<title>Near-infrared optical properties of ex-vivo human skin and subcutaneous tissues using reflectance and transmittance measurements</title>

Abstract

The vast majority of "non-invasive" measurements of human tissues using near infrared spectroscopy rely on passing light through the dermis and subdermis of the skin. Accurate knowledge of the optical properties of these tissues is essential to put into models of light transport and predict the effects of skin perfusion on measurements of deep tissue. Additionally, the skin could be a useful accessible organ for non-invasively determining the constituents ofblood flowing though it.Samples of abdominal human skin (including subdermal tissue) were obtained from either post mortem examinations or plastic surgery. The samples were separated into a dermal layer (epidermis and dermis, 1 .5 to 2 mm thick), and a sub-cutaneous layer comprised largely of fat. They were enclosed between two glass coverslips and placed in an integrating sphere to measure their reflectance and transmittance over a range of wavelengths from 600 to 1000 urn. The reflectance and transmittance values were converted into average absorption and reduced scattering coefficients by comparison with a Monte Carlo model of light transport. Improvements to the Monte Carlo model and measurement technique removed some previous uncertainties.The results show excellent separation of reduced scattering and absorption coefficient, with clear absorption peaks of hemoglobin, water and lipid. The effect oftissue storage upon measured optical properties was investigated.

Quantitative spatially resolved measurement of tissue chromophore concentrations using photoacoustic spectroscopy: application to the measurement of blood oxygenation and haemoglobin concentration

“…The intralipid (of lipid concentration 1.5%) had an absorption coefficient of 0.05 mm −1 and a reduced scattering coefficient of approximately 1.3 mm −1 at 975 nm. These values are similar to those found in biological tissue (Troy et al 1996, Simpson et al 1997. For certain experiments, a small amount of blood (representing the capillary bed) and a near-infrared dye (ADS780WS) were also added to the intralipid suspension.…”

Clinical Feasibility of Diffuse Optical Spectroscopic Imaging for Sarcoma

“…With the instrumentation improvements developed in this project and further characterization of tissues, I remain optimistic that a prognostic marker will be found. (Firbank et al, 1993) bone matrix bovine 658 0.007 3 (Pifferi et al, 2004) 1.32 (Firbank et al, 1993) Continued on next page 1.25 (Simpson et al, 1997) abdominal subdermal tissue (fat) human 650 0.011 1.2 (Simpson et al, 1997) abdominal subdermal tissue (fat) human 670 0.01 1.2 (Simpson et al, 1997) abdominal subdermal tissue (fat) human 800 0.01 1.2 (Simpson et al, 1997) adipose bovine 633 0.0026 1.2 (Kienle et al, 1996) adipose bovine 751 0.0021 1 (Kienle et al, 1996) adipose breast human 640 0.0045 1.18 (Taroni et al, 2009) adipose breast human 660 0.0035 1.15 (Taroni et al, 2009) adipose breast human 700 0.07 0.86 (Peters et al, 1990) adipose breast human 900 0.075 0.79 (Peters et al, 1990) fat tissue simulation 920 0.03 1.2 (Wassmer et al, 2009) fat tissue simulation 920 0.1 1.2 (Wassmer et al, 2009) fat tissue simulation 980 0.1 1.17 (Wassmer et al, 2009) fat tissue simulation 1064 0.08 1.15 (Wassmer et al, 2009) subcutaneous adipose tissue human 633 0.013 1.26…”

Selective photobiomodulation for emotion regulation: model-based dosimetry study

“…Specifically, the values of optical properties were taken from the literature, including muscles, 33,34 blood vessels (based on circulating blood values), 35 skull, 36,37 skin, 38 CSF, 39 and GM/ WM. 40 Since the optical properties for CSF were not directly available for 850 and 980 nm, 39 the reduced scattering coefficient μ 0 s for CSF at these two wavelengths was assumed to be 0.01 mm −1 , whereas the absorption coefficient of CSF was estimated to be close to that of water.…”