| 251. |
- Svensson, Jenny, et al.
(author)
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Tissue temperature measurements during interstitial laser therapy using Cr3+-doped crystals at the fiber tip
- 2003
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In: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 5142:1, s. 30-41
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Conference paper (peer-reviewed)abstract
- In this project a technique to optically measure the temperature is evaluated. The measurement is to be performed through optical fibres during photodynamic laser treatments or laser thermo therapy of malignant tumours. For this technique Cr3+-doped crystals were used. The lifetime of the ions' fluorescence were measured, since the fluorescence is strongly temperature dependent. A piece of a crystal was attached to the tip of an optical fibre. The crystal was excited at 635 nm, which is the wavelength most frequently used for photodynamic treatment. An accuracy in the temperature measurement of
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| 252. |
- Svensson, Jenny, et al.
(author)
-
Tissue temperature monitoring during interstitial photodynamic therapy
- 2005
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In: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 5698:1, s. 126-136
-
Conference paper (peer-reviewed)abstract
- During δ-aminolevulinic acid (ALA) based Interstitial Photodynamic Therapy (IPDT) a high light fluence rate is present close to the source fibers. This might induce an unintentional tissue temperature increase of importance for the treatment outcome. In a previous study, we have observed, that the absorption in the tissue increases during the treatment. A system to measure the local tissue temperature at the source fibers during IPDT on tissue phantoms is presented. The temperature was measured by acquiring the fluorescence from small Cr3+-doped crystals attached to the tip of the illumination fiber used in an IPDT-system. The fluorescence of the Alexandrite crystal used is temperature dependent. A ratio of the intensity of the fluorescence was formed between two different wavelength bands in the red region. The system was calibrated by immersing the fibers in an Intralipid solution placed in a temperature controlled oven. Measurements were then performed by placing the fibers interstitially in a pork chop as a tissue phantom. Measurements were also performed superficially on skin on a volunteer. A treatment was conducted for 10 minutes, and the fluorescence was measured each minute during the illumination. The fluorescence yielded the temperature at the fiber tip through the calibration curve. The measurements indicate a temperature increase of a few degrees during the simulated treatment
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| 253. |
- Svensson, Jenny, et al.
(author)
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Tumor selectivity at short times following systemic administration of a liposomal temoporfin formulation in a murine tumor model
- 2007
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In: Photochemistry and Photobiology. - 0031-8655. ; 83:5, s. 1211-1219
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Journal article (peer-reviewed)abstract
- Meso-tetra(hydroxyphenyl)chlorin (mTHPC) (INN: Temoporfin) is one of the most potent photodynamically active substances in clinical use. Treatment protocols for Temoporfin-mediated photodynamic therapy often rely on drug-light intervals of several days in order for the photosensitizer to accumulate within the target tissue, though tumor selectivity is limited. Here, the mTHPC localization was studied at 2-8 h following systemic administration of a liposomal Temoporfin formulation (0.15 mg kg(-1) b.w.) in HT29 human colon adermcarcinoma in NMRI nu/nu mice. Photosensitizer distribution within tumor and internal organs was investigated by means of high performance liquid chromatography following chemical extraction, as well as in situ fluorescence imaging and point-monitoring fluorescence spectroscopy. For tumor tissue, the Temoporfin concentrations at 4 h (0.16 +/- 0.024 ng mg(-1)) and 8 h (0.18 +/- 0.064 ng mg(-1)) were significantly higher than at 2 It (0.08 +/- 0.026 ng mg(-1)). The average tumor-to-muscle and the tumor-to-skin selectivity were 6.6 and 2, respectively, and did not vary significantly with time after photosensitizer injection. In plasma, the Temoporfin concentration was low (0.07 +/- 0.07 ng mg(-1)) and showed no significant variation with time. Our results indicate a rapid biodistribution and clearance from the bloodstream. Within the same type of organ, data from both fluorescence methods generally exhibited a significant correlation with the extraction results.
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| 254. |
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| 255. |
- Svensson, Tomas, et al.
(author)
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High sensitivity gas spectroscopy of porous, highly scattering solids
- 2008
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In: Optics Letters. - 0146-9592. ; 33:1, s. 80-82
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Journal article (peer-reviewed)abstract
- We present minimalistic and cost-efficient instrumentation employing tunable diode laser gas spectroscopy for the characterization of porous and highly scattering solids. The sensitivity reaches 3 x 10(-6) (absorption fraction), and the improvement with respect to previous work in this field is a factor of 10. We also provide the first characterization of the interference phenomenon encountered in high-resolution spectroscopy of turbid samples. Revealing that severe optical interference originates from the samples, we discuss important implications for system design. In addition, we introduce tracking coils and sample rotation as new and efficient tools for interference suppression. The great value of the approach is illustrated in an application addressing structural properties of pharmaceutical materials.
