple scattering regime. This paper describes our initial attempts at applying DWS to the study of the discrete blood samples of both healthy donors and patients with the cardiac ischemia. The subsequent experiments provide a verification of DWS of blood cells shape monitoring under multiple scattering.