| 1. |
- Häggblad, Erik, 1972-, et al.
(författare)
-
A diffuse reflectance spectroscopic study of UV-induced erythematous reaction across well-defined borders in human skin
- 2010
-
Ingår i: Skin research and technology. - : Wiley. - 0909-752X .- 1600-0846. ; 16:3, s. 283-290
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction The colour of tissue is often of clinicaluse in the diagnosis of tissue homeostasis andphysiological responses to various stimuli.Determining tissue colour changes and borders,however, often poses an intricate problem and visualexamination, constituting clinical praxis, does notallow them to be objectively characterized orquantified. Demands for increased inter- and intraobserverreproducibility have been incentives for theintroduction of objective methods and techniques fortissue colour (e.g. erythema) evaluation. The aim ofthe present paper was to study the border zone of anUVB provoked erythematous response of humanskin in terms of blood volume and oxygenationmeasured by means of diffuse reflectancespectroscopy using a commercial probe. Material and Methods A provocation model, basedon partial masking of irradiated skin areas, definestwo erythema edges at every skin site responding tothe UV irradiation. In every subject, 5 test sites wereexposed with a constant UV light irradiance (14mW/cm2), but with different exposures times (0, 3,6, 9, 12 seconds). An analysis of the spectral datameasured across the two edges was performed for every scan line. The oxygenized and deoxygenizedhemoglobin contents were estimated in everymeasurement point, using a modified Beer-Lambertmodel. Results The fit of the experimental data to the model derived by the modified Beer-Lambert law was excellent (R2>0.95). Analyzing data for the chromophore content showed that the erythematous response in provoked areas is dominated by the increase in oxyhemoglobin. The width for the left and right border zone was estimated to 1.81±0.93 mm and 1.90±0.88 mm respectively (M±SD). The unprovoked area between the two edges was estimated to 0.77±0.68 mm. Conclusion While the chosen data analysis performed satisfactory, the ability of the probe design to differentiate spatial aspects of a reaction with abrupt borders was found to be suboptimal resulting in a probable overestimation of the erythematous edge slope. Probe modification or imaging are possible solutions.
|
|
| 2. |
- Ilias, Michail A., 1971-
(författare)
-
Single exposure phototesting and assessment of pigmented skin lesions : quantitative methods in terms of blood perfusion estimates
- 2003
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns the development of quantitative phototesting for the investigation of individual skin sensitivity to ultraviolet (UV) radiation, and the assessment of pigmented skin lesions (PSL) in terms of blood perfusion estimates. In both cases, laser Doppler perfusion imaging (LDPI) was used to quantify the perfusion.The proposed phototesting method is based on a single exposure to a divergent UVB beam, which produces a continuous, radially attenuating dose field covering an area with a diameter of 4.5 cm. In order to meet the demands posed by this approach, two-dimensional dosimetry was developed, the entire dose field was adapted to the standard erythemal action spectrum for humans, and a spatially resolving technique (LDPI) was used for objective quantification of the skin response. Data analysis methods were developed, enabling the determination of minimal erythemal dose (MED) and the extraction of dose-response information. The method was evaluated on a normal material (20 subjects), proving a good reproducibility of the MED and enhanced possibilities to extract individual dose-response information. In the study of anti-inflammatory effects (16 subjects) of topically applied substances, linear curve-fitting (0.89 ≤ R2 ≤ 0.98) was shown to adequately describe the relationship between dose and response in the dose range immediately above the MED. The gradient of the derived post MED-lines was used as a measure of the response aggressiveness. The results are promising and warrant further evaluation, e.g. in the investigation of patients with suspected photodermatoses.This thesis also presents a method for the extraction and presentation of blood perfusion data of pigmented skin lesions in conjunction with optical information on the lesions' spatial extent. The boundaries of pigmented lesions could successfully be delineated, using standard image processing steps, in the total light intensity images given by LDPI. Classical blood perfusion measures such as mean perfusion and perfusion quotients was confined to the ROI, making relevant comparison to corresponding values of neighbouring healthy tissue possible. This data analysis approach was used on a pooled group of PSL showing promising results. The method may prove to be a useful adjunct in the discriminative assessment of pigmented skin lesions.
|
|
| 3. |
- Ilias, Michail A., 1971-, et al.
(författare)
-
Single exposure phototesting utilizing a divergent ultraviolet beam
- 1999
-
Ingår i: Skin research and technology. - : Wiley. - 0909-752X .- 1600-0846. ; 5:4, s. 255-259
-
Tidskriftsartikel (refereegranskat)abstract
- Background/aims: Confident diagnosis of photosensitivity in patients with light dermatoses requires skin exposure to well determined ultraviolet (UV) light doses, most often from a solar simulator. The traditional test procedure results in a rough classification of skin sensitivity based on the minimal erythema dose (MED) found for each patient. The limited number of constant irradiance doses used during phototesting decreases the precision of the MED value. In the present study we aimed at developing the technical system for the determination of MED by using a single, centrifugally attenuating, UVB provocation.Methods: A divergent UV beam was achieved with the help of an optic lens. To investigate the irradiance profile, an irradiance acquisition system was built that produced three-dimensional intensity maps. In addition, a laser Doppler perfusion imaging (LDPI) system was introduced in the evaluation of the skin response along with visual readings of the same exposed areas, in order to add a quantitative aspect to the assessment of erythema. The procedure was used on one test subject.Results: The divergent UV beam showed the desired profile. With the current setup 20 different UV-dose levels could be discriminated. Relevant UV-dose levels were determined and tested on a subject, which in practice gave results in the form of visual assessment as well as LDPI-images. The visual or LDPI diameter gave the MED. Within the skin reaction, irradiance and the laser Doppler values could be compared mm for mm.Conclusions: A more accurate MED determination with a single UV exposure seems to be feasible by using the proposed method. Though further investigation is required, the technique appears to offer new possibilities for the association of dose to response. In addition LDPI is possibly a useful complement to the visual readings of the skin responses, since the method gives a quantification of the grade of erythema, as opposed to visual (+, ++, +++) readings that are subjective and at best semiquantitative.
|
|
| 4. |
- Ilias, Michail A., et al.
(författare)
-
Visible, Hyperspectral Imaging Evaluating the Cutaneous Response to Ultraviolet Radiation
- 2007
-
Ingår i: Imaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues V. - : SPIE - International Society for Optical Engineering. - 9780819465542 ; , s. 644103-1-644103-12
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In vivo diagnostics of skin diseases as well as understanding of the skin biology constitute a field demanding characterization of physiological and anatomical parameters. Biomedical optics has been successfully used, to qualitatively and quantitatively estimate the microcirculatory conditions of superficial skin. Capillaroscopy, laser Doppler techniques and spectroscopy, all elucidate different aspects of microcirculation, e.g. capillary anatomy and distribution, tissue perfusion and hemoglobin oxygenation. We demonstrate the use of a diffuse reflectance hyperspectral imaging system for spatial and temporal characterization of tissue oxygenation, important to skin viability. The system comprises: light source, liquid crystal tunable filter, camera objective, CCD camera, and the decomposition of the spectral signature into relative amounts of oxy- and deoxygenized hemoglobin as well as melanin in every pixel resulting in tissue chromophore images. To validate the system, we used a phototesting model, creating a graded inflammatory response of a known geometry, in order to evaluate the ability to register spatially resolved reflectance spectra. The obtained results demonstrate the possibility to describe the UV inflammatory response by calculating the change in tissue oxygen level, intimately connected to a tissue's metabolism. Preliminary results on the estimation of melanin content are also presented.
|
|
