&lt;title&gt;Experimental set-up and Monte-Carlo model for the determination of optical tissue properties in the wavelength range 330 to 1100 nm&lt;/title&gt;

Roggan, A.; Albrecht, Hans Joerg; Doerschel, Klaus; Minet, Olaf; Mueller, Gerhard J.

doi:10.1117/12.199205

Cited by 34 publications

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“…The three parameters can be measured either consecutively with a single integrating sphere as in this study or simultaneously with a double integrating sphere. 19,20 The latter experimental arrangement provides an elegant technique for monitoring time-dependent changes in optical properties caused by any external stimulus. However, since no time-dependent phenomena were studied here, there was no advantage in using a double integrating sphere.…”

Section: Introductionmentioning

confidence: 99%

“…17 This new experimental approach with multiwavelength detection enabled us to determine a complete set of optical properties, g, s , and a , versus the wavelength in only three measurements, compared with the many measurements needed when probing one wavelength at a time with a monochromator setup. 10,17,20,23 Three measurements performed on each liver sample were completed within 25 min after resection and resulted in a total of 57 spectra ͑600 -1050 nm͒ of each optical parameter of the tissue g, s , and a . Thirty measurements were performed on 10 untreated liver samples, 15 measurements were made on the darkened treated central area, and 12 on the paler peripheral region of the remaining nine treated samples included in the study.…”

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confidence: 99%

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

et al. 1998

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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 Ϯ 7% over the entire spectral range following thermotherapy, and a corresponding relative increase in the scattering and absorption coefficients of 23 Ϯ 8% and 200 Ϯ 100%, respectively. An increase of on average 200 Ϯ 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 g 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 m, respectively, yielding particle sizes in the same range as the size of a mitochondrion.

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Section: Introductionmentioning

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

et al. 1998

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“…This proves that the observed effect is connected to the photochemical reaction in the tissue, for which a combination of photosensitizers and light is needed. Additionally, Roggan et al 23 showed that tissue coagulation caused by hyperthermia results in unchanged absorption coefficients and in increased scattering coefficients-the very opposite to that observed during PDT irradiation.…”

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“…To obtain a complete set of optical properties, several Monte Carlo simulations are necessary, in a so-called inverse Monte Carlo routine, to fit the measured reflectance and transmittance to the simulated values. 23 We have dealt with this by making a table of Monte Carlo-simulated data, from which the optical properties can be determined by fast spline interpolations. The disadvantage is that a new table must be constructed for each sample geometry used.…”

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Measurements of the optical properties of tissue in conjunction with photodynamic therapy

1995

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A simple optical dosimeter was used to measure the light intensity in rat liver and muscle in vivo with fibers positioned at different depths to investigate whether the light penetration changed during photodynamic therapy 1PDT2. The results were then correlated with measurements of the three optical-interaction coefficients µ s , µ a , and g for wavelengths in the range 500-800 nm for PDT-treated and nontreated rat liver and muscle tissue in vitro. A distinct increase in the absorption coefficient was seen immediately after treatment, in agreement with the decreasing light intensity observed during the treatment, as measured with the optical dosimeter. The collimated transmittance was measured with a narrow-beam setup, and an optical integrating sphere was used to measure the diffuse reflectance and total transmittance of the samples. The corresponding optical properties were obtained by spline interpolation of Monte Carlo-simulated data. To ensure that the measured values were correct, we performed calibration measurements with suspensions of polystyrene microspheres and ink.

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Heat-resistant cylindrical diffuser for interstitial laser coagulation: Comparison with the bare-tip fiber in a porcine liver model

Heisterkamp¹,

Hillegersberg²,

Sinofsky³

et al. 1997

Lasers Surg. Med.

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<title>Experimental set-up and Monte-Carlo model for the determination of optical tissue properties in the wavelength range 330 to 1100 nm</title>

Cited by 34 publications

References 0 publications

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

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

Measurements of the optical properties of tissue in conjunction with photodynamic therapy

Heat-resistant cylindrical diffuser for interstitial laser coagulation: Comparison with the bare-tip fiber in a porcine liver model

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