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| 256. |
- Svensson, Tomas, et al.
(author)
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In vivo optical characterization of human prostate tissue using near-infrared time-resolved spectroscopy.
- 2007
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In: Journal of Biomedical Optics. - : SPIE-Intl Soc Optical Eng. - 1083-3668. ; 12:1, s. 014022-014022
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Journal article (peer-reviewed)abstract
- The development of photodynamic therapy into a modality for treatment of prostate cancer calls for reliable optical dosimetry. We employ, for the first time, interstitial time-resolved spectroscopy to determine in vivo optical properties of human prostate tissue. Nine patients are included in the study, and measurements are conducted prior to primary brachytherapy treatment of prostate cancer. Intrasubject variability is examined by measuring across three tissue volumes within each prostate. The time-resolved instrumentation proves its usefulness by producing good signal levels in all measurements. We are able to present consistent values on reduced scattering coefficients (mu(s)'), absorption coefficients (mu(a)), and effective attenuation (mu(eff)) at the wavelengths 660, 786, and 916 nm. At 660 nm, mu(s)' is found to be 9 +/- 2 cm(-1), and mu(a) is 0.5 +/- 0.1 cm-1. Derived values of mu(eff) are in the range of 3 to 4 cm-1 at 660 nm, a result in good agreement with previously published steady state data. Total hemoglobin concentration (THC) and oxygen saturation are spectroscopically determined using derived absorption coefficients. Derived THC values are fairly variable (215 +/- 65 mu M), while derived values of oxygen saturation are gathered around 75% (76 +/- 4%). Intrasubject variations in derived parameters correlate (qualitatively) with the heterogeneity exhibited in acquired ultrasound images.
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| 257. |
- Svensson, Tomas, et al.
(author)
-
Near-infrared photon time-of-flight spectroscopy of turbid materials up to 1400 nm
- 2009
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In: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 80:6
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Journal article (peer-reviewed)abstract
- Photon time-of-flight spectroscopy (PTOFS) is a powerful tool for analysis of turbid materials. We have constructed a time-of-flight spectrometer based on a supercontinuum fiber laser, acousto-optical tunable filtering, and an InP/InGaAsP microchannel plate photomultiplier tube. The system is capable of performing PTOFS up to 1400 nm, and thus covers an important region for vibrational spectroscopy of solid samples. The development significantly increases the applicability of PTOFS for analysis of chemical content and physical properties of turbid media. The great value of the proposed approach is illustrated by revealing the distinct absorption features of turbid epoxy resin. Promising future applications of the approach are discussed, including quantitative assessment of pharmaceuticals, powder analysis, and calibration-free near-infrared spectroscopy.
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| 258. |
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| 259. |
- Svensson, Tomas, et al.
(author)
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Optical porosimetry and investigations of the porosity experienced by light interacting with porous media.
- 2010
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In: Optics Letters. - 1539-4794. ; 35:11, s. 1740-1742
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Journal article (peer-reviewed)abstract
- We investigate how light samples disordered porous materials such as ceramics and pharmaceutical materials. By combining photon time-of-flight spectroscopy and sensitive laser-based gas sensing, we obtain information on the extent to which light interacts with solid and pore volumes, respectively. Comparison with mercury intrusion porosimetry shows that light predominantly interacts with the solid. Analysis based on a two-state model does not fully explain observations, revealing a need for refined modeling. Nonetheless, excellent correlation between actual porosity and the porosity experienced by photons demonstrates the potential of nondestructive optical porosimetry based on gas absorption.
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| 260. |
- Svensson, Tomas, et al.
(author)
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Towards accurate in vivo spectroscopy of the human prostate
- 2008
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In: Journal of Biophotonics. - : Wiley. - 1864-063X .- 1864-0648. ; 1:3, s. 200-203
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Journal article (peer-reviewed)abstract
- The recent interest in photodynamic therapy of human prostate cancer is accompanied by a need for techniques for in vivo monitoring of optical and physiological characteristics. We propose time-of-flight (TOF) spectroscopy in combination with Monte Carlo evaluation as a reliable optical technique for quantitative assessment of absorption, scattering, hemoglobin content and tissue oxygenation in the human prostate. For the first time, we demonstrate Monte Carlo-based evaluation of in vivo TOF photon migration data. We show that this approach is crucial in order to avoid the large errors associated with the use of time-resolved diffusion theory of light propagation in prostate-like tissues. This progress also allows us to present the first in vivo scattering spectroscopy of human prostate tissue. Furthermore, TOF spectroscopy. in contrast to the more common steady-state approach, is insensitive to bleedings, and has been found highly reliable (100% success rate). (C) 2008 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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