The effectivc attenuation coefficient of piglet lung was measured in vitro at 632.8 nm. Interstial fibres with isotropic tips were used to measure the fluence rate as a function of the distance from an isotropic light source. In vitro measurements at 632.8 nm on a lung that was insufflated with oxygen from 50 to 150 ml showed that the cffcctivc attenuation coefficient decreases as a function of the volume of air in the lung (at 50 ml [1 - - 0.297 ±0.011 mm-1, at 100 ml μeff= 0.150 ± 0.007 mm-1, and at 150 ml μeff= 0.136 +. 0.015 mm-1). A single in vitro measurement at 790 nm at an insufflated lung volume of 100 ml gave a comparable result (μeff = 0.175 +. 0.004 mm-1). A decrease in effective attenuation coefficient with an increase in lung volume was explained by Mie-theory. The effective attenuation coefficient, calculated with μs and g from Mie-theory, showed a deviation < 22% from the measured in vitro values.

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Medical Optical Tomography: Functional Imaging and Monitoring 1993

Beck, J.F. (Johan F.), van Staveren, H., Posthumus, P., Sterenborg, D., & van Gemert, M. (1993). Optical properties of tissue, experimental results (Or: The influence of lung volume on the optical properties of in vitro piglet lung at 632.8 nm). In Proceedings of SPIE - The International Society for Optical Engineering (pp. 193–210). doi:10.1117/12.2283757