Tissue viability imaging (TiVi) in the assessment of divergent beam UV-B provocation

Abstract

In routine clinical phototesting and in basic research, naked eye dermatological assessment is the "gold standard" for determining the patient's minimal erythemal dose (MED). In UV-B testing with a divergent, radially attenuating beam of characterised dosimetry, laser Doppler perfusion imaging has been previously used to give quantitative description of reactivity to doses above the MED in addition to a "single-dose" objective determination of the MED itself. In the present paper, the recently developed tissue viability imaging (TiVi) technology is presented for the first time as a reliable, easily applicable, high-resolution alternative to LDPI in the divergent beam testing concept. Data obtained after provocation with a range of doses was analysed in order to determine the reaction diameter, which can be related to the MED using field dosimetry. The dose-response features of exposure above the MED and the relationship between naked eye readings and the diameter were determined from the image data. TiVi data were obtained faster than LDPI data and at a higher spatial resolution of 100 μm instead of 1 mm. A tool was developed to centre over the erythema area of the acquired image. Response data could be plotted continuously against dose. Thresholding of processed images compared to naked eye "gold standard" readings showed that the normal skin value +4 standard deviations produced a good fit between both methods. A linear fitting method for the dose-response data provided a further method of determination of the reaction diameter (MED). Erythemal "volume under the surface (VUS)" for the reaction provided a new concept for visualising information. TiVi offers advantages over LDPI in the acquisition and analysis of data collected during divergent beam testing. An increased amount of data compared to traditional phototesting is easily and more objectively obtained which increases applicability in the clinical and research environment.

Reflectance spectroscopy: to shed new light on the capillary refill test

“…Other methods quantifying skin reaction after blanching pressure are available [19][20][21]32], some of which have been used previously in similar applications [23,26,33,34]. The advantage of TiVi is its correlation with RBC concentration whereas other devices focus more on the general colour change of skin, possibly making data more sensitive to each subjects skin colour.…”

The tissue viability imaging system—Suitable method for discovering minimal skin changes in occupational screenings? Results of a cross‐sectional field study

“…Orthogonal polarization filters enable the evaluation of deeper skin layers and the microvascular vessel bed situated there . There had been no large studies with application of this measurement in screenings for hand eczema thus far, but clinical experiments appeared promising …”

“…18,19 There had been no large studies with application of this measurement in screenings for hand eczema thus far, but clinical experiments appeared promising. 17,[20][21][22] In this study, we tested the application of the TiVi system for occupational screenings in a field study, using the HEROS for comparison. HEROS is a quantitative skin score for the hands, suitable for manifest hand eczema but also for detecting minimal skin lesions in persons with mostly healthy skin.…”

Polarized Light Spectroscopy for Measurement of the Microvascular Response to Local Heating at Multiple Skin Sites

“…TiVi is a digital camera-based technique that measures the concentration of RBC in the upper dermis [27]. Based on polarized light spectroscopy, TiVi produces RBC concentration images with high spatial resolution, which makes it a powerful technique for measurement on relatively large skin sites, such as with phototesting [28] and pharmacological provocations [17]. The technique has been shown to perform favorably compared with LDF when perfusion is low [17,39], which is commonly the case in skin, and it is insensitive to motion artifacts [27].…”