Image based system for the qualification of skin erythema

Skin allergy tests are the main procedure for diagnosing IgE-mediated reactions; which are commonly known as allergy. These reactions are produced by an overreaction of the immune system to substances that get in contact with the body, called allergens. From the skin allergy tests, the most commonly performed procedures are the skin prick tests (SPTs), which are based on introducing a small drop of allergen within the epidermis. If an allergic reaction occurs, histamine is released, causing local blood vessels to dilate, and thus, increasing the concentration of RBCs. Consequently, the local skin region becomes red in appearance, which is known as erythema. In addition, another symptom of this reaction is the increase in venules’ permeability, which produces a leakage of plasma (mainly composed by water). Then, extracellular fluid accumulates and a wheal appears. The dimensions of this wheal are used to determine if an specific allergen provokes a hypersensitivity reaction or not. This diagnostic method is based on visual appearance, which is subjected to userdependency. There is not an standardized way for measuring the wheal diameter, nor the erythematous area dimensions. Therefore, the objective of this work is to implement an image based system for performing an automatic diagnosis for hypersensitivity reactions. To achieve this, skin optical properties and light propagation within tissue are studied. Besides, for this purpose, absorbance and scattering coefficients for hemoglobin (contained in erythema) and water (contained in edema) are used for determining the illumination setup of the system. The specified wavelengths enhance visual appearance of erythema’s and edema’s light reflectance. From these values, absorption maps are built, which are then used to quantify both chromophore’s concentrations. The implementation of this system would mean an standardization for allergy tests diagnosis, as well as a cost reduction in experts training.Ingeniería Biomédic