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Single exposure phototesting utilizing a divergent ultraviolet beam
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
Linköping University, Department of Biomedicine and Surgery, Dermatology. Linköping University, The Institute of Technology.
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-0012-7867
1999 (English)In: Skin research and technology, ISSN 0909-752X, E-ISSN 1600-0846, Vol. 5, no 4, 255-259 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
1999. Vol. 5, no 4, 255-259 p.
National Category
Medical and Health Sciences
URN: urn:nbn:se:liu:diva-30206DOI: 10.1111/j.1600-0846.1999.tb00138.xLocal ID: 15700OAI: diva2:251028
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2016-05-04
In thesis
1. Single exposure phototesting and assessment of pigmented skin lesions: quantitative methods in terms of blood perfusion estimates
Open this publication in new window or tab >>Single exposure phototesting and assessment of pigmented skin lesions: quantitative methods in terms of blood perfusion estimates
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2003. 68 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 839
National Category
Medical and Health Sciences
urn:nbn:se:liu:diva-24502 (URN)6626 (Local ID)91-7373-722-4 (ISBN)6626 (Archive number)6626 (OAI)
Public defence
2003-09-19, Viktoriasalen, Universitetssjukhuset, Linköping, 09:15 (Swedish)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2013-01-02

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