| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Arildsson, Mikael, 1967-, et al.
(författare)
-
Skin capillary appearance and skin microvascular perfusion due to topical application of analgesia cream
- 2000
-
Ingår i: Microvascular Research. - : Elsevier BV. - 0026-2862 .- 1095-9319. ; 59:1, s. 14-23
-
Tidskriftsartikel (refereegranskat)abstract
- Local topical analgesia changes basal skin perfusion and its regulation. In particular, the response induced by local heating, which in nontreated skin comprises a rapidly increased perfusion followed by a normalization within 30 s, is altered to a delayed and persistent perfusion increase. The response dependency to the analgesia cream application time, that is, the intradermal penetration of the analgesics and in which vascular plexa the response occurs, is not known. The aim of this study was to assess changes in the appearance of superficial skin capillaries and skin microvascular perfusion changes due to different application periods of topical analgesia cream (EMLA). Twelve subjects were treated with EMLA and placebo applied to the volar side of each forearm, respectively. The treatment areas were assigned different application times (20 min, 40 min, 1 h, 2 h, and 3 h). The areas were cleared from the creams and shortly thereafter provoked during 9 s with a probe heated to 45°C. To assess capillary number density and skin perfusion, capillary microscopy, and Laser Doppler perfusion imaging (LDPI), respectively, were used. The number density of physiologically active capillary was significantly decreased with longer application times of EMLA (P < 0.005). The LDPI-signal showed a persistent perfusion increase after provocation associated with increasing application time of the cream. This perfusion pattern was not seen after 20 min of treatment, but was present in 9 of 12 subjects after 3 h of treatment. No significant relationship between changes in the capillary number density and the LDF measurement was found. In conclusion, a longer application time and therefore a higher intradermal concentration and a deeper penetration of the analgesics was associated with a delayed and persistent perfusion increase after local heating. There was a discrepancy between changes in capillary number density and skin perfusion, indicating that the perfusion increase does not occur in the capillaries but in the deeper lying vessels. Hence, the contribution of the capillary perfusion to the LDF-signal is smaller than previously anticipated. Capillary number density and presumably their perfusion were decreased with longer application times.
|
|
| 9. |
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
- Asker, Claes, et al.
(författare)
-
Datorbaserad kapillärmikroskopi
- 1994
-
Ingår i: Läkarsällskapets Riksstämma,1994.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
|
|
| 13. |
|
|
| 14. |
|
|
| 15. |
|
|
| 16. |
|
|
| 17. |
- Ewerlöf, Maria, 1987-, et al.
(författare)
-
Estimation of skin microcirculatory hemoglobinoxygen saturation and red blood cell tissue fractionusing a multispectral snapshot imaging system : a validation study
- 2021
-
Ingår i: Journal of Biomedical Optics. - : SPIE - International Society for Optical Engineering. - 1083-3668 .- 1560-2281. ; 26:2
-
Tidskriftsartikel (refereegranskat)abstract
- Significance: Hemoglobin oxygen saturation and red blood cell (RBC) tissue fraction are important parameters when assessing microvascular status. Functional information can be attained using temporally resolved measurements performed during stimulus–response protocols. Pointwise assessments can currently be conducted with probe-based systems. However, snapshot multispectral imaging (MSI) can be used for spatial–temporal measurements.Aim: To validate if hemoglobin oxygen saturation and RBC tissue fraction can be quantified using a snapshot MSI system and an inverse Monte Carlo algorithm.Approach: Skin tissue measurements from the MSI system were compared to those from a validated probe-based system during arterial and venous occlusion provocation on 24 subjects in the wavelength interval 450 to 650 nm, to evaluate a wide range of hemoglobin oxygen saturation and RBC tissue fraction levels.Results: Arterial occlusion results show a mean linear regression R2 = 0.958 for hemoglobin oxygen saturation. Comparing relative RBC tissue fraction during venous occlusion results in R2 = 0.925. The MSI system shows larger dynamic changes than the reference system, which might be explained by a deeper sampling including more capacitance vessels.Conclusions: The snapshot MSI system estimates hemoglobin oxygen saturation and RBC tissue fraction in skin microcirculation showing a high correlation (R2 > 0.9 in most subjects) with those measured by the reference method.
