| 1. |
- Nilsson, A. M. K., et al.
(författare)
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Changes in spectral shape of tissue optical properties in conjunction with laser-induced thermotherapy
- 1998
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Ingår i: Applied Optics. - 2155-3165. ; 37:7, s. 1256-1267
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Tidskriftsartikel (refereegranskat)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.
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| 2. |
- Nilsson, A. M. K., et al.
(författare)
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Measurements of the optical properties of tissue in conjunction with photodynamic therapy
- 1995
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Ingår i: Applied Optics. - 2155-3165. ; 34:21, s. 4609-4619
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Tidskriftsartikel (refereegranskat)abstract
- 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 (PDT). The results were then correlated with measurements of the three optical-interaction coefficients mu(s), mu(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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| 3. |
- Nilsson, A. M. K., et al.
(författare)
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Near infrared diffuse reflection and laser-induced fluorescence spectroscopy for myocardial tissue characterisation
- 1997
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Ingår i: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. - 1386-1425. ; 53:11, s. 1901-1912
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Tidskriftsartikel (refereegranskat)abstract
- In order to evaluate the potential of cardiovascular tissue characterisation using near-infrared (NIR) spectroscopy, spectra in a previously unexplored wavelength region 0.8-2.3 mu m were recorded from various pig heart tissue samples in vitro: normal myocardium (with and without endo/epicardium), aorta; fatty and fibrous heart tissue. The spectra were analysed with principal component analysis (PCA), revealing several spectroscopically characteristic features enabling tissue classification. Several of the identified spectral features could be attributed to specific tissue constituents by comparing the tissue signals with spectra obtained from water, elastin, collagen and cholesterol as well as with published data. The results obtained with the NIR spectroscopy technique in terms of its potential to classify different tissue types were compared with those from laser-induced fluorescence (LIF) using 337 nm excitation. LIF and NIR spectroscopy can in combination with PCA be used to discriminate between all previously mentioned tissue groups, apart from fatty versus fibrous tissue (LIF) and aorta versus fibrous tissue (NIR), respectively. The NIR analysis was improved by focusing the PCA to the wavelength segment 2.0-2.3 mu m, resulting in successful spectral characterisation of all cardiovascular tissue groups.
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| 4. |
- Nilsson, Annika M. K., et al.
(författare)
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T-matrix computations of light scattering by red blood cells
- 1998
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The electromagnetic far field, as well as near field, originating from light interaction with a red blood cell (RBC) volume equivalent spheroid, were analyzed utilizing T-matrix theory. This method is a powerful tool which enables the influence of cell shape on the angular distribution of scattered light to be studied. General observations were that the three-dimensional shape, as well as optical thickness apparent to the incident field, affect the forward scattering. The back scattering was influenced by the shape of the surface facing the incident beam. Furthermore, sphering as well as elongation of an oblate shaped RBC into a volume equivalent sphere or prolate shaped spheroid, respectively, were theoretically modeled in order to imitate physiological phenomena caused, e.g., by sphering agents, heat or increased shear stress of flowing blood. Both sphering and elongation were shown to decrease the intensity of the forward directed scattering, thus yielding lower g-factors. The sphering made the scattering pattern independent of the azimuthal scattering angle φs, while the elongation induced more apparent φs-dependent patterns. The light scattering by an RBC volume equivalent spheroid, was thus found to be highly influenced by the shape of the scattering object. A near-field radius, rnf, was evaluated as the distance to which the maximum intensity of the total near field had decreased to 2.5 times that of the incident field. It was estimated to 2-24.5 times the maximum radius of the scattering spheroid, corresponding to 12-69 µm. When the absorption properties of a red blood cell were incorporated in the computations, the near-field radius was only slightly reduced by 0.2-0.6 times the maximum radius. As the near-field radius was shown to be larger than a simple estimation of the distance between the RBCs in whole blood, the assumption of independent scattering, frequently employed in optical measurements on whole blood, seems inappropriate. This also indicates that results obtained from diluted blood, cannot be extrapolated to whole blood, by multiplying with a simple concentration factor.
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| 5. |
- Nilsson, Annika M. K., et al.
