| 1. |
- Anderson, C., et al.
(författare)
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Changes in skin circulation after microdialysis probe insertion visualized by laser Doppler perfusion imaging
- 1994
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Ingår i: Journal of Investigative Dermatology. - 0022-202X .- 1523-1747. ; 102:5, s. 807-811
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Tidskriftsartikel (refereegranskat)abstract
- Microdialysis makes possible in vivo estimation of endogenous and exogenous substances in the dermal extracellular space. Insertion of the microdialysis probe and its subsequent presence in the skin may affect both the reactivity of the skin test site and the measurement of target substances. Laser Doppler flowmetry is a non-invasive method for estimating cutaneous blood flow. A further development of this technique, laser Doppler perfusion imaging, has been used to study the time course of the circulatory changes caused in the area of microdialysis probe insertion. Laser Doppler perfusion imaging was performed prior to, during, and after microdialysis probe insertion in the skin of the ventral forearm in three subjects. Probe insertion caused an increase in skin blood perfusion in the whole test area. About 15 min after probe insertion, the flare, which is presumed to be of chiefly axon reflex origin, began to subside and the circulatory response could be seen to center around the site of insertion and the tip of the probe. Skin perfusion levels had returned to near normal levels within 60 min. Local anesthesia of the point of guide insertion inhibited the flare, but did not affect circulatory reactivity in the skin nearby. Both microdialysis and laser Doppler perfusion imaging seem to be promising new methods in dermatologic research.
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| 2. |
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| 3. |
- Troilius, A., et al.
(författare)
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Evaluation of Portwine Stain Perfusion by Laser Doppler Imaging and Thermography Before and After Argon Laser Treatment
- 1992
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Ingår i: Acta Dermato-Venereologica. - 0001-5555. ; 72:1, s. 6-10
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Tidskriftsartikel (refereegranskat)abstract
- Thirteen patients with port wine stains (PWS) were treated with argon laser therapy. Before and at different points in time following treatment, skin blood perfusion and temperature were mapped with laser Doppler imaging and thermography. In nine patients no elevation in blood perfusion was observed in the PWS in comparison with the surrounding normal skin before treatment. In the remaining four patients a significantly (p less than 0.01) higher blood flow was recorded within the PWS. Immediately after treatment nine patients showed elevated perfusion within the PWS. During the first two days following treatment, all patients showed a gradually decreasing hyperperfusion in the borderline between the PWS lesion and surrounding skin. Immediately after treatment 10 patients had a significantly (p less than 0.01) higher temperature in the PWS than in normal skin. During the first 24 h following treatment, an elevated perfusion was in general accompanied by a tissue temperature increase. Three and a half months after argon laser treatment, three patients showed excellent clinical results with no remaining PWS spots or scarring. Two of these patients had had both elevated perfusion and temperature in the PWS prior to treatment.