|
|
| 18. |
- Ewerlöf, Maria, 1987-
(författare)
-
Multispectral imaging of hemoglobin oxygen saturation in skin microcirculation
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The ability to measure microcirculatory parameters such as hemoglobin oxygen saturation is important since it mirrors the microcirculatory state of the body. The microcirculation delivers oxygen and nutrients to the cells of the body and, if impaired, may be a sign of circulatory failure. Human skin microcirculation can be accessed non-invasively with bio-optical technologies, where skin acts as a diagnostic window. Diffuse reflectance spectroscopy (DRS) is a technique that access skin microcirculatory parameters, especially hemoglobin oxygen saturation. Basic systems are fiber optic probebased and measure in one point, often in firm contact with the skin. Multispectral diffuse reflectance imaging (MSI) enables spatially resolved DRS, imaging skin optical parameters from spectrally resolved backscattered intensities. Spectral information detected by MSI systems contain information on, e.g., hemoglobin oxygen saturation and optical properties of the tissue. Both spatial and temporal resolved information of hemoglobin oxygen saturation is beneficial for better diagnostics in most clinical applications, e.g., to monitor progression of wound healing processes, or other microcirculatory diseases reflected in hemoglobin spectral changes. Analysis of acquired MSI multispectral data cubes to access information on tissue parameters with high contrast to these variations can be performed in several ways using models and simulations. Time resolved continuous measurements that are spectrally and spatially resolved generate large amounts of data, requiring both storage space and fast analysis. Reducing the number of wavelengths is one way to limit the amount of data, if it does not reduce the quality of interpreted results. Therefore, in my work, I investigated theoretically how to reduce the number of wavelengths, and later implemented my findings using a snapshot MSI camera. Monte Carlo (MC) simulations were used to estimate hemoglobin oxygen saturation from captured MSI data. I also performed temporally resolved in vivo measurements on healthy test subjects during vascular occlusion provocations with a 16-channel snapshot MSI system. The acquired data were analyzed using two different methods: inverse MC and trained artificial neural networks (ANNs). For inverse MC, the acquired spectrum was iteratively compared to simulated spectra, where different optical properties were used for the simulation, trying to find the best fit. ANNs were trained to intensity data measured with the MSI system, using concurrently measured hemoglobin oxygen saturation values from a validated probe-based system as target data. The results and outcome of this thesis indicate good possibility to accurately estimate hemoglobin oxygen saturation with as few as four wavelengths. Estimated hemoglobin oxygen saturation values from analysis of in vivo measurements from the 16-channel snapshot MSI camera show high conformance to values measured by the validated probe-based system. Using the ANN-approach reduces time for analysis of a 512 × 270-pixel image to 0.056 s, compared to 1 h 58 min required by the inverse MC algorithm to analyze the same data. The method enables real-time analysis, and is, consequently, preferable in many clinical situations.
|
|
| 19. |
- Ewerlöf, Maria, 1987-, et al.
(författare)
-
Multispectral snapshot imaging of skin microcirculatory hemoglobin oxygen saturation using artificial neural networks trained on in vivo data
- 2022
-
Ingår i: Journal of Biomedical Optics. - Bellingham, WA, United States : SPIE - International Society for Optical Engineering. - 1083-3668 .- 1560-2281. ; 27:3
-
Tidskriftsartikel (refereegranskat)abstract
- Significance: Developing algorithms for estimating blood oxygenation from snapshot multispectral imaging (MSI) data is challenging due to the complexity of sensor characteristics and photon transport modeling in tissue. We circumvent this using a method where artificial neural networks (ANNs) are trained on in vivo MSI data with target values from a point-measuring reference method.Aim: To develop and evaluate a methodology where a snapshot filter mosaic camera is utilized for imaging skin hemoglobin oxygen saturation (SO2), using ANNs.Approach: MSI data were acquired during occlusion provocations. ANNs were trained to estimate SO2 with MSI data as input, targeting data from a validated probe-based reference system. Performance of ANNs with different properties and training data sets was compared.Results: The method enables spatially resolved estimation of skin tissue SO2. Results are comparable to those acquired using a Monte-Carlo-based approach when relevant training data are used.Conclusions: Training an ANN on in vivo MSI data covering a wide range of target values acquired during an occlusion protocol enable real-time estimation of SO2 maps. Data from the probe-based reference system can be used as target despite differences in sampling depth and measurement position.
|
|
| 20. |
|
|
| 21. |
|
|
| 22. |
- Hellem, S., et al.
