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Changes in spectral shape of tissue optical properties in conjunction with laser-induced thermotherapy

Nilsson, A. M. K.; Sturesson, Christian LU ; Liu, D. L. and Andersson-Engels, Stefan LU (1998) In Applied Optics 37(7). p.1256-1267
Abstract
We measured the optical properties on samples of rat liver tissue before and after laser-induced thermotherapy performed in vivo with Nd:YAG laser irradiation. This made it possible to monitor not only the influence of coagulation on the scattering properties but also the influence of damages to vessels and heat-induced damage to blood on the absorption properties. An experimental integrating-sphere arrangement was modified to allow the determination of the g factor and the absorption and scattering coefficients versus the wavelength in the 600-1050-nm spectral region, with the use of a spectrometer and a CCD camera, The results show a relative decrease in the g factor of on average 21 +/- 7% over the entire spectral range following... (More)
We measured the optical properties on samples of rat liver tissue before and after laser-induced thermotherapy performed in vivo with Nd:YAG laser irradiation. This made it possible to monitor not only the influence of coagulation on the scattering properties but also the influence of damages to vessels and heat-induced damage to blood on the absorption properties. An experimental integrating-sphere arrangement was modified to allow the determination of the g factor and the absorption and scattering coefficients versus the wavelength in the 600-1050-nm spectral region, with the use of a spectrometer and a CCD camera, The results show a relative decrease in the g factor of on average 21 +/- 7% over the entire spectral range following thermotherapy, and a corresponding relative increase in the scattering and absorption coefficients of 23 +/- 8% and 200 +/- 100%, respectively. An increase of on average 200 +/- 80% was consequently found for the reduced scattering coefficient. The cause of these changes in terms of the Mie-equivalent average radius of tissue scatterers as well as of the distribution and biochemistry of tissue absorbers was analyzed, utilizing the information yielded by the gr factor and the spectral shapes of the reduced scattering and absorption coefficients. These results were correlated with the alterations in the ultrastructure found in the histological evaluation. The average radius of tissue scattering centers, determined by using either the g factors calculated on the basis of Mie theory or the spectral shape of reduced scattering coefficients calculated on the Mie theory, was estimated to be 21-32% lower in treated than in untreated liver samples. The Mie-equivalent average radii of scattering centers in untreated liver tissue deduced by the two methods corresponded well and were found to be 0.31 and 0.29 pm, respectively, yielding particle sizes in the same range as the size of a mitochondrion. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Applied Optics
volume
37
issue
7
pages
1256 - 1267
publisher
OSA
external identifiers
  • scopus:0001402263
ISSN
2155-3165
language
English
LU publication?
yes
id
45b4420f-3368-43cc-8b52-5daa57b22124 (old id 35055)
date added to LUP
2007-06-19 14:34:39
date last changed
2017-02-05 03:32:32
@article{45b4420f-3368-43cc-8b52-5daa57b22124,
  abstract     = {We measured the optical properties on samples of rat liver tissue before and after laser-induced thermotherapy performed in vivo with Nd:YAG laser irradiation. This made it possible to monitor not only the influence of coagulation on the scattering properties but also the influence of damages to vessels and heat-induced damage to blood on the absorption properties. An experimental integrating-sphere arrangement was modified to allow the determination of the g factor and the absorption and scattering coefficients versus the wavelength in the 600-1050-nm spectral region, with the use of a spectrometer and a CCD camera, The results show a relative decrease in the g factor of on average 21 +/- 7% over the entire spectral range following thermotherapy, and a corresponding relative increase in the scattering and absorption coefficients of 23 +/- 8% and 200 +/- 100%, respectively. An increase of on average 200 +/- 80% was consequently found for the reduced scattering coefficient. The cause of these changes in terms of the Mie-equivalent average radius of tissue scatterers as well as of the distribution and biochemistry of tissue absorbers was analyzed, utilizing the information yielded by the gr factor and the spectral shapes of the reduced scattering and absorption coefficients. These results were correlated with the alterations in the ultrastructure found in the histological evaluation. The average radius of tissue scattering centers, determined by using either the g factors calculated on the basis of Mie theory or the spectral shape of reduced scattering coefficients calculated on the Mie theory, was estimated to be 21-32% lower in treated than in untreated liver samples. The Mie-equivalent average radii of scattering centers in untreated liver tissue deduced by the two methods corresponded well and were found to be 0.31 and 0.29 pm, respectively, yielding particle sizes in the same range as the size of a mitochondrion.},
  author       = {Nilsson, A. M. K. and Sturesson, Christian and Liu, D. L. and Andersson-Engels, Stefan},
  issn         = {2155-3165},
  language     = {eng},
  number       = {7},
  pages        = {1256--1267},
  publisher    = {OSA},
  series       = {Applied Optics},
  title        = {Changes in spectral shape of tissue optical properties in conjunction with laser-induced thermotherapy},
  volume       = {37},
  year         = {1998},
}