| 1. |
- Holm, Åsa, 1969-, et al.
(författare)
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Mechanical manipulation of polymorphonuclear leukocyte plasma membranes with optical tweezers causes influx of extracellular calcium through membrane channels
- 1999
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Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 37:3, s. 410-412
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Tidskriftsartikel (refereegranskat)abstract
- Optical tweezers are used mechanically to manipulate the plasma membrane of polymophonuclear leukocytes attached to the bottom of a glass manipulation chamber. The laser trapping beam is dragged across the membrane of cells in calcium-containing and calcium-depleted extracellular medium. This treatment causes a significant rise in the intracellular calcium concentration compared with controls, in cells in calcium-containing medium (239.8±49.0% against 75.4±16.4%, respectively), but not in cells in calcium-depeleted medium (69.1±9.6% against 83.4±18.5%, respectively), indicating that the calcium rise is caused by an influx of calcium from the environment. The rise in calcium concentration is blocked (23.5±7.1% against 17.1±4.1%, respectively) by the addition of lansoprazole, indicating that the influx is not due to unspecific membrane damage caused by the mechanical manipulation of the cell. It can therefore be concluded that mechanical manipulation of the neutrophil membrane, in the piconewton force range exerted by the optical tweezer, does not damage the plasma membrane but stimulates a mechanically inducible, membrane channel-mediated influx of extracellular calcium.
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| 2. |
- Johansson, Anders, et al.
(författare)
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A spectroscopic approach to imaging and quantification of cartilage lesions in human knee joints
- 2011
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Ingår i: Physics in Medicine and Biology. - : IOP. - 0031-9155 .- 1361-6560. ; 56:6, s. 1865-1878
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Tidskriftsartikel (refereegranskat)abstract
- We have previously described a technology based on diffuse reflectance of broadband light for measuring joint articular cartilage thickness, utilizing that optical absorption is different in cartilage and subchondral bone. This study is the first evaluation of the technology in human material. We also investigated the prospects of cartilage lesion imaging, with the specific aim of arthroscopic integration. Cartilage thickness was studied ex vivo in a number of sites (n = 87) on human knee joint condyles, removed from nine patients during total knee replacement surgery. A reflectance spectrum was taken at each site and the cartilage thickness was estimated using the blue, green, red and near-infrared regions of the spectrum, respectively. Estimated values were compared with reference cartilage thickness values (taken after sample slicing) using an exponential model. Two-dimensional Monte Carlo simulations were performed in a theoretical analysis of the experimental results. The reference cartilage thickness of the investigated sites was 1.60 ± 1.30 mm (mean ± SD) in the range 0–4.2 mm. Highest correlation coefficients were seen for the calculations based on the near-infrared region after normalization to the red region (r = 0.86) and for the green region (r = 0.80).
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| 5. |
- Johansson, Anders, et al.
(författare)
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Spectroscopic Measurement of Cartilage Thickness in Arthroscopy: Ex Vivo Validation in Human Knee Condyles
- 2012
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Ingår i: Arthroscopy. - : WB Saunders. - 0749-8063 .- 1526-3231. ; 28:10, s. 1513-1523
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To evaluate the accuracy of articular cartilage thickness measurement when implementing a new technology based on spectroscopic measurement into an arthroscopic camera. Methods: Cartilage thickness was studied by ex vivo arthroscopy at a number of sites (N = 113) in human knee joint osteoarthritic femoral condyles and tibial plateaus, removed from 7 patients undergoing total knee replacement. The arthroscopic image spectral data at each site were used to estimate cartilage thickness. Arthroscopically derived thickness values were compared with reference cartilage thickness as measured by 3 different methods: needle penetration, spiral computed tomography scanning, and geometric measurement after sample slicing. Results: The lowest mean error (0.28 to 0.30 mm) in the regression between arthroscopic and reference cartilage thickness was seen for reference cartilage thickness less than 1.5 mm. Corresponding values for cartilage thickness less than 2.0 and 2.5 mm were 0.32 to 0.40 mm and 0.37 to 0.47 mm, respectively. Cartilage thickness images-created by pixel-by-pixel regression model calculations applied to the arthroscopic images-were derived to demonstrate the clinical use of a camera implementation. Conclusions: On the basis of this investigation on osteoarthritic material, when one is implementing the spectroscopic method for estimating cartilage thickness into an arthroscopic camera, errors in the range of 0.28 to 0.30 mm are expected. This implementation does not, however, influence the fact that the spectral method performs less well in the cartilage thickness region from 1.5 to 2.5 mm and cannot assess cartilage thicker than 2.5 mm. Clinical Relevance: Imaging cartilage thickness directly in the arthroscopic camera video stream could serve as an interesting image tool for in vivo cartilage quality assessment, in connection with cartilage diagnosis, repair, and follow-up.
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| 6. |
- Öberg, Åke, 1937-, et al.
(författare)
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Assessment of cartilage thickness utilising reflectance spectroscopy
- 2004
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Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 42:1
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Tidskriftsartikel (refereegranskat)abstract
- A new principle for cartilage layer thickness assessments in joints is presented. It is based on the differences between the absorption spectra of cartilage and subchondral bone (containing blood). High-resolution ultrasound measurements of cartilage thickness were compared with reflection spectroscopy data from the same area of bovine hip joint condyles. A simple mathematical model allowed calculation of thickness and comparison with ultrasound data. The cartilage thickness was changed by being ground in short episodes. For thicker cartilage layers, a high degree of reflection in the 400-600nm wavelength interval was seen. For thinner cartilage layers, the characteristics of the spectra of blood and bone dominated those of cartilage. The mean (±SD) thickness of intact cartilage was 1.21± 0.30 mm (n = 30). In an exponential regression model, spectroscopic estimation of cartilage thickness showed a correlation coefficient of r= 0.69 (n = 182). For thinner cartilage layers (d<0.5mm), the mean model error was 0.19±0.17mm. Results from a bi-layer Monte Carlo simulation supported the assumption of an exponential relationship between spectroscopy data and reference ultrasound data. The conclusion is that optical reflection spectroscopy can be used for cartilage layer thickness assessment.
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| 7. |
- Öberg, Åke, 1937-, et al.
(författare)
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Characterisation of the cartilage/bone interface utilising reflectance spectroscopy
- 2001
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Ingår i: 23rd Annual International Conference IEEE EMBS,2001. - : IEEE. - 0780372115 ; , s. 3002-3004
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Konferensbidrag (refereegranskat)abstract
- Optical reflection spectra of the cartilage/bone interface from hip joints of cows were studied. When comparing to ultrasonic measurement, it was found that cartilage thickness could be extracted using optical reflectance spectroscopy. For thicker cartilage layers, a high reflection for the wavelengths 400-600 nm was seen, and for thinner cartilage layers, the characteristic spectra of blood and bone dominated. The optical reflectance spectra may be used to characterise cartilage, and specifically cartilage thickness, in connection with in situ diagnosis or autologous chondrocyte implantation (ACI).
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