(författare)
-
Bone blood flow
- 1989
-
Ingår i: Laser-Doppler Blood Flowmetry, Kluwer Academic Publishers.
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
|
|
| 23. |
|
|
| 24. |
|
|
| 25. |
|
|
| 26. |
- Häggblad, Erik, 1972-, et al.
(författare)
-
Reflectance spectroscopy
- 2000
-
Ingår i: Eight Int Symp CNVD 2000,2000. ; , s. 45-50
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
|
|
| 27. |
|
|
| 28. |
- Ilias, Michail, 1971-, et al.
(författare)
-
Assessment of pigmented skin lesions in terms of blood perfusion estimates
- 2004
-
Ingår i: Skin research and technology. - : Wiley-Blackwell Publishing Inc.. - 0909-752X .- 1600-0846. ; 10:1, s. 43-49
-
Tidskriftsartikel (refereegranskat)abstract
- Background/aims: Cutaneous malignant melanoma is a disease of increasing clinical and economical importance. The prognosis is good with early diagnosis. The chief differential diagnosis is benign melanocytic naevus, a common lesion in Caucasians. Attempts have been made to use bioengineering techniques to aid in the initial diagnosis. The present study proposes a method of extracting possibly discriminative blood perfusion properties in pigmented skin lesions by combining information on the lesions' blood perfusion with optical or visual information of their spatial extent.Methods: A total of 46 blood perfusion measurements were performed on 22 pigmented skin lesions, the ultimate diagnosis of which was three histologically proven malignant melanomas, four histologically proven benign naevi and fifteen naevi assessed by two specialist dermatologists as being benign. Laser Doppler perfusion imaging gave two different types of two-dimensional data sets (64×64 pixels), one representing the total backscattered light intensity at each measurement point (TLI image) and the second corresponding to perfusion values. The boundaries of each examined lesion were derived from the TLI image employing greyscale thresholding, thus resulting in an estimated region of interest (ROI) approximating the optical extent of the lesion. The ROI was superimposed on the perfusion image and extraction of perfusion features was then performed.Results: The processing of the TLI images was successful in delineating the lesions' boundaries. The first hypothesis that the mean perfusion quotients in MM and benign naevi are equal could not be rejected at the chosen 5% level of significance. The second hypothesis that the mean percent-age of elevated perfusion values (image pixels) within the ROI shows no difference between MM and benign naevi could be rejected at a 5% level of significance.Conclusions: This study has presented a method of extracting blood perfusion parameters of pigmented skin lesions by combining blood perfusion information with information on the lesion's optical extent. The proposed method of presenting data could prove to be a useful discriminative adjunct in the assessment of pigmented skin lesions.
|
|
| 29. |
|
|
| 30. |
|
|
| 31. |
|
|
| 32. |
|
|
| 33. |
|
|
| 34. |
|
|
| 35. |
|
|
| 36. |
- Latorre, Malcolm, 1967-
(författare)
-
The Physical Axon : Modeling, Simulation and Electrode Evaluation
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electrodes are used in medicine for detection of biological signals and for stimulating tissue, e.g. in deep brain stimulation (DBS). For both applications, an understanding of the functioning of the electrode, and its interface and interaction with the target tissue involved is necessary. To date, there is no standardized method for medical electrode evaluation that allows transferability of acquired data. In this thesis, a physical axon (Paxon) potential generator was developed as a device to facilitate standardized comparisons of different electrodes. The Paxon generates repeatable, tuneable and physiological-like action potentials from a peripheral nerve. It consists of a testbed comprising 40 software controlled 20 μm gold wires embedded in resin, each wire mimicking a node of Ranvier. ECG surface Ag-AgCl electrodes were systematically tested with the Paxon. The results showed small variations in orientation (rotation) and position (relative to axon position) which directly impact the acquired signal. Other electrode types including DBS electrodes can also be evaluated with the Paxon.A theoretical comparison of a single cable neuronal model with an alternative established double cable neuron model was completed. The output with regards to DBS was implemented to comparing the models. These models were configured to investigate electrode stimulation activity, and in turn to assess the activation distance by DBS for changes in axon diameter (1.5-10 μm), pulse shape (rectangular biphasic and rectangular, triangular and sinus monophasic) and drive strength (1-5 V or mA). As both models present similar activation distances, sensitivity to input shape and computational time, the neuron model selection for DBS could be based on model complexity and axon diameter flexibility. An application of the in-house neuron model for multiple DBS lead designs, in a patient-specific simulation study, was completed. Assessments based on the electric field along multiple sample planes of axons support previous findings that a fixed electric field isolevel is sufficient for assessments of tissue activation distances for a predefined axon diameter and pulse width in DBS.
