| 1. |
- Fridolin, Ivo, 1971-, et al.
(författare)
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On-line monitoring of solutes in dialysate using wavelength-dependent absorption of ultraviolet radiation
- 2003
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Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 41:3, s. 263-270
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the study was to assess the wavelength dependence of the UV absorbance during monitoring of different compounds in the dialysate. UV absorbance was determined by using a double-beam spectrophotometer on dialysate samples taken at pre-determined times during dialysis, over a wavelength range of 180–380 nm. Concentrations of several removed substances, such as urea, creatinine, uric acid, phosphate and β 2-microglobulin, were determined in the blood and in the spent dialysate samples using standard laboratory techniques. Millimolar extinction coefficients, for urea, creatinine, monosodium phosphate and uric acid were determined during laboratory bench experiments. The correlation between UV absorbance and substances both in the dialysate and in the blood was calculated at all wavelengths. A time-dependent UV absorbance was determined on the collected dialysate samples from a single dialysis session over a wavelength range of 200–330 nm. The highest contribution from observed compounds relative to the mean value of the absorbance was found around 300 nm and was approximately 70%. The main contribution to the total absorbance from uric acid was confirmed at this wavelength. The highest correlation for uric acid, creatinine and urea was obtained at wavelengths from 280 nm to 320 nm, both in the spent dialysate and in the blood. The wavelength region with the highest correlation for phosphate and β 2-microglobulin, with a suitable UV-absorbance dynamic range, was from 300 to 330 nm. In the wavelength range of 220–270 nm the highest absorbance sensitivity for the observed substances was obtained. A suitable wavelength range for instrumental design seems tobe around 290–330 nm. The relatively high correlation between UV absorbance and the substances in the spent dialysate and in the blood indicates that the UV-absorbance technique can estimate the removal of several retained solutes known to accumulate in dialysis patients.
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| 2. |
- Fridolin, Ivo, 1971-, et al.
(författare)
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Optical non-invasive technique for vessel imaging : II. A simplified photon diffusion analysis
- 2000
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Ingår i: Physics in Medicine and Biology. - : Institute of Physics (IOP). - 0031-9155 .- 1361-6560. ; 45:12, s. 3779-3792
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this paper is to explain theoretically the origin of previously presented experimental results by an optical non-invasive method using NIR for imaging blood vessels based on a specific combination of several physical parameters. The theoretical model is based on the diffusion approximation derived from the transport theory deep in a bulk tissue. An analytical solution was obtained describing photon behaviour under certain conditions during vessel identification. The modelled results indicate that the vessel identification facility depends upon source-detector separation and vessel depth, and does not depend essentially on the radiant power from the light source. The solution offers a relatively simple theoretical explanation of the experimental results and can be applied to several other clinical applications using similar technical solutions.
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| 3. |
- Fridolin, Ivo, 1971-
(författare)
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Photon propagation in tissue and in biological fluids : applied for vascular imaging and haemodialysis monitoring
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on the photon propagation in tissue and in biological fluids in two main areas: (1) optical vessel imaging and (2) monitoring solutes removed in haemodialysis.The aim of the optical vessel imaging study was to design and assess a new optical scanning technique for vessel imaging using NIR radiation. The results indicated that veins could be determined at three vascular levels (superficial, intermediate and deep) down to 3 mm. Moreover, experimental results demonstrated that the vessel imaging facility depends upon source-detector separation, relative position, and vessel depth and does not depend essentially on the radiant power from the light source. After vessel imaging the technique can potentially be used to monitor several physiological parameters on a selected vascular bed (e.g. local blood flow, oxygen saturation).The theoretical model, based on the diffusion approximation, was developed to explain theoretically the origin of experimental results. An analytical solution was obtained describing photon propagation under certain conditions during vessel identification. The modelled results confirmed previously obtained experimental results.A new optical method for monitoring solutes in a spent dialysate using absorption of UV-radiation was developed. The obtained on-line UV-absorbance curve demonstrates the possibility to follow a single haemodialysis session continuously and to monitor deviations in the dialysator performance using UV-absorbance. The experimental results indicated that the UV-absorbance correlates well to the concentration of several solutes known to accumulate in dialysis patients indicating that the technique can be used to estimate the removal of retained substances.Furthermore, a clinical study suggested that the delivered dialysis dose in terms of the traditional urea Kt/V could be estimated by on-line measurement of the UV-absorption in the spent dialysate. This means that the UV-method may add a new methodology for improvement of the quality and adequacy of the dialysis.An investigation of the wavelength dependence of the UV-absorbance when monitoring different compounds in the dialysate showed that the UV-absorbance correlates well to several small molecular weight solutes ( < 200 D), around 290-310 nm. The highest contribution to the total absorbance from the observed compounds was confirmed in this wavelength region. The results indicated, that it might be possible to measure the elimination of several substances that are retained in the uraemic patients and with potential clinical significance. From thisviewpoint, the UV-absorbance monitoring technique may become a more universal method to ensure the quality and adequacy of the dialysis.
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| 4. |
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| 5. |
- Lindberg, Lars-Göran, 1951-, et al.
(författare)
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Non-invasive optical dialysate monitoring
- 1999
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Ingår i: Congress of the European Renal Association, European Dialysis and Transplant Association,1999.
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Konferensbidrag (refereegranskat)
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