(författare)
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T-matrix computations of light scattering by red blood cells
- 1998
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Ingår i: Applied Optics. - 1559-128X. ; 37:13, s. 2735-2748
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Tidskriftsartikel (refereegranskat)abstract
- The electromagnetic far field, as well as the near field, originating from light interaction with a red blood cell ~RBC! volume-equivalent spheroid, was analyzed by utilizing the T-matrix theory. This method is a powerful tool that makes it possible to study the influence of cell shape on the angular distribution ofscattered light. General observations were that the three-dimensional shape, as well as the optical thickness apparent to the incident field, affects the forward scattering. The backscattering was influenced by the shape of the surface facing the incident beam. Furthermore sphering as well as elongation of an oblate RBC into a volume-equivalent sphere or a prolate spheroid, respectively, was theoretically modeled to imitate physiological phenomena caused, e.g., by heat or the increased shear stress of flowing blood. Both sphering and elongation were shown to decrease the intensity of the forward-directed scattering, thus yielding lower g factors. The sphering made the scattering pattern independent ofazimuthal scattering angle fs, whereas the elongation induced more apparent fs-dependent patterns. The light scattering by a RBC volume-equivalent spheroid was thus found to be highly influenced by the shape of the scattering object. A near-field radius rnf was evaluated as the distance to which the maximum intensity of the total near field had decreased to 2.5 times that of the incident field. It was estimated to 2–24.5 times the maximum radius of the scattering spheroid, corresponding to 12–69 mm. Because the near-field radius was shown to be larger than a simple estimation of the distance between the RBC’s in whole blood, the assumption of independent scattering, frequently employed in opticalmeasurements on whole blood, seems inappropriate. This also indicates that one cannot extrapolate the results obtained from diluted blood to whole blood by multiplying with a simple concentration factor.
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| 6. |
- Wang, I, et al.
(författare)
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Superficial blood flow following photodynamic therapy of malignant non-melanoma skin tumours measured by laser Doppler perfusion imaging
- 1997
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Ingår i: British Journal of Dermatology. - : Oxford University Press (OUP). - 1365-2133 .- 0007-0963. ; 136:2, s. 184-189
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Tidskriftsartikel (refereegranskat)abstract
- Laser Doppler perfusion imaging offers a new modality for in vivo monitoring of the superficial blood perfusion in biological tissue, In this study, the superficial blood perfusion of malignant nonmelanoma skin tumours and the surrounding normal skin was measured in conjunction with photodynamic therapy (PDT) using topical delta-aminolaevulinic acid (ALA)-induced protoporphyrin IX as a photosensitizer. The results clearly show that, in contradiction to PDT with the intravenously administered photosensitizer Photofrin, no direct vascular damage can be seen, With the topical sensitization the brood perfusion is increased immediately after the treatment irradiation. The increased brood now is seen up to a week after treatment, in a similar way as for an inflammatory reaction. Despite this, all basal cell carcinoma and squamous cell carcinoma in situ lesions in this study healed without any sign of residual tumour after the treatment, suggesting an efficient direct tumour cell destruction induced by PDT.
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| 7. |
- Wang, L., et al.
(författare)
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Superficial Blood flow Following Photodynamic Therapy of Malignant Skin Tumours Measured by Laser Doppler Perfusion Imaging
- 1997
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Ingår i: British Journal of Dermatology. - : Oxford University Press (OUP). - 0007-0963 .- 1365-2133. ; 136:2, s. 184-189
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Tidskriftsartikel (refereegranskat)abstract
- Laser Doppler perfusion imaging offers a new modality for in vivo monitoring of the superficial blood perfusion in biological tissue. In this study, the superficial blood perfusion of malignant nonmelanoma skin tumours and the surrounding normal skin was measured in conjunction with photodynamic therapy (PDT) using topical ò–aminolaevulinic acid (ALA)–induced protoporphyrin IX as a photosensitizer. The results clearly show that, in contradiction to PDT with the intravenously administered photosensitizer photofrin. no direct vascular damage can be seen. With the topical sensitization the blood perfusion is increased immediately after the treatment irradiation. The increased blood flow is seen up to a week after treatment, in a similiar way as for an inflammatory reaction. Despite this, all basal cell carcinoma and squamous cell carcinoma in situ lesions in this study healed without any sign of residual tumour after the treatment, suggesting an efficient direct tumour cell destruction induced by PDT.
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