B scanning evaluation of irritant reactions with binary transformation and image analysis

In order to characterize and quantify irritant skin reactions, 12 women aged 18 to 45 underwent 5 patch tests with sodium lauryl sulfate at the following concentrations: 0.5, 1, 2, 3 and 5%. The tests, applied on volar forearm skin, were removed after a 24-h application. Evaporimetry and B scanning were carried out at the beginning and at 24, 48 and 72 h after patch test application. Echographic recordings were performed by Dermascan C (Cortex Technology, Hadsund, Denmark). After the acquisition, the echographic images were processed by a dedicated software (Dermavision 2D, Cortex Technology, Hadsund, Denmark) enabling the selection of amplitudes of interest and the transformation into a binary colour system. By attributing one colour to a selected amplitude band, part of an image can be highlighted and assessed by a value corresponding to the number of pixels (picture elements). For the evaluation of the images, 2 bands were chosen. The first, ranging from 201 to 255 is able to highlight hyperreflecting parts of the pictures (epidermis, lower part of the dermis); the second, ranging from 0 to 30, marks the hypo-echogenic part of the tissue, which is the site of inflammation. The evaluation by means of the 201-255 amplitude band showed a marked decrease of the echogenicity of the epidermis which was more pronounced at 24-h determinations and for higher concentrations of sodium lauryl sulphate (SLS), whereas the increase in pixel numbers, shown by the 0-30 band, was slight and apparent only for high SLS concentrations. Echographic data and transepidermal water loss (TEWL) values showed a good correlation.(ABSTRACT TRUNCATED AT 250 WORDS)