Modelling the sampling volume for skin blood oxygenation measurements

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 μm, 400 μm and 800 μm). 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 μm 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 μm samples primarily epidermal layers and papillary dermis, whereas spacings of 400–800 μm sample upper blood net dermis and dermis.

[1]  Francis A. Duck,et al.  Optical Properties of Tissue including Ultraviolet and Infrared Radiation , 1990 .

[2]  M. H. Koelink,et al.  Laser Doppler velocimetry and Monte Carlo simulations on models for blood perfusion in tissue. , 1995, Applied optics.

[3]  S. Arridge.  Photon-measurement density functions. Part I: Analytical forms. , 1995, Applied optics.

[4]  J. Schmitt,et al.  Optical scattering properties of soft tissue: a discrete particle model. , 1998, Applied optics.

[5]  D K Harrison,et al.  Use of lightguide spectrophotometry to quantify skin oxygenation in a variable model of venous hypertension , 1995, The British journal of surgery.

[6]  R. Steiner,et al.  Spatially resolved absolute diffuse reflectance measurements for noninvasive determination of the optical scattering and absorption coefficients of biological tissue. , 1996, Applied optics.

[7]  L. Goldsmith.  Physiology, biochemistry, and molecular biology of the skin , 1991 .

[8]  M. Kohl,et al.  Near-infrared optical properties of ex vivo human skin and subcutaneous tissues measured using the Monte Carlo inversion technique. , 1998, Physics in medicine and biology.

[9]  P. Saint-Pierre,et al.  Optimal times for constrained nonlinear control problems without local controllability , 1997 .

[10]  F. Duck.  Physical properties of tissue , 1990 .

[11]  Howard I. Maibach,et al.  Models in dermatology , 1987 .

[12]  B CHANCE,et al.  Spectrophotometry of intracellular respiratory pigments. , 1954, Science.

[13]  A. Young,et al.  Chromophores in human skin. , 1997, Physics in medicine and biology.

[14]  Gf Odland,et al.  The structure of the skin , 1991 .

[15]  P. Corcuff,et al.  Morphometry of human epidermis in vivo by real-time confocal microscopy , 2004, Archives of Dermatological Research.

[16]  L Wang,et al.  MCML--Monte Carlo modeling of light transport in multi-layered tissues. , 1995, Computer methods and programs in biomedicine.

[17]  John A. Parrish,et al.  Optical Properties of Human Skin , 1982 .

[18]  David H. Sliney,et al.  Optical Radiation Hazards to the Skin , 1980 .

[19]  M. Schweiger,et al.  Theoretical and experimental investigation of near-infrared light propagation in a model of the adult head. , 1997, Applied optics.

[20]  J. B. Dawson,et al.  A theoretical and experimental study of the optical properties of in vivo skin , 1981 .

[21]  Lihong V. Wang,et al.  Monte Carlo Modeling of Light Transport in Tissues , 1995 .

[22]  Valery V. Tuchin,et al.  Tissue optics, light distribution, and spectroscopy , 1994 .

[23]  A. Jakobsson,et al.  Prediction of sampling depth and photon pathlength in laser Doppler flowmetry , 1993, Medical and Biological Engineering and Computing.

[24]  A. Welch,et al.  A review of the optical properties of biological tissues , 1990 .

[25]  S. A. Prahl,et al.  A Monte Carlo model of light propagation in tissue , 1989, Other Conferences.

[26]  Gert Nilsson,et al.  Monte Carlo simulations of light interaction with blood vessels in human skin in the red-wavelength region , 1998, Photonics West - Biomedical Optics.

[27]  Alfano,et al.  When does the diffusion approximation fail to describe photon transport in random media? , 1990, Physical review letters.

[28]  R. Doornbos,et al.  The determination of in vivo human tissue optical properties and absolute chromophore concentrations using spatially resolved steady-state diffuse reflectance spectroscopy. , 1999, Physics in medicine and biology.

[29]  M. L. Godeau,et al.  [The skin]. , 1977, Soins; la revue de reference infirmiere.

[30]  J. S. Lee,et al.  Atmospheric scattering of middle uv radiation from an internal source. , 1978, Applied optics.

[31]  Max Born,et al.  Principles of optics - electromagnetic theory of propagation, interference and diffraction of light (7. ed.) , 1999 .

[32]  C. J. Everett,et al.  A practical manual on the Monte Carlo method for random walk problems , 1960 .

[33]  S. Arridge,et al.  A Monte Carlo investigation of optical pathlength in inhomogeneous tissue and its application to near-infrared spectroscopy. , 1993, Physics in medicine and biology.