| 1. |
- Abrahamsson, Christoffer, et al.
(författare)
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Time and wavelength resolved spectroscopy of turbid media using light continuum generated in a crystal fiber
- 2004
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Ingår i: Optics Express. - 1094-4087. ; 12:17, s. 4103-4112
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Tidskriftsartikel (refereegranskat)abstract
- We report a novel system for time-resolved diffuse remission spectral measurements, based on short light continuum pulses generated in an index-guided crystal fiber, and a spectrometer-equipped streak camera. The system enables spectral recordings of absorption and reduced scattering coefficients of turbid media in the wavelength range 500 - 1200 nm with a spectral resolution of 5 nm and a temporal resolution of 30 ps. The optical properties are calculated by fitting the solution of the diffusion equation to the time-dispersion curve at each wavelength. Example measurements are presented from an apple, a finger and a pharmaceutical tablet. (C) 2004 Optical Society of America.
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| 2. |
- Abrahamsson, Christoffer, et al.
(författare)
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Time-resolved NIR spectroscopy for quantitative analysis of intact pharmaceutical tablets
- 2005
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 77:4, s. 1055-1059
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Tidskriftsartikel (refereegranskat)abstract
- Near-infrared (NIR) spectroscopy is a useful technique for quantitative measurements of intact tablets, but it suffers from limitations due to the fact that changes in the physical properties of a sample strongly affect the recorded spectrum. In this work, time-resolved transmission NIR spectroscopy was utilized to conduct quantitative measurements of intact tablets. The technique enables separation of the absorption properties of the sample from the scattering properties and can therefore handle changes of the physical parameters of the samples in a better way than conventional NIR transmission spectroscopy. The experiments were conducted using a pulsed Ti:sapphire laser coupled into a nonlinear photonic crystal fiber as light source. The light transmitted through the sample was measured by a time-resolving streak camera. A comparison of the results from the time-resolved technique with the results from conventional transmission NIR spectroscopy was made using tablets containing different concentrations of iron oxide and manufactured with different thicknesses. A PLS model made with data from the time-resolved technique predicted samples 5 times better than a PLS model made data from the conventional NIR transmission technique. Furthermore, an improvement to predict samples with physical properties outside those included in the calibration set was demonstrated.
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| 3. |
- af Klinteberg, C, et al.
(författare)
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Compact medical fluorosensor for minimally invasive tissue characterization
- 2005
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 76:3
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Tidskriftsartikel (refereegranskat)abstract
- A compact fiber-optic point-measuring fluorosensor fully adapted to clinical studies is described. The system can use two excitation wavelengths, 337 and 405 nm, obtained from a nitrogen laser directly, or after dye laser conversion, respectively. The image intensifier used in the spectrometer can be gated with a variable time delay, allowing also time-resolved spectra to be extracted, with a time resolution of about 4 ns. Moreover, diffusely scattered white light can be spectrally recorded. The system is fully computer controlled enabling short recording times in clinical application, which are illustrated.
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| 4. |
- af Klinteberg, C, et al.
(författare)
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In vivo absorption spectroscopy of tumor sensitizers with femtosecond white light
- 2005
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Ingår i: Applied Optics. - 2155-3165. ; 44:11, s. 2213-2220
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Tidskriftsartikel (refereegranskat)abstract
- A system based on a femtosecond white-light continuum and a streak camera was used for recordings of the in vivo absorption spectra of the tumor-seeking agent disulphonated aluminum phthalocyanine. Measurements for different drug doses were performed on tumor tissue (muscle-implanted adenocarcinoma) and normal muscle tissue in rats. It was found that the shape of the spectrum is tissue dependent. The peak of the absorption spectrum is blueshifted in tumor tissue as compared with the muscle. Thus the contrast in the drug-related absorption can be altered by up to a factor of 2 from the primary drug molecular-concentration contrast between normal muscle and tumor by the proper selection of the illumination wavelength.
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| 5. |
- af Klinteberg, C, et al.
(författare)
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Kinetic fluorescence studies of 5-aminolaevulinic acid-induced protoporphyrin IX accumulation in basal cell carcinomas
- 1999
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Ingår i: Journal of Photochemistry and Photobiology, B: Biology. - 1011-1344. ; 49:2-3, s. 120-128
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Tidskriftsartikel (refereegranskat)abstract
- Laser-induced fluorescence (LIF) investigations have been performed in connection with photodynamic therapy (PDT) of basal cell carcinomas and adjacent normal skin following topical application of 5-aminolaevulinic acid (ALA) in order to study the kinetics of the protoporphyrin TX (PpIX) build-up. Five superficial and 10 nodular lesions in 15 patients are included in the study. Fluorescence measurements are performed prior to the application of ALA, 2, 4 and 6 h port ALA application, immediately post PDT (60 J cm(-2) at 635 nm), and 2 h after the treatment. Hence, the build-up, photobleaching and re-accumulation of PpIX can be followed. Superficial lesions show a maximum PpIX fluorescence 6 h post ALA application, whereas the intensity is already the highest 2-4 h after the application in nodular lesions. Immediately post PDT, the fluorescence contribution at 670 Mm from the photoproducts is about 2% of the pre-PDT PpIX fluorescence at 635 nm. Two hours after the treatment, a uniform distribution of PpIX is found in the lesion and surrounding normal tissue. During the whole procedure, the autofluorescence of the lesions and the normal skin does not vary significantly from the values recorded before the application of ALA. (C) 1999 Elsevier Science S.A. All rights reserved.
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| 6. |
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| 7. |
- Albert, F, et al.
(författare)
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Laser produced X-ray source in the 10-60 keV range at 1 kHz. Modified irradiation schemes in order to reach medical imaging quality
- 2001
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Ingår i: Journal de Physique IV. - : EDP Sciences. - 1155-4339. ; 11:PR2, s. 429-432
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Tidskriftsartikel (refereegranskat)abstract
- By tightly focusing ultra-short pulses from a Ti:sapphire terawatt laser onto a high-Z metallic target, hard x-ray pulses of short duration are produced. In most of our previous work concerning x-rays, a 150 mJ laser pulse with a 110 A duration has been used. Using mostly tin and tantalum targets, hard x-rays in the 10-60 keV range have been produced and used in differential absorption imaging around the K-alpha absorption edge of a contrast agent and also in imaging employing gated viewing for suppression of scattered radiation. In order to increase the x-ray yield (shortening the acquisition time) an increase in the laser repetition rate is desirable while still staying in the K-alpha energy regime. We have used a I kHz repetition-rate laser delivering 35 fs pulses in order to work towards these goals. We have clear evidence of hard x-ray generation above 30 keV, even for low laser pulse energies. We also studied the effect of a fs prepulse. The medical imaging capability of the source was explored. The use of a prepulse has been optimized in order to improve the image quality as well as the overall x-ray generation yield.
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