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

Abstract

In order to characterize and quantify allergic skin reactions, 12 nickel sensitized women aged 18 to 45 underwent 5 patch tests with nickel sulfate in petrolatum at the following concentrations: 0.5, 1, 2, 3 and 5%. The tests, performed on volar forearm skin, were removed after a 24-h application. B scanning evaluations were carried out at the beginning and at 24, 48 and 72 h after patch test application using Dermascan C (Cortex Technology, Hadsund, Denmark). After obtaining echographic images, there were processed by a dedicated programme (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 hyper-reflecting 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. This method showed a progressive increase in the number of low reflecting pixels according to the nickel patch test concentration and to the elapsing of time. On the contrary, at 24 h there was a decrease in pixel values concerning the hyper-reflecting band. This evaluation method proved useful in assessing the intensity of patch test responses.