|
|
| 37. |
|
|
| 38. |
|
|
| 39. |
|
|
| 40. |
|
|
| 41. |
|
|
| 42. |
|
|
| 43. |
|
|
| 44. |
|
|
| 45. |
|
|
| 46. |
|
|
| 47. |
- Majedy, Motasam, 1983-, et al.
(författare)
-
Spectral characterization of liquid hemoglobin phantoms with varying oxygenation states
- 2022
-
Ingår i: Journal of Biomedical Optics. - Bellingham, WA, United States : SPIE - The International Society for Optics and Photonics. - 1083-3668 .- 1560-2281. ; 27:7
-
Tidskriftsartikel (refereegranskat)abstract
- Significance: For optical methods to accurately assess hemoglobin oxygen saturation in vivo, an independently verifiable tissue-like standard is required for validation. For this purpose, we propose three hemoglobin preparations and evaluate methods to characterize them.Aim: To spectrally characterize three different hemoglobin preparations using multiple spectroscopic methods and to compare their absorption spectra to commonly used reference spectra.Approach: Absorption spectra of three hemoglobin preparations in solution were characterized using spectroscopic collimated transmission: whole blood, lysed blood, and ferrous-stabilized hemoglobin. Tissue-mimicking phantoms composed of Intralipid, and the hemoglobin solutions were characterized using spatial frequency-domain spectroscopy (SFDS) and enhanced perfusion and oxygen saturation (EPOS) techniques while using yeast to deplete oxygen.Results: All hemoglobin preparations exhibited similar absorption spectra when accounting for methemoglobin and scattering in their oxyhemoglobin and deoxyhemoglobin forms, respectively. However, systematic differences were observed in the fitting depending on the reference spectra used. For the tissue-mimicking phantoms, SFDS measurements at the surface of the phantom were affected by oxygen diffusion at the interface with air, associated with higher values than for the EPOS system.Conclusions: We show the validity of different blood phantoms and what considerations need to be addressed in each case to utilize them equivalently.
|
|
| 48. |
|
|
| 49. |
|
|
| 50. |
- Mørk, Cato, et al.
(författare)
-
Microvascular arteriovenous shunting is a probable pathogenetic mechanism in erythromelalgia
- 2000
-
Ingår i: Journal of Investigative Dermatology. - : Elsevier BV. - 0022-202X .- 1523-1747. ; 114:4, s. 643-646
-
Tidskriftsartikel (refereegranskat)abstract
- Erythromelalgia is a condition consisting of red, warm, and burning painful extremities. Symptoms are relieved by cold and aggravated by heat. A wide variety of etiologic conditions can cause erythromelalgia, but one common pathogenetic mechanism, microvascular arteriovenous shunting, has been hypothesized. The aim of this study was to test this hypothesis. Quantification of skin microvascular perfusion using laser Doppler perfusion imaging and skin temperature at rest and after central body heating was performed in 14 patients with erythromelalgia and 11 controls. Attacks of erythromelalgia were induced in eight patients after heat provocation. In the plantar region of the foot, the location of numerous anatomical arteriovenous shunts, these patients significantly increased the skin perfusion as compared with asymptomatic patients with erythromelalgia and controls. In the dorsal region with few arteriovenous shunts no significant differences between the groups were demonstrated. The results show a relation between clinical symptoms and increased perfusion in the region of numerous anatomical arteriovenous shunts, and support the hypothesis of increased thermoregulatory arteriovenous shunt flow during attacks in primary erythromelalgia.
|
|