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| 4. |
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| 5. |
- Wårdell, Karin, 1959-
(författare)
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Laser Doppler perfusion imaging : methodology and skin applications
- 1994
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Over the last decade a number of emerging technologies have become available for the non-invasive study of skin anatomy and physiology. In this thesis, a method for mapping tissue perfusion based on the laser Doppler technique is presented together with some of the associated experimental and clinical applications.The laser Doppler perfusion imager is a novel computer-controlled system for two-dimensional mapping of tissue blood flow that uses a low power He-Ne laser beam to sequentially scan a tissue surface. At each measurement site the beam illuminates the tissue volume to a depth of a few hundred micrometers. In the presence of moving blood cells, partially Doppler-broadened backscattered light is detected by a photodetector and processed to form a value scaled linearly to perfusion. A full format image includes 64x64 measurement sites corresponding to a 12 cm x 12 cm area and is captured in 4.5 minutes. When all measurement values have been recorded, processed and stored, a color-coded perfusion image showing the spatial heterogeneity of the tissue perfusion is displayed on a monitor. In addition, data analysis functions such as statistics, profile generation and image subtraction can be performed. A theory describing the influence on the output signal by the distance between the object and the detector as well as the incident angle is presented. Changes in distance and incident angle cause a variation in'the number of coherence areas on the detector surface and thereby an alteration in the system amplification factor. To correct for the distance dependence, the laser beam is made slightly divergent by the use of a lens system. The angular dependence is corrected for in the software. By the use of a flow simulator, a linear relationship between the processor output signal and red blood cells up to a concentration of 0.2% was confirmed. The spatial and temporal system-related noise was found to be less than 0.3% and 0.5% of the maximum value, respectively.Spatial and temporal variations in normal forearm skin perfusion were investigated with laser Doppler perfusion imaging and a comparison with topographic laser Doppler flowmetry mapping was performed revealing substantial heterogeneity in normal skin blood flow. By the use of electrical nerve stimulation the extent, intensity and time course of the cutaneous axon reflex response was investigated. Changes in skin circulation after microdialysis probe insertion visualized the hyperperfusion induced both at the point of insertion and at the probe tip. The perfusion in port wine stains before and after argon laser treatment was studied and compared to the clinical results.
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| 6. |
- Wårdell, Karin, et al.
(författare)
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Laser Doppler Perfusion Imaging by Dynamic Light Scattering
- 1993
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Ingår i: IEEE Transactions on Biomedical Engineering. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9294 .- 1558-2531. ; 40:4, s. 309-316
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Tidskriftsartikel (refereegranskat)abstract
- A laser Doppler perfusion imaging technique based on dynamic light scattering in tissue is reported. When a laser beam sequentially scans the tissue (maximal area approximately 12 cm*12 cm), moving blood cells generate Doppler components in the backscattered light. A fraction of this light is detected by a remote photodiode and converted into an electrical signal. In the signal processor, a signal proportional to the tissue perfusion at each measurement point is calculated and stored. When the scanning procedure is completed, the system generates a color-coded perfusion image on a monitor. A perfusion image is typically built up of data from 4096 measurement sites, recorded during a time period of 4 min. This image has a spatial resolution of about 2 mm. A theory for the system inherent amplification factor dependence on the distance between individual measurement points and detector is proposed and correction measures are presented. Performance results for the laser Doppler perfusion imager obtained with a flow simulator are presented. The advantages of the method are discussed.
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| 7. |
- Wårdell, Karin, et al.
(författare)
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Spatial heterogeity in normal skin perfusion recorded with laser Doppler imaging and flowmetry
- 1994
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Ingår i: Microvascular Research. - 0026-2862 .- 1095-9319. ; 48:1, s. 26-38
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Tidskriftsartikel (refereegranskat)abstract
- Spatial and temporal variations in forearm skin perfusion captured by laser Doppler perfusion imaging (LDI) have been compared with topographic maps recorded by laser Doppler flowmetry. In order to determine the shortest LDI sampling time required at each measurement site, with an adequate signal-to-noise ratio and with the ability to display the heterogeneity in skin perfusion, the noise-limited resolution of the LDI system as well as various sampling times were tested. The noise-limited resolution for medium and high light intensities were less than 0.5% (temporal) and 0.3% (spatial) of full scale. A sampling time of 1 sec was selected and image presentation was made by performing bilinear interpolation between perfusion values. The same area (10 x 10 mm) was mapped with LDI and topographic mapping at seven different sites. In addition, a larger area covering the surrounding skin was recorded with LDI. The small area recordings with LDI and topographic mapping could be identified in the larger LDI image. High-and low-perfusion spots coincided between the two systems. Temporal variations were studied by repeated LDI recordings of the same areas as above. Small spots were selected in the areas and plotted versus time. Without provocation, the total perfusion changes at each spot showed large variations, but the relative perfusion levels between neighboring spots persisted. Provocation with heat increased the perfusion in all spots.
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| 8